Showing papers on "Iodine published in 2007"

A Mild and Environmentally Benign Oxidation of Thiols to Disulfides

Abstract: Thiols were effectively oxidized into disulfides by reacting with hydrogen peroxide in the presence of a catalytic amount of iodide ion or iodine.

Breast milk iodine and perchlorate concentrations in lactating Boston-area women.

Abstract: Context: Breastfed infants rely on adequate maternal dietary iodine intake. Objective: Our objective was to measure breast milk iodine and perchlorate, an inhibitor of iodide transport into the thyroid and potentially into breast milk, in Boston-area women. Participants: The study included 57 lactating healthy volunteers in the Boston area. Measurements: Breast milk iodine and perchlorate concentrations and urine iodine, perchlorate, and cotinine concentrations were measured. For comparison, iodine and perchlorate levels in infant formulae were also measured. Results: Median breast milk iodine content in 57 samples was 155 μg/liter (range, 2.7–1968 μg/liter). Median urine iodine was 114 μg/liter (range, 25–920 μg/liter). Perchlorate was detectable in all 49 breast milk samples (range, 1.3–411 μg/liter), all 56 urine samples (range, 0.37–127 μg/liter), and all 17 infant formula samples (range, 0.22–4.1 μg/liter) measured. Breast milk iodine content was significantly correlated with urinary iodine per gram ...

Iodine catalyzed preparation of amidoalkyl naphthols in solution and under solvent-free conditions ☆

Abstract: A one-pot three-component reaction of 2-naphthol, aldehydes and urea or amides has efficiently been carried out in the presence of iodine in dichloroethane at room temperature or under solvent-free conditions at higher temperature to form the corresponding amidoalkyl naphthols in high yields.

The Ultraviolet Filter Benzophenone 2 Interferes with the Thyroid Hormone Axis in Rats and Is a Potent in Vitro Inhibitor of Human Recombinant Thyroid Peroxidase

Abstract: Endocrine disrupting chemicals (EDCs), either plant constituents or contaminants deriving from industrial products, may interfere with the thyroid hormone (TH) axis. Here, we examined whether selected EDCs inhibit the key reactions of TH biosynthesis catalyzed by thyroid peroxidase (TPO). We used a novel in vitro assay based on human recombinant TPO (hrTPO) stably transfected into the human follicular thyroid carcinoma cell line FTC-238. F21388 (synthetic flavonoid), bisphenol A (building block for polycarbonates), and the UV filter benzophenone 2 (BP2) inhibited hrTPO. BP2 is contained in numerous cosmetics of daily use and may be in regular contact with human skin. Half-maximal inhibition in the guaiacol assay occurred at 450 nmol/liter BP2, a concentration 20- and 200-fold lower than those required in case of the TPO-inhibiting antithyroid drugs methimazole and propylthiouracil, respectively. BP2 at 300 nmol/liter combined with the TPO substrate H(2)O(2) (10 mumol/liter) inactivated hrTPO; this was, however, prevented by micromolar amounts of iodide. BP2 did not inhibit iodide uptake into FRTL-5 cells. In BP2-treated rats (333 and 1000 mg/kg body weight), serum total T(4) was significantly decreased and serum thyrotropin was significantly increased. TPO activities in the thyroids of treated animals were unchanged, a finding also described for methimazole and propylthiouracil. Thus, EDCs, most potently BP2, may disturb TH homeostasis by inhibiting or inactivating TPO, effects that are even more pronounced in the absence of iodide. This new challenge for endocrine regulation must be considered in the context of a still prevailing iodide deficiency in many parts of the world.

The impact of iodised salt or iodine supplements on iodine status during pregnancy, lactation and infancy.

Abstract: Objectives: Monitoring of iodine status during pregnancy, lactation and infancy is difficult as there are no established reference criteria for urinary iodine concentration (UI) for these groups; so it is uncertain whether iodized salt programs meet the needs of these life stages. Design and Subjects: The method used in this paper was: 1) to estimate the median UI concentration that reflects adequate iodine intake during these life stages; and 2) to use these estimates in a review of the literature to assess whether salt iodisation can control iodine deficiency in pregnant and lactating women, and their infants. Results: For pregnancy, recommended mean daily iodine intakes of 220-250 mg were estimated to correspond to a median UI concentration of about 150 m gl 21 , and larger surveys from the iodine sufficient countries have reported a median UI in pregnant women $140 m gl 21 . Iodine supplementation in pregnant women who are mild-tomoderately iodine deficient is beneficial, but there is no clear affect on maternal or newborn thyroid hormone levels. In countries where the iodine intake is sufficient, most mothers have median breast milk iodine concentration (BMIC) greater than the concentration (100-120 m gl 21 ) required to meet an infant’s needs. The median UI concentration during infancy that indicates optimal iodine nutrition is estimated to be $100 m gl 21 . In iodine-sufficient countries, the median UI concentration in infants ranges from 90-170 m gl 21 , suggesting adequate iodine intake in infancy.

