Distribution Pattern of Muscle Fiber Types in the Perivertebral Musculature of Two Different Sized Species of Mice

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. V V C 2010 Wiley-Liss, Inc.

Morphology of the Lumbar Transversospinal Muscles Examined in a Mouse Bearing a Muscle Fiber‐Specific Nuclear Marker

“…They described a multifidus muscle originating from the transverse process and spanning four vertebrae to attach to the spinous process of the fourth vertebrae craniad, and the rotatores muscles are described as spanning only one vertebral level. This indicates that Hesse et al (2010) found no TSP muscle fibers spanning two or three vertebral levels, and therefore the observations in these mouse species differ from the results of our investigation. Although we also found that some TSP muscles spanned four vertebral segments, our specimens also had muscle fibers spanning one, two, three, and four vertebral levels.…”

“…Our observations of the attachment points of the MLC3F-nlacZ mouse TSP muscles correlate well with the general pattern reported in some species of mice (M. musculus and Micromys minutus) (Hesse et al, 2010) and other mammals (Slijper, 1946;Brink and Pfaff, 1980;Stubbs et al, 2006), with muscles existing in the space between the transverse and spinous processes and attaching in a regular, repeated pattern to bony sites throughout the lumbar spine.…”

“…Rinker (1954) observed these muscles in the cotton rat (Sigmodon), rice rat (Oryzomys), wood rat (Neotoma), and deer mouse (Peromyscus maniculatus), stating that the TSP muscles in these animals spanned only three segments. A recent investigation by Hesse et al (2010) examined the paravertebral muscles of Mus musculus and Micromys minutus. They described a multifidus muscle originating from the transverse process and spanning four vertebrae to attach to the spinous process of the fourth vertebrae craniad, and the rotatores muscles are described as spanning only one vertebral level.…”

“…This muscle group has also been described in some laboratory animals such as the golden hamster (Mesocrecitus auratus) (Salih and Kent, 1964) and Albino rat (Rattus norvegicus albinus) (Brink and Pfaff, 1980). However, there is little information available on the normal morphology of the paravertebral muscles of the laboratory mouse (Hesse et al, 2010). This is an issue because the mouse is increasingly the model system of choice for developmental and genetic studies aimed at understanding the mammalian phenotype (Higuchi and Abe, 1987;Elliott and Sarver, 2004;Nelson and Nebert, 2004;Wang et al, 2005), therefore a thorough understanding of normal mouse morphology is essential for interpretation of abnormalities arising from genetic manipulations.…”

Reduced sensory synaptic excitation impairs motor neuron function via Kv2.1 in spinal muscular atrophy

“…3C–D). Additionally, SMA vulnerable slow twitch muscles like the QL 24 did not express parvalbumin (Supplementary Fig. 4).…”