The cytoskeleton, apoptosis, and gene expression in T lymphocytes and other mammalian cells exposed to altered gravity.
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Animals↗
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Results for “Gravity, Altered”
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Osteogenesis in altered gravity.
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Animals↗
Altered gravity conditions affect early EGF-induced signal transduction in human epidermal A431 cells.
Epidermal growth factor (EGF) activates a well-characterized signal transduction cascade in human A431 epidermal carcinoma cells. Among the early responses evoked by EGF are receptor clustering, cell rounding, and early gene expression. These processes have been studied under various gravity conditions. In addition, we have investigated signalling pathways as induced by 12-O-tetradecanoylphorbol-13-acetate (TPA), forskolin, and A23187 that bypass the EGF receptor, but mimic the partial activation of signal transduction pathways. Hypergravity, simulated microgravity, and real microgravity have been obtained by means of centrifuge, fast-rotating clinostat, and sounding rocket, respectively. EGF-induced c-fos gene expression is suppressed in simulated microgravity (clinostatting) and even more so in real microgravity, while hypergravity increases early gene expression. This indicates that gravity inhibits early EGF-induced signal transduction. However, neither microgravity nor clinostatting affect EGF-induced EGF receptor clustering, suggesting that inhibition of EGF-induced signal transduction by microgravity and clinostatting is independent of EGF receptor clustering. EGF-induced cell rounding is enhanced under clinostatting, while hypergravity does not significantly influence this process. Furthermore, both under clinostatting and real microgravity, EGF- and TPA-induced c-fos expression is decreased, while forskolin and A23187-induced c-fos expression remains unaltered. These observations demonstrate that gravity affects specific components in the EGF-induced signal transduction circuitry, in particular the protein kinase C pathway which is common to EGF and TPA activated intracellular signalling.
Calcimycin↗
Altered gravity modulates 5-lipoxygenase in human erythroleukemia K562 cells.
Mammalian lipoxygenases catalyse the first committed step in the so-called "arachidonate cascade", leading to the production of potent bioactive molecules, such as leukotrienes, lipoxins and hepoxilins. Leukotrienes interact with G protein-couple receptors involved in neuronal plasticity and T lymphocyte activation, lipoxins activate leukocytes, hepoxilines control the insulin release and stimulate the phospholipase C. Lipoxygenase (linoleate:oxygen oxidoreductase; E.C. 1.13.11.34; 5-LOX) are responsible for lymphocyte maturation and programmed death (apoptosis) of neuronal cells. Therefore, 5-LOX might be Space relevant, because among the most striking effects of Space enviroment are indeed those on T lymphocyte activation, neuronal cell growth and suspectedly apoptosis. In this study, the possible effects of the force of gravity on the activity and expression of 5-LOX have been investigated by subjecting human erythroleukemia K562 cells to simulated hypogravity or hypergravity.
Arachidonate 5-Lipoxygenase↗
[Spatiotemporal properties of the bioconvection pattern formed by Tetrahymena and the effects of altered gravity on the pattern formation].
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Animals↗
Antibody binding in altered gravity: implications for immunosorbent assay during space flight.
A single antibody-incubation step of an indirect, enzyme-linked immunosorbent assay (ELISA) was performed during microgravity, Martian gravity (0.38 G) and hypergravity (1.8 G) phases of parabolic flight, onboard the NASA KC-135 aircraft. Antibody-antigen binding occurred within 15 seconds; the level of binding did not differ between microgravity, Martian gravity and 1 G (Earth's gravity) conditions. During hypergravity and 1 G, antibody binding was directly proportional to the fluid volume (per microtiter well) used for incubation; this pattern was not observed during microgravity. These effects in microgravity may be due to "fluid spread" within the chamber (observed during microgravity with digital photography), leading to greater fluid-surface contact and subsequently antibody-antigen contact. In summary, these results demonstrate that: i) ELISA antibody-incubation and washing steps can be successfully performed by human operators during microgravity, Martian gravity and hypergravity; ii) there is no significant difference in antibody binding between microgravity, Martian gravity and 1 G conditions; and iii) a smaller fluid volume/well (and therefore less antibody) was required for a given level of binding during microgravity. These conclusions indicate that reduced gravity would not present a barrier to successful operation of immunosorbent assays during spaceflight.
Antigen-Antibody Reactions↗
[Effects of altered gravity on the culture of unicellular eucaryotic organisms, Bursaria truncatella (Ciliophora)].
