Home About us Contact
|
Home About us Contact | ||
|
|
||
Dibenzo
Kinds of Dibenzo Selected AbstractsClose Proximity Dibenzo[a,c]phenazine,Fullerene Dyad: Synthesis and Photoinduced Singlet Energy TransferEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 18 2010Rajeev K. Dubey Abstract A dibenzo[a,c]phenazine,fullerene (DBPZ-C60) dyad in which two chromophores are linked in close proximity to each other has been synthesized and studied in detail by optical spectroscopy to explore a new energy donor,acceptor system. The dyad was prepared by Prato reaction between 11-formyldibenzo[a,c]phenazine and fullerene. 3,5-Di- tert -butylbenzyl group was introduced onto the fulleropyrrolidine unit to achieve adequate solubility of the dyad. A thorough study of the photophysical properties of the dyad and relevant reference compounds, performed by means of steady state and time resolved spectroscopic measurements, has revealed the presence of highly efficient (ca. 98,%) and extremely fast (ken = 5,×,1011 s,1) intramolecular photoinduced singlet,singlet energy-transfer process from singlet excited state of the DBPZ moiety to fullerene. In both polar and nonpolar environment transduction of singlet excited state energy governs the excited state deactivation, but the efficiency and rate of energy transfer were found to be higher in nonpolar solvents in comparison to polar. The DBPZ singlet excited state decays within 2 and 4.7 ps in toluene andbenzonitrile, respectively, via singlet,singlet energy transfer to produce a fullerene singlet excited state which decays with a life time of 1.5 ns to give a very long-lived fullerene triplet state as final populated excited state. [source] High-Performance Field-Effect Transistor Based on Dibenzo[d,d,]thieno[3,2- b;4,5- b,]dithiophene, an Easily Synthesized Semiconductor with High Ionization Potential,ADVANCED MATERIALS, Issue 19 2007H. Gao Three simple, controlled steps are all it takes to synthesize the title pentacene analogue DBTDT (see figure). The material's high ionization potential, high thermal and photostability, high mobilities, and an on/off ratio larger than 106 at a substrate temperature of ca.,36,°C, as reported here, suggest that DBTDT will be extremely valuable for applications in plastic organic electronics. [source] Synthesis and photorefractivity of poly[methyl-3-(7-dibenzo[a,g]carbazolyl)-propylsiloxane]JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 5 2008In Kyu Moon Abstract 7H -Dibenzo[a,g]carbazole-substituted polysiloxane (PSX-[a,g]BCz) has been synthesized by hexachloroplatinate (IV) hydrate polymerization from poly(methylhydrosiloxane) and 7-ally-7H -dibenzo[a,g]carbazole. PSX-[a,g]BCz composite showed large orientational birefringences because of both large dipole moments and high-polarizability anisotropies of P-IP-DC chromophore associated with the effective conjugation along the polyene. The 50-,m thick photorefractive material containing 30 wt % 2-[3-[(E)-2(piperidino)-1-ethenyl]-5,5-dimethyl]-2-cyclohexenyliden]malononitrile showed a diffraction efficiency of 51% at 55 V/,m, which corresponded to a ,n of 3.45 × 10,3. PSX-[a,g]BCz composite shows a fast time constant of 0.42 s at 34 °C and 55 V/,m, which corresponded to the space-charge field of 12 V/,m under 70 V/,m. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1783,1791, 2008 [source] Design of Living Ring-Opening Alkyne Metathesis,ANGEWANDTE CHEMIE, Issue 40 2010Dr. Felix R. Fischer Es lebt: Ein gespanntes cyclisches Alkin mit Dibenzo[a,e][8]annulen-Struktur geht eine Ringöffnungsmetathesepolymerisation (ROMP) zur Bildung eines hochmolekularen Poly(ortho -phenylens) mit alternierenden Ethyl- und Ethinylbrücken entlang dem Polymerrückgrat ein. Der Molybdänalkylidin-Katalysator wurde gezielt darauf abgestimmt, zwischen gespannten und ungespannten Alkinen unterscheiden zu können, und es resultiert ein lebendes Polymer mit beispiellos niedriger Polydispersität. [source] Synthesis, Structure, and Photophysical Properties of Dibenzo[de,mn]naphthacenes,ANGEWANDTE CHEMIE, Issue 39 2010Tsun-Cheng