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At least 667 records · Page 37Linked to original sources
PubMed1996

Erythropoietin under real and simulated microgravity conditions in humans.

The aim of this study was to analyze the time course of erythropoietin (EPO) during Earth-bound microgravity simulations such as bed rest, isolation and confinement (IC), head-down tilt (HDT; -6 degrees), and immersion to evaluate which factors could contribute to alterations in EPO under real microgravity conditions during and after short- (< 10 days) and long-term (> 6 mo) spaceflights. During bed rest (24h), no significant changes in EPO could be observed. Subjects confined in a diving chamber facility for 60 days showed a decrease in EPO. In the recovery period a slight increase was observed, but EPO concentrations did not reach the pre-IC control level. In the control period before HDT, subjects showed normal resting values for EPO, but on day 2 of HDT the EPO concentrations were decreased (P < 0.01). Later the EPO levels remained below the control value and were increased after HDT (P < 0.05). After immersion (24 h) increased EPO concentrations could be determined (P < 0.05). During a short-term spaceflight the astronauts showed in-flight (day 4) decreased and unchanged EPO concentrations. During a long-term spaceflight, 24 h after recovery, the cosmonaut showed slightly elevated EPO concentration, which increased markedly during the following days. It is concluded that 1) HDT (-6 degrees) causes a rapid decrease in EPO in humans, 2) IC per se leads to diminished EPO concentrations, 3) EPO regulation in humans during short- and long-term spaceflights might be different, 4) changes in central blood volume, i.e., central venous pressure, seem to be involved in the modulation of EPO production and release under simulated and real microgravity conditions, and 5) the HDT (-6 degrees) Earth-bound simulation reflects mostly the changes in EPO production and release observed under real microgravity conditions in humans.

Adult↗
PubMed2004

Hindlimb unloading depresses corneal epithelial wound healing in mice.

C57BL/6 mice were subjected to hindlimb unloading (HU) for a period of 3 wk to determine the possible effects on epithelial wound healing. A standardized corneal epithelial wound was performed, and parameters of the inflammatory response and reepithelialization were analyzed over an observation period of 96 h. Wound closure was significantly retarded in mice during HU with reepithelialization being delayed by approximately 12 h. Both epithelial migration and cell division were significantly depressed and delayed. The inflammatory response to epithelial wounding was also significantly altered during HU. Neutrophils, as detected by the Gr-1 marker, were initially elevated above normal levels before wounding and during the first few hours afterward, but there was a significant reduction in neutrophil response to wounding at times where neutrophil influx and migration in controls were vigorous. A similar pattern was seen with CD11b+CD11c+ cells (monocyte lineage). Langerhans cells are normally resident within the peripheral corneal epithelium. They respond to injury by initially leaving the epithelial site within 6 h and returning to normal levels by 96 h, 2 days after reepithelialization is complete. During HU, this pattern is distinctly different, with Langerhans cell numbers slowly diminishing, reaching a nadir at 96 h, which is significantly below normal. Evidence for systemic effects of HU is provided by findings that collagen deposition within subcutaneous sponges was significantly reduced during HU. In conclusion, HU, a ground-based model simulating some physiological aspects of spaceflight, impairs wound repair of corneas. Multiple factors, both local and systemic, likely contribute to this delayed wound healing.

Animals↗
PubMed1993

Relationship between hind-limb muscle atrophy and serum enzymes in tail suspended rats.

Many studies on the effects of gravity have been reported using animals or human being since the gravity influences the biological body in space. Especially suspension techniques for rat have been used as a microgravity simulation. This study is a report on the relation between serum enzymes such as CK and muscle atrophy, caused by tail suspension in rats.

Alanine Transaminase↗
PubMed1999

The effect of simulated microgravity conditions on the TNF-alpha production by human PBMCS.