The paper reports the results of experiments with centrifugation and clinostating. Growth rate, cellular division and several morphofunctional characteristics of unicellular organisms of infusoria Bursaria truncatella in culture were studied under normal (1 g), elevated (hypergravity at 2 and 5 g), and compensated gravity. The data point to certain changes in the functional activity and morphology of cells consequent to long-time cultivation under these conditions. The observed regularities in the dynamics of B.truncatella growth and shifts in its physiology and morphology due to hypergravity or compensated gravity support our earlier proposed working hypothesis about the dominance of functional activity over morphological properties in sensitivity of unicellular organisms to perception and realization of the gravitational stimulus.
Animals↗
Feedback hypothesis and the effects of altered gravity on formation and function of gravireceptors of mollusks and fish.
Popular hypothesis based on the idea of simple feedback mechanism that correlates gravity level and weight of test mass cannot explain the variety of the effects of altered gravity on development and function of gravireceptors. The reaction of organisms to the change of gravity depends on the gravisensitivity of the physical and chemical processes corresponding to specific phases of development and may have no relation to any feedback mechanisms of compensation of altered weight of the test mass. The present work analyzes the hypothesis of feedback and shows the ambiguity of possible effects of the altered gravity on formation and function of gravireceptors basing on the data from mollusks and fish.
Animals↗
Comparative characteristic of mitochondria ultrastructural organization in Chlorella cells under altered gravity conditions.
Results from experiments that used cells from the unicellular alga Chlorella vulgaris (strain Larg-1) grown on a clinostat, demonstrated the occurrence of rearrangements in cellular organelles, including changes in the mitochondrial ultrastructure compared to controls. Changes in mitochondrial structure were observed in auto- and heterotrophic regimes of cells grown in altered gravity conditions, especially in long-term experiments. The mitochondrial rearrangements become apparent during cell proliferation, which resulted in an increase in the relative volume of mitochondria per cell: up to 2.7 +/- 0.3% in short-term clino-rotation (2.2 +/- 0.1% in the control) and up to 5.3 +/- 0.4% and 5.1 +/- 0.4% in long-term clinorotation (2.3 +/- 0.2% in the control). The size of the mitochondria and their cristae increased in cells grown under long-time clinorotation. In addition, hypertrophied organelles, not typical for this strain, were observed. These changes in the cells were accompanied by increased electron density of the matrix and a well-ordered topography of the cristae. To examine the separation of oxidative phosphorylation and respiration, an inhibitory agent 2,4-dinitrophenol (2,4-DNP) was applied to cells which resulted in insignificant volume changes of the mitochondria (2.5 +/- 0.4% versus 2.1 +/- 0.2% in the control). The increase of mitochondrial size with regularly arranged cristae, with more condensed matrix and extension of cristae areas of clino-rotated cells, may demonstrate higher functional activity of the mitochondria under altered gravity conditions. Changes observed early in clinorotated cells, in particular the increased level of respiration, adenylate content (especially ATP) and more intensive electron-cytochemical reactions of Mg2(+)-ATPase and succinate [correction of succinat] dehydrogenase (SDH) in mitochondria (including hypertrophic organelles), also suggest increased activity of mitochondria from cells grown under altered gravity conditions compared to controls.
2,4-Dinitrophenol↗
Subnucleolar location of fibrillarin and NopA64 in Lepidium sativum root meristematic cells is changed in altered gravity.
Fibrillarin and the plant nucleolin homolog NopA64 are two important nucleolar proteins involved in pre-rRNA processing. In order to determine the effects of the altered gravity environment on the nucleolus, we have investigated the location of fibrillarin and NopA64 in nucleolar subcomponents of cress (Lepidium sativum L.) root meristematic cells grown under clinorotation, which reproduces an important feature of microgravity, namely, the absence of the orienting action of a gravity vector, and compared it to the location in control cells grown in normal 1 g conditions. Prior to these experiments, we report here the characterization of cress fibrillarin as a 41 kDa protein which can be isolated from meristematic cells in three nuclear fractions, namely, the soluble ribonucleoprotein fraction, the chromatin fraction, and the nuclear-matrix fraction. Furthermore, as reported for other species, the location of both fibrillarin and NopA64 in the cress cell nucleolus was in zones known to contain complex ribonucleoprotein particles involved in early pre-rRNA processing, i.e., processomes. Under altered gravity, a decrease in the quantity of both fibrillarin and NopA64 compared to controls was observed in the transition zone between fibrillar centers and the dense fibrillar component, as well as in the bulk of the dense fibrillar component. These data suggest that altered (reduced) gravity results in a lowered level of functional activity in the nucleolus.
Blotting, Western↗
Numerical simulation of local blood flow in the carotid and cerebral arteries under altered gravity.
