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At least 19 recordsLinked to original sources
PubMed1992

Control of thyroid secretion: effects of stimulators of protein kinase C, thyrotropin, and calcium mobilization on secretion of iodinated compounds from sheep thyroid cells.

We have compared and contrasted the abilities of TSH and agents capable of discretely activating the cAMP-dependent protein kinase, protein kinase C, or calcium mobilization to influence the secretion of iodinated compounds from cells prelabeled with iodide and blocked from further organification with methimazole. We found that calcium mobilization induced by A23187, protein kinase C activation induced by 12-O-tetradecanoyl phorbol 13-acetate (TPA) and TSH all stimulated the secretion of iodinated compounds. The effects of TSH were mimicked by forskolin and those of TPA by a synthetic diacylglycerol, sn-1,2-dioctanoylglycerol. The effects of TPA were partially inhibited by staurosporine whereas those of TSH were not. Epidermal growth factor and norepinephrine were without effect on thyroid secretion. The effects of A23187 and TPA were synergistic. The effects of TSH and TPA were not and the increased secretion induced by either agent was partially prevented by the combination. Preincubation of cells with TSH desensitized the cells to further stimulation by TSH but the stimulatory effects of TPA were unaffected. Exposure of cells to medium without calcium also induced loss of iodinated compounds which was partially prevented by TSH or forskolin but not TPA. TSH did not stimulate the rapid production of inositol trisphosphate production. We conclude that the mechanisms by which TSH (through stimulation of cAMP) and stimulators of other intracellular pathways exert their effects on secretion of iodocompounds, differ. Activation of protein kinase C and acute production of inositol trisphosphate do not appear to be involved in the mechanism of action of TSH in stimulating thyroid secretion but calcium mobilization is implicated.

Alkaloids↗
PubMed2004

Synchrotron radiation-based experimental determination of the optimal energy for cell radiotoxicity enhancement following photoelectric effect on stable iodinated compounds.

This study was designed to experimentally evaluate the optimal X-ray energy for increasing the radiation energy absorbed in tumours loaded with iodinated compounds, using the photoelectric effect. SQ20B human cells were irradiated with synchrotron monochromatic beam tuned at 32.8, 33.5, 50 and 70 keV. Two cell treatments were compared to the control: cells suspended in 10 mg ml(-1) of iodine radiological contrast agent or cells pre-exposed with 10 microM of iodo-desoxyuridine (IUdR) for 48 h. Our radiobiological end point was clonogenic cell survival. Cells irradiated with both iodine compounds exhibited a radiation sensitisation enhancement. Moreover, it was energy dependent, with a maximum at 50 keV. At this energy, the sensitisation calculated at 10% survival was equal to 2.03 for cells suspended in iodinated contrast agent and 2.60 for IUdR. Cells pretreated with IUdR had higher sensitisation factors over the energy range than for those suspended in iodine contrast agent. Also, their survival curves presented no shoulder, suggesting complex lethal damages from Auger electrons. Our results confirm the existence of the 50 keV energy optimum for a binary therapeutic irradiation based on the presence of stable iodine in tumours and an external irradiation. Monochromatic synchrotron radiotherapy concept is hence proposed for increasing the differential effect between healthy and cancerous tissue irradiation.

Carcinoma, Squamous Cell↗
PubMed1994

Effect of thyroid hormones and other iodinated compounds on the transition of monocytes into veiled/dendritic cells: role of granulocyte-macrophage colony-stimulating factor, tumour-necrosis factor-alpha and interleukin-6.

