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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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Morphological and biochemical changes in soleus and extensor digitorum longus muscles of rats orbited in Spacelab 3

Muscle atrophy in rats exposed to hypogravity for seven days aboard Spacelab 3 is examined. Hindlimb muscles were harvested 12-16 days postflight, and prepared for enzyme studies and electron microscopy. Simple cell shrinkage was found, with a mean fiber area decrease of 35.8 percent for soleus and 24.9 percent for extensor digitorum longus (EDL) flight muscle fibers, as compared with control muscle fibers. EDL and soleus muscles showed increases in alkaline myofibrillar ATPase, alpha glycerophosphate dehydrogenase, and glycogen, and a decrease in NADH dehydrogenase staining. The 26 percent increase in calcium activated protease suggests that the focal degradation of myofibrils is the key process of myofibril breakdown. The presence in the flight soleus muscles of one percent necrotic fibers is unexplained. The observed shift towards histochemical fast-muscle type properties is consistent with previous findings.

Riley, D. A.↗
NASA NTRS1985

The use of suspension models and comparison with true weightlessness

A resume is presented of various papers concerning the effect of weightlessness on particular physiological and biochemical phenomena in animal model systems. Findings from weightlessness experiments on earth using suspension models are compared with results of experiments in orbit. The biological phenomena considered include muscle atrophy, changes in the endocrine system, reduction in bone formation, and changes in the cardiovascular system.

Musacchia, X. J.↗
NASA NTRS1987

Growth factor involvement in tension-induced skeletal muscle growth

New muscle tissue culture techniques were developed to grow embryonic skeletal myofibers which are able to differentiate into more adultlike myofibers. Studies on mechanical simulation of cultured muscle cell growth will now be more directly applicable to mechanically-induced growth in adult muscle, and lead to better models for understanding muscle tissue atrophy caused by disuse in the microgravity of space.

Vandenburgh, Herman W.↗
NASA NTRS1987

Growth hormone secretion during space flight and evaluation of the physiological responses of animals held in the research animal holding facility

The spaceflight of the Research Animal Holding Facility (RAHF) on the Space Laboratory 3 (SL 3) provided the opportunity to evaluate the suitability of the RAHF for housing and maintaining experimental animals during spaceflight, and to determine changes in the secretion of growth hormone during spaceflight. Using ground-based studies the following were investigated: the optimum conditions for creating gravitational force on space flight animals; neural pathways that may play a role in the space flight syndrome; and the time course of muscle atrophy due to hypodynamia and hypokenesia in hindlimb-suspended animals and the role of growth hormone in these processes.

Fast, Thomas N.↗
NASA NTRS1986

Increased response to insulin of glucose metabolism in the 6-day unloaded rat soleus muscle

Hind leg muscles of female rats were unloaded by tail cast suspension for 6 days. In the fresh-frozen unloaded soleus, the significantly greater concentration of glycogen correlated with a lower activity ratio of glycogen phosphorylase (p less than 0.02). The activity ratio of glycogen synthase also was lower (p less than 0.001), possibly due to the higher concentration of glycogen. In isolated unloaded soleus, insulin (0.1 milliunit/ml) increased the oxidation of D(U-C-14) glucose, release of lactate and pyruvate, incorporation of D-(U-C-14) glucose into glycogen, and the concentration of glucose 6-phosphate more (p less than 0.05) than in the weight-bearing soleus. At physiological doses of insulin, the percent of maximal uptake of 2-deoxy-D-(1,2-H-3) glucose/muscle also was greater in the unloaded soleus. Unloading of the soleus increased, by 50 percent the concentration of insuling receptors, due to no decrease in total receptor number during muscle atrophy. This increase may account for the greater response of glucose metabolism to insulin in this muscle. The extensor digitorum longus, which generally shows little response to unloading, displayed no differential response of glucose metabolism to insulin.

