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At least 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Histochemical carbonic anhydrase in rat inner medullary collecting duct

Rat inner medullary collecting duct (IMCD) secretes substantial amounts of H+. However, carbonic anhydrase (CA), a concomitant of H+ secretion, has been generally reported absent in this segment. To reexamine this problem, we investigated CA and the morphological phenotypes of cells comprising the IMCD by CA histochemistry, using a modified Hansson technique with light and electron microscopy. Throughout the medulla, tubule cells exhibit histochemical CA activity. In the initial third of the inner medulla, a small proportion have features of intercalated cells and demonstrate some degree of CA activity. However, the majority population in the early portions of the IMCD appears to consist of principal cells. These also show CA staining of widely variable intensity, both among and within cells. A third cell type, previously called "IMCD cells", appears in the middle portion of the IMCD and is the only cell type present near the papilla tip. In contrast to previous reports, these "IMCD cells" have histochemical CA staining, also of highly variable intensity. These results demonstrate that stainable carbonic anhydrase to support acidification is present throughout the rat IMCD, both in intercalated cells and in some cells clearly not of this type. Therefore, the presence of CA is not specific for the intercalated cell type and suggests that other cell types may participate in acid secretion in IMCD.

NASA Discipline Musculoskeletal↗
NASA NTRS1992

Interaction between alpha 2-adrenergic and angiotensin II systems in the control of glomerular hemodynamics as assessed by renal micropuncture in the rat

The hypothesis that renal alpha 2 adrenoceptors influence nephron filtration rate (SNGFR) via interaction with angiotensin II (AII) was tested by renal micropuncture. The physical determinants of SNGFR were assessed in adult male Munich Wistar rats 5-7 d after ipsilateral surgical renal denervation (DNX). DNX was performed to isolate inhibitory central and presynaptic alpha 2 adrenoceptors from end-organ receptors within the kidney. Two experimental protocols were employed: one to test whether prior AII receptor blockade with saralasin would alter the glomerular hemodynamic response to alpha 2 adrenoceptor stimulation with the selective agonist B-HT 933 under euvolemic conditions, and the other to test whether B-HT 933 would alter the response to exogenous AII under conditions of plasma volume expansion. In euvolemic rats, B-HT 933 caused SNGFR to decline as the result of a decrease in glomerular ultrafiltration coefficient (LpA), an effect that was blocked by saralasin. After plasma volume expansion, B-HT 933 showed no primary effect on LpA but heightened the response of arterial blood pressure, glomerular transcapillary pressure gradient, and LpA to AII. The parallel results of these converse experiments suggest a complementary interaction between renal alpha 2-adrenergic and AII systems in the control of LpA.

NASA Discipline Cardiopulmonary↗
NASA NTRS1987

Fragility and composition of growing rat bone after one week in spaceflight

To gain some insight into the early effects of spaceflight on skeletal metabolism, we quantified the major chemical constituents and a noncollagenous protein, osteocalcin, in the third-lumbar vertebrae and humeri from 8-wk-old rats that were part of the 7-day NASA Spacelab 3 flight experiments. The ratio of calcium to hydroxyproline in the humeral diaphysis increased from 8.5 in preflight to 9.8 in ground simulation control and only to 8.9 in flight bones. There was no demonstrable change in the fraction of nonmineralized collagen. Osteocalcin content was reduced in the humerus and vertebra. Reduced accumulation of mineral and osteocalcin with no associated decrease in collagen in flight animals suggests that both mineralization and collagen metabolism are impaired in growing animals during spaceflight within a few days after launch. Strength tests of the humeri of flight rats showed substantial deficits that appeared to be related, not only to the reduced bone mass, but also to the composition and quality of new bone formed.

