Autoradiographic Differentiation of Tritium and Another β-Emitter by A Combined Colour-Coupling and Double Stripping-Film Technique

This technique distinguishes cells labelled with 3H, with 14C, or with both isotopes together, in the same histological preparation. The technique depends on the application of two layers of autoradiographic stripping film, separated by a thin layer of celloidin. The first layer (in contact with the tissue) records predominantly the distribution of 3H in the sample, the second exclusively that of 14C. The silver grains in one layer are coloured by dye-coupling, which enables the grains in the two layers to be differentiated without the need for separate focussing. The merits of stripping film over liquid emulsion are: rigid control of the thickness and uniformity of the film is assured; an inert celloidin layer of 0.1 μ or less can be applied between the two films; and the thickness of each film can be chosen to suit emission characteristics of the radioisotopes.