Showing papers on "Iodine published in 1989"

Excess iodide inhibits the thyroid by multiple mechanisms

Abstract: The many nonsubstrate effects of iodide in the thyroid appear to be due to at least four mechanisms: 1) a possible anion effect of iodide for which the supporting data are conflicting; 2) an inhibition of organic iodine formation (the so-called Wolff-Chaikoff effect); 3) the iodination of critical enzymes in the thyroid gland; and 4) the inhibition of cellular processes by iodinated products such as oxidized iodine itself, or an oxidation reaction involving iodine. The separation into these categories is not firm, but circumstantial evidence suggests that the mechanisms are different. In addition, high levels of iodide will saturate the iodide pump (Ki ≈3×10−5M) (1). In this case, however, the amounts of iodide which enter the thyroid cell remain large, despite transport saturation and are replaced by diffused iodide. Hence this subject will not be discussed here.

Iodine Inhibits the Proliferation of Rat Thyroid Cells in Culture

Abstract: We have explored the mechanisms whereby iodine inhibits thyroid growth using as models both the FRTL5 line of rat thyroid follicular cells that require TSH for growth and the M12 line of mutant cells that grow in the absence of TSH. Between 0.01-1.0 mM, NaI produced a dose-dependent inhibition of TSH stimulation of [3H]thymidine incorporation and replication in FRTL5 cells as well as spontaneous growth in M12 cells. Iodide also inhibited the cAMP-dependent growth of FRTL5 cells induced by forskolin and (Bu)2cAMP, as well as the cAMP-independent mitogenesis induced by insulin-like growth factor-I. The effect of iodide to inhibit both TSH- and insulin-like growth factor-I-stimulated growth in FRTL5 cells was abolished by concomitant culture with methimazole, and no iodide inhibition of growth was observed in L6 myoblasts and BRL 30E hepatocytes. Exposure of cells to iodide under conditions that resulted in inhibition of TSH-stimulated growth did not significantly alter the ability of TSH to increase the intracellular cAMP concentration, nor did iodide alter two responses to TSH in FRTL5 cells that depend upon an increase in cAMP concentration: down-regulation of TSH receptor and cytoskeletal reorganization. We conclude that iodide exerts its inhibitory action on the growth of thyroid cells at multiple loci related to both the cAMP-dependent and cAMP-independent pathways of mitogenic regulation.

Alterations in Thyroid Blood Flow Induced by Varying Levels of Iodine Intake in the Rat

Abstract: Thyroid hormone biosynthesis depends upon the presence of adequate amounts of thyroidal iodine, and during fluctuations in dietary iodine intake, relatively constant thyroid hormone levels are maintained by various homeostatic mechanisms. These mechanisms include an enhancement of iodide pump efficiency and organification when iodine intake is limited, and significant decreases in iodide uptake and hormone synthesis when excess iodine intake occurs. The present study was designed to determine whether acclimation to different dietary iodine regimens is associated with changes in thyroid blood flow and to assess the time course of any such alterations in relation to pituitary-thyroid axis hormone levels. Male Sprague-Dawley rats were fed a diet containing low (LID), high (HID), or normal (CTR) iodine concentrations. Three, 7, 14, or 133 days after starting these dietary regimens, the animals were anesthetized with ketamine/pentobarbital, and thyroid blood flows were assessed using the reference sample version of the microsphere technique. At the same times and at weekly intervals throughout the 133 days of treatment, blood samples for the determination of TSH, T4, and T3 levels were obtained. Additionally, thyroidal immunoreactive vasoactive intestinal peptide (VIP) was measured at the end of the experiments. LID treatment increased thyroid blood flows to 240%, 350%, and 240% of levels in control rats at 7, 14, and 133 days of treatment, respectively. Thyroid weight was also elevated above levels in control animals at each of these times. A slight decrease in plasma T4 levels occurred over the 133 days of LID treatment; however, this dietary regimen did not alter circulating levels of T3 or TSH or thyroidal VIP concentration. HID treatment had opposite effects, in general, to those of LID. Thyroid blood flows were decreased by 34%, 56%, 46%, and 35% after 3, 7, 14, and 133 days of treatment with HID, respectively. Circulating levels of T4 were increased over the 133 days of HID treatment, whereas plasma levels of T3 and TSH and thyroid weights remained unchanged from those in control rats over this period of study. A small decrease in thyroidal VIP concentrations coincident with the decrease in thyroid blood flow was observed at the beginning of the HID treatment. Neither LID nor HID had any effect on blood pressure, cardiac output, or blood flow in other organs. These data demonstrate that acclimation to changes in dietary iodine intake in the rat include alterations in thyroid blood flow which are reciprocal to the iodine intake level and appear to be independent of circulating TSH levels.

