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At least 991 records · Page 55Linked to original sources
PubMed1991

[Results of hematological examinations of crew members of the space vehicles EO-2, EO-3 and EO-4].

The authors' opinion that adaptation inhibition of erythron functioning under weightlessness produces an unfavourable effect on the optimal physical state of a cosmonaut and his working capacity in the post-flight period has been confirmed by the analysis of certain hematological parameters studied in cosmonauts. The data obtained have necessitated investigation of threshold values of erythron functioning under weightlessness, and creation of artificial gravitation on board the piloted space ship to normalize erythropoiesis. Investigation of these problems of space hematology would be helpful in validation of the limits of human's long-term stay under weightlessness, and in the pre- and post-flight period management.

Adaptation, Physiological↗
PubMed1990

Effect of short-term spaceflight on the contractile properties of rat skeletal muscles with different functions.

In the biosatellites "Cosmos-1514" and "Cosmos-1667" rats were exposed to weightlessness in the space for either 5 or 7 days. The contractile properties of the soleus, extensor digitorum longus (EDL), brachialis, plantar, gastrocnemius and triceps (caput mediale) muscles were studied after return to earth. The muscles of animals living freely (vivarium group) and animals kept under conditions identical to those on the biosatellite (synchronous group) served as controls. The myofibrils were preserved by glycerol treatment. The ATP-Ca+(+)-induced isometric tension as well as the speed of contraction were registered, through a signal transformer, on a potentiometric recorder. The experimental results are concomitantly recorded numerically and graphically on a Citizen 1200 printer and analyzed with a Commodore 128D computer. During the short-term spaceflight the greatest weight loss and decrease of contractile power was seen in the slow soleus muscle, i.e. weightlessness and immobilization led to the degeneration and weakening of mainly the tonic muscle fibres. Nevertheless after the short-term spaceflight, even with the present improved and sophisticated methods, the authors were unable to demonstrate, changes indicating muscle transformation which had been previously seen in rats exposed to weightlessness for 18.5 days.

Adaptation, Physiological↗
PubMedDate not supplied

Enhancement of viral pathogenesis in mice maintained in an antiorthostatic suspension model: coordination with effects on interferon production.

Both rodents and men returning from spaceflight and the attendent microgravity or weightlessness conditions have exhibited alterations in immune responses and, in particular, interferon production. We have utilized a model for antiorthostatic (20 degrees head-down tilt). hypokinetic, hypodynamic suspension of mice that simulates some aspects of weightlessness. Female Swiss/Webster mice that are normally resistant to infection with the D variant of encephalomyocarditis virus showed a marked increase in susceptibility to infection when suspended. This correlated with a drop in interferon production. Control, orthostatically suspended mice (no head-down tilt) showed no increase in susceptibility to the virus. These data suggest that maintenance of mice in the antiorthostatic suspension model for simulating some aspects of weightlessness yielded increased susceptibility to virus infection that was coincident with inhibited interferon production.

Animals↗
PubMed1988

[Influence of the redistribution of liquid volumes on atrial natriuretic factor].

Several studies evidence that volume or pressure increase stimulates atrial natriuretic factor (ANF) secretion by atrial cardiocyte stretch. In order to study the relationship between plasma renin activity (PRA) and ANF plasma level in experimental weightlessness, six healthy male subjects were submitted to antigravity (anti-g) suit inflation which shifts fluid in the thoracic region. Firstly, blood samples were taken at rest after 15 mn in supine position, secondly after 25 mn in upright position with and without anti-g suit. During the tilt test, plasma ANF decreased from 35 +/- 4.1 to 28 +/- 6.6 pg/ml (p less than 0.05) without anti-g suit and rose to 38 +/- 4.1 pg/ml (p less than 0.05) with anti-g suit. This demonstrates the stimulating effect of weightlessness on the ANF release. During the same tilt test PRA increased from 2.69 +/- 0.29 to 4.76 +/- 0.83 ng/ml/h that evidences the perfusion pressure fall on the intrarenal baroreceptors. Anti-g suit inflation abolished this PRA response to the orthostatism, since PRA increase was only 3.23 +/- 0.79 ng/ml/h (p less than 0.05). ACTH and aldosterone levels do not change significantly. These results demonstrate that ANF and PRA which have opposite effects on aldosterone release and Na excretion, change in opposite sens during fluid shifts, to produce antinatriuresis in upright position, or natriuresis in experimental weightlessness.