Wu Zethrene wurden durch Pd-katalysierte Cyclodimerisierung von 1-Ethinyl-8-iodnaphthalenen synthetisiert (siehe Schema). Die Strukturen dieser Cycloaddukte wurden durch Röntgenstrukturanalyse bestätigt, wobei die Bindungslängen offenbaren, dass die zwei zentralen sechsgliedrigen Ringe der Titelverbindung nicht aromatisch sind. [source] Ring Expansions of Tetrahydroprotoberberines and Related Dibenzo[c,g]azecines Modulate the Dopamine Receptor Subtype Affinity and SelectivityARCHIV DER PHARMAZIE, Issue 4 2010Maria Schulze Abstract The affinities of tetrahydroprotoberberines for dopamine receptors dramatically decrease after cleaving the central C-N bond to the analogous ten-membered dibenzo[c,g]azecines [1]. In the present work, we also synthesized eleven-membered homologues of these heterocycles and measured the affinities of the resulting dibenzazaundecenes and their underlying homoberberines for human dopamine receptors as well as the cytotoxic effects of all target compounds on human glia cells. The tetracyclic iso-C-homoberberine-derivatives revealed to be D4 -selective antagonists, while all other active compounds showed a significant D1/D5 selectivity. Distances in energy-minimized conformations were measured in order to explain our findings. [source] ChemInform Abstract: Efficient Synthesis of Dibenzo[a,c]cyclohepten-5-ones via a Sequential Suzuki,Miyaura Coupling and Aldol Condensation Reaction.CHEMINFORM, Issue 39 2009Young Lok Choi Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Palladium-Catalyzed Annulation of vic-Bis(pinacolatoboryl)alkenes and -phenanthrenes with 2,2,-Dibromobiaryls: Facile Synthesis of Functionalized Phenanthrenes and Dibenzo[g,p]chrysenes.CHEMINFORM, Issue 8 2009Masaki Shimizu Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Synthesis of Multi-Substituted Dibenzo[b,d]furan.CHEMINFORM, Issue 38 2008Jitendra M. Gajera Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: A New Concise Strategy for Synthesis of Dibenzo[b,f]thiepins and Related Fused Symmetrical Thiepin Derivatives.CHEMINFORM, Issue 13 2008Hamid Shirani Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Denitrocyclization in Synthesis of Dibenzo[b,f][1,4]thiazepin-11(10H)-ones and Their Derivatives.CHEMINFORM, Issue 12 2008Alexey V. Smirnov Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Chemoselective Synthesis of New Dibenzo[d,f]-1,3-dioxepines and 12H-Dibenzo[d,g]-1,3-dioxocinesCHEMINFORM, Issue 30 2007Graziella Tocco Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Synthesis of Dibenzo[b,g][1,5]diazoninedione and Isoindolo[2,1-a]quinazoline Derivatives.CHEMINFORM, Issue 27 2006Mehdi Bakavoli Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Direct, Two-Step Synthetic Pathway to Novel Dibenzo[a,c]phenanthridines.CHEMINFORM, Issue 37 2005Fatima Churruca Abstract For Abstract see ChemInform Abstract in Full Text. [source] Facile Synthesis and X-Ray Structure of Alkoxy-Functionalized Dibenzo[fg,op]naphthacenes.CHEMINFORM, Issue 48 2003Xiao Hong Cheng Abstract For Abstract see ChemInform Abstract in Full Text. [source] Synthesis of the Dibenzo[f,h]phthalazine and Dibenzo[f,h]cinnoline Skeleton via a "Suzuki,Pd-Catalyzed Intramolecular Arylation" and a "Suzuki,Pschorr" Approach.CHEMINFORM, Issue 44 2003Pal Tapolcsanyi Abstract For Abstract see ChemInform Abstract in Full Text. [source] Carbanion-Induced Synthesis of Dibenzo[a,c]cycloheptenes Through Ring Transformation Reactions of 2H-Pyran-2-one.CHEMINFORM, Issue 40 2002Vishnu Ji Ram Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: An Expeditious One-Pot Synthesis of Dibenzo[a,g]fluorene.CHEMINFORM, Issue 52 2001Bimal K. Banik Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Dibenzo[b,h][1,4,7]thiadiazonines: Examples of a Novel Ring System.CHEMINFORM, Issue 50 2001Alan R. Katritzky Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Platinum Complexes of Dibenzo[1,2]Dithiin, Dibenzo[1,2]Dithiin Oxides and Related Polyaromatic Hydrocarbon LigandsCHEMISTRY - A EUROPEAN JOURNAL, Issue 3 2006Stephen M. Aucott Dr. Abstract The synthesis of platinum