Evidence for Three Fast Myosin Heavy Chain Isoforms in Type II Skeletal Muscle Fibers in the Adult Llama (Lama glama)

Anatomy Unit, Department of Physiology and Basic Sciences, Faculty of Veterinary Sciences, University of Buenos Aires, Buenos Aires, Argentina.
Journal of Histochemistry and Cytochemistry (Impact Factor: 1.96). 09/2001; 49(8):1033-44. DOI: 10.1177/002215540104900811
Source: PubMed

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.

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    • "(Graziotti et al., 2001; Hyatt et al., 2010; Kohn and Myburgh, 2007; Toniolo et al., 2004 "
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    ABSTRACT: Skeletal muscle fibre type, cross-sectional area (CSA), maximum enzyme capacities and fibre oxidative capacities were investigated in three southern African antelope species. Muscle samples from blesbok (Damaliscus pygargus phillipsi), mountain reedbuck (Redunca fulvorufula) and greater kudu (Tragelaphus strepsiceros) were collected post mortem from the Vastus lateralis and analysed for myosin heavy chain (MHC) isoform content, citrate synthase (CS), 3-hydroxyacyl Co A dehydrogenase (3-HAD), phosphofructokinase (PFK), lactate dehydrogenase (LDH) and creatine kinase (CK) activities. Histochemistry and immunohistochemistry were performed to determine relative fibre oxidative capacity, fibre type and cross-sectional area (CSA). Type IIX fibres were the most abundant fibre type in all three species, ranging from 43 to 57%. Kudu had less type IIX fibres than mountain reedbuck and blesbok (P<0.05), values confirmed by their respective MHC isoform content. Blesbok had the smallest fibres, followed by mountain reedbuck and finally kudu (P<0.001). Overall, all three species had high oxidative and glycolytic capacities, but species differences were found. Kudu had the lowest CS activity, followed by blesbok and mountain reedbuck, but the highest PFK, LDH and CK activities. This study confirmed large variation in oxidative capacities within a single fibre type, as well as overlap between the fibre types with no distinct differences between the three species. The fibre type profile of each species is discussed and confirms some of their physical attributes and capabilities.
    Biology Open 10/2014; 3(11). DOI:10.1242/bio.20149241 · 2.42 Impact Factor
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    • "A battery of four monoclonal antibodies was used with the following specificities for MHC isoforms: BA-F8, MHC slow/I (Graziotti, Ríos, & Rivero, 2001); SC-71, MHC 2a & 2x (Lefaucheur et al., 2002); 10 F5, MHC 2b (Lucas, Kang, & Hoh, 2000); BF-35, MHC slow/I & 2a (Quiroz- Rothe & Rivero, 2004).The antibodies were purchased from DSHB (Iowa City, Iowa, USA). Moreover, the specificities of these four monoclonal antibodies for MHC isoforms were demonstrated from the porcine LD muscle as presented in the previous report (Kim, Jeong, et al., 2013). "
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    ABSTRACT: The aim of this study is to type fibers from porcine longissimus dorsi (LD) muscles according to their distribution of myosin heavy chain (MHC) isoforms as well as to investigate fiber characteristics. Four pure types, including types I, IIA, IIX, and IIB were labeled and two hybrid fiber types were subdivided into type IIAX and IIXB by immunohistochemistry using four monoclonal antibodies. Porcine LD muscles were found to have 92.79 (number) and 92.10% (area) of pure type composition, while the composition of hybrid fibers was 8.22 (number) and 9.71% (area). The activities of myosin ATPase increased in the following order: type I, IIAX, IIA=IIX=IIB and IIXB. The succinate dehydrogenase and glycerol-3-phosphate dehydrogenase activities were higher in fiber types I and IIB, respectively. The characteristics of hybrid fibers were observed that their characteristics did not lie between the properties for their respective pure phenotypes.
    Meat Science 10/2013; 96(2PA):712-718. DOI:10.1016/j.meatsci.2013.09.028 · 2.62 Impact Factor
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    • "These results indicate that the training-induced fiber type transformation from Type IIX to Type IIA plays an important role in depressing the generation of free radicals after exercise. However, mitochondrial oxygen consumption and mitochondrial enzyme content are greater in Type IIA fiber than Type IIX fiber [1, 9]. Thus, it seems that electron leakage via the mitochondrial respiratory chain during exercise is more severe in Type IIA. "
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    ABSTRACT: Although high oxygen consumption in skeletal muscle may result in severe oxidative stress, there are no direct studies that have documented free radical production in horse muscles after intensive exercise. To find a new parameter indicating the muscle adaptation state for the training of Thoroughbred horses, we examined free radical formation in the muscle by using electron paramagnetic resonance (EPR). Ten male Thoroughbred horses received conventional training for 18 weeks. Before and after the training period, all horses performed an exhaustive incremental load exercise on a 6% incline treadmill. Muscle samples of the middle gluteal muscle were taken pre-exercise and 1 min, 1 hr, and 1 day after exercise. Muscle fiber type composition was also determined in the pre-exercise samples by immunohistochemical staining with monoclonal antibody to myosin heavy chain. We measured the free radical in the muscle homogenate using EPR at room temperature, and the amount was expressed as relative EPR signal intensity. There was a significant increase in Type IIA muscle fiber composition and a decrease in Type IIX fiber composition after the training period. Before the training period, the mean value of the relative EPR signal intensity showed a significant increase over the pre-exercise value at 1 min after the exercise and an incomplete recovery at 24 hr after the exercise. While no significant changes were found in the relative EPR signal intensity after the training period. There was a significant relationship between percentages of Type IIA fiber and change rates in EPR signal intensity at 1 min after exercise. The measurement of free radicals may be useful for determining the muscle adaptation state in the training of Thoroughbred horses.
    Journal of Equine Science 07/2011; 22(2):21-8. DOI:10.1294/jes.22.21
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