Dystrophin in limb skeletal muscle fibers and creatinkinase leakage after acute +3 Gz acceleration in rhesus monkeys

Intensive muscle tension induces significant blood accumulation of enzymes and structural proteins of the muscle origin. Altered macromolecular permeability of the sarcolemma is attributed to integrity of sarcolemmal cytoskeleton, mainly to dystrophin-sarcoglycan (DSG) complex. It is known that intensive tension of the antigravity extensor muscles is observed under conditions of gravitational overloading. We assumed that acute exposure to hypergravity would lead to serum accumulation of creatine phosphokinase (CK) associated with considerably altered integrity of the dystrophin layer in fibers of extensor muscles.     

Effect of weightlessness and movement restraint on structure and metabolism of M. soleus in monkeys after space flight

After staying in real and simulated weightlessness, the most obvious changes were recorded in the "slow" tonic muscles like m. soleus, the protein loss in the fibres being greater than the loss of other components, water included.     

Influence of repetitive Gz acceleration on structural and metabolic profile of m. vastus lateralis in monkeys exposed to 30 day bedrest

It was shown that changes in structural and metabolic indices of extensor muscles of the lower extremities were usually found in man after exposure to space flight or to bed rest. Similar changes were also observed in monkeys, space-flown on "Kosmos" biosatellites. Response to weightlessness and to restraint was found to be different in m. soleus and in m. vastus lateralis. Therefore, it is important to study structural and metabolic changes of m. vastus lateralis fibers under conditions of gravitational unloading in monkeys, who have motor apparatus similar to that of man, and are much more fruitful object of research. It is assumed that artificial gravity can serve as a countermeasure, aimed at diminishing effects of gravitational unloading. We have studied the effect of repeated gravity overloading, created by means of a centrifuge, on structural and metabolic indices of monkey m. vastus lateralis at the background of 30 day head down tilt bed rest (BR).     

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.     

Effects of Ca2+(-)binding agent on unloaded rat soleus: muscle morphology and sarcomeric titin content

It had been hypothesized and recently shown that the exposure to gravitational unloading brought out to sufficient accumulation of Ca2+ in the myoplasm of soleus muscle fibers. Some authors believe that this dramatic Ca2+ accumulation induces the muscle protein degradation (including cytoskeletal proteins) by means of Ca 2(+)-activated proteases. For instance, the loss of giant sarcomeric cytoskeletal protein titin which is believed to determine the elasticity properties of muscle fibers, may contribute to the fiber stiffness decrease under unloading conditions. The study was designed to test the hypothesis suggesting that intracellular Ca2+ binding by means of EDTA administration would allow to attenuate hypogravity-induced atrophic changes including changes in myofibrillar proteins of skeletal muscle fibers.