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At least 271 records · Page 15Linked to original sources
PubMed1997

Validity of a heart rate monitor during work in the laboratory and on the Space Shuttle.

Accurate heart rate measurement during work is required for many industrial hygiene and ergonomics situations. The purpose of this investigation was to determine the validity of heart rate measurements obtained by a simple, lightweight, commercially available wrist-worn heart rate monitor (HRM) during work (cycle exercise) sessions conducted in the laboratory and also during the particularly challenging work environment of space flight. Three different comparisons were made. The first compared HRM data to simultaneous electrocardiogram (ECG) recordings of varying heart rates that were generated by an ECG simulator. The second compared HRM data to ECG recordings collected during work sessions of 14 subjects in the laboratory. Finally, ECG downlink and HRM data were compared in four astronauts who performed cycle exercise during space flight. The data were analyzed using regression techniques. The results were that the HRM recorded virtually identical heart rates compared with ECG recordings for the data set generated by an ECG simulator. The regression equation for the relationship between ECG versus HRM heart rate data during work in the laboratory was: ECG HR = 0.99 x (HRM) + 0.82 (r2 = 0.99). Finally, the agreement between ECG downlink data and HRM data during space flight was also very high, with the regression equation being: Downlink ECG HR = 1.05 x (HRM) -5.71 (r2 = 0.99). The results of this study indicate that the HRM provides accurate data and may be used to reliably obtain valid data regarding heart rate responses during work.

Adult↗
PubMed1989

A step in embryonic axis specification in Xenopus laevis is simulated by cytoplasmic displacements elicited by gravity and centrifugal force.

Determination of the body pattern in Xenopus embryos is known to involve at least six steps. One of these steps can be experimentally simulated by inclining the fertilized egg with respect to gravity or centrifugal force (10-30 g x 4 min, directed 90 degrees to the animal-vegetal axis). In these eggs, the dorsal structures of the body axis form from the side of the egg that was uppermost in the gravitational or centrifugal field. This topography is seen even if the sperm entry point side (the prospective ventral side in control eggs) was uppermost. In addition, conjoined twin embryos form at very high frequencies in response to certain conditions of single or double centrifugation. Cytological analysis shows that the dorsal structures invariably form from the side(s) of the egg away from which vegetal cytoplasm was displaced. This is similar to the situation in the unperturbed egg, where the subcortical cytoplasm of the vegetal hemisphere rotates some 30 degrees relative to the surface, and the dorsal structures form from the side of the egg away from which the subcortical cytoplasm moved. The displacements elicited by centrifugation probably substitute for the normal displacements brought about by the subcortical rotation. These and other data suggest that the subcortical rotation is a crucial step in the process of axis determination. The subcortical rotation is an autonomous activity of the activated egg, and can displace cytoplasm against gravity. I believe that the subcortical rotation will function normally at microgravity, and I expect that overall development and axis polarity at microgravity will be normal. This will be tested in spaceflight.

Animals↗
PubMed1996

Regulative development of Xenopus laevis in microgravity.

To test whether gravity is required for normal amphibian development, Xenopus laevis females were induced to ovulate aboard the orbiting Space Shuttle. Eggs were fertilized in vitro, and although early embryonic stages showed some abnormalities, the embryos were able to regulate and produce nearly normal larvae. These results demonstrate for the first time that a vertebrate can ovulate in the virtual absence of gravity, and that the eggs can develop to a free-living stage.

Animals↗
PubMed1990

Cosmos 1887 mission overview: effects of microgravity on rat body and adrenal weights and plasma constituents.

The Cosmos 1887 biosatellite carried 10 male rats and 2 rhesus monkeys on its 12.5-day mission. Upon re-entry the Vostok vehicle overshot the designated landing site, which resulted in fasting of the animals for 42 h, exposure to cage temperatures of 12-15 degrees C, and 2 days delay in death of the rats. No overt untoward effects of the delayed recovery were apparent. Tissues from the rats were harvested by Soviet scientists, appropriately preserved, and provided to U.S. investigators. Flight rats grew more slowly and had larger adrenal glands than earth gravity controls. Analysis of plasma revealed increased concentrations of hepatic alkaline phosphatase, glucose, urea nitrogen, and creatinine in flight rats. In contrast, electrolytes, total protein, albumin, corticosterone, prolactin, and immunoreactive growth hormone levels were unchanged. However, testosterone concentration was marginally decreased after flight and thyroid hormone levels were suggestive of reduced thyroid function. Due to the possible effects of reentry and the delay in recovery of the animals, it is not clear what relationship postflight levels of plasma constituents bear to their concentrations in flight.

