REGULATION OF THE INITIATION OF HEMOGLOBIN SYNTHESIS IN THE BLOOD ISLAND CELLS OF CHICK EMBRYOS: V. QUALITATIVE STUDIES OF THE EFFECTS OF PROFLAVINE

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Abstract
Most blastodiscs explanted before the 1-somite stage of development onto medium containing 20 μg of proflavine/ml failed to form any detectable hemoglobin, whereas the majority explanted at later stages formed hemoglobin visible to the naked eye. Formation of hemoglobin by 2-somite blastodiscs was suppressed by proflavine at 50 μg/ml, but 6-somite blastodiscs formed visible quantities of hemoglobin. Incorporation of leucine into protein was inhibited by proflavine, and almost the same amount of inhibition was produced at both concentrations of inhibitor for all developmental stages examined.Net incorporation of uridine into acid-precipitable material was moderately inhibited by 20 μg of proflavine/ml, and almost totally suppressed by 50 μg of proflavine/ml. Only polynucleotides of low molecular weight accumulated in blastodiscs treated with either concentration of proflavine, but preformed stable RNA's were not degraded in the presence of inhibitor. Proflavine appeared to inhibit synthesis of, or cause degradation of, new RNA of high molecular weight at both concentrations. Accumulation of RNA of low molecular weight continued at a low proflavine concentration, but little additional RNA accumulated at a high proflavine concentration.