Figure 3.

Irradiation targeted to the right hemisphere of OT of medaka embryonic brain. AO-staining of the irradiated brain 24 h after the irradiation demonstrated that AO-positive apoptotic neurons were induced only in the irradiated right hemisphere (dotted circle in B). By contrast, AO-positive apoptotic cells were induced throughout the whole brain when the whole embryonic brain was irradiated with broad beam (10 Gy) (A). When AO-positive apoptotic neurons were induced only in the irradiated right hemisphere (B), only the microglia positioned in the irradiated right hemisphere express l-plastin as shown by WISH (D), in contrast to that microglia were activated to express l-plastin in the whole brain after whole-brain irradiation (C). At the later phase of phagocytosis, 42 h after the irradiation, a large number of microglia express ApoE, not only in the irradiated right hemisphere (black arrows in G), but also in the left hemisphere (red arrow in G), which was not irradiated (F), in a similar manner to that observed after whole-brain irradiation (E). Schematic drawings of the abscopal effect in microglial activation are shown in G. Scale bars = 100 μm.