“Type grouping” in skeletal muscles after experimental reinnervation

Abstract

Effects of experimental nerve regeneration were studied in the gastrocnemius and plantaris muscles of adult guinea pigs with histochemical techniques. Nerve regeneration was produced by one of 3 methods group A, simple nerve crush; group C, nerve section and immediate end-to-end suture. A marked degree of type grouping of muscle fibers was observed in the reinner-vated muscles of group C animals. Slight type grouping was present in group B animals, whereas in group A animals the normal mosaic pattern was found. With a Ag technique, marked collateral branching of the subterminal axons was demonstrated in reinnervated muscles of group C animals. Type grouping was related to abundant collateral branching of the regenerating axons. Type grouping was concluded to be one sign of neuronal regeneration in the experimental animal. This study supports the earlier hypothesis that the type grouping occurring in chronic neuropathies in human beings is due to reinnervation by collateral sprouting of intact motor axons, but the study did not rule out other possible mechanisms which may produce type grouping.