Biomedical subjects

N Daugeras-Bernard

Publications and source records attributed to N Daugeras-Bernard.

5 recordsLinked to original sources

PubMed1993

Excess iodide and thyroid function in the developing chick embryo.

The effects of adding excess iodide (I-) to egg yolks were studied on the quantity of iodide transferred to the chick embryo and on thyroid function from Days 8 to 18 of incubation. Following injection of either 0.5 or 1 mg of iodide into the yolk on the second day of incubation, embryonic plasma iodine levels increased significantly over levels of controls at the same age. These increases were proportional to the amount of excess iodide in the yolk. Moreover, a constant ratio between the iodine levels of the allantoic fluid and the plasma was maintained for any given day of incubation. Up to Day 10, the iodine content of the embryonic thyroid was closely correlated with the increased plasma iodine concentrations. After Day 10, concomitant with the establishment of the hypothalamo-adenohypophyseal-thyroid axis, the increase in thyroid iodine no longer paralleled that of plasma iodine, but was only twice that of controls. As thyroid weight doubled in these treated embryos, thyroid iodine concentrations of control and treated embryos were similar. Iodide excess did not block thyroid iodine organification, nor was there any modification of iodine distribution among the different iodo-amino acids. Moreover, despite the doubling of thyroid hormone content in the goiters of treated embryos, circulating levels of thyroid hormones in control and treated embryos were not different.

Allantois↗

PubMed1991

Gene transfer into intact vertebrate embryos.

Intact chick embryos at 40 h incubation were transfected in vivo with chimeric vectors expressing chloramphenicol acetyl transferase (CAT) under different promoter sequences. The cationic lipid, dioctadecylamidoglycyl spermine (DOGS) used as the transfecting agent had no noticeable toxic effects on embryonic development. CAT activity was monitored 48 h post-transfection on homogenates of embryos dissected free of all annexes. Of the various constructs tested, those containing the AP-1 response element linked to CAT (TRE-tk-CAT) gave high expression and consistent enzyme responses within groups. Co-transfection experiments in which embryos were exposed simultaneously to a CAT vector containing the cAMP response element and to a vector expressing the catalytic subunit of protein kinase A showed that the promoters of the introduced genes can be regulated by their respective transacting factors. This method may therefore represent a general tool for introducing genes into intact vertebrate embryos at precise developmental times.

Animals↗

PubMed1980

Iodine supply to the thyroid gland in the developing chick embryo.

During embryonic development of the chick it was found that 81% of the iodine deposited in the egg yolk, principally in the form of iodine, I-, was transferred to the embryo. Changes in plasma iodide levels, [I-], showed that transport is low between days 8 and 9 of incubation ([I-] = 2 micrograms/dl) and increased from day 10 ([I-] = 3 micrograms/dl) to day 20 ([I-] = 77 micrograms/dl). This increase of [I-], coupled with an increase in total blood flow through the thyroid gland, results in an increasing supply of iodide to the thyroid throughout the incubation period. Our results and those of other workers suggest the existence of bidirectional exchanges of iodide between the embryo and the yolk which may be under pituitary control.

Animals↗

PubMed1980

[Thyroid function and iodine metabolism in the chicken embryo].

Iodine is accumulated in the egg yolk during oogenesis. It is transferred during incubation through the walls of the yolk sac (extraembryonic endomesoderm surrounding the yolk) to the extraembryonic, and thence to the embryonic circulation. Iodine exchanges would probably occur between both compartments, the egg yolk and the embryonic blood in which the iodine level increases from day 10 to 20 of incubation. The increase of thyroid gland iodine content parallels that of the plasma iodine level. Our results suggested that the pituitary gland, which acts directly on the developing thyroid gland, might also influence the iodine exchanges across the yolk sac wall, thereby affecting the thyroid by increasing the iodine supply.

Animals↗

PubMed1976

[Course of thyroxinemia during the development of the chick embryo. Influence of hypophysectomy].

Plasma thyroxine (T4) level of intact and hypophysectomized Chick embryos has been determined for the incubation interval 10 to 18 days. T4, which is the main circulating thyroid hormone, exists as early as day 10. The plasma T4 level of controls increases as power function of time from day 10 to day 17. Hypophysectomy (on day 2) produces a decrease of the plasma T4 level, but only from day 11, which accounts for the beginning of a pituitary control of the thyroid secretion after day 10.

Animals↗