Date of Award

2012

Document Type

Scholarly Project

Degree Name

Doctor of Physical Therapy (DPT)

Department

Physical Therapy

First Advisor

Mark Romanick

Abstract

Background: Aging is associated with sarcopenia and a change of composition in muscle fibers. Ames dwarf mice have been found to have a decreased susceptibility to the deleterious effects of the aging process, when compared to a normal mouse counterpart. This study looks at the muscle composition of the Ames dwarf mouse compared to the normal mouse by analyzing two muscles, extensor digitorum longus (EDL) and soleus (Sol).

Methods: Researchers harvested hind limb muscles from Ames dwarf mice and normal mice. The fours muscles were EDL, Sol, Gastrocnemius/Plantaris, and tibialis anterior (TA). EDL and Sol were sliced and stained with fast and slow twitch and H&E stains. Muscle cell diameter and fast and slow twitch percentage were measured through images obtained. Results:

Results for EDL found no significant difference between age of mice. A significant difference was found when comparing the total means of the type of mice. For Sol, a significant interaction was found (p<.001) between mouse types and age. A significant difference in mouse types (dwarf and normal) was found at 3 months and also 12 months. A significant difference was found between normal mice at 3 and 12 months, while no significant difference was found between dwarf mice at 3 and 12 months. Percentages of fast and slow twitch muscle fibers also tended to show a difference.

Discussion: These results suggest that there are physiological differences between normal and Ames dwarf mice in muscle size and fiber type composition. Researchers expected to find a significant decrease is muscle cell diameter as the mouse aged; however, results showed that the muscle cell diameter actually increased with age. This may be due to the mouse not reaching full maturity during the age groups used in this study. Further research is needed to substantiate the results of this study. Researchers suggest analyzing age groups closer to those of senescence of these animals (eg, 24 months).

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