Key result
Among 218 single fibers of human jaw muscles, 100 were hybrid fibers co-expressing multiple MyHC isoforms in highly variable proportions, suggesting a large range of contractile properties.
Observational
Human jaw muscles contain a high proportion of hybrid fibers with varying MyHC isoform compositions, suggesting a large diversity in contractile properties.
Indicates unexpected diversity in jaw muscle contractility; leaves open implications for orofacial disorders and requires functional validation.
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.
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Korfage et al. (2003) reported an observational. Myosin heavy-chain (MyHC) isoform composition analysis was evaluated on Proportion of each MyHC isoform within hybrid fibers. Among 218 single fibers of human jaw muscles, 100 were hybrid fibers co-expressing multiple MyHC isoforms in highly variable proportions, suggesting a large range of contractile properties.
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