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PubMed2004

Protein patterns of the Brassica rapa ovules and seeds under altered gravity.

Electrophoretic investigation of protein patterns of Brassica rapa L. ovules and seeds from plants grown under clinorotation and in the laboratory control was carried out. Ovules at different stages (7 and 18 days after pollination) and mature seeds were analyzed. Polymorphism of seed storage proteins of B. rapa was taken into consideration in analysis of changes in ovule protein patterns under clinorotation. The appearance of a protein component in the region of about 43 kDa was detected in protein patterns of 7-day-old and 18-day-old ovules in the clinostat variants. Under altered gravity, in 18-day-old ovules, the appearance of a protein in the region of about 70 kDa was also revealed. The appearance of the protein component with the similar mobility (about 43 kDa) in ovules of different age from plants grown at clinorotation suggests that synthesis of this protein may be associated with the plant response to altered gravity. However, the investigation of the nature of this protein and its role requires further research to rule out its appearance because of genotypic differences between ovules of the control and experimental variants.

2S Albumins, Plant↗

PubMed2006

Effects of altered gravity on the actin and microtubule cytoskeleton of human SH-SY5Y neuroblastoma cells.

Human SH-SY5Y neuroblastoma cells were used to study the effects of altered gravity on the actin and microtubule cytoskeleton dynamics. A cholinergic stimulation of the cells during a 6 min period of changing gravity (3 parabolas) resulted in an enhanced actin-driven protrusion of evoked lamellipodia. Likewise, the spontaneous protrusive activity of nonactivated cells was promoted during exposure to changing gravity (6 up to 31 parabolas). Ground-based experiments revealed a similar enhancement of the spontaneous and evoked lamellar protrusive activity when the cells were kept at 2 g hypergravity for at least 6 min. This gravity response was independent of the direction of the acceleration vector in respect to the cells. Exposure of the cells to "simulated weightlessness" (clinorotation) had no obvious influence on this type of lamellar actin cytoskeleton dynamics. A 20 min exposure of the cells to simulated weightlessness or to changing gravity (6 to 31 parabolas) - but not to 2 g (hypergravity, centrifugation) - resulted in an altered arrangement of microtubules indicated by bending, turning, and loop formation. A similar altered arrangement was shown by microtubules which had polymerized into lamellipodia after release from a taxol block at simulated weightlessness (clinorotation) or during changing gravity (5 parabolas). Our data suggest that in human SH-SY5Y neuroblastoma cells, microgravity affects the dynamics and spatial arrangement of microtubules but has no influence on the Rac-controlled lamellar actin cytoskeleton dynamics and cell spreading. The latter, however, seems to be promoted at hypergravity.

Acetylcholine↗

PubMed1997

Vestibular function and sensory interaction in altered gravity.

The effects of weightlessness on vestibular function have been studied since the beginning of manned spaceflight. The results of these studies have been highly variable and to some extent even contradictory, which makes it difficult to draw unambiguous conclusions. This variability is probably due to at least three factors: (1) individual differences in the adaptive process, (2) non-standardized experimental methods and conditions, (3) a lack of integrated experiments. For this reason, we have used a single integrated approach with a specially developed battery of tests. The results thus obtained for 21 cosmonauts on short- and long-term flights are reviewed here, and discussed in the light of the results obtained by others. Changes in the operation of the vestibular system and in all functions based on vestibular afferent input are commonly observed in spaceflight. These changes are characteristic for the process of adaptation and re-adaptation to altered gravity. They occur in a high proportion of persons exposed to such conditions, although there are individual differences with regard to severity, nature, time and duration of occurrence, and the dynamics of the process. Analysis of the observations in a large number of cosmonauts has permitted to distinguish three types of adaptation of the system to altered gravity. The first type of adaptation is characterized by a strong response to any stimulus during the initial adaptation period. The second type of adaptation is characterized by responses that are drastically decreased or even absent. The third type of adaptation is distinguished by the selective response of the sensory system to certain types of stimulation only. After long-term missions the process of re-adaptation usually takes a more severe course than the earlier process of adaptation to microgravity. Both adaptation and re-adaptation follow an undulating course, in which adaptation and re-adaptation are alternating. This is most conspicuous during long-term flights, and it suggests that in the initial stage of adaptation to weightlessness the vestibular input plays a dominant role, while at the end of the adaptation process the visual input prevails.

Eye Movements↗

PubMed2004

Bioconvective pattern formation of Tetrahymena under altered gravity.

