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At least 541 records · Page 30Linked to original sources
PubMed2003

[Development of a measurement and control system of human centrifuge].

OBJECTIVE: To develop measurement and control system for human centrifuge to simulate arbitrary hypergravity curves. METHOD: The human centrifuge is controlled by the upper and lower level computers. The measurement and control computer is as upper, and the real-time controller as lower. RESULT: The system performance could satisfy the requirement of the human centrifuge. CONCLUSION: The measurement and control system can achieve a high control precision. It is safe, reliable and easy to operate.

Centrifugation↗
PubMed2003

The content of heat shock protein 47 (HSP47), a collagen-specific stress protein, changes with gravitational conditions in skeletal muscle.

It is well known that unloading of skeletal muscle with spaceflight or tail suspension leads rat soleus muscle atrophy. Previously, we reported that one of small heat shock protein (sHSP), alpha B-crystallin shows an early dramatic decrease in atrophied rat soleus muscle (Atomi et al, 1991). In this report, we focused to study the gravitational responses of another HSP, which may be reactive to the gravity. HSP47, a collagen-specific stress protein, has been postulated to be a collagen-specific molecular chaperone localized in the ER (Nagata et al, 1992). Western blot analysis revealed that HSP47 in slow skeletal muscle decreases at 5 days after tail suspension (TS) and increased at 5 days recovery after 10 days of TS as compared with the control level. Hypothetically, HSP47 in slow soleus muscle increases at 5 days after hypergravity (HG) induced by the centrifugation. The content of HSP47 in soleus muscle was strongly affected by gravity conditions.

Animals↗
PubMed2003

Effect of gravity stress on fidelity of DNA double-strand break repair.

DNA double strand break (DSB) causes many cytotoxic effects such as cellular lethality, somatic mutation, and carcinogenesis. Fidelity of DSB repair is a important factor that determines the quality of genomic stability. It is known that the most of DSBs are properly repaired on the earth, however, little is known whether those are rejoined at the same fidelity even under the space environment. One of the DSB repair pathway, homologous recombination (HR), allows the cells to repair their DSBs with error free. Therefore, the efficiency of HR is a good index to assess the fidelity of DSB repair. In order to clarify the effect of gravity stress on HR pathway, we established a cell line that can detect a site-specific DNA repair via HR. The cells carrying a reporter construct for HR were incubated under hypergravity condition after induction of site specific DSB. Our preliminary results suggest that the gravity stress may affect the HR efficiency.

Cell Cycle Proteins↗
PubMed2005

[Effect of long-term hypergravitation on the skeletal-muscular tissue in rats].

The space flight or simulated gravitational unloading lead to the muscle atrophy, slow-to-fast transformation of muscle fibers and myofibrillar damages both in humans and animals (1, 7, 13, 17). This process could be prevented by the exercise training during space flight (1), (partly) by periodic weight support during unloading (13). It has been demonstrated in these studies that there is some level of force production necessary for the maintenance of skeletal muscle properties. It is known that adaptation to the physical training frequently induces augmentation in cross-sectional area (CSA) of muscle fibers (MF), transformation of fibers, augmentation of mitochondrial volume density, and increase in absolute volume of myofibrillas. Numerous observations suggest importance of gravitational loading in regulating muscle mass. The centrifuging is believed to be useful for preventing muscle functional and structural losses under microgravity. But there are few studies designed to investigate effect of artificial gravity on the skeletal musculature (2, 7). Our objective was to investigate structural adaptation in slow-twitch soleus muscle (percentage of connective tissue and central nuclei, fiber size, myosin heavy chain isotope, myofibrillar proteins and mitochondria volume density) after 19 and 33 days of hypergravity.

Adaptation, Physiological↗
PubMed2004

The mechanisms underlying neuromuscular changes in microgravity environment.

We reported that the levels of electromyogram in soleus muscle and the afferent neurogram recorded at L5 segmental level of the spinal cord were instantly decreased in response to exposure to microgravity (micro-G) environment created during a parabolic flight, although these activities were constantly presented at 1-G. It was also observed that the soleus muscle length was passively shortened in micro-G due to the plantarflexion of ankle joint. Similar phenomena were also induced by acute hindlimb suspension at 1-G. Further, the soleus muscle atrophied, if the dorsal root at L5 was transected. These results suggested that the unloading-related effects on muscle are closely associated with the inhibition of the afferent input. However, effects of gravity on most of the cells in the whole body can not be removed, although hindlimb suspension can inhibit the antigravity activity of rat hindlimb muscles. And parabolic flight can create micro-G only for a short period of time. Further, effects of hypergravity before and after micro-G are unavoidable. Therefore, further experiments utilizing space environment are essential.

