こう合挙上ラットそしゃく筋の崩壊，再生過程における組織学的，組織化学的研究

Abstract

The present study attempts to elucidate histologic changes and histochemical characteristics of masticatory muscles in rats under bite raising.The bite of experimental rats was raised with 2mm at the mesial surface of the 1st molar by a bite raising appliance, bilaterally and/or unilaterally. The animals were killed 3, 6 and 12 hours, and 1, 2, 3, 5, 7, 10, 15, 20, 30, 60, and 120 days after bite raising. Fresh frozen sections of superficial and deep masseter, temporal, and anterior and posterior digastric muscles were made for myosin ATPase, NADH-tetrazolium reductase, acid phosphatase, acetylcholine-esterase, macrophage, and laminin stainings. The other part of the masseter muscle were used for electronmicroscopic studies.Histologically, alterations in muscle fibers of masticatory muscles following bite raising were found in superficial and deep masseter muscles under bilateral and/or unilateral bite raising, and not found in temporal and digastric muscles. The muscle fibers were conspicuously changed in the deep masseter muscle as compared to the superficial one, irrespective of bilateral or unilateral bite raising. The inflammatory cells appeared among the muscle fibers at 6 hours after bite raising, those cells infiltrated some muscle fibers on day 1, and muscle fibers were regenerated on day 7. During muscle fiber regeneration following bite raising, the I-like type and IIC type muscle fibers identified in superficial masseter muscles. These muscle fiber types are unusual in the normal superficial masseter muscle. Immunohistochemically, most of inflammatory cells in masseter muscle following bite raising were characterized by the existence of positive reaction for anti-macrophage antibody and acid phosphatase staining. The basement membranes of regenerated muscle fibers in inflammatory foci of both superficial and deep masseter muscles were already detected with laminin staining in 3-day specimens. Ultrastructually, myofibrils in 1- and 2-day specimens showed phagocytosis by macrophages, and regeneration of myofibrils and triads in 3-day specimen was recognized.The increase of mandibular alveolar bone height on the untreated side following unilateral bite raising was observed by measuring the dry skull.