Bioconvection is a result of the negative gravitactic behavior of microorganisms. When the top-heavy density gradient generated by gravitaxis grows sufficiently large, an overturning convection occurs leading to a formation of characteristic patterns, which involve highly concentrated aggregation of cells into extended two-dimensional structures. Although gravity is a crucial factor, few experiments have been done with reference to gravity as an experimental variable. In order to gain an insight into the hydrodynamic as well as biological dependence of the convective motion on gravity, we investigated changes in bioconvective patterns of Tetrahymena under altered gravity acceleration generated by a long-arm centrifuge. Bioconvective patterns recorded of three different cell strains (T. pyriformis, T. thermophila and its behavioral mutant, TNR) were analyzed quantitatively using space-time plot and Fourier analysis. For example, under subcritical conditions, when T. pyriformis (1.0 x 10(6) cells ml(-1)) was placed in a 2 mm-deep chamber, no spatial pattern was observed at 1 g. When the suspension was centrifuged, however, patterns began to appear as acceleration increased over a critical value (1.5 g), and then remained steady. The formation was reversible, i.e. the patterns disappeared again as acceleration decreased. Under supracritical conditions, i.e. when a suspension of the same density was placed in a 4 mm-deep chamber, a steady state pattern was formed at 1 g. The pattern spacing in the steady state was observed to decrease stepwise in response to step increases in acceleration. Fourier analysis demonstrated that for TNR the mean wave number changed almost simultaneously with step changes in acceleration, whereas the responses were less sharp in the wild-type strains. This may suggest that the locomotor phenotype of the cell, such as its avoiding response ability, has a crucial role in bioconvective pattern formation. These findings are discussed in relation to former theoretical studies.

Animals↗

PubMed1998

Neurobiology of fish under altered gravity conditions.

In vertebrates (including man), an altered gravitational environment such as weightlessness can induce malfunction of the inner ear, based on an irregular dislocation of the otoliths from the corresponding sensory epithelia. This dislocation leads to an illusionary tilt, since the otolithic inputs are not in register with other sensory organs. This results in an intersensory conflict. Vertebrates in orbit therefore face severe orientation problems. In humans, the intersensory conflict may additionally lead to a malaise, commonly referred to as space motion sickness (SMS). During the first days in weightlessness, the orientation problems (and SMS) disappear, since the brain develops a new compensatory interpretation of the available sensory data. The present review reports the neurobiological responses-particularly in fish-observed at altered gravitational states, concerning behaviour and neuroplastic reactivities. Recent investigations employing microgravity (spaceflight, parabolic aircraft flights, clinostat) and hyper-gravity (laboratory centrifuges as ground based research tools) yielded clues and insights into the understanding of the respective basic phenomena. The possible sources of human space sickness (a kinetosis) and of the space adaptation syndrome (when a sensory reinterpretation of gravitational and visual cues takes place) are particularly highlighted with regard to the functional significance of bilaterally asymmetric otoliths (weight, size).

Animals↗

PubMed1994

Altered gravity affects succinate dehydrogenase reactivity in specific nuclei of fish brain.

The effect of long-term (10 days) altered gravitational conditions upon succinate dehydrogenase (SDH) reactivity in total brain as well as in individual brain nuclei of developing cichlid fish larvae has been investigated by means of semiquantitative histochemical methods (densitometric grey value analysis). Increasing acceleration from near weightlessness (spaceflight) via 1 g controls to 3 g hypergravity (centrifuge) resulted in slightly increased total brain SDH reactivity. When focusing on distinct neuronal integration centres within the same brains in order to find the anatomical substratum of the gross histochemical data, significant effects of altered gravity on vestibulum-related brain parts were obtained. The total brain results may therefore represent the sum of such particular indirect effects but may also comprise in addition a non vestibular-related general and therefore direct influence of altered gravitational conditions, possibly on all cells.

Animals↗

PubMed1996

Influence of long-term altered gravity on the swimming performance of developing cichlid fish: including results from the 2nd German Spacelab Mission D-2.

