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PubMed2000

[Weightlessness and heat stress on astronauts].

Thermal emergency situations have more than once been encountered since the beginning of manned space flights in 1961. This article contemplates human thermal tolerance in weightlessness as complicated with headward [correction of headword] fluid shifts, plasma volume loss, cardiovascular deconditioning, reduced exercise capacity and energy metabolism changes, etc. With these considerations, it is necessary to further investigate the thermoregulation in spaceflight for the health and safety of astronauts.

Acclimatization↗
PubMed2002

[Changes in potassium currents of vascular smooth muscle cells isolated from hindquarter arteries of rats after 4 weeks simulated weightlessness].

The changes in potassium currents of vascular smooth muscle cells (VSMCs) isolated from saphenous arteries and the 2nd-6th order branches of the mesenteric arteries of 4-week tail-suspended rats (SUS) were examined using whole cell patch clamp technique. The resting potential (RP) of the VSMCs from SUS group was more negative compared with that of the control group (CON).The whole cell potassium current densities of VSMCs isolated from the saphenous arteries and small mesenteric arteries in SUS group were significantly larger than those of the CON group.The BK(Ca) and K(V) current densities of VSMCs from saphenous arteries and small mesenteric arteries from SUS group were also significantly larger than those from the CON group.It is speculated that the hyperpolarization of VSMCs and decreased calcium influx through voltage-dependent calcium channels might be one of the electrophysiological mechanisms involved in the depressed vasoreactivity of hindquarter arteries induced by simulated weightlessness.

Animals↗
PubMed1976

Heat exchange between the organism and environment under conditions of weightlessness; methodical approach.

The spontaneous streaming of air around surfaces of warm bodies conditioned by gravitation is missing in the weightless condition. This implies a change in the thickness of the surface air layer and its interference with the heat output of an organism. The paper describes the use of an electric dynamic katathermometer (EDK) for automatic and continuous scanning of heat output and presents results of measuring basic characteristics of the surface layer under defined laboratory conditions, and their relation to heat output.

Air Movements↗
PubMed2003

[Effects of "Qiang Gu Kang Wei" compound prescription on biochemical indices of bone and related organs in rats under simulated weightlessness].

OBJECTIVE: To investigate effects of "Qiang Gu Kang Wei" prescription on biochemical indices of bone and related organs in tail-suspended rats. METHOD: Rats were tail-suspended (-30 degrees) for 21 d to simulate weightlessness. The effect of this prescription on biochemical indices such as Ca, P in serum, osteocalcin (BGP) in serum and bone, oxyproline hydroxyproline (Hyp) in bone, alkaliphosphatase (ALP) in serum, small intestine and bone in these rats were examined. RESULT: Comparing with the normal control, serum Ca decreased significantly (P<0.05) while serum P showed only a trend to decrease, at the same time BGP dropped in both serum and bone (P<0.05) and Hyp dropped only in bone (P<0.05). There was significant decrease of ALP activity in serum, small intestine and bone (P<0.01 or P<0.05) in suspended rats. The prescription showed different effects with different doses. In all the three dose groups (30 g/kg, 20 g/kg, 10 g/kg) Ca and P in serum levels increased (P<0.01 or P<0.05), BGP in serum and bone improved (P<0.05) or showed only a trend to increase. ALP activity increased in serum, small intestine and bone (P<0.05). Increase of Hyp in bone was found in the middle and the small dose groups (P<0.05). CONCLUSION: This prescription shows an effect of improving biochemical indices in bone and related organs such as serum and small intestine in tail-suspended rats. But no distinct concentration-dependence was found.

Alkaline Phosphatase↗
PubMedDate not supplied

Sperm motility under conditions of weightlessness.

The aim of this study was to determine the differences in motility of frozen and thawed bull spermatozoa under conditions of weightlessness compared with ground conditions. The tests were performed within a series of scientific and technologic experiments under microgravity using sounding rockets in the Technologische Experimente unter Schwerelosigkeit (TEXUS) program launched in Kiruna, North Sweden. Using a computerized sperm motility analyzer, significant differences were found in sperm motility under microgravity compared with sperm under gravitational conditions on earth. Computer analysis showed alterations in straight line and curvilinear velocity, as well as in linearity values. The amount of progressively motile spermatozoa, including all spermatozoa with a velocity > 20 microns/second, increased significantly from 24% +/- 9.5% in the reference test to 49% +/- 7.6% in the microgravity test. In conclusion, there is strong evidence that gravity influences sperm motility.

Animals↗
PubMed2003

[Effects of simulated weightlessness and mechanical loading on bone interstitial fluid flow in rats].

