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PubMed1992

The Biological Flight Research Facility.

NASA Ames Research Center (ARC) is building a research facility, the Biological Flight Research Facility (BFRF), to meet the needs of life scientists to study the long-term effects of variable gravity on living systems. The facility will be housed on Space Station Freedom and is anticipated to operate for the lifetime of the station, approximately 30 years. It will allow plant and animal biologists to study the role of gravity, or its absence, at varying gravity intensities for varying periods of time and with various organisms. The principal difference between current Spacelab missions and those on Space Station Freedom, other than length of mission, will be the capability to perform on-orbit science procedures and the capability to simulate Earth gravity. Initially the facility will house plants and rodents in habitats which can be maintained at microgravity or can be placed on a 2.5 m diameter centrifuge. However, the facility is also being designed to accommodate future habitats for small primates, avian and aquatic specimens. The centrifuge will provide 1 g for controls and will also be able to provide gravity from 0.01 to 2.0 g for threshold gravity studies as well as hypergravity studies. Included in the facility are a service unit for providing clean chambers for the specimens and a glovebox for manipulating the plant and animal specimens and for performing experimental protocols. The BFRF will provide the means to conduct basic experiments to gain an understanding of the effects of microgravity on the structure and function of plants and animals, as well as investigate the role of gravity as a potential countermeasure for the physiological changes observed in microgravity.

Adaptation, Physiological↗
PubMed1990

Life sciences issues affecting space exploration.

The U.S. space program is undertaking a serious examination of new initiatives in human space exploration involving permanent colonies on the Moon and an outpost on Mars. Life scientists have major responsibilities to the crew, to assure their health, productivity, and safety throughout the mission and the postflight rehabilitation period; to the mission, to provide a productive working environment; and to the scientific community, to advance knowledge and understanding of human adaptation to the space environment. Critical areas essential to the support of human exploration include protection from the radiation hazards of the space environment, reduced gravity countermeasures, artificial gravity, medical care, life support systems, and behavior, performance, and human factors in an extraterrestrial environment. Developing solutions to these concerns is at the heart of the NASA Life Sciences ground-based and flight research programs. Facilities analogous to planetary outposts are being considered in Antarctica and other remote settings. Closed ecological life support systems will be tested on Earth and Space Station. For short-duration simulations and tests, the Space Shuttle and Spacelab will be used. Space Station Freedom will provide the essential scientific and technological research in areas that require long exposures to reduced gravity conditions. In preparation for Mars missions, research on the Moon will be vital. As the challenges of sustaining humans on space are resolved, advances in fundamental science, medicine and technology will follow.

Adaptation, Physiological↗
PubMed1997

Sympathetic nerve response to microgravity induced by parabolic flight.

The aim of this study was to clarify how muscle sympathetic nerve activity (MSNA) in humans, which plays an important role in blood pressure control against gravity, is altered under microgravity conditions. Subjects were seated in a jet aircraft with their legs extended. MSNA was recorded microneurographically from the tibial nerve of the sitting subjects with simultaneous monitoring of electrocardiogram, blood pressure, respiration, and intrathoracic blood volume during parabolic flights. In the Air Force training area, the aircraft made parabolas up to 10 times. At the entry to microgravity, intrathoracic blood volume increased, systemic blood pressure was elevated, and MSNA was suppressed. However, this MSNA suppression lasted only 10-15 sec, and then followed by an enhancement to the end of the parabolas. We conclude that MSNA is suppressed at the onset of microgravity during parabolic flight in response to loading of the cardiopulmonary volume receptor due to a cephalad body fluid shift. However, this MSNA suppression is transient during such dynamic gravitational changes as those induced by parabolic flight, probably modulated by arterial baroreceptors.

Adult↗
PubMed1991

Pedalling in space as a countermeasure to microgravity deconditioning.

