抄録
Effects of tenotomy (T) and/or denervation (D) on the properties of plantaris muscle fibers were studied in wild type (WT) and mdx mice. Distal tendons of the left plantarflexors were ablated in the T group. Sciatic nerve of the left limb was transected (–5mm) at the gluteal region in the D group. Both treatments were performed for T+D. The contralateral side was kept intact as the control. After 2 weeks, the plantaris muscles of both mice were sampled bilaterally and frozen in the liquid nitrogen-cooled isopentane. Subsequently, the serial cross sections were cut at 10 μm thickness and the immunohistochemical staining for the type I or II myosin heavy chain (MHC) or the nuclear staining was performed. The muscle was predominantly composed of fibers expressing only type II MHC (93%) in both mice. The remaining fibers (7%) were expressing type I+II MHC. The percent distribution of central-nucleated fibers was 58% in mdx mice, although few fibers contained the central-nuclei in WT mice. The percentage of the central-nucleated fibers was not affected by T, D, or T+D in both mice. The fiber cross-sectional area (CSA) was significantly decreased following D or T+D vs. contralateral side. Only in T group, CSA was significantly decreased in central nuclei fibers, but not in fibers without central nuclei. The magnitude of the response was similar between WT and mdx mice. The results suggested that the mechanism responsible for the plasticity of plantaris muscle is different from that of soleus muscle (Terada et al., J. Gravit. Physiol., 2005). [J Physiol Sci. 2007;57 Suppl:S95]
