0 5 10 15 20 (%) Radiation dose (cGy) 100~199 200~299 300~399 400~499 500+ Frequency of abnormal cells A Stem Cell Fusion genes for leukemia Gamma and Neutron Rays Hypothesis: Organ stem cell hit theory Masato Tomonaga, M.D., PhD. Oslo, Norway, March 2013 An evidence: Chromosome aberrations in short-distance survivors (a) (b) 5’ A B C D F G X Y E A B C D F G X Y E White Cells Red Cells Chromosomal Abnormalities and Destruction of Genes Neutrons and gamma rays released by the atomic bombs directly destroyed body cells of the hibukasha (atomic bomb victims). Radiation also affected hematopoietic function, which caused acute radiation sickness and death to many victims. The cause of aftereffects of the atomic bomb radiation can be found in the destruction of DNA which forms chromosomes. When affected by bomb radiation, cell molecules would cause ionization and generate oxygen, which then would destroy gene information of the DNA. Many are restored, but unrestored stem cells, after an incubation period can start to proliferate abnormally and turn into cancer cells. This figure shows the frequency of radiation-induced chromosomal aberrations in hematopoietic stem cells in the peripheral blood (GM-CFC, BFU-E) among atomic bomb survivors exposed to a radiation dose of 100 cGy (1 centigray + 1 rad) or more. The proportion of cells with abnormal chromosomes among the stem cells investigated is shown by dose. There is a positive correlation between the proportion and dose. Amenomori et al, Exp. Hematol. 16, 19088. This figure shows the chromosomal abnormality in the hematopoietic stem cells in the peripheral blood (A) and abnormality in the peripheral T-lymphocyte (B) observed in a high-dose survivor, indicating that the radiation-induced damage involves the level of totipotent hematopoietic stem cells. Amenomori et al, Exp. Hematol. 16, 19088.