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C.b. Dissanayake - One of the best experts on this subject based on the ideXlab platform.
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Geochemistry of endemic goitre, Sri Lanka
Applied Geochemistry, 2009Co-Authors: C.b. Dissanayake, Rohana ChandrajithAbstract:Abstract A large section of the population living in the wet climatic zone of Sri Lanka is prone to endemic goitre, which is mainly caused by the lack of I. In Sri Lanka, an area in which 40% of the inhabitants are afflicted by goitre, the I content in soil and water was still observed to be high relative to other goitrous regions of the world, indicating the possible importance of other factors such as Goitrogens in the aetiology of endemic goitre. Cluster analysis of the geochemical data showed that the endemic goitre region lies in the group with lowest I, alkali earths, Cl, NO3-, Fe and Mn.
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selenium and iodine in soil rice and drinking water in relation to endemic goitre in sri lanka
Science of The Total Environment, 2000Co-Authors: F M Fordyce, C C Johnson, Udaya R B Navaratna, Don J Appleton, C.b. DissanayakeAbstract:Endemic goitre has been reported in the climatic wet zone of south-west Sri Lanka for the past 50 years, but rarely occurs in the northern dry zone. Despite government-sponsored iodised salt programmes, endemic goitre is still prevalent. In recent years, it has been suggested that Se deficiency may be an important factor in the onset of goitre and other iodine deficiency disorders (IDD). Prior to the present study, environmental concentrations of Se in Sri Lanka and the possible relationships between Se deficiency and endemic goitre had not been investigated. During the present study, chemical differences in the environment (measured in soil, rice and drinking water) and the Se-status of the human population (demonstrated by hair samples from women) were determined for 15 villages. The villages were characterised by low ( 25%) goitre incidence (NIDD, MIDD and HIDD, respectively). Results show that concentrations of soil total Se and iodine are highest in the HIDD villages, however, the soil clay and organic matter content appear to inhibit the bioavailability of these elements. Concentrations of iodine in rice are low (≤58 ng/g) and rice does not provide a significant source of iodine in the Sri Lankan diet. High concentrations of iodine (up to 84 μg/l) in drinking water in the dry zone may, in part, explain why goitre is uncommon in this area. This study has shown for the first time that significant proportions of the Sri Lankan female population may be Se deficient (24, 24 and 40% in the NIDD, MIDD and HIDD villages, respectively). Although Se deficiency is not restricted to areas where goitre is prevalent, a combination of iodine and Se deficiency could be involved in the pathogenesis of goitre in Sri Lanka. The distribution of red rice cultivation in Sri Lanka is coincident with the HIDD villages. Varieties of red rice grown in other countries contain anthocyanins and procyanidins, compounds which in other foodstuffs are known Goitrogens. The potential goitrogenic properties of red rice in Sri Lanka are presently unknown and require further investigation. It is likely that the incidence of goitre in Sri Lanka is multi-factorial, involving trace element deficiencies and other factors such as poor nutrition and Goitrogens in foodstuffs.
Reynaldo Patino - One of the best experts on this subject based on the ideXlab platform.
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regulation of gonadal sex ratios and pubertal development by the thyroid endocrine system in zebrafish danio rerio
General and Comparative Endocrinology, 2013Co-Authors: Prakash Sharma, Reynaldo PatinoAbstract:We examined associations between thyroid condition, gonadal sex and pubertal development in zebrafish. Seventy-two-hour postfertilization larvae were reared in untreated medium or in the presence of Goitrogens (sodium perchlorate, 0.82 mM; methimazole, 0.15 and 0.3 mM) or thyroxine (1 and 10 nM) for 30 days. Thyrocyte height, gonadal sex and gonadal development were histologically determined at 45 and 60 days postfertilization (dpf). Thyrocyte hypertrophy, an index of hypothyroidism, was observed at 45 and 60 dpf in perchlorate-treated but only at 45 dpf in methimazole-treated fish. Similarly, gonadal sex ratios were biased toward ovaries relative to control animals at 45 and 60 dpf in perchlorate-treated fish but only at 45 dpf in methimazole-treated fish. Gonadal sex ratios were biased toward testes at 45 and 60 dpf in thyroxine-treated fish. Spermatogenesis was delayed in testes from goitrogen-treated fish at 60 dpf relative to control values, but was unaffected in testes from thyroxine-treated individuals. Oogenesis seemed to be nonspecifically delayed in all treatments relative to control at 60 dpf. This study confirmed the previously reported association between hypothyroid condition and ovarian-skewed ratios, and hyperthyroid condition and testicular-skewed ratios, and also showed that male pubertal development is specifically delayed by experimental hypothyroidism. The simultaneous recovery from the hypothyroid and ovary-inducing effects of methimazole by 60 dpf (27 days post-treatment) suggests that the ovary-skewing effect of Goitrogens is reversible when thyroid conditions return to basal levels before developmental commitment of gonadal sex. Conversely, the masculinizing effect of hyperthyroidism seems to be stable and perhaps permanent.
