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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Electroslag and electrogas welding

These two new joining methods perform welding in the vertical position, and therein lies the secret of their impressive advantages in material handling, in weld preparation, in welding speed, in freedom from distortion, and in weld soundness. Once the work has been set in the proper vertical position for welding, no further plate handling is required. The molten filler metal is held in place by copper shoes or dams, and the weld is completed in one pass.

Campbell, H. C.↗
NASA NTRS1975

Modulating the pituitary-adrenal response to stress

Serotonin is believed to be a transmitter or regulator of neuronal function. A possible relationship between the pituitary-adrenal secretion of steroids and brain serotonin in the rat was investigated by evaluating the effects of altering brain 5-hydroxy tryptamine (HT) levels on the daily fluctuation of plasma corticosterone and on the response of the pituitary-adrenal system to a stressful or noxious stimulus in the rat. The approach was either to inhibit brain 5-HT synthesis with para-chlorophenyl alanine or to raise its level with precursors such as tryptophan or 5-hydroxy tryptophan.

Vernikos-Danellis, J.↗
NASA NTRS1975

Stress-induced changes in corticosteroid metabolism

Because plasma and urine corticosteroid concentrations are influenced by several factors in addition to adrenal cortex secretion, the effect of stress on all of these factors was determined in order to interpret the plasma and urine concentrations. Progress on the investigation is reported.

Tacker, M. M.↗
NASA NTRS1975

Parathyroid hormone, calcitonin, and vitamin D 1974: Present status of physiological studies and analysis of calcium homeostasis

The role of parathyroid hormone, calcitonin, and vitamin D in the control of calcium and bone metabolism was studied. Particular emphasis was placed on the physiological adaptation to weightlessness and, as a potential model for this purpose, on the immobilization characteristic of space flight or prolonged bed rest. The biosynthesis, control of secretion, and metabolism of these hormonal agents is considered.

Potts, J. T., Jr.↗
NASA NTRS1975

Control mechanisms of circadian rhythms in body composition: Implications for manned spaceflight

The mechanisms that underlie the circadian variations in electrolyte content in body fluid compartments were investigated, and the mechanisms that control the oscillations were studied in order to investigate what effects internal desynchronization in such a system would have during manned space flight. The studies were performed using volunteer human subjects and squirrel monkeys. The intercompartmental distribution of potassium was examined when dietary intake, activity, and posture are held constant throughout each 24-hour day. A net flux of potassium was observed out of the body cell mass during the day and a reverse flux from the extracellular fluid into the body cell mass during the night, counterbalanced by changes in urinary potassium excretion. Experiments with monkeys provided evidence for the synchronization of renal potassium excretion by the rhythm of cortisol secretion with the light-dark cycle. Three models of the circadian timing system were formalized.

Ede, M. C. M.↗
NASA NTRS1974

Alterations in acid-base homeostasis during water immersion in normal man

The effects of water immersion on renal bicarbonate and acid excretion were assessed in 10 normal male subjects. Immersion resulted in a highly significant progressive increase in the rate of sodium and bicarbonate excretion, and in urine pH. Immersion was also associated with a significant increase in urine P-CO2; this increase presupposes a maintained rate of hydrogen secretion in the distal tubular segment. The rapidity of onset of the bicarbonaturia (2 hrs of immersion) and the concomitant increase in urinary P-CO2 suggest that enhanced bicarbonate excretion of immersion cannot be completely accounted for by immersion-induced suppression of aldosterone, and that the natriuresis and bicarbonaturia of immersion is mediated in part by an increased proximal rejection of sodium and bicarbonate.

Epstein, M.↗
NASA NTRS1975

Experimental study of the constituents of space wash water

This report presents experimental data, obtained under controlled conditions, which quantify the various constituents of human origin that may be expected in space wash water. The experiments were conducted with a simulated crew of two male and two female subjects. The data show that the expected wash water contaminants originating from human secretions are substantially lower than theoretical projections indicated. The data presented are immediately useful and may have considerable impact on the tradeoff comparisons among various unit processes and systems under consideration by NASA for recycling space wash water.

