| Research purposes:The study confirms that astronauts will appear musUlar atrophy when they under zero gravity conditions in space and with weightlessness time prolong, the degree of muscle atrophy will increase weight. Weightlessness caused the skeletal muscle lesions and damage, which not only affect the astronauts flying time and efficiency, but also affect their ability of re-adaptation when they return to the ground. At present, exercise is the commonly used measurement in spaceflight to deal with muscle atrophy. But the research of exercise in muscle atrophy has studied not so much. According to observe the effect of exercise on rat gastrocnemius regulatory factors expression of GDF-8, MyoD, Smad3,mRNA, the Exercise undertook preliminary research and disUssion on preventing weightlessness muscle atrophy.Research materials and methods:These 28 male SD rats were randomly divided into 4 groups, namely the control group (C), treadmill group (E), loss of control recombinant (U) and the loss of recombinant treadmill (EU), n=7 each. Establish hind limb suspension treadmill model and control group, and after eight weeks the control group and treadmill group measures the wet weight of the right gastrocnemius muscle; with HE stain measures gastrocnemius muscle fibers of left leg's CSA, and uses the method of RT-PCR to measure GDFG-8, MyoD and Smad3mRNA expression in gastrocnemius; after eight weeks'exercise training, loss of control recombinant and the loss of recombinant treadmill make simulated weightlessness for 2 weeks. After ten weeks, the rats were killed for the experiment. At the same way, measures the wet weight of the right gastrocnemius muscle. Use SPSS11.5 statistical software for data processing.Research results:1) Body weight, wet weight and weight to body weight ratio:the loss of recombinant treadmill body weight was less than the control group, which had highly significant differences, but the weight was lower descend than the control group. Gastrocnemius muscle weight: treadmill group wass lower than the control group, and had significant differences. The loss of recombinant treadmill was lower than the control group, but without the meaning of Statistics. Weight to body weight ratio:there were no significance differences between treadmill group and the control group; the loss of recombinant treadmill was higher than loss of control recombinant, and had significant differences.2) Gastrocnemius cross sectional area: treadmill group was lower than the control group, and had significant differences; the loss of recombinant treadmill was lower than loss of control recombinant, and had no significant differences. Gastrocnemius muscle regulatory factor expression: the expression of myogenic regulatory factor MyoDmRNA, treadmill group compared with the control group had highly significant differences; the expression MyoDmRNA of the loss of recombinant treadmill was higher than the control group, and had highly significant differences; muscle growth inhibitory factor GDF-8 mRNA expression, treadmill group was lower than the control group, and had highly significant differences. The loss of recombinant treadmill group was lower than loss of control recombinant (U), and had highly significant differences; Smad3 gene m RNA expression, treadmill group was lower than control group, but has no significant differences; the loss of recombinant treadmill (EU) is lower than loss of control recombinant (U), and has highly significant differences.Research Conclusions:(1) Certain intensity exercises can make the rats'weight of treadmill group loss and gastrocnemius weight decrease; the rats are simulated weightlessness after two weeks, the loss of recombinant treadmill and loss of control recombinant's gastrocnemius weight was reduced, but the rate of the loss of recombinant treadmill was less than loss of control recombinant's weight in the gastrocnemius muscle; the loss of recombinant treadmill's wet weight/weight was higher than the control group in gastrocnemius muscle, and it was more significant than loss of control recombinant. It shows that exercise plays a preventive role in muscle atrophy Weightlessness.(2) A certain intensity exercise made gastrocnemius muscle CBA smaller than the control group, and the loss of recombinant treadmill and loss of control recombinant had no significant differences in restructuring; the loss of recombinant treadmill of CSA muscle fibers was less than loss of control recombinant of CBA muscle fibers' descend. Therefore, exercise can play a role on preventing musUlar atrophy of simulated weightlessness.(3) A certain intensity exercise led to the expression of myogenic regulatory factors MyoD mRNA increased and muscle growth inhibitor of GDF-8 mRNA expression decreased, which promoting muscle growth. After the Simulated weightlessness, the loss of recombinant treadmill myogenic regulatory factor MyoD mRNA expression was higher than loss of control recombinant, but muscle growth inhibitor of GDF-8 mRNA, Smad3m RNA expression was lower than loss of control recombinant. Therefore, GDF-8, MyoD and the Smad3 may be involved in the exercise to prevent muscle atrophy of weight loss.(4) Exercise training has some effects on resisting or preventing weightlessness muscle atrophy.
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