,,nasa ,,sp-#ib ,significant ,achievements in ,space ,bioscience #aieh-aifd ,scientific and ,technical ,information ,division #aiff ,,national ,,aeronautics ,,and ,,space ,,administration ,washington1 ,d4,c4 ,for sale by the ,superintendent of ,documents1 ,u4,s4 ,government ,printing ,office ,washington1 ,d4,c41 #bjdjb--,price #ee cents ,foreword ,this volume is one of a series which summarize the progress made during the period #aieh through #aifd in discipline areas covered by the ,space ,science and ,applications ,program of the ,united ,states4 ,in this way1 the contribution made by the ,national ,aeronautics and ,space ,administration is highlighted against the background of overall progress in each discipline4 ,succeeding issues will document the results from later years4 ,the initial issue of this series appears in #aj volumes 7,,nasa ,special ,publications #ia to #ajj7 which describe the achievements in the following areas3 ,astronomy1 ,bioscience1 ,communications and ,navigation1 ,geodesy1 ,ionospheres and ,radio ,physics1 ,meteorology1 ,particles and ,fields1 ,planetary ,atmospheres1 ,planetology1 and ,solar ,physics4 ,although we do not here attempt to name those who have contributed to our program during these first #f years1 both in the experimental and theoretical research and in the analysis1 compilation1 and reporting of results1 nevertheless we wish to acknowledge all the contributions to a very fruitful program in which this country may take justifiable pride4 ,homer ,e4 ,newell ,associate ,administrator for ,space ,science and ,applications1 ,,nasa ,preface ,this summary of certain aspects of the space biology program of the ,national ,aeronautics and ,space ,administration brings together some results of ,,nasa research and ,,nasa-sponsored research under grants and contracts from #aieh through #aifd4 ,closely related research even though not sponsored by ,,nasa is also included4 ,the space biology program has had a late start in comparison with the space physics program1 and only a token program existed before #aifb4 ,much of the present research involves preparation of space-flight experiments and obtainment of adequate baseline information4 ,perhaps half the research results reported are derived from the ,,nasa program4 ,additional information is included from many other sources1 especially the ,u4,s4 ,air ,force with its long history of work in aviation and aerospace medicine4 ,relatively few biological space-flight experiments have been undertaken4 ,these have been to test life-support systems and to demonstrate1 before manned space flight1 an animal's capability to survive4 ,few critical biological experiments have been placed in orbit by ,,nasa1 but a biosatellite program will soon make a detailed study of the fundamental biological effects of weightlessness1 biorhythms1 and radiation4 ,the search for extraterrestrial life has been limited to ground-based research and planning for planetary and lunar landings4 ,life-detection experiments have been developed and tested1 and an important and exciting program is being planned to detect and study extraterrestrial life1 if it exists4 ,interest in space biology has been slow in developing1 and there has been some caution and controversy in the scientific community4 ,however1 increased interest is starting to push forward the frontier of this new and important scientific field1 and future outlook appears to be optimistic4 ,this summary was written and compiled by the members of the ,bioscience ,programs ,division of the ,office of ,space ,science and ,applications4 ,the report was edited and chapters #a1 #c1 #f1 and #g were written by ,dale ,w4 ,jenkins1 ,chief1 ,environmental ,biology2 chapter #b1 by ,gregg ,mamikunian1 ,staff ,scientist1 ,exobiology2 chapters #d and #h1 by ,richard ,e4 ,belleville1 ,chief1 ,behavioral ,biology2 and chapter #e1 by ,george ,j4 ,jacobs1 ,chief1 ,physical ,biology4 ,contents page #a ,,background 4444444444444444444444444444444444444444 44444444444 #a #b ,,exobiology 4444444444444444444444444444444444444444 44444444444 #e #c ,,environmental ,,biology 4444444444444444444444444444444444444444 #bc #d ,,behavioral ,,biology 4444444444444444444444444444444444444444 444 #dc #e ,,molecular ,,biology ,,and ,,bioinstrumentation 444444444444444444444 #eg #f ,,flight ,,programs 4444444444444444444444444444444444444444 444444 #fe #g ,,manned ,,space ,,flight 4444444444444444444444444444444444444444 44 #gg #h ,,significance ,,of ,,the ,,achievements 44444444444444444444444444444 #aaa ,,references 4444444444444444444444444444444444444444 4444444444444 #aai chapter #a ,background ,the biological program of the ,national ,aeronautics and ,space ,administration had a late start4 ,a small life sciences group1 organized in #aieh1 was concerned with life support and use of primates for system and vehicle testing for the ,mercury program4 ,three small suborbital flights of biological materials were flown in space4 ,the ,bioscience ,program ,office of the ,office of ,space ,science and ,applications was organized in #aifb4 ,the goals of the ,bioscience ,program are3 7#a7 to determine if extraterrestrial life exists anywhere in the solar system and to study its origin1 nature1 and level of development1 if it is present2 7#b7 to determine the effects of space and planetary environments on ,earth organisms1 including man2 7#c7 to conduct biological research to develop life support and protective measures for extended manned space flight2 and 7#d7 to develop fundamental theories in biology relative to origin1 development1 and relationship to environment4 ,research and development has been carried out to design life-detection experiments and instruments for future flights to ,mars and to develop experiments to study the effects of the space environment on living organisms4 ,a biosatellite program1 started in #aifc1 has the first of six flights scheduled for #aiff4 ,space exploration has demanded a rigorous development1 especially in the biosciences area4 ,investigation of the solar system for exotic life forms1 the environmental extremes to which ,earth organisms 7including man7 are being exposed1 the possibilities for modification of planetary environments by biological techniques yet to be developed1 and the problems of communication in biosystems are areas which have required refinement of the theoretical framework of biology before progress could be made rapidly enough to keep pace with technological advances in transportation4 ,of all the sciences1 biology alone has not yet benefited from comparisons with the universe beyond ,earth4 ,it is reasonable to suppose that breakthroughs might be made in biology on the basis of comparisons with life from other worlds4 ,organisms elsewhere may have found alternatives to processes we think of as basic characteristics of life4 ,in contrast1 physical science has advanced sufficiently to provide a great body of laws which may be expressed in mathematical terms1 and by which phenomena may be predicted with complete accuracy4 ,a well-known characteristic of biological phenomena is variability4 ,the ,darwinian concept of evolution is perhaps the only pervading generalization in biology4 ,this concept has been supported by evidence of a hereditary mechanism in the discovery of genes and gene mutations4 ,space bioscience represents the convergence of main disciplines with a single orientation1 whose direction is determined by the problems of manned space travel which have1 in turn1 created a host of bioengineering problems concerned with supporting man in space4 ,foremost among these questions is the possibility of the existence of extraterrestrial life4 ,the field which is concerned with the search for extraterrestrial life has come to be called exobiology4 ,in addition to the challenge of great technological problems which must be solved1 exobiology is so closely related to the central scientific questions in biological science that it is considered by some to be the most significant pursuit in all of science4 ,one of the major opportunities already presented by the advances in propulsion systems is the ability to escape from the influence of the ,earth1 which has made possible the study of organism-environment relationships1 particularly the role that environmental stimuli play in the establishment and maintenance of normal organization in living systems4 ,transcending even these formidable objectives of space bioscience is an objective shared by all life sciences1 the discovery of nature's scheme for coding the messages contained in biological molecules4 ,extraterrestrial biology seeks to find not only evidence of life now present1 but the vestigial chemicals of its previous existence4 ,the ways and means have already been made available to study molecules on whose long1 recorded messages is written the autobiography of evolution--the history of living organisms extending back to the beginnings of life4 ,on this same basis1 it is now within the realm of science to foresee the means of predicting the development of life from primordial1 nonliving chemical systems4 ,closely allied to the search for extraterrestrial life is research which seeks to identify the materials and the conditions which are the prerequisites of life4 ,space bioscience research is now extending human knowledge of fundamental biological phenomena1 both in space and on ,earth1 just as the physical sciences explore other aspects of the universe4 ,the accomplishment of bioscience objectives is totally dependent upon advances in the technology of space flight4 ,a highly developed launch-vehicle capability is essential to accomplish the long-duration missions required in the search for extraterrestrial life4 ,life on other planets in the solar system 7with emphasis on ,mars7 will be investigated by full exploitation of space technology which will allow both remote 7orbiter7 and direct 7lander7 observations of the planetary atmosphere1 surface1 and subsurface4 ,certain characteristics of terrestrial life1 such as growth and reproduction1 provide a basis for relatively simple experiments which may be used on early missions to detect the existence of life on ,mars4 ,later missions will provide extensive automatic laboratory capabilities for analyzing many samples taken from various depths and locations4 ,because of the hypothetical nature of current experiment designs1 it is likely that visual observations of the planet will be required4 ,many technical problems are involved in storing and transmitting the large amounts of data over planetary distances4 ,such visual observations might very well be crucial in interpreting results from other experiments4 ,critical to all exploration of the ,moon and planets are the requirements to3 7#a7 prevent contamination of the environment with ,earth organisms and preserve the existing conditions of the planet for biological exploration2 7#b7 provide strict quarantine for anything returned to ,earth from the ,moon and planets4 ,the biological exploration of ,mars is a scientific undertaking of the greatest significance4 ,its realization will be a major milestone in the history of human achievement4 ,the characterization of life1 if present1 and study of the evolutionary processes involved and their relationship to the evolution of terrestrial life would have a great scientific and philosophical impact4 ,what is at stake is nothing less than knowledge of our place in nature4 ,extended ,earth orbital flights with subhuman specimens will be used to determine the effects on ,earth organisms of prolonged weightlessness1 radiation1 and removal from the influence of the ,earth's rotation4 ,such flights of biosatellites and other suitable spacecraft are expected to3 7#a7 establish biological specifications for extending the duration of manned space flight2 7#b7 provide a flexible means of testing unforeseen contingencies1 thus providing an effective biological backup for manned missions2 7#c7 yield experimental data more rapidly by virtue of the greater number and expendability of subjects2 7#d7 anticipate possible delayed effects appearing in later life or in subsequent generations1 through use of animal subjects with more rapid development and aging2 7#e7 develop and test new physiological instrumentation techniques1 surgical preparations1 prophylactic techniques1 and therapeutic procedures which are not possible on human subjects2 and 7#f7 provide a broad background of experience and data which will permit more accurate interpretations of observed effects of space flight on living organisms1 including man4 chapter #b ,exobiology ,the possibility of discovering an independent life form on a planet other than ,earth presents an unequaled challenge in the history of scientific search4 ,therefore1 the detection of life within the solar system is a major objective of space research in the foreseeable future4 ,the scientific data presently available concerning the possible existence of a ,martian life form and the chemical constitution of the surface of ,mars are disappointingly few4 ,in fact1 it is impossible to make a statement about any of the many surface features1 other than the polar caps1 with any degree of certainty4 ,the observational results have been accounted for by many conflicting hypotheses which can only be resolved by the accumulation of new evidence4 ,the arguments supporting the existence of ,martian life 7ref4#a7 are based on the following observations3 7#a7 ,the various colors1 including green1 exhibited by the dark areas 7#b7 ,the seasonal changes in the visual albedo and polarization of the dark areas 7#c7 ,the ability of the dark areas to regenerate after an extensive duststorm 7#d7 ,the presence of absorption bands at #c4c-c4g1 attributed to organic molecules ,conflicting interpretations of the above observations have been advanced4 ,the argument based on the colors is inconclusive1 and several workers have suggested that the color is a contrast effect with the bright-reddish continents4 ,the meager quantitative data have been discussed by pik 7ref4#b7 who has reduced ,kozyrev's photometric observations of the very dark area of ,syrtis ,major to intrinsic reflectivities by allowing for the estimated atmospheric attenuation and reflectivity4 ,kuiper 7ref4#c7 similarly demonstrated the absence of the near-infrared reflection maximum1 which is characteristic of most green plants1 indicating that chlorophyll was not responsible for the color4 ,the second and third arguments remain the most cogent4 ,however1 serious limitations are imposed on the second if the severity of the ,martian climate is considered4 ,fcas 7ref4#d7 has photometrically measured the seasonal changes in the fine structure of the dark areas of ,mars and concludes that-- 7#a7 ,the dark areas of ,mars show periodic variation of intensity following the cycle of the darkening element 7#b7 ,the average intensity of the dark area1 not including the action of the darkening waves1 increases from the poles toward the equator 7#c7 ,the action of each of the darkening waves decreases from the poles toward the equator4 ,this decrease is balanced in the equatorial zone by the combined action of the two darkening waves alternately originating at the two poles4 ,the mechanism of the darkness-generating element seems to be constant for all latitudes during the ,martian year4 ,the variation in intensity has been explained recently by nonlife mechanisms for ,depressio ,hellespontica 7an area showing one of the greatest seasonal changes7 7ref4#b74 ,similar nonlife mechanisms may be applicable to the other dark regions1 and1 thus1 the darkening can be used only as circumstantial evidence in support of a ,martian life form4 ,if inorganic interpretations of the seasonal albedo variation are accepted1 then an inorganic interpretation must also be advanced for the polarization variation4 ,two possibilities can be suggested3 7#a7 ,a change in surface texture1 caused by varying absorption of atmospheric constituents1 causing both the albedo and polarization to change in the manner observed 7#b7 ,a change in surface texture1 in which the surface material becomes rougher1 which also explains the observed polarization data 7ref4#e7 ,the third argument against the regenerative feature of the dark areas being a life process has been advanced by ,kuiper 7ref4#f74 ,it is based on atmospheric circulation causing dust1 presumably lava1 to be blown on the dark areas of ,mars during the late summer1 autumn1 and winter1 and then removed during the spring4 ,mamikunian and ,moore have recently advanced the similar explanation that carbonaceous chondrites or asteroidal matter may induce the observed phenomenon if they are abundant on the planet's surface4 ,the pulverized chondritic material will exhibit a high degree of opacity due to localization and1 hence1 a change in polarization characteristics and a decrease in polarization following mixing of the chondritic material with indigenous surface minerals4 ,the fourth observational argument1 the ,sinton bands 7ref4#g71 has been shown to be at least doubtful4 ,rea1 ,belsky1 and ,calvin 7ref4#h7 recorded infrared reflection spectra for a large number of inorganic and organic samples1 including minerals and biological specimens1 for the purpose of interpreting the #c-to-#a spectrum of ,mars4 ,these authors state that a previous suggestion that the ,martian bands be attributed solely to carbohydrates is not a required conclusion4 ,at the same time they fail to present a satisfactory alternate explanation1 and the problem remains unsolved4 ,more recently1 ,rea et al4 7ref4#i7 noted the similarity between the #c4eh and #c4fi minima in the ,martian infrared spectra and those of ,d,o-,,hdo-,h,o mixtures and1 particularly1 of ,,hdo4 ,with all this marked disagreement in interpreting the observational data concerning ,mars1 it becomes clearly evident that an experimental approach to the detection of life on ,mars should provide the maximum positive information possible4 ,some life-detection experiments developed with ,,nasa support have been summarized by ,quimby 7ref4#aj74 ,the schema of the biological exploration of a planet is to conduct a series of complementary experiments proceeding from general to specific4 ,the general experiments will examine gross characteristics of the planet's environment and surface for determining the probability of an active biota 7life74 ,data from the general experiments will be significant in-- 7#a7 ,defining the nature of specific experiments in which life detection is the major objective2 and 7#b7 ,providing a high degree of confidence in undertaking specific experiments1 since indications from the gross characterization of the planet in question will influence the choice and design of the specific experiments4 ,the biological exploration of planets is then to be defined as the search for those parameters relevant to the origin1 development1 sustenance1 and degradation of life in a planetary environment4 ,this definition will give rise to a critical question for each progressively specific and complex experiment to determine-- 7#a7 ,the existence of life on the planet 7#b7 ,the degree of similarity or dissimilarity 7structure and function7 with respect to terrestrial life 7#c7 ,the origin of this planetary life ,the immediate objective of the biological explorations of the planet is to define the state of the planetary surface1 which may exhibit the following properties3 7#a7 ,a prebiota 7defined as the absence of life7 7#b7 ,an active biota 7defined as the presence of life7 7#c7 ,an extinct biota 7defined as evidence of former life7 ,the identification and the detailed characterization of each of the above stages of planetary development constitute the subject matter of the biological exploration of the planets and1 specifically1 ,mars4 ,,the ,,experimental ,,investigation ,,of ,,chemical ,,evolution ,attempts have been made to simulate and approximate models of primitive ,earth conditions for abiogenic synthesis1 and successful synthesis of essential biochemical constituents necessary for maintaining life has been partly accomplished4 ,urey 7ref4#aa7 has clearly pointed out the possible role of a reducing atmosphere in the synthesis of prebiological organic molecules4 ,miller 7ref4#ab7 synthesized a variety of amino acids in a reducing atmosphere by means of an electrical discharge4 ,a variety of organic compounds have been synthesized by the action of various energy sources upon reducing atmospheres1 and several investigators have extended the ,urey-,miller-type reactions to synthesize nucleic acid components 7ref4#ac71 adenosine triphosphate 7ref4#ad71 and a host of biologically essential organic compounds4 ,it is likely that in the synthesis of organic moieties1 simple and specific molecules were first produced when the planets had a reducing atmosphere4 ,further complexity or degradation of the organic compounds produced varied1 depending on the geochemical changes of the planet's surface1 the atmospheric constituents1 the degree of interaction between surface and atmosphere1 and the rate of the organic synthesis4 ,oparin 7ref4#ae7 presented the most detailed mechanisms for the spontaneous generation of the first living organism arising in a sea of organic compounds synthesized in a reducing atmosphere on ,earth4 ,it is generally accepted that1 under favorable conditions1 life can arise by spontaneous generation4 ,a primary requirement for this initiation is that there be abundant organic compounds concentrated in one or more specific zones4 ,these simple organic molecules would undergo modification to develop a greater structural complexity and specificity1 finally giving rise to a living organism4 ,therefore1 because of the ease with which organic compounds can be synthesized under reducing conditions1 planetary surfaces may contain an abundant source of similar organic matter4 ,however1 difficulties arise in postulating steps for further organization or modification of the above synthesized organic matter into a living state4 ,most of the original organic matter produced in the primary reducing atmospheres of the various planets may have been quite similar4 ,however1 major variations between planets1 in chemical evolution beyond the prebiotic stage1 must have been the rule rather than the exception4 ,the primary interest in this area of research has been the realization of the possible existence of organic molecules on planetary surfaces and1 particularly1 ,mars4 ,pertinent synthesis may be either biological or abiological4 ,research conducted in the simulation of cosmochemical synthesis has used most of the available solar spectrum4 ,simulation experiments devised to study the effects of these energies on the assumed early atmosphere of the ,earth have yielded products that play a dominant role in molecular and biochemical organization of the cell4 ,calvin 7ref4#af7 irradiated water and carbon dioxide in a cyclotron1 obtaining formaldehyde and formic acid4 ,miller 7ref4#ag7 found that when methane1 ammonia1 water1 and hydrogen were subjected to a high-frequency electrical discharge1 several amino acids were produced along with a variety of other organic compounds4 ,corroborating experiments established that the synthesis of amino acids occurred readily4 ,the apparent mechanism for the production of amino acids is as follows3 aldehydes and hydrogen cyanide are synthesized in the gas phase by the electrical discharge4 ,these substances react together and also together with ammonia in the water phase of the system to give hydroxy and amino nitriles1 which are then hydrolyzed to hydroxy and amino acids4 ,among the major constituents were aspartic acid1 glutamic acid1 glycine1 -alanine1 and -alanine4 ,the ,miller-,urey reaction mixture has been extended and several modifications introduced4 ,or 7ref4#ah7 introduced hydrogen cyanide into the system as the primary gas component4 ,adenine was obtained when ,or heated a concentrated solution of hydrogen cyanide in aqueous ammonia for several days at temperatures up to #ajj ,c4 ,adenine is an essential component of nucleic acids and of several important coenzymes4 ,guanine and urea were the two other products identified in the hydrogen cyanide reaction4 ,or further obtained guanine and uracil as products of nonenzymatic reactions by using certain purine intermediates as starting materials4 ,ponnamperuma 7ref4#ai7 also obtained adenine upon irradiation of methane1 ammonia1 hydrogen1 and water1 using a high-energy electron beam as the source of energy of irradiation4 ,these results indicate that adenine is very readily synthesized under abiotic conditions4 ,adenine1 among the biologically important purines and pyrimidines1 has the greatest resonance energy1 thus making its synthesis more likely and imparting greater radiation stability to the molecule4 ,the formation of adenine and guanine1 the purines in ,,rna and ,,dna1 by a relatively simple abiological process lends further support to the hypothesis that essential biochemical constituents of life may have originated on ,earth by a gradual chemical evolution and selection4 ,in this respect1 the examination of planetary surfaces--specifically ,mars--presents practical implications for current research on the problem of chemical evolution4 ,when ,ponnamperuma et al4 7ref4#ad7 exposed adenine and ribose to ultraviolet light in the presence of phosphate1 adenosine was produced4 ,when the adenine and ribose were similarly exposed in the presence of the ethyl ester of polyphosphoric acid1 adenosine diphosphate 7,,adp7 and adenosine triphosphate 7,,atp7 were produced4 ,the abiological formation of ,,atp was a major stride along the path of chemical evolution1 since ,,atp is the principal free energy source of living organisms4 ,oparin 7ref4#ae7 postulated that -amino acids could have been formed nonbiologically from hydrocarbons1 ammonia1 and hydrogen cyanide at a time when the ,earth's atmosphere contained these substances in high concentrations4 ,oparin's hypothesis has received strong experimental support1 as evidenced by the work of ,miller 7ref4#ab74 ,bernal 7ref4#bj7 has emphasized the role played by ultraviolet light in the formation of organic compounds at a certain stage of the ,earth's evolution4 ,generally it has been believed that the first proteins or foreprotein were nonbiologically formed by the polycondensation of preformed free amino acids 7ref4#ba74 ,akabori 7ref4#bb7 proposed a hypothesis for the origin of the foreprotein and speculated that it must have been produced through reactions consisting of the following three steps4 ,the first step is the formation of aminoacetonitrile from formaldehyde1 ammonia1 and hydrogen cyanide4 ,,ch,o ,,nh ,,hcn -------- ,h,n--,,ch--,,cn ,h,o ,the second is the polymerization of aminoacetonitrile on a solid surface1 probably absorbed on clay1 followed by the hydrolysis of the polymer to polyglycine and ammonia4 x ,h,n--,,ch--,,cn -------- 7--,,nh--,,ch--,c--7 ,,nh x ,h,o ,v 7--,,nh--,,ch--,,co--7 x ,,nh ,the third step is the introduction of side chains into polyglycine by the reaction with aldehydes or with unsaturated hydrocarbons4 ,akabori has demonstrated experimentally the formation of cystinyl and cysteinyl residue in his above-postulated mechanism4 ,fox's theory of thermal copolymerization 7ref4#bc7 suggests that proteins or like molecular units could have been formed in the ,earth's crust1 under geothermal conditions4 ,the accumulated amino acids were heat polymerized and transported into the primary oceans for further modifications4 ,fox has obtained polymers consisting of all #ah amino acids usually present in proteins4 ,the polymerization is generally done at #afj ,c to #bjj ,c1 although in the presence of polyphosphoric acid it can be accomplished at temperatures below #ajj ,c4 ,molecular weights increased from #cfjj in a proteinoid made at #afj ,c to #hfjj in one made at #aij ,c4 ,fox showed that when hot saturated solutions of thermal copolymers containing the #ah common amino acids were allowed to cool1 large numbers of uniform1 relatively firm1 and elastic spherules separate4 ,these range from #j4b to #fj in diameter and are quite uniform within each preparation4 ,various chemical observations suggest the presence of peptide bonds in the structural organization of these proteinoids4 ,continuing observations of these microspheres have established further characteristics that point to the possibility of their interpretation as a kind of primitive protein macromolecule with self-organizing properties1 such that a primitive form of cell1 with boundary and other properties1 might form4 ,in laboratory experiments the behavior of gram-negative and gram-positive microspheres in dilute alkali parallels that of gram-negative and gram-positive bacteria 7ref4#bc74 ,furthermore1 time-lapse studies indicate that the proteinoid microspheres undergo a septate kind of fission1 mimicking cell division as shown in figure #a4 ,cytochemical studies show that the microsphere's boundary is membranelike in having a primitive selectivity4 ,electron micrographs of sections of stained microspheres also indicate the presence of a boundary4 ,oparin 7ref4#ae7 states that the type of organization peculiar to life could only result from the evolution of a multimolecular organic system separated from its environment by a distinct boundary but constantly interacting with this environment4 ,in his concept of coacervates as precell models1 ,oparin 7ref4#bd7 indicates that present-day protoplasm possesses a number of features similar to coacervate structure4 ,these coacervates could represent the starting point for evolution leading to the origin of life4 ,moreover1 in the course of their evolution the initial systems may gradually become more complex4 ,oparin also showed 7ref4#ae7 that mixing solutions of different proteins and other substances of high molecular weight produced these coacervate droplets4 ,these droplets are characterized by the formation of a surface layer with altered structure and mechanical properties1 thus providing a somewhat selective barrier in which to house a molecular system capable of replication4 ,however1 these coacervates are unstable structurally4 ,illustration3 ,figure #a4--,protenoid microspheres undergoing septate fission4 ,small microspheres and filamentous associations thereof are also shown 7ref4#be74 ,the ,,nasa program has further provided considerable impetus for continuing research with respect to the chemical evolution of life1 since its life-detection experiments may encounter prebiological molecules in their search for extraterrestrial life on other planetary surfaces4 ,in the area of exobiological research1 the significant accomplishments to date have been-- 7#a7 ,the reconstruction of some of the pathways which may have led to the origin of life1 by means of laboratory simulation of processes yielding prebiological organic molecules 7#b7 ,the developments in experimental and theoretical biology2 specifically1 the role of nucleic acid-protein interactions in storage and transmission of information both within living cells and from generation to generation of cells 7#c7 ,the suspected role of ,,dna in information storage and the development of new concepts of the coding mechanism in ,,dna that may lead to a universal biological theory embracing evolutionary1 as well as homeostatic1 adaptation to environment and learned behavioral systems ,with the essential biochemical constituents of life and the mechanism of replication beginning to be understood1 the challenge for the synthesis of living matter by abiogenic experimental techniques has become to many scientists the ultimate goal of the scientific era4 ,,nasa has established an exobiology laboratory at ,ames ,research ,center in addition to the sizable support of research at various academic centers of excellence for the continuation of abiogenic synthesis4 ,although research on organochemical evolution is in its infancy1 the data from relatively few experiments have already created an immense enthusiasm for knowledge of the biochemical pathways of evolution4 ,this kind of research will ultimately elucidate the terrestrial evolution of life and1 perhaps1 the nature of life on other planetary bodies and the distribution of life in our galaxy4 ,this program1 with its vast demands on the scientific community at large1 is coordinated with related endeavors of a number of ,federal agencies4 ,it is allied with certain biochemical studies at the ,national ,institutes of ,health for the eventual elucidation of the dynamic pathways in cosmochemical synthesis of life's essential biochemical constituents4 ,,meteorites ,,and ,,organic ,,geochemistry ,meteorites ,a significant area of exobiological research is the investigation of a special class of stony meteorites known as carbonaceous chondrites4 ,it is increasingly apparent that almost all life-detection concepts rely on the eventual analysis of the solid materials that may be available on ,mars and other planetary surfaces4 ,cosmic dust and meteorites are two classes of material bodies that reach the ,earth from outer space4 ,the carbonaceous chondrites are the only extraterrestrial materials known to contain organic carbon4 ,the study of meteorites has generated an astonishing diversity of hypotheses4 ,there is agreement at only one point3 that meteorites are preserved chunks of very ancient1 perhaps primordial1 planetary matter and that when we are able to understand the curious structures and chemical and isotopic variations in the meteorites1 we will also know a great deal about early planetary 7and perhaps preplanetary7 history4 ,meteorites provide a more representative sample of average planetary matter than the highly differentiated crust of the ,earth4 ,although it is known that the meteorite parent bodies ceased to be geochemically active shortly after their formation1 some #d billion years ago1 there is no consensus on the nature of the meteorite parent bodies1 not even on such basic properties as size1 location1 and multiplicity4 ,this is not surprising because the meteorite samples commonly available for study represent only about #aj to #aj of the parent body4 ,carbonaceous ,meteorites ,analysis and characterization of the chemical constituents 7organic7 of carbonaceous chondrites1 including the possible mechanism of their formation1 may be expected to improve methods of analyzing samples from the ,moon and planets and of interpreting remote automated biological analyses on the planets' surfaces4 ,carbon has been detected in all meteorites analyzed2 however1 both the amount and forms present vary considerably4 ,among the forms of meteorite carbon are diamond1 graphite1 cohenite 7,fe1,ni1,co7,c1 moissanite ,si,c1 calcite ,ca,c,o1 dolomite 7,ca1,mg7,,co1 bruennerite 7,mg1,fe7,,co4 ,a summary of the results of carbon analyses on large numbers of meteorites is given in table ,i 7ref4#bf74 ,table ,i4--,meteorite ,carbon ---------------------------------------- ------------------------- ,meteorite group ,number ,mean carbon content1 analyzed percent by weight ---------------------------------------- ------------------------- ,pallasites #aj #j4jh ---------------------------------------- ------------------------- ,ureilites #b 4#fi ---------------------------------------- ------------------------- ,bronzite chondrites #ab 4#je ---------------------------------------- ------------------------- ,hypersthene chondrites #h 4#jd ---------------------------------------- ------------------------- ,enstatite chondrites #h 4#bi ---------------------------------------- ------------------------- ,carbonaceous chondrites #af #b4jd ---------------------------------------- ------------------------- ,most meteorites possess only traces of carbon1 and studies of this carbon indicate that it is composed largely of graphite1 cohenite1 and moissanite1 with some diamond4 ,however1 studies of the carbon in the carbonaceous chondrites have failed to detect any of these forms4 ,some carbonates are present in a minority of the carbonaceous group1 but account for only a small percentage of the total carbon 7perhaps about #aj percent of the total ,c in type ,i only74 ,the carbonaceous chondrites contain organic carbon4 ,the word organic is not used in a biological sense1 merely as a chemical term to describe compounds of carbon other than carbonates1 bicarbonates1 and carbides4 ,no evidence has been found of any form of carbon other than organic1 except for traces of carbonates4 ,various studies have demonstrated possible methods of estimating the total amount of organic matter present in meteorites4 ,wiik 7ref4#bg7 has suggested that organics can be estimated by measuring the loss of weight on ignition4 ,unfortunately1 this method has several disadvantages and gives very low values4 ,corrections must be made for weight gains due to oxidation of reduced constituents1 such as ,fe,o1 ,fe1 ,ni1 and ,co1 and for weight losses due to ,h,o1 ,s1 etc4 ,the water loss is exceedingly difficult to estimate1 as part comes from the combustion of organic hydrogen and part comes from the loss of mineral-bound water4 ,the carbon also proves difficult to combust completely1 and high temperatures 7over #ajjj ,c7 are required for efficient conversion to ,,co4 ,in one study the major fraction of organic matter removed proved to have a carbon content of about #dg percent 7ref4#bh74 ,thus1 if all the meteorite carbon is present as organic matter of approximately this composition1 total organics must be approximately double the carbon content2 that is1 #b percent by weight carbon indicates #d percent by weight organic matter4 ,this estimate may be too low1 for ,mueller 7ref4#bi7 has extracted a major organic fraction containing only #bd percent carbon2 however1 this work has not been confirmed for other meteorites4 ,briggs and ,mamikunian 7ref4#bf7 have pointed out that only #be percent of the organic matter has been extracted1 and only about #e percent of this has been chemically characterized4 ,most of this #e percent is a complex mixture of hydroxylated aromatic acids together with hydrocarbons of the aliphatic1 napalicyclic1 and aromatic series4 ,small amounts of amino acids1 sugars1 and fatty acids are also present4 ,thus far1 these chemical analyses point to an abiogenic origin for the organic matter1 and no conclusive evidence exists of biological activity on the meteorite parent body4 ,microbiological investigations of samples of the carbonaceous chondrites have yielded only inconclusive evidence on the problem of organized elements4 ,several of these microstructures from different carbonaceous chondrites are illustrated in a paper by ,mamikunian and ,briggs 7ref4#cj74 ,it has been difficult to identify the organized structures1 and most do not have morphologies identical to known terrestrial micro-organisms4 ,however1 they may prove to be a variety of mineral grains1 droplets of organic matter and sulfur1 as well as a small amount of contaminating terrestrial debris4 ,a comparison between the photographs of the organized elements observed in the ,orgueil and ,ivuna meteorites and the synthetic proteinoid microspheres observed by ,fox 7ref4#be7 point to similarities between the two4 ,one inference from this finding is that the organized elements in carbonaceous chondrites were never alive but1 rather1 should be considered as natural experiments in molecular evolution4 ,also1 these similarities strengthen the belief that the laboratory experiments are similar to the natural experiments in space4 ,in cooperation with the ,smithsonian ,astrophysical ,observatory1 ,,nasa has a network to track meteors in the ,midwest 7,south ,dakota1 ,nebraska1 ,kansas1 ,oklahoma1 ,iowa1 ,missouri1 and ,illinois74 ,photographs of meteor trails are used for scientific study1 and attempts are made to track and recover meteorites for examination for traces of organic material of extraterrestrial origin4 ,fundamental research in terrestrial organic geochemistry has shown that ancient sediments and drill core samples subjected to organic analysis contain certain stable biochemical components of past life4 ,this preserved record is significant not only in studies of early-life chemical pathways but also in studies of the interaction of organic matter with the geological factors4 ,since life on any planetary body will interact with the soil1 or surface material1 it is of interest to understand the relationship4 ,,concepts ,,for ,,detection ,,of ,,extraterrestrial ,,life ,it is not possible to present completely convincing evidence for the existence of extraterrestrial life4 ,the problem often reduces to probabilities and to estimates of observational reliability4 ,in almost all cases the evidence is optimistically considered strongly suggestive of--or1 at the worst1 not inconsistent with--the existence of extraterrestrial life4 ,alternatively1 there is a pessimistic view that the evidence advanced for extraterrestrial life is unconvincing1 irrelevant1 or has another1 nonbiological explanation4 ,in studies of the laboratory synthesis of life-related compounds and its significance concerning the origin of life1 several results seem to suggest that organochemical synthesis is a general process1 occurring perhaps on all planets which retain a reducing atmosphere4 ,the temperature ranges must be such that precursors and reaction products are not thermally dissociated4 ,the reaction rates for the synthesis of more complex organic molecules diminish to a negligible value when the temperature range is below #ajj ,c4 ,besides the planetary parameter of temperature1 an even more fundamental necessity for a living state exists--a liquid solvent system4 ,for terrestrial life forms1 water serves this purpose4 ,water has this and other properties of biological significance because of hydrogen bonding between adjacent molecules in the liquid state4 ,ultraviolet radiation could serve as an extraterrestrial energy source for organic synthesis4 ,research shows that1 while an atmosphere is important1 living systems can survive a wide range of ambient pressures and are little affected by a wide range of magnetic field strengths4 ,oxygen is not a prerequisite for all living