Letters to the editor: Chelated bismuth as a stain in electron microscopy.

Abstract

Observations on the use of Bi as a routine stain for electron microscopy are reported. Chelated Bi was employed as the staining reagent in thin sections, both alone and in combination with U and Pb. Electron micrographs of rat renal proximal tubule, and basal cells of the epithelium of the armadillo Dasypus novemcinctus vas deferens using these 2 staining techniques are discussed. Staining thin sections with Bi reagent after staining with U and Pb imparts a degree of contrast superior to that obtained with Bi alone or with conventional stains. In some tissues examined little contrast was gained in staining grids with Pb following the sequential application of U and Bi. Staining is much less intense when the application of Bi precedes that of U and Pb. The increase in staining intensity of Bi following treatment of tissue sections with U and Pb suggests that chelated Bi might bind in a similar manner. The mechanism of action is not clear, but this technique may be useful to electron microscopists seeking to enhance contrast in tissues difficult to stain with conventional means.