Relevance of iodine intake as a reputed predisposing factor for thyroid cancer

Abstract: Iodine is a trace element that is essential for the synthesis of thyroid hormone.Both chronic iodine deficiency and iodine excess have been associated withhypertrophy and hyperplasia of follicular cells, attributed to excessive secretion ofTSH. This may be associated to thyroid cancer risk, particularly in women. Exper-imental studies have documented thyroid cancer induction by elevation ofendogenous TSH, although in a small number of animals. Iodine deficiency asso-ciated with carcinogenic agents and chemical mutagens will result in a higher inci-dence of thyroid malignancy. Inadequate low iodine intake will result in increasedTSH stimulation, increased thyroid cell responsiveness to TSH, increased thyroidcell EGF-induced proliferation, decreased TGF β1 production and increased angio-genesis, all phenomena related to promotion of tumor growth. Epidemiologicalstudies associating iodine intake and thyroid cancer led to controversial and con-flicting results. There is no doubt that introduction of universal iodine prophylax-is in population previously in chronic iodine-deficiency leads to a changing pat-tern of more prevalent papillary thyroid cancer and declining of follicular thyroidcancer. Also anaplastic thyroid cancer is practically not seen after years of iodinesupplementation. Iodine excess has also been indicated as a possible nutritionalfactor in the prevalence of differentiated thyroid cancer in Iceland, Hawaii and,more recently, in China. In conclusion: available evidence from animal experi-ments, epidemiological studies and iodine prophylaxis has demonstrated a shifttowards a rise in papillary carcinoma, but no clear relationship between overallthyroid cancer incidence and iodine intake. (Arq Bras Endocrinol Metab2007;51/5:701-712)Keywords: Iodine; Thyroid cancer; Iodine deficiency; Iodine excess; Carcino-genic agents; Environmental effect

Thyroid autoimmunity in the current iodine environment.

Abstract: Iodine is essential for thyroid function. Thyroid disorders related to iodine deficiency decreased progressively with the continuous iodine prophylaxis and the increased iodine intake. An adverse effect resulting from iodine prophylaxis may be the induction of thyroid autoimmunity. Although experiments performed in animal models suggest that iodine could initiate or exacerbate thyroid autoimmunity, the role of iodine in humans remains controversial. Several observational studies in areas with adequate or high iodine intake suggest that there is an increase in the incidence of thyroid autoimmune disease. Moreover, intervention studies suggest that increased iodine intake may enhance thyroid autoimmunity too. However, not all studies generated the same findings, probably because of genetic, racial, and environmental differences. It seems that autoimmune exacerbation is a transient phenomenon. Studies have shown that in persons presenting thyroid antibodies, the levels of these antibodies progressively decrease when the majority of them react against a nonspecific pattern of thyroglobulin (Tg) epitopes. However, in a small number of these persons, the anti-Tg antibodies are similar to those in patients with patent thyroid autoimmune disease, reacting against specific immunodominant Tg epitopes, and their levels persist. One possible attractive explanation is that enhanced iodine intake increases the antigenicity of Tg through the incorporation of iodine into its molecule and the formation of iodinated Tg epitopes or even the generation of noniodinated pathogenetic Tg epitopes that are normally cryptic.

Modelling iodide - iodate speciation in atmospheric aerosol: Contributions of inorganic and organic iodine chemistry

Abstract: The speciation of iodine in atmospheric aerosol is currently poorly understood. Models predict negligible iodide concentrations but accumulation of iodate in aerosol, both of which is not confirmed by recent measurements. We present an updated aqueous phase iodine chemistry scheme for use in atmospheric chemistry models and discuss sensitivity studies with the marine boundary layer model MISTRA. These studies show that iodate can be reduced in acidic aerosol by inorganic reactions, i.e., iodate does not necessarily accumulate in particles. Furthermore, the transformation of particulate iodide to volatile iodine species likely has been overestimated in previous model studies due to negligence of collision-induced upper limits for the reaction rates. However, inorganic reaction cycles still do not seem to be sufficient to reproduce the observed range of iodide – iodate speciation in atmospheric aerosol. Therefore, we also investigate the effects of the recently suggested reaction of HOI with dissolved organic matter to produce iodide. If this reaction is fast enough to compete with the inorganic mechanism, it would not only directly lead to enhanced iodide concentrations but, indirectly via speed-up of the inorganic iodate reduction cycles, also to a decrease in iodate concentrations. Hence, according to our model studies, organic iodine chemistry, combined with inorganic reaction cycles, is able to reproduce observations. The presented chemistry cycles are highly dependent on pH and thus offer an explanation for the large observed variability of the iodide – iodate speciation in atmospheric aerosol.

