@misc{oai:repo.qst.go.jp:00070494,
 author = {Suto, Yumiko and Akiyma, Miho and Hirai, Momoki and Yuuki, Masanori and Tominaga, Takako and Nakayama, Fumiaki and Suzuki, Tosikazu and Sugiura, Nobuyuki and Akashi, Makoto and 數藤 由美子 and 穐山 美穂 and 平井 百樹 and 結城 政則 and 富永 隆子 and 中山 文明 and 鈴木 敏和 and 杉浦 紳之 and 明石 真言},
 month = {Sep},
 note = {In the conventional dicentric chromosome assay (DCA), the linear-quadratic dose response equation has been established for doses less than 6 Gy.  At higher doses, DCA does not provide accurate dose response relationships due to mitotic delay, poor mitotic index and a high proportion of complex chromosomal aberrations.  In case of partial body exposure, however, induction and transmission of chromosomal damage at high dose irradiation should be analyzed to assess the biological effects of radiation.  The objective of this work is to characterize chromosomal aberrations induced by high-dose irradiation in cultured lymphocytes.
     Peripheral blood samples were exposed to 15 Gy gamma-ray (60Co source, 0.51 Gy/min).  Isolated lymphocytes were cultured in RPMI1640 medium supplemented with 20% fetal bovine serum, 2% phytohaemagglutinin and 30 mM bromodeoxyuridine (BrdU).  Cells were harvested at 48 h, 50 h, 52 h, 54 h, 56 h, 72 h and 96 h after culture initiation.  For the 72 h sample, multicolor fluorescence in situ hybridization (M-FISH) was conducted to analyze complex chromosome aberrations.
     The first mitotic peak appeared at 52-54 h.  Interestingly, cells containing aberrant chromosomes with as many as 8-10 centromeres were observed.  Average dicentric equivalent count per cell ranged from 9.0 to 9.5 in 48 h – 56 h samples.  In the 72 h sample, 20% of the dividing cells were in the 2nd metaphase.  It should be noted that 70% of the 2nd metaphase cells were tetraploid cells including endoreduplicated cells.  The high degree of polyploidy noted in our material suggests that irradiation may exert an effect on the replication process, in addition to the structural damage.  M-FISH analyses revealed that in certain cells, aberrant chromosomes were accurately replicated in the polyploidization process.  In the 96 h sample, cells at the third metaphase with octaploid chromosomes were found.
     In conclusion, a certain population of peripheral blood lymphocytes was found to transit to the second and even third mitoses after high-dose in vitro irradiation, persisting with severe chromosome aberrations.  The occurrence of polyploidization and endoreduplication following high-dose irradiation described here validated the reported fact that after high dose radiotherapy, tetrapliod cells were observed in the circulating blood of patients., 14th International Comgress of Radiation Research},
 title = {Induction and persistence of cytogenetic damage in cultured peripheral blood lymphocytes following 15 Gy gamma-irradiation},
 year = {2011}
}