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PubMedDate not supplied

[Role of the endocrine glands in divergence of plastic processes and energy metabolism in rats after extended exposure to hypergravity: cytologic investigation].

Cytologic and morphometric investigations of the hypothesis, thyroid, thyroid and pancreas of rats after 19-d centrifugation at 2G revealed suppression of somatotropic hormone production by hypophyseal somatotrophs and insulin by pancreatic beta-cells, and intensification of thyrotrophic hormone production by hypophyseal thyreotrophs, thyroxin by thyreoid parenchyma and glucagon by pancreatic alpha-cells. These change in hormone production are viewed as an endocrine mechanism of the divergence of plastic processes and energy metabolism in animals subjected to chronic exposure to hypergravity.

Animals↗
PubMed1997

Hypergravity and aging in Drosophila melanogaster. 9. Conditioned suppression and habituation of the proboscis extension response.

In a first experiment, the conditioned suppression of the proboscis extension response (PER) to sucrose was measured in young, middle-aged and old male Drosophila melanogaster flies living at either 1, 3 or 5 g. Flies were starved and then subjected to a learning task involving a sucrose stimulus, followed by an aversive one applied to their forelegs. In this learning task, flies learn to not extend their proboscis when walking on sucrose. Flies which have lived in hypergravity (HG) had a lower number of PER suppressions than 1 g ones, and this finding was mainly due to young and middle-aged flies. In a second experiment, the habituation of the PER was studied using as stimulation sucrose solutions 2-fold (first experiment), 4-fold (second one) or 8-fold (third one) higher than the individual sucrose threshold. Middle-aged and old flies habituated more slowly than young flies in the second and third experiments. In the third experiment, a decreasing speed of habituation was observed when gravity increased; this result was mainly due to young flies, and no gravity effect was observed in the other two age groups. This whole set of results suggests that HG-kept flies do not age faster than 1 g ones, as far as these learning and habituation tasks are concerned. It seems possible that HG acts like a mild stress to which flies adapt; if applied for a long time, HG could induce a premature aging, as observed in the previous papers of this series.

Aging↗
PubMed1998

Control of isometric force in hypergravity.

BACKGROUND: Previous work suggests that proprioceptive signals are degraded in hypergravity (hyper-G). We therefore, expected that production of finely graded force is disturbed as well. METHODS: Subjects produced isometric force with their thumb and index finger upon verbal instruction, before, during and after exposure to +1.5 Gz and +3 Gz. Produced force was orthogonal to the direction of gravity. RESULTS: In hyper-G, responses to a given target value were significantly higher (by about 400 pond) than in normal gravity, while the modulation of produced force with target force didn't change. The results in +1.5 Gz and +3 Gz were quantitatively similar, and a positive aftereffect was found. CONCLUSIONS: Subjects underestimate by a constant amount the force they produce in hyper-G. Our results are reminiscent of similar findings with pointing and grasping movements in hyper-G.

Adult↗
PubMed1998

EMG activity of three rat hindlimb muscles during microgravity and hypergravity phase of parabolic flight.

BACKGROUND: In man, quantifications of the motor activity have mainly been performed to study changes in posture and locomotion after space-flight. On the contrary, physiological data relative to the motor activity have never been obtained in animals in real microgravity. HYPOTHESIS: The purpose of this study was to evaluate, in rats, the immediate effect of real microgravity on the neuromuscular activity of three hindlimb muscles. METHODS: Under aseptic conditions, the soleus (SOL), lateral gastrocnemius (LG) and tibialis anterior (TA) muscles of rat hindlimb were implanted each with a pair of electrodes. Their electromyographic (EMG) activity was analyzed before, during, and after parabolas, a parabola being composed of two 2 G episodes separated by one 0 G episode. Each episode lasted about 25 s. RESULTS: Our results showed that, when compared to normal gravity (1G), hypergravity increased the EMG activity in the ankle extensors SOL and LG, whereas microgravity immediately induced a redistribution in the motor activity between the two antagonists, SOL and TA. CONCLUSIONS: An immediate adaptation occurred in the motoneuronal recruitment of rat hindlimb muscles at the onset of changes in gravity level. This could be interpreted in terms of a short-term adaptative process involving peripheral mechanisms initiated by changes in activity of muscle spindles.

