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PubMedDate not supplied

[Reaction of various components of the erythrocyte system to periodic action of submaximal loads].

During repeated exposures of rats to hypergravity two stages of catabolic and adaptive developments in red blood were distinguished. The first stage that lasted about a week was characterized by decrease of resistance and hemolysis of red blood cells, hemosiderosis in the spleen, circulation hypoxia in the liver. The second stage was characterized by the predominance of adaptive processes, viz. increased activity of red blood cells, enhanced erythropoiesis in the spleen pulp, and appearance of highly active hepatocytes.

Acceleration↗
PubMed1991

Epidermal growth factor-induced cell rounding is sensitive to simulated microgravity.

Epidermal growth factor (EGF) induces rapid rounding of A431 human epidermoid carcinoma cells. This process is dependent upon temperature and EGF concentration. To investigate the possible influence of gravity variations on EGF-induced cell rounding of A431 cells, experiments were performed using a fast-rotating clinostat and centrifuge, thereby simulating microgravity and higher gravity values, respectively. We demonstrated that simulated microgravity conditions enhance EGF-induced cell rounding significantly, whereas hypergravity values do not show significant effects on this process. These results suggest that simulated microgravity modulates growth factor-induced signal transduction.

Adaptation, Physiological↗
PubMed1991

Prediction of space motion sickness susceptibility by disconjugate eye torsion in parabolic flight.

The hypothesis of asymmetric otolith function asserts that physiological or anatomical differences in the two sides of the bilateral gravity-sensing otolith apparatus of the inner ear may be well compensated on Earth, but when exposed to novel gravitational states, the prior compensatory stratagems may be ineffective, leading to unstable vestibular responses and causing the phenomenon of space motion sickness. To investigate this hypothesis, spontaneous eye torsion, a reflex governed by the otolith organs, was examined in the upright position during the hypo- and hypergravity of parabolic flight aboard NASA's KC-135 aircraft in nine former astronauts whose history of space motion sickness was revealed after data analysis had been completed. Results showed that astronauts who had been sick in space had significantly higher scores of disconjugate eye torsion in parabolic flight, and that their responses were consistently different in 1.8 G relative to 0 G compared to astronauts who had not been sick in space. In 1 G, there were no differences in disconjugate eye torsion between the subjects. The results support the asymmetry hypothesis and offer a possible predictive test of space motion sickness.

Disease Susceptibility↗
PubMed1990

Instability of ocular torsion in zero gravity: possible implications for space motion sickness.

Inherent asymmetries of the gravity-sensitive otolith organs of the inner ear may be well-compensated in ordinary 1 G, but rendered unstable in novel gravitational states. Several aspects of ocular counterrolling and spontaneous eye torsion, reflexes governed by the otoliths, were examined during the hypo- and hypergravity in parabolic flight on the NASA KC-135 aircraft. Among the subjects were two astronauts, one who had suffered space motion sickness during his mission and one who had not. Using an observed separation of scores of torsional instability at 0 G as the criterion, we divided our 10 subjects into the 5 highest and 5 lowest scorers, reminiscent of the approximately 50% who do and the 50% who do not experience space motion sickness (SMS). The astronaut who had had SMS was in the high group; and the one who had not was in the low group. At 1.8 G, the groups defined at 0 G were significantly different in the instability measure. They were also significantly different at both 0 G and 1.8 G in another measure, that of torsional variability. There were no differences between the groups in amplitude of eye torsion in 0 G or 1.8 G. None of the tests were significantly different in 1 G. The results suggest that these tests of eye torsion on the KC-135 might differentiate those who would experience SMS from those who would not. Proof of this speculation awaits replication of the study using only astronaut subjects.

Gravitation↗
PubMed1979

Space gerontology.

The initiation of the shuttle program, with the possibility of flying older persons and persons other than trained astronauts, makes it necessary to examine the effects of the weightless environment throughout the life cycle. The model of a hypothalamic clock as the timing mechanism for lifespan suggests that weightlessness and hypergravity may prove useful tools in the investigation of aging processes. For these reasons geriatrics and gerontology enter into the field of aerospace biology, both practically in crew selection and in the development of clinically useful data on the nature of human age changes and their control.

Aerospace Medicine↗
PubMed1980

Effects of chronic centrifugation on skeletal muscle fibers in young developing rats.

