Dysmyelination in the sciatic nerves of dystrophic mice.

Ultrastructural alterations were observed in the sciatic nerve of dystrophic mice. Myelin sheaths were abnormal in shape, abruptly ceased beyond a node of Ranvier, leaving the axon naked. These changes were seen in both afferent and efferent nerve fibres. Apparent embryonal Schwann cells and Schwann cells which were associated with increased lysosomes in the cytoplasm were observed in the proximal portion. There is a relative decrease in Schwann cells in the cross-section of the radicular parts, and a relative increase in the distal parts. The mean number of neurotubules per unit area was smaller while the mean number of the neurofilaments was larger in U-axons, in the dystrophic mice than in the controls. In M-fibres, neurotubules and neurofilaments showed no significant difference between systrophic and control mice.