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The following principles, derived from the experience of medical support during past spaceflights, can provide a basis for a system of health monitoring and diagnosis during long-term and interplanetary missions: a system of preflight medical screening; medical screening on a systemic basis, which may include purposeful diagnosis in subsystems following the method of hierarchic structure; use of an individual approach; correction of the medical program with respect to the space crew status; assessment of the interrelations of the entire complex of parameters; utilization of the methods of correlation, classification and identification to elicit interrelations between different functions; evaluation of shifts in body functions and their adequacy to ambient conditions; continuity of medical examinations during all pre-flight stages, during flight and after completion of flight; analysis of information and anamnestic data by means of data bases; confidentiality of medical conclusions. Discussed are a classification of unfavorable microgravity-related syndromes, possible impairments due to abnormal situations, and some approaches to the prediction of the risk of various diseases, in relation to the construction of a conceptual diagnostic model for interplanetary missions. In the interest of medical monitoring special significance is attributed to the knowledge of individual norms for each crew member and of his unique peculiarities. Such data can be compiled by means of statistical analysis (single and multidimensional analysis) of the results of medical examinations and of observations during selection, training and tests. Selection of necessary physiological parameters, functional loads and data processing techniques which can be used in combination with other data sources for inflight diagnosis should be based on the following principles: the use of informative, non-invasively registered parameters and functional tests to reveal adverse states or most probable diseases; the possibility to assess the dynamics of physiological parameters and the status of the regulatory systems, and to predict possible developments in the body; the possibility to check the efficiency of countermeasures; the possibility to differentiate a physiological state adapted to the current environment from a pathological state; the possibility to differentiate between specific and non-specific reactions; the possibility to differentiate defensive, adaptive or compensatory phenomena from pathological manifestations. This paper describes the application of single- and multidimensional, statistical methods to process diagnostic information, to reduce the vector dimension of the chosen parameters, and to classify and identify individual and crew physiological standards providing the ability to assign an individual to a suitable team. Thus it will be possible to acquire comprehensive and statistically reliable information in compact format, and thus to perform a more incisive analysis and diagnosis of various states by comparing them with the baseline preflight data. These theoretical considerations constitute the basis for a conceptual model for medical diagnosis in long-term orbital and interplanetary missions. The paper contains a section dealing with the practical aspects of medical monitoring and diagnostic examinations during Mir missions. The program of medical monitoring for long-term Mir missions incorporates on-line monitoring during intravehicular and extravehicular activities, routine daily examinations, periodic extensive medical examinations accomplished on schedule or an indication. The Mir program includes cardiovascular investigations at rest and during functional loading, testing of the cosmonaut muscular systems, validation of the standard training protocols, occasional blood and urine analysis, incl. serum immunoglobulins, and blood cell counts. (ABSTRACT TRUNCATED)

The effects exposing rats to space flights of various lengths in a series of COSMOS satellites are reported based on an evaluation of plasma hormone levels and several enzyme activities in the tissues. The results after space flights are compared with those obtained from rats exposed to acute or repeated stress. Space flight induced selective morphological responses in the corticotrophs and gonadotrophs of the pituitary. Plasma levels of ACTH did not change, but plasma growth hormone and TSH levels decreased after longer space flights (>14 days), while prolactin in the plasma increased after short flights (5-7 days). Plasma corticosterone was higher after all flights. Catecholamine levels in plasma increased only after long space flights. These changes in plasma hormone levels affected the activities of enzymes involved in the amino acid metabolism of the liver and lipolysis in the adipose tissues. Norepinephrine level and catecholamine synthesizing enzyme activity in the hypothalamus did not change in flight rats. The norepinephrine content, however, decreased in several nuclei selected from the hypothalamus of flight rats. Increases in plasma insulin and glucose were noted in rats after space flight. Glucagone values in plasma remained unchanged. Comparing these results from flight rats against rats exposed to acute or repeated stress indicate that long stays in microgravity do not represent intensive stressogenic stimulus of the adrenocortical and sympathetic adrenomedullar systems, and hormone alterations observed after space flight may be due primarily to acute stressor activity resulting from a return to Earth's gravity (gravitational stress).

