中华鳖胸腺显微和亚显微结构及其在进化上的意义

THE MICROSTRUCTURE, ULTRASTRUCTURE OF THYMUS IN TRIONYX SINENSIS AND ITS SIGNIFICANCE IN EVOLUTION

应用透射电子显微镜观察了中华鳖胸腺的显微和亚显微结构。发现中华鳖胸腺从结构上可分为皮质和髓质，皮质富含淋巴细胞，髓质富含上皮性网状细胞。在各发育期中华鳖胸腺皮质、髓质交界处和髓质区有明显的囊状胸腺小体和交错突细胞。在200g以上的成年鳖胸腺内发现有同心圆状胸腺小体。电镜下，胸腺内淋巴细胞分为大、中、小3型。上皮性网状细胞从亚显微结构上分为支持型和分泌型。胸腺囊包括细胞内囊和细胞间囊，以细胞内囊居多。部分毛细血管管腔与淋巴细胞之间出现具4层结构的血一胸腺屏障。60g左右幼鳖胸腺部分皮质区已开始出现退化。至500g左右的成年鳖胸腺萎缩，淋巴细胞稀少，皮质、髓质结构消失。一部分胸腺组织已被肌样细胞代替。在50g左右的幼鳖和500g成年鳖胸腺内尚观察到甲状旁腺组织，腺细胞主要由主细胞构成。文中讨论了中华鳖胸腺显微、亚显微结构与功能的关系及其在水生脊椎动物免疫进化上的意义。

The thymus of Tronyx sinensis was composed of lobules. Each lobule was divided into the cortex, relatively rich in lymphocytes and the medulla, relatively rich in epithelial-reticuar cells. During development period, there were cystoid thymic corpuscles and interdigitating cells in thymic medulla and cortico-medullary border. Concentric thymic corpuscles were observed in thymus of mature Trionyx sinensis (over 200g). Three types of thymic lymphocytes, large,medium and small, and two types of epithelial-reticular cells, supporting and secretory, were found to exist. Intercellular thymic cysts and intracellular epithelial ones were found, with the former being predominent. There were blood-thymus barriers consisting of four layers between some capillary cavities and Lymphocytes. Part of thymus cortex in Trinyx sinensis (at 60g body weight) appeared to be degenerated. Up to mature stage (500g), the thymus atrophied, the number of lymphocytes decreased, and the structure of cortex and medulla disappeared. Part of the involutive thymus was replaced by myoid cells. The parathyroid gland was embeded in thymus of immature (50g) and mature (500g) Trionyx sinensis, and the gland was mainly composed of chief cells. The significance of the evolutive changes in the microstructure, and ultrastructure of Trionyx sinensis thymus in relation to the function and evolution has been discussed.