Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Weightlessness Simulation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 703 records · Page 39Linked to original sources
PubMedDate not supplied

[Muscle atrophy in microgravity and during its simulation].

Summarized are the results of comparative analysis of morphological changes in rat's skeletal muscles after microgravity and its simulation. On completion of space flight, hindlimb muscles of rats exhibited atrophy developed in space microgravity in consequence of the lack of weight-bearing loads and changes solely in the slow anti-g muscles due to the hemodynamic disorders appearing after space flight. Immobilization combined with clinostatting cannot be a veridical laboratory model of microgravity, as horizontally positioned animals still possess weight and, besides, experience severe chronic stress of immobilization. Tail suspension with the head-end permanently down and the hind limbs out of use appeared the most demonstrative model of the space microgravity effects. With this model, the hindlimb muscles underwent changes identical to what had been observed in space flown animals. Data of the simulation studies suggest stabilization of muscle atrophy at a certain level and an earlier and stronger reaction to the hindlimb unloading in young rats as compared to old animals. Skeletal muscles in females and males responded to suspension similarly in spite of difference in the hormonal status.

Animals↗
PubMed1997

Influence of simulated microgravity on the longevity of insect-cell culture.

Simulated microgravity within the NASA High Aspect Rotating-Wall Vessel (HARV) provides a quiescent environment to culture fragile insect cells. In this vessel, the duration of stationary and death phase for cultures of Spodoptera frugiperda cells was greatly extended over that achieved in shaker-flask controls. For both HARV and control cultures, S. frugiperda cells grew to concentrations in excess of 1 x 10(7) viable cells ml-1 with viabilities greater than 90%. In the HARV, stationary phase was maintained 9-15 days in contrast to 4-5 days in the shaker flask. Furthermore, the rate of cell death was reduced in the HARV by a factor of 20-90 relative to the control culture and was characterized with a death rate constant of 0.01-0.02 day-1. Beginning in the stationary phase and continuing in the death phase, there was a significant decrease in population size in the HARV versus an increase in the shaker flask. This phenomenon could represent cell adaptation to simulated microgravity and/or a change in the ratio of apoptotic to necrotic cells. Differences observed in this research between the HARV and its control were attributed to a reduction in hydrodynamic forces in the microgravity vessel.

Animals↗
PubMed1999

Cultures of human liver cells in simulated microgravity environment.

We used microgravity-simulated bioreactors that create the unique environment of low shear force and high-mass transfer to establish long-term cultures of primary human liver cells (HLC). To assess the feasibility of establishing HLC cultures, human liver cells obtained either from cells dissociated by collagenase perfusion or minced tissues were cultured in rotating vessels. Formation of multidimensional tissue-like spheroids (up to 1.0 cm) comprised of hepatocytes and biliary epithelial cells that arranged as bile duct-like structures along newly formed vascular sprouts were observed. Electron microscopy revealed clusters of round hepatocytes and bile canaliculi with multiple microvilli and tight junctions. Scanning EM revealed rounded hepatocytes that were organized in tight clusters surrounded by a complex mesh of extracellular matrix. Also, we observed that co-culture of hepatocytes with endothelial cells stimulate albumin mRNA expression. In summary, a simulated microgravity environment is conducive for the establishment of long-term HLC cultures and allows the dissection of the mechanism of liver regeneration and cell-to-cell interactions that resembles in vivo conditions.

Albumins↗
PubMed1994

Human cardiovascular response to sympathomimetic agents during head-down bed rest: the effect of dietary sodium.

Changes in sympathoadrenal function and cardiovascular deconditioning have long been recognized as a feature of the physiological adaptation to microgravity. The deconditioning process, coupled with altered hydration status, is thought to significantly contribute to orthostatic intolerance upon return to Earth gravity. The cardiovascular response to stimulation by sympathomimetic agents before, during, and after exposure to simulated microgravity was determined in healthy volunteers equilibrated on normal or high sodium diets in order to further the understanding of the deconditioning process.

Adult↗
PubMed1986

Cardiovascular system and microgravity simulation and inflight results.

Main results of cardiovascular investigation, performed with ultrasound methods during the common French/Soviet flight aboard Salyut VII in June 1982, are compared to variations of the same parameters studied during ground-based simulations on the same subject or observed by other investigators during various ground-based experiences. The antiorthostatic bed rest simulation partly reproduces microgravity conditions and seems to be better adaptated to cardiac hemodynamics, despite some differences, and to the cerebral circulation, than to the inferior limb circulation.

Aerospace Medicine↗
PubMed2001

Microarray analysis of genes differentially expressed in HepG2 cells cultured in simulated microgravity: preliminary report.

