Life-Shortening and Carcinogenesis in Mice Irradiated Neonatally with X Rays

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Abstract
The characteristics of life-shortening and carcinogenesis were investigated in X-irradiated neonatal B6WF1 mice. Animals were irradiated within 24 h after birth and allowed to complete their normal life-span. Mean life-span was shortened linearly with dose at a rate of 9.1% per 100 R for females and 9.8% for males. The spectrum of neoplastic diseases was apparently modulated by X-irradiation, showing neonatal B6WF1 mice to be highly susceptible to the induction of thymic lymphoma, liver tumor and pituitary tumor. The dose-response relationship for thymic lymphoma could be described by a linear-quadratic model, and linearly could be rejected. Thymic lymphoma developed after a short latent period, resulting in death between 100 and 450 days of age. Liver and pituitary tumors increased with increasing dose up to 400 R and decreased thereafter. The latent period for liver tumor development was apparently shortened with increasing doses. Pituitary tumor developed in excess only in females after a long latent period.