Adaptation, Physiological↗
PubMed1993

Hypergravity, aging and longevity in Drosophila melanogaster.

1. Drosophila melanogaster flies have been used in studies of the effect of hypergravity (HG) on aging and longevity. 2. There is no clear longevity decrease with the gravity level up to 4 g and, even at 7 g, flies still live for roughly 40 days. 3. The HG-related changes in fecundity suggest that flies counteract an increased metabolic demand. 4. Viability is barely affected in HG. 5. These results show that flies remain able to lay viable eggs and to live for a fairly long life, even at high HG levels. 6. The study of three behavioral traits affected by aging (climbing activity, pattern of movement, spontaneous locomotor activity) suggests that flies age faster in HG, while no HG effect is clearly detected at young age. 7. These results are observed at HG levels where longevity is not yet affected. 8. Results are discussed in relation with Pearl's rate of living theory (1928).

Aging↗
PubMedDate not supplied

Hypergravity and aging in Drosophila melanogaster: 7. New longevity data.

Longevity of mated and virgin Drosophila melanogaster flies was observed at various gravity levels (1-7.38 g). A slight longevity decrease was observed in the 1-5.14 g range for virgin males, and a larger one in the 5.14-7.38 g range. The effect of gravity was larger for females in the 1-5.14 g range, and at the highest gravity level, both sexes had roughly the same longevity, which however remained high (around 40 days). The longevity of mated flies was lower than that of virgins at 1 g, and only a slight longevity decrease was observed in the 1-7.38 g range in females, this decrease being larger for males. Hypergravity appears to have no dramatic effects on life span and to be of lower importance than the simple effect of mating. This study confirms previous results obtained in the 1-5.02 g range with virgin flies (Le Bourg and Lints, 1989).

Animals↗
PubMed2005

Microchip separations in reduced-gravity and hypergravity environments.

Microfabricated fluidics technology, e.g., lab-on-a-chip devices, offers many attractive features for performing chemistry and biochemistry on space-based platforms. We have constructed a portable, battery-operated microfluidic platform that was tested under reduced gravity and hypergravity conditions that would be experienced in space flight and launch. This device consisted of a microchip, microchip holder, two 0-8-kV high-voltage power supplies, a high-voltage switch, a solid-state diode-pumped green laser, an optical train, a channel photomultiplier, and an inertial mass measurement unit all under the control of a laptop computer and powered by 10 D-cell alkaline batteries. The unit was tested on NASA's reduced gravity research aircraft at gravity levels that are relevant to NASA's intended use of bioreporter-based microchips for environmental monitoring of space and planetary environments on manned and unmanned spacecraft. Over the course of two flights, 834 fast electrophoretic separations of four amino acids were performed under a variety of gravitational environments including zero-g, Martian-g, lunar-g, and approximately 1.8-g. All separations were performed in less than 12 s and automatically analyzed. After correction with an internal migration standard, the migration time reproducibilities were all <1% relative standard deviation.

Journal Article↗
PubMed1983

Hypergravic fields and parallel controllers for thermoregulation.

To test the proposal that mammals have parallel neurocontrollers for temperature regulation, Long-Evans hooded male rats were exposed to cold while in a 3-G field. When exposed to cold, these rats consumed 35% less oxygen/min at 3 G than they did when exposed to cold at 1 G. However, rats acclimated for 6 wk to 5 degrees C consumed oxygen at the same rate during cold exposure at 3 G as at 1 G. Because cold-acclimated rats generate heat primarily by nonshivering thermogenesis while rats acclimated to room temperature rely to a greater extent on shivering, the 35% decrease in oxygen consumption of cold-exposed room-temperature rats in 3-G fields may reflect an inactivation of shivering. These oxygen consumption measurements, together with measurements of core and tail temperatures of rats in 3-G fields, are consistent with the proposal that neurocontrollers for thermoregulation are arranged in parallel and can be uncoupled by hypergravic fields.

Acclimatization↗
PubMed1988

Effects of hypergravity environment of the ultrastructure of the golden hamster parathyroid gland.