Analyzing the mechanism responsible for changes in the circulatory system which develop in microgravity depends on the results of medical examinations during long-term space flights. The primary component involves the elimination of gravity-related deformities and mechanical tension among body structures responsible for modifying gravireceptor impulse inputs, fluid redistribution and functional load reductions in the muscular system. This causes the circulatory system to change. The influence of these factors on the circulatory system is substantiated through theoretic-physiological fundamental principles during long-term space flights.

Microgravity is known to have a substantial effect on fluid homeostasis. The research described here was planned as part of the first joint Russian-U.S. science program carried out during a Shuttle flight. The aim of the program was to study the nature of the changes in fluid homeostasis induced by microgravity, as well as to determine the possible mechanisms underlying the regulation of fluid balance under conditions of spaceflight. To determine the effects of spaceflight on the homeostasis of fluid and electrolytes, measurements were taken of total body water, extracellular fluid plasma volumes, levels of regulatory hormones, and nutrient consumption before, during, and after a nine-day flight. Changes in renal function were studied before and after the flight. In these 2 subjects, weightlessness was not associated with a decreased extracellular fluid volume. However, there were the characteristic decreases in plasma atrial natriuretic peptide concentrations, and increases in plasma and urinary cortisol. Results indicated decreased urine volume, even through the first 48 hours of flight. Fluid volumes and glomerular filtration rate were increased after landing, probably related to the saline-loading countermeasure used by Shuttle crewmembers. The information obtained as a result of this research will facilitate the development of future research programs, as well as preventive measures for future long-duration spaceflights.

Eight healthy untrained male volunteers pedalled a cycle ergometer according to two exercise protocols: the first involved step-wise increasing physical exercise to maximal (MPE); the second involved prolonged (35 min) submaximal physical exercise (PPE) at 70% of the individual's maximal oxygen uptake. Each volunteer performed these exercise twice, following either an intravenous injection of phosphocreatine (PCr) or a placebo of an isotonic NaCl solution. Anaerobic threshold (AT) was determined from the point of departure of the ventilatory response from linearity and from the sudden increase in venous blood lactate concentrations during MPE. After exercise following placebo administration we observed increases in concentrations of blood substrates, plasma adrenocorticotropin (ACTH), growth hormone and cortisol and in the number of glucocorticoid receptors in lymphocytes without changes in the dissociation constant. Intravenous administration of PCr (starting 1 day before exercise) led to an increase in the total workload (on average by 5.8%) and in AT (on average by 6.8%) during MPE and to a better tolerance of exercise during PPE. Following PCr administration we observed lower blood lactate concentrations and different patterns of some enzyme activities, less pronounced changes in plasma ACTH and cortisol concentrations and in glucocorticoid binding in lymphocytes, but no changes in plasma growth hormone concentrations compared to the placebo. The results showed that intense physical exercise led not only to increases in blood hormone concentrations but also to an increase in the density of glucocorticoid receptors in lymphocytes. Intravenous PCr injection led to smaller changes in ACTH and cortisol concentrations as well as to a lower activation of glucocorticoid binding in lymphocytes.

The system of countermeasure of microgravity effects has been developed in Russia that allowed to perform safely long-term space flights. This system that includes different means and methods such as special regimens of physical exercises, axial loading ("Pingiun") and antigravity suits, low body negative pressure device (LBNP, "Chibis") and "cuffs" and others has been used with certain variations at certain stages of flight in 27 successfully accomplished space flights that lasted from 60 to 439 days. The pre-, in- and postflight studies performed in 57 crew members of these flights have shown that the system of countermeasure is effective in preventing or diminishing to a great extent almost all the negative effects of weightlessness in flights of a year and more duration and that the intensity and duration of changes recorded in different body systems after flights do not correlate significantly to flight durations, correlating strongly to the volume and intensity of physical exercises used during flight and especially during concluding stage of it.

