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In two studies in which 12 test subjects participated there has been investigated the possibility for alimentary correction of some metabolic changes developing in man as a result of different stress effects. It is indicated that the ration supplemented by alimentary means (phosphatic concentrate, vitamins, glucose, some mineral elements) produced corrective action on the studied parameters of the lipid and protein metabolism.

Three experimental series, in which 20 test subjects took part, were carried out to investigate the effect of super-erythemic doses of ultraviolet irradiation on metabolic parameters. It was found that UV irradiation of 12-15% of the skin area led not only to skin changes but also to functional changes in certain organs and systems, which was indicated by variations of metabolic parameters.

Four volunteers were enclosed for 40 days in a hypercapnic environment. Their average age was 41-59 years, body weight, 66-90 kg, and height 173-182 cm. During the study the ambient temperature was 19-23 degrees C, relative humidity, 50 +/- 20%; pO2, 19-19.5%; and pCO2, 1.3%. On test days 21-22 and 38-39 pCO2 was increased to 4% and pO2 was decreased to 17%. The time, within which pCO2 was increased to 4% on test days 38-39 when compared to test days 21-22, grew 1.5-fold and amounted to 40 hours. The subjects had three meals a day, consuming canned foodstuffs, the caloric value of which was 2982 kcal/day. In the study the following parameters were measured: malonic dialdehyde in venous blood; catalase, lactate, pyruvate, urea, acid-base content, gases in capillary blood; total nitrogen, ammonia, urea, creatinine and uric acid in 24-hour urine samples. Nitrogen balance and protein nutrition index were calculated. Results were processed using Student's t-test. During exposure lipid peroxidation increased and catalase decreased; malonic dialdehyde in blood increased, being correlated with lower hydrocarbons in exhaled air; gas and energy turnover during hypercapnic intervals enhanced. The above changes in the exhaled air composition, gas and energy turnover, biochemical blood and urine parameters remained within adaptation norm. By the second week of the recovery period the above parameters, except for nitrogen metabolism which remained slightly inhibited, returned to the normal.

In three series of experiments of 120, 49 and 180 days in duration 36 test subjects were exposed to clinostatic and antiorthostatic hypokinesia. Human requirements for various nutrients were defined under hypokinetic conditions. It was demonstrated that during bed rest exercises together with adequate nutrition and after bed rest certain nutrients can serve as efficient countermeasures against metabolic changes.

Two 60-day studies in which 10 healthy volunteers participated were carried out. In both studies stress situations were simulated by a chamber rise to an altitude of 8000 m, anticipation of exposure to acceleration, and psychological tests. The changes found were dependent on both the type of the stressor applied and duration of the exposure. Nutrient supplements did not influence the adrenocortical function of the adrenals.

The effect of spaceflight simulation factors (ascent to an altitude of 8,000 m, anticipation of centrifugation, psychological test, hypokinesia, and enclosure in an altitude chamber) on the content of free and protein-bound 11-hydroxycorticosteroids in plasma was studied. This exposure produced changes in the total and fractional content of the hormones. The changes depended on the simulation factor, duration of its action, and functional status of test subjects.

Nitrogen metabolism in 16 test subjects and 8 cosmonauts kept on a diet containing dehydrated products and foodstuffs preserved by other methods (15% and 85%, respectively) was studied. The health state and excretion of end-products of nitrogen metabolism in those people gave evidence that the dietary protein met well bodily requirements under normal conditions, in simulated flight, and in real flight aboard Salyut-6.

Studies of the effects of space flight simulation factors on lipid metabolism showed that space diets developed for space flights of different duration (dehydrated foodstuffs alone or in combination with foods preserved by other methods) did not produce noticeable changes in lipid metabolism. Nevertheless, other factors, i.e. hypokinesia, intake of nerobol during hypokinesia, an altered work-rest cycle, an increased carbon monoxide concentration (up to 15 mg/m3) influenced lipid metabolism.

Renal excretion of ascorbic acid, thiamin and 4-pyridoxic acid was studied in 18 test subjects exposed for 182 days to head-down tilt. Two groups of subjects (6 subjects each) performed exercises of different work load and the third - control - group was exposed to hypokinesia as such. It was shown that exercises produced a beneficial effect on vitamin metabolism. It is recommended to develop preliminary adaptation to the work load planned as a countermeasure in real or simulated weightlessness.

The effect of a changed atmosphere, hypoxia, hypercapnia, their combinations and different motor activities on the adrenocortical function was studied in 36 test subjects kept in an 8 m3 altitude chamber. Human adaptation to the environmental changes developed with an active involvement of the adrenal cortex. The level and direction of the changes depended on both the force of the influences and on the initial state of the test subjects.

The content of lactate dehydrogenase, amino transferases and creatine kinase was measured in the test subjects of three age groups (41-50, 50-57, and 26-33 years) exposed to head-down tilt, linear acceleration, exercise, and emotional stress. The enzyme activity increased in response to head-down tilt, acceleration and exercise. The enzyme content normalized under the influence of selected nutrients.

Hormonal regulation of metabolism was investigated in test subjects of three age groups: group 1 included test subjects of 41-50 years old, group 2 test subjects of 50-57 years old, and group 3 test subjects of 26-33 years old. Test subjects from groups 1 and 2 were exposed to head down tilt (-8 degrees) as well as linear acceleration of 3 GZ for 1 min and exercises of 450-1050 kgm before and after the tilt test. Group 3 test subjects were exposed to neuro-emotional stress before, during and after the head-down test. Exposure to head-down tilt, acceleration and exercises caused adaptive changes in humoral regulation of metabolism in the test subjects of groups 1 and 2. Food supplements given to group 3 test subjects produced a normalizing effect on humoral regulation of metabolism.