Animals↗
PubMed2004

The change of HSP47, collagen specific molecular chaperone, expression in rat skeletal muscle may regulate collagen production with gravitational conditions.

It is well known that unloading of skeletal muscle with spaceflight leads skeletal muscle atrophy. However, it remains unclear how the extracellular matrix within the muscle and the connective tissues such as tendon and ligament respond to reduced mechanical load including microgravity, although they have been thought to play important roles in both the transmission of force and the signal transduction between cells and tissues. Type-I collagen and type-IV collagen, both of the major components of extracellular matrix and connective tissues. We focused on change of these collagen synthesis with mechanical load. To obtain an insight into the effects of gravitational changing on the protein metabolism of collagen in skeletal muscle during mechanical unloading, reloading after unloading, we investigated changes in the amount of Heat shock protein 47 (HSP47), has been postulated to be a collagen-specific molecular chaperone localized in the ER (Nagata et al, 1992). Western blot analysis revealed that HSP47 in rat soleus muscle decreases at 5 days after hindlimb suspension (HS). On the other hand, HSP47 in rat soleus muscle increases at 5 days after hypergravity (HG) induced by the centrifugation. RT-PCR analysis showed HSP47 mRNA decreased with HS earlier, as compared with collagen type-I and type-IV mRNA. From these results, the amount of HSP47 changing by gravitational condition may effect on signal transfers in the primary stage of adaptation and the change of HSP47 expression in skeletal muscle may regulate collagen production with gravitational conditions.

Animals↗
PubMed2004

Global and temporal regulation of gene expression in Xenopus kidney cells in response to presumed microgravity generated by 3D clinostats.

We documented changes in morphology and gene expression of the renal epithelial cell line A6 derived from Xenopus leavis adult kidney induced by long-term culturing with three dimensional clinostats. An oligo microarray analysis on A6 cells showed that mRNA levels of 52 out of 8091 genes were significantly altered in response to clinorotation. Upregulation or downregulation of gene expression became evident on day 8 and day 10 while there was no significant change on day 5. However, on day 15, expression of 18 out of 52 genes resumed to the levels similar to its original levels while remaining 33 genes maintained altered levels of expression. Quantitative analyses of gene expression by real-time PCR confirmed that changes in mRNA levels of selected genes were found only under clinorotation but not under hypergravity (7 G) and ground control (1 G). Morphological changes including loss of dome-like structures, disassembly of E-cadherin adherence junctions and disassembly of cortical actin were also observed over 10 days of culturing with clinorotation. The results revealed genes which expression was altered specifically in A6 cells cultured under clinorotation.

Actins↗
PubMed2004

Development of sensory motor reflexes in 2 G exposed rats.

During gestation and early postnatal development, the animal's size and weight rapidly increase. Within that period, gravity affects sensory and motor development. We studied age-dependent modifications of several types of motor reflexes in 5 groups of rats conceived, born and reared in hypergravity (HG; 2 g). These rats were transferred to normal gravity (NG; 1 g) at various postnatal days, and their behavioral reflexes were compared with a control group which was constantly kept under NG. HG induced a retarded development of vestibular dependent reflexes. Other types of motor behavior were not delayed.

Animals↗
PubMed2004

ECG voltage modifications as response to gravity changes.

The aim of the study was to analyze ECG (QRS) voltage responses to body fluid shift due to gravity chances. Acute changes in gravity were created by two ways: 1) changes in gravity value during parabolic flights (within 27 subjects 45 ECG have been analyzed); 2) changes in gravity direction due to rotation of the body during postural tests (within 11 subjects 14 ECG have been analyzed). Results and conclusions. Gravity change leads to body fluid shift and changes of intrathoracic organs and tissues electroconduction. It influences on ECG voltage. During parabolic flights in up-right position: R amplitude in Z axis increases in hypergravity (+0.19 mV) and decreases in microgravity (-0.24 mV). During postural tests, R amplitude in Z axis increases in orthostatic position (+0.09 mV) and decreases in antiorthostatic position (-0.025 mV). Changes in QRS voltage during parabolic flights are more important than during postural tests. This could be due to more effective blood redistribution during parabolic flights.