This study presents qualitative and quantitative data concerning gravity-dependent changes in the swimming behaviour of developing cichlid fish larvae (Oreochromis mossambicus) after a 9 resp. 10 days exposure to increased acceleration (centrifuge experiments), to reduced gravity (fast-rotating clinostat), changed accelerations (parabolic aircraft flights) and to near weightlessness (2nd German Spacelab Mission D-2). Changes of gravity initially cause disturbances of the swimming performance of the fish larvae. With prolonged stay in orbit a step by step normalisation of the swimming behaviour took place in the fish. After return to 1g earth conditions no somersaulting or looping could be detected concerning the fish, but still slow and disorientated movements as compared to controls occurred. The fish larvae adapted to earth gravity within 3-5 days. Fish seem to be in a distinct early developmental stages extreme sensitive and adaptable to altered gravity; However, elder fish either do not react or show compensatory behaviour e.g. escape reactions.

Adaptation, Physiological↗

PubMed1991

Vector-averaged gravity alters myocyte and neuron properties in cell culture.

To investigate whether changes in the gravitational field of developing neurons and myocytes affect cellular development, we rotated cultures of embryonic spinal neurons and myocytes in a horizontal clinostat. Rotation in the clinostat produces, from the cells' perspective, a "vector-free" gravity environment by continuous averaging of the vector. In this way, rotation in the clinostat simulates the microgravity of space where the gravity vector is substantially reduced. At rotation rates of 1-50 rpm, cellular and nuclear areas of myocytes were significantly enlarged and the number of presumptive nucleoli increased. In neurons, frequent and large swellings appeared along neuritic shafts. Some of these changes were reversible after cessation of rotation. Since our data are generally consistent with findings from other cell types subjected to spaceflight, we suggest that the vector-free gravity environment of the clinostat appears to simulate, at least in part, the microgravity of space. Our data further show that cellular processes are sensitive to altered gravity and suggest that cell development in the microgravity of space may be significantly altered.

Animals↗

PubMed1991

Epidermal growth factor-induced expression of c-fos is influenced by altered gravity conditions.

Epidermal growth factor (EGF) activates a well characterized signal transduction system in human A431 epidermoid carcinoma cells, which leads to rapid and transient expression of the c-fos proto-oncogene. In order to investigate the influence of altered gravity on EGF-induced signal transduction, we have studied the EGF-induced c-fos expression under simulated hypo- and hypergravity conditions. In this report we show that EGF-induced fos expression is decreased under simulated hypogravity conditions, while hypergravity has a stimulatory effect on EGF-induced fos expression. These results show that the EGF-activated signal transduction system is influenced by gravity, and that gravity exerts its effects already in the early phases of the signal transduction cascade.

Blotting, Northern↗

PubMed2004

CNS development under altered gravity: cerebellar glial and neuronal protein expression in rat neonates exposed to hypergravity.

The future of space exploration depends on a solid understanding of the developmental process under microgravity, specifically in relation to the central nervous system (CNS). We have previously employed a hypergravity paradigm to assess the impact of altered gravity on the developing rat cerebellum. The present study addresses the molecular mechanisms involved in the cerebellar response to hypergravity. Specifically, the study focuses on the expression of selected glial and neuronal cerebellar proteins in rat neonates exposed to hypergravity (1.5 G) from embryonic day (E)11 to postnatal day (P)6 or P9 (the time of maximal cerebellar changes) comparing them against their expression in rat neonates developing under normal gravity. Proteins were analyzed by quantitative Western blots of cerebellar homogenates; RNA analysis was performed in the same samples using quantitative PCR. Densitometric analysis of Western blots suggested a reduction in glial (glial acidic protein, GFAP) and neuronal (neuronal cell adhesion molecule, NCAM-L1, synaptophysin) proteins, but the changes in individual cerebellar proteins in hypergravity-exposed neonates appeared both age- and gender-specific. RNA analysis suggested a reduction in GFAP and synaptophysin mRNAs on P6. These data suggest that exposure to hypergravity may interfere with the expression of selected cerebellar proteins. These changes in protein expression may be involved in mediating the effect of hypergravity on the developing rat cerebellum.

Animals↗

PubMed1996

Correlation of altered gravity and cytochrome oxidase activity in the developing fish brain.

The mitochondrial enzyme, cytochrome oxidase, was localized cytochemically in the nucleus magnocellularis, a primary relay nucleus of vestibular information within the area octavolateralis in the fish brain. Cichlid fish larvae were analyzed after long-term exposure (9 days) to altered gravity situations: increased acceleration in a centrifuge (3 g) and near weightlessness during space flight. Controls (1 g) were reared under identical conditions in the centrifuge but without rotation on earth or with an acceleration resulting in gravity of 1 g in space shuttle. Quantification of highly reactive mitochondria reveals a correlation of gravity and cytochrome oxidase activity: low enzyme activity in respect to 1 g controls under near weightlessness conditions and an increased activity after hyper-g exposure in a centrifuge. This gravity effect on the energy metabolism of vestibular nuclei of developing cichild fish seems to reflect adaptational processes in response to gravity stimulation.