Our earlier space experiments demonstrated that the interferon production of human lymphocytes in microgravity is 4-8 times higher than those of the synchronous ground controls in vitro (Talas et al. 1983). These data suggested that the microgravity has a significant effect on cells. Since the possibilities to perform space-experiments are very limited and our study raised many interesting questions, we wished to simulate microgravity conditions in our laboratory. For this reason we purchased a Rotary Cell Culture System (RCCS) equipment to study different cell lines and human peripheral blood mononuclear cells (PBMCs) in experimental microgravity conditions. RCCS is a horizontally rotated bubble free culture vessel with membrane diffusion gas exchange. We report here an analysis of TNF-alpha (tumor necrosis factor-alpha) production by human PBMCs (control cultures exposed to simulated microgravity in RCCS). The cells were incubated in the presence or absence of either NDV (Newcastle Disease Virus) or one of the different forms (PHA-M or -P) of Phytohaemagglutinin.

Cell Culture Techniques↗
PubMed1994

Effects of exercise on rats subjected to tail suspension.

Deterioration of vital functions is observed in living organisms in microgravity. However, this deterioration can be arrested by adequate exercises. In this study, utilizing tail suspension in rats to simulate microgravity, we examined the influence of running exercise every other day on blood constituents, visceral parameters, and muscles.

Alkaline Phosphatase↗
PubMed2000

Effects of clinostat-microgravity on bone and calcium metabolism in rats.

Decreases in bone minerals and tissue volume after space flight have been observed in humans and animals, with a variety of results. Such data obtained from space flight experiments have given unsatisfactory results due to short periods of space flight and differences in age, body weights, and strain of animals used. Therefore, ground-based animal models have been developed in order to elucidate changes in bone affected by space flight. For example, a tail-suspended rat model has been established to study the effects of microgravity on bones by producing hind limb unloading. However, problems with this model due to the remaining forelimb loading and the unusual changes in blood current require the development of a new model simulating the physiological conditions of space flight. So we developed a three-dimension clinostat as an apparatus to produce a simulated microgravity similar to space flight by rotating rats equally in all directions. The purpose of the present study is to examine the effects of clinostat-microgravity on bone metabolism in rats.

Adrenal Glands↗
PubMed2006

[Three-dimensional spheroid model for cultivating WB-F344 cells in simulated microgravity].

Three-dimensional (3D) culture of cells could closely mimic the in vivo situation with regard to cell function and microenvironment compared with plane monolayer cultured cells. In this paper, we established 3D culture of rat WB-F344 cells with rotary cell culture system (RCCS) to simulate microgravity environment, and examined cells proliferation, morphology, microstructure, E-cadherin protein quantity and mRNA expression of adhesion molecules by count the number of cells, optical microscope, transmission electron microscope and reverse transcriptase-polymerase chain reaction (RT-PCR). The results demonstrated that cells were polyhedron with lots of micovilli and mitochondria, which grow well and packed together densely to form irregular aggregates. Adjacent cells were connected with desmosome and tight junction. With the regard, the aggregates behaved 3D growth characteristics. Moreover, compared with control, mRNA level of Fibronectin and E-cadherin protein were increased, the changes maybe is the part mechanism in this microgravity simulated cells culture models which strengthened cells junction. This rotating 3D model might facilitate the study of interactions of cell-cell, cell-matrix and the mechanisms.

Animals↗
PubMed1989

The biological clock of Neurospora in a microgravity environment.

The circadian rhythm of conidiation in Neurospora crassa is thought to be an endogenously derived circadian oscillation; however, several investigators have suggested that circadian rhythms may, instead, be driven by some geophysical time cue(s). An experiment was conducted on space shuttle flight STS-9 in order to test this hypothesis; during the first 7-8 cycles in space, there were several minor alterations observed in the conidiation rhythm, including an increase in the period of the oscillation, an increase in the variability of the growth rate and a diminished rhythm amplitude, which eventually damped out in 25% of the flight tubes. On day seven of flight, the tubes were exposed to light while their growth fronts were marked. Some aspect of the marking process reinstated a robust rhythm in all the tubes which continued throughout the remainder of the flight. These results from the last 86 hours of flight demonstrated that the rhythm can persist in space. Since the aberrant rhythmicity occurred prior to the marking procedure, but not after, it was hypothesized that the damping on STS-9 may have resulted from the hypergravity pulse of launch. To test this hypothesis, we conducted investigations into the effects of altered gravitational forces on conidiation. Exposure to hypergravity (via centrifugation), simulated microgravity (via the use of a clinostat) and altered orientations (via alterations in the vector of a 1 g force) were used to examine the effects of gravity upon the circadian rhythm of conidiation.

