Abnormally combined myelinated and unmyelinated nerves in dystrophic mice.

Abnormally combined M- and U-nerves were observed in the peripheral nerves of C57BL dystrophic mice. They were counted in the sciatic nerves of the dystrophic mice 3 times more frequently than in control mice. The myelin disappeared beyond the nodes of Ranvier just as in the dysmyelination of dystrophic mice. Some of the U-axons inside the myelin were enveloped by Schwann cell cytoplasm while others were not. The myelinated U-axons contained cored vesicles, dilated endoplasmic reticulum and degenerate mitochondria. These abnormalities might cause disordered function and be related to the pathophysiology of murine muscular dystrophy.