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At least 343 records · Page 19Linked to original sources
PubMed1997

[Adaptation of myocardial function to simulated weightlessness].

To observe the changes in myocardial function and calcium ion release of sarcoplasmic reticulum in rats under simulated weightlessness, 24 Sprague-Dawley male rats were divided into control (CON), 8 week tail-suspension (SUS) and recovery for 2 weeks (RE) groups. The results showed that there was no change in resting tension of myocardial twitch in SUS. While the developed tension (DT) of myocardial twitch significantly decreased in SUS as compared with CON. The time to peak tension (TPT) and time to half relaxation (T1/2R) of myocardial twitch were prolonged in SUS. DT, TPT and T1/2R recovered to their corresponding control values after 2 w of recovery from tail-suspension. The early recovery curve of force-interval relation in SUS was in a higher position over that of CON, but the rest potentiation and rest depression curve was positioned under that of CON. These results suggested that there might be an adaptative change in myocardial function in medium- or long-term tail-suspended rats while 8 w tail-suspension reduces calcium ion release from cardiac sarcoplasmic reticulum in rats.

Adaptation, Physiological↗
PubMed1997

[Thermoregulation under simulated weightlessness].

The effect of simulated weightlessness on thermoregulation was studied in 5 subjects. The experiment consisted of 3d baseline measurements, 7d head-down bed rest and 2d recovery. Circadian rhythm was assessed by continuous measurements of rectal temperature and skin temperature with 2h intervals. Heat Stress Protein 70 (HSP70) was measured by Western-blot Dot method and the facial surface temperature distribution was measured by HR-2 infrared thermography. The results showed that rectal temperature keeps the wake-sleep variation, but the circadian rhythm changed during bed rest, and the change of rectum temperature rhythm appeared mainly in the early-days of bed rest; HSP70 and facial surface temperature increased during bed rest.

Bed Rest↗
PubMed1997

Effects of weightlessness on photosynthesizing cells structure of plant.

It was established early that the signs of accelerated aging of both plant leaves and of moss chloronema were observed in seedlings of high plants and in Funaria hygrometrica protonema under long term growing under weightlessness. It was observed the structure changing of photosynthesizing cells in Arabidopsis thaliana, Epidendrum radicans and Pisum sativum leaves. Authors found out the extension and vesiculation of thylakoids between chloroplast granas. They observed thylakoids partly destroying under 96 and 110 days microgravity influence. But some questions are still opened: 1. Are these changes consequence of accelerated differentiation and aging photosynthesizing cells? 2. Do the definite changes appear in photosynthesizing cells during short-term microgravity influence? Therefore the study of mesophyll cells ultrastructure of leaves that finished growth by tension in microgravity was the idea of our experiment.

Adenosine Triphosphate↗
PubMed1993

Swimming velocity of Paramecium under the conditions of weightlessness.

During the 6 min-lasting "free-fall conditions" (4 x 10(-6) g) of the parabolic flight of a sounding rocket Paramecium aurelia cells showed an increase of 7.5 % in their mean swimming velocity. A detailed analysis revealed that the kinetic response was transient: after 3 min the velocity decreased to the speed of the former horizontal swimming at 1 g. Control experiments simulating the influence of vibration and hypergravity during launch of the rocket lead to the conclusion that the increase of the velocity during the parabolic flight was exclusively induced by the transition to 0 g. An increased velocity was also observed under the condition of simulated weightlessness on a fast-rotating clinostat microscope.

Acceleration↗
PubMed1996

Phenomenology of spatial illusory reactions under conditions of weightlessness.

Sensory interaction and sensory adaptation in short- and long-lasting space flights (SF) and the dynamics of stability of adaptive shifts were studied by the phenomenology of spontaneous and visually induced illusory reactions. It was shown that perceptive impairment developed during the initial adaptation to microgravity should be considered regular reactions of sensory systems under given environmental conditions rather than special features of the individuals examined. The classification of spontaneous illusory reactions (SIR) under conditions of microgravity and the results of investigation of the vertical vection (vection is a visual illusion evoked by the optokinetic stimulation) are presented. The following previously unknown phenomena were registered for the first time: inversion of the vertical vection illusion (VVI) evoked by vertical and sinusoidal optokinetic stimulation, impairment of perception of the body schema during VVI, change in the character of VVI, and development of VVI asymmetry. During long-lasting existence under conditions of weightlessness the anomalous perceptive reactions continued to be registered episodically (the period of adaptation was replaced by that of deadaptation). A hypothesis was suggested for the possible mechanisms of the phenomena found. [Translated from Fiziologiya Cheloveka, vol. 21, no. 4, p. 50-62, July-August, 1995]

Adaptation, Physiological↗
PubMed1997

Erythrocyte deformation in simulated weightless human and rabbits.

