Increase of muscle fiber number induced by spontaneous running exercise

以雌性断奶大鼠为实验动物，研究了自发运动引起的肌肉肥大对纤维数量的影响。动物被随机分配到运动组(E组)或久坐对照组(C组)。运动动物被放置在钢笼中，自由进入转轮进行自发运动。运动后7周，E组心脏、腓肠肌、股四头肌、缝匠肌重量明显增加。对缝匠肌的肌纤维数量进行了观察，发现缝匠肌的大部分纤维从起始处一直延伸到每个肌束的起始处。萨托里乌斯，肌肉修长，被分成几个部分进行调查。在硝酸处理后，由两个人在解剖显微镜下分离每一根纤维，通过轮廓投影仪计数纤维数量。另一种不同的方法是在肌肉横切面的光学显微镜下计数纤维数量。这两种方法证实了…的显著增加自发跑步运动后，肥大的肌肉中纤维数量增多，不同部位的纤维数量不同，缝匠肌中部纤维数量最多，最靠近起始处和起止点的部位纤维数量减少。在肌肉中部，尽管肌纤维面积没有变化，但运动肌肉的总纤维数显著高于对照肌肉。而在肌肉起始区和起始区，E组的纤维面积显著增加，但总纤维数无明显变化。差示干涉显微镜下可见运动肌肉中部有大量细小纤维，呈锥形。E组的DNA和RNA含量明显高于C组，尤其是在肌肉中部。因此，我们得出结论，肌肉肥大归因于肌肉中部纤维数量的增加和起始部和起止部纤维面积的增加，这一结论得到了生化数据的支持。此外，干涉显微镜表明，中间纤维数量的增加部分是由于出现了锥形纤维。较少

The effect of spontaneous running exercise, which induced muscular enlargement, on fiber number was studied using female weaning rats. Animals were randomly assigned to either an exercising (E) group or a sedentary control (C) group. Exercising animals were placed in steel cages free access to running wheel for spontaneous exercise. After 7 weeks of exercise, muscle weights i.e., heart, gastrocnemius, quadriceps and sartorius increased significantly in E group. Muscle fiber number was investigated in sartorius of which most fibers run the length of each fascicle from its origin to insertion. Sartorius, long muscle, was divided into several sections for the investigation. Fiber number was counted through profile projector by two persons isolating each single fiber under a dissecting microscope after nitric acid tratment.In another different approach, fiber number was counted on photomicrographs of the transverse sections of the muscle. The two approaches confirmed significant increase o … More f fiber number in enlarged muscle following spontaneous running exercise.Fiber number varied in different regions of the muscle, showing the peak of number in the middle of sartorius and decreasing number in regions closest to the origin and insertion. In the middle of the muscle, the total fiber number of exercised muscle increased significantly as compared with control muscle, although muscle fiber area did not change. On the other hand, in the regions of origin and insertion of the muscle, fiber area of E group increased significantly but the total fiber number did not change. There appeared many small fibers in the middle of exercised muscle, which was found to be tapering fiber under a differential interference microscope. DNA and RNA contents in E group were much more than those in C group, espeially in the middle of the muscle. Thus, we concluded that muscle hypertrophy was attributed to increased fiber number in the middle of the muscle and increased fiber area in regions of the origin and insertion, being supported by the biochemicala data. Further, an interference microscopy demonstrated that increase of fiber number in the middle was partly due to appearance of tapering fiber. Less