The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
Changzhou Yan - One of the best experts on this subject based on the ideXlab platform.
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Diastereoisomer specific effects of hexabromocyclododecanes on hepatic aryl hydrocarbon receptors and cytochrome p450s in zebrafish danio rerio
Chemosphere, 2015Co-Authors: Chao Fang, Ling Qiu, Sijun Dong, Xian Zhang, Changzhou YanAbstract:Abstract In order to elucidate the mechanism for Diastereoisomer-specific toxicity and metabolism of hexabromocyclododecanes (HBCDs) in biota, zebrafish (Danio rerio) were exposed to different concentrations of individual HBCD Diastereoisomers (α-, β- and γ-HBCD) in water for 7 and 21 d. We examined the gene expression of aryl hydrocarbon receptor (AHR) and cytochrome P450 (CYP), as well as ethoxyresorufin-O-deethylase (EROD) activity in zebrafish livers. Exposure to different HBCD Diastereoisomers caused different expression of AHRs in zebrafish livers. For instance, 10 and 100 μg L−1 of α- and β-HBCD up-regulated the expressions of ahr1a and ahr1b in zebrafish liver, whereas 10 and 100 μg L−1 of γ-HBCD down-regulated them after 7 d exposure. α-HBCD showed the most significant up-regulation of ahr1a and ahr1b expression, whereas γ-HBCD showed the most significant down-regulation of their expression among three HBCD Diastereoisomers. Moreover, HBCDs could affect the expression of CYP1s as well as EROD activity in a gene-specific and Diastereoisomer-specific manner. α-, β- and γ-HBCD inhibited cyp1a expression but enhanced the expression of cyp1b1 and cyp1c1. α-, β- and γ-HBCD showed different degrees of effect on the same CYP1 gene in a concentration-dependent way. The different effects of HBCD Diastereoisomers on these genes we examined and EROD activity not only indicate Diastereoisomer-specific toxic effect, but also in turn explain Diastereoisomer-specific accumulation of HBCDs in zebrafish.
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Diastereoisomer and enantiomer specific accumulation depuration and bioisomerization of hexabromocyclododecanes in zebrafish danio rerio
Environmental Science & Technology, 2012Co-Authors: Lifeng Lin, Changzhou Yan, Xian ZhangAbstract:In this study, zebrafish (Danio rerio) were exposed to two dietary concentrations of individual HBCD Diastereoisomers (α-, β-, and γ-HBCD) for 42 days, followed by clean food for 21 days, to examine bioaccumulation, depuration, and enantiomer fractions (EFs) of HBCD Diastereoisomers and to test the bioisomerization of HBCDs in fish. The depuration of α-, β-, and γ-HBCD in zebrafish followed the first-order process. Bioaccumulation parameters of the three Diastereoisomers differed between low and high dose, suggesting that the bioaccumulation of them is concentration dependent. Calculated assimilation efficiencies (AEs), biomagnification factors (BMFs), and half-lives (t1/2) of α-HBCD were the highest among the three Diastereoisomers. Furthermore, the study showed that zebrafish could biotransform γ-HBCD to α-HBCD. The highest AE, BMF, and t1/2 of α-HBCD and bioisomerization of γ-HBCD to α-HBCD could explain why α-HBCD appears to be dominant in biota samples. The EFs for α- and γ-HBCD in zebrafish estimate...
Xian Zhang - One of the best experts on this subject based on the ideXlab platform.
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Diastereoisomer specific effects of hexabromocyclododecanes on hepatic aryl hydrocarbon receptors and cytochrome p450s in zebrafish danio rerio
Chemosphere, 2015Co-Authors: Chao Fang, Ling Qiu, Sijun Dong, Xian Zhang, Changzhou YanAbstract:Abstract In order to elucidate the mechanism for Diastereoisomer-specific toxicity and metabolism of hexabromocyclododecanes (HBCDs) in biota, zebrafish (Danio rerio) were exposed to different concentrations of individual HBCD Diastereoisomers (α-, β- and γ-HBCD) in water for 7 and 21 d. We examined the gene expression of aryl hydrocarbon receptor (AHR) and cytochrome P450 (CYP), as well as ethoxyresorufin-O-deethylase (EROD) activity in zebrafish livers. Exposure to different HBCD Diastereoisomers caused different expression of AHRs in zebrafish livers. For instance, 10 and 100 μg L−1 of α- and β-HBCD up-regulated the expressions of ahr1a and ahr1b in zebrafish liver, whereas 10 and 100 μg L−1 of γ-HBCD down-regulated them after 7 d exposure. α-HBCD showed the most significant up-regulation of ahr1a and ahr1b expression, whereas γ-HBCD showed the most significant down-regulation of their expression among three HBCD Diastereoisomers. Moreover, HBCDs could affect the expression of CYP1s as well as EROD activity in a gene-specific and Diastereoisomer-specific manner. α-, β- and γ-HBCD inhibited cyp1a expression but enhanced the expression of cyp1b1 and cyp1c1. α-, β- and γ-HBCD showed different degrees of effect on the same CYP1 gene in a concentration-dependent way. The different effects of HBCD Diastereoisomers on these genes we examined and EROD activity not only indicate Diastereoisomer-specific toxic effect, but also in turn explain Diastereoisomer-specific accumulation of HBCDs in zebrafish.
