[Assessment of the risk factors for urolithiasis in cosmonauts during long flights].

Twelve cosmonauts flown aboard the Mir orbital station for 6-12 months and twelve candidates for cosmonauts were examined in an effort to determine a degree of urolithiasis risk. Prior to flight, on flight day 310 (in one cosmonaut) and after flight, the daily urinary excretion of the components influencing lithiasis formation was determined as well as a computer-aided calculation of urine saturation by lithogenic salts was performed (Ch. Pak, USA).

[Effect of long-term space flight on erythrocyte metabolism and the function of the erythrocyte membrane].

This paper presents the data about red blood cell metabolism and the structure and function of erythrocyte membranes obtained from two cosmonauts after their 326- and 160-day flights. In both cases we observed inhibition of energy formation (decrease of the rate of glycolysis and ATP content) and enhancement of oxidative processes (decrease of reduced glutathione and activity of antioxidative enzymes). The above changes in the metabolic status of erythrocytes are correlated with shifts at the membrane level, particularly with variations of membrane lipids, phospholipid spectrum and ratios of phospholipid fractions, alteration of membrane-bound enzymes (ATPase) and increase of cell resistance to acid hemolysis.

[Metabolic characteristics during 120-day head-down tilt hypokinesia].

Nine healthy test subjects, aged 25 to 44 years, were exposed to bed rest (at -5 degrees) for 120 days. Venous blood and 24-hour urine samples were used to measure Na, K, total and ionized Ca, Mg, total protein, protein fractions, creatinine, urea, uric acid, malate, isocitric and lactate dehydrogenases, aspartate and alanine aminotransferases, and creatine phosphokinase and its isoforms, acid and alkaline phosphatase and its isoenzymes. Prolonged exposure to head-down tilting resulted in a negative balance of fluid and electrolytes, lowered concentration of total protein and albumins, and an increased concentration of urea and creatinine, basic products of protein metabolism.

[Bioelectrical activity of the heart and blood electrolytes in virtually healthy subjects during 120-day head-down tilt hypokinesia].

Electrocardiographic parameters and serum concentrations of potassium, sodium, calcium (total and ionized) and magnesium in 6 essentially healthy men, aged 30-45 years, were measured before, during and after 120-day head-down tilt at -4.5 degrees. A close correlation was demonstrated between T-wave depression and serum concentrations of potassium (direct correlation) and calcium and magnesium (inverse correlation).

[Ion-regulating function of the human kidneys during prolonged space flight and in simulation studies].

Ten cosmonauts who performed 30- to 175-day space flights on board Salyut-4 and Salyut-6, and 50 test subjects exposed to head-down tilt (-4 degrees) for 182 days were examined. In actual and stimulated weightlessness renal excretion of calcium and potassium increased, reaching maximum during the 4-6th weeks. Before and after flight the test subjects were exposed to loading salt tests.

[Kaliuretic function of the kidneys in humans with different degrees of motor activity and at bed rest].

The kaliuretic function of the kidneys was studied in 12 healthy test subjects during the 49-day head-down tilting (--4 degrees). The results suggest that the selection of optimal exercises and dietary potassium intake may prevent changes in the potassium metabolism and the renal kaliuretic function both during bed rest and weightlessness as well as facilitate a rapid recovery of potassium homeostasis on return to Earth.