Adrenocorticotropic Hormone↗
PubMed1985

Early central venous pressure changes in the rat during two different levels of head-down suspension.

The head-down suspension (i.e. antiorthostatic hypokinesia) rat is used to simulate the circulatory effects of weightlessness. However, little is known about the early cardiovascular adaptive response to simulated weightlessness and the effects of varying degrees of head-down suspension. Therefore, the purpose of this study was to characterize the early central venous pressure changes to two different levels of head-down suspension in the rat. Unanesthetized, unrestrained, female Sprague-Dawley rats (wt: 298 +/- 18 gms, mean +/- S.D.) with chronically implanted central venous pressure catheters were subjected to either a 45 degrees C head-down tilt angle (Group A, N = 8) or a 20 degrees head-down tilt angle (Group B, N = 8) using the tail-traction technique of head-down suspension. Central venous pressure increased significantly (p less than 0.05) in both groups of rats during head-down suspension with the absolute pressure level significantly (p less than 0.05) higher in Group A rats compared to Group B rats during the first 8 h of the study. At 24 h, the rats in Group B appeared to adapt earlier to head-down suspension because central venous pressure decreased to the previous baseline level whereas it remained increased in Group A rats. We conclude that the level of head-down suspension significantly affects the early central venous pressure response and subsequent cardiovascular adaption to simulated weightlessness in rats.

Animals↗
PubMed1979

Comparison of physiological effects of head-down tilting and immersion on the human body.

Among the methods simulating weightlessness, effects on the human body, head-down tilting and water immersion are very useful. The purpose of the present investigation was to carry out a comparative study of water balance and water-protein composition of the blood using the above two methods to simulate the physiological effects typical of an acute stage of weightlessness adaptation. The results of the 7-d head-down tilting and immersion experiments allow the following conclusions: More pronounced changes in water balance and water-protein composition of the blood during immersion seem to indicate that immersion produces a greater effect on the human body; The pattern of changes during immersion and tilting suggests that the adaptation period to immersion takes a longer time; These findings give evidence that immersion, compared with head-down tilting, reproduces more closely effects of acute adaptation to simulated weightlessness.

Adaptation, Physiological↗
PubMed1983

Alterations in calcium homeostasis and bone during actual and simulated space flight.

The weightlessness experienced in space produces alterations in calcium homeostasis. Gemini, Apollo, and Skylab astronauts exhibited a negative calcium balance due primarily to hypercalciuria. In addition, the bone mineral density of the calcaneus declined by approximately 4% in Skylab crew members after 84 d of orbital flight. The negative calcium balance and loss of calcaneal bone mineral in normal adults subjected to prolonged bed rest was comparable to that observed in space. The pathogenesis of bone loss during space flight and bed rest is not well understood due to the lack of histomorphometric data. It is also uncertain whether osteoporotic changes in astronauts are corrected postflight. The observed bone loss would be reversible and of no long-term consequence if the only abnormality was an increased remodeling rate. However, altered bone cell activity would probably result in irreversible bone loss with the premature development of senile osteoporosis many years after space flight. The main skeletal defect in growing rats placed in orbit aboard Soviet Cosmos biosatellites appears to be diminished bone formation. Bone resorption was not elevated during weightlessness. Although cortical bone returned to normal postflight, the decline in trabecular bone mass was somewhat persistent. These studies established that the modeling of a growing skeleton was altered in a weightless environment, but do not necessarily imply that a remodeling imbalance occurs in adults during space flight. However, various forms of simulated space flight inhibited bone formation during both skeletal modeling and the remodeling of adult bone.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1982

[Past and present medical and biological studies in Italy on microgravity].

