Use of poly(vinylpyrrolidone) and poly(vinyl alcohol) for cryoultramicrotomy

Summary Specimens infused with or suspended in a mixture of 10–30% poly(vinylpyrrolidone) and 2.07–1.61m sucrose can often be more easily frozen-sectioned than those infused with sucrose alone. The pH of such a mixture can be efficiently adjusted to neutrality by using Na₂CO₃. Use of poly(vinylpyrrolidone) causes little or no increase in the background level of immunolabelling. Adsorption staining of ultrathin frozen sections with a mixture of uranyl acetate and poly(vinyl alcohol), i.e. a simple thin-embedding of the sections in such a mixture, produces positive staining effects that are often enough to delineate structures of many organelles. When OsO₄-treated frozen sections are stained with uranyl acetate and further adsorption-stained with a mixture of lead citrate and poly(vinyl alcohol), the overall staining effects are similar to those observed in double-stained conventional sections.A large portion of the findings was reported as a part of the author's presentation in the 11th International Congress on Electron Microscopy, held in Kyoto, Japan, in 1986.