[Relationship between the structural state of chromatin and the biosynthesis of rapidly labeling nuclear RNA in the thymuses of rats subjected to total x-irradiation].

Accumulation of polydeoxyribonucleotides (PDN) was studied in thymus of rats, subjected to total body X-ray irradiation at doses 400 and 800 rad. The content of PDN correlated with the time of treatment; its low-polymer components prevailed after irradiation with 800 rad. Protein/DNA ratio was decreased in DNP within 30 min after the irradiation and it returned to the initial level within 4 hrs. Capacity of DNP to make a complex with actinomycin D was inhibited within 30 min; however it exceeded the control level within 4 hrs after irradiation. Biosynthesis of nuclear RNA, estimated by incorporation of 14C-uridine, was distinctly decreased within the whole experimental period.