systems4 ,while it is sometimes concluded that free oxygen is needed for all but the simplest organisms1 less efficient metabolic processes coupled with higher food collection efficiency--or a more sluggish metabolism--would seem to do just as well4 ,earth is the only planet in the solar system on which molecular oxygen is known to be present in large amounts4 ,since plant photosynthesis is the primary source of atmospheric oxygen1 it seems safe to infer that no other planet has large-scale plant photosynthesis accompanied by the production of oxygen4 ,the possibility of the existence of extraterrestrial life raises the important question of man's being able to detect it4 ,research on extraterrestrial life detection is predicated on the ability to develop ways to detect it even when the living systems are based on principles entirely different from those on ,earth4 ,the substitution of various molecules for those of known biological significance to living organisms as we know them has been investigated2 the substitution of ,,nh for ,,oh in ammonia-rich environments leads to a diverse1 and biologically very promising1 chemistry4 ,the hypothesis that silicon may replace carbon does not support the construction of extraterrestrial genetics based on silicon compounds4 7,silicon compounds participate in redistribution reactions which tend to maximize the randomness of silicon bonding1 and the stable retention of genetic information over long time periods is thus very improbable47 ,evidence relevant to life on ,mars has been summarized by ,sagan 7ch4 #a of ref4#aj73 ,the ,origin of ,life ,in the past decade1 considerable advances have been made in our knowledge of the probable processes leading to the origin of life on ,earth4 ,a succession of laboratory experiments has shown that essentially all the organic building blocks of contemporary terrestrial organisms can be synthesized by supplying energy to a mixture of the hydrogen-rich gases of the primitive terrestrial atmosphere4 ,it now seems likely that the laboratory synthesis of a self-replicating molecular system is only a short time away from realization4 ,the syntheses of similar systems in the primitive terrestrial oceans must have occurred--collections of molecules which were so constructed that1 by the laws of physics and chemistry1 they forced the production of identical copies of themselves out of the building blocks in the surrounding medium4 ,such a system satisfies many of the criteria for ,darwinian natural selection1 and the long evolutionary path from molecule to advanced organism can then be understood4 ,since nothing except very general primitive atmospheric conditions and energy sources are required for such syntheses1 it is possible that similar events occurred in the early history of ,mars and that life may have come into being on that planet several billions of years ago4 ,its subsequent evolution1 in response to the changing ,martian environment1 would have produced organisms quite different from those which now inhabit ,earth4 ,simulation ,experiments ,experiments have been performed in which terrestrial micro-organisms have been introduced into simulated ,martian environments1 with atmospheres composed of nitrogen and carbon dioxide1 no oxygen1 very little water1 a daily temperature variation from #bj to -#fj ,c1 and high ultraviolet fluxes4 ,it was found that in every sample of terrestrial soil used there were a few varieties of micro-organisms which easily survived on ,mars4 ,when the local abundance of water was increased1 terrestrial micro-organisms were able to grow4 ,indigenous ,martian organisms may be even more efficient in coping with the apparent rigors of their environment4 ,these findings underscore the necessity for sterilizing ,mars entry vehicles so as not to perform accidental biological contamination of that planet and obscure the subsequent search for extraterrestrial life4 ,direct ,searches for ,life on ,mars ,the early evidence for life on ,mars--namely1 reports of vivid green coloration and the so-called canals--are now known to be largely illusory4 ,there are three major areas of contemporary investigation3 visual1 polarimetric1 and spectrographic4 ,as the ,martian polar ice cap recedes each spring1 a wave of darkening propagates through the ,martian dark areas1 sharpening their outlines and increasing their contrast with the surrounding deserts4 ,these changes occur during periods of relatively high humidity and relatively high daytime temperatures4 ,a related dark collar1 not due to simple dampening of the soil1 follows the edge of the polar cap in its regression4 ,occasional nonseasonal changes in the form of the ,martian dark regions have been observed and sometimes cover vast areas of surface4 ,observations of the polarization of sunlight reflected from the ,martian dark areas indicate that the small particles covering the dark areas change their size distribution in the spring1 while the particles covering the bright areas do not show any analogous changes4 ,finally1 infrared spectroscopic observations of the ,martian dark areas show three spectral features which1 to date1 seem to be interpretable only in terms of organic matter1 the particular molecules giving rise to the absorptions being hydrocarbons and aldehydes4 ,however1 see p4 #g and ,rea et al4 7ref4#i74 ,taken together1 these observations suggest1 but do not conclusively prove1 that the ,martian dark areas are covered with small organisms composed of familiar types of organic matter1 which change their size and darkness in response to the moisture and heat of the ,martian spring4 ,we have no evidence either for or against the existence of more advanced life forms4 ,there is much more information which can be garnered from the ground1 balloons1 ,earth satellites1 ,mars flybys1 and ,mars orbiters1 but the critical tests for life on ,mars can only be made from landing vehicles equipped with experimental packages4444 ,results of ,kaplan et al4 7ref4#ca7 indicate that ,mars has no detectable oxygen1 but does contain small amounts of water vapor1 more abundant carbon dioxide1 possibly a large surface flux of solar ultraviolet radiation1 and estimated daily temperature variations of #ajj ,c at many latitudes4 ,studies have shown that terrestrial micro-organisms can survive these extremely harsh environments4 ,furthermore1 a variety of physiological and ecological adaptations might enable the biota to survive the low nighttime temperatures and intracellular ice crystallization4 ,less evidence is available to support the possibility of extraterrestrial life on other planets4 ,the ,moon has no atmosphere1 and extremes of temperature characterize its surface4 ,however1 the ,moon could have a layer of subsurface permafrost beneath which liquid water might be trapped4 ,the temperatures of these strata might be biologically moderate4 ,studies by ,davis and ,libby 7ref4#cb7 on the atmosphere of ,jupiter support the possibility of the production of organic matter in its atmosphere in a manner analogous to the processes which may have led to the synthesis of organic molecules in the ,earth's early history4 ,it is difficult to assess the possibility that life has evolved on ,jupiter during the #d- or #e-;billion-year period in which the planet has retained a reducing atmosphere4 ,the question of extraterrestrial life and of the origin of life is interwoven4 ,discovery of the first and analysis of its nature may very well elucidate the second4 ,the oldest form of fossil known today is that of a microscopic plant similar in form to common algae found in ponds and lakes4 ,scientists know that similar organisms flourished in the ancient seas over #b billion years ago4 ,however1 since algae are a relatively complex form of life1 life in some simpler form could have originated much earlier4 ,organic material similar to that found in modern organisms can be detected in these ancient deposits as well as in much older ,precambrian rocks4 ,although the planets now have differing atmospheres1 in their early stages the atmospheres of all the planets may have been essentially the same4 ,the most widely held theory of the origin of the solar system states that the planets were formed from vast clouds of material containing the elements in their cosmic distribution4 ,it is believed that the synthesis of organic compounds preceding the origin of life on ,earth occurred before its atmosphere was transformed from hydrogen and hydrides to oxygen and nitrogen4 ,this theory is supported by laboratory experiments of ,calvin 7ref4#af71 ,miller 7ref4#cc71 and ,or 7ref4#cd74 ,the ,earth's present atmosphere consists of nitrogen and oxygen in addition to relatively small amounts of other gases2 most of the oxygen is of biological origin4 ,some of the atmospheric gases1 in spite of their low amounts1 are crucial for life4 ,the ultraviolet-absorbing ozone in the upper atmosphere and carbon dioxide are examples of such gases4 ,significant in the search for extraterrestrial life are the data 7e4g41 planet's temperature7 transmitted by ,mariner ,,ii1 which was launched from ,cape ,canaveral on ,august #bg1 #aifb1 and flew past ,venus on ,december #ad1 #aifb4 ,mariner ,,ii's measurements showed temperatures on the surface of ,venus of the order of #hjj ,f1 too hot for life as known on ,earth4 ,the question ,is life limited to this planet8 can be considered on a statistical basis4 ,although the size of the sample 7one planet7 is small1 the statistical argument for life elsewhere is believed by many to be very strong4 ,while ,mars is generally considered the only other likely habitat of life in our solar system1 ,shapley 7ref4#ce7 has calculated that more than #ajj million stars have planets sufficiently similar in composition and environment to ,earth to support life4 ,of course1 yet unknown factors may significantly reduce or even eliminate this probability4 ,,spacecraft ,,sterilization ,the search for extraterrestrial life with unmanned space probes requires the total sterilization of the landing capsule and its contents4 ,scientists agree that terrestrial organisms released on other planets would interfere with exobiological explorations 7refs4 ref4#cf-ref4#dc74 ,any flight that infects a planet with terrestrial life will compromise a scientific opportunity of almost unequaled proportions4 ,studies on microbiological survival in simulated deep-space conditions 7low temperature1 high ultraviolet flux1 and low dose levels of ionizing radiation7 indicate that these conditions will not sterilize contaminated spacecraft 7refs4 ref4#dd-ref4#dh74 ,furthermore1 many terrestrial sporeformers and some vegetative bacteria1 especially those with anaerobic growth capabilities1 readily survive in simulated ,martian environments 7refs4 ref4#di-ref4#ed74 ,it has been estimated that a single micro-organism with a replication time of #cj days could1 in #h years of such replication1 equal in number the bacterial population of the ,earth4 ,this potential could result not only in competition with any ,martian life1 but in drastic changes in the geochemical and atmospheric characteristics of the planet4 ,to avoid such a disaster1 certainly the first1 and probably many succeeding landers on ,mars1 must be sterile--devoid of terrestrial life 7ref4#ee74 ,since the space environment will not in itself kill all life aboard1 the lander must leave the ,earth in a sterile condition4 ,the sterility of an object implies the complete absence of life4 ,the presence of life or the lack of sterility may be proven2 but the absence of life or sterility cannot be proven1 for the one viable organism that negates sterility may remain undetected4 ,many industrial products which must be guaranteed as sterile cannot be tested for sterility in a nondestructive manner4 ,a similar situation exists in determining the sterility of a spacecraft4 ,certification of sterility--based on experience with the sterilizing process used1 knowledge of the kinetics of the death of micro-organisms1 and computation of the probability of a survivor from assays for sterility--is the only accurate approach to defining the sterility of such treated items4 ,macroscopic life can be readily detected and kept from or removed from the spacecraft1 but the detection and removal of microscopic and submicroscopic life is an extremely difficult task4 ,the destruction of micro-organisms can be achieved by various chemical and physical procedures4 ,sterilizing agents have been evaluated not only for their ability to kill microbial life on surfaces and sealed inside components1 but also for the agents' effects on spacecraft reliability as well 7refs4 ref4#ef-ref4#ei74 ,of the available agents1 only heat and radiation will penetrate solid materials4 ,radiation is expensive1 hazardous1 difficult to control1 and apparently damages more materials than does heat4 ,heat1 therefore1 has been selected as the primary method of spacecraft sterilization and will be used1 except in specific instances where radiation may prove to be less detrimental to the reliability of critical parts 7ref4#fj74 ,the sterilization of spacecraft is a difficult problem if flight reliability is not to be impaired4 ,the development of heat-resistant parts will enable the design and manufacture of a heat-sterilizable spacecraft4 ,without careful microbiological monitoring of manufacture and assembly procedures1 many bacteria could be trapped in parts and subassemblies4 ,to permit sterilization at the lowest temperature-time regimen that will insure kill of all organisms1 the microbiological load inside all parts and subassemblies must be held to a minimum4 ,the role of industrial clean rooms in reducing the biological load on spacecraft is currently being defined4 ,,nasa-supported studies indicate that biological contamination in industrial clean rooms for extended time periods is about #a logarithm less 7tenfold reduction71 compared with conditions in a well-operated microbiological laboratory 7ref4#fa74 ,with the use of clean-room techniques and periodic decontamination by low heat cycles or ethylene oxide treatment1 it should be possible to bring a spacecraft to the point of sterilization with about #aj organisms on board 7ref4#fj74 ,the sterilization goal established for ,mars landers is a probability of less than #a in #aj #jjj 7#aj7 that a single viable organism will be present on the spacecraft4 ,laboratory studies of the kinetics of dry-heat kill of resistant organisms show that at #ace ,c the number of bacterial spores can be reduced #a logarithm 7#ij percent7 for every #b hours of exposure 7refs4 ref4#eh and ref4#fb74 ,the reduction in microbial count needed is the logarithm of the maximum number on the spacecraft 7#aj7 plus the logarithm of the reciprocal of the probability of a survivor 7#aj71 or a total of #aj logarithms of reduction in microbial count4 ,thus1 with an additional #b logarithms added as a safety factor1 a total of #ab logarithms of reduction in count has been accepted as a safe value which can be achieved by a dry-heat treatment of #ace ,c for #bd hours4 ,this is the heat cycle that is currently under study and being developed for use in spacecraft sterilization 7ref4#fj74 ,however1 other heat treatments at temperatures as low as #aje ,c for periods of #cjj hours or longer are under study 7ref4#fc74 ,based on results to date1 it is reasonable to believe that a full complement of heat-sterilizable hardware will be available when needed for planetary exploration4 ,every effort is being made to improve the state of the art to a point where spacecraft can not only withstand sterilization temperatures1 but will be even more reliable than the present state-of-the-art hardware that is not heated4 chapter #c ,environmental ,biology ,,biological ,,effects ,,of ,,weightlessness ,,and ,,zero ,,gravity ,high priority has been given to studies of weightlessness4 ,gravity is one of the most fundamental forces that acts on living organisms1 and all life on ,earth except the smallest appears to be oriented with respect to gravity1 although certain organisms are more responsive to it than others4 ,the gravity force on ,earth is #a g1 but this force may be experimentally varied from zero g1 or weightlessness1 to many thousands of g's4 ,zero gravity or decreased gravity occurs during freefall1 in parabolic trajectory1 or during orbit around the ,earth4 ,gravitational force decreases by the square of the distance away from the ,earth's center4 ,it is reduced about #e percent at about #bjj nautical miles' altitude4 ,gravitational force greater than #a g can be obtained by acceleration1 deceleration1 or impact4 ,it also can be increased by using a centrifuge which adds a radial acceleration vector to the #a g of ,earth4 ,on the ground1 the biological effects of gravity have been studied at #a g1 and experimentally1 forces of many g have been produced4 ,in addition1 modifications of the effects of the #a-;g force have been induced by suspension of the organism in water or by horizontal immobilization of an erect animal such as man4 ,the biological effects of such modification have been of significant value in understanding some of the possible consequences of human exposure to the zero-g environment of space4 ,weightlessness in an ,earth-orbiting satellite occurs when the continuous acceleration of ,earth's gravity is exactly counterbalanced by the continuous radial acceleration of the satellite4 ,in such a weightless state1 organisms are liberated from their natural and continuous exertion against #a g1 but this liberation may carry with it certain serious physical penalties4 ,some of the physical processes which probably have the greatest biological effects are 7#a7 convective flow of fluid1 e4g41 protoplasmic streaming1 transport of nutrient materials1 oxygen1 waste products1 and ,,co from the immediate environment of the cell1 and 7#b7 sedimentation occurring within cells2 substances of higher density sediment in a gravitational field1 and those of lighter density rise4 ,a separation of particles of different densities probably occurs4 ,the removal of gravity would change a distribution of particles like mitochondria by #aj percent 7ref4#fd74 ,gravity has effects on the physical processes involved in mitosis and meiosis4 ,study under weightlessness might contribute to our understanding of the general cellular information-relay process4 ,a gravitational effect is known in the embryonic development of the frog ,rana sylvatica4 ,after fertilization1 the eggs rotate in the gravitational field so that the black animal hemisphere is uppermost4 ,development becomes abnormal if this position is disturbed4 ,if the egg is inverted following the first cleavage and held in this position1 two abnormal animals result1 united like ,siamese twins4 ,this phenomenon appears to be related to the gravitational separation of low- and high-density components of the egg4 ,the size of the egg is about #a to #b mm and is suspended in water of about the same density4 ,this system is very sensitive to gravity2 and1 under weightlessness1 the separation of different density components might be irregular1 leading to aberrant development4 ,when certain aquatic insect eggs are inverted1 subsequent development results in shortened abnormal larvae4 ,the directional growth of plant shoots and plant roots is probably due to this sedimentation phenomenon1 particularly the effect on movement of auxins 7ref4#fe74 ,free convection flow is a major transport process1 and under its influence the mixing of substances is much more effective than when diffusion operates alone4 ,free convection flow is a macroscopic phenomenon which increases not only with g1 but varies also approximately with the five-fourths power of the bulk concentration involved4 ,whether or not convection is important at the microscopic level remains an experimentally unsolved question4 ,the ,grashoff number limits free convection to the macroscopic domain4 ,it would appear in weightlessness that the contribution of free convective flow would be small and that only diffusion should occur4 ,this phenomenon would cause equilibration to occur much more slowly than that occurring with free convection and diffusion4 ,the absence of convective transfer raises a problem as to how nutrients may be obtained and waste products removed in living cells during weightlessness4 ,in a liquid substrate1 nutrients and oxygen would be depleted1 and waste products would accumulate around the cell4 ,absence of gravity may have far-reaching consequences in the homeostatic aspects of cell physiology4 ,the outstanding characteristics of living cells which are most likely to be influenced by the absence of gravity are the ability of the cell to maintain its cytoplasmic membrane in a functional state1 the capacity of the cell to perform its normal functions during the mitotic cycle1 and the capacity of the cytoplasm to maintain the constant reversibility of its sol-gel system 7ref4#ff74 ,two-phase systems1 e4g41 air-in-water and air-in-oil1 possess entirely different characteristics at zero g than at #a g4 ,these physical differences in phase interaction could well be suspected of interfering with the orientation and flow pattern of cell constituents1 thus hindering the cellular processes involved in the movement1 metabolism1 and storage of nutrients and waste4 ,on the basis of theoretical calculations1 weightlessness can be expected to have some effect even on one individual cell if its size exceeds #aj microns in diameter 7ref4#fd74 ,cell colonies might be affected4 ,in larger cells there may be a redistribution of enzyme-forming systems which give rise to polarization4 ,the low surface tension of the cell membrane lends itself to hydrostatic stress distortion1 implying an alteration in permeability and thus an almost certain alteration of cell properties under low gravity conditions4 ,another aspect of gravity that affects the growth and development of living organisms is the directionality of the gravitational field4 ,in fact1 some plants are so sensitive that they are able to direct their growth with as little stimulus as a #aaj gravitational field4 ,investigations of plant growth in altered gravitational fields are underway at ,argonne ,national ,laboratory and ,dartmouth ,college4 ,the ,argonne ,laboratory has designed and developed a #d-pi1 or omnidirectional1 clinostat4 ,by rotating a plant so that the force of gravity is distributed evenly over all possible directions1 the directional effects of gravity are eliminated1 simulating some aspects of the zero-g state4 ,it was shown that certain plants grew more slowly and had fewer and smaller leaves1 while others had about #be percent greater replication of fronds and had greater elongation of certain plant parts4 ,it will be extremely interesting to compare these effects under zero-g conditions in orbiting spacecraft4 ,the effect of gravity in transporting growth hormones in plants has been demonstrated at ,dartmouth ,college using radiocarbon-labeled growth hormones4 ,plant geotropisms and growth movements have been studied and biosatellite experiments developed4 ,anatomy is considered a derivative adaptation to gravity 7ref4#fg74 ,a large background of plant research exists on the effect of orientation on plant responses4 ,information from clinostat experiments is considered susceptible of extrapolation to low gravity conditions because the threshold period for gravitational triggering is relatively long4 ,once over critical minimum dimensions1 the major effects of low gravity would be assumed to occur in those heterocellular organisms that develop in more or less fixed orientation with respect to terrestrial gravity and which respond to changes in orientation with relatively long induction periods2 these are the higher plant orders4 ,on the other extreme are the complex primates which respond rapidly1 but whose multiplicity of organs and correlative mechanisms are susceptible to malfunction and disorganization4 ,it may be suggested that the heterocellular lower plants and invertebrates will be less affected4 ,perturbations of the environment to which the experimental organism is exposed must be limited or controlled to reduce uncertainties in interpretation of the results4 ,at the same time1 the introduction of known perturbations may assist in isolating the effects due solely to gravity4 ,study of de novo differentiation and other phenomena immediately after syngamy may be of particular importance4 ,study of anatomical changes after exposure of the organism to low gravity is important4 ,,biological ,,effects ,,of ,,space ,,radiation ,this section includes part of the ,summary of the ,panel on ,radiation ,biology of the ,environmental ,biology ,committee ,space ,science ,board1 ,,nas_/,,nrc 7#aifc71 and results of research by the ,bioscience ,programs1 ,,nasa4 ,radiation sources in space are of three types3 galactic cosmic radiation1 ,van ,allen belts1 and solar flares with an intense proton flux4 ,cosmic radiation has higher energy levels than radiation produced by manmade accelerators4 ,the ,panel on ,radiation ,biology1 while recognizing the need for radiobiological studies of an applied nature with reference to manned flight programs1 stated that it would be shortsighted for the ,united ,states to confine its efforts to the solution of immediate problems since1 in the long run1 successful exploration of space will be aided by the contributions of basic research4 ,both the immediate biological research program and the continuing program for basic studies should be built upon the large body of existing knowledge of radiation effects4 ,the attitude that all radiobiological experiments need be repeated in the space environment should be resolutely rejected4 ,since fundamental radiobiology cannot be performed easily in space1 it has been recommended that1 wherever possible1 these investigations be carried out in ground laboratories in preference to flying laboratories4 ,space environment does vary from the terrestrial environment1 but the variations are not so great as to lead to the expectation of strikingly different biological effects of radiation in space4 ,however1 it is conceivable that radiations whose effects are well known under terrestrial conditions may have some unsuspected biological effects when combined with unusual features of the space environment3 e4g41 zero g4 ,previous space radiobiological studies have depended solely on very low and inaccurately measured doses of ambient space radiation4 ,it has been difficult to distinguish between the observed response levels and the random noise2 thus1 experiments have been inconclusive4 ,biological ,effects of ,heavy ,ions and ,mesons ,the biological effects of heavy ions 7especially ,z#b7 and mesons are of specific interest to space radiobiology4 ,controlled ,radiobiological ,experiments in ,space ,there is the remote possibility that the radiobiological response may be modified by factors as yet unknown and perhaps not susceptible to terrestrial study4 ,experiments have been designed to settle this matter including the exposure of biological materials during space flight which meet the following criteria of reliability3 7#a7 the use of well-known biological systems1 e4g41 mutation induction or chromosome breakage2 7#b7 the use of a sufficient number of individuals in the experiment to guarantee statistical precision on the results2 7#c7 the exposure of the system to known quantities and qualities of radiation2 7#d7 the use of adequate controls4 ,high-altitude balloon ascents of the #aicj's initiated study of the biological effects of cosmic rays4 ,they were limited to the exploration of secondary cosmic radiation effects4 ,after ,world ,war ,,ii1 the research extended to the use of ,v-#b rockets fired from the ,white ,sands ,proving ,ground4 ,interest returned to balloons and a significant program was underway by #aiej1 first using mice and then hamsters1 fruit flies1 cats1 and dogs4 ,these flights gave no evidence of radiation damage4 ,however1 it was realized that the flights were too far south to obtain a significant exposure1 and more northerly flights began in #aiec4 ,mice and guinea pigs were flown on these later flights4 ,chase 7ref4#fh7 showed the most unequivocal results to that time1 a statistically significant increase in light hairs on black animals and the streaks of white hair up to #aj times wider than expected4 ,brain lesions were detected in the guinea pigs flown on ,man ,high in #aieg4 ,many other types of biological material were sent aloft in an effort to further corroborate existing information and to investigate genetic and developmental effects of cosmic radiation4 ,from the earlier ,v-#b rocket flights to the ,jupiter missile launchings of the monkeys ,able and ,baker1 cosmic-ray research was continued1 but the short flight durations of these vehicles did not provide substantial information4 ,the ,,usaf ,discoverer satellite program has given impetus to cosmic-ray research and provided for longer staytimes4 ,it has been difficult to separate radiation effects from other space-flight factors3 therefore1 some of the alterations observed are still subject to debate4 ,vibration1 acceleration1 and weightlessness appear to be the three most important additional parameters4 ,measurements of radiation dosage have been made by chemical and photographic dosimetry1 ion chambers1 and biological dosimetry4 ,all evidence to date indicates that radiation exposure levels are not hazardous to man at present orbital altitudes up to #bjj nautical miles4 ,most biological materials flown so far have been for the express purpose of investigating space-radiation levels and effects4 ,the biological materials have ranged from tissue cultures to entire organisms and from phage and bacterial cells to man4 ,the studies have required much of the space and weight resources allotted biology by the ,u4,s4,s4,r4 and the ,united ,states4 ,they have been accompanied by ground-based controls4 ,the ,vostok series provided the following data3 7#a7 ,a small1 but statistically significant1 increase was observed in the percentage of chromosome aberrations in the rootlet cells of air-dried wheat and pea seeds after germination4 ,in this case only1 the increase did not depend on flight duration4 7#b7 ,lysogenic bacteria exhibited an increase of genetic alterations and increased phage production4 ,length of flight was associated with increased bacteriophage production by the lysogenic bacteria4 ,there was an increase of recessive lethals coupled with nonconvergence of chromosomes 7sex linked7 in the fruit fly4 ,a stimulation of cell division in wheat and pea seeds was observed4 ,cultures of human cells exposed to space-flight factors did not differ significantly from terrestrial controls with respect to such indicators as proliferation rate1 percentage of mortality and morphological1 antigenic1 and cultural properties4 ,repeated flights of the identical ,he,la cells revealed that there was a longer latent period for restoration of growth capacity than in cells carried into space once or not flown at all4 7#c7 ,the most definite radiation effects observed were only revealed in genetic tests4 ,no harmful influence on those characteristics affecting the viability of the organism has been discovered4 ,the ,air ,force ,discoverer series launched from the west coast had a few successful flights incorporating organisms4 ,with severe environmental stress and long recovery times1 data on radiation exposure were equivocal up to ,discoverer ,,xvii and ,,xviii when cultures of human tissue were flown1 recovered1 and assessed for radiation exposure effects4 ,comparison with ground-based controls revealed no measurable differences4 ,radiation dosimetry from the ,mercury series established that minimal exposures were encountered at those orbital altitudes4 ,a typical example is the ,,ma-#h flight of ,w4 ,m4 ,schirra1 ,jr41 during which the body surface dosage was less than #cj millirads4 ,,nasa has supported fundamental radiation studies at the ,oak ,ridge ,national ,laboratory and the ,lawrence ,radiation ,laboratory4 ,emphasis has been placed on the biological effects of high-energy proton radiation and particulate radiation from accelerators4 ,at the ,,nasa ,ames ,research ,center extensive fundamental studies are being carried out on the effects of radiation1 especially in the nervous system4 ,it has been demonstrated that deposits accumulate in the brain following exposure to large doses of ionizing particle radiation as well as after ,x-irradiation4 ,these deposits1 referred to as a chemical lesion1 result from an accumulation of glycogen4 ,the formation of these deposits during exposure to large doses of ,x-irradiation was not increased in environments of #ii4e percent oxygen and increased atmospheric pressure4 ,,simulation ,,of ,,planetary 7,,martian7 ,,environments ,attempts have been made to simulate to some degree the various parameters of the ,martian environment1 such as atmospheric composition1 pressure1 radiation flux1 temperatures1 and the day-night as well as seasonal cycles4 ,certain factors for ,mars cannot yet be simulated1 such as soil composition1 gravitational field1 magnetic field1 and electrical field4 ,caution is required in interpreting all simulation experiments4 ,how ,earth organisms respond to simulated ,martian environments probably has nothing to do with life on ,mars1 but these experiments may show whether or not anything in the environment of ,mars makes life as we know it impossible4 ,we must expect that on ,mars1 life will have evolved and have adapted over long periods of time under conditions which are quite different from conditions on ,earth4 ,the simulation experiments also provide some information about the possibility of contaminating the planet ,mars1 or any planet1 with organisms from ,earth4 ,in addition1 they give us some clues about the possibilities of adaptation and evolution of life under these conditions4 ,from an evolutionary point of view1 if life has developed on ,mars1 we expect it to have evolved at least to a microbial stage4 ,on ,earth1 micro-organisms are the most ubiquitous and numerous forms of life4 ,this fact should be considered in studying extraterrestrial bodies4 ,micro-organisms have been selected as the best test organisms1 and bacteria and fungi have been used because they are durable and easy to grow4 ,also1 because of their rapid growth1 many generations can be studied in a relatively short period of time4 ,the organisms include chemoautotrophic bacteria1 which are able to synthesize their cell constituents from carbon dioxide by energy derived from inorganic reactions2 anaerobic bacteria1 which grow only in the absence of molecular oxygen2 photoautotrophic plants such as algae1 lichens1 and more complex seed plants2 and small terrestrial animals4 ,organisms have been collected from tundra1 desert1 hot springs1 alpine1 and saline habitats to obtain species with specialized capabilities to conserve water1 balance osmotic discrepancies1 store gases1 accommodate to temperature extremes1 and otherwise meet stresses4 ,an attempt is made in these simulation experiments to extend these processes across the possible overlapping microenvironments which ,earth and ,mars may share4 ,scientists have developed various special environmental simulators1 including ,mars jars and ,marsariums4 ,these have made possible controlled temperatures1 atmospheres1 pressures1 water activities1 and soil conditions for duplicating assumed ,martian surface4 ,a complex simulator1 developed by ,young et al4 7ref4#eb71 reproduces the formation of a permafrost layer with some water tied up in the form of ice beneath the soil surface4 ,this simulator serves as a model to study the wave of darkening1 thus supporting the hypothesis that the pole-to-equator wave of darkening is correlated with the availability of subsurface water4 ,the simulator is a heavily insulated #b-;cu-ft capacity chamber with an internal pressure of #j4a atm4 ,the chamber contains a soil mixture of limonite and sand and an atmosphere of carbon dioxide and nitrogen4 ,with the use of a liquid nitrogen heat exchanger at one end and an external battery of infrared lamps at the other end1 the temperature simulates that of ,mars from pole to equator4 ,thermocouples throughout the soil monitor the temperatures in the chamber4 ,zhukova and ,kondratyev 7ref4#fi7 designed a structure measuring #ajjaejahj cm4 ,micro-organisms were placed at the surface of a copper bar made in a special groove separated by glass cloth4 ,copper was selected as one of the best heat-conduction materials permitting a rapid change of temperature4 ,the lower end of the bar was immersed into a mixture of dry ice and ethyl alcohol1 which made it possible to create a temperature of -#fj ,c4 ,heating was performed by an incandescent spiral4 ,as the knowledge concerning the ,martian environment becomes more refined1 scientists can more accurately simulate this environment under controlled conditions in the laboratory4 ,determination of the effects of the ,martian environment on ,earth organisms will permit better theorization on the forms of life we might find on ,mars and will permit us to estimate the potential survival of ,earth contaminants on ,mars4 ,however1 until the environmental conditions of ,mars are defined more accurately1 the experiments must be changed continually to fit newly determined conditions4 ,therefore1 existing simulation data are made less valid for comparison4 ,the data resulting from the simulation experiments for ,mars have been compiled in table ,,ii1 and the experiments are summarized below4 ,the earliest simulation studies were carried out by the ,air ,force1 and the studies during the past #f years have been supported by ,,nasa4 ,recently1 these studies have received less support or have been terminated in favor of critical studies on the effects of biologically important environmental extreme factors on ,earth organisms4 ,these critical studies permit establishing the extreme environmental factor parameters in which ,earth life can grow or survive4 ,these data will have valuable application to the consideration of life on any planet1 to the design of life-detection instruments1 to the sterilization of space vehicles1 and to the problem of contamination of planets4 ,some exploratory experimental studies are in progress to study the capabilities of organisms to grow under the assumed conditions on ,jupiter4 ,these include studies at high pressure with liquid ammonia1 methane1 and other reducing compounds4 ,early experiments simulating ,martian conditions using soil bacteria were carried out by ,davis and ,fulton 7ref4#gj7 at the ,air ,force ,school of ,aviation ,medicine1 ,san ,antonio1 ,tex4 ,mixed populations of soil bacteria were put in ,mars jars with the following conditions3 #fe-mm ,hg pressure1 #a percent water or less1 nitrogen atmosphere1 sandstone-lava soil1 and a temperature day-night cycle of #be to -#be ,c4 ,the moisture was controlled by desiccating the soil and adding a given amount of water4 ,experiments1 conducted up to #aj months1 demonstrated that obligate aerobes died quickly4 ,the anaerobes and sporeformers survived4 ,although a small increase in the total number of organisms indicated growth1 the increases in the number of bacteria may have been due to breaking up clumps of dirt4 ,roberts and ,irvine 7ref4#ga7 reported that1 in a simulated ,martian environment1 colony counts of a sporeforming bacterium1 ,bacillus cereus1 increased when #h percent moisture was added4 ,moisture was considered more important than temperature or atmospheric gases inasmuch as a simulated ,martian microenvironment containing #h percent moisture permitted germination and growth of endospores of ,clostridium sporogenes4 ,increases in colony counts of ,bacillus cereus appeared to be influenced by temperature cycling 7ref4#gb74 ,table ,,ii4--,survival and ,growth of ,organisms in ,simulated ,planetary 7,martian7 ,environments ---------------------------------------- -------------------------- ,species ,survival1 ,moisture ,temperature1 months ,c ---------------------------------------- -------------------------- ,conditions on ,mars3 #adg -#gj to #cj ---------------------------------------- -------------------------- ,anaerobic #f ,low1 -#fj to #bj sporeformers 7,ca,s,o7 ,clostridia1 ,bacillus planosarcina ---------------------------------------- -------------------------- ,anaerobic #f ,low1 -#fj to #bj nonsporeformers 7,ca,s,o7 ,pseudomonas1 ,rhodopseudomonas ---------------------------------------- -------------------------- ,anaerobes ,growth ,very wet -#ge to #be ,aerobacter aerogenes1 ,pseudomonas sp4 ---------------------------------------- -------------------------- ,clostridium1 #aj #a -#be to #be ,corynebacteria percent ,thin short rod or less ---------------------------------------- -------------------------- ,bacillus cereus #b #j4e -#be to #be percent soil ---------------------------------------- -------------------------- ,clostridium sporogenes #a #h4d -#be to #be 7growth7 percent ---------------------------------------- -------------------------- ,clostridium botulinum #aj ,lyophilized -#be to #be ---------------------------------------- -------------------------- ,klebsiella pneumoniae #f ,lyophilized -#be to #be ---------------------------------------- -------------------------- ,bacillus subtilis var4 #d #b percent -#be to #be globigii ---------------------------------------- -------------------------- ,sarcina aurantiaca #d #j4e percent -#be to #be ---------------------------------------- -------------------------- ,clostridium tetani #b or less #a percent -#fj to #be ---------------------------------------- -------------------------- ,aspergillus niger ,over #f hr ,very dry -#fj to #be ---------------------------------------- -------------------------- ,aspergillus oryzae ,over #f hr ,very dry -#fj to #be ---------------------------------------- -------------------------- ,mucor plumbeus ,over #f hr ,very dry -#fj to #be ---------------------------------------- -------------------------- ,rhodotorula rubra ,over #f hr ,very dry -#fj to #be ---------------------------------------- -------------------------- ,pea1 