An In Ovo Study of Actinomycin-D Effects on Early Chick Development

Abstract

The effects of actinomycin-D on stage 1 chick blastoderms has been studied in ovo. After 48 hours exposure to 2.0 ug actinomycin-D/egg, blood island formation took place while all other organogenesis was inhibited. Visual observation of treated blastoderms indicated hemoglobin synthesis to have taken place also. These results imply that a mRNA(s) is transcribed by stage 1 in chick for blood island development. Histosections imply that translation of this system takes place about 26 hours or less after stage 1 treatment. Preliminary tests with the fluorescent dye, acridine orange, specific for RNA and DNA, indicated that neo-synthesis of RNA was inhibited 6 hours after treatment. Some cells were found to contain abundant RNA in the cytoplasm which may be the precursor information for the blood vascular system. A new in ovo technique designed to overcome anomalous development due to handling was designed for this study. Precautions to in ovo culturing are described and a possible cause of anomalous in ovo development is discussed.