Treatment of Iodine Deficiency in School-Age Children Increases Insulin-Like Growth Factor (IGF)-I and IGF Binding Protein-3 Concentrations and Improves Somatic Growth

Abstract: Context: Iodine deficiency in utero impairs fetal growth, but the relationship between iodine deficiency and postnatal growth is less clear. Objective: The objective of the study was to determine whether iodine repletion improves somatic growth in iodine-deficient children and investigate the role of IGF-I and IGF binding protein (IGFBP)-3 in this effect. Design, Participants, and Interventions: Three prospective, double-blind intervention studies were done: 1) in a 10-month study, severely iodine-deficient, 7- to 10-yr-old Moroccan children (n = 71) were provided iodized salt and compared with children not using iodized salt; 2) in a 6-month study, moderately iodine-deficient, 10- to 12-yr-old Albanian children (n = 310) were given 400 mg iodine as oral iodized oil or placebo; 3) in a 6-month study, mildly iodine-deficient 5- to 14-yr-old South African children (n = 188) were given two doses of 200 mg iodine as oral iodized oil or placebo. At baseline and follow-up, height, weight, urinary iodine (UI), t...

Iodine speciation in rain and snow: Implications for the atmospheric iodine sink

Abstract: [1] Atmospheric iodine models currently predict iodate as the only stable iodine sink species in the troposphere. However, it is shown here using ion chromatograph inductively coupled plasma-mass spectroscopy (IC-ICP-MS) that iodate is the least abundant iodine species in precipitation (rain and snow) collected from various locations in southern Germany, the Swiss Alps, and Patagonia (Chile). The majority of iodine is associated with organic compounds (average 56%) followed by iodide (average 27%). Although the exact structure of the organic fraction remains ambiguous and is probably of higher molecular weight, a smaller portion of the iodo-organic compounds are anionic (5–20% of total I). One of these anionic organo-I peaks is present in all rain and most snow chromatograms and is generally responsible for 5–18% of total iodine. This suggests a ubiquitous atmospheric iodine species. The data indicate that organic iodine compounds play an important role in the global atmospheric iodine cycle and the atmospheric iodine sink. As such, future tropospheric iodine models must consider organic-I reactions.

Neonatal thyroid screening as a monitoring tool for the control of iodine deficiency.

Abstract: In conditions of iodine deficiency, the frequency distribution of neonatal thyroid-stimulating hormone (TSH) is shifted towards elevated values. Elevated serum TSH in the neonate indicates insufficient supply of thyroid hormones to the developing brain, and therefore constitutes the only indicator that allows prediction of brain damage, which is the main complication of iodine deficiency. This paper reviews studies on neonatal thyroid function in iodine deficiency and confirms the former statement by WHO/UNICEF/ICCIDD that the frequency of neonatal TSH above 5 mU/L blood is below 3% in conditions of normal iodine supply, that a frequency of 3-19.9% indicates mild iodine deficiency and that frequencies of 20-39.9% and above 40% indicate moderate to severe iodine deficiency, respectively. Neonatal thyroid screening appears as a particularly sensitive index in the monitoring of iodine supply at a population level.

On the mobility and potential retention of iodine in the Callovian–Oxfordian formation

Abstract: Iodide sorption experiments were conducted on clay stone samples originating from the Callovian–Oxfordian formation under experimental conditions as close as possible to in situ conditions. The total natural iodine content of the formation is shown to be very constant throughout the formation, ranging from 2 to 3 ppm. This range is in agreement with a past iodine accumulation in the marine organic matter of the sediment before and during deposition, and early diagenesis. At variance with total iodine, the leached iodine concentrations are variable. If leached iodine is considered to represent porewater solute iodine, its concentration can be calculated and ranges from 0 (below detection limit) to ∼60 μmol/L and represents 0–25% of the total iodine. The reason for this variability is not understood. Sorption isotherms were determined either for natural 127 I − solutions or for 131 I − spiked 127 I − solutions, with concentrations ranging from 10 −9 to 10 −3 mol/L at solid to liquid ratios from 10 to 200 g/L. No or little sorption was encountered, K d values being in the range 0–0.5 L/kg with statistical and analytical error bands being greater than the K d values, with the exception of one experiment at low solid to liquid ratio (10 g/L), showing significant K d values of ∼25 L/kg. In sorption experiments with natural 127 I − and at the lowest added iodide concentrations ( −6 mol/L) an apparent negative K d was obtained due to the iodide content in the solid porewater that was leached once the solid was suspended. The low affinity of iodide for argilite is thus confirmed. However, based only on these results and given the extent of the error bands, one cannot discard a limited iodide uptake. Literature data on iodide diffusion on similar rock materials have already shown that iodide does not behave like chloride. The retention mechanism of radio-iodide is discussed in the light of the present results and diffusion data. A model involving isotopic exchange between the natural iodine content of the geological formation and radio-iodine allows all of the results to be described. Not all the iodine in the formation appears to participate in isotopic exchange reactions with the solution. A quantification of the isotopically labile fraction of iodine would allow the effect of isotopic exchange on radio-iodide migration throughout the Callovian–Oxfordian formation to be assessed and predicted.