Since 1957, Italian workers have been carrying out experiments on the physiological and pathological effects of the weightlessness encountered during space travel. Most of this work has been done at the Air Force Aviation Medicine Study and Research Centre, Rome, while other research has been conducted at the Department of Human Physiology, University of Milan. Various original devices (axis subgravitis tower, triaxial clinostats, etc.) have been devised and constructed to simulate partial and total weightlessness. They have been employed well ahead of actual space flights in investigations of the effects of weightlessness on vestibular function, sensory and muscle coordination, the position of the diaphragm and its adjacent viscera, locomotion, plant growth, rapid adaptation phenomena, etc. One experiment conducted during orbital flight was called Orbiting Frog Otolith. This investigated vestibular function under statis and dynamic conditions in the absence of weight. An Italian three-dimensional ballistocardiography experimental project will be conducted during the first Spacelab flight.

Electrocardiography↗
PubMedDate not supplied

[Animal experiments on the cosmos series biosatellites (results and prospects)].

Results of animal (rat) experiments carried out onboard biosatellites Cosmos-605, 690, 782, 936 and 1129 are presented with emphasis on changes in metabolism and musculo-skeletal system. The modifying effect of weightlessness on the animal radiosensitivity is considered. The use of artificial gravity as a countermeasure against adverse effects of weightlessness is discussed. As an immediate perspective, primate experiments aimed at a detailed study of mechanisms of weightlessness induced changes in the structure and function of the cardiovascular, musculo-skeletal and vestibular systems are described.

Adaptation, Physiological↗
PubMed1978

[Morphologic study of rat adrenals following flight aboard biosatellites "Cosmos-605" and "Cosmos-782"].

Dynamics of morphological changes of the rat adrenals was investigated on the first day and 25--27 days after a prolonged exposure to weightlessness. Analysing the general histological picture of the adrenal cortex during the first hours of the flight (presence of a subglomerular sudanophilic layer and distinct zones in other cortical parts), it is possible to conclude that by the completion of the flight the cortical substance has reached a definite degree of normalization, hence the animals have adopted to the flight conditions. Morphological signs of elevated functional cortical activity 9--11 h after the flight, such as enlarged nuclear volume of the fascicular zone cells and delipoidization of the internal parts of the cortex could be treated as manifestation of an acute stress-reaction developing in the animals after landing. Evaluating morphological manifestation of the acute stress-reaction observed in animals at transition from weightlessness to the earth level of gravitation, it is possible to conclude that there are no signs of depletion in the adrenal cortical function and hence, adaptive possibilities in the organism are preserved after a prolonged exposure to weightlessness.

Acute Disease↗
PubMedDate not supplied

[Role of dynamic factors of space flight in the pathogenesis of lymphoid organ involution (experimental morphologic study)].

The role of the dynamic factors in accidental involution of lymph organs has been investigated in a ground-based study simulating a 20-day space flight. It has been inferred from the study that lymph organ involution observed in rats exposed to prolonged space flights is caused by chronic and acute stresses. Chronic stress is associated with weightlessness and leads to hypoplasia of lymph organs; acute stress is connected with the transition from weightlessness to normal gravity (gravity stress), thus enhancing chronic stress induced lymph tissue hypoplasia. Spleens of both weightless and hypokinetic rats show inhibition of erythropoiesis and accumulation of hemosiderine due to accelerated erythrocyte degradation caused by diminished motor activity.

Acute Disease↗
PubMedDate not supplied

[Morphologic changes in the lungs of rats after a flight aboard biosatellite "Cosmos-936"].

