Hareramadas B, Rai U
Department of Zoology, University of Delhi, India.
Indian J Exp Biol. 2001 Jul;39(7):629-35.
Light microscopic and ultrastructural studies of thymus in wall lizard showed remarkable season dependent structural changes. In winter, the thymus was involuted and its cortico-medullary differentiation was not distinct. Thymocytes were sparsely distributed. The epithelial cells exhibited atrophic features such as an appreciable decrease in the nuclear-cytoplasmic ratio and accordingly reduction in cell organelles. The reconstruction of thymus commenced during spring and it became fully developed with marked delineation of cortico-medullary regions during summer. The thymus was then densely populated with thymocytes and epithelial cells showed voluminous cytoplasm having numerous cell organelles. The thymus regression started again by the beginning of autumn. The results suggest that the thymic development in wall lizard have inverse relationship with the androgen level, as the testicular steroidogenic activity was seen maximum during winter and least in summer. This assumption gets support by castration and testosterone replacement experiments. Castration of lizards during winter resulted in profound development of thymus with an appreciable increase in thymocytes mainly in the cortex region . The cortex became delineated from the medulla. Following testosterone treatment, the thymus underwent regression and was comparable to testis-intact lizard's thymus during winter season. After withdrawal of testosterone treatment, the thymus exhibited dense lymphoid and thymocyte population with a demarcation of cortico-medullary regions and sub-cortical region was regenerated.
对壁虎胸腺的光学显微镜和超微结构研究显示，其结构存在显著的季节性变化。冬季时，胸腺萎缩，皮质-髓质分化不明显。胸腺细胞分布稀疏。上皮细胞呈现萎缩特征，如核质比明显降低，相应地细胞器减少。胸腺的重建始于春季，并在夏季完全发育，皮质-髓质区域有明显的界限。此时胸腺中胸腺细胞密集，上皮细胞显示出含有大量细胞器的丰富细胞质。到秋季初，胸腺又开始退化。结果表明，壁虎胸腺的发育与雄激素水平呈负相关，因为睾丸类固醇生成活性在冬季最高，夏季最低。这一假设得到了去势和睾酮替代实验的支持。冬季对蜥蜴进行去势导致胸腺显著发育，胸腺细胞明显增加，主要集中在皮质区域。皮质与髓质区分开来。睾酮处理后，胸腺发生退化，与完整睾丸蜥蜴冬季时的胸腺相当。停止睾酮处理后，胸腺呈现密集的淋巴细胞和胸腺细胞群体，皮质-髓质区域有界限，皮质下区域再生。
