title: The histochemistry of reactive masticatory muscle hypertrophy.
abstract: There are two types of hypertrophy of the muscles of mastication in man: reactive hypertrophy, the more common form; and nonreactive enlargements-myositic, genetic, myopathic, and idiopathic. Reactive hypertrophy develops when the masticatory muscle workload is increased by local bone and dental disorders; such triggers are not powerful but act over long periods, thus demanding increased endurance. Exercise for endurance has a greater effect on the muscles of mastication than it has on the large muscles of the limbs; these react solely by stimulating the oxidative metabolism of type 1 fibers, whereas masticatory muscle reacts structurally by hypertrophy and progressive type 1 fiber predominance. Eventually enzyme instability of type 1 fibers and end stage atrophy of type 2 fibers may appear. Unexpectedly, lesions have also been found in control masticatory muscle, in particular type 2 fiber specific atrophy like that seen in long-standing acquired autoimmune myasthenia gravis. It is suggested that the adverse lesions in hypertrophied and control masticatory muscle are the consequence of post-activation fatigue.
authors.affiliation: Department of Pathology (Neuropathology), University of Leeds, England.
authors.forename: D G
authors.initials: DG
authors.lastname: Harriman
mesh_terms: D000328:Adult; D001706:Biopsy; D002102:Cadaver; D005260:Female; D006651:Histocytochemistry; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006984:Hypertrophy; D008297:Male; D008410:Masticatory Muscles / Q000201:enzymology* / Q000473:pathology*; D008875:Middle Aged; D009218:Myosins / Q000378:metabolism; D012016:Reference Values; D013703:Temporal Muscle / Q000378:metabolism / Q000473:pathology
chemical_list: D009218:Myosins