Date of Defense


Date of Graduation



Biological Sciences

First Advisor

John Spitsbergen

Second Advisor

Cindy Linn

Third Advisor

Julie VanGyseghem


In the years to come, the number of people above the age of 65 is projected to increase and the average life expectancy is expected to rise. With the aging population facing greater health risks and higher healthcare costs, strategies must be developed to ensure longer, healthier lives for US (United States) citizens and the global population. One detriment that comes with aging is sarcopenia, the loss of function and mass of the skeletal muscle due to a decrease in nerve-to-muscle innervation. The protein content of Glial Cell Line-Derived Neurotrophic Factor (GDNF), a protein produced by skeletal muscle, has a positive correlation with the structure and function of the neuromuscular junction, that is, the more GDNF content the more nerve-to-muscle innervation and plasticity of the pre- and post-synapse. Due to this, GDNF content can be indicative of what is happening at the neuromuscular junction and the denervation that occurs there. In skeletal muscle, there are three different muscle types: Type 1A, Type 2A, and Type 2B. Given that as aging and sarcopenia occur, the amount of GDNF content decreases and the amount of fast-twitch glycolytic muscle fiber types decreases while the amount of slow-twitch oxidative fiber types increases, GDNF content can be an indicator of neuromuscular junction health with the amount of each muscle fiber types that are present. Previous research in this lab, based on unpublished dissertation work suggests that long-term exercise can be a powerful component in combating loss of muscle structure and function in rats of both males and females but has not yet considered different rat strains. However, there yet to be studies conducted comparing different rat strains, with different pre-exposed conditions. In that way, the aim of this study is to visualize the muscle fiber type distribution of two different rat strains at an early age in attempt to set preliminary research to show whether there are differences in rat strains before exercise, aging, and the onset of associated risk factors with specific rat strains. This investigation involved analyzing the left lateral gastrocnemius of two rat strains to characterize different muscle fiber types through immunohistochemistry and visualization using a LEICA microscope. Overall, this study proved to be inconclusive given the limited data and therefore fails to reject the hypothesis that there will not be significant differences in the muscle fiber type distribution in the two rat strains at a young age. To further understand the potential differences of rat strains at young ages additional studies must be conducted.

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