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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Thermoregulatory responses to preoptic cooling in unrestrained rabbits

Rabbits at ambient temperatures within the thermal neutral zone show two different metabolic responses to preoptic cooling. One response type is defined by a preoptic thermal sensitivity that shifts with ambient temperature and a 'set point' that remains constant. The other response type is defined by a set point that shifts with ambient temperature and a preoptic thermal sensitivity that remains constant. Both response types can be modeled by a single equation. Nonmetabolic thermoregulatory responses are not significantly different between the two response types.

Mcewen, G. N., Jr.↗
NASA NTRS1978

Body mass, composition, and food intake in rabbits during altered acceleration fields

Mature male Polish rabbits were subjected to varying gravitational fields in an animal centrifuge in order to evaluate the effects of acceleration and deacceleration on body mass, body composition, and food intake. The acceleration field intensity was increased by 0.25-G increments to a maximum of 2.5 G at intervals which permitted physiological adaptation at each field. Control animals of the same age were maintained at earth gravity under identical conditions of constant-light environment at a room temperature of 23 + or - 5 C. It is shown that increasing the acceleration-field intensity leads to a decrease in body mass. The regulated nature of this decreased body mass is tested by the response to an additional three-day fasting of animals adapted physiologically to 2.5 G. Ad libitum food intake per kg body mass per day tends to increase in chronically accelerated animals above 1.75 G. Increase in water content in centrifuged animals after physiological adaptation to 2.5 G is the result of decreasing body fat. Body mass and food intake returned to the precentrifuged levels of control animals within six weeks after cessation of centrifugation.

Katovich, M. J.↗
NASA NTRS1978

A microangiographic study of the effect of hyperthermia on the rabbit bladder

A model was used to study the effect of hyperthermia on a normal tissue. The model selected was the rabbit bladder and the end point measured was the changes in the micro-vasculature of the bladder wall. It was already demonstrated clinically that hot water bladder infusions produce regression in bladder tumors.

Hietala, S. O.↗
NASA NTRS1980

Experimental coronary sclerosis induced by immobilization of rabbits: A new model of arteriosclerosis

A new method for producing arteriosclerosis with coronary insufficiency in rabbits by means of immobilization is described and discussed. The experimentally induced atherosclerosis develops due to hypodynamics imposed by the reduced muscular activity without overloading with exogenous cholesterol. The atherosclerosis and coronary insufficiency are associated. With variations in the duration and extent of immobilization, coronary insufficiency alone or with atherosclerosis can be produced.

Tyavokin, V. V.↗
NASA NTRS1980

Effect of excessive saccharose administration on metabolic processes in the liver of rabbits with restricted mobility

The administration of saccharose (3 g per 1 kg for 2 months) intensified changes encountered in hypokinesia. There was a more marked increase in the content of cholesterol, pre-beta and beta-lipoproteins, phospholipids, and glycosaminoglycans in the blood. At the same time, the administration of saccharose improved the course of metabolic processes in the liver of immobilized rabbits, restored to normal levels the reduced glycogen level, the rate of glycolysis and the conversion of cholesterol to bile acids and their discharge in the cystic bile.

Rylnikov, Y. P.↗
NASA NTRS1983

Peptide and non-peptide opioid-induced hyperthermia in rabbits

The intracerebroventricular administration of prototype nonpeptide opioid receptor (mu, kappa, and sigma) agonists, morphine, ketocyclazocine, and N-allyl-normetazocine was found to induce hyperthermia in rabbits. The similar administration of peptide opioids like beta-endorphin (BE), methionine-enkephalin (ME), and its synthetic analogue D-ala2-methionine-enkephalinamide (DAME) was also found to cause hyperthermia. Results indicate that only the liver-like transport system is important to the ventricular inactivation of BE and DAME. Prostaglandins and norepinephrine were determined not to be involved in peptide and nonpeptide opioid-induced hyperthermia. In addition, cAMP was not required since a phosphodiesterase inhibitor, theophylline, did not accentuate the hyperthermia due to peptide and nonpeptide opioids. Naloxone-sensitive receptors were found to be involved in the induction of hyperthermia by morphine, BE, ME, and DAME since naloxone attenuated them. However, the hyperthermic response to ketocyclazocine and N-allyl-normetazocine was not antagonized by naloxone.

Kandasamy, S. B.↗
NASA NTRS1984

Late effects from particulate radiations in primate and rabbit tissues

In connection with studies regarding the hazards posed by ionizing radiations to man in space, the U.S. Air Force conducted an experiment about 20 years ago. In this experiment a large number of young rhesus monkeys was exposed to proton fluxes similar to those to be anticipated during solar flares. After irradiation, the animals were kept at the USAF School of Aerospace Medicine in Texas. The monkeys have been employed in investigations concerning aspects of late radiation damage. These investigations are discussed, taking into account the propagation of fibroblasts from irradiated monkeys. The results of the investigations are evaluated, giving attention also to experiments with white rabbits. It is found that, except in the case of major solar flares, when acute radiation damage could lead quickly to death, the hazards to astronauts from space radiations arise from such debilitating late effects as cataracts, damage to the central nervous system and benign tumors, and life-threatening neoplasia.