Lungs of 20 rats flown aboard Cosmos-936 for 18.5 days and sacrificed within 5-13 hours (8 weightless and 4 centrifuged rats) and 25 days (4 weightless and 4 centrifuged rats) after recovery were studied histologically. An identical number of lung specimens were withdrawn from rats of synchronous and vivarium controls. Lungs of the flight rats did not show any pathological changes or morphological signs of prolonged congestion, thus indicating the lack of hypertension in pulmonary circulation. Lungs of the flight rats exhibited an increased leukocyte count, which was more marked in the weightless rats killed 8-13 hours postflight. The elevation in the count of neutrophilic leukocytes in the flight rats was due to peripheral neutrophilia which is a manifestation of an acute stress-reaction. An exposure of rats to artificial gravity was responsible for a lesser increase in the count of neutrophilic leukocytes.

Animals↗
PubMedDate not supplied

Mechanisms of development of morphological changes in mammals aboard biological satellites.

After orbital space flights lasting 19.5--22.5 days, disturbances are observed in mineral metabolism in rats, which are morphologically manifested as osteoporosis of the spongy sections of long hollow skeletal bones, periosteocytic osteolysis of them, atrophy and dystrophy of skeletal muscles, and inhibition of erythroid growth of bone marrow, which occurred and developed in weightlessness as a result of deprivation of motor activity due to removal (or reduction) of static load from the musculoskeletal system. Development of stress reaction, which is apparently intensified at certain stages of flight (lift off and touchdown) and during transition from weightlessness to conditions of gravitational force on earth, leads to corresponding changes in the structure and cellular composition of lymphoid organs, and to changes in the hypothalamic-hypophyseal neurosecretory system, adrenal glands, and other organs. Changes in the receptor apparatus of the vestibular system are associated with local circulatory changes occurring during weightlessness and G forces, while retinal injuries are associated with the effect of heavy charged particles of cosmic radiation. All changes are reversible and disappear completely or to a substantial degree a month after completion of the flight.

Animals↗
PubMed1993

Effects of microgravity on interstitial muscle receptors affecting heart rate and blood pressure during static exercise.

Afferent nerve fibers from receptors situated in the interstitium of skeletal muscles can induce cardiovascular reflexes. It has been shown that these interstitial muscle receptors are also sensitive to the local state of hydration: increased heart rates and blood pressure values were seen during dynamic and static exercise after local dehydration on earth. Since weightlessness leads to a persisting fluid loss in the lower part of the body, we hypothesized that leg exercise in space would augment heart rate and blood pressure responses to a similar extent as during local, interstitial dehydration on earth. Initial measurements during weightlessness were obtained in one subject after 6 days of space flight. Heart rate and blood pressure responses to light static foot plantar flexion (18% of maximal voluntary contraction) were recorded in two sessions. To eliminate the influence of muscle perfusion, exercise was performed during a period of arterial occlusion obtained by means of pneumatic cuffs at mid-thigh level. Identical protocols were used in the pre- and postflight controls, which were performed both in the sitting posture and in a -90 degrees tilted sitting posture assumed 30-40 min before arterial occlusion. During weightlessness the exercise responses of heart rate and systolic and diastolic blood pressure closely followed the tracings obtained with the tilted sitting posture on ground. The response amplitudes in these states of reduced lower limb volumes (about 20/min and 20 mmHg, respectively) exceeded the responses in the supine position by a factor of at least 2.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Pressure↗
PubMed1977

Nutrition and responses to zero gravity.

Prior to the Mercury program, extensive efforts were undertaken to find ways of minimizing the mass of in-flight food systems. Such efforts were directed to the use of dehydrated, energy-dense foodstuffs and to the possibilities of nutrient recyclization. As the space program became a reality, nutritional scientists were more concerned with the mechanics of food consumption in weightless flight and with the problems of structuring convention foods in a way that would facilitate their use in weightlessness. It soon became clear that there was no substantial impediment to normal gastrointestinal function in flight, and attention was shifted to more subtle metabolic phenomenons. It became apparent that slight changes occurred in skeletal density, muscle mass, and overall body composition. Recognition of these changes led to extensive ground-based simulation studies and carefully designed in-flight experiments. Data are presented on the requirements for metabolic energy in flight and on the losses that have been observed in the major elemental constituents of the body. It is concluded that convincing evidence is not yet avialable on the ability of man to adapt to long-term weightless flight. Although his nutritional requirements are qualitatively similar during flight, the sophisticated manipulation of nutrient profiles shows promise of counteracting some of the deteriorative processes that are known to occur.

