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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 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Cardiac beta-adrenergic receptors and coronary hemodynamics in the conscious dog during hypoxic hypoxia.

The mechanisms by which acute hypoxia (10% and 5% oxygen) mediates changes in coronary blood flow and cardiac function were investigated in the conscious dog. When the dogs breathed hypoxic gas mixtures through a tracheostomy, both arterial and coronary sinus oxygen tensions were significantly decreased. With 5% oxygen, there were significant increases in heart rate (25%), maximum left ventricular dP/dt (39%), left circumflex coronary artery blood flow (163%), and left ventricular oxygen consumption (52%), which were attenuated by beta-adrenergic blockage with propranolol. When electrical pacing was used to keep the ventricular rate constant during hypoxia, there was no significant difference in coronary blood flow before and after beta blockade. Beta-adrenergic receptor activity in the myocardium participates in the integrated response to hypoxia although it may not cause active vasodilation of the coronary vessels.

Erickson, H. H.↗
NASA NTRS1972

Microbial response to space environment, part B

The performance of the microbial response to space environment experiment is considered excellent by all investigators. For most microbial systems, only preliminary survival data are available at this time. None of the available data indicate space flight-mediated changes in cell viability or recovery. One quite important observation has been made at this early date, however. The eggs produced after mice had been infected with N. dubius larvae demonstrated a significant decrease in hatchability when compared to identical ground controls. Except for the fact that the Apollo 16 flight larvae had been on board the command module, treatment of the flown larvae and ground control larvae was the same; neither had been exposed to UV irradiation. The significance and implications of this finding are currently being studied.

Taylor, G. R.↗
NASA NTRS1972

Effects of endotoxin on monoamine metabolism in the rat.

Examination of effects of administered endotoxin on catecholamine metabolism in the rat brain, sympathetic neurons, and adrenal medulla. It is found that endotoxin, administered intraperitoneally, lowers the norepinephrine content in peripheral sympathetic neurons and the brain, and the catecholamine content in the adrenal medulla. It also accelerates the disappearance of H3-norepinephrine from all these tissues. It is therefore suggested that the effects of endotoxin on body temperature may be mediated in part by central non-adrenergic neurons.

Pohorecky, L. A.↗
NASA NTRS1973

Crew microbiology (DTO 71-19)

States of microbial imbalance as a result of human altitude chamber confinement occurred, for the most part, only in those genera and species of bacteria, yeast, and fungi which are classified as transients and are not part of the true indigenous flora of the crewmembers. Inasmuch as no crew illness events occurred and only subtle changes in the indigenous flora were noted, it appears that confinement of 56-days in a Skylab simulated environment does not mediate toward shifts in bacterial populations which have obvious clinical significance.

Wooley, B. C.↗
NASA NTRS1974

The effect of continuous low dose-rate gamma irradiation on cell population kinetics of lymphoid tissue

Cellular response and cell population kinetics were studied during lymphopoiesis in the thymus of the mouse under continuous gamma irradiation using autoradiographic techniques and specific labeling with tritiated thymidine. On the basis of tissue weights, it is concluded that the response of both the thymus and spleen to continuous low dose-rate irradiation is multiphasic. That is, alternating periods of steady state growth, followed by collapse, which in turn is followed by another period of homeostasis. Since there are two populations of lymphocytes - short lived and long-lived, it may be that different phases of steady state growth are mediated by different lymphocytes. The spleen is affected to a greater extent with shorter periods of steady-state growth than exhibited by the thymus.

Foster, B. R.↗
NASA NTRS1974

Human auditory evoked potentials. II - Effects of attention

Attention directed toward auditory stimuli, in order to detect an occasional fainter 'signal' stimulus, caused a substantial increase in the N1 (83 msec) and P2 (161 msec) components of the auditory evoked potential without any change in preceding components. This evidence shows that human auditory attention is not mediated by a peripheral gating mechanism. The evoked response to the detected signal stimulus also contained a large P3 (450 msec) wave that was topographically distinct from the preceding components. This late positive wave could also be recorded in response to a detected omitted stimulus in a regular train and therefore seemed to index a stimulus-independent perceptual decision process.