To create a life support system based on biological and physical-chemical processes is the optimum solution providing full-valued conditions for existence and efficient work of people at a lunar base. Long-standing experience in experimental research or closed ecosystems and their components allows us to suggest a realistic functional structure of the lunar base and to estimate qualitatively its parameters. The original restrictions are as follows: 1) the basic source of energy to support the biological processes has to be the solar radiation; 2) the initial amount of basic biological elements forming the turnover of substances (C, O, H, P, K, N) has to be delivered from Earth; 3). Moon materials are not to be used in the biological turnover inside the base; 4) the base is to supply the crew fully with atmosphere and water, and with 90% (A scenario) or 40% (B scenario) of food. Experimental data about the plant productivity under the "Moon" rhythm of light and darkness allow us to suggest that the A scenario requires per one human: plant area--40 m2 irradiated during the lunar day by 250-300 W/m2 PAR producing 1250 g of dry biomass a terrestrial day; a heterotrophic component of "biological incineration" of inedible plant biomass (800 g/day) including the aquaculture of fish to produce animal products and contaminating the environment less than birds and mammals, and the culture of edible mushrooms; a component of physical-chemical correction for the LSS environment including the subsystems of: deep oxidation of organic impurities in the atmosphere and of water, organic wastes of human activity and that biological components (420 g/day) CO2 concentration in "Moon" nights, damping O2 in "Moon" days, etc. The stock of prestored or delivered from Earth substances (food additions, seeds, etc.) to be involved in biological turnover is to be about 50 kg/year per man. Increase of the mass of prestored substances per man up to 220 kg/year would reduce twice the plant area and consumed amount of radiant energy to exclude the components of "biological incineration" and physical-chemical destruction of organic wastes.

The article presents data concerning the osmolality and concentration of electrolytes and hormones regulating their balance for blood serum of 223 cosmonauts and astronauts. The obtained results allow us to judge the constancy of physicochemical parameters for the blood serum of healthy individuals and how they react to extreme conditions of space flight. The parameters used for evaluation included not just absolute values for the examined indices, but also how they responded to space flight, the dependence on baseline values and the interrelationship between ions. These data are important to predict the effect of exposure to extreme conditions and point to what extent the effect depends on the characteristics of the individual.

The biorhythmological structure of water-electrolyte metabolism was studied in humans during 7-day "dry" immersion. Results were processed with a set of mathematical methods in order to identify a parameter which would allow to obtain scientifically valid, reliable data without violation of any ethic constraints inherent to investigations with healthy test-subjects. Even this period of immersion gravely impacted functioning of kidney as an executive organ in the system of water-electrolyte homeostasis. Data of this study point to applicability of Cosinor analysis for quantitative assessment of fluctuation patterns in parameters of close to harmonical circadian rhythms, and variation analysis and normalized mean for rhythms of arbitrary forms.

In a number of flights, cosmonauts and astronauts have experienced aggravation of their health status and general condition in the initial hours and days in a weightless environment. One of the trigger mechanisms for the onset of these unfavourable conditions at the start of space flight is a redistribution of body fluids and a blood shift towards the head. To ensure controlled hypohydration as a countermeasure to the deleterious effects of 0-g and to investigate the feasibility to control adaptation, six cosmonauts were administered lasix once a day during the first 3 days of a mission. All data of the experiment (correction test, questionnaire, hematocrit) were recorded on a special form in the logbook and transmitted to the control centre for processing. Results showed that the diuretic weakened the sensation of discomfort and improved the cosmonauts' general condition. Objective indices of the correction test indicate an increased work ability of cosmonauts. After hypohydration, circulating plasma volumes in the group were reduced by 6.8 + 1.0% on average.