bean1 tomato1 rye1 #j4c ,moist #be sorghum1 rice4 ---------------------------------------- -------------------------- ,winter rye #j4f ,moist -#aj to #bc ---------------------------------------- -------------------------- ,table ,,ii4--,survival and ,growth of ,organisms in ,simulated ,planetary 7,martian7 ,environments ---------------------------------------- ------------------------------ ,species ,atmospheric ,n1 ,,co1 ,substrate pressure1 percent percent mm ,hg ---------------------------------------- ------------------------------ ,conditions on ,mars3 #he1 #c to #cj #beae1 #aa ---------------------------------------- ------------------------------ ,anaerobic #gf #ie #e ,air-dried sporeformers soil ,clostridia1 ,bacillus planosarcina ---------------------------------------- ------------------------------ ,anaerobic #gf #ie #e ,air-dried nonsporeformers soil ,pseudomonas1 ,rhodopseudomonas ---------------------------------------- ------------------------------ ,anaerobes #gfj #ajj 787 ,difco ,aerobacter infusion aerogenes1 broth ,pseudomonas sp4 ---------------------------------------- ------------------------------ ,clostridium1 #fe #ajj 787 ,soil ,corynebacteria ,thin short rod ---------------------------------------- ------------------------------ ,bacillus cereus #fe #id #b4ba ,sandstone soil ---------------------------------------- ------------------------------ ,clostridium sporogenes #fe #id #b ,enriched soil ---------------------------------------- ------------------------------ ,clostridium botulinum #fe #ie #j to ,lava soil #j4e ---------------------------------------- ------------------------------ ,klebsiella pneumoniae #fe #ie #j to ,lava soil #j4e ---------------------------------------- ------------------------------ ,bacillus subtilis var4 #he #ie #j4c ,media globigii ---------------------------------------- ------------------------------ ,sarcina aurantiaca #he #ie #j4c ,desert soil ---------------------------------------- ------------------------------ ,clostridium tetani #he #ie #j4c ,soil ---------------------------------------- ------------------------------ ,aspergillus niger #gf #ie4e #j4be ,glass cloth on copper bar ---------------------------------------- ------------------------------ ,aspergillus oryzae #gf #ie4e #j4be ,do4 ---------------------------------------- ------------------------------ ,mucor plumbeus #gf #ie4e #j4be ,do4 ---------------------------------------- ------------------------------ ,rhodotorula rubra #gf #ie4e #j4be ,do4 ---------------------------------------- ------------------------------ ,pea1 bean1 tomato1 rye1 #ge #ajj #j ,filter sorghum1 rice4 paper ---------------------------------------- ------------------------------ ,winter rye #gf #ih #j4bd ,soil ---------------------------------------- ------------------------------ ,studies of the effects of simulated ,martian environments on sporeforming anaerobic bacteria were carried out by ,hawrylewicz et al4 7ref4#di74 ,they showed that the encapsulated facultative anaerobe1 ,klebsiella pneumoniae1 survived under simulated ,martian atmosphere for #f to #h months1 but were less virulent than the freshly isolated organisms4 ,spores of the anaerobe ,clostridium botulinum survived #aj months in the simulator4 ,hagen et al4 7ref4#ec7 found that the addition of moisture to dry-simulated ,martian soil did not improve the survival of ,bacillus subtilis or ,pseudomonas aeruginosa4 ,bacillus cereus spores survived1 with added organic medium plus moisture1 but no germination of the spores resulted4 ,hawrylewicz et al4 7ref4#di7 put rocks from ,antarctica bearing various lichens in simulated ,martian conditions in a large desiccator4 ,they found that the algal portion of a lichen1 ,trebouxia erici1 showed only slight resistance to the ,martian environment4 ,they also pointed out the effect moisture had on the physical condition of lichens4 ,the undersurface of a lichen has great water-absorbing capability1 and the slightest amount of moisture on a rock surface is absorbed by the lichen which can turn green in #ae minutes4 ,scher et al4 7ref4#ea7 exposed desert soils to simulated environmental conditions and diurnal cycles of ,mars4 ,the atmosphere consisted of #ie percent nitrogen and #e percent carbon dioxide 7no oxygen7 and was dried1 using calcium sulfate as a desiccant4 ,the total atmospheric pressure was #j4a atm4 ,the temperature ranged from -#fj to #bj ,c in #bd-;hour cycles4 ,one hour was spent at the maximum and at the minimum temperatures4 ,the chambers were irradiated with ultraviolet1 #becg 1 with a dose of #aj ergs_/cm1 which is comparable to a daily dose found on ,mars1 and easily exceeds the mean lethal dose for unprotected bacteria4 ,soil aliquots were removed weekly and incubated at #cj ,c4 ,the scoring was done both aerobically and anaerobically4 ,sporeforming obligate and facultative anaerobes1 including ,clostridium1 ,bacillus1 and ,planosarcina1 and nonsporeforming facultative anaerobes1 including ,pseudomonas and ,rhodopseudomonas1 were found4 ,the experimental chambers were frozen and thawed cyclically up to #f months4 ,organisms that were able to survive the first freeze-thaw cycle were able to survive the entire experiment4 ,the ultraviolet irradiation did not kill subsurface organisms1 and a thin layer of soil served as an ultraviolet shield4 ,all of the samples showed survivors4 ,young et al4 7ref4#eb7 assumed that water is present on ,mars1 at least in microenvironments1 and that nutrients would be available4 ,the primary objective of their experiments was to determine the likelihood of contaminating ,mars with ,earth organisms should a space probe from ,earth encounter an optimum microenvironment in terms of water and nutrients4 ,the experiments used bacteria in liquid nutrient media4 ,the environment consisted of a carbon dioxide-nitrogen atmosphere1 and the temperature cycling was -#gj to #be ,c1 with a maximum time above freezing of #d hours4 ,aerobacter aerogenes and ,pseudomonas sp4 grew in nutrient medium under ,martian freezing and thawing cycles4 ,atmospheric pressure was not a significant factor in the growth of bacteria under these conditions4 ,silverman et al4 7ref4#dg7 studied bacteria and a fungus under extreme--but not ,martian--conditions4 ,spores of five test organisms 7,b4 subtilis var4 niger1 ,b4 megaterium1 ,b4 stearothermophilus1 ,clostridium sporogenes1 and ,aspergillus niger7 and soils were exposed while under ultrahigh vacuum to temperatures of from -#aij to #agj ,c for #d to #e days4 ,up to #be ,c there was no loss in viability2 at higher temperatures1 differences in resistivity were observed4 ,at #hh ,c1 only ,b4 subtilis and ,a4 niger survived in appreciable numbers2 at #ajg ,c1 only ,a4 niger spores survived2 none were recoverable after exposure to #abj ,c4 ,b4 subtilis survived at atmospheric pressure and #ij ,c for #e days1 but none of the other spores were viable alter #b days4 ,four groups of soil organisms 7mesophilic1 aerobic1 and anaerobic bacteria1 molds1 and actinomycetes7 were similarly tested in the vacuum chamber4 ,from one sample only actinomycetes survived #abj ,c1 while one other soil sample yielded viable bacteria after exposure to #agj ,c4 ,several organisms resisted #abj ,c in ultrahigh vacuum for #d to #e days4 ,when irradiated with gamma rays from a cobalt #fj source1 differences were observed between vacuum-dried spores irradiated while under vacuum and those exposed to air immediately before irradiation4 ,a reduction of from one-third to one-ninth of the viability of spores irradiated in vacuum occurred with vacuum-treated spores irradiated in air4 ,siegel et al4 7ref4#gc71 in approximate simulations of ,martian environments1 studied tolerances of certain seed plants1 such as cucumbers1 corn1 and winter rye1 to low temperatures and lowered oxygen tensions4 ,lowered oxygen tensions enhanced the resistance of seedlings1 particularly cucumber and rye to freezing1 and lowered the minimum temperature required for germination4 ,germination of seeds in the absence of liquid water has also been studied4 ,in this case1 seeds of xerophytes have been suspended in air at #ge-mm ,hg pressure above water4 ,the air was thus saturated4 ,germination was slow but did occur4 ,siegel et al4 7refs4 ref4#gc and ref4#gd7 found that the growth rate of several higher plants was enhanced by certain gases usually thought to be toxic1 such as ,n,o4 ,this finding is significant inasmuch as the presence of nitrogen oxides in the ,martian atmosphere has been cited as evidence for the nonexistence of plants on that planet by ,kiess et al4 7ref4#ge74 ,exploratory survival tests showed that various mature plants1 as well as the larvae1 pupae1 and adult specimens of a coleopteran insect1 were undamaged when exposed to at least #dj hours of an atmosphere containing #if4e percent ,n,o1 #j4g percent ,o1 and #b4h percent ,n4 ,lichens are of interest because of their ability to survive and thrive under extreme environmental conditions on ,earth4 ,biological activity of slow-growing lichens was detected by metabolic gas exchange1 ,,co detection being especially convenient4 ,siegel points out that this method is sensitive and nondestructive1 to be preferred to staining techniques1 which at present are limited because they are only semiquantitative1 subjective1 and destructive of the lichen4 ,a ,russian study of simulated planetary environments has been performed with good simulation but for periods of only #b to #f hours4 ,comments on simulation experiments made by ,zhukova and ,kondratyev 7ref4#fi7 are presented as follows3 ,on the basis of modern conceptions on ,martian conditions it is difficult to imagine that higher forms of animals or plants exist on the planet4 ,a ,martian change of seasons similar to that of our planet empowers us to think that there is a circulation of an organic substance on ,mars1 which cannot exist without participation of microbic forms of life4 ,microorganisms are the most probable inhabitants of ,mars although the possibility is not excluded that their physiological features will be very specific4 ,that is why the solution of the problem concerning the character of life on ,mars is of exceptional interest4 ,but still the answer to this question can be verified only by simulating ,martian conditions1 taking into account the information obtained from astrophysicists4 ,experiments aimed at creating artificial ,martian climatic conditions have been started quite recently2 their number is not large since they cannot be combined with the results of numerous experiments investigating the effect of extreme factors on microorganisms4 ,the result of the effect of such physicochemical parameters of the medium as pressure1 sharp temperature changes1 the absence of oxygen and insolation1 depends on their combination and simultaneity4 ,these examples convincingly show that while simulating ,martian conditions one should strive to the most comprehensive complex of simultaneously acting factors4 ,the creation of individual climatic parameters acting successively leads to absolutely different1 often opposite results4 ,it should be mentioned also that refusal to imitate insolation and the performance of experiments with specimens of soil which itself has protective effect on cells of microorganisms1 but not with pure culture of bacteria1 are usual shortcomings in the bulk of studies on this problem4 ,it appears that organisms from ,earth might survive in large numbers when introduced to ,martian environment4 ,whether these organisms will be capable of growth and explosive contamination of the planet in a biological sense or not is highly questionable4 ,the likelihood of an organism from ,earth finding ideal conditions for growth on ,mars seems extremely low4 ,however1 the likelihood of an organism from ,earth serving as a contaminant for any life-detection device flown to ,mars for the purpose of searching out carbon-based life is considerably higher4 ,the chance that life has originated and evolved on ,mars is a completely separate question and much more difficult to answer4 ,it would be interesting to attempt to determine possible evolutionary trends which might occur on a planet by means of selection of organisms in a simulated planetary environment4 ,rapid genetic selection combined with radiation and chemicals to speed up mutation rate under these conditions should reveal possible evolutionary trends under the planetary environmental conditions4 ,this could be attempted after the planetary environments are more accurately defined4 ,,extreme ,,and ,,limiting ,,environmental ,,parameters ,,of ,,life ,the question of the existence of extraterrestrial life is one of the most important and interesting biological questions facing mankind and has been the subject of much controversial discussion and conjecture4 ,many of the quantitative1 and even qualitative1 environmental constituents of the planets also are still subjects of controversy and speculation4 ,best guesses about a relatively unknown planetary environment1 combined with lack of information about the capabilities of ,earth life to grow in extreme environments1 do not provide the basis for making informed scientific estimates4 ,life on ,earth is usually considered to be relatively limited in its ability to grow1 reproduce1 or survive in extreme environmental conditions4 ,while many common plants and animals 7including man7 are quite sensitive to1 or incapable of1 surviving severe chemical and physical changes or extremes of environment1 a large number of micro-organisms are highly adapted and flourish in environments usually considered lethal4 ,certain chemoautotrophic bacteria require high concentrations of ammonia1 methane1 or other chemicals to grow4 ,anaerobic bacteria grow only in the absence of oxygen4 ,besides adapting to the extremes of environments on ,earth1 life is also capable of growing and reproducing under extreme environmental conditions not normally encountered3 e4g41 from a few rad of radiation in normal habitats to #aj or more rad from artificial sources1 from #j4e gauss of ,earth magnetism to #afg #jjj gauss in manmade magnetic fields1 and from #a-;g force of gravity to #aaj #jjj g4 ,the extreme ranges of physical and chemical environmental factors for growth1 reproduction1 and survival for ,earth micro-organisms are phenomenally large4 ,life is ubiquitous on ,earth and is found in almost every possible environment1 including the most severe habitats1 from the bottom of the ocean to the highest mountain tops and from cold ,arctic habitats to hot springs1 as well as in volcanic craters1 deep wells1 salt flats1 and mountain snowfields4 ,earth life has become adapted to1 and has invaded1 nearly every habitat1 no matter how severe4 ,the physiological and morphological adaptations of life are exceedingly diverse and complex4 ,surprisingly1 the extreme parameters or ranges of the physical and chemical environmental factors permitting growth1 reproduction1 and other physiological processes of ,earth organisms have not been critically compiled4 ,a partial compilation of certain selected environmental factors has been made by ,vallentyne 7ref4#gf74 ,a compilation of available published data on certain environmental extremes1 particularly from recent ,,nasa-supported research 7compiled by ,dale ,w4 ,jenkins1 in press71 is presented in tables ,,iii to ,,vi4 ,these data can serve as a starting point for a more intensive literature review by specialists1 critical evaluation1 standardization of end points1 and especially to point out areas where critical experimentation is urgently needed4 ,this critical compilation involves a review of a very broad and complex range of subjects involved in many different disciplines with widely scattered literature4 ,since the effects of many of the specific environmental factors are harmful1 it is difficult to select a point on a scale from no effect to death and use some criteria to say that normal or even minimal growth and reproduction are occurring4 ,the effects of environmental factors are dependent on 7#a7 the specific factor1 times1 7#b7 the concentration or energy1 times1 7#c7 the time of exposure or application of the factor4 ,many reports1 especially older ones1 do not give all of the necessary data to permit proper evaluation4 ,a complicating factor is that the effect of each factor depends on the other factors before1 during1 and after its application4 ,the condition of the organism itself is a great variable4 ,proper evaluation requires the critical review by a variety of biological specialists1 physicists1 and chemists4 ,to determine the potential of ,earth organisms to survive or grow under other planetary environmental conditions1 a number of experiments have been carried out attempting to simulate planetary environments1 especially of ,mars1 as reviewed previously4 ,while the results are of real interest1 they do not provide much basic information4 ,further1 as the ,martian environment is more accurately defined1 the experimental conditions are changed4 ,in addition1 some experimenters have altered certain factors1 such as water content1 to allow for potential microhabitats or for areas which might contain more water at certain times4 ,table ,,iii4--,extreme ,physical ,environmental ,factors ---------------------------------------- ------------------------- ,physical ,minimum ,organism factors ---------------------------------------- ------------------------- ,temperature -#cj ,c ,algae 7photosynthesis71 pink yeast 7growth7 ---------------------------------------- ------------------------- ,magnetism #j-ej gamma 7#aj ,human gauss7 ---------------------------------------- ------------------------- ,gravity #j g ,human1 plants1 animals ---------------------------------------- ------------------------- ,pressure #aj mm ,hg 7#e days7 ,mycobacterium smegmatis ---------------------------------------- ------------------------- ,microwave #j ,w_/cm ---------------------------------------- ------------------------- ,visible #j ft-c ,animals1 fungi1 bacteria ---------------------------------------- ------------------------- ,ultraviolet #j erg_/cm ---------------------------------------- ------------------------- ,x-ray #j rad ---------------------------------------- ------------------------- ,gamma ray #j rad ---------------------------------------- ------------------------- ,acoustic #j dyne_/cm ---------------------------------------- ------------------------- ,table ,,iii4--,extreme ,physical ,environmental ,factors ---------------------------------------- ------------------------------ ,physical ,maximum ,organism ,activity factors ---------------------------------------- ------------------------------ ,temperature #ajd ,c 7#ajjj ,desulfovibrio ,grows and reduces atm7 desulfuricans sulfate ---------------------------------------- ------------------------------ ,magnetism #afg #jjj ,neurospora #a hr--no effect1 gauss ,arbacia ,arbacia ,drosophila development delayed ---------------------------------------- ------------------------------ ,gravity #djj #jjj g ,ascaris eggs #a hr--eggs hatch1 #dj #aaj #jjj g ,escherichia coli days' growth ---------------------------------------- ------------------------------ ,pressure #adjj atm ,marine organisms ,growth ---------------------------------------- ------------------------------ ,microwave #bdej ,mc_/sec ,drosophila #fh hr1 growth not #j4c to #a affected ,w_/cm ---------------------------------------- ------------------------------ ,visible #ej #jjj ft-c ,chlorella1 ,seconds1 #ag #jjj ft-c higher plants recurrently continuous ---------------------------------------- ------------------------------ ,ultraviolet #aj erg_/cm1 ,bean embryos ,suppressed growth #becg ---------------------------------------- ------------------------------ ,x-ray #baj rad ,bacteria ,growth ---------------------------------------- ------------------------------ ,gamma ray #b4deaj rad ,microcoleus ,continued growth ,phormidium ,synechococcus ---------------------------------------- ------------------------------ ,acoustic #adj db or ,man ,threshold of pain #fejj dyne_/cm at #j4jb to #d4h kcs_/sec ---------------------------------------- ------------------------------ ,table ,,iv4--,extreme ,low and ,high ,temperature ,effects ,permitting ,life ,processes ---------------------------------------- ------------------------- ,minimum ,organism ,activity or condition temperature1 ,c ---------------------------------------- ------------------------- -#aa ,bacteria ,growth 7on fish7 ---------------------------------------- ------------------------- -#ab ,bacteria ,growth ---------------------------------------- ------------------------- -#ab ,molds ,growth ---------------------------------------- ------------------------- -#ae ,pyramidomonas ,swimming ---------------------------------------- ------------------------- -#ae ,dunaliella salina ,swimming ---------------------------------------- ------------------------- -#ah ,mold ,growth ---------------------------------------- ------------------------- -#ah ,yeast ,growth ---------------------------------------- ------------------------- -#ah ,aspergillus ,growth 7in glycerol7 glaucus ---------------------------------------- ------------------------- -#ah to -#bj ,mold ,growth 7in fruit juice7 ---------------------------------------- ------------------------- -#ah to -#bj ,pseudomonads ,growth 7in fruit juice7 ---------------------------------------- ------------------------- -#bj ,bacteria ,growth ---------------------------------------- ------------------------- -#bj ,bacteria ,growth ---------------------------------------- ------------------------- -#bj ,bacteria ,luminescence development accelerated ---------------------------------------- ------------------------- -#bj to -#bd ,insect eggs 7diapause7 ---------------------------------------- ------------------------- -#cj ,algae ,photosynthesis ---------------------------------------- ------------------------- -#cj ,pink yeast ,growth 7on oysters7 ---------------------------------------- ------------------------- -#cj ,lichens ,photosynthesis ---------------------------------------- ------------------------- -#bj to -#dj ,lichens and conifers ,photosynthesis ---------------------------------------- ------------------------- -#dd ,mold spores ,sporulation and germination ---------------------------------------- ------------------------- ,table ,,iv4--,extreme ,low and ,high ,temperature ,effects ,permitting ,life ,processes ---------------------------------------- -------------------------- ,maximum ,organism ,activity or condition temperature1 ,c ---------------------------------------- -------------------------- #gc ,thermophilic organisms ,growth 7,p metabolism7 ---------------------------------------- -------------------------- #gc ,phormidium 7alga7 ,acclimatized ---------------------------------------- -------------------------- #gj to #gc ,bacillus calidus ,growth and spore germination ---------------------------------------- -------------------------- #gj to #gd ,bacillus cylindricus ,growth and spore germination ---------------------------------------- -------------------------- #gj to #ge ,bacillus tostatus ,growth and spore germination ---------------------------------------- -------------------------- #hj ,bacillus ,cultured in laboratory stearothermophilus ---------------------------------------- -------------------------- #hc ,sulfate-reducing ,found in a well bacteria ---------------------------------------- -------------------------- #hi ,sulfate-reducing ,found in oil waters bacteria ---------------------------------------- -------------------------- #fe to #he ,sulfate-reducing ,cultured in laboratory bacteria ---------------------------------------- -------------------------- #hi ,micro-organisms ,found in hot springs ---------------------------------------- -------------------------- #ie ,bacillus coagulans ,in #hj min4 sporulation activation ---------------------------------------- -------------------------- #aaj ,bacillus coagulans ,in #f min1 sporulation activation ---------------------------------------- -------------------------- #ajd ,desulfovibrio ,grow and reduce sulfate desulfuricans at #ajjj atm ---------------------------------------- -------------------------- ,table ,v4--,extreme ,temperature ,limits of ,survival ---------------------------------------- ---------- ,minimum ,organism temperature ,c ---------------------------------------- ---------- -#aij ,yeast bacteria1 #aj species ---------------------------------------- ---------- -#aig ,trebouxia erici from lichens ---------------------------------------- ---------- -#aig ,protozoa1 ,anguillula ---------------------------------------- ---------- -#beb ,yeasts1 molds1 bacteria1 #aj species ---------------------------------------- ---------- -#bec ,black currant1 birch ---------------------------------------- ---------- -#bgc ,bacteria1 many species ---------------------------------------- ---------- -#bgc ,bacteria1 many species ---------------------------------------- ---------- -#bgb ,desiccated rotifers ---------------------------------------- ---------- -#bfi ,human spermatozoa ---------------------------------------- ---------- ,table ,v4--,extreme ,temperature ,limits of ,survival ---------------------------------------- -------------------------- ,maximum ,organism ,time of exposure temperature ,c ---------------------------------------- -------------------------- #adj ,bacterial spores #e-;hr immersion ---------------------------------------- -------------------------- #agj-bjj ,desiccated rotifers #e min ---------------------------------------- -------------------------- #aea ,desiccated rotifers #ce min ---------------------------------------- -------------------------- #aej ,clostridium tetani #ahj min ---------------------------------------- -------------------------- #agj ,aerobic bacteria1 molds4 #e days at actinomycetes #fajmm ,hg ---------------------------------------- -------------------------- #abg 7dry7 ,bacteria 7in activated charcoal7 #fj min ---------------------------------------- -------------------------- #aaj 7wet7 ,bacillus subtilis var4 niger #djj min ---------------------------------------- -------------------------- #abj ,bacillus subtilis var4 niger #djj min ---------------------------------------- -------------------------- #ada ,bacillus subtilis var4 niger #gj min ---------------------------------------- -------------------------- #afj ,bacillus subtilis var4 niger #ae min ---------------------------------------- -------------------------- #ahj ,bacillus subtilis var4 niger #b min ---------------------------------------- -------------------------- #ahh ,bacillus subtilis var4 niger #a min ---------------------------------------- -------------------------- #abj 7wet7 ,bacillus stearothermophilus #be min ---------------------------------------- -------------------------- #abj 7dry7 ,bacillus stearothermophilus #ajj min ---------------------------------------- -------------------------- #ada ,bacillus stearothermophilus #ab min ---------------------------------------- -------------------------- #afj ,bacillus stearothermophilus #b min ---------------------------------------- -------------------------- #aff ,bacillus stearothermophilus #a min ---------------------------------------- -------------------------- ,table ,,vi4--,extremes of ,chemical ,environmental ,factors ,permitting ,growth or ,activity ---------------------------------------- ---------------- ,chemical ,minimum ,organism factor ---------------------------------------- ---------------- ,o #j ,he,la cells1 ,cephalobus1 anaerobic bacteria ---------------------------------------- ---------------- ,o 7ozone7 #j ---------------------------------------- ---------------- ,h #j ---------------------------------------- ---------------- ,h,o ,aw #j4dh ,pleurococcus vulgaris ---------------------------------------- -- ,aw #j4e ,xenopsylla cheopis 7prepupae7 ---------------------------------------- ---------------- ,h,o #j ---------------------------------------- ---------------- ,he #j ---------------------------------------- ---------------- ,,co #j ---------------------------------------- ---------------- ,,co #j ---------------------------------------- ---------------- ,,ch #j ---------------------------------------- ---------------- ,,ch,o #j ---------------------------------------- ---------------- ,,ch,,oh #j ---------------------------------------- ---------------- ,n #j ---------------------------------------- ---------------- ,,no #j ---------------------------------------- ---------------- ,,no #j ---------------------------------------- ---------------- ,n,o #j ---------------------------------------- ---------------- ,ar #j ---------------------------------------- ---------------- ,na,cl1 ,na,,so1 ,na,h,c,o ---------------------------------------- ---------------- ,h,s #j ---------------------------------------- ---------------- ,h,,so #j ---------------------------------------- ---------------- ,cu ---------------------------------------- ---------------- ,zn ---------------------------------------- ---------------- p,h #j ,acontium velatum ,thiobacillus thioodixans ---------------------------------------- ---------------- ,eh -#dej m,v ,sulfate-reducing bacteria at p,h #i4e ---------------------------------------- ---------------- ,table ,,vi4--,extremes of ,chemical ,environmental ,factors ,permitting ,growth or ,activity ---------------------------------------- ------------------------------ ,chemical ,maximum ,pressure1 ,time1 ,organism ,activity factor atm days ---------------------------------------- ------------------------------ ,o #ajj #a ,plants1 ,growth animals ---------------------------------------- ------------------------------ ,o #ajj ppm #e ,armillaria ,growth 7ozone7 --------------------------- mellea ----------------- #ejj ppm #e ,light emission ---------------------------------------- ------------------------------ ,h #ajj ,various ,germination plants ---------------------------------------- ------------------------------ ,h,o ,aw #a4j #a ,various ,growth aquatic organisms ---------------------------------------- ------------------------------ ,h,o #j4cd ,rye ,germination enhanced ---------------------------------------- ------------------------------ ,he #ajj ,wheat1 rye1 ,germination rice ---------------------------------------- ------------------------------ ,,co #ajj ,rye ,germination ---------------------------------------- ---------------------- #hj #a4a #d ,hydrogenomonas ,growth ---------------------------------------- ------------------------------ ,,co #ajj #a4a #d ,rye ,growth and germination ---------------------------------------- ------------------------------ ,,ch #ajj #a4a #d ,rye ,germination ---------------------------------------- ------------------------------ ,,ch,o #ej ,rye ,germination ---------------------------------------- ------------------------------ ,,ch,,oh #ej ,rye ,germination ---------------------------------------- ------------------------------ ,n #ajj 4#a #aj ,various plants ,germination and root growth ---------------------------------------- ------------------------------ ,,no #ah 4#jah #aj ,sorghum1 rice ,germination and root growth ---------------------------------------- ------------------------------ ,,no #ah 4#jah #aj ,rye1 rice ,germination and root growth ---------------------------------------- ------------------------------ ,n,o #ajj #a4b #d ,rye ,germination ---------------------------------------- ---------------------- #if4e #a4g ,rye ,germination ------------------------------------ ,tenebrio ,survival molitor ---------------------------------------- ------------------------------ ,ar #ajj #a4b #b ,rye ,germination ---------------------------------------- ------------------------------ ,na,cl1 #fg ,photosynthetic ,growth ,na,,so1 bacteria ,na,h,c,o ---------------------------------------- ------------------------------ ,h,s #j4if ,desulfovibrio ,growth g_/liter desulfuricans ---------------------------------------- ------------------------------ ,h,,so #g ,acontium ,growth velatum ------------------------------- ,thiobacilli ,growth1 reproduction ---------------------------------------- ------------------------------ ,cu #ab ,thiobacillus ,growth g_/liter ferrooxidans ---------------------------------------- ------------------------------ ,zn #ag ,thiobacillus ,growth g_/liter ferrooxidans ---------------------------------------- ------------------------------ p,h #ac ,plectonema ,growth nostocorum ------------------------------- ,nitrobacter ,growth ------------------------------- ,nitrosomonas ,growth ---------------------------------------- ------------------------------ ,eh #hej m,v ,iron bacteria ,growth at p,h #c ---------------------------------------- ------------------------------ chapter #d ,behavioral ,biology ,,effects ,,of ,,the ,,space ,,environment ,,on ,,behavior ,,nasa was established in #aieh1 shortly after the ,russian launching of the second ,earth satellite ,sputnik ,,ii1 the first vehicle to carry life into orbit around the ,earth4 ,this accomplishment was preceded by the pioneering work of ,henry et al4 7ref4#gg71 in which animals were exposed briefly to low-gravity states in ,aerobee rockets4 ,a motion-picture camera photographed the behavior of two white mice in rotating drums during this series of flights1 which marked the first time that simple psychological tests were made on animals in the weightless condition4 ,while this behavioral experiment was relatively simple1 it provided the basic concepts for recent studies which involved rotation of animals during the weightless state4 ,subsequent flights such as ,project ,,mia 7,mouse-in-,able7 reflected a preoccupation with physiologic measures 7refs4 ref4#gh and ref4#gi71 although the flights of ,baker and ,able included preflight and postflight performance studies 7ref4#hj74 ,able's behavior was recorded in detail on in-flight film1 but none of the behavior was programed or under experimental control4 ,the first flights in which behavior or performance was explicitly programed were those of ,sam and ,miss ,sam in flights of the ,little ,joe rocket with the ,mercury capsule1 launched from ,wallops ,island in #aiei and #aifj 7ref4#ha74 ,the first major space achievement in the behavioral sciences was the successful in-flight measurement of the behavior of the chimpanzee ,ham in early #aifa1 in which the pretrained animal performed throughout the flight4 ,the second achievement along these lines was in #aifb when the chimpanzee ,enos made several orbits around ,earth and performed continuously on a complex behavioral task4 ,the tasks which the animals performed during these flights have been described in detail by ,belleville et al4 7ref4#hb71 and the results of the in-flight performance have been presented by ,henry and ,mosely 7ref4#hc74 ,these early flights provided much of the technological framework on which current biological experiments on organisms during flights of extended duration are based4 ,due largely to the efforts of ,grunzke 7refs4 ref4#hd and ref4#he71 the apparatus needed to sustain animals during space flight1 such as zero-g watering and feeding devices1 are now commonplace 7ref4#hf74 ,advanced systems of programing stimulus presentations and recording responses1 developed for ,project ,mercury1 may now be seen in many basic research laboratories throughout the country4 ,several other noteworthy advances have been made as an outgrowth of the ,mercury animal flights4 ,immediately before the orbital flight ,,ma-#e1 in which the chimpanzee ,enos was employed1 it was unexpectedly found that this #e-year-old animal was hypertensive4 ,subsequent centrifuge studies showed that its vascular responses exceeded those of a control group4 ,consideration of the animal's preflight experience led to speculation concerning the origin of this hypertension4 ,an explanation of the high-blood-pressure responses detected in ,enos has been pursued by ,meehan et al4 7ref4#hg74 ,persistent hypertension has been produced in other laboratory chimpanzees restrained in the same manner as those participating in space flight and exposed to demanding performance tasks1 a demonstration which has important implications for prolonged manned space flight and for cardiovascular medicine in general4 ,studies more directly concerned with behavior and performance have been extended from those of ,project ,mercury4 ,these extensions have been in the following directions3 7#a7 the establishment and maintenance of complex behavioral repertoires under conditions of full environmental control1 7#b7 the refinement of behavioral techniques for assessing sensory and motor processes1 and 7#c7 the maintenance of sustained performance under conditions of long-term isolation and confinement and preliminary extension of such experimental analysis to man4 ,numerous studies with primate subjects1 including several at ,ames ,research ,center1 have been devoted to developing methods for maintaining optimum performance in environments with limited sources of stimulation4 ,monkeys1 baboons1 and chimpanzees1 for example1 have been isolated for periods of longer than #b years with no decrement in performance on complicated behavioral tasks 7ref4#hh74 ,the behavioral techniques used in these studies are closely related to those employed on human subjects under ,,nasa sponsorship at the ,university of ,maryland 7ref4#hi74 ,the essence of these techniques is in the proper programing of environmental stimuli 7ref4#ij74 ,it is not sufficient to provide the subject with his physiological requirements for survival1 but he must be given the psychological motivation for using these provisions4 ,this statement1 of course1 is an oversimplification of the problem1 but it serves to illustrate the essence of these experimental programs4 ,gravity has long been known as one of the major factors influencing various life processes and the orientation of both plants and animals4 ,one of the most challenging problems of space research has been to define this influence more precisely4 ,related to the effect of gravity on living processes is the problem of the effects of weightlessness4 ,of particular interest to psychologists are the possible modifications an altered gravitational environment might produce in behavioral patterns basic to the animal's maintenance and survival1 such as eating1 sensory and discriminative processes1 development and maturation1 and learning capacity 7ref4#ia74 ,one prominent method of studying gravitational effects is to simulate an increase in gravity by centrifugation4 ,smith et al4 7ref4#ib7 and ,winget et al4 7ref4#ic7 have investigated the effects of long-term acceleration on birds1 primarily chickens1 while ,wunder 7refs4 ref4#id and ref4#ie7 and his coworkers 7refs4 ref4#if-ref4#ii7 have used fruit flies1 mice1 rats1 hamsters1 and turtles4 ,the general findings are that1 when animals are subjected to a prolonged period of acceleration of moderate intensity1 they exhibit decreased growth1 delayed maturation1 and an increase in the size of certain muscles and organs1 dependent on the species4 ,with regard to the decreased growth effect1 the data of these investigators show some exceptions4 ,when the gravitational increase is kept below a certain limit1 growth was greater than that of controls in the fruit fly1 turtle1 mouse1 and chicken4 ,the limit below which enhancement of growth was observed varied with the species studied4 ,the data on food intake do not present a consistent picture4 ,wunder 7ref4#id7 found that food intake in accelerated mice was markedly reduced from that of nonaccelerated control animals4 ,smith1 however1 found that in chickens1 food intake increased up to #cf percent over controls and has derived an exponential relation between food intake and acceleration4 ,after six generations of selective breeding1 ,smith has produced a strain of chickens better adapted to prolonged exposure to high g4 ,a very relevant finding of their research with birds was that exposure to chronic acceleration in some way appears to interfere with habituation to rotatory stimulation4 ,chickens who were being subjected to chronic acceleration were given repeated rotatory stimulation tests to estimate their labyrinthine sensitivity4 ,this study revealed that centrifuged animals showed a marked reduction in labyrinthine sensitivity4 ,this result appeared to persist after the acceleration was terminated4 ,in animals who developed gait or postural difficulties as a result of acceleration1 there was no evidence of a postnystagmus in response to the rotatory stimulation test1 which the investigators point out may be evidence of a lesion in the labyrinth or its neural pathways4 ,smith has implicated social factors as interfering with acceleration effects4 ,his subjects were typically accelerated four or six to a cage4 ,when groups were mixed midway through the experiment1 they exhibited a higher mortality rate and incidence of acceleration symptoms than did groups whose constituency remained unchanged4 ,at the ,u4,s4 ,naval ,school of ,aerospace ,medicine1 numerous studies have been conducted on the effects of slow rotation on the behavior and physiology of humans and animals 7ref4#ajj74 ,rotation initially produces decrements in performance1 but adaptation to a rotating environment ensues quite rapidly 7refs4 ref4#aja-ref4#ajc74 ,perceptual distortion1 nystagmus1 nausea1 and other signs of discomfort are common responses to slow rotation4 ,these symptoms are generally reduced with continued exposure 7adaptation74 ,interestingly1 however1 adaptation is delayed when the subjects are exposed to a fixed reference outside their rotating environment4 ,at ,,nasa-,ames1 rodents have been used in experiments by ,weissman and ,seldeen to delimit the stimulus effects of rotation4 ,in these experiments the subjects must discriminate between different speeds of rotation in order to obtain food reinforcement4 ,the results thus far provide evidence that these animals are capable of discriminating between the different speeds at which they are being rotated4 ,the range of speeds studied was #j-be rpm1 with tests of discrimination