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At least 685 records · Page 38Linked to original sources
PubMed1988

[Dehydrogenase activity in skeletal muscles of rats after long-term exposure to weightlessness].

Malate- and isocytratedehydrogenase activity in mitochondrial and cytoplasmic fractions and lactate dehydrogenase activity in hindlimb muscles have been studied at different stages after 18.5-day flight on a biosatellite "Cosmos-1129" and after 20-day hypokinesia. A decrease in dehydrogenase activity has been found on the first postflight day. The enzyme activities returned to the control values in mitochondria, and in the cytoplasm they were greater by day 6 postflight. It was concluded that hypokinesia did not reveal all the effects of microgravity on the whole system but some enzyme alterations in the muscle resembled those observed during the flight. The effects may be caused by the inhibition of both aerobic and anaerobic metabolic pathways under the effect of microgravity.

Animals↗
PubMedDate not supplied

[Morphological study of early changes in rat bones during exposure to simulated weightlessness].

By histomorphometric methods tibial bones and lumbar vertebrae of rats exposed for 7 days to hypokinesia or head-down suspension were investigated. Both hypokinesia and suspension led to osteoporosis of the tibial metaphyseal spongiosa which was primarily induced by bone growth inhibition and probably by increased bone resorption. No signs of osteoporosis were seen in tibial diaphyses. In contrast to tibial bones, osteoporosis of the spongiosa of lumbar vertebrae was found only in hypokinetic rats. It is concluded that during exposure to simulated microgravity early signs of osteoporosis occur in the tibial spongiosa and that changes in the spongy matter of tubular bones and vertebrae are similar and systemic. It is suggested that an acute stress-reaction in response to simulated microgravity plays a certain role in the development of osteoporosis.

Animals↗
PubMed1987

Rotation speed of labyrinthectomized fish during short-duration weightlessness.

This study used blind unilaterally labyrinthectomized goldfish of 5 to 15 cm body length. These goldfish were flown in parabolic flights to temporarily effect the loss of the second vestibular apparatus. Flights took place between 1 and 72 h after the operation. Attitude in 3 axes was recorded on video and analyzed from single-frame pictures for speed and direction of rotation about the roll (fish's body longitudinal) axis. Labyrinthectomy resulted in a rotation pattern consistent with literature under normal Earth-G conditions. Under diminished G-influence, the rotations, contrary to our expectation, did not stop, but, rather, increased in speed by a factor of 2 to 4. The direction of rotation did not change. The fish readapted to the low-G environment rapidly and returned to the rotation speeds observed before entry into the parabolas during the 5 to 7 s of parabola duration. Current theories for the generation of adaptation are discussed and their merits in explaining the experimental data are compared.

Adaptation, Physiological↗
PubMedDate not supplied

[Effect of weightlessness and hypokinesia on the velocity-strength properties of human muscles].

Before and after exposure to short- and long-term microgravity and prolonged bed rest velocity and strength parameters of leg muscles were measured by isokinetic dynamometry. It was found that long-term exposure to microgravity produced a more distinct decline of muscle strength than short-term exposure. At the same time prolonged bed rest led to greater strength losses than microgravity of comparable duration. After long-term flights individual variability of changes was twice as high as after prolonged bed rest. A comparable analysis of the above exposures demonstrated that the changes observed after long-duration exposures were associated with atrophic changes due to disuse while those seen after short-term effects were induced, as shown previously, by reflex tonic shifts related to support unloading.

Bed Rest↗
PubMedDate not supplied

[Contractile function of the heart during weightlessness according to the results of 3-dimensional ballistocardiography].

In the joint Soviet-Indian space flight the method of spatial ballistocardiography was used to investigate the cardiac function in flight. The piezoelectric transducer was placed between the scapulae and its orientation was varied relative to the three axes of the body. Measurements were taken twice before, twice during and twice after flight. Ballistocardiograms were analyzed in terms of their amplitude, time and spectral parameters. It was found that in microgravity the energy of cardiac contractions developed spatial redistribution. It was also demonstrated that the cardiovascular function showed individual variability.

Adaptation, Physiological↗
PubMedDate not supplied

[The maternal-fetal system as an object for the study of mechanisms of the physiologic effect of weightlessness].

The place of embryological investigations in the program of mammalian experiments onboard the Cosmos biosatellites is discussed. The mother-fetus system is viewed as a specific loading test for studying the reserve potentials of the mammalian body in microgravity. It has been demonstrated that mammalians (Wistar rats) flown during the third term of their pregnancy can maintain homeostasis of the developing fetus within the limits that provide the normal development of physiological functions. Significant individual variations in animal responses to microgravity have also been found.

Adaptation, Physiological↗
PubMedDate not supplied

[Morphogenesis of the brain of rats developing under conditions of weightlessness].

Macroscopic and light microscopic examinations of the brain of 18-day fetuses, and neonate 15-, 30- and 100- day rats whose embryonic development from day 13 to day 18 occurred in space flight on Cosmos-1514 did not reveal any changes in the brain structures of the fetuses or pups of the three ages. However, the brain of the 18-day fetuses that developed in flight showed signs of insufficient tissue oxygenation, trends toward delayed cell migration in the cortex and delayed differentiation of neurosecretory cells of the hypothalamic supraoptic nuclei. The cell differentiation rate returned to normal during continued embryogenesis after flight at 1 g.

Animals↗