Adult↗
PubMed2004

Development of the locomotor system in 2 G exposed rats.

Several studies have shown the detrimental effects of microgravity exposure on the locomotor development in young rats. The opposite situation, i.e. hypergravity, which strongly stimulates several sensory systems and in particular the vestibular system, has unknown effects on the development of locomotion. This study reports 1) the temporal course of walking development of rats which were conceived and born in 2 g, and subsequently transferred to 1 g at different postnatal ages, and 2) the correlated modifications of soleus and tibialis anterior muscles.

Adaptation, Physiological↗
PubMed2004

Ground based studies of gene expression in Arabidopsis exposed to gravity stresses.

As a link in the preparation of the MULTIGEN experiment, which will take place on the International Space Station, ground based studies of the gene expression in Arabidopsis thaliana were performed. Microarray technology was used to screen Arabidopsis seedlings exposed to simulated hypogravity on a Random Positioning Machine and a 1 x g control sample. This screening showed differential expression in 177 out of approximately 8000 genes. Some of these genes can be grouped into functional categories, e.g. general metabolism, biogenesis of cellular components, cellular transport and transport facilitation, and cell rescue and defense response. However, about 50% of the genes encode proteins with unknown function. Based on the above results a new "in-house" cDNA microarray was constructed. Some of the selected genes on this microarray (e.g. Xyloglucan endotransglycosylase, At2g18800) showed differential expression both in Arabidopsis exposed to hypergravity and simulated hypogravity by use of a centrifuge and a Random Positioning Machine.

Arabidopsis↗
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↗
PubMed1994

Effects of microgravity and increased gravity on bone marrow of rats.

Astronauts have a reduction in their red cell mass when exposed to microgravity. This is probably mainly due to a physiological response to decreased energy requirements. Further studies of erythropoiesis were carried out in microgravity on rats flown on Soviet Biosatellite 2044 and in hypergravity by centrifugation at 2G. Studies included: bone marrow cell differential counts, clonal studies of RBC colony formation, and plasma erythropoietin determinations. In the bone marrow of Cosmos flight animals there was a slight increase in granulocytic cells and in centrifuged animals, a slight decrease in the percentage of erythroid cells which led to an increased M:E ratio. The bone marrow cells of flight and centrifuged rats responded to erythropoietin. Cosmos flight animals' cells formed fewer CFU-E than the controls but this was reversed in the centrifuge studies. There were no essential differences in the erythropoietin levels of test groups as compared to control groups.

Animals↗
PubMed1994

Cardiovascular responses to repetitive exposure to hyper- and hypogravity states produced by parabolic flight.

Physiologic changes to repetitive hyper- and hypogravity stresses occurring during eight to ten parabolas on NASA's KC-135 aircraft were studied. Hemodynamic responses in 11 subjects in 4 different postures (supine, standing, sitting, and semisupine Space Shuttle launch position) were determined using noninvasive impedance cardiography. Five seconds of heart rate, cardiac index, thoracic fluid index, stroke index, ejection velocity index, and ventricular ejection time data were averaged during four different gravity (g) states: 1.3g (before parabola onset); 1.9g (parabola entry); 0g (parabola peak); and 1.7g (parabola exit) for each subject. The standing position was associated with the largest changes in the cardiovascular response to hypo- and hypergravity. The thoracic fluid index did not indicate a headward redistribution during transition from a simulated launch position to weightlessness. Analysis of the eight to ten parabolas revealed that, in general, values obtained at 1.8g differed from 1.6g, 0g differed from 1.6 and 1.3g, and 1.6g differed from 1.3g. The factors of gravity, thoracic fluid index, and cardiac index exhibited significant differences that were most likely to occur between parabola 1 versus parabolas 6, 7, and 8, and parabola 2 versus parabolas 4 through 8. Only the parameter of thoracic fluid index exhibited significance for parabolas 3 versus parabolas 6 and 7.

Adult↗
PubMed2002

Microgravity modifies protein kinase C isoform translocation in the human monocytic cell line U937 and human peripheral blood T-cells.

