Polychlorinated biphenyls (PCBs) exert a broad range of toxicity via both parent compounds and their metabolites. Our previous study showed that hydroquinone (H2Q) metabolites of PCBs act as cosubstrates for prostaglandin H synthase (PGHS), and are oxidized by this enzyme to corresponding quinones (Q). The goal of this thesis is to illuminate the PGHS-mediated toxicity of lower chlorinated PCBs. It is hypothesized that PGHS catalyzes two sequential one-electron oxidations of PCB-H2Q to semiquinone (SQ), and Q that interact with biomolecules, such as amino acids, glutathione (GSH), protein, and DNA. In addition, the oxidation of H2Q by PGHS results in an elevation of downstream prostaglandin (PG) production in vivo. Employing 4-chlorobiphenyl-2f,5f-hydroquinone (4-CB-2f,5f-H2Q) as a model compound, I found that PGHS-2 catalyzes the one-electron oxidation of 4-CB-2f,5f-H2Q to SQ. An unusual electronically distorted SQ spectrum was observed as a result of the mixture of two different SQ species, a quartet and a doublet. Fate of 4-CB-2f,5f-SQ and/or Q in the presence of biomolecules was further investigated in the next study. 4-CB-2f,5f-SQ/Q reacts readily with the thiol-containing molecules, such as cysteine, and GSH. Oligonucleotides, and DNA did not form a covalent adduct with 4-CB-2f,5f-SQ but preferably stabilized 4-CB-2f,5f-SQ by pi-stacking interaction under the assay conditions. The in vivo study of downstream PG production in rats treated with 4-CB-2f,5f-H2Q revealed that PGE2 was significantly elevated in ratsf kidneys at 24 h post intratracheal instillation. The increased PGE2 production was correlated with an elevation of alveolar macrophages. These findings suggest two possible mechanisms of enhanced PGE2 production: i) 4-CB-2f,5f-H2Q as a cosubstrate for PGHS in kidney, and 2) release of cytokines from macrophages, leading to stimulation of PGE2 production in other tissues but released and accumulated in kidney for excretion. In summary, the toxicity of lower chlorinated PCBs metabolites is potentially mediated by PGHS. Quinones generated from the PGHS metabolic pathway covalently bind to GSH resulting in GSH depletion, and oxidative stress. The intercalation or pi-stacking of SQ in DNA may be implicated in genotoxicity as a result of the change in DNA structure.

No description available.

Os bifenilos policlorados (PCBs) são compostos organoclorados que apresentam 209 congêneres sendo que alguns deles são muito tóxicos. Foram produzidos por mais de 30 anos sendo utilizados principalmente no setor eletroeletrônico. Devido à legislação brasileira não prever substituição de equipamentos, ainda em funcionamento, que contenham PCBs estes podem tomar-se fontes potenciais de contaminação no ambiente. Neste aspecto a região do Vale do Paraiba, por ter um parque industrial diversificado (químico, eletrônico e mecânico) iniciado na década de 50, pode apresentar essas fontes. O rio Paraíba do Sul é o principal recurso hídrico sendo utilizado para captação de água para abastecimento e também como receptor de efluentes industriais e esgotos domésticos. Nele também é praticada a pesca de subsistência pela população ribeirinha. Devido às características de bioconcentração no fígado de peixe por organoclorados, decidiu-se utilizá-lo como bioindicador. Assim pode ser verificada a presença de PCBs na região avaliando-se os níveis de contaminação que podem colocar em risco as populações ribeirinhas. Na metodologia analítica proposta, foram encontrados de 48 a 159 ng/g de PCBs totais para a traíra e 12 a 34 ng/g de PCBs totais para o mandi. A recuperação alcançada foi na faixa de 50 a 100%. Os valores do limite de detecção para os 13 congêneres estudados se encontraram na faixa de 1 a 3 ng/g. Os congêneres mais genotóxicos (PCB 77 e 126) foram encontrados principalmente na traira com 20 ± 9 ng/g (PCB 77) e 21 ± 3 ng/g (PCB126), enquanto que o mandi apresentou principalmente o PCB 77 com 8 ± 2 ng/g. Estas avaliações são preliminares e necessitam de maiores estudos para se determinar a extensão do grau de contaminação e as possíveis fontes de contaminação por estes compostos. / The chlorinated biphenyls are organochlorinated compound with around 209 congeners some them are very toxic. They were produced during 30 years and used mainly in the eletronic equipment (transformers and capacitors). Brazilian legislation don\'t obligate the substitution of equipaments containing PCBs that are still being used. So this could be a signifincat source of environrnent contamination. The industries have settled the Paraíba Valley since 50\'s that can represent the major source of PCBs. The South Paraíba river main hidric source that has been used caption for water suplly and subsistent fishing. It receives also industrial efluents and domestic sewer. In spite of bioconcentration characteristics of organochIorinated in fishes\'liver, this organ was decided to be used as bioindicator. PCB\' s level can be avaliated indiretly, analysing the exposure of some species of fishes, and arevall contamination around the fish population. From this proposed analytical method total PCBs from traira here found nearly 32 to 143 ng/g in liver and 8 to 26 ng/g in mandi\'s liver. The aproached recuperation were about 50 to 100%, the limit detection for these 13 congeners were around 1 to 3ng/g. The most genotoxic congeners were found in traira (PCB 77 20 ± 9ng/g and PCB 12621 ± 3ng/g) and other hand, it was only in mandi PCB 77 8 ± 2ng/g. These evalutions are preliminar and necessites further studies to determine the extension of contarnination and the possibly source these compound\' s contamination.

