Regional variation in IIM myosin heavy chain expression in the temporalis muscle of female and male baboons (Papio anubis)

Abstract

Objective The purpose of this study was to determine whether high amounts of fast/type II myosin heavy chain (MyHC) in the superficial as compared to the deep temporalis muscle of adult female and male baboons(Papio anubis) correlates with published data on muscle function during chewing. Electromyograpic (EMG) data show a regional specialization in activation from low to high amplitude activity during hard/tough object chewing cycles in the baboon superficial temporalis (Wall et al., 2007, 2008). A positive correlation between fast/type II MyHC amount and EMG activity will support the high occlusal force hypothesis. Design Deep anterior temporalis (DAT), superficial anterior temporalis (SAT), and superficial posterior temporalis (SPT) muscle samples were analyzed using SDS-PAGE gel electrophoresis to test the prediction that SAT and SPT will show high amounts of fast/type II MyHC compared to DAT. Serial muscle sections were incubated against NOQ7.5.4D and MY32 antibodies to determine the breadth of slow/type I versus fast/type II expression within each section. Results Type I and type IIM MyHCs comprise nearly 100% of the MyHCs in the temporalis muscle. IIM MyHC was the overwhelmingly predominant fast MyHC, though there was a small amount of type IIA MyHC (≤5%) in DAT in two individuals. SAT and SPT exhibited a fast/type II phenotype and contained large amounts of IIM MyHC whereas DAT exhibited a type I/type II (hybrid) phenotype and contained a significantly greater proportion of MyHC-I. MyHC-I expression in DAT was sexually dimorphic as it was more abundant in females. Conclusions The link between the distribution of IIM MyHC and high relative EMG amplitudes in SAT and SPT during hard/tough object chewing cycles is evidence of regional specialization in fiber type to generate high occlusal forces during chewing. The high proportion of MyHC-I in DAT of females may be related to a high frequency of individual fiber recruitment in comparison to males.

Expression of myosin heavy chain isoforms mRNA transcripts in the temporalis muscle of common chimpanzees ( Pan troglodytes )

“…Our findings on the mRNA transcripts of the MyHC isoforms in Pan troglodytes are markedly different from those of other investigators analyzing the percentages of different types of muscle fibers by histochemistry and immunohistochemistry in Macaca mulatta (Maxwell et al, 1979;Miller and Farias, 1988), Macaca irus (Rowlerson et al, 1983), Cebus apella (Andreo et al, 2002), and Papio anubis (Wall et al, 2013). These differences may be due to the presence of hybrid fibers expressing more than one MyHC isoform, which can hinder the determination and quantification of each type of fiber (Pette and Staron, 2000;Korfage and Van Eijden, 2003).…”

“…The composition of muscle fibers and the expression patterns of the MyHC isoforms in the temporalis muscle of non-human primates have been studied by histochemistry in Macaca mulatta (Maxwell et al, 1979;Miller and Farias, 1988) and Cebus apella (Andreo et al, 2002), by immunohistochemistry in Macaca irus (Rowlerson et al, 1983), and by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) in Papio anubis (Wall et al, 2013). Using ATPase staining, Miller and Farias (1988) found that the temporalis muscle of Macaca mulatta had 47.9-58.5% of type IIX fibers, 27.3-42.6% of type IIA fibers, and 6.6-21.3% of type I fibers.…”

“…Using ATPase staining together with indirect immunoperoxidase staining, Rowlerson et al (1983) found that the central temporalis in Macaca irus had 86% of type IIM fibers and 14% of type I fibers. A study using SDS-PAGE to analyze the temporalis in Papio anubis found 87-88.7% expression of the MyHC-IIM isoform in the anterior and 85.2-90.8% expression in the posterior superficial temporalis, while the MyHC-I isoform was the only other isoform expressed (Wall et al, 2013). In the deep temporalis, the MyHC-IIM isoform was expressed at 60.7% in males and 14.4% in females, while the MyHC-IIA isoform was expressed at less than 5% and the MyHC-I isoform at 38.1% in males and 83.3% in females (Wall et al, 2013).…”

Jaw‐Muscle Fiber Architecture and Leverage in the Hard‐Object Feeding Sooty Mangabey are not Structured to Facilitate Relatively Large Bite Forces Compared to Other Papionins

“…In a preliminary analysis of jaw‐adductor fiber types, C. atys muscles expressed an abundance of Type I fibers (Taylor et al, ), notably more than has been previously observed for macaques (Maxwell et al, ; Miller and Farias, ) or baboons (Wall et al, ). These preliminary findings of a fatigue‐resistant fiber phenotype suggest that Type I fibers may be advantageous to sooty mangabeys whose feeding behavior involves frequent crushing of relatively large, hard seeds.…”

Ontogenetic changes to muscle architectural properties within the jaw‐adductor musculature of Macaca fascicularis

“…For example, changes in muscle fiber phenotype during development may impact upon dietary ecology by altering the contractile capabilities of the adductor musculature. Sexually dimorphic differences in muscle fiber profile are reported in adult P. anubis by Wall, Briggs, Huq, Hylander, & Schachat () in which males possess a higher concentration of type‐II fibers, enabling them to generate faster and more powerful bites. This same trend was reported by Maxwell, Carlson, McNamara, & Faulkner () within M. mulatta , and a similar relationship within M. fascicularis was predicted by Terhune et al .…”