[Physiological basis of goiter transformation of the thyroid gland and the pathogenesis of euthyroid goiter].

Endemic goiter disease develops as a result of iodine insufficiency in the environment, that induces advancing reproduction of thyrocytes realized by endomitosis. Eventually goiter-transformed gland ceases responding to the lack of iodine in the environment, that is due to the destruction of thyrocyte ++thyroreceptors. It should be taken into account that goiter disease depends upon the female sexual hormones.

[Characteristics of thyrocyte multiplication in proliferating thyroid epithelium].

Although the thyroid parenchyma is characterized by high proliferative ability, mitoses in it are seldom observed. Earlier it was considered that the main type of thyrocyte reproduction was amitotic division. However, biochemical investigations of late showed that the thyroid parenchyma during rapid growth in tissue culture intensively incorporated thymidine, this being an evidence of DNA replication indicating mitoses.

[Correlations between the functional activity and proliferation of the thyroid parenchyma. The proliferative forms of the parenchyma of the thyroid].

Multiple thyroid adenomas formed by straight or coiled epithelial cords developed in experiments on adult male rats as a result of prolonged intermittent 6-MTU administration. Such epithelial cords could be sometimes observed in thyroid parenchyma regeneration after partial thyroidectomy. These cords originated from thyrocytes of the follicle epithelium.

[Use of luminescence microspectral analysis for evaluating the synthetic activity of testicular incretory cells].

A study was made of the synthetic activity of Leydig's cells in the testes of rabbit fetuses at different stages of intrauterine development by the method of luminescent microspectral analysis and the results were compared with the level of testosterone determined by a radioimmunoassay in the blood plasma of these fetuses. The data obtained by both methods showed correlation. A conclusion has been made as to a possibility of the use of the luminescent microspectral method to study the synthetic activity of cells of the endocrine glands.

[Interrelation of prolactin and calcitonin].

Intraperitoneal prolactin injection (3.5 U/200 g bw, daily, for 5 days) caused a marked rise in blood calcitonin concentration in female Wistar rats. It is common knowledge that exogenous calcitonin administration results in an obvious drop of blood prolactin level.

Effect of thymus on the thyroid and pituitary thyrotropic function.

Thymus inflammation induced in infantile guinea pigs and rabbits by administration of melted paraffin drops into the thymic parenchyma resulted in enhancement of the thyroid functional activity. Thymosin injections provoked an identical effect. In both variants of these experiments the pituitary thyrotropin level remained within the norm.

[Factor inhibiting gonocyte division in the testes of the rabbit fetus].

A factor of protein nature selectively inhibiting the division of gonocytes was isolated from the extracts of testes of the 27 and 29 day old rabbit foetuses by the method of gel-chromatography with Sephadex G-100. Its molecular mass equals 30 000. This factor is also present in the testes of newborn, one month old and adult rabbits.

[Role of the thyroid hormone in the functioning of the hypophyseal-adrenal-gonad system of rabbits].

The influence of a long-term T4 injection on the gonadal and adrenal androgenic function as well as on the hypophyseal gonadotropic activity was studied in experiments on adult male rabbits, using histological and hormonal methods. It was shown that in rabbits with experimental moderate thyroxin toxicosis the testicular testosterone secretion is inhibited, whereas the adrenal testosterone secretion is compensatory enhanced. The level of hypophyseal gonadotropins tends to rise.

[An inhibin-like factor in the testes of fetal and newborn rats].

A factor of protein nature that inhibits the proliferation of gonocytes and, probably, their ingress into meiosis and stimulates the development of some components of the blood-testicular barrier was isolated from the testis of 19-20-day-old fetuses and young rats of the first two weeks of life. It is assumed that the inhibin-like factor is formed in the testicular network. The time at which the receptors for the factor under discussion may occur in the cells of the testis of Wistar rat fetuses is discussed.

[Parafollicular cells in the regenerating thyroid gland].

Ten days after partial thyroidectomy (excision of the lower half of the thyroid left lobe) made in mature male rabbits, functional activity of thyrocytes markedly rose. That was the organism compensatory reaction to the decreased thyroid hormone production due to the enhancement of the pituitary thyrotropin secretion. However, parafollicular cells detected by the Sawicki method underwent reduction in the number and size, which was fairly appreciable in the regenerating thyroid lobe and insignificant in the lobe left intact.

[Sex differences in the development of the thyroid gland in human prenatal ontogeny].