Three groups of 30-d old male and female rats were centrifuged for 2, 4, 8, and 16 weeks, after which their soleus and plantaris muscles were analysed for changes in proportion of muscle fiber types. The groups were: earth control, maintained at earth gravity without rotation; rotation control, subjected to a gravitational force of 1.05 G and 28 rpm; and rotation experimental, subjected to a gravitational force of 2 G and 28 rpm. Muscle fibers were classified into four fiber types on the basis of actomyosin ATPase activity as slow oxidative, fast oxidative glycolytic, and either fast glycolytic (plantaris) or intermediate (soleus). Hypergravity resulted in an increase in slow oxidative fibers in soleus and the deep region of plantaris. Chronic rotation of males resulted in a decreased proportion of slow oxidative fibers in soleus relative to the earth control, but not of females treated similarly. The relationship of body weight to the changes in proportion of slow oxidative fibers is discussed.

Adenosine Triphosphatases↗
PubMed1984

Impairment of thermogenesis and heat conservation in rats during 3 hours of 3-G exposure.

Heat conservation and production were studied in rats at 3 G and at 1 G. A closed-circuit system that includes a Krogh-type spirometer for the continuous measurement of oxygen consumption was used to determine heat production. At the same time, core temperature (Tc) and tail temperature (Tt) were also measured. During the first 20 min at 3 G, oxygen consumption increased by at most 18% in some of the rats and fell by up to 15% in the remaining rats. However, in all rats at 3 G, there was a fall of Tc during this time. Thus, the initial fall of Tc at 3 G was independent of concurrent changes in the rate of oxygen consumption. Furthermore, the rapid fall in Tc during the initial exposure to hypergravity was not due to reduced heat production (since oxygen consumption was variable and in some rats increased) but to an increase in heat loss. Even after 3 h at 3 G, when heat conservation mechanisms had recovered, the rate of oxygen consumption in rats was not significantly increased relative to the 1 G rate; hence thermogenesis was not activated to rewarm the animal.

Animals↗
PubMed1978

Time course of change in soleus muscle fibers of rats subjected to chronic centrifugation.

Soleus muscles from three groups of rats were analysed for changes in muscle fiber populations and diameters after being subjected to chronic centrifugation. The experimental groups were: earth control, raised at earth gravity with no rotation; rotation control, subjected to a gravitational force of 1.03 g and 30 rpm; and rotation experimental, subjected to a gravitational force of 2 g and 30 rpm. One male and one female of each group were killed at 7, 14, 21, 35, 42, 45, 49, 56 and 60 d after initiation of the experiment. Hypergravity resulted in an increase in the proportion of slow oxidative fibers. The time course of change in their muscle fiber populations is plotted. The time course of change in the ratio of body weight to muscle fiber diameter in the rotation control animals differed from that of the earth control and rotation experimental animals.

Aerospace Medicine↗
PubMed1978

Effects of fracture trauma, estrone treatment, and 2-G environment on the epiphyseal cartilage zones of developing avian radii.

Female birds subjected to closed fracture of the right radius at 2 weeks post-hatching were allowed to heal for 14 d at either earth gravity (1 G) or a 2-G hypergravity state, with saline-injected controls and 0.2- and 0.4-mg estrone (estrogen) treated groups. Animals were sacrificed following the last injection and radii were routinely processed histologically for micrometer measurements of the mid-coronal height and width of the cartilage zones of the proximal and distal epiphyses. Proximal epiphyses of estrone-treated, normo-gravity chicks showed a decreased growth in height of the articular, proliferating, and hypertrophic cartilage zones and an increased interstitial growth of the hypertrophic and calcified layers of estrone-treated, 2-G animals. Growth in height of the cartilage layers of the distal epiphyses of fractured radii was primarily stimulated when estrone-treated chicks were also exposed to the 2-G state. Appositional growth of all cartilage layers of the proximal and distal epiphyses of normo-gravity birds was increased by 0.2 mg estrone. In addition, growth in the width of all cartilage layers of the distal epiphyses of 2-G animals was increased with the administration of 0.4 mg estrone.

Animals↗
PubMed1980

Effect of hypogravity on human lymphocyte activation.

