A NEGATIVE CONTRAST STAIN FOR ULTRA-THIN FROZEN-SECTIONS

Ultra-thin frozen sections are ideal substrates for immunolabeling in high resolution electron microscopy. However, visualization of subcell ular structures is inferior to that obtained with corresponding plasti c sections. Although negative staining is generally effective and even superior to positive staining, the accumulated stain is often too hea vy, obscuring morphology and markers used for immunocytochemical local ization of antigens. This paper describes the development of a modifie d negative contrast staining technique in which a high concentration o f uranyl acetate is mixed with methyl cellulose at a low pH. Applicati on of this stain to cryosections of cells and tissue resulted in impro ved visualization of morphological structures characterized by negativ e images of membranes and cell organelles. Use of this stain is advant ageous for morphological and immunocytochemical studies involving ultr a-thin frozen sections. (C) 1994 Wiley-Liss, Inc.