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283 results on '"Bull, Richard J."'

4. Absorption and disposition of bromate in F344 rats

Author

Bull, Richard J., Kolisetty, Narendrababu, Zhang, Xiaoling, Muralidhara, Srinivasa, Quiñones, Oscar, Lim, Kok Yong, Guo, Zhongxian, Cotruvo, Joseph A., Fisher, Jeffrey W., Yang, Xiaoxia, Delker, Don, Snyder, Shane A., and Cummings, Brian S.

Published
2012
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21. Response

Author

Hrudey, Steve E., Bull, Richard J., Cotruvo, Joseph A., Paoli, Greg, and Wilson, Margaret

Published
2014
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27. Development of a rat and human PBPK model for bromate and estimation of human equivalent concentrations in drinking water.

Author

Campbell Jr, Jerry L., Bull, Richard J., and Clewell III, Harvey J.

Subjects
*INTESTINAL physiology, *BIOLOGICAL models, *MOUTH physiology, *ANIMAL experimentation, *BIOAVAILABILITY, *DRINKING (Physiology), *WATER supply, *RATS, *BROMATES, *BIOACCUMULATION, *OSMOLAR concentration, *TUMORS, *BIOLOGICAL assay
Abstract

A physiologically based pharmacokinetic (PBPK) model was developed to described uptake, disposition and clearance of bromate in the rat using published experimental data in rat. The rodent bromate model was extrapolated to human using species-specific physiological parameters and standard interspecies scaling of rate constants. The bromate model is kinetically linear (i.e. AUC and Cmax) across the range of drinking water concentrations used in the cancer bioassays (15 to 500 ppm). This is likely the result of the poor oral bioavailability of bromate due to high reduction rates in the intestinal tract. The bromate PBPK model was used to assess the human equivalent drinking water concentration (HEC) consistent with average plasma concentrations in the rodent bioassays. At drinking water concentrations <500 mg/L, the predicted HEC was two to three fold lower than the bioassay concentration and was dependent on the reported drinking water intake reported in the bioassay. [ABSTRACT FROM AUTHOR]

Published
2021
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33. Comparison of the Effects of Iodine and Iodide on Thyroid Function in Humans

Author

Robison, Linda M, Bull, Richard J, Sylvester, Paul W, Birkenfeld, Paul, and Lang, Jerome

Subjects
Aerospace Medicine
Abstract

The present experiment in humans failed to confirm the differential effect of I(sub 2) on maintenance of serum T(sub 4) concentrations relative to the effects of I(-) that was observed in prior experiments in rats. The reaction of I(sub 2) with metabolites of thyroid hormones in the intestine that appears responsible for this effect in rats probably also exists at some level in humans. The present results suggest that the concentrations of such metabolites in the human intestinal tract are too small to significantly affect circulating concentration of T(sub 4). However, based on the elevations in TSH, there should be some concern over the potential impacts of chronic consumption of iodine in drinking water.

Published
1995

35. Thyroid effects of iodine and iodide in potable water

Author

Bull, Richard J, Thrall, Karla D, and Sherer, Todd T

Subjects
Man/System Technology And Life Support
Abstract

Experiments are reviewed which examine the comparative toxicological effects of iodide (I) and iodine (I2) when used to disinfect drinking water. References are made to a subchronic study in rats, a comparison of the distribution of radiolabeled I and I2, and a demonstration of thyroxine formation in the gastrointestinal tract. The results of the study of the rats are examined in detail; the findings show that I and I2 have opposite effects on the concentrations of thyroid hormones in blood. Iodide slightly decreases circulating thyroxine, while I2 significantly increases the thyroxine concentrations, decreases triiodothyronine levels, and does not change the weight of the thyroid gland. The related effects of I2 ingestion are set forth in detail and are shown to be unique to I2 contamination. Iodine can counteract the effects of iodide and should therefore be used as a disinfectant in drinking water.

Published
1991

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