Biological Clocks↗
PubMedDate not supplied

Induction of vascular endothelial phenotype and cellular proliferation from human cord blood stem cells cultured in simulated microgravity.

Recent studies have demonstrated that stem cells derived from adult hematopoietic tissues are capable of trans-differentiation into non-hematopoietic cells, and that the culture in microgravity (microg) may modulate the proliferation and differentiation. We investigated the application of microg to human umbilical cord blood stem cells (CBSC) in the induction of vascular endothelial phenotype expression and cellular proliferation. CD34+ mononuclear cells were isolated from waste human umbilical cord blood samples and cultured in simulated microg for 14 days. The cells were seeded in rotary wall vessels (RWV) with or without microcarrier beads (MCB) and vascular endothelial growth factor was added during culture. Controls consisted of culture in 1 G. The cell cultures in RWV were examined by inverted microscopy. Cell counts, endothelial cell and leukocyte markers performed by flow cytometry and FACS scan were assayed at days 1, 4, 7 and at the termination of the experiments. Culture in RWV revealed significantly increased cellular proliferation with three-dimensional (3D) tissue-like aggregates. At day 4, CD34+ cells cultured in RWV bioreactor without MCB developed vascular tubular assemblies and exhibited endothelial phenotypic markers. These data suggest that CD34+ human umbilical cord blood progenitors are capable of trans-differentiation into vascular endothelial cell phenotype and assemble into 3D tissue structures. Culture of CBSC in simulated microg may be potentially beneficial in the fields of stem cell biology and somatic cell therapy.

Antigens, CD34↗
PubMed2003

[Control of morphogenesis of woody plant by gravity on earth].

Using the weeping branch of Japanese flowering cherry tree and its woody stem of the seedling grown under simulated microgravity condition by three dimensional clinostat, it was elucidated that the morphogenesis of its secondary xylem supporting the plant itself to grow upward is seriously controlled by gravity on earth with a sedimentable amyloplast as its sensor. Space experiment of woody plant is expected to elucidate such problem.

Gravitation↗
PubMed1995

The senescence of oat leaf segments is promoted under simulated microgravity condition on a three-dimensional clinostat.

Plants have evolved on the earth, indicating the morphology, growth and development, and life cycle of plants are highly influenced by gravity as well as other environmental stimuli. Indeed, simulated microgravity on a clinostat or hypergravity on a centrifuge has recently been reported to change the growth and development of plants (Hoson et al. 1992, 1993, 1995, Rasmussen et al. 1994, Kasahara et al. 1995). Senescence is a final drastic phenomenon in life cycle of plants, which is characterized by the loss of total chlorophyll and protein, and/or the formation of the abscission (Osborne 1973, Thimann 1977, Addicott 1982). Many environmental stimuli as well as the qualitative and quantitative changes of plant hormones have been reported to affect plant senescence. Among those stimuli, light is the most important factor to regulate plant senescence (Leopold 1964). Dark condition promotes leaf senescence due to the decrease in endogenous level of cytokinin and/or the increase in that of abscisic acid or ethylene (Tetley and Thimann 1974, Gepstein and Thimann 1980). However, there are few reports concerning the effect of gravity on leaf senescence. Strenuous effort to learn leaf senescence under microgravity condition has been done using a three-dimensional (3-D) clinostat. In this paper, we report that simulated microgravity condition on a 3-D clinostat promoted the senescence of oat leaf segments in the dark. A possible mechanism of microgravity condition on promoting the senescence is also discussed.

