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N Bagchi

Publications and source records attributed to N Bagchi.

10 recordsLinked to original sources
PubMed1992

What makes silica toxic?

Published data suggest that particle charge could be related to its toxicity. Respirable particles containing silica were therefore collected in foundries and their charge measured. These particles carried high levels of positive charge that were related to low humidity. Incubating these particles with pulmonary macrophages from mice produced detectable activities of collagenase, a precursor of silicosis. These experiments confirm that the toxicity of silica particles is likely to be because of the positive charge they carry.

Animals↗
PubMed1992

The role of iodine in thyroid autoimmunity: from chickens to humans: a review.

Evidence has been presented to support the idea that iodine plays an important role in autoimmune thyroiditis. Excessive amounts induce thyroiditis in genetically susceptible animal strains, while intrathyroidal depletion of iodine prevents disease in strains susceptible to severe thyroiditis. While the mechanisms by which iodine promotes thyroiditis is unknown, several hypotheses have been proposed. (1) T and/or B cells may react specifically to iodinated portions of thyroglobulin (Tg) so that severe iodine depletion renders Tg non-immunogenic. (2) A defect in the iodine processing machinery in thyroid epithelial cells of a susceptible person or animal may, in the presence of iodine, result in elevated levels of oxygen or iodine radicals, which could damage membrane lipids or proteins. (3) Defective iodine processing may result in the iodination of lipid or proteins (other than Tg) which could act either as immunogens or polyclonal activators.

Animals↗
PubMed1991

Uptake and metabolism of iodine is crucial for the development of thyroiditis in obese strain chickens.

To assess the importance of the role of thyroidal iodine in the pathogenesis of thyroiditis in the obese strain (OS) chicken, a model of spontaneous and severe disease, we studied the effect of antithyroid drugs that reduce thyroidal iodine or prevent its metabolism. Reduction of thyroidal iodine was achieved with KClO4, an inhibitor of iodine transport and mononitrotyrosine (MNT), a drug that promotes loss of thyroidal iodine as iodotyrosines. A regimen consisting of KClO4 and MNT administration beginning in ovo and continuing after hatching reduced thyroidal infiltration to 2% of control values and decreased thyroglobulin antibody (TgAb) production for as long as 9 wk. Untreated birds had severe disease by 5 wk of age. The suppression of disease was independent of TSH, not mediated by generalized immunosuppression and reversed by excess dietary iodine. Two drugs that inhibit the metabolism of iodine, propylthiouracil (PTU) and aminotriazole, reduced thyroidal infiltration and TgAb levels, although to a lesser extent. When splenocytes from OS chickens with thyroiditis were transferred to Cornell strain (CS) chickens, a related strain that develops late onset mild disease, only the recipients that were iodine supplemented developed thyroiditis. In conclusion, autoimmune thyroiditis in an animal model can be prevented by reducing thyroidal iodine or its metabolism and optimal effects require intervention at the embryonic stage.

Amitrole↗
PubMed1991

Thyroidal iodine metabolism in obese-strain chickens before immune-mediated damage.

Several studies have shown that iodine plays a role in spontaneous autoimmune thyroiditis in man and other animals. In addition, abnormalities of iodine metabolism have been found in patients with Hashimoto's thyroiditis and in chickens of the obese strain (OS), an animal model of spontaneous autoimmune thyroiditis. We have examined several parameters of iodine metabolism before immune damage in this model and in the related Cornell strain (CS), a strain which develops a late-onset mild thyroiditis, to discover a possible causal relationship between altered iodine metabolism and the initiation of autoimmunity. Thyroglobulin was purified from individual chicken thyroid glands and analysed for iodine by the ceric sulphate method. Analogous to the thyroglobulin of Hashimoto's patients, the iodine content of OS thyroglobulin (27 atoms/molecule) was lower than that of normal-strain thyroglobulin (46 atoms/molecule) when the chickens were provided with a normal diet. Also, under conditions of TSH suppression, the iodine content of OS thyroglobulin (18 atoms/molecule) was lower than that of CS thyroglobulin (36 atoms/molecule) and of normal-strain thyroglobulin (32 atoms/molecule). In contrast with Hashimoto's patients, however, the OS and CS chickens had practically no inorganic iodide in their thyroid glands; electrophoretic analysis of thyroid homogenates revealed that essentially all (greater than 99.62%) 125I was organified by 16 h in all strains of birds tested. Despite the relatively poor iodination of thyroglobulin exhibited by OS chickens, they did not iodinate additional 'unique' proteins, when examined by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) of thyroid proteins labelled with 125I in vivo.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1977

Effect of inorganic iodide on thyroglobulin hydrolysis in cultured thyroid glands.

The process of thyroglobulin hydrolysis in mouse thyroid glands labelled in vitro was studied from 2-24 h after they had been maintained in tissue culture. The culture medium was supplemented with mononitrotyrosine to prevent deiodination of iodotyrosines. Hydrolysis of labelled thyroglobulin, under these conditions, led to the release of labelled iodotyrosines and iodothyronines. The rate of formation of these compounds was measured as an index of thyroglobulin hydrolysis (TH). TH was markedly stimulated by TSH. NaI inhibited TSH stimulation of TH at a concentration of 10(-5)M or greater. NaI, at similar concentrations,also markedly diminished or abolished the incorporation of 131I into thyroidal proteins from radioiodide-supplemented media. The addition of various inhibitors of iodination effectively blocked the effect of iodide on TH. In experiments where radioimmunossay was used to measure medium hormone concentrations, the release of unlabelled thyroxine (T4) and triiodothyronine (T3) induced by TSH was found to be significantly decreased in the presence of 10(-4)M NaI. These studies demonstrate that iodide inhibits the hydrolysis of thyroglobulin at or near concentrations which also inhibit iodination of thyroidal proteins. The present data suggest that formation of an iodinated compound is necessary for the effect of iodide. In addition, these studies demonstrate the utility of this in vitro system for the investigation of thyroid physiology.

Hydrolysis↗
PubMedDate not supplied

Aldosteronism.

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Adrenocorticotropic Hormone↗