Demonstration of Phenolic Compounds in Plant Tissues by An Osmium-Iodide Postfixation Procedure

Abstract: A simple procedure to stain phenols in plant tissues is described. Postfixation with an aqueous solution prepared by mixing 2 cc of 2% osmium tetroxide and 8 cc of 3% potassium iodide yields brilliant visualization of phenol-containing vacuoles in different tissues of plants (e.g., coffee, oak, tobacco and spruce) bearing high concentration of phenolic compounds. Areas bearing phenols become dark gray to black. Chemical experiments demonstrate that osmium-potassium iodide (Os-KI) mixture reacts rapidly with several naturally occurring plant phenols, developing black solutions from which black solids precipitate. Phenols containing omicron-dihydroxy groups react with Os-KI solution more rapidly than other structurally different phenols. Therefore, omicron-dihydroxy units in an aromatic ring seem to function as primary sites of reactivity with the osmium-iodide complexes.

Treatment of iodine deficiency diseases

Abstract: This invention relates to a composition for use in the treatment or prevention of iodine deficiency diseases or disorders such as fibrocystic dysplasia of the breast, breast cancer, endometriosis, ovarian cysts and premenstrual syndrome. More particularly, this invention relates to a composition for the treatment or prevention of iodine deficiency diseases or disorders, the composition comprising elemental iodine (I 2 ) which may also be referred to as metallic iodine or iodine metal. The elemental iodine can be used with any pharmaceutically acceptable carrier.

The structure of a methyl iodide monolayer adsorbed on graphite

Abstract: The structure of an adsorbed layer of methyl iodide on graphite has been determined by a combination of X-ray and neutron diffraction. The iodine atom positions were determined from the X-ray pattern and the methyl group positions from the neutron pattern. The experimentally determined unit cell has lattice parameters a = 1·540 nm, b = 0·578 nm and β = 90°. There are four molecules in the unit cell arranged to give two zig-zag chains of iodine atoms. Within the chain the iodine atoms are separated by 0·383 nm, which is similar to the value of 0·389 nm for bulk methyl iodide. The methyl groups are arranged so that the orientations of the molecular dipole moments in the two chains are opposed. All four molecules lie approximately flat on the surface and the layer resembles the (010) plane of the bulk crystal.

Iodimetric determination of iodate, bromate, hypochlorite, ascorbic acid and thiourea using flow injection amperometry

Abstract: Iodate, bromate and hypochlorite were determined as iodine by flow injection amperometry at a platinum or glassy carbon electrode by injecting them into an eluent 0.20 M in hydrochloric acid and 0.024 M in potassium iodide or an eluent 2 M in sulphuric acid and 0.12 M in potassium iodide. The rectilinearity range is from 10–3 to 10–7M. Organic compounds that can be oxidised or iodinated by iodine were determined on-line by injecting them in acidic solution into an iodate-iodide eluent and observing the decrease in the iodine signal. The determination was also performed by injecting a pre-reacted solution of iodine and the organic compound and monitoring the excess of iodine.

Untersuchungen zur Photolyse von Diaryliodoniumsalzen

Abstract: Investigations on Photolysis of Diaryliodonium Salts The photolysis of diaryliodonium salts in solution leads to various competitive and consecutive reactions. Upon irradiation, the excited state desactivates mainly through homolytic cleavage of the CI-bond, but to a minor extent also through heterolytic cleavage of the same bond. Thus, several photolysis products have been obtained: aromatics, new iodonium salts, iodoaromatics, substitution products of the solvent, protonic acid in aqueous solutions, iodide and iodate ions and iodine. In the case of diphenyliodonium iodide the yields of iodine are higher compared to those of other salts because of electron transfer processes. The quantum yields of the disappearance of the iodonium salt (ΦI) and of the formation of protonic acids (ΦP) are equal within the experimental error. These values do not depend on the nature of the solvent, with the exception of H-donor solvents, on the initial salt concentration and on oxygen. But, they depend strongly on the light intensity and on the substituent at the aromatic ring. The ΦP-data also depend on the oxidation potential of the anion used. For diphenyliodonium chloride, the quantum yield of iodobenzene formation reaches only the half of the values for ΦI and ΦP. A kinetic scheme is given for the explanation of the light intensity dependence, which is based on 1. and 2. order reactions of intermediates formed by the homolytic pathway. It is assumed, that the electron transfer reaction by iodide salts proceeds only between the iodide ion and the intermediate products.

