On the Incidence of Leukemias in Hiroshima During the Past Fifteen Years from 1946 to 1960

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l. Rats bearing Yoshida sarcoma were irradiated by X-rays under the following conditions: Deep therapy installation 160 kVp; filter of 1.0 mm Al; 386 r/minute; five different dosages, namely l0,000 r, 3,000 r, 2,000 r, 1,000 r and 500 r were administered in single irradiations to total body of rats. 2. Type B cells with characteristic chromosome breaks or degenerated chromosomes were induced by X-irradiation with high doses such as 10,000 r, 5,000 r, 2,000 r and 1,000 r. They were unsuitable for cytological observations. A-cells with few chromosome breaks were obtained with the highest frequency 10 minutes after 500 r irradiation. These cells were the most suit,able for the observation of chromosome breakages. 3 Idiograms of 34 tumor stem cells containing chromosome breaks were analysed. The chromosomes of the Yoshida sarcoma comprise three namely .J-, V- and rod-shaped types. Among them breaks in the rod-shaped chromosomes occurred at much higher frequency than in the other two types. 4. The localization of breaks was examined statistical]y. The great majority of chromosome breaks occurred m the middle parts of chromosome arms In all, J-. V- and road-shaped chromosomes.
日本放射線影響学会の論文