Distribution pattern of muscle fiber types in the perivertebral musculature of two different sized species of mice

B Hesse, MS Fischer, N Schilling - The Anatomical Record …, 2010 - Wiley Online Library
B Hesse, MS Fischer, N Schilling
The Anatomical Record: Advances in Integrative Anatomy and …, 2010Wiley Online Library
Many physiological parameters scale with body size. Regarding limb muscles, it has been
shown that the demands for relatively faster muscles, less postural work, and greater heat
production in small mammals are met by lower proportions of Type I and conversely higher
proportions of Type II fibers. To investigate possible adaptations of the perivertebral
musculature, we investigated the proportion, spatial distribution, and cross‐sectional area
(csa) of the different muscle fiber types in the laboratory and harvest mouse. Serial cross …
Abstract
Many physiological parameters scale with body size. Regarding limb muscles, it has been shown that the demands for relatively faster muscles, less postural work, and greater heat production in small mammals are met by lower proportions of Type I and conversely higher proportions of Type II fibers. To investigate possible adaptations of the perivertebral musculature, we investigated the proportion, spatial distribution, and cross‐sectional area (csa) of the different muscle fiber types in the laboratory and harvest mouse. Serial cross sections from the posterior thoracic to the lumbo‐sacral region were prepared and Type I, IIA, and IIB fibers identified using enzymehistochemistry. The general distribution of Type I and IIB fibers, as well as the more or less equal distribution of IIA fibers, resembles the pattern found in other mammals. However, the overall proportion of Type I fibers was very low in the laboratory mouse and particularly low in the harvest mouse. Muscular adaptations to a small body size were met primarily by increased Type IIA fiber proportions. Thereby, not all muscles or muscle regions similarly reflected the expected scaling effects. However, our results clearly show that body size is a critical factor when fiber‐type proportions are compared among different sized mammals. Anat Rec, 293:446–463, 2010. © 2010 Wiley‐Liss, Inc.
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