The mean life span of animals killed by a specific type of tumor is influenced by competing risks. The parametric inference method of Noda et al. was applied to a set of mouse experimental data in order to correct for the appearance of observed life span distribution under competing risks and to test statistical significances of difference between corrected mean life spans. Data were from an experiment on tumors induced in mice by X-rays: whole body irradiated with 600 R; head with 800 R; trunk or lower body with 800 R. The statistically significant changes were found: Whole body irradiation shortened the mean latent period of malignant lymphomas whereas the head irradiation shortened the latent periods of none of tumors. Trunk irradiation shortend mean latent periods of lung tumors. Lower body irradiation showed a tendancy to shorten the mean latent periods of mammary tumors. Results that differed from the above were obtained when there was no correction for competing risks.

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2''-Deoxyguanosine in aqueous solution (5 × 10⁴ mol/dm³) was irradiated with ⁶⁰Co gamma-rays under N₂0. Products were separated by gel chromatography (Cellulofine GC-15-m) and high performance liquid chromatography (Inertsil ODS-2). 2-Amino-4-hydroxy-5-formamido-6-(2 deoxyribosyl)-aminopyrimidine was one of the main radiolytic products. The formation of 2, 5-diamino-4-hydroxy-6-(2''-deoxyribosyl)-formamidopyrimidine was detected, this compound being verified by measuring its ultraviolet absorption spectrum and analyzing its trimethylsilylated derivative by gas chromato-mass spectrometry. Its yield in terms of 2-amino-4-hydroxy-5-formamido-6-(2''-deoxyribosyl)-aminopyrimidine was 1 : 3.

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