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Biomedical subjects

T L Nemirovskaia

Publications and source records attributed to T L Nemirovskaia.

18 recordsLinked to original sources
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↗
PubMed2000

[Concentration of macroergic phosphates and oxidative potential of skeletal muscles].

It is known that a long-duration decline of high-energy phosphate (HP) level in skeletal muscles, induced by administration of beta-guanidinpropionic acid (beta-GPA), is followed by an increase in mitochondrial enzyme activities (MEA). The same increase in MEA was observed in the course of physical exercise training. Under gravitational inloading decrease in MEA and increase in the level of high-energy phosphates occurred. If changes in (HP) level are believed to trigger the alterations in MEA, the increase in high-energy phosphate levels in muscles is to lead to a decline in MEA as well. The present work was purposed to reveal if changes in HP level under different contractile activity levels may be associated with changes in oxidative potential in the skeletal muscles.

Animals↗
PubMed2000

[Ultrastructure of skeletal muscle fibers in monkeys after space flight].

It is known that exposure of humans and animals to microgravity causes reduction in the cross-sected area of muscle fibers and muscle atrophy. These changes also involve ultrastructural alterations in muscle fibers. Therefore primates, that are physiologically close to humans, are to be examined to help a better understanding of the nature of these ultrastructural changes is muscles and muscle fibers. Although failed to find any relevant published data on the quantitative aspects of ultrastructural changes in muscle fibers of space-flown primates we believe that it is important to examine these aspects. The postflight study of monkey's m. soleus, and m. vastus lateralis did not reveal any significant changes in volume density of the myofibrillar apparatus. Mitochondria of m. soleus showed a distinct reduction in volume density, being more obvious in the subsarcolemmal zone than in the central one. Mitochondria of m. vastus lateralis showed a decrease (P > 0.05) in volume density. Following the flight, m. soleus and m. vastus lateralis of the monkeys showed a significant increase in the mean area of myofibrils, and a trend towards a decrease in the number of myofibrils per 100 micron 2. Besides, m. soleus showed a significant increase in the mean area of mitochondria, and a trend towards a decrease in the number of mitochondria per 100 micron 2. In m. vastus lateralis of the monkeys after space flight the number opf mitochondria tended to decrease and the mean area showed differential changes. It can be postulated that these phenomena may be associated with a reduction in the diffusion surface of mitochondria resulting from the diminished myofibrillar volume.

Animals↗
PubMed2000

[Dynamics of human muscle fibers atrophy during long-term head-down hypokinesia].

The dynamics of atrophy in the muscles-extensors of the leg and thigh during long-term hypokinesia was studied with the model of head-down tilt (HDT -6 degrees) in a series of two experiments (120 and 60 days in duration) with participation of men and women. Dynamics of the cross-sectional area of human muscular fibers was characterized by similar atrophy of the fast and slow fibers on the first stage of HDT. Later on, the size of fast fibers in m. soleus and m. gastrocnemius lateralis reached plateau whereas the size of slow fibers continued to diminish. These were only fast fibers that underwent further atrophy in locomotor m. vastus lateralis. A supposition can be made that the controversy between literature data on the character of atrophy of muscular fibers in experiments with human subjects and rodents is primarily linked with different rates of atrophy developed by muscles in various species; besides, investigators describe different stages of one process. Analysis of the benefit from preventive exercises for the muscular atrophy control during HDT indicated that locomotor (with loading restraint belts) and resistive exercises can preclude slow fibers atrophy under the conditions of hypokinesia.

Adaptation, Physiological↗
PubMed1993

[The effect of spaced hypobaric hypoxia on the maximal hydraulic conductivity of the vascular bed, the supply of capillaries to and the size of the muscles fibers in rats].

6-7-month-old male Wistar rast were divided into three groups. On group of rats remained intact and lived under normal conditions (Group 1; n = 12). Groups 2 (n = 12) and 3 (n = 14) were exposed in hypobaric chamber (18-20 h a day and 2 h a day, respectively) for 2 weeks. The partial O2 pressure was maintained equivalent to 5000 m altitude. The hypoxia produced decreases of structural vascular resistance in hindquarters in Group 2 by 20-25% and in Group 3 by 17-20% (p < 0.05) under all perfusion pressure values. No significant changes in capillary density, capillary per fibre ratio in m. extensor hallucis proprius were found in rats exposed to hypobaric hypoxia for both durations. The cross-sectional area type I fibres (but not II fibres) (CSA) in Group 2 was significantly (p < 0.05) decreased (611 +/- 44 microns 2 vs 779 +/- 49 microns 2 in controls), continuous hypoxia produces significant reduction in type I fibre diffusion distances.

Animals↗
PubMed1993

[Effect of training on the structural-metabolic indicators in athletes' skeletal muscles].

Muscle biopsy samples were taken from m.vastus lateralis of ski-runners during the training season and 4 months after training (consisting presumably of aerobic exercises). Metabolic enzyme activities, fiber cross-sectional areas, capillary supply indices and parameters of oxygen uptake by intact mitochondria in skinned fibers were measured. Training did not induce any appreciable changes in the NADH-tetrazolium reductase activity, maximal oxygen uptake by mitochondria, mean fiber size or capillary density. At the same time, there were significant increases in the cytochrome c oxidase activity, respiratory control index and creatine-stimulated respiratory rate. The activities of alpha-glycerophosphate dehydrogenase, malate dehydrogenase and myoglobin peroxidase as well as the basal respiratory rate of mitochondria decreased as a result of training. The data obtained testify to the possibility of qualitative adaptations in the respiratory chain of mitochondria.

Adolescent↗
PubMedDate not supplied

[The morphological adaptation of the fibers of the human m. triceps surae during local endurance training].

Under investigation were effects of local endurance training of triceps of the calf in physically active volunteers who performed plantar bending in the talocrural articulation 3-4 times a week for 8 weeks with 30% of the maximum arbitrary effort for 40 minutes with 60 movements a minute. The exercise was fulfilled by one foot only. The local training resulted in a 19% greater density of capillaries in the triceps of the calf and in 30% greater amount of capillaries per a fiber. No significant changes were found during training in the ratio of the I and II types of fibers and in their area of cross section, although a tendency for hypertrophy of the Ist type fibers was noticed. Changes in the cross section area of the Ist type fibers and capillary density during training had a considerable negative interrelation. These findings show that the character of the muscle response to training is determined by a correlation of the parameters characterizing its initial state and the parameters of the morphological optimum, corresponding to the given level of functional activity.

Adaptation, Physiological↗
PubMedDate not supplied

[The adaptation of human skeletal muscle fibers during aerobic training].

Effect of training on dimensions of muscle fibres of fast twitch and slow-twitch types were studied in three groups of subjects: local training of m. triceps surae (volunteers) in laboratory conditions, training of amateur joggers and of elite racers--skiers. Significant negative correlations between initial level and training-induced changes of muscle fibre cross sectional areas were demonstrated. The correlations found indicate that muscle fibre dimensions of people using similar endurance training programme tend to some certain level which is likely to be the optimal for this type of training. Dimensions of muscle fibre may significantly change as the result of traiining, probably, only in the case, when their initial values differ from the optimal one.

Adaptation, Physiological↗