The action of solvents on the ultrastructural appearance of keratohyalin and the horny layer in guinea-pig back epidermis.

Abstract

SUMMARY Various solvents were used to remove osmium-reactive phospholipids and free fats from guinea-pig back epidermis before post-fixation in osmium. After extraction, the osmium stained material which remained was probably due to proteins with reactive amino acids. After brief fixation in glutaraldehyde, followed by immersion of the tissue in pyridine, a phospholipid solvent, followed by osmium post-fixation, the unkeratinized epidermal cells were practically unstained. Removal of phospholipid from the keratohyalin granules revealed them as aggregates of smaller particles, probably the protein component. The thickened plasma membranes of the horny cells were darkly stained in osmium. Removal of material from the interiors of these cells left empty spaces between the meshwork of filaments, indicating absence of matrix keratin. The contrast between the darkly stained keratinized cell membranes and filaments, and unstained unkeratinized cells was marked after lipid extraction.