Putnam, D. F.↗
NASA NTRS1976

EPA/ECLSS consumables analyses for the Spacelab 1 flight

The results of electrical power system (EPS) and environmental control/life support system (ECLSS) consumables analyses of the Spacelab 1 mission are presented. The analyses were performed to assess the capability of the orbiter systems to support the proposed mission and to establish the various non propulsive consumables requirements. The EPS analysis was performed using the shuttle electrical power system (SEPS) analysis computer program. The ECLSS analysis was performed using the shuttle environmental consumables requirements evaluation tool (SECRET) program.

Steines, G. J.↗
NASA NTRS1975

Sympathetic neural control of indoleamine metabolism in the rat pineal gland

The mechanisms responsible for the acceleration in rat pineal biosynthetic activity in response to prolonged exposure to darkness or to immobilization were investigated in animals whose pineals were surgically denervated. Some animals were adrenalectomized to remove one potential source of circulating catecholamines, and some were subjected to a partial chemical sympathectomy accomplished by a series of intravenous injections of 6-hydroxydopamine. Results suggest that N-acetyltransferase (NAT) activity can be enhanced either by release of norepinephrine from sympathetic terminals within the pineal or from sympathetic nerve terminals elsewhere. The stress of immobilization stimulates the pineal by increasing circulating catecholamines. Photic control of pineal function requires intact pineal sympathetic innervation, since the onset of darkness apparently does not cause a sufficient rise in circulating catecholamines to stimulate the pineal. The present studies suggest that nonspecific stress triggers increased biosynthesis and secretion of melatonin; it is possible that this hormone may participate in mechanisms of adaptation.

Lynch, H. J.↗
NASA NTRS1976

The control of calcium metabolism by parathyroid hormone, calcitonin and vitamin D

Advances in analysis of chemistry and physiology of parathyroid hormone, calcitonin, and Vitamin D are described along with development of techniques in radioassay methods. Emphasis is placed on assessment of normal and abnormal patterns of secretion of these hormones in specific relation to the physiological adaptations of weightlessness and space flight. Related diseases that involve perturbations in normal skeletal and calcium homeostasis are also considered.

Potts, J. T., Jr.↗
NASA NTRS1977

The thyroid and environmental stress in mammals

The effects of hyperoxia at ambient pressure on thyroid function and thyroid hormone metabolism have been assessed. Thyroidal activity was depressed in mice and rats by exposure to hyperoxia, due at least in part to a decrease in the rate of secretion of pituitary thyrotropin. The effects of hyperoxia on the peripheral deiodination of thyroxine were dependent on the concentration of oxygen employed and/or the duration of exposure. When significant changes were observed a reduction in the rate of deiodination and in the deiodinative clearance of T sub 4 occurred. Hyperoxia also resulted in a marked fall in circulating T sub 4 concentration and a decrease in T sub 4-binding activity in serum. Many of these effects of hyperoxia were prevented by the concomitant administration of large amounts of Vitamin E. These decreases in thyroid function and T sub 4 metabolism were associated with a decrease in the rate of whole body oxygen consumption. It was concluded that the deleterious effects of oxygen in the rat were not due to an oxygen induced hyperthyroid state in the peripheral tissues. Thyroxine was shown to be essential for survival during acute cold stress.

Galton, V. A.↗
NASA NTRS1976

Effects of subfornical organ extracts on salt-water balance in the rat

The subfornical organ (SFO) is a circumventricular structure located at the junction of the lamina terminalis and the tela choroidea of the third cerebral ventricle. SFO is histologically regarded as a neurosecretory structure, although the physiological effects or biochemical nature of such secretions are not yet ascertained. Results are presented for an experimental study designed to determine whether SFO extracts alter parameters associated with salt-water balance in the rat. The data obtained support the conclusion that SFO contains some water-soluble substance(s), easily released by incubation, dialyzable and heat stable, which influences the salt-water balance after injection into ventricular cerebrospinal fluid. Whether other brain tissues or plasma contains the same or similar material is not yet convincingly established. The observation that one or more active constituents are easily released from SFO upon incubation in potassium-enriched medium may be of value.

