Limb myosin heavy chain isoproteins and muscle fiber types in the adult goat (Capra hircus)

Patients with obstructive sleep apnea (OSA) often exhibit fatigued or inefficient upper airway dilator and constrictor muscles; an upper airway dilator, the geniohyoid (GH) muscle, is a particular example. Intermittent hypoxia (IH) is a frequent concomitant of OSA, and it may trigger muscle fiber composition changes that are characteristic of a fatigable nature. We examined effects of short-term IH on diaphragmatic and GH muscle fiber composition and fatigue properties by exposing 24 rats to alternating 10.3% O2-balance N2 and room air every 480 s (240 s duty cycle) for a total duration of 5, 10, 15, 20, or 30 h. Sternohyoid fiber composition was also examined. Control animals were exposed to room air on the same schedule. Single-fiber analyses showed that GH muscle fiber types changed completely from myosin heavy chain (MHC) type 2A to MHC type 2B after 10 h of exposure, and the conversion was maintained for at least 30 h. Sternohyoid muscle fibers showed a delayed transition from MHC type 2A/2B to MHC type 2B. In contrast, major fiber types of the diaphragm were not significantly altered. The GH muscles showed similar tension-frequency relationships in all groups, but an increased fatigability developed, proportional to the duration of IH treatment. We conclude that short-term IH exposure alters GH muscle composition and physical properties toward more fatigable, fast-twitch types and that it may account for the fatigable upper airway fiber types found in sleep-disturbed breathing.

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Immunohistochemical Analysis of Myosin Heavy Chain Expression in Laryngeal Muscles of the Rabbit, Cat, and Baboon

Journal of Histochemistry & Cytochemistry ◽

10.1369/jhc.2008.951756 ◽

2008 ◽

Vol 56 (10) ◽

pp. 929-950 ◽

Cited By ~ 9

Author(s):

Hannah S. Rhee ◽

Joseph F.Y. Hoh

Keyword(s):

Myosin Heavy Chain ◽

Heavy Chain ◽

Fiber Type ◽

Immunohistochemical Analysis ◽

Muscle Fiber Types ◽

Fiber Types ◽

Laryngeal Muscles ◽

Myhc Isoforms ◽

Posterior Cricoarytenoid ◽

Myhc Expression

We studied myosin heavy chain (MyHC) expression and fiber type distribution in laryngeal muscles in the rabbit, cat, and baboon using immunohistochemistry with highly MyHC-specific antibodies. Two types of variation in MyHC expression were found: between muscles of different function within species and within specific muscles between species. Within species, thyroarytenoid (Ta), an adductor, had faster MyHCs and fiber type profiles than the abductor, posterior cricoarytenoid (PCA), which expressed faster MyHCs than the vocal fold tensor, cricothyroid (CT). Between species, laryngeal muscles generally expressed faster MyHCs in small animals than in larger ones: extraocular (EO) MyHC was expressed in the Ta and PCA of the rabbit but not in the cat and baboon, whereas 2B MyHC was expressed in these muscles of the cat but not of the baboon. The CT expressed only MyHC isoforms and fiber types found in the limb muscles of the same species. These results are discussed in light of the hypothesis that the between-species variations in laryngeal muscle fiber types are evolutionary adaptations in response to changes in body mass and respiratory frequency. Within-species variations in fiber types ensure that protective closure of the glottis is always faster than movements regulating airflow during respiration.

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Heterogeneity of myosin heavy-chain expression in fast-twitch fiber types of mature avian pectoralis muscle

Biochemistry and Cell Biology ◽

10.1139/o96-078 ◽

1996 ◽

Vol 74 (5) ◽

pp. 715-728 ◽

Cited By ~ 30

Author(s):

B. W. C. Rosser ◽

D. M. Waldbillig ◽

M. Wick ◽

E. Bandman

Keyword(s):

Monoclonal Antibodies ◽

Myosin Heavy Chain ◽

Muscle Fiber ◽

Heavy Chain ◽

Fiber Types ◽

Pectoralis Muscle ◽

Western Blots ◽

Myhc Isoforms ◽

Fast Twitch ◽

Myhc Expression

The aims of this study are to investigate the diversity of myosin heavy-chain (MyHC) expression among avian fast-twitch fibers, and to test the hypothesis that dissimilar MyHC isoforms are found in each of the principal avian fast-twitch fiber types. MyHCs within the muscle fibers of the pectoralis of 31 species of bird are characterized using immunocytochemical methods. A library of 11 monoclonal antibodies previously produced against chicken MyHCs is used. The specificity of these antibodies for MyHCs in each of the muscles studied is confirmed by Western blots. The results show that avian fast-twitch glycolytic fibers and fast-twitch oxidative-gylcolytic fibers can contain different MyHCs. Among the species studied, there is also a conspicuous variety of MyHC isoforms expressed. In addition, the results suggest that two epitopes are restricted to chickens and closely allied gallinaceous birds. There are no apparent correlations between MyHC epitope and presupposed contractile properties. However, the presence of different isoforms in different fast-twitch fiber types suggests a correlation between isoform and contractile function.Key words: muscle, fiber, myosin, avian.

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Type IIx myosin heavy chain transcripts are expressed in type IIb fibers of human skeletal muscle

AJP Cell Physiology ◽

10.1152/ajpcell.1994.267.6.c1723 ◽

1994 ◽

Vol 267 (6) ◽

pp. C1723-C1728 ◽

Cited By ~ 269

Author(s):

V. Smerdu ◽

I. Karsch-Mizrachi ◽

M. Campione ◽

L. Leinwand ◽

S. Schiaffino

Keyword(s):

Myosin Heavy Chain ◽

Heavy Chain ◽

Untranslated Regions ◽

Muscle Fiber Types ◽

Fiber Types ◽

Gene Products ◽

Hybrid Fibers ◽

Mhc Genes ◽

Two Populations

Several members of the sarcomeric myosin heavy chain (MHC) gene family have been mapped in the human genome but many of them have not yet been identified. In this study we report the identification of two human skeletal MHC genes as fast IIa and IIx MHC based on pattern of expression and sequence homology with the corresponding rat genes in the 3'-translated and untranslated regions. The distribution of these two gene products as well as that of the beta/slow MHC gene was analyzed in human skeletal muscles by in situ hybridization. The distribution of beta/slow, IIa, and IIx MHC transcripts defines three major muscle fiber types expressing a single MHC mRNA, i.e., either beta/slow, IIa, or IIx MHC mRNA, and two populations of hybrid fibers coexpressing beta/slow with IIa or IIa with IIx MHC mRNA. Fiber typing by ATPase histochemistry shows that IIa MHC transcripts are more abundant in histochemical type IIa fibers, whereas IIx MHC transcripts are more abundant in histochemical type IIb fibers.

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