Developed at NASA, the rotary cell culture system (RCCS) allows the creation of unique microgravity environment of low shear force, high-mass transfer, and enables three-dimensional (3D) cell culture of dissimilar cell types. Recently we demonstrated that a simulated microgravity is conducive for maintaining long-term cultures of functional hepatocytes and promote 3D cell assembly. Using deoxyribonucleic acid (DNA) microarray technology, it is now possible to measure the levels of thousands of different messenger ribonucleic acids (mRNAs) in a single hybridization step. This technique is particularly powerful for comparing gene expression in the same tissue under different environmental conditions. The aim of this research was to analyze gene expression of hepatoblastoma cell line (HepG2) during early stage of 3D-cell assembly in simulated microgravity. For this, mRNA from HepG2 cultured in the RCCS was analyzed by deoxyribonucleic acid microarray. Analyses of HepG2 mRNA by using 6K glass DNA microarray revealed changes in expression of 95 genes (overexpression of 85 genes and downregulation of 10 genes). Our preliminary results indicated that simulated microgravity modifies the expression of several genes and that microarray technology may provide new understanding of the fundamental biological questions of how gravity affects the development and function of individual cells.

Cell Culture Techniques↗
PubMed2002

Experimental analysis of gravitational effects on amphibian gastrulation.

The effects of simulated microgravity on blastopore (Bp) formation were analysed in Xenopus laevis and Cynops pyrrhogaster embryos. Simulated microgravity produced by clinostat rotation shifted the Bp-forming region toward the vegetal pole, more markedly in Cynops embryos than in Xenopus embryos. The simulated microgravity induced aggregation of endoderm cells at the center of the embryo and separation between the endoderm and presumptive mesoderm (PM). These findings suggest that clinostat treatment disrupts cell-to-cell interaction between endoderm and PM by increasing the separation between them and, as a result, Bp formation may be shifted towards the vegetal pole.

Animals↗
PubMed1994

Simulation of gravitational field variation on fluid-filled biological membranes.

The knowledge of the behavior of biological organs in a gravitational field is important to understand the functioning of the human body in the aerospace environment. The disturbances in biological transport processes in microgravity have indicated adverse effects on humans engaged in space operations. The relationship between the deformations in the biological organs and the transport phenomena that take place in them has been long established and widely reported in biological sciences and engineering literature. A number of soft tissue organs such as brain, lungs, heart, kidney, bladder, stomach, and the circulatory system can be modeled as fluid-filled membranes. In this investigation, a mathematical model of a fluid-filled biological membrane is developed, and its deformation and spatial configuration in a variable gravitational field are calculated. The variation in the gravitational field in the range 1g to zero-g is simulated by partial submergence of the fluid-filled membrane which, by virtue of buoyancy, gains an effective density as if it is in a different gravitational field. The equations of motion are derived using the theory of large elastic deformations and numerically solved in conjunction with a constitutive equation suitably selected for the biological membrane.

Biological Transport↗
PubMed1998

[Identification of gravity-related esterases (grEST1 and grEST2) in carrot callus cells].

A horizontal clinostat which mimics the microgravity in space was used to study its effects on carrot cells. After using boric acid buffer (pH 8.8) as extraction medium, PAGE pattern of esterase isozymes of carrot callus cells displayed 8 bands of which the activities of only 2 were affected by microgravity. They were named grEST1 and grEST2, where grEST stands for gravity-related esterase. The rates of increase in activity of them in carrot cells when cultured on a rotating horizontal clinostat were lower than that cultured in normal gravitational environments, and the difference increased with the culture time. The activities of grEST1 and grEST2 in carrot callus cells subjected to horizontal rotation were found to return to their original levels after being placed under normal gravity (1 x g) for 7 days. We suggest that the effect of simulated microgravity conditions on grEST1 and grEST2 activities in carrot callus cells is through affecting their synthesis. In addition, the activities of grEST1 and grEST2 were not inhibited by eserine, acetylcholine iodide, diisopropyl fluorophosphate and p-chloromercuribenzoate, which indicates that they are acetylesterases.

Acetylcholine↗
PubMed2003

Daily 4-h head-up tilt is effective in preventing muscle but not bone atrophy due to simulated microgravity.

