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Evidence for three fast myosin heavy chain isoforms in type II skeletal muscle fibers in the adult llama (Lama glama).
J Histochem Cytochem. 2001 Aug; 49(8):1033-44.JH

Abstract

Skeletal muscle fiber types classified on the basis of their content of different myosin heavy chain (MHC) isoforms were analyzed in samples from hindlimb muscles of adult sedentary llamas (Lama glama) by correlating immunohistochemistry with specific anti-MHC monoclonal antibodies, myofibrillar ATPase (mATPase) histochemistry, and quantitative histochemistry of fiber metabolic and size properties. The immunohistochemical technique allowed the separation of four pure (i.e., expressing a unique MHC isoform) muscle fiber types: one slow-twitch (Type I) and three fast-twitch (Type II) phenotypes. The same four major fiber types could be objectively discriminated with two serial sections stained for mATPase after acid (pH 4.5) and alkaline (pH 10.5) preincubations. The three fast-twitch fiber types were tentatively designated as IIA, IIX, and IIB on the basis of the homologies of their immunoreactivities, acid denaturation of their mATPase activity, size, and metabolic properties expressed at the cellular level with the corresponding isoforms of rat and horse muscles. Acid stability of their mATPase activity increased in the rank order IIA>IIX>IIB. The same was true for size and glycolytic capacity, whereas oxidative capacity decreased in the same rank order IIA>IIX>IIB. In addition to these four pure fibers (I, IIA, IIX, and IIB), four other fiber types with hybrid phenotypes containing two (I+IIA, IIAX, and IIXB) or three (IIAXB) MHCs were immunohistochemically delineated. These frequent phenotypes (40% of the semitendinosus muscle fiber composition) had overlapped mATPase staining intensities with their corresponding pure fiber types, so they could not be delineated by mATPase histochemistry. Expression of the three fast adult MHC isoforms was spatially regulated around islets of Type I fibers, with concentric circles of fibers expressing MHC-IIA, then MHC-IIX, and peripherally MHC-IIB. This study demonstrates that three adult fast Type II MHC isoproteins are expressed in skeletal muscle fibers of the llama. The general assumption that the very fast MHC-IIB isoform is expressed only in small mammals can be rejected.

Authors+Show Affiliations

Anatomy Unit, Department of Physiology and Basic Sciences, Faculty of Veterinary Sciences, University of Buenos Aires, Buenos Aires, Argentina.No affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

11457931

Citation

Graziotti, G H., et al. "Evidence for Three Fast Myosin Heavy Chain Isoforms in Type II Skeletal Muscle Fibers in the Adult Llama (Lama Glama)." The Journal of Histochemistry and Cytochemistry : Official Journal of the Histochemistry Society, vol. 49, no. 8, 2001, pp. 1033-44.
Graziotti GH, Ríos CM, Rivero JL. Evidence for three fast myosin heavy chain isoforms in type II skeletal muscle fibers in the adult llama (Lama glama). J Histochem Cytochem. 2001;49(8):1033-44.
Graziotti, G. H., Ríos, C. M., & Rivero, J. L. (2001). Evidence for three fast myosin heavy chain isoforms in type II skeletal muscle fibers in the adult llama (Lama glama). The Journal of Histochemistry and Cytochemistry : Official Journal of the Histochemistry Society, 49(8), 1033-44.
Graziotti GH, Ríos CM, Rivero JL. Evidence for Three Fast Myosin Heavy Chain Isoforms in Type II Skeletal Muscle Fibers in the Adult Llama (Lama Glama). J Histochem Cytochem. 2001;49(8):1033-44. PubMed PMID: 11457931.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Evidence for three fast myosin heavy chain isoforms in type II skeletal muscle fibers in the adult llama (Lama glama). AU - Graziotti,G H, AU - Ríos,C M, AU - Rivero,J L, PY - 2001/7/18/pubmed PY - 2001/8/3/medline PY - 2001/7/18/entrez SP - 1033 EP - 44 JF - The journal of histochemistry and cytochemistry : official journal of the Histochemistry Society JO - J Histochem Cytochem VL - 49 IS - 8 N2 - Skeletal muscle fiber types classified on the basis of their content of different myosin heavy chain (MHC) isoforms were analyzed in samples from hindlimb muscles of adult sedentary llamas (Lama glama) by correlating immunohistochemistry with specific anti-MHC monoclonal antibodies, myofibrillar ATPase (mATPase) histochemistry, and quantitative histochemistry of fiber metabolic and size properties. The immunohistochemical technique allowed the separation of four pure (i.e., expressing a unique MHC isoform) muscle fiber types: one slow-twitch (Type I) and three fast-twitch (Type II) phenotypes. The same four major fiber types could be objectively discriminated with two serial sections stained for mATPase after acid (pH 4.5) and alkaline (pH 10.5) preincubations. The three fast-twitch fiber types were tentatively designated as IIA, IIX, and IIB on the basis of the homologies of their immunoreactivities, acid denaturation of their mATPase activity, size, and metabolic properties expressed at the cellular level with the corresponding isoforms of rat and horse muscles. Acid stability of their mATPase activity increased in the rank order IIA>IIX>IIB. The same was true for size and glycolytic capacity, whereas oxidative capacity decreased in the same rank order IIA>IIX>IIB. In addition to these four pure fibers (I, IIA, IIX, and IIB), four other fiber types with hybrid phenotypes containing two (I+IIA, IIAX, and IIXB) or three (IIAXB) MHCs were immunohistochemically delineated. These frequent phenotypes (40% of the semitendinosus muscle fiber composition) had overlapped mATPase staining intensities with their corresponding pure fiber types, so they could not be delineated by mATPase histochemistry. Expression of the three fast adult MHC isoforms was spatially regulated around islets of Type I fibers, with concentric circles of fibers expressing MHC-IIA, then MHC-IIX, and peripherally MHC-IIB. This study demonstrates that three adult fast Type II MHC isoproteins are expressed in skeletal muscle fibers of the llama. The general assumption that the very fast MHC-IIB isoform is expressed only in small mammals can be rejected. SN - 0022-1554 UR - https://www.unboundmedicine.com/medline/citation/11457931/Evidence_for_three_fast_myosin_heavy_chain_isoforms_in_type_II_skeletal_muscle_fibers_in_the_adult_llama__Lama_glama__ L2 - https://journals.sagepub.com/doi/10.1177/002215540104900811?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub=pubmed DB - PRIME DP - Unbound Medicine ER -