title: Differences in myosin heavy-chain composition between human jaw-closing muscles and supra- and infrahyoid muscles.
abstract: Jaw-closing muscles have architectural features suited to force production; supra- and infrahyoid muscles are better adapted to produce velocity and displacement. It was hypothesized that this difference in function would be reflected in myosin heavy-chain (MyHC) composition (equivalent to contraction velocity) and fibre-type cross-sectional area (equivalent to force). MyHC composition was determined in muscles obtained from eight human cadavers, using monoclonal antibodies against MyHC isoforms. Jaw closers contained 4.2 times fewer type IIA fibres and 5.2 times more hybrid fibres than suprahyoid muscles, and 3.9 times fewer type IIA fibres and 3.2 times more hybrid fibres than the infrahyoid muscles. In the jaw closers, MyHC-I was expressed in approx. 70% of all fibres (pure+hybrid), in the suprahyoid muscles in approx. 40%, and in the infrahyoid muscles in approx. 46%. In the jaw closers, type I fibres were 40% larger in diameter than in the supra- and infrahyoid muscles. It can be concluded that the jaw closers have characteristics of slow muscles, and that the supra-/infrahyoid muscles have characteristics of fast muscles.
authors: Department of Functional Anatomy, Academic Center for Dentistry Amsterdam, Meibergdreef 15, 1105 AZ, Amsterdam, The Netherlands. j.a.korfage@amc.uva.nl
authors: J A
authors: JA
authors: Korfage
authors: Y T
authors: YT
authors: Schueler
authors: P
authors: P
authors: Brugman
authors: T M
authors: TM
authors: Van Eijden
mesh_terms: D000368:Aged; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008410:Masticatory Muscles / Q000033:anatomy & histology* / Q000737:chemistry*; D018656:Muscle Fibers, Fast-Twitch / Q000737:chemistry / Q000145:classification; D018657:Muscle Fibers, Slow-Twitch / Q000737:chemistry / Q000145:classification; D018995:Myosin Heavy Chains / Q000737:chemistry*; D009334:Neck Muscles / Q000033:anatomy & histology* / Q000737:chemistry*
chemical_list: D018995:Myosin Heavy Chains