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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Nuclear morphometric analysis of osteoblast precursor cells in periodontal ligament, SL-3 rats

Five small (55 days old, 196 +/- 5 g) (mean +/- SE) and five large (83 days old, 382 +/- 4 g) Sprague-Dawley strain, specific pathogen-free rats were exposed to a 7-day spaceflight and 12-h postflight recovery period. As measured in 3-micron sections, periodontal ligament (PDL) fibroblastlike cells were classified according to nuclear size: A + A' (40-79), B (80-119), C (120-169), and D (greater than or equal to 170 microns 3). Since the histogenesis sequence is A----A'----C----D----osteoblast, the relative incidence of A + A' to C + D is an osteogenic index. No difference in A + A' or C + D cells in small rats may reflect partial recovery of preosteoblast formation (A----C) during the 12-h postflight period. Large flight rats demonstrated increased numbers of A + A', indicating an inhibition of preosteoblast formation (A----C). At least in the older group, a 7-day flight is adequate to reduce PDL osteogenic potential (inhibition in PDL osteoblast differentiation and/or specific attrition of C + D cells) that does not recover by 12-h postflight.

Flight Experiment↗
NASA NTRS1992

Effects of prior exercise on the action of insulin-like growth factor I in skeletal muscle

Prior exercise increases insulin sensitivity for glucose and system A neutral amino acid transport activities in skeletal muscle. Insulin-like growth factor I (IGF-I) also activates these transport processes in resting muscle. It is not known, however, whether prior exercise increases IGF-I action in muscle. Therefore we determined the effect of a single exhausting bout of swim exercise on IGF-I-stimulated glucose transport activity [assessed by 2-deoxy-D-glucose (2-DG) uptake] and system A activity [assessed by alpha-(methylamino)isobutyric acid (MeAIB) uptake] in the isolated rat epitrochlearis muscle. When measured 3.5 h after exercise, the responses to a submaximal concentration (0.2 nM), but not a maximal concentration (13.3 nM), of insulin for activation of 2-DG uptake and MeAIB uptake were enhanced. In contrast, prior exercise increased markedly both the submaximal (5 nM) and maximal (20 nM) responses to IGF-I for activation of 2-DG uptake, whereas only the submaximal response to IGF-I (3 nM) for MeAIB uptake was enhanced after exercise. We conclude that 1) prior exercise significantly enhances the response to a submaximal concentration of IGF-I for activation of the glucose transport and system A neutral amino acid transport systems in skeletal muscle and 2) the enhanced maximal response for IGF-I action after exercise is restricted to the signaling pathway for activation of the glucose transport system.

Non-NASA Center↗
NASA NTRS1992

Effects of systemic carbidopa on dopamine synthesis in rat hypothalamus and striatum

Significant concentrations of carbidopa (CD) were found in rat hypothalamus, striatum, and in striatal microdialysis efflux after intraperitoneal administration of the drug. Efflux levels peaked one hour after administration of 100 mg/kg at 0.37 micrograms/ml, or about 2% of serum levels. Concurrent CD levels in hypothalamus and striatum were about 2.5% and 1.5%, respectively, of corresponding serum levels. Levels of dopamine and its principal metabolites in striatal efflux were unaffected. The removal of the brain blood by saline perfusion decreased the striatal and hypothalamic CD concentrations only by 33% and 16%, respectively. In other rats receiving both CD and levodopa (LD), brain L-dopa, dopamine and 3,4-dihydroxyphenylacetic acid (DOPAC) levels after one hour tended to be proportionate to LD dose. When the LD dose remained constant, increasing the CD dose dose-dependently enhanced L-dopa levels in the hypothalamus and striatum. However dopamine levels did not increase but, in contrast, decreased dose-dependently (although significantly only in the hypothalamus). CD also caused dose-dependent decrease in striatal 3-O-methyldopa (3-OMD) and in striatal and hypothalamic homovanillic acid (HVA), when the LD dose was 50 mg/kg. We conclude that, at doses exceeding 50 mg/kg, sufficient quantities of CD enter the brain to inhibit dopamine formation, especially in the hypothalamus. Moreover, high doses of LD/CD, both of which are themselves catechols, can inhibit the O-methylation of brain catecholamines formed from the LD.

