Meeting Abstract

P2-24   -   Combining confocal imaging and SDS-page to measure variation in mitochondrial volume and fiber type in primate skeletal muscle Aikens, BL*; Pinc, GJ; O'Neill, MC; VandenBrooks, JM; Midwestern University; Midwestern University; Midwestern University; Midwestern University breanna.aikens@midwestern.edu

The evolution of primate musculoskeletal physiology requires a tradeoff between power generation and endurance capability. Previously, myosin heavy chain (MHC) content has been used as a proxy for estimating muscle performance. A predominance of MHC I isoforms should reduce dynamic force and power output and is hypothesized to facilitate repetitive, low cost contractile behavior associated with increased mitochondrial volume, while a predominance of MHC II should increase dynamic force and power output with comparatively less mitochondrial volume. However, while the ratio of MHC slow twitch type I isoforms to MHC fast twitch type II isoforms varies across primate and terrestrial mammals, fiber type analysis alone has been unable to fully predict aerobic differences and muscle performance in primates. Additionally, mitochondrial measurements using TEM have not matched the whole muscle fiber type analyses and has shown to be inadequate in estimating muscle energetics due to a small area being extrapolated to the whole fiber calculation. Here, we demonstrate a new technique combining confocal microscopy and SDS-page which allowed us to determine the fiber type and mitochondrial volume of the entire fiber length in the same muscle fiber to attempt to resolve this conundrum. This technique was applied to the gastrocnemius and vastus lateralis muscles in three macaque individuals allowing us to analyze mitochondrial volume and fiber type of individual fibers within 1) the same muscle, 2) different muscles, and 3) between individuals. Images were analyzed for total mitochondrial volume relative to total fiber volume using Amira 3D. Our results demonstrate that a combination of fiber type analysis and mitochondrial measurement better predicts muscle performance providing important new insight into the musculoskeletal evolution in primates.