Sakashita T, Doi M, Yasuda H, Takeda H, Fuma S, Nakamura Y, Häder D-P
National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage, Chiba 263-8555, Japan.
Int J Radiat Biol. 2002 Nov;78(11):1055-60. doi: 10.1080/09553000210166592.
To study the effects of high-energy carbon ion irradiation on negative gravitaxis in the photosynthetic flagellate Euglena gracilis strain Z in a dose-response-dependent manner.
Cells were exposed to 290 MeV amu(-1) carbon ion from the Heavy Ion Medical Accelerator in Chiba (HIMAC) at 12 doses (0, 1, 5, 7.5, 10, 15, 20, 50, 75, 100, 150, 200 Gy for water). r was used to quantify negative gravitaxis observed in a recently developed biomonitoring system.
Negative gravitaxis of Euglena was significantly affected by irradiation at a dose >7.5 Gy, 28 h after irradiation. Negative gravitaxis recovered after a few days. The rising phase of r during the first 30 s of orientation was independent of irradiation dose. The recovery mechanism itself was damaged by 290 MeV amu(-1) carbon ions at a dose >50 Gy.
The results indicate that negative gravitaxis in Euglena may be affected by the radiation experienced during a space experiment especially during the occurrence of solar flares. The analyses of time needed to reorient to the gravitational vector suggest that the steering control of the flagellar apparatus is affected by exposure to the 290 MeV amu(-1) carbon ion irradiation, resulting in an altered beating pattern of a flagellum and/or changes of the cell form during reorientation.
以剂量反应依赖的方式研究高能碳离子辐照对光合鞭毛虫纤细裸藻Z株负趋地性的影响。
细胞暴露于千叶重离子医学加速器（HIMAC）产生的290 MeV amu(-1)碳离子下，设置12个剂量（以水计为0、1、5、7.5、10、15、20、50、75、100、150、200 Gy）。r用于量化在最近开发的生物监测系统中观察到的负趋地性。
辐照后28小时，剂量>7.5 Gy时，裸藻的负趋地性受到显著影响。几天后负趋地性恢复。定向最初30秒内r的上升阶段与辐照剂量无关。剂量>50 Gy时，290 MeV amu(-1)碳离子会破坏恢复机制本身。
结果表明，裸藻的负趋地性可能会受到太空实验期间尤其是太阳耀斑发生时所经历辐射的影响。对重新定向至重力矢量所需时间的分析表明，鞭毛装置的转向控制受到290 MeV amu(-1)碳离子辐照的影响，导致鞭毛摆动模式改变和/或重新定向期间细胞形态变化。
