Cortical microtubule reorganization in protoplasts isolated from Brassica napus hypocotyl is affected by gravity.
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Brassica↗
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Simulation models of weightlessness in mammalian's developmental program.
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Animals↗
Human +Gx tolerance with the use of anti-G suits during descent from orbit of the Soyuz space vehicles.
Previous investigations have shown the necessity of anti-G protection of cosmonauts on the stage of descent from orbit. Purpose of this research is to evaluate effectiveness of an elastic anti-G suits in opposing the descent accelerations in the Soyuz space vehicles.
Acceleration↗
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↗
The influence of short term gravity changes on mouse spleen lymphocytes in vitro (microfluorimetry with probes).
Despite of the great successes achieved in gravitational cell biology, problem of mechanisms underlying cell effects of gravity is far from being solved. Available data are very contradictory, because of the differences in experimental conditions: gravity value, exposition time, type of cells and other factors. Besides, there are no satisfactory methods to avoid additional influence of various biologically active factors on cells during the space experiments. It is absolutely clear, that successful development in this field may be provided only by investigations in controlled experimental conditions, including analysis of cell functional activity and state of cell regulatory systems. One of the most adequate approaches for these scientific tasks is cell microfluorimetry with using of fluorescent probes. The study of influence of short-term pattern changes in gravity (clinostation and centrifugation) on hydrolytic activity of intracellular content of mouse spleen lymphocytes, leakage of accumulated fluoresce in and intracellular pH is the goal of present research.
Animals↗
Gravisensitivity of cells of several types.
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Animals↗
Effect of low acceleration simulator training on +Gz acceleration tolerance level.
The goal of this paper was studying the effectiveness of frequently repeated low values of long duration acceleration on circulatory system response during gradual onset rate of acceleration on a human centrifuge.
Acceleration↗
Venous tone and repeated +Gz accelerations.
The purpose of the present work was to study in vivo in rat the consequences of repeated exposures to sustained +Gz centrifugations on the venous pressure and on the venous tone, that one evaluated by measuring the equilibrium pressure of all vessels in the circulation when the flow is null or MCFP (mean circulatory filling pressure).
Acceleration↗
Physiological response of pilots to the LBNP-, flight-, and centrifuge load.
The possibility of the LBNP method's utilization at persons with low resistance of the cardiovascular system to the orthostatic load is a matter one of the research projects of IAM. We concentrated in previous stages our effort on an evaluation of basic physiological responses of the organism to this type of a load and on determination of reliable markers of the precollapse state. After analysis of results of examinations of 64 probands' set we defined qualifying criteria to the prediction for selection of individuals with the insufficient orthostatic resistance. Verification of experimental results by the comparison with well-established examination methods, during a real flight load and at the examination in a human centrifuge, is a goal of the following research activity. In current period of the task's solution the physiological response to an LBNP load has been compared with the physiological response to the load during real flight in an aircraft.
Acceleration↗
High sustained +Gz acceleration: physiological adaptation to high-G tolerance.
Since the early 1940s, a significant volume of research has been conducted in an effort to describe the impact of acute exposures to high-G acceleration on cardiovascular mechanisms responsible to maintaining cerebral perfusion and conscious in high performance aircraft pilots during aerial combat maneuvers. The value of understanding hemodynamic characteristics that underlie G-induced loss of consciousness has been instrumental in the evolution of optimal technology development (e.g., G-suits, positive pressure breathing, COMBAT EDGE, etc.) and pilot training (e.g., anti-G straining maneuvers). Although the emphasis of research has been placed on the development of protection against acute high +Gz acceleration effects, recent observations suggest that adaptation of cardiovascular mechanism associated with blood pressure regulation may contribute to a protective 'G-training' effect. Regular training at high G enhances G tolerance in humans, rats, guinea pigs, and dogs while prolonged layoff from exposure in high G profiles (G-layoff) can result in reduced G endurance. It seems probable that adaptations in physiological functions following chronically-repeated high G exposure (G training) or G-layoff could have significant impacts on performance during sustained high-G acceleration since protective technology such as G-suits and anit-G straining maneuvers are applied consistently during these periods of training. The purpose of this paper is to present a review of new data from three experiments that support the notion that repeated exposure on a regular basis to high sustained +Gz acceleration induces significant physiological adaptations which are associated with improved blood pressure regulation and subsequent protection of cerebral perfusion during orthostatic challenges.