STS-51B Shuttle Project↗
NASA NTRSDate not supplied

Reanalysis of Rat Data from Spacelab Life Sciences 2 (SLS-2) to Reveal Research Gaps in Spaceflight Data

Using and analyzing the legacy data obtained in space life sciences missions has the potential to provide researchers a complete picture of the molecular changes associated with space without further experimentation. This project’s objective is to extract, filter, organize, and analyze all Rattus norvegicus data and metadata obtained from Columbia’s Spacelab Life Sciences 2 (SLS-2, STS-58) mission to explore the ways that we can compile information from model organisms, in our case rats, to create a reliable model to understand biological mechanisms in response to these space flight changes. By reusing rare space legacy data coupled with data analysis techniques, we can combine individual preexisting datasets with current ones to gain new, comprehensive insights about the effects of spaceflight on our bodies. Our methods can also lead to the creation of a standardized pipeline that could be applied to other space life science datasets for analysis. In this review, every biological experiment conducted on rats in the SLS-2 Mission was studied with our pipeline to create a new biological library and model that could be used by scientists from around the world to make novel discoveries and develop new hypotheses from this priceless information without the limitation of the costs of spaceflight experimentation.

rats↗
NASA NTRS1971

Effect of 90-day continuous exposure to methylisobutylketone on dogs, monkeys and rats

Continuous exposure of rats, dogs and monkeys to 410 mg/cu M methylisobutylketone vapor (MIBK) was conducted to evaluate the provisional spacecraft exposure limit of 20 ppm established by the Space Science Board in 1968. The exposure, conducted in a simulated space cabin environment, did not produce any measurable changes in dogs or monkeys. Rats developed hyaline droplet nephrosis within 2 weeks of exposure which was reversible upon removal from the MIBK even after 90 days. The data obtained indicated that the 60-minute emergency exposure limit of 100 ppm and the 90- and 1000-day provisional limits as established by the Space Science Board contain a wide margin of safety.

Macewen, J. D.↗
NASA NTRS1971

Prolongation of RBC survival in the hypophysectomized rat.

Red blood cell (RBC) survival was prolonged in hypophysectomized rats. While the rate of random hemolysis was decreased in some hypophysectomized hosts, in all directly injected and cross-transfused hypophysectomized rat hosts, there was a significant prolongation of the phase of senescent death. In contrast, RBCs from hypophysectomized donors survived normally in normal hosts. These experiments are further evidence of a relationship between RBC aging and metabolic rate, and suggest an intimate involvement with the calorigenic hormones.

Landaw, S. A.↗
NASA NTRS1971

Short term response of insulin, glucose, growth hormone and corticosterone to acute vibration in rats.

Study carried out to obtain some notion of the initial phasing and interactive effects among some hormones known to be responsive to vibration stress. Sprague-Dawley derived rats were exposed to the acute effects of confinement and confinement with lateral (plus or minus G sub y) vibration. The coincident monitoring of glucose, insulin, growth hormone, and corticosterone plasma levels, during and immediately subsequent to exposure to brief low level vibration, exhibits the effects of inhibition of insulin release by epinephrine. The ability of insulin (IRI) to return rapidly to basal levels, from appreciably depressed levels during vibration, in the face of elevated levels of glucose is also shown. Corticosterone responds with almost equal rapidity, but in opposite phase to the IRI. The immuno-assayable growth hormone (IGH) dropped from a basal level of 32 ng/ml to 7.3 ng/ml immediately subsequent to vibration and remained at essentially that level throughout the experiment (60 min). Whether these levels represent a real fall in the rat or whether they merely follow the immuno-logically deficient form is still in question.

Dolkas, C. B.↗
NASA NTRS1971

Erythropoietic radiosensitivity of the rat during altitude acclimatization.

The effect of a sublethal dose (300 R) of X-radiation upon the erythropoietic system of the rat, during 60-day acclimatization to moderate hypoxia (3,800 m altitude), was studied. Past work has shown that hypoxic animals are damaged less by radiation than animals irradiated in a normal environment; therefore, it was postulated that if, after acclimatization to hypoxia the bone marrow oxygen tension returns to sea-level values, these animals should suffer radiation damage equivalent to animals at sea level. The principal parameters followed were the rate of depletion of injected Fe-59 from the plasma of chronically catheterized rats, and its subsequent reappearance in the circulating erythrocytes. After 20 days of acclimatization, both parameters for altitude-irradiated animals returned to the values of animals irradiated at sea level, previously having reflected increased erythropoiesis. In altitude nonirradiated animals the parameters indicated erythropoietic stimulation persisting up to 45 days acclimatization. The protective effect of the hypoxia on the stem cells vanished during acclimatization, presumably as cellular oxygen tension rose.

