Histochemical and biochemical plasticity of muscle fibers in the little brown bat (Myotis lucifugus) |
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Authors: | R M Brigham C D Ianuzzo N Hamilton M B Fenton |
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Institution: | (1) Department of Biology, York University, M3J 1P3 North York, Ontario, Canada;(2) Department of Physical Education, York University, M3J 1P3 North York, Ontario, Canada;(3) Present address: Department of Biological Sciences, Division of Ecology (Behavioural Ecology Group), University of Calgary, T2N 1N4 Calgary, Alberta, Canada |
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Abstract: | Summary Fiber composition, and glycolytic and oxidative capacities of the pectoralis, gastrocnemius, and cardiac muscles from active and hibernating little brown bats (Myotis lucifugus) was studied. The data were used to test two hypotheses: First, since hibernating bats maintain the capability of flight and make use of leg muscles to maintain a roosting position all winter, the fiber composition of the pectoralis and gastrocnemius muscles should not change with season. Second, we tested the hypothesis of Ianuzzo et al. (in press), who propose that the oxidative potential of mammalian cardiac muscle should increase with increasing heart rate while glycolytic potential should not. Our results indicate that the fiber composition of the pectoralis muscle was uniformly fast-twitch oxidative (FO)_ regardless of the time of year, as predicted. However, the gastrocnemius muscle exhibited a change in FO composition from 83% in active to 61% in hibernating animals. Contrary to the variable change in histochemical properties with metabolic state, a trend of reduced maximal oxidative (CS) and glycolytic (PFK) potential during hibernation in both flight and leg muscles was apparent. The oxidative potential of flight and leg muscles decreased by 15.2% and 56.5%, respectively, while the glycolytic potential of the same muscles decreased by 23.5% and 60.5%, respectively. As predicted, the glycolytic potential of cardiac muscle remained constant between active and hibernating bats, although there was a significant decrease (22.0%) in oxidative potential during hibernation.Abbreviations
FO
fast-twitch oxidative
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FG
fast-twitch glycolytic
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SO
slow-twitch oxidative
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Vmax
maximal enzyme activity
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PFK
phosphofructokinase
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CS
citrate synthase |
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Keywords: | Histology Biochemistry Muscle physiology Hibernations Metabolism |
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