In previous studies the activity of the sympathoadrenal system (SAS) in cosmonauts during space flights was evaluated by measuring plasma catecholamines (CA) levels and urinary CA and their metabolites concentrations. Plasma CA levels are accepted indicators of SAS activity, however, they are determined by the plasma clearances as well as the rates of CA release (spillover-SO) into the bloodstream. Nowadays methods are available which evaluate not only plasma levels of CA but also their release, spillover, uptake, reuptake, degradation and also CA synthesis in vivo measured by plasma levels of dihydroxyphenylalanine (DOPA). Plasma concentrations of DOPA, the CA noradrenaline (NE), adrenaline (ADR), and dopamine (DA), the deaminated catechol metabolites dihydroxyphenylglycol (DHPG) and dihydroxyphenylacetic acid (DOPAC), and the O-methylated metabolites methoxyhydroxyphenylglycol (MHPG) and homovanillic acid (HVA) were measured during immobilization stress (IMO) in conscious rats. Radiotracer methods were used to measure NE SO. IMO markedly increased arterial NE levels but NE SO was less elevated because the NE clearance was slightly reduced in IMO rats. Simultaneous measurements of plasma CA and their metabolites provide another means to obtain information about SAS function. For instance, dissociation between changes of plasma DHPG and NE levels can indicate changes in neuronal reuptake of NE. We found marked parallel increases in plasma NE and DHPG levels during acute IMO; however after repeated IMO, plasma NE levels were increased but DHPG responses were less pronounced suggesting a reduced NE reuptake. DOPA, the CA precursor, circulates in plasma at a concentration higher than NE. During stress, increased sympathoneural outflow stimulates DOPA synthesis and release into the circulation supporting the view that changes in plasma DOPA levels during stress reflect in vivo changes in the rate of CA synthesis. We propose to measure the new plasma indicators of SAS activity in cosmonauts and/or in animals before, during and after space flights.

In one cosmonaut, we investigated lower body negative pressure (LBNP)-induced capillary fluid shifts which we hypothesized would be changed by microgravity (micrograms) adaptation. Sound pulse velocity (SV) was determined in whole blood and plasma samples, using a new method that could detect 0.1% protein concentration changes. Experiments were performed 3 months preflight (supine), during space flight (6th day in orbit), and postflight (supine; 4th day after landing). Antecubital blood was taken at the beginning (3 min: time a) and after shut-down (+2 min: time b) of 40 min LBNP (-15/-30/-35 mm Hg for 15/15/10 min, respectively), since in control experiments with multiple sampling on Earth, the largest difference (increase) between blood and plasma SV was observed between a and b. Our cosmonaut had a 1.6 m/s increase in blood sound pulse velocity (BSV) preflight and a 4.0 m/s increase postflight, whereas BSV stayed unchanged in flight. Plasma sound pulse velocity (PSV) increased 1.2 m/s preflight and 1.7 m/s postflight, whereas PSV did not rise (-0.4 m/s) in flight. This would indicate profoundly altered LBNP-induced fluid dynamics in flight, compared to control (1-g) conditions. On the 4th day postflight, blood and plasma sound velocity increased more with LBNP than preflight, indicating greater hemoconcentration than under control conditions. In summary, the data suggest: 1) altered fluid shifts between blood and interstitial compartments during LBNP with 6 d adaptation to microgravity; and 2) increased hemoconcentration during LBNP early after a 10-d spaceflight.(ABSTRACT TRUNCATED AT 250 WORDS)

