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At least 379 records · Page 21Linked to original sources
PubMed1988

A new technique for iliac crest biopsy in rhesus monkeys for use in weightlessness experiments: some results of ground studies.

The similarity of major physiological functions between man and monkey make non-human primates a suitable model, especially for experiments in weightlessness. Bone tissue of rhesus monkeys can easily be analysed by histological techniques in order to appreciate the effects of hypogravity upon the skeletal system. A technique for iliac crest biopsy has been developed in a laboratory. It is to be used on rhesus monkeys used in various experimental situations, and especially after exposure to the space environment.

Animals↗
PubMed1987

Effects of prolonged weightlessness on self-motion perception and eye movements evoked by roll and pitch.

Seven astronauts reported translational self-motion during roll stimulation 1-3 h after landing following 5-7 d of orbital flight. Two reported strong translational self-motion perception when they performed pitch head motions during entry and while the orbiter was stationary on the runway. One of two astronauts from whom adequate data were collected exhibited a 132 degrees shift in the phase angle between roll stimulation and horizontal eye position 2 h after landing. Neither of two from whom adequate data were collected exhibited increased horizontal eye movement amplitude or disturbance of voluntary pitch or roll body motion immediately postflight. These results are generally consistent with an otolith tilt-translation reinterpretation model and are being applied to the development of apparatus and procedures intended to preadapt astronauts to the sensory rearrangement of weightlessness.

Electrooculography↗
PubMed1987

Rotation test in the weightless phase of parabolic flight.

Human test-persons and pigs were subjected to pendular swing movements during parabolic flight. The rotary-induced nystagmus frequency in pigs increased during a G-load of more than 1.5 G. In the trajectory from zero G to 1.5 G the nystagmus SPV in pigs increased. In human subjects weightlessness suppressed the rotary-induced nystagmus, and gravitational conditions over 2 G increased the nystagmus amplitude. Nystagmus responses in experienced test-persons proved to be independent of changes in G-load. The differences in the results in man and pig support the assumption that rotary-induced nystagmus is not solely a response of the cupulae and the otoliths, but is also affected by tactile and somatosensory stimulation.

Animals↗
PubMed1987

Body volume changes during simulated weightlessness: an overview.

It has been hypothesized that many of the adaptive processes that occur in man during exposure to space involve the rapid headward shift of tissue fluids, blood, and other fluids during the first few hours of spaceflight. A total of 53 men and women between the ages of 22 and 55 years were tested during four bed rest studies lasting between 4 h and 7 d to define the segmental volume changes that took place during simulated weightlessness. Impedance plethysmography can be used to measure baseline resistance (Ro) changes of the calf, thigh, total leg, pelvic, torso, and arm segments before, during, and after each bed rest exposure. Records of Ro were analyzed to determine the fluid volume and volume change of each segment during each test sequence.

Adaptation, Physiological↗
PubMedDate not supplied

[Paramecium test for toxic substances in the blood of humans exposed to conditions simulating weightlessness].

The Paramecium test was for the first time used to measure the build-up of toxic substances in the healthy man exposed to simulated weightlessness. The most distinct changes were seen on bed rest days 3 and 7-8 in all test subjects (41 subjects). After bed rest day 8 the parameter reached a plateau, the toxicity level stopped to increase, but the Paramecium test time remained shorter than normal. It can therefore be suggested that the prognosis of any disease that may develop in this situation will be worse. In view of this it is important to improve the prophylaxis and treatment of endogenous and exogenous intoxications during space flight and to provide active detoxication based on the purification of biological fluids by sorption.

Adult↗
PubMed1986

Plasma viscosity elevations with simulated weightlessness.

