. Electron microscopy; proceedings of the Stockholm Conference, September, 1956. Electron microscopy. Chick Embryo Thyroid 175. Fig. 3. Tli>roi(.i from a just-hatched chick. The canalicular structures are well developed. In the apical part of some cells, osmiophilic granules and vacuoles, developed from canaliculi, are scattered. Note a sinusoidal capillary with endothelial cells. Magnification - follicles ditVcrcnliatc and colloid develops (17, 21). Interrelationships exist between these two groups of phenomena (18). Indeed, previous works on the thyroid of adult mammals ha\c shown that th
. Electron microscopy; proceedings of the Stockholm Conference, September, 1956. Electron microscopy. Chick Embryo Thyroid 175. Fig. 3. Tli>roi(.i from a just-hatched chick. The canalicular structures are well developed. In the apical part of some cells, osmiophilic granules and vacuoles, developed from canaliculi, are scattered. Note a sinusoidal capillary with endothelial cells. Magnification - follicles ditVcrcnliatc and colloid develops (17, 21). Interrelationships exist between these two groups of phenomena (18). Indeed, previous works on the thyroid of adult mammals ha\c shown that the radioiodine is included in the follicular colloid, after a short passage through the glandular cells (II, 12). The radioiodinc is also stored in ihc colloid of the chick embryo thyroid (10). The iodine metabolism o\ the th\roid is therefore related to the colloid whose synthesis follows the apparition o\ the canalicular structures. Their sudden extension, between 12 and 13 days, explains the rapid increase of colloid dcsclopment and radioiodine uptake. The factors governing the formation of the cana- liculi are an interesting subject for research. The most important point seems to be the embryonic hypophysis as shown by the use of thyroxine and tetramethyl thiourea. Indeed, following treatment with thyroxine, the formation of canaliculi and, consequently, the col- loid elaboration are strongly inhibited. This hor- mone is known to act by the way o\ the hypophysis whose thyrotrophic function is reduced by a high level of thyroxine. On the other hand, the antithyroid compound produces an excessive canalicular devel- opment. This is due to the increase of the whose high level is demonstrated by the hypertrophy of the chick embryo thyroid (I, 8). In conclusion, the development of the canalicular structures depends on the hypophysis which so controls the histophysiological differentiation of the thyroid, after 12 days. This explains the modifications of the embryonic thyroi
Size: 1567px × 1595px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookcollectionameri, bookcollectionbiodiversity