The fine structure of the parathyroid glands of golden hamsters exposed to 2, 5 or 10 g environment for 5 h was studied. In the centrifuged hamsters, many secretory granules are located in a peripheral position just beneath the plasma membrane of chief cells, and the Golgi complexes and cisternae of the granular endoplasmic reticulum are significantly increased compared with those of control animals. There are no significant differences between the control and centrifuged animals with regard to secretory granules, large secretory granules, lysosomes, vacuolar bodies and lipid droplets. These findings suggest that the secretory activity of the parathyroid gland may be stimulated in response to hypergravity environment.

Animals↗
PubMed1992

Ultrastructure of the parathyroid gland of fetal and pregnant golden hamsters subjected to hypergravity environment.

The ultrastructure of the parathyroid glands of fetal and pregnant golden hamsters exposed to 5-gravity environment was studied. In the centrifuged fetal animals the Golgi complexes associated with some prosecretory granules were significantly increased compared with those of the control fetal animals, and several secretory granules were located in a peripheral position just beneath the plasma membrane. In the centrifuged pregnant animals the Golgi complexes associated with numerous prosecretory granules were significantly increased, cisternae of the granular endoplasmic reticulum appeared to be increased compared with those of the control pregnant animals, many secretory granules were located in the peripheral cytoplasm and several granules were situated close to the plasma membrane. These findings suggest that in the parathyroid glands of the fetal golden hamsters as well as the pregnant animals the synthesis and release of parathyroid hormone may be stimulated in response to a hypergravity environment.

Animals↗
PubMed1989

Hypergravity and ageing in Drosophila melanogaster. 1. Fecundity.

In Drosophila melanogaster daily fecundity has been recorded throughout life of flies kept at various gravity levels (1-5 g). Hypergravity (HG) did not decrease total fecundity but modified its expression during life. The 1 g group could be opposed to the various HG groups, i.e. a clear regression of the various fecundity items on the HG level could not be disclosed. Results are discussed in relation with Pearl's rate of living theory.

Aging↗
PubMed1989

Hypergravity and ageing in Drosophila melanogaster. 2. Longevity.

Longevity of Drosophila melanogaster flies was observed at various gravity levels in three different breeding conditions of decreasing quality. A slight longevity decrease was observed in the 1-4 g range of the two best conditions. In the third one, a large decrease was observed in all hypergravity groups. Longevity decreased at 5 g in the first two groups (no data collected for the third one). Results are discussed in relation with Pearl's rate-of-living theory.

Aging↗
PubMed1989

Hypergravity and ageing in Drosophila melanogaster. 3. Viability.

The viability of Drosophila melanogaster was measured in three conditions: (1) of eggs from parents living at different gravity levels (1-5 g), developed at 1 g; (2) of eggs from parents living at 1 g, developed at different gravity levels, and (3) of eggs developed at the gravity at which their parents were kept. Hypergravity (HG) decreased viability to a low extent in all three cases (75% of emergence in the worst case). The effects of keeping parent flies in HG and of growing their offspring in HG were not cumulative. The results are discussed in relation with Pearl's rate of living theory.

Aging↗
PubMed1992

Hypergravity and aging in Drosophila melanogaster. 6. Spontaneous locomotor activity.

The spontaneous locomotor activity (SLA) of Drosophila melanogaster flies kept at various gravity levels (1-5 g) was recorded in both longitudinal and cross-sectional experiments. No gravity level effect could be detected in the longitudinal one, probably because these flies were allowed (for technical reasons) to rest at 1 g for 15% of their life. By contrast, flies kept at 5 g in the cross-sectional experiment had lower SLA scores at middle and old age than both 1 and 3 g-kept flies. The results of this series of experiments on hypergravity (HG) effects on three forms of locomotor activity (climbing activity, patterns of movement and SLA) allow to conclude that aging is accelerated in HG, even if no longevity decrease could be detected in the 1-4 g range.

Aging↗
PubMedDate not supplied

[Effect of accelerations, hypergravity and hypokinesia on protein metabolism in Japanese quail. I. Effect on muscle composition].