bisphosphine complexes of biphenyl- 2,2,-dichalcogenates and the oxides of dibenzo[1,2]dithiin and related ligand systems by oxidative addition to [Pt(PPh3)4] is reported. We also describe the synthesis of a new compound, dibenzothiophen-4-yldiselenide and its simple platinum complex (obtained by oxidative addition). All complexes have been fully characterised, principally by using multinuclear NMR spectroscopy and in six cases by means of single-crystal X-ray diffraction studies. The majority are simple S/S or Se/Se complexes, however the addition of dibenzo[1,2]dithiin trioxide to [Pt(PPh3)4] gives a bimetallic system, [Pt{2-[S(O)],2,-[S(O)2]-biphen}(PPh3)]2, containing a central Pt2S2O2 core in which the ligand behaves as a tridentate S,S,O donor. [source] Selective Adsorption of Polychlorinated Dibenzo- p -dioxins and Dibenzofurans by the Zeosils UTD-1, SSZ-24, and ITQ-4CHEMISTRY - A EUROPEAN JOURNAL, Issue 1 2004Ralph Jäger Dr. Abstract Zeosils are microporous solids with a pure silica framework. Due to their hydrophobic properties, zeosils are ideal host materials for the adsorption of hydrophobic guest molecules. We tested zeosils with different pore diameters (UTD-1, SSZ-24 and ITQ-4 as well as CIT-5) for the selective adsorption of the polychlorinated dibenzo- p -dioxins and dibenzofurans. This group of highly toxic substances contains 210 congeners that possess similar chemical properties, but differ in their size and shape. In the experiment, polychlorinated dibenzo- p -dioxins and dibenzofurans were extracted from fly ash of a waste incinerator, adsorbed on amorphous silica, then thermally desorbed and flushed over a sequential arrangement of the zeosils at elevated temperature by a stream of nitrogen. ITQ-4 with the smallest pore diameter was placed first, followed by SSZ-24 and, finally, by UTD-1 with the largest pore diameter. After the experiment, the zeosils were analysed for their contents of the different congeners. The results show that the sorption of the congeners occurs selectively and that it is governed by the size and the shape of the dioxin molecules, which in turn depend on the number of chlorine atoms and the pattern of chlorine substitution (regioisomers). Geometrical reasoning as well as molecular dynamics calculations on the zeosil structures and on the dioxin molecules were helpful in rationalising the results. This work represents an especially complex case of the molecular sieving effect and may lead to a selective on-line monitoring of the concentrations of dioxin molecules in waste gases of industrial combustion processes. The size- and shape-selective sorption of dioxin molecules may also bear some resemblance to the molecular recognition process that occurs in nature at the aryl hydrocarbon receptor. [source] Formation of Trichlorinated Dibenzo- p -dioxins from 2,4-Dichlorophenol and 2,4,5-Trichlorophenolate: A Theoretical StudyCHEMPHYSCHEM, Issue 11 2006Ernesto Suįrez Abstract The reaction of the 2,4,5-trichlorophenolate anion with 2,4-dichlorophenol to afford trichlorinated dibenzo- p -dioxins (T3CDDs) is investigated at the B3LYP/6-31+G(d) and B3LYP/6-311+G(3df,2p)//B3LYP/6-31+G(d)+ZPVE(B3LYP/6-31+G(d)) levels of theory. The first stage of the process corresponds to the formation of a predioxin, which can evolve through four different routes. Two of them lead directly to the products 2,3,7-T3CDD and 1,3,8-T3CDD, and the other two afford different predioxin-type intermediates, which in turn can evolve through all or some of the four routes to give new predioxins or T3CDD. Consequently, the theoretical results obtained show plainly the complex chemistry implied in the formation of dioxins from chlorophenols via anionic mechanisms by disclosing all the critical structures through which the system evolves, thus allowing assessment of the viability of the different mechanistic routes and the accessible products. The statistical thermodynamics treatment at 1 atm and 298.15, 600, 900, and 1200 K indicates that at higher temperatures, the Gibbs energy barrier for the formation of the