A system consisting of two mechanically coupled counter rotating bicycles, moving on the inner wall of a cylindrical space module, is proposed to prevent microgravity deconditioning. The two pedalling subjects generate a centrifugal acceleration vector (ac) simulating gravity. This last depends on the peripheral velocity (v) and on the radius of gyration (R): ac = v2/R. Since R is constant and equal to the inner radius of the space module, any desired value of ac can be achieved by selecting the appropriate v value. The corresponding mechanical (w) and metabolic (VO2) powers can then be calculated on the basis of the biomechanical and anthropometric characteristics of the system and subjects. It is shown that if R = 2 m, in order to attain ac = 1 g at the feet, v = 4.5 m s-1, w = 60 W and VO2 = 1.2 litres min-1. However if R = 6 m, then v = 7.8 m s-1, w = 140 W and VO2 = 3 litres min-1. The average arterial pressures prevailing at the head and feet levels in the two above conditions can also be calculated as 95, 150 and 80, 170 mmHg, respectively for a mean arterial pressure of 100 mmHg at the aortic bulbus. In conclusion, by selecting appropriately the radial dimensions of the space module in order to minimize: (1) vestibular disturbances, (2) head to feet centrifugal acceleration gradients and (3) manufacturing costs, it may be possible to combine exercise and simulated gravity, with no need for additional external power.

Aerospace Medicine↗
PubMed1998

Influence of modified gravity on growth and structure of Vaucheria sessilis (Xanthopyceae).

The constant presence of gravity force in the evolution of life on Earth caused the adaptation for its pressure and dependence of growth and morphogenesis of high plants on gravity, and appearance of gravitaxises of unicellular organisms. The modern investigations demonstrated the ability even of prokaryotic organisms for sensitivity of gravity modifications Erdmann et al., 1997). Object of current investigation was siphonaceous alga Vaucheria sessilis with branching thallome without septs. Vaucheria does not demonstrate gravitropic reaction, and does not possess statolite-like structure. It is important to note that graviresponse of such kind of objects was under investigation for the first time. The definite structure of cytoskeleton permits the functions of cytoskeleton elements to be analyzed in course of graviresponse. Siphonaceous algae are new and promising objects in gravitational cell biology. This investigation was intended to compare the graviresponse of Vaucheria detected on different experimental models of modified gravity.

Cell Nucleus↗
PubMed1998

Changes in muscle sympathetic nerve activity and effect of breathing maneuvers during microgravity induced by parabolic flight in humans.

UNLABELLED: This study aimed to clarify how muscle sympathetic nerve activity (MSNA) in humans, which plays an important role in blood pressure control against gravity, is altered under microgravity (microG) conditions, and how the MSNA change is modified by breathing maneuvers. Ten subjects seated themselves in a jet aircraft with their knees extended. MSNA was recorded microneurographically from the left tibial nerve with simultaneous monitoring of ECG, blood pressure, respiration, and intrathoracic blood volume estimated by the impedance method during parabolic flight in a jet aircraft. In half of the parabolas, their respiration was controlled at 0.25 Hz by a metronome. RESULTS: MSNA was enhanced under hypergravity just before microG entry, and immediately suppressed by microG induced by parabolic flight. The suppression was more marked with controlled than with uncontrolled respiration (51.6 +/- 7.2 vs 82.8 +/- 2.5%, mean +/- SE, 1G=100%). MSNA changes during microG correlated significantly to changes in blood pressure and intrathoracic blood volume. The blood pressure fall 10 to 15 sec after microG entry was less prominent with controlled than with uncontrolled respiration. We conclude that changes in arterial blood pressure and intrathoracic blood volume modulate MSNA during microG induced by parabolic flight, depending largely on breathing maneuvers.

Adult↗
PubMed1998

Manned interplanetary missions: prospective medical problems.

The present review aimed to suggest approaches to prospective medical problems related to the health maintenance of space crews during future manned interplanetary, particularly Martian, missions up to 2-3 years with a possible stay on a planet with gravity different from that on Earth. The approaches are based on knowledge so far obtained from our analysis of the medical support of long-term orbital flights up to one year, as well as on the consideration of specific conditions of interplanetary missions. These specific conditions include not only long-term exposure to microgravity, but also a prolonged stay of unpredictable duration (2-3 years) on board a spacecraft or on a planet without direct contact with Earth, and living in a team with a risk of psychological incompatibility and the impossibility of an urgent return to Earth. These conditions necessitate a highly trained medical person in the crew, diagnostic tools and equipment, psychophysiological support, countermeasures, as well as the means for urgent, including surgical, treatment on board a spacecraft or on a planet. In this review, the discussion was focused on the following predictable medical problems during an interplanetary mission; 1) unfavorable effects of prolonged exposure to microgravity, 2) specific problems related to Martian missions, 3) medical monitoring, 4) countermeasures, 5) psychophysiological support and 6) the medical care system.