being made at intervals of less than #e rpm4 ,experiments such as these will lead to the development of techniques for measuring rotational sensitivity in many species1 including man4 ,the optimum configuration of manned spacecraft will depend1 in part1 upon biomedical considerations4 ,a voluminous literature now exists on the possible hazards to man of prolonged exposure to zero-g conditions4 ,should prolonged weightlessness prove to be a serious detriment to health1 consideration must be given to design concepts which provide artificial gravity4 ,no data exist on the minimum gravity requirements necessary to sustain basic biological functions for extended periods4 ,a limit of #j4b g has been given as the lower level at which man can walk unaided 7ref4#ajd74 ,it has also been recommended that angular velocity be maintained at the lowest possible level in order to minimize the occurrence of vestibular disturbances4 ,these recommendations are based on human-factor requirements1 rather than upon biological considerations1 which may significantly modify these values4 ,in recent studies1 a technique has been devised which promises to provide reliable criteria for biological acceptability1 since it is based on fundamental biological and behavioral principles4 ,as animals progress up the evolutionary stale1 their survival depends less and less upon stereotyped physiological reactions which occur in reflex fashion1 in response to environmental stimulation4 ,in higher organisms1 survival depends more upon the capacity of organisms to modify their behavior4 ,at the highest levels of functional efficiency1 the ultimate form of adaptation is seen--the manipulation of the environment by the organism4 ,developments in behavioral science now permit us to utilize the adaptive behavior of animals to investigate many problems of biological interest4 ,recent studies on the self-selection of gravity levels represent a further attempt to exploit the adaptive capacities of animals1 in order to provide information relevant to problems of space exploration4 ,one such project allows animals to select their own gravity environment in an apparatus designed to create g-forces through centrifugal action by rotation at #fj rpm 7ref4#aje74 ,the surface of this centrifuge is parabolic1 so that the resultant of the centrifugal g and the ,earth's gravity is always normal to the surface4 ,when the animal moves away from the center1 increasing the radius of rotation1 it is exposed to increasing gravity4 ,motion toward the center reduces the gravity level4 ,by this means1 an animal is free to select its own gravity environment4 ,when the animal moves toward or away from the center1 he is moving from one tangential velocity to another4 ,he is therefore acted upon by a third force--due to ,coriolis acceleration4 ,the effects of ,coriolis forces are a major problem difficult to eliminate in studies such as these1 but they must be taken into account in the design of spacecraft which produce artificial gravity by rotation4 ,motion of the head in any direction not parallel to the centrifugal force vector would result in bizarre stimulation of the semicircular canals and consequent motion sickness4 ,this effect is likely to become even more pronounced if the sensitivity of these organs is increased by prolonged exposure to reduced gravity4 ,methods such as these are currently being developed for conducting a refined psychophysical analysis of gravity1 including studies by ,lange and ,broderson on the perception of angular1 linear1 and ,coriolis acceleration4 ,the results of animal studies such as these will be of great value in arriving at a decisive judgment concerning the need for artificial gravity in a manned orbiting space station1 or other vehicles designed for long-term occupancy4 ,to aid in the interpretation of in-flight data1 other studies are underway to determine the functions of the vestibular system1 as a principal brain center related to orientation in space and to the physiology of posture and movement1 as well as with the influences of acceleration1 rotation1 and weightlessness4 ,experiments are presently being conducted on monkeys and cats in order to trace these complex neurological connections and to determine their functional organization4 ,,biological ,,information ,,systems ,the nature of memory has been the subject of considerable speculation in the past4 ,it has long been felt intuitively that retention of information in the central nervous system involves either an alteration of preexisting material or structure1 or1 alternatively1 synthesis of materials not present previously4 ,the cellular site of operational alteration was unknown but1 again intuitively1 was felt to be closely associated with the synapses4 ,the problems faced by early investigators were great2 but nevertheless much information relevant to the question of biological information storage was obtained4 ,with the relatively recent advent of more refined tools and methodologies1 there has been rapid progress4 ,a significant amount of the work which has been conducted in the area of biological information and communication systems is easily classified as basic research 7refs4 ref4#ajf-ref4#aji74 ,this discussion will be limited to those aspects closely related to the fields of molecular biology and experimental psychology1 which seem to have universal application to all known animal life forms4 ,studies involving the basic principles of acquisition1 processing1 storage1 and retrieval of information in living systems are emphasized4 ,early ,work ,early speculations on the operational nature of memory have been based upon relatively little experimental evidence4 ,charles ,darwin observed that domestic rabbits had smaller brains than their wild counterparts1 and attributed this to lack of exercise of their intellect1 senses1 and voluntary movements4 ,unfortunately1 subsequent studies of the brains of men with greatly differing intellectual capability did not substantiate the hypothesis4 ,idiots sometimes had larger brains than geniuses4 ,later1 an idea proposed by ,ramon y ,cajal came into favor4 ,since brain cells did not increase in number after birth1 he proposed that memory involved the establishment of new and more extended intercortical connections4 ,unfortunately1 methods were not available to test this hypothesis adequately and it has remained until quite recently in the realm of conjecture4 ,another major hypothesis was that there were two or more stages in the information storage process4 ,the final form the information took in the brain was called a brain engram1 or memory trace4 ,however1 prior to the formation of the engram1 a transitory process denoted as reverberational memory was postulated to exist for a relatively short time 7minutes to hours7 7refs4 ref4#ajf and ref4#ajg74 ,this hypothesis was used by ,pauling to explain why an elderly chairman of a board could brilliantly summarize a complex #h-;hour meeting and yet1 after its conclusion and his return to his office1 not even remember having attended the meeting4 ,thus1 this individual's reverberational memory functioned well1 but advanced years had seriously impaired his brain's ability to form a permanent engram4 ,similar1 although less dramatic1 observations in other situations are not uncommon4 ,a wide variety of experiments have been conducted to study this aspect of memory and to relate it to the process whereby the information is transformed to a more stable form 7refs4 ref4#aaj-ref4#aab74 ,more recently1 the concept of a specific biochemical activity during the process of long-term storage of information has gained considerable favor4 ,initially1 neither the site nor the nature of the change was well defined4 ,quite recent studies by ,krech et al4 7refs4 ref4#aac and ref4#aad71 ,bennett et al4 7ref4#aae71 ,rosenzweig et al4 7refs4 ref4#aaf and ref4#aag7 support the view that alteration of the levels of acetylcholinesterase at cortical synapses play an important role in information storage4 ,these studies will be discussed in a later section4 ,however1 these authors do not claim that the changes observed are unambiguously related to the storage of memory4 ,it may well be that the alterations observed are in some way related to this process but are still secondary to some other1 more basic1 process4 ,an alternative hypothesis is that the information resides in its ultimate form in some more central structure of the neurone than the synapse4 7,it has even been postulated that the basic information is stored in nonneuronocortical material47 ,perhaps ,halstead was the first to postulate the involvement of nucleoprotein in this process 7ref4#ajg74 ,from the biochemist's point of view1 this is an extremely attractive hypothesis4 ,both proteins and nucleic acids possess sufficient possible permutations of structure to permit storage of a lifetime's accumulation of information in an organ the size of the brain4 ,from the previously known ability of the nucleic acids to code genetic information1 they are the prime suspects4 ,however1 from the known regulatory ability of nucleic acids in specific protein synthesis1 it is possible that the final repository is protein4 ,recent ,biochemical ,studies ,among the foremost investigators of the chemistry and biochemistry of the central nervous system is ,holger ,hyden at the ,university of ,gteborg1 ,sweden4 ,he and others 7refs4 ref4#aah-ref4#abj7 have for many years performed elegant microanalytical studies of single nerve cells4 ,the evidence which ,hyden has obtained is consistent with the hypothesis that the initial electrical reverberations in the brain induce a change in the molecular structure of the ribonucleic acid 7,,rna7 of the neurones which1 in turn1 leads to a subsequent deposition of specific proteins4 ,it is well known from other investigations that a major role of ,,rna in any type of cell is to specify and mediate synthesis of the protein enzymes of the cells4 ,thus1 in this hypothesis1 it is only necessary to postulate the modification of brain ,,rna by the activities associated with reverberational memory4 ,particularly pertinent to this hypothesis are observations that-- 7#a7 ,large nerve cells have a very high rate of metabolism of ,,rna and proteins1 and1 of the somatic cells1 are the largest producers of ,,rna4 7#b7 ,vestibular stimulation by passive means leads to an increase in the ,,rna content of the ,deiters nerve cells of rabbits 7ref4#aba74 ,the protein content of these cells is also increased4 7#c7 ,changes in the ,,rna composition of neurones and glia of the brainstem occur during a learning situation4 ,animals were trained over a period of #d to #e days to climb a steeply inclined wire to obtain food4 ,the big nerve cells and the glia of their lateral vestibular apparatus were analyzed1 since the ,deiters neurones present in this structure are directly connected to the middle ear4 ,the amount of ,,rna was found to be increased in the nerve cells2 and1 more significantly1 the adenine-to-uracil ratio of both the nuclear ,,rna of nerve cells and glia cells became significantly increased 7ref4#aai74 ,a variety of control experiments were conducted4 ,although there was an increase in ,,rna content of these cells in animals exposed to passive stimulation1 there was no change in the ratio of adenine to uracil4 ,nerve cells from the reticular formation1 another portion of the brain1 had only an increased content of ,,rna with no base-ratio change4 ,animals subjected to a stress experiment involving the vestibular nucleus showed only an increase in content of ,,rna4 ,littermates living in cages on the same diet as learning animals showed no change in content of ,,rna4 ,thus1 it would appear that the change in the base ratio of the ,,rna synthesized is not due to increased neurone function per se1 but is more directly related to the learning process4 ,the fact that this was nuclear ,,rna implies that it was immediately related to chromosomal ,,dna4 7#d7 ,neuronal ,,rna with changed cytosine-guanine ratios synthesized during a short period of induced protein synthesis could be blocked by actinomycin ,d4 ,it was concluded1 therefore1 that the ,,rna was immediately ,,dna dependent and directly related to the genetic apparatus4 ,rats which were normally right handed were forced to modify their handedness in order to obtain food4 ,the ,,rna of nerve cells in that part of the cortex1 whose destruction destroys the ability to transfer handedness1 was analyzed4 ,a significant increase in ,,rna of nerve cells of the fifth to sixth cortical layers on the right side of the brain was observed4 ,the corresponding nerve cells on the opposite side of the same brain served as controls4 ,there was an increase in ,,rna and a significant increase in the purine bases relative to the pyrimidine bases in the learning side of the cortex4 ,when the animals were not forced to learn a new procedure1 only an increase of ,,rna was observed1 with no change in base ratio4 ,frank ,morrell1 head of the ,neurology ,department at ,stanford ,medical ,school1 has also been active in this field during the past #f years4 ,he has found that if a primary epileptic lesion is induced on one side of the cortex1 a secondary mirror lesion eventually develops in the contralateral homologous cortex4 ,this secondary lesion1 which showed self-sustaining epileptiform discharge1 could be isolated1 whereupon the epileptiform discharge disappeared4 ,this was interpreted as learned behavior of the secondary lesion4 ,from changes in the staining properties of the secondary lesion1 ,morrell concluded that changes in ,,rna had occurred in the cell4 ,changes in the composition of the ,,rna could not be shown by these techniques4 ,at the ,university of ,california at ,berkeley1 ,drs4 ,rosenzweig1 ,bennett1 and ,krech have conducted extensive studies related to this topic4 ,these investigators have directed their efforts toward demonstrating alterations in the cerebral cortex of animals exposed to continuing learning situations or continuously deprived of sensory stimulation4 ,in a recent publication 7ref4#aaf71 which also summarizes a considerable amount of previous work1 they report studies which demonstrate the following3 7#a7 ,rats given enriched experience develop1 in comparison with their restricted littermates1 greater weight and thickness of cortical tissue and an associated proportional increase in total acetylcholinesterase activity of the cortex4 7#b7 ,the gain in weight of cortical tissue is relatively larger than the increase in enzymatic activity4 ,acetylcholinesterase activity increases in other portions of the brain even though tissue weight decreases4 7#c7 ,the changes appear in a variety of lines of rats1 although differing in amount between strains4 7#d7 ,the changes are observed in both the young and adult animals4 ,the previous studies were comparisons between experience-enriched animals and animals maintained in isolation4 ,animals which were housed in colonies1 but given no special treatment1 showed intermediate effects in those situations studied4 ,the ,berkeley group emphasized that the finding of changes in the brain subsequent to experience does not prove that the changes have anything to do with memory storage1 but do establish the fact that the brain can respond to environmental pressure4 ,however1 the results are compatible with the hypothesis that long-term memory storage involves the formation of new somatic connections among neurones4 ,calculations of the amount of additional material required to permit this to exist are compatible with the increases observed4 ,a number of investigators have studied the effects of antimetabolites and drugs on the learning process4 ,since their specific metabolic effects are known in other tissues1 the rationale is that if these materials do interfere with memory1 then specific types of metabolic activities may be implicated in the deposition of the engram4 ,one of the initial studies of this type was conducted by ,dingman and ,sporn 7ref4#abb71 presently at the ,national ,institute of ,mental ,health4 ,they showed that #h-;azaguanine1 a purine antagonist1 injected intra-cisternally was incorporated into the ,,rna of the brains of rats4 ,associated with this incorporation was an impairment of the maze-learning ability of the animals4 ,these findings have been confirmed4 ,flexner and his associates injected puromycin1 an inhibitor of protein synthesis1 into the brains of mice1 which were then trained to perform in a maze4 ,losses of short-term or long-term memory were obtained1 depending upon the site of the injection4 ,the results indicate that the hippocampal region is the site of recent memory4 ,the hippocampal region is of interest in connection with memory processes for a number of other reasons4 ,adey et al4 7ref4#abc7 and his group observed a transient fall in electrical impedance in this region when cats learned to perform in a ,t-maze in response to a visual cue4 ,it was supposed that the electrodes were situated within glial cells of the dendritic zone of the hippocampal pyramidal cell layer4 ,extinction of the learned habit abolished the briefly evoked impedance changes1 which subsequently reappeared with retraining4 ,a number of other studies more or less indirectly implicate ,,rna in the learning processes4 ,for instance1 in retinal cells of rabbits raised in darkness1 there was virtually no ribonucleoprotein as compared with normal amounts in the cells of animals raised in light 7ref4#abd74 ,further1 maintenance of normal electrical activity of isolated perfused cat brains is highly dependent upon the presence of the ribonucleic acid precursors1 uridine and cytidine1 in the perfusate 7ref4#abe71 and severe derangements occur if any of a variety of pyrimidine antagonists are added 7ref4#abf74 ,brief electrical stimulation of cat cortical tissue causes an increase in nucleic acid cytidine and adenine1 thus indicating a synthesis of altered polynucleotides4 ,finally1 injections of ,,rna in animals have shown interesting effects4 ,when given at a dose of #aaf mg_/kg daily for #a month1 rats showed an enhanced response and greater resistance to extinction in a shock-motivated behavioral response4 ,it has been shown by another group that injections of ,,rna enhance the ability of young animals to learn various tasks4 ,planaria have been used in a variety of studies which seem to bear on the problem of memory4 ,quite recent evidence by ,bennett1 ,calvin1 and their associates has cast somewhat of a pall over the studies2 nevertheless1 the work may have some validity4 ,interest in the use of flatworms1 particularly planaria1 for study of memory began with a demonstration by ,mc,connell that these simple animals could undergo conditioning 7ref4#abg74 ,subsequently1 it was found that some conditioning was retained when the animal was transected and allowed to regenerate4 ,the retention of training was found in both new animals1 although the very simple brain1 really only two ganglia1 was in the head section 7ref4#abh74 ,apparently1 some diffusely distributed component of the animal was responsible for retention of learning4 ,evidence has accumulated to indicate that this material is ,,rna4 ,among this evidence is the following3 7#a7 ,the two halves of a trained planaria were allowed to regenerate in a solution containing ,,rna-destroying enzymes4 ,whereas the head ends retained some training1 no retention was observed in the animals derived from the tail end 7ref4#abi74 7#b7 ,when pieces of trained planaria were fed to untrained animals1 the untrained cannibal required a shorter time to become trained to a criterion4 ,it would appear that the digestive system of planaria is so simple that the material responsible for the transfer of the information was not broken down4 7#c7 ,when ,,rna1 obtained from trained planaria1 is injected into the digestive tract of untrained animals1 there is a transfer of information4 ,,neurophysiology ,excerpt from ref4#acj4 ,neurophysiological studies concern the functions of the nervous system--in particular the central nervous system 7,,cns7--under normal1 simulated1 and actual flight conditions4 ,of paramount importance is the maintenance of equilibrium and orientation in three-dimensional space4 ,the ability of man and his close relatives among the vertebrates to maintain these functions depends on an integrated sensory input from the vestibular organ2 the eyes2 the interoceptors of the muscles1 tendons1 joints1 and viscera2 and the exteroceptors of the skin4 ,certain parameters of the environmental and space-flight conditions drastically affect man's ability to maintain equilibrium and spatial orientation4 ,centrifugal forces modify or reverse the directional vector of gravity4 ,linear acceleration may increase enormously1 as may angular stimulation4 ,the sensory organs listed above are unreliable under such conditions4 ,the very organ which is designed specifically to furnish information on spatial orientation may malfunction in man while he is in flight4 ,thus1 with respect to sensory orientation1 these labyrinthine organs are by no means precision instruments4 ,the use of classical histological methods and the observation of equilibrium disturbances resulting from operative interference with the internal ear have in the past been the two principal sources of knowledge concerning the structure and function of the labyrinth1 but the answers given to various questions vary considerably in their value4 ,the development of electrophysiological techniques and the refinement in recent years of the ultrastructural analysis by means of the electron microscope may allow more precise experimental studies of the correlation of function and structure4 ,before considering vestibular impulses in their bulbar and descending spinal pathways1 a recent study concerning the generation of impulses in the labyrinth must be mentioned4 ,von ,bekesy's finding 7ref4#aca7 of the direct current potentials in the cochlea aroused speculation about the existence of similar labyrinthine potentials4 ,such dc potentials were also detected in the semicircular canal of the guinea pig by ,trincker 7ref4#acb71 who measured the potential changes in the endolymph1 surface of the cupula1 or side of the crista during cupular deflection4 ,it seems likely1 however1 that the effects do not represent the physicochemical changes in the cupula but the electrical potentials in the nerve and nerve endings of the crista4 ,attempts at differentiating these effects have failed so far4 ,great expectations are brought by the advances of microchemistry1 microphysiology1 and physical chemistry with regard to the excitatory processes1 the generation of the nerve impulse4 ,quite apart from a need to understand vestibular nerve discharges and patterns more adequately in such terms1 the analysis of the vestibular system has in the past revealed general biological principles which were not readily discernible through the examination of other tissues 7ref4#acc74 ,the neural connections of the vestibular organ consist of numerous chains of neurons1 reciprocally linked in many ways and having their synapses in various anatomical nuclei4 ,all the chains work in intimate collaboration1 and the final pattern of reflex responses is attributable largely to the highly complex integrating activity of the center4 ,the labyrinthine function is automatic1 carried out in a reflex fashion3 in other words1 mostly below the level of consciousness4 ,the brain centers through which the labyrinth elicits the various appropriate muscular reactions of the head1 body1 limbs1 and eyes--the righting1 the postural1 and the ocular reflexes--represent an intricate mechanism4 ,before we can hope for a satisfactory understanding of their functional organization1 we will have to know their anatomy in more detail4 ,thus1 we are confronted with a fruitful field for the exploration of basic mechanisms of neuronal activity4 ,major advances dining the last years have provided us with new information about the neuroanatomy of the vestibular system 7refs4 ref4#acd-ref4#acg74 ,vestibular impulses entering the brainstem ascend and descend the neuroaxis and cross the midline4 ,it was previously believed that the vestibular apparatus had only subcortical projections4 ,recently1 however1 it has been established by means of electrophysiological methods that the organ is represented by a projection area in the cerebral cortex of some animals 7refs4 ref4#ach-ref4#ada74 ,the use of brief electrical stimulation of the vestibular nerve in order to elicit a cortical response has been of great value for the mapping of these areas4 ,among a great variety of sensory receptors1 the vestibular ones are capable of evoking the most widespread somatovisceral effects throughout the body4 ,moreover1 vestibular effects seem to be imperious and less dependent upon the state of readiness of the nervous system4 ,as a consequence of the extensive distribution of vestibular effects1 there are many opportunities for central integration4 ,proprioceptive and vestibular systems are both known to be active in posture and locomotion2 streams of impulses arising from the receptors in each of these systems must converge to influence the activity of the final common path4 ,the state of the motor centers of the spinal cord1 as affected by vestibular stimulation1 has been tested by dorsal root and other sensory input interventions4 ,these experiments have provided us with insight into the mechanisms concerned with the vestibular control of spinal reflexes 7refs4 ref4#adb-ref4#adf74 ,it has long been known that the vestibular apparatus is essential for the development of motion sickness4 ,commonplace subjective experience of nausea relates to visceral changes mediated through autonomic efferent pathways and may ultimately involve rhythmic somatic nerve discharges to skeletal muscles responsible for retching and vomiting4 ,however1 very little is known about the central nervous mechanisms responsible for elaboration of the whole syndrome4 ,since the maintenance of vestibular bombardment for some length of time seems essential for the development of motion sickness1 one would presume this to be an instance of slow temporal summation4 ,experimental findings demonstrate a powerful effect of temporal summation upon somatic motor outflow during vestibular stimulation 7ref4#adg71 and not upon parasympathetic outflow4 ,the practical implication of these studies is closely related to physiological effects of weightlessness4 ,based on experimental evidence from short weightless periods obtained in aircraft1 it was concluded that when the exposure becomes longer1 there may develop minor physiologic disturbances which1 if cumulative or irritating1 may cause or enhance psychiatric symptoms 7ref4#adh74 ,although the zero-g condition1 per se1 does not cause spatial disorientation if visual cues are provided1 the astronauts reported a temporary loss of orientation during the orbital flight while they were engaged in activities which diverted their attention4 ,however1 no disturbing sensory inputs were observed during the weightless period4 ,violent head maneuvers within the limited mobility of the helmet were performed in every direction without illusions or vertigo4 ,the subjective sensations of tumbling forward after sustainer engine cutoff reported by the ,mercury astronauts1 and ,titov's motion sickness attacks1 which were particularly dismaying during head movements1 were well within the entire range of psychosomatic experiences already obtained during aerodynamic trajectories 7ref4#adi74 ,interestingly enough it now appears that the otolithic output in mammals including man is the differential of linear acceleration1 and therefore unaffected by zero g4 ,of interest in this connection are the problems which may be encountered during and following long-term exposure to weightlessness4 ,although there is no evidence of adverse effects on operative behavior1 the possibility of biological disturbances on a cellular or subcellular level1 which may cause a deterioration of the somatic basis1 has been repeatedly stressed4 ,whether effects of this sort will occur or whether the organism will be able to adapt is still an open question4 ,since motion sensitivity based on vestibular stimulation differs widely among individuals1 the selection of astronauts may solve the problem of zero-g vestibular disturbance4 ,reports from the ,,ma-#h 7,sigma #g7 and ,vostok ,,iii and ,,iv flights seem to support this assumption4 ,moreover1 experiments are being made in the slow rotation room at the ,naval ,school of ,aviation ,medicine to study the ,coriolis effects which arise when artificial gravity is produced by angular acceleration4 ,since man can adapt to wave motion on shipboard within a few days1 a similar process may be expected to occur in the case of long-term weightlessness 7ref4#aej74 chapter #e ,molecular ,biology and ,bioinstrumentation ,to support biological investigations in space and to accumulate baseline data needed for manned space flight1 ,,nasa has conducted a program in laboratory research and theory4 ,a multidisciplinary approach has included such fields as ecology1 physiology1 organic and biological chemistry1 engineering1 electronics1 and optics4 ,emphasis in this program has been placed on qualitative and theoretical rather than purely descriptive research1 and the investigation of fundamental biological phenomena at all levels1 from the molecular to the total life form4 ,,molecular ,,biology ,research in molecular biology has included chemical1 physical1 biological1 and theoretical investigations of prebiological conditions on ,earth and1 possibly1 on other planets2 studies of cellular inclusions2 genetic material 7,,dna and ,,rna7 and coding2 as well as energy transfer in biological systems4 ,the understanding of prebiological conditions on ,earth1 and possible conditions on other planets1 depends upon the nature of the complex chemical species which might be encountered4 ,scientists have shown that biologically important compounds1 such as amino acids1 can be generated by applying an electrical discharge1 ultraviolet radiation1 or heat to a gaseous mixture4 ,biologically interesting compounds can be removed from such a system by condensation or absorption2 however1 in the limited time and space available in such experiments1 many compounds are not produced in sufficient quantity to be measured4 ,the ,national ,biomedical ,research ,foundation 7,,nbrf7 and the ,national ,bureau of ,standards 7,,nbs7 are conducting an investigation on equilibria in multielement systems4 ,the distribution of molecular species at equilibrium is independent of the way equilibrium was reached and is dependent only on pressure1 temperature1 and elemental composition4 ,many of the conditions which might have arisen naturally can be approximated by thermodynamic equilibrium4 ,compounds which can be formed at equilibrium need no special mechanism to explain their presence4 ,however1 special mechanisms have to be sought for those compounds which could not be so produced and which would have been required for the structure and nutrition of the first living organisms4 ,in the absence of precise knowledge of the composition of the primitive planetary atmospheres1 equilibrium concentrations with a wide range of temperatures1 pressures1 and elemental compositions are being investigated by ,,nbrf and ,,nbs4 ,these investigators have postulated that the maximum atmospheric pressure may have approached #ajj atm if the primitive ,earth was sufficiently hot and if an appreciable portion of the water on ,earth's surface today was present on primitive ,earth4 7,if the present oceans were to evaporate1 the surface pressure would be approximately #cjj atm47 ,low pressures of #aj atm and temperatures between #ejj and #ajjj ,k are being used4 ,a large range of ,n1 ,o1 ,c1 and ,h compositions are being investigated for interesting and plausible combinations of factors4 ,in these calculations an ,,ibm #gjij computer is being used to obtain data on a very large number of combinations of chemicals4 ,other chemical species will be added as the research continues4 ,some results of this study give an insight into the variety of biologically significant chemicals which might have existed during ,earth's primitive prebiological condition or may now exist on the surfaces and in the atmospheres of other planets 7refs4 ref4#aea-ref4#aec74 ,the general method described by ,white et al4 7ref4#aeb71 minimizing the free energy of the system1 was used4 ,the solution was approached by an iterative process1 starting with an initial guess of concentrations of the compounds4 ,at each step1 ,m#a linear equations are solved where ,m is the number of elements in the system4 ,in addition to listing of the concentrations of all compounds included in each problem1 the results of three-element problems have been expressed on a triangular composition diagram for convenience4 ,a coarse grid of #fj points is used to survey all elemental compositions1 with finer grids being used in regions of particular interest4 ,the calculated concentrations of the compounds at each composition are stored1 and finally a series of triangular diagrams is printed out1 each showing the concentrations of as many as four compounds at the grid points4 ,figure #b shows the results obtained in the ,c1 ,h1 and ,o systems4 ,organic compounds in concentrations greater than #aj mole fraction are found everywhere except where free ,o1 is present4 ,solid carbon theoretically becomes stable along the lower dashed line at #ejj ,k4 ,however1 reactions producing it are very slow4 ,the supersaturated region beyond the line of potential carbon formation was also investigated4 ,a threshold was found where polynuclear aromatic compounds are sufficiently concentrated to form a liquid phase4 ,these conditions may have been involved in the primordial formation of asphaltic petroleum4 ,illustration3 ,figure #b4--;,equilibrium diagram for the system ,c-,h-,o4 ,jukes and associates 7ref4#aed7 at the ,university of ,california at ,berkeley have been investigating the code for amino acids in protein synthesis1 the key for translating the sequence of bases in ,,dna into the sequence of amino acids in proteins4 ,the amino acid code was solely a matter of theory until ,nirenberg and ,matthaei 7ref4#aee7 at the ,national ,institutes of ,health carried out a crucial experiment4 ,this experiment bridged the last remaining gap separating theoretical genetics and test-tube biochemistry4 ,it now became experimentally possible to search for codes for all #bj amino acids concerned in the synthesis of proteins4 ,the amino acid bases of ,,dna are3 ,a1 adenine2 ,c1 cytosine2 ,g1 guanine2 ,t1 thymine2 and ,u1 uracil1 which replaces thymine in ,,rna4 ,there are only #af ways of arranging ,a1 ,c1 ,g1 and ,t in pairs4 ,for this and other reasons it is thought that a triplet of three consecutive bases is needed to code for each amino acid4 ,the sequences of bases in a strand of ,,dna are known to be unrestricted with respect to the order in which they occur2 apparently any one of the four bases can be next to any of the other four1 although1 of course1 each base must be paired with the corresponding complementary base in the adjacent strand4 ,since the same freedom is true of the amino acid sequences in the polypeptide chains of proteins1 any one of the #bj amino acids can occur next to any other4 ,moreover1 the sequences in ,,dna are subject to mutational changes in which one base replaces another1 or bases are added to or deleted from the ,,dna4 ,such rearrangements plus the possibility of lengthening of ,,dna molecules are numerous enough to account for all the genetics of living forms since the first appearance of life on ,earth4 ,most of our knowledge is based on experiments with synthetic ,,rna carried out with extracts of ,e4 coli4 ,the majority of the work has been at ,nirenberg's laboratory at the ,national ,institutes of ,health and at ,ochoa's laboratory at ,new ,york ,university 7ref4#aee74 ,various combinations of ,a1 ,c1 ,g1 and ,u were used in preparing the synthetic ,,rna molecules that are used in experiments to explore the code4 ,these molecules are made by incubating a mixture of ribonucleoside diphosphates with a specific enzyme1 polynucleotide phosphorylase4 ,an important property of this enzyme is that it condenses the nucleoside diphosphates into polynucleotide strands containing random sequences depending on the proportion of each base4 ,for example1 if the enzyme were furnished with a mixture of #e parts of ,a and #a part of ,c1 it would make strands containing1 on the average1 #be sequences of ,,aaa1 #e of ,,aac1 #e of ,,aca1 #e of ,,caa1 and #a each of ,,acc1 ,,cac1 and ,,cca4 ,the proportion of triplets within the strands of a polynucleotide is reflected in the proportion of amino acids in polypeptides that are obtained in the cell-free system4 ,most of the present knowledge of the amino acid code is based on this concept4 ,all the proposed codes have been discovered by this experimental approach where synthetic ,,rna molecules are used as artificial messenger ,,rna4 ,representative of another class of activities in molecular biology is the examination of passive ion flux across axon membranes4 ,this work is being done by ,goldman at the ,national ,naval ,medical ,center4 ,the question of stimulus transmission by nerve tissue is far from simple1 and the ion concentrations associated with nerve membranes is a significant part of the answer4 ,because the space environment may very well produce alterations in these ion potentials1 an investigation of their natures and significance becomes extremely important4 ,a working theory is now being developed as a result of this study4 ,vital cell processes1 chemical transformations1 and mechanisms that provide energy for cell maintenance and activity have been studied by ,kiesow 7refs4 ref4#aeg and ref4#aeh7 at the ,naval ,medical ,research ,institute4 ,the common objective of all phases of this project is the elucidation of reaction steps in which energy and matter are transformed in living systems4 ,compared with photosynthetic organisms1 chemosynthetic bacteria offer distinct advantages for the study of energy assimilation4 ,these studies have led to the following experimental findings4 ,with the energy from oxidation of nitrite1 ,,no-- to nitrate1 ,,no-- as an inorganic source1 and with added organic chemical energy from the hydrolysis of adenosinetriphosphate 7,,atp7 to adenosinediphosphate 7,,adp7 and inorganic phosphate1 chemosynthetic bacteria are capable of reducing diphosphopyridinenucleotide 7,,dpn7 to ,,dpnh1 in a coupled oxidoreduction-dephosphorylation4 ,thus1 in the crucial step of chemosynthesis1 ,,atp is consumed1 not produced4 ,however1 in simultaneously proceeding cell respiration1 the energy donor1 ,,dpnh1 is oxidized and generates more ,,atp than is required for ,,dpn reduction4 ,this breeder cycle for ,,dpnh--with different ratios of cell respiration and biosynthesis--results in a net production of either ,,dpnh1 or ,,atp1 or both4 ,production of ,,dpnh in the cycle leads immediately to the assimilation of ,c from ,,hc,o--4 ,these observations explain the bacteria's energy source without the classical hypotheses of either direct phosphorylation or direct ,,co reduction by inorganic chemical or electromagnetic energy4 ,the cycle transforms the free energy of nitrite oxidation into the free energy of the organic compounds4 ,cell respiration and elementary biosynthesis proceed through structure-bound enzyme systems in the same fraction of subcellular particles4 ,three components1 two cytochromes and one flavoprotein1 have been identified4 ,a thermodynamic analysis of the ,,dpnh breeder cycle appears to be attainable by measurements of redox potentials and calorimetric determinations of heats of reaction4 ,studies are also being conducted by ,pollard and associates at ,pennsylvania ,state ,university in an attempt to formulate a theoretical basis for the description of the processes of synthesis1 growth1 division1 and differentiation of the living cell4 ,such a theory would be basic to an understanding of very primitive life forms or prebiological material which might be found elsewhere in the universe4 ,for these purposes1 studies are being undertaken in macromolecular reproduction which differ from the studies involving cellular genetic material4 ,theories concerning the problem of replication of cellular structures and information storage in two-dimensional systems are being developed4 ,theories are also being developed about the mechanisms which control and regulate receptor and enzymatic activities within the cell4 ,one study involved the rate of mutation in cells and disposed of the suggestion that the process of mutation consists of a tunneling of proton from one base to another in ,,dna4 ,such a suggestion can no longer be advanced as a major explanation of mutations4 ,work is also being conducted on the centrifugation of cells of ,e4 coli4 ,it has been shown that cells exposed to as little as #ajj g have a modification in their function4 ,this has been looked at from the point of view of thymine uptake1 which would be concerned with the formation of ,,dna1 and also from the point of view of the induction of an enzyme1 which would correspond to the transcription of the ,,dna4 ,preliminary experiments in the latter case indicate considerable centrifugation effect4 ,the thymine uptake is affected1 but not nearly as much as formerly thought4 ,further work is in progress in this area4 ,important work has been completed on the cells of ,e4 coli grown on maltose1 which can be induced to produce betagalactosidase by the addition of thiomethyl galactoside4 ,if cells are irradiated shortly after induction1 the transcription of the ,,dna ceases and the enzyme produced by the messenger ,,rna is observed to reach a maximum4 ,this enables the calculation of the half-life of unstable messenger ,,rna4 ,the half-life for this decay is readily measurable1 and values are given over a temperature range of #ag ,c 7#e4b minimum7 to #de ,c 7#j4ef minimum74 ,these agree