[Effect of the genotype on the reactivity of the hypothalamo-hypophyseal-adrenal system of chick embryos].

Studies have been made on embryos of two hen lines selected by their reaction to cold stress (highly and lowly reactive ones). The adrenals of 16-day chick embryo react to the injection of the ACTH by synthesis of glucocorticoids and by their secretion into the blood. The rate of this reaction is higher in highly reactive line of hens.

[Formation of a reaction of the hypothalamo-hypophyseal-adrenal cortex system to cooling in chick embryogenesis].

The content of glucocorticoids in the suprarenals and blood of chick embryos increased from the 12th till the 15th day of incubation. The intensive accumulation of glucocorticoids in the glands was accompanied by a relatively small increase of their concentration in blood plasma from the 15th till the 19th day. No adrenocortical reaction to cooling was registered in the 12 and 13 days old embryos.

[Imprinting of temperature effects in the embryogenesis of the hypothalamo-hypophyseal-adrenal system of domestic hens].

Three groups of chick embryos were subjected to periodic cold exposures at the 1st (I), 2nd (II) and 3rd (III) weeks of incubation. Within the first month after hatching, glucocorticoid content of the blood plasma was measured in chicks. The reaction of the adrenals to corticotropin was checked in 2-month chicks.

[Detection of the critical period of pituitary-adrenal system development during postembryonic chicken ontogenesis].

Studies have been made on postembryonic development of the hypophyseal-adrenal system in domestic hens. Most significant functional rearrangements were observed at the 3rd week of life, when corticosteroid content of the blood plasma decreased threefold. Birds subjected to a series of cold stresses at this time, exhibited more rapid sexual maturation, more rapid reaction of the adrenals to exogenous corticotropin and higher resistance to unfavourable factors.