Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Space 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 109 records · Page 6Linked to original sources
PubMed2001

Permanent depression of plasma cGMP during long-term space flight.

The purpose of this study was to investigate plasma concentrations of cyclic guanosine monophosphate (cGMP) and atrial natriuretic peptide (ANP) during and after real and simulated space flight. Venous blood was obtained 3 min after the beginning and 2 min after the lower body negative pressure maneuver in two cosmonauts preflight (supine), inflight, and postflight (supine) and in five other subjects before, at the end, and 4 days after a 5-day head-down tilt (-6 degrees) bed rest. In cosmonaut 1 (10 days in space), plasma cGMP fell from preflight 4.3 to 1.4 nM on flight day 6, and was 3.0 nM on the fourth day after landing. In cosmonaut 2 (438 days in space), it fell from preflight 4.9 to 0.5 nM on on flight day 3, and stayed <0.1 nM with 5, 9, and 14 months in space, as well as on the fourth day after landing. Three months after the flight his plasma cGMP was back to normal (6.3 nM). Cosmonaut 2 also displayed relatively low inflight ANP values but returned to preflight level immediately after landing. In a ground-based simulation on five other persons, supine plasma cGMP was reduced by an average of 30% within 5 days of 6 degrees head-down tilt bed rest. The data consistently demonstrate lowered plasma cGMP with real and simulated weightlessness, and a complete disappearance of cGMP from plasma during, and shortly after long-duration space flight.

Adult↗
PubMed1979

An exploration of perception of body boundary, personal space, and body size in elderly persons.

A study of 108 elderly persons using the Body Distortion Questionnaire and the personal space simulation technique test did not support hypotheses that elderly persons with a large personal space will have a larger distortion of body boundary, a larger perception of large body size, a smaller perception of small body size, a larger distortion of body size, and a larger body distortion than elderly persons with a small personal space. The analyses with one-tail t tests showed elderly persons with a small personal space have a larger perception of large body size and a larger distortion of body size than elderly persons with a large personal space. When the extremes of personal space were used the results were the same. Males have a larger personal space and greater distortion of skin perceptions than females.

Aged↗
PubMedDate not supplied

Bone and body mass changes during space flight.

Body mass, calcium and skeletal changes occur in humans who have worked in microgravity. Physiologic changes are seen as early as one week and are still occurring 312 days into space flight. The physiologic changes in bone and mineral metabolism may be among those which limits long duration space flight if an adequate countermeasure is not developed. The purpose of this paper is to summarize what is known about calcium dynamics and bone mineral changes as well as associated changes of body mass induced by space flight. The data reported is from a variety of studies conducted in both actual and simulated space flight.

Aerospace Medicine↗
PubMedDate not supplied

[Effect of actoprotectors on the work capacity of operators during modeling of various factors of space flight].

This paper presents experimental findings indicating that bemithyl, an actoprotective agent, has a beneficial effect on the health status and work capacity of operators during simulated space flight and 56-hour continuous work. The drug enhanced psychophysiological tolerance of the operators and improved the quality of their work: the quality of their compensatory tracking was on the average 10% higher, the number of errors of their porsuit tracking was 1.8 times lower, and the time of visual signal detection was 2.4 times shorter as compared to the placebo controls.

Adaptation, Physiological↗
PubMedDate not supplied

Development and use of an animal model for investigations on rotator cuff disease.