The paper discusses the results of five studies on 35 test subjects conducted to test diets of dehydrated products to be used in prolonged space flights. The studies have demonstrated that a diet consisting of only dehydrated food products can be used for a prolonged time (up to 1 year). Dehydrated foods after a 2-year storage and proton irradiation at a dose of 24,000 rad retain their biological value and assure an adequate nutritional status. On this basis a space diet composed of dehydrated foods has been developed.

Simulated stress conditions (rise to a simulated altitude of 8000 m, anticipation of an exposure to acceleration, mental work to be done under the conditions of time deficiency, "success" or "failure") brought about changes in the protein, carbohydrate, vitamin metabolism, heart rate, adrenal function, and peripheral blood. Nutrient ingredients (vitamins, glucose, minerals, phosphatid concentrate) added to the diet before and during stressful exposures were shown to correct the parameters studied.

This paper presents physiological and hygienic evaluations of the food supply of Salyut-7 crews in normal conditions, simulation and actual flights of various duration (211, 150, 237, 165 and 126 days). The examinations have shown that the diets used have provided satisfactory health conditions and good nutritional status of the crewmembers.

Two experiments were performed on 16 test subjects (13 men and 3 women) to study stress-effects on the blood content of sugar and cholesterol. The test subjects were given a nutritionally balanced diet of canned food-stuffs. The caloric value of the diet was adequate to energy expenditures. In the first experiment, the test subjects were also given vitamin E, nicotinic acid and other vitamins constituting the polyvitamin complex Aerovit. In the second experiment, they were additionally supplemented with calcium and potassium salts, glucose and phosphatid concentrate. The stress-agent was a test in the rotating chair in the first experiment and a psychologic test (mental work within a limited period of time to reach success or failure) in the second experiment. The content of sugar and cholesterol before and after the stress-effects did not differ significantly. This can be attributed to the prophylactic effect of the nutritional factor on carbohydrate and lipid metabolism in an emotionally stressed man.

The content of histamine and serotonin was measured in test subjects exposed to: I experimental series--bed rest at an angle of +6, -2 or -6 degrees; II experimental series--neuro-emotional stress, III experimental series--an increased concentration of ammonium in the enclosure. The exposure to the factors that simulated space flight effects (i. e., orthostatic hypokinesia at -6 degrees and neuro-emotional stress and anticipation of rotation in the centrifuge) led to an increase of histamine and serotonin and a decrease of histaminepectic activity. Consumption of selected nutritional agents a day before and on the day of exposure to the neuro-emotional stress improved the content of histamine and serotonin as well as histamine-pectic activity.

The effect of prolonged enclosure, changed diet, atmosphere and hypokinesia on lipid metabolism was investigated in 115 test subjects during 27 experimental runs. It was concluded that the changes in lipid metabolism occurred primarily due to reduced work load.

Forty-two healthy volunteers, aged 19 to 49, participated in three bed rest studies of 69 to 180 days in duration. The test subjects were kept on the diet consisting of dehydrated foods: fresh, stored for up to 2 years, and exposed to proton irradiation at a dose of 24,000 rad. Metabolism of amino acids was investigated under these conditions. It was concluded that during prolonged storage and irradiation proteins of dehydrated foods retained their biological value. This allows their use in long-term space flights.

The effect of various ammonia concentrations in an enclosed atmosphere on man's adrenocortical system was investigated in five experiments on 20 young healthy test subjects. The most pronounced changes in the adrenocortical system developed when the ammonia content was 5 mg/m3.

Twenty one test subjects exposed to head-down tilt for 120 days were subdivided to four groups: Group 1--nine subjects used as controls, Group 2--three bed rested subjects who performed regular exercises, Group 3--four bed rested subjects who were given selected drugs, including Vitamin F-99 that influenced lipid metabolism, and Group 4--four bed rested subjects who performed regular exercises and received Vitamin F-99. At different stages of bed rest and recovery the content of lipoprotein fractions and lipids of different classes in serum was measured by thin-layer chromatography. The concentration of cholesterol in biliary lipids was determined. In Group 1 and 2 subjects bed rest led to a drastic and significant increase of cholesterol esters in blood, a decrease of phospholipids, variations of triglycerides and non-esterified fatty acids, and a lower percentage content of alpha-lipoproteins. The use of Vitamin F-99 produced positive changes in the above parameters of lipid metabolism (it normalized the level of cholesterol and phospholipids). In Group 4 subjects the effect of exercise combined with drugs was most distinct.

The biological value of the protein component of three modifications of the Salyut space diet was measured in laboratory studies and in simulated space flights. Three experimental runs of up to 68 days in duration were carried out on 20 volunteers. During the study the following parameters of protein metabolism were measured: total protein and protein fractions in serum; urea, uric acid and creatinine in blood; total nitrogen, urea, ammonia, uric acid and creatinine in urine. The results obtained showed that the diet modifications provided an adequate nutritional status and a normal level of the above parameters of protein metabolism.

The paper describes the use of advanced space diets of three prime crews who made 96-, 140- and 175-day flights aboard Salyut-6. It is concluded that the diets facilitated maintenance of a good nutrient status, high work capacity and normal health condition.

Changes in metabolism and digestive function seen in 8 test subjects during 49-day head-down tilt returned to normal in those kept on supplemented diets (protein, polyunsaturated fatty acids and minerals) faster than in the untreated subjects. It is concluded that such supplements are beneficial for the recovery of health status after prolonged head-down tilt.

The present paper summarizes the experimental data on influence of antiorthostatic hypokinesia (49 days) and rationalized nutrition during the rehabilitation period (30 days) on metabolic processes. On the basis of these data a well balanced diet is recommended for the rehabilitation period which follows a long-term bed rest.