Polychlorinated biphenyls (PCBs) are persistent environmental chemicals. Mono-hydroxylated polychlorinated biphenyls (OH-PCBs) are PCB metabolites found commonly in human blood, environmental water and sediment samples. Detection of small amounts of PCBs and their OH-PCB metabolites in biological matrices from epidemiological and laboratory studies remains a challenge. The application of aptamers is studied as a means to identify and quantify PCBs and OH-PCBs. Aptamers are single stranded short oligonucleotides that arrange into unique shape of three-dimensional structures when binding to their target. Like antibodies they have high affinity and specificity for their specific target. The hypothesis is that aptamers can identify PCBs and PCB metabolites in environmental and biological samples. To test this hypothesis, three different OH-PCBs, 4’-OH-PCB3, 4-OH-PCB72 and 2-OH-PCB106 along with 4-OH-biphenyl as a control, were covalently attached to beads with carboxylic acid groups on their surface. Several methods were explored to characterize covalent binding of OH-PCBs to the beads: FTIR-spectroscopy, Dynamic Light Scattering (DLS) and Zeta-Potential (ZP) measurements. The beads were then used in in vitro assays to test binding of two different aptamers specific to OH-PCBs. In this study, these aptamers were tested for the ability to distinguish structurally different OH-PCB congeners and other environmental pollutants. In future studies, aptamers can be selected for a PCB metabolite of interest, 4’-OH-PCB3, via a modified form of Systemic Evolution of Ligands by Exponential Enrichment (SELEX). Single stranded DNA (ssDNA) aptamers generated will be applied as a biosensor for the detection and quantification of traces of 4’-OH-PCB3.

In this dissertation I compare concentrations of polychlorinated biphenyls (PCBs) and hydroxylated PCBs (OH-PCB) in serum of children and their mothers from urban and rural U.S. communities, determine the variability of these concentrations from year to year, and report the detection of OH-PCBs in sediment from a Lake Michigan waterway and original commercial Aroclors. I developed extraction and analytical methods for the analysis of PCBs and OH-PCBs in 377 human serum samples and 20 sediment samples. I also developed a quality assurance protocol and analyzed more than 300 quality control samples for the purpose of generating an accurate, reproducible, representative, and precise data set. I found that concentrations of PCBs were much higher in mothers than their children, and concentrations of OH-PCBs were slightly higher in mothers than their children. Children were enriched in lower molecular weight PCBs indicating the importance of environmental exposure to their blood concentrations. I also determined that concentrations were similar between the urban and rural residents. These concentrations were similar to concentrations reported in the U.S. general population and other populations without high dietary PCB intake. In East Chicago and Columbus Junction participants, concentrations of OH-PCBs demonstrated a strong positive relationship with PCBs. Variability in PCB and OH-PCB concentration from the first year to the second in most participants exceeded the estimated analytical variability. Observed variability could be due to exposure differences, physiological changes such as metabolism and weight, or a combination. I also discovered the presence of OH-PCBs in the sediment from the Indiana Harbor and Ship Canal (IHSC), a Lake Michigan Waterway. In a first-approach, evidence from analysis of the correlations between OH-PCBs and PCBs in the same sediment is consistent with limited biotic activity. I also report OH-PCBs as contaminants in original commercial Aroclors, and OH-PCB profile similarities between the Aroclors and sediment suggest that Aroclors are the major source of OH-PCB contamination in IHSC. This is a significant finding because OH-PCB contamination of sediment exists anywhere that PCB contamination from Aroclors is present.

