ABSTRACT
It is extremely difficult, if not impossible, to reconcile the conflicting claims of those who have treated different cells and tissues with exogenous RNA. Some authors (e.g. Niu, Cordova & Niu, 1961 ; Niu, Cordova & Radbill, 1962) maintain that RNA extracts alter the course of cell differentiation to conform in morphological terms to the source of the RNA; in the same vein, Amos, Askonas & Soeiro (1964) have shown that, under certain conditions, RNA from mouse and bacterial cells can stimulate chick embryo fibroblasts to synthesize protein related antigenically to the origin of the RNA. Shepley, Ambrose & Kirby (1965), however, obtained stimulation of growth with permanent morphological changes in baby hamster kidney fibroblasts by the addition of RNA from a variety of sources.
On the other hand, Holoubek, Fanshier & Crocker (1966) showed that nuclear RNA synthesis in Ehrlich ascites cells was inhibited for 6–8 h by the addition of homologous or rat liver RNA and our results are similar in that rat liver RNA extract has been shown to have an adverse effect on the growth and survival of chick embryo fibroblasts.