Feasibility study of the determination of iodide, tin, arsenic, selenium and hydrogen carbonate in groundwater by inductively coupled plasma atomic emission spectrometry using a membrane gas-liquid separator

Abstract: The feasibility of the use of a silicone-rubber gas-liquid separator for the determination of iodide, As, Se, Sn and hydrogen carbonate in groundwaters has been investigated. Iodide is determined after oxidation to iodine, As, Se and Sn after reduction to their respective hydrides and hydrogen carbonate by displacement from solution as carbon dioxide. The gaseous species are separated from solution across the silicone-rubber membrane and are swept into the injector stream of an inductively coupled plasma for analysis. Low parts per billion detection limits are obtained in all instances. The advantages and limitations of this method, compared with existing techniques, are discussed with reference to each species as are developmental possibilities.

Transient thyrotoxicosis induced by Japanese kombu

Abstract: Iodine-induced thyrotoxicosis (ITT) has not been reported in Japan. We found that excessive intake of Japanese kombu could elicit ITT. Two Japanese women, 42 and 59 years old, developed thyrotoxicosis one month and one year, respectively, after having eaten foods containing 28-140 mg/day of iodine, calculated from their daily diet. Both patients had high concentrations of serum T3, low ratios of serum T3/T4 or T4/r-T3 compared with untreated Graves' disease, and high concentrations of serum inorganic iodine compared with the mean (M +/- SD: 2.05 +/- 0.99 micrograms/dl) plus 2SD in people eating common foods. Their thyrotoxic signs and symptoms disappeared, and their serum T4, T3, r-T3 and T4/r-T3 normalized one month after the prohibition of kombu intake. To clarify the source of iodine, the iodine content of the kombu and the iodine concentration in water in which the kombu was immersed were measured. Ninety-nine % of the iodine was found in water after 15 min boiling. These findings suggest that a daily intake of more than 28 mg/day of iodine in a diet containing kombu might induce ITT.

Transient primary hypothyroidism in the newborn: experience of the Victorian Neonatal Thyroid Screening Programme.

Abstract: Between May 1977 and December 1986, the Victorian Thyroid Screening Programme tested approximately 570 000 newborns for congenital hypothyroidism. One hundred and sixty-six cases of primary hypothyroidism, confirmed by formal thyroid function tests, were identified, of which 24 were later found to be transient. In addition, there were two patients with permanent dyshormonogenesis who passed through a stage of being biochemically euthyroid and so could have been diagnosed mistakenly as transient hypothyroidism. Fourteen of the transient cases were due to excessive intake of iodine. In two, this was due to maternal ingestion of iodide during pregnancy and in 12 the babies received large amounts of topical iodine antiseptic. Two cases were caused by maternal anti-thyroid antibodies and in eight instances the cause was unknown. The large number of cases due to the topical application of iodine antiseptic emphasizes the need for caution when using this substance in neonates.

La goitrigenèse expérimentale.

Abstract: Nodules formation in goiter is still poorly understood due to the lack of an adequate animal model. The key role of iodine in the increased heterogeneity of iodine metabolism and in cold follicle formation has been demonstrated. Administration of iodide excess to goitrous mice induces follicle cell necrosis and thyroiditis. Necrosis and inflammation can be prevented by reducing the iodine dose, giving T3 or T4, or combining iodide with antithyroid drugs or vitamin E. This suggest that iodide toxicity is related to excessive production of free radicals. During inflammation, Ia positive interstitial cells were increased in number whereas no Ia expression was seen in follicular cells.