To assess the potential value of intermittent artificial gravity as an efficient countermeasure, our previous studies have showed that daily 4-h standing (STD) is sufficient in counteracting muscle atrophy but not bone atrophy induced by simulated microgravity. The aim of the present study was to determine whether intermittent gravitational loading by daily 2-h or 4-h, +45 degrees head-up tilt (HUT) is more effective than STD in counteracting muscle and, particularly, bone atrophy due to simulated microgravity. Sprague-Dawley male rats weighing 290-300 g were subjected to a 28-d tail-suspension to simulate microgravity deconditioning. Daily HUT for 2, or 4 h was used to provide intermittent gravitational loading in foot-ward and tail-ward directions. The results showed that 4 h/d HUT was sufficient, and 2 h/d was less effective, in preventing adverse changes in muscle weights, fiber types, and cross-sectional areas (CSA) of muscles due to a 28-d simulated microgravity. The % protections by 4 h/d HUT in maintaining the CSAs of type I fibers in soleus, medial and lateral gastrocnemius and extensor digitorum longus muscles were 103%, 82%, 102%, and 83%, respectively. However, according to changes in physical and mechanical properties of femur, daily 4-h HUT was ineffective in attenuating the adverse changes in bone due to a 28-d simulated microgravity. Reductions in wet, dry, and ash weights and decreases in mechanical strength of femur did not show significant improvement by daily 2-h or 4-h HUT. Taken together, the findings indicate that the countermeasure effectiveness of daily 2-h or 4-h HUT for muscles is comparable with that by daily STD with the same durations. Daily 4-h HUT, as 4-h STD, is also ineffective in attenuating adverse changes in bone mass, but seems partially effective in preventing declines in mechanical properties due to simulated microgravity.

Animals↗
PubMedDate not supplied

Certain approaches to the development of on-board automated training system.

Perspectives of long-term space programs make it necessary to develop autonomous computer expert system for crew-members physical state control. The purpose of the work--to develop a set of objective formalizable physiological indices of working capacity suitable for reliable algorithmization of physical state control. Investigations were performed in on-earth microgravity simulation (3- and 7-day dry immersion, 6 subjects; 4-month antiorthostatic hypokinesy, 10 subjects) with volunteers' participation as well with 34 members of MIR-station expeditions during flights. Model exercise investigations were made also with 20 young male volunteers to evaluate the validity of different physical state indices. A set of indices was found which, being simple enough for measuring, performs to get satisfactory adequate evaluations of current organism physical state in long-term real or simulated microgravity. It was proved that some ergometric indices along with heart rate derivatives could reflect real working ability even better than traditional characteristics of organism energy systems state.

Aerospace Medicine↗
PubMedDate not supplied

Activation of nuclear transcription factor-kappaB in mouse brain induced by a simulated microgravity environment.

Microgravity induces inflammatory responses and modulates immune functions that may increase oxidative stress. Exposure to a microgravity environment induces adverse neurological effects; however, there is little research exploring the etiology of these effects resulting from exposure to such an environment. It is also known that spaceflight is associated with increase in oxidative stress; however, this phenomenon has not been reproduced in land-based simulated microgravity models. In this study, an attempt has been made to show the induction of reactive oxygen species (ROS) in mice brain, using ground-based microgravity simulator. Increased ROS was observed in brain stem and frontal cortex with concomitant decrease in glutathione, on exposing mice to simulated microgravity for 7 d. Oxidative stress-induced activation of nuclear factor-kappaB was observed in all the regions of the brain. Moreover, mitogen-activated protein kinase kinase was phosphorylated equally in all regions of the brain exposed to simulated microgravity. These results suggest that exposure of brain to simulated microgravity can induce expression of certain transcription factors, and these have been earlier argued to be oxidative stress dependent.

Animals↗
PubMed1998

Peripheral vascular changes after short-term simulated microgravity.

Cardiovascular deconditioning and orthostatic intolerance are the main symptoms experienced by astronauts after space flights. Alterations in the cardiovascular neural regulation have been implicated in the genesis of these disorders, but the mechanisms have not been clearly established. Alterations in the reflex control of circulation from the arterial and cardiopulmonary baroreceptive areas have been mainly hypothesized on the basis of long-term simulated microgravity studies. However, symptoms of orthostatic intolerance, and even fainting, are also observed after short-term exposure to simulated micro-G conditions. The possibility does exist that short-term exposure to micro-G conditions could affect the cardiovascular regulation differently from long-term exposure. Previous studies from this laboratory have shown that arterial baroreflex control of heart rate is not altered after 4 hours Head Down (HD) at -6 degrees, whereas it is significantly decreased after 28 days. Again, the role played by possible disturbances of the vasomotor regulation in the genesis of orthostatic intolerance after short term exposure to simulated microgravity has not yet been clarified. The aim of this study was therefore to evaluate peripheral blood flow changes following 2 and 4 h HD -6 degrees in healthy volunteers.

Adult↗
PubMed2005

A 3D analysis of hindlimb motion during treadmill locomotion in rats after a 14-day episode of simulated microgravity.

