@misc{oai:repo.qst.go.jp:00071110,
 author = {Choi, V.W.Y. and Kobayashi, Alisa and Konishi, Teruaki and Oikawa, Masakazu and H., Cheng Shuk and Yu, K.N. and 小林 亜利紗 and 小西 輝昭 and 及川 将一},
 month = {May},
 note = {The microbeam irradiation system (Single-Particle Irradiation System to Cell, acronym as SPICE) at the National Institute of Radiological Sciences (NIRS), Japan, was employed to irradiate dechorionated embryos of the zebrafish, Danio rerio, at 5 h post fertilization (hpf) by microbeam protons each having an energy of about 3.4 MeV. In the first part of the experiments, only 1 position on the cells was irradiated, with 10, 20, 40, 80, 100, 200, 400, 500, 600, 800, 1000 or 2000 protons. In the second part of the experiments, 10 separate positions on the cells were irradiated, each with 5, 10, 20, 40, 50, 60, 80, 100, 200, 500, 800 or 1000 protons. The levels of apoptosis in zebrafish embryos at 25 hpf were quantified through terminal dUTP transferase-mediated nick end-labeling (TUNEL) assay, with the apoptotic signals captured by a confocal microscope. Both parts of experiments revealed a triphasic dose-response for zebrafish embryos, including (1) a sub-hormetic zone with an increase in apoptotic signals for a small number of irradiated protons per position, (2) a hormetic zone with a reduction of the apoptotic signals below the spontaneous level for a larger number of irradiated protons per position, and (3) a toxic zone with an increase in apoptotic signals again if the number of irradiated protons per position was further increased. When comparing the two experiments, it was interesting to note that the transition from the sub-hormetic zone to the hormetic zone occurred for a similar number of irradiated protons per position, while the transition from the hormetic zone to the toxic zone occurred for a similar number of total irradiated protons. Possible reasons would be discussed., Heavy Ion in Therapy and Space Radiation Spymposium 2013},
 title = {Response of 5 hpf zebrafish embryos to low-dose microbeam protons},
 year = {2013}
}