High-speed autoradiography of 3H-thymidine-labelled nuclei

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Abstract
High-speed autoradiography with stripping film of 3H-thymidine-labelled cells was tested. The tests involved: (a) various times of immersion of emulsion-covered cell preparations in the mixture of dioxane-PPO-POPOP, at 20°C, (b) exposure of cell preparations and blanks for various times at either −70°C or +20°C, with different humidity levels. Autoradiographs of good quality could be produced by 2-min immersion in the scintillator, exposure time ≥1 h at either temperature and relative humidity 20–30%. A linear relationship between autoradiographic efficiency and exposure time of 1–7 h was found at either temperature, although the efficiency of autoradiographs exposed at −70°C was by approximately 30% higher than that of autoradiographs exposed at +20°C. Background values of autoradiographs dried with a fan and exposed for 1/4–7h at either −70°C or +20°C were 0.6–0.8 grain/100 μm2. Theoretical calculations and experimental data showed that high-speed autoradiographs are 30–50 times more efficient as compared with conventional stripping film autoradiographs, thus allowing a shortening of the respective exposure time. Theoretical aspects of efficiency and resolution of high-speed autoradiography are considered.