Several reports have indicated that scintillators enhance the intensity of radioautographic reactions. If this were the case, the use of scintillators would shorten the exposure time of radioautographs and the production of radioautographs would be accelerated. It was, therefore, decided to examine the effect of scintillators on the intensity of radioautographs in a quantitative manner over uniformly labeled test specimens. Reaction intensities with or without scintillators were compared using Kodak NTB2
emulsion for light microscopy and Ilford L4 and Sakura NR-H2
emulsion for electron microscopy. In addition, the background fog was quantitatively evaluated. No increase in the intensity of the radioautographs was observed under the following conditions: pretreatment of tissue sections with scintillator solutions before
emulsion coating and exposure; treatment with scintillator solutions after
emulsion coating but before exposure; treatment with scintillator solutions during exposure; contact with a
plastic scintillator film throughout exposure. Heightened reaction intensity was obtained only when scintillators were applied during the histological processing of tissues. The impregnation of tissue blocks with PPO (2,5-Diphenyloxazole) and
POPOP (1,4-bis-2-(5-phenyloxazolyl)-benzene) during
dehydration, infiltration and
Epon embedding produced a 20% increase of reaction intensity in light microscope radioautographs using NTB2
emulsion and a 75% increase in electron microscope radioautographs using L4
emulsion.