The effect of hypokinesia, hypergravity achieved by centrifugation and additional weight load on the content and composition of proteins and nucleic acids in the chest and pelvic muscles of four groups of quails (Coturnix coturnix japonica) was studied. The first group was used as controls, the second included hypokinetic birds, the third was made of birds with an additional weight load (the load was a double weight of the animal) and the fourth group included birds exposed to acceleration of 3 g. The birds were exposed to the above effects for 1 to 6 hours during 8 days. They were given identical food through forced feeding. The content of total proteins, sarcoplasmatic proteins, DNA and RNA, cholesterol and esterified fatty acids was measured in chest and pelvic muscles. The composition of total lipids was examined in pelvic muscles. The level of corticosterone was determined in the blood plasma. The above experimental variants made it possible to discriminate individual contributions of acceleration, additional weight load and hypo-inesia to the effect. Weight load and acceleration decreased and hypokinesia increased the content of total proteins in the pelvic muscles. During an exposure to acceleration and hypokinesia the content and the portion of sarcoplasmatic proteins decreased and during an exposure to weight load increased significantly. Acceleration did not exert a significant effect on the RNA and DNA content in muscles. The content of esterified fatty acids increased under the influence of acceleration and hypokinesia and decreased significantly under the influence of additional weight.

Acceleration↗
PubMed2002

Neurobehavioural responses to hypergravity environment in the CD-1 mouse.

Behavioural responses of CD-1 mice exposed to 2 g hypergravity (HG; 60 or 120 min) were investigated during adolescence and at adulthood. To characterise motion sickness (MS), pica behaviour, a reliable MS index measured through kaolin consumption, and spontaneous activity were evaluated before, during and after HG exposure. Short- and/or long-lasting effects on emotional responses, exploratory behaviour and spatial learning performances were also investigated and brain levels of nerve growth factor (NGF) and brain derived neurotrophic factor (BDNF) assessed. An increased pica behaviour during post rotational days and a reduction in spontaneous activity during rotation indicated a mild sickness associated with HG, and susceptibility to MS was sex and age related. Short- and long-lasting effects of exposure were also observed, rotated mice showing altered emotional/anxiety behavioural profiles and impaired spatial learning performances. Moreover, central NGF levels were markedly increased after rotation, while minor changes were observed in BDNF levels.

Research Support, Non-U.S. Gov't↗
PubMed2002

Influence of hypergravity on hypothalamic vasopressin and oxytocin neurons in rats.

This study was aimed to evaluate the reaction of the vasopressin (VP) and oxytocin (OT) neurons of the supraoptic nucleus (SON) in rats to single or repeated hypergravity (HG). Special attention was paid to the tyrosine hydroxylase (TH) expression in VP neurons as a marker of the neuron activation. Rats were revolved in a centrifuge with overloading 2G for 5 days or 34 days as well as for 34 days plus 5 days with an interval of 39 days between two rotations. Control rats were kept in a centrifuge room. Radioimmununoassay, quantitative and semi-quantitative immunocytochemistry and in situ hybridization were used to evaluate: a) VP concentration in the pituitary posterior lobe (PL) and in plasma; b) the number of VP-, OT- and TH-immunoreactive neurons in the SON; c) the optic density of VP-, OT- and TH-immunoreactive materials in cell bodies (SON) and distal axons (PL), d) the optic density of VP and OT mRNAs signals (S35) in the whole SON on microfilms. According to our data, VP neurons were strongly activated during HG (5 days or 34 days) that was manifested in the functional hypertrophy of the neurons, greatly increased concentrations of VP mRNA in the SON and VP in plasma, the onset of the TH expression. The neurons showed initially (5 days) the functional insufficiency (VP release > VP synthesis) followed by their adaptation (subsequent 29 days) to the increased need in VP (VP release < VP synthesis). No reaction of VP neurons was observed to repeated HG. In contrast to VP neurons, OT neurons did not react to short-term HG or showed functional depression after the long-term treatment.

Journal Article↗
PubMed2002

Influence of 2G-hypergravity on the right atrium secretory cardiomyocytes of rats.

For elucidation of secretory cardiomyocytes adaptation to prolonged and repeated influence of changed gravity the ultrastructural and morphometrical analysis of right atrium cells was made in rats after they were exposed to primary and repeated 2G-centrifugation in ground-based experiment. It was found prolonged 2G-hypergravity resulted in hypertrophy of right atrium cardiomyocytes and stimulated of their mitochondrial associative activity and granular secretion; repeated influence induced changes differed from those after single influence.

Journal Article↗