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PubMed1981

The action of simulated and true weightlessness on the digestive tract of rats.

Rats on board the Soviet Cosmos 936 satellite for l8 1/2 days showed a decreased glycoprotein secretion from the salivary mucous glands, stomach and intestine, and an increased leucine aminopeptidase and acid phosphatase content from the small intestine. Grimelius positive cells were activated. One group of rats were centrifuged at 1 g during the flight to simulate terrestrial gravity. Some investigations have suggested that under these conditions muscular and cardiac disorders diminished. In the digestive tract the benefits of centrifugation at 1 g are minimal and limited to a few glycoprotein components. The digestive changes are probably the expression of a stress response, unrelated to weightlessness. Similar changes, concomitant with a glycocorticoid hypersecretion, were found in rats after 15 days of hypokinesia on Earth. These digestive changes persisted even in adrenalectomized rats.

Acid Phosphatase↗
PubMed1992

[Vertebral, femoral and radial bone density in simulation of prolonged weightlessness. Experience with healthy volunteers].

Disturbances in bone tissue induced by weightlessness in man are incompletely known. All we possess are indirect data which show negativation of the calcium-phosphate balance and bone density measurements mainly in peripheral bones (calcaneum and radius bones). Staying in supine position with the head down (the so-called anti-orthostatic position) is a means of simulating on earth the effects of weightlessness in space flights. We studied the changes in vertebral, femoral and radial bone densities that might occur in 7 healthy volunteers subjected to two 1-month period of bed rest with strict (-6 degrees) anti-orthostatic position. No significant variation was recorded at the end of each period. When the two periods were added the mean vertebral bone loss was -0.9 percent per month. This figure was comparable to that found in similar studies performed in the USA with longer periods of bed rest. The bone loss in such experiments was 4 to 8 times less than that reported for pathological immobilization. Further simulation studies are needed to evaluate the bone loss kinetics and to test the effectiveness of the preventive measures used in spatial flights.

Adult↗
PubMed2001

X-ray-induced chromosome aberrations in human lymphocytes in vitro are potentiated under simulated microgravity conditions (Clinostat).

The influence of simulated microgravity weightlessness on the outcome of radiation-induced chromosomal aberrations was investigated using the clinostat as a tool to simulate weightlessness conditions. Treatments were performed in the G0 phase of human lymphocytes with 1.5 Gy of X-rays alone or in combination with the DNA synthesis inhibitor of 1-beta-D-arabinofuranosylcytosine (ara-C) to check also for possible specific radiation-induced DNA repair processes impairment (excision repair caused by base damage) under microgravity conditions. The results obtained, which confirmed previous findings, showed significantly higher increases of aberrant cells and hence total number of aberrations compared to the parallel treatments performed 'on ground'. For what concern ara-C its contribution in terms of potentiation in the induction of aberrant cells was equivalent in absolute terms under simulated microgravity conditions and 'on ground' indicating that excision repair caused by base damage and inhibited by ara-C is not affected by simulated microgravity. A possible explanation for this outcome could quote two major factors: i) Enhanced probability that under simulated microgravity conditions the reactive DSB are spatially brought together to better interact, hence increasing the probability of mis-rejoining. ii) Alternatively chromatin structure could be modified under simulated microgravity conditions generating different quality and quantities of DNA lesions compared to treatments performed 'on ground'.

Antimetabolites, Antineoplastic↗
PubMed1999

[The pharmacological correction of hemodynamics during the simulation of the early period of adaptation to weightlessness].

Investigations of volunteered subjects in whom antiorthostatic hypokinesia was modeled by tilting the cranial end of the body by -15 degrees were to answer whether pharmacological countermeasures of the vestibular/autonomous syndrome (motion sickness, sea sickness) alter the orthostatic tolerance and cardiovascular parameters. As was stated, the drugs allow controlled correction of hemodynamic resistance to the head-down tilt. Ephedrine, phencarol, ephedrine combined with scopolamine and pipolphen, and stugeron normalized cerebral circulation. Medicaments were unable to moderate the sympathoadrenal reaction to the head-down tilt; however, blood concentrations of catecholamines were significantly lower than in the control. The greatest effect was achieved using ephedrine and ephedrine plus pipolphen.