Iodine and bromine speciation in snow and the effect of orographically induced precipitation

Abstract: Iodine is an essential trace element for all mam- mals and may also influence climate through new aerosol formation. Atmospheric bromine cycling is also important due to its well-known ozone depletion capabilities. Despite precipitation being the ultimate source of iodine in the ter- restrial environment, the processes effecting its distribution, speciation and transport are relatively unknown. The aim of this study was to determine the effect of orographically induced precipitation on iodine concentrations in snow and also to quantify the inorganic and organic iodine and bromine species. Snow samples were collected over an altitude profile ( 840 m) from the northern Black Forest and were analysed by ion-chromatography - inductively coupled plasma mass spectrometry (IC-ICP-MS) for iodine and bromine species and trace metals (ICP-MS). All elements and species concen- trations in snow showed significant ( r 2 >0.65) exponential decrease relationships with altitude despite the short (5 km) horizontal distance of the transect. In fact, total iodine more than halved (38 to 13 nmol/l) over the 840 m height change. The results suggest that orographic lifting and subsequent precipitation has a major influence on iodine concentrations in snow. This orographically induced removal effect may be more important than lateral distance from the ocean in determining iodine concentrations in terrestrial precipitation. The microphysical removal process was common to all ele- ments indicating that the iodine and bromine are internally mixed within the snow crystals. We also show that organ- ically bound iodine is the dominant iodine species in snow (61-75%), followed by iodide. Iodate was only found in two samples despite a detection limit of 0.3 nmol/l. Two un- known but most likely anionic organo-I species were also identified in IC-ICP-MS chromatograms and comprised 2- 10% of the total iodine. The majority of the bromine was inorganic bromide with a max. of 32% organo-Br.

Iodine prophylaxis—the protective factor against stomach cancer in iodine deficient areas

Abstract: Background Poland has one of the highest death rates for stomach cancer in Europe. Moderate iodine deficiency and in consequence high goitre prevalence led to the implementation in 1996 of a very efficient mandatory model of iodine prophylaxis, based on household salt iodisation (30 ± 10mg KI/1 kg of salt).

Novel and efficient synthesis of 1-iodoalkynes

Abstract: Treatment of terminal alkynes with (diacetoxyiodo)benzene, potassium iodide, and copper(I) iodide afforded 1-iodo-alkynes in good to excellent yields under mild conditions.

Hydrogen peroxide-dependent uptake of iodine by marine Flavobacteriaceae bacterium strain C-21.

Abstract: The cells of the marine bacterium strain C-21, which is phylogenetically closely related to Arenibacter troitsensis, accumulate iodine in the presence of glucose and iodide (I−). In this study, the detailed mechanism of iodine uptake by C-21 was determined using a radioactive iodide tracer, 125I−. In addition to glucose, oxygen and calcium ions were also required for the uptake of iodine. The uptake was not inhibited or was only partially inhibited by various metabolic inhibitors, whereas reducing agents and catalase strongly inhibited the uptake. When exogenous glucose oxidase was added to the cell suspension, enhanced uptake of iodine was observed. The uptake occurred even in the absence of glucose and oxygen if hydrogen peroxide was added to the cell suspension. Significant activity of glucose oxidase was found in the crude extracts of C-21, and it was located mainly in the membrane fraction. These findings indicate that hydrogen peroxide produced by glucose oxidase plays a key role in the uptake of iodine. Furthermore, enzymatic oxidation of iodide strongly stimulated iodine uptake in the absence of glucose. Based on these results, the mechanism was considered to consist of oxidation of iodide to hypoiodous acid by hydrogen peroxide, followed by passive translocation of this uncharged iodine species across the cell membrane. Interestingly, such a mechanism of iodine uptake is similar to that observed in iodine-accumulating marine algae.