Figure 4

electron micrograph of thyroid follicular cells in (a) sham operated rats, (b) ovariectomized rats and (c) ovariectomized rats treated with estradiol. (a) This is a part of a thyroid follicle. The follicles are bounded with a basement membrane (double arrows) and surrounded with capillaries (Cap). Two follicular cells with rounded nuclei (N) and a parafollicullar cell (P) could be demonstrated. In the follicular cells; saccules of Golgi apparatus (curved arrow), prominent endoplasmic reticular cisternae (thick arrows), rounded mitochondria (arrow heads), lysosomes (dashed arrows) intracytoplasmic colloid vesicles (thin arrows) with mild apical vacuolization near the center of the follicle (C) could be demonstrated (EM × 2000). (b) There are rounded nuclei of follicular cells (N), while the mitochondria (arrow heads) and endoplasmic reticular cisternae (thick arrows) showed no remarkable changes. Intracytoplasmic colloid vesicles (thin arrows) were more prominent while the apex of the cell facing colloid (C) showed microvilli (double arrows) and many lysosomes (dashed arrows) with apical vacuolization could be clearly demonstrated (EM × 2000). (c) There are oval nuclei (N), endoplasmic reticular cisternae (thick arrows) and prominent rounded mitochondria (arrow heads) were comparable to the control group. Large amount of intracytoplasmic colloid vesicles (thin arrows) were much more evident, while the apex of the cell facing colloid (C) showed microvilli (double arrows) with much more apical vacuolization and many lysosomes (dashed arrows) (EM × 2000).