initial predioxin is clearly the rate-determining step for the whole process, but at lower temperatures the Gibbs energy barrier for this step is similar to those for its evolution into 2,3,7-T3CDD. This result is in contrast with previous proposals that the closure of the central ring is the rate-limiting step. Finally, according to our results the rate constant for the formation of polychlorinated dibenzo- p -dioxins increases with the temperature, in agreement with the experimental observation that the conversion of trichlorophenols increases when going from 600 to 900 K in the gas phase in the absence of catalysts, and with DFT molecular dynamics results. [source] Tobacco smoke carcinogens and breast cancerENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 2-3 2002Stephen S. Hecht Abstract Cigarette smoking is an established cause of a variety of cancer types, but its role in breast cancer etiology is not clear. In this report, the potential role of cigarette smoke carcinogens as causes of human breast cancer is evaluated. Of over 60 known carcinogens in tobacco smoke, several are known to induce mammary tumors in laboratory animals: benzo[a]pyrene (B[a]P), dibenzo[a,l]pyrene (DB[a,l]P), 2-toluidine, 4-aminobiphenyl, 2-amino-3-methylimidazo[4,5- f]quinoline (IQ), 2-amino-1-methyl-6-phenylimidazo[4,5- b]pyridine (PhIP), 1,3-butadiene, isoprene, nitromethane, ethylene oxide, and benzene. Studies in humans demonstrate that tobacco constituents can reach breast tissue. The uptake and metabolic activation of mammary carcinogens such as polycyclic aromatic hydrocarbons (PAHs) and 4-aminobiphenyl are frequently higher in smokers than in nonsmokers. Although it is likely that specific mammary carcinogens in tobacco smoke can reach breast tissue, evidence is lacking at the present time. Some PAHs present in cigarette smoke can be metabolized to sterically hindered diol epoxides, which are potent mammary carcinogens. Thus, compounds such as benzo[c]phenanthrene (B[c]P), not classically considered to be a strong carcinogen in rodents, could nevertheless be metabolized in humans to diol epoxides carcinogenic to the breast. Collectively, the link between smoking and breast cancer is plausible but has been difficult to establish, probably because of the low carcinogen dose. Environ. Mol. Mutagen. 39:119,126, 2002. © 2002 Wiley-Liss, Inc. [source] Interaction between halogenated aromatic compounds in the Ah receptor signal transduction pathwayENVIRONMENTAL TOXICOLOGY, Issue 5 2004Guosheng Chen Abstract Many toxic and biochemical responses to halogenated aromatic compounds (HACs) such as polychlorinated biphenyls (PCBs) and polychlorinated dibenzo- p -dioxins (PCDDs) are mediated through the aryl hydrocarbon receptor (AhR), which is an intracellular cytosolic target for HACs. Environmental exposure to HACs almost always involves complex mixtures of congeners, some of which can antagonize the action of potent HACs such as 2,3,7,8-tetrachlorodibenzo- p -dioxin (TCDD). In this work we studied TCDD and representative PCB congeners, alone and in mixture, for their effect on CYP1A gene transcription and protein levels in primary rat hepatocytes. Together with our previous work, our results suggest that formation of the Ah receptor-ligand-DRE (dioxin response element) complex is the principal point of divergence in the mechanism between an AhR agonist and an AhR antagonist. The coplanar PCBs 77 and 126 and the mono- ortho PCB 156 were full agonists toward CYP1A1 gene transcription and CYP1A protein levels, showing typical additive behavior with TCDD to the target molecule AhR. In contrast, the nonplanar PCB 153 antagonized the action of TCDD, even at concentrations that occupied a significant fraction of AhR molecules. Competitive inhibition explains the commonly reported decrease of ethoxyresorufin- O -deethylase (EROD) activity when PCBs are present in high concentrations and the antagonism of PCBs to the EROD activity of TCDD. The result is that Western blotting offers a much more reliable measure of CYP1A protein concentration