Adaptation, Physiological↗
PubMed1996

Body fluid metabolism at actual and simulated microgravity.

Recent observations from space missions indicate that weightlessness does not induce an increase in diuresis and natriuresis in astronauts. Rather, both oral fluid and sodium intake as well as renal fluid and sodium output appear reduced compared with the preflight condition. In addition, influences of reduced energy intake may be more important for total body fluid content inflight than generally assumed. Decreases in plasma volume and observations of upper body edema formation inflight indicate, in addition, an increased extravasation as a result of the headward fluid shift in weightlessness. Current simulations models of microgravity for body fluid metabolism are valid for simulations of the central fluid shift occurring in microgravity. Since weightlessness appears to decrease central venous pressure and does not induce an increased renal fluid and sodium excretion, while simulations models have opposite effects, additional models to simulate adaptation of body fluid metabolism to weightlessness might be necessary.

Adaptation, Physiological↗
PubMed1982

The effects of horizontal body casting on blood volume, drug responsiveness, and +Gz tolerance in the Rhesus monkey.

To simulate the weightless condition, eight rhesus monkeys, instrumented with solid-state pressure transducers, were horizontally restrained in body casts for 28 d. Blood volume decreased an average of 13% after 14 d of restraint, due mainly to a drop in plasma volume. Aortic pressure and heart rate responses to norepinephrine and phenylephrine decreased after 14 d of restraint. The monkeys did not show a statistically significant decreased tolerance to a 90 degree sudden upright tilt after horizontal restraint. During the fifth week of casting, four animals were subjected to +Gz acceleration tests on a centrifuge. The acceleration tolerance of the casted monkeys was significantly reduced compared to four similarly instrumented control animals. These findings indicate that the cardiovascular deconditioning associated with simulated weightlessness results from an inability to maintain central blood volume during orthostatic stress.

Acceleration↗
PubMed1992

Global approach to simulation: a gateway to long-term human presence in space.

The establishment of an autonomous European manned space capability is an objective set up by the ESA Council Meeting at the ministerial level, in 1985/1987. ESA's Long-Term Programme Office (LTPO), charged of the preparation of the programme for a European Manned Space Infrastructure (EMSI), started during 1988 to build up an intellectual framework in the domain of long-duration manned space missions. EMSI scope was eventually extended to embrace Moon/Mars missions and bases. Several exploratory studies on problems related to human factors in long-duration space missions were initiated by LTPO. The work of an ad-hoc group of experts (SIMIS Group) has been focused during 1989/1990 on the planning for simulation of such missions with a broad mandate, covering the physiological, psychological and operational aspects of long-duration exposure to microgravity and isolation/confinement. Preliminary results of SIMIS activities are reported. The HYDREMSI experiment, carried out in a terrestrial, analogous environment for 72 days during 1989, is described as an example of the envisaged simulations.

Astronauts↗
PubMed2005

Magnetic levitation-based Martian and Lunar gravity simulator.

Missions to Mars will subject living specimens to a range of low gravity environments. Deleterious biological effects of prolonged exposure to Martian gravity (0.38 g), Lunar gravity (0.17 g), and microgravity are expected, but the mechanisms involved and potential for remedies are unknown. We are proposing the development of a facility that provides a simulated Martian and Lunar gravity environment for experiments on biological systems in a well controlled laboratory setting. The magnetic adjustable gravity simulator will employ intense, inhomogeneous magnetic fields to exert magnetic body forces on a specimen that oppose the body force of gravity. By adjusting the magnetic field, it is possible to continuously adjust the total body force acting on a specimen. The simulator system considered consists of a superconducting solenoid with a room temperature bore sufficiently large to accommodate small whole organisms, cell cultures, and gravity sensitive bio-molecular solutions. It will have good optical access so that the organisms can be viewed in situ. This facility will be valuable for experimental observations and public demonstrations of systems in simulated reduced gravity.

Animals↗
PubMed1999

Microgravity effects on water flow and distribution in unsaturated porous media: analyses of flight experiments.