This contribution summarizes the results of investigations of water-electrolyte metabolism and its hormonal regulation conducted in cosmonauts who performed long-term space flights (from 18 to 366 days) aboard the space stations Salyut and Mir and compares them with the results obtained during various NASA flights. The role of the kidneys in ion metabolism regulation was assessed by various water-salt load tests before and after flights. In addition, the results of a year-long space flight and of medical experiments performed during the 237- and 241-day missions by the physicians and cosmonaut-researchers Atkov and Polyakov are reviewed in detail. In spite of interindividual variations, metabolic, and endocrine studies during prolonged space flights showed a reduction in body mass, usually with a reduction in body water and electrolytes and considerable changes in blood hormone concentrations and urinary hormone excretion. These changes reflect the processes of extended adaptation to a new environment. It is likely that shifts in electrolyte metabolism in weightlessness are primarily due to metabolic changes that diminish the tissue ability for ion retention and to concomitant changes in the endocrine status. The postflight examinations revealed changes in fluid-electrolyte metabolism and in the function of the kidneys which indicated a hypohydration status and a stimulation of hormonal systems responsible for fluid-electrolyte homeostasis in order to readapt to the normal gravitation. Postflight decline in osmotic concentration of urine in cosmonauts was accompanied by an altered response to antidiuretic hormone and was probably caused by changes in the functional state of the kidneys. We conclude that detailed knowledge of the alterations in water-electrolyte metabolism and its hormonal regulation on different stages of space flight are important prerequisites for the development of countermeasures to space deconditioning and thus for increased human efficiency in space. In addition, these data contribute to an increase in our general knowledge on the regulation of kidney function.

During 1986-1990 seven prime spacecrews (16 cosmonauts) have flown on-board the Mir orbital complex. The longest space mission duration was 366 days The principal objectives of the medical tasks were the maintenance of good health and performance of the spacecrews and conducting medical research programs which included study of the cardiovascular, motor, endocrine, blood, immune, and metabolic systems. Results obtained point to the ability of humans to readily adapt to a year-long stay in space and maintain good health and performance. Readaptation had a similar course as after other previous long-term space flights of up to 8 months in duration. Primary body system changes were not qualitatively different from findings after flights aboard the Salyut 6 and 7 space stations. In this case, during and after an 11-12 month flight, body system alterations were even less severe which was a result of adequate countermeasure use, their systematic and creative employment and maintenance of required environments to support life and work in space.

As we enter a phase of space exploration that will involve long-duration flights, there is a need to use ground-based models to study the long-term effects of countermeasures to prevent the loss of bone mineral in microgravity. Mineral balances, hormone levels, and bone density were measured for 360 days in nine bed rest subjects treated with an exercise program used by cosmonauts. Four of these subjects received the bisphosphonate, ethane-1-hydroxy-1-disphosphonate, 900 mg daily, a drug known to inhibit bone resorption. Compared to a 120 day control period, the bisphosphonate combined with exercise reduced negative calcium balances by 50% for the first 120 days, 80% for the second 120 days, and 69% during the third 120 days. Exercise alone had no effect until the second 120 day period, when calcium balance improved 52%. Negative phosphorus balances were not affected by either treatment. Magnesium balances were negative during the first 120 days and returned to nearly normal during the last 240 days in both groups. The combined exercise and bisphosphonate treatment prevented increases in serum ionized calcium and decreases in plasma calcitonin during the first 120 days, as well as trends toward decreases in the mineral density of the femoral neck. These results suggest that bisphosphonates can be efficiently used together with exercise to reduce calcium loss and prevent some of the changes in mineral metabolism during long-term simulated microgravity.

Because astronauts confront unprecedented hazards, manned space exploration has to proceed gradually and cautiously, each new step being taken with the benefit of what has been learned during earlier stages about bodily requirements. As well as helping to protect the lives of astronauts, however, space medicine is proving to have valuable applications in global health care.

The health condition and work capacity of space travellers during many flights remained adequate. Medical examinations performed during and after space flights consistently revealed the following symptom-complexes: space motion sickness, changes in the muscles system, hemodynamics, fluid-electrolyte balance and its regulation, calcium metabolism and bone density, transient erythrocytopenia and immunity decline. This paper presents a detailed discussion of the changes observed in space flight.