NASA Discipline Regulatory Physiology↗
NASA NTRS1991

Palmitate stimulates glucose transport in rat adipocytes by a mechanism involving translocation of the insulin sensitive glucose transporter (GLUT4)

In rat adipocytes, palmitate: a) increases basal 2-deoxyglucose transport 129 +/- 27% (p less than 0.02), b) decreases the insulin sensitive glucose transporter (GLUT4) in low density microsomes and increases GLUT4 in plasma membranes and c) increases the activity of the insulin receptor tyrosine kinase. Palmitate-stimulated glucose transport is not additive with the effect of insulin and is not inhibited by the protein kinase C inhibitors staurosporine and sphingosine. In rat muscle, palmitate: a) does not affect basal glucose transport in either the soleus or epitrochlearis and b) inhibits insulin-stimulated glucose transport by 28% (p less than 0.005) in soleus but not in epitrochlearis muscle. These studies demonstrate a potentially important differential role for fatty acids in the regulation of glucose transport in different insulin target tissues.

NASA Discipline Cell Biology↗
NASA NTRS1990

Histomorphometric and electron microscopic analyses of tibial epiphyseal plates from Cosmos 1887 rats

Previous studies have shown that the changes seen in the bones of growing rats exposed to microgravity are due in part to changes that occur in the growth plate during spaceflight. In this study, growth plates of rats flown aboard Cosmos 1887 (12.5-day flight plus 53.5-h recovery at 1 g) were analyzed using light and electron microscopy and computerized planimetry. The proliferative zone of flight animals was found to be significantly (P less than or equal to 0.01) larger than that of controls, while the reserve and hypertrophic/calcification zones were significantly reduced. Flight animals also had more cells per column in the proliferative zone than did controls and less in the hypertrophic/calcification region. The total number of cells, however, was significantly greater in flight animals. No difference was found in perimeter or in shape factor, but area was significantly less in flight animals. Electron microscopy showed that collagen fibrils in flight animals were wider than in controls. Since the time required for a cell to cycle through the growth plate is 2-3 days at 1 g, the results reported here represent both the effects of exposure to microgravity and the initial stages of recovery from that exposure.

Non-NASA Center↗
NASA NTRS1992

Dietary protein deficiency reduces lysosomal and nonlysosomal ATP-dependent proteolysis in muscle

When rats are fed a protein deficient (PD) diet for 7 days, rates of proteolysis in skeletal muscle decrease by 40-50% (N. E. Tawa, Jr., and A. L. Goldberg. Am. J. Physiol. 263 (Endocrinol. Metab. 26): E317-325, 1992). To identify the underlying biochemical adaptations, we measured different proteolytic processes in incubated muscles. The capacity for intralysosomal proteolysis, as shown by sensitivity to methylamine or lysosomal protease inhibitors, fell 55-75% in muscles from PD rats. Furthermore, extracts of muscles of PD rats showed 30-70% lower activity of many lysosomal proteases, including cathepsins B, H, and C, and carboxypeptidases A and C, as well as other lysosomal hydrolases. The fall in cathepsin B and proteolysis was evident by 3 days on the PD diet, and both returned to control levels 3 days after refeeding of the normal diet. In muscles maintained under optimal conditions, 80-90% of protein breakdown occurs by nonlysosomal pathways. In muscles of PD rats, this ATP-dependent process was also 40-60% slower. Even though overall proteolysis decreased in muscles of PD rats, their capacity for Ca(2+)-dependent proteolysis increased (by 66%), as did the activity of the calpains (+150-250%). Thus the lysosomal and the ATP-dependent processes decrease coordinately and contribute to the fall in muscle proteolysis in PD animals.

