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At least 865 records · Page 48Linked to original sources
PubMed1993

[Movement disorders in weightlessness].

The system MONIMIR has been developed to study the coordination of eye, head and arm movements as well as spinal reflexes in microgravity and was used during three spaceflights on board of the station MIR. The following investigations in the course of the experiment MONIMIR were performed: (1) slow head movements in three planes, (2.3) fast pointing movements of eyes, head and arm to acoustic and visual targets, (4) tracking movements of eyes, head and arm to visual targets, (5) head and arm movements based on short term memory and (6) patellar-tendon-reflex. In microgravity different functions and effectors showed different nature and degree of disturbance and different courses in adaptation; in most of the tests exactness and velocity of head and arm movement was decreased; head movements were more disturbed than arm movements; fast pointing movements were more severely affected than slow tracking movements which partly improved; visual controlled movements showed better adaptation as only proprioceptive controlled movements; the patellar-tendon-reflex was highly increased. Disturbances were most pronounced in the early stage of the spaceflights; at later stages most of the performances improved. Methods and results can be used not only for improvement of election and health control of cosmonauts/astronauts for future longterm space missions but also for diagnostics and research of adaptational processes in course of diseases or extreme conditions on earth.

Extraterrestrial Environment↗
PubMed1993

[The interstitial organ in weightlessness: a clinico-physiologic model].

We performed an experiment within the 1991 Austromir mission, 3 months preflight, on the 6th inflight and 4th postflight days, respectively. Primary goal was to measure changes in venous blood and plasma sound velocity (BSV, PSV) with lower body suction (LBNP). Contrasting earth-based findings, there was no increase in BSV nor PSV with LBNP inflight. Postflight, the elevation in both values was greater than expected. Taken together with LBNP data from the German 1992 Mir cosmonaut, we propose the hypothesis that the dynamics of tissue fluid exchange is profoundly influenced by m-g adaptation. A further goal of the experiment was to determine volume- and stress-sensitive hormones. The results need validation by additional flight data and might be considered as an important contribution to our understanding of the normal functioning and pathophysiology of the interstitial organ.

Adaptation, Physiological↗
PubMed1993

[Visuo-vestibular interaction in determination of orientation behavior in weightlessness].

We measured vertical vection during a short term space flight and 2 long term space flights to evaluate the state of adaptation to microgravity. The first phase of microgravity adaptation showed with major changes of vertical vection perception such as "inverted vection". This method will be used to reveal mechanisms of adaptation to altered vestibular inputs.

Adaptation, Physiological↗
PubMed1994

[The effect of weightlessness on embryonic development of striated muscles in Japanese quail].

In the conditions of gravitationless state, the development of skeletal muscles and myocardium was identical in experimental, synchronous and laboratory control. There were not larger differences between the investigated groups of animals. Myofibrils were in the stage of myofibrillogenesis. They were mostly disarrayed, but they already formed sarcomeres, without marked boundaries between I and A zones. Sarcoplasm contained large amounts of ribosomes and polyribosomes. Mitochondria were intensively splitting, and they contained small numbers of mitochondrial particles. Osmiophilic bodies and granules were detected frequently. Sarcoplasmic reticulum and Golgi apparatus were well developed. Our findings are in agreement with the results published in papers dealing with the embryonal development of striated muscles.

Animals↗
PubMedDate not supplied

[Effects of weightlessness on sensorimotor interaction in the operator'work: proprioceptive feedbacks].

During the 2nd Soviet-French Space Flight an operator ability to reproduce from memory the different positions of handles was studied. It is indicated that the temporal parameters of movement and the number of distinguishable positions of handle were not significantly influenced by microgravity effect. However, the accuracy of setting the handle to a given position at the beginning of the flight was significantly lower with an error towards a decrease of handle deflection angle. It is assumed that the cause of this is the proprioceptive feedbacks changes.

Feedback↗
PubMed1993

Evaluation of the torsional VOR in weightlessness.

The experimental concept and findings from a recent manned orbital spaceflight are described. Together with ongoing terrestrial and parabolic studies, the present experiment is intended to further our knowledge of the sensory integrative processing of information from the semicircular canals and the otolithic receptors, and to quantify the presumed otolithic adaptation to altered gravito-inertial force environments in a more reliable manner than to date. The experiment included measurement of the basic vestibulo-oculomotor response during active head rotation about each of the three orthogonal axes. Priority was given to the recording of ocular torsion, as elicited by head oscillation about the roll axis, and thus due to the concomitant stimulation of the semicircular canals and otolith receptors. Videooculography was employed for the measurement of eye movements; head movement was measured by three orthogonally arranged angular rate sensors and a triaxial linear accelerometer device. All signals were recorded synchronously on a video/data recorder. Preliminary results indicate alterations in the torsional VOR under zero-g conditions, suggesting an adaptive modification of the torsional VOR gain over the course of the 6-day orbital flight. In addition, the inflight test findings yielded discrepancies between intended and performed head movement, indicating impairment in sensorimotor coordination under prolonged microgravity conditions.

