Significant Achievements in Space Bioscience 1958-1964 Part 15

It is difficult to estimate the minimum protein requirement of an adult man. The generally accepted criterion of minimum adequate protein nutrition in the adult is the maintenance of nitrogen balance at minimum intake. The minimum protein requirements depend on endogenous nitrogen loss. a.n.a.lysis of the little data available indicates a best estimate of 2 mg of nitrogen per kilocalorie of basal energy expenditure. However, this figure is higher than that noted in experiments in some human subjects.

After minimum nitrogen requirements and minimum amino acid requirements have been established, studies will be directed toward investigating caloric restriction and adaptation to restriction of calories. It has been suggested that caloric restriction in animals and man results in apparent decreased energy need for the same activity. This apparent paradox has never been explained. It has been shown that there is adaptation to repeated episodes of caloric restriction both in animals and man, so that subsequent periods of caloric restriction result in decreased rate of weight loss, nitrogen loss, and longer survival.

Additional experiments are urgently required to determine the metabolic demands for minerals-in particular, the metabolic balance of calcium, pota.s.sium, sodium, and phosphorus. Under conditions of high water consumption, large mineral losses are to be expected. Failure to replace these can cause an imbalance which could impair the efficiency of the individual to the extent of endangering the flight.

a.n.a.lysis of samples taken in flight, both of urine and feces, should be made. Respiratory quotients can be determined in flight, blood samples should be taken before and immediately after flight for a.n.a.lyzing selected components (in simulator studies these could be taken periodically), and nutritional intakes (which would be facilitated by formula diets) must be measured and a.n.a.lyzed.

Short-Range Technology

There are many practical difficulties in providing for food storage and accessibility in s.p.a.cecraft. The packaging of food materials, both dehydrated and liquid, has proceeded satisfactorily under the supervision of the Food and Container Inst.i.tute. If packaging materials are to be made to withstand very high relative humidities and large variations in temperature, additional investigations are required, since such containers are not yet available. In packaging, serious consideration must be given to the ease with which the food may be reached and eaten.

If dehydrated formula foods are to be fed on short-term missions, additional work is required on the rehydration of such formulas. Present methods of water measurement under weightless conditions are not satisfactory, and better methods will have to be contrived.

Long-Term Nutritional Problems

There is a dearth of metabolic information, even for short-duration flights, without which changes in metabolic patterns to longer flights cannot be extrapolated. However, using scattered information, certain changes which may be encountered can be hypothesized. Decalcification of bone and changes in water-holding capacity of the body may be antic.i.p.ated. It is also possible that changes in proportion of fat to lean body ma.s.s could be experienced and should be considered in nutritional planning. Nutritional requirements depend on size, particularly lean body ma.s.s, s.e.x, physiological state, and individual metabolic rates. Therefore, individuals for s.p.a.ce flight should be screened with these factors in mind if it is desirable to minimize food intake in long flights. The factors which influence the total nutritional requirements of the individual also influence his mental and physical responses to stress.

Synthetic Foods

The development of food materials other than those derived directly from animal or vegetable origin is of interest. Advantages of such diets may be low residue, ease of storage, rehydration, and manipulation.

Experiments with chemically defined synthetic diet for humans have been carried out by Medical Sciences Research Foundation, San Mateo, Calif.

The complete liquid diet is composed of required amino acids, fat, carbohydrate, vitamins, and minerals. A cubic foot of the diet (50 percent solids in H2O) supplies 2500 calories per day for 1 month, and has been given a variety of artificial flavors.

This synthetic diet has been fed to human volunteers for 6 months in a pilot study at the California Medical Facility, Vacaville, Calif., and the results are being reviewed. Schwarz Bioresearch, Inc., is studying the storage, stability, and packaging of chemically defined synthetic diets for human and animal flights.

Food Production in s.p.a.ce

Long-term feeding in s.p.a.ce depends upon a payload of stored food unless food is produced during flight. If sufficient propulsive energy is available, the duration of missions using stored food may be quite long.

However, in emergencies in which a mission lasts longer than planned, survival may depend on the ability to produce food extraterrestrially.

