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Journal Articles

A Mathematical model of radiation-induced responses in a cellular population including cell-to-cell communications

Hattori, Yuya; Suzuki, Michiyo; Funayama, Tomoo; Kobayashi, Yasuhiko; Yokoya, Akinari; Watanabe, Ritsuko

Radiation Protection Dosimetry, 166(1-4), p.142 - 147, 2015/09

 Times Cited Count:4 Percentile:53.24(Environmental Sciences)

Cell-to-cell communication is one of the important factors to understand the mechanisms of radiation-induced responses such as radiation-induced bystander effects at low doses. In the present study, we propose simulation-based analyses of the intercellular signal transmissions between the individual cells in the cellular population. We developed the transmissions of two types of signals, i.e., X is transmitted via culture medium and Y is transmitted via gap junctions based on the diffusion equation. To observe the cell cycle as the response of cell induced by the signals, X and Y, we represented the cell cycle as a virtual clock including several check-point pathways and the cyclic process (G1, S, G2, M phases). The cellular population was divided into the grids (cells), and the signals and the clock were calculated for each grid. The signals, X, Y, were transmitted to the cells and stopped the clocks at the check points. Furthermore, the radiation was modeled as the radiation signal, Z, which affected the clock and the signals, X and Y. We input the radiation signal, Z, to specific cells, and simulated the behaviors of the clock of each cell and signals, X and Y. We will discuss the usefulness of our model for investigating the mechanisms of radiation-induced responses of the cell cycle via cell-to-cell communications.

Journal Articles

Live-cell imaging study of mitochondrial morphology in mammalian cells exposed to X-rays

Noguchi, Miho; Kanari, Yukiko; Yokoya, Akinari; Narita, Ayumi; Fujii, Kentaro

Radiation Protection Dosimetry, 166(1-4), p.101 - 103, 2015/09

 Times Cited Count:0 Percentile:100(Environmental Sciences)

Journal Articles

Visualisation of cell cycle modifications by X-ray irradiation of single HeLa cells using fluorescent ubiquitination-based cell cycle indicators

Kaminaga, Kiichi; Noguchi, Miho; Narita, Ayumi; Sakamoto, Yuka; Kanari, Yukiko; Yokoya, Akinari

Radiation Protection Dosimetry, 166(1-4), p.91 - 94, 2015/09

 Times Cited Count:5 Percentile:45.16(Environmental Sciences)

Journal Articles

Real-time observation of irradiated HeLa-cell modified by fluorescent ubiquitination-based cell-cycle indicator using synchrotron X-ray microbeam

Narita, Ayumi; Kaminaga, Kiichi; Yokoya, Akinari; Noguchi, Miho; Kobayashi, Katsumi*; Usami, Noriko*; Fujii, Kentaro

Radiation Protection Dosimetry, 166(1-4), p.192 - 196, 2015/09

 Times Cited Count:2 Percentile:73.66(Environmental Sciences)

For the knowledge about irradiation effects of mammalian cells depending on the cell cycle, most of them had been analyzed by statistical approches. Our purpose is to establish the method for real-time observation of irradiated cells under a microscope. Fluorescent ubiquitination-based cell cycle indicator (FUCCI) human cancer (HeLa) cells (red indicates G1; green, S/G2) were exposed to a synchrotron X-ray microbeam. Cells in either G1 or S/G2 were selectively irradiated according to cell color observed in the same microscopic field in a culture dish. Time-lapse micrographs of the irradiated cells were acquired for 24 h after irradiation. The cell cycle was strongly arrested by irradiation at S/G2 and never progressed to G1. In contrast, cells irradiated at G1 progress to S/G2 with a similar time course as non-irradiated control cells. These results show single FUCCI cell exposure and live cell imaging are powerful methods for studying radiation effects on the cell cycle.

Oral presentation

Calculation of heavy ion-induced DNA damage based on microdosimetric quantities

Watanabe, Ritsuko; Yokoya, Akinari; Hashimoto, Shintaro; Sato, Tatsuhiko

no journal, , 

The microscopic distribution of energy deposition is an essential factor to determine the relative biological effectiveness (RBE) of heavy ions. Although the linear energy transfer (LET) is the most generally used parameter for comparison of RBE, microdosimetric quantities as lineal energy (y) are considered to be more suitable parameter, as they reflects the ionization densities in microscopic sites. In this study, we focus on the evaluation of the number of DNA damage in relation to the microdosimetric quantities in the sites of sub-cellular sizes by Monte Carlo simulation. The numbers of double strand breaks (DSB), complex damages were calculated around the several mono-energetic ions. In the presentation, the number of DNA damage induced in the microscopic site correlated with the lineal energy and also the spatial distribution of the damages along the ion trajectories will be shown and discussed in terms of the cell-survival fraction models.

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