Individual protein kinase C (PKC) isoforms fulfill distinct roles in the regulation of the commitment to differentiation, cell cycle arrest, and apoptosis in both monocytes and T-cells. The human monocyte like cell line U937 and T-cells were exposed to microgravity, during spaceflight and the translocation (a critical step in PKC signaling) of individual isoforms to cell particulate fraction examined. PKC activating phorbol esters induced a rapid translocation of several PKC isoforms to the particulate fraction of U937 monocytes under terrestrial gravity (1 g) conditions in the laboratory. In microgravity, the translocation of PKC beta II, delta, and epsilon in response to phorbol esters was reduced in microgravity compared to 1 g, but was enhanced in weak hypergravity (1.4 g). All isoforms showed a net increase in particulate PKC following phorbol ester stimulation, except PKC delta which showed a net decrease in microgravity. In T-cells, phorbol ester induced translocation of PKC delta was reduced in microgravity, compared to 1 g, while PKC beta II translocation was not significantly different at the two g-levels. These data show that microgravity differentially alters the translocation of individual PKC isoforms in monocytes and T-cells, thus providing a partial explanation for the modifications previously observed in the activation of these cell types under microgravity.

Blotting, Western↗
PubMed1983

Suppression of morphogenesis in embryonic mouse limbs exposed in vitro to excess gravity.

This paper is a report of the first investigation of the effect of excess gravity on in vitro mammalian limb chondrogenesis. Limb buds from mice of various gestational stages were exposed to excess gravity (2.6G) using a culture centrifuge. Both forelimbs and hind limbs were cultured and the development of various limb elements was scored after four to six days. The 2.6G force significantly depressed the development of limb elements when applied during the teratogen-sensitive period of chondrogenesis. There was a proximodistal gradient of sensitivity to excess gravity in the limb with proximal structures being less susceptible than distal ones. In some cases, proximal limb elements present prior to explantation disappeared upon exposure to excess gravity. Hypergravity's teratogenic effect is assumed to operate via changes in tension and/or pressure on the cells, accompanied by alterations in cell morphometry and membrane properties.

Animals↗
PubMed1993

Otolith responses in man during parabolic flight.

The influence of the varying gravito-inertial (Gz) force during parabolic flight on human otolith function was investigated experimentally. It was hypothesised that a varying Gz force profile initiates an otolith-ocular response that manifests itself in modulation of optokinetic nystagmus slow-phase eye velocity (OKN-SPV). Six subjects were seated in the ESA-Caravelle, facing perpendicular to the aircraft's longitudinal axis. The Gz profile was subsequently 1.8 Gz pull-up, 0 Gz microgravity, and 1.8 Gz recovery, each phase lasting about 20 s. Vertical eye movements were recorded with electro-nystagmography throughout the parabolic manoeuvre. Conditions were: (1) visual fixation, (2) darkness and (3) optokinetic stimulation of 50 deg/s in an upward or downward direction, projected on a cylindrical screen at 0.6 m viewing distance. No consistent nystagmus or gaze shift was measured in darkness. With optokinetic stimulation, however, ANOVA revealed downward enhancement of OKNSPV by 5 degrees/s in 1.8 Gz hypergravity, as compared with the 0 Gz condition and the 1 Gz condition. It is concluded that an otolith-ocular pathway modulates optokinetic eye movements in parabolic flight.

Adult↗
PubMed1990

Visually-induced tilt during parabolic flights.

A helmet-mounted visual display system was used to study visually induced sensations of self-motion (vection) about the roll, pitch and yaw axes under normal gravity condition (1g) and during the microgravity and hypergravity phases of parabolic flights aboard the NASA KC-135 aircraft. Under each gravity condition, the following parameters were investigated: (1) the subject's perceived body vertical with eyes closed and with eyes open gazing at a stationary random dot display; (2) the magnitude of sensations of body tilt with respect to the subjective vertical, while the subject viewed displays rotating about the roll, pitch and yaw axes; (3) the magnitude of vection; (4) latency of vection. All eleven subjects perceived a definite "up and down" orientation throughout the course of the flight. During the microgravity phase, the average magnitudes of perceived body tilt and self-motion increased significantly, and there was no significant difference in vection latency. These results show that there is a rapid onset of increased dependence on visual inputs for perception of self-orientation and self-motion in weightlessness, and a decreased dependence on otolithic and somatosensory graviceptive information. Anti-motion sickness drugs appear not to affect the parameters measured.

Aerospace Medicine↗