Rohana Chandrajith - One of the best experts on this subject based on the ideXlab platform.
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Geochemistry of endemic goitre, Sri Lanka
Applied Geochemistry, 2009Co-Authors: C.b. Dissanayake, Rohana ChandrajithAbstract:Abstract A large section of the population living in the wet climatic zone of Sri Lanka is prone to endemic goitre, which is mainly caused by the lack of I. In Sri Lanka, an area in which 40% of the inhabitants are afflicted by goitre, the I content in soil and water was still observed to be high relative to other goitrous regions of the world, indicating the possible importance of other factors such as Goitrogens in the aetiology of endemic goitre. Cluster analysis of the geochemical data showed that the endemic goitre region lies in the group with lowest I, alkali earths, Cl, NO3-, Fe and Mn.
Thomas R. Zoeller - One of the best experts on this subject based on the ideXlab platform.
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Transient Maternal Hypothyroxinemia Potentiates the Transcriptional Response to Exogenous Thyroid Hormone in the Fetal Cerebral Cortex Before the Onset of Fetal Thyroid Function: A Messenger and MicroRNA Profiling Study
2016Co-Authors: Hongyan Dong, Seo-hee You, Mike G. Wade, Carole L. Yauk, Thomas R. ZoellerAbstract:Hongyan Dong and Seo-Hee You have contributed equally to the work and should be considered Co-first authors. Thyroid hormone (TH) is essential for brain development both before and after birth. We have used gene expression microarrays to ident-ify TH-regulated genes in the fetal cerebral cortex prior to the onset of fetal thyroid function to better understand the role of TH in early cortical development. TH levels were transiently manipulated in preg-nant mice by treatment with Goitrogens from gestational day (GD) 13–16 and/or by injection of TH 12 h before sacrifice on GD 16. The transcriptional response to exogenous TH in the GD 16 fetal cortex was potentiated by transient goitrogen treatment, suggesting that the hypothyroxinemic brain is a different substrate upon which TH can act, or that robust compensatory mechanisms are induced by transient hypothyroxinemia. Several known TH-responsive genes were identified including Klf9, and several novel TH-responsive genes such as Appbp2, Ppap2b, and Fgfr1op2 were identified i
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Transient Maternal Hypothyroxinemia Potentiates the Transcriptional Response to Exogenous Thyroid Hormone in the Fetal Cerebral Cortex Before the Onset of Fetal Thyroid Function: A Messenger and MicroRNA Profiling Study
2016Co-Authors: Hongyan Dong, Seo-hee You, Mike G. Wade, Carole L. Yauk, Thomas R. ZoellerAbstract:Hongyan Dong and Seo-Hee You have contributed equally to the work and should be considered Co-first authors. Thyroid hormone (TH) is essential for brain development both before and after birth. We have used gene expression microarrays to ident-ify TH-regulated genes in the fetal cerebral cortex prior to the onset of fetal thyroid function to better understand the role of TH in early cortical development. TH levels were transiently manipulated in preg-nant mice by treatment with Goitrogens from gestational day (GD) 13–16 and/or by injection of TH 12 h before sacrifice on GD 16. The transcriptional response to exogenous TH in the GD 16 fetal cortex was potentiated by transient goitrogen treatment, suggesting that the hypothyroxinemic brain is a different substrate upon which TH can act, or that robust compensatory mechanisms are induced by transient hypothyroxinemia. Several known TH-responsive genes were identified including Klf9, and several novel TH-responsive genes such as Appbp2, Ppap2b, and Fgfr1op2 were identified in which TH response elements were confirmed. We also identified specific microRNAs whose expression in the fetal cortex was af-fected by TH treatment, and determined that Ppap2b and Klf9 are the target genes of miR-16 and miR-106, respectively. Thus, a complex redundant functional network appears to coordinate TH-mediated gene expression in the developing brain
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doi: 10.1210/en.2005-0778 Polychlorinated Biphenyls Exert Selective Effects on Cellular Composition of White Matter in a Manner Inconsistent with Thyroid Hormone Insufficiency
2013Co-Authors: David S. Sharlin, Ruby Bansal, Thomas R. ZoellerAbstract:Developmental exposure to polychlorinated biphenyls (PCBs) is associated with a variety of cognitive deficits in humans, and recent evidence implicates white matter development as a potential target of PCBs. Because PCBs are suspected of interfering with thyroid hormone (TH) signaling in the developing brain, and because TH is important in oligodendrocyte development, we tested the hypothesis that PCB exposure affects the development of white matter tracts by disrupting TH signaling. Pregnant Sprague Dawley rats were exposed to the PCB mixture Aroclor 1254 (5 mg/kg), with or without cotreatment of Goitrogens from gestational d 7 until postnatal d 15. Treatment effects on white matter development were determined by separately measuring the cellular density and proportion of myelin-associated glycoprotein (MAG)-positive, O4-positive, and glial fibrillary acidic protei
Prakash Sharma - One of the best experts on this subject based on the ideXlab platform.