Aerospace Medicine↗
PubMed1993

[The effect of weightlessness on the early stages of the posttraumatic regeneration of the rat soleus muscle].

The regeneration process in soleus muscle of the rats flown on board of the biosatellite "Cosmos-2044" for 14 days was studied. The muscle was crashed in the middle 2 days before the flight. The delay of regeneration process in comparison with controls was revealed by electron microscopic examination of the muscles. Destructive changes prevailed in muscle fibers, in myoblasts and newly formed muscle tubes as well.

Animals↗
PubMedDate not supplied

[Effect of weightlessness on the course of the reparative process in the muscles of the biosatellite Kosmos-2044 rats].

The repair process in the soleus and gastrocnemius muscles of SPF Wistar rats flown for 14 days on the biosatellite Cosmos-2044 was investigated. The muscles were injured 2 days before launch by means of clamp forceps. The exposure inhibited the process but did not impair its phasic development. As a result, the reparative field diminished and took the size of an atrophic muscle; thinner myofibers appeared that originated from the ends of injured atrophic fibers and fibers that underwent splitting. It is postulated that repair inhibition is caused by the same mechanisms that produce muscle atrophy in microgravity. It is suggested that both repair inhibition and muscle atrophy are induced by disorders in the neurotrophic regulation of metabolism due to partial disuse.

Animals↗
PubMedDate not supplied

[The effect of weightlessness on fracture healing of rats flown on the biosatellite Cosmos-2044].

Two days before launch of the biosatellite Cosmos-2044 five rats were exposed to surgical intervention: their fibulas were cut bilaterally. The purpose was to study the effect of microgravity on bone fracture healing. Histologically and histomorphometrically it was demonstrated that healing was inhibited; as a result, bone callus was poorly developed and bone fragment consolidation was inadequate. An increase in the relative volume of osteoid and a simultaneous decrease in the number and activity of osteoblasts point to mineral disorders of newly formed bone in microgravity. Study of untreated tibia showed that exposure to microgravity led to osteoporosis of proximal metaphyses. This osteoporosis was produced by inhibited neoformation and enhanced resorption of bone. Comparative analysis of injured fibula and untreated tibia of rats exposed to real microgravity for 14 days or tail suspended demonstrated similarity of changes. This indicates that tail suspension can be viewed as an adequate simulation of microgravity with respect to changes in hindlimb bones.

Animals↗
PubMed1995

[Role of the hypophysis, hormonal growth inducers and physical exercises in the regulation of function of thyrocytes, C-cells and parathyrocytes in rats during simulated weightlessness].

Immunohistochemistry and histomorphometry were employed to assay thyroid and parathyroid glands in hypophysectomized rats following a10-day tail suspension in head-down position and daily injection of either physiological solution or growth hormone or insulin-like growth factor 1 on the background of physical exercise, i.e. ascent up a 1 m high staircase with a load fastened to the tail. Hypophysectomy was found to cause atrophic/sclerotic changes in the thyroid and parathyroid glands, and dramatically suppress the functional activity of thyrocytes, C-cells (calcitonin producers) and parathyrocytes (parathormone producers). Assumingly, the impairing effect of hypophysectomy on C-cells and parathyrocytes is consequent to the reduced production of thyroid hormones and concomitant moderation of metabolism. The suspension by tail added somewhat to the severity of changes in thyroid and parathyroid glands under the effect of hypophysectomy, whereas the injection of growth hormone or insulin-like growth factor 1 slightly stimulated thyrocytes, C-cells, and parathyrocytes activities; however, it failed to offset the hypophysectomy-provoked developments. Although the activities of thyrocytes, C-cells or parathyrocytes were not affected by physical exercise, there was a mild C-cell proliferation.

Animals↗
PubMed1995

[Spontaneous and visually induced illusory responses in weightlessness (results of the Austrian-Russian experiment "Optovert" performed within the framework of the program "Austromir", part I)].