Picton, T. W.↗
NASA NTRS1974

Effects of positive acceleration /+Gz/ on renal function and plasma renin in normal man

The effects of positive radial centrifugation (+Gz) on plasma resin activity (PRA) and renal function were assessed in 15 normal male subjects under carefully controlled conditions of Na, K, and water intake. Twenty minutes of +2.0 Gz resulted in significant decreases in the mean rate of sodium excretion and creatine clearance and in a doubling of PRA in seven sodium-depleted subjects (10 meq Na intake). In eight sodium-replete subjects (200 mq Na intake), 30 min of +2.0 Gz was also associated with a decrease in the mean rate of sodium excretion. As a consequence of a concurrent decrease in creatine clearance, the fractional excretion of sodium during centrifugation did not differ from control, suggesting that the changes in Na excretion were mediated primarily by renal hemodynamic factors, although enhanced renal tubular sodium reabsorption may also have played a role.

Epstein, M.↗
NASA NTRS1974

Effects of an anti-G suit on the hemodynamic and renal responses to positive /+Gz/ acceleration

The effects of the currently used U.S. Air Force (CSU-12/P) anti-G suit on renal function during positive radial acceleration (+Gz) were assessed in seven normal male subjects in balance on a 200 meq sodium diet. Following suit inflation in the seated position, +2.0 Gz for 30 min resulted in a decrease in the rate of sodium excretion from 125 plus or minus 19 to 60 plus or minus 14 microeq/min, which persisted during a 25-min recovery period. Fractional excretion of sodium also decreased significantly during +Gz. The magnitude of the antinatriuresis was indistinguishable from that observed during +Gz without suit inflation. In contrast to the antinatriuresis observed during centrifugation without suit, however, the antinatriuresis with suit was mediated primarily by an enhanced tubular reabsorption of sodium.

Shubrooks, S. J., Jr.↗
NASA NTRS1973

Drug effects on neuroendocrine regulation; Proceedings of the International Symposium, Snowmass-at-Aspen, Colo., July 17-19, 1972

Subjects related to the characterization of neuroendocrine systems are discussed, taking into account the need for the precise identification and rigorous description of their operations. Steroid effects on neuroendocrine system performance are considered along with biogenic amine effects on neuroendocrine systems and the influence of drugs of abuse on neuroendocrine behavior. Other topics explored include pituitary-adrenal influences on avoidance and approach behavior of the rat, the adrenocortical mediation of the effects of early life experiences, and the implication of noradrenaline in avoidance learning in the rat. Individual items are announced in this issue.

Zimmermann, E.↗
NASA NTRS1974

Studies of hypokinesia in animals to solve urgent problems of space biology and medicine

The effects of hypokinesia on animals were studied by observing: (1) hormonal and mediator balance of the body; (2) gas exchange and tissue respiration; (3) protein content in skeletal muscles; (4) structure of skeletal muscles; and (5) function of skeletal muscles. Sharp limitation of motor activity causes interconnected processes of a dystropic and pathological character expressed as a reduction in the force of various muscle group with disturbance of velocity properties and motor coordination due to disturbances in the control link of the neuromuscular system.

Baranski, S.↗
NASA NTRS1975

Physiological mechanisms of the effect of weightlessness on the body

Experimental data show that physiological reactions observed under weightlessness conditions are caused by: (1) The direct effect of weightlessness, as a consequence of decrease (""disappearance'') of the weight of body tissues and organs; and (2) the mediated effect of weightlessness, as a result of changes in the functional state of the central nervous system and the cooperative work of the analyzers. The human body adopts to weightless conditions under the prolonged effects of it. In this case, four periods can be distinguished: The first period, a transitional process lasting from 1 to 24 hours; second period, initial adaptation to conditions of weightlessness and readjustment of all functional systems of the body; the third period, adaptation to the unusual mechanical conditions of the external environment, lasting from 3 to 8 days and more; and the fourth period, the stage of possible imbalance of the functions and the systems of some astronauts, as a result of the prolonged effect of weightlessness.

