Stephen T. Kinsey

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Most marine mammals are hypothesized to routinely dive within their aerobic dive limit (ADL). Mammals that regularly perform deep, long-duration dives have locomotor muscles with elevated myoglobin concentrations that are composed of predominantly large, slow-twitch (Type I) fibers with low mitochondrial volume densities (V(mt)). These features contribute(More)
Muscle fiber hypertrophic growth can lead to an increase in the myonuclear domain (MND), leading to greater diffusion distances within the cytoplasmic volume that each nucleus services. We tested the hypothesis that hypertrophic growth in the white muscle of fishes was associated with increases in the mean DNA content of nuclei, which may be a strategy to(More)
A fundamental principle of physiology is that cells are small in order to minimize diffusion distances for O(2) and intracellular metabolites. In skeletal muscle, it has long been recognized that aerobic fibers that are used for steady state locomotion tend to be smaller than anaerobic fibers that are used for burst movements. This tendency reflects the(More)
Skeletal muscle fibre size is highly variable, and while diffusion appears to limit maximal fibre size, there is no paradigm for the control of minimal size. The optimal fibre size hypothesis posits that the reduced surface area to volume in larger fibres reduces the metabolic cost of maintaining the membrane potential, and so fibres attain an optimal size(More)
Muscle fibers that power swimming in the blue crab Callinectes sapidus are <80 microm in diameter in juveniles but grow hypertrophically, exceeding 600 microm in adults. Therefore, intracellular diffusion distances become progressively greater as the animals grow and, in adults, vastly exceed those in most cells. This developmental trajectory makes C.(More)
The time- and orientation-dependence of metabolite diffusion in giant muscle fibers of the lobster Panulirus argus was examined using (31)P- and (1)H-pulsed-field gradient nuclear magnetic resonance. The (31)P resonance for arginine phosphate and the (1)H resonances for betaine, arginine/arginine phosphate and -CH(2)/-CH groups were suitable for measurement(More)
The muscles that power swimming in the blue crab, Callinectes sapidus, grow hypertrophically, such that in juvenile crabs the cell diameters are <60 microm, whereas fibers of the adult crabs often exceed 600 microm. Thus, as these animals grow, their muscle fibers greatly exceed the surface area to volume ratio and intracellular diffusion distance limits of(More)
Diameters of some white locomotor muscle fibers in the adult blue crab, Callinectes sapidus, exceed 500 microm whereas juvenile white fibers are <100 microm. It was hypothesized that aerobically dependent processes, such as metabolic recovery following burst contractions, will be significantly impeded in the large white fibers. In addition, dark aerobic(More)
Increased AMP-activated protein kinase (AMPK) activity leads to enhanced fatty acid utilization, while also promoting increased ubiquitin-dependent proteolysis (UDP) in mammalian skeletal muscle. β-guanidinopropionic acid (βGPA) is a commercially available dietary supplement that has been shown to promote an AMPK-dependent increase in fatty acid utilization(More)
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