than does the EROD assay, despite the greater convenience of the latter. © 2004 Wiley Periodicals, Inc. Environ Toxicol 19: 480,489, 2004. [source] Patterns of organic contaminants in eggs of an insectivorous, an omnivorous, and a piscivorous bird nesting on the Hudson River, New York, USAENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2010Christine M. Custer Abstract Belted kingfisher (Ceryle alcyon), spotted sandpiper (Actitus macularia), and tree swallow (Tachycineta bicolor) eggs were collected in 2004 from the upper Hudson River, New York, USA. This area is one of the most polychlorinated biphenyl (PCB)-contaminated locations in North America. Multivariate analyses indicated among species differences in the concentration and composition of PCB congeners, polychlorinated dibenzo- p -dioxin (PCDD), and dibenzofuran (PCDF, PCDD-F when combined with PCDDs) congeners, and chlorinated pesticides. Total PCB concentrations followed the typical food chain biomagnification paradigm of higher concentrations in piscivorous bird eggs and lower concentrations in eggs of species that feed at lower trophic levels. Concentrations in the insectivorous swallows (geometric mean,=,6.8,µg/g wet wt) were approximately half the concentrations present in the piscivorous kingfisher (11.7,µg/g) or omnivorous sandpiper (12.6,µg/g). In contrast, PCB toxic equivalents (TEQs) were higher in swallows (1,790,pg/g wet wt) than in either kingfishers (776,pg/g) or sandpipers (881,pg/g). This difference can be mainly attributed to higher PCB77 concentrations in swallows relative to the other two species. Also contrary to the accepted food-chain paradigm, the sum of PCDD-F concentrations and the sum of their TEQs were higher in swallows than in either sandpipers or kingfishers. Metabolic pathway differences in the respective food chains of the three species probably accounted for the differences observed in PCB TEQ, total PCDD-F, and PCDD-F TEQ concentrations among species. Environ. Toxicol. Chem. 2010;29:2286,2296. © 2010 SETAC [source] Exposure and effects assessment of resident mink (Mustela vison) exposed to polychlorinated dibenzofurans and other dioxin-like compounds in the Tittabawassee River basin, Midland, Michigan, USA,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2008Matthew J. Zwiernik Abstract Historically, sediments and floodplain soils of the Tittabawassee River (TR; MI, USA) have been contaminated with polychlorinated dibenzofurans (PCDFs), polychlorinated dibenzo- p -dioxins (PCDDs), and polychlorinatedbiphenyls (PCBs). Median concentrations of 2,3,7,8-tetrachlorodibenzo- p -dioxin equivalents (TEQs) based on 2006 World Health Organization tetrachloro-dibenzo- p -dioxin toxic equivalency factors (TEFs) in the diet of mink (Mustela vison) ranged from 6.8 × 10,1 ng TEQ/kg wet weight upstream of the primary source of PCDF to 3.1 × 101 ng TEQ/kg wet weight downstream. Estimates of toxicity reference values (TRVs) derived from laboratory studies with individual PCDDs/PCDFs and PCB congeners or mixtures of those congeners, as well as application of TEFs, were compared to site-specific measures of mink exposure. Hazard quotients based on exposures expressed as concentrations of TEQs in the 95th percentile of the mink diet or liver and the no-observable-adverse-effect TRVs were determined to be 1.7 and 8.6, respectively. The resident mink survey, however, including number of mink present, morphological measures, sex ratios, population age structure, and gross and histological tissue examination, indicated no observable adverse effects. This resulted for multiple reasons: First, the exposure estimate was conservative, and second, the predominantly PCDF congener mixture present in the TR appeared to be less potent than predicted from TEQs based on dose,response comparisons. Given this, there appears to be great uncertainty in comparing the measured concentrations of TEQs at this site to TRVs derived from different congeners or congener mixtures. Based on the lack of negative outcomes for any measurement endpoints examined, including