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At least 271 records · Page 15Linked to original sources
PubMed2002

Responses of rat left ventricle cardiomyocytes to constant 2G-hypergravity.

2G-hypergravity during 33-days led to hypertrophy of cardiomyocytes (CMC) in rat left ventricle accompanied by capillary number and diameter growth. CMC ultrastructure was normal at all experimental stages. Number of intermitochondrial junctions (IMJ) rose after 33 days of 2G in subsarcolemmal pericapillary zone of CMC, indicating probably to enlarged CMC energy needs. Changes in myocardium achieved during 33 days of 2G were reversible at 39 days of 1G (except IMJ number). Repeated 5-days 2G influence (after 33 days of primary 2G influence followed by 39 days of 1G) led again to CMC hypertrophy and to IMJ number rise in all zones of mitochondria localisation. Primary 5-days 2G influence didn't result in CMC hypertrophy, IMJ number rose only in subsarcolemmal pericapillary zone.

Journal Article↗
PubMed2002

Effects of hypergravity exposure on plasma oxytocin concentration in pregnant and lactating rat dams.

Rat dams and offspring were exposed to 1.5-g, 1.75-g or 2.0-g hypergravity (hg) from gestational day [G] 11 until postnatal day [P] 10. To ascertain the role of maternal factors in reduced postnatal body weights of offspring developed in hg, the dams' lactational hormones were measured. Oxytocin (OT), the major hormone responsible for milk ejection, was reduced in hg dams whereas prolactin (Prl), involved in milk production, was unchanged. Video analyses of nursing behavior revealed that hg dams spent more time nursing relative to 1-g controls. We hypothesized impaired milk transfer from dam to pup, however pup body weight gains following a discrete suckling episode were comparable across conditions. Changes in lactational hormones and nursing behavior by dams exposed to hg do not account for reduced body masses of their offspring.

NASA Center ARC↗
PubMed2002

Effects of microgravity and hypergravity on early development stages of Xeonopus laevis.

The aim of this work is to evaluate the development of X.l. in modified gravity conditions. The simulation of hyper and microgravity was performed utilizing: an hyperfuge, a Clinostat and later on a Random Positioning Machine (RPM, 3d Clinostat). The effect of hypergravity on embryos is significantly higher than that of microgravity; the exposure of embryos to 3xg for 3 days before and after hatch causes an activation of HSP-60 and HSP-70. Embryos exposed to 3xg during the first 3 days of development are very sensitive and show a retard of development, with a lower content of DNA, neutral glycolipids and gangliosides compared to controls.

Journal Article↗
PubMedDate not supplied

[Dehydrogenase activity of the liver in rats following 30 days' exposure to hypergravity].

In response to 30-day centrifugation at 2.0 or 1.1 G rats showed decreases in liver mitochondrial and cytoplasmic NAD-dependent malate dehydrogenase and NADH-dependent isocitrate dehydrogenase. These changes can be considered as a decline of energetic and biosynthetic processes in the liver in response to hypodynamics and hypergravity. After cessation of centrifugation the liver enzymes returned to the pretest level: cytoplasmatic dehydrogenases on the 2nd day and mitochondrial malate dehydrogenase on the 7th day of recovery.

Animals↗
PubMed1988

Ocular torsion in upright and tilted positions during hypo- and hypergravity of parabolic flight.

Four subjects considered resistant to motion sickness were tested in KC-135 parabolic flight to examine ocular torsion at hypo- and hypergravity. Three of these showed no significant torsion at zero G in either the upright position or when tilted 30 degrees to right or left. At 1.8 G in the tilted positions they showed greater ocular counterrolling than at 1 G. None of these three subjects became motion sick. The fourth subject showed eye torsion toward his left in all positions at zero G. This leftward bias could also be seen at 1.8 G when tilted left ear down, the side that induces rightward counterrolling. There he had less eye torsion than at 1 G. This subject became motion sick. All subjects had normal counterrolling in ground-based testing. These results support the hypothesis that asymmetry of the utricular system may be well compensated in the normal 1 G environment, but unmasked in unaccustomed gravitational situations, suggesting a possible predictive test for space adaptation syndrome.

Adult↗
PubMed1985

Hypergravity induced prolactin surge in female rats.

