Improved lipid visualization with a modified osmium tetroxide method using ultrasonic treatment and intensification...

Formalin fixed autopsy tissue containing lipids were cut into 1-5 mm thick blocks, washed well, then postfixed in 2% OsO4 in 0.03 M veronal acetate buffer for 30, 60, 90, 120, or 180 min with or without ultrasonic treatment. Tissues exposed to ultrasound for 90 min showed superior penetration of OsO4 and well preserved histological architecture. Tissues also were immersed for 1 hr in veronal acetate buffer (pH 7.4) containing 0.5% imidazole or triazole and compared with untreated controls. Paraffin sections, 4 microns thick, were examined under a light microscope with an image analyzer. Both intensity and percentage area of osmium blackening were significantly higher in samples immersed in imidazole or triazole than in untreated controls. No difference was observed between imidazole- and triazole-immersed samples. The OsO4 method, modified by ultrasound treatment and imidazole- or triazole-immersion, can be applied to routine formalin fixed autopsy materials for improved lipid visualization.