jaw lesions, a sentinel indicator of possible adverse effects, and direct measures of effects on individual mink and their population, it was concluded that current concentrations of PCDDs/PCDFs were not causing adverse effects on resident mink of the TR. [source] Polychlorinated naphthalenes and other dioxin-like compounds in Elbe River sedimentsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2008Werner Brack Abstract Contamination of Elbe River (Germany) sediments with dioxin-like toxicants was investigated following the 500-year flood (flood that statistically occurs once in 500 years) of 2002. It was hypothesized that large amounts of particulate matter from river beds and associated dioxin-like toxicants were mobilized and transported during this flood event. The investigation focused on polychlorinated naphthalenes (PCNs) that have not been determined previously in the Elbe River. The in vitro H4IIE- luc assay was used as an overall measure for toxicants capable of binding to the aryl hydrocarbon receptor (AhR). The assay was combined with congener-specific instrumental analyses and fractionation to quantify PCN contributions to total AhR-mediated activity relative to polychlorinated dibenzo- p -dioxins and dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs). Penta- to octachloron-aphthalene concentrations of 30 ng/kg dry weight up to 13 ,g/kg dry weight were found in Elbe River sediments downstream of Bitterfeld. Concentrations of penta- to octachloronaphthalenes, however, were only approximately 3 ,g/kg dry weight at a site in the vicinity of Bitterfeld, where a level of approximately 3 mg/kg dry weight was reported before the flood. Also, the congener pattern of PCNs at this site changed after the flood, and PCN patterns reported previously for Bitterfeld and assigned to chlor-alkali electrolysis with graphite electrodes could now be observed at the sites from downstream of Bitterfeld and Magdeburg. Whereas PCDD/Fs dominated the dioxin-like activity in the middle and lower Elbe River, PCNs contributed as much as 10% of the total AhR-mediated activity. The contribution of PCBs was less significant (maximum, 0.2%). Thus, in Elbe River sediments, PCNs should be considered as relevant contaminants and be included in future monitoring and risk assessment programs. [source] Predicting world health organization toxic equivalency factor dioxin and dioxin-like polychlorinated biphenyl levels in farmed atlantic salmon (Salmo salar) based on known levels in feedENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2007Marc H. G. Berntssen Abstract Assimilation and elimination rate constant of dietary polychlorinated dibenzo- p -dioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (DLPCBs) with a World Health Organization toxic equivalency factor (WHO-TEF) were estimated in market-size Atlantic salmon (Salmo salar) using fish that were previously fed vegetable oil,based (low in PCDD/Fs and DLPCBs) or fish oil,based (high in PCDD/Fs and PCBs) diets. At the start of the kinetic trial, half the fish that were fed fish oils were fed vegetable oil feeds and inverted (cross-over design) for five months. The assimilation efficiencies of the PCDD/F congeners were more variable (3,89%) and, generally, were lower than those of the DLPCBs (70,80%). Among the PCDD/F congeners, the assimilation efficiency of the most toxic tetra- and pentachlorinated PCDD/Fs was greater than that of higher-chlorinated PCDD/Fs. Elimination rates for DLPCBs were higher than those for PCDD/Fs. Lower-chlorinated PCDDs had a lower elimination rate than the higher-chlorinated PCDDs, but no differences were observed among PCDF congeners or DLPCB congeners. Kinetic parameters were used to predict the level of WHO-TEF dioxins and DLPCBs in Atlantic salmon reared in a large-scale facility under commercial conditions. Predictions were based on preanalyzed levels of these organochlorines in feeds with three different replacement levels (0, 30, and 60%) of vegetable oil. A simple one-compartmental, first-order kinetic model was used to predict