A comparative study of the thyroid gland development in the human male and female embryos and prefoetuses was carried out. The development of incretory part of the testicles was shown to occur earlier than the differentiation of follicles in the thyroid gland and the appearance of colloid in it. Sexual differences were noted in the appearance of follicles, connective tissue, nerve fibres in the thyroid gland (earlier in the male foetuses).

[Effect of the male sex hormone and its 5 alpha-reduced metabolites on the function of the thyroid in vivo and in vitro].

The administration of testosterone propionate, dihydrotestosterone and androstandiol to male rats was followed by different changes in thyroid function. Testosterone propionate exerted a stimulating effect, whereas its metabolites induced marked depression of thyroid functional activity in the experiments in vivo. In vitro both sex hormones and 5-alpha-reduced metabolites inhibited radioactive iodine absorption by rat thyroid slices and human thyrotoxic struma.

[Mechanism of androgenopoiesis disorder in stress].

Experiments on pubertal male rabbits were made to study the effect of prolonged stress (daily one-hour immobilization and electrocutaneous stimulation for a fortnight) on hormonal and structural gonadal function. The prolonged action of stress was shown to result in the drastically lowered testicular androgenopoiesis. Inhibition of testosterone secretion by the tests was not determined by structural disorders of the hormone-producing Leydig cells which were functionally activated under the conditions described.

[Effect of sympathetic impulses on parafollicular cells (K-cells) of the thyroid gland].

Reaction of K-cells (detectable by the Savitsky method) to stimulation of the superior cervical sympathetic ganglia or to their removal was examined in experiments on male rabbits. Stimulation of the sympathetic ganglia attained as a result of application to them of a ringlet made of solid silver wire produced a marked rise of the number and size of K-cells, with the serotonin content in the thyroid gland being significantly increased as compared to the initial level. Bilateral cervical sympathectomy entailed a reduction in the serotonin content and in the size of K-cells.

[Pathogenetic problems of goiter].

The extrafollicular growth (hyperplasia) of the thyroid parenchyma resulting in the development of epithelial goiter begins with proliferation of thyrocytes of the follicular wall (sometimes called "clear cells" and erroneously identified with the parafollicular cells or C-cells). An important role in the pathogenesis of goiter disease belongs to the transition of the thyroid parenchyma hyperplasia from the initial adaptative (compensatory) reaction which arises under conditions of thyroid hormone production deficiency into the irreversible pathological process of indefinite duration after restoration of the euthyroid state of the patient. It may be assumed that this transition results from stabilization of gradually increasing shift of protein biosynthesis in the thyrocytes towards preferential thyroalbumin formation at the expense of thyroglobulin.

[Current problems of pathogenesis of thyrotoxicosis].

According to current concepts, thyrotoxicosis should be regarded as an autoimmune disease in which signs of a delayed type of hypersensitivity are found. The functional excitation of the thyroid gland is caused and maintained by the appearance of lymphocytes sensitized for responding to autoantigens of thyrocytes and for production of thyrostimulating autoantibodies. The course of thyrotoxicosis is aggravated by the disorder of homeostatic mechanisms which normally oppose the hyperfunction of the thyroid gland and the effect of the excess of thyroid hormones.

[Functional and structural changes in the adrenal cortex of rabbits under conditions of chronic inflammation of the prostate gland].

Investigation of the state of the rabbit adrenal cortex under conditions of depression of the incretory activity of the testicles resulting from chronic inflammation of the prostate showed progressive hyperplasia of the reticular zone of the adrenal cortex; as to the glomerular zone, it failed to display any marked pathological changes, and the fascicular zone demonstrated some signs of hypoplasia. Thus, the normal or elevated androgen excretion observed in the experimental male rabbits, was provided by an intensified activity of the reticular zone of the adrenal cortex, despite a decrease in testosterone biosynthesis in the testes.

[Catecholamine concentration in the hypothalamus following alteration of pituitary adrenocorticotropic function].

Norepinephrine, epinephrine and serotonin levels were studied in male rabbit hypothalamus and midbrain under the influence of different factors potentiating the hypophysial adrenocorticotropic function. Intensification of this adrenohypophysial function was accompanied by a certain decrease in the hypothalamic and midbrain norepinephrine level and by the appearance of epinephrine normally absent here. The role of serotonin in the regulation of the investigated pituitary function was not revealed since potentiation of this function was observed both with the lowered and with the elevated concentrations of this monoamine in the hypothalamus.