Effect and mechanism of simulated weightlessness (SWL) in humans and rabbits erythrocyte deformation were studied. Erythrocyte deformation and membrane fluidity in humans and rabbits, and erythrocyte morphology and hemorreology indices in control and HDT rabbits were measured. The results were a decrease in erythrocyte deformation and membrane fluidity in humans and rabbits during SWL, a significant increase in abnormal erythrocyte, blood viscosity, hematocrit, fibrinogen, and red blood cell aggregation index in HDT rabbits. These results show that the changes in erythrocyte shape, increase of erythrocyte internal viscosity and changes in erythrocyte visco-elasticity may be causing the decrease of erythrocyte deformation in SWL humans and rabbits.

Adolescent↗
PubMed1998

[Effects of hypoxia and qigong on urine malondialdehyde, superoxide dismutase and circulating endothelial cell in humans during simulated weightlessness].

Changes of lipid hyperoxidation and amount of circulating endothelial cells under simulated weightlessness and factors that may influence these changes were observed in 3 groups of subjects (5 in each group) exposed to 17d - 6 degrees head down bed rest (HDBR), HD-BR+ hypoxia and HDBR + qigong respectively. The results showed: (1) simple HDBR promotes antioxidation activity and attenuates hyperoxidation of lipids, and hypoxia and have some influence on the former but not on the latter; (2) circulating endothelial cells decreased significantly after simple HDBR for 7 d but recovered to normal when HDBR continued for 17 d. Hypoxia showed no influence on this effect while Qigong alleviated it significantly. It suggests that (1)both hypoxia and Qigong have some influence on the promotion of antioxidation activity but have no influence on the production of oxygen free radicals. (2) Qigong shows some antagonistic effect against the attenuation of circulating endothelial cells by HDBR.

Bed Rest↗
PubMed1998

Alteration of vasoreactivity of mesenteric arteries in rats after two-week simulated weightlessness.

To investigate the effects of simulated weightlessness on vasoreactivity of mesenteric arteries, rats were tail-suspended for two weeks, and vasoreactivity were studied in vitro using isolated mesenteric arterial ring. The results showed that maximal contractile responses to KCl (10-80 mmol/L) and phenylephrine (PE, 10(-10)-10(-4) mol/L) were attenuated in arterial rings isolated from tail-suspended rats. After constriction caused by 10(-7) mol/L PE, maximal dilatory responses induced by sodium nitroprusside (SNP, 10(-10)-10(-4) mol/L) were not different between tail-suspended and control groups. These data indicated that contractile ability of mesenteric artery was diminished by tail-suspension, whereas the dilatory capacity of arterial smooth muscle was not altered.

Animals↗
PubMed1998

[Effects of simulated weightlessness and irradiation on metabolism of rat myocardial cells cultured in vitro].

To investigate the changes of the metabolism of rat myocardiac cells cultured in vitro under simulated weightlessness and gamma-irradiation, rat myocardiac cells were rotated on a horizontal clinostat, and irradiated with 2Gy 60Co gamma-ray. The results showed: (1) after irradiation, the LDH activity and SOD concentrations showed a significant increase, and the MDA concentration also increased. (2) After irradiation, LDH activity increased 60% on the 3rd day, and SOD concentration almost doubled on the first day. (2) MDA concentration also increased but it reduced to normal after the 3rd day. (3) Simple rotation on the clinostat showed no effect on the parameter, but there was a synergistic effect when it was combined with gamma-irradiation.

Animals↗
PubMed1998

[Noninvasive evaluation of cardiovascular autonomic regulation and its application in physiological studies under weightlessness].

Recent progress in the noninvasive evaluation methods of cardiovascular autonomic regulation, including autonomic function tests, baroreflex function assessment, and heart rate, blood pressure variability analysis were discussed, and the results of applying these methods in physiological studies on head-down bed rest, head-up tilt, lower body negative pressure and aerobic training were reported. It suggests that noninvasive evaluation methods of cardiovascular autonomic regulation are effective means in weightlessness physiology study.

Aerospace Medicine↗
PubMed2000

[A study of effects of head-down bed-rest simulated weightlessness on phonetic features of Chinese].

OBJECTIVE: To study the changes of phonetic features of Chinese speech during head-down bed-rest (HDBR) simulated weightlessness. METHOD: During -6 degrees HDBR in 6 healthy subjects (20-30 years), acoustic-phonetic features were analyzed. RESULT: The duration of utterance was slightly increase in the first two days, and recovered after the fourth day of HDBR; mean energy decreased along with time of bed rest, t-tests showed that the decrease in energy of utterances was very significant; a decrease in fundamental frequencies under HDBR was also significant. CONCLUSION: There were certain changes in the acoustic phonetic features under HDBR, some of them were significant.

Adult↗
PubMed1975

Effects of prolonged weightlessness on the swimming pattern of fish aboard Skylab 3.