the level of sum WHO toxic equivalents for PCDD/Fs and DL-PCBs. The predicted values varied by 0 to 11% from the measured values in the commercially reared salmon. [source] Congener-specific toxicokinetics of polychlorinated dibenzo- p -dioxins, polychlorinated dibenzofurans, and coplanar polychlorinated biphenyls in black-eared kites (Milvus migrans): Cytochrome P4501A,dependent hepatic sequestrationENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2006Akira Kubota Abstract Concentrations of dioxins and related compounds (DRCs), such as polychlorinated dibenzo- p -dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (Co-PCBs), were determined in black-eared kites (BEKs; Milvus migrans) collected from the Kanto district in Japan. Total 2,3,7,8-tetra-CDD toxic equivalents (TEQs) were in the range of 99 to 3,800 pg/g lipid weight in the liver and 42 to 760 pg/g lipid weight in the pectoral muscle. Three congeners, including PCB 126, 2,3,4,7,8-penta-CDF, and 1,2,3,7,8-penta-CDD, made a greater contribution to total TEQs in both tissues. Levels of ethoxy-resorufin- O -deethylase activity and a cross-reactive protein with anti-rat cytochrome P4501A (CYP1A) polyclonal antibodies showed no significant correlation with hepatic TEQs. This may be attributed to low sensitivity and insufficient TEQ levels to cause CYP1A induction, high metabolic potential of a series of congeners, and influence of CYP1A inducers other than DRCs. Most of the PCDD/Fs and non- ortho Co-PCBs exhibited a total TEQ- and CYP1A-dependent increase in the liver to muscle concentration ratios, implying their concentration-dependent hepatic sequestration in which CYP1A was involved. Comparison of the toxicokinetics in avian species revealed that BEKs possibly have higher potentials than common cormorants for metabolizing and sequestering certain congeners in the liver in terms of hepatic concentration profiles and liver:muscle concentration ratios, respectively. These results clearly indicate that the toxicokinetics of DRCs is congener-, tissue-, and species-specific as well as concentration-dependent. Therefore, CYP1A expression is one of the critical factors that determine the toxicokinetics in wild avian species. [source] Effects of maternally transferred organochlorine contaminants on early life survival in a freshwater fishENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2005Thomas A. Johnston Abstract Laboratory research has shown that female fish can pass toxic organochlorines (OCs) from their bodies to their eggs, killing their offspring if sufficient quantities are transferred. We conducted a controlled incubation study using gametes from a wild, OC-contaminated walleye (Sander vitreus) population (Bay of Quinte, Lake Ontario, Canada) in order to assess among-female variation in offspring early life survival in relation to ova concentrations of planar OCs (polychlorinated dibenzo- p -dioxins and furans and planar polychlorinated biphenyls) and a suite of other maternal and ova characteristics. Equal volumes of ova from each female were fertilized, pooled, and incubated together as an experimental cohort. Relative survival of each female's offspring was estimated as the proportion of surviving larvae (at ,5 d posthatch) that she contributed to the cohort as determined by microsatellite DNA parentage assignment. Total planar OC concentration (expressed as toxic equivalency of 2,3,7,8-tetrachloro-dibenzo- p -dioxin) of ova was positively related to maternal age and size and to ova lipid content. However, early life survival did not decline with increasing ova planar OC concentrations. Similarly, we observed no significant relationships between early life survival and ova thiamine content, ova fatty acid composition, or maternal age or size. Early life survival was more strongly correlated with date of spawn collection, thyroid hormone status of the ova, and ovum size. Maternally transferred planar OCs do not appear to negatively influence female reproductive success in this walleye population. [source] | |||||||||||||||||||||||||||||||||||||