Bed rest studies which simulate weightlessness have demonstrated marked changes in the state of hydration of subjects as well as decrements in aerobic capacity. These two phenomena may be linked through increases in blood viscosity which is altered by a loss of free water and which, in turn, influences blood flow needed for aerobic muscular work. This study examines changes in the rheologic properties of blood which attend changes in plasma volume with bed rest in humans and correlates these changes with alterations in aerobic capacity. Eight healthy human subjects were studied on the 6th day of bed rest during two consecutive 10-d bed rest periods separated by a 14-d recovery interval designed to simulate the flight-layover schedule of shuttle astronauts. Plasma viscosity was measured with a Wells-Brookfield viscometer, plasma volume by dye dilution, and maximal aerobic capacity (VO2max) by recumbent cycle ergometry. Bed rest resulted in significant increases in hematocrit and in total plasma protein concentration and fibrinogen concentration, both of which contribute to an elevation in plasma viscosity. The greater than 20% increase in fibrinogen concentration was much greater than could be explained by hemoconcentration. VO2max decreased significantly in the first but not the second bed rest cycle. In many individuals, a decrease in plasma volume and aerobic capacity was coupled with elevated plasma viscosity and hematocrit; however, significant correlations between these variables were lacking. Although significant rheologic perturbations do occur with bed rest, in this study, blood viscosity elevation failed to directly correlate with the reduction in VO2max.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

[Effect of pharmacological agents to prevent the motion sickness syndrome on the cardiovascular system in simulating the early period of adaptation to weightlessness].

The application of pharmacological agents, preventing the motion sickness syndrome in modelling the early stages of adaptation to weightlessness by means of 6-hour antiorthostatic influence (-15 degrees), does not exert a negative action on the human cardiovascular system. The given agents normalize partially cerebral circulation, eliminating changes induced by antiorthostatic influence.

Adaptation, Physiological↗
PubMedDate not supplied

[Current concepts concerning the genesis of vestibulo-vegetative disorders in weightlessness].

The up-to-date hypotheses of the genesis of vestibulo-vegetative disorders in weightlessness are taken under critical analysis. Preference is given to the concept which attaches greatest importance to the changes in stereotyped interactions of analyzers responsible for space perception. It is, however, emphasized that neither hypothesis can account for all the phenomena seen in crewmembers in orbital flight. It is, therefore, indicated that mechanisms of vestibulo-vegetative disorders need further study. It is believed that the most promising line of research is to study the role of endogenous factors determining individual variations of motion sickness susceptibility.

Autonomic Nervous System↗
PubMed1985

Otolith tilt-translation reinterpretation following prolonged weightlessness: implications for preflight training.

Observations with three astronauts yielded two major findings. First, perceived self-motion during sinusoidal roll differed immediately postflight from preflight. Between 70 and 150 min after landing, roll was perceived primarily as linear translation. Secondly, more horizontal eye movement was elicited by roll stimulation immediately postflight relative to both preflight and later postflight observations. These results support an "otolith tilt-translation reinterpretation" hypothesis, which has clear implications for understanding astronaut reports of space motion sickness during the early period of orbital flight. A proposal for "prophylactic adaptation training" which may provide preflight adaptation to weightlessness, derives from this research.

Adaptation, Physiological↗
PubMedDate not supplied

[Labyrinthine and extralabyrinthine mechanisms of the development of motion sickness in weightlessness].

This paper describes an important problem of aerospace medicine, i. e. space motion sickness. The review surveys relevant Soviet and foreign publications. On their basis, including their own data, the authors discuss possible mechanisms of the sickness symptom-complex in the weightless state. The authors put forth their own ideas concerning current hypotheses of space motion sickness and discuss potential applicability of the theoretical concepts with respect to the prevention of this adverse symptom-complex. The authors describe selected outlines in the study of mechanisms of space motion sickness and in the development of specific countermeasures.

Afferent Pathways↗
PubMed1986

[Critical remarks on the interpretation of the thermal reaction of the labyrinth to weightlessness and evidence for the validity of the extended Bárány theory].

The literature on the biophysics of the vestibular apparatus in weightlessness is reviewed. The results of caloric in the prone position are compared to those in the supine position. The rate of convection and expansion of the endolymph are evaluated. Bárány's theory continues to be valid, because the rate of convection forms a greater proportion of the effective total stimulus than expansion.

Caloric Tests↗
PubMedDate not supplied

[Psychological adaptation and work capacity during simulated weightlessness].

In two-head-down tilt studies of 7 and 8 days in duration variations in the work capacity of 24 test subjects were examined and the following stages were distinguished: habituation, stable work capacity, and unstable compensation. Among the test subjects two groups were discriminated: those with plastic and those with inert types of adaptation to a changed environment. It is concluded that the plastic-type people can better and faster adapt to head-down tilt and therefore can work more efficiently during an acute stage of adaptation to weightlessness.