Cultures of human lymphocytes were exposed to the mitogen concanavalin A in a low-G environment generated by a fast rotating clinostat. DNA-synthesis was determined by incorporation of 3H-thymidine as the parameter for activation, cell ultrastructure was analyzed by electron microscopy, and cell movements were recorded by a cinecamera. The results were compared with 1-G controls. The cells cultured at low G show: (i) depression of activation by 50%, (ii) appearance of "mitochondria-rich" cells, and (iii) enhanced formation of pseudovilli and uropods. Our investigations in vitro at low and high G and reports on the effect of spaceflights on lymphocytes from cosmonauts and astronauts suggest that hypogravity depresses, whereas hypergravity enhances, lymphocyte activation by mitogens. This study is complementary to an experiment which will study the in vitro activation of lymphocytes in weightlessness during the first Spacelab mission.

Cell Movement↗
PubMed1995

[The adaptive-compensatory reactions in adjusting to space flights].

In this paper an evolutionary approach is used to substantiate the steps of life evolution on Earth towards overcoming the gravitational forces with the formation of metabolic cycles controlling the energetic of anti-G processes. The step of an adaptation to hypogravity was similar to return of surface animals to an aquatic environment. The impossibility of coming back to land was the "price" of adaptation to the aquatic environment. This phenomenon was used by the author as a logical model of human adaptation to a weightless environment. The concept of adaptation is examined from two points of view: adaptation and compensation. The scheme contains 4 steps of adaptation to space mission environments: Step I-preadaptation (phase of primary reactions); Step II-compensation of body structures not being in line with the conditions of a novel environment; Step III-the formation of parameters of an organism corresponding to the norm of adaptation to weightlessness; Step IV-the return of cosmonauts to Earth under hypergravity conditions. In compliance with these steps we consider the tasks of supporting space missions to facilitate body readaptation after return to Earth, i.e., to decrease the "price" of adaptation.

Adaptation, Physiological↗
PubMed1994

[Mineral metabolism in man under altered gravitation].

The book contains data about the functions and the metabolism of mineralized tissues, and the results of investigations of bone tissue and calcium metabolism during manned space missions and ground-based simulations. Consideration is given to the bone strength characteristics under experimental hypo- and hypergravity. The role of hormonal and physical/chemical factors in the mechanisms of iron control alterations in man during space missions of various lengths is analyzed. Evaluated is the efficiency of different countermeasures opposing the shifts in electrolyte exchange and bone mineral losses in these conditions. A concept is proposed for hypogravity-induced changes in the mineral metabolism and bone tissue status. The book is addressed to biologists, physiologists, biochemists, specialists in space biology and aerospace medicine.

Aerospace Medicine↗
PubMed1994

The location of the third cleavage plane of Xenopus embryos partitions morphogenetic information in animal quartets.

Analysis of the developmental potential of animal quartets (the set of four animal blastomeres isolated from the 8-cell stage Xenopus embryo) provided insight into the manner in which morphogenetic information is distributed along the animal-vegetal axis. Gravity treatments were employed to alter the partitioning plane. Animal quartets isolated from embryos exposed to simulated weightlessness had larger animal blastomeres, and they formed structures such as a groove and a protrusion more often than 1g-control animal quartets. Animal quartets with an unusual non-horizontal third cleavage plane were also found to have a higher frequency of protrusion formation than animal quartets with a typical horizontal cleavage plane. The increase in the frequency seen in simulated weightlessness animal quartets was not due to their increased size. Fusing two animal quartets isolated from hypergravity (3g) exposed embryos (small blastomeres and low incidence of protrusions) did not affect the frequency of protrusion formation. Molecular analyses revealed that a partial induction was associated with the protrusion formation. Transcripts of the dorsal lip specific homeobox gene, goosecoid, and alpha-cardiac actin were detectable by PCR amplification in the animal quartet with a protrusion, and alpha-cardiac actin mRNA was found by whole-mount in situ hybridization to be localized in the protrusion. Taken together, all these results are consistent with the notion that both animal and vegetal information is necessary for normal development and the partitioning of morphogenetic information into animal quartets results in gravity-dependent differential morphogenesis and gene regulation.

Actins↗
PubMedDate not supplied

[Gravity and animal development].