There presented the results of studying the mechanisms of intersensory interactions and sensory adaptations, the dynamics of the stability of adaptive changes in the short- and long-term space missions by phenomenology of spontaneous and visually-induced illusory responses. It is shown that adaptation to microgravity even under good subjective health condition and the absence of anomalous subjective reactions was accompanied the change in the interaction of the sensory systems. For the first time there recorded the previously unknown phenomena: an inversion of vertical vection illusion (VVI) on vertical and sinusoidal optokinetic stimulation; disruption of the perception of body scheme at the instant of VVI; the change of character and the initiation of VVI asymmetry; the decrease of thresholds and the intensity increase of VVI. In the period of long-term stay in microgravity the anomalous perceptive reactions (the period of predominating adaptation gave way to the period of predominance of disadaptation). The hypothesis for the mechanisms of revealed changes was suggested.

Adaptation, Physiological↗
PubMed1996

Evidence of sensory conflict and recovery in carp exposed to prolonged weightlessness.

BACKGROUND: Evidence in support of the sensory conflict hypothesis for space motion sickness (SMS) is still needed. HYPOTHESIS: We hypothesized that sensory conflict and recovery processes should be demonstrated in intact fish during initial days of microgravity exposure, as a disturbance and restoration of the dorsal light response (DLR; a functional model of visual-graviceptor interaction), respectively. We also expected that this would be true in an otolith-removed fish if it had been fully compensated for dysfunction before the exposure. METHODS: The DLR of carp (Cyprinus carpio) was examined intermittently during the 8-d mission of Spacelab-J. Two carp, normal and labyrinthectomized (LB), made the flight. RESULTS: In the normal carp, the DLR was unstable for the first 3 d inflight but gradually recovered thereafter. The recovery was characterized by gradual restoration of the DLR tilt speed. The LB fish whose otoliths had been removed 2 mo before the flight maintained DLR at the first inflight test session (22 h after launch), but DLR was disrupted at 2 d as in normal fish. The recovery process could not be evaluated in this fish, because the EEG cable which was attached to the fish for supplementary study became tightly twisted and thus immobilized the fish for the remainder of the experiment. CONCLUSION: These findings provided additional evidence in fish for sensory-motor disorder and readjustment during the early phase of microgravity, thus supporting the sensory conflict hypothesis for SMS.

Animals↗
PubMed1977

Prolonged weightlessness effect on postflight plasma thyroid hormones.

Blood drawn before and after spaceflight from the nine Skylab astronauts showed a statistically significant increase in mean plasma thyroxine (T-4) of 1.4 microgram/dl and in thyroid-stimulating hormone (TSH) of 4 muU/ml. Concurrent triiodothyronine (T-3) levels decreased 27 ng/dl indicating inhibited conversion of T-4 to T-3. The T-3 decrease is postulated to be a result of the increased cortisol levels noted during and following each mission. These results confirm the thyroidal changes noted after the shorter Apollo flights and show that thyroid hormone levels change during spaceflight.

Cholesterol↗
PubMed1977

Behavioral analyses of killifish exposed to weightlessness in the Apollo-Soyuz test project.

Two groups of killifish, Fundulus heteroclitus, which were flown aboard Apollo-Soyuz, were subjected to postflight behavioral testing. The first group examined consisted of a graded series of embryos representing key developmental stages at orbital insertion (32-h, 66-h, and 128-h stages; pre-liftoff fertilization times). The tests revealed that the young adults from the flight 32-h stage had a significantly decreased positive geotaxis and increased negative phototaxis when compared with ground controls. These findings suggested a greater sensitization of the least-developed flight stage to post-hatching environmental influences. The second group consisted of 21-d old juveniles which were subjected to light orientation tests soon after recovery. No significant differences were detected.

Animals↗
PubMed1996

[Awareness of the subjective vertical in weightlessness (results of Austrian-Russian experiment Optovert performed within the framework of the program Austromir, part III)].

Data about intersensory interactions and adaptations, dynamics of the adaptive shifts were obtained in short- and long-term space missions basing on the indices of the subjective optical vertical awareness evaluated in experiment "OPTOVERT" with the use of dedicated ingenious techniques and hard- and software. As was shown, the function of subjective optical vertical (SOV) awareness remained unaltered in microgravity; however, in the period of adaptation there was a significant growth of error in SOV awareness in the darkness, and against the vertical optokinetic stimulation. In prolonged microgravity SOV error returns to the norm both in the darkness and during stimulation while arising asymmetry differs from background in magnitude and directivity, exceeds the physiological norm and sustains throughout a mission. After flight the asymmetry magnitude and directivity gradually regain the background values.

Adaptation, Physiological↗