Structure‐function relationships of the flexor carpi radialis muscle compared among four species of mammals

Abstract

Investigations of the structure and function of the flexor carpi radialis muscle (FCR) in the cat have led to the hypothesis that the compartmentalized (nonuniform) distribution of fiber types within the muscle relate to the complex motor skills of the cat. To test this hypothesis a study was undertaken to compare the FCR in four mammalian species of similar body size but with different forelimb motor tasks. The species chosen were: dog, opossum, armadillo, and cat. Comparisons were made among species with regard to general muscle morphology, fiber types and sizes, fiber proportions, and fiber distributions. The FCR of all species was morphologically similar and contained three muscle fiber types (SO, FOG, and FG). The mean area of muscle fibers was largest in opossum, while the FCR fibers of dogs were smallest. The percentage of SO fibers in the dog FCR was greater than in the other species studied. The opossum FCR also contained a high percentage of SO fibers. The armadillo FCR consisted of a high percentage of FG fibers. In the cat FCR the percentages of all three fiber types were similar. For each species, individual fiber proportions were in agreement with the results for fiber percentages. Compartmentalized distribution of fiber types existed in each species with the dog having the most compartmentalized fiber type distribution and the cat the least compartmentalized distribution. Therefore it seems that the compartmentalized organization of the FCR is not related to any specialized motor task, but may be a generalized pattern associated with motor patterns shared among all species studied.

Comparison of muscle cell fiber types and oxidative capacity in gracilis, rectus femoris, and triceps brachii muscles in the ferret (Mustela putorius furo) and the domestic dog (Canis familiaris)

“…They concluded that skeletal muscle of the untrained foxhound was already highly adapted for oxidative metabolism. In contrast, Guazzelli Filho et al McConathy et al (1983) felt their type IIB fibers may have been the same type that others identified as IIC, although these fibers constituted 23% of the muscle examined. Van de Graaff et al (1977) failed to find physiologic or anatomic evidence for fast-twitch glycolytic fibers in ankle extensors of the skunk.…”

“…Some authors have identified the type I1 fibers in canine muscle specifically as IIA (Braund et al, 1978), others (McConathy et al, 1983) identified both IIA and IIB fibers, whereas yet others after identifying IIA fibers have left open the possibility of additional type I1 subtypes (Snow et al, 1982;Parsons et al, 1985). It is evident that ATPase staining techniques are of limited value in definitively answering the question of which fiber types are present in these species.…”

Functional Morphology of the Forelimb of the Nine-Banded Armadillo (Dasypus novemcinctus): Comparative Perspectives on the Myology of Dasypodidae

“…Lastly, the m. flexor carpi radialis of D. novemcinctus was previously determined to have a large distribution of fast, glycolytic fibers (McConathy et al 1983), which infers the MHC-2B isoform fiber type. This finding should be interpreted with caution because expression of the fast 2B isoform in a mammal as large as D. novemcinctus is somewhat surprising, and thus it is not known if MHC-2B expression represents an adaptive function or phylogenetic retention.…”

Pattern of Myosin Heavy Chain Isoforms in Different Fibre Types of Canine Trunk and Limb Skeletal Muscles

“…Similarly, the published data regarding the metabolic properties of canine muscle fibres are controversial, especially in the instance of fast fibre types. In most studies it was demonstrated that all the type II fibres are moderately to highly oxidative [Braund et al, 1978;Snow et al, 1982;Aguera et al, 1990;Rivero et al, 1994;Latorre et al, 1993a, b], but it has also been reported that fast fibres are only slightly oxidative [Guy and Snow, 1981;McConathy et al, 1983].…”