Electron microscopic study of optic nerves of macular mice.

The optic nerve of the macular mouse as a model of Menkes' disease was examined by electron microscopy. Since hemizygote macular mice die at 14 or 15 days of age, they were treated with 50 micrograms CuCl2 per 0.1 ml distilled water at 7 days of age. The optic nerves of 1-month-old hemizygote macular mice treated with copper showed hypomyelination and unmyelinated axons, while 1-month-old heterozygote macular mice had focal demyelination of axons. The number of myelinated axons in treated hemizygotes and heterozygotes was statistically significantly lower than that in the control littermates. Oligodendrocytes form myelin sheaths. Since oligodendrocytes of the hemizygote macular mice may have lower activities of cuproenzymes, such as cytochrome oxidase and superoxide dismutase, hypomyelination is assumed to be caused by the dysfunction of oligodendrocyte.