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Revisiting the peculiar regional distribution of muscle fiber types in rat Sternomastoid Muscle

The sternomastoid (SM) muscle in rodents is known to have a peculiar distribution of fiber types with a steep gradient from surface to deep region. We here further characterize this peculiar regional distribution by quantitative histochemical morphometrys. In Hematoxylin-Eosin (H-E) stained transver...

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Detalles Bibliográficos
Autores principales: Ravara, Barbara, Gobbo, Valerio, Incendi, Damiana, Porzionato, Andrea, Macchi, Veronica, Caro, Raffaele De, Coletti, Dario, Martinello, Tiziana, Patruno, Marco
Formato: Online Artículo Texto
Lenguaje:English
Publicado: PAGEPress Publications, Pavia, Italy 2018
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5895988/
https://www.ncbi.nlm.nih.gov/pubmed/29686819
http://dx.doi.org/10.4081/ejtm.2018.7302
Descripción
Sumario:The sternomastoid (SM) muscle in rodents is known to have a peculiar distribution of fiber types with a steep gradient from surface to deep region. We here further characterize this peculiar regional distribution by quantitative histochemical morphometrys. In Hematoxylin-Eosin (H-E) stained transverse cryosections harvested in the medial portion of the muscle we counted around 10.000 myofibers with a mean diameter of 51.3±12.6 (μm). Cryisections of the SM stained by SDH reaction clearly show two distinct regions, toward the deep surface of the muscle a 40% area that contains packed SDH-positive myofibers, while the remaining area of the SM toward the external surface presents a more checker-board appearance. On the other hand, in the deep region of SM type 1 (slow contracting) muscle fibers, caracterized by positive acidic ATPase pH 4.35 reaction, are only the 24.5% of the fibers in the deep area of SM muscles, being restricted to the deepest region. The 75.5% of the myofibers in the deep region are of the fast contracting types (either 48.4% 2A, SDH –positive fibers or 27.1% 2B, SDH-negative fibers, respectively). As expected the 2B muscle fibers, acidic ATPase pH 4.3-negative and SDH-negative, present the largest size, while Type 1 fibers, acidic ATPase pH 4.3-positive and SDH-positive, present the smallest size in rat SM muscle. Based on present and previous observations, comparison of change in absolute number and/or percentage of the fiber types in any experimental model of muscle atrophy/hypertrophy/plasticity/pathology /recovery in the rat SM, and possibly of all mammals, will ask for morphometry of the whole muscle cross-sections, muscle sampling by bioptic approches will provide only comparable data on the size of the different types of muscle fibers.