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regulation of gonadal sex ratios and pubertal development by the thyroid endocrine system in zebrafish danio rerio
General and Comparative Endocrinology, 2013Co-Authors: Prakash Sharma, Reynaldo PatinoAbstract:We examined associations between thyroid condition, gonadal sex and pubertal development in zebrafish. Seventy-two-hour postfertilization larvae were reared in untreated medium or in the presence of Goitrogens (sodium perchlorate, 0.82 mM; methimazole, 0.15 and 0.3 mM) or thyroxine (1 and 10 nM) for 30 days. Thyrocyte height, gonadal sex and gonadal development were histologically determined at 45 and 60 days postfertilization (dpf). Thyrocyte hypertrophy, an index of hypothyroidism, was observed at 45 and 60 dpf in perchlorate-treated but only at 45 dpf in methimazole-treated fish. Similarly, gonadal sex ratios were biased toward ovaries relative to control animals at 45 and 60 dpf in perchlorate-treated fish but only at 45 dpf in methimazole-treated fish. Gonadal sex ratios were biased toward testes at 45 and 60 dpf in thyroxine-treated fish. Spermatogenesis was delayed in testes from goitrogen-treated fish at 60 dpf relative to control values, but was unaffected in testes from thyroxine-treated individuals. Oogenesis seemed to be nonspecifically delayed in all treatments relative to control at 60 dpf. This study confirmed the previously reported association between hypothyroid condition and ovarian-skewed ratios, and hyperthyroid condition and testicular-skewed ratios, and also showed that male pubertal development is specifically delayed by experimental hypothyroidism. The simultaneous recovery from the hypothyroid and ovary-inducing effects of methimazole by 60 dpf (27 days post-treatment) suggests that the ovary-skewing effect of Goitrogens is reversible when thyroid conditions return to basal levels before developmental commitment of gonadal sex. Conversely, the masculinizing effect of hyperthyroidism seems to be stable and perhaps permanent.
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role of thyroid hormones in the development of gonadal sex external morphology and intestinal system of zebrafish danio rerio
2012Co-Authors: Prakash SharmaAbstract:We examined associations between thyroid condition, gonadal sex and pubertal development in zebrafish. Seventy-two-hour postfertilization larvae were reared in untreated medium or in the presence of Goitrogens (sodium perchlorate, 0.82 mM; methimazole, 0.15 and 0.3 mM) or thyroxine (1 and 10 nM) for 30 days. Thyrocyte height, gonadal sex and gonadal development were histologically determined at 45 and 60 days postfertilization (dpf). Thyrocyte hypertrophy, an index of hypothyroidism, was observed at 45 and 60 dpf in perchlorate-treated but only at 45 dpf in methimazoletreated fish. Similarly, gonadal sex ratios were biased toward ovaries relative to control animals at 45 and 60 dpf in perchlorate-treated fish but only at 45 dpf in methimazoletreated fish. Gonadal sex ratios were biased toward testes at 45 and 60 dpf in thyroxinetreated fish. Spermatogenesis was delayed in testes from goitrogen-treated fish at 60 dpf relative to control values, but was unaffected in testes from thyroxine-treated individuals. Oogenesis seemed to be nonspecifically delayed in all treatments relative to control at 60 dpf. This study confirmed the previously reported association between hypothyroid Texas Tech University, Prakash Sharma, December 2012 37 condition and ovarian-skewed ratios, and hyperthyroid condition and testicular-skewed ratios, and also showed that male pubertal development is specifically delayed by experimental hypothyroidism. The simultaneous recovery from the hypothyroid and ovary-inducing effects of methimazole by 60 dpf (27 days post-treatment) suggests that the ovary-skewing effect of Goitrogens is reversible when thyroid conditions return to basal levels before developmental commitment of gonadal sex. Conversely, the masculinizing effect of hyperthyroidism seems to be stable and perhaps permanent.