Eventually it will be desirable or necessary to produce food beyond the confines of Earth.

The nutritional requirements of the crew will be influenced by such factors as activity, physical and psychological stress, individual size of the members, and individual metabolic rates. The food intake will have to be adjusted to meet these requirements. It is necessary to know the nutritional requirements of each astronaut and the way in which these are altered by the conditions of s.p.a.ce flight in order to estimate needs on long missions. Without this information, the food supplies for the longer flights may be too much, too little, or improperly balanced.

Where dependence would not be on stored food alone, but on food produced en route, more exact information on requirements is needed to determine the capacity of food production units.

In the discussion of bioregenerative systems, it was suggested that food materials could be produced by photosynthetic organisms (e.g., algae, duckweed, and other higher plants) or by nonphotosynthetic organisms (e.g., _Hydrogenomonas_). In contrast to the use of living organisms, reprocessing waste materials by chemical treatment or the actual synthesis of high-energy compounds has been suggested. No chemical system has yet been demonstrated as workable for the economical production of food in s.p.a.ce, and the systems considered produce materials which may be converted to food, but are not food as such.

Algal cultures have had the most extensive investigation as food in s.p.a.ce, but the technical problems of using this material as a food source have not yet been solved. It is apparent from the investigations to date that algae will require treatment before they can be used as food. In limited trials, difficulties have been experienced with amino acid deficiencies, digestibility, high residues, and gastric distress.

Processing methods which would be applicable in s.p.a.ce travel and the possibility of secondary conversion by other animals or plants should be systematically investigated.

chapter 8

_Significance of the Achievements_

SIGNIFICANCE TO SCIENCE

One of the most critical research areas of the s.p.a.ce program is bioscience. Of both practical and philosophical significance in exploring the origins of life and the possibilities of life on other planets, bioscience also promises much in medical aspects. s.p.a.ce offers biologists completely new environmental factors, such as the effects of zero gravity and of removal from Earth's rotation. These effects have been studied in attempts to advance understanding of basic mechanisms of physiology and biological rhythms. These studies can be of great value in dealing with problems of disease and metabolic disorders.

Biological research is fundamental to the problem of successfully protecting and sustaining man in the peculiar and hostile s.p.a.ce environment. Understanding human requirements and variations in their response to various environmental factors offers value in medical research for human survival and comfort. The many technological discoveries and advancements in electronic and engineering equipment greatly enhance medical diagnosis, treatment of disease, and the extension of human life.

The life sciences, biology and medicine, are fundamental to the success of manned exploration of s.p.a.ce, which marks a unique and significant development in the long history of man's conquest of new frontiers.

Those who pioneered other frontiers on land and sea and in the air were not forced to await biological and medical research. Even the pioneers of aerial flight began their efforts without first seeking biomedical data. The search for such data followed flight experience and, indeed, was made only after problems arose.

Project Mercury, NASA's first program for manned s.p.a.ce flight, stimulated immediate and extensive studies in the life sciences to sustain man in s.p.a.ce. Before a vehicle could be designed to carry an astronaut into s.p.a.ce, antic.i.p.ated biomedical problems a.s.sociated with s.p.a.ce flight were studied. Life-support systems were designed to offer adequate protection from environmental stresses peculiar to s.p.a.ce, such as zero gravity, removal from Earth's rotation, and high-energy cosmic radiation. These life-support systems used knowledge already gained from research for manned s.p.a.ce flight by the U.S. Air Force.

Our entry into s.p.a.ce 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 endeavor. As man goes farther into s.p.a.ce, the hazards increase; 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 s.p.a.ce itself.

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 speculation. There is one prediction, however, that can be made with considerable certainty by reason of historical precedent-the opportunity to investigate a totally new area, such as is offered by s.p.a.ce exploration, is certain to produce a burst of scientific interest as soon as the path is charted by a few pioneers.

Over the next few decades a progressively larger proportion of biological interest will turn to s.p.a.ce. We may well expect that the discoveries made here will revolutionize some of our concepts of biology.

It should be fully realized that the acc.u.mulation 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 Nation.