very well with half-lives measured by others by inducing for short times and measuring the course of enzyme formation4 ,the rate of transcription is involved in the kinetics of cessation of enzyme induction1 and the rate of transcription can be measured4 ,arrhenius plots for this rate and the rate of decay are given1 and the activation energies measured are about #af #jjj cal_/mole4 ,the cessation of transcription is linked to the degradation1 possibly of only one strand1 of ,,dna4 ,pollard has suggested that one important action of ionizing radiation is concerned with the transcription of the genetic message into ,,rna4 ,clayton and ,adler 7ref4#aei7 showed that induced catalase synthesis in ,rhodopseudomonas spheroides is inhibited by low doses of ,x-rays1 giving experimental support to the idea4 ,pollard and ,vogler 7ref4#afj71 using cells in which the process of induction involved permease1 showed that there is some sensitivity to gamma radiation4 ,novelli et al4 7ref4#afa7 found a reduced sensitivity as compared with colony formation1 but it is still a considerable sensitivity4 ,the process of induction of an enzyme indicates that the transcription of the genetic message is repressed by something which can be acted on by a small molecule1 the inducer1 to remove repression and permit the formation of messenger ,,rna1 which then acts to make the enzyme4 ,the messenger ,,rna undergoes decay through a process which is still not clear4 ,very elegant measurements by ,kepes 7ref4#afb7 show that for the messenger ,,rna for betagalactosidase1 the half-life is #a4jb min at #cg ,c and #b4je min at #be ,c4 ,the time of onset of enzyme formation after induction was found to be about #c minutes4 ,if the process of transcription is indeed sensitive to ionizing radiation1 then the irradiation of cells which have just been induced should show formation of the enzyme to the extent of formation of new messenger ,,rna within a few minutes1 plus the formation of the enzyme while the messenger ,,rna is decaying4 ,this pattern was found by ,clayton and ,adler4 ,the experiments conducted by ,pollard and associates amplify and extend their work and also agree with the work of ,kepes 7ref4#afb74 ,,bioinstrumentation ,fernandez-,moran 7refs4 ref4#afc-ref4#afe71 at the ,university of ,chicago1 has devised a new multielectrode electrostatic lens which he has incorporated into an electron microscope4 ,this necessitated the development of a novel high-voltage power source and voltage regulator of extreme stability and accuracy4 ,some promising work has now been done on superconducting lenses4 ,in a series of experiments with a simple electron microscope without pole pieces1 using high-field superconducting niobium-zirconium solenoid lenses in an open air core1 liquid helium ,dewar1 electron microscopic images of test specimens have been recorded while operating at #cb #bjj gauss in a persistent current mode1 with regulated accelerating potentials of #d to #h kilovolts4 ,these preliminary experiments have demonstrated the exceptional stability of the images 7both short term and long term7 over a period of #d to #h hours and the relatively high quality of the images4 ,progress has been made on the viscosimeter for high intrinsic viscosities4 ,this is now working1 and the viscosity of ,,dna preparations has been measured4 ,it is hoped to use the viscosimeter to study the variation in ,,dna viscosity as a function of the cell cycle4 ,an instrument is under development by ,wald at the ,university of ,pittsburgh to automatically analyze cytogenetic material and1 thus1 extend cytogenetic methodology both for research and as a biological monitoring procedure1 using automatic electronic scanning and computer analysis of chromosomes4 ,chromosomal aberrations can thus be monitored under unusual and abnormal conditions such as weightlessness and radiation1 since chromosomes are very sensitive to stress situations4 ,in this device a sample will be prepared and automatically inserted under a microscope lens4 ,the device will then scan1 identify1 and photograph on #ce-mm film a predetermined number of mitotic cells and process the film4 ,the data will be recorded under the direct control of a digital computer4 ,the computer will perform a detailed quantitative analysis of the pictorial data4 ,significant effort has been expended in the development of instrumentation for measuring and recording electrophysiological information4 ,one such instrument1 developed by the ,franklin ,institute1 ,philadelphia1 ,pa41 is a temperature-sensing microprobe4 ,this microprobe is an implantable and remote broadcasting instrument4 ,these developments are associated1 in part1 with training programs so that competent individuals may be trained not only in electronics but also in the biological uses of the devices they construct4 ,a project of interest1 conducted at the ,stanford ,research ,institute1 is the investigation of the uses of an extremely sensitive method for measuring magnetic susceptibility having the possibility of detecting macroscopic quantum effects in macromolecules of biological interest4 ,good progress has been made in the first #ae months of a project devoted to the development and initial use of equipment specifically designed for this purpose4 ,a new superconducting circuit1 together with superconducting magnetic shields1 has been constructed4 ,this apparatus can measure the magnetic susceptibility of small organic samples at temperatures between #a and #cjj ,k in fields up to #dj #jjj gauss4 ,it can detect flux changes of #aj gauss-cm1 which is equivalent to detecting a change in specific susceptibility of #a in #aj in a #ajj-mg sample under an applied field of #aj #jjj gauss4 ,several hundred preliminary measurements were made on samples of coronene4 ,the most reliable of these were in agreement with published values of the magnetic susceptibility of coronene4 ,experience during these measurements led to changes which have resulted in an apparatus well suited to the measurements on macromolecules4 ,an improved version of the superconducting circuit now available shows promise of a further improvement in sensitivity by a factor of more than a thousand 7ref4#aff74 ,living organisms possess many unique processes and systems which are complex and poorly understood4 ,the new theoretical approaches1 combined with laboratory studies1 are expected to result in advances which will expand both our scientific and technological horizons4 chapter #f ,flight ,programs ,,balloons ,biological and medical experiments carried out on balloon flights1 both manned and unmanned1 antedate the establishment of ,,nasa4 ,aside from the early use of balloons in flights that could be called simply flight-survival studies1 balloons have made important contributions to our present knowledge of the effects of cosmic radiation and to various aspects of space travel4 ,the achievements of the ,strato-,lab and ,man ,high series by the ,u4,s4 ,navy and ,air ,force include a wealth of information on balloon travel and on the survival of man at altitudes close to and above #ajj #jjj feet4 ,generally1 balloon launches of animals1 which reached a maximum in #aiec when #bc balloons were released1 have established the feasibility of a program of extended manned balloon flights to high altitudes4 ,atmospheric life studies outside the area of cosmic radiation effects have been comparatively few4 ,results from two manned flights1 ,strato-,lab ,i and ,,ii1 indicate that the flights did produce pronounced changes in white blood cell count2 however1 the data suggest that these changes were due to psychological rather than physical stress4 ,exposure to altitudes above #ij #jjj feet for a total of #fb hours did not produce any general behavioral change in two ,java monkeys1 according to other balloon flights4 ,many of these flights were effective in testing equipment1 telemetering devices1 and in pointing the way for other flights4 ,stratoscope ,i and ,,ii1 originally undertaken by the ,office of ,naval ,research 7,,onr71 are projects involving various astronomical observations with the aid of a balloon-borne telescope and television and camera systems4 ,,nasa cooperated with ,,onr on ,stratoscope ,,ii 7#cf-;inch telescope compared with ,stratoscope ,i's #ab-;inch telescope7 which has already resulted in significant discoveries about the nature of the planets and stars4 ,water vapor has been identified in the atmosphere of cool red stars and an analysis of the ,martian spectra showed a greater abundance of carbon dioxide than had previously been believed4 ,since the balloon-borne telescope was carried beyond ,earth's obscuring atmosphere1 the ,stratoscope projects have yielded valuable photographs of the ,sun1 stars1 and various planets4 ,,rockets ,,and ,,satellites ,historically1 biological experiments aboard rockets and satellites have been limited to a piggyback and noninterference basis on military rockets4 ,for the past few years1 however1 as the effort toward manned space flight leading to lunar and ,martian landings increased1 more attention was devoted to experiments designed to show the effects of the space environment on living systems4 ,as in the balloon flight programs1 the ,u4,s4 ,army1 ,navy1 and ,air ,force played an important role1 reaching what might be considered a high point with the successful launch and recovery of a ballistic rocket experiment with monkeys ,able and ,baker4 ,aerobee rockets as well as ,thor ,,irbm's carried biological payloads consisting of mice and monkeys on six launches1 contributing to our knowledge of the effects of weightlessness and radiation on higher animals4 ,van der ,wal and ,young 7ref4#gh7 used ,thor-,able combinations to serve as boosters for lifting a #bj-pound biocapsule to a peak altitude of #adjj miles and over a distance of about #ecjj miles from ,cape ,canaveral to the west coast of ,africa4 ,weightlessness was attained for a period of almost #dj minutes4 ,during reentry into the atmosphere1 a peak deceleration of about #fj g was reached4 ,each of the three capsules flown carried one mouse 7,mouse-in-,able72 two of the mice were instrumented for heart-rate telemetry4 ,although all three mice were lost1 the two experiments with ,laska and ,benji yielded physiological results4 ,the experimenters designed effective instrumentation for registering the electrical activity of the mouse's heart through a single commutated telemetry channel4 ,records were obtained for both animals during various portions of the flight4 ,the results indicate that both animals were alive when the nose cones hit the water4 ,two ,south ,american squirrel monkeys 7,gordo and ,baker7 and a rhesus monkey 7,able7 were launched into space from ,cape ,canaveral in #aieh and #aiei by ,u4,s4 ,army ,jupiter missiles4 ,the vehicles reached speeds of approximately #aj #jjj mph and altitudes of #cjj miles on flights which lasted about #ae min4 ,time courses of cardiac and respiratory rates 7ref4#hj7 of the two squirrel monkeys showed that the noise of the engine at liftoff immediately produced an increase in their heart rates4 ,respiration also increased temporarily1 but slowed later with increasing acceleration4 ,heart rates fluctuated considerably during launch acceleration1 which reached about #ae g at cutoff4 ,the period of free flight and weightlessness was characterized by pronounced fluctuations of heart activity in the postacceleration phase4 ,thereafter1 the heart rate of ,baker remained relatively constant1 whereas the cardiac activity of ,gordo fluctuated markedly and decreased slowly almost to the end of his flight4 ,slight changes1 which were transient and not pathological in nature1 were also noted in the electrocardiogram4 ,gordo's respiration was very shallow during maximum launch acceleration1 when ,baker's reached its highest value1 only to be approximated again during reentry when forces of about #ce g were encountered4 ,able's cardiac and respiratory rates indicated that1 after an initial startle reaction1 the heart rate dropped transiently and then increased steeply1 reaching a maximum of #bei during the #aj-second interval at peak acceleration4 ,respiration increased only slightly throughout the launching phase4 ,there was a period of tachycardia during postacceleration weightlessness1 after which the heart rate declined steadily and was disturbed only by several startling missile events4 ,at the end of the subgravity phase1 ,able's cardiac rate was slightly below normal4 ,although the periods of high g force and free flight were short1 the extremes were considerable1 and the changes from one state to the next were rapid4 ,in spite of this1 the cardiovascular1 hemodynamic1 and electrocardiographic phenomena were remarkably well maintained4 ,apparently the animals were not in serious plight at any time4 ,that psychological factors entered into the observed phenomena is clearly evident from the increase in cardiac rate associated with the noise of the engine prior to liftoff and also from the cinematographic record of facial expressions4 ,nevertheless1 the integrated responses indicated that the animals' physiological states remained sufficiently normal to insure a safe flight4 ,,little ,,joe ,,flights ,the first step in an attempt at animal verification of the adequacy of the ,mercury flight program was the development of two tests by ,,nasa in collaboration with the ,u4,s4 ,air ,force ,school of ,aviation ,medicine in which there would be a biomedical evaluation of the accelerations experienced during the abort of a ,mercury flight at and shortly after liftoff4 ,these flights were launched at the ,,nasa ,wallops ,station with a ,little ,joe solid-fuel launch vehicle4 ,two ,little ,joe launches were made with activation of the escape rockets during the boost phase to secure maximum acceleration2 only a brief period of weightlessness was attained4 ,the first launch was on ,december #d1 #aiei1 and the other on ,january #ba1 #aifj4 ,a #cf by #ah-;inch sealed1 #abe-pound1 cylindrical capsule containing the subject1 an #h-pound ,macaca mulatta1 the necessary life-support system1 and associated instrumentation was flown in a boilerplate model of the ,mercury spacecraft4 ,the rhesus monkeys were named ,sam and ,miss ,sam4 ,the flight profile included maximum accelerations of about #aj to #ab g and periods of about #c minutes at #jj4jb g4 ,the peak altitude obtained in the last ballistic flight was about #bhj #jjj feet4 ,the experimental capsule was pressurized at #a atmosphere with #ajj percent oxygen at the start of the experiment and fell to just below a half atmosphere of oxygen due to breathing during flight4 ,the capsule temperature was kept between #aj and #bj ,c in both flights4 ,the measurements taken from the rhesus monkeys were the electrocardiogram1 respiration1 body temperature1 eye movements1 and bar pressing1 but only partial results were obtained in the first flight4 ,oxygen tension1 total pressure1 capsule temperature1 and relative humidity were recorded4 ,both animals were recovered alive and did not show pathologic alterations in their physiologic and psychological reactions4 ,,mercury ,,animal ,,test ,,flights ,in the ,mercury animal test program a ,redstone missile carried the chimpanzee ,ham on a ballistic flight to a height of #aee miles to provide animal verification of the success with which the ,mercury system could be applied to manned flight4 ,the male chimpanzee was trained to perform a two-phased reaction task during the #af minutes of flight4 ,the chimpanzee ,enos was put into orbit for #c hours and #bj minutes4 ,results of the two flights gave the following information3 7#a7 ,pulse and respiration rates during both the ballistic 7,,mr-#b7 and the orbital 7,,ma-#e7 flights remained within normal limits throughout the weightless state4 ,effectiveness of heart action1 as evaluated from the electrocardiograms and pressure records1 was also unaffected by the flights4 7#b7 ,blood pressures1 both arterial and venous1 were not significantly changed from preflight values during #c hours of the weightless state4 7#c7 ,the performance of a series of tasks involving continuous and discrete avoidance1 fixed ratio responses for food reward1 delayed response for a fluid reward1 and solution of a simple oddity problem was unaffected by the weightless state4 7#d7 ,animals trained in the laboratory to perform during simulated acceleration1 noise1 and vibration of launch and reentry were able to maintain performance throughout an actual flight4 ,from the results of the ,,mr-#b and ,,ma-#e flights1 the following conclusions were drawn3 7#a7 ,the numerous objectives of the ,mercury animal test program were met4 ,the ,,mr-#b and ,,ma-#e tests preceded the first ballistic and orbital manned flights1 respectively1 and provided valuable training in countdown procedures and range monitoring and recovery techniques4 ,the bioinstrumentation was effectively tested and the adequacy of the environmental control system was demonstrated4 7#b7 ,a #g-minute 7,,mr-#b7 and a #c-;hour 7,,ma-#e7 exposure to the weightless state were experienced by the subjects in an experimental design which left visual and tactile references unimpaired4 ,there was no significant change in the physiological state or performance of the animals as measured during a series of tasks of graded motivation and difficulty4 7#c7 ,questions were answered concerning the physical and mental demands that the astronauts would encounter during space flight1 and it was shown that these demands would not be excessive4 7#d7 ,it was also demonstrated that the young chimpanzee can be trained to be a highly reliable subject for space-flight studies4 ,the suborbital ballistic flight of ,ham on ,january #ca1 #aifa1 was the prelude to ,alan ,r4 ,shepard's suborbital space flight1 while the orbital flight of ,enos on ,november #bi1 #aifa1 preceded the orbital flight of ,john ,h4 ,glenn4 ,the fact that we now categorize these events as belonging to the rather distant past1 although they occurred only about #d years ago1 serves to emphasize the pace of development in the exploration of space4 ,while the chimpanzee program may pale in the light of subsequent successes1 its scientific and technological contribution should not be overlooked4 ,the significance of this project can be fully appreciated1 and its contribution judged1 only by considering the lack of knowledge existing at the time of its conception4 ,in addition to its essential training function1 this project verified the feasibility of manned space flight through operational tests of the ,mercury life-support system4 ,it demonstrated that complex behavioral processes and basic physiological functions remained essentially unperturbed during brief exposures to space flight4 ,the ,mercury chimpanzee program marked the first time that physiological and behavioral assessment techniques were combined for evaluating the functional efficiency of the total organism in space4 ,perhaps the ultimate contribution of this program was in providing the framework of knowledge upon which future scientific experiments on biological organisms1 exposed to flights of extended durations1 must be based4 ,biosatellite experiments designed to seek more subtle and elusive effects of prolonged space flight on biological functioning will require even more refined and difficult techniques1 but will depend heavily on the groundwork laid in these early steps of ,project ,mercury4 ,a summary of the more important animal suborbital and orbital flights during the period #aieg to #aifd is presented in table ,,vii4 ,in another ,,nasa-supported flight1 ,,nerv #a1 various experiments were carried in a suborbital flight of #bj minutes4 ,neurospora molds showed a surprisingly high level of mutation1 but the control molds also had high rates4 ,the ,discoverer ,,xvii and ,,xviii flights1 to which the ,air ,force contributed1 resulted in many interesting findings relative to the responses of living systems to space flight4 ,on the ,discoverer ,,xvii flight1 samples of human gamma globulin and rabbit antiserum specific for human gamma globulin showed an increase in reactivity1 and samples of synovial and conjunctival cells showed no changes in their cytological characteristics4 ,discoverer ,,xviii was launched during a massive solar flare which lasted for the first #ac hours of the #dh-orbit1 #c-;day flight4 ,neurospora conidia1 nerve tissue1 algae1 human bone marrow1 eyelid tissue1 gamma globulin1 and cancer cells were put in orbit4 ,the results indicated that biological specimens may be able to withstand radiation from solar flares with a minimum of shielding and that aluminum shielding may be better than lead4 ,in #aidi1 the ,u4,s4,s4,r4 began a systematic1 uninterrupted research program in biological space experimentation4 ,they have studied the effects of physical stress1 immune reactions1 psychobiology and behavior1 genetics1 and responses to environmental factors such as spacecraft dynamics and ambient radiation4 ,the organisms and biological materials included tobacco mosaic and influenza viruses2 ,t#b and ,t#d bacteriophage2 ,bacillus aerogenes2 lysogenic bacteria2 ,clostridium butyricum2 ,escherichia coli2 actinomycetes2 yeasts2 ,chlorella pyrenoidosa2 seeds of fir1 pine1 onion1 corn1 lettuce1 wheat1 cabbage1 carrot1 buckwheat1 cucumber1 beet1 ,euonymus1 fennel1 mustard1 pea1 broad bean1 tomato1 and nutmeg2 ,tradescantia paludosa2 ,ascaris eggs2 snail spawn2 ,drosophila melanogaster2 loach roe2 frog eggs and sperm2 guinea pigs2 mice2 rats2 hamsters2 rabbits2 dogs2 monkeys2 human and rabbit skin2 ,he,la tissue cultures and other tissues 7refs4 ref4#afg and ref4#afh74 ,table ,,vii4--,orbital and ,suborbital ,animal ,flights for #aieg-fd ---------------------------------------- ------------------------ ,year ,animal subject ,flight profile ---------------------------------------- ------------------------ ,united ,states ---------------------------------------- ------------------------ #aieh ,mice ,wickie1 #adjj miles4 ,none of the three ,laska1 and flights were recovered4 ,benji ---------------------------------------- ------------------------ #aieh ,squirrel monkey #cjj-mile maximum altitude over a ,old ,reliable #acjj-mile distance via a ,jupiter rocket4 ,not recovered4 ---------------------------------------- ------------------------ #aiei ,rhesus monkeys #cjj-mile maximum altitude over a ,able and ,baker #aejj-mile distance via a ,jupiter rocket4 ,recovered4 ---------------------------------------- ------------------------ #aiei ,black mice #ejj seconds of weightlessness in ,discoverer ,,iii via a ,thor-,able rocket4 ,the ,discoverer vehicle did not go into orbit and the animals were lost4 ---------------------------------------- ------------------------ #aiei ,rhesus monkey #ec-mile altitude in ,little ,joe4 ,sam ,recovered4 ---------------------------------------- ------------------------ #aifj ,rhesus monkey #i-mile altitude in ,little ,joe4 ,miss ,sam ,recovered4 ---------------------------------------- ------------------------ #aifj ,c-#eg black mice #fej-mile altitude over a #ejjj-mile distance via ,atlas ,,rvx-#b;,a4 ,recovered4 ---------------------------------------- ------------------------ #aifa ,chimpanzee ,ham #aef-mile altitude over a #dad-mile distance via a ,redstone booster1 ,mercury capsule4 ,recovered4 ---------------------------------------- ------------------------ #aifa ,chimpanzee ,enos #b ,earth orbits4 #ahc minutes of weightlessnessat an apogee of #adf miles anda perigee of #ii miles4 ,atlas booster1 ,mercury capsule4 ,recovered4 ---------------------------------------- ------------------------ ,soviet ,union ---------------------------------------- ------------------------ #aieh ,dogs ,belyanka #bhj-mile altitude in hermetically and ,pestraya sealed cabin4 ,recovered4 ---------------------------------------- ------------------------ #aiei ,dog ,otyazhnaya ,over #ajj-mile altitude4 ,recovered4 and a rabbit ---------------------------------------- ------------------------ #aifj ,dogs ,belka and #af ,earth orbits 7#bd hours7 via ,strelka1 #ba ,sputnik ,v4 ,first successful recovery black and #ba white of living creature from orbital mice flight4 ---------------------------------------- ------------------------ #aifj ,dogs ,pchelka and #af ,earth orbits 7#bd hours74 ,mushka ,spacecraft destroyed during reentry4 ---------------------------------------- ------------------------ #aifa #a dog1 mice1 #a ,earth orbit at an apogee of #aee guinea pigs1 and miles and a perigee of #aad miles4 frogs ,recovered4 ---------------------------------------- ------------------------ #aifa ,dog ,laetzpochka #a ,earth orbit4 ,recovered4 ---------------------------------------- ------------------------ ,france ---------------------------------------- ------------------------ #aifa ,rat ,hector #ie-mile attitude in a capsule boosted by a ,veronique rocket4 ,recovered4 ---------------------------------------- ------------------------ #aifc ,cat ,felicette #ie-mile altitude in a capsule boosted by a ,veronique rocket4 ,over #e min of weightlessness4 ,recovered4 ---------------------------------------- ------------------------ ,,the ,,nasa ,,biosatellite ,,program ,from ref4#afi4 ,the space environment offers a unique opportunity to study the basic properties of living ,earth organisms with new tools and opens up new areas of research for which biological theory fails to provide adequate predictions4 ,unique components of the space environment of biological importance are weightlessness or greatly decreased gravity1 the imposition of an environment disconnected from ,earth's #bd-;hour rotation 7particularly its effect on biorhythms71 and cosmic radiation with energies and particle sizes unmatched by anything produced artificially on ,earth 7ref4#afi74 ,as progress is made in the manned exploration of space1 the biological effects of its unique environmental factors become of greater importance4 ,it is essential to determine the effects of space environment on man's ability to perform physical and mental tasks4 ,in addition1 it is necessary to develop those systems required for his survival and for his physiological and psychological well-being1 both in space and in his subsequent resumption of normal life patterns4 ,despite nearly a century of research and development in environmental physiology1 a number of phenomena will be encountered in long-term space flight with which we have had neither the experience that would enable us to predict the effects nor to develop the necessary protective or remedial measures 7ref4#agj74 ,many of the experimental programs in bioscience are being carried out or planned so that the deleterious effects of these phenomena may be determined1 predicted1 or avoided before they are encountered in manned flight4 ,biological experimentation has been carried out in orbiting spacecraft by ,soviet and ,american scientists preparatory to manned space flight4 ,these first-generation exploratory experiments had the following objectives3 7#a7 ,to discover whether complex organisms could survive space conditions and to test life-support systems 7#b7 ,to determine whether complex organisms 7dogs and primates7 could survive launch1 orbital space flight1 reentry1 and recovery 7#c7 ,to determine the effects of space radiation and any obvious effects of weightlessness on biological organisms ,these biological studies indicate that manned space flight was practicable1 and the various cosmonaut and astronaut flights have proven the validity of the results4 ,the ,national ,academy of ,sciences' ,space ,science ,board summer study 7ref4#aga7 recommended that-- ,,nasa should exploit special features of the space environment as unique situations for the general analysis of the organism-environment relationships including1 especially1 the role environmental inputs play in the establishment and maintenance of normal organization in the living system4 ,,nasa should support studies in ground-based and in orbiting laboratories biosatellites on the biological effects of gravity fields both above and below normal4 ,this should be considered a major responsibility of ,,nasa in the area of environmental opportunities4 ,,nasa should support studies of biological rhythms in plants and animals including man as part of its effort in environmental biology4 ,investigate by observation of rhythms in organisms in space in 7a7 polar and equatorial low orbits2 7b7 orbits less than1 equal to and greater than #bb1jjj miles4 ,properly designed experiments should be conducted to explore the effects of different environmental factors when these impinge simultaneously on test organisms4 ,the ,panel on ,gravity of the ,space ,science ,board 7ref4#fg7 stated that the major effects of low gravity would be expected in heterocellular organisms that develop in more or less fixed orientation with respect to terrestrial gravity and which respond to changes in orientation with relatively long induction periods1 including the higher plants4 ,on the other extreme are the complex primates which respond rapidly1 but whose multiplicity of organs and correlative mechanisms make the occurrence of malfunction and disorganization probable1 but not certain4 ,the ,panel recommended emphasis on early embryogenesis and histogenesis1 particularly of plants during exposure to low gravity1 and anatomical studies after low gravity4 ,they stated that perturbations of the environment to which the experimental organism is exposed must be limited or controlled to reduce uncertainties in interpretation of results4 ,at the same time1 the introduction of known perturbations may assist in isolating the effects due solely to gravity4 ,ground-based clinostats and centrifuges should be used in conjunction with the experiments1 and an attempt should be made to extrapolate effects of low gravity with the clinostat4 ,the study of the effects of unique or unknown space environmental factors will probably yield unexpected results which may drastically modify future technical approaches4 ,the results from these biosatellite studies will have broad application to longer term1 manned space flight1 including manned space stations and lunar and planetary exploration4 ,the biosatellite program is a second-generation series of carefully planned and selected experiments1 including some highly sophisticated experiments which have required several years of baseline study and equipment development4 ,these orbiting recoverable biosatellites will provide opportunities for critical testing of major biological hypotheses in the areas of genetics1 evolution1 and physiology4 ,the scientific community showed great interest in the biosatellite program1 and scientists from universities1 industry1 and ,government have submitted #ahe flight experiments involving primates and other mammals1 vertebrate and invertebrate animals1 micro-organisms1 and plants4 ,the selected biosatellite experiments include studies at the cellular1 tissue1 and organism levels1 including embryological development and growth experiments at the tissue level and physiological1 behavioral1 reproductive1 and genetic studies at the organism level4 ,the experiments are divided into six categories3 7#a7 ,primates 7#b7 ,mammals 7nonprimate7 7#c7 ,animal1 cellular1 and egg 7#d7 ,plant morphogenesis1 photosynthesis1 and growth 7#e7 ,biorhythm 7#f7 ,radiation ,twenty experiments have been selected for flight to study the effects of weightlessness and decreased gravity during #c- to #cj-;day orbital periods4 ,the experiments include a wide variety of plants and animals from single-celled organisms to higher plants and animals4 ,the effects of weightlessness on the primate will be studied1 especially the central nervous1 the cardiovascular1 and the skeletal systems during #cj-;day orbits4 ,experiments have been selected to study the genetic and somatic effects of weightlessness combined with a known source of radiation 7,sr7 to determine if there are any antagonistic or synergistic effects 7ref4#agb74 ,experiments are also included for studying the effects of the unique environment of the ,earth-orbiting satellite and removal from the ,earth's rotation in relation to biological rhythms of plants and animals4 ,six biosatellites are included in the presently approved program1 with the first flight in #aiff4 ,they will be launched from ,cape ,kennedy by the improved two-stage1 thrust-augmented ,thor-,delta into a nearly equatorial circular orbit at an altitude of #ahj-bjj miles for periods up to #cj days4 ,recovery will be by ,air ,force airplane during capsule_/parachute descent4 ,the spacecraft weigh #ajjj-abjj pounds1 have a #bhj-pound recoverable capsule and1 while in orbit1 will not experience greater than #a_/aj #jjj g of acceleration4 ,the life-support system will provide an environment at sea-level pressure of #hj percent nitrogen1 #bj percent oxygen1 and no more than #j4e percent carbon dioxide with a temperature of #ge ,f #e ,f4 ,all experiments are in various stages of development or testing and flight test hardware has been and is being constructed4 ,the experiments and hardware are being subjected to preflight tests simulating launch and recovery stresses4 ,rhesus1 pigtail1 and squirrel monkeys have been subjected to the dynamic forces of the simulated flight under conditions of complete1 partial1 and no restraint4 ,three types of centrifuges have been used to simulate the flight profile4 ,primates were fully instrumented with deep brain electrode implants1 implanted catheters1 and other implanted sensors4 ,during centrifugation1 motion pictures were taken4 ,these primates were semirestrained in form-fitted couches which allowed movement of the body while facing the accelerative force in a ventrodorsal position 7eyeballs in74 ,in this series of tests1 all primates were normal following the tests and exhibited no unusual behavior or effects4 ,x-rays showed that implanted catheters and electrodes remained in place1 and there were no movements causing tissue damage4 ,however1 when the primates were placed with their backs toward the accelerative force1 dorsoventral 7eyeballs out71 the animals suffered visible damage4 ,at #f g there was no visible stress1 but at #h g swelling of the lower eyelids was noticeable4 ,at #aa g both eyelids were swollen shut4 ,in the biosatellite program1 primates will be placed in the semirestraint couches in a position facing accelerative forces1 ventrodorsal 7eyeballs in71 to prevent these effects4 chapter #g ,manned ,space ,flight ,,bioregenerative ,,life-,,support ,,systems ,placing a man in space requires a complete life-support system capable of supplying sufficient oxygen1 food1 and water and removing excess carbon dioxide1 water vapor1 and human body wastes4 ,in addition1 the oxygen1 carbon dioxide1 and pressure must be maintained at a suitable level4 ,any accumulated toxic products and noxious odors must be removed4 ,in the spacecraft the human is confined in a restricted environment in which it is necessary to establish a balanced microcosm or closed ecological system4 ,this is an enormous biological and bioengineering problem4 ,weight1 size1 simplicity of operation1 and reliability particularly are important factors4 ,for relatively short missions involving one or several astronauts1 food1 oxygen1 and water can be stored and made available as required1 and the various waste products can be stored4 ,on longer missions1 particularly those involving more than one astronaut1 efficient chemical or biological regenerative systems will be required4 ,any regenerative system introduces a fixed cost in weight of processing equipment and energy requirements4 ,chemical1 or partially regenerative1 methods for providing breathing oxygen by the regeneration of metabolic products such as water vapor and carbon dioxide include the thermal decomposition of water and ,,co1 photolysis and radiolysis of water1 electrolysis of fused carbonates and aqueous solutions1 and the chemical reduction of ,,co with ,h1 followed by electrolysis of the water formed4 ,chemical regenerative systems have been developed to remove excess carbon dioxide and water vapor from the atmosphere4 ,nonbiological regenerative systems are time limited by the amount of food1 water1 and oxygen that can be carried or recovered4 ,these physical-chemical processes show great potential1 but they also present many difficulties1 including requirements for extremely high temperatures and considerable amounts of power1 the formation of highly toxic materials1 and high susceptibility to inactivation4 ,none of the presently studied nonbiological processes can function as completely as a bioregenerative system4 ,all these nonbiological systems have unrealistic supply requirements and produce unusable wastes4 ,consequently1 for long planetary missions the bioregenerative systems1 though also beset with problems1 are potentially far superior to their physical and chemical counterparts4 ,table ,,viii shows average daily metabolic data for a #gj-kg astronaut4 ,a man breathes about #aj cubic feet of air per minute1 or #djj #jjj liters1 daily4 ,the expired air contains about #d percent carbon dioxide4 ,man normally breathes air containing #j4jc percent ,,co1 but can withstand comfortably about #a4e percent ,,co4 ,anything in excess of #a4e percent will produce labored breathing1 headaches1 and1 if greatly exceeded1 death4 ,a man exhales about #a4a pounds of water per day and this1 in addition to water from perspiration and other sources1 must be removed from the air4 ,table ,,viii4--,average ,daily ,metabolic ,data for a #gj-kg1 #be-,year-,old ,astronaut ,with ,normal ,spacecrew ,activity ,from ref4#agc ---------------------------------------- ------------------------- ,o input1 kg #j4hfb ---------------------------------------- ------------------------- ,,co output1 kg #a4jef ---------------------------------------- ------------------------- ,drinking water1 liters #b4e ---------------------------------------- ------------------------- ,food rehydrating water1 liters #a ---------------------------------------- ------------------------- ,caloric value of food1 kcal #cjjj ---------------------------------------- ------------------------- ,water output3 ---------------------------------------- ------------------------- ,urine1 liters #a4f ---------------------------------------- ------------------------- ,respiration and perspiration1 liters #b4ac ---------------------------------------- ------------------------- ,feces1 kg #j4ji ---------------------------------------- ------------------------- ,total heat output1 ,btu #aa #ajj ---------------------------------------- ------------------------- ,two types of biological regenerative systems have been proposed4 ,the photosynthetic closed ecological system was proposed as early as #aiea4 ,this involves the use of single-celled algae or higher plants1 including floating aquatic and terrestrial plants1 and requires the interaction of light energy with ,,co and ,h,o to produce ,o and plant cells4 ,another system1 proposed in #aifa1 involves electrolysis of water into oxygen and hydrogen1 and the concurrent use of ,hydrogenomonas bacteria which take up hydrogen1 some oxygen1 carbon dioxide1 and urine yielding water and bacterial cells4 ,table ,,ix4--,requirements for ,regenerative ,life-,support ,systems ---------------------------------------- ----------------------------- ,requirements _/ ,requirements _/ #a man #c men 7#bgj man-day ,system mission7 --------------------------------------- ,weight1 ,power1 ,weight1 ,power1 kg k,w kg k,w ---------------------------------------- ----------------------------- ,partial chemoregenerative #ccb #a4ge ---------------------------------------- ----------------------------- ,li,o,h #abe #a4dj ---------------------------------------- ----------------------------- ,na,o,h #aee #g4fh ---------------------------------------- ----------------------------- ,,co-,h #cd 4#cf ---------------------------------------- ----------------------------- ,full bioregenerative--algae3 ---------------------------------------- ----------------------------- ,artificial illumination #aaf #aj4dj #eia #be4jj ---------------------------------------- ----------------------------- ,solar illumination #ajc #a4gj #cef 4#fj ---------------------------------------- ----------------------------- ,electrolysis-hydrogenomonas #ee 4#be #abi #b4fj ---------------------------------------- ----------------------------- ,from ref4#agd4 ,from ref4#age4 ,from ref4#agf4 ,includes instrumentation and food storage4 ,the values given in table ,,ix indicate relative weights and powers required by various systems to provide the gaseous environment for manned space cabins4 ,if one considers operating temperatures and hazards1 other systems may offer advantages which offset the weight and power advantages of the hydrogen reduction of ,li,o,h systems4 ,research is being conducted by ,,nasa on life-support-system technology applicable to missions planned for #bj years in the future4 ,life-support systems include the requirements for supplying breathing gases1 control of contaminants in the cabin atmosphere1 water reclamation1 food supply1 and personal hygiene4 ,the disciplines involved in such systems include biology and microbiology1 cryogenic fluid handling at zero g1 heat transfer1 and thermal integration with other systems1 such as power4 ,the physiological1 psychological1 and sociological problems of the crew are also being considered4 ,photosynthetic ,system ,green plants contain chlorophyll which captures light energy thermodynamically required to convert carbon dioxide and water into carbohydrate which can subsequently be transformed into other foods such as protein and fat4 ,during this process1 carbon dioxide is consumed1 and an approximately equal amount of oxygen gas is liberated4 ,as a first approximation1 photosynthesis is the reverse of the oxidative metabolism of animal life3 ,oxidation ,c,h,o #f,o -------------- #f;,,co #f;,h,o heat ,photosynthesis #f;,,co #f;,h,o light -------------- ,c,h,o #f,o ,the photosynthetic process in plants and respiration during photosynthesis have been studied intensively1 and several metabolic pathways have been elucidated4 ,mechanisms