OSMIUM-TETROXIDE AND RUTHENIUM TETROXIDE ARE COMPLEMENTARY REAGENTS FOR THE PREPARATION OF EPIDERMAL SAMPLES FOR TRANSMISSION ELECTRON-MICROSCOPY

Ruthenium tetroxide and osmium tetroxide were compared as post-fixativ es in the preparation of human epidermis for transmission electron mic roscopic examination, Both reagents revealed characteristic lamellar g ranules within the granular layer and extruded lamellar granule conten ts in the upper granular layer. The transformation of the granule cont ents into multilamellar sheets at the interface between the granular a nd cornified layers and the persistence of these sheets through all le vels of the stratum corneum were demonstrated only with ruthenium tetr oxide fixation. Therefore, the reactivity of osmium tetroxide with iso lated epidermal lipids was examined, The failure of osmium tetroxide t o reveal membrane structures in the stratum corneum can be explained b y its inability to react with many of the lipid components of these me mbranes, rather than to selective removal of lipids during tissue proc essing, as was formerly believed, Ruthenium tetroxide, a stronger oxid izing agent than osmium tetroxide, overcomes this problem but has othe r severe limitations as a post-fixative.