Light and Electron Microscopic Study of the Thyroid Gland of the Camel (Camelus dromedarius)

Abstract

The thyroid gland of sexually immature dromedary camels was studied using both light and electron microscopy. The thyroid gland contained follicles of different sizes in both summer and winter. However, most of the follicles were large in summer and small in winter. The large follicles were lined by very low cuboidal or semi-squamous follicular cells whereas the small ones were lined by high cuboidal or low columnar follicular cells. Electron microscopy showed that the very low cuboidal follicular cells were poor in organelles and were considered hypoactive. High cuboidal follicular cells on the other hand, were rich in organelles that included mitochondria, cisternae of rough endoplasmic reticulum, secretory vesicles, colloid droplets, heterosomes and autophagic vacuoles; they were considered to be very active. The possible role played by these organelles is synthesis of thyroglobulin and liberation of tri- and tetraiodothyronine is discussed. A few degenerate follicular cells were infrequently encountered in the camel thyroid. Parafollicular (C) cells were not seen in this study either with light or electron microscopy.

Secretory Processes in Follicular Cells of the Thyroid Gland of the Indian Sheath-tailed Bat, Taphozous longimanus (Hardwicke): A Ultrastructural Study

“…The follicular cells of large follicles are synthetically inactive during late pregnancy. Similar observations are reported in thyroid glands of camels during summer (Abdel-Magied et al 2000) and in wood chuck, Marmota monax during winter (Krupp et al 1977).…”

“…Seasonal variation in the morphology of the thyroid gland has been studied in many mammals (Krupp et al 1977, Atoji et al 1999, Shimokawa et al 2002, Abdel-Magied et al 2000. They reported similar ultrastructural features of thyroid gland as in T. longimanus supporting present observations.…”

Ultrastructure of the Thyroid Gland in Adult West African Dwarf Goat (Capra hircus)

“…These variations may be due to species and climatic differences. The thyroid of goat possesses features as seen in some domestic animals studied like sheep, camel (Abdel-Magied et al, 2000;Mubarak & Sayed, 2005). These features included the presence of few stunted microvilli, highly dilated cisternae of rough endoplasmic reticulum and abundance of apical vesicles, colloid droplets and lysosomes in the cytoplasm of follicular cells.…”

Histologic and ultrastructural observations on the thyroid gland of the White Fulani (Zebu) cattle in Northern Nigeria

“…Lysosomal digestion of colloid droplets facilitates the release of T3 and T 4 hormones from colloid droplets into the follicular cell cytoplasm (Norris, 2007), which will then be actively secreted into the adjacent capillary bed at the base of the cell. The presence of colloid droplets have been also described in several mammals (Fujita, 1975), including sexually immature camel (Camelus dromedarius) (Abdel-Magied et al, 2000) and several cold-blooded vertebrates (Lynn and Wachowski, 1951).…”