Using a specific and sensitive radio-immunoassay involving separation and extraction procedures, we measured the concentration of saliva and plasma atrial natriuric factor (ANF) and cyclic guanosine monophosphate (cGMP) in men before and during a 10 h head-down tilt at -6 degrees. Saliva values closely correlated with plasma for ANF (r = 0.7-0.95) and for cGMP (r = 0.65-1). During this dynamic test, the mean concentrations of ANF and cGMP were significantly higher after 15 and 45 min, respectively, this increase persisting for 3.5 h. We concluded that the concentration of ANF in saliva may be significantly affected by a marked fluid shift from the lower to the upper half of the body. This is the first time that the presence of ANF and cGMP has been demonstrated in saliva. The great advantage of studying saliva is that it can be obtained non-invasively in athletes or during space flight. This methodology will be used during the Soviet-French space flight (Antares Project) planned for 1992.

The ratio of reabsorption of osmotically free water to osmolal clearance in individual urine voids was about the same before and after short-term spaceflights (the points fall on the same regression line). This ratio was reduced after long-term flights, so that the regression lines for pre- and postflight values have different slopes. This change in the function relating the two factors was accompanied by increased vasopressin in blood plasma and probably was caused by altered cellular reaction to vasopressin. The decrease in the effect of vasopressin may have been caused by development of hypokalemia and hypercalcemia in the cosmonauts, and decrease in cellular potassium in the outer renal medulla (this effect was observed in experiments on rats after flights on biosatellites). We established that, in addition to cAMP, cGMP and inositol trisphosphate participate in cellular reactions to vasopressin. Increases in the concentration of cGMP and decrease in the formation of inositol trisphosphate in the presence of neomycin increase the hydro-osmotic effect of vasopressin. We hypothesize that modulation of the effect of vasopressin in cosmonauts is due to change in the functional state of their kidneys.

The basic goal of medical investigations during and after the 366-day mission was to accumulate data about physiological responses to such a long exposure to microgravity. In flight, cardiovascular and other systems were examined in detail and the efficacy of countermeasures used was assessed. After flight, physiological systems were also followed very carefully. According to the preliminary data, the medical results obtained during and after flight give evidence that man can well adapt to a year-long space flight, maintaining good health and adequate work capacity. The readaptation process was very similar to that observed after shorter flights (6-11 months). As compared to former flights, no new or qualitatively different changes in the vital systems of the body were seen. The observations indicate that the duration of manned space missions can be further increased.

The activity of the sympathoadrenal system in cosmonauts was studied by measuring plasma and urinary catecholamines and their metabolites and conjugates. The appliance Plasma 02 was used for collecting, processing, and storing blood and urine samples from the cosmonauts during the course of a 25-day flight on board the station Mir. Plasma and urine concentrations of adrenaline (A), noradrenaline (NA), and dopamine (DA) as well as urinary levels of vanillylmandelic acid (VMA) and homovanillic acid (HVA), and plasma levels of catecholamine sulphates were determined before, during and after the space flight. Plasma NA levels were slightly elevated on day 9 and plasma A on day 20, whereas plasma DA levels were unchanged. However, most of the changes were within the normal range of control values. Sulphates of plasma catecholamines did not change during flight but they were significantly elevated after landing. Urinary levels of A, NA, DA, VMA, and HVA were comparable with preflight values but were elevated at the different intervals studied after landing. The results obtained suggest that in the short period of about 9 days of the cosmonaut's stay in space the sympathoadrenal system was slightly activated indicating a mild stressful influence of the initial period of flight. This short-term space flight compared to long-term flight did not as markedly activate the sympathoadrenal system during the process of re-adaptation to Earth's gravity after landing. Our data suggest that weightlessness is not a stressful factor activating the sympathoadrenal system but it sensitizes the responsiveness of this system during the re-adaptation period after space flight.

