Department of Zoology, University of Kerala, Kariavattom, Thiruvananthapuram 695581, India.
Zoology (Jena). 2010 May;113(3):175-83. doi: 10.1016/j.zool.2009.11.002. Epub 2010 May 23.
We tested the hypothesis that melanin has a role as a molecule within the thyroid-mediated cascade. Light microscopic and ultrastructural changes in the skeletal muscle during tail resorption in tadpoles of the tropical frog Clinotarsus curtipes Jerdon (Anura: Ranoidea) were observed. Light microscopic analysis at metamorphic stage XVIII showed a melanized epidermis. A gradual migration of melanocytes from the epidermis to the dermis and filopodia of melanocytes pervading the skeletal muscle preceded tail resorption. The invasion of melanocytes into the muscle bundles coincided with the breakdown of the muscle bundles into sarcolytes and the arrival of macrophages at this site. This would suggest that the melanocyte-sarcolyte association signals the arrival of macrophages at these sites as metamorphosis progressed. Melanophages, macrophages with melanin granules, were observed at the climax stage of XXIII. The sarcolytes and the melanin granules were phagocytosed by macrophages so as to completely cleanse the exocytic muscle debris and the melanin granules. The presence of large melanomacrophage centers in the tadpole liver at metamorphic climax suggests that these phagocytic macrophages were further processed in the liver and, likely, in the spleen. It is proposed that melanin, a byzantine molecule, has a role in the cascade of events leading to tail resorption in anuran tadpoles.
我们检验了一个假说，即黑色素作为甲状腺介导级联反应中的一种分子发挥作用。观察了热带青蛙 Clinotarsus curtipes Jerdon（无尾目：Ranoidae）在尾巴吸收过程中骨骼肌的光镜和超微结构变化。在变态阶段 XVIII 的光镜分析显示出黑色素化的表皮。黑色素细胞从表皮逐渐迁移到真皮和黑色素细胞的丝状伪足，在尾巴吸收之前渗透到骨骼肌中。黑色素细胞侵入肌肉束与肌肉束分解成肌原纤维和巨噬细胞到达该部位同时发生。这表明随着变态的进行，黑色素细胞与肌原纤维的结合标志着巨噬细胞到达这些部位。在 XXIII 阶段的高潮期观察到含有黑色素颗粒的黑色素吞噬细胞。巨噬细胞吞噬肌原纤维和黑色素颗粒，以彻底清除外分泌肌肉碎片和黑色素颗粒。在变态高潮期，蝌蚪肝脏中存在大的黑色素巨噬细胞中心，表明这些吞噬性巨噬细胞在肝脏中进一步被处理，可能在脾脏中也被处理。因此，黑色素作为一种复杂的分子，在无尾目蝌蚪尾巴吸收的级联反应中发挥作用。
