A Simplified Technique for Electron Microscope Autoradiography

Abstract

Two techniques are commonly used in applying nuclear track emulsions to specimens for electron microscope autoradiography: the loop method of Caro and van Tubergen (1962) and the flat substrate method of Salpeter and Bachmann (1964). Both of these techniques are applicable with Ilford L4 emulsion, but the high resolution emulsion Eastman Kodak NTE can be used conveniently only with the flat substrate method since it is difficult to obtain a film of NTE emulsion on a loop. Although the loop method has the advantage that it can be applied directly to grid-mounted specimens, it is difficult to obtain an emulsion layer of uniform and appropriate thickness. The flat substrate method now generally preferred involves coating sections mounted on a glass-supported flat collodion film with liquid emulsion, either by dipping or pipetting, exposing and processing the emulsion, and then transferring emulsion, specimen, and film to a grid. This method allows for a uniform application of emulsion to the section, but the final stripping of the complex of collodion film, section and emulsion from the glass slide often leads to specimen damage or loss. For an excellent detailed description of the various steps in specimen preparation, see Kopriwa (1973).