Search NASA⌕ Search

SEARCH · Search NASA

Results for “atrophy”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
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.↗
NASA NTRS1990

Experiment K-6-07. Metabolic and morphologic properties of muscle fibers after spaceflight

The present study demonstrates that the general capability of skeletal muscle to maintain its proteins decreases rapidly in response to space flight. The present findings suggest further that the magnitude of enzymatic and cell volumes changes in response to space flight depend on several factors including the muscle and its fiber type composition. It appears that in order to associate physiological relevance to the observed enzymatic changes, cell volume should be considered also. Although it remains unclear as to the stimulus, or lack of stimulus, that triggers the rapid changes in muscle proteins in response to space flight, ground-based models of muscle atrophy suggest that the reduction in mechanical loading of muscle may be more important than the total amount of activation over a 24-hr period.

Edgerton, R.↗
NASA NTRS1990

Experiment K-6-08. Biochemical and histochemical observations of vastus medialis

Muscles of the hindlimb in the rat have been used to demonstrate the effects of unloading in weightlessness and in animal models used to mimic weightlessness. The vastus medialis (VM) is discussed here. Samples were obtained from rats exposed to weightlessness for 12 days in Cosmos 1887 (Experiment K-6-08, coordinated by Dr. V.S. Oganov). The principal objective of this study was to ascertain if the vastus medialis responded to 12 days of microgravity exposure. The loss in muscle mass is greatest, -43 percent, when comparing F vs B, and least, -13 percent, when comparing F vs. V. Taken at face value these differences may be misleading. Due to the variability of the muscle weight in the basal group, these muscle mass losses may be exaggerated. In terms of percent water, there were no differences between the flight and the control groups. In spite of the limited sample, researchers conclude that muscle mass changes in the VM are not significant. Although some of the morphological parameters suggest a small degree of atrophy in the vastus medialis, the biochemical analyses (protein, RNA and DNA) suggest that these may be minimal and functionally nonsignificant. The relatively similar CS and LDH activities of VM from F and various control groups, as well as the lack of difference in LPL activity between F and S rats, suggests that there is little or no effect on the oxidative or glycolytic function of this muscle. Since the VM is chiefly a mixed fast twitch muscle, these metabolic indices of energy production are relatively unchanged. The results of VM studies are in agreement with previous observations of another type II fast twitch muscle, the EDL, from SL-3 rats which did not respond markedly to weightlessness and whole body suspension.

Musacchia, X. J.↗
NASA NTRS1990

Experiment K-6-10. Effects of zero gravity on myofibril protein content and isomyosin distribution in rodent skeletal muscle

The purpose of this experiment was to investigate the effects of 12 days of zero gravity (0G) 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 the two control groups (p less than 0.05). Compared to the two control groups, VI weight was lower by 23 percent (p less than 0.10); whereas no such reduction was observed for the VL muscle. Myofibril yields (mg protein/g of muscle) in the VI were 35 percent lower in the FG compared to the 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 0G. Analysis of myosin isoforms indicated that slow-myosin 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 space flight. Myofibril ATPase activity of the VI was increased in the FG compared to controls, which is consistent with the observation of preferential slow-myosin degradation. These data suggest that muscles containing a high percent of slow-twitch fibers undergo greater degrees of myofibril protein degradation than do muscles containing predominantly fast-twitch fibers in response to a relatively short period of 0G exposure, and the primary target appears to be the slow-myosin molecule.

Baldwin, K.↗
NASA NTRS1990

Experiment K-6-17. Structural changes and cell turnover in the rats small intestine induced by spaceflight

The purpose of this project was to test the hypothesis that the generalized, whole body decrease in synthetic activity associated with microgravity conditions of space flight as evidenced by negative nitrogen balance and muscle atrophy (Nicogossian and Parker, 1982; Oganov, 1981), as well as inhibited lymphocyte proliferation (Bechler and Cogoli, 1986), would be evident in cells characterized by a rapid rate of turnover. As a model, researchers chose to study the turnover of mucosal cells lining the jejunum of the small intestine, since these cells are among the most rapidly proliferating in the body. Under normal conditions, epithelial cells that line the small intestine are continually produced in the crypts of Lieberkuhn. These cells migrate out of the crypts onto intestinal villi, are progressively pushed up the villus as new crypt cells are formed, and ultimately reach the tip of villi where they are then descquamated. In rats, the entire process, from initial proliferation in crypts to desquamation, takes approximately 2 days (Cairnie et al., 1965; Lipkin, 1973). In this study, researchers determined the mitotic index for mucosal cells lining the proximal, middle, and distal regions of the jejunum in rats from three treatment groups (synchronous control, vivarium control and flight), and measured the depth of the crypts of Lieberkuhn and the length of villi present in each of the three jejunal regions sampled.