Adaptation, Physiological↗
PubMed1985

Response to muscular exercise following repeated simulated weightlessness.

The effect of repeated weightlessness exposures on maximal aerobic capacity was determined when seven healthy men (36-48 yr) underwent two 10-d bedrest (BR) periods in the -6 degrees headdown position, which were separated by a 14-d recovery period. No prescribed exercise was performed by the subjects during the course of the experiment. A graded supine cycle ergometer test consisting of 4 min of unloaded pedaling at 60 rpm followed by increased work rate of 15 W X min-1 until volitional fatigue (max) was performed before (pre) and after (post) the first and second BR periods, i.e., BR1 and BR2, and again 14 d after BR2 (REC). During exercise, submaximal and maximal oxygen uptake (VO2), ventilation (VE), heart rate (HR), systolic (SBP) and diastolic (DBP) blood pressures were measured and the gas exchange anaerobic threshold (AT) was determined. Plasma volume (Vp, T-1824) and body composition were measured pre- and post-BR1 and BR2 and following REC. Compared to the respective pre-BR control values, VO2max decreased (p less than 0.05) by 8.7% after BR1 and 5.2% after BR2 but returned to pre-BR values following 14 d REC. Submaximal and maximal HR increased (p less than 0.05) post-BR1 and BR2 but returned to pre-BR levels after REC. The AT and Vp decreased (p less than 0.05) post-BR1 and BR2 but returned to pre-BR levels after REC. Body weight increased (p less than 0.05) gradually during the experiment and did not return to control values.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

[Effect of weightlessness and and its simulations on the mechanical properties of the bones of animals undergoing torsion].

Mechanical properties (stress and strain) of bones from rats of different ages exposed to weightlessness, hypodynamia or hypokinesia were examined upon torsion. As compared to the controls, the femur of Cosmos-1129 rats showed high deformability. Also, skeletal bones of young rats proved more sensitive to hypodynamia than those of adult animals.

Aging↗
PubMedDate not supplied

[Antiorthostatic hypokinesia as an approximate model of weightlessness].

Eight test subjects were exposed to a five-day bed rest experiment in the recumbent and head-down position (at an angle of 0 degrees,--4 degrees,--8 degrees, and--12 degrees) to study the physiological effects of the exposure. The head-down tilting at--4 degrees and--12 degrees was shown to simulate physiological effects of real space flight better than bed rest at 0 degrees. The results made it possible to model an acute stage of weightlessness adaptation and to assay the contribution of gravity-induced blood redistribution to the physiological reactions.

Adult↗
PubMedDate not supplied

[Morphological effects of weightlessness and their pathogenesis].

The paper summarizes the results of morphological and histochemical investigations of rats flown onboard the Soviet biological satellites of the Cosmos series. The changes in different functional systems and organs have been found to be related. The paper contains hypotheses concerning the pathogenesis of the changes detected. It is emphasized that most changes are induced by a reduction of load upon the musculoskeletal system in weightlessness.

Adaptation, Physiological↗
PubMedDate not supplied

[Hemopoietic status of rats exposed to weightlessness].

This paper summarizes experimental data on the erythropoiesis of rats flown on Cosmos biosatellites for 18-22 days. The histogenesis of the hemopoietic tissue is investigated at the level of stem cells, dividing-maturing pool and mature blood cells (erythrocytes). In weightlessness inhibition of the erythropoiesis in various skeletal sites occurs. Flight data are compared with hemopoietic findings in hypokinetic rats. Possible mechanisms underlying red blood disorders in humans during space flight are discussed.

Animals↗
PubMed1984

[Biological effects of weightlessness at the cellular level. Comparative study of cultures of Paramecia aboard the orbital station Salyut-6 and a stratospheric balloon].

In order to distinguish the effects of cosmic rays from those of weightlessness at the cellular level, we performed experiments aboard stratospheric balloon, where gravity is equal to 1 g and cosmic radiation roughly equal to that aboard Salyut-6. The results suggest that the stimulation of cell proliferation is probably due to cosmic rays, metabolic changes being related to microgravity.

Calcium↗