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PubMed1991

[Effects of hypergravity on migration, proliferation and function of mouse osteoblastic cell line MC3T3-E1].

The purpose of this study was to investigate the hypergravity-induced responses and their mediators of osteoblastic cell line, MC3T3-E1. The synchronized G1 or the S Phase cells were exposed to 5 and 18 x g hypergravity at 37 degrees C. The migration velocity was measured and the morphology was observed. MC3T3-E1 cells were cultured for 1, 2 or 3 days at 37 degrees C, exposing to 5, 10, 20 and 40 x g hypergravity. The proliferation, prostaglandin E2 (PGE2) production rate and alkaline phosphatase (ALPase) activity were measured. The results were as follows: 1) In the G1 phase of the cell cycle, the migration of MC3T3-E1 cells was increased by 18 x g. In the S phase, the morphology altered depending on the g-stress. 2) The proliferation of MC3T3-E1 cells was enhanced at 20 and 40 x g but reduced at 10 x g. The proliferation of HeLa cells and JTC-12 cells was also enhanced at 40 x g. 3) Indomethacin (10(-5)M) reduced the proliferation of MC3T3-E1 cells induced by 40 x g. But indomethacin (10(-5)M) did not reduce the proliferation of HeLa cells. 4) The increase of the released PGE2 from the cells depended on the time (1-8h) and the gravity (1-40 x g). 5) The increase of the ALPase activity of MC3T3-E1 cells also depended on the gravity. These results suggest that the hypergravity enhanced the proliferation of MC3T3-E1 cells via PGE2-mediated mechanism.

Alkaline Phosphatase↗

PubMed1990

Electron microscopic study of the parathyroid gland of the calcium-treated hamster subjected to hypergravity environment.

The ultrastructure of the parathyroid glands of calcium-treated golden hamsters subjected to 5 gravity environment was studied. In the calcium-treated animals exposed to hypergravity environment, the Golgi complexes and cisternae of the granular endoplasmic reticulum were significantly decreased compared with those of the animals exposed to hypergravity environment only and appeared to increase compared with those of the calcium-treated animals, but were almost similar to those of the control animals. In addition, many chief cells contained some prosecretory granules in the Golgi areas, some secretory granules situated close to the plasma membrane and many lysosomes. The morphology of the parathyroid glands in the calcium-treated animals exposed to hypergravity environment resembled that of the control animals. These results suggest that the parathyroid glands suppressed by treatment of calcium and stimulated in response to hypergravity environment may indicate the secretory activity of the parathyroid glands of the control animals.

Animals↗

PubMed1986

Effects of hypergravity on "whole-blood" cultures of human lymphocytes.

The purpose of this paper is to present a detailed description of the effects of hypergravity on the mitogenic response of human lymphocytes to concanavalin A. The effect on cultures of lymphocytes isolated from peripheral blood are compared with those on whole-blood cultures obtained by diluting fresh blood with culture medium 1:10. Whole-blood cultures of lymphocytes from crew members will be investigated inflight on the Spacelab missions D-1 in 1985 and SLS-1 in 1987. In hypergravity there is an increase in lymphocyte activation of up to 500%. A similar increase can be induced by pre-incubating the cultures in hypergravity prior to exposure to concanavalin A at 1 G. The effect is less evident in cultures of isolated lymphocytes. The influence of autologous plasma and erythrocytes has also been investigated. Plasma and hypergravity have a synergistic and positive effect on lymphocyte activation, i.e. cultures of separated lymphocytes show the highest activation when incubated at 10 G and supplemented with autologous plasma. Conversely, erythrocytes depress lymphocyte activation.

Adaptation, Physiological↗

PubMed1980

Hypergravity and estrogen effects on avian anterior pituitary growth hormone and prolactin levels.

