Abstract
The effects of gamma-rays on the thymus in the adult fish of Oryzias latipes were studied. Fish were subjected to a single whole-body irradiation of the dose ranging from 0 to 8 kR. Through the histological sections, the quantitative treatment was performed on the changes in thymus volume and mitotic activity of thymocytes after irradiation. The thymus in the irradiated fish exhibited a sudden drop in its volume on day 1-3 post-irradiation, subsequently followed by its regeneration. The change in mitotic index of thymocytes, especially in the regeneration phase, showed a dose-dependent behavior (same level as the control for 10 and 25 R; an overshoot for 100 and 200 R; a gradual recovery for 1 and 2 kR; no mitosis for 4 and 8 kR).
