Jimpy mouse myelin revisited with freeze-fracture.

Corpus callosum, cerebellum, and spinal cord from Jimpy mice, and control littermates, 15 and 21 days old, were prepared for freeze-fracture in a "cryofract" apparatus. The few myelinated axons in the Jimpy exhibited a striking paucity of particles in myelin P faces, though tight junctions were present. In addition, small maculae of particles were found on these P faces. Peripheral myelin appeared normal, both for the quantity and disposition of particles on their P faces.