Journal ArticleDOI
Mitochondrial distribution and glycogen dynamics suggest diffusion constraints in muscle fibers of the blue crab, Callinectes sapidus.
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The present results suggest that cellular organization, SAV, and intracellular diffusion distances also impose constraints on aerobic processes in C. sapidus.Abstract:
The scaling of mitochondrial distribution, citrate synthase activity, and post- contractile glycogen recovery was examined in muscle fibers of the blue crab, Callinectes sapidus. The fast-twitch muscle fibers of C. sapidus can reach extremely large dimensions, which may impose constraints on aerobic metabolic processes. However, muscle cells from small crabs are not giant, meaning that during development muscle fibers cross and greatly exceed the surface area to volume (SAV) and diffusion threshold that is adhered to by the cells of most organisms. Cell diameters in the smallest size class were C100 mm, while the largest size class had cell diameters in excess of 500 mm. In the smallest cells, the fractional area of subsarcolemmal and intermyofibrillar mitochondria was similar. However, in the largest cells, mitochondria were almost exclusively subsarcolemmal. Total fractional area of mitochondria was highest in the largest cells due to a proliferation of subsarcolemmal mitochondria. In contrast, citrate synthase activity decreased as cell size increased. Following burst contractile activity, glycogen concentrations decreased significantly and remained depressed for several hours in muscle comprised of giant cells, consistent with previous findings that anaerobic glycogenolysis fuels certain components of post-contractile recovery. However, in muscle composed of the smallest muscle cells, glycogen levels did not decrease significantly following burst activity. While normal scaling of aerobic metabolism would predict a slower aerobic recovery in larger animals, the present results suggest that cellular organization, SAV, and intracellular diffusion distances also impose constraints on aerobic processes in C. sapidus. J. Exp. Zool. 297A:read more
Citations
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Journal ArticleDOI
Evolved changes in the intracellular distribution and physiology of muscle mitochondria in high-altitude native deer mice.
TL;DR: In this paper, the authors used high-altitude adapted populations of deer mice to examine whether changes in mitochondrial physiology or intracellular distribution in the muscle contribute to hypoxia resistance.
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Molecules in motion: influences of diffusion on metabolic structure and function in skeletal muscle
TL;DR: Experimental measurements of metabolic fluxes, diffusion distances and diffusion coefficients, coupled with reaction–diffusion mathematical models in a range of muscle types has started to reveal some general principles guiding muscle structure and metabolic function.
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The long and winding road: influences of intracellular metabolite diffusion on cellular organization and metabolism in skeletal muscle.
TL;DR: The effect of diffusion distance on O(2) flux in muscle has been the subject of quantitative analyses for a century, but the influence of ATP diffusion from mitochondria to cellular ATPases on aerobic metabolism has received much less attention as discussed by the authors.
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Thermal plasticity of mitochondria: a latitudinal comparison between Southern Ocean molluscs.
TL;DR: Foot muscle of the limpet and the clam have the physiological plasticity to respond to their warmer, more variable thermal environment, and mitochondrial density was very low, 1-2% in both species, suggesting that low temperature compensation of mitochondrial density is not a universal evolutionary response of Antarctic marine ectotherms.
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The influence of oxygen and high-energy phosphate diffusion on metabolic scaling in three species of tail-flipping crustaceans
TL;DR: An examination of the influence of O2 and HEP diffusion on the observed rate of aerobic flux in muscle revealed that diffusion limitation was minimal under most conditions, suggesting that diffusion might act on the evolution of fiber design but usually does not directly limit aerobic flux.
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Scaling, why is animal size so important?
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A simple analysis of the "phosphocreatine shuttle"
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