Acceleration↗
The effect of brief headward acceleration on human G tolerance.
OBJECTIVE: To generate, on a multi-axial centrifuge, a negative to positive acceleration profile that reproduces the physiological reaction and subjective symptoms experienced by agile aircraft pilots. Previous research will be summarized and current status of research described. METHODS: Experiments have been accomplished with the Dynamic Environment Simulator (DES) using different profile generating techniques. The DES was programmed with a set of open-loop profiles that provided five second duration baseline exposures ranging from +1.4 Gz down to -2 Gz followed by rapid transition to positive G levels up 2 to 8 +Gz. Volunteer subjects were instrumented and trained to report visual symptoms. RESULTS: Both profile generation approaches produce the reduced cardiovascular and subjective tolerance in a subset of subjects tested. Accumulated stress and motion sickness are factors in quantitative measures. Use of the anti-G straining maneuver may only temporarily alleviate the symptoms with a second period of visual symptoms even as the G load is removed. Positive pressure breathing for G (PBG) does not appear to exacerbate the effect, but the advantages gained from PBG may be lost when a sustained G pull is preceded by a negative G push. CONCLUSIONS: The utility and limitations of using a multi-axial centrifuge for the study of negative to positive G transitions have been described. Greater study is necessary on multiple factors affecting the effect and large numbers of volunteer subjects are needed.
Acceleration↗
Mathematical models for predicting straining G-level tolerances in reclined subjects.
Mathematical models that predict straining G-level tolerances of subjects reclined > 55 degrees are described. Straining G-level tolerances are defined as those G-levels of exposures that require the use of the anti-G straining maneuver (AGSM). A subject reclined > 55 degrees has a reduced inspiratory volume that limits the maximum intrathoracic pressure that can be developed that is the basis for the AGSM. Therefore the inability to perform a maximum AGSM reduces the maximum G-level that can be tolerated. G-level tolerances of subjects at seat-back angles between 75 degrees and 55 degrees are modeled. The use of positive pressure breathing (PBG) to increase G-level tolerance is considered. Maximum G-level tolerances are dependent upon anti-G suit pressures (psi) used and are predicted as follows: 55 degrees = 11.7 and 12.7 G with 7 and 10 psi; 65 dergrees = 12.1 and 12.8 G with 6 and 9 psi; and 75 degrees = 13.4 and 14.2 G with 5 and 8 psi anti-G suit pressure.
Acceleration↗
Effects of hyper +Gz acceleration on cardiovascular function, visual evoked potentials and cerebral blood flow in anesthetized rats.
Sustained hyper-gravity acceleration, particularly along the long axis of the body of animals or man (Gz), produces significant mal-effects on subjects, and hence it has been well studied, The most common syndromes of Gz application were cardio-vascular de-conditioning, and black-out, red-out, and loss of consciousness, which finally lead subjects into death. However, in most previous studies, the duration of applied Gz was rather short. In the present experiments, we can use longer duration of 1000 seconds. In addition, recent technological innovation make it possible to record directly local cerebral blood flow at a target cortical area with a Laser Doppler flow meter. We used this innovated method to measure local cerebral blood flow of rats in relation to visual evoked potentials (VEPs) under hyper-Gz acceleration. Also we recorded cardio-vascular parameters like heart rate from ECG, systolic and diastolic blood pressure and correlated them with cerebral blood flow and VEPs.
Acceleration↗
Change-over coordination structure of astronauts' voluntary movements during orbital flight conditions.
Formation and development of human motor function in phylogenesis and ontogenesis is known to be under the influence of Earth's gravitational field. So the relatively constant neuromotor and mass-inertial proportions between motor system's elements have been formed with human being during evolution process. This facilitated the development of enough stabile and reliable coordination structures of genotypical and phenotypical acquirements with human being. Essential changes in the coordination structure of many capital motor acquirements have been observed due to micro-gravitation during orbital flight conditions.