Plants grown in porous media are part of a bioregenerative life support system designed for long-duration space missions. Reduced gravity conditions of orbiting spacecraft (microgravity) alter several aspects of liquid flow and distribution within partially saturated porous media. The objectives of this study were to evaluate the suitability of conventional capillary flow theory in simulating water distribution in porous media measured in a microgravity environment. Data from experiments aboard the Russian space station Mir and a U.S. space shuttle were simulated by elimination of the gravitational term from the Richards equation. Qualitative comparisons with media hydraulic parameters measured on Earth suggest narrower pore size distributions and inactive or nonparticipating large pores in microgravity. Evidence of accentuated hysteresis, altered soil-water characteristic, and reduced unsaturated hydraulic conductivity from microgravity simulations may be attributable to a number of proposed secondary mechanisms. These are likely spawned by enhanced and modified paths of interfacial flows and an altered force ratio of capillary to body forces in microgravity.

Capillary Action↗
PubMed2000

Altered gravity downregulates aquaporin-1 protein expression in choroid plexus.

Aquaporin-1 (AQP1) is a water channel expressed abundantly at the apical pole of choroidal epithelial cells. The protein expression was quantified by immunocytochemistry and confocal microscopy in adult rats adapted to altered gravity. AQP1 expression was decreased by 64% at the apical pole of choroidal cells in rats dissected 5.5-8 h after a 14-day spaceflight. AQP1 was significantly overexpressed in rats readapted for 2 days to Earth's gravity after an 11-day flight (48% overshoot, when compared with the value measured in control rats). In a ground-based model that simulates some effects of weightlessness and alters choroidal structures and functions, apical AQP1 expression was reduced by 44% in choroid plexus from rats suspended head down for 14 days and by 69% in rats suspended for 28 days. Apical AQP1 was rapidly enhanced in choroid plexus of rats dissected 6 h after a 14-day suspension (57% overshoot, in comparison with control rats) and restored to the control level when rats were dissected 2 days after the end of a 14-day suspension. Decreases in the apical expression of choroidal AQP1 were also noted in rats adapted to hypergravity in the NASA 24-ft centrifuge: AQP1 expression was reduced by 47% and 85% in rats adapted for 14 days to 2 G and 3 G, respectively. AQP1 is downregulated in the apical membrane of choroidal cells in response to altered gravity and is rapidly restored after readaptation to normal gravity. This suggests that water transport, which is partly involved in the choroidal production of cerebrospinal fluid, might be decreased during spaceflight and after chronic hypergravity.

Animals↗
PubMed2001

[Prevention of altitude decompression sickness during simulation of egress from the cabin of space vehicle with hypobaric artificial atmosphere].

Based on the proposed semiempiric nomograms, the study was aimed at selection and investigation of normoxic N2-O2 hypobaric atmosphere (HA) at 93-73 kPa, and evaluation of effectiveness of the gas mixture against the altitude decompression sickness (ADS) during 6-hr simulation of extravehicular activities at 37 kPa without prebreathing. Subjects were 22 healthy males from 20 to 50 yr. old. In all, 115 experiments were performed. Twenty-four hours in HA at 93 kPa and subsequent transition to 37 kPa led up to development of ADS symptoms by one subject in one of 27 experiments (3.7%), and emergence of venous gas bubbles (USI) with the intensity of 2, 70, and 19 points by the Spenser scale in 9 experiments (33.3%). Lower HA pressures (86 kPa, 80 kPa and 73 kPa) did not give rise to ADS though the occurrence of venous GB distinctly tended downward (30.6%, 14.3% and 11.8%) and so did the intensity of their entry into the pulmonary circulation (2, 40, 18 points; 1, 80, 19 points, and 2, 00, 15 points, respectively). Minimal ADS risk was observed in HA at 80 kPa and 73 kPa and did not reach 4% at the confidence level of 95%.

Adult↗
PubMed1998

Launch conditions might affect the formation of blood vessels in the quail chorioallantoic membrane.

