Physical working capacity and factors responsible for it after exposure to 120-day antiorthostatic hypokinesia

The effect of 120-day antiorthostatic hypokinesia on human physical working capacity and functional state was studied. The study revealed two adaptation phases: the first phase is characterized by a significant decrease in working capacity and the second by relative readaptation. However, the unfavorable effect of 120-day antiorthostatic hypokinesia was evident as a decrease in the effectiveness of function of the cardiorespiratory system that increased the physiological cost of physical work.     

Effect of hypokinesia on nucleic acid and protein metabolism in the lymphoid organs of rats

Metabolism of nucleic acids and protein by lymphoid cells of the rat spleen and thymus was studied under conditions of 22-day hypokinesia. It was shown that in the course of hypokinesia the loss of cellular mass by the spleen and thymus was associated with varied biochemical changes in the remaining lymphoid cells. The thymocytes showed a significant activation of nucleic acid and protein biosynthesis. Meanwhile in spleen lymphocytes, DNA and RNA metabolism was inhibited with no appreciable changes in protein metabolism. Potential mechanisms of changes in metabolism of thymus and spleen lymphocytes under long-term hypokinesia are discussed.     

Physiological Cost of Physical Exercise and Mitochondrial Volume in Working Muscles of Subjects Exposed to Long-Term Hypokinesia: Effects of Local Resistance Exercise

The results of changes in the physiological cost of 30-min submaximal aerobic bicycle ergometric exercise and characteristics of the mitochondrial apparatus of m. vastus lateralis were assessed comparatively during 120-day (–6°) antiorthostatic hypokinesia either without prophylactic measures or with low-intensity resistance exercise training for 60 days using a Penguin exercise suit. Hypokinesia was accompanied by an increase in the working heart rate and lactate accumulation in the blood during the test exercise, as well as by a decrease in the myofibril size and the volume density of mitochondria in the m. vastus lateralis fibers. The patterns of dynamic changes in the lactate concentration in the blood during exercise training and in the volume density of central mitochondria were found to be similar. A correlation between the rate of lactate accumulation in the blood during the test exercise and the volume density of mitochondria in the working muscle appeared after long-term (60 days) exposure to hypokinesia. The use of the Penguin exercise suit in dynamic mode during prolonged (60-day) exposure to hypokinesia completely prevented the following effects: atrophy of slow-type fibers, a decrease in the volume density of central mitochondria, and an increase in the level of lactate accumulation in the blood under conditions of a standard submaximal aerobic exercise load. The correlation links between the oxidative potential of working muscle and the energy supply of muscular work are discussed.     

Interhemisphere Asymmetry of the Pro-/Antioxidant Systems in the Rat Brain: Effects of Hypokinesia and Extrahigh-Frequency Electromagnetic Radiation

We studied changes in the interhemisphere asymmetry of the intensity of lipid peroxidation (LPO) and total content of thiol groups (TTG) in the rat cerebral neocortex. These indices characteristic for animals with different motor phenotypes (dextrals, sinistrals, and ambidextrals) were measured in the control and under the influence of hypokinesia, low-intensity millimeter-range electromagnetic radiation (mmR EMR), and their combination. The development of hypokinetic stress in rats (after 10-day-long motor restriction) resulted in a sharp activation of LPO and suppression of thiol/disulfide metabolism in the neocortex of rats with different types of motor asymmetry. Hypokinesia was accompanied by considerable drops in the coefficients of interhemisphere asymmetry (up to reversal of their signs); this can be related to decreases in the resistivity of the organism to stress and adaptability to external influences. When intact animals with different types of motor asymmetry were irradiated with mmR EMR, the intensity of LPO in the neocortex of both hemispheres decreased concurrently with intensification of thiol/ disulfide metabolism. The combined influence of hypokinesia and mmR EMR led to considerably smaller shifts in the above indices, as compared with those after isolated action of hypokinesia. When mmR EMR influenced animals were kept under conditions of normal motor mode and motor restriction, the signs of the coefficients of asymmetry of the indices under study did not change, while the intensity of interhemisphere asymmetry increased. We suppose that this is related to an increase in the adaptability of the organism to the action of stressor factors.     

