Meeting Abstract

5.6  Thursday, Jan. 3  Contrasting Patterns of Masticatory Myosin Expression in Carnivora and Primates REISER, PJ*; BICER, S; GLENDING, C; Ohio State University; Ohio State University; Ohio State University reiser.17@osu.edu

Masticatory (�superfast�) myosin heavy chain (MHC-mast) is expressed in jaw-closing muscles of members of several classes – Chondrichthyes (e.g., sharks), Reptilia (e.g., caimans, crocodiles, terrapins), and Mammalia (e.g., some bats, carnivores, most primates). The feeding behavior and diets of animals expressing MHC-mast varies markedly. Furthermore, expression of MHC-mast in primates may be related more to defensive behavior rather than to mastication. The objective of this study was to compare patterns of MHC-mast expression in jaw-closing muscles between members of Carnivora (domesticated dog and free-living raccoon) and Primates (macaque and cynomologus monkeys). Samples from multiple sites along the superficial and deep layers of the masseter and temporalis muscles were analyzed with SDS-PAGE and the relative amounts of each MHC isoform in each sample were determined by scanning densitometry. The results indicate that the pattern of MHC-mast expression differs markedly between Carnivora and Primates, with this isoform predominating at every site of both muscles in the former and being much more restricted to specific regions within both muscles in the latter. The relative proportions of each of four MHC isoforms are constant throughout dog and raccoon masseter and temporalis. Five MHC isoforms are expressed in macaque and cynomologus masseter and temporalis, with MHC-mast predominating in some regions and slow, type I MHC predominating in other regions. We conclude that marked differences in the MHC-mast expression pattern in jaw-closing muscles exist between members of Carnivora and Primates, presumably in accordance with differences in masticatory muscle motor functions. Supported by the National Science Foundation.