COLLABORATIVE RESEARCH: Muscle fiber size as a determinant of metabolic design

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Most cells are small, with dimensions 100mm along the shortest axis. Small size promotes a high surface area to volume ratio and short intracellular diffusion distances, both of which are thought to be necessary design features of cells. However, cells of some organisms are nearly 10-fold larger than the norm. In some crustaceans, muscle fibers from juvenile animals have "normal" dimensions (100mm), but as the animals grow, some of these fibers may exceed 600mm. Attaining such a large size while maintaining function should be difficult or impossible, which raises the question: What are the rules and tradeoffs that govern cell size? The effects of developmental increases in cell size will be examined in isolated fast-twitch muscle fibers of the blue crab, Callinectes sapidus. Size-associated changes in muscle structure, metabolism, and contraction will be examined using methods that include electron microscopy, chemical assays, nuclear magnetic resonance and polarographic measurements of oxygen consumption. In addition, a reaction-diffusion mathematical model will be generated to aid interpretation of experimental data. This study constitutes a novel view of cellular energetics that is broadly applicable. Once the rules are established for an extreme model system, the approach can be applied to traditional models. This will be particularly useful for studying the impact of energetic challenges like hypoxia, exercise regimes and developmental processes, all of which are inherently linked to cell size. This is a collaboration of biologists and chemical engineers. The lead institution (UNCW) emphasizes undergraduate education, and undergraduate students will work alongside graduate students and the PIs. The research environment at the lead institution will be enhanced by the project's multi-disciplinary approach, and students will benefit from facilities and expertise at the collaborating institution. At the collaborating institution (FSU), the work will also involve training of undergraduate and graduate students. Mathematical modeling will form the basis for the dissertation of at least one graduate student, and undergraduate participation will be sought for all phases of the project.