Os bifenilos policlorados (PCBs) são compostos organoclorados que apresentam 209 congêneres sendo que alguns deles são muito tóxicos. Foram produzidos por mais de 30 anos sendo utilizados principalmente no setor eletroeletrônico. Devido à legislação brasileira não prever substituição de equipamentos, ainda em funcionamento, que contenham PCBs estes podem tomar-se fontes potenciais de contaminação no ambiente. Neste aspecto a região do Vale do Paraiba, por ter um parque industrial diversificado (químico, eletrônico e mecânico) iniciado na década de 50, pode apresentar essas fontes. O rio Paraíba do Sul é o principal recurso hídrico sendo utilizado para captação de água para abastecimento e também como receptor de efluentes industriais e esgotos domésticos. Nele também é praticada a pesca de subsistência pela população ribeirinha. Devido às características de bioconcentração no fígado de peixe por organoclorados, decidiu-se utilizá-lo como bioindicador. Assim pode ser verificada a presença de PCBs na região avaliando-se os níveis de contaminação que podem colocar em risco as populações ribeirinhas. Na metodologia analítica proposta, foram encontrados de 48 a 159 ng/g de PCBs totais para a traíra e 12 a 34 ng/g de PCBs totais para o mandi. A recuperação alcançada foi na faixa de 50 a 100%. Os valores do limite de detecção para os 13 congêneres estudados se encontraram na faixa de 1 a 3 ng/g. Os congêneres mais genotóxicos (PCB 77 e 126) foram encontrados principalmente na traira com 20 ± 9 ng/g (PCB 77) e 21 ± 3 ng/g (PCB126), enquanto que o mandi apresentou principalmente o PCB 77 com 8 ± 2 ng/g. Estas avaliações são preliminares e necessitam de maiores estudos para se determinar a extensão do grau de contaminação e as possíveis fontes de contaminação por estes compostos. / The chlorinated biphenyls are organochlorinated compound with around 209 congeners some them are very toxic. They were produced during 30 years and used mainly in the eletronic equipment (transformers and capacitors). Brazilian legislation don\'t obligate the substitution of equipaments containing PCBs that are still being used. So this could be a signifincat source of environrnent contamination. The industries have settled the Paraíba Valley since 50\'s that can represent the major source of PCBs. The South Paraíba river main hidric source that has been used caption for water suplly and subsistent fishing. It receives also industrial efluents and domestic sewer. In spite of bioconcentration characteristics of organochIorinated in fishes\'liver, this organ was decided to be used as bioindicator. PCB\' s level can be avaliated indiretly, analysing the exposure of some species of fishes, and arevall contamination around the fish population. From this proposed analytical method total PCBs from traira here found nearly 32 to 143 ng/g in liver and 8 to 26 ng/g in mandi\'s liver. The aproached recuperation were about 50 to 100%, the limit detection for these 13 congeners were around 1 to 3ng/g. The most genotoxic congeners were found in traira (PCB 77 20 ± 9ng/g and PCB 12621 ± 3ng/g) and other hand, it was only in mandi PCB 77 8 ± 2ng/g. These evalutions are preliminar and necessites further studies to determine the extension of contarnination and the possibly source these compound\' s contamination.

No description available.

No description available.

No description available.

No description available.