Acute initial exposure to hypergravity (HG) was previously found to induce prolonged diestrous in rats, which was followed by return to normal estrous cycling upon more prolonged exposure to continuous HG. Bromergocryptine was found to prevent this prolonged diestrous. In this study we found that in female rats 20 h of 3.14 G exposure (D-1 1200 h until D-2 0800 h) can induce prolactin surge at D-2 1600 h. Shorter exposure time (8 h), or exposure during a different part of the estrous cycle (19 h: from D-1 0700 h until D-2 0200 h) could not elicit this prolactin surge. Similar exposure of male rats to HG did not alter significantly their prolactin levels. It is possible that the hypothalamus of male and female rats responds differently to stimulation by HG.

Animals↗
PubMed1984

Hypergravity effects on litter size, nursing activity, prolactin, TSH, T3, and T4 in the rat.

Hypergravity (HG) adapted rats were tested for mating ability, gestational time, fetal and newborn mortality, and nursing performances. Plasma and pituitary PRL and TSH and plasma T3 T4 were determined during 48 h peripartum. No difference was noticed in mating ability and gestation time. The number of fetuses was reduced in the HG rats (1 G- 12.9 +/- 0.5, 2.16 G-10.5 +/- 0.4, 3.14 G-9.4 +/- 0.5). None of the 3.14 G rats nursed their young, all of which were cannibalized. Of the 2.16 G rats, 50% nursed their pups, of which only half survived to weaning. The initial pituitary PRL of HG rats was lower than 1 G, but it increased postpartum, while the plasma PRL, which was very low, continued to decrease. Only postpartum was there a difference in plasma PRL between rats that previously nursed and those which did not nurse at 2.16 G. HG rats had lower T3 levels, indicating a hypermetabolic state during the peripartum, which worsened their normal relative hypothyroid state of pregnancy. Our conclusions are that exposure of pregnant rats to HG above 3 G has a lethal effect on the fetuses and newborns. Maternal PRL and T3 changes are possible reasons for this.

Adaptation, Physiological↗
PubMedDate not supplied

[Comparative analysis of weightlessness and hypergravity effects on erythropoiesis in male and female mammals].

The paper summarizes the data obtained in the investigations of bone marrow and blood of Wistar rats exposed to microgravity (Cosmos biosatellites) or 2 G hypergravity (centrifuge). Males, females and pregnant females at various stages of pregnancy have been examined. Under the gravity in the range of +/- 1 G with respect to the earth gravity, in all experiments there were similar changes in erythroid hemopoiesis: a decrease in the total count of blood red cells of bone marrow; a decline in the blood reticulocyte concentrations. There changes in the erythroid part of the rats bone marrow were practically the some in space flights of 7, 14 and 22 days of duration in the centrifuge experiments with animals there alterations were maximal following a 5-day exposure and were absent after one month. Possible reasons of the above changes are discussed stay in 2 G environment.

Animals↗
PubMed1991

Responses of the photosynthetic flagellate, Euglena gracilis, to hypergravity.

Motility and orientation has been studied in the unicellular photosynthetic flagellate, Euglena gracilis, using real time image analysis capable of tracking up to 200 cells simultaneously in the slow rotating centrifuge microscope (NIZEMI) which allows one to observe the cells' swimming behavior during centrifugation accelerations between 1 g and 5 g. At 1 g the cells show a weak negative gravitaxis, which increases significantly at higher accelerations up to about 3 g. Though most cells were capable of swimming even against an acceleration of 4.5 g, the degree of gravitaxis decreased and some of the cells were passively moved downward by the acceleration force; this is true for most cells at 5 g. The velocity of cells swimming against 1 g is about 10% lower than that of cells swimming in other directions. The velocity decreases even more drastically in cells swimming against higher acceleration forces than those at 1 g. The degree of gravitactic orientation drastically decreases after short exposure to artificial UV radiation which indicates that gravitaxis may be due to an active physiological perception rather than a physical effect such as an asymmetry of the center of gravity within the cell.

Acceleration↗
PubMed1996

Cardiovascular responses of semi-arboreal snakes to chronic, intermittent hypergravity.

