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PubMedDate not supplied

[Compensatory-adaptive reactions of regional hemodynamics to weightlessness during a long space flight].

This paper discusses regional hemodynamics and vascular regulation during and after space flights of over 3 months in duration. Mechanisms of cardiovascular adaptation to weightlessness are described. The postflight differences in the recovery of regional hemodynamics seem to depend on the individual characteristics, age-related changes of the cardiovascular system, as well as the countermeasures and rehabilitation measures performed during and after flight.

Adaptation, Physiological↗
PubMed1983

Fluid shifts in vascular and extravascular spaces during and after simulated weightlessness.

To simulate weightlessness in a normal-gravity environment, eight male subjects were tilted 5 degrees head-down for 8 h to determine vascular and extravascular shifts of fluid. Most of the initial loss of leg volume during head-down tilt represented a passive shift of venous blood toward the head. Facial edema, headache, nasal congestion, and a pronounced diuresis were associated with this redistribution of blood volume. As measured by the wick-catheter technique during head-down tilt, interstitial fluid pressure in lower-leg muscle and overlying subcutaneous tissues decreased by 7.4 and 4.4 mmHg, respectively. Interstitial fluid was shifted from the lower legs at a rate of 12 ml X h-1. Dehydration of lower-leg tissues probably resulted from decreased capillary blood pressure within these tissues during tilt. Other transcapillary pressures were unchanged. The abrupt alterations in local blood pressure upon changes in body posture were probably sufficient to explain all shifts of vascular and extravascular fluid. In this regard, countermeasures may be necessary to maintain precapillary-muscle tone during long space flights in order to prevent swelling of lower-leg tissues upon readjustment to Earth's gravity.

Airway Obstruction↗
PubMed1984

An expandable surgical chamber for use in conditions of weightlessness.

An expandable surgical chamber of transparent polyvinyl has been designed to provide a sterile environment for minor surgical procedures performed in conditions of weightlessness. Contamination of the cabin with blood and other debris is prevented while performing surgery. The patient's extremity is inserted through a cuff into the surgical chamber. The cuff may be inflated for rapid hemostasis. All instruments and suture material are stored within the chamber.

Equipment Design↗
PubMedDate not supplied

[Ultrasonic studies and calcium content of the bones in experimental animals during limited mobility and weightlessness].

The velocity of ultrasonic propagation, calcium content, and femur size of rats exposed to actual and simulated weightlessness were investigated. The exposure slowed down the ultrasonic velocity in bones. The effect of the calcium content on the ultrasonic velocity in various bone sites was different: as a rule, there was a positive correlation in diaphyses and a negative correlation in epiphyses. These specific features should be taken into consideration when new methods of bone ultrasonic diagnostics will be developed.

Animals↗
PubMed1981

[Man in the condition of weightlessness (author's transl)].

In the space flights by the USA and USSR to date adequate experience has been obtained on the adaptation of man to living conditions in space--with the technical assistance of an artificial protective atmosphere in the space ship or space suit--and to the singular factor of "weightlessness" (microgravity, low gravity) and how he re-adjusts again after returning to a gravitational field. There is no ultimate or absolute physiological barrier for long term space flight--with one exception: decalcification of the skeleton. For short space flights, however, space sickness is a serious disorder.

Adaptation, Physiological↗
PubMed1978

[Characteristics of the microcirculatory bed of the gastrocnemius muscle of rats under conditions of weightlessness].

Quantitative histological investigations of capillaries in the gastrocnemius muscle of rats after 18.5 days on board the artificial satellite "Cosmos-936" have demonstrated that the number of functioning capillaries decrease by about 30% under conditions of weightlessness. Decrease in the number of functioning capillaries in the gastrocnemius muscle is also observed in animals subjected to artificial gravitation (acceleration 1 g) during the flight. The main role in lowered blood supply of the muscles is supposed to play the lack of kinetic but not static loading on the muscles.

Animals↗
PubMedDate not supplied

Physiological mechanisms of adaptation to weightlessness. Data from experiments with animals in earth-orbit biosatellites.

Four experiments were carried out with mammals (white laboratory rats) in Kosmos biosatellites. The experimental results indicate that rather prolonged weightlessness does not cause pathological changes in internal organs. Changes were discovered in the metabolic and hormonal status of the organisms, allowing us to consider an 18-22-day space flight as a moderately stressful activity. Changes in the musculoskeletal system involved atrophy of particular muscle groups, adaptive transformation of the contractile properties of some of them, osteoporosis, and decreased durability of bony tissue. There was a decrease in the ATPase activity of myocardial myosin, and there were changes in the erythrocytic system: decreased erythrocytic hemopoietic activity, increased levels of spontaneous hemolysis of erythrocytes, etc. All the described changes were reversible, and examination of the animals 25 days after their return to Earth showed practically complete normalization of the parameters studied.

Adaptation, Physiological↗
PubMedDate not supplied

[Physiological and biochemical characteristics of the cells of a carrot gall tumor developing in weightlessness].