are being studied to explain the inhibitory effect of strong visible light on this process4 ,this program may lead to the use of chloroplasts or chlorophyll without cells in future photosynthetic bioregenerative systems for long-term space travel4 ,one of the prime considerations of a closed ecological system is that the environmental gases shall remain physiologically tolerable to all of the ecologic components4 ,ideally1 a photosynthetic gas exchange organism should possess a high ratio of gas exchange to total mass 7considering all equipment and material incidental to growth1 harvesting1 processing1 and utilization72 and a controllable assimilation rate to maintain steady-state gas composition4 ,it should also be 7#a7 amenable to confining quarters which may be imposed by inflexibility of rocket or space station design2 7#b7 genetically and physiologically stable and highly resistant to anticipated stresses2 7#c7 edible and capable of supplying most or all human nutritional requirements2 7#d7 capable of utilizing raw or appropriately treated organic wastes2 and 7#e7 amenable to water recycling as demanded by other components of the ecosystem4 ,higher ,plants ,efforts to utilize multicellular plants as photosynthetic gas exchangers have been somewhat neglected1 since it has been assumed by many that algae would be more efficient4 ,the family ,lemnaceae 7duckweeds7 are small primitive aquatic plants with a minimum of tissue differentiation4 ,practically all of the cells of the plant contain chlorophyll and are capable of photosynthetic activity4 ,they reproduce principally by asexual budding of parent leaflike fronds4 ,they can be grown readily on moist surfaces 7ref4#agg7 on almost any medium suitable for the growth of autotrophic plants4 ,with duckweeds the problems of gaseous exchange and harvesting are simplified and the volume of medium can be greatly decreased as compared with algae4 ,ney 7ref4#agg7 obtained a very high gas exchange rate with duckweeds4 ,using small cultures under controlled optimal conditions of temperature1 light 7#fjj-ajjj ft-c71 and ,,co1 concentration1 he estimated that #b4c m of frondal surface of duckweed1 at a gas exchange rate of #aj4h liters m_/hr would provide sufficient gas exchange for one man4 ,this would produce about #be grams of dry plant material per hour4 ,a few nutritional studies have been carried out with duckweeds4 ,nakamura 7ref4#agh7 considered ,wolffia as a possible source of food for space travel and found that it contained carbohydrate #be-fj percent1 protein #h-aj percent1 fat #ah-bj percent1 minerals #f-h percent 7all dry weights71 and vitamins ,b1 ,b1 and ,c1 with ,c the most abundant4 ,one of the desirable features of a duckweed system is that the gas exchange is direct between the atmosphere and the plant and does not require dissolving the respiratory gases in a bulky fluid system which introduces special engineering difficulties in zero- or low-gravity conditions4 ,in the design of equipment for photosynthetic studies1 careful consideration should be given to the material used in the construction of the unit4 ,most plastic materials are subject to photo-oxidative degradation1 with ,,co as one of the products4 ,when air is recirculated through plastic tubing and transparent rigid plastics in the presence of light1 considerable quantities of ,,co are given off4 ,with high-intensity illumination such as sunlight1 a ,,co buildup of several hundred parts per million is not uncommon4 ,also1 plant pigments such as the carotenoids and chlorophylls will react similarly when exposed to light of high intensity4 ,if the plants die1 then ,,co is released quite rapidly4 ,at ,colorado ,state ,university the responses of plants to high-intensity radiation 7ultraviolet to infrared7 are being studied4 ,plants from high mountaintops that are exposed to greater ultraviolet light are being studied for specialized adaptations4 ,the effect of temperature on photosynthesis is being explored4 ,various plants are also being studied under germ-free conditions4 ,screening of higher plants for possible use in bioregenerative systems at ,connecticut ,agriculture ,experiment ,station resulted in the selection of corn1 sugarcane1 and sunflower4 ,under optimal conditions it has been shown that #ajj to #acj ft of leaf surface are required to support an astronaut4 ,plants considered as possible food sources include soybeans1 peanuts1 rice1 and tomatoes1 which can be combined with algae to give a well-balanced and reasonably varied diet4 ,hydroponic systems use large quantities of water1 but progress is being made in reducing this4 ,the possibility of using animals in the closed ecological system is open to question1 particularly in the absence of gravity1 and much work remains to be done on using plant materials as animal food and on the disposal of wastes4 ,animals which have been considered are crustaceans1 fish1 chickens1 rabbits1 and goats4 ,algae ,algae have the fastest growth rate and are among the most efficient plants for oxygen and food production4 ,it has been amply demonstrated by ,myers 7ref4#agi7 and other workers that ,chlorella can be used in a closed ecological system to maintain animals such as mice and a monkey4 ,the use of algae for supplying ,o and food1 and for removing ,,co and odors has been considered by many authors for use in spacecraft1 space platforms1 and for establishing bases on the ,moon or ,mars4 ,estimates of total efficiency are based on extrapolated laboratory data and vary widely1 since many different types of data have been used as a basis for these estimates4 ,the respired air containing about #d-e percent ,,co is bubbled into the ,chlorella culture1 at either atmospheric or increased pressure4 ,air containing a high percentage of oxygen and saturated with moisture is released from the algal system4 ,the use of algae for several purposes might require from one to three separate algal systems4 ,for food production1 ,chlorella produces #ej percent protein and #ej percent lipids in high-nitrogen media4 ,in low-nitrogen media1 it produces #he percent lipids4 ,proper choice of ,chlorella strains and media will produce not only the necessary calories but also the necessary specific nutrients required4 ,certain strains are more effective in ,o production1 and others in the use of urine and other wastes4 ,some of the early estimates1 using ,chlorella grown at #be ,c1 for supplying these requirements for a single man in space include the following3 #afh kg of algal suspension 7ref4#agi71 #bjj kg of algal suspension and #ej kg of equipment including pumps 7refs4 ref4#ahj and ref4#aha71 and #ajj kg of algal suspension and #ej cubic feet for equipment and gas exchange 7ref4#ahb74 ,using the blue-green alga ,synechocystis1 #fjj kg of algal suspension would be required1 according to ,gafford and ,craft4 ,these estimates are based on preliminary studies1 are quite high1 and are not of real practical value4 ,other studies have indicated an extremely efficient algal system which offers a real potential for a practical and effective gas exchanger 7ref4#ahc74 ,a thermophilic strain of ,chlorella with an optimum growth temperature of #ci ,c and an optimum temperature for photosynthesis of about #dj ,c can increase its cell mass #aj #jjj-;fold per day4 ,when operating at one-half maximum efficiency1 this alga produces #ajj times its cell volume of oxygen per hour4 ,burk et al4 7ref4#ahc7 state3 ,future engineering development should lead to a space requirement1 per adult person1 of no more than #c to #e cubic feet of algal culture1 equipment1 and instrumentation for adequate purification of air4 ,the requirements of this system would require additional energy in the form of light and of small amounts of nitrogenous and mineral material for the algae4 ,the light source used by ,burk et al4 7ref4#ahc7 is a tungsten filament quartz lamp the size of a pencil1 which has a long life1 produces a luminous flux #e-aj times greater than sunlight on ,earth1 and operates at a #aj-ab percent light efficiency4 ,research is being carried out on algal regenerative systems by about #dj or #ej laboratories in the ,united ,states4 ,,nasa is supporting several basic studies on photosynthesis1 the physiology of algae1 and engineering pilot-plant development4 ,much of the research on algae is being supported by the ,air ,force4 ,most algal studies have been carried out in small units and the data obtained have been used as a basis for extrapolating logistic values for the use of these organisms in manned space vehicles4 ,myers 7ref4#agi7 has shown that the quantity of algae necessary to support a man 7with an assumed ,o requirement of #fbe liters per day7 would yield about #fjj-gjj grams dry weight of new cells per day4 ,if algal growth in mass cultures could be maintained in a steady-state concentration of #b4e gram dry weight per liter with such a growth rate as to yield #aj grams weight per liter per day1 the volume of algal culture would be #fj-gj liters and the total mass of the system would approximate #bjj-bej pounds4 ,using an #h-liter system1 ,ward et al4 7ref4#agf7 have produced algal concentrations of #e-g grams of dry algae per liter with a high-temperature algal strain4 ,the maximum growth rate observed with the culture was #j4cge gram dry weight per liter per hour1 or #i grams dry weight per liter per day4 ,this was accomplished by using #a-;centimeter layers of culture and a light intensity of #hjjj foot-candles4 ,the culture system consisted of a rectangular plastic chamber having an area of #j4e square meter and illuminated on each side to an intensity of #djjj foot-candles 7cool-white74 ,to produce #be liters of oxygen per hour1 an area of #h4c square meters 7#he square feet7 would be required4 ,the major problem in large-scale production of algae is that of illumination4 ,conversion of electricity to light has an efficiency of only #aj to #bj percent4 ,in addition1 the maximum efficiency of light utilization by ,chlorella algae lies in the range of #ah-bb percent4 ,this results in a maximum efficiency of only #d percent for photosynthetic systems4 ,another problem involved in conversion of electricity to light is the production of heat which has to be removed even with thermophilic algae4 ,with a human demand of #fjj liters of oxygen per day1 the minimum electrical requirement becomes #d k,w4 ,no large-scale culture has yet been managed at anything close to this minimum figure4 ,another problem is the poor penetration of light into concentrated cultures of algae4 ,this necessitates construction of large tanks of only about -inch thickness4 ,this results frequently in fouling of the surfaces of the tank by algae and makes the removal of the excess algae difficult4 ,production of #a liter of oxygen results in the production of #a gram dry weight of algae4 ,although a small amount of ,,co is produced by some algae1 it can probably be removed by catalytic oxidation4 ,other problems include mutation and genetic drift of the algae and the necessity for maintaining bacteria-free cultures4 ,there are also difficulties in maintaining a sterile culture if urine is to be used as a nitrogen source4 ,while there is a potential for using algae as food1 more research is required before it can be determined what quantity and methods of processing can be used4 ,research and development on algae is much greater than on both the higher plants and the electrolysis-,hydrogenomonas systems together4 ,the difference between the photosynthetic and electrolysis-chemosynthetic systems is the way electrical energy is made available to the organisms4 ,in the photosynthetic system1 electrical energy is converted to light which the algae or plants transform into chemical energy4 ,in the chemosynthetic process1 electrical energy is transformed into the chemical energy of hydrogen gas which is used by the bacteria4 ,both organisms use the chemical energy available to them to synthesize cell material with similar degrees of efficiency4 ,the problem is to make the conversion of electricity to available chemical energy as efficient as possible4 ,in photosynthetic systems much energy is lost in the conversion of electricity to light1 a process only #aj-bj percent efficient at best4 ,when this is combined with the loss from the inefficient use of light by plants1 an overall efficiency of about #d percent is obtained4 ,in the electrolysis-,hydrogenomonas system1 the two steps are very efficient4 ,electrolysis cells can operate at up to #he percent efficiency and the overall efficiency can be up to seven times that of a photosynthetic system4 ,,electrolysis-,,hydrogenomonas ,,system ,electrolysis is carried out in a closed unit containing an electrolyte 7,,koh solution7 with an anode and a cathode4 ,these cells produce a maximum yield 7#fj-hj percent or more7 in gas production per unit of power consumption4 ,according to ,dole and ,tamplin 7ref4#ahd71 a unit capable of producing enough oxygen to sustain one man would be highly reliable1 weigh approximately #ah kg1 and require a power input of #j4be k,w4 ,one approach to zero-gravity operation is to rotate the electrolysis cell as described by ,clifford and ,mc,callum 7ref4#ahe7 and ,clifford and ,faust 7ref4#ahf74 ,the smallest known electrolysis cell under development uses this artificial gravity to separate oxygen from the anode and electrolyte1 while the dry hydrogen gas permeates through the foil cathode1 fabricated from palladium-silver alloy4 ,this electrolysis cell1 which would provide breathing oxygen for three men1 has a volume of #a4d liters1 weighs #d4e kg1 and requires #j4fg k,w1 excluding auxiliary equipment1 and has an efficiency of #hd percent4 ,the chemosynthetic conversion is carried out by the hydrogen bacteria4 ,by the oxidation of molecular hydrogen1 supplied from the electrolysis of water1 energy is made available for biosynthesis4 ,the generation of this biological energy is mediated by the stable enzyme hydrogenase which is present in the bacteria4 ,on the average1 the oxidation of #d moles of ,h is required for the conversion of #a mole of ,,co 7the hourly production of a man74 ,the removal of this amount of ,,co would thus require the cleavage of #d moles of water4 ,in addition1 to supply oxygen for human respiration 7at a rate of #a mole of ,o per hour7 the cleavage of two additional moles of water is required4 ,therefore1 the chemosynthetic regeneration and human respiration together would require1 on the average1 the splitting of #f moles of water per hour4 ,the material balance for electrolysis1 biosynthesis1 and human metabolism1 with gram molecular weights in parentheses1 are shown in equations 7#a7 to 7#c71 respectively3 #f;,h,o -------------- #c,o #f;,h 7#ajh7 -------------- 7#if7 7#ab7 7#a7 ,the bacterial synthesis requires #f moles of ,h1 #b moles of ,o1 and #a mole of ,,co 7from the astronaut71 as shown in equation #b3 #f;,h #b,o ,,co -------------- ,,ch,o #e;,h,o 7#ab7 7#fd7 7#dd7 -------------- 7#cj7 7#ij7 7#b7 ,the respiration of the astronaut requires #a food mole 7,,ch,o7 representing about #abj kcal1 and #a mole of ,o1 as shown in equation #c3 ,,ch,o ,o -------------- ,,co ,h,o 7#cj7 7#cb7 -------------- 7#dd7 7#ah7 7#c7 ,the metabolic data in table ,,viii show that the ,,co of the astronaut and the bacteria must balance at about #a4jef kg per day4 ,the water relations are not completely balanced1 but are fairly close4 ,about #b4f liters per day of water are split by electrolysis4 ,the astronaut has an intake of #c4e liters of water per day1 #b4e liters for drinking and #a liter for preparing dehydrated food4 ,the output is about #a4f liters of urine and #b4a liters of water of respiration and perspiration per day1 or a total output of #c4g liters1 with the #j4b-liter excess due mainly to water of metabolism4 ,the bacteria-produced water1 amounting to #b4b liters per day1 and the excess from the astronaut would supply #b4d liters toward balancing the #b4f liters of water electrolyzed4 ,bacterial ,culture ,hydrogen bacteria are characterized by their ability to metabolize and multiply in a strictly inorganic medium1 when supplied with ,h1 ,,co and ,o in required amounts4 ,they can be grown in batch culture or in continuous culture using different methods of supplying entire medium or components on a demand feed system4 ,a medium was developed for batch culture of ,hydrogenomonas eutropha by ,repaske 7ref4#ahg7 with quantitation of a number of components including trace minerals4 ,experiments by ,bongers 7ref4#ahh7 showed that a simplified medium1 using laboratory-grade chemicals1 could be used4 ,a definite requirement was found for magnesium and ferrous iron 7,fe74 ,the optimal growth requirements observed for ,hydrogenomonas eutropha are shown in table ,x4 ,table ,x4--,optimum ,growth ,requirements of ,hydrogenomonas eutropha ---------------------------------------- ----------------- ,culture parameter ,optimum value ---------------------------------------- ----------------- ,cell density1 g 7dry weight7_/liter #aj ---------------------------------------- ----------------- ,temperature1 ,c #ce ---------------------------------------- ----------------- ,pressure1 atm #a ---------------------------------------- ----------------- p,h 7phosphate buffer7 #f4h 7#f4d-h4j7 ---------------------------------------- ----------------- ,h1 percent #ge ---------------------------------------- ----------------- ,o1 percent #ae ---------------------------------------- ----------------- ,,co1 percent #aj ---------------------------------------- ----------------- ,urea ,,co7,,nh71 g_/liter #a ---------------------------------------- ----------------- ,mg,s,o#g;,h,o1 g_/liter #j4a ---------------------------------------- ----------------- ,fe7,,nh77,,so71 g_/liter #j4jjh ---------------------------------------- ----------------- ,the effects of temperatures ranging from #bj to #db4e ,c on the growth rates of ,hydrogenomonas eutropha were studied by ,bongers 7ref4#ahi71 and the optimal temperature was found to be about #ce ,c4 ,experiments at #be and #ce ,c indicated that the efficiency of energy conversion was essentially identical at both temperatures4 ,hydrogenomonas requires1 as part of its substrate1 a mixture of three gases3 hydrogen1 oxygen1 and carbon dioxide4 ,experiments were performed by ,bongers 7ref4#ahi7 to determine the toleration limits of the three gases4 ,growth rates were found to be identical when hydrogen varied from #e to #hj percent4 ,nearly identical growth was obtained when ,,co partial pressures were #e to #fj percent1 being slightly lower at higher partial pressures4 ,the organism was highly sensitive to oxygen concentration4 ,dissolved oxygen concentrations above #j4ac m,m were found to inhibit cell division2 energy utilization was also affected by oxygen concentration4 ,at #j4b m,m oxygen concentration1 the efficiency of energy conversion was approximately half the value observed with #j4je m,m4 ,another parameter of importance is the total volume of suspension which would be required to balance the metabolic needs of one man4 ,the volume of suspension is determined by the conversion capacity of a unit volume4 ,this capacity is a function of the cell concentration2 hence1 the more cells that can be packed in a unit volume of suspension 7and adequately provided with ,h1 ,o1 and ,,co71 the less the volume of suspension required4 ,results of experiments by ,bongers 7refs4 ref4#aij and ref4#aia7 on conversion capacity-density relationships show that the rate of ,,co conversion obtained with suspensions up to approximately #aj grams 7dry weight7 per liter is linear with relation to density4 ,this indicates that the supply of ,h1 ,o1 and ,,co is adequate4 ,upon a further increase in cell concentration1 the conversion rate still increases but not linearly4 ,the highest amount of ,,co taken up per liter of suspension was approximately #b liters per hour4 ,at these very high cell concentrations1 the relationship between rate of conversion and density is no longer linear4 ,this is demonstrated when the conversion rate is calculated per unit cell weight instead of per unit suspension volume4 ,the rate per gram dry weight per liter decreases from #adf to #fh ml of ,,co per hour4 ,with a suspension at a density of approximately #aj grams1 the conversion of #a4a liters of ,,co per liter per hour is obtained4 ,at a ,,co output of #bb liters per man per hour1 #bj liters of suspension would be sufficient to balance the gas exchange needs of one man4 ,at higher cell concentrations1 less volume of suspension would suffice if gas equilibration could be maintained at the higher consumption rates to avoid anaerobic conditions which could lead to a shift in metabolism4 ,in the final analysis1 the technical problem of gas transfer from the gas to the liquid phase determines the optimal cell concentration and1 therefore1 the required suspension volume4 ,from data presently available1 it can be concluded that1 using the slow-growing ,h4 facilis1 the volume of suspension required to support one man is about #ejj liters4 ,using ,h4 eutropha1 ,schlegel 7ref4#aib7 calculated a suspension volume of #ff liters with #a gram dry weight of bacteria per liter4 ,in recent ,,nasa-supported research1 the amount of culture medium has been estimated using improved cultivation methods and conditions4 ,for batch culture1 the data show that from #aj to #ff liters would be required per man1 with a best practical estimate of #bj liters at #i to #aj grams dry weight of bacteria per liter 7ref4#aia74 ,for continuous culture using the turbidostat1 the present data indicate a demand for some #cj liters of suspension1 and a volume of #bj liters 7at approximately #aj grams dry weight of bacteria per liter7 as a realistic goal4 ,in the foregoing section1 the material balance for gases and water was discussed4 ,it was shown that a close match could be obtained with these components of the closed environment4 ,less abundant1 though no less important1 are the nonwater components of urine and feces4 ,the urine is important for the content of fixed nitrogen and other products of man's metabolism and serves as a very effective substrate for cultivation of hydrogen bacteria4 ,maximum closure of the system necessitates utilization of the urea in urine as a nitrogen source4 ,the average man produces #a4b to #a4f liters of urine per #bd-;hour period4 ,this contains about #j4jjjje gram per liter of iron1 #j4aac gram per liter of magnesium1 and #bd4e grams per liter of urea 7ref4#aic74 ,as shown in table ,x1 each liter of bacterial medium requires #j4jjh gram per liter of ,fe7,,nh77,,so71 about #j4a gram of ,mg,s,o#g;,h,o1 and #a4j gram per liter of urea4 ,in comparing the daily urine output with the estimated required ingredients of a bacterial medium1 a relatively close balance is observed1 with the exception of iron4 ,for the fixation of #bd moles of ,,co 7#bhh grams of ,c7 produced per man per day1 the production of about #fdj grams dry bacterial mass is required4 ,at an average ,n-content of #ab percent1 the nitrogen requirement would be some #ajj grams4 ,a comparison of daily output 7urine7 and daily requirement by the bacterial suspension reveals that only #aj to #cc percent of this amount could be recovered from average urine4 ,to obtain a material balance1 either the man must be fed a protein-rich diet or the bacterial suspension must be grown under conditions which lead to the production of a cell mass relatively low in protein content4 ,experiments have indicated that nitrogen starvation of the bacterial culture might be a promising solution4 ,culture staging 7cultivation under nitrogen-rich conditions1 followed by cultivation in the absence of substrate nitrogen and subsequent harvesting for food processing7 will probably be the most promising means of nitrogen economy in the closed environment4 ,as discussed in a following section1 a biomass of relatively high lipid content can be obtained under conditions of nitrogen starvation4 ,continuous ,culture of ,hydrogenomonas ,bacteria ,growth of hydrogen bacteria in a batch culture1 after an initial period of adjustment1 becomes steady and rapid during the exponential growth phase4 ,this steady state of growth is temporary and ceases when nutrient substrate or gas concentrations drop to limiting values4 ,for long periods a continual supply of nutrients must be provided4 ,growth then occurs under steady-state conditions for prolonged periods1 and such factors as p,h1 concentration of nutrient1 oxygen1 and metabolic products 7which change during batch culture7 are all maintained constant in continuous culture4 ,two methods can be used for control of continuous cultures3 the turbidostat and the chemostat4 ,in the turbidostat1 regulation of medium input and cell concentration is controlled by optically sensing the turbidity of the culture4 ,the dilution rate varies with the population density of the culture and maintains the density within a narrow range4 ,organisms grow at the maximum rate characteristic of the organism and the conditions4 ,the growth rate can be changed by modifying the nutrient medium1 gas concentration1 or incubation temperature4 ,a disadvantage of the turbidostat is that all nutrient concentrations in the culture chamber are necessarily higher than the minimum1 resulting in inefficient utilization of nutrients4 ,the turbidostat system for continuous culture of ,hydrogenomonas bacteria1 developed by ,battelle ,memorial ,institute 7ref4#aid71 includes electrolysis of water in a separate unit4 ,hydrogen and oxygen are fed separately up to the point of injection into the culture vessel1 and the mixed volume is kept very small to minimize am possibility of explosion4 ,however1 the two gases may be injected simultaneously if there is a demand for both4 ,in the chemostat1 growth of the organisms is limited by maintaining one essential nutrient concentration below optimum4 ,a constant feed of medium1 with one nutrient in limiting concentration and with constant removal of culture at the same rate1 is used to achieve the steady state4 ,the dilution rate is set at an arbitrary value1 and the microbial population is allowed to find its own level4 ,by appropriate setting of the dilution rate1 the growth rate may be held at any desired value from slightly below the maximum possible to nearly zero4 ,this constitutes a self-regulating system and allows selection of a desired growth rate4 ,a combined electrolysis-chemostat method1 developed by ,magna ,corp41 maintained the hydrogen-producing electrode of an electrolysis cell in the bacterial culture4 ,resting cells of ,hydrogenomonas eutropha consumed hydrogen produced at the cathode of an electrolysis cell built into a specially constructed ,warburg flask4 ,attempts to immobilize ,hydrogenomonas cells on a porous conductor were partially successful4 ,this system could lower the volume requirements compared with those for the isolated subsystems4 ,disadvantages of this integrated system include electrolysis of the bacterial medium1 possibly resulting in toxic breakdown products1 and the possible effects of electric power and the ,,koh electrolyte on the bacteria4 ,the main disadvantage of an integrated system would be the disparity between optimal conditions for efficient electrolysis and efficient bacterial conversion1 particularly temperature and p,h1 with the combination possibly resulting in considerably higher power and weight demands4 ,both continuous-culture approaches are being studied with ,,nasa support4 ,the turbidostat offers the greatest potential efficiency in weight and volume1 but uses nutrient materials less efficiently and is more complex4 ,the chemostat is less efficient in weight and volume1 but has greater simplicity and reliability4 ,hydrogenomonas eutropha has been grown in #ae-liter batch cultures and in #b4a-liter continuous cultures4 ,a #bj-liter continuous culture1 sufficient to balance the requirements of a man1 is under development4 ,the potential problem areas in large-scale continuous production of the bacteria include assuring genetic stability1 preventing or controlling bacteriophage and foreign bacterial contamination1 and preventing heterotrophic growth caused by exposure to organic material from the urine4 ,genetics of hydrogen bacteria and phage infection have been studied by ,de,cicco4 ,research on these problems indicates that they are not of major importance1 but cause significant effects and must be eliminated or controlled4 ,bacterial ,composition and ,nutrition ,hydrogenomonas bacteria can be used for at least part of the astronauts' diet4 ,the washed bacteria have a mild taste and are being studied for their total energy content1 protein and lipid digestibility1 and vitamin content4 ,carbon and nitrogen balances1 and respiratory quotient are to be determined in animals fed the bacteria as their sole food source4 ,no toxic constituents have been discovered4 ,sonicated and cooked bacteria1 when fed to white rats as #ab percent of the solids of a nutritionally balanced diet1 were eaten readily and produced no ill effects4 ,net utilization of the protein appears to be somewhat lower than casein and about the same as legume proteins4 ,the composition of ,hydrogenomonas eutropha is shown in table ,,xi4 ,the composition of the bacteria varies with the age and growth phase of the cells and with the medium and gas available4 ,it is possible to modify the growth conditions to grow the type of bacteria desired for nutritive purposes4 ,hydrogenomonas cells contain about #ge percent water4 ,of the dry weight1 about #gd percent is protein1 calculated as #f4be times the nitrogen content4 ,table ,,xi shows the amino acid composition to be comparable with other bacterial proteins1 except for higher tryptophan and methionine values4 ,table ,,xi--,analysis of ,hydrogenomonas eutropha ,cells ,grown in ,continuous ,culture ,from ref4#aid ---------------------------------------- ------------------------- ,constituent ,percent by weight ---------------------------------------- ------------------------- ,moisture #gd4ee ---------------------------------------- ------------------------- ,fat 4#dd ---------------------------------------- ------------------------- ,ash #a4gc ---------------------------------------- ------------------------- ,nitrogen #c4jb 7wet7 ------------------- #aa4hg 7dry7 ---------------------------------------- ------------------------- ,protein 7,n #f4be7 #ah4ij 7wet7 ------------------- #gd4bf 7dry7 ---------------------------------------- ------------------------- ,amino acids 7dry weight7 ---------------------------------------- ------------------------- ,alanine #d4dg ---------------------------------------- ------------------------- ,arginine #c4da ---------------------------------------- ------------------------- ,aspartic acid #d4cb ---------------------------------------- ------------------------- ,cystine 4#jh ---------------------------------------- ------------------------- ,glutamic acid #g4fg ---------------------------------------- ------------------------- ,glycine #b4gf ---------------------------------------- ------------------------- ,histidine 4#ie ---------------------------------------- ------------------------- ,isoleucine #b4ag ---------------------------------------- ------------------------- ,leucine #d4jd ---------------------------------------- ------------------------- ,lysine #b4fe ---------------------------------------- ------------------------- ,methionine #a4ad ---------------------------------------- ------------------------- ,phenylalanine #b4bj ---------------------------------------- ------------------------- ,proline #b4jf ---------------------------------------- ------------------------- ,serine #a4hj ---------------------------------------- ------------------------- ,threonine #b4ae ---------------------------------------- ------------------------- ,tryptophan 4#gh ---------------------------------------- ------------------------- ,tyrosine #a4gi ---------------------------------------- ------------------------- ,valine #c4jc ---------------------------------------- ------------------------- ,trace amounts of the following were also found3 methionine sulfoxide1 citrulline1 alpha-amino-n-butyric acid1 homocitrulline1 glucosamine1 galactosamine1 methionine sulfoximine1 ethionine1 and ethanolamine4 ,the lipid content of rapidly growing cells is normally quite low 7#j4de to #b4c percent crude ether extractable lipids74 ,the most important lipid is poly-beta-hydroxybutyric acid1 which is stored under the growing conditions of insufficient nitrogen or oxygen supply 7refs4 ref4#ahg and ref4#aia74 ,under these conditions1 this unusual polymer constitutes up to #hj percent of the dry weight4 ,while the monomer itself1 beta-hydroxybutyric acid1 is rapidly and efficiently used in cell metabolism1 the nutritive value of the polymer is yet to be determined4 ,the fatty acids found include lauric1 myristic1 palmitic1 palmitoleic1 heptadecaenoic1 ,c#ag saturated7871 stearic1 linoleic1 and linolenic787 7ref4#aie74 ,application to ,spacecraft ,system ,a bioregenerative life-support system will be required in long manned space flight1 especially with several astronauts such as would be required for a manned mission to ,mars in the #aihj time period4 ,while almost #ae years is a long leadtime1 the biological research and engineering problems are formidable1 and a system would have to be developed at least #e years before the mission4 ,the power and weight requirements for both chemical and biological regenerative life-support systems were presented in table ,,viii4 ,these should be considered tentative best estimates based on present data4 ,the use of bioregenerative systems in spacecraft systems has been studied by ,bongers and ,kok 7ref4#age7 who put the electrolysis-,hydrogenomonas system in proper perspective with the following statement3 ,the bioregenerative systems are more or less in a transitory phase between research and development4 ,the power data can be considered fairly accurate1 at least within #bj percent4 ,the postulated weight data1 however1 represent approximations1 particularly with respect to auxiliary equipment and construction materials4 ,also omitted are the weight penalties most probably involved in the processing of the solid output of the exchangers1 elegantly defined as potential food4 ,further research is required in this area to evaluate the regenerative systems1 especially the bacteria1 with respect to this potential4 ,furthermore1 as yet there is no experimental proof that the growth rates of the heavy bacterial suspensions can be realized in a large design1 determined on a relatively small scale with fairly precise control of physiological conditions and gas exchange4 ,this aspect may affect considerably the weight involved in a chemosynthetic balanced system4 ,nevertheless1 at present1 this approach still seems most promising4 ,,cabin ,,atmospheres ,includes part of ref4#aif4 ,in the first ,u4,s4 manned space flight program1 ,project ,mercury1 and in the face of very severe weight limitations1 a cabin atmosphere of pure oxygen at one-third atmospheric pressure was adopted4 ,this choice probably represented the greatest simplification which could be achieved readily and1 at the same time1 provide protection against some of the risks of rapid decompression4 ,although breathing pure oxygen at higher pressures was known to be attended by some undesirable physiological effects1 the short duration of the flights to be undertaken1 and the low pressure employed1 suggested that no harmful results would result in this case4 ,that these expectations were generally borne out is now history4 ,preparations for space flights of longer duration--many weeks or months--present similar problems and require special attention to phenomena which may be either undetectable or of trivial significance on a time scale of a few days4 ,physiological ,criteria in the ,choice of ,cabin ,atmosphere ,if maintenance of normal respiratory function were the only consideration1 a cabin atmosphere of about sea-level composition and pressure might be an ideal and straightforward choice for manned spacecraft4 ,in fact1 this atmosphere has been used in the manned space flights conducted by the ,u4,s4,s4,r4 ,no other atmosphere has been shown to be more satisfactory from the physiological point of view1 and the tedious respiratory studies which should accompany the use of other atmospheres can be avoided4 ,nevertheless1 the formidable problems of spacecraft design and the necessary precautions for safeguarding the crew from accident require that other atmospheric compositions and pressures be considered4 ,for example1 if a cabin at #a-;atm pressure were decompressed to space suit pressure 7#j4c atm71 the occupants would develop decompression sickness2 i4e41 bends4 ,several engineering considerations argue for low cabin pressures and pure oxygen composition4 ,among these are structural design1 weight of atmospheric gas storage and control equipment1 and the difficulty of contriving pressure suits which allow operation at pressures near one atmosphere4 ,such departures from the normal human gaseous environment1 however1 require the demonstration of an acceptable level of safety and physiological performance4 ,the limits of the composition and pressure of acceptable cabin atmospheres are then set by-- 7#a7 ,a pure oxygen atmosphere at a pressure which will provide an alveolar oxygen partial pressure equal to that provided by air at sea level 7#b7 ,a mixed gas 7oxygen and inert gas7 atmosphere having a pressure and composition that will allow decompression to the highest acceptable suit pressure without the risk of bends ,a numerical value for the lower limit 7#a7 is approximately #j4b atm of pure oxygen4 ,the upper limit 7#b7 is determined by the operating pressure and composition of the space-suit atmosphere and may be of the order of #j4e atm for a cabin atmosphere of #ej percent oxygen4 ,it is necessary to determine the astronaut's ability to survive and perform his duties in any atmosphere selected4 ,atelectasis and ,pulmonary ,edema ,localized or diffuse collapse of alveoli in the lungs may1 if the condition persists1 lead to arterial hypoxia which may be extremely undesirable under the stresses of space flight4 ,the alveoli are probably unstable when pure oxygen is breathed2 they tend to collapse if there is blockage of the airways1 especially at low pressures4 ,this collapse occurs because each of the gases present in the alveoli 7oxygen1 water vapor1 and carbon dioxide7 is subject to prompt and complete absorption from the alveoli by the blood4 ,the alveoli are normally stabilized against collapse by the presence of inert and relatively insoluble gas 7nitrogen7 and an internal coating of lipoprotein substances with low surface tension4 ,theoretical and experimental results strongly suggest the desirability of using oxygen-inert gas atmospheres for long missions to avoid atelectasis and other gas absorption phenomena1 such as retraction of the eardrum4 ,however1 further experimental evidence is required both to confirm this point and to establish its upper limit of suitability of pure oxygen atmospheres4 ,at ,ohio ,state ,university in #aifb1 scientists studied the effect on young rats exposed for #bg days to #ajj percent oxygen 7with no nitrogen71 at a reduced barometric pressure equivalent to #cc #jjj feet altitude4 ,the rats showed no difference in growth rate1 oxygen consumption1 food and water intake1 or behavior from control rats in air at #a atm4 ,oxygen ,toxicity ,it has long been known that breathing pure oxygen at normal atmospheric pressure often produces pulmonary irritation and other toxic effects both in man and animals4 ,this knowledge has occasioned concern over the use of pure oxygen atmospheres in spacecraft4 ,the effect of #ajj percent oxygen at a simulated altitude of #bf #jjj feet for #f weeks was studied using white rats at ,oklahoma ,city ,university under a ,,nasa grant4 ,radioactive carbon techniques revealed a #ae-percent reduction of metabolism in the #ajj-percent oxygen-exposed rats1 compared with rats in air at #a atmosphere4 ,there was a #bj-percent decrease in lipid metabolism in the liver compared with controls1 but no decrease in heart metabolism4 ,there was no gross change in body weight4 ,the ,white ,leghorn chick between #b and #g weeks old is markedly resistant to the toxic effects of #a atm of ,o4 ,continuous exposure 7,ohio ,state ,university7 for as long as #d weeks did not cause deaths1 obvious morbidity1 or any signs of pulmonary damage on gross autopsy4 ,nevertheless1 the hyperoxia had some adverse effects1 primarily reducing the growth rate to between three-fourths to one-fourth of normal2 reducing feed intake per unit body weight to three-fourths of normal2 slowing respiratory rate by #cj percent2 decreasing erythrocytes1 hemoglobin1 and hematocrit by #i to #ab percent2 and causing reversible histological changes in the lungs4 ,arterial ,o tensions were elevated over #cjj-mm ,hg1 but arterial p,c,o and blood p,h were unaffected4 ,no residual effects were noted upon return to air breathing4 ,it is possible that the anatomical peculiarities of the avian lung play some role in the chicks' resistance to hyperoxia1 but it is also possible that this resistance is a function of age1 similar to the tolerance shown by the young rat but not the adult4 ,carbon ,dioxide ,tolerance ,studies of ,,co tolerance in submarine crews indicate that no loss of performance is involved if the concentration in air at normal pressure does not exceed #a4e percent with exposures of #cj to #dj days4 ,however1 biochemical adaptive changes were observed at this concentration4 ,inert-,gas ,components ,if other investigations establish the need for an inert gas in manned spacecraft atmospheres1 gases other than nitrogen may be considered4 ,compared with nitrogen1 the physical properties or helium and neon offer advantages with respect to solubility in body fluids1 storage weight1 and thermal properties4 ,studies at ,ohio ,state ,university in #aifd1 under a ,,nasa grant1 showed that helium substituted for nitrogen in a closed container causes humans to feel cold at a