Adaptation, Physiological↗
PubMed2000

Life in extreme environments: how will humans perform on Mars?

This review of astronaut extravehicular activity (EVA) and the details of American and Soviet/Russian spacesuit design focuses on design recommendations to enhance astronaut safety and effectiveness. Innovative spacesuit design is essential, given the challenges of future exploration-class missions in which astronauts will be called upon to perform increasingly complex and physically demanding tasks in the extreme environments of microgravity and partial gravity.

Extravehicular Activity↗
PubMed2000

Medicine on Mars.

Explore the source record for details and available documents.

Adaptation, Physiological↗
PubMed2001

[Structural and metabolic characteristics of m. vastus lateralis of monkeys during 30-day hypokinesia: effects of prophylactic Gz-accelerations].

Studies of m. vastus lateralis in Rhesus monkeys exposed to weightlessness on board of the Russian biosatellites showed the profound changes of the muscle structural and metabolic profile. It is known that exposure to head-down tilt berets (BR) induces the similar changes though not so pronounced. It is supposed that the artificial gravity application is one of the promising countermeasure means purposed to prevent from the unfavourable effects of exposure to weightlessness. The present work was aimed to study the effects of the artificial gravity on structural and metabolic characteristics of hind-limb muscle in monkeys exposed to BR. 11 monkeys were subjected to 30 day 6 head down tilt BR.5 animals of them (group BR + Gz) were exposed also to daily rotation on the centrifuge (1.4 G for 5-20 min), the other animals (BR) were under only pure BR during the study. In BR animals the m. vastus lateralis slow-twitch (ST) and fast-twitch (FT) fiber size decreased by 25.4% and 12.7% respectively. In group BR + Gz the ST and FT fiber cross-sectional area was reduced by 18.7% and 8.1% respectively. The area percentage of the connective tissue compartment in BR animals increased from 4.6% to 6.8%. Capillary per fibre ratio was reduced by 9.6% and 8.6% in BR and BR + Gz monkeys respectively. The less pronounced level of capillary reduction as compared to level of fibre size decrease led to the increase of the capillary density by 13% in BR group, and no change in BR + Gz one. No changes in succinate dehydrogenase (SDH) activity were revealed in fibres of BR animals (this phenomenon may be the consequence of the proportional decrease of the oxidative potential and fibre size). In BR + Gz monkeys the SDH activity were found to be significantly elevated by 22.2% and 28.6% in ST and FT fibres respectively. Thus the data obtained show that chronic application of Gz tends to diminish the intensity of structural and metabolic changes in skeletal muscles under simulated microgravity.

Acceleration↗
PubMed2001

[Biomedical problems of artificial gravity: overview and challenge].

The limitations of the currently used exercise-based countermeasures and the scientific rationale for the gravity-based countermeasures are addressed. Then, an overview of the physiological effects and requirements for the two types of artificial gravity (AG), i.e., the continuous AG provided by full-time spinning of the entire space system/habitat and the intermittent AG by incorporating a short-arm centrifuge into the spacecraft, is presented. Finally, significance and challenge faced in future research on biochemical problems of artificial gravity are discussed.

Adaptation, Physiological↗
PubMed2001

[Counter-effect of intermittent +Gz exposures on vasoreactivity in decline in hind body arteries of rats under simulated weightlessness].

