Fine structure of a third epithelial component of the thyroid gland of the rat

Abstract

Duct-like structures made of cells different from follicular or light cells were observed with the electron microscope in the thyroid glands of 16 rats. The wall of most of the ducts was made of two types of cells: (1) the lumen-bordering cells, mostly cuboidal or columnar, with short microvilli, and ( 2 ) the subjacent squamous cells, arranged in one or several layers of cells displaying numerous desmosomes and dense bundles of tonofilaments. Both cell types showed intricate folding of the plasma membrane at sites of cell-to-cell contact, an abundance of free ribosomes and nuclear indentations. In one occasion mucous-like cells were found. The lumen contained a finely granular homogeneous material as well as cell remnants. The ducts were located among the follicles, and were usually discrete from them; but on four occasions the epithelium of the duct was seen in direct continuity with that of a thyroid follicle. Only one case of a light cell associated with a duct was observed while many of these cells were associated with thyroid follicles.

Thyroid Calcitonin Cells and Unusual Follicles in the Fox

“…A similar situation has been reported earlier in the rat by Calvert and Isler [1970]. According to them, 'The con tinuity of ducts with follicles is a new fact which shows that the lateral outgrowths do not remain aloof from the development of the thyroid tissue, but associate with the fol licular tissue.…”

“…These cysts, which in the pres ent paper will be called 'unusual follicles', have been given various names by several investigators [Watzka, 1933;Axelrad and Leblond, 1955;Sehe, 1966;Calvert and Isler, 1970;Neve and Woilman, 1971;Woilman and Neve, 1971;Calvert, 1972;Das, 1976, 1978;Booth and Ghoshal, 1978]. In the house shrew (Suncus murinus), it is interesting to note that these cysts are invariably restricted to the internal parathyroid .…”

Telomerase expression and proliferative activity suggest a stem cell role for thyroid solid cell nests

“…The ultimobranchial body origin of solid cell nests was first proposed by Erdheim in 1904, 24 and marked similarities were pointed out between the solid cell nests and the ultimobranchial body of the rat, 25 dog, 26 and bull. 27 The unusual association of solid cell nests with thymic, [28][29][30][31] parathyroid, 28,29 adipose, 1,30 fibrous, 32 cartilaginous, 1,32 and salivary gland-type tissues 32 has been documented, and together with the production of mucins 1,28,33,34 reinforces the endodermal, ultimobranchial body origin of solid cell nests.…”

The cysts in C cell complexes of dog thyroids studied by immunoperoxidase staining and autoradiography.

“…Cyst structures have been observed in the thyroid glands of various mammalian species (WETZEL and WOLLMAN, 1969;CALVERT and ISLER, 1970;ZELANDER and KIRKEBY, 437 1977). They are usually called "ultimobranchial cysts", though not necessarily of an ultimobranchial origin (WoLLMAN and NEvE,1971).…”