Non-NASA Center↗
NASA NTRS1990

Effects of zero gravity on myofibril content and isomyosin distribution in rodent skeletal muscle

The purpose of this experiment was to investigate the effects of 12.5 days of zero gravity (0 g) exposure (Cosmos 1887 Biosputnik) on the enzymatic properties, protein content, and isomyosin distribution of the myofibril fraction of the slow-twitch vastus intermedius (VI) and the fast-twitch vastus lateralis (VL) muscles of adult male rats. Measurements were obtained on three experimental groups (n = 5 each group) designated as flight group (FG), vivarium control (VC), and synchronous control (SC). Body weight of the FG was significantly lower than that of the two control groups (P less than 0.05). Compared with the two control groups, VI weight was lower by 23% (P less than 0.10), whereas no such pattern was apparent for the VL muscle. Myofibril yields (mg protein/g muscle) in the VI were 35% lower in the FG than in controls (P less than 0.05), whereas no such pattern was apparent for the VL muscle. When myofibril yields were expressed on a muscle basis (mg/g x muscle weight), the loss of myofibril protein was more exaggerated and suggests that myofibril protein degradation is an early event in the muscle atrophy response to 0 g. Analysis of myosin isoforms indicated that slow myosin (Sm) was the primary isoform lost in the calculated degradation of total myosin. No evidence of loss of the fast isomyosins was apparent for either muscle following spaceflight. Myofibril ATPase activity of the VI was increased in the FG compared with controls, which is consistent with the observation of preferential Sm degradation. These data suggest that muscles containing a high percentage of slow-twitch fibers undergo greater degrees of myofibril protein degradation than muscles containing predominantly fast-twitch fibers in response to a relatively short period of 0 g exposure, and the primary target appears to be the Sm molecule.

NASA Program Flight↗
NASA NTRS1986

Spaceflight effects on adult rat muscle protein, nucleic acids, and amino acids

Exposure to conditions of weightlessness has been associated with decrements in muscle mass and strength. The present studies were undertaken to determine muscle responses at the cellular level. Male Sprague-Dawley rats (360-410 g) were exposed to 7 days of weightlessness during the Spacelab-3 shuttle flight (May 1985). Animals were killed 12 h postflight, and soleus (S), gastrocnemius (G), and extensor digitorum longus (EDL) muscles were excised. Muscle protein, RNA, and DNA were extracted and quantified. Differential muscle atrophy was accompanied by a significant (P less than 0.05) reduction in total protein only in S muscles. There were no significant changes in protein concentration (mg/g) in the muscles examined. In S muscles from flight animals, sarcoplasmic protein accounted for a significantly greater proportion of total protein that in ground controls (37.5 vs. 32.5%). Tissue concentrations (nmol/g) of asparagine-aspartate, glutamine-glutamate, glycine, histidine, and lysine were significantly reduced (from 17 to 63%) in S muscles from flight animals, but only glutamine-glutamate levels were decreased in the G and EDL. Muscle DNA content (microgram) was unchanged in the tissues examined, but S muscle DNA concentration (micrograms/mg) increased 27%. RNA content (micrograms) was significantly (P less than 0.025) reduced in S (-28%) and G(-22%) muscles following spaceflight. These results identify specific alterations in rat skeletal muscle during short term (7-day) exposure to weightlessness and compare favorably with observations previously obtained from ground-based suspension simulations.

short duration↗
NASA NTRS1992

Exercise training, glucose transporters, and glucose transport in rat skeletal muscles