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Diastereoisomer and enantiomer specific accumulation depuration and bioisomerization of hexabromocyclododecanes in zebrafish danio rerio
Environmental Science & Technology, 2012Co-Authors: Lifeng Lin, Changzhou Yan, Xian ZhangAbstract:In this study, zebrafish (Danio rerio) were exposed to two dietary concentrations of individual HBCD Diastereoisomers (α-, β-, and γ-HBCD) for 42 days, followed by clean food for 21 days, to examine bioaccumulation, depuration, and enantiomer fractions (EFs) of HBCD Diastereoisomers and to test the bioisomerization of HBCDs in fish. The depuration of α-, β-, and γ-HBCD in zebrafish followed the first-order process. Bioaccumulation parameters of the three Diastereoisomers differed between low and high dose, suggesting that the bioaccumulation of them is concentration dependent. Calculated assimilation efficiencies (AEs), biomagnification factors (BMFs), and half-lives (t1/2) of α-HBCD were the highest among the three Diastereoisomers. Furthermore, the study showed that zebrafish could biotransform γ-HBCD to α-HBCD. The highest AE, BMF, and t1/2 of α-HBCD and bioisomerization of γ-HBCD to α-HBCD could explain why α-HBCD appears to be dominant in biota samples. The EFs for α- and γ-HBCD in zebrafish estimate...
F. Seutter-berlage - One of the best experts on this subject based on the ideXlab platform.
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Stereoselective oxidation of styrene to styrene oxide in rats as measured by mercapturic acid excretion.
Xenobiotica, 2008Co-Authors: L. P. C. Delbressine, F. L. M. Smeets, Peter J Van Bladeren, F. Seutter-berlageAbstract:1. Administration of styrene (I) and styrene oxide (II) to rats resulted in the excretion of 2-hydroxymercapturic acids, N-acetyl-S-(1-phenyl-2-hydroxyethyl)cysteine (III) and N-acetyl-S-(2-phenyl-2-hydroxyethyl)cysteine (IV). Each appeared to be a mixture of Diastereoisomers.2. Administration of optically pure styrene oxide resulted in formation of one set of Diastereoisomers. Racemic styrene oxide gave equal amounts of Diastereoisomers. Thus the opening of the epoxide ring by glutathione S-transferases was stereospecific and the transferases showed no preference for one of the isomers of styrene oxide.3. After administration of styrene the observed ratio of the Diastereoisomers for both hydroxymercapturic acids was about 1 :4. This leads to the conclusion that there is a stereoselective oxidation of styrene to styrene oxide, with a preference for the R-isomer.
Yvon Fréchette - One of the best experts on this subject based on the ideXlab platform.
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Concise synthesis of yingzhaosu C and epi-yingzhaosu C by peroxyl radical cyclization. Assignment of relative configuration
Tetrahedron Letters, 1995Co-Authors: John Boukouvalas, Roxane Pouliot, Yvon FréchetteAbstract:Abstract The antimalarial peroxide yingzhaosu C and its Diastereoisomer (epi-yingzhaosu C) have been synthesized by means of tandem peroxyl radical cyclization-oxygen entrapment. The relative configuration of yingzhaosu C is assigned as cis (3) on account of NMR data for both Diastereoisomers, (2) and (3), and their precursors (8) and (9).
Chao Fang - One of the best experts on this subject based on the ideXlab platform.
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Diastereoisomer specific effects of hexabromocyclododecanes on hepatic aryl hydrocarbon receptors and cytochrome p450s in zebrafish danio rerio
Chemosphere, 2015Co-Authors: Chao Fang, Ling Qiu, Sijun Dong, Xian Zhang, Changzhou YanAbstract:Abstract In order to elucidate the mechanism for Diastereoisomer-specific toxicity and metabolism of hexabromocyclododecanes (HBCDs) in biota, zebrafish (Danio rerio) were exposed to different concentrations of individual HBCD Diastereoisomers (α-, β- and γ-HBCD) in water for 7 and 21 d. We examined the gene expression of aryl hydrocarbon receptor (AHR) and cytochrome P450 (CYP), as well as ethoxyresorufin-O-deethylase (EROD) activity in zebrafish livers. Exposure to different HBCD Diastereoisomers caused different expression of AHRs in zebrafish livers. For instance, 10 and 100 μg L−1 of α- and β-HBCD up-regulated the expressions of ahr1a and ahr1b in zebrafish liver, whereas 10 and 100 μg L−1 of γ-HBCD down-regulated them after 7 d exposure. α-HBCD showed the most significant up-regulation of ahr1a and ahr1b expression, whereas γ-HBCD showed the most significant down-regulation of their expression among three HBCD Diastereoisomers. Moreover, HBCDs could affect the expression of CYP1s as well as EROD activity in a gene-specific and Diastereoisomer-specific manner. α-, β- and γ-HBCD inhibited cyp1a expression but enhanced the expression of cyp1b1 and cyp1c1. α-, β- and γ-HBCD showed different degrees of effect on the same CYP1 gene in a concentration-dependent way. The different effects of HBCD Diastereoisomers on these genes we examined and EROD activity not only indicate Diastereoisomer-specific toxic effect, but also in turn explain Diastereoisomer-specific accumulation of HBCDs in zebrafish.