Staining of oral epithelium with the zinc iodide-osmium reaction

Some of the parameters affecting the staining of keratinized oral epithelium with the zinc iodide-osmium reaction were examined using light and electron microscopy and electron probe microanalysis. Factors examined were block size, incubation temperature and the effect of aldehyde prefixation. Large blocks (4 mm cube) were subdivided after incubation and the staining of the centre and edge compared. Generally the reaction was more variable at the edge than in the centre. Small block (1 mm cube) showed a more intense reaction when incubated at 24 degrees C than at 4 degrees C. In all these preparations, final reaction product was seen over Golgi systems, lysosome-like bodies, membrane-coating granules and, in the more intensely stained regions, over endoplasmic reticulum and nuclear membranes as well. In prefixed material, mitochondria were frequently stained in addition to the other organelles. Energy dispersive analysis showed the reaction product to be similar in all preparations and to contain high levels of zinc and osmium but not iodine.