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At least 649 records · Page 36Linked to original sources
PubMedDate not supplied

[Pattern of vestibular reactions and sensory interactions in weightlessness (data of the experiment "Optokinesis")].

This paper presents results of studying spontaneous and evoked optokinetic, opto-oculomotor and vestibulo-oculomotor reactions in microgravity. The examinations were performed during the 7-day Soviet-Indian and 237-day Salyut-7 missions. During an early stage of adaptation to microgravity the following changes occurred: enhanced spontaneous activity of the eyes, including spontaneous nystagmus in one of the crewmembers, decline of the efficiency of saccadic pursuit (disappearance of saccades in the course of pursuit of a moving stimulus, decrease of the saccadic amplitude, emergence of correction microsaccades in response to fixation events), and decrease of the threshold of the optokinetic nystagmus. The compensatory counter-rotation of the eyeballs during head side-to-side movements with open eyes in dark glasses did not disappear but slightly decreased, being slightly accompanied by low-amplitude nystagmus. When rocking the head with open eyes, one of the cosmonauts showed a complete eye destabilization and other cosmonauts displayed high-amplitude nystagmus. In response to head rotation with open eyes they developed clonic nystagmus. Vestibular stimulation in the form of active head movements helped to normalize the pattern of opto-ocular responses.

Adaptation, Physiological↗
PubMedDate not supplied

[Central and general hemodynamics in healthy persons during simulated weightlessness].

The pumping and contractile functions of the left ventricle were investigated during combined exposure to water immersion and head-down tilt (at -6 degrees) that simulated microgravity. This 7-day exposure caused noticeable changes in central and systemic circulation which developed as a function of time. It is assumed that the deficiency of venous blood return seen on test days 1-3 was a compensatory response to initial blood displacement which was induced by a reduction of the circulating blood volume. The reduction was in turn a result of responses from volumoreceptors of the heart and intrathoracic vessels to "excessive" intrathoracic blood volume.

Adult↗
PubMedDate not supplied

[Effect of simulated weightlessness on calcium metabolism and the condition of bone tissue in experimental animals].

Male rats of the Wistar strain were for 40 days exposed to hypokinesia and hypodynamia. After exposure bone biochemical, physical, chemical, morphological and strength parameters were investigated. Both simulation studies led to changes in calcium and phosphorus metabolism but the nature of bone changes was different. It is concluded that the efficacy of drugs used as countermeasures in animal simulation experiments should be assessed by both exposures, viz. small size cages and suspension, because they reproduce different mechanisms of potential bone lesions in microgravity. It is also inferred that various countermeasures should be used in combination to yield the best results.

Animals↗
PubMedDate not supplied

[Characteristics of optokinetic, opto-oculomotor and vestibulo-oculomotor reactions in weightlessness].

Investigations of spontaneous and evoked optokinetic, optooculomotor, and vestibulooculomotor reactions in microgravity are described. The investigations were performed during the 7-day Soviet-Indian flight and during the 237-day Salyut-7 flight. At an early period of adaptation to microgravity spontaneous oscillations of the eyeballs were enhanced: spontaneous nystagmus (in one of the subjects), lower effectiveness of saccadic pursuit (saccade elimination during the pursuit of a moving target, decrease of saccade amplitude, appearance of corrective microsaccades during fixation turns and pursuit), decline of the optokinetic nystagmus threshold. Compensatory eye counterrotation, when the head moved from side-to-side in the frontal plane with eyes open and dark glasses on, did not disappear but attenuated slightly; it was followed by low amplitude nystagmus. When the head moved with eyes open, one of the crewmembers showed complete eye destabilization while others--high amplitude nystagmic oscillations. When the head turned around with eyes open, clonic nystagmus occurred.

Electronystagmography↗
PubMedDate not supplied

[Ultrastructure of the submandibular glands in rats kept in weightlessness].

Submandibular salivary glands of male rats weighing 330-350 g were examined after space flight and ground-based control study. Light microscopy was carried out using hematoxylin-eosin staining and PAS-reaction. Electron microscopy was performed using glutaraldehyde and osmium tetroxide fixation and contrasting according to Reynolds. Light microscopy revealed no destructive changes in the gland parenchyma; differences between flight and control rats remained within physiological limits. Electron microscopy of acinar cells of flight animals showed chromatin condensation, darkening of cells and nuclei, appearance of electron-dense vacuoles, fragmentation fo the granular endoplasmatic reticulum as well as enlargement of interstitial spaces, lumens of acini and intercellular canaliculi, loosening of basal membranes, and thinning of capillary walls. Electron microscopy of acinar cells of control rats demonstrated chromatin condensation in nuclei and fragmentation of the GER. Thus, both animal groups exhibited ultrastructural signs of inhibition of the synthesis and excretion of salivary protein. In addition, flight animals showed increased excretion and, probably, secretion of water and electrolytes. Examinations of granulocytes revealed enlargement of secretory granules in both animal groups, the largest granules being seen in flight animals. They also showed mitochondrial swelling which was most significant in control rats. After the ground-based study cells of the striated compartment also displayed a very distinct mitochondrial swelling which may reduce the reabsorption capacity and enhance salivation of the compartment. However the mechanism of these changes seems to be different from that underlying changes after real space flight.

Animals↗
PubMed1989

[Structural changes in the dental hard substances and jaw bones of animals due to short-duration weightlessness].

Molars, incisors and parts of corpus mandibulae from a total of 40 male, 30 female (WISTAR SPF), who were exposed for a short-time microgravity, and of their 90 d old offspring were examined. It was calculated the carbonateapatite content in the teeth and in bone in percent by infrared spectroscopy. In terms of quantitative parameters the substances of the space flight group versus the controls varied clearly. Quality and size of these changes depend from sex, investigated material and time of space flight. It can be concluded that an accommodation to the flight stress is possible without any functional disorders also in the oral system.

Animals↗
PubMedDate not supplied

[Psychophysiological characteristics of the sensorimotor activity of operators after short-term simulated weightlessness].

Changes in operator's sensorimotor activity and their effect on the control of a dynamic object after short-term exposure to simulated hypogravity were investigated. Hypogravity effects were simulated by a 6-day head-down tilt (-10 degrees) study and a 1-day water immersion study. Changes in the structure of actions seen after study (greater use of controllers in the longitudinal axis, alteration of bioelectric activity of muscles involved in movement arrangement, shift of their spectral power toward higher frequencies) are considered as objective indicators of disrupted automatism of controlling skills. A peculiar psychic compensation of disorders in the coordination structure of movements was a longer time used to control the position and movement of an object in the longitudinal plane. Partial disruption of automatized controlling skills after short-term exposure to simulated hypogravity facilitates a decrease in operator's reliability, when he is to perform sophisticated and precise functions.

Humans↗
PubMedDate not supplied

[Effect of weightlessness on the reproductive system of mammals].

This paper summarizes experimental data available about the effect of microgravity on the reproductive system and reproductive function of mammals. The flight experiment on female rats has shown that fetuses can grow and develop when the maternal organisms is exposed to microgravity. The data concerning the effect of microgravity on the reproductive function of mammalian males are limited and controversial. Analyzing them, it can be noted that the changes seen are small and reversible and that cells involved in spermatogenesis show greater resistance to space flight factors than other continuously renovating cell populations. Future approaches to the experimental investigations in this area are discussed. It is emphasized that fertilization and early stages of mammalian development in space flight deserve special study.

Animals↗