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At least 667 records · Page 37Linked to original sources
PubMedDate not supplied

[Activity of the sympathetico-adrenal system in humans during modeling of weightlessness].

The state of the sympathico-adrenal system (SAS) before and during three days of suited immersion was investigated in six male subjects on the basis of renal excretion of adrenaline (A), noradrenaline (NA), dopamine (DA) and DOPA according to Vasilyev. Computer-aided analysis of the experimental data by the method of principal components showed that the SAS was functionally stressed in all subjects. Suited immersion that simulated hemodynamic, metabolic and vestibulo-motor effects of microgravity helped to distinguish between men with sustained and lowered capabilities of the SAS which are largely determined by the A-, NA-, and mixed type of its function. Clinical manifestations of A-crises in all subjects pointed to central genesis of SAS reactions to simulated microgravity. A correlation between the decline of SAS reserve capabilities and the level of the vestibulo-autonomic syndrome during suited immersion as well as drastic decrease of physical work capacity after immersion was established. It is emphasized that correction of unstable states of the SAS functional activity acquires special importance.

Adrenal Glands↗
PubMedDate not supplied

[Serum enzyme activity of healthy subjects during modeling of the effects of weightlessness].

The enzymic activity of blood of healthy male volunteers was examined during 8-day bed rest in the horizontal and head-down (-6 degrees) position, water immersion up to the neck and 6-hour head-down tilt (-15 degrees). Alkaline phosphatase, cholinesterase (CE), leucine arylamidase (LA), glutamate dehydrogenase (GDH) and gamma-glutamyl transpeptidase (GGTP) were measured. During horizontal bed rest the activities of all the enzymes, except for GDH, decreased in a moderate degree which was very distinct at an early stage of exposure. The activity of GDH and CE decreased significantly after the exposure. The enzymic activity tended to decline during head-down tilt at -6 degrees. The LA and GGTP activity decreased to a greater extent, being statistically significant during head-down tilt at -6 degrees and in the recovery period. The enzymic activity insignificantly increased during water immersion and 6-hour head-down tilt at -15 degrees, remaining in some cases elevated during 5 days after exposure. The lower activity of enzymes (which was significant for some of them) during horizontal and antiorthostatic bed rest was primarily associated with diminished motor activity, whereas increased enzymic activity was related to the gravity-induced blood shift to the intrathoracic area.

Adult↗
PubMedDate not supplied

[Problems of variability in weightlessness].

The genetic (cytogenetic) effects of microgravity have been under study for about 30 years. This line of research developed through three periods. Initially, biologists raised the question whether microgravity may act as a lethal factor or a strong mutagen. Many flight experiments gave a negative answer to it. The major goal of the second period was to identify the effects of microgravity at the chromosomal and cellular levels. Such effects, statistically significant although small in value, were detected in Tradescantia paludosa and Drosophila melanogaster microspores. These findings were confirmed by American and--later--by European investigators. The third period addresses the entire problem of variability in microgravity. This approach can be implemented on the basis of a comprehensive program of research that will include experiments at different levels: from the gene to the population level. The basic objective of the program is to clarify the role of the genetic apparatus in the adaptation of living systems to microgravity and, consequently, to determine the role of gravity in the evolution of life on the Earth.

Adaptation, Biological↗
PubMedDate not supplied

[Phenomenology and mechanisms of changes in the basic functions of the human body in weightlessness].

In the course of the space era the duration of manned flights increased from 108 minutes to 326 days. During the flights a large number of biomedical investigations were carried out to study the phenomenology and mechanisms of space flight effects on the human body. It was demonstrated that exposure to microgravity produced most significant changes. Short-term effects include space adaptation syndrome changes associated with fluid shifts and changes in movement coordination. Long-term effects involve various changes in the musculoskeletal system, cardiovascular system, metabolism and its regulation, endocrine system, blood and immunity system. This paper describes symptom-complexes that are consistently observed in space flight, discusses mechanisms of changes and adaptation of vital physiological systems, and outlines main periods of changes during and after flight.

Adaptation, Physiological↗
PubMed1988

[Weightlessness and elementary biological processes].

This book gives comprehensive review of the role of gravity in fundamental biological processes. The book surveys the results of experiments on precellular and unicellular organisms, plant and animal cultured cells and tissues, fungi and actinomycetes, higher plants, and insects. The book discusses essentially every experiment performed in real flights, including those in which the combined effect of microgravity and ionizing radiation was investigated, as well as many clinostat and centrifuge studies. In orbital flights unicellular organisms exhibited no gravity-dependent processes. The maximum size and basic morphology of unicellular organisms developed obeying the second law of thermodynamics do not therefore depend on space or time. Fungi retained all their properties except for gravitational ordering. Higher plants developed normally through seed-to-seed cycles: from the stage of seed germination to that of maturation of next generation seeds. Plants changed all their gravity-dependent movements. Since plant movements are irreversible, this affected their final shape, although the basic structure and size remained unaltered. The frequency of spontaneous and radiation--induced mutations changed insignificantly. The rotation of generations of plants and animals taken under study developed in a normal way. The morphological, physiological and genetic status of present-day organisms has developed under the effect of the gravity force that plays three different parts: as the creator and transformer of the abiotic environment, as the factor of natural selection, and as the factor of environmental physiology eliciting stable mechanical stresses. The effects of these gravity roles are implemented by different mechanisms and actualized in different time scales. The uneventful development of the basic biological processes in microgravity is an important factor that makes possible long-term space missions. From this point of view, the road to outer space is open to man in terms of his biology.

Animals↗
PubMedDate not supplied

[Hemodynamics in monkeys in the initial period of adaptation to weightlessness].

Using pre-implanted electrodes and transducers, arterial pressure and linear blood flow velocity in the common carotid artery of the rhesus-monkey Gordyi were measured during his space flight on a Cosmos biosatellite and ground-based control experiments. As compared to the prelaunch level, blood pressure remained unchanged, blood flow velocity increased significantly and blood flow resistance in the area decreased during the first hours after insertion into orbit. During subsequent flight days mean daily values of blood pressure increased and blood flow returned to the baseline level, although they showed distinct day-night variations. Daily variations of blood flow velocity and its ratio to cardiac output gave evidence that the circulation system of the rhesus-monkey under study rapidly adapted to microgravity conditions.

Adaptation, Physiological↗