Human Saliva as a Convenient Source of Ribonuclease By S. BRADBURY

Saliva, heated to 80° C for 10 minutes and centrifuged to remove mucus, is used as a source of ribonuclease. Slides of mouse pancreas incubated in this for 3 hours at 6o° C show complete removal of cytoplasmic basiphilia. Incubation of control slides in distilled water before staining is essential in order to avoid errors due to possible solution of basiphil material in aqueous media. Errors due to incomplete elimination of the salivary amylase are prevented by using the PAS reaction to check the absence of all diastatic activity. Formaldehyde and phenyl isocyanate are used as specific enzyme inhibitors. If these are added to the saliva before use, the ribonuclease is inactivated, and there is then scarcely any action on the cytoplasmic basiphilia. With these controls, incubation of slides in prepared saliva, followed by staining with basic dyes, may be used in histochemistry as a means of localizing ribonucleic acid.