It was previously found that voluntary wheel running induces an increase in the insulin-sensitive glucose transporter, i.e., the GLUT4 isoform, in rat plantaris muscle (K. J. Rodnick, J. O. Holloszy, C. E. Mondon, and D. E. James. Diabetes 39: 1425-1429, 1990). The present study was undertaken to determine whether 1) the increase in muscle GLUT4 protein is associated with an increase in maximally stimulated glucose transport activity, 2) a conversion of type IIb to type IIa or type I muscle fibers plays a role in the increase in GLUT4 protein, and 3) an increase in the GLUT1 isoform is a component of the adaptation of muscle to endurance exercise. Five weeks of voluntary wheel running that resulted in a 33% increase in citrate synthase activity induced a 50% increase in GLUT4 protein in epitrochlearis muscles of female Sprague-Dawley rats. The rate of 2-deoxy-glucose transport maximally stimulated with insulin or insulin plus contractions was increased approximately 40% (P less than 0.05). There was no change in muscle fiber type composition, evaluated by myosin ATPase staining, in the epitrochlearis. There was also no change in GLUT1 protein concentration. We conclude that an increase in GLUT4, but not of GLUT1 protein, is a component of the adaptive response of muscle to endurance exercise and that the increase in GLUT4 protein is associated with an increased capacity for glucose transport.

NASA Discipline Cell Biology↗
NASA NTRS1987

Histomorphometric analysis of rat skeleton following spaceflight

Male Sprague-Dawley rats were placed in orbit for 7 days aboard the space shuttle. Bone histomorphometry was performed in the long bones and lumbar vertebrae of flight rats and compared with data derived from ground-based control rats. Trabecular bone mass was not altered during the 1st wk of weightlessness. Strong trends were observed in flight rats for decreased periosteal bone formation in the tibial diaphysis, reduced osteoblast size in the proximal tibia, and decreased osteoblast surface and number in the lumbar vertebra. For the most part, histological indexes of bone resorption were normal in flight rats. The results indicate that 7 days of weightlessness are not of sufficient duration to induce histologically detectable loss of trabecular bone in rats. However, cortical and trabecular bone formation appear to be diminished during the 1st wk of spaceflight.

Non-NASA Center↗
NASA NTRS1986

Otoconia as test masses in biological accelerometers: what can we learn about their formation from evolutionary studies and from work in microgravity?

This paper reviews previous findings and introduces new material about otolith end organs that help us to understand their functioning and development. In particular, we consider the end organs as biological accelerometers. The otoconia are dealt with as test masses whose substructure and evolutionary trend toward calcite may prove significant in understanding formation requirements. Space-flight helps illuminate the influence of gravity, while right-left asymmetry is suggested by study of certain rat strains.

Non-NASA Center↗
NASA NTRS1993

Two-dimensional spatiotemporal coding of linear acceleration in vestibular nuclei neurons

Response properties of vertical (VC) and horizontal (HC) canal/otolith-convergent vestibular nuclei neurons were studied in decerebrate rats during stimulation with sinusoidal linear accelerations (0.2-1.4 Hz) along different directions in the head horizontal plane. A novel characteristic of the majority of tested neurons was the nonzero response often elicited during stimulation along the "null" direction (i.e., the direction perpendicular to the maximum sensitivity vector, Smax). The tuning ratio (Smin gain/Smax gain), a measure of the two-dimensional spatial sensitivity, depended on stimulus frequency. For most vestibular nuclei neurons, the tuning ratio was small at the lowest stimulus frequencies and progressively increased with frequency. Specifically, HC neurons were characterized by a flat Smax gain and an approximately 10-fold increase of Smin gain per frequency decade. Thus, these neurons encode linear acceleration when stimulated along their maximum sensitivity direction, and the rate of change of linear acceleration (jerk) when stimulated along their minimum sensitivity direction. While the Smax vectors were distributed throughout the horizontal plane, the Smin vectors were concentrated mainly ipsilaterally with respect to head acceleration and clustered around the naso-occipital head axis. The properties of VC neurons were distinctly different from those of HC cells. The majority of VC cells showed decreasing Smax gains and small, relatively flat, Smin gains as a function of frequency. The Smax vectors were distributed ipsilaterally relative to the induced (apparent) head tilt. In type I anterior or posterior VC neurons, Smax vectors were clustered around the projection of the respective ipsilateral canal plane onto the horizontal head plane. These distinct spatial and temporal properties of HC and VC neurons during linear acceleration are compatible with the spatiotemporal organization of the horizontal and the vertical/torsional ocular responses, respectively, elicited in the rat during linear translation in the horizontal head plane. In addition, the data suggest a spatially and temporally specific and selective otolith/canal convergence. We propose that the central otolith system is organized in canal coordinates such that there is a close alignment between the plane of angular acceleration (canal) sensitivity and the plane of linear acceleration (otolith) sensitivity in otolith/canal-convergent vestibular nuclei neurons.

