Effects Of Hypergravity Research Articles

Early Amphibian (Anuran) Morphogenesis Is Sensitive to Novel Gravitational Fields

Anuran amphibian embryos ( Xenopus laevis and Rana dybowskii) are sensitive to novel gravitational fields. Under simulated weightlessness, (i) the location of the first horizontal cleavage furrow was shifted toward the vegetal pole at the eight-cell stage; (ii) the position of the blastocoel was more centered, and the number of cell layers in the blastocoel roof was increased at the blastula stage; (iii) the dorsal lip appeared closer to the vegetal pole at the gastrula stage; and (iv) head and eye dimensions were enlarged at the hatching tadpole stage. Effects of simulated hypergravity were opposite to those of simulated weightlessness, except that hypergravity, unlike simulated weightlessness, reduced the number of primordial germ cells in feeding tadpoles. Despite those dramatic differences in the early embryogenesis, tadpoles at the feeding stage are largely indistinguishable from controls.

Enhancing Effect of Hypergravity on Development of Cardiac and Skeletal Muscles of Chick Embryos

Fertilized eggs of White Leghorn chickens were incubated for 11 days at 37°C in normal condition and then for 7 days under hypergravity (2G) induced by centrifugation. Then the morphologies of muscles isolated from their heart ventricle and femur were examined. The cardiac and skeletal muscle cells of the 2G-group were more densely packed and regularly organized than those of the control group. Collagen and lattice fibers were also more abundant in stroma of the 2G-group. Electron microscopical studies showed that after hypergravity treatment, muscle cells contained a larger number of myofibrils forming larger bundles with clear electron dense Z-bands in the cytoplasm. These results show that hypergravity enhances the development of muscle cells.

Changes in the utricular otoconia of the chick embryo developed under 2G-gravity

Whether or not vestibular adaptation occurs upon exposure to altered gravity is an important human problem. Studies have been performed to ascertain whether morphological changes in vestibular organs occur in animal models upon exposure to microgravity. On the other hand, the morphological changes which occur in vestibular organs under hypergravity have not yet been fully elucidated and morphological changes in the otoconia of the chick embryo exposed to hypergravity during the embryonic period remain to be thoroughly examined. The purpose of this paper is to clarify the effects of hypergravity on vestibular organs, especially its effects on otoconial formation in the developing chick embryo. Thus, we designed an apparatus which creates artificial gravity, creating approximately 2G gravity by means of centrifugation. The utricular macula was chosen for study because it can be prepared for examination with a minimum of dissection artifacts. The data presented show that morphological changes were confined to otoconial size alterations according to scanning electron microscopic observations. Giant otoconia were observed along the marginal zones of utricle .

Inhibitory effect of hypergravity on the bone resorption of chick and rat embryonic bone

Inhibitory effect of hypergravity on the bone resorption of chick and rat embryonic bone

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.

Synaptic plasticity and gravity: ultrastructural, biochemical and physico-chemical fundamentals.

On the basis of quantitative disturbances of the swimming behaviour of aquatic vertebrates ("loop-swimming" in fish and frog larvae) following long-term hyper-g-exposure the question was raised whether or not and to what extent changes in the gravitational vector might influence the CNS at the cellular level. Therefore, by means of histological, histochemical and biochemical analyses the effect of 2-4 x g for 9 days on the gross morphology of the fish brain, and on different neuronal enzymes was investigated. In order to enable a more precise analysis in future-microgravity-experiments of any gravity-related effects on the neuronal synapses within the gravity-perceptive integration centers differentiated electron-microscopical and electronspectroscopical techniques have been developed to accomplish an ultrastructural localization of calcium, a high-affinity Ca2(+)-ATPase, creatine kinase and cytochrome oxidase. In hyper-g animals vs. 1-g controls, a reduction of total brain volume (15%), a decrease in creatine kinase activity (20%), a local increase in cytochrome oxidase activity, but no differences in Ca2+/Mg(2+)-ATPase activities were observed. Ultrastructural peculiarities of synaptic contact formation in gravity-related integration centers (Nucleus magnocellularis) were found. These results are discussed on the basis of a direct effect of hyper-gravity not only on the gravity-sensitive neuronal integration centers but possibly also on the physico-chemical properties of the lipid bilayer of neuronal membranes in general.

