RNA Metabolism during Regeneration in Stentor coeruleus

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Abstract
RNA accumulates in both macronucleus and cytoplasm in Stentor. Levels are higher at 8 hr., near the end of regeneration, than at 4 hr. With both actinomycin D and 5-flurouracil. levels which inhibit RNA synthesis in mammalian cells are initially ineffective in supppressing regeneration in Stentor, but after exposure for relatively long periods, levels of macronuclear and cytoplasmic RNA are reduced and regeneration is inhibited. Very high levels (15-25/ml) of actinomycin D inhibit regeneration in Stentor if added before achievement of stage 4, but if added at the 6th hr., regeneration is completed. The critical product emanating from the macronucleus prior to stage 4 is probably messenger RNA. The high degree of polyploidy of the macronucleus probably protects the organism from antimetabolites which operate on genetic loci. RNA at 0.5 mg/ml concentration prevent regeneration, and appear to destroy RNA in Stentor: organisms containing almost no DNA can regenerate after a short lag period.