Two fingerling fish and 50 embryonated eggs of (Fundulus heteroclitus) were flown aboard Skylab 3 in a plastic bag aquarium. Videographic picutres were taken with the on-board color-TV camera on flight Days 3 and 22 and video tapes were made for later evaluation on the ground. When observed first after 3 d in orbital weightlessness, both fish swam in tight circles for a considerable fraction of the observed time resembling the "looping behavior" as observed in previous studies with goldfish in parabolic aircraft flight. The frequency of looping diminished slowly after the third day until normal swimming was prevalent. At flight Day 22, both fish swam normally with their backs turned toward the light source. Looping episodes could still be provoked at this time by gentle shaking of the bag aquarium. Of the fish eggs carried aboard, 96% hatched during the mission. The hatch fry displayed normal swimming behavior.

Animals↗
PubMed1964

Calcium metabolism under conditions of weightlessness.

This is a brief report on the possible effects of weightlessness on calcium metabolism. Interest in this topic is based on common, clinical experience: immobilization from any cause is accompanied by skeletal rarefaction and hypercalcuria.

Aerospace Medicine↗
PubMed1975

Influence of simulated weightlessness on the rate of anomalies of the flour beetle Tribolium confusum.

Experiments with Tribolium confusum showed that the morphological characteristics of the beetles are modified by simulated weightlessness (fast running clinostat). Because of possible side effects due to differences in fertility of inbred lines, the first experiments were made with a genetically heterogeneous stock. Thereafter experiments were confirmed with inbred beetles. For both stocks a rise of mainly wing anomalies resulted from rotation of whole cultures of beetles within horizontal tubes. The extent to which these anomalies are teratogenetic or genetic has not yet been analysed in detail.

Animals↗
PubMed2002

[The changes of cardiovascular response to orthostatic stress caused by hypovolemia induced by weightlessness: a simulation study].

We introduced the method of computer simulation in the studies of gravitational physiology. Based on work of Melchior (1994), we developed a mathematical model that can be used to stimulate cardiovascular responses to orthostatic stress (lower body negative pressure, LBNP). The model includes 7 sub-models: the redistribution of blood, the filling of left ventricle, left ventricle working, peripheral circulation, control of heart rate (HR), control of peripheral resistance and control of venous tone. Then we simulated the changes of blood pressure (BP) and heart rate during lower body negative pressure, and the results agreed well with the results of our human experiment. By using the developed model, we also simulated the effects of hypovolemia on the BP, HR and shock index during orthostatic stress. The simulation results indicate that the cardiovascular responses to orthostatic stress change significantly when the decrease of blood volume is more than 15% of the total blood volume. However, if the amount of the decrease of blood volume is less than 5% of the total blood volume, HR and BP could be maintained in normal range by the regulation of baroreflex during LBNP. Our simulation results suggest that hypovolemia may be the main cause of orthostatic intolerance induced by weightlessness.

Adult↗
PubMed1977

Effect of weightlessness and of artificial gravity on irradiated lettuce seeds.

In our previous studies on board the artificial earth satellite Cosmos 368, the cosmic apparatus Zond 8 and the orbital station Salyut it has been demonstrated that space-flight factors (SFF) have a definite effect on poorly active biological systems, such as dry lettuce seeds. The technical possibilities on board the biosatellite Cosmos 782 (the availability of an on-board centrifuge) allowed us to obtain some new data concerning the mechanisms of the SFF effects. Irradiated seeds of lettuce (Lactuca sativa L.) were exposed in space flight for 22 days either to weightlessness conditions only or to a centrifugal field. Data have been obtained characterizing the cytogenetical and physiological processes in seeds of various series of the experiment. An attempt is made to analyse the role of individual SFF in the changes observed.

Centrifugation↗
PubMed2002

[Microgravity and weightlessness: experimental model accelerates nutritional pathology].

Short space flights affect nutritional intakes, body composition and functional parameters. Prolonged space flights (SF) over weeks or months further worsen these alterations and result in acute or chronic physical deterioration at earth return. Current planning of SF to Mars, with microgravity conditions for more than 2 years, stresses the need for developing and optimising a nutritional program and physical countermeasures to prevent body mass atrophy and functional body alterations. This review presents the models of microgravity simulation on earth and the main effects of weightlessness on body composition, protein metabolism, hormonal profile and muscle function. It summarizes contradictory findings related to the oxidative stress related to SF. It discusses potential countermeasures (nutrition, physical activity) to the negative effects of microgravity on human body. Future research possibilities in ground and space medicine are evoked.

Aerospace Medicine↗
PubMed2000

[Influence of weightlessness on water and electrolytes balance in body].

The balance of water and electrolytes plays an important role in enabling the human body to adapt to spaceflight. This paper introduced the research methods, and changes in water and electrolytes balance during and after space flight. The mechanism and the hazard of the disorder of water and electrolytes caused by weightlessness were discussed.

Adaptation, Physiological↗