Ultrastructural and cytochemical studies on the rat masseter muscle following occlusal alteration.

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Effects of the occlusal alteration on the rat masseter muscle have been studied ultrastructurally, furthermore Mg2+-ATPase activities were observed cytochemically to suppose cellular metabolism. Unilateral upper molars of 7-week-old rats were extracted to make the occlusal alteration. At intervals of 3 and 5 days, 1, 3, 6, 12 and 16 weeks, following surgical procedure, the masseter muscle on the extraction side was sampled. Morphological changes and localization of Mg2+-ATPase activities were examined by means of an electron microscope. At 3 days to 1 week after occlusal alteration, it was observed that architectural changes of myofibrils included partially abnormal running of myofibrils and fragmentation of the Z-band. Sarcoplasmic reticulum and the T-system underwent a swelling-like transformation, 3 weeks after experimental procedure. Moreover, some of the myofibrils became narrow with the reduction of myofilamerits. These changes became conspicuous after 16 weeks. The ATPase activities in normal masseter muscle was localized in the sarcolerruna, caveolae, terminal cisternac of the sarcoplasmic reticulum and matrix of mitochondoria. At 16 weeks after extraction, the ATPase activities decreased as compared with the control muscle. These findings suggest that occlusal alteration may lead to abnormal conditions of muscular tissue of masseter resembled disuse atrophy or denervation atrophy.
社団法人日本口腔外科学会の論文