SIGNIFICANCE FOR PRACTICAL APPLICATIONS

It can be predicted as confidently for s.p.a.ce biology as for other s.p.a.ce sciences that the economic costs will be amply repaid in the long run by applications of s.p.a.ce-oriented biotechnology to other fields of biology and medicine. There are inevitable substantial, though indirect, contributions of NASA's continuing efforts in s.p.a.ce biology.

NASA-supported biological research has many practical applications and "spinoffs" which contribute to the fields of health and medicine, food and agriculture, and industry and manufacturing. Some of these are presented to show the range and value of applications which have resulted from basic and applied biological research. In addition to those listed are many others from the biosatellite program, particularly in the fields of bioengineering and miniaturization.

Health and Medicine

Solar cells, which have powered s.p.a.ce systems, are now being used as a power source in studies on brain function. A miniaturized solar cell developed by General Electric provides enough power, under ordinary house lights, to stimulate an animal's brain and to telemeter respiratory, cardiovascular, and brain-wave data while the animal is allowed to move about freely. Such a system is now used by the National Inst.i.tute of Mental Health Laboratory at Rethesda, Md.

Scientists at the Ames Research Center have devised a new technique for studying organic compounds, whether synthesized in the laboratory or produced by a living system. This technique is based on a property of matter called optical activity. Previous methods of measuring optical activity have been plagued by low sensitivity. The new method is many tunes more sensitive and represents a real contribution to modern a.n.a.lytical instrumentation.

Studies on calcium metabolism and bed rest simulating weightlessness are adding knowledge on the prevention of demineralization of the skeleton; treatment of Paget's disease and osteoporosis prevention of muscular atrophy; the cause and treatment of renal calculi (kidney stones); optimal calcium for the human diet; and the factors influencing calcium absorption, metabolism, and excretion. The results will have great importance in bone healing and repair, care and treatment of fracture cases, treatment of paraplegics, and treatment of polio patients and similar cases. These grant studies at Texas Woman's University have also proven that the X-ray bone densitometry method can accurately detect changes in the skeleton.

A primary objective of the planetary exploration program is the detection of possible extraterrestrial life. The study of the fundamental properties of living things on Earth is restricted to the type of life which has evolved and survived here. Life which has been exposed to totally different environmental conditions may have markedly different physiological characteristics. 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 importance. Advancement in the treatment of disease and the problems of aging are among the many possible consequences.

New developments in such techniques as ultraviolet spectrophotometry, polarimetry, and gas chromatography will find use in the detection of biochemicals and other compounds in hospitals and in toxicology and pathology laboratories. They will also be useful in studies of atmospheric pollutants such as smog.

Studies of the chemistry of living systems, molecular biology, and biophysics of cellular processes will create a better understanding of the basic mechanisms of life, leading to an understanding of both inherited and acquired disease, especially neoplastic conditions and chemical disturbances incident to mental disease.

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 a.n.a.lysis for recording, counting, and sorting chromosomes.

Structural changes in blood cell chromosomes can indicate the degree of radiation damage as well as damage resulting from various environmental stresses. Accordingly, this instrument, when developed, can be used as a radiation dosimeter in civil defense by swiftly detecting the degree and type of chromosomal aberrations in blood cells. Thus, casualties in nuclear attack could be quickly detected and treated. This system would also be useful for nuclear industrial plants and for military maneuvers.

In medicine, various disease trends could be monitored. (Chromosomes exhibit anomalies in leukemia and mental r.e.t.a.r.dation as well as in other states.) In s.p.a.ce exploration and experimentation, the device can spot monitor radiation dose levels as well as changes resulting from any of the environmental stresses experienced in s.p.a.ce. This apparatus can be modified for use as an extraterrestrial-life-detecting instrument by scanning the growth of cells (or cellular inclusions), computing rates, and telemetering changes to the researcher.

Investigations of rhythmic phenomena of various physiological systems can result in knowledge of the utmost importance to medicine. Rhythmic phenomena are found in the cardiovascular system of normal humans.

Changes in these rhythms have the potential of foretelling abnormalities (heart disease, arteriosclerosis) before outward signs are manifested, allowing for earlier diagnosis, treatment, and control or cure.