Processes employing iodine-iodide etching solutions

Abstract: Aqueous iodine-iodide etching solutions are employed in the recovery of precious metals. Elemental iodine is precipitated from spent etching solutions and used to supply both the iodine and iodide of new etching solutions. Prior to extraction of the elemental iodine, used solutions, if not substantially contaminated, may be oxidized and recycled for further precious metal recovery. Aqueous etching solutions of hydriodic acid and iodine, or of ammonium iodide and iodine may be employed. Etching in such solutions, as well as in solutions of iodine and an alkali metal iodide, such as potassium iodide, may be accelerated by the use of small amounts of hydrogen peroxide (or equivalents) during etching.

Upper limit of iodine in infant formulas.

Abstract: Iodine is the rate-limiting substrate for thyroid hormone synthesis by the thyroid gland and must be available in threshold amounts to prevent goiter and hypothyroidism. Because excess iodine can inhibit thyroxine synthesis, an upper limit of iodine in infant formulas of 75 microg/100 kcal was proposed by the Food and Drug Administration in 1985. Review of recent studies of iodine physiology in infants and iodine content of milk suggests that a safe upper limit of iodine intake by normal, term infants should not exceed 100 microg/kg body wt daily. Given this limit and assuming the total intake of iodine to be derived from formula, the recommendation of 1985 still seems reasonable.

Solid concentrate iodine composition

Abstract: A solid iodine concentrate composition comprising an iodine complex, and a solidifier wherein said iodine complex comprises a complexing agent and an iodine source present in a ratio of at least 1.5:1.

Influence of iodine deficiency on human fetal thyroid gland and brain

Abstract: In order to evaluate the influence of prenatal iodine deficiency on the thyroid gland and brain in man, we studied therapeutically aborted fetuses collected from a severely iodine deficient endemic goiter and cretinism area before and after 5 year iodized salt utilization. Fetuses from a non-endemic area served as the normal controls1,2,3.

Total organic carbon and gas chromatography-mass spectroscopy methods to determine total carbon and hydrocarbons in mercuric iodide single crystals

Abstract: Total organic carbon was determined by measuring the CO 2 produced by combustion in a sealed quartz vessel. The CO 2 was quantified by nondispersive IR and by titration using commercial detectors. The total organic carbon was found to be around 10–100 μg/g in both starting materials and in single crystals. Gas chromatography-mass spectroscopy (GC/MS) measurements were made on hexane extracts of mercuric iodide (HgI 2 ) dissolved in potassium iodide solution. Hydrocarbons starting with C 10 (DIENE) and up to C 26 were found. In addition, phthalates, such as diethyl and dioctyl phthalate were also found. Some of the organic compounds, for example, such hydrocarbons as branched nC 16 , nC 20 , nC 21 , nC 22 , nC 23 , and nC 24 , were present in some HgI 2 materials in quantities of the order of weight ppm, but were eliminated in the purification process and were not found in the single crystals. Other organic compounds such as the phthalates were not always eliminated and were identified in the single crystals. In general, the GC/MS could identify only hydrocarbons of C 10 and higher which account for only a few percent of the total organic carbon determined by oxidation.

Down regulation of hypertrophied follicular cell volume in thyroid hyperplastic gland.

Abstract: In the present study, changes in thyroid follicular cell volume and its regulation have been investigated during the early involution of a hyperplastic goitre. Male Wistar rats were administered an iodine deficient diet for 6 months with propylthiouracil (PTU, 0.15%) during the last two months. At the end of iodine deficiency (day 0), some rats were killed and the others received a normal iodine diet. These rats were killed after different periods of iodine refeeding. Thyroid follicular cell volume was very high in hyperplastic gland whereas thyroid protein concentration was low. Thyroid follicular cell volume quickly decreased when rats were normally iodine refed, whereas thyroid protein concentration increased. Electron microscopal observations showed that thyroid follicular cells retained their endocrine aspect in hyperplastic state and throughout the iodine refeeding period. Using concomitant stereological and biochemical techniques, it is shown that the amount of cellular iodide and an unknown iodinated compound strongly increased during the early iodine refeeding. Plasma TSH was high on day 0 and remained at this level until day 8 whereas plasma T3 and T4 were low on day 0 and remained at this low level until day 4. The present data show that the involution of thyroid follicular cell volume is induced by iodide and mediated by an iodinated compound at least in the initial phase, and is independent of plasma TSH, T3, T4, so indicating the involvement of a thyroid autoregulatory mechanism. These changes in cell volume may be of importance in ion transport, i.e. in the metabolism of thyroid follicular cell during the early involution of the hyperplastic goitre.