Abstract

Morphological, biochemical, and physiological properties of longterm (6 mo) immobilized skeletal muscles of a nonhuman primate were studied in seven Galago senegalensis which were immobilized at the ankle and knee of one hind limb with an external brace. Electromyographic activity of the ipsilateral and contralateral quadriceps and muscles of the calf were assessed after 5 and 6 mo of immobilization. The EMG was markedly reduced in the immobilized muscles compared to the contralateral control when the brace was intact and the animal moving freely. Without exception, extensor muscles atrophied more than flexors. The soleus, a slow-twitch muscle atrophied more than any other muscle of the lower leg but the same was not true of the vastus intermedius the analogous muscle of the thigh. Slow-twitch oxidative fibers (SO) were atrophied more than fast-twitch oxidative glycolytic fibers (FOG), and FOG tended to atrophy more than fast-twitch glycolytic fibers (FG). The immobilized soleus and vastus intermedius had a smaller percentage of SO fibers than their controls, suggesting that they had faster contraction times. With respect to alterations in reduced nicotinamide adenine dinucleotide diaphorase activity, no consistent pattern was observed except for a greater coarseness of staining granules and more homogeneous dispersion of the granules throughout the cross-section of the fibers. No changes were found in phosphorylase, lactate dehydrogenase, or succinate dehydrogenase specific activity or in myoglobin concentration in homogenates of ankle flexors or the vastus lateralis. Myosin ATPase, but not actomyosin ATPase activity was significantly less in the immobilized gastrocnemius-plantaris muscles. No change in contractile properties related to speed were observed in the plantaris. This muscle did exert more twitch and tetanic tension per gram of muscle in the immobilized leg.

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