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

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 degrees C, (b) exposure of cell preparations and blanks for various times at either -70 degrees C or +20 degrees C, with different humidity levels. Autoradiographs of good quality could be produced by 2-min immersion in the scintillator, exposure time greater than or equal to 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 degrees C was by approximately 30% higher than that of autoradiographs exposed at +20 degrees C. Background values of autoradiographs dried with a fan and exposed for 1/4--7 h at either -70 degrees C or +20 degrees C were 0.6--0.8 grain/100 micron2. 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.