Lett, J. T.↗
NASA NTRS1985

Increase of plasma renin activity in male and female rabbits subjected to dysbaric conditions

The renin-angiotensin-aldosterone system may be implicated in hemodynamic alterations occurring in dysbaric disorders. This report concerns changes in plasma renin activity (PRA) induced by exposure of rabbits to a compression-decompression schedule that does not normally produce clinical manifestations of decompression sickness. The results revealed a significant increase in PRA in 19 of 23 animals following dysbaric exposure. Mean PRA rose from 1.18 ng ang I/ml hr (preexposure) to 2.40 ng ang I/ml hr (postexposure). The increase was particularly pronounced in female animals (217 percent). Asymptomatic intravascular gas bubbles (silent bubbles) were detected by gross or microscopic examination in the majority of the animals. Renin elaboration and secretion in asymptomatic dysbaric exposures may be mediated by bradykinin and/or prostaglandins released or activated in a chain reaction triggered by silent gas bubbles. This hypothesis is also applicable to increased PRA in altitude decompression. Alternatively elevation of PRA may result from decreased renal perfusion when dysbaric disorders are complicated by significant hypovolemia.

Chryssanthou, C.↗
NASA NTRS1988

Identifying motor and sensory myelinated axons in rabbit peripheral nerves by histochemical staining for carbonic anhydrase and cholinesterase activities

Carbonic anhydrase (CA) and cholinesterase (CE) histochemical staining of rabbit spinal nerve roots and dorsal root ganglia demonstrated that among the reactive myeliated axons, with minor exceptions, sensory axons were CA positive and CE negative whereas motor axons were CA negative and CE positive. The high specificity was achieved by adjusting reaction conditions to stain subpopulations of myelinated axons selectively while leaving 50 percent or so unstained. Fixation with glutaraldehyde appeared necessary for achieving selectivity. Following sciatic nerve transection, the reciprocal staining pattern persisted in damaged axons and their regenerating processes which formed neuromas within the proximal nerve stump. Within the neuromas, CA-stained sensory processes were elaborated earlier and in greater numbers than CE-stained regenerating motor processes. The present results indicate that histochemical axon typing can be exploited to reveal heterogeneous responses of motor and sensory axons to injury.

Riley, Danny A.↗
NASA NTRS1989

Morphological study of the innervation pattern of the rabbit sinoatrial node

The pattern of sinoatrial (SA) node innervations in rabbit was elucidated using a newly developed highly reproducible cholinesterase/silver impregnation staining procedure which made it possible to delineate large nerves, fine processes, and ganglion cells. The SA node and dominant pacemaker sites were identified by microelectrode recording. A generalized pattern of innnervation was recognized, which includes a large ganglionic complex inferior to the SA node; two or more moderately large nerves traversing the SA node parallel to the crista terminalis; nerves entering the intercaval region from the septum, the superior vena cava, and the inferior vena cava to impinge on the SA node; and a fine network of nerve processes, which was particularly dense in the SA node. From the location and distribution of the nerves and ganglionic branches, it can be inferred that the neural network in the intercaval region is capable of performing complex modulatory and integrative functions among the structures within this region.

Roberts, L. A.↗
NASA NTRS1994

Effects of Ar-40 and Fe-56 ions on retinal photoreceptor cells of the rabbit: Implications for manned missions to Mars

Losses of photoreceptor cells (rods) from the retinas of New Zealand white (NZW) rabbits were detectable within 2 years after localized acute irradiation of optic and proximal tissues with greater than or equal to 7 Gy of 530 MeV u(exp -1) Ar-40 ions or greater than or equal to 2 Gy of 465 MeV u(exp -1) Fe-56 ions in the Bragg plateau region of energy deposition. Those limits were determined only from an analysis of variance of dose groups because the shapes of the dose response curves at early post-irradiation times are not known, a concern being addressed by experiments in progress. Losses of photoreceptor cells for the period 0.5-2.5 years post-irradiation, determined by provisional linear regression analysis, were approxiamtely 1.7% Gy(exp -1) and 2.5% Gy(exp.-1) for Ar-40 and Fe-56 ions, respectively.

Williams, G. R.↗
NASA NTRS1995

Effect of Blockade of Nitric Oxide Synthesis on the Renin Secretory Response to Frusemide in Conscious Rabbits

The enzyme nitric oxide synthase is present in the macula densa and may participate in the control of renin secretion by the adjacent juxtagiomerular cells. In the present study, we investigated the effect of inhibiting nitric oxide synthase on the renin secretory response to frusemide, which stimulates renin secretion by blocking Na(+)-K(+)-2Cl(-) co-transport in the macula densa. Injection of frusemide in 12 conscious rabbits elicited a transient increase in mean arterial pressure from 84 +/- 2 to 92 +/-3 mm Hg at 5 min (P less than 0.01) and a sustained increase in heart rate from 246 +/- 6 to 281 +/- 10 beats/min at 45 min (P less than 0.01). Plasma renin activity increased from 8.0 +/- 1.2 to 14.3 +/- 1.8, 12.4 +/- 1.6 and 11.6 +/- 1.5 pmol/2h ml at 15, 30 and 45min respectively (P less than 0.01). There were no changes in plasma sodium and potassium concentrations or osmoiality. Inhibition of nitric oxide synthase with N(sup G)-nitro-L- arginine methyl ester increased mean arterial pressure by 9 mm Hg, decreased heart rate and plasma renin activity, and markedly suppressed the renin response to frusemide (from 4.6 +/- 0.7 to 7.6 +/- 1.7, 4.7 +/- 1.0 and 4.6 +/- 0.7pmol/2h ml at 15, 30 and 45 min respectively). By contrast, infusion of an equipressor dose of phenylephrine did not suppress the renin response to frusemide. Histochemical studies with the NADPH diaphorase technique confirmed the presence of nitric oxide synthase in the macula densa, and suggested that enzyme activity is increased by treatment with frusemide. These results are consistent with a role for the L- arginine-nitric oxide pathway in the modulation of renin secretion by the macula densa.

Reid, Ian A.↗