Henriksen, Erik J.↗
NASA NTRS1987

Bone and muscle - The structural system in long duration space missions

Losses of bone mineral and muscle mass have been observed, and in varying degrees measured, following all long duration missions in space. These observations portend an unacceptable threat to the crews' ability to return to earth, without protracted rehabilitation, following periods of a year or more in microgravity. The impact to crew capabilities and productivity in space is not well understood. Past research has dealt with bone loss and muscle atrophy as two separate problems with little discernible relationship. This paper reviews the available information on both and suggests a combined structural approach for future research.

Buchanan, Paul↗
NASA NTRS1987

Size and metabolic properties of single muscle fibers in rat soleus after hindlimb suspension

The effect of 28-day-long hind-limb suspension (HS) combined with 10 daily forceful lengthening contractions of the limb on the morphological and metabolic properties of individual fibers of the soleus was studied in rats, using quantitative histochemical techniques. Compared with nonsuspended controls (CON), soleus wet weights of HS rats were decreased by 49 percent; the fibers staining lightly for myosin ATPase ('light-ATPase' fibers) atrophied more than the 'dark-ATPase' fibers. Single-fiber alpha-glycerophosphate dehydrogenase (GPD) and succinate dehydrogenase (SDH) activities were higher in HS than in CON rats. Daily forceful lengthening contractions did not prevent the HS-induced changes. The results support the view that the soleus fibers can change from a slow-twitch oxidative to a fast-twitch oxidative-glycolytic profile, but rarely to a fast-twitch glycolytic one, and that the SDH and GPD activities per volume of tissue can be increased even when there are severe losses of contractile proteins.

Hauschka, Edward O.↗
NASA NTRS1987

Size and metabolic properties of fibers in rat fast-twitch muscles after hindlimb suspension

The effect of hind-limb suspension (HS) on single fibers of the medial gastrocnemius (MG) and the tibialis anterior (TA) muscles were studied in rats. Fiber area and the activities of succinate dehydrogenase (SDH) and alpha-glycerophosphate dehydrogenase (GPD) were determined in tissue sections using an image analysis system. After 28 days of HS, the MG atrophied 28 percent, whereas the TA weight was maintained. Both dark- and light-ATPase fibers in the deep region of the MG had decreased cross-sectional areas following HS, with the atrophic response being twice as great in the light-ATPase fibers than in the dark-ATPase fibers. Following HS, mean SDH activities of both fiber types were significantly lower in the MG and TA than in the CON; by contrast, mean GPD activities were either maintained at the CON level or were higher in both MG and TA muscles. The data suggest an independence of the mechanisms determining the muscle fiber size and the metabolic adaptations associated with HS.

Roy, Roland R.↗
NASA NTRS1986

Dexamethasone regulates glutamine synthetase expression in rat skeletal muscles

The regulation of glutamine synthetase by glucocorticoids in rat skeletal muscles was studied. Administration of dexamethasone strikingly enhanced glutamine synthetase activity in plantaris and soleus muscles. The dexamethasone-mediated induction of glutamine synthetase activity was blocked to a significant extent by orally administered RU38486, a glucocorticoid antagonist, indicating the involvement of intracellular glucocorticoid receptors in the induction. Northern blot analysis revealed that dexamethasone-mediated enhancement of glutamine synthetase activity involves dramatically increased levels of glutamine synthetase mRNA. The induction of glutamine synthetase was selective in that glutaminase activity of soleus and plantaris muscles was not increased by dexamethasone. Furthermore, dexamethasone treatment resulted in only a small increase in glutamine synthetase activity in the heart. Accordingly, there was only a slight change in glutamine synthetase mRNA level in this tissue. Thus, glucocorticoids regulate glutamine synthetase gene expression in rat muscles at the transcriptional level via interaction with intracellular glutamine production by muscle and to mechanisms underlying glucocorticoid-induced muscle atrophy.

Max, Stephen R.↗
NASA NTRS1987

Physiological responses during whole body suspension of adult rats

The objective of this study was to characterize responses of adult rats to one and two weeks of whole body suspension. Body weights and food and water intakes were initially reduced during suspension, but, while intake of food and water returned to presuspension levels, body weight remained depressed. Diuresis was evident, but only during week two. Hindlimb muscle responses were differential, with the soleus exhibiting the greatest atrophy and the EDL a relative hypertrophy. These findings suggest that adult rats respond qualitatively in a manner similar to juveniles during suspension.