Developing female chicks with fractured right radii were maintained for 14 d at either earth gravity (1 G) or a hypergravity state (2 G). The birds at 1 G were divided into groups which received daily injections of 1) saline, 2) 200 micrograms estrone, and 3) 400 micrograms estrone for 14 d. The 2-G birds were divided into three similarly treated groups. All 2-G birds showed significantly lower body weights than did 1-G birds. Anterior pituitary (AP) glands were excise; and analyzed for growth hormone and prolactin content by analytical electrophoresis. The 1-G chicks receiving either dose of daily estrogen showed increased AP growth hormone levels, whereas hypergravity alone did not affect growth hormone content. Chicks exposed to daily estrogen and hypergravity displayed reduced growth hormone levels. AP prolactin levels were slightly increased by the lower daily estrogen dose in 1-G birds, but markedly reduced in birds exposed only to hypergravity. Doubly-treated chicks displayed normal prolactin levels. Reduced growth in 2-G birds might be due, in part, to reduced AP levels of prolactin and/or growth hormone.

Animals↗

PubMed1996

Regeneration of guinea pig facial nerve: the effect of hypergravity.

Exposure to moderate hypergravity improves the regenerative capacity of sectioned guinea-pig facial nerve. The improvement in regeneration is tri-directional as follows: a) an average 1.7 fold increase in rate of regeneration in guinea pigs subjected to hypergravity; b) a 25% enhancement of facial muscle activity following the exposure to hypergravity; and c) improvement in the quality of regeneration from an esthetic standpoint. A good correlation was recorded between the histological structure of the severed nerve at the end of the regeneration and the clinical results.

Animals↗

PubMed1996

Otoconial alterations after embryonic development in hypergravity.

The relation between prolonged hypergravity and structural adaptation of otoconia was studied in hamsters (n = 56). Three groups of hamsters (n = 27), were conceived and born in a centrifuge: group 1 (n = 10) 1 month under 2.5 G, group 2 (n = 9) 5 months under 2.5 G and 4 months under 1 G, group 3 (n = 8) 1 month under 2.5 G and 8 months under 1 G. Control hamsters (n = 29) were conceived and born under 1 G (1 month old, n = 7; 9 months old, n = 22). Histological study of the otoconial layers (energy dispersive x-ray element analysis and scanning electron microscopy) showed similar calcium content, size, and shape in utricular and saccular otoconia in all groups. Different were the utricular otoconial size classes, large, medium-sized, and small. The area with small otoconia increased in group 1 (p = 0.002). In group 2, the large otoconial area decreased (p = 0.001) and the medium-sized one increased (p < 0.001). In group 3, the large otoconial area decreased (p = 0.003) and the medium-sized one increased (p = 0.007). For age-related effects we found group 1 with an increased area of large otoconia (p = 0.001) and a decreased medium-sized one compared to groups 2 (p < 0.001) and 3 (p = 0.02). Hypergravity during formation of otoconia does not affect calcium content, size, or shape, but changes relative size of the areas with large, medium-sized, or small otoconia and the development of these areas. This resulted in a structural adaptation to hypergravity.

Animals↗

PubMed1998

Ultrastructural aspects of otoliths and sensory epithelia of fish inner ear exposed to hypergravity.

The present electron microscopical investigations were directed to the question, whether alterations in the gravitational force might induce structural changes in the morphology of otoliths or/and inner ear sensory epithelia of developing and adult swordtail fish (Xiphophorus helleri) that had been kept either under long-term moderate hypergravity (8 days; 3g) or under short-time extreme hypergravity (10 minutes up to 9g). The otoliths of adult and neonate swordtail fish were investigated by means of scanning electron microscopy (SEM). Macular epithelia of adult fish were examined both by SEM and transmission electron microscopy (TEM). The saccular otoliths (sagittae) of normally hatched adult fish revealed an enormous inter- (and even intra-; i.e. left vs. right) individual diversity in shape and size, whereas the otoliths of utricles (lapilli) and lagenae (asterisci) seemed to be more constant regarding morphological parameters. The structural diversity of juvenile otoliths was found to be less prominent as compared to the adults, differing from the latter regarding their peculiar crystalline morphology. Qualitative differences in the fine structure (SEM) of otoliths taken from adult and larval animals kept under 3g in comparison to 1g controls could not be observed. The SEM and TEM investigations of sensory epithelia also did not reveal any effects due to 3g stimulation. Even extreme hypergravity (more than 7g) for 10 minutes did not result in distinct pathological changes.