The activity of the sympathetic adrenal system in cosmonauts exposed to a stay in space lasting for about half a year has so far been studied only by measuring catecholamine levels in plasma and urine samples taken before space flight and after landing. The device "Plasma 01", specially designed for collecting and processing venous blood from subjects during space flight on board the station Salyut-7 rendered it possible for the first time to collect and freeze samples of blood from cosmonauts in the course of a long-term 237-day space flight. A physician-cosmonaut collected samples of blood and urine from two cosmonauts over the period of days 217-219 of their stay in space. The samples were transported to Earth frozen. As indicators of the sympathetic adrenal system activity, plasma and urine concentrations of epinephrine and norepinephrine as well as urine levels of the catecholamine metabolites metanephrine, normetanephrine, and vanillylmandelic acid were determined before, during and after space flight. On days 217-219 of space flight plasma epinephrine and norepinephrine levels were slightly increased, yet not substantially different from normal. During stress situations plasma norepinephrine and epinephrine levels usually exhibit a manifold increase. On days 217-219 of space flight norepinephrine and epinephrine levels in urine were comparable with pre-flight values and the levels of their metabolites were even significantly decreased. All the parameters studied, particularly plasma norepinephrine as well as urine norepinephrine, normetanephrine, and vanillylmandelic acid, reached the highest values 8 days after landing. The results obtained suggest that, in the period of days 217-219 of the cosmonauts stay in space in the state of weightlessness, the sympathetic adrenal system is either not activated at all or there is but a slight activation induced by specific activities of the cosmonauts, whereas in the process of re-adaptation after space flight on Earth this system is considerably more markedly activated.

Experiments are described on the dynamics of the renal excretion of water and electrolytes, osmotically active substances and osmotically free water during bed rest. In short-term experiments (up to 10-14 days) renal changes are mainly associated with haemodynamic disturbances and fluid redistribution, whereas in longer duration experiments (up to 50 days) they are brought about by metabolic changes.

This paper reviews existing hypotheses concerning the mechanisms of adaptation of the vestibular apparatus and related somatosensory systems to microgravity with reference to the flight data. Having in view theoretical concepts and experimental data accumulated in space flights, a conceptual model of the development of a funtional system responsible for the termination of vestibular dysfuntion and space motion sickness manifestations is presented. It is also shown that changes in the hormonal status during motion sickness induced by vestibular stimulation give evidence that endocrine regulation of certain functions can be involved in adaptive responses.

In order to prevent and correct hypohydration and negative electrolyte balance, the effects of exercises, lower body negative pressure (LBNP) and water-salt supplements (WSS) were investigated in more than 100 test subjects during 14-, 49- and 182-d headdown tilt tests (-4 degrees). A combined use of WSS and LBNP during regular exercises led to a distinct water and sodium retention. These changes were mainly determined by the stimulation of the renin-angiotension-aldosterone and antidiuretic systems. After these countermeasures were tested in simulation studies, they were used by 12 cosmonauts during the 63- and 185-d space flights. The detailed analysis of the postflight examinations of the crewmembers suggests that these countermeasures may exert a beneficial effect on fluid-electrolyte balance.

Manned missions onboard orbital stations Salyut-6 and Salyut-7 have led us to the conclusion that a long-term space mission can be viewed as a complex socio-man-machine system whose effectiveness largely depends on the quality of interaction between its subsystems. When analyzing and assessing the reliability of this system, it is important to consider ethical aspects, because they concern human relations, permeating its very component and in the long run determining its efficiency. Psychological and medical examinations before, during and after manned missions have helped us to identify the major points of interaction of the subsystems which require adequate monitoring and optimization using socio-psychological and organization-technical approaches: arrangement and evaluation of the quality of work, arrangement of proper leisure, psychological comfort in the interpersonality and intergroup relations during prolonged space missions. This paper also discusses adaptive changes in the mental and physical state due to prolonged exposure to space flight factors such as microgravity and confinement.

In order to clarify biochemical adaptation of the human body to short-term microgravity, metabolic and hormonal parameters were investigated in 20 cosmonauts who performed orbital flights of 4 to 14 d in duration. The specific feature of adaptation to this exposure is the transition to a new level of hormonal regulation with a significant increase of the content (production) of glucocorticoids, catecholamines, components of the renin-angiotensin-aldosterone system, which determines a modified activity of tissue hormones, and fluid-electrolyte homeostasis, as well as simultaneous increase of insulin secretion that diminishes the metabolic effects of glucocorticoids and catecholamines.