The paper presents the results of experiments with the carrot tissues infected with Agrobacterium tumefaciens flown onboard the biosatellite Cosmos-1129 in cooperation with the US scientists. Postflight, the respiratory activity of tumour cells was determined and K+ and Na+ permeability of cell membranes was measured. The resulting data give evidence that in weightlessness the development of the carrot gall tumour is accompanied by changes in the above physiological and biochemical parameters. The changes are, however, within the physiological limits, leading to no pathologies of the whole cell.

Plant Tumors↗
PubMed1982

Effects of various countermeasures against the adverse effects of weightlessness on central circulation in the healthy man.

The effect of lower body negative pressure, local negative pressure below the knee joint, and both pneumatic and mechanical occlusion cuffs at the upper third of the femur on central circulation, oxidative metabolism, and acid-base equilibrium of blood was studied on eight healthy male volunteers with doublelumen Swan-Ganz flow-directed thermodilution catheters implanted for 7 d into the pulmonary artery. The counter-measures against the adverse effects of weightlessness were used in two regimens: regimen I at -30, -50, +40 torr and regimen II at -60, -100, and +60 torr. The parameters were recorded in recumbency, during the head up tilt at 70 degrees for 15 min, and then during the head-down tilt at -20 degrees for 60 min. After the first 20 min of anti-orthostasis, the effects of the above countermeasures in the two regimens were investigated. The tile-induced changes in central circulation, those observed during application of the countermeasures, and the effect of different countermeasures were studied on a comparative basis. It was demonstrated that the highly informative method of implantation of catheters into the pulmonary artery can be successfully used in biomedical investigations of normal men.

Acid-Base Equilibrium↗
PubMedDate not supplied

[Potential for modelling the hemodynamic effects of weightlessness by exposure to increased pressure].

Venous and arterial circulation was investigated by simulating cephalad blood shifts generated by an exposure of test subjects (n = 15) to lower body positive pressure (+25 mm Hg) and head-down tilts (at -8 degrees and -15 degrees). At LBPP and tilt -15 degrees arterial pressure increased by 5-15%. During tilt -8 degrees jugular vein blood filling increased by 8-94% in the course of the first 3 hrs and then decreased reaching the baseline (horizontal position) level. During LBPP the parameter changed in a similar manner (increased by 2-50%). During tilt -15 degrees the parameter grew by 10-110% and remained elevated. The exposures gave rise to bradycardia which was more pronounced during -8 degrees and LBPP. The data obtained give evidence that circulation changes during LBPP and head-down tilts are identical. This suggests that LBPP can be used to simulate the effect of cephalad blood shifts, one of the most important effects of weightlessness on the human body.

Adult↗
PubMedDate not supplied

[Effect of weightlessness on the water fern Azolla].

An exposure to 6-day weightlessness of the fern Azolla pinnata R. Br. symbiotically related to the nitrogen fixing alga Anabena azollae did not affect the main biological characteristics (growth, development and morphological structure) of both fern plants and algae. The exposure did not influence the growth rate or subsequent Azolla generations on the Earth.

Life Support Systems↗
PubMedDate not supplied

[Comparative study of the effect of weightlessness and artificial gravity on the density, ash, calcium, and phosphorus content of calcified tissues].

The studies were carried out on 30 rats flow for about 19 days aboard the biosatellite Cosmos-936 (5 centrifuged rats including) and 25 ground-based control rats. Postflight the centrifuged rats did not show significant differences in the density, mineral saturation, distribution of vascular channels in bones, ash, calcium and phosphorus content in skeletal bones and teeth as compared with the parameters in synchronous and vivarium controls. In the weightless rats these values were significantly lowered.

Animals↗
PubMed1995

[The reactions to weightlessness exposure: adaptation or disease?].

The arguments characterizing the poor theoretical validity and low profitability of the concept of "weightlessness disease" developed during recent few years by its authors are advanced. The morphofunctional rearrangements occurred in the body during space flights are considered as the result of adaptation-disadaptation rearrangements directed towards supporting the equilibrium with a set of reduced environmental requirements. Understanding the mechanisms of adaptation rearrangements creates the real but not forced basis for developing the measures for cosmonauts health stabilization and spaceflight safety.

Adaptation, Physiological↗
PubMed1993

Spatial orientation and posture during and following weightlessness: human experiments on Spacelab Life Sciences 1.

The 4 payload crew members of the Spacelab Life Sciences 9-day space flight in 1991 were subjected to limited vestibular testing in flight as well as pre and post flight. Major differences in individual "perceptual style" appeared in their reaction to the visual-vestibular stimuli in the rotating dome experiment, and especially in the extent to which nondirectional tactile cues served to anchor the subjective vertical and body postural reactions. The ability of subjects to point to remembered target positions was degraded in space, which produced a tendency to point low in some subjects in flight. The eye movements and subjective response to sudden stops and head pitching following continuous spinning (dumping) were measured both in space and on the ground. Although subjective duration of inflight rotation for the dumping tests was shorter than that for the preflight tests, the postrotatory nystagmus, with or without head pitch, was lengthened in time constant relative to preflight. Ground tests, in addition to the flight experiments, investigated the changes following weightlessness in subjective and oculomotor reactions to whole body tilt, the ability to balance with eyes open and closed; leg muscles strength and stamina as related to posture; visual field dependence; and the perceptual and oculomotor reactions to horizontal linear acceleration. Several of these tests, as well as post-flight measures of motion sickness susceptibility, revealed subtle evidence of neurovestibular alterations that lasted a week or more following the 10-day orbital exposure.

