Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.6.4.1 (myosin ATPase)
 1,140 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Muscle biopsies of the vastus lateralis muscle taken before and after 18 weeks of resistance training were compared by preparing frozen cross sections for electron microscopy and using adjacent sections for fiber typing by myosin ATPase activity. Quantitative ultrastructural changes were observed in histochemically-identified muscle fiber types of twelve young women who underwent the training. The percentage of type IIB fibers decreased and IIA fibers increased. The cross-sectional area of all major fiber types increased with training. The absolute volume of myofibrils, intermyofibrillar space, and mitochondria increased with training for most major fiber types (type I, IIA and IIAB), but the relative volume percentages were not significantly changed because of corresponding fiber hypertrophy. Mean mitochondrial size for types I and IIA and myofibril size for types IIC and IIB increased significantly with training. The capillary number per fiber and density did not change with training. Activity levels were measured for selected glycolytic and oxidative enzymes. Cytochrome oxidase and hexokinase increased significantly with training, while creatine kinase, citrate synthase, phosphofructokinase, glyceraldehyde phosphate dehydrogenase and hydroxyacyl CoA dehydrogenase enzymes were not significantly altered. The results suggest that this type of high-repetition resistance training causes the intracellular components of all fiber types to increase proportionally with an increase in fiber size. In addition, the enzyme analysis indicates the muscle as a whole may increase its oxidative phosphorylation capacity in conjunction with the decreased percentage of type IIB fibers.
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PMID:Muscle fiber types of women after resistance training--quantitative ultrastructure and enzyme activity. 825 33

Marked changes in muscle function occur after birth, with the response being dependent on developmental stage. Therefore, postnatal cellular ontogeny of functionally distinct skeletal muscles was investigated in the pig, a large mammal born at a relatively advanced stage of development. Assessment of myofibre contractile (type I slow/type II fast) and metabolic (oxidative/glycolytic) properties at Days 0, 2, 5 and 14 revealed type-specific differences in hypertrophy and differentiation. Type I fibre proportions increased significantly in soleus and diaphragm, especially between Days 0 and 5, and rhomboideus showed a similar trend, but in longissimus there was a slight decrease during Days 0-2. Cytochrome oxidase activity was relatively high and similar among myofibres in all muscles at birth, and fibres with low activity were not detected until Day 5. In contrast with previous reports, glycolytic fibres were present in all muscles at birth; postnatal changes in alpha-glycerophosphate dehydrogenase activity were both muscle- and myofibre-specific. Hence, although myosin ATPase activity and metabolic properties of porcine myofibres are well developed at birth, they continue to mature postnatally. This suggests that postnatal muscle development can be modulated by extrinsic factors, even in mammals born at a relatively advanced stage of development.
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PMID:Postnatal development and differentiation of myofibres in functionally diverse porcine skeletal muscles. 962 94