normally comfortable temperature4 ,studies with animals have shown that in a helium atmosphere there is greater heat loss due to the increased conducting capacity and probably greater evaporative capacity4 ,in #f days at #ba percent oxygen and #gi percent helium at #a-;atmosphere pressure1 young rats grew at the same rate as controls1 but drank more water1 excreted more urine1 and had a higher rate of food and oxygen consumption than controls in air at #a atmosphere4 ,men are being tested on a bicycle ergometer in saturated and low relative humidity helium atmospheres to study heat balance4 ,mice were exposed to #hj percent argon and #bj percent oxygen continuously at #a-;atmosphere pressure for #ce days at ,oklahoma ,city ,university4 ,carbon #ad studies of metabolism showed a slight slowing and a twofold to threefold increase in fat deposition4 ,bends ,decompression1 whether accidental 7due to damage of the spacecraft7 or intentional 7as in the use of the pressure suit outside the capsule71 carries the risk of bends if the inert gases dissolved in the tissues and body fluids come out of solution4 ,the magnitude of this risk is determined to a very considerable extent by-- 7#a7 ,individual susceptibility 7#b7 ,the extent to which the nitrogen 7or other inert gas7 concentrations of tissues and body fluids have been reduced 7#c7 ,the magnitude and rate of the inert-gas1 partial pressure change on decompression ,the probability of getting bends is reduced by-- 7#a7 ,selection of bends-resistant individuals 7#b7 ,thorough denitrogenation before flight 7#c7 ,limitation of decompressive pressure changes by appropriate choice of cabin atmosphere pressure and composition 7#d7 ,space-suit pressure setting ,in some cases1 further improvements might be obtained by using1 in the cabin atmosphere1 an inert-gas component which has a lower solubility in tissue and body fluids or less tendency than nitrogen to form bubbles4 ,fire ,hazard ,experience indicates that fires in pure oxygen atmospheres1 even at low pressures 7e4g41 #a_/c atm71 are extremely difficult to extinguish4 ,while this phenomenon has nothing to do with respiratory physiology1 the risk on flights of long duration may be so serious as to demand special measures4 ,unless effective countermeasures can be devised1 this risk may argue very strongly against the use of such atmospheres in the future4 ,further experimental investigation is required4 ,acceleration ,effects on the ,lungs and ,pulmonary ,circulation ,forces produced by high acceleration overdistend one part and compress another part of the lungs4 ,blood flow diminishes in some parts of the lungs and increases in others4 ,fluid leaks from the blood into the tissues and into the air sacs in parts of the lungs4 ,these effects cause difficulty in breathing1 low arterial oxygen saturation1 and impaired consciousness during high sustained acceleration and1 to a lesser extent1 after its cessation4 ,they must be considered when selecting the best gas to be breathed1 since a high partial pressure of oxygen is favorable for consciousness1 but a low inert-gas concentration during acceleration is unfavorable for rapid lung recovery afterward4 ,,physiological ,,problems ,a study of the manned space flights and laboratory observations to date suggests that during long periods of weightlessness1 some physiological difficulties may arise which may produce serious effects on human performance4 ,although recent experience gives no grounds for expecting insuperable difficulties1 neither the quantity nor quality of the available observations permits the conclusion that long-term exposure to weightlessness will not have serious consequences4 ,the critical role to be played by the astronaut demands that every effort be made to identify in advance those phenomena which may affect performance1 and to study their qualitative and quantitative relationships so that proper precautions can be taken4 ,lawton 7ref4#aig71 in reviewing the literature on prolonged weightlessness1 found few instances in which physiological function was truly gravity dependent4 ,he stated that the physiological systems likely to be most affected by weightlessness were the musculoskeletal system1 the cardiovascular system1 and the equilibrium senses4 ,subsequent experience proved this to be the case4 ,mc,cally and ,lawton 7ref4#aih7 analyzed the data from experiments since #aifa and concluded that much more basic laboratory work is necessary4 ,studies using immobilization1 immersion1 and cabin-confinement techniques were recommended approaches toward simulating weightlessness4 ,much of the difficulty in obtaining precise information of anticipated problems arises from a lack of knowledge of normal mammalian physiology4 ,many of these deficiencies can be remedied in the laboratory4 ,in space-flight development1 however1 two distinct investigational approaches can be adopted4 ,the first of these may be characterized as empirical and incremental2 that is1 the capabilities of the astronaut are explored in successive flights involving relatively modest increases in difficulty or severity of the environmental conditions4 ,in this way it is hoped to ascertain the human limitations without running too great a risk4 ,the second approach can be described as fundamental3 determining by a series of controlled experiments the effects of exposure to space-flight conditions upon comparative mammalian physiology1 with emphasis on man4 ,a fundamental understanding of the observed effects would be sought so that predictions for new situations and possible ways to control them could be made with confidence4 ,it is not possible now to predict for flights of #cj days or more-- 7#a7 ,the effects of sudden reimposition of reentry accelerations and terrestrial gravity 7#b7 ,changes in body fluid distribution and composition 7#c7 ,the effects of violent physical effort on respiratory and cardiovascular systems in prolonged weightlessness 7#d7 ,central nervous system functions1 especially coordination1 skilled motor performance1 judgment1 and sleep-wakefulness cycles ,,nasa has emphasized that planning for manned space programs involves a systematic extension from physiological observations in animals to man1 and finally the establishment of man as part of the man-vehicle system design4 ,moreover1 these studies require the evaluation of central nervous1 cardiovascular1 respiratory1 gastrointestinal1 and other systems as a matrix in mutual interdependence4 ,there is particular interest in the effects of weightlessness on flights exceeding #cj days4 ,mammalian flights of about #cj days also merit attention1 including the development of the life-support systems which must precede such a program4 ,development of facilities for biological experiments may well be an important requirement for studies in anticipation of manned flights of longer duration than ,apollo4 ,unless the biological satellite programs of the type mentioned above are successful in providing the necessary data1 a manned orbiting laboratory may also be important in studies of shorter range4 ,general ,studies of ,biological ,rhythmicity ,the effects of weightlessness on the organism as a whole may be manifested by important changes in certain integrated behavioral patterns having an inherently rhythmic character4 ,modifications in basic behavioral patterns and performance may occur as disruptions of rhythmic physiological phenomena1 which are themselves the end product of interrelated functional activity in a number of physiological systems1 such as the neuroendocrine1 cardiovascular1 and central nervous systems4 ,measurements of interdependent components of biological rhythmicity are beginning to be analyzed by methods well established in physics--including correlation and spectral analyses1 and phase modulation and variance in rhythmic processes4 ,a wide variety of physiological functions can be treated as periodic variables in the analysis1 including rhythmicities in cardiac output and blood pressure1 respiration1 brain waves1 and the slower tides of appetite1 and sleep-wakefulness4 ,the importance of such investigations argues for their inclusion in forthcoming flight programs4 ,their experimental simplicity is an additional advantage4 ,biorhythms have been discussed in more detail in the section on ,environmental ,biology4 ,effects of ,weightlessness on the ,cardiovascular ,system ,earlobe oximetry1 indirect measurements of blood flow and of blood pressure by finger plethysmography or impedance plethysmography1 and ballistocardiographic techniques have potential application to manned space flight4 ,adaptation to prolonged exposure to weightlessness or to lunar gravity may cause difficulties when the astronaut is exposed again to reentry forces and terrestrial gravity4 ,it is possible that these adaptive changes may thus produce unacceptable effects on performance or cause risk to life4 ,it is important to obtain experimental evidence on this subject4 ,it is common knowledge that following a stay in bed1 dizziness1 faintness1 and weakness characterize arising1 and that a feeling of general weakness may persist for several days4 ,the phenomenon has been investigated in a number of laboratories4 ,one approach has been to put healthy young subjects to bed1 and even in extensive casts for periods of #b or #c weeks or more4 ,two major findings have emerged from these studies4 ,first1 a substantial adjustment in the blood circulatory system occurs1 which is termed the hypodynamic state4 ,second1 there is a large decrease in the skeletal and muscle mass of the body4 ,there are two kinds of evidence for the hypodynamic state3 measurement of parameters of circulatory function1 and measurement of the response of the individuals to a quantitatively imposed mild gravitational load4 ,after #c weeks in bed1 otherwise healthy persons exhibit an increase of more than #bj percent in heart rate2 a reduction of #aj to #bj percent in total blood volume1 primarily as a result of reduction of plasma volume2 and a decrease in heart size of about #h percent4 ,coupled with these cardiovascular changes is a reduction of #aj percent in the basal metabolic rate4 ,it appears as though the circulation and metabolism are reset to a lower functional level commensurate with the reduced demands placed on the whole organism4 ,after #c weeks of bed rest1 all of the subjects tested showed pronounced orthostatic hypotension4 ,after tilting1 the average heart rate increased by #cg beats per minute1 the systolic blood pressure fell some #ab-mm ,hg1 and some of the subjects fainted4 ,the measurements were continued for #af days after the bed-rest period1 and it was round that recovery was not quite complete when the experiment was terminated4 ,there is little question that in prolonged exposures to the weightless state1 there is a fair probability of extensive circulatory adjustments1 the seriousness of which cannot yet be foretold4 ,while it is likely that the astronauts will adapt successfully to long periods of weightlessness at some new circulatory functional level1 the remote possibility exists that the circulatory changes may be progressive to the point of ultimate failure4 ,metabolic ,effects of ,weightlessness ,without metabolic information1 accurate planning of environmental systems for long flights is difficult4 ,importance is also attached to early evaluation of weightlessness effects on body-fluid equilibria4 ,the results of ,earth orbital flights and of terrestrial water-immersion experiments suggest the occurrence of undesirable changes1 although no effects leading to operational incapacity have yet arisen4 ,in both recumbency and immersion1 a similar redistribution of body fluids occurs4 ,it has been suggested that recumbency may affect an extracellular fluid-volume receptor mechanism which by decreasing aldosterone secretion by the adrenal gland1 would decrease sodium reabsorption by the renal tubules4 ,aldosterone excretion decreases during recumbency and during standing in water1 but increases while standing in air4 ,there is also evidence for cardiac atrial volume receptor mechanisms which respond to increased filling of the left atrium with reflex inhibition of release of pituitary antidiuretic hormone 7,,adh71 resulting in diuresis 7,henry-,gauer reflex74 ,altered fluid equilibrium in buoyant states is accompanied by shifts in intracellular and extracellular electrolyte distribution1 especially sodium and potassium4 ,evidence from recumbency studies indicates a strong correlation between loss of erect posture or weight bearing and excretion of calcium stores in bone4 ,a bone ,x-ray densitometry method has been developed by ,mack1 at ,texas ,woman's ,university1 for accurately determining the loss of bone mineral 7#b percent accuracy7 in humans and animals4 ,the heel bone and spine are ,x-rayed using a calibrated aluminum wedge as a standard4 ,this technique will be used for preflight and postflight analysis of the primate being flown in the #cj-;day biosatellite4 ,comparative appraisal of bone mineral behavior in astronauts participating in the ,gemini and ,apollo programs will be invaluable for future flight missions4 ,bed rest and immobilization studies by ,mack have shown loss of skeletal mineral and increased calcium in the urine and excreta4 ,four bed-rest studies1 each extending for #b weeks1 compared different levels of calcium intake4 ,four men were used in each study and served as their own controls during extended ambulatory periods4 ,during #b-week periods1 up to #aj percent of calcium mineral was lost from the heel bone4 ,calcium was also determined in the urine and feces4 ,in other studies1 isometric exercises reduced loss of bone mineral during bed rest4 ,excretion of calcium in the urine is accompanied by risk of its deposition as calculi or kidney stones in the urinary tract4 ,currently1 changes in calcium metabolism resulting from weightlessness over periods up to #b weeks is not considered a hazard requiring precautionary measures4 ,flights in excess of #b weeks1 however1 constitute a problem serious enough to warrant study on the #aa-;day orbital flights and the #cj-;day biosatellite primate mission4 ,therapeutic immobilization1 post-poliomyelitis immobility1 and experimental restraint in normal subjects lead to a negative calcium balance1 with hypercalciuria4 ,central ,nervous ,system ,functions in ,weightlessness ,the wide range of individual tolerances to the disturbing effects of vestibular stimulation has emphasized the importance of this factor in astronaut selection4 ,at the same time1 vestibular functions must be considered jointly with visual task performance1 since both have special significance for such maneuvers as vehicle docking4 ,vestibular function in the weightless state remains almost completely unknown4 ,limited evidence from animal and manned space flights suggests that head turning1 resulting from vestibular stimulation1 may seriously interfere with visuomotor performance1 but that susceptibility to these disturbances is significantly different between individuals and that partial adaptation occurs relatively quickly4 ,,nasa is currently collecting extensive baseline electroencephalogram data under controlled conditions in a form suitable for mathematical analysis4 ,data are being taken from about #bjj subjects in major national and overseas centers4 ,it is intended that this study will assist in astronaut selection and monitoring in space4 ,studies on many effects of weightlessness on nervous functions require monitoring of the autonomic nervous system1 including such autonomic effects as gastrointestinal activity1 secretion1 lacrimation1 salivation1 sweating1 and the central control of respiration4 ,urinary estimations of catecholamines and #e-;hydroxyindoleacetic acid would provide important data on autonomic system activity if collected in flight and compared with preflight and postflight controls4 ,major areas have been outlined in which prolonged weightlessness may be expected to interfere with performance1 judgment1 and1 ultimately1 chances of survival4 ,these include cardiovascular1 metabolic1 central nervous1 psychophysiological1 and biorhythmic effects4 ,they have been dealt with separately and in sequence1 but have not been intended to be viewed as hierarchic4 ,the relative scarcity of data necessarily precludes such an evaluation4 ,soviet experience with zero gravity and weightlessness has increased their emphasis on this space-flight factor and was an important topic at the ,may #aifd ,,cospar meeting4 ,discussion of the postflight medical status of ,bykovsky 7#e-;day flight7 and ,tereshkova 7#c-;day flight7 revealed a concern for the significance of prolonged weightlessness and the presence of postflight physical debility and fatigue following ,vostok flights #c through #f4 ,these changes persisted for several days4 ,among the physiological conditions singled out for mention were-- 7#a7 ,body fluids-- ,cosmonauts have shown a postflight weight loss of #a4i to #b4d kg apparently resulting from a redistribution of body fluid in response to elimination of the hydrostatic pressure gradients caused by ,earth gravity4 ,there is the suggestion that this redistribution is complete within the first #bd hours of flight4 ,titov is reported to have been dehydrated alter his flight with early hemoconcentration4 ,these findings directly support predictions made from ground-based research4 7#b7 ,cardiovascular-- ,postflight orthostatic tachycardia is reported for ,titov as long as #bc hours after landing2 at #dh hours there was significant residual intolerance to the upright posture4 ,cosmonauts have demonstrated a #bj- to #ce-percent increase in oxygen consumption during the standard postflight exercise test4 ,in both of these areas there was a return to normal within the postflight period of study4 ,the ,soviets have continued their biological experiments in space with the ,vostok_/,voshkod series4 ,fixing of histologic specimens in flight by ,bykovsky demonstrated a critical role for man and made possible an expanded experimental program4 ,biopackages have become more complex with each succeeding flight4 ,with the exception of postflight orthostatic intolerance after the third and fourth ,mercury flights1 changes as a result of exposure to a zero-gravity environment have not been noted by ,u4,s4 investigations in space4 ,ground-based research proceeds here at an advanced pace and is supported in large measure by both the ,,usaf and ,,nasa4 ,a study of the relationships among renal and systemic hemodynamics1 neurohumoral cardiovascular regulation1 and renal excretory function in differently positioned subjects is underway1 as are studies of acceleration tolerance4 ,,depressed ,,metabolism ,in anticipation of prolonged manned space flights1 ,,nasa has sponsored research related to metabolism depression4 ,the daily food requirements1 for example1 of astronauts during a voyage of several months can constitute a major portion of the weight and storage capacity of the spacecraft4 ,a somewhat promising and fundamental approach to this problem is the reduction of the astronauts' daily metabolic requirements4 ,it has been suggested that astronauts on prolonged space missions be put in a state of suspended animation until their destination is reached4 ,though this sounds fantastic1 #aj years ago no cell had been frozen to cryogenic temperatures and survived4 ,today it is commonplace for tissues to be frozen1 stored at low temperatures1 and thawed and then to maintain their viability and function4 ,animal metabolism may be depressed by reducing body temperature1 as in hibernation and hypothermia4 ,other means by which metabolism can be lowered include drugs and electronarcosis4 ,hibernation is a nonstressful state and results in a great decrease in metabolism4 ,however1 human beings are not hibernators1 and much research is needed before the mechanism of hibernation is understood1 and the possibility of inducing it in humans evaluated4 ,hypothermia is the direct cooling of the body to temperatures where metabolism is substantially depressed4 ,extracorporeal circulation systems combined with cooling are in routine use in most medical centers throughout the world4 ,hypothermia is not an ideal solution1 however1 since general body hypothermia is a stressful condition4 ,pharmacologic induction of hypothermia can be accomplished by such drugs as chlorpromazine and harbamil4 ,other drugs can be used to depress metabolism1 but all have some disadvantage4 ,in recent years there has been a growing interest in electronarcosis1 the induction of sleep by an electric current4 ,although potentially valuable1 this method is far from routine application4 ,outstanding advances have been made in metabolism suppression4 ,recent progress in the biochemistry and physiology of hibernation and hypothermia have shown that the oxygen requirements of individual mammals1 organs1 and tissues can be reduced4 ,when the chemical composition of the blood and the cardiac output are sufficient to meet cellular requirements1 regulatory mechanisms remain effective and animal survival is assured4 ,in contrast1 when oxygen transport is interrupted1 a reduction in cellular activity occurs and regulation is impaired4 ,in induced hypothermia1 the low temperature slows the rates of all processes and modifies the action of metabolites and other substances4 ,this in itself is not harmful1 as shown by the true hibernating animal 7e4g41 ground squirrel71 but will become disastrous as soon as anoxia and chemical imbalance begin to develop4 ,the phenomenon of natural hibernation is being investigated in the laboratory in the hope that the unusual tolerance of hibernating animals to reduced metabolism and low body temperature may some day be produced artificially in ordinary laboratory animals and man4 ,experiments with the ground squirrel1 a typical hibernator1 show that the artificially cooled ground squirrel does not tolerate such long periods of low body temperature as does a naturally hibernating animal4 ,other studies of the brown adipose tissue 7fat71 which is present in most hibernating mammals1 show it to be essential to hibernation4 ,indications that brown fat has a thermogenic role in rats exposed to low temperatures suggest that this may be the case in true hibernators 7ref4#aii74 ,arousal of the hibernating animal by cold is triggered by sympathetically activated thermogenesis in areas of brown fat so located1 relative to the vasculature1 that the heat is transferred to areas of the body concerned with normal metabolic and nervous activity4 ,soviet work comparing various depressed metabolic states and resistances to acceleration shows deep winter hibernation to be most effective1 followed by deep hypothermia1 and drug narcosis as the least effective4 ,experimental evidence is being accumulated to show that hibernation and hypothermia somewhat protect animals against radiation4 ,clinical studies on irradiation of cancer patients indicate that lowering the body temperature reduces cellular metabolism and thus decreases tissue sensitivity to gamma radiation 7ref4#bjj74 ,the use of prolonged hypothermia1 hibernation1 drugs1 and electronarcosis appears to hold some potential for reducing astronauts' metabolic requirements4 ,if one or mote of these methods become practical1 human requirements for food and oxygen could be drastically reduced4 ,simultaneously1 these methods may afford radiation protection and acceleration tolerance4 ,,nutrition ,,in ,,space ,includes part of ref4#bja4 ,see also ref4#bjb4 ,the human body can use food stores so that the nutritional requirements can be reduced for a short time4 ,this will vary widely among individuals and each individual may exhibit characteristic patterns of nutritional behavior4 ,during reduced food intake1 muscular efficiency may not change significantly over a period of #d to #f days2 unfortunately1 however1 mental activity begins to decline after #bd hours4 ,feeding requirements can be divided into two categories3 short term 7for missions of less than #ba days7 and long term4 ,since dehydration can occur in a matter of hours under adverse conditions1 water requirements must be considered as a special case4 ,water ,requirements ,water requirements are extremely critical and the amount supplied should not under any circumstances be kept to a minimum4 ,rather1 a large margin of safety should be allowed4 ,present data on water requirements show a very strong dependence upon suit inlet temperatures4 ,in the absence of an accurately controlled suit temperature1 water requirements can easily double4 ,if this should occur1 the mission would probably have to be aborted1 since it is doubtful if electrolyte balance would be maintained at such high rates of water loss4 ,normal or even extreme conditions of the terrestrial environment usually include diurnal variation in temperature which may modify water needs4 ,these conditions will not be obtained in the spacecraft4 ,in addition to ground-based experiments1 measurements of water intake should be made under actual flight conditions4 ,data from short-term flights should be used for extrapolation to longer missions4 ,formula ,diets ,the tacit assumption which now prevails1 ,astronauts even on short-term missions require a diet of great variety1 is apparently not well supported4 ,in many parts of the world1 people live on a monotonous diet consisting of only a few types of food with no apparent ill effects1 provided their nutritional requirements are satisfied4 ,experimental evidence from many sources 7e4g41 the ,army ,medical ,research and ,nutrition ,laboratory7 shows that individuals can be kept on a single disagreeable formula diet for as long as #fj to #ij days without harm4 ,since highly motivated individuals are chosen for space flights1 it is unlikely that they would object to the monotony of a formula diet and would probably prefer its simplicity4 ,also1 there are definite possibilities of developing a much more acceptable formula than present types4 ,there is no reason to anticipate adverse effects from the use of formula diets in short-term flights4 ,formula diets would be extremely desirable for short-term flights4 ,a formula diet 7a rehydrated liquid formula could be used7 would considerably reduce the number of manipulations and the time required for in-flight preparation1 compared to a varied diet4 ,these two improvements could contribute materially to the safety of a flight1 since the astronauts would not be preoccupied with food preparation for so long a period1 and the food could be dispensed without removing suit components1 such as gloves4 ,storage requirements could be simplified with this type of diet4 ,weight1 however1 would not be lowered without the development of more refined formulas than those now available4 ,formula diets could readily be adapted to the determined metabolic requirements of the individual astronaut4 ,packaging problems will be simplified by using formula diets1 which can easily be given a variety of flavors and colors4 ,waste ,the problem of waste production is intimately related to nutrition and can be solved or simplified by dietary changes4 ,any diet should be adjusted for the minimum production of feces1 before and during even short flights4 ,water will be sequestered by accumulation in the feces1 and the net loss1 under normal conditions1 would be approximately #dj to #fj grams per man per day4 ,flatus can be a serious problem1 since considerable concentrations of toxic gases may accumulate4 ,the purification system for the recirculated atmosphere must be able to remove these1 although the diet should be planned to minimize the problem4 ,the collection of urine and its storage is of importance1 particularly on short-term flights1 and individual packaging and labeling of urine specimens will be necessary for the analyses4 ,metabolism ,an accurately measured intake of nutrients1 calories1 and water is necessary for determining metabolic demands imposed in any space flight4 ,there is insufficient knowledge to predict total metabolic requirements under the numerous stresses which can be anticipated4 ,simulator studies are of great importance even for short-duration flights4 ,the two most important variables to be considered in establishing the minimal diet are protein and energy requirements4 ,,nasa is supporting research at the ,university of ,california 7,berkeley7 to determine these requirements and to estimate individual variation in healthy young men4 ,the possibility of minimizing need through biological adaptation is being explored4 ,it is difficult to estimate the minimum protein requirement of an adult man4 ,the generally accepted criterion of minimum adequate protein nutrition in the adult is the maintenance of nitrogen balance at minimum intake4 ,the minimum protein requirements depend on endogenous nitrogen loss4 ,analysis of the little data available indicates a best estimate of #b mg of nitrogen per kilocalorie of basal energy expenditure4 ,however1 this figure is higher than that noted in experiments in some human subjects4 ,after minimum nitrogen requirements and minimum amino acid requirements have been established1 studies will be directed toward investigating caloric restriction and adaptation to restriction of calories4 ,it has been suggested that caloric restriction in animals and man results in apparent decreased energy need for the same activity4 ,this apparent paradox has never been explained4 ,it has been shown that there is adaptation to repeated episodes of caloric restriction both in animals and man1 so that subsequent periods of caloric restriction result in decreased rate of weight loss1 nitrogen loss1 and longer survival4 ,additional experiments are urgently required to determine the metabolic demands for minerals--in particular1 the metabolic balance of calcium1 potassium1 sodium1 and phosphorus4 ,under conditions of high water consumption1 large mineral losses are to be expected4 ,failure to replace these can cause an imbalance which could impair the efficiency of the individual to the extent of endangering the flight4 ,analysis of samples taken in flight1 both of urine and feces1 should be made4 ,respiratory quotients can be determined in flight1 blood samples should be taken before and immediately after flight for analyzing selected components 7in simulator studies these could be taken periodically71 and nutritional intakes 7which would be facilitated by formula diets7 must be measured and analyzed4 ,short-,range ,technology ,there are many practical difficulties in providing for food storage and accessibility in spacecraft4 ,the packaging of food materials1 both dehydrated and liquid1 has proceeded satisfactorily under the supervision of the ,food and ,container ,institute4 ,if packaging materials are to be made to withstand very high relative humidities and large variations in temperature1 additional investigations are required1 since such containers are not yet available4 ,in packaging1 serious consideration must be given to the ease with which the food may be reached and eaten4 ,if dehydrated formula foods are to be fed on short-term missions1 additional work is required on the rehydration of such formulas4 ,present methods of water measurement under weightless conditions are not satisfactory1 and better methods will have to be contrived4 ,long-,term ,nutritional ,problems ,there is a dearth of metabolic information1 even for short-duration flights1 without which changes in metabolic patterns to longer flights cannot be extrapolated4 ,however1 using scattered information1 certain changes which may be encountered can be hypothesized4 ,decalcification of bone and changes in water-holding capacity of the body may be anticipated4 ,it is also possible that changes in proportion of fat to lean body mass could be experienced and should be considered in nutritional planning4 ,nutritional requirements depend on size1 particularly lean body mass1 sex1 physiological state1 and individual metabolic rates4 ,therefore1 individuals for space flight should be screened with these factors in mind if it is desirable to minimize food intake in long flights4 ,the factors which influence the total nutritional requirements of the individual also influence his mental and physical responses to stress4 ,synthetic ,foods ,the development of food materials other than those derived directly from animal or vegetable origin is of interest4 ,advantages of such diets may be low residue1 ease of storage1 rehydration1 and manipulation4 ,experiments with chemically defined synthetic diet for humans have been carried out by ,medical ,sciences ,research ,foundation1 ,san ,mateo1 ,calif4 ,the complete liquid diet is composed of required amino acids1 fat1 carbohydrate1 vitamins1 and minerals4 ,a cubic foot of the diet 7#ej percent solids in ,h,o7 supplies #bejj calories per day for #a month1 and has been given a variety of artificial flavors4 ,this synthetic diet has been fed to human volunteers for #f months in a pilot study at the ,california ,medical ,facility1 ,vacaville1 ,calif41 and the results are being reviewed4 ,schwarz ,bioresearch1 ,inc41 is studying the storage1 stability1 and packaging of chemically defined synthetic diets for human and animal flights4 ,food ,production in ,space ,long-term feeding in space depends upon a payload of stored food unless food is produced during flight4 ,if sufficient propulsive energy is available1 the duration of missions using stored food may be quite long4 ,however1 in emergencies in which a mission lasts longer than planned1 survival may depend on the ability to produce food extraterrestrially4 ,eventually it will be desirable or necessary to produce food beyond the confines of ,earth4 ,the nutritional requirements of the crew will be influenced by such factors as activity1 physical and psychological stress1 individual size of the members1 and individual metabolic rates4 ,the food intake will have to be adjusted to meet these requirements4 ,it is necessary to know the nutritional requirements of each astronaut and the way in which these are altered by the conditions of space flight in order to estimate needs on long missions4 ,without this information1 the food supplies for the longer flights may be too much1 too little1 or improperly balanced4 ,where dependence would not be on stored food alone1 but on food produced en route1 more exact information on requirements is needed to determine the capacity of food production units4 ,in the discussion of bioregenerative systems1 it was suggested that food materials could be produced by photosynthetic organisms 7e4g41 algae1 duckweed1 and other higher plants7 or by nonphotosynthetic organisms 7e4g41 ,hydrogenomonas74 ,in contrast to the use of living organisms1 reprocessing waste materials by chemical treatment or the actual synthesis of high-energy compounds has been suggested4 ,no chemical system has yet been demonstrated as workable for the economical production of food in space1 and the systems considered produce materials which may be converted to food1 but are not food as such4 ,algal cultures have had the most extensive investigation as food in space1 but the technical problems of using this material as a food source have not yet been solved4 ,it is apparent from the investigations to date that algae will require treatment before they can be used as food4 ,in limited trials1 difficulties have been experienced with amino acid deficiencies1 digestibility1 high residues1 and gastric distress4 ,processing methods which would be applicable in space travel and the possibility of secondary conversion by other animals or plants should be systematically investigated4 chapter #h ,significance of the ,achievements ,,significance ,,to ,,science ,one of the most critical research areas of the space program is bioscience4 ,of both practical and philosophical significance in exploring the origins of life and the possibilities of life on other planets1 bioscience also promises much in medical aspects4 ,space offers biologists completely new environmental factors1 such as the effects of zero gravity and of removal from ,earth's rotation4 ,these effects have been studied in attempts to advance understanding of basic mechanisms of physiology and biological rhythms4 ,these studies can be of great value in dealing with problems of disease and metabolic disorders4 ,biological research is fundamental to the problem of successfully protecting and sustaining man in the peculiar and hostile space environment4 ,understanding human requirements and variations in their response to various environmental factors offers value in medical research for human survival and comfort4 ,the many technological discoveries and advancements in electronic and engineering equipment greatly enhance medical diagnosis1 treatment of disease1 and the extension of human life4 ,the life sciences1 biology and medicine1 are fundamental to the success of manned exploration of space1 which marks a unique and significant development in the long history of man's conquest of new frontiers4 ,those who pioneered other frontiers on land and sea and in the air were not forced to await biological and medical research4 ,even the pioneers of aerial flight began their efforts without first seeking biomedical data4 ,the search for such data followed flight experience and1 indeed1 was made only after problems arose4 ,project ,mercury1 ,,nasa's first program for manned space flight1 stimulated immediate and extensive studies in the life sciences to sustain man in space4 ,before a vehicle could be designed to carry an astronaut into space1 anticipated biomedical problems associated with space flight were studied4 ,life-support systems were designed to offer adequate protection from environmental stresses peculiar to space1 such as zero gravity1 removal from ,earth's rotation1 and high-energy cosmic radiation4 ,these life-support systems used knowledge already gained from research for manned space flight by the ,u4,s4 ,air ,force4 ,our entry into space has put us at the threshold of fundamental and far-reaching discoveries in the biological realm which have profound implications for other areas of human thought and endeavor4 ,as man goes farther into space1 the hazards increase2 but past accomplishments indicate that the road ahead holds more promise than peril and that the vistas of knowledge that may be foreseen are as vast as space itself4 ,almost everything which now can be said about the effects of extraterrestrial environments and about life on the ,moon or the planets lies in the realm of pure speculation4 ,there is one prediction1 however1 that can be made with considerable certainty by reason of historical precedent--the opportunity to investigate a totally new area1 such as is offered by space exploration1 is certain to produce a burst of scientific interest as soon as the path is charted by a few pioneers4 ,over the next few decades a progressively larger proportion of biological interest will turn to space4 ,we may well expect that the discoveries made here will revolutionize some of our concepts of biology4 ,it should be fully realized that the accumulation and dissemination of biological and other scientific information is not only of great value to science and humanity but is of tremendous import to the prestige of the ,nation4 ,,significance ,,for ,,practical ,,applications ,it can be predicted as confidently for space biology as for other space sciences that the economic costs will be amply repaid in the long run by applications of space-oriented biotechnology to other fields of biology and medicine4 ,there are inevitable substantial1 though indirect1 contributions of ,,nasa's continuing efforts in space biology4 ,,nasa-supported biological research has many practical applications and spinoffs which contribute to the fields of health and medicine1 food and agriculture1 and industry and manufacturing4 ,some of these are presented to show the range and value of applications which have resulted from basic and applied biological research4 ,in addition to those listed are many others from the biosatellite program1 particularly in the fields of bioengineering and miniaturization4 ,health and ,medicine ,solar cells1 which have powered space systems1 are now being used as a power source in studies on brain function4 ,a miniaturized solar cell developed by ,general ,electric provides enough power1 under ordinary house lights1 to stimulate an animal's brain and to telemeter respiratory1 cardiovascular1 and brain-wave data while the animal is allowed to move about freely4 ,such a system is now used by the ,national ,institute of ,mental ,health ,laboratory at ,rethesda1 ,md4 ,scientists at the ,ames ,research ,center have devised a new technique for studying organic compounds1 whether synthesized in the laboratory or produced by a living system4 ,this technique is based on a property of matter called optical activity4 ,previous methods of measuring optical activity have been plagued by low sensitivity4 ,the new method is many tunes more sensitive and represents a real contribution to modern analytical instrumentation4 ,studies on calcium metabolism and bed rest simulating weightlessness are adding knowledge on the prevention of demineralization of the skeleton2 treatment of ,paget's disease and osteoporosis prevention of muscular atrophy2 the cause and treatment of renal calculi 7kidney stones72 optimal calcium for the human diet2 and the factors influencing calcium absorption1 metabolism1 and excretion4 ,the results will have great importance in bone healing and repair1 care and treatment of fracture cases1 treatment of paraplegics1 and treatment of polio patients and similar cases4 ,these grant studies at ,texas ,woman's ,university have also proven that the ,x-ray bone densitometry method can accurately detect changes in the skeleton4 ,a primary objective of the planetary exploration program is the detection of possible extraterrestrial life4 ,the study of the fundamental properties of living things on ,earth is restricted to the type of life which has evolved and survived here4 ,life which has been exposed to totally different environmental conditions may have