The Action of Ribonuclease on Fixed Tissues

Abstract

To study the optimal conditions for histochemical use of ribonuclease on fixed tissues, the factors of (1) type of fixation, (2) temperature, pH, type of buffer and length of incubation, (3) concentration of enzyme, and (4) staining and dehydration of sections were observed on rabbit pancreas- The fixing fluids studied were sublimate-alcohol, Bouin''s, Zenker-acetic, Zenker-formol, Petrunkevich''s cupric-paranitrophenol, 10% neutral formalin, SUSA, Carnoy, Bensley''s chrom-sublimate, absolute ethyl alcohol and acetone. Formaldehyde was a satisfactory fixative, although others might be preferred for special purposes. Of the five buffers tested, McIlvaine''s citric-acid-disodium-phosphate mixture was the most satisfactory. The optimum concentration of ribonuclease and length of incubation varied greatly after the 11 different types of fixation. Until the degree and optimum conditions of specific action have been more precisely established by further experiments, it is suggested that this histo-chemical reaction only be interpreted as a confirmatory test which is, under the best conditions, only relatively specific for ribonucleic acid and not highly quantitative.