Abe S, Kasahara N, Amano M, Yoshii M, Watanabe H, Ide Y
Oral Health Science Center and Department of Anatomy, Tokyo Dental College, 1-2-2 Masago, Mihama-ku, Chiba 261-8502, Japan.
Bull Tokyo Dent Coll. 2000 Aug;41(3):119-22. doi: 10.2209/tdcpublication.41.119.
Histological changes in the masseter muscle were observed over time in mdx mice, a muscular dystrophy model. It was found that marked necrosis occurs about the time of weaning at around 4 weeks of age; then the tissue actively regenerates at 8 weeks and stabilizes as regenerated muscle with centronuclei at 15 weeks old. This study examined the centronucleus in regenerated muscle. The process from necrosis to regeneration in muscle fibers occurs a little later in the masseter muscle than in other limbic muscles. Regenerated muscles observed around 15 weeks after birth showed a moth-eaten appearance. Transmission Electron Microscope (TEM) observation of transverse sections of muscle fibers revealed that myofibrils surrounded lost regions in the area showing a moth-eaten appearance. Thus, some defensive mechanism may affect the ability of muscle fibers to maintain a function close to normal in mdx mice even though the muscle fibers develop muscular dystrophy. The function of the masseter muscle drastically changes from sucking to mastication behavior at around 4 weeks, and this was considered to influence the morphological changes in the muscle tissue. The moth-eaten appearance seen at 15 weeks may represent an appropriate myofibril reconstruction preventing invasion of the lost regions.
在肌肉萎缩症模型mdx小鼠中，随着时间推移观察了咬肌的组织学变化。结果发现，在约4周龄断奶时出现明显坏死；然后在8周时组织积极再生，并在15周龄时稳定为具有中央核的再生肌肉。本研究检查了再生肌肉中的中央核。咬肌中肌纤维从坏死到再生的过程比其他肢体肌肉稍晚发生。出生后约15周观察到的再生肌肉呈现出虫蚀样外观。对肌纤维横切面的透射电子显微镜（TEM）观察显示，在呈现虫蚀样外观的区域，肌原纤维围绕着缺失区域。因此，即使肌纤维发生肌肉萎缩症，某些防御机制可能会影响mdx小鼠肌纤维维持接近正常功能的能力。咬肌的功能在约4周时从吸吮行为急剧转变为咀嚼行为，这被认为会影响肌肉组织的形态变化。15周时出现的虫蚀样外观可能代表了一种适当的肌原纤维重建，可防止缺失区域受到侵袭。