Although both intrinsic and extrinsic factors have been implicated in the cause of rotator cuff disease, previous studies have not been designed to test hypotheses of this disease, partly because of the lack of an appropriate animal model. Thirty-three animals were evaluated according to a 34 item checklist of criteria to determine their appropriateness as an animal model for investigations on the rotator cuff. Only the rat shoulder satisfactorily fulfilled all criteria, with a prominent supraspinatus tendon passing under an enclosed arch. Once the rat was identified, 36 rats were randomized to three experimental groups. One group (n = 12) was treated with an intratendinous injection of bacterial collagenase simulating an acute intrinsic injury, another group (n = 12) was treated with an acromial alteration to reduce the subacromial space simulating an external compression, and the third group (n = 12) was treated with a combination of both modifications. Significant increases in cellularity, number of fibroblasts, and collagen disorganization were seen in all experimental tendons compared with a contralateral control group. Semiquantitative grading of histologic sections revealed marked changes in all groups at 4 and 8 weeks. Injuries appeared to be healing at 12 weeks except in the combination group, which seemed to demonstrate persistent alterations. This study supports the rat as an appropriate model for investigating rotator cuff disease. In addition, this study demonstrates that both intrinsic and extrinsic alterations can induce changes in the supraspinatus tendon, which may have similarities to human tendon disease.

Animals↗
PubMed1990

Reproduction in the space environment: Part I. Animal reproductive studies.

Mankind's exploration and colonization of the frontier of space will ultimately depend on men's and women's ability to live, work, and reproduce in the space environment. This paper reviews animal studies, from microorganisms to mammals, done in space or under space-simulated conditions, which identify some of the key areas which might interfere with human reproductive physiology and/or embryonic development. Those space environmental factors which impacted almost all species included: microgravity, artificial gravity, radiation, and closed life support systems. These factors may act independently and in combination to produce their effects. To date, there have been no studies which have looked at the entire process of reproduction in any animal species. This type of investigation will be critical in understanding and preventing the problems which will affect human reproduction. Part II will discuss these problems directly as they relate to human physiology.

Animals↗
PubMed2001

Quantification of solute entry into cochlear perilymph through the round window membrane.

The administration of drugs to the inner ear via the round window membrane is becoming more widely used for both clinical and experimental purposes. The actual drug levels achieved in different regions of the inner ear by this method have not been established. The present study has made use of simulations of solute movements in the cochlear fluids to describe the distribution of a marker solute in the guinea pig cochlear fluid spaces. Simulation parameters were derived from experimental measurements using a marker ion, trimethylphenylammonium (TMPA). The distribution of this ion in the cochlea was monitored without volume disturbance using TMPA-selective microelectrodes sealed into the first and second turns of scala tympani (ST). TMPA was applied to perilymph by irrigation of the intact round window membrane with 2 mM solution. At the end of a 90 min application period, TMPA in the first turn, 1.4 mm from the base of ST, reached an average concentration of 330 microM (standard deviation (S.D.) 147 microM, n = 8). TMPA in the second turn, 7.5 mm from the base of ST reached a concentration of 15 microM (S.D. 33 microM, n = 5). The measured time courses of TMPA concentration change were interpreted using the Washington University Cochlear Fluids Simulator (V 1.4), a public-domain program available on the internet at http ://oto.wustl.edu/cochlea/. Simulations with parameters producing concentration time courses comparable to those measured were: (1) round window permeability: 1.9 x 10(-80 cm/s; (2) ST clearance half-time: 60 min; (3) longitudinal perilymph flow rate: 4.4 nl/min, directed from base to apex. Solute concentrations in apical regions of the cochlea were found to be determined primarily by the rate at which the solute diffuses, balanced by the rate of clearance of the solute from perilymph. Longitudinal perilymph flow was not an important factor in solute distribution unless the bony otic capsule was perforated, which rapidly caused substantial changes to solute distribution. This study demonstrates the basic processes by which substances are distributed in the cochlea and provides a foundation to understand how other applied substances will be distributed in the ear.

Animals↗
PubMedDate not supplied

[Biological research in space].

The paper presents the results of investigations carried out during the last two decades on various biological objects--microorganisms, plant seeds, insects, higher and lower plants, fish and amphibians--in real and simulation space flights. The paper discusses the current knowledge of the biological role of gravity and possible mechanisms of adaptation to weightlessness as well as the suitability of different biological objects for further space studies. Most experiments conducted in real space flights have lent support to the theoretical studies of the level and limits of weightlessness effects upon biological systems. Analysis of the data obtained in space and ground-bound experiments suggests that molecular processes are indifferent to an altered gravity and that energy metabolism plays an important role in adaptation of biological systems to zero-g.

