Presentation Establishment of localized irradiation to the kidney and analysis of the radiation sensitivity of the hematopoietic cells in adult medaka (Oryzias latipes)

Keita, Ohashi(東京大)  ,  Tomomi, Watanabe-Asaka(東京大)  ,  Nagata, Kento  ,  Takako, Yasuda(東京大)  ,  Funayama, Tomoo  ,  Suzuki, Michiyo  ,  Shoji, Oda(東京大)  ,  Hiroshi, Mitani(東京大)

2017-08-30
Description
The kidney is a hematopoetic tissue in medaka (Oryzias latipes) and the hematopietic tissue is sensitive to irradiation. We have been obsereved reduction of hematopietic cells in the kidney by carbon ion beam irradiation up to 2.2 mm in depth of medaka using Takasaki Ion Accelerators for Advanced Application (TIARA) of National institutes for Quantum and Radiological Science and Technology (Nagata.<i>et</i>.<i>al</i>., 2016). In this study, we made further analyses to clarify the radiation response of hematopoetic tissues by peripheral blood cell number and histologically evaluation of the kidney. When the 15 Gy of carbon ion beam was irradiated from the dorsal and ventral side of the kidney, the number of prripheral blood cell was decreased and increased from control 8 days after irradiation, respectively. This result confirmed the histological alterations of our preveous study. Neither the number of the peripheral blood cell nor the heamatopietic cells in the kidney recovered as the control to the 28 days after the irradiation of carbon ion beam from the dorsal side, whereas the histology of the kidney was recovered without increase of the number of the blood cell 28 days after the whole body irradiation by 15 Gy of gamma rays (137Cs). We then shielded medaka with 5-mm-thick acrylic plate with a hole on the position of the kidney to irradiate only kidney area, and irradiated 15 Gy one side or both sides on the kidney from the dorsal side. Seven days after the irradiation, the atrophy and reduction of hematopoietic cells were observed in the irradiated kidney and numbers of the blood cell were fewer in the kidney irradiated group than control. We are now establishing a precise local irradiation system that using heavy-ion microbeam of QST-Takasaki (diameter 250 μm) to analyze the local alterations by the irradiation. It is known that phenylhydrazine (PHZ) cause anemia and anemia may induce proliferation of hematopietic cells. So we used PHZ on medaka as an proliferation activator of the hematopoietic cells. Contrary to our expectation, the number of peripheral blood cells did not decrease 7 days after irradiation. This result suggests that hematopoietic cells become radiation resistant when proliferation was induced.In this study, we established a local irradiation system and clarified the radiation sensitivity of hematopoietic cells in different cell states. These results can contribute to reveal the mechanism of radiation response.
第23回小型魚類研究会

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