title: Non-induction of radioadaptive response in zebrafish embryos by neutrons.
abstract: In vivo neutron-induced radioadaptive response (RAR) was studied using zebrafish (Danio rerio) embryos. The Neutron exposure Accelerator System for Biological Effect Experiments (NASBEE) facility at the National Institute of Radiological Sciences (NIRS), Japan, was employed to provide 2-MeV neutrons. Neutron doses of 0.6, 1, 25, 50 and 100 mGy were chosen as priming doses. An X-ray dose of 2 Gy was chosen as the challenging dose. Zebrafish embryos were dechorionated at 4 h post fertilization (hpf), irradiated with a chosen neutron dose at 5 hpf and the X-ray dose at 10 hpf. The responses of embryos were assessed at 25 hpf through the number of apoptotic signals. None of the neutron doses studied could induce RAR. Non-induction of RAR in embryos having received 0.6- and 1-mGy neutron doses was attributed to neutron-induced hormesis, which maintained the number of damaged cells at below the threshold for RAR induction. On the other hand, non-induction of RAR in embryos having received 25-, 50- and 100-mGy neutron doses was explained by gamma-ray hormesis, which mitigated neutron-induced damages through triggering high-fidelity DNA repair and removal of aberrant cells through apoptosis. Separate experimental results were obtained to verify that high-energy photons could disable RAR. Specifically, 5- or 10-mGy X-rays disabled the RAR induced by a priming dose of 0.88 mGy of alpha particles delivered to 5-hpf zebrafish embryos against a challenging dose of 2 Gy of X-rays delivered to the embryos at 10 hpf.
authors: Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Ave., Kowloon Tong, Hong Kong.
authors: Candy Y P
authors: CY
authors: Ng
authors: Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Ave., Kowloon Tong, Hong Kong.
authors: Eva Y
authors: EY
authors: Kong
authors: Research, Development and Support Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage, Chiba 263-8555, Japan Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan.
authors: Alisa
authors: A
authors: Kobayashi
authors: Research, Development and Support Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage, Chiba 263-8555, Japan.
authors: Noriyoshi
authors: N
authors: Suya
authors: Research, Development and Support Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage, Chiba 263-8555, Japan.
authors: Yukio
authors: Y
authors: Uchihori
authors: Department of Biomedical Sciences, City University of Hong Kong, Tat Chee Ave., Kowloon Tong, Hong Kong State Key Laboratory in Marine Pollution, City University of Hong Kong, Tat Chee Ave., Kowloon Tong, Hong Kong.
authors: Shuk Han
authors: SH
authors: Cheng
authors: Research, Development and Support Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage, Chiba 263-8555, Japan tkonishi@nirs.go.jp peter.yu@cityu.edu.hk.
authors: Teruaki
authors: T
authors: Konishi
authors: Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Ave., Kowloon Tong, Hong Kong State Key Laboratory in Marine Pollution, City University of Hong Kong, Tat Chee Ave., Kowloon Tong, Hong Kong tkonishi@nirs.go.jp peter.yu@cityu.edu.hk.
authors: Kwan Ngok
authors: KN
authors: Yu
mesh_terms: D000512:Alpha Particles; D000818:Animals; D017209:Apoptosis / Q000528:radiation effects; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000528:radiation effects*; D009502:Neutrons; D015027:Zebrafish / Q000196:embryology*
keywords: NASBEE; hormesis; neutrons; radioadaptive response; zebrafish embryos