Aging↗

PubMed2002

Effects of hypergravity on the morphological properties of the vestibular sensory epithelium. I. Long-term exposure of rats after full maturation of the labyrinths.

The effect of prolonged exposure to hypergravity on the morphology of vestibular epithelia of rats was investigated. At the age of 1 month, i.e., when vestibular end organs are fully maturated, three rats were transferred to a hypergravity environment of 2.5 g inside a large radius centrifuge. After 9 months, vestibular epithelia of these animals and of three control animals were immunohistochemically labeled for actin and tubulin. The apical cross-sectional area of epithelial cells of hypergravity exposed rats appeared to be smaller in all end organs. Area reduction was 1.9% in the saccule (not significant), 5.0% in the utricle (p < 0.005), and 11.6% in the crista (p<<0.001). No indications for a deterioration of vestibular functioning were observed.

Actins↗

PubMed1997

Altered behaviour in hamsters conceived and born in hypergravity.

We studied vestibular function in 37 hamsters (1 month old) conceived and born in either hypergravity (n = 21) or normal gravity (n = 16). Four groups were made: (1) HL group: 20 weeks in 2.5 G and 14 weeks in 1 G; (2) HS group: 4 weeks in 2.5 G and 30 weeks in 1 G; (3) CON group: 34 weeks in 1 G; and (4) ROT group: 4 weeks in 1 G, 16 weeks in rotation in 1 G, at the centre of the centrifuge and 14 weeks 1 G. When the hamsters were 4 weeks old, their locomotor activity, swimming ability, and air-righting was assessed. We found that HL and HS hamsters had no disturbances during locomotion in 1 G but their swimming ability was disturbed (swimming underwater, circling, and decreased speed of swimming). The HL hamsters showed less activity during 2.5 G and showed fewer correct air-rightings than the other groups. Differences between groups in swimming ability and the number of correct air-righting responses remained even after 3 months of normal gravity. Based on these findings, we suggest that the persistent behavioural disturbances are caused by the embryonal development of the hamsters in a hypergravity environment. Furthermore, hypergravity and rotation each have a different effect on behaviour.

Age Factors↗

PubMed1999

A mild stress, hypergravity exposure, postpones behavioral aging in Drosophila melanogaster.

Flies were submitted to two weeks of hypergravity in a centrifuge (3 or 5 g), starting at the second day of imaginal life, and their behavior (spontaneous locomotor activity, patterns of movement, and climbing activity) was observed from removal of the centrifuge to an older age; the usual effects of age on these behaviors were generally observed. Hypergravity-kept flies had worse behavioral scores on removal of centrifuge than those always kept at 1 g. When they aged, they got either similar or better scores than 1 g flies, which indicates that their behavioral aging may be slower. These results show that a mild stress such as hypergravity, which has been previously shown to increase the longevity of males and resistance to heat shock in both sexes, is an environmental manipulation postponing aging in flies.

Aging↗

PubMed1995

Effect of hypergravity on vestibular compensation in guinea pigs.

The effect of hypergravity on vestibular compensation was studied in guinea pigs. Pharmacological labyrinthectomy was performed by injecting chloroform into the middle ear cavity under ether anesthesia. The guinea pigs were exposed to hypergravity on a centrifuge. The animals were divided into four groups: a group stimulated with 2G after labyrinthectomy of the right ear, a group stimulated with 2G after labyrinthectomy of the left ear to evaluate the influence of the centrifugal rotation, a group stimulated with acceleration and deceleration alone, and a control group which was maintained under similar conditions, but without centrifugation. Head deviation and nystagmus were recorded and analysed to assess the process of compensation at 1, 3, 5, 7 and 9 h after labyrinthectomy. The 2G-stimulated group showed faster compensation in head deviation than the control group. In this study, the hypergravity stimulation seemed to facilitate the compensation in head deviation.

Adaptation, Physiological↗

PubMed2001

[Altered behaviour and expression of Fos in rats born in hypergravity and their re-adaptation to the normal gravity].