This study describes the effect of simulated microgravity in rat on kinematics and electromyographic activity during treadmill locomotion. The analysis was performed in rats submitted to 14 days of hindlimb unloading (HU), in rats submitted to hindlimb unloading and then authorized to recover for 7 days (REC), and in aged-matched control rats (CON). Movements of the right hindlimb were measured with a 3D-optical analyzer (SAGA3 system) and five small infrared-reflective disks positioned on the skin, recorded by three CCD cameras. Results showed that HU rats exhibited hyperextensions at the end of the stance phase. By contrast, during the major part of the step, the ankle was less extended than CON. Possible origins of the changes are discussed. This leads to the question of how important is sensory input in the regulation of the locomotor pattern after HU. Data obtained in REC animals showed that 1 week of recovery allowed the restoration of a good locomotor performance. However, the limb motion remained abnormal, and at contrary to HU rats: higher extension during the step, except at push-off when the limb was in hyperflexion. We concluded that simulated microgravity involves a dual adaptive process: a first one during unloading, and a second one during the period of recovery, which is not a simple return to initial characteristics of the locomotor pattern.

Adaptation, Physiological↗
PubMed1999

Dynamics of blood pressure and pulse interval duration in rats after 14 day suspension.

At present, the pronounced changes in cardiovascular system observed in microgravity and on returning to 1 g are mostly attributed to the regulatory disturbances. The tail suspension model is used to simulate the effects of microgravity on muscle, bone and, on cardiovascular system of rats. Having in mind all limitations of this method, we decided to use it for analysis of the acute effects of cessation of tail suspension on regulation of cardiovascular system in rats.

Animals↗
PubMed2001

Decreased +gz tolerance following lower body positive pressure: simulated push-pull effect.

OBJECTIVE: The purpose of this study was to attempt to simulate the push-pull maneuver on a single-axis human centrifuge using lower body positive pressure (LBPP), and to observe the effect of the push-pull maneuver on +Gz tolerance. METHODS: Six volunteers participated in the experiment. They were subjected to LBPP of up to 300 mm Hg for 1 min. Blood pressure (BP) and heart rate (HR) were monitored before, during and after LBPP. Immediately after LBPP, +Gz tolerance was measured on a human centrifuge. RESULTS: During LBPP, systolic BP (SBP) and diastolic BP (DBP) increased significantly, mean arterial pressure (MAP) increased but not significantly, and HR decreased significantly. After LBPP, SBP and MAP decreased significantly, while DBP and HR decreased but not significantly. In all subjects, +Gz tolerance decreased after LBPP. The decreased value was 0.70 +/- 0.06 G, maximum 1.0 G and minimum 0.5 G. CONCLUSION: The push-pull maneuver can be simulated on a single-axis human centrifuge using LBPP. The physiologic effects of LBPP were similar to those of -Gz. We observed that +Gz tolerance decreased after LBPP, which confirmed the push-pull effect from the experiment.

Acceleration↗
PubMed2004

Neurogenic constrictor response of isolated small renal arteries in rats after 2-week simulated microgravity.

The study was aimed at investigation of the effects of 2-week tail suspension upon the constrictor responses of isolated small renal arteries in rats. 1st-2nd-order branches of renal artery were perfused with saline under the constant flow conditions. Constrictor responses to electrical stimulation of periarterial nerves, noradrenaline and serotonin were investigated. In post-suspension rats as compared to controls the response to nerve stimulation was slightly reduced during 15-Hz stimulation, but similar at smaller frequencies. Thus, simulated microgravity has no prominent effect of neurogenic responses of renal vessels, in agreement with non-changed density of periarterial adrenergic nerve plexus. Along with that, in post-suspension rats impairment of prejunctional sympathetic mechanisms might be compensated by augmented sensitivity of vascular smooth muscle to vasoconstrictors.

Animals↗
PubMed2003

[Image analysis of cardiac muscle cytoskeleton under simulated microgravity based on gray-level co-occurrence matrix (GLCM)].

OBJECTIVE: To study morphological changes of the cytoskeleton-microtubule (MT) of the fetal rat cardiac myocytes under simulated microgravity, and to quantify its image by utilizing the gray level co-occurrence matrix (GLCM) parameters of the image. METHOD: Cytoskeleton images, including cellular microphotographs taken under normal or microgravity (clinostat) conditions, were quantified by gray level co-occurrence matrix parameters, and the pharmacological counter effect of quercetin against the influences of microgravity was estimated with these parameters. RESULT: The results showed that the texture of microtubules in the image became worse under simulated microgravity environment. It also showed that quercetin has certain counter effect against the influence of microgravity. CONCLUSION: The microtubule of the cardiac myocytes cytoskeleton becomes diffused under microgravity, and the GLCM parameters can well describe these variation. Quercetin has certain counter-effect against the influence of microgravity.

Animals↗