A computational fluid dynamics (CFD) approach was presented to model the blood flows in the carotid bifurcation and the brain arteries under altered gravity. Physical models required for CFD simulation were introduced including a model for arterial wall motion due to fluid-wall interactions, a shear thinning fluid model of blood, a vascular bed model for outflow boundary conditions, and a model for autoregulation mechanism. The three-dimensional unsteady incompressible Navier-Stokes equations coupled with these models were solved iteratively using the pseudocompressibility method and dual time stepping. Gravity source terms were added to the Navier-Stokes equations to take the effect of gravity into account. For the treatment of complex geometry, a chimera overset grid technique was adopted to obtain connectivity between arterial branches. For code validation, computed results were compared with experimental data for both steady-state and time-dependent flows. This computational approach was then applied to blood flows through a realistic carotid bifurcation and two Circle of Willis models, one using an idealized geometry and the other using an anatomical data set. A three-dimensional Circle of Willis configuration was reconstructed from subject-specific magnetic resonance images using an image segmentation method. Through the numerical simulation of blood flow in two model problems, namely, the carotid bifurcation and the brain arteries, it was observed that the altered gravity has considerable effects on arterial contraction/dilatation and consequent changes in flow conditions.
Acceleration↗
[Altered gravity affects subnucleolus localization of fibrillarin and NopA64, the most important proteins of rRNA processing].
Fibrillarin and plant nucleolin homologue NopA64 are two important nucleolar proteins involved in pre-rRNA processing. To understand better the effects of the altered gravity environment on the nucleolus functioning we have investigated the location of fibrillarin and NopA64 in nucleolar subcomponents of cress (Lepidium sativum L.) root meristematic cells grown under simulated microgravity that was compared to the control cells grown in normal conditions at I g. Cress fibrillarin was first shown to have the molecular weight 41 kDa. Both fibrillarin and NopA64 in the cress cell nucleolus are located in the zones known to contain processing pre-rRNA molecules as it has been previously reported in other species. The data confirm participation of these proteins in processomes--RNP complex particles involved in pre-rRNA processing. Under altered gravity a decrease in the quantity of both fibrillarin and NopA64 in the transition zone between fibrillar centres and the dense fibrillar component was observed, compared to control, which could point out to a lowering of the level of early pre-rRNA processing in these experimental conditions. This decrease was also detected in the bulk of the dense fibrillar component. These data support the idea that altered (reduced) gravity results in lowering the level of functional activity of the nucleolus.
Cell Nucleolus↗
Body mass change during altered gravity: spaceflight, centrifugation, and return to 1 G.
To assess the effect of gravity on growth, immature rats (130-200 g) were studied during chronic altered gravity exposure and while transitioning between gravity fields. Body mass gain of rats (n = 12) exposed to 14 days of microgravity (spaceflight) was evaluated and compared to mass gain of 1 G controls. Spaceflight did not affect mass gain. Six rats exposed to 1 G following spaceflight, when compared to controls, experienced a significant (0 < 0.05) post-flight mass loss over 48 h of 13 g. Over subsequent days, however, this loss was compensated for, and no difference from 1 G controls was noted after 5 days. Exposure to hypergravity (2 G) for 16 days was evaluated [(n = 6/group): Centrifuge (C); On Center Control (OCC); Centrifuge Control (CC)]. Body mass of centrifuged and OCC rats was reduced within 24 h, with OCCs regaining control mass within 13 days. The mass difference (44 g) in centrifuged animals persisted, however, with no subsequent difference in rate of mass gain between centrifuged animals and controls over Days 3-16 (3.7 +/- 0.1 vs. 3.9 +/- 0.1 g/day, respectively). Transitioning from 2 G to 1 G resulted in a mass increase within 48 hours for centrifuged animals. Over Days 3-16 at 1 G, the rate of gain for centrifuged animals continued to increase (3.1 +/- 0.1 g/day compared to 2.1 +/- 0.1 g/day for controls); differences from control, however, were still noted on Day 16. Transitioning to an increase in a gravity field causes acute losses in body mass. In hypergravity, the acute reduction in body mass persists but the rate of mass gain is normal. Animals returning to 1 G, after acute changes, adjust to attain control mass.
Adaptation, Physiological↗
Lipid peroxidation and polyamine metabolism in K562 cells subjected to altered gravity.
The mechanisms underlying cell sensitivity to the gravistimulus are still largely unknown. Recently, the oxidation of membrane lipids and the alteration of polyamine content have been shown to be involved in several cellular processes, from cell growth and differentiation, to aging and resistance to (a)biotic stress. Such an involvement was mediated by the modification of the activity and expression of lipoxygenase (LOX; E.C. 1.13.11.12) and diamine oxidase (DAO; E.C. 1.4.3.6), the enzymes which control membrane properties (LOX) and the catabolism of polyamines (DAO), respectively. In this study, the possible effects of altered gravity on membrane lipid peroxidation and polyamine metabolism were investigated, by subjecting human erythroleukemia K562 cell cultures to simulated hypogravity (by clinorotation) or hypergravity (by centrifugation).
