Date of Award

2011

Document Type

Scholarly Project

Degree Name

Doctor of Physical Therapy (DPT)

Department

Physical Therapy

First Advisor

Mark Romanick

Abstract

Skeletal muscle fiber type composition has not been studied in the long-lived Ames dwarf mouse when compared to its wild-type counterpart. Hindlimb soleus skeletal muscle from two 3-month old dwarf and two 3-month old wild-type mice was analyzed for muscle fiber size, proportion of type I (slow-twitch) and type II (fast-twitch) muscle fibers, myonuclei content per muscle fiber, and total cross sectional area of the muscle. Results revealed a significant difference in muscle fiber size (t(58)=-9.71, p<.001) with the wild-type mice demonstrating significantly larger muscle fibers. Descriptive statistics reveal a larger proportion of type I muscle fibers in the Ames dwarf mouse when compared to the wild-type mouse (2:1 ratio of type I to type II muscle fibers in the dwarf mice, nearly equal ratio in the wild-type mice). Myonuclei content reveals slightly more nuclei per muscle fiber in the wild-type mouse (1.035 more nuclei per fiber). Cross-sectional area analysis reveals that the wild-type mouse has a substantially larger soleus muscle than the Ames dwarf. The increased proportion of type I fibers in the Ames dwarf mouse could contribute to the heightened antioxidant defenses previously discovered in dwarf skeletal muscle. This study has several methodological limitations including small sample size, inadequate microscopic views, and analysis of only one muscle and age group of mice. Future studies should include a larger sample size of both genotypes with specimens of varying ages, and include a larger selection of muscles.

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