MORPHOLOGICAL AND FUNCTIONAL DIFFERENTIATION OF THYROID GLANDS OF THE CHICK EMBRYO / 解剖学报

ABSTRACT

The morphological and functional differentiation of the thyroid gland of chick embryos of 7～21 days was studied by histological, histochemical and autoradiographic methods.On the 7th day, a few small PAS-positive colloid droplets appeared within the epithelial cells, the capacity of which to concentrate ~3H-leucine was demonstrated by autoradiographic method. On the 8th day, numerous colloid droplets were present within and between the epithelial cells which began to form primary follicles. The cells were capable of selectively concentrating ~(131)Ⅰ. By the 9th day, the gland was apparently divided into peripheral and central zones. The epithelial cells in the peripheral zone were arranged denser and their concentrating capacity for both ~3H-leucine and ~(131)Ⅰ was stronger than that of the cells in the central zone. By the 10 th day, small follicles became distinct in the deeper part of the peripheral zone. Local aggregation of silver grains of ~(131)Ⅰ and deposits in the colloid material of the follicular lumen were visible. After the 13th day, follicles of various sizes were formed progressively throughout the gland. It appears from these data that the morphological and functional differentiation of the thyroid gland of the chick embryo is performed initially in the deeper area of the peripheral zone of the gland.The synthesis of the cytoplasmic colloid droplets as well as the iodination of the thyroglobulin were traced by autoradiographic technique. The results indicate that both processes are taking place within the thyroid cells, and the radioactive products are secreted into the follicular lumen thereafter.