Based on the literature data and the author's findings, a comparative-and-physiological analysis of the responses of the animals of a different evolutionary level to micro- and hypergravity has been attempted. The experimental data accumulated by this time show a good fit to N.N.Sirotinin's concept about an evolution of the resistance and the reactivity: the high tolerance to a changed gravity in the insects, the presence of reaction in fish and amphibians mainly in most early developmental stages or in reduced (having high sensitivity) lay, a wide range of the responses to a changed gravity in birds and mammals. The investigative prospects in the field of gravitational biology of the development are discussed.

Adaptation, Physiological↗
PubMed1996

Comparative electronmicroscopical investigations on the influences of altered gravity on cytochrome oxidase in the inner ear of fish: a spaceflight study.

The regional metabolic activity in the otolithic sensory epithelia of the inner ear of a cichlid fish (Oreochromis mossambicus) was investigated on light- and electronmicroscopical level using the cytochemical method for detection of cytochrome oxidase activity. In adult animals a characteristic distribution of mitochondria with high enzyme activity was found in sensory and non-sensory cells of otolithic sensory epithelia, which was correlated with regions with a high energy demand. These findings were the basis for studies on the influence of long-term altered gravity conditions in developing larvae: hypogravity (10(-4) g in spaceflight), normal gravity (1 g in a centrifuge in space and 1 g on earth) and hypergravity (3 g in a laboratory centrifuge). Cytochrome oxidase activity was quantified in different parts of the sensory hair cell synapse in the vestibular sensory epithelia utricle and saccule: apical and basal cytoplasm, postsynaptic area of the afferent synapse and presynaptic region of the efferent synapse. Our results show that the energy metabolism of utricle, but not of saccule is decreased after microgravity exposure during the 2nd German Spacelab Mission D-2. However, a general effect of the spaceflight is detectable in both sensory epithelia. Long-term exposure to increased acceleration (3 g) had no effects on cytochrome oxidase activity in inner ear sensory epithelia.

Animals↗
PubMed1977

Femur-bending properties as influenced by gravity: II. Ultimate load, moment, and stress for 3-G mice.

Material strength as approximated from bending studies of fresh femurs grew during 1 to 8 weeks of hypergravity at rates which were not measurably affected, even though the animal's body growth was measurably slower. As a result, femurs could support greater ultimate loads, moments, and stresses when compared to control bones of comparable rotational moments of their cross-sectional areas. Chronic centrifugation simulated 3.1 G for 45 male. Swiss Webster mice compared to 37 control animals. Effects were most noticeable after the first week of exposure and for younger animals. Effect were only about 50% that noted in comparable treatment of rats. This suggests that four times more mice than rats may be necessary for space-experiments designed to test the effects of weightlessness.

Animals↗
PubMed1996

[Formation of a unified system of mental regulation of activities and functional state of the flyer during effects of piloting strain].

The article describes the method of improving professional dependability of pilot impacted by aerobat g-loads through formation of a unified system for psychic regulation of his activity and status of the psychological function in the process of training on flight simulator. To this end, the simulator was retrofitted with an adaptive training circuit to establish functional and correction feedback by changing the intensity of display brightness proportionally to the degree of "g-load" and effectiveness of countermeasures applied to simulate visual disorders due to hypergravity. Data from real flights with high aerobat g-loads proved effectiveness of the proposed training scenarios as judged by increased probability of administration of breathing (0.9 vs. 0.4) and muscular (1.0 vs. 0.8) countermeasures by members of the experimental group against their controls. Besides, the trained pilots had no visual disorders, whereas this was the case in 28% of their controls. Possible mechanisms of how to form a unified system for psychic regulation in which implementation of a task is kept under permanent conscious control and self-control of the psychological function is essentially accomplished on the level of automated habits are the subject of the authors' discussion.

Aerospace Medicine↗
PubMed1996

Graviresponses in Paramecium biaurelia under different accelerations: studies on the ground and in space

Behavioural responses to different accelerations below 1 g and up to 5 g were investigated in Paramecium biaurelia by using a centrifuge microscope on Earth and in space during a recent space flight. Increased stimulation (hypergravity) enhanced the negative gravitactic and the gravikinetic responses in Paramecium biaurelia within seconds. Cells did not adapt to altered gravitational conditions. Repetitive stimulation did not change the graviresponses. The minimum acceleration found to induce gravitaxis was between 0.16 and 0.3 g.

Journal Article↗