Aerospace Medicine↗
PubMed1994

Application of physiologically based pharmacokinetic models for assessing drug disposition in space.

Exposure to weightlessness induces physiologic changes that may lead to pharmacokinetic and pharmacodynamic alterations of drugs administered to crew members in flight. Preliminary data from flight and ground-based studies indicate that pharmacologically significant changes occur in the kinetics of medications given in weightlessness and in simulated microgravity (head-down bed rest). Conducting flight studies on all available medications to identify the changes in their pharmacokinetic behavior in weightlessness is not feasible. An alternative approach for obtaining such information is to use computer simulations employing physiologically based pharmacokinetic (PBPK) models. Information thus obtained would be helpful in predicting the therapeutic effectiveness of medications in space, and also in developing plans for flight studies. This paper presents a brief review of relevant physiologic factors and pharmacokinetic implications of space flight, and includes a preliminary PBPK model for estimating plasma concentration-time profiles of acetaminophen under different experimental conditions.

Acetaminophen↗
PubMed2000

Effects of orbital spaceflight on human osteoblastic cell physiology and gene expression.

During long-term spaceflight, astronauts lose bone, in part due to a reduction in bone formation. It is not clear, however, whether the force imparted by gravity has direct effects on bone cells. To examine the response of bone forming cells to weightlessness, human fetal osteoblastic (hFOB) cells were cultured during the 17 day STS-80 space shuttle mission. Fractions of conditioned media were collected during flight and shortly after landing for analyses of glucose utilization and accumulation of type I collagen and prostaglandin E(2) (PGE(2)). Total cellular RNA was isolated from flight and ground control cultures after landing. Measurement of glucose levels in conditioned media indicated that glucose utilization occurred at a similar rate in flight and ground control cultures. Furthermore, the levels of type I collagen and PGE(2) accumulation in the flight and control conditioned media were indistinguishable. The steady-state levels of osteonectin, alkaline phosphatase, and osteocalcin messenger RNA (mRNA) were not significantly changed following spaceflight. Gene-specific reductions in mRNA levels for cytokines and skeletal growth factors were detected in the flight cultures using RNase protection assays. Steady-state mRNA levels for interleukin (IL)-1alpha and IL-6 were decreased 8 h following the flight and returned to control levels at 24 h postflight. Also, transforming growth factor (TGF)-beta(2) and TGF-beta(1) message levels were modestly reduced at 8 h and 24 h postflight, although the change was not statistically significant at 8 h. These data suggest that spaceflight did not significantly affect hFOB cell proliferation, expression of type I collagen, or PGE(2) production, further suggesting that the removal of osteoblastic cells from the context of the bone tissue results in a reduced ability to respond to weightlessness. However, spaceflight followed by return to earth significantly impacted the expression of cytokines and skeletal growth factors, which have been implicated as mediators of the bone remodeling cycle. It is not yet clear whether these latter changes were due to weightlessness or to the transient increase in loading resulting from reentry.

Alkaline Phosphatase↗
PubMed2001

Revised hypothesis and future perspectives.

Results from space have been unexpected and not predictable from the results of ground-based simulations. Therefore, the concept of how weightlessness and gravity modulates the regulation of body fluids must be revised and a new simulation model developed. The main questions to ask in the future are the following: Does weightlessness induce a diuresis and natriuresis during the initial hours of space flight leading to an extracellular and intravascular fluid volume deficit? Can sodium in excess be stored in a hitherto unknown way, particularly during space flight? Why are fluid and sodium retaining systems activated by spaceflight? Why are the renal responses to saline and water stimuli in space attenuated compared with those of ground simulations? How can the effects of weightlessness on fluid and electrolyte regulation be correctly simulated on the ground? The information obtained from space may be of relevance to fluid and electrolyte balance in edematous patients.

Blood Volume↗