Abscisic Acid↗
PubMed1998

Cellular adhesion in neoplastic and syngeneic normal cells under altered gravitational conditions.

The major objective of several experiments performed in space in the last 15 years was to establish whether single cells are sensitive to gravity. It was found in certain cells that reduced gravity leads to profound changes of a number of physiological functions like genetic expression, cell proliferation, signal transduction and cytoskeleton structure. In cell biology studies microgravity can be simulated on Earth in the clinostat. Nearly all data on experiments in the clinostat are related to cells cultured in suspension and, therefore, to adhesion-independent cells. In contrast, several biological phenomena as neoplastic transformation, cell differentiation, in-vitro cellular aging, contact inhibition and cellular adhesion require mainly cellular systems that are adhesion-dependent. The purpose of this work was: a) to study the behaviour of two rat cell strains (neoplastic SGS/4A and syngeneic fibroblasts FG) in order to test whether adhesion-dependent cells are suitable for clinorotation and b) to investigate cell-cell and cell-substratum adhesion in these cells kept under simulated low-g in the fast rotating clinostat and in hypergravity at l0g in the centrifuge.

Animals↗
PubMed2001

Selective impairment of excitatory pressor responses after prolonged simulated microgravity in humans.

The haemodynamic and autonomic effects of prolonged exposure to simulated microgravity were assessed non-invasively in seven healthy volunteers completing a 42-day -6 degrees head down tilt. Before, during and after head down tilt, subjects were exposed to moderate excitatory stimuli (mental arithmetic and static handgrip) to gauge possible progressive impairment of pressor responses. Before and after head down tilt, subjects were also exposed to orthostatic stress, to assess influences of simulated microgravity on orthostatic defence. Simple haemodynamics (heart rate and systolic arterial blood pressure), linear (i.e., oscillatory) components of beat-by-beat variability, non-linear properties (i.e., corrected conditional entropy (CCE)) of RR interval variability, and baroreflex slope furnished a non-invasive evaluation of autonomic regulatory mechanisms. Pressor responses to mental arithmetic and to handgrip were markedly impaired after 42 days head down tilt, whereas responses in markers of autonomic regulation were not modified. Standing, performed 8 days after head down tilt to limit the risk of syncope, still induced a variable degree of hypotension, with signs of progressively greater sympathetic activation than before head down tilt. Simulated microgravity-induced reduction of pressor responses, in spite of largely maintained autonomic activation, favours the hypothesis of a peripheral impairment of cardiovascular homeostasis. rights reserved.

Autonomic Nervous System↗
PubMed2006

Effects of simulated microgravity on the morphology and function of neonatal porcine cell clusters cultured with and without Sertoli cells.

Human islet allografts are well known to induce full and sustained remission of hyperglycemia, with complete normalization of key metabolic parameters. Nevertheless, acquiring human islets, even from cadaveric human donor pancreases, remains a significant impediment to successful transplantation therapy for diabetes. To overcome this difficulty, neonatal porcine cell clusters (NPCCs) have been considered for human islet substitutes because they are easily obtained by collagenase digestion of the neonatal piglet pancreas. Currently, the major hurdle in using NPCCs for xenograft is the delay (time lag) in achieving the posttransplant normalization of blood glucose levels in animal diabetic recipients. The present work is the first attempt to evaluate whether incubation of NPCCs in simulated microgravity, in the presence or absence of Sertoli cells (SC), may reduce the maturation time lag of beta-cells by differentiation acceleration in vitro, thereby expediting production, viability, and acquisition of functional competence of pretransplantation beta-cell-enriched islets. Following a 3-day incubation period, NPCCs maintained in conventional culture, NPCCs incubated in simulated microgravity in the HARV biochamber, and NPCCs plus co-incubated SC in simulated microgravity were examined for viability, morphology, and insulin secretion. Results show that NPCCs grown alone in the HARV biochamber are superior in quality, both in terms of viability and functional competence, when compared to other culture pretreatment protocols. This finding strongly suggests that NPCC pretreatment in simulated microgravity may enhance the transplantation success of NPCCs in the diabetic recipient.