Effect of hypokinesia and the combined action of gravitational load and hypokinesia on the structure of the hepatic portal system]

General hypokinesia during 1--6 weeks resulted in dilatation of the interlobular veins. sinusoids and central veins. The sequence of alterations corresponded to terms of hypokinesia. After exposure to "gravitation stress--hypokinesia for 1--6 weeks" stagnation in the portal system of the liver was less than after exposure to hypokinesia alone, but unevenness of lumens in the interlobular veins and sinusoids was more pronounced. The foci of the vessel spasm were determined. The signs of stagnation in the system of the portal vein and unevenness of the width of all the links of the portal bed were most pronounced after combination "hypokinesia for 1--6 weeks-- gravitation stress".     

Effect of gravitational loads and hypokinesia on the structure of the blood vessels of the tongue in the rabbit]

The vessels of the tongue were studied in 120 rabbits in 5 series of experiments methods of injection, clearing, rentgenography, silver nitrate impregnation after V. V. Kuprijanov and a histological method. The animals were rotated in a centrifuge with a 1 m radius. For hypokinesia the animals were placed in small cages. Gravitation stress mainly caused changes in the capillary-venous part of the circulatory bed (dilatation of vessels). Under conditions of hypokinesia morphological changes were most pronounced in terminal portions of the arterial part of the bed, arterioles and precapillaries. Successive exposure to both factors caused no specific changes. Preliminary training to stressess failed to prevent the appearance of considerable morphological changes in blood vessels of the tongue.     

Mitotic activity of the lymphocytes of the thymus cortex in hypokinesia during the period of readaptation

The changes in the weight and mitotic index were studied in the cortex of the thymus of Wistar rats during 10-day hypokinesia and 10-day readaptation (restoration). 24 hours after immobilization of the animals the mitotic index was 2 times as lower. No complete readaptation was attained during 10-day hypokinesia. No readaptation was attained during 10-day hypokinesia. In readaptation the stage of secondary stress was found (the mitotic index was 3.5 times as reduced), the stage of genuine restoration being revealed after 10 days.     

Effect of weak alternating ultra-low frequency magnetic fields on the development of the hypercoagulation syndrome in immobilized rats

The experimental results are given concerning the effect of variable magnetic field (VMF) with the frequency of 8 Hz and intensity 4 A/m on some parameters of rat haemocoagulation system under standard mobile regime as well as under prolonged hypokinesia. It is stated that repeated daily exposition of VMF causes hypocoagulational blood shift in intact animals. Under the effect of simultaneous VMF and hypokinesia the correction of hypercoagulational shift induced by animal hypokinesia was detected. The highest VMF effect was observed in prolonged experiments. A conclusion is drawn concerning the ability of VMF with the given parameters to limit the development of rat blood hypercoagulation under hypokinesia.     

Cardiovascular Function in Humans Using Thigh Cuffs during Seven Days of Simulated Microgravity

Data are summarized on changes in the human cardiovascular system associated with the use of cuffs during seven days of antiorthostatic hypokinesia simulating weightlessness. Eight subjects participated in two series of experiments, of which one was carried out with and the other (the control) without cuffs wrapped snugly around the upper third of the thighs. The parameters of the systemic hemodynamics, the cardiac function, and the hemodynamics of the cervicocephalic region and the lower limbs recorded under control and experimental conditions were analyzed. Without cuffs, changes in the hemodynamics during antiorthostatic hypokinesia were caused by displacement of body fluids in the cranial direction. The subjects responded favorably to the use of cuffs during antiorthostatic hypokinesia: most of their hemodynamic parameters remained at the baseline level, and signs of venous stasis in the cervicocephalic region were alleviated. Although the leg veins were distended in subjects wearing thigh cuffs during antiorthostatic hypokinesia, no pathological changes in the veins were detected during or after the experiment. Cuff usage during antiorthostatic hypokinesia lasting for seven days did not produce a cumulative effect on the cardiovascular system. These results justify the use of thigh cuffs in the initial period of adaptation to simulated or real weightlessness.     

