Ultrastructure of the radial components of the mouse optic nerve and its changes during Wallerian degeneration.

Radial components of the optic nerve of the mouse were studied by using thin sections and freeze-fracture replicas. The investigations were performed on normal optic nerves, as well as on those undergoing Wallerian degeneration following eyeball enucleation. Normal radial components in thin sections were observed as a series of light lines composed of small electron-lucent dots situated in the interperiod lines across the myelin sheath. They are frequently found in those parts of the myelin sheath lying near the outer and inner processes of the oligodendroglia. Radial components in freeze-fracture replica were observed as a parallel array of many ridges composed of a row of particles. The particles of radial components located in the deeper part of the myelin sheath lose their linear arrangement and fall into disorder in a relatively early post-operative period. The parallel array of rows of particles located closely beneath the outer processes of the oligodendroglia remained intact for a long period, even in a markedly distorted myelin sheath. The present observations suggest that the radial components are resistant against the disintegration of the myelin lamellae during Wallerian degeneration.