Gaugl, J. F.↗
NASA NTRS1972

Effects of continuous exposure to high gravity on gravity preference in rats.

Rats were chronically centrifuged in excess of 2.0 g for 6 or 12 mo. They were given four 24-hr gravity-preference tests in a spiral centrifuge in which they could adjust the gravity level imposed by locomoting inward or outward radially along a track. Chronically centrifuged rats (Group CC) spent as much time at 2.0 g as at 1.0 g while normally raised controls (Group NC) selecdonly 1.0 g. Group CC initially selected 2.0 g and a preference for 1.0 g developed over the four test sessions. These results suggest that hypergravity is not necessarily an aversive stimulus and that gravity preference may depend initially upon the reference level involved. The ultimate selection of 1.0 g by chronically centrifuged animals suggests that a preference for a familiar gravity environment is replaced by a preference for low-gravity stimuli.

Mccoy, D. F.↗
NASA NTRS1971

Ultrastructural changes in rat lung during long-term exposure to oxygen.

The pathogenesis of oxygen toxicity in the lung of rats was studied by electron microscopy. The following long-term effects were established: (1) a progressive destruction of the blood-air barrier beginning with the endothelial cell layer; (2) a profuse edema in the interstitial spaces in the pleural space in the alveoli and in the cytoplasm and organelles; (3) a continuing increase in the quantity and complexity of the alveolar exudate; (4) gradual hemolysis of red blood cells; and (5) eventual subsiding of the interstitial edema in surviving rats with a concomitant development of emphysema.

Harrison, G. A.↗
NASA NTRS1972

A common modality of action of simulated space stresses on the oxidative metabolism of ethylmorphine, aniline and p-nitroanisole by male rat liver.

High gravity, cold and starvation elicited similar responses in male Simonson rats. These responses included a decreased rate in body weight gain, increased metabolism of aniline and p-nitroanisole, and no consistent pattern of change in the metabolism of ethylmorphine. Cold and starvation increased the amount of hepatic cytochrome P-450, while hypobaric-hyperoxia caused no change in any of the parameters measured. When 1% acetone was given to the rats in their drinking water, the effects on drug metabolism were similar to those produced by food restriction in that the metabolism of aniline and p-nitroanisole was increased, and the metabolism of ethylmorphine unchanged. The type I binding spectrum of acetone suggests that it is either a substrate, inhibitor, or both for hepatitic oxidative enzymes.

Furner, R. L.↗
NASA NTRS1972

Effect of hypergravity on the circadian rhythms of white rats.

The effects of artificial gravity on the circadian rhythm of white rats was observed by comparing feeding activity at 1.0 and 1.75 g. The feeding cycle data were obtained by observing the number of feeding switch responses, as well as the amount of food obtained, as a function of time. One of the three subjects clearly established a free-running cycle with a period of 24.742 hr. During a 40-day exposure to the 1.75 g environment, the subjects maintained the same feeding cycle period which was established at 1.0 g. While the results of this study indicate that the activity rhythms of rats are insensitive to gravity levels between 1.0 and 1.75 g, the effects of gravity levels below 1.0 g are yet to be determined.

Lafferty, J. F.↗
NASA NTRS1973

Effect of low temperature on metabolism of rat liver slices and epididymal fat pads.

Study of low temperature effects on the metabolism of radioisotope-tagged glucose and palmitate in rat liver slices and epididymal fat pads. The obtained data suggest that the oxidative capacity of rat liver and adipose tissue is maintained at low temperatures to a greater degree than the synthetic capacity. It was concluded that sufficient energy can be produced at 17 C for maintenance of essential tissue functions by these two tissues but that the energy requirements may not be met at 7 C.

