| With the development of clinical and space medicine, the disuse atrophy has received increasingly attention. The clinical practice and animal experiment have proved that skeletal muscles of human being and rat all would become atrophy to a certain extent after a period of disuse. The skeletal muscles of ground squirrel,a species of hibernating rodent, will be undoubtedly in a condition of disuse during several months of hibernation. However, it's muscles has no signs of atrophy after the hibernation. Our experiment have studied the effects of disuse on configuration and function of EDL in ground squirrel. Therefore, discovering the mechanism of anti-disuse atrophy of ground squirrel in primary will provide new science document and research methods to prevention of disuse atrophy.Objective: Observing the changes of EDL of ground squirrel in control group,taile-suspend group in different seasons(summer,autumn,winter), study the effects of disuse on configuration and function of EDL in ground squirrel.Methods: 1.The type of muscle fiber of EDL in ground squirrel were determined bymATPase histochemical method ,Contractile function of EDL muscle in ground squirrel was obsverved using Powerlab system and electronical stimulator. 2.The CSA and percentage composition of every muscle fibre type of EDLwere measured by Motic Images plus 2.0 software.Results:1. The comparison of configuration and muscle fiber type of EDL in normal ground squirrel in different seanson(summer, autum and winter).(1) The ratio of EDL weight to body weight have no obviously change in groundsquirrel in summer, autumn and winter.(2)The CSA of type I fiber of EDL of ground squirrel in summer was(2561.03±326.60) um~2, the CSA of type II fiber of EDL of ground squirrel in summer was (3606.71±294.76) um~2. Compared with summer, The CSA of type I and II fibers of EDL of ground squirrel in autumn decreased 14.50% and 11.16%, respectively, the CSA of type I and II of EDL in hibernation ground squirrel was(2404.29±158.57) um~2, (3329.49±173.54) um~2 , the CSA of EDL have no change in summer, autumn ,winter.(3) The composition percentage of type I and II of EDL in ground squirrle in summer were (9.74±3.50)%, ( 90.26±3.50 ) %. In autumn were ( 5.43±1.41 ) %,(90.41±1.40) %.; In hibernation were (9.59±1.40) %, (90.41±1.40) %; compared with summer,winter group, the composition percentage of type I muscle fiber was decreased remarkably in autumn .2. The effection of tale-suspend (14 days)on configuration and muscle fiber type of EDL in ground squirrel in different seanson(summer, autum, winter).(1) The body weight of control group in different season, was increased but have no markedly difference, there is no remarkably change in the body weight of tail-suspend group in summer ,autumn in experiment. But the body weight of tail-suspend group decreased 9.59% in winter.(2) In the process of experiment, compare with the control group(summer) ,the muscle wet weight of EDL, the ratio of EDL weight to body weigh in tail-suspend group have no change in summer; in autumn ,winter it were reduce remarkably in muscle wet weight of EDL ,but the ratio of EDL weight to body weight showed no change in autumn and winter.(3) Compared with summer control group , The CSA of type I and II fibres of EDL in summer tail-suspend group were respectively reduce: 19.12%, 19.97% ; Compared with autumn control group , The CSA of type I and II fibres of EDL in autumn tail-suspend group were respectively reduce: 24.11%,21.51%; Compared with winter control group , The CSA of type I and II fibres of EDL in winter tail-suspend group were respectively reduce 24.99%,27.39%.(4) Compared with control group (summer autumn winter),The percentage composition of muscle fiber in tail-suspend ground squirrel in different season have no change, the muscle type have not transformed.3. The effection of tail-suspend on muscle function of EDL of ground squirrel inwinter.(1) In control group(activity), the EDL peak isometric twitch tension was (6.92±0.37) g, the maximum titanic tension was (13.25±1.71) g ; In tail-suspend group, the EDL peak isometric twitch tension was (4.94±0.48 ) g, the maximum titanic tension was (9.01±1.17) g ; compared with control group, the peak isometric twitch tension reduced 26.81%, the maximum titanic tension reduced 32%.(2) The time to 50% peak tension (TP50) and time to peak tension (TPT) in tail-suspend group are (28.75±11.48) and (72.50±24.44) ms, compared with control group have no change. How ever botb50% relaxation time (RT50) and 75% relaxation time (RT75) showed increase in tail-suspend group, but don't present significant difference compared with control group. 4. The effection of hibernation on configuration and muscle fibre type in EDL in ground squirrel.(1) the body weight continuously decreased , the EDL weight decreased in the same time, The ratio of EDL weight to body weight showed a continuous increase in hibernation ground squirrel.. When the individual had been hibernating for 1 month, 2 month, AH(2-3d), the body weight decreased: 10.35%, 18.48%, 40.07%, the EDL muscle wet weight decreased: 9.49%,6.54%,26.70% ; The ratio of EDL weight to body weight of prehibernation was (0.408±0.060) , when the individuals had been hibernating for 1month, 2month and awake for (2-3d), the ratio increased -0.01%,19.61% and 31.08%.(2) In the period of hibernation ,the CSA of EDL muscle fibres increased, the type I and II fibres of EDL in prehibernating ground quirrel were (2189.79±358.67) and 3204.14±320.74) um~2 , when the individuals had been hibernating for 1month, 2month ; the CSA of type I fibre increased 9.80%, 3.18% ,and the CSA of type II fibre increased 3.91%, 3.47%. The CSA of EDL muscle fibre decreased in awaked 2-3 days,when the ground squirrel awaked 2-3 days, the type II of EDL muscle fibre recove to normal state, compared with pre-hibernation , Hibernating for 1 month , 2month , the CSA of type I deceased 16.75%, 24.18%, 19.32%; type II decreased 7.68%, 11.15%, 10.77%.(3) In hibernation the percentage of type I increased and type II decreased of EDL, the type II transform to type I, the percentage composition of type I and type II fibres of EDI in pre-hibernating ground squirrel were (5.43±1.41) % and (94.57±1.41) %, when the individuals had been hibernating for 1month, 2month and AH(2-3d),the percentage composition of type I fibre increased 76.61%, 64.46%, 134.99%, respectively. And the type II decreased 4.40%, 3.70%, and 7.75%.Conclusion1. The ratio of muscle weight to body weight have no change, the CSA of EDL fibre didin't present significant difference in ground quirrle in different season. in the autumn the percentage composition of type I decreased.2. In experiment (summer,autumn,winter), Compared with control (summer)group, the wet weight of EDL of tail-suspend(summer) ground squirrel have no change; but decreased in autumn,winter; the ratio of EDL wet weight to body weight have no change in taile-suspend group in different seasons. the CSA of EDL muscle fibre decreased, the percentage composition of EDL muscle fibres have no change in taile-suspend group defferent sensons.3. In winter, the contraction of EDL function had been receded, the time of tension didn't present significant change.4. In hibernating season, the body weight of ground squirrel decreased , the CSA of EDL fibre incrased, the percentage composition of type I of EDL increased. When the individual aroused from hibernation, the CSA comeback to normal. |
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