Amine Oxidase (Copper-Containing)↗
Altered gravity modulates prostaglandin H synthase in human K562 cells.
In this study, we extended our previous observations on the effects of altered gravity on the "lipoxygenase pathway", by ascertain the possible role of the force of gravity in modulating the activity and expression of PHS in human erythro-leukemia K562 cells.
Arachidonate 5-Lipoxygenase↗
Lipoxygenase activity in altered gravity.
Lipoxygenases are a family of enzymes which dioxygenate unsaturated fatty acids, thus initiating lipoperoxidation of membranes or the synthesis of signalling molecules, or inducing structural and metabolic changes in the cell. This activity is the basis for the critical role of lipoxygenases in a number of pathophysiological conditions, both in animals and plants. We review the effects of microgravity on the catalytic efficiency of purified soybean (Glycine max) lipoxygenase-1, as well as the modulation of the activity and expression of 5-lipoxygenase in human erythroleukemia K562 cells subjected to altered gravity. We also outline the molecular properties of the lipoxygenase family and discuss its possible involvement in space-related processes, such as apoptosis (programmed cell death) and immuno-depression. Finally, we discuss the modulation of cyclooxygenase activity and expression in K562 cells exposed to altered gravity, because cyclooxygenase catalyzes the oxidation of arachidonate through a pathway different from that catalyzed by lipoxygenase activity.
Animals↗
Adaptations of the vestibular system to short and long-term exposures to altered gravity.
Long-term space flight creates unique environmental conditions to which the vestibular system must adapt for optimal survival of a given organism. The development and maintenance of vestibular connections are controlled by environmental gravitational stimulation as well as genetically controlled molecular interactions. This paper describes the effects of hypergravity on axonal growth and dendritic morphology, respectively. Two aspects of this vestibular adaptation are examined: (1) How does long-term exposure to hypergravity affect the development of vestibular axons? (2) How does short-term exposure to extremely rapid changes in gravity, such as those that occur during shuttle launch and landing, affect dendrites of the vestibulocerebellar system? To study the effects of longterm exposures to altered gravity, embryonic rats that developed in hypergravity were compared to microgravity-exposed and control rats. Examination of the vestibular projections from epithelia devoted to linear and angular acceleration revealed that the terminal fields segregate differently in rat embryos that gestated in each of the gravitational environments.To study the effects of short-term exposures to altered gravity, mice were exposed briefly to strong vestibular stimuli and the vestibulocerebellum was examined for any resulting morphological changes. My data show that these stimuli cause intense vestibular excitation of cerebellar Purkinje cells, which induce up-regulation of clathrin-mediated endocytosis and other morphological changes that are comparable to those seen in long-term depression. This system provides a basis for studying how the vestibular environment can modify cerebellar function, allowing animals to adapt to new environments.
Adaptation, Physiological↗
Altered gravity downregulates aquaporin-1 protein expression in choroid plexus.
Aquaporin-1 (AQP1) is a water channel expressed abundantly at the apical pole of choroidal epithelial cells. The protein expression was quantified by immunocytochemistry and confocal microscopy in adult rats adapted to altered gravity. AQP1 expression was decreased by 64% at the apical pole of choroidal cells in rats dissected 5.5-8 h after a 14-day spaceflight. AQP1 was significantly overexpressed in rats readapted for 2 days to Earth's gravity after an 11-day flight (48% overshoot, when compared with the value measured in control rats). In a ground-based model that simulates some effects of weightlessness and alters choroidal structures and functions, apical AQP1 expression was reduced by 44% in choroid plexus from rats suspended head down for 14 days and by 69% in rats suspended for 28 days. Apical AQP1 was rapidly enhanced in choroid plexus of rats dissected 6 h after a 14-day suspension (57% overshoot, in comparison with control rats) and restored to the control level when rats were dissected 2 days after the end of a 14-day suspension. Decreases in the apical expression of choroidal AQP1 were also noted in rats adapted to hypergravity in the NASA 24-ft centrifuge: AQP1 expression was reduced by 47% and 85% in rats adapted for 14 days to 2 G and 3 G, respectively. AQP1 is downregulated in the apical membrane of choroidal cells in response to altered gravity and is rapidly restored after readaptation to normal gravity. This suggests that water transport, which is partly involved in the choroidal production of cerebrospinal fluid, might be decreased during spaceflight and after chronic hypergravity.
Animals↗