Adaptation, Physiological↗
PubMed1981

Survival of microorganisms in space: a review.

Spores of Bacillus subtilis were exposed to selected factors of space (vacuum, solar UV radiation, heavy ions of cosmic radiation), and their response was studied after recovery. These investigations were supplemented by ground-based studies under simulated space conditions. The vacuum of space did not inactivate the spores. However, vacuum-induced structural changes in the DNA, and probably in the proteins, caused a supersensitivity to solar UV radiation. This phenomenon is caused by the production of specific photoproducts in DNA and protein, which cannot be removed by normal cellular repair processes. In vegetative bacterial cells, exposed to vacuum, cell dehydration led to damage of the cell membrane, which could be partly repaired during subsequent incubation. The high local effectiveness of the cosmic heavy ions further decreases the chance that spores can survive for any length of time in space. Nonetheless, a spore travelling through space and protected from ultraviolet radiation could possibly survive an interplanetary journey. Such a situation favors panspermia as a possible explanation for the origin of life.

Bacillus subtilis↗
PubMed2000

A virtual source model for Monte Carlo modeling of arbitrary intensity distributions.

A photon virtual source model was developed for simulating arbitrary, external beam, intensity distributions using the Monte Carlo method. The source model consists of a photon fluence grid composed of a matrix of square elements, located 25-cm downstream from the linear accelerator target. Each particle originating from the fluence map is characterized by the seven phase space parameters, position (x, y, z), direction (u, v, w), and energy. The map was reconstructed from fluence and energy spectra acquired by modeling components of the linear accelerator treatment head using the Monte Carlo code MCNP4B. The effect of contaminant electrons is accounted for by the use of a sub-source derived from a phase-space simulation of a 25-MV linac treatment head using the code BEAM. The BEAM sub-source was incorporated into the MCNP4B phase-space model and is sampled using a field-size dependent sampling ratio. A Gaussian blurring kernel is convolved with the photon fluence map to account for the finite focal spot size and scattering effects from structures such as the flattening filter and MLC leaves. Depth dose and profile source calculations for 6-MV and 25-MV photon beams, for 5 x 5 cm2, 10 x 10 cm2, and 15 x 15 cm2 field sizes, are in good agreement with measurement and are well within acceptability criteria suggested by the AAPM Task Group Report No. 53. Irregular field calculations compared with film measurement and with a 3-D pencil beam algorithm show that the source model is capable of accurately simulating arbitrary MLC fields.

Biophysical Phenomena↗
PubMed2000

Can daily centrifugation prevent the haematocrit increase elicited by 6-degree, head-down tilt?

A measure to counteract the effects of low or zero gravity is required for long-term space flight, such as the manned Mars mission scheduled by the National Aeronautics and Space administration (NASA) for 2014. We conducted a series of centrifugation experiments with humans, using a short-arm centrifuge (radius 1.8 m, made by First Medical Co., Tokyo, Japan). We employed 6-degree, head-down tilt (HDT) for 4 days to simulate space flight. Ten healthy male volunteers underwent 4-day HDT and a 2-G daily centrifuge load for 60 min in the +Gz direction and measurements, such as haematocrit, 24-h urine volume, body weight and electrocardiogram (ECG) were made. There was no significant increase in the haematocrit during the HDT period, although our previous studies had shown a significant increase during HDT. A 60-min daily load of +2 Gz appears to be effective in reversing the haematocrit increase due to 4-day HDT.

Adult↗
PubMed1995

The feasibility of Doppler monitoring during EVA.