Animals↗

PubMedDate not supplied

On the influence of altered gravity on the growth of fish inner ear otoliths.

Inner ear stones (otoliths) of developing cichlid fish (Oreochromis mossambicus) were marked with the calcium tracer alizarin-complexone (AC) at 1g-earth gravity before and after a longterm (20 days) stay of the animals at moderate hypergravity conditions (3g; centrifuge). AC deposition at the otoliths resulted in two fluorescence bands, which enclosed the area grown during exposure to altered gravity. This area was measured with regard to size and asymmetry (size difference between the left and the right stones). Both utricular and saccular otoliths (lapilli and sagittae, respectively) were significantly smaller after hyper-g exposure as compared to parallely raised 1 g-control specimens. The asymmetry concerning the lapilli was pronouncedly decreased in comparison to the 1g-controls. These findings suggest, that the growth and the development of bilateral asymmetry of otoliths is guided by the environmental gravity vector. Some of the hyper-g animals revealed a kinetotic behaviour at the transfer from hyper-g to normal 1g-earth gravity conditions, which was qualitatively similar to the behaviour observed in previous experiments at the transfer from 1 g to microgravity in the course of parabolic aircraft flights. The lapillar asymmetry of kinetotic samples was found to be significantly higher than that of normally behaving experimental specimens. This result supports an earlier theoretical concept, according to which human static space sickness might be based on asymmetric utricular otoliths

Animals↗

PubMed1995

Development and altered gravity dependent changes in glucose-6-phosphate dehydrogenase activity in the brain of the cichlid fish Oreochromis mossambicus.

Glucose-6-phosphate dehydrogenase activity was studied in the brain of the cichlid fish Oreochromis mossambicus during early ontogenetic development. In general a slight but continuous decrease in enzyme activity was found (9.5 +/- 0.5 nmol substrate cleaved per mg protein and per min at developmental stage 13 [= 1 day post hatch at 28 degrees C] to a value of 7.9 +/- 0.6 in adult brain). In order to investigate the possible influence of altered gravity during early ontogenetic brain development, fish larvae were exposed to an increased acceleration of three times earth gravity (3 g) or to functional weightlessness in a fast-rotating clinostat for 7 days. A significant increase of brain G6PDH activity of approx. 15% was found after exposure to hyper gravity, whereas a significant decrease of the enzyme activity, approximately 10%, was detected following functional weightlessness in respect to the corresponding 1 g controls. Analyses concerning the regain of normal control enzyme activity of the larvae revealed dramatic fluctuations within the first 5 h after exposure to an increased acceleration of 3 g. Thereafter, between day 1 and day 3 after exposure, brain glucose-6-phosphate dehydrogenase decreased slowly. At day 3 after exposure no further differences of the hyper-g larvae compared to the controls were found. Only slight changes in total brain glucose-6-phosphate dehydrogenase activity occur during ontogenetic development of cichlid fish. This suggests that a more or less constant enzyme activity is important during brain development, but is reacting very sensitively to changes in the environmental factor gravity.

Acceleration↗

PubMed1996

Comparative electronmicroscopical investigations on the influences of altered gravity on cytochrome oxidase in the inner ear of fish: a spaceflight study.

The regional metabolic activity in the otolithic sensory epithelia of the inner ear of a cichlid fish (Oreochromis mossambicus) was investigated on light- and electronmicroscopical level using the cytochemical method for detection of cytochrome oxidase activity. In adult animals a characteristic distribution of mitochondria with high enzyme activity was found in sensory and non-sensory cells of otolithic sensory epithelia, which was correlated with regions with a high energy demand. These findings were the basis for studies on the influence of long-term altered gravity conditions in developing larvae: hypogravity (10(-4) g in spaceflight), normal gravity (1 g in a centrifuge in space and 1 g on earth) and hypergravity (3 g in a laboratory centrifuge). Cytochrome oxidase activity was quantified in different parts of the sensory hair cell synapse in the vestibular sensory epithelia utricle and saccule: apical and basal cytoplasm, postsynaptic area of the afferent synapse and presynaptic region of the efferent synapse. Our results show that the energy metabolism of utricle, but not of saccule is decreased after microgravity exposure during the 2nd German Spacelab Mission D-2. However, a general effect of the spaceflight is detectable in both sensory epithelia. Long-term exposure to increased acceleration (3 g) had no effects on cytochrome oxidase activity in inner ear sensory epithelia.