Adaptation, Physiological↗
PubMed1993

Crucial effects of weightlessness on human orientation.

This contribution examines the consequences of two remarkable experiences of subjects in weightlessness, 1) the missing of sensations of trunk tilt and of the respective concomitant reflexes when the head is tilted with respect to the trunk, and 2) the persistence of a perception of "up" and "down," that is, of the polarity of the subjective vertical (SV) in the absence of, as well as in contradiction to, visual cues. The first disproves that the necessary head-to-trunk coordinate transformation be achieved by adding representations of the respective angles gained by utricles and neck receptors, but corroborates an extant model of cross-multiplication of utricular, saccular, and neck receptor components. The second indicates the existence of force-independent components in the determination of the SV. Although the number of subjects is still small and experimental conditions are not as homogeneous as desired, measurements and/or reports on the ground, in parabolic, and in space flight point to the decisive role of the saccular z-bias, that is, of a difference of the mean resting discharges of saccular units polarized in the rostrad and the caudad (+/- z-) direction.

Humans↗
PubMed1977

The urinary excretion of collagen degradation products by quadriplegic patients and during weightlessness.

Urinary total hydroxyproline, peptide-bound hydroxyproline, hydroxylysine glycosides, and calcium were measured in three healthy individuals subjected to weightlessness for eighty-four days and in three young quadriplegic patients. The former group had significant calciuria but no evidence of collagen degradation. The latter group, however, had conspicuous calciuria and also excreted large amounts of collagen breakdown products. This documented degradation of matrix may be related to the continuous calciuria, osteoporosis, and cutaneous dystrophic changes occurring in quadriplegics.

Calcium↗
PubMed1996

Swimming behavior of fish during short periods of weightlessness.

BACKGROUND: Birds and fish show tumbling and spinning movements when subjected to short periods of weightlessness during parabolic flight. The reason for this behavior is not clear. HYPOTHESIS: The semicircular canal system is a rotation-detecting device; however, it seems that linear accelerations have an influence, too. Microgravity induces rotatory sensations which leads to a compensatory behavior (e.g., rotatory movements). METHODS: The swimming behavior of goldfish was studied with the fish in four different conditions: normal fish (group I); fish with one eye recently removed (group II); fish with both eyes recently removed (group III); and fish with both eyes removed 10 months previously (group IV). Further, a group of naturally blind (e.g., not surgically treated) cavefish (group V) were involved in the study also. All procedures conformed to the guiding principles as required in the Dutch Law on Care and Use of Animals. RESULTS: Three main different patterns of abnormal swimming behavior could be observed: tumbling (pitch), corkscrew movements (pitch and roll), and spinning movements (roll). NF did not shown any special swimming pattern. One-eyed fish (group II): mostly corkscrew movements (62%). Blind fish (group III): a mixture of the three movements (17, 22 and 25%). Blind fish (group IV): mostly spinning movements (20%). Cavefish (group V): tumbling (21%), corkscrew movements (12%) and spinning movements (58%). CONCLUSION: Vision is the dominant cue, explaining the behavior of normal goldfish. When vision is absent, the fish relies on vestibular information with respect to orientation. The swimming behavior is presumably caused by an attempt to compensate rotatory illusions. As all movements were shown in the planes of the vertical canals, we conclude that these canals play a dominant role when fish are deprived from proper otolith information.

Animals↗
PubMedDate not supplied

Postural equilibrium following exposure to weightless space flight.

Postural equilibrium performance by the Skylab 1/2, 3, and 4 crewmen following exposure to weightlessness of 28, 59, and 84 days respectively was evaluated using a modified version of a quantitative ataxia test developed by Graybiel and Fregly. Performance for this test was measured under two sets of conditions. In the first, the crewman was required to maintain postural equilibrium on narrow metal rails (or floor) with his eyes open. In the second condition, he attempted to balance with his eyes closed. A comparison of the preflight and postflight data indicated moderate postflight decrements in postural equilibrium in three of the crewmen during the eyes open test condition. However, in the eyes closed condition, a considerable decrease in ability to maintain balance on the rails was observed postflight for all crewmen tested. The magnitude of the change was most pronounced during the first postflight test day. Improvement was slow; however, on the basis of data obtained, recovery of preflight baseline levels of performance was evidently complete at the end of approximately two weeks for all crewmen. The findings are explained in terms of functional alterations in the kinesthetic, touch, vestibular and neuromuscular sensory mechanisms induced by the prolonged absence of a normal 1-G gravitational environment.

Gravitation↗