During extravehicular activities (EVA) outside the spacecraft, astronauts have to work under reduced pressure in a space suit. This pressure reduction induces the risk of decompression sickness (DCS) by the formation of gas bubbles from excess nitrogen dissolved in the organism by breathing air at normal pressure. Under laboratory conditions the gas bubbles moving in the blood stream can be detected by the non-invasive ultrasonic Doppler method. By early detection of excessive bubble formation the development of DCS symptoms may be prevented by early application of preventative measures. The method could also be useful when applied in the space suit in order to compare the results of laboratory tests with operational results, because there is a discrepancy according to the DCS risk of laboratory experiments and actual EVA missions, where no symptoms have been reported yet. A prototype Doppler sensor has been developed and implemented in the Russian Orlan suit. To investigate the feasibility of this method under simulated space conditions, the equipment has been used in a series of 12 thermovacuum chamber tests with suited subjects, where intravenous bubble formation was compared to unsuited control experiments. In more than 50% of the suited tests good Doppler recordings could be achieved. In some cases with unsatisfying results the signal could be improved by breathholding. Although the results do not yet allow any conclusion about a possible difference between suited and unsuited subjects due to the small number of tests performed, the method proved its feasibility for use in EVA suits and should be further developed to enhance the safety of EVA procedures.

Aerospace Medicine↗
PubMed1998

Evaluation of risk from space radiation with high-energy heavy ion beams.

The most challenging radiation in space consists of fully ionized atomic elements with high energy for which only the few lowest energy ions can be stopped in shielding materials. The health risk from exposure to these ions and their secondary radiations generated in shield materials is poorly understood since there are few human data and a systematic study in relevant animal model systems has not been made. The accuracy of risk prediction is described as the major limiting factor in the management of space radiation risk. The expected impact of systematic studies is examined using the limited available biological data and models. Given the limitations of current predictions, models must be developed that are able to incorporate the required fundamental scientific data into accurate risk estimates. The important radiation components that can be provided for laboratory testing are identified. The use of ground-based accelerator beams to simulate space radiation is explained and quantitative scientific constraints on such facilities are derived. Three facilities, one each in the United States, in Germany and in Japan, currently have the partial capability to satisfy these constraints. A facility has been proposed using the Brookhaven National Laboratory Booster Synchrotron in the United States; in conjuction with other on-site accelerators, it will be able to provide the full range of heavy ion beams and energies required.

Aerospace Medicine↗
PubMed1993

[Dielectric behavior of isolated rat submandibular glands: simulation with a vesicle-inclusion cell model].

In an attempt to correlate the passive electrical properties of the secretory tissue with its structure, I measured AC admittances for isolated rat submandibular glands, over the frequency range between 100 Hz and 500 MHz. Animals were divided into three groups: control and treatment with two different secretagogues, isoproterenol and pilocarpine. Dielectric dispersions observed from control glands had two characteristic frequencies at 2.6 kHz and 59 kHz; the former was of the alpha-type and the latter of the beta-type. Secretagogue-stimulated glands exhibited broader beta-dispersion curves. These dispersion data were analysed on the basis of a "two-shell model" with vesicle inclusions, in which two concentric shells represent the cell membrane and the nuclear envelope, and membrane-bounded vesicles are meant for secretory granules dispersed in the inter-shell space. Simulation by this model generated a good fit to data from the three groups. The analyses revealed that: (i) electric capacities for the cell and granular membranes were 2.1 and 0.9 microF/cm2, respectively; (ii) the conductivity of extracellular matrix was close to that of blood plasma; (iii) the conductivity ratio between cytoplasm and extracellular matrix was approx. 0.4; and (iv) the conductivity ratio between intragranular space and cytoplasm was approx. 0.7.

Animals↗
PubMedDate not supplied

High speed electrophoresis simulation for optimization of continuous flow electrophoresis and high performance capillary techniques: Part I. Computer model.

A computer program for high-speed simulation and optimization of electrophoretic processes has been developed for carrier-free systems of all kinds. The calculations are based on the one-dimensional dynamic (transient-state) model. The three-dimensional geometry of the simulation space can be chosen deliberately. With a highly efficient transport algorithm instead of complicated integration schemes for the transport equations, the calculation time can be effectively spent on various important parameters such as ionic strength, temperature, Joule heat, activity coefficients and concentration changes due to membranes. The parameter set of any carrier free electrophoretic method (i.e., continuous-flow electrophoresis, capillary isotachophoresis and high performance capillary zone electrophoresis) can be imported directly into the computer program by means of a graphic user interface. The program performs overnight-simulation of any electrophoretic system containing up to 15 components.