Animals↗

PubMed1998

Changes in plant mitochondria ultrastructure and respiration intensity in altered gravity.

Analysis of experimental results involving both animals and plants showed that cell mitochondria considerably changed regarding organelles shape, matrix density, number and size of cristae. However, oxidative-reductive enzymes did not lose their activity (2). Moreover, there are some data concerning an increase in respiration intensity of plants grown on a horizontal clinostat (3) and in seedlings being on board of Biosatellite-11 (4). Similar rearrangements in mitochondria are also observed during clinorotation (5). Taking into account that energy supply of cells during their adaptation to various factors considerably depends on the functional activity of these organelles along with ultrastructure the activity of some enzymes of energetic and oxidative metabolism as well as the level of cell respiration in altered gravity was studied.

Ca(2+) Mg(2+)-ATPase↗

PubMed1999

Exposure to altered gravity affects all stages of endochondral cartilage differentiation.

Chondrogenesis has a number of well-defined steps: (1) condensation, which involves cell aggregation, adhesion and communication; (2) activation of cartilage genes, which is accompanied by rounding up of the cells and intracellular differentiation; and (3) production and secretion of cartilage specific matrix molecules. Our studies show that each of these steps is affected by exposure to gravitational changes. Clinorotation and centrifugation affected initial aggregation and condensation. In the CELLS experiment, where cells were exposed to microgravity after some condensation occurred preflight, intracellular differentiation and matrix production were delayed relative to controls. Once cartilage has developed, in rats, further differentiation (hypertrophy, matrix production) was also affected by spaceflight and hind limb suspension. For the process of chondrogenesis to proceed as we know it, loading and other factors present at 1g are required at each step of the process. This requirement means that not only will skeletal development and bone healing, processes involving chondrogenesis, be altered by long term exposure to microgravity, but that continuous intervention will be necessary to correct any defects produced by altered gravity environments.

Animals↗

PubMed2004

Peculiarities [correction of Pfculiarities] of lipid accumulation in Brassica rapa L. embryos on different stages development under altered gravity.

Accumulation of lipid inclusions in Brassica rapa embryos generated under slow horizontal clinorotation and in the laboratory control were analyzed by histochemical methods. The research of lipid accumulation was carried out on consecutive stages of the embryo development, from the moment of two-cellular proembryo formation up to the stages of their full differentiation (21-22-day-old embryos). Accumulation of lipid drops was revealed for the first time at early stages of embryogenesis in this species, beginning from 3-day-old embryos (ball-like stage of embryo development) under clinorotation and in the laboratory control. The quantity of lipid inclusion was estimated by morphometrical analysis. Statistically significant differences between the clinorotation and laboratory control variants in quantity of lipid drops per cell were revealed from 6-day-old embryos (heart-shaped stage). Especially pronounced differences were noted in differentiated embryos (beginning from 12-day-old embryos) under horizontal clinorotation in comparison with the laboratory control. The registered differences testify about influence of altered gravity conditions on lipid accumulation in Brassica rapa embryos.

Brassica rapa↗

PubMed1998

Plant cells in vitro under altered gravity.

Establishing the role of gravity in plant requires information about how gravity regulates the metabolism of individual cells. Plant cells and tissues in vitro are valuable models for such purpose. Disrupted intercellular relations in such models have allowed to elucidate both the gravity role in non-specialised to gravity plant cells and the correlative relation role of an intact plant organism. The data obtained from non-numerous space and clinostat experiments with plant cells in vitro have demonstrated that their metabolism is sensitive to g-environment. The most experiments have shown a decrease in the biomass production and cell proliferation of spaceflight samples compared with ground controls, although there is study reporting of increased biomass production in an anise suspension culture and D. carota crown gall tissue culture. At the same time, results of experiments with single carrot cells and tomato callus culture demonstrated similarities in differentiation process in microgravity and in ground controls. Noted ultrastructural arrangement in cells, especially mitochondria and plastids, have been related to altered energy load and functions of organelles in microgravity, as well as changes in the lipid peroxidation and the content of malonic dyaldehyde in a haplopappus tissue culture under altered gravity supposed with modification of membrane structural-functional state. This article focuses on growth aspects of the cultured cells in microgravity and under clinostat conditions and considers those aspects that require further analysis.

Asteraceae↗