Histological analyses of irradiation-induced apoptotic cells in the brains and eyes during later period of embryogenesis.

<p>(A) shows schematic image of embryonic head. Frontal plastic sections (C–N) and cryo-sections (O–T) of the embryonic brain were prepared at the level of the solid line shown in A. Apoptotic cells were examined in the brain and eye (squared area with dotted line in B). Nissl-stained sections of embryos 24 h after irradiation of 3 dpf (C, I) 4 dpf (D, J) and 5 dpf (E, K) and respective controls (F, L), (G, M), and (H, N). Immunohistochemical sections with anti-cleaved-caspase3 of embryos 24 h after irradiation of 3 dpf (O) 4 dpf (Q) and 5 dpf (S). Magnified images in squared area with dotted outlines in O, Q and S are shown in P, R and T, respectively. In irradiated 3 dpf embryos, pyknotic cells were present in the marginal area of the OT (arrow in C) and in the eye (arrowheads in I) and cleaved-caspase 3-positive apoptotic neurons are present in the brain (arrows in O and P) and eyes (arrowheads in O). Fewer apoptotic cells were found in the brain (arrows in D, Q and R) and eyes (arrowheads in J and Q) of irradiated 4 dpf embryos, and no apoptotic cells were found in irradiated 5 dpf embryos (E, K, S and T). No pyknotic cells were present in the brain and eyes of sham controls of 4–6 dpf embryos (F–H and L–N), respectively. Scale bars = 50 μm.