Phillips, R. W.↗
NASA NTRS1990

Experiment K-6-21. Effect of microgravity on 1) metabolic enzymes of type 1 and type 2 muscle fibers and on 2) metabolic enzymes, neutransmitter amino acids, and neurotransmitter associated enzymes in motor and somatosensory cerebral cortex. Part 1: Metabolic enzymes of individual muscle fibers; part 2: metabolic enzymes of hippocampus and spinal cord

The individual fibers of any individual muscle vary greatly in enzyme composition, a fact which is obscured when enzyme levels of a whole muscle are measured. The purpose of this study was therefore to assess the changes due to weightless on the enzyme patterns composed by the individual fibers within the flight muscles. In spite of the limitation in numbers of muscles examined, it is apparent that: (1) that the size of individual fibers (i.e., their dry weight) was reduced about a third, (2) that this loss in dry mass was accompanied by changes in the eight enzymes studied, and (3) that these changes were different for the two muscles, and different for the two enzyme groups. In the soleus muscle the absolute amounts of the three enzymes of oxidative metabolism decreased about in proportion to the dry weight loss, so that their concentration in the atrophic fibers was almost unchanged. In contrast, there was little loss among the four enzymes of glycogenolysis - glycolysis so that their concentrations were substantially increased in the atrophic fibers. In the TA muscle, these seven enzymes were affected in just the opposite direction. There appeared to be no absolute loss among the oxidative enzymes, whereas the glycogenolytic enzymes were reduced by nearly half, so that the concentrations of the first metabolic group were increased within the atrophic fibers and the concentrations of the second group were only marginally decreased. The behavior of hexokinase was exceptional in that it did not decrease in absolute terms in either type of muscle and probably increased as much as 50 percent in soleus. Thus, their was a large increase in concentration of this enzyme in the atrophied fibers of both muscles. Another clear-cut finding was the large increase in the range of activities of the glycolytic enzymes among individual fibers of TA muscles. This was due to the emergence of TA fibers with activities for enzymes of this group extending down to levels as low as those found in control soleus muscles. It would be interesting to know if this represents a transition stage, and whether with prolonged weightlessness most of the fibers would be transformed into a low glycogenolytic type.

Lowry, O.↗
NASA NTRS1990

Influence of 7 days of hindlimb suspension and intermittent weight support on rat muscle mechanical properties

The effect of intermittent periods of weight support on a decrease in mass of the soleus (Sol) and medial gastrocnemius (MG) muscles atrophied by hindlimb suspension (HS) was investigated in rats subjected to continuous HS for seven days or an HS plus intermittent (10 min every 6 hrs of slow walking on a treadmill) weight support (HS-WS). After 7 d HS, the Sol weight relative to body weight was 21 and 9 percent lower in Hs and HS-WS, respectively, than in control rats. Maximum tetanic tension/muscle mass ratio was significantly lower in HS than in controls; the HS-WS rats had values similar to controls, whereas the maximum tetanic tension/muscle weight was significantly elevated in HS-WS compared to controls. Contraction times were 25 percent faster in the Sol and unchanged in the MG of HS rats, indicating that a low-force short-duration exercise regime results in a significant functional recovery in the 'slow' Sol, whereas the 'fast' MG is less affected.

Pierotti, David J.↗
NASA NTRS1989

A unique problem of muscle adaptation from weightlessness: The deceleration deficiency

Decelerator problems of the knee are emphasized since the lower leg musculature is known to atrophy in response to weightlessness. However, other important decelerator functions are served by the shoulder muscles, in particular the rotator cuff muscles. Problems in these muscles often result in tears and dislocations as seen in baseball pitchers. It is noteworthy that at least one device currently exists that can measure concentric and eccentric muscle loading including a submaximal simulated free weight exercise (i.e., force-controlled) and simultaneously record integrated EMG analysis appropriate for assessment of all muscle functional activities. Studies should be undertaken to provide information as to the performance of maximal and submaximal exercise in space travelers to define potential problems and provide rationale for prevention.

Stauber, William T.↗
NASA NTRS1989

Exercise issues related to the neuromuscular function and adaptation to microgravity

Explored here is the question of whether astronauts can perform extravehicular activities effectively, efficiently, and productively. The loss of muscle mass, movement control, central nervous system function, muscle atrophy and fatigue, all consequent to weightlessness exposure, are discussed. The author recommends more research in these areas.

Edgerton, Reggie↗
NASA NTRS1989

Work, exercise, and space flight. 2: Modification of adaptation by exercise (exercise prescription)

The fundamentals of exercise theory on earth must be rigorously understood and applied to prevent adaptation to long periods of weightlessness. Locomotor activity, not weight, determines the capacity or condition of the largest muscles and bones in the body and usually also determines cardio-respiratory capacity. Absence of this activity results in rapid atrophy of muscle, bone, and cardio-respiratory capacity. Upper body muscle and bone are less affected depending upon the individual's usual, or 1-g, activities. Methodology is available to prevent these changes but space operations demand that it be done in the most efficient fashion, i.e., shortest time. At this point in time we can reasonably select the type of exercise and methods of obtaining it, but additional work in 1-g will be required to optimize the time.

Thornton, William↗