NASA Discipline Neuroscience↗
NASA NTRS1992

Effect of total parenteral nutrition, systemic sepsis, and glutamine on gut mucosa in rats

The effect of the combination of total parenteral nutrition (TPN) and systemic sepsis on mucosal morphology and protein synthesis was investigated. Rats were given a standard TPN mixture consisting of glucose (216 kcal.kg-1.day-1), lipid (24 kcal.kg-1.day-1), and amino acids (1.5 g N.kg-1.day-1) for 5 days. On the 5th day the rats (n = 37) were randomized into four groups according to diet as follows: 1) control nonseptic on standard TPN, 2) control nonseptic on TPN with glutamine, 3) septic on standard TPN, and 4) septic with the TPN supplemented with glutamine. Twenty hours after the injection of Escherichia coli, the rats were given a 4-h constant infusion of [U-14C]leucine to determine the mucosal fractional protein synthesis rates. The following results were obtained. 1) Histological examination showed that systemic sepsis caused tissue damage to the ileum and jejunum. 2) Glutamine supplementation attenuated these changes. 3) There were no visible changes to the colon either from glutamine supplementation or sepsis. 4) Sepsis was associated with an increase in mucosal protein synthesis and decreased muscle synthesis. 5) Addition of glutamine to the TPN mix further increased protein synthesis in the intestinal mucosa of septic rats.

Non-NASA Center↗
NASA NTRS1992

Effects of spaceflight in the adductor longus muscle of rats flown in the Soviet Biosatellite COSMOS 2044. A study employing neural cell adhesion molecule (N-CAM) immunocytochemistry and conventional morphological techniques (light and electron microscopy)

The effects of spaceflight upon the "slow" muscle adductor longus were examined in rats flown in the Soviet Biosatellite COSMOS 2044. The techniques employed included standard methods for light microscopy, neural cell adhesion molecule (N-CAM) immunocytochemistry and electron microscopy. Light microscopic observations revealed myofiber atrophy and segmental necrosis accompanied by cellular infiltrates composed of macrophages, leukocytes and mononuclear cells. Neural cell adhesion molecule immunoreactivity (N-CAM-IR) was seen on the myofiber surface and in regenerating myofibers. Ultrastructural alterations included Z band streaming, disorganization of myofibrillar architecture, sarcoplasmic degradation, extensive segmental necrosis with apparent preservation of the basement membrane, degenerative phenomena of the capillary endothelium and cellular invasion of necrotic areas. Regenerating myofibers were identified by the presence of increased amounts of ribosomal aggregates and chains of polyribosomes associated with myofilaments. The principal electron microscopic changes of the neuromuscular junctions showed axon terminals with a decrease or absence of synaptic vesicles replaced by microtubules and neurofilaments, degeneration of axon terminals, vacant axonal spaces and changes suggestive of axonal sprouting. The present observations suggest that alterations such as myofibrillar disruption and necrosis, muscle regeneration and denervation and synaptic remodeling at the level of the neuromuscular junction may take place during spaceflight.

NASA Experiment Number COS 2044-10↗