Summy-Long, J. Y.↗
NASA NTRS1976

Experimental study of the constituents of space wash water

Data are presented that quantify some of the various constituents of human origin that may be expected in space wash water. The experiments were conducted under controlled conditions with a simulated crew of two male and two female subjects. The data show that the expected wash water constituents originating from human secretions are substantially lower than theoretical projections have indicated. Average daily quantities as well as individual extremes are given for both shower and laundry water. In addition, concentrations are presented for a projected model of wash water usage in a space station.

Colombo, G. V.↗
NASA NTRS1977

Effect of bedrest on circadian rhythms of plasma renin, aldosterone, and cortisol

Previous studies of normal men after 5 d of bedrest showed that circulatory instability on head-up tilt or standing is preceded by increased plasma renin activity (PRA) at bedrest. In the present study, the circadian rhythms of PRA, aldosterone, and cortisol have been observed in five normal men on a constant diet. In ambulatory controls, PRA and aldosterone increased normally after standing. On the third morning of bedrest, PRA was higher than before, and at noon, PRA was higher than in standing controls. The nocturnal peaks of PRA resulting from episodic renin secretion during sleep were higher after bedrest. Plasma aldosterone was also increased by bedrest. The findings are compatible with the theory that intermittent beta-adrenergic nerve activity during sleep is increased after bedrest, but other factors, such as loss of body sodium and a lower plasma volume, may also be involved.

Chavarri, M.↗
NASA NTRS1978

Zero gravity and cardiovascular homeostasis. The relationship between endogenous hyperprolactinemia and plasma aldosterone

Prolactin, thyrotropin and aldosterone were measured by radioimmunoassay and plasma renin activity by the radioimmunoassay of angiotensin I in normal women before and after the intravenous injection of 200 micrograms of thyrotropin releasing hormone. Prolactin increased at 15 minutes following thyrotropin releasing hormone. Plasma renin activity was not different from control levels during the first hour following the administration of thyrotropin releasing hormone, nor did the plasma aldosterone concentration differ significantly from the control levels during this period. However, with upright posture, an increase in aldosterone and in plasma renin activity was noted, demonstrating a normal capacity to secrete aldosterone. Similarly, no change in aldosterone was seen in 9 patients with primary hypothyroidism given thyrotropin releasing hormone, despite the fact that the increase in prolactin was greater than normal. These data demonstrate that acutely or chronically elevated serum prolactin levels do not result in increased plasma aldosterone levels in humans.

Haber, E.↗
NASA NTRS1977

Potential use of nutritional factors to optimize performance under stress

A study of the effects of amino acids on hypothalamo-pituitary capacity to secrete ACTH, and the response of the adrenal gland in terms of corticosterone level in the plasma was discussed in the first part of this report. Second, the report includes a study of the response of protein metabolism in various levels of corticosterone elevation in the plasma. This second part is regarded as having considerable significance for space travel, since this data indicate a threshold level of plasma corticosteroids above which there is increased catabolism of muscle protein.

Munro, H. N.↗
NASA NTRS1978

Hormonal indices of tolerance to +Gz acceleration in female subjects

As a possible predictive test for screening Space Shuttle passengers, the secretions of the pituitary adrenal system and the adrenal medulla have been studied in conjunction with exposure to gravitational acceleration three times the normal level. The 12 female subjects in the test were divided into ambulatory and bedrest groups. Before bedrest, a high tolerance to centrifugation appeared to be linked to increases in plasma ACTH and cortisol. This relationship did not hold after bedrest. The correlation between tolerance to centrifugation and 24-hour urinary epinephrine-to-norepinephrine ratios was not significant.

Vernikos-Danellis, J.↗