Muscle spindles of the rat sternomastoid muscle

  • Walter Giuriati | walter.giuriati@unipd.it Department of Biomedical Sciences, Interdepartmental Research Institute of Myology, University of Padova, Padova, Italy.
  • Barbara Ravara Department of Biomedical Sciences, Interdepartmental Research Institute of Myology, University of Padova, Padova; A-C M-C Foundation for Translational Myology, Padova, Italy. http://orcid.org/0000-0002-0159-3245
  • Andrea Porzionato Department of Neurosciences, Section of Human Anatomy, University of Padova, Padova, Italy.
  • Giovanna Albertin Department of Neurosciences, Section of Human Anatomy, University of Padova, Padova, Italy.
  • Carla Stecco Department of Neurosciences, Section of Human Anatomy, University of Padova, Padova, Italy.
  • Veronica Macchi Department of Neurosciences, Section of Human Anatomy, University of Padova, Padova, Italy.
  • Raffaele De Caro Department of Neurosciences, Section of Human Anatomy, University of Padova, Padova, Italy.
  • Tiziana Martinello Department of Comparative Biomedicine and Food Science, University of Padova, Legnaro, Padova, Italy.
  • Chiara Gomiero Department of Comparative Biomedicine and Food Science, University of Padova, Legnaro, Padova, Italy.
  • Marco Patruno Department of Comparative Biomedicine and Food Science, University of Padova, Legnaro, Padova, Italy.
  • Dario Coletti Sorbonne Universités, UPMC Université Paris 06 (CNRS, UMR 8256, INSERM ERL U1164), Institut Biologie Paris-Seine, Paris, France; Department of Anatomy, Histology, Forensic Medicine & Orthopaedics, School of Medicine Sapienza University of Rome, Rome, Italy; Interuniversity Institute of Myology, Rome, Italy.
  • Sandra Zampieri Department of Biomedical Sciences, Interdepartmental Research Institute of Myology, University of Padova, Padova, Italy; A&C M-C Foundation for Translational Myology, Padova, Italy; Physiko- und Rheumatherapie, St. Poelten, Austria.
  • Alessandra Nori Department of Biomedical Sciences, Interdepartmental Research Institute of Myology, University of Padova, Padova, Italy.

Abstract

The sternomastoid (SM) muscle in rodents presents a peculiar distribution of fiber types with a steep gradient from the ventral, superficial, white portion to the dorsal, deep, red region, where muscle spindles are restricted. Cross section of the medial longitudinal third of the rat SM contains around 10,000 muscle fibers with a mean diameter of 51.28±12.62 (μm +/- SD). Transverse sections stained by Succinate Dehydrogenase (SDH) reaction clearly presents two distinct regions: the dorsal deep red portion encompassing a 40% cross section area contains a high percentage of packed SDH-positive muscle fibers, and the ventral superficial region which contains mainly SDH-negative muscle fibers. Indeed, the ventral superficial region of the rat SM muscle contains mainly fast 2B muscle fibers. These acidic ATPase pH 4.3-negative and SDH-negative 2B muscle fibers are the largest of the SM muscle, while the acidic ATPase pH 4.3-positive and SDH-positive Type 1 muscle fibers are the smallest. Here we show that in thin transverse cryosections only 2 or 3 muscle spindle are observed in the central part of the dorsal deep red portion of the SM muscle. Azan Mallory stained sections allow at the same time to count the spindles and to evaluate aging fibrosis of the skeletal muscle tissue. Though restricted in the muscle red region, SM spindles are embedded in perimysium, whose changes may influence their reflex activity. Our findings confirm that any comparisons of changes in number and percentage of muscle spindles and muscle fibers of the rat SM muscle will require morphometry of the whole muscle cross-section. Muscle biopsies of SM muscle from large mammals will only provide partial data on the size of the different types of muscle fibers biased by sampling. Nonetheless, histology of muscle tissue continue to provide practical and low-cost quantitative data to follow-up translational studies in rodents and beyond.

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Published
2018-12-13
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Section
Original Articles
Supporting Agencies
AFM (2017–20603), ANR (2013-J13R191), EFEM 2016, IBPS (2014), NIH (2013-1R01CA108857-01subcontractor), UPMC Emergence (2011-EME1115)
Keywords:
rat, sternomastoid muscle, muscle spindles, fiber types, translational studies
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How to Cite
Giuriati, W., Ravara, B., Porzionato, A., Albertin, G., Stecco, C., Macchi, V., De Caro, R., Martinello, T., Gomiero, C., Patruno, M., Coletti, D., Zampieri, S., & Nori, A. (2018). Muscle spindles of the rat sternomastoid muscle. European Journal of Translational Myology, 28(4). https://doi.org/10.4081/ejtm.2018.7904

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