Changes in behaviour relevant to the vestibular system were studied in Long-Evans rats which were fertilized, born and housed in 2 acceleration of gravity for 4 months and thereafter exposed to 1 acceleration of gravity, and expression of Fos protein in the brain stem was examined. Data from the hypergravity rats were compared respectively with those from the rotation group and the labyrinthectomized group. Static and locomotion modes of the hypergravity rats were changed, tension of extensor was enhanced and the abilities in locomotion equalization and orientation in swimming and air-righting response were reduced. The adaptation process varied with different behaviours. The time for recovery of the ability of orientating in swimming was the longest, taking more than 1 month. The Fos protein expression provides a useful tool for mapping brain functional activities after sensory stimulation, showing a low basal level in normal and labyrinthectomized groups. The hypergravity rats, on the other hand, exhibited more Fos-positive cells in the superior colliculus, inferior colliculus, periaqueductal gray, raphe dorsal nucleus and solitary nucleus. In contrast, the inferior olivary nuclei, locus coeruleus and vestibular nuclei were not strongly labeled. These spatial patterns of Fos expression suggest that a decrease in gravity-inertial force may activate a neural pathway different from the vestibulo-olivar pathways activated by an increase in gravity-inertial force.

Adaptation, Physiological↗

PubMed1993

Activity of ornithine decarboxylase in muscle of Japanese quail in hypergravity conditions.

Ornithine decarboxylase (ODC) is the rate limiting enzyme in the synthesis of polyamines which are generally required for animal cell proliferation. Because of many different stimuli changing the activity of ODC, the effect of hypergravity on muscle ODC activity in Japanese quail was investigated. Adult Japanese quail cockerels were exposed to 2G in the centrifuge permanently for 96 hours. The activity of ODC was determined by radioisotopic method in supernatant of homogenised breast and fibular muscles (m. pectoralis minor, m.superficialis fibularis). The activity of ODC was higher in breast muscle than in the fibular muscle in both, control and experimental groups. Exposition of quail to hypergravity evokes approximately 2 fold increase of ODC activity in both breast and fibular muscles. The results suggest that 96 hours of permanent hypergravitation (2G) caused activation of polyamine synthesis and their involvement in biochemical processes of adaptation to hypergravity.

Adaptation, Physiological↗

PubMed1998

Microgravity and hypergravity effect on survival and reproduction of microinvertebrates.

Preliminary to carry out long-term experiments on the International Space Station (ISS) using living orgainisms, the capacity of the experimental organisms to cope with perturbations of gravity should be tested. Actually, animals have evolved under gravity, because on earth gravity force cannot be eluded, and several features that influence life-history traits may be affected by the presence of gravity. Among the other features, feeding efficiency may be affected by gravity if the animals feed by filtering suspended particles, creating currents that carry the particulate food to their mouth opening. In presence of gravity the food particles tend to sink to the bottom and filter-feeders must be able to suspend and collect the particles with some apparatus such as ciliary wreaths. It can be predicted that hypergravity, increasing the particle sedimentation rate, will reduce the animal filtering efficiency, while microgravity will increase filtering rate. Differently, some bacteriophagous animals do not possess structures to collect their food, but commonly live and move into sediment and feed on the bacteria upon encounter. Hypergravity will apply higher pressure on their bodies, and could force them to adhere to some surface and to reduce their displacement, and microgravity could impede adhesion to the surface and make food item encounters improbable. Thus, gravity perturbations may affect animal life-history traits, such as survival or fecundity, by influencing their feeding efficiency. In this study we exposed a filter-feeding organism (Macrotrachela quadricornifera, Rotifera Bdelloidea) and a bacteriophagous one (Panagrolaimus rigidus, Nematoda) to both microgravity and hypergravity to test their reproduction capacity under such stressful conditions, and their suitability as models for experiments on the ISS.

Animals↗

PubMed2001

Stimulation of DNA polymerase alpha by hypergravity generated by centrifugal acceleration.