OBJECTIVE: To investigate the effects of simulated weightlessness and mechanical loading on bone interstitial fluid flow. METHOD: Thirty-six male Sprague-Dawley [correction of Spargue-Danley] rats were divided into 3 groups: the control group, the tail-suspension group, and the tail-suspension plus mechanical loading group, with four rats in each group. All the rats were injected via a lateral tail vein with horseradish peroxidase on the 21st day of the experiment. Tibial tissue specimens were explanted, fixed, decalcified and cut into 30 micrometers frozen sections 3 h after the intravenous injection. RESULT: There were less peroxidase reaction product in the bony matrix and bone lacunae in tail-suspended rats than the control and tail-suspended plus mechanical loading rats. CONCLUSION: Tail-suspension decreased fluid movement through the bone, while mechanical loading increased it.

Animals↗
PubMed2003

[Effects of Qiang Gu Kang Wei prescription on morphology of bone in rats under simulated weightlessness].

OBJECTIVE: To investigate effects of Qiang Gu Kang Wei prescription on bone morphology in tail-suspended rats. METHOD: Rats were tail-suspended (-30 degrees) for 21 d to simulate weightlessness. The effects of this prescription on thickness of periost and cortex at epiphyseal plate of tibial shaft and 3 mm under it were examined. The effects of this prescription on histology and ultrastructure of tibia were also observed. RESULT: Compared with the normal control, cortex at both epiphyseal plate of tibial shaft and 3 mm under it in suspended rats thinned significantly (P<0.01 or P<0.05). Histological observation showed that in bone of suspended rats, uncalcific matrix was more, bone cells' number was lower and their appearance was more infantile, osteoblasts were less and smaller, while osteoclasts were more and larger, haversian system of transection also showed more irregular than in bone of normal control. Ultrastructure observation showed that the function of osteoblasts was inhabited and that of osteoclasts was active. All the three doses groups of the prescription could increase cortex at either epiphyseal plate of tibial shaft or 3 mm under it (P<0.01 or P<0.05) compared with the tail-suspended group. The appearance of bone in the three groups was improved as well under optical or electron microscope. CONCLUSION: This prescription could improve abnormal change in bone morphology resulted from being tail-suspended in rats and make it normal.

Animals↗
PubMed2003

[Effects of clinorotation-induced weightlessness on growth factor and ERK signal transduction in cultured cardiac fibroblasts].

OBJECTIVE: To study the changes of expression and secretion of some growth factors and ERK1/2 activation in cardiac fibroblasts under clinorotation conditions. METHOD: Primary cultured neonatal rat cardiac fibroblasts were clinorotated to simulate weightlessness. The bFGF and TGF(beta)1 expressions in the cells and Ang II concentration in the medium were detected by western blotting and radioimmunoassay respectively. The expression and phosphorylated level of ERK1/2 were analyzed by western blotting. RESULT: Compared to the control group, bFGF expression and Ang II concentration increased in clinorotation group, but there was no evident change in TGF(beta)1 expression. At the same time, the expression of ERK1/2 increased but their phosphorylated level decreased. CONCLUSION: Different growth factors responds to clinorotation by different ways. As one of the most important reactions of growth factor signal downstream pathways, ERK1/2 activation is inhibited in clinorotation.

Angiotensin II↗
PubMed2005

[Study on weightlessness dynamics simulated by neutral buoyancy in air-driven shell].

OBJECTIVE: To provide theoretical support for weightlessness experiment simulated by neutral buoyancy. METHOD: An air-driven shell structure was simplified into a rigid body with constant mass and variable volume. Then, rigid body dynamic model and gasdynamic model of air-driven spherical shell were established. Finally, the kinematical laws and the residual pressure variety laws of air-driven spherical shell were obtained under constant mass-flux condition by computer simulation. RESULT: Under constant mass-flux condition, neutral buoyancy balance of air-driven spherical shell was unstable. CONCLUSION: The key to achieve stable neutral buoyancy balance is the design of the system controller.

Air Movements↗
PubMed2004

Longterm conditions of mimicked weightlessness influences the cytoskeleton in thyroid cells.

Weightlessness influences the human immune and hormone system, reduces bone mass, leads to muscle atrophy and cardiac atrophy. Effects on control mechanisms for proliferation, programmed cell death and differentiation are well documented. The principal aim of this study was to investigate changes of the cytoskeleton in thyroid cells cultured in vector-averaged gravity under clinostat rotation. After 12 hours the formation of multicellular spheroids started. An increase of extracellular matrix proteins and beta 1-integrin was observed. Laser scanning confocal microscopy of ML-1 follicular thyroid carcinoma cells and normal thyroid HTU-5 cells immunostained with anti-cytokeratin to demonstrate these intermediate filaments revealed that cytokeratin filaments extended from centers, were thickened, coalesced and shortened as compared to control cells. Moreover, vimentin was highly disorganized. The vimentin network formed a coiled aggregate closely associated with the nucleus. Western blot analyses of talin, alpha- and beta-tubulin showed a clear increase of these proteins in cells cultured under simulated 0 g. Our data suggest that the effects of microgravity on cultured human thyroid cells are accompanied by noticeable functional cellular changes. Future studies to clarify the pathway that regulate the observed integrin activation and the mechanisms by which they function have to be performed.

