HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 292/5/C1915    most recent 00601.2006v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (3) Citing Articles via Google Scholar Google Scholar Articles by Toniolo, L. Articles by Mascarello, F. Search for Related Content PubMed PubMed Citation Articles by Toniolo, L. Articles by Mascarello, F.

MUSCLE CELL BIOLOGY AND CELL MOTILITY

Fiber types in canine muscles: myosin isoform expression and functional characterization

¹Department of Anatomy and Physiology and ²Department of Veterinary Sciences, University of Padova; ³Department of Experimental Medicine, University of Pavia; and ⁴Italian Institute of Myology, Padova, Italy

Submitted 5 December 2006 ; accepted in final form 22 January 2007

This study was aimed to achieve a definitive and unambiguous identification of fiber types in canine skeletal muscles and of myosin isoforms that are expressed therein. Correspondence of canine myosin isoforms with orthologs in other species as assessed by base sequence comparison was the basis for primer preparation and for expression analysis with RT-PCR. Expression was confirmed at protein level with histochemistry, immunohistochemistry, and SDS-PAGE combined together and showed that limb and trunk muscles of the dog express myosin heavy chain (MHC) type 1, 2A, and 2X isoforms and the so-called "type 2dog" fibers express the MHC-2X isoform. MHC-2A was found to be the most abundant isoform in the trunk and limb muscle. MHC-2X was expressed in most but not all muscles and more frequently in hybrid 2A-2X fibers than in pure 2X fibers. MHC-2B was restricted to specialized extraocular and laryngeal muscles, although 2B mRNA, but not 2B protein, was occasionally detected in the semimembranosus muscle. Isometric tension (P_o) and maximum shortening velocity (V_o) were measured in single fibers classified on the basis of their MHC isoform composition. Purified myosin isoforms were extracted from single muscle fibers and characterized by the speed (V_f) of actin filament sliding on myosin in an in vitro motility assay. A close proportionality between V_o and V_f indicated that the diversity in V_o was due to the different myosin isoform composition. V_o increased progressively in the order 1/slow < 2A < 2X < 2B, thus confirming the identification of the myosin isoforms and providing their first functional characterization of canine muscle fibers.

dog; muscle fiber types; single fiber mechanics; in vitro motility

This article has been cited by other articles:

				O. Friedrich, C. Weber, F. v. Wegner, J. S. Chamberlain, and R. H. A. Fink Unloaded Speed of Shortening in Voltage-Clamped Intact Skeletal Muscle Fibers from wt, mdx, and Transgenic Minidystrophin Mice Using a Novel High-Speed Acquisition System Biophys. J., June 15, 2008; 94(12): 4751 - 4765. [Abstract] [Full Text] [PDF]