Effects of hypergravity on proliferation and differentiation of osteoblast-like cells

We investigated the effects of hypergravity on DNA synthesis and alkaline phosphatase (ALP) activity in cloned osteoblast-like cells. MC3T3-E1. Hypergravity (5 × g) stimulated DNA synthesis in these cells in a time-dependent manner and increased it approximately up to 150% of that of the control (1 × g). 12- O-Tetra-decanoylphorbol-13-acetate (TPA), a protein kinase C activator, and insulin-like growth factor I (IGF-I) enhanced DNA synthesis additively with hypergravity (5 × g). An increase in ALP activity induced by 10% fetal calf serum (FCS) was suppressed by hypergravity (2 × g, 5 × g). Five × g completely suppressed the increase in ALP activity. TPA and hypergravity (2 × g) suppressed the increase in ALP activity induced by FCS additively. Hypergravity (5 × g) showed no significant effect on cAMP nor cGMP production in these cells, but increased prostaglandin E 2 (PGE 2) production. Exogenous PGE 2 stimulated DNA synthesis in these cells but had little effect on 10% FCS-induced ALP activity. These results suggest that hypergravity stimulates proliferation but suppresses differentiation of osteoblast-like cells through a pathway independent of the activation of protein kinase C and the production of cyclic nucleotides, and that hypergravity and IGF-I stimulate proliferation of these cells through an independent signal transduction pathway. Moreover, our data strongly suggest that PGE 2 mediates the signalling of hypergravity on the proliferation of osteoblast-like cells.

Effects of Hypergravity to Human Body

Effects of Hypergravity to Human Body

Effects of gravitational profiles on the rat's thermoregulatory response to cold.

Unrestrained rats were subjected to a 1-h period of cold exposure during centrifugation to characterize their ability to regulate core temperature (Tc) and to determine if this regulation was dependent on the amplitude of the hypergravic field before the cold exposure. Tc was measured in unrestrained rats by the use of a thermistor implanted adjacent to the carotid artery. One hour of cold exposure applied over the last hour of either a 1-, 4-, 7-, 13-, 19-. 25-, or 37-h period at 3 G evoked a decrease in Tc of about 3 degrees C. This fall in Tc was significantly greater than changes in Tc in cold-exposed rats at 1 G. No significant differences were found between the measured decreases in Tc observed for the 1-h cold exposures during the first 37 h at 3 G. However, when rats were subjected concurrently to cold and acceleration after 8 days at 3 G, they exhibited a smaller fall in Tc, suggesting a partial recovery of the acceleration-induced impairment of temperature regulation. In another series of experiments, the gravitational field profile was changed in amplitude in three different ways during the 3-h period preceding the 1-h cold exposure at 3 G. Despite the different gravitation field profiles before cold, the magnitude of the fall in Tc over the 1-h period of cold exposure was the same of all cases. These results suggest that the thermoregulatory impairment has a rapid onset, it a manifestation of an ongoing effect of hypergravity, and is not dependent on the prior G profile. The inability of rats to maintain Tc when cold exposed may be transient as indicated by the partial recovery of regulation by the 8th day.

Effects of hypergravity on rat fertillity, pregnancy, parturition and survival.

The effect of persistent centrifugation at a relatively low gravitational force of 1 to 1.47 X g on the fertility, pregnancy, delivery, and survival of rats was studied. The longevity of the adult rats was not apparently affected by the experimental conditions, but that of the newborns was significantly (p less than .005) shortened. There was also a tendency for females to abort which appeared to be related, in part, to the length of gestation at the beginning of the experiment. The degree of damage increased as the distance from the axis of the centrifuge apparatus increased. Male fertility was also impaired following removal from the apparatus.

