Diaminobenzidine as a myelin stain in semithin plastic sections

A diaminobenzidine (DAB) stain for myelin in glutaraldehyde fixed, osmicate d, semithin epoxy sections is described. One or 1.5 mu m sections, dried on to slides, are first etched with a 1:2 dilution of saturated sodium ethoxid e:absolute ethanol, then incubated in 0.05% aqueous DAB with 0.01% hydrogen peroxide, DAB specifically stains osmium fixed myelinated nerve fibers. Th is permits high resolution light microscopic study of myelinated nerve fibe rs in semithin sections of tissues that also can be studied by electron mic roscopy.