Adrenal Glands↗
PubMed1997

Evaluation of cardiac rhythm disturbances during extravehicular activity.

This study represents the first systematic evaluation of dysrhythmias before, during, and after spaceflight including extravehicular activity (EVA). The data, based on 7 Shuttle crew members, revealed a nonsignificant decrease in ventricular and supraventricular ectopy during EVA, suggesting that the incidence of dysrhythmias is no greater during EVA than with any other phase of a mission or preflight.

Adult↗
PubMed1994

Pyrolysis-gas chromatography/mass spectrometry analyses of biological particulates collected during recent space shuttle missions.

Biological particulates collected on air filters during shuttle missions (STS-40 and STS-42) were identified using pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). A method was developed for identifying the atmospheric particles and their sources through the analysis of standard materials and the selection of "marker" compounds specific to the particle type. Pyrolysis spectra of biological standards were compared with those of airborne particles collected during two space shuttle missions; marker compounds present in the shuttle particle spectra were matched with those of the standards to identify the source of particles. Particles of 0,5--1-mm diameter and weighing as little as 40 micrograms could be identified using this technique. The Py-GC/MS method identified rat food and soilless plant-growth media as two sources of particles collected from the shuttle atmosphere during flight.

Air Pollutants↗
PubMed1990

Morphological and biochemical examination of Cosmos 1887 rat heart tissue: Part I--Ultrastructure.

Morphological changes were observed in the left ventricle of rat heart tissue from animals flown on the Cosmos 1887 biosatellite for 12.5 days. These tissues were compared to the synchronous and vivarium control hearts. While many normal myofibrils were observed, others exhibited ultrastructural alterations, i.e., damaged and irregular-shaped mitochondria and generalized myofibrillar edema. Analysis of variance (ANOVA) of the volume density data revealed a statistically significant increase in glycogen and a significant decrease in mitochondria compared to the synchronous and vivarium controls. Point counting indicated an increase in lipid and myeloid bodies and a decrease in microtubules, but these changes were not statistically significant. In addition, the flight animals exhibited some patchy loss of protofibrils (actin and myosin filaments) and some abnormal supercontracted myofibrils that were not seen in the controls. This study was undertaken to gain insight into the mechanistic aspects of cardiac changes in both animals and human beings as a consequence of space travel (1). Cardiac hypotrophy and fluid shifts have been observed after actual or simulated weightlessness and raise concerns about the functioning of the heart and circulatory system during and after travel in space (2-4).

Actins↗
PubMed1996

Capillary movement of liquid in granular beds in microgravity.

A more complete understanding of the dynamics of capillary flow through an unsaturated porous medium would be useful for the development of an effective water and nutrient delivery system for the growth of plants in space. An experiment was conducted on the Mir Space Station that used an experimental cuvette called "Capillary Test Bed" to compare fluid migration under terrestrial laboratory conditions by positioning the cuvette such that the hydrostatic force is negated and on Mir under microgravity conditions. Differences in fluid migration in the cuvette were observed with migration being slower in microgravity compared with some ground control experiments.

Capillary Action↗
PubMed1995

Amphibian development in the virtual absence of gravity.

To test whether gravity is required for normal amphibian development, Xenopus laevis females were induced to ovulate aboard the orbiting Space Shuttle. Eggs were fertilized in vitro, and although early embryonic stages showed some abnormalities, the embryos were able to regulate and produce nearly normal larvae. These results demonstrate that a vertebrate can ovulate in the virtual absence of gravity and that the eggs can develop to a free-living stage.

Animals↗
PubMed1989

Phase separated membrane bioreactor: results from model system studies.

The operation and evaluation of a bioreactor designed for high intensity oxygen transfer in a microgravity environment is described. The reactor itself consists of a zero headspace liquid phase separated from the air supply by a long length of silicone rubber tubing through which the oxygen diffuses in and the carbon dioxide diffuses out. Mass transfer studies show that the oxygen is film diffusion controlled both externally and internally to the tubing and not by diffusion across the tube walls. Methods of upgrading the design to eliminate these resistances are proposed. Cell growth was obtained in the fermenter using Saccharomyces cerevisiae showing that this concept is capable of sustaining cell growth in the terrestrial [correction of terrestial] simulation.

Carbon Dioxide↗
PubMed1988

The endocrine system in space flight.

