Ultrastructure of the thyroid in dwarf mice

Abstract

The thyroid gland of Snell's dwarf mice consists of small follicles with flattened epithelium, partly differentiated cords and undifferentiated masses. Many adipocytes are found. The ultimobranchial cysts are well developed. Parafollicular cells are normal. In the partly organized cords, microfollicular cells are some small follicles limited by two or three cells are seen. The presence of these structures led us to think that they represent the first stages of normal folliculogenesis, described as the fusion of two adjacent unicellular microfollicles. Their further growth is the result of the coalescing of small adjacent follicles or of cellular multiplication. The presence of undifferentiated masses and partly differentiated cords, in dwarf mice, seems due to a developmental arrest rather than to aberrant development. This disorder of organogenesis is ascribed mainly to a lack of pituitary growth hormone.

Defining thyrotropin-dependent and -independent steps of thyroid hormone synthesis by using thyrotropin receptor-null mice

“…Several lines of hypothyroid mice are studied today, for example, the Snell Dwarf mouse (27), the cog mouse (28), and the hyt mouse (13). Of the preexisting models, the hyt mouse is the only model of hypothyroidism resulting from a TSHR mutation.…”

Hormonal and other Inherited Growth Disturbances in Mice with Special Reference to the Snell Dwarf Mouse.

“…The defect is limited to the follicles, the C-cells are not disturbed (12,81,82,89,136,147,250,253). Follicles are small with flattened epithelium, as in hypophysectomized rats and mice.…”

Thyroid Calcitonin Cells and Unusual Follicles in the Fox

“…It has been reported that in the guinea pig [Klapper, 1946], mouse [ Wetzel and Wollman, 1969] and rat Wollman and Neve, 1971;Krupp, 1972;Calvert, 1975] the UBB gives rise to ultimobranchial cysts. Cordier et al [1976] believed that these cysts in dwarf mice are the endodermal remnants of the UBB after the migration of parafollicular cells. However, the final fate of ultimobranchial cells is yet to be deter mined in mammals [Booth and Ghoshal, 1978],…”