Animals↗
PubMed1998

Psychophysiological and neuroendocrine interrelations in conditions of antiorthostatic hypokinesia.

The study of psychophysiological status' interaction and interrelation with parameters of a neurohumoral regulation is important for perfection of medical and psychological support of high serviceability of the crew-members in conditions of space flight. Long-term bed rest in a head-down tilt (BRHDT, antiorthostatic hypokinesia) is used for simulation of prolonged influence of microgravity on a human body in ground-based conditions. The main objective of the present work was to reveal main links of psychophysiological state with neurohumoral parameters in BRHDT.

Bed Rest↗
PubMed2001

Expression of cell adhesion molecules and lymphocyte-endothelium interaction under simulated hypogravity in vitro.

Using histochemical staining and FACS-analysis we have studied the basal and TNF-alpha induced expression of E-selectin, ICAM-1 and VCAM-1 in human umbilical vein endothelial cells (ECs) exposed to simulated hypogravity. Control ECs did not contain detectable amounts of E-selectin or VCAM-1 but were ICAM-1 positive. As soon as after 6-8 hrs of clinorotation at 5 RPM the cellular content of ICAM- 1 increased. Moreover, hypogravity potentiated the effect of inflammatory cytokines (TNF-alpha and IL-1) on ICAM-1 expression. No increase in E-selectin or VCAM-1 expression was observed in ECs exposed to hypogravity itself. However, hypogravity reduced E-selectin and VCAM-1 expression in cell cultures activated by cytokines, more visible at their low (5-10 U/ml) concentrations. Both, control and clinorotated ECs poorly supported spontaneous lymphocyte adhesion; the adhesion of PMA-activated leukocytes was 15-20-fold higher. The interaction of unstimulated lymphocytes with cytokine-activated endothelium was more noticeable but significantly lower in cultures exposed to hypogravity. Activated blood cells interacted with endothelium more effectively, particularly, under hypogravity. Obtained results suggest that EC adhesion molecule expression and endothelium-lymphocyte interaction are altered under simulated hypogravity conditions in direction of increase of endotlielial adhesiveness for activated blood cells.

Cells, Cultured↗
PubMed2006

Gravity replacement during running in simulated microgravity.

INTRODUCTION: During treadmill exercise on the International Space Station (ISS), a restoring load from a subject load device (SLD) is applied through a shoulder-and-waist harness to pull the exercising crewmember toward the treadmill surface. The capacity of this arrangement to provide 1-g-like reaction forces may be critical for effective use of the treadmill as a countermeasure to musculoskeletal changes during prolonged spaceflight. This study in simulated microgravity evaluated the comfort and function during running of the ISS harness used with a new SLD in a system that allows more even distribution of the load between the waist and shoulders. METHODS: Using a zero-gravity locomotion simulator, 12 subjects completed three 5-min running trials at a constant speed (3.35 m x s(-1)) using three SLD loads [50%, 75%, and 100% of bodyweight (BW)] presented at random and a shoulder-to-waist loading ratio of 50:50. Subjective ratings of discomfort, ground reaction forces (GRFs), and SLD loads were collected. RESULTS: A load of 100% BW resulted in similar GRF profiles (peak and rate of change of force) to those reported for 1-g running over ground and were also comfortably tolerated (mean Borg scale rating 3.9/10). DISCUSSION: With an appropriate harness and SLD system, 1-g-like GRF profiles can be generated at the feet during simulated microgravity running. Such forces can be achieved with a level of discomfort rated better than "somewhat uncomfortable," suggesting that running with 1-g loads could be an effective component of musculoskeletal countermeasures during long-duration spaceflight.

Adult↗