Astronauts↗
Pain in the arms induced by markedly increased intravascular pressure decreases after repeated exposures to moderately increased pressures.
It is well documented that exposure to high gravitational (G)-load in the head-to-foot direction may induce arm pain. Such G-induced arm pain is of vascular origin and caused by markedly increased pressure in the arm vessels. It has been hypothesized that the arm pain is due to pressure-induced overdistension of local blood vessels. Indeed, elevation of local intravascular pressure to levels that induce considerable arm pain results in distension of both veins and arteries. There appears to be a paucity of data regarding the effects of repeatedly increasing intravascular pressure in the arms. Accordingly, the purpose of the present study was to investigate the effect of iterative exposures to moderate pressure elevations in the arm vessels (here termed "pressure training") on the pressure distension relationships of the vessels and on pressure-induced arm pain. To experimentally induce increased transmural pressure over the vessel walls of the arms we used a modified version of a method described elsewhere; this method has also proven a useful tool for simulating G-induced arm pain.
Adaptation, Physiological↗
Sympathetic response to horizontally linear acceleration in humans.
There is considerable evidence that stimulation of the vestibular system has effects on the activities of sympathetic preganglionic neurons in animals and of postganglionic nerves in animals and humans. In previous studies, we showed that the muscle sympathetic nerve activity (MSNA) from the human tibial nerve is enhanced after caloric vestibular stimulation (Cui et al. 1997), whereas the skin sympathetic nerve activity is suppressed during the nystagmus evoked by the caloric vestibular stimulation (Cui et al. 1999). These results suggest that the stimulation of the horizontal semicircular canal has effects on sympathetic outflows to muscle and skin in humans. However, much less is known about the MSNA response to dynamic stimulation of otolith organs in humans. To clarify this issue, we used a linear accelerator to stimulate the vestibular organs, especially otolith organs, and observed the MSNA and hemodynamic responses during movement.
Acceleration↗
G-factor as a tool in basic research: mechanisms of orthostatic tolerance.
The inability to tolerate upright standing posture due to development of orthostatic hypotension is a clinical problem experienced by more than 500,000 people in the United States. In addition, orthostatic intolerance is an operational problem since as many as 25 to 64 percent of the crew members from U.S. space shuttle flights have been reported to experience presyncopal incidents during postflight stand tests. Last year alone, more than 10,000 cases of unexplained syncope were reported in active duty personnel in all U.S. military services. Many clinical investigations have focused on measurements of physiological functions in patients with orthostatic instability in an effort to identify possible mechanisms that underlie the problem. Although this approach has provided important insight into mechanisms associated with syncope, identification of causal relationships are limited by pre-existing pathologic conditions. Causal relationships can be better defined when physiological mechanisms that underlie blood pressure regulation are altered in healthy subjects by increasing or decreasing their gravity environment (so-called "G-factor" approach) and subsequent changes in orthostatic tolerance are induced. The purpose of this paper is to review data on physiological functions measured from healthy human subjects who have undergone exposure to various levels of low or high gravity in an effort to assess our understanding about mechanisms of orthostatic tolerance. Specifically, results from human subjects exposed to bedrest, spaceflight, and high sustained acceleration will be used to provide insight into the plasticity of mechanisms underlying adaptations of blood pressure regulation orthostatic performance.
Baroreflex↗
[Cardiovascular reactions to gravitational force in different directions].
OBJECTIVE: To observe the features of the cardiovascular reactions to gravitational forces along different axes of the body. METHOD: Dogs were exposed to gravitational forces along axes of body on an animal centrifuge. RESULT: It was found that when the direction of G force changed from +Gz to +Gx, the predominating effect on the cardiovascular system changed from the drop of eye level blood pressure to the increase of central venous pressure, and the reactions of the organism changed from a presson reflex of the arterial system to the inhibition of cardiac activities at higher G levels. The turning point was found to be at the back angle of 75 degrees with respect to the direction of the gravitational force. CONCLUSION: These findings provide an important reference for choosing the optimal seat back angle in a manned space vehicle.
Acceleration↗