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


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.

Download full-text


Available from: Clara Rios, Aug 06, 2015
  • Source
    • "(Graziotti et al., 2001; Hyatt et al., 2010; Kohn and Myburgh, 2007; Toniolo et al., 2004 "
    [Show abstract] [Hide abstract]
    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
  • Source
    • "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). "
    [Show abstract] [Hide abstract]
    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
  • Source
    • "Four were pure fibre types expressing a single MyHC isoform (I, IIA, IIX and IIB), and three were hybrid phenotypes co-expressing two isoforms (I + IIA – result not shown, IIAX and IIXB; Fig. 3). The immunoreactivity of these fibre types with the battery of antibodies used here has previously been reported in llamas (Graziotti et al. 2001, 2004). On the basis of the myofibrillar ATPase reaction after acid preincubation at pH 4.45, muscle fibres were divided into four main categories, while hybrid fibres had intermediate reactions with respect to pure phenotypes (Table 1; Fig. 3a). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Like other camelids, llamas (Lama glama) have the natural ability to pace (moving ipsilateral limbs in near synchronicity). But unlike the Old World camelids (bactrian and dromedary camels), they are well adapted for pacing at slower or moderate speeds in high-altitude habitats, having been described as good climbers and used as pack animals for centuries. In order to gain insight into skeletal muscle design and to ascertain its relationship with the llama's characteristic locomotor behaviour, this study examined the correspondence between architecture and fibre types in two agonist muscles involved in shoulder flexion (M. teres major - TM and M. deltoideus, pars scapularis - DS and pars acromialis - DA). Architectural properties were found to be correlated with fibre-type characteristics both in DS (long fibres, low pinnation angle, fast-glycolytic fibre phenotype with abundant IIB fibres, small fibre size, reduced number of capillaries per fibre and low oxidative capacity) and in DA (short fibres, high pinnation angle, slow-oxidative fibre phenotype with numerous type I fibres, very sparse IIB fibres, and larger fibre size, abundant capillaries and high oxidative capacity). This correlation suggests a clear division of labour within the M. deltoideus of the llama, DS being involved in rapid flexion of the shoulder joint during the swing phase of the gait, and DA in joint stabilisation during the stance phase. However, the architectural design of the TM muscle (longer fibres and lower fibre pinnation angle) was not strictly matched with its fibre-type characteristics (very similar to those of the postural DA muscle). This unusual design suggests a dual function of the TM muscle both in active flexion of the shoulder and in passive support of the limb during the stance phase, pulling the forelimb to the trunk. This functional specialisation seems to be well suited to a quadruped species that needs to increase ipsilateral stability of the limb during the support phase of the pacing gait. Compared with other species, llama skeletal muscles are well suited for greater force generation combined with higher fatigue resistance during exercise. These characteristics are interpreted as being of high adaptive value, given the llama's habitat and its use as a pack animal.
    Journal of Anatomy 05/2012; 221(2):151-63. DOI:10.1111/j.1469-7580.2012.01520.x · 2.10 Impact Factor
Show more