Change in patterns of inhibition by actinomycin D of uridine-H 3 incorporation into salivary gland RNA of [formula omitted] at different larval ages

Abstract

Recent work from this laboratory has shown striking variations in the salivary gland RNA metabolism during the larval development ( Lara and Hollander, 1967; Armelin, Meneghini and Lara, unpublished results). These results are substantiated by the data of the present study on the kinetics of uridine-H 3 incorporation into that RNA at two distinct periods of larval life — before and during the appearance of the giant puffs. It was also observed that, at both these stages, inhibition by actinomycin revealed the presence of unstable RNA classes. However, before the appearance of the giant puffs, the inhibition by the antibiotic is followed by a rather unexpected recovery of incorporation capacity. This effect is possibly due to an active DNA multiplication at this particular stage.