Cardiovascular functions were studied in semi-arboreal rat snakes (Elaphe obsoleta) following long-term, intermittent exposure to +1.5 Gz (head-to-tail acceleration) on a centrifuge. Snakes were held in a nearly straight position within horizontal plastic tubes during periods of centrifugation. Centrifugal acceleration, therefore, subjected snakes to a linear force gradient with the maximal force being experienced at the tail. Compared to non-centrifuged controls, Gz-acclimated snakes showed greater increases of heart rate during head-up tilt or acceleration, greater sensitivity of arterial pressure to circulating catecholamines, higher blood levels of corticosterone, and higher blood ratios of prostaglandin F 2 alpha/prostaglandin E2. Cardiovascular tolerance to increased gravity during graded Gz acceleration was measured as the maximum (caudal) acceleration force at which carotid arterial blood flow became null. When such tolerances were adjusted for effects of body size and other continuous variables incorporated into an analysis of covariance, the difference between the adjusted mean values of control and acclimated snakes (2.37 and 2.84 Gz, respectively) corresponded closely to the 0.5 G difference between the acclimation G (1.5) and Earth gravity (1.0). As in other vertebrates, cardiovascular tolerance to Gz stress tended to be increased by acclimation, short body length, high arterial pressure, and comparatively large blood volume. Voluntary body movements were important for promoting carotid blood flow at the higher levels of Gz stress.

Adaptation, Physiological↗
PubMed1991

Orientation of the photosynthetic flagellate, Peridinium gatunense, in hypergravity.

The photosynthetic freshwater flagellate, Peridinium gatunense, uses both positive phototaxis and negative gravitaxis to move upwards in the water column. At higher fluence rates approaching those at the surface of their habitat, the cells tend to become unoriented and thus stop their upward movement. Orientation and motility of Peridinium gatunense has been studied in the slow rotating centrifuge microscope (NIZEMI), which allows observation of swimming behavior during centrifugation acceleration between 1 g and 5g. The movement vectors were analyzed by real time image analysis capable of tracking many cells simultaneously. At 1 g the orientation was not very precise, but the degree of orientation increased significantly at higher acceleration forces up to about 3 g. Most cells were capable of swimming even against an acceleration vector of 3.8 g; at higher acceleration forces the cells were not able to cope with the centrifugal force. The linear velocity of cells swimming against 1 g was about 20% lower than that of cells moving in other directions. The velocity decreased even more in cells swimming against higher acceleration forces.

Animals↗
PubMedDate not supplied

Readaptation of the vestibuloocular reflex to 1g-condition in immature lower vertebrates (Xenopus laevis) after micro- or hypergravity exposure.

The effects of altered gravitational conditions (AGC) on the development of the static vestibulo-ocular reflex (VOR) and readaptation to 1g were investigated in the amphibian Xenopus laevis. Tadpoles were exposed to microgravity during the German Space Mission D-2 for 10 days, using the STATEX closed survival system, or to 3g for 9 days during earth-bound experiments. At the beginning of AGC, the tadpoles had not yet developed the static VOR. The main results were: (i) Tadpoles with microgravity- or 3g-experience had a lower gain of the static VOR than the 1g-controls during the 2nd and 5th post-AGC days. (ii) Readaptation to response levels of 1g-reared controls usually occurred during the following weeks, except in slowly developing tadpoles with 3g-experience. Readaptation was less pronounced if, during the acute VOR test, tadpoles were rolled from the inclined to the normal posture than in the opposite test situation. It is postulated that (i) gravity is necessarily involved in the development of the static VOR, but only during a period including the time before onset of the first behavioural response; and (ii) readaptation which is superimposed by the processes of VOR development depends on many factors including the velocity of development, the actual excitation level of the vestibular systems and the neuroplastic properties of its specific pathways.

Adaptation, Physiological↗
PubMed1996

The slow rotating centrifuge microscope NIZEMI--a versatile instrument for terrestrial hypergravity and space microgravity research in biology and materials science.

NIZEMI (slow rotating centrifuge microscope) is a tool for optical investigations of small biological and non-biological specimens during variable accelerations. Two laboratory models for ground research designed for accelerations from 1 to 5 x g and 10 x g respectively are used for terrestrial research, especially in gravitational biology. A space facility was developed and built for the Spacelab mission IML-2 during which eight experiments were performed successfully. The specifications and topic design features of the NIZEMI models are presented in this paper.