Computer Simulation↗
PubMed1999

Hormonal changes in humans during spaceflight.

Readers of this review may feel that there is much more that we do not know about space endocrinology than what we know. Several reasons for this state of affairs have been given: 1. the complexity of the field of endocrinology with its still increasing number of known hormones, releasing factors and precursors, and of the interactions between them through various feedback mechanisms 2. the difficulty in separating the microgravity effects from the effects of stress from launch, isolation and confinement during flight, reentry, and postflight re-adaptation 3. the experimental limitations during flight, such as limited number of subjects, limited number of samples, impossibility of collecting triple samples for pulsatile hormones like growth hormone 4. the disturbing effects of countermeasures used by astronauts 5. the inadequacy of postflight samples for conclusions about inflight values 6. limitations of conclusions from animal experiments and space simulation studies The endocrinology field is divided in to nine systems or axes, which are successively reviewed: 1. Rapid bone demineralization in the early phase of spaceflight that, when unopposed, leads to catastrophic effects after three months but that slows down later. The endocrine mechanism, apart from the effect of exercise as a countermeasure, is not yet understood. 2. The hypothalamic-pituitary-adrenal axis is involved in stress reactions, which complicate our understanding and makes postflight analysis dubious. 3. In the hypothalamic-pituitary-gonadal axis, pulsatility poses a problem for obtaining representative values (e.g., for luteinizing hormone). Reproduction of rats in space is possible, but much more needs to be known about this aspect, particularly in women, before the advent of space colonies, but also in males because some evidence for reversible testicular dysfunction in space has been found. 4. The hypothalamic-pituitary-somato-mammotrophic axis involves prolactin and growth hormone. The latter also acts as a stress hormone and its secretion is greatly decreased in spaceflown rats, but not in astronauts, which may be due to differences in the regulation of growth hormone secretion between rats and humans. 5. The hypothalamic-pituitary-thyroid axis involves the thyroid hormones thyroxine and triiodothyronine, which are lowered in space, suggesting mild hypothyroidism. 6. The renin-angiotensin-aldosterone axis, which regulates water and electrolytes, involves antidiuretic hormone and two natriuretic peptides and shows paradoxical behavior in space. 7. Erythrocyte mass regulation involves erythropoietin, and space anemia is still not explained. 8. The endocrine pancreas involves insulin and glucagon, with loss of insulin sensitivity in space due to lack of exercise, which phenomenon requires more study before the advent of space colonies. 9. The sympathetic system acts through epinephrine, norepinephrine and dopamine and seems to have an increased activity in space in contrast to what had been widely believed. From the foregoing conclusions, it is clear that much further study is needed in all fields of space endocrinology. On the other hand, future studies will allow us to understand what happens in a given endocrine subsystem in the absence of the "gravity factor", the perturbing factor to which the human race has become adapted through thousands of years of evolution. This should provide us with a fuller understanding of the internal homeostatic mechanisms. An important point is that some endocrine systems seem to undergo changes in space that resemble those observed during senescence, but after spaceflight, recovery always occurs within weeks or months after return. This is particularly true for the systems regulating bone and muscle metabolism and reproduction, exactly as happens with the immune, neurosensory, and cardiovascular systems. Further space research may help us find new insights in the pathophysiology of aging and hopefully define novel prev

Animals↗
PubMed1993

[Human gas and energy exchange in space flight and simulation research].

Human gas-energy exchange under extreme conditions is considered in the above work. Major attention is given to energy exchange and external respiration of humans in space flight, as well as in the models of space vehicles and during simulation of physiological effects of weightlessness.

Energy Metabolism↗