Hillyard, L. A.↗
NASA NTRS1973

Helium-cold induced hypothermia in the white rat.

Hypothermia was induced in white rats by exposing them to low ambient temperatures (about 0 C) and a gaseous atmosphere of 80% helium and 20% oxygen (helox). Biological survival, in which revival from hypothermia to normothermia is achieved, and clinical survival, in which one or more functional attributes are monitored in the hypothermic animal until it dies, are examined. The helium-cold method appears to produce a hypothermic state in the rat quite similar to that resulting from such techniques as ice water immersion or hypercapnia + hypoxia. There is a direct relationship between body weight and percent survival. Despite the fact that they require a longer period to become hypothermic, the heavier animals are better able to survive.

Musacchia, X. J.↗
NASA NTRS1973

Nonthermal metabolic response of rats to He-O2, N2-O2, and Ar-O2 at 1 atm.

Experiments were performed to describe qualitatively and quantitatively the nonthermal metabolic response of rats to normoxic mixtures of helium, nitrogen, or argon at 1 atm ambient pressure. Hypoxic mixtures were similarly tested to determine any differences in hypoxic response as a function of the diluent gas. Rats exposed to argon for 5 days had a reduced metabolic rate relative to nitrogen, as evidenced by oxygen and food consumption, CO2 production, and the catabolism of radiosubstrates. While some parameters indicated that helium increased metabolic rate, oxygen consumption did not significantly differ from that in nitrogen. The physiologic and metabolic response to an imposed hypoxia varied among the different environments. Certain indices suggested that the hypoxic effects were less severe in helium and more pronounced in argon than in nitrogen. The mechanisms by which the diluent gases produced the observed changes could not be identified, but some possibilities are discussed.

Schatte, C. L.↗
NASA NTRS1974

Observations on saccules of rats exposed to long-term hypergravity

The saccules of 15 centrifuged rats and 15 control rats were examined for morphological alterations resulting from long-term exposure to hypergravity. Minimal changes were found confined to the otolithic membrane. They were a slight decrease in the overall volume of otolithic membrane, a redistribution of otoconia in the direction of the gravitational force, and a more pronounced 'accessory' membrane. These changes were interpreted as purely mechanical effects of hypergravity, causing accelerated displacement of otoconia and subsequent entrapment of some of them on inferior portions of the primary otolithic membrane and 'accessory' membrane.

Lim, D. J.↗
NASA NTRS1974

Fine structural changes in the lateral vestibular nucleus of aging rats

The fine structure of the lateral vestibular nucleus was investigated in Sprague-Dawley rats, that were sacrified at 4 weeks, 6-8 weeks, 6-8 months, and 18-20 months of age. In the neuronal perikaria, the following age-associated changes were seen with increasing frequency with advancing age: rodlike nuclear inclusions and nuclear membrane invaginations; cytoplasmic dense bodies with the characteristics of lipofuscin; and moderate disorganization of the granular endoplasmic reticulum. Dense bodies were also seen in glial cells. Rats 18 to 20 months old showed dendritic swellings, axonal degeneration, and an apparent increase in the number of axosomatic synaptic terminals containing flattened vesicles (presumed to be inhibitory in function).

Johnson, J. E., Jr.↗
NASA NTRS1976

Functional and anatomical characteristics of the nerve-brown adipose interaction in the rat

Experiments were conducted on 12 male rats to study the coupling of signals from the sympathetic nervous system to the brown adipose tissue. Analysis of electron photomicrographs revealed considerable morphological heterogeneity among the nerves entering and leaving the interscapular fat pad. In response to electrical simulation of the nerves, the temperature of the brown fat increased following a rapid but transient temperature drop. Such changes were observed only on the ipsilateral side, indicating that the innervation to the interscapular brown fat of the rat is functionally bilateral rather than diffuse. The finding that brown fat is capable of responding in a graded fashion correlates well with observations suggesting that clusters of brown adipocytes may be electrically coupled.

Flaim, K. E.↗