Biological Science Disciplines↗
PubMed1974

Effect of hypergravity and hyperthermia on antidiuretic hormone secretion.

The effect of acceleration and hyperthermia on the antidiuretic hormone secretion (ADH) was investigated in rats both separately and simultaneously. The two conditions of stress elicited a rise in plasma ADH concentration in proportion to their intensity. Concomitant exposure to the two factors produced an additional effect. The parallel histochemical studies using methods for demonstrating RNA, proteins and the neurosecretory material in the supraoptic nucleus, showed the synthesis and depletion of the hormone content in correlation with the plasma concentration of ADH.

Animals↗
PubMed1980

Gravity and land plant evolution: experimental induction of lignification by simulated hypergravity and water stress.

The ability to lignify cell walls has long been associated with the upright condition and sometimes massive body of the land plant, and gravitational regulation of lignification has been demonstrated by clinostat/centrifuge techniques. Previous centrifuge experiments were conducted using plants in the early stages of growth, hence already programmed for immediate lignification. Elodea, an aquatic Angiosperm long believed to be incapable of lignification synthesizes lignin or lignin-like phenolics during 6 days incubation at 80 g . Yields in some cases exceeded stationary controls by as much as 300%. Supporting data were obtained using bean cotyledons. Exposure to 80 g induced lignification in extra-vascular tissue along with vascular lignin deposits. The loss of a buoyant medium also deprived early land plants of unlimited water: the lignin content in cucumber seedlings grown in water is reduced 50% or more relative to pot grown plants but water stress elevates lignin content as much as 100%. This suggests that the water status of the land environment may have provided a "backup" or "reinforcement" signal for an adaptive axial support system.

Biological Evolution↗
PubMed2005

Contributions of lower limb and abdominal compression to ventilation inhomogeneity in hypergravity.

Gravito-inertial load in the head-to-foot direction (Gz) and compression of the lower body half by an anti-G suit (AGS) are both known to influence ventilation distribution in the lungs. To study the interaction of Gz and AGS and to asses the separate contributions from lower limbs and abdominal compressions to large and small-scale ventilation inhomogeneities nine males performed SF6/He vital capacity (VC) single-breath washouts at 1, 2, and 3 Gz in a centrifuge, with abdominal and/or lower limbs compressions. SF6/He and (SF6-He) phase III slopes were used for determination of overall and small-scale ventilation inhomogeneity. Closing volume and phase IV height were used as measures of large-scale inhomogeneity. VC decreased marginally with G-load but markedly with lower limbs compression. Small-scale ventilation inhomogeneity increased slightly with G-load, but substantially with AGS pressurization. Small-scale ventilation inhomogeneity increased with AGS pressurization. Large-scale inhomogeneity increased markedly with G-load. Translocation of blood to the lungs might be the key determinant for changes in small-scale ventilation inhomogeneity when pressurizing an AGS.

Abdomen↗
PubMedDate not supplied

Taxane recovery from cells of Taxus in micro- and hypergravity.

Cell suspension cultures of Taxus cuspidata produce taxanes that are released from the outer surface of cells into the culture medium as free and bound alkaloids. Paclitaxel (Taxol (TM)), is an anti-cancer drug in short supply. It has a taxane ring derived from baccatin III and a C-13 phenylisoserine side-chain. This drug is produced over a wide range of gravitational forces. Monoclonal and polyclonal antibodies to paclitaxel, baccatin III, and the C-13 phenylisoserine side chain were combined in multiple-labeling studies to localize taxanes and paclitaxel on cell surfaces or on particles released into the culture medium. Bioreactor vessel design altered the composition of taxanes recovered from cells in simulated microgravity. At 10(-2) and 2x10(-4)g, taxane recovery was reduced but biomass growth and percent paclitaxel was significantly increased. At 1 to 24g, growth was reduced with a significant recovery of total taxanes with low percent paclitaxel. Bound paclitaxel was also localized in endonuclease-rich fragmenting nuclei of individual apoptotic cells. A model is presented comprising TCH (touch) genes encoding enzymes that modify taxane-bearing xylan residues in cell walls, the calcium-sensing of gravitational forces by the cytoplasm, and the predisposition of nuclei to apoptosis. This integrates the adaptive physiological and biochemical responses of drug-producing genomes with gravitational forces.

Apoptosis↗