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PubMed1975

Thyroid metabolism in the recessive sex-linked dwarf female chicken. 1. Age related changes in thyroid hormone synthesis and circulating thyroid hormone levels.

Age related changes in the levels of circulating thyroid hormones as well as the type of hormones synthesized in the thyroid glands from normal and sex-linked recessive dwarf, female chickens were studied. The impact of the presence of the dwarf gene on the parameters measured was minimal but significant alterations in the types of hormones produced in the thyroid gland with increasing age were observed. As the birds approached sexual maturity, the synthesis of triiodothyronine increased sharply such that the ratio of triiodothyronine (T3): tetraiodothyronine (T4) was approximately 15:1. This was in contrast to the T3:T4 ratio of younger birds which was approximately 0.7:1.0. This shift in hormone synthesis was reflected in relatively more circulating T3 in laying hens when compared with younger birds. It was also noted that four week old dwarf birds had higher circulating T3 values than those found for the normals.

Age Factors↗
PubMedDate not supplied

[The function of thyroid glands subjected to deep freezing (--196 degrees)].

The function of the thyroid gland transplanted after being frozen to --196 degrees C was studied in experiments on rats. The gland was transplanted to thyroidectomized animals. Glands frozen without the use of cryoprotective agents and also in the presence of a cryoprotector--polyethyleneoxide with a mol. wt. of 400 (PEO-400) were used. Besides, a study was made of the effect of different rates of chilling on the thyroid gland. In assessment of the gland function a determination was made of tissue respiration, of I-131 consumption, and blood thyroid hormone content. To assess the cryoprotective effect of PEO-400 and for the choice of its optimal concentration the NMR method and roentgenostructural analysis werea applied. The thyroid gland proved to take and to retain its capacity to hormone formation after its freezing to the temperature of --196 degrees C according to a special program in the presence of PEO-400.

Animals↗
PubMed1975

[Deiodase activity in rats following an overdose of thyroid hormone].

The L-DIT and L-T4 deiodinating activity in supernatants from liver or kidney homogenates of normal rats or rats loaded with T4, T3 or TSH, was investigated. Deiodination of L-DIT occurs in liver supernatants twice as much as in liver, referring to mg of protein of g of tissue, while the deiodination of L-T4 seems rather equal. The over all rate of deiodination, however, reaches in liver for L-DIT the threefold, for L-T4 the fivefold value, as compared with kidney. Short periods of loading do not alter deiodination of L-DIT in liver or kidney at all; but lead to significant elevation of L-T4-deiodination in liver tissue. Higher doses or longer periods of loading cause a significant rise of L-DIT-deiodination in liver and kidney, while the L-T4-deiodination in liver is significantly decreased and in kidney significantly elevated.

Animals↗
PubMed1975

[Thyroid gland function in heatstroke].

Development of thermal stroke in rats with the action of high external temperature (45 degrees C) was accompanied by a reduction of accumulation of I131 in the thyroid gland, a fall in the protein-bound-iodine--I131 and in the amount of thyroxin in the peripheral blood plasma, and also by a fall in the rate of disappearance from the blood of Nal131 injected intravenously. A relative decrease of the content of mono- and particularly of diiodthyrosines, and also, slightly, of iodthyronines occurred in the trypsine hydrolyzates of the thyroid gland at the moment of the thermal stroke development.

Animals↗
PubMedDate not supplied

[Effect of thyroid hormones on the calcium pump in sarcoplasmic reticulum].

In vitro thyroxine inhibited accumulation of Ca2+ by fragments of sarcoplasmic reticulum, isolated from rabbit sceletal muscles. The inhibitory effect of thyroxine was responsible for its direct action on Ca2+ dependent ATPase. Half-maximal inhibition of the enzymatic activity occurred at the same concentrations of thyroxine using both membrane-bound and highly purified solubilized forms of Ca2+-ATPase (15--20 micrometer and 10 micrometer of the hormone, respectively). Triiodothyronine was similar in the effect but not diiodothyrosine, which did not possess the hormonal activity. The data obtained suggest that thyroid hormones affect the mechanism of dephosphorylation in ATP-hydrolase reaction.

Animals↗