Immunoelectron microscopic demonstration of thyroglobulin and thyroid hormones in rat thyroid gland

We have developed a post-embedding immunogold technique for electron microscopic localization and quantitation of thyroglobulin (TG), thyroxine (T4), and triiodothyronine (T3) in rat thyroid. Labeling for TG was located on rough endoplasmic reticulum, Golgi apparatus, exocytotic vesicles, luminal colloid, colloid droplets, and lysosomes, whereas labeling for thyroid hormones was located on luminal colloid, colloid droplets, and lysosomes. We tested different procedures of fixation, dehydration, embedding, polymerization, and immunoincubation to optimize ultrastructural preservation and immunolabeling. Fixation with glutaraldehyde and osmium was possible with retained antigenicity. Dehydration temperature and the choice of embedding resin were the two crucial factors for good immunolabeling. Low-temperature dehydration greatly improved immunolabeling and could be combined with embedding in the methacrylate LR White or the epoxide Agar 100 (equivalent of Epon 812) polymerized at 40-60 degrees C, as the temperature during subsequent embedding and polymerization was of little importance for the immunoreactivity. Labeling on LR White sections was always higher than on Agar 100 sections. Various etching procedures were tested without improved specific labeling. Etching with hydrochloric acid gave nonspecific labeling of certain cell compartments.     

Molecular weight of the thyroglobulin messenger RNA of sheep thyroid gland

Poly(A)+ mRNA from sheep thyroid total or thyroglobulin-specific polysomes obtained by immunological precipitation, was purified by two cycles of chromatography on oligo(dT)-cellulose. Upon electrophoresis in 98 % formamide-polyacrylamide gels, the purified RNA showed a major species of M_r 2.8×10⁶. The correlation found between the very high concentration of this species and its thyroglobulin messenger activity in the reticulocyte lysate protein synthesis system demonstrates that the thyroglobulin mRNA contains enough bases to code for the thyroglobulin peptide chain (M_r 300 000).     

Morphological study of the neurosecretory hypothalamo-hypophyseal system and thyroid gland in intestinal carcinogenesis]

Pathomorphology of the neurosecretory hypothalamo-hypophyseal system and the thyroid gland of 150 rats of both sexes was investigated in intestinal carcinogenesis induced by 1.2-dimethyl hydrazine. Inhibition of the neurosecretory activity of paraventricular and supraoptical nuclei as well as atrophic changes in th: thyroid gland were found to be associated with the latent period of carcinogenesis. The arising of the intestinal tumor is accompanied by hypertrophy of neurons and their nuclei, by a decrease in the neurosecretory substance content and the thyroid gland tendency to return to normal. The tumor spreading provoked neuron hypertrophy and the reduction of the neurosecretory substance as well and pronounced atrophic changes in the thyroid gland.     

Content of thyroglobulin polyribosomes in normal and pathological thyroid cells]

The content of individual thyreoglobulin (TG) polyribosomes in human thyroid gland was studied in healthy persons and in patients with thyroid pathology. The content of TG polyribosomes makes up to 16.2% in normal thyroid tissue and is found to decrease down to 7.8% and 7% under nodal euthyroid goiter and toxic adenoma, respectively. This content is decreased to 12.5% under diffuse toxic goiter and is intermediate between nodal and diffuse toxic goiter under mixed goiter (9.4%).     

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.