Electron microscope autoradiography with special reference to the problem of resolution.

Abstract

1. A method of electron microscope autoradiography was established using nuclear research emulsions manufactured in japan: Sakura NR-H1 and NR-H2. Several biological applications were performed, and simultaneously the improvement in resolution was studied.2. The aim of electron microscope autoradiography is to reveal the exact localization of certain substances at the macromolecular level. In order to attain this object the establishment of an extremely fine grain development method is indispensable.3. Although the limit of resolution in electron microscope autoradiography is supposed to be the diameter of silver halide grains in emulsion, it may be improved by considering the fact that the contact area between the silver grain and the section surface is the minimum unit of resolution.4. Thiamine, labelled with 3H, was made insoluble and precipitated with chloroplatinic acid at fixation. Developed silver grains completely overlap the B1-PtCl6 precipitates.5. The minimum resolution of the electron microscope authoradiogrphy was determined histologically to be within 100A. The following hypothesis is proposed to explain this high resolution although the introduction of extremely fine grain development is also considered one of the factors.Some of latent images are formed at the contact point (surface) between the polyhedral silver halide grain and the section surface. The latent image seems to be formed by the impact of β-particles from directly below, and since it is in contact with the section it remains in place even after development and gelatin removal. This latent image finally becomes a developed silver grain in the electron microscope autoradiogram.