This paper presents the results of medical investigations performed in the Salyut-7 8-month mission in which a professional physician took part. The paper contains anthropometric measurements, results of investigating the vestibular function, cardiovascular function at rest and in response to multi-step tests (with emphasis on echocardiographic measurements), metabolic parameters and hormonal status. It also discusses medical aspects of the extravehicular activity. The medical investigations, although some new methods were applied, provided the continuity of methodical approaches and data accumulated in previous missions.

In the first experimental series, 10 healthy male test subjects with a high susceptibility to motion sickness showed a significant increase of ACTH, cortisol, STH, prolactin, ADH, aldosterone concentrations, and plasma renin activity after vestibular tests. The 10 subjects with a moderate susceptibility exhibited a still higher increase of the hormones, except plasma renin. The 8 test subjects with a low susceptibility displayed a considerable increase in ACTH, cortisol, and STH after vestibular stimulation. In the second experimental series, the increase of STH, cortisol, ADH, aldosterone and renin occurred immediately after rotation in the moderate susceptibility subjects and an hour after exposure in the high susceptibility subjects. This may be indicative of specific immediate adaptation mechanisms or excitation transfer in the CNS in high susceptibility persons. In the third experimental animal series, the permeability of the blood-brain barrier for 125I and IgG increased after rotation. Greater concentrations of potassium, chloride, and urea in CSF are suggestive of an inhibition process activation in the CNS and, probably, of an active urea transport by the vascular plexus epithelium which maintains constant osmotic pressure of cerebral extracellular fluid and prevents hyper-hydration of CNS neurons.

Brattleboro homo- (DI) and heterozygous (HZ) rats with total or partial deficiency of the antidiuretic hormone (ADH) and also 10-14-day old Wistar rats irresponsive to ADH were used to examine the possible causes of inadequate responses to ADH in cosmonauts after space flights and in humans after prolonged bedrest in antiorthostasis (-60). The experimental results suggested that changes in the intrarenal osmotic gradients, as well as in the aggregate state of the ADH receptors as a result of the decreased ADH blood level under hypogravitation, might be a cause of the inadequate response to ADH in cosmonauts during readaptation to the Earth's gravity.

Calcium metabolism, its hormonal regulation and renal calciuretic function were investigated in 20 healthy volunteers during 120- and 182-day head-down tilt studies. The content of total and ionized calcium and parathyroid hormone was found to increase during the study. The concentration of calcitonin increased at an early stage of exposure and decreased thereafter. This resulted in negative calcium balance which was on the average 5, 6g per month. Measurements of iliac bone biopsies showed calcium decrease and phosphorus increase.

This study was conducted on the pilot specialist of the Salyut 7-Soyuz T9 complex during a 150 days space flight. Glucose tolerance tests were made 3 days before flight, on days 60 and 88 during flight and on days 25 and 55 after flight. The study confirms the decrease of fasting plasma glucose observed during the 3 Skylab missions and demonstrates blunted glucose tolerance curves. The changes were not found during ground based studies using bed rest to simulate weightlessness state. The origin of this abnormality is discussed.

Ten cosmonauts, who performed 30-175-day space flights aboard Salyut-4 and Salyut-6, and over 60 test subjects who were exposed to bed rest of up to 182 days and immersion of up to 56 days, were examined. The renal excretion of potassium and calcium increased, reaching a maximum by the 4-6th weeks in prolonged space flights and simulation studies. During the load tests with potassium and calcium salt, excretion postflight was much higher than preflight. During potassium chloride load tests a positive correlation between the blood content of aldosterone and potassium excretion existed, whereas during calcium lactate load tests an increased calcium excretion was accompanied by a decrease in blood parathyroid hormone concentration. The most probable cause of the negative ion balance in weightlessness is the reduced capacity of tissues to retain electrolytes due to the decreased ion pool capacity. Different exercises have been shown to exert a beneficial effect on electrolyte metabolism.