Iodine

About: Iodine is a research topic. Over the lifetime, 8936 publications have been published within this topic receiving 139981 citations. The topic is also known as: I & element 53.

Necrosis of follicular cells and discharge of thyroidal iodine induced by administering iodide to iodine-deficient dogs.

Abstract: The administration of large doses of stable iodide to dogs with natural or experimentally-induced iodine deficiency causes the discharge of prelabeled organic and inorganic iodine from the thyroid. The discharge of thyroidal iodine is manifested by significant elevations in PB131I and serum non-precipitable 131I levels within 12–14 hr after an oral iodide load and by pronounced depletion of stainable colloid in histologic sections of the gland. In some dogs the discharge is preceded or accompanied by necrosis of the epithelium in larger follicles which have vacuolated colloid. The necrosis is evident by as early as 5½ hr after oral administration of 0.5 mg I–/kg or more but is prevented by as little as 0.05 mg I–/kg given 24 hr before the load. Neither C1O4– nor SCN– produce the necrosis in susceptible dogs when given in doses of 2.5 mg/kg. Susceptibility to the cytotoxic effect of excess iodide appears to be related to certain kinetic characteristics of the iodine-deficient gland.

Ice nucleation by coprecipitated silver iodide and silver bromide.

Abstract: The ability of silver iodide to cause freezing of supercooled water is improved if up to 30 percent of the iodine atoms in the crystal are replaced with bromine atoms.

Iodine Fortification Plant Screening Process and Accumulation in Tomato Fruits and Potato Tubers

Abstract: Iodine is an essential microelement for human health, and the recommended daily allowance (RDA) of such element should range from 40 to 200 µg day −1 . Because of the low iodine contents in vegetables, cereals, and many other foods, iodine deficiency disorder (IDD) is one of the most widespread nutrient-deficiency diseases in the world. Therefore, investigations of I uptake in plants with the aim of fortifying them can help reach the important health and social objective of IDD elimination. This study was conducted to determine the effects of the absorption of iodine from two different chemical forms—potassium iodide (I − ) and potassium iodate (IO − 3)—in a wide range of wild and cultivated plant species. Pot plants were irrigated with different concentrations of I − or IO − 3, namely 0.05% and 0.1% (w/v) I − and 0.05%, 0.1%, 0.2%, and 0.5% (w/v) IO − 3. Inhibiting effects on plant growth were observed after adding these amounts of iodine to the irrigation water. Plants were able to tolerate high levels of iodine as IO − 3 better than I − in the root environment. Among cultivated species, barley (Hordeum vulgare L.) showed the lowest biomass reductions due to iodine toxicity and maize (Zea mays L.) together with tobacco (Nicotiana tabacum L.) showed the greatest. After the screening, cultivated tomato and potato were shown to be good targets for a fortification-rate study among the species screened. When fed with 0.05% iodine salts, potato (Solanum tuberosum L.) tubers and tomato (Solanum lycopersicum L.) fruits absorbed iodine up to 272 and 527 µg/100 g fresh weight (FW) from IO − 3 and 1,875 and 3,900 µg/100 g FW from I − . These uptake levels were well more than the RDA of 150 µg day −1 for adults. Moreover, the agronomic efficiency of iodine accumulation of potato tubers and tomato fruits was calculated. Both plant organs showed greater accumulation efficiency for given units of iodine from iodide than from iodate. This accumulation efficiency decreased in both potato tubers and tomato fruits at iodine concentrations greater than 0.05% for iodide and at respectively 0.2% and 0.1% for iodate. On the basis of the uptake curve, it was finally possible to calculate the doses of supply in the irrigation water of iodine as iodate (0.028% for potato and 0.014% for tomato) as well as of iodide (0.004% for potato and 0.002% for tomato) to reach the 150 µg day −1 RDA for adults in 100 g of such vegetables, to efficiently control IDD, although these results still need to be validated.

Enzymatic iodination of protein. Kinetics of iodine formation and protein iodination catalyzed by horse-radish peroxidase.

Abstract: 1. The initial rate of I2 formation catalyzed by horse-radish peroxidase exhibited a clear sigmoid relationship with respect to the concentration of I−. These data were found to fit an equation based on a model which predicts a second-order dependence on iodide concentration and are consistent with a bimolecular reaction between two I−ions on the surface of the enzyme. Such a model presumes two sites for the substrate on the enzyme. 2. The initial rate of lysozyme iodination also exhibited a clear sigmoid relationship with respect to concentration of I−. The sigmoidicity increased with the lysozyme concentration. These experimental data fit a random-ordered sequence of substrate fixation but with one of the two possible sequences kinetically preferred. These results also suggest that lysozyme interacts with the enzyme and that there are two sites for substrate addition on the surface of the enzyme. 3. When the ratio of the concentrations of both substrates, iodide and lysozyme, is varied, the rates of formation of each product, I2 or iodinated protein, also vary; the lower the iodide/protein ratio, the lower the I2 yield and the higher the rate of protein iodination. Studies on the influence of pH on the nature of the product showed that I2 formation is favored at acidic pH and protein iodination at more alkaline pH. These results are also consistent with a two-site model for the enzyme, both sites being able to fix either two iodide ions or one iodide ion and one lysozyme molecule. The affinity of the sites for each one of the two substrates differs according to the pH. This conclusion was confirmed by the observation that iodination of free tyrosine could be obtained with very good yields provided that the pH of the reaction was adjusted to avoid either complete dimerization of free tyrosine, which is favored at alkaline pH, or I2 formation which is favored at low pH. 4. These results and other quantitative data on the stoichiometry of H2O2 consumption do not establish unequivocally which is the oxidized iodide-reacting species, I+ or I°. However, they indicate that I2 is not the iodinating species in the protein iodination reaction catalyzed by horse-radish peroxidase.