markedly different physiological characteristics4 ,the impact of the new information obtainable from the study of extraterrestrial life upon the sciences of medicine and biology will unquestionably be of fundamental and far-reaching importance4 ,advancement in the treatment of disease and the problems of aging are among the many possible consequences4 ,new developments in such techniques as ultraviolet spectrophotometry1 polarimetry1 and gas chromatography will find use in the detection of biochemicals and other compounds in hospitals and in toxicology and pathology laboratories4 ,they will also be useful in studies of atmospheric pollutants such as smog4 ,studies of the chemistry of living systems1 molecular biology1 and biophysics of cellular processes will create a better understanding of the basic mechanisms of life1 leading to an understanding of both inherited and acquired disease1 especially neoplastic conditions and chemical disturbances incident to mental disease4 ,the ,university of ,pittsburgh is conducting a study to increase the availability of cytological technique in research and as a monitoring procedure by developing an automatic electronic scanning device using computer analysis for recording1 counting1 and sorting chromosomes4 ,structural changes in blood cell chromosomes can indicate the degree of radiation damage as well as damage resulting from various environmental stresses4 ,accordingly1 this instrument1 when developed1 can be used as a radiation dosimeter in civil defense by swiftly detecting the degree and type of chromosomal aberrations in blood cells4 ,thus1 casualties in nuclear attack could be quickly detected and treated4 ,this system would also be useful for nuclear industrial plants and for military maneuvers4 ,in medicine1 various disease trends could be monitored4 7,chromosomes exhibit anomalies in leukemia and mental retardation as well as in other states47 ,in space exploration and experimentation1 the device can spot monitor radiation dose levels as well as changes resulting from any of the environmental stresses experienced in space4 ,this apparatus can be modified for use as an extraterrestrial-life-detecting instrument by scanning the growth of cells 7or cellular inclusions71 computing rates1 and telemetering changes to the researcher4 ,investigations of rhythmic phenomena of various physiological systems can result in knowledge of the utmost importance to medicine4 ,rhythmic phenomena are found in the cardiovascular system of normal humans4 ,changes in these rhythms have the potential of foretelling abnormalities 7heart disease1 arteriosclerosis7 before outward signs are manifested1 allowing for earlier diagnosis1 treatment1 and control or cure4 ,the spacecraft sterilization program requires the use of rooms having the lowest attainable level of bacterial contamination4 ,the rate of dissemination of bacteria from the humans in the room is basic to the problem4 ,data on this matter are being obtained through support of the ,communicable ,disease ,center of the ,u4,s4 ,public ,health ,service4 ,the findings are affecting the measures used in surgical practice to lower infection rates4 ,studies on the physiology of hibernation in mammals are important to understand temperature regulation and the mechanism of survival at low body temperatures4 ,the purpose of this type of research is to understand and use reduced metabolic activity in astronauts on future extended space flight4 ,other applications involve studies of the mechanisms of injury and freezing biological organisms1 for improving techniques in hypothermic surgery1 pathology1 and preservation of tissue for human grafting4 ,food and ,agriculture ,gathering agricultural information by remote sensing of ,earth's surface from aircraft1 balloons1 and satellites has a potential application in research and development4 ,current needs for data gathered in this way include crop and livestock surveys for marketing planning2 soil mapping2 crop disease1 insect1 and weed surveys2 soil conservation management and research2 and crop acreage control programs4 ,as population and world trade increase1 the needs will become even more intense for regularly scheduled synoptic surveys of the world's agricultural lands for crop plantings and harvests2 determining the condition of crops as affected by drought1 disease1 or insect outbreaks2 and studies of the lands suitable for agricultural development in underdeveloped countries4 ,the only way that worldwide synoptic surveys can be made is by using orbiting platforms4 ,the ,,nasa nutrition program for developing diets for prolonged manned and animal space flight lends itself to civil defense purposes2 military maneuvers where space and weight are prime considerations2 polar and desert exploration2 reducing hunger in underdeveloped countries2 and detecting metabolic diseases as well as diseases of infancy and old age4 ,for space research such a diet can be used on prolonged manned space flights1 animal experiments in space1 manned orbiting laboratories1 and space and planetary stations4 ,studies on the packaging and stability of foods under various conditions of humidity1 temperature1 and radiation will lead to better processing and storage4 ,learning how microbial spores are transported by air is important to biology1 agriculture1 and medicine4 ,besides spreading crop destruction1 microbial spores produce allergic responses in some human beings4 ,to obtain the facts1 not only the biology of micro-organisms but also the weather factors that induce the flight of mature spores must be known4 ,thus1 both biological and meteorological problems are involved4 ,data obtained under a ,,nasa contract with the ,general ,mills ,electronic ,division 7now part of ,litton ,industries1 ,inc47 indicate that spores of fungi are present in low numbers in the stratosphere4 ,a reservoir of spores exists which cannot be brought down by the normal scrubbing mechanisms of rainfall and other meteorological disturbances in the troposphere4 ,this finding has important implications for reducing the spread of agricultural crop diseases and for protecting persons suffering from allergies4 ,this project has indicated the necessity for designing novel biological samplers for use in the stratosphere4 ,such samplers will aid in determining various pollutants of the atmosphere4 ,the ,,nasa program for developing sterile spacecraft for the biological exploration of ,mars will contribute improved methods of sterilization that can be applied to the canning industry4 ,studies on sterilization at low temperatures for long periods of time are being supported by ,,nasa at the ,massachusetts ,institute of ,technology and the ,communicable ,disease ,center and the ,sanitary ,engineering ,center of the ,public ,health ,service4 ,the developing capability is making possible the heat sterilization of products that never before could be thoroughly sterilized4 ,in preparing for missions to search for extraterrestrial life1 research on the psychrophilic or cold bacteria1 on halophytic or salt bacteria1 and on specialized bacteria and other organisms growing in extreme environments is defining the extremes under which life can exist4 ,increased knowledge about organisms that can grow in or on refrigerated1 dried1 or salted foods and other materials should have practical applications for food storage and preservation4 ,research on psychrophilic bacteria is being conducted by ,whirlpool ,corp4 and the ,,nasa ,ames ,research ,center4 ,theoretical studies of ,martian life involve investigations of plant and bacterial spores4 ,many of these forms are spoilage organisms and some produce lethal toxins4 ,this work has potential importance for food processing and for obtaining more precise knowledge of how wounds become infected4 ,the program for investigating possible forms of life on ,mars includes a thorough study of anaerobic micro-organisms4 ,this research has led to the discovery of new types of nitrogen-fixing bacteria other than the familiar types found in the root nodules of leguminous plants4 ,thus1 it may be possible to use these microorganisms1 or the principles involved1 in the incorporation of vital atmospheric nitrogen into terrestrial soils which are now unproductive4 ,industry and ,manufacturing ,batteries that have been developed in the space program to endure high sterilization temperatures for extended times will have greatly increased shelf life at normal storage temperatures and will be serviceable after many hours of baking at high temperatures4 ,currently1 the highest quality tape recorders are subject to imperfect reproduction because the tapes are heat labile2 i4e41 they soften and stretch when warm4 ,the development of high-quality magnetic tapes for space-data recorders is an outgrowth of the materials developed to meet spacecraft sterilization requirements4 ,these improved tapes will be useful for all types of recording--industry1 automation controls1 home1 and studio4 ,,outlook ,,for ,,bioscience--,,major ,,problems ,the problems undertaken are among the most challenging1 if not the most challenging1 man faces on the space frontier4 ,these include the quest for the origin of life1 the explanation of life and life processes1 the elucidation of the environment's role in establishing and maintaining normal organization in living organisms1 the possibility of extraterrestrial life on other planets--the concern of exobiology4 ,the greatest promise for their solution lies in advances in biological theory rather than other avenues of research2 therefore1 it is fortunate that the need to solve them has come at a time when developments in experimental biology are at a high level4 ,in addition1 technological developments in electronics and engineering are providing new and wonderful instruments for this great exploration into the sources of life4 ,many of these have had practical application that has made possible important advances in medical diagnosis and treatment4 ,the broad national space goals initially charted by ,,nasa have gone beyond space flight in near-,earth orbit to lunar and interplanetary exploration by man and machine4 ,for such missions1 more intensive and comprehensive research in the life sciences is needed4 ,before manned voyages for extended periods into deep space will be possible1 solutions must be found for problems such as the development of bioregenerative life-support systems1 communication with nonhuman species1 and the development of new methods for transferring knowledge to the human brain4 ,the problems are all of the type that could perhaps be solved by truly great advances in biological theory1 and probably not by any other avenue4 ,references ref4#a ,rea1 ,d4 ,g43 ,the ,evidence for ,life on ,mars4 ,nature1 vol4 #bjj1 #aifc1 p4 #aad4 ref4#b pik1 ,e4 ,j43 ,spectroscopic ,evidence of ,vegetation on ,mars4 ,irish ,astron4 ,j41 vol4 #e1 #aieh1 pp4 #ab-ac4 ref4#c ,kuiper1 ,g4 ,p43 ,visual ,observations of ,mars1 #aief4 ,astrophys4 ,j41 vol4 #abe1 #aieg1 p4 #cjg4 ref4#d ,fcas1 ,j4 ,h43 ,seasonal ,evolution of the ,fine ,structure of the ,dark ,areas of ,mars4 ,planetary ,space ,sci41 vol4 #i1 #aifb1 p4 #cga4 ref4#e ,dollfus1 ,a43 ,interpretation of the 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,astrophys4 ,j41 vol4 #aci1 #aifd1 p4 #a4 ref4#cb ,davis4 ,d4 ,r42 and ,libby1 ,w4 ,f43 ,positive ,ion ,chemistry4 ,science1 vol4 #add1 #aifa1 p4 #iia4 ref4#cc ,miller1 ,s4 ,l43 ,production of ,some ,organic ,compounds ,under ,possible ,primitive ,earth ,conditions4 ,j4 ,am4 ,chem4 ,soc41 vol4 #gg1 #aiee1 p4 #bce4 ref4#cd ,or1 ,j43 ,experimental ,cosmochemistry4 ,in ,current ,aspects of ,exobiology4 ,g4 ,mamikunian and ,m4 ,h4 ,briggs1 eds41 ,pergamon ,press 7,new ,york71 #aife4 ref4#ce ,shapley1 ,h43 ,of ,stars and ,men4 ,beacon ,press 7,boston71 #aieh1 pp4 #aa and #aeg4 ref4#cf ,lederberg1 ,j42 and ,cowie1 ,d4 ,b43 ,moondust4 ,science1 vol4 #abg1 #aieh1 pp4 #adgc-adge4 ref4#cg ,,cetex3 ,development of ,international ,efforts ,to ,avoid ,contamination by ,extraterrestrial ,exploration4 ,science1 vol4 #abh1 #aieh1 pp4 #hhg-hhi4 ref4#ch ,,cetex3 ,contamination by ,extraterrestrial ,exploration4 ,nature1 vol4 #ahc1 #aiei1 pp4 #ibe-ibh4 ref4#ci ,sagan1 ,c43 ,biological ,contamination of the ,moon4 ,proc4 ,natl4 ,acad4 ,sci4 ,u4,s41 vol4 #df1 #aifj1 pp4 #cic-dja4 ref4#dj ,davies1 ,r4 ,w42 and ,communizis1 ,m4 ,g43 ,sterilization of ,space ,vehicles ,to ,prevent ,extraterrestrial ,biological ,contamination4 ,proc4 #ajth ,intern4 ,astro4 ,congr41 ,springer-,verlag 7,vienna71 #aifj1 pp4 #die-ejd4 ref4#da ,lederberg1 ,j43 ,exobiology3 ,approaches to ,life ,beyond the ,earth4 ,science1 vol4 #acb1 #aifj1 pp4 #cic-djj4 ref4#db ,brown1 ,a4 ,h43 ,report of the ,working ,subgroup on ,space ,probe ,sterilization4 ,a ,review of ,space ,research4 ,natl4 ,acad4 ,sci4-,natl4 ,res4 ,council1 ,publ4 #ajgi1 #aifb1 ch4 #aj4 ref4#dc ,imshenetskii1 ,a4 ,a43 ,prospects of the ,development of ,exobiology4 ,in ,space ,research ,,iii1 ,w4 ,priester1 ed41 ,north-,holland ,publ4 ,co4 7,amsterdam71 #aifc4 ref4#dd ,portner1 ,d4 ,m42 ,spiner1 ,d4 ,r42 ,hoffman1 ,r4 ,k42 and ,phillips1 ,c4 ,r43 ,effect of ,ultrahigh ,vacuum on ,viability of ,microorganisms4 ,science1 vol4 #acd1 #aifa1 p4 #bjdg4 ref4#de ,morelli1 ,f4 ,a42 ,fehlner1 ,f4 ,p42 and ,stembridge1 ,c4 ,h43 ,effects of ,ultra-,high ,vacuum on ,bacillus subtilis var4 niger4 ,nature1 vol4 #aif1 #aifb1 pp4 #ajf-ajg4 ref4#df ,davis1 ,n4 ,s42 ,silverman1 ,g4 ,j42 and ,keller1 ,w4 ,h43 ,combined ,effects of ,ultrahigh ,vacuum on the ,viability of ,some ,spores and ,soil ,organisms4 ,appl4 ,microbiol41 vol4 ,,ii1 #aifc1 pp4 #bjb-baa4 ref4#dg ,silverman1 ,g4 ,j42 ,davis1 ,n4 ,s42 and ,keller1 ,w4 ,h43 ,exposure of ,microorganisms to ,simulated ,extraterrestrial ,space ,ecology4 ,in ,life ,sciences and ,space ,research ,,ii1 ,m4 ,florkin and ,a4 ,dollfus1 eds41 ,north-,holland ,publ4 ,co4 7,amsterdam71 #aifd1 pp4 #cgb-chd4 ref4#dh ,imshenetskii1 ,a4 ,a42 ,bogrov1 ,n42 and ,lysenko1 ,s43 ,resistance of ,microorganisms to ,high ,vacuum4 ,doklady ,akad4 ,nauk ,,sssr1 vol4 #aed1 #aifd1 pp4 #aahh-aaij4 ref4#di ,hawrylewicz1 ,e4 ,j42 ,gowdy1 ,b42 and ,ehrlich1 ,r43 ,microorganisms ,under a ,simulated ,martian ,environment4 ,nature1 vol4 #aic1 #aifb1 p4 #dig4 ref4#ej ,packer1 ,e42 ,scher1 ,s42 and ,sagan1 ,c43 ,biological ,contamination of ,mars4 ,part ,,ii4 ,cold and ,aridity as ,constraints on the ,survival of ,terrestrial ,microorganisms in ,simulated ,martian ,environments4 ,icarus1 vol4 #b1 #aifc1 pp4 #bib-caf4 ref4#ea ,scher1 ,s42 ,packer1 ,e42 and ,sagan1 ,c43 ,biological ,contamination of ,mars3 ,i4 ,survival of ,terrestrial ,microorganisms in ,simulated ,martian ,environments4 ,in ,space ,research ,,iv4 ,p4 ,muller1 ed41 ,north-,holland ,publ4 ,co4 7,amsterdam71 #aifd4 ref4#eb ,young1 ,r4 ,s43 ,deal1 ,p4 ,h42 ,bell1 ,j42 and ,allen1 ,j4 ,l43 ,bacteria ,under ,simulated ,martian ,conditions4 ,in ,space ,research ,,iv1 ,p4 ,muller1 ed41 ,north-,holland ,publ4 ,co4 7,amsterdam71 #aifc4 ref4#ec ,hagen1 ,c4 ,a42 ,hawrylewicz1 ,e4 ,j42 and ,ehrlich1 ,r43 ,survival of ,microorganisms in a ,simulated ,martian ,environment4 ,appl4 ,microbiol41 vol4 #ab1 #aifd1 pp4 #bae-bah4 ref4#ed ,hawrylewicz1 ,e4 ,j42 ,hagen1 ,c4 ,a42 and ,ehrlich1 ,r43 ,response of ,microorganisms to a ,simulated ,martian ,environment4 ,in ,life ,sciences and ,space ,research ,,iii1 ,m4 ,florkin1 ed41 ,north-,holland ,publ4 ,co4 7,amsterdam71 #aife4 ref4#ee ,nicks1 ,o4 ,w42 and ,reynolds1 ,o4 ,e43 ,decontamination and ,sterilization of ,lunar and ,planetary ,spacecraft4 ,science1 vol4 #adb1 #aifc1 pp4 #eci-edj4 ref4#ef ,phillips1 ,c4 ,r42 and ,hoffman1 ,r4 ,k43 ,sterilization of ,interplanetary ,vehicles4 ,science1 vol4 #acb1 #aifj1 pp4 #iia-iie4 ref4#eg ,hobby1 ,g43 ,review of ,,nasa-,,jpl ,spacecraft ,sterilization ,program4 ,a ,review of ,space ,research4 ,natl4 ,acad4 ,sci4-,nat4 ,res4 ,council1 ,publ4 #ajgi1 #aifb1 ch4 #aj4 ,app4 ,,iii4 ref4#eh ,bruch1 ,c4 ,w42 ,koesterer1 ,m4 ,g42 and ,bruch1 ,m4 ,k43 ,dry-,heat ,sterilization3 ,its ,development and ,application to ,components of ,exobiological ,space ,probes4 ,develop4 ,ind4 ,microbiol41 vol4 #d1 #aifc1 pp4 #ccd-cdb4 ref4#ei ,koesterer1 ,m4 ,g43 ,thermal ,death 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,spacecraft ,sterilization4 ,jet ,propulsion ,lab41 #aife4 ref4#fd ,pollard1 ,e43 ,pilot ,theoretical ,study of the ,effect of ,weightlessness and ,densely ,ionizing ,radiation on ,single ,cells4 ,progr4 ,rept4 on ,contract ,ns,g-#ahb-fb4 ,,nasa1 #aifb4 ref4#fe ,lyon1 ,c4 ,j43 ,auxin ,transport in ,leaf ,epinasty4 ,plant ,physiol41 vol4 #ch1 #aifc1 pp4 #efg-egd4 ref4#ff ,mc,kinney1 ,r42 ,montgomery1 ,p4 ,o',b42 and ,gell1 ,c4 ,f43 ,a ,study of the ,effects of ,zero ,gravity on ,cell ,physiology4 ,in ,physical and ,biological ,phenomena in a ,weightless ,state4 ,second ,,aas ,symp4 ,phys4 ,biol4 ,phenomena ,under ,zero ,gravity ,conditions4 ,e4 ,t4 ,benedikt and ,r4 ,w4 ,halliburton1 eds41 ,advan4 ,astronaut4 ,sci41 vol4 #ad1 #aifc1 pp4 #bia-cjf4 ref4#fg ,committee on ,environmental ,biology3 ,report of ,panel on ,gravity4 ,space ,science ,board1 ,natl4 ,acad4 ,sci4-,natl4 ,res4 ,council1 #aifd4 ref4#fh ,chase1 ,h4 ,b43 ,cutaneous ,effects of ,primary ,cosmic ,radiation4 ,j4 ,aviation ,med41 vol4 #be1 #aied1 p4 #chh4 ref4#fi ,zhukova1 ,a4 ,i42 and ,kondratyev1 ,i4 ,i43 ,on ,artificial ,martian ,conditions ,reproduced for ,microbiological ,investigations4 ,in ,life ,sciences and ,space ,research ,,iii1 ,m4 ,florkin1 ed41 ,north-,holland ,publ4 ,co4 7,amsterdam71 #aife1 pp4 #abj-abf4 ref4#gj ,davis1 ,i42 and ,fulton1 ,j4 ,d43 ,microbiological ,studies on ,ecological ,considerations of the ,martian ,environment4 ,,usaf ,,sam ,review1 vol4 #b1 #aiei1 p4 #fj4 ref4#ga ,roberts1 ,t4 ,s42 and ,irvine1 ,l4 ,a43 ,studies ,with a ,simulated ,martian ,environment4 ,germination and ,growth of ,bacterial ,spores4 ,tech4 ,doc4 ,rept4 #fc-ge4 ,,usaf ,school ,aerospace ,med41 #aifc4 ref4#gb ,roberts1 ,t4 ,l42 and ,wynn1 ,e4 ,s43 ,studies ,with a ,simulated ,martian ,environment4 ,bacterial ,survival and ,soil ,moisture ,content4 ,tech4 ,doc4 ,rept4 #fb-aba4 ,,usaf ,school ,aerospace ,med41 #aifb4 ref4#gc ,siegel1 ,s4 ,m42 ,giumarro1 ,c42 and ,latterall1 ,r43 ,behavior of ,plants ,under ,extraterrestrial ,conditions3 ,seed ,germination in ,atmospheres ,containing ,nitrogen ,oxides4 ,proc4 ,natl4 ,acad4 ,sci4 ,u4,s41 vol4 #eb1 #aifa1 pp4 #aa-ac4 ref4#gd ,siegel1 ,s4 ,m42 ,halpern1 ,l4 ,a42 ,giumarro1 ,c42 ,renwick1 ,g42 and ,davis1 ,g43 ,martian ,biology3 ,the ,experimentalist's ,approach4 ,nature1 vol4 #aic1 #aifc1 pp4 #cbi-cca4 ref4#ge ,kiess1 ,c4 ,c42 ,corliss1 ,c4 ,h42 and ,kiess1 ,h43 ,evidence for ,oxides of ,nitrogen in the ,atmosphere of ,mars4 ,science1 vol4 #aca1 #aifj1 p4 #acai4 ref4#gf ,vallentyne1 ,j4 ,r43 ,environmental ,biophysics and ,microbial ,ubiquity4 ,ann4 ,n4,y4 ,acad4 ,sci41 vol4 #ajh1 #aifc1 pp4 #cdb-ceb4 ref4#gg ,henry1 ,j4 ,p42 ,ballinger1 ,e4 ,r42 ,maher1 ,p4 ,j42 and ,simons1 ,d4 ,g43 ,animal ,studies of the ,subgravity ,state ,during ,rocket ,flight4 ,j4 ,aviation ,med41 vol4 #bc1 #aieb1 p4 #dba4 ref4#gh ,van der ,wal41 ,f4 ,l42 and ,young1 ,w4 ,d43 ,a ,preliminary ,experiment ,with ,recoverable ,biological ,payloads in ,ballistic ,rockets4 ,project ,,mia4 ,rept4 #gae-eh1 ,am4 ,rocket ,soc41 #aieh4 ref4#gi ,van der ,wal1 ,f4 ,l42 and ,young1 ,w4 ,d43 ,project ,,mia 7,mouse-in-,able7 ,experiment on ,physiological ,response to ,space ,flight4 ,,ars ,j41 vol4 #bi1 #aied1 p4 #gaf4 ref4#hj ,graybiel1 ,a42 ,holmes1 ,r4 ,a42 ,beischer1 ,d4 ,e42 ,champlin1 ,g4 ,e42 ,pedigo1 ,g4 ,p42 ,hixson1 ,w4 ,c42 ,davis1 ,t4 ,r4 ,a42 ,barr1 ,n4 ,l42 ,kistler1 ,w4 ,g42 ,niven1 ,j4 ,t42 ,wilbarger1 ,e42 ,stullken1 ,d4 ,e12 ,augerson1 ,w4 ,s42 ,clark1 ,r42 and ,berrian1 ,j4 ,h43 ,an ,account of ,experiments in ,which ,two ,monkeys ,were ,recovered ,unharmed ,after ,ballistic ,space ,flight4 ,aerospace ,med41 vol4 #cj1 #aiei1 p4 #hga4 ref4#ha ,green1 ,c4 ,d42 ,welch1 ,b4 ,e42 ,brown1 ,w4 ,l42 ,lamb1 ,l4 ,e42 ,tang1 ,p4 ,c42 ,gisler1 ,d4 ,b42 and ,blodgett1 ,h4 ,c43 ,studies of ,escape ,from ,ballistic ,space ,vehicles4 ,rept4 #fa-bi1 ,school ,aviation ,med41 sec4 #a1 pp4 #a-bd2 sec4 #b1 pp4 #a-af1 #aifa4 ref4#hb ,belleville1 ,r4 ,e42 ,rohles1 ,f4 ,h42 ,grunzke1 ,m4 ,e42 and ,clark1 ,f4 ,c43 ,development of a ,complex ,multiple ,schedule in the ,chimpanzee4 ,j4 ,exp4 ,anal4 ,behav41 vol4 #f1 #aifc1 pp4 #edi-eef4 ref4#hc ,henry1 ,j4 ,p42 and ,mosely1 ,j4 ,d43 ,results of the ,project ,mercury ,ballistic and ,orbital ,chimpanzee ,flights4 ,,nasa ,,sp-#ci1 #aifc4 ref4#hd ,grunzke1 ,m4 ,e43 ,a ,liquid ,dispenser for ,primates4 ,j4 ,exp4 ,anal4 ,behav41 vol4 #d1 #aifa1 p4 #cbf4 ref4#he ,grunzke1 ,m4 ,e43 ,feeding ,devices for ,use ,with ,primates in ,space ,flight4 ,tech4 ,doc4 ,rept4 #fa-ce1 ,,usaf ,missile ,develop4 ,center1 #aifa4 ref4#hf ,gilbert1 ,g4 ,a43 ,a ,zero ,gravity ,pellet ,dispenser for ,use ,with ,primates in ,long-,term ,space ,flights4 ,,arl ,tech4 ,rept4 #fd-ae1 #aifd4 ref4#hg ,meehan1 ,j4 ,p42 ,fineg1 ,j42 and ,mosely1 ,j4 ,d43 ,the ,effect of ,restraint and ,training on the ,arterial ,pressure of the ,immature ,chimpanzee4 ,federation ,proc41 vol4 #bc1 #aifd4 ref4#hh ,findley1 ,j42 and ,weissman1 ,n43 ,counting in a ,baboon4 ,paper presented at ,psychonomic ,soc4 ,meeting 7,new ,york71 #aifa4 ref4#hi ,findley1 ,j42 and ,brady1 ,j4 ,v43 ,exposure to ,total and ,continuous ,environmental ,control ,with a ,single ,human ,organism4 ,paper presented at ,symp4 at #gth ,annual ,meeting1 ,human ,factors ,soc4 7,palo ,alto1 ,calif471 #aifc4 ref4#ij ,findley1 ,j43 ,an ,experimental ,outline for ,building and ,exploring ,multioperant ,behavior ,repertories4 ,j4 ,exp4 ,anal4 ,behav41 vol4 #e1 #aifb1 pp4 #aac-aaf4 ref4#ia ,beasley1 ,j42 and ,seldeen1 ,b43 ,the ,effect of ,prolonged ,acceleration on ,eating and ,performance4 ,,nasa ,,tm ,x-#ed3jgg1 #aifd4 ref4#ib ,smith1 ,a4 ,h42 ,winget1 ,c4 ,m42 and ,kelly1 ,c4 ,f43 ,growth and ,survival of ,birds ,under ,chronic ,acceleration4 ,growth1 vol4 #bc1 #aiei1 p4 #ig4 ref4#ic ,winget1 ,c4 ,m42 ,smith1 ,a4 ,h42 and ,kelly1 ,c4 ,f43 ,effects of ,chronic ,acceleration on ,induced ,nystagmus in the ,fowl4 ,j4 ,appl4 ,physiol41 vol4 #ag1 #aifb1 p4 #gji4 ref4#id ,wunder1 ,c4 ,c43 ,food ,consumption of ,mice ,during ,continual ,centrifugation4 ,proc4 ,iowa ,acad4 ,sci41 vol4 #fh1 #aifa1 pp4 #faf-fbd4 ref4#ie ,wunder1 ,c4 ,c43 ,survival of ,mice ,during ,chronic ,centrifugation4 ,aerospace ,med41 vol4 #cc1 #aifb1 pp4 #hff-hgj4 ref4#if ,wunder1 ,c4 ,c42 ,lutherer1 ,l4 ,c42 and ,dodge1 ,c4 ,h43 ,survival and ,growth of ,organisms ,during ,life-,long ,exposure to ,high ,gravity4 ,aerospace ,med41 vol4 #cd1 #aifc1 pp4 #e-aa4 ref4#ig ,dodge1 ,c4 ,h42 and ,wunder1 ,c4 ,c43 ,growth of ,turtles ,during ,continual ,centrifugation4 ,proc4 ,iowa ,acad4 ,sci41 vol4 #fi1 #aifb1 pp4 #eid-eii4 ref4#ih ,oyama1 ,j42 and ,platt1 ,w43 ,effects of ,deceleration on ,rats ,exposed to ,prolonged ,centrifugation4 ,nature1 vol4 #bjc1 #aifd1 pp4 #gff-gfg4 ref4#ii ,matthews1 ,b4 ,h4 ,c43 ,adaptation to ,centrifugal ,acceleration4 ,j4 ,physiol41 vol4 #abb1 #aiec1 p4 #ca4 ref4#ajj ,riccio1 ,d43 ,the ,effects of ,vestibular ,stimulation on ,performance ,under ,several ,schedules of ,reinforcement4 ,paper presented at ,eastern ,psych4 ,assoc4 ,meeting 7,atlantic ,city1 ,n4,j471 #aife4 ref4#aja ,guedry1 ,f4 ,e42 and ,biberman1 ,n43 ,apparent ,adaptation ,effects in ,vestibular ,reactions4 ,rept4 #bic1 ,,usa ,med4 ,res4 ,lab41 #aieg4 ref4#ajb ,guedry1 ,f4 ,e42 ,cramer1 ,r4 ,l42 and ,koella1 ,w4 ,p43 ,experiments on the ,rate of ,development and ,rate of ,recovery of ,apparent ,adaptation ,effects in the ,vestibular ,system4 ,rept4 #cch4 ,,usa ,med4 ,res4 ,lab41 #aieh4 ref4#ajc ,guedry1 ,f4 ,e42 and ,graybiel1 ,a43 ,the ,appearance of ,compensatory ,nystagmus in ,human ,subjects as a ,conditional ,response ,during ,adaptation to a ,continuously ,rotating ,environment4 ,rept4 #eca1 ,,usa ,med4 ,res4 ,lab41 #aifb4 ref4#ajd ,loret1 ,b4 ,j43 ,optimization of ,manned ,orbital ,satellite ,vehicle ,design ,with ,respect to ,artificial ,gravity4 ,,asd ,tech4 ,rept4 #fa-fhh1 ,wright-,patterson ,,afb1 ,ohio1 #aifa4 ref4#aje ,belleville1 ,r4 ,e42 ,clark4 ,f4 ,c42 and ,lange1 ,k4 ,o43 ,the ,behavior of ,small ,animals ,under the ,accelerative ,conditions ,found in ,space ,travel4 ,,nasa ,,tt ,f-#ijhj1 #aifd4 ref4#ajf ,hebb1 ,d4 ,o43 ,the ,organization of ,behavior4 ,john ,wiley ,sons1 ,inc41 #aidi4 ref4#ajg ,jeffress1 ,l4 ,a43 ,cerebral ,mechanisms in ,behavior4 ,john ,wiley ,sons1 ,inc41 #aiea4 ref4#ajh ,konorsky1 ,j43 ,mechanisms in ,animal ,behavior4 ,symp4 ,soc4 ,exp4 ,biol41 vol4 #d1 ,academic ,press1 #aiej4 ref4#aji ,eccles1 ,j4 ,c43 ,the ,neurophysiological ,basis of ,mind4 ,oxford ,univ4 ,press 7,london71 #aiec4 ref4#aaj ,thorpe1 ,w4 ,h43 ,learning and ,instinct in ,animals4 ,methuen 7,london71 #aief4 ref4#aaa ,sperry1 ,r4 ,w43 ,on the ,neural ,basis of the ,conditioned ,response4 ,brit4 ,j4 ,anim4 ,behav41 vol4 #c1 #aiee1 p4 #da4 ref4#aab ,burns1 ,b4 ,d43 ,the ,mammalian ,cerebral ,cortex4 ,monographs ,physiol4 ,soc4 7,london71 vol4 #e1 #aieh4 ref4#aac ,krech1 ,d42 ,rosenzweig1 ,m4 ,r42 and ,bennett1 ,e4 ,l43 ,dimensions of ,discrimination and ,level of ,cholinesterase ,activity in ,cerebral ,cortex of the ,rat4 ,j4 ,comp4 ,physiol4 ,psychol41 vol4 #di1 #aief1 p4 #bfa4 ref4#aad ,krech1 ,d42 ,rosenzweig1 ,m4 ,r42 and ,bennett1 ,e4 ,l43 ,correlation ,between ,brain ,cholinesterase and ,brain ,weight ,within ,two ,strains of ,rats4 ,am4 ,j4 ,physiol41 vol4 #aif1 #aiei1 pp4 #ca-cb4 ref4#aae ,bennett1 ,e4 ,l42 ,rosenzweig1 ,m4 ,r42 ,krech1 ,d42 ,karlsson1 ,h42 ,dye1 ,n42 and ,ohlander1 ,a43 ,individual1 ,strain1 and ,age ,differences in ,cholinesterase ,activity of the ,rat ,brain4 ,j4 ,neurochem41 vol4 #c1 #aieh1 p4 #aec4 ref4#aaf ,rosenzweig1 ,m4 ,r42 ,krech1 ,d42 and ,bennett1 ,e4 ,l43 ,effect of ,pentobarbital ,sodium on ,adaptive ,behavior in the ,rat4 ,science1 vol4 #abc1 #aief1 pp4 #cga-cgb4 ref4#aag ,rosenzweig1 ,m4 ,r42 ,krech1 ,d42 and ,bennett1 ,e4 ,l43 ,a ,search for ,relations ,between ,brain ,chemistry and ,behavior4 ,psychol4 ,bull41 vol4 #eg1 #aifj1 p4 #dgf4 ref4#aah ,hyden1 ,h43 ,biochemistry of the ,central ,nervous ,system4 ,pergamon ,press 7,new ,york71 #aiei4 ref4#aai ,hyden1 ,h42 and ,egyhazi1 ,e43 ,nuclear ,,rna ,changes of ,nerve ,cells ,during a ,learning ,experiment in ,rats4 ,proc4 ,natl4 ,acad4 ,sci4 ,u4,s41 vol4 #dh1 #aifb1 p4 #acff4 ref4#abj ,brachet1 ,j42 and ,mirsky1 ,a4 ,e43 ,the ,cell3 ,biochemistry1 ,physiology1 ,morphology4 ,vol4 ,,iv1 ch4 #e4 ,academic ,press 7,new ,york71 #aifj4 ref4#aba ,tower1 ,d4 ,b42 and ,schade1 ,j4 ,p43 ,structure and ,function of the ,cerebral ,cortex4 ,elsevier 7,new ,york71 #aifj4 ref4#abb ,dingman1 ,w42 and ,sporn1 ,m4 ,b43 ,the ,incorporation of #h-;,azaguanine ,into ,rat ,brain ,,rna and ,its ,effect on ,maze ,learning by the ,rat4 ,an ,inquiry ,into the ,biochemical ,basis of ,memory4 ,j4 ,psychiatric ,res41 vol4 #a1 #aifa1 pp4 #a-aa4 ref4#abc ,adey1 ,w4 ,r42 ,kado1 ,r4 ,t43 ,didio1 ,j42 and ,schindler1 ,w4 ,j43 ,impedance ,changes in ,cerebral ,tissue ,accompanying a ,learned ,discriminative ,performance in the ,cat4 ,exp4 ,neurol41 vol4 #g1 #aifc1 pp4 #bhb-bic4 ref4#abd ,brattgard1 ,s4 ,o43 ,acta ,radiol4 ,suppl41 vol4 #if1 #aieb1 p4 #a4 ref4#abe ,geiger1 ,a43 ,correlation of ,brain ,metabolism and ,function by the ,use of a ,brain ,perfusion ,method ,in ,situ4 ,physiol4 ,rev41 vol4 #ch1 #aieh1 pp4 #a-bj4 ref4#abf ,geiger1 ,a43 ,metabolism of the ,nervous ,system4 ,d4 ,richter1 ed41 ,pergamon ,press 7,new ,york71 #aieg4 ref4#abg ,thompson1 ,r42 and ,mc,connell1 ,j43 ,classical ,conditioning in the ,planarian ,dugesia dorotocephala4 ,j4 ,comp4 ,physiol4 ,psychol41 vol4 #dh1 #aiee1 p4 #fe4 ref4#abh ,mc,connell1 ,j4 ,v42 ,jacobson1 ,a4 ,l42 and ,kimble1 ,d4 ,p43 ,effects of ,regeneration ,upon ,retention of a ,conditioned ,response in the ,planarian4 ,j4 ,comp4 ,physiol4 ,psychol41 vol4 #eb1 #aiei1 p4 #a4 ref4#abi ,corning1 ,w4 ,c42 and ,john1 ,e4 ,e43 ,effects of ,ribonuclease on ,retention of a ,conditioned ,response in ,regenerating ,planarians4 ,science1 vol4 #acd1 #aifa1 p4 #acfc4 ref4#acj ,gerathewohl1 ,s4 ,j42 and ,gernandt1 ,b4 ,e43 ,physiological and ,behavioral ,sciences1 ,vol4 #a1 ,,nasa ,,sp-#aa1 #aifb1 pp4 #cii-dac4 ref4#aca ,von ,bekesy1 ,g4 ,j43 ,,dc ,potentials and ,energy ,balance of the ,cochlear ,partition4 ,acoust4 ,soc4 ,am41 vol4 #bc1 #aiea1 p4 #egf4 ref4#acb ,trincker1 ,d43 ,bestandspotentiale in ,bogengangssystem des ,meerschweinchens und ihre ,anderungen bei ,experimentellen ,cupula-,ablenkunges4 ,arch4 ,ges4 ,physiol41 ,bd4 #bfd1 #aieg1 p4 #cea4 ref4#acc ,livingston1 ,r4 ,b43 ,neural ,mechanisms of the ,auditory and ,vestibular ,systems4 ,ch4 #be1 ,g4 ,l4 ,rasmussen and ,w4 ,f4 ,windle1 eds41 ,charles ,c ,thomas 7,springfield1 ,ill471 #aifj4 ref4#acd ,brodal1 ,a43 ,neural ,mechanisms of the ,auditory and ,vestibular ,systems4 ,g4 ,l4 ,rasmussen and ,w4 ,f4 ,windle1 eds41 ,charles ,c ,thomas 7,springfield1 ,ill471 #aifj4 ref4#ace ,brodal1 ,a42 ,pompeiano1 ,o42 and ,walberg1 ,f43 ,the ,vestibular ,nuclei and ,their ,connections1 ,anatomy1 and ,functional ,correlations4 ,charles ,c ,thomas 7,springfield1 ,ill471 #aifj4 ref4#acf ,carpenter1 ,m4 ,b43 ,neural ,mechanisms of the ,auditory and ,vestibular ,systems4 ,ch4 #bb1 ,g4 ,l4 ,rasmussen and ,w4 ,f4 ,windle1 eds41 ,charles ,c ,thomas 7,springfield1 ,ill471 #aifj4 ref4#acg ,dow1 ,r4 ,s42 and ,moruzzi1 ,g43 ,the ,physiology and ,pathology of the ,cerebellum4 ,univ4 ,minn4 ,press 7,minneapolis71 #aieh4 ref4#ach ,kempinsky1 ,w4 ,h43 ,cortical ,projection of ,vestibular and ,facial ,nerves in the ,cat4 ,j4 ,neurophysiol41 vol4 #ad1 #aiea1 p4 #bjc4 ref4#aci ,mickle1 ,w4 ,a42 and ,ades1 ,h4 ,w43 ,a ,composite ,sensory ,projection ,area in the ,cerebral ,cortex of the ,cat4 ,am4 ,j4 ,physiol41 vol4 #agj1 #aieb1 p4 #fhb4 ref4#adj ,walzl1 ,e4 ,m42 and ,mountcastle1 ,v43 ,projection of ,vestibular ,nerve to ,cerebral ,cortex of the ,cat4 ,am4 ,j4 ,physiol41 vol4 #aei1 #aidi1 p4 #eie4 ref4#ada ,anderson1 ,s42 and ,gernandt1 ,b4 ,e43 ,acta ,oto-,laryngol4 ,suppl41 vol4 #aaf1 #aied1 p4 #aj4 ref4#adb ,gernandt1 ,b4 ,e42 and ,thulin1 ,c4 ,a43 ,vestibular ,mechanisms of ,facilitation and ,inhibition of ,cord ,reflexes4 ,am4 ,j4 ,physiol41 vol4 #agb1 #aiec1 pp4 #fec-ffj4 ref4#adc ,gernandt1 ,b4 ,e42 and ,terzuolo1 ,c4 ,a43 ,effect of ,vestibular ,stimulation on ,strychnine-,induced ,activity of the ,spinal ,cord4 ,am4 ,j4 ,physiol41 vol4 #ahc1 #aiee1 pp4 #a-h4 ref4#add ,gernandt1 ,b4 ,e42 ,katsuki1 ,y42 and ,livingston1 ,r4 ,b43 ,functional ,organization of ,descending ,vestibular ,influences4 ,j4 ,neurophysiol41 vol4 #bj1 #aieg1 pp4 #dec-dfi4 ref4#ade ,gernandt1 ,b4 ,e42 and ,gilman1 ,s43 ,vestibular and ,propriospinal ,interactions and ,protracted ,spinal ,inhibition by ,brain ,stem ,activation4 ,j4 ,neurophysiol41 vol4 #bc1 #aifj1 pp4 #bfi-bhg4 ref4#adf ,gernandt1 ,b4 ,e42 and ,gilman1 ,s43 ,interactions ,between ,vestibular1 ,pyramidal and ,cortically ,evoked ,extrapyramidal ,activities4 ,j4 ,neurophysiol41 vol4 #bc1 #aifj1 pp4 #eaf-ecc4 ref4#adg ,akert1 ,k42 and ,gernandt1 ,b4 ,e43 ,electroencephalog4 ,clin4 ,neurophysiol41 vol4 #ad1 #aifb1 p4 #chc4 ref4#adh ,gerathewohl1 ,s4 ,j42 and ,ward1 ,j4 ,e43 ,the ,physics and ,medicine of the ,upper ,atmosphere and ,space4 ,o4 ,o4 ,benson and ,h4 ,strughold1 eds41 ,john ,wiley ,sons1 ,inc41 #aifj1 ch4 #bf4 ref4#adi ,gerathewohl1 ,s4 ,j43 ,personal ,experiences ,during ,short ,periods of ,weightlessness ,reported by ,sixteen ,subjects4 ,astronaut4 ,acta1 vol4 #b1 #aief1 pp4 #b,o#e-bag4 ref4#aej ,henry1 ,j4 ,p42 ,augerson1 ,w4 ,s42 ,belleville1 ,r4 ,e42 ,douglas1 ,w4 ,k42 ,grunzke1 ,m4 ,k42 ,johnston1 ,r4 ,s42 ,laughlin1 ,p4 ,c42 ,mosely1 ,j4 ,d42 ,rohles1 ,f4 ,h42 ,voas1 ,r4 ,b42 and ,white1 ,s4 ,c43 ,effects of ,weightlessness in ,ballistic and ,orbital ,flight4 ,aerospace ,med41 vol4 #cc1 #aifb1 pp4 #ajef-ajfh4 ref4#aea ,dayhoff1 ,m4 ,o42 ,lippincott1 ,e4 ,r42 and ,eck1 ,r4 ,v43 ,thermodynamic ,equilibria in ,prebiological ,atmospheres4 ,science1 vol4 #adf1 #aifd1 p4 #adfa4 ref4#aeb ,armstrong1 ,g4 ,t42 ,furukawa1 ,g4 ,t42 and ,hilsenrath1 ,j43 ,a ,survey of ,thermodynamic ,properties of the ,compounds of the ,elements ,,chnops4 ,,nbs ,rept4 #heba1 ,u4,s4 ,dept4 ,com41 #aifd4 ref4#aec ,white1 ,w4 ,b42 ,johnson1 ,s4 ,m42 and ,dantzig1 ,g4 ,b43 ,j4 ,chem4 ,phys41 vol4 #bh1 #aieh1 p4 #gea4 ref4#aed ,jukes1 ,t4 ,h43 ,present ,status of the ,amino ,acid ,code4 ,j4 ,am4 ,dietet4 ,assoc41 vol4 #de1 #aifd1 p4 #eag4 ref4#aee ,nirenberg1 ,m4 ,w42 and ,matthaei1 ,j4 ,h43 ,the ,dependence of ,cell-,free ,protein ,synthesis in ,e4 coli upon ,naturally ,occurring or ,synthetic ,polyribonucleotides4 ,proc4 ,natl4 ,acad4 ,sci4 ,u4,s41 vol4 #dg1 #aifa1 p4 #aehh4 ref4#aef ,ochoa1 ,s43 ,chemical ,basis of ,heredity1 the ,genetic ,code4 ,experientia1 vol4 #bj1 #aifd1 p4 #eg4 ref4#aeg ,kiesow1 ,l43 ,the ,energy-,transforming ,step in ,nitrobacter-,chemosynthesis4 ,biochem4 ,z41 ,bd4 #cch1 #aifc1 p4 #djj4 ref4#aeh ,kiesow1 ,l43 ,on the ,assimilation of ,energy ,from ,inorganic ,sources in ,autotrophic ,forms of ,life4 ,proc4 ,natl4 ,acad4 ,sci4 ,u4,s41 vol4 #eb1 #aifd1 p4 #ihj4 ref4#aei ,clayton1 ,r4 ,k42 and ,adler1 ,h4 ,i43 ,protein ,synthesis and ,viability in ,x-,irradiated ,rhodopseudonomonas spheroides4 ,biochim4 ,biophys4 ,acta1 vol4 #ef1 #aifb1 p4 #beg4 ref4#afj ,pollard1 ,e42 and ,vogler1 ,c43 ,radiation ,action on ,some ,metabolic ,processes in ,e4 coli4 ,radiation ,res41 vol4 #ae1 #aifa1 p4 #aji4 ref4#afa ,novelli1 ,g4 ,d42 ,kameyama1 ,t42 and ,eisenstadt1 ,j4 ,m43 ,cold ,spring ,harbor ,symp4 ,quant4 ,biol41 vol4 #bf1 #aifa1 p4 #acc4 ref4#afb ,kepes1 ,a43 ,kinetics of ,induced ,enzyme ,synthesis4 ,determination of the ,mean ,life of a ,galactosidase-,specific ,messenger ,,rna4 ,biochim4 ,biophys4 ,acta1 vol4 #gf1 #aifc1 p4 #bic4 ref4#afc ,fernandez-,moran1 ,h43 ,new ,approaches in ,correlative ,studies of ,biological ,ultrastructure by ,high-,resolution ,electron ,microscopy4 ,j4 ,roy4 ,microscop4 ,soc41 vol4 #hc1 #aifd1 p4 #ahc4 ref4#afd ,fernandez ,moran1 ,h43 ,electron ,microscope-,medicines ,research3 ,tool of ,unfulfilled ,promise4 ,j4 ,am4 ,med4 ,assoc4 #ahi1 #aifd1 p4#ca4 ref4#afe ,fernandez ,moran1 ,h43 ,electron ,microscope ,with ,high ,field ,superconducting ,solenoid ,lenses4 ,proc4 ,natl4 ,acad4 ,sci4 ,u4,s41 vol4#ec1 #aife1 p4 #dde4 ref4#aff ,deaver1 ,b4 ,s4 ,jr42 ,swedlund1 ,j4 ,b42 and ,bradley1 ,h4 ,jr43 ,magnetic ,properties of ,some ,macromolecules of ,biological ,interest4 ,final ,rept4 ,,phu #dfdd4 ,stanford ,res4 ,inst41 #aifd4 ref4#afg ,sisakyan1 ,n4 ,m43 ,problems of ,space ,biology4 ,vol4 ,i1 ,,ussr ,acad4 ,sci4 ,publ4 ,house 7,moscow7 #aifb4 ref4#afh ,sisakyan1 ,n4 ,m4 and ,yazdovskiy ,v4 ,i413 ,problems of ,space ,biology4 ,vol4 ,,iii4 ,,ussr ,acad4 ,sci4 ,publ4 ,house 7,moscow71 #aifd4 ref4#afi ,jenkins ,d4 ,w413 ,the ,,nasa ,biosatellite ,program4 ,in ,life ,sciences and ,space ,research ,,iii1 ,m4 ,florkin1 ed14 ,north-,holland ,publ4 ,co4 7,amsterdam71 #aife1 pp4 #bcj-bdj4 ref4#agj ,pack ,n43 ,the ,effects of ,weightlessness on ,mammals4 ,space ,biology3 ,proc4 #bdth ,annual ,biol4 ,colloq41 ,oregon ,st4 ,univ41 #aifc1 pp4 #fe-gd4 ref4#aga ,anon43 ,a ,review of ,space ,research4 ,ch4 #i1 ,natl4 ,acad4 ,sci4-,natl4 ,res4 ,council4 ,publ4 #ajgi1 #aifb4 ref4#agb ,committee on ,environmental ,biology3 ,report of ,panel on ,radiation ,biology4 ,space ,science ,board1 ,natl4 ,acad4 ,sci4-,natl4 ,res4 ,council1 #aifc4 ref4#agc ,taleot1 ,j4 ,m43 ,life ,support in ,space ,operations4 ,air ,univ4 ,rev41 vol4 #af1 #aife1 pp4 #db-eb ref4#agd ,del ,duca1 ,m4 ,g42 ,konecci1 ,e4 ,b42 and ,ingelfinger ,a4 ,l43 ,life ,support-the ,next ,generation4 ,space ,aeronautics1 vol4 #da1 #aifd1 pp4 #hd-ia4 ref4#age ,bongers4 ,l42 and ,kok ,b43 ,life ,support for ,space ,missions4 ,develop4 ,ind4 ,micro-biol41 vol4 #e1 #aifd1 pp4 #ahc-aie4 ref4#agf ,ward1 ,c4 ,h42 ,wilks4 ,s4 ,s42 and ,craft1 ,h4 ,l42 ,use of ,algae and ,other ,plants in the ,development of ,life ,support ,systems4 ,am4 ,biol4 ,teacher1 vol4 #be1 #aifc1 pp4 #eab-eba4 ref4#agg ,ney ,l4 ,f43 ,gas ,exchange by the ,duckweed ,family4 ,,onr ,contract ,no4 ,nonr-#bhhg7jj71 ,stanford ,res4 ,inst41 #aifj4 ref4#agh ,nakamura1 ,h43 ,a ,study of ,wolffia as a ,new ,food4 ,rept4 ,microalgal ,res4 ,inst4 ,japan41 vol4 #a1 #aifj1 pp4 #g-ac4 ref4#agi ,myers1 ,j43 ,basic ,remarks on the ,use of ,plants as ,biological ,gas ,exchangers in a ,closed ,system4 ,in ,epitome of ,space ,medicine4 ,j4 ,aviation ,med41 vol4 #be1 #aied1 pp4 #djg-daa4 ref4#ahj ,bowman1 ,n4 ,j43 ,the ,food and ,atmosphere ,control ,problems on ,space ,vessels4 ,j4 ,brit4 ,interplanet4 ,soc1 vol4 #ab1 #aiec1 pp4 #aah-abc4 ref4#aha ,bowman1 ,n4 ,j43 ,the ,food and ,atmosphere ,control ,problems on ,space ,vessels4 ,part ,,ii4 ,the ,use of ,algae for ,food and ,atmosphere ,control4 ,j4 ,brit4 ,interplanet4 ,soc4 ,vol4 #ab1 #aiec1 pp4 #aei-aff4 ref4#ahb ,bassham1 ,j4 ,a43 ,experiments ,with ,photosynthetic ,gas ,exchangers4 ,proc4 ,world ,symp4 ,appl4 ,solar ,energy1 ,phoenix1 ,ariz41 #aiee1 pp4 #ce-ej4 ref4#ahc ,burk ,d42 ,hobby1 ,g42 and ,gaucher1 ,t43 ,closed-,cycle ,air ,purification ,with ,algae4 ,proc4 ,first ,intern4 ,symp4 ,submarine ,space ,med4 ,macmillan ,co4 7,new ,york71 #aieh4 ref4#ahd ,dole1 ,s4 ,h42 and ,tamplin1 ,a4 ,r43 ,the ,sabatier ,reaction for ,inorganic ,recovery of ,oxygen in ,manned ,space ,capsules4 ,in ,closed ,circuit ,respiratory ,systems ,symp4 ,tech4 ,rept4 #fj-egd1 ,wright ,air ,develop4 ,div41 #aifj1 pp4 #bci-bhg4 ref4#ahe ,clifford1 ,j4 ,e42 and ,mc,callum1 ,j43 ,research on the ,electrolysis of ,water ,under ,weightless ,conditions4 ,,amrl-,tech4 ,doc4 ,rept4 #fb-dd1 #aifb4 ref4#ahf ,clifford1 ,j42 and ,faust1 ,c43 ,research on ,electrolysis of ,water ,with a ,hydrogen ,diffusion ,cathode ,to ,be ,used in a ,rotating ,cell4 ,,amrl-,tech4 ,doc4 ,rept4 #fb-id1 #aifb4 ref4#ahg ,rupaske1 ,r43 ,nutritional ,requirements for ,hydrogenomonas eutropha4 ,j4 ,bacteriol1 vol4 #hc1 #aifb1 pp4 #dah-dbb ref4#ahh ,bongers1 ,l43 ,chemosynthetic ,gas ,exchanger4 ,quarterly ,progress ,rept4 ,no4 #d on ,,nasa ,contract ,n,a,sw-#iga1 #aife1 #bc pp4 ref4#ahi ,bongers1 ,l43 ,chemosynthetic ,gas ,exchanger4 ,ann4 ,rept4 on ,,nasa ,contract ,n,a,sw-#gac1 #aifd1 #dd pp4 ref4#aij ,bongers1 ,l43 ,chemosynthetic ,gas ,exchanger4 ,rept4 ,,rm #aec-aifc4 ,martin-,marietta ,space ,systems ,div4 7,baltimore1 ,md471 #aifc ref4#aia ,bongers1 ,l43 ,sustaining ,life in ,space--,a ,new ,approach4 ,aerospace ,med41 vol4 #ce1 #aifd1 pp4 #aci-add4 ref4#aib ,schlegel1 ,h4,g43 ,die ,verwendung von ,h-oxydierenden ,bakterien zur ,regenerierung der ,atemluft4 ,raumfahrtforschung1 ,bd4 #h4 ,nr4 #b1 #aifd1 pp4 #fe-fg4 ref4#aic ,webb4 ,p41 ed43 ,bioastronautics ,data ,book4 ,,nasa ,,sp-#cjjf1 #aifd4 ref4#aid ,foster4 ,j4 ,f42 and ,litchfield1 ,j4 ,h43 ,a ,continuous ,culture ,apparatus for the ,microbial ,utilization of ,hydrogen ,produced by ,electrolysis of ,water in ,closed-,cycle ,space ,systems4 ,biotech4 ,bioeng41 vol4 #f1 #aifd1 pp4 #dda-def4 ref4#aie ,callaway4 ,d42 and ,margen1 ,s43 ,nutritional ,properties of ,hydrogenomonas eutropha4 ,semiann4 ,progr4 ,rept41 ,,nasa ,grant ,,ngr-#je-jjc-7jhi71 #aife4 ref4#aif ,working ,group on ,gaseous ,environment for ,manned ,spacecraft3 ,summary ,report4 ,space ,science ,board4 ,,nas_/,,nrc1 #aifc4 ref4#aig ,lawton1 ,r4 ,w43 ,physiological ,considerations ,relevant to the ,problem of ,prolonged ,weightlessness4 ,astronaut4 ,set4 ,rev41 vol4 #d1 #aifb1 pp4 #a-af4 ref4#aih ,mc,cally1 ,m42 and ,lawton4 ,r4 ,w43 ,the ,pathophysiology of ,disuse and the ,problem of ,prolonged ,weightlessness3 ,a ,review4 ,,amrl-,tech4 ,doc4 ,rept4 #fc-c1 ,aerospace ,med4 ,div4 7,wright-,patterson ,,afb1 ,ohio71 #aifc4 ref4#aii ,smith1 ,r4 ,e42 and ,hock1 ,r4 ,j43 ,brown ,fat3 ,thermogenic ,effector of ,arousal in ,hibernators4 ,science1 vol4 #adj1 #aifc1 p4 #aii4 ref4#bjj ,storer4 ,j4 ,b42 and ,hempelman ,l4 ,h43 ,hypothermia and ,increased ,survival ,rate of ,infant ,mice ,irradiated ,with ,x-rays4 ,am4 ,j4 ,physiol41 vol4 #aga1 #aieb1 pp4 #cda-cdh4 ref4#bja ,working ,group on ,nutrition and ,feeding ,problems3 ,summary ,report4 ,space ,science ,board4 ,man-in-,space ,comm41 ,,nas_/,,nrc1 #aifc4 ref4#bjb ,anon43 ,conference on ,nutrition in ,space and ,related ,waste ,problems4 ,,nasa ,,sp-#gj1 #aifd4 99 ,u4,s4 ,,government ,,printing ,,office #aiff - ,o - #gih #ebj ,transcription note ,the following typographic errors have been corrected3 - 99p4 #b1 l4 #af399 to be called #8exobiology4 ---- to be called exobiology4 - 99,table ,,iii4- ,ultraviolet_/,maximum399 #aj erg_/cm1 #becg ---- #aj erg_/cm1 #becg - 99p4 #eh1 l4 #ad-ae399 approximately #cjj atm7 ---- approximately #cjj atm47 - 99p4 #hj1 l4 -#b399 7#fjj-ajjj ftc7 ---- 7#fjj-ajjj ft-c7 - 99p4 #hg1 l4 #a399 #j4b-m,m ---- #j4b m,m - 99p4 #ii1 l4 #a-b399 faintsess ---- faintness - 99p4 #ajd1 l4 #b399 hiberation ---- hibernation - 99p4 #aaf1 l4 #ai399 processsing ---- processing - 99p4 #aba1 l4 #a399 ,hoffman1 ,r4 ,k41 ---- ,hoffman1 ,r4 ,k42 - 99p4 #abd1 l4 -#aj399 ,rosenszweig ---- ,rosenzweig - 99p4 #abh1 l4 #bi399 ,,amrl ,tech4 ,doc4 ,rept4 ---- ,,amrl-,tech4 ,doc4 ,rept4 ,variant spelling3 ,both forms microorganism and micro-organism have been retained1 as quoted from different sources or bibliographic reference titles4 ,tables3 ,where necessary1 the widths of columns have been adjusted1 and some tables have been split to accommodate the width restrictions on this text format4 ,split tables have had blank lines inserted in order to maintain the alignment between the two parts should they be rejoined at a future date4 ,in the original text1 ,table ,,vi was split over two pages but has been rejoined in this version4 ,references3 ,for ease of searching1 references in the text1 as well as those in the list of references1 have been enclosed in square brackets1 e4g4 ref4#c4 ,,utf-#h characters3 ,this version contains ,,utf-#h characters to represent ,greek letters1 subscripts1 superscripts and some punctuation4 ,if these characters do not appear correctly1 you may need to select a different font4 ,in order for the table columns to line up correctly1 this will need to be a monospaced1 or fixed-width1 font4