OSMIUM-CONTAINING COMPOUNDS WITH MULTIPLE BASIC OR ACIDIC GROUPS AS STAINS FOR ULTRASTRUCTURE

Osmium coordination compounds were prepared with a variety of acidic or basic ligands to produce water-soluble, brown-black monomers and occasional polymers bearing multiple basic or acidic groups. These colored osmium-containing substances served as basic or acidic stains in light microscopy that produced staining results similar to the familiar acidophilic or basophilic dyes. When ultrathin sections of glutaraldehyde-fixed, Araldite-embedded tissues were incubated in aqueous solutions of these osmium-containing stains for 3-18 hr, good contrast in the electron microscope was given to acidic or basic ultrastructures. The potentialities of the stains are illustrated and some results are correlated with chemical features of the stains.