Toluidine blue staining on Epon semithin sections: effect of an oil differentiation.

Semithin sections from glutaraldehyde-osmium fixed, Epon embedded tissues were stained by alkaline toluidine blue and subjected to prolonged oil treatment. This procedure resulted in progressive bleaching of sections, while a few cell structures remained highly stained. The possible mechanism of this "differentiation" effect induced by the oil treatment is briefly analyzed.