As a part of the first joint USA-Russian MIR/Shuttle program, fertilized quail eggs were flown on the MIR 18 mission. Post-flight examination indicated impaired survival of both the embryos in space and also of control embryo exposed to vibrational and g-forces simulating the condition experienced during the launch of Progress 227. We hypothesized that excess mechanical forces and/or other conditions during the launch might cause abnormal development or the blood supply in the chorioallantoic membrane (CAM) leading to the impaired survival of the embryos. The CAM, a highly vascularized extraembryonic organ, provides for the oxygen exchange across the egg shell and is thus pivotal for proper embryonic development. To test our hypothesis, we compared angiogenesis in CAMs of eggs which were either exposed to the vibration and g-force profile simulating the conditions at launch of Progress 227 (synchronous controls), or kept under routine conditions in a laboratory incubator (laboratory controls). At various time points during incubation, the eggs were fixed in paraformaldehyde for subsequent dissection. At the time of dissection, the CAM was carefully lifted from the egg shell and examined as whole mounts by bright-field and fluorescent microscopy. The development of the vasculature (angiogenesis) was assessed from the density of blood vessels per viewing field and evaluated by computer aided image analysis. We observed a significant decrease in blood-vessel density in the synchronous controls versus "normal" laboratory controls beginning from day 10 of incubation. The decrease in vascular density was restricted to the smallest vessels only, suggesting that conditions during the launch and/or during the subsequent incubation of the eggs may affect the normal progress of angiogenesis in the CAM. Abnormal angiogensis in the CAM might contribute to the impaired survival of the embryos observed in synchronous controls as well as in space.

Allantois↗
PubMed1984

A suspension model for hypokinetic/hypodynamic and antiorthostatic responses in the mouse.

Hypokinetic/hypodynamic and antiorthostatic responses to weightlessness and bedrest were simulated in mice using a suspension technique. Animals were suspended for 1 or 2 weeks in an antiorthostatic posture and positioned to permit freedom of movement but eliminate load bearing by the hindlimbs. Suspended mice exhibited reduced food and water intakes and rapid 10% decrease in body weight to a level which was maintained for the remainder of the suspension period. Diuresis was evident in suspended mice, but the natriuresis and kaliuresis previously observed in the suspended rat were not evident. Differential hindlimb muscle atrophy (soleus greater than plantaris = gastrocnemius greater than EDL) and increased excretion of urea and ammonia were also noted in suspended mice. Postsuspension recovery studies indicated that the recovery process was highly effective. These results document specific responses to hypokinesia/hypodynamia and antiorthostasis in the mouse and demonstrate similarities in the responses of mice and rats to suspension. These studies expand the utility of the suspension model and suggest that the mouse may be useful in future studies simulating both weightlessness and bedrest.

Adrenal Glands↗
PubMed1989

Potential sites for the perception of gravity in the acellular slime mold Physarum polycephalum.

Recently a gravisensitivity of the acellular slime mold Physarum polycephalum, which possesses no specialized gravireceptor, could be established by conducting experiments under simulated and under real near weightlessness. In these experiments macroplasmodia showed a modulation of their contraction rhythm followed by regulation phenomena. Until now the perception mechanism for the gravistimulus is unknown, but several findings indicate the involvement of mitochondria: A) During the impediment of respiration the 0g-reaction is inhibited and the regulation is reduced. B) The response to a light stimulus and the following regulation phenomena strongly resemble the behavior during exposure to 0g, the only difference is that the two reactions are directed into opposite directions. In the blue-light reaction a flavin of the mitochondrial matrix seems to be involved in the light perception. C) The contraction rhythm as well as its modulations are coupled to rhythmic changes in the levels of ATP and calcium ions, involving the mitochondria as sites of energy production and of Ca(++)-storage. So the mitochondria could be the site of the regulation and they possibly are the receptor sites for the light and gravity stimuli. Also the observation of a morphologic polarity of the slime mold's plasmodial strands has to be considered: Cross-sections reveal that the ectoplasmic wall surrounding the streaming endoplasm is much thinner on the physically lower side than on the upper side of the strand--this applies to strands lying on or hanging on a horizontal surface. So, in addition to the mitochondria, also the morphologic polarity may be involved in the perception mechanism of the observed gravisensitivity and of the recently established geotaxis. The potential role of the nuclei and of the contractile elements in the perception of gravity is also discussed.

Adenosine Triphosphate↗
PubMedDate not supplied

[Effect of weightlessness and and its simulations on the mechanical properties of the bones of animals undergoing torsion].

Mechanical properties (stress and strain) of bones from rats of different ages exposed to weightlessness, hypodynamia or hypokinesia were examined upon torsion. As compared to the controls, the femur of Cosmos-1129 rats showed high deformability. Also, skeletal bones of young rats proved more sensitive to hypodynamia than those of adult animals.

Aging↗