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Yachi, Yoshie*; Yoshii, Yuji*; Matsuya, Yusuke; Mori, Ryosuke*; Oikawa, Joma*; Date, Hiroyuki*
Scientific Reports (Internet), 9(1), p.17649_1 - 17649_8, 2019/11
Times Cited Count：6 Percentile：36.9(Multidisciplinary Sciences)Radiation weighting factor for photon and electron is defined as 1.0 independently these energies. However, it should be noted that the biological effects after 29 kVp X-rays is relative higher than standard 200 kVp X-rays at the endpoint of 
. And it is of importance to evaluate electrons generated via interaction of photons with matter. Here, we evaluated the energy concentration along electron track (dose-mean lineal energy) on chromosome (micron-meter) scales by Monte Carlo simulation, and measured the DNA double-strand breaks (DSBs) induction. From the cell experiments, the DSBs induction after diagnostic X-rays exposure (60-100 kVp) is higher than those with therapeutic X-rays (6 MV). In the relation between the dose-mean lineal energy and the number of DSBs, it was shown that lower energy photons might induce more biological impact due to the interaction by low energy electron. This study implies that radiation weighting factor for photon and electron should not be unity.
Oikawa, Joma*; Matsuya, Yusuke; Hamada, Nobuyuki*; Date, Hiroyuki*
no journal, ,
Risk of cataract after exposure has drawn an attention, however its onset mechanisms and the responses to low-dose exposure remain unclear. In recent years, it has been reported that human lens epithelial cells (HLEC1) induce excessive proliferation after exposure with more than 2 Gy, which might be related with cataract onset mechanism. In this study, to clarify the excessive proliferation in HLEC1, a cell colony model was developed by using agent-based model based on NetLogo. This model includes several parameters such as cell cycle, contact inhibition, upper limit of number of cell divisions to reproduce the experimental colony size of non-irradiated cells. From the model study, it was found that excessive proliferation after exposure can be reproduced by considering shortening the cell cycle and increasing the upper limit of cell division. These findings contribute to effective estimation for excessive proliferation of lens epithelial cells and cataract risk after exposure.
Oikawa, Joma*; Matsuya, Yusuke; Hamada, Nobuyuki*; Date, Hiroyuki*
no journal, ,
To estimate the risk of radiation cataract following exposure to low dose of ionizing radiation is of importance. However, mechanisms of radiation cataract remain uncertain. Human lens epithelial cells (HLEC1) shows excessive proliferation after exposure above 2 Gy. In this regard, it is necessary for clarifying the relation between the excessive proliferation and the cataract induction. Here, we developed a cell colony model for HLEC1 based on in vitro experiments. We measured cell-cycle and cell growth curve, and then developed the colony model considering cell-cycle time and the limit of cell division number. As the results, we found that shorten the cell cycle time and multiple subpopulation of cells should be considered to reproduce the experimental colony size distribution. The experiments and model estimation suggest that the HLEC1 are heterogeneous population for growth, which may be influential to radiation cataract induction.
