Electron Microscopic Studies on the Development of the Thyroid Gland of the Chick Embryo

Light and electron microscope study on developing intestinal mucosa in rat fetuses with special reference to the obliteration of the intestinal lumen.

“…In short, morphological events during the formation and enlargement of the intra-epithelial cavity involve the formation of a macula occludens, formation of the intra-epithelial cavity within the macula occludens and an increase in cell numbers surrounding the cavity by mitosis. Similar phenomena were observed during the formation and enlargement of thyroid follicles (FUJITA and TANIZAWA, 1966;ISHIMURA and FUJITA, 1979). Cell degeneration, often found during the stage of obliteration (MATHAN et al, 1976;MOXEY and TRIER, 1978;NAKAMURA and KOMURO, 1983; the present study), seems to assist in making space for the enlargement of the intraepithelial cavity and the main intestinal lumen.…”

Ultrastructural and Cytochemical Studies on the Thyroid Gland of Normal Metamorphosing Frogs (<i>Rana japonica</i> Guenther)

“…The primitive follicle lumens appear between adjacent cells near the Golgi field and many vesicles occur around the lumen. Similar results were published by FUJITA and TANIZAWA (1966) about the chick embryo. In addition numerous lysosomes appear, probably to digest the pigment granules which exist abundantly in the cytoplasm in early developing stages.…”

“…In early development of the frog thyroid gland, the thyroid anlage cells involve many lipid droplets, yolk droplets and pigment granules. This is contrasted by the fact that no lipid droplets, yolk droplets and pigment granules are found in the thyroid cells of the rat embryo (ISHIKAWA, 1965) and chick embryo (FUJITA and TANIZAWA, 1966). The development of other cytoorganellae in the thyroid cell is very poor both in the larval frog and in the rat and chick embryo.…”

Electron Microscopic Observations on the Thyroid Gland of Two Species of Teleost, <i>Semicossyphus reticulatus</i> and <i>Sebastiscus marmoratus</i>

“…In the lamprey thyroid , the follicle cells, some of which are ciliated, have (FUJITA and TANIZAWA 1966), and by the electron microscopic studies of 125I radioautography of the mouse (FUJITA 1968), FUJITA has denied his old opinion and has believed that the large less dense or large dense droplets correspond to a reabsorbed material in the higher vertebrate thyroid. From this view, the large less dense or dense droplets in the fish thyroid are also considered to be the reabsorbed material.…”