Objective. To investigate the counter-effect of intermittent artificial gravity, the present study examined vasoreactivity changes of femoral and mesenteric arteries in rats subjected to simulated weightlessness plus standing or centrifugation. Method. Forty male Sprague-Dawley rats were divided into simultaneous control (CON), simulated weightlessness (SUS), simulated weightlessness plus 1 h standing (STD1), simulated weightlessness plus 1.5 G centrifugation (1.5 G), and simulated weightlessness plus 2.6 G centrifugation (2.6 G) groups. Responses of arteries to vasoconstrictor were examined in vitro using isolated femoral and mesenteric arterial rings. Result. The contractile responsiveness to KCl or PE of femoral and mesenteric arterial rings isolated from SUS significantly decreased as compared with CON. And those of STD1 and the two centrifuged groups significantly enhanced as compared with that of SUS. Whereas there was no difference among STD1, 1.5 G, 2.6 G and CON. Conclusion. Simulated weightlessness may result in decreased contractile responses to KCl and PE of rat femoral and mesenteric arteries. Both STD1, 1.5 G, and 2.6 G prevented the decrease of contractile response to KCl and PE of femoral arteries.

Animals↗
PubMed1972

OFO experimental techniques and preliminary conclusions: is artificial gravity needed during prolonged weightlessness?

The technique of single unit recording from body systems generating electrical pulses coherent with their basic function (CNS, muscles, sense organs) has been proved feasible during the OFO A orbital flight, an automatic physiological experiment. All microelectrode implants survived the lift off of a Scout vehicle. The far-reaching impact of such a technique in biological space research and in the laboratory is discussed. The results of recording 155 hours of orbital flight of pulses from the nerve fibres of four vestibular gravity sensors in two bull frogs indicate that the vestibular organ adjusts to zero g. As all the other biological changes observed during orbit are due to lack of exercise, it is concluded that artificial gravity might not be necessary during prolonged space missions or on low gravity celestial bodies.

Animals↗
PubMed1977

Effect of weightlessness and of artificial gravity on irradiated lettuce seeds.

In our previous studies on board the artificial earth satellite Cosmos 368, the cosmic apparatus Zond 8 and the orbital station Salyut it has been demonstrated that space-flight factors (SFF) have a definite effect on poorly active biological systems, such as dry lettuce seeds. The technical possibilities on board the biosatellite Cosmos 782 (the availability of an on-board centrifuge) allowed us to obtain some new data concerning the mechanisms of the SFF effects. Irradiated seeds of lettuce (Lactuca sativa L.) were exposed in space flight for 22 days either to weightlessness conditions only or to a centrifugal field. Data have been obtained characterizing the cytogenetical and physiological processes in seeds of various series of the experiment. An attempt is made to analyse the role of individual SFF in the changes observed.

Centrifugation↗
PubMed1976

Physiological changes associated with long-term increases in acceleration.

The long-term retention of organisms in increased acceleration fields is an experimental approach towards understanding the biological consequences of earth gravity. Such treatment, called chronic acceleration, simulates a change in gravity and requires exposed organisms to adapt physiologically to the new environment. Information from chronic acceleration supplements that from space physiology in understanding gravitational physiology. Many of the responses in long-term exposure to increased acceleration are those which would be anticipated from the imposed symmetrical loading. For example, increased requirements for posture and locomotion induce appropriate changes in musculo-skeletal organs. Displacement of body fluids and increased hydrostatic pressures lead to greater blood volumes and increased tissue hydration. However, there are also specific acceleration effects which cannot be so directly interpreted. Among these are decreases of mature body size and of depot fat, which are proportional in degree to field strength. The role of chronic acceleration research in the development of gravitational biology and its relationship to earth-orbital experiments are considered. The applicability of chronic acceleration studies with human subjects towards planning of deep space exploration is also discussed.

Acceleration↗
PubMed2002

G-induced vestibular dysfunction ('the wobblies') among aerobatic pilots: a case report and review.

G-induced vestibular dysfunction (GIVD) is a condition well known to aircraft pilots who experience high positive and negative G loads during unlimited-aerobatic competitions and air-show demonstrations. After landing and walking from their aircraft, pilots with GIVD manifest an extremely unstable gait, which they call the wobblies. This article includes a report of one such case of GIVD, which to the author's knowledge is the first published case report of this condition in the medical literature. The author also discusses what is known and theorized about the pathogenesis of GIVD, and he reviews its diagnosis, treatment, and prevention.

Adult↗