Hormones are important effectors of the body's response to microgravity in the areas of fluid and electrolyte metabolism, erythropoiesis, and calcium metabolism. For many years antidiuretic hormone, cortisol and aldosterone have been considered the hormones most important for regulation of body fluid volume and blood levels of electrolytes, but they cannot account totally for losses of fluid and electrolytes during space flight. We have now measured atrial natriuretic factor (ANF), a hormone recently shown to regulate sodium and water excretion, in blood specimens obtained during flight. After 30 or 42 h of weightlessness, mean ANF was elevated. After 175 or 180 h, ANF had decreased by 59%, and it changed little between that time and soon after landing. There is probably an increase in ANF early inflight associated with the fluid shift, followed by a compensatory decrease in blood volume. Increased renal blood flow may cause the later ANF decrease. Erythropoietin (Ep), a hormone involved in the control of red blood cell production, was measured in blood samples taken during the first Spacelab mission and was significantly decreased on the second day of flight, suggesting also an increase in renal blood flow. Spacelab-2 investigators report that the active vitamin D metabolite 1 alpha, 25-dihydroxyvitamin D3 increased early in the flight, indicating that a stimulus for increased bone resorption occurs by 30 h after launch.

Aerospace Medicine↗
PubMed1992

Comparative study of spermatogonial survival after x-ray exposure, high LET (HZE) irradiation or spaceflight.

Spermatogonial cell loss has been observed in rats flown on Space Lab 3, Cosmos 1887, Cosmos 2044 and in mice following irradiation with X-ray or with high energy (HZE) particle beams. Spermatogonial loss is determined by cell counting in maturation stage 6 seminiferous [correction of seminferous] tubules. With the exception of Iron, laboratory irradiation experiments (with mice) revealed a similar pattern of spermatogonial loss proportional to the radiation dose at levels less than 0.1 Gy. Helium and Argon irradiation resulted in a 5% loss of spermatogonia after only 0.01 Gy exposure. However, significant spermatogonial loss (45%) occured at this radiation level with Iron particle beams. The loss of spermatogonia during each space flight was less than 10% when compared to control (non-flight) animals. This loss, although small, was significant. Although radiation may be a contributing factor in the loss of spermatogonia during space flight, exposure levels, as determined by dosimetry, were not significant to account for the total cell loss observed.

Animals↗
PubMed1990

Effects of spaceflight on the spermatogonial population of rat seminiferous epithelium.

Testes from rats flown on Cosmos 1887 were compared with vivarium control and synchronous control samples. The mean weights of flight testes, normalized for weight per 100 g, were 6.4% less when compared with the vivarium controls. Counts of spermatogonia from tissue sections (seminiferous tubules in maturation stage 6) from five animals in each group revealed 4% fewer spermatogonia in flight testes compared with synchronous controls and 11% fewer spermatogonia in flight samples compared with vivarium controls.

Animals↗
PubMed1993

Autogenic feedback training improves pilot performance during emergency flying conditions.

Studies have shown that autonomous mode behavior (AMB) is one cause of aircraft fatalities caused by pilot error. In AMB cases, the pilot is in a high state of psychological and physiological arousal and tends to focus on one problem, while ignoring more critical information. The following study, conducted under the auspices of the U.S. National Aeronautics and Space Administration's (NASA) Ames Research Center, examined the effect of training in physiological self-recognition and regulation, as a means of improving crew cockpit performance. Seventeen pilots were assigned to the treatment and control groups matched for accumulated flight hours.

Accidents, Aviation↗
PubMed1984

Miniature triaxial metastable ionization detector for gas chromatographic trace analysis of extraterrestrial volatiles.

Gas chromatography has found highly successful application in NASA's flight programs. Gas chromatographs have been flown to both Mars and Venus where detailed compositional measurements were made. These instruments were quite small and relatively sensitive when compared to commercially available instruments; however, they do not appear adequate for future missions currently being planned. The earlier flight GC's had incorporated thermistor bead thermal conductivity cells as the detector. This detector requires very precise temperature control and only provides about 1 ppm sensitivity. Temperature stabilization causes the detector to be quite heavy, i.e., about 200 g. Greater sensitivity will be required for measurements of trace components in extraterrestrial environments. Review of other detector types revealed the metastable ionization detector as a likely candidate because of its superior thermal stability and high sensitivity. The metastable detector, first described by Lovelock as an argon ionization detector, has been studied and somewhat modified by others. The commercial design by Hartmann and Dimick was used for comparison purposes in our work. In the past, three features of the metastable detector are prominent: it has part-per-billion sensitivity, contamination must be carefully controlled, and anomalous response is common. Since it is an ionization detector, however, temperature instabilities do not cause the major perturbations experienced by the thermal conductivity detectors. This paper describes a miniature metastable ionization detector featuring an unconventional electrode configuration, whose performance characteristics parallel those of traditional design, while its weight is quite small. The prototype has been used in our laboratories routinely for 2 years, and the concept will be incorporated into a flight GC for use in the Space Shuttle.

Astronomy↗