Proliferative activity of the hepatocytes at different times of day during prolonged hypokinesia

The white male Wistar rats were exposed to hypokinesia during 10 days. Essential oppression of the mitotic division of hepatocytes in the rats' liver at the hypokinesia was revealed. The cellular division was exposed to the daily oscillations. The quantity of mitoses prevailed in the day and evening. In these conditions the quantity of binucleate cells increased as compared with the control. The deficit of mitoses stipulates the delay of postnatal weight of liver at the hypokinesia. Binucleate hepatocytes are the analog of the polyploid cells and their large population compensates for the increased organism's need in liver function in the experiment.     

Influence of gravitational overload and hypokinesia on the structure of the vascular bed of the stomach]

Under study were effects of gravitation stresses, total hypokinesia and their combinations on blood vessels of the stomach. The work was carried out in 130 rabbits, 16 of them being used to study the normal structure of the gastric vascular bed. The vascular bed was injected with the Gerota's mass followed by clearing, making histological preparations and roentgenography. The investigation has revealed both quantitative and qualitative changes in the structure of the gastric blood vessels. The maximum endurable stress of the ventro-dorsal direction causes morphological shifts less pronounced than stresses of longitudinal directions. With prolonged terms of hypokinesia (1-12 weeks) morphological changes became more pronounced in all the layers of the stomach. A combination of successive gravitation stresses and hypokinesia during 4-12 weeks aggravated morphological changes which occurred after exposure to isolated above factors. The animals subjected to maximum endurable stresses before and after 4-week hypokinesia developed vascular changes more typical for the effects of gravitation. The pretraining of animals did not give a pronounced positive effect on the changes of the angioarchitectonics of all the gastric layers after a repeated stress following 4-week hypokinesia.     

Modelling of the parkinsonian syndrome by the administration of kainic acid into the caudate nucleus

The experiments on rats have shown that bilateral administration of kainic acid (0.1-0.15 microgram) into the rostral parts of caudate nuclei led to the development of hypokinesia and rigidity. An increase in the electrical activity--the formation of the generator of pathologically increased excitement (GPIE) was noted in a zone of kainic acid injection. Rigidity and hypokinesia were attenuated and the GPIE activity was depressed after cyclodol (1-10 mg/kg) or L-DOPA (100-200 mg/kg) administration. Combined administration of cyclodol (2 mg/kg) and L-DOPA (50 mg/kg) induced potentiated antiparkinsonian effect. Dopamine microinjections into the GPIE area depressed its activity and abolished rigidity and hypokinesia. These data suggest that the Parkinson syndrome develops under the influence of GPIE induced by kainic acid administration into caudate nuclei.     

Effect of general hypokinesia on the blood vessels of the medulla oblongata, pons and midbrain of the rabbit]

The work was performed on 40 rabbits. After injection of the blood system with Gerota's mass 120 mu horizontal sections were cleared after A. M. Malygin and stained with hematoxylin and eosin after Van Gieson. It was shown that within 1--3 weeks of staying in small cages the animals had dilated vein all areas of the brain under investigation. Within 4-12 weeks there appeared deformity, sharp sinuosity, disorders in usual orientation of vessels. Within 13-16 weeks of hypokinesia both qualitative and quantitative changes in blood vessels became more pronounced. It was also shown that readaptation for 1--3 weeks after 4--13 weeks of hypokinesia failed to repair the normal structure of blood vessels of the brain and that in all the parts under study the reactions of the circulatory bed structure to hypokinesia were of the same type.     

Morphology of the wall of some main arteries normally and in limited motor activity]

Effects of different periods of hypokinesia upon the structure of the main arteries wall and the microcirculatory bed of the aorta adventitia were studied in rabbits by histological methods. It was shown that hypokinesia lasting more than 4 weeks resulted in the atrophy of the medical sheath and dystrophy of the elastic framework in the wall of main arteries. In the microcirculatory bed of the aorta adventitia there occurred blood stagnation, the integrity of the microvessels wall (mainly capillaries, postcapillaries and venules) was broken. The degree of the above morphological changes depends on duration of hypokinesia.     

