The functional state of the thyroid gland following partial pancreatectomy]

In Wistar rats a study was made of a functional condition of the thyroid gland 1, 6 and 24 hours after partial pancreatectomy. The following signs-served as criteria of a functional condition of the gland: the amount of neutrone-activated iodine in iron, iodine-absorptive capacity of the gland by I131, the amount of protein-bound stable and radioactive iodine in the blood, a morphological condition of the gland structures. It was demonstrated that, despite the initial intensification of the process of synthesis and secretion in the thyroid gland, its secretory activity fell by the end of the experiment. This reduction is regarded as an adaptive response to partial insulin deficiency.     

Functional state of the thyroid gland during systemic graft vs host reaction

Triiodothyronine (T3), thyroxine (T4) and thyroid stimulating hormone (TSH) serum content was measured in mice during systemic "graft-versus-host" reaction (GVHR), using radioimmunoassay. It was demonstrated that on the 3rd day after GVHR induction the levels of these hormones did not differ from the control values. T3 and T4 concentrations and 125I absorption by thyroid gland diminished by day 10. At the same time TSH level remained unchanged. On day 24 after GVHR induction T3 and T4 content was significantly reduced, although TSH concentration exceeded the control value. 125I absorption was enhanced as compared to the value observed on day 10. The data obtained show the vigorous inhibition of thyroid gland function during systemic GVHR.     

Functional significance of the thyroid gland

On the basis of literature data and our own findings, the paper presents the current concepts of the production, secretion, transport, catabolism, mechanisms of action, and effects in the organism of thyroid hormones during eu-, hypo-, and hyperthyrosis. The nervous, humoral, and immune mechanisms of regulation of the secretory activity of the thyroid gland and changes in its functional activity in ontogenesis are discussed.     

Functional and morphological characterization of rat thyroid gland at remote periods following single high and low dose radiation exposure

A study of the morphological structure and functional activity of the rat thyroid gland was carried out after 22 months following a single exposure to external radiation. The 3-month-old animals were irradiated with doses of 0.25, 0.5, 1.0, 2.0 and 5.0 Gy. Blood was assayed for thyroxin (T4) and triiodothyronine (T3) levels, while liver tissue--for NADP-MDH activity and thyroid tissue--for thyroperoxidase activity. The thyroid was studied histologically, morphometrically and by electron microscope. The decreased T4 concentrations 2.59-fold in the 5.0 Gy group, the increased T3/T4 in the 2.0 and 0.25 Gy groups, the reduced diameter of cellular nuclei and follicles, the flat follicular epithelium and diminished number of thyrocyte ultrastructures indicate thyroid hypofunction in the irradiated animals. The morphological changes are characterized by enhanced diffuse and focal sclerotic changes in thyroid, most pronounced at high irradiation doses (1.0-5.0 Gy), whereas the hemosiderosis foci suggest that the structural changes are consequences of radiation-induced destructive injuries in the gland parenchyma. Two of the thyroids (0.5 Gy) demonstrate foci with pronounced lymphoid infiltration, while follicular carcinomas were detected in 4 thyroids (2.0 Gy), and in one thyroid (0.5 Gy) in one thyroid (5.0 Gy). The remote effects of radiation were dose-dependent destructive, sclerotic and atrophic processes, decreased functional activity, stimulation of development of autoimmune aggression and carcinogenesis in thyroid.     

Functional state of the thyroid gland in the postnatal period in mink of different genotypes]

The thyroid gland functional state was studied by means of 131J-triiodothyronine in minks of two genotypes. The thyroid activity in the standard (dark brown) minks increased from the 3--4th month of postnatal ontogenesis (July--August) and decreased gradually by the 6th month (november). Similar changes in the thyroid activity were found in the Hedlung (white) minks as well. Their thyroid activity was, however, markedly higher on the 3rd month than in the standard minks.     

Structural-functional state of the thyroid gland after thymectomy]

The dynamics of morphologic and biochemical indices of the thyroid gland in puberal rats has been considered. The data obtained suggest that the thymus hormones deficiency in blood circulation after thymectomy affect thyroid-stimulating functions of adenopituitary and thyroliberin production in hypothalamus that results in significant depression of thyroid function, whereas the enhancement of thyroid function to 20-month follow-up has no central genesis but is rather a result of autoimmune processes activation when thymus is removed.     

Postradiation changes in the thyroid gland and skeletal muscle after exposure to iodine-131

The functional status of rat skeletal muscles was studied at dormancy and during the intensive muscular work under conditions of repeated administration of iodine 131 in doses causing reversible and irreversible damages to thyroid gland (the absorbed doses were from 0.27 to 266 Gy). The biochemical changes in muscles were transient; they correlated with the thyroid gland status and lifetime of animals and were displayed during the first 15 days and 2-12 months after the start of the isotope injection.