Morphology of the Second Kind of Follicle in the Guinea Pig Thyroid Gland

Abstract

The second type of follicle (S follicle) was studied in the thyroid gland of young and mature guinea pigs. A marked activity to non-specific esterase was used as a marker system for the S follicle. Usually a single S follicle was situated in the upper central two-thirds of each lobe occupying 0.5–2.7 mm of the length of the lobe. The S follicle could in both animal groups be divided into three parts, an upper, a middle, and a lower part. The upper tubular part consisted of cuboidal and cylindrical, strong-reacting cells completely separated from the thyroid follicles by connective tissue. The middle part was further subdivided into an irregular follicle without contact to the thyroid follicles, and a distended follicle with several contact areas to the thyroid follicles. An increasing amount of flattened, weak-reacting cells interpreted as thyroid follicle cells were encountered in the S follicle wall adjacent to the contact areas. In young animals the lower part had a tubular appearance like that seen in the upper part, while the lower part of the S follicle in mature animals were more follicle like.

Fine Structure of the Second Kind of Thyroid Follicles in Mature Guinea Pigs

“…This type has been observed in the mouse [Gorbman, 1947;Sato et al, 1966;Wetzel and Wollman, 1969;Wollman and Neve, 1971b], the cream hamster [Ketelbant-Ballasse and Neve, 1976], and the guinea pig \Zelander and Kirkeby, 1977Kirkeby, , 1978aKirkeby and Zelander, 1979]. A pre vious light microscopical study [Juhl, 1981] performed on 2-to 3-month-old and 12-to 14-month-old guinea pigs has shown that the second type of follicle (S-follicle) in this species is a complex, elongated, and dis torted structure positioned in the upper twothirds of the thyroid lobe. It may appropri ately be divided in an upper tubular part, a middle part subdivided into an irregular and a distended follicle and, furthermore, in a lower part which is tubular in the young ani mals and more follicle-like in the mature animals.…”

“…In order to recognize the S-follicle, every second section was preincubated for 30 min in a 0.02 M phos phate buffer containing an inhibitor (0.001 M HgClj) at pH 7.2 at room temperature, and thereafter incu bated for 1 min in a medium using a-naphthyl acetate as substrate and hexazonium pararosanilin as capture agent (Pearse, 1972], This method has previously been shown to demonstrate non-specific esterase activity in the cells of the S-follicle exclusively, whereas the reac tion is inhibited in all other thyroid cells [Kirkeby, 1976a, b;Zelander and Kirkeby, 1977;Juhl, 1981], Complete series of sections containing the S-follicle were thereafter selected for electron microscopy. The sections were handled as tissue blocks and postfixed for 1-2 h in O s04 (1%), treated with tannic acid, blockstained with uranyl acetate, dehydrated in a graded series of ethanol, and embedded in Epon 812.…”

“…This cell can clearly be distinguished from the S-follicle cell by means of its con tents of numerous widely dilated cisternae of rough-surfaced endoplasmic reticulum dispersed throughout the cytoplasm, and by absence of hemi-desmosomes and pinocytose vesicles in the basal part. As no secre tory granules and very few colloid-contain ing vacuoles are seen, these cells display an ultrastructure which is characteristic for a hypoactive thyroid follicle cell [Ekholm, 1964], In a previous paper [Juhl, 1981] it was suggested that the distended follicle may be regarded as a kind of mixed follicle [e.g., Calvert, 1975] as cells with a morphology and an enzymatic activity similar to those of thyroid follicle cells were observed in this part of the follicle at the light microscopic level. The finding of cells with an ultrastruc ture corresponding to that of thyroid follicle cells in the present study strongly supports this suggestion.…”

Histomorphology and Histochemistry of the Thyroid and Parathyroid Glands in Sheep - An Overview

“…Tsuchiya et al, (1984) observed that the thyroid follicles in pig were round or oval in shape, the large follicles being more common in the superficial regions of the thyroid gland. Juhl (1981) opined that in addition to the regular thyroid follicles, the second type of follicle (S follicle) was observed in the thyroid gland of the young and mature guinea pigs which consisted of an upper, middle and a lower part. The upper part was tubular.…”

“…The proportion of active colloid in pigs at the second week of age was lower than during the first week (Studzinski et al, 1979). Juhl (1981) stated that the colloid-like substance in the distended part of the second kind of follicles (S follicles) in guinea pigs appeared more diluted and somewhat granular in contrast to the homogenous more electrondense colloid in the thyroid follicles. Kelly et al, (1984) described that in the human thyroid, the colloid cells of Langendorff were slender cells with pyknotic nuclei and darkly stained cytoplasm that often appeared to be filled with the colloid.…”