Adaptation of the Human Body to Simulated Weightlessness: Clinical Studies

Problems of adaptation of functional systems of the human body to conditions of continuous weightlessness are considered (prolonged stay under conditions of antiorthostatic hypokinesia and in an immersion medium). It was revealed that, during adaptation to these conditions, polymorphic clinicofunctional disorders develop, transforming into clinicophysiological syndromes, the most frequently observed being autonomic vascular malfunction, asthenoneurotic syndrome, detraining of the blood circulatory system, trophic and neuromuscular disorders, statokinetic syndrome, pain syndrome, and metabolic and hormonal disorders. The severity of the specified disorders and the duration of the recovery period depend on the duration of hypokinesia and the intensity and regularity of application of preventive measures during hypokinesia. The most probable pathophysiological mechanisms of adverse effects of continuous hypokinesia (maladaptation) on functional systems of the human body are described.     

Effect of gamma radiation on the immunobiological and immunochemical properties of cholera exotoxin. I. Change in the biological activity of nonpurified cholera exotoxin as affected by ionizing radiation

Crude cholera exotoxin (filtrate toxin) was irradiated with increasing doses of gamma radiation. A significant drop in enterotoxicity, in the activity of the permeation factor and a decrease in toxicity were shown to occur as radiation doses increased. Radiation doses of 50-70 kGy were found to completely inactivate enterotoxicity in liquid toxic preparations. A higher radioresistance of dried preparations in comparison with liquid ones was registered: inactivation occurred at 150-200 kGy. Different batches of the initial filtrate toxin had varying radiosensitivity. The sterilizing effect of gamma radiation was achieved at doses of 20 kGy for liquid preparations and 30 kGy for dried preparations. During the prolonged storage of the irradiated preparations of crude toxin (the term of observation being 1.5 years) at different temperatures no reversion of toxicity was found to occur, while their immunogenic properties remained unchanged.     

The phasic structure of early disorders of functional capacity following irradiation in rats

In experiments with rats it was shown that an early decrease in physical efficiency after irradiation involves some partially mutually superimposed phases. Phases of excitation, hypokinesia and neurological disorders are identified in early transient inefficiency followed by phases of an early transient diminution of efficiency and a reversible disturbance of the accomplishment of the known operations. Simultaneously, there is a phase of an irreversible decrease of the informational capacity of CNS as well as the tolerance to early transient in efficiency upon repeated exposure.     

Energy-dependent transport of Ca2+ and lipid peroxidation in the sarcoplasmic reticular membranes of rats during hypokinesia

Thirty-day hypokinesia in Wistar rats did not affect the rate of Ca2+ transport and the activity of Ca-ATPase in light and heavy fractions of sarcoplasmic reticulum of primarily white muscles. As hypokinesia was raised up to 90 days, these indicators increased. The intensity of lipid peroxidation in sarcoplasmic reticulum was lower in hypokinetic animals.     

Metabolism of skeletal muscle proteins in experimental hypokinesia in rats

Using a radioindicator method, the metabolism of sarcoplasmic and myofibrillar proteins was studied in vivo at different stages of hypokinesia in rats. It was shown that the true muscle atrophy and the lowered content of both protein fractions during the first two weeks are due to sharp inhibition of sarcoplasmic protein biosynthesis as well as to deceleration of biosynthesis and acceleration of degradation of actomyosin. In hypokinesia the muscle mass does not increase within 3-8 weeks largely due to the acceleration of degradation of the de novo synthesized components of contractile proteins. In early hypokinesia a stressory mechanism plays an essential role in the pathogenesis of protein metabolism disturbances.     

The level of lymphocytes in the peripheral blood as a criterion of the degree of severity of acute radiation sickness (based on materials from the accident at the Chernobyl Nuclear Power Station)

A study was made of the peripheral blood lymphocyte level as a function of gamma-radiation dose after single gamma-radiation attack resulted from Chernobyl disaster. After the initial drop an average level of lymphocytes was stabilized by day 2 after exposure and no further systematic decrease in the number of lymphocytes occurred. The accuracy of prognostication of the severity of acute radiation sickness, determined by the average lymphocyte level on days 3-6 amounted to as low as 50%. However, when the neighbouring, by the severity, groups of patients were taken into account, the accuracy was 88%.