Abstract
The substrate film method for localizing RNAse activity has been the object of further studies, and various steps of the original procedure have been modified. The modifications concern mainly the type of RNA used as substrate and the preparation of gelatin-RNA films. Moreover, a technique proposed by other authors for exposing films to tissue sections was found to present interesting advantages and has been adopted. The modified procedure proved more convenient than the original method, and a higher resolution was achieved in the present work. This report describes the revised procedure for localizing RNAse activity in tissue sections, exposes the advantages of the various modifications and presents the results obtained with different rat tissues, namely, the testis, intestine, brain, kidney, pancreas and ovary.