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Renal blood flow and extracellular volume, renal and cardiac effects on sodium excretion, and abnormal circulatory state effects on cardiac rate and blood pressure - dog & human physiology
Regression curves computed from urinary calcium excretion and bone mass data obtained from men in bed rest and ambulatory studies
Effect of unilateral renal vasodilatation on sodium excretion by infusing acetylcholine into renal artery of dogs
Regulation of sodium excretion in dog, and effects of atrial size and function upon secretion of sodium load - circulatory response to upright tilt
Regulation of sodium excretion in healthy, obese volunteers, and circulatory response to orthostatic stress in man
Desynchronization and resynchronization of human circadian rhythms of activity, body temperature and urine excretion during isolation in underground bunker in various conditions
Urine osmolality of centrifuged rats compared with ad libitum or pair-fed control animals, indicating enhanced free water excretion and antidiuretic hormone involvement
Circadian rhythms and biochemical analyses of urinary excretion of chimpanzees in simulated space environments
Weightlessness effects on hydroxycorticosteroid excretion determined by 56 day bed rest study
Development of radioimmunoassay system for measurement of urinary antidiuretic hormone excretion
Antidiuretic action of chlorpropamide in mammalian kidney, considering intrarenal infusions effect on urinary concentration, free water clearance, glomerular filtration and sodium excretion
The effects of a very low calcium diet, with variable high and low protein intake, on the dynamics of calcium metabolism and the mechanism of calciuretics, are examined. The experiment, using male subjects, was designed to study the role of intestinal calcium absorption on urinary calcium excretion, and the rate of production of endogeneously secreted calcium in the gastrointestinal tract. The study showed an average of 70% fractional absorption rate during very low calcium intake, and that a decrease in renal tubular reabsorption of calcium is responsible for calciuretic effects of high protein intake. The study also indicates that there is a tendency to develop osteoporosis after long periods of low calcium intake, especially with a concurrent high protein intake.
Preflight and postflight urine and plasma samples from the Gemini 7 and Gemini 9 crewmembers were analyzed. Electrolyte and water retention observed immediately postflight was consistent with the assumption that the Gauer-Henry atrial reflex was responsive to a change from the weightless to the unit-gravity environment. Immediately postflight, plasma 17-hydroxycorticosteroid concentrations were increased and plasma uric acid concentration was decreased. The increased excretion of 17-hydroxycorticosteroids immediately postflight probably was caused by the stress of entry. The postflight increase of plasma protein, and the slightly smaller increase of plasma electrolytes postflight, was consistent with an inflight water and electrolyte loss that resulted in postflight retention of water and electrolytes.
Study of the antinatriuretic effect of acute thoracic inferior vena cava (TIVC) constriction in the absence of alterations in renal perfusion pressure. A comparison is made of the effects of equivalent degrees of TIVC and abdominal inferior vena cava constriction on arterial pressure, renal hemodynamics, and electrolyte excretion.
A cosmic radiation dose to the Apollo 17 crew of 1.3 R was calculated from the specific activities of Na-24 in their postflight urine specimens. The specific activities of K-42, Cr-51, Co60, and Sb-124, introduced by injection into the astronauts, are extremely high in these specimens. The Fe-59 and Cs-137 levels are also reported and appear to be normal. The concentrations of Na, K, Rb, Cs, Ca, Sr, Ba, Cr, Fe, Co, Ag, Au, Zn, Cd, Hg, Sn, As, Sb, Se, Br, Sc, La, Sm, Eu, Tb, Hf, Ta, and Th were measured in urine specimens from the Apollo 17 astronauts by neutron activation analysis. Strontium, barium, gold, cadmium, lanthanum, samarium, europium, terbium, thorium, and tin are reported for the first time. The concentrations or excretion rates of bromine and the alkali metals exhibit singificantly reduced postflight levels and are generally lower than values observed for previous missions. Chromium concentrations reflect radiochromium injections.
Two bedrest studies of 56 days each have been conducted to evaluate the effects of prolonged bedrest on circadian synchrony and endocrine and metabolic function. Measurements included the pituitary-adrenal, thyroid, parathyroid, insulin-glucose-growth hormones, catecholamine excretion, body temperature, and heart rate. The results indicated that a rigorous regimen of exercise did not prevent the endocrine and metabolic effects of prolonged bedrest. Changes in circadian, endocrine, and metabolic functions in bedrest appear to be due to changes in hydrostatic pressure and lack of postural cues rather than to inactivity, confinement, or the bleeding schedule. Prolonged bedrest, particularly beyond 24 days, resulted in rhythm desynchronization in spite of well regulated light/dark cycles, temperature, humidity, activity, and meal times and meal composition and in increased lability of all endocrine parameter measured. It also resulted in an apparent insensitivity of the glucose response to insulin, of cortisol secretion to ACTH, and of growth hormone secretion to hypoglycemia.
Fluid and caloric balance has been calculated for the Apollo 17 crew. This included measurement of nitrogen, water, and caloric value of the ingested food and the volume and nitrogen content of the excreted urine and feces. Body composition changes were determined from total body water and extracellular fluid volume differences. The body composition measurements made it possible to divide the weight loss into lean body mass and adipose tissue losses. From this division a caloric equivalent was calculated. These tissue losses indicated that the caloric requirements of the mission were considerably greater than the actual caloric intake. The 3.3 kilo mean loss of body weight represented 1 kilo of lean body mass and 2.3 kilos of adipose tissue. Calculated fluid balance was more positive during the mission than during the control period. These changes are unlike the body composition and fluid balance changes reported in bedrested subjects.
Eight male subjects were subjected to continuous bedrest for 24-80 weeks for the purpose of studying metabolic responses. Three of the subjects did supine exercises daily during part of the study. Adrenal function was examined in relation to adrenal cortical and medullary excretions. The results reveal an increase in hydrocortisone throughout the test period, a decrease in norepinephrine and no change in epinephrine. These data suggest that exercise could decrease the severity of deconditioning caused by bedrest.