Kasyan, I. I.↗
NASA NTRS1975

Role of stretch reflex in voluntary movements

The stretch reflex is often described as a spinal servomechanism, a device for assisting in the regulation of muscle length. Observation of the EMG response to mechanical interruption of voluntary movements fails to demonstrate a significant role for spinal reflexes at 40 msec latency. Two functional responses with latencies of 120 msec and 200 msec, implying supraspinal mediation, are observed.

Gottlieb, G. L.↗
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 NTRS1976

The Identification of Scientific Programs to Utilize the Space Environment

A program to identify and develop ideas for scientific experimentation on the long duration exposure facility (LDEF) was completed. Four research proposals were developed: (1) Ultra pure germanium gamma ray radiation detectors in the space environment, intended to develop and demonstrate an X-ray and gamma-ray spectroscopy system incorporating a temperature cyclable high-purity germanium detector and diode heat pipe cryogenic system for cooling, (2) growth, morphogenesis and metabolism of plant embryos in the zero-gravity environment, to investigate if the space environment induces mutations in the embryogenic cells so that mutants of commercial significance with desirable attributes may be obtained, (3) effect of zero gravity on the growth and pathogenicity of selected zoopathic fungi. It is possible that new kinds of treatment for candidiasis, and tichophytosis could eventuate from the results of the proposed studies, and (4) importance of gravity to survival strategies of small animals. Gravitational effects may be direct or mediate the selection of genetic variants that are preadapted to weightlessness.

Kulacki, F. A.↗
NASA NTRS1975

Prostaglandin control of renal circulation in the unanesthetized dog and baboon

Effects of indomethacin and meclofenamate, inhibitors of prostaglandin synthesis, were evaluated in the regulation of renal blood flow in conscious and anesthetized dogs and in tranquilized baboons, instrumented with arterial pressure catheters and renal blood flow probes. Indomethacin, 10 mg/kg, did not alter renal blood flow or resistance significantly in the conscious dog. In the anesthetized dog, however, indomethacin caused a reduction in renal blood flow and an elevation of renal vascular resistance. Meclofenamate, 4 mg/kg, reduced renal flow and increased renal vascular resistance in conscious dogs. In conscious dogs and tranquilized primates, indomethacin and meclofenamate reduced the reactive hyperemia in the renal bed. Methoxamine and angiotensin II infused in graded doses induced significantly greater renal vasoconstriction in conscious dogs in the presence of indomethacin. Thus, in the conscious animal, prostaglandins appear to play only a minor part in the control of renal circulation at rest, but they are of greater importance in mediating the renal responses to reactive hyperemia and to vasoconstriction.

Swain, J. A.↗
NASA NTRS1976

Histamine H2 receptor - Involvement in gastric ulceration

The involvement of the H1 and H2 receptors for histamine in the pathogenesis of gastric ulcers was investigated in rats. Metiamide, an H2 receptor antagonist, reliably reduced ulceration produced by stress alone or by a combination of stress and aspirin. In contrast, pyrilamine, which blocks only the H1 receptor, was without effect under these same conditions. The results support the hypothesis that histamine mediates both stress and stress plus aspirin induced ulceration by a mechanism involving the H2 receptor.

Brown, P. A.↗
NASA NTRS1976

Reflex limb dilatation following norepinephrine and angiotensin II in conscious dogs

The extent to which norepinephrine (NE) and angiotensin II (AN) constrict the mesenteric, renal, and iliac beds in conscious dogs is evaluated with a view to elicit opposing reflex actions tempering the vasoconstriction in the limb of the animals tested. The afferent and efferent mechanisms mediating this reflex are analyzed. It is shown that intravenous NE and AN cause striking reflex iliac dilatation in the limb of the conscious dog. The afferent arc of this reflex involves both arterial baroreceptor and vagal path-ways, whereas the efferent mechanism involves an interaction of alpha-adrenergic and histaminergic receptors.

Vatner, S. F.↗