Radiation-Induced Mitotic Delay in Sea Urchin Eggs Treated with Puromycin and Actinomycin D

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Abstract
The mitotic delay arising from exposure to radiation and inhibitors of RNA and protein synthesis was measured. Eggs that had been inseminated with normal or [gamma]- Irradiated sperm were exposed to puromyein at various intervals after fertilization. The irradiation of the sperm extended the period of sensitivity to puromycin-lnduced mitotic delay. This experiment suggests that an Inhibition of protein synthesis is Involved In radiation-Induced mitotic delay. Fertilized sea urchin eggs were incubated with puromyein for approximately 30 mln. and washed. Mitotic delay resulted. This puromyein treatment extended the -ray-sensitive portion of the mitotic cycle by as much as 20 mln. This experiment suggests that protein synthesis must occur before the cells can pass through the radiation-sensitive portion of the mitotic cycle. Actinomycin D did not increase the amount of delay found after irradiation of either sperm or eggs. This experiment Indicates that the messenger RNA required for the essential radiation-sensitive protein synthesis Is present In the unfertilized egg.