Cell Differentiation↗
PubMedDate not supplied

[The acceleration of ultrastructure changes of synapses in somatosensory cortex of the rats at repeated simulation of weightlessness effects].

The electronmicroscopica/study of brain somatosensory cortex in the rats, exposed to postponed for a long time repeated lack of support load on hindlimbs by means of tail-suspension, has been revealed in hindlimb area of cortex the changes of ultrastructure of axodendritic synapses and neurons pointing out the acceleration of decrease in functional activity of synapses and neurons in 3-4 layers at postponed for a long time repeated simulation of weightlessness effects.

Animals↗
PubMedDate not supplied

[The embryonic development of birds in weightlessness].

During the period from March 4 through 24, 1990 an egg-to-egg cycle of quail incubation on the orbital station Mir was completed. Out of 35 eggs, that developed in space, 8 normal hatchlings emerged, 6 of which were able to get out of the egg-shell without any help. Subsequent observations showed that the hatchlings could not get adapted to the weightless environment or know to remain fixed to the wired floor, due to which they were unable to peck.

Adaptation, Physiological↗
PubMedDate not supplied

[The effect of hypothermia and oxygenation on the cardiorespiratory system in man exposed to experimental weightlessness].

It has been established that hypothermia in experimental weightlessness, as compared to normal conditions, was characterized by a considerably smaller deficit of erythrocytes in the energy balance and reduced gas exchange level, despite unidirectional changes in hemodynamic parameters. Unlike in hypothermia, an increase in oxygen concentration in the inhaled gas mixture had no noticeable effect on the parameters of the cardiorespiratory system studied.

Adult↗
PubMedDate not supplied

Morphometric ultrastructural analysis of muscle fibers and neuromuscular junction in rats kept under conditions of weightlessness for 21 days.

The aim of the study was qualitative and quantitative analysis of muscles and neuromuscular junctions of m. quadriceps, m. diaphragma and m. soleus in rats after being kept for 21 days under conditions of weightlessness. Degenerative changes were noted in both of these subjects and their intensity depended on the kind of fibres. The disorders were most pronounced in fibres and neuromuscular junctions of the soleus muscle in which red fibres prevail.

Animals↗
PubMedDate not supplied

[State of skeletal muscle fibers in rats during physical exercise after anti-orthostatic tail suspension in modeling the weightlessness].

The state of myofibers of types I, IIA and IIB of biceps femoris m. of Wistar rats exposed to tail suspension for 14 or 21 days was investigated after they experienced a 15-minute locomotor load: running on a treadmill or hindlimb stretching. In all types of myofibers both exposures prevented the development of most structural and metabolic changes that occurred in response to suspension simulating the physiological effects of weightlessness. The distribution and level of variations of muscle parameters depended on the kind of exposure and type of myofibers.

Animals↗
PubMed1978

[Structural and functional organization of the vestibular apparatus in rats maintained under weightless conditions for 19.5 days aboard the satellite "Cosmos-782"].

Vestibular apparatus was investigated in rats subjected to weightlessness for 19.5 days in the satelite "Cosmos-782" and experienced acceleration on launching and landing. Some structural and functional changes were noted. They were seen in otolith clinging to the utricular receptor surface and in the peripheral arrangement of the nucleolus in the nuclei of the receptor cells. It is also possible that increased edema of the vestibular tissue resulted in destruction of some receptor cells, and within the otolith--changes in the form and structure of otoconia. In the horizontal crista the cupula was separated.

Acceleration↗
PubMed1978

Effect of prehatching weightlessness on adult fish behavior in dynamic environments.

At 16-17 months of age, three groups of fish from the embryonated eggs in the ASTP killifish experiment were subjected to postflight tests consisting of rapidly changing environments. It was found that the group of fish with the least amount of development at orbital insertion (A-32) had a decreased rheotropism for both the moving background and the rotating water current tests when compared to ground control fish. Exposure to parabolic aircraft flight conditions revealed that the A-32 fish were less disoriented during zero gravity periods and were hypersensitive to high-gravity periods. These results suggested a modified vestibular competency due to a 9-d prehatching weightlessness exposure.

Adaptation, Physiological↗
PubMed1979

Ultrastructural development of the vestibular system under conditions of simulated weightlessness.

Electronmicroscopy was used to track the development of the gravity system of frog embryos and larvae which have bred for 5, 7, and 10 d after egg fertilization under conditions of simulated weightlessness on the fast-running horizontal clinostat. Although no differences in the morphologic structure of the organ between test and control animals could be found up to 7 d of development, there is a significant accumulation of vacuoles in sensory epithelia of frog larvae develpoping for 10 d (stage 17) in simulated zero G.

Animals↗