Stimulation of human peripheral blood monocytes with the thyroid hormones tri-iodothyronine (T3) and thyroxine (T4) enhanced their ability to mature into cytologically and functionally characteristic veiled/dendritic cells. Veiled/dendritic cell transition induced by T3 and T4 was dependent on the production of granulocyte-macrophage colony-stimulating factor (GM-CSF), tumour necrosis factor-alpha (TNF alpha) and interleukin-6 (IL-6) in the culture, since the addition of antibodies specific for GM-CSF, TNF alpha and IL-6 to the culture system had blocking effects. The addition of antibodies to macrophage colony-stimulating factor and IL-1 had no effects. Contaminating T cells and B cells did not contribute to the transition of monocytes to veiled/dendritic cells, and it is therefore likely that the GM-CSF, TNF alpha and IL-6 produced in the culture system were derived from the monocytes themselves. Stimulation of the blood monocytes with an optimal concentration of metrizamide (14.5%), reverse T3 (rT3; 2 x 10(-10) M) or highly iodinated thyroglobulin (Tg; 2 x 10(-11) M) also resulted in an increased transition of monocytes to veiled/dendritic cells, but to a lesser extent in comparison with the thyroid hormones (T3, 31 +/- 6% and T4, 25 +/- 5% vs rT3, 22 +/- 8% and Tg with an iodination grade of 0.37%: 20 +/- 4% veiled/dendritic cells). Administration of anti-GM-CSF, anti-TNF alpha and anti-IL-6 to the culture system also had blocking effects on the transition from monocytes to veiled/dendritic cells induced by the iodinated compounds. The mechanisms by which such iodinated compounds act on the monocyte to veiled/dendritic cell transition can only be speculated on (interference H2O2-generating system?).

Antibodies, Monoclonal↗
PubMed1978

Chemical determination of iodinated compounds in human thyroid.

As a tool with which to detect iodinated compounds in human thyroid specimens, we have reevaluated a nonincineration technique which has so far been employed in the determination of thyroxine-iodine in peripheral blood. The catalytic action of iodoamino acids in the Ce-As reaction was enhanced by a small amount of Cl2. On the contrary, a large amount of Cl2 inhibited the reaction unexpectedly. Among iodide, iodotyrosine and iodothyronine, iodide was the most effective catalyst in the Ce-As reaction and iodothyronine was the least effective one. Protein seemed to inhibit this reaction of thyroglobulin. But the result of iodine content in thyroglobulin by this technique agreed well with that by incineration when measured 127I was corrected by percent activity of dializable part of the total activity of 131I-thyroglobulin with the same protein concentration, after the NaClO treatment. The results of human thyroid specimens were as follows: the thyroglobulin content of five normal subjects was 8.0 +/- 1.5% of wet thyroid weight. That of Hashimoto's disease was significantly decreased which seemed compatible with the decrease in iodine content of thyroglobulin, whereas thyroglobulin content of Graves disease treated with 1-methyl, 2-mercaptoimidazole followed by a large dose of iodide was well preserved in spite of a lower degree of iodination of thyroglobulin. As for the distribution of iodoamino acids-iodine in normal thyroid, T4 was 20.5 +/- 0.7%. This technique ultimately looks promising as a tool with which to study intrathyroidal iodine metabolism in human.

Adult↗
PubMed1953

Studies on the stability of iodine compounds in iodized salt.

Contributions made by five groups of investigators to the knowledge of the stability of different iodine compounds in salt, and of the extent of the losses of iodine which may occur when iodized salt is exposed to different conditions of storage and use, are discussed by the author.STABILITY OF THE IODINE COMPONENT IN IODIZED SALT IS DETERMINED BY: (1) moisture content of the salt and humidity of the atmosphere; (2) light, heat, and other meteorological factors; (3) impurities in the salt; (4) acidity or alkalinity of the mixture; and (5) the form in which iodine is present.When potassium iodide or sodium iodide is used as the iodizing agent, the iodide content of the salt will remain constant and its distribution will remain uniform for many months if the salt is packed dry in a container with an impervious lining and kept dry, preferably in a cool place and away from strong light. When these conditions cannot be met, it is desirable to iodize salt with potassium iodate. Under adverse conditions of moisture, heat, and sunlight, the iodine content of salt iodized with potassium iodate remains relatively constant.

Hot Temperature↗