Abstract
AbstractThe myofibrillar ATPase histochemical reaction was utilized to determine the proportion of the two basic histochemical fiber types in three “mixed” skeletal muscles of guinea pig after denervation. In five normal control animals, there was no significant difference in the proportion of fiber types on the two sides. In 12 experimental animals from 6–27 weeks after right sciatic neurectomy, the intensity of the myosin ATPase activity was not appreciably altered in the denervated muscle fibers but the type II (dark) fibers underwent preferential atrophy. The fiber type ratio between denervated and control sides in the experimental animals was not significantly different from the same values in the normal control animals. This allowed the conclusion that, up to 27 weeks after denervation, the histochemical typing of a fiber by the myofibrillar ATPase reaction probably reflects the original fiber type. This reaction is the preferred method for fiber typing in denervated guinea pig muscle, especially since most other histochemical reactions show markedly reduced activity of muscle enzymes after denervation and are unsuitable for fiber typing. The soleus, which normally contains only type I fibers, showed numerous type II fibers at 27 weeks after denervation and this was interpreted as a dedifferentiating process.
Published Version
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