Effect of chronic centrifugation on the structural development of the musculoskeletal system of the rat.

25 female Sprague-Dawley rats were placed on a 3.66 m radius centrifuge and subsequently exposed almost continuously for 810 days to 2.76 G. Compared to normal gravity controls, the most noticeable effect of hypergravity was the inhibition of growth of the centrifuged animals. The rats exposed to hypergravity showed on average a smaller femur length (-6.5%), a smaller cross-sectional area (-7.7%, when expressed linearly, i. e. (area/pi)1/2), and smaller outer and inner cross-sectional radii (linearly -9.3% and -12.3%) at the mid-shaft of the femoral bones. The growth inhibition of 3 hind-leg muscles was on average significantly less ranging from (-3.5% to -4.1%), compared to the growth inhibition of the linear dimension of the femur. Statistically there was no difference in the slope and elevation of the regression of the square-root of the cross-sectional area divided by pi on the length of the femur between centrifuged animals and their 16 age matched controls. In the weight control group of 24 animals, comprised of 34,74, and 102 day old rats, the corresponding regression line was parallel and lower in elevation by -12.8%, compared to the line for the centrifuged and age control groups. But, compared to the regression derived from all control animals ranging from 34 to 840 days of age, the cross-sectional area at the mid-shaft of the femur was 8.4% greater in the rats exposed to 2.76 G for 810 days. The slopes of the regression of the outer radius at mid-shaft on the length of the femur were the same in the centrifuged group and in the weight and age control groups of animals. But, the regression lines differed in elevation by -4.4% on average between the centrifuged and age control animals. The line for the regression of the inner radius at the mid-shaft on the length of the femur was parallel and lower in elevation by -7.6% in the centrifuged animals compared to the line for the age controls. But, compared to all control animals living at normal gravity, the outer radius was increased by 3.0% and the inner radius was decreased by 5.7% in the animals exposed to 2.76 G for 810 days. Since the centrifuged animals were all 840 days old, while the controls were from 34 to 840 days old, only further experiments comparing centrifuged and control animals of the same age at various growth stages will be able to furnish evidence for an unambiguous bone hypertrophy. The regressions of the cube-root of body weight on length of the femur deviate significantly in the 3 groups of animals. The heavier rats of the age control group have relatively shorter femurs than the lighter animals. The opposite applies to the centrifuged and the weight control groups of rats. Although the rats on the centrifuge are markedly smaller in overall body size than the controls, they exhibit on average the same absolute muscle weights as the animals at earth gravity, if rats of the same overall body size are compared...

Effects of chronic rotation and hypergravity on muscle fibers of soleus and plantaris muscles of the rat

Three lines of F 3 Sprague-Dawley rats derived from a single mating were raised either outside the centrifuge at earth gravity (earth control), or under chronic rotation in the center of the centrifuge at 1.03 g (rotation control), or in the rim of the centrifuge at 2 g (rotation experimental). The rats were killed at 3 months of age, and serial sections of plantaris and soleus muscles were stained for succinic dehydrogenase activity, and for actomyosin ATPase activity following preincubation at pH 10.2. Muscle fibers in a cross-sectional unit area of soleus and both the superficial and deep regions of plantaris were identified as to fiber type according to an enzyme profile and counted. The proportion of each fiber type was calculated, and the diameter of 24 fibers of each type was measured. Analysis of variance was used to determine the effect of experimental treatment and sex on populations and diameters. In soleus, the fiber population shifted from 82% slow oxidative fibers in the controls to 100% slow oxidative fibers in the rotation experimentals in response to the stress of hypergravity. In plantaris, chronic rotation resulted in an increase in fast glycolytic fibers and a corresponding decrease in fast oxidative glycolytic fibers, in both the rotation control and experimental rats. The population changes were similar in both sexes. Muscle fiber diameters were similar in both controls, indicating no response to the stress of chronic rotation. A sexual dichotomy was noted in response to hypergravity, with muscle fiber diameters increasing in females, but decreasing in males.