Steffen, J. M.↗
NASA NTRS1988

Problems in analysis of data from muscles of rats flow in space

Comparison of hind-limb muscles of rats flown on Spacelab-3 or tail-traction-suspended showed that 11-17 h reloading postflight might have altered the results. Soleus atrophied; plantaris, gastrocnemius, and extensor digitorum longus grew slower; and tibialis anteiror grew normally. In both flight and simulated soleus and plantaris, higher tyrosine and greater glutamine/glutamate ratio indicated negative protein balance and increased glutamine production, respectively, relative to controls. Aspartate was lower in these muscles. Reloading generally decreased tyrosine, but increased aspartate and glutamine/glutamate. These data showed that 12 h of reloading after flight is characterized by reversal, to varying extents, of the effects of unloading.

Tischler, Marc E.↗
NASA NTRS1988

Comparative morphometry of fibers and capillaries in soleus following weightlessness (SL-3) and suspension

This work is a continuation of efforts to assess responses of rat skeletal muscle to weightlessness (W) and earthside laboratory experiments with unloading of hind limbs. The soleus is a slow-twitch, load-bearing (antigravity) muscle. Both exposure to W and to the hypokinesia/hypodynamia of whole-body suspension (WBS) results in soleus atrophy. Cross-sectional areas of both slow- and fast-twitch fibers decrease during 7 days of W or 7 or 14 days of WBS. Density and area changes tended to reverse to control levels during 7 days of recovery (R) following WBS. Capillary density was increased with 7 days of W or 7 or 14 days of WBS. During 7 days of R the capillary density returned toward control levels. In summary, the reduction in fiber cross-sectional areas and the increase in fiber and capillary densities support the hypothesis that in both W and WBS there is a loss in soleus muscle cell mass and not in fiber numbers.

Musacchia, X. J.↗
NASA NTRS1988

Changes in fiber composition of soleus muscle during rat hindlimb suspension

A technique in which the gravitational load in the rear limbs of rats was chronically reduced is used to study soleus muscle atrophy in near-zero-gravity conditions. The results show a decline in the number of fibers in groups that contained the slow isoenzyme of myosin and which were classified as type I. The total number of fibers did not change, and fibers containing the intermediate isoenzyme and those classified as type IIa increased. The results are consistent with either a change in the composition within existing fibers or a simultaneous loss of slow fibers accompanied by de novo synthesis of intermediate and fast fibers.

Templeton, G. H.↗
NASA NTRS1989

Muscle changes with eccentric exercise: Implications on earth and in space

Recent investigations of fluid pressure, morpholo gy, and enzyme activities of skeletal muscle exercised eccentrically or concentrically in normal human subjects are reviewed. Intramuscular pressures were measured before, during, and after submaximal exercise and correlated with subjective muscle soreness, fiber size, water content, and blood indices of muscle enzymes. High intensity eccentric exercise is characterized by post exercise pain, elevated intramuscular pressures, and swelling of both type 1 and 2 fibers as compared to concentric exercise. Thus, long periods of unaccustomed, high level eccentric contraction may cause muscle injury, fiber swelling, fluid accumulation, elevated intramuscular pressure, and delayed muscle soreness. Training regimens of progressively increasing eccentric exercise, however, cause less soreness and are extremely efficacious in increasing muscle mass and strength. It is proposed that on Earth, postural muscles are uniquely adapted to low levels of prolonged eccentric contraction that are absent during weightlessness. The almost complete absence of eccentric exercise in space may be an important contributor to muscle atrophy and therefore equipment should be designed to integrate eccentric contractions into exercise protocols for long-term spaceflight.

