Masking of pleomorphic glycogen sites by methanolic uranyl acetate

Abstract

Rat liver tissue was fixed in 2.5% glutaraldehyde buffered with cacodylic acid (pH 7.3) for 2 hr, washed twice in buffer, and postfixed in 2% osmium tetroxide at 4 C for 1 hr. The tissue then was dehydrated, infiltrated with and embedded in Epon by routine proocdures. The ultra thin sections from this tissue, when stained with spectroscopic grade methanol saturated with uranyl acetate (SMUA) for 1 min followed by aqueous lead citrate (PbCi) (Reynolds 1963) for 5 min at room temperature, showed a uniform staining of all major allular components ercept glycogen. The SMUA appeared to be specific for ribonucleoprotein granules, rendering them more prominent in the cytoplasm due to the lack of glycogen staining. The question of glycogen removal from the sections due to SMUA treatment was evaluated using various extractions and staining methods. It appeared that SMUA pretreatment alters the subsequent binding ability of lead salts, resulting in lack of glycogen staining, although it does not remove the glycogen from the sections.