Gravity alteration is known to influence cell proliferation. Here we tested the effects of hypergravity on the action of DNA polymerase alpha, one of the DNA replication enzymes in eukaryotes. Hypergravity was produced by horizontal centrifugal acceleration with a hand-made rotator. The reaction rate of DNA polymerase alpha in centrifuge tubes increased along with the acceleration up to 4g, when a plateau was reached. In contrast, no stimulation was observed with primase, DNA polymerase epsilon, and the E. coli DNA polymerase I Klenow fragment. Kinetic analysis of DNA polymerase alpha reactions revealed that, under high gravity conditions, the K(m) value for template DNA decreased while the V(max) stayed constant. In contrast, the centrifugal acceleration did not affect the K(m) values for deoxyribonucleoside triphosphates. These results suggest that the hypergravity enhances the activity of DNA polymerase alpha by increasing the affinity of the enzyme for template DNA. Such enhancement was more prominent with a low concentration of DNA polymerase alpha under low ionic conditions.

Animals↗

PubMed1991

Hypergravity signal transduction in HeLa cells with concomitant phosphorylation of proteins immunoprecipitated with anti-microtubule-associated protein antibodies.

We have shown that hypergravity (35g) stimulates production of inositol 1,4,5-trisphosphate (IP3) and decreases adenosine 3',5'-cyclic monophosphate (cAMP) levels in HeLa cells. IP3 production rapidly increased 1.5- and 2.1-fold greater (P less than 0.05) than the control after 2- and 5-min exposures to 35g, respectively. The intracellular cAMP levels, determined in the presence of isobutylmethylxanthine, were decreased by 11% (P less than 0.05) and 16% (P less than 0.01) relative to the control after 10- and 20-min exposures to 35g, respectively. The phosphorylation of proteins which were immunoprecipitated by antibodies recognizing microtubule-associated proteins (ipMAPs) was also apparent after exposure of these cells to hypergravity. In the detergent-insoluble fraction, phosphorylation of a 115-kDa protein was significantly enhanced compared to the control after a 5-min exposure to 35g. In the detergent-soluble fraction, phosphorylation of a 200-kDa protein was observed served after a 20-min exposure to 35g. Our study suggests that IP3 and cAMP may act as second messengers in hypergravity signal transduction. Phosphorylation of ipMAPs in both the detergent-soluble and -insoluble fractions suggests that cytoskeletal structures may be influenced by gravity.

1-Methyl-3-isobutylxanthine↗

PubMed1989

Effects of hypergravity environment on the parathyroid gland of the propranolol-treated golden hamster.

The fine structure of the parathyroid glands of propranolol-treated hamsters subjected to 5 x gravity environment was studied. In the parathyroid glands of the propranolol-treated hamsters exposed to hypergravity environment, the volume density occupied by the Golgi complexes and cisternae of the granular endoplasmic reticulum was increased as compared to that of propranolol-treated hamsters and was decreased as compared to that of hamsters exposed to a hypergravity environment but was almost similar to that of control hamsters. In addition, many chief cells contained rich free ribosomes, abundant mitochondria and some secretory granules located in the peripheral cytoplasm. These findings suggest that the parathyroid gland which may be suppressed by treatment of propranolol and stimulated in response to a hypergravity environment indicates the secretory activity of the control parathyroid gland.

Animals↗

PubMed1991

Electron-microscopic study of the parathyroid gland of epinephrine-treated golden hamsters subjected to hypergravity environment.

The ultrastructure of the parathyroid glands of golden hamsters subjected to 5-gravity environment after administration of epinephrine was studied. In the epinephrine-treated animals exposed to a hypergravity environment, the Golgi complexes associated with numerous prosecretory granules were significantly increased compared with those of the control, centrifuged and epinephrine-treated animals, as well as the cisternae of the granular endoplasmic reticulum compared with those of the control and centrifuged animals. In addition, many secretory granules were situated close to the the plasma membrane of the chief cells in the epinephrine-treated animals exposed to a hypergravity environment. Those observations suggest that the secretory activity of the parathyroid gland may be markedly stimulated in the epinephrine-treated animals exposed to a hypergravity environment.

Animals↗