Hargens, Alan R.↗
NASA NTRS1989

Exercise effects on the size and metabolic properties of soleus fibers in hindlimb-suspended rats

The effects of four-week-long hind-limb suspension (HS) of rats on the size the soleus muscle fibers and the activity of succinate dehydrogenase (SDH) in dark and light ATPase fibers were investigated together with the efficacy of an endurance exercise (EX) program (daily treadmill exercise for 1.5 h/day at 20 m/min and a 30-percent grade) in ameliorating HS-induced changes. It was found that, in comparison to age-matched controls, the soleus wet weight decreased by 69 and 30 percent in HS and HS-EX rats, respectively, and the percent of dark ATPase fibers increased from 10 percent in controls to 19 and 17 percent, respectively. The values of the integrated fiber activity (activity/min times muscle area) showed a net loss of SDH in both the light and dark ATPase fibers of HS rats, but only in the light ATPase fibers of the HS-EX rats, indicating that exercise ameliorated but did not prevent the muscle fiber atrophy induced by HS.

Graham, Scot C.↗
NASA NTRS1989

Characteristics and preliminary observations of the influence of electromyostimulation on the size and function of human skeletal muscle during 30 days of simulated microgravity

The effect of transcutaneous electromyostimulation (EMS) on the development of atrophy and the loss of strength in lower limb musculature in humans exposed to microgravity was determined in three subjects who received EMS twice daily in a 3-d on/1-d off cycle on their dominant leg during 30 days of bedrest. The output waveform from the stimulator was sequenced to the knee extensors, knee flexors, ankle extensors, and ankle flexors, and caused three isometric contractions of each muscle group per minute. It was found that, in the dominant leg, EMS acted to attenuate the changes caused by bedrest, such as reductions in the leg volume, muscle compartment size, cross-sectional area of slow- and fast-twitch fibers, strength, and aerobic enzyme activities, and an increase in leg compliance.

Duvoisin, Marc R.↗
NASA NTRS1989

Human tolerance to space flight

Medical studies of astronauts and cosmonauts before, during, and after space missions have identified several effects of weightlessness and other factors that influence the ability of humans to tolerate space flight. Weightlessness effects include space motion sickness, cardiovascular abnormalities, reduction in immune system function, loss of red blood cells, loss of bone mass, and muscle atrophy. Extravehicular activity (EVA) increases the likelihood that decompression sickness may occur. Radiation also gives reason for concern about health of crewmembers, and psychological factors are important on long-term flights. Countermeasures that have been used include sensory preadaptation, prebreathing and use of various air mixtures for EVA, loading with water and electrolytes, exercise, use of pharmacological agents and special diets, and psychological support. It appears that humans can tolerate and recover satisfactorily from at least one year of space flight, but a number of conditions must be further ameliorated before long-duration missions can be considered routine.

Huntoon, C. L.↗
NASA NTRS1989

Cardiovascular, renal, electrolyte, and hormonal changes in man during gravitational stress, weightlessness, and simulated weightlessness: Lower body positive pressure applied by the antigravity suit

Because of their erect posture, humans are more vulnerable to gravitational changes than any other animal. During standing or walking man must constantly use his antigravity muscles and his two columns, his legs, to balance against the force of gravity. At the same time, blood is surging downward to the dependent portions of the body, draining blood away from the brain and heart, and requiring a series of complex cardiovascular adjustments to maintain the human in a bipedal position. It was not until 12 April 1961, when Yuri Gagarin became the first human being to orbit Earth, that we could confirm man's ability to maintain vital functions in space -- at least for 90 min. Nevertheless, man's adaptation to weightlessness entails the deconditioning of various organs in the body. Muscles atrophy, and calcium loss leads to loss of bone strength as the demands on the musculoskeletal system are almost nonexistent in weightlessness. Because of the lack of hydrostatic pressures in space, blood rushes to the upper portions of the body, initiating a complex series of cardioregulatory responses. Deconditioning during spaceflight, however, first becomes a potentially serious problem in humans returning to Earth, when the cardiovascular system, muscles and bones are suddenly exposed to the demanding counterforce of gravity -- weight. One of the main purposes of our studies was to test the feasibility of using Lower Body Positive Pressure, applied with an antigravity suit, as a new and alternative technique to bed rest and water immersion for studying cardioregulatory, renal, electrolyte, and hormonal changes in humans. The results suggest that Lower Body Positive Pressure can be used as an analog of microgravity-induced physiological responses in humans.

Kravik, Stein E.↗