title: Myosin heavy-chain isoform composition of human single jaw-muscle fibers.
abstract: Diversity in muscle contractile properties is based on the variability of contractile properties of single muscle fibers which in turn is related to the presence of different myosin heavy-chain (MyHC) isoforms. Human jaw muscles are featured by many hybrid fibers expressing more than one MyHC isoform. The purpose of this study was to determine the proportion of each isoform within these fibers for evaluation of the fiber's capacity of producing a large diversity in contractile properties. Electrophoretic separation of MyHC isoforms was performed on 218 single fibers of the temporalis and digastric muscles. Of these fibers, 100 were classified as hybrid fibers. Most hybrid fibers co-expressed MyHC-IIA and -IIX (n = 62); a smaller number co-expressed MyHC-I and -IIA (n = 14), MyHC-I and -IIX (n = 12), and MyHC-I, -IIA, and -IIX (n = 12). The proportions of the individual MyHC isoforms in the hybrid fibers varied highly, suggesting a large range of contractile properties among these fibers.
authors.affiliation: Department of Functional Anatomy, Academic Center for Dentistry Amsterdam (ACTA), Meibergdreef 15, 1105 AZ Amsterdam, The Netherlands. j.a.korfage@amc.uva.nl
authors.forename: J A M
authors.initials: JA
authors.lastname: Korfage
authors.forename: T M G J
authors.initials: TM
authors.lastname: Van Eijden
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002102:Cadaver; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction; D018656:Muscle Fibers, Fast-Twitch / Q000737:chemistry / Q000648:ultrastructure; D018485:Muscle Fibers, Skeletal / Q000737:chemistry* / Q000648:ultrastructure; D018657:Muscle Fibers, Slow-Twitch / Q000737:chemistry / Q000648:ultrastructure; D018995:Myosin Heavy Chains / Q000032:analysis*; D024461:Myosin Type I / Q000032:analysis; D009334:Neck Muscles / Q000737:chemistry / Q000648:ultrastructure*; D024507:Nonmuscle Myosin Type IIA / Q000032:analysis; D020033:Protein Isoforms / Q000032:analysis; D013703:Temporal Muscle / Q000737:chemistry / Q000648:ultrastructure*
chemical_list: D020033:Protein Isoforms; D024461:Myosin Type I; D024507:Nonmuscle Myosin Type IIA; D018995:Myosin Heavy Chains