No description available.

No description available.

Carboxylesterase enzymes hydrolyze a wide variety of ester-containing xenobiotics to yield carboxylic acids. It has now been determined that these enzymes catalyze the ethanolic transesterification of ester-containing compounds. Perhaps the most widely publicized and significant transesterification reaction is the conversion of cocaine (COC) to cocaethylene (CE) in the presence of ethanol. The formed CE possesses pharmacological activity, nearly identical to COC, a longer half-life and is more toxic than COC. We hypothesized that the transesterification of COC to CE is not unique and other compounds containing carboxyl ester groups might undergo transesterification in the presence of ethanol. Both methyl-ester and ethyl-ester-containing compounds were investigated using an in vitro and in vivo paradigm. Cocaethylene (CE), meperidine (MEP) and methylphenidate (MPH) are all compounds containing carboxyl ester groups which are extensively metabolized to carboxylic acids. Excised liver from male Sprague-Dawley rats were homogenized and centrifuged at 9,000g and the S9 fraction collected. Each drug investigated was separately incubated with S9 at 37°C with and without ethanol or ²H₆-ethanol. Parent drugs and predicted ethyl-ester formation products were assayed via gas chromatography/mass spectrometry (GC/MS). The experiments were repeated in vivo in rats. Animals were dosed with drug in the absence or presence of ethanol or ²H₆-ethanol. Plasma was collected and assayed for parent drug and ethyl-ester formation products by GC/MS. Pharmacokinetic parameters were calculated for both in vitro and in vivo experiments. 2-Meperidine and 2-cocaethylene were formed from MEP and CE, respectively, in the presence of ²H₆-ethanol. The pharmacokinetics of meperidine and cocaethylene were significantly altered, increasing t1/2, when ethanol was given in combination with drug. Ethylphenidate (EPH) was formed both in vivo and in vitro when MPH and ethanol were administered. There was no significant change in MPH pharmacokinetics in the presence of ethanol both in vitro and in vivo. EPH administered to male Sprague-Dawley rats increased locomotor activity in equal intensity and duration to MPH. All ethanolic transesterification reactions investigated were completely inhibited by the addition of specific and non-specific carboxylesterase inhibitors in vitro, implicating a carboyl esterase-mediated transesterification process.

Chlorinated acetaldehydes have recently been the focus of research due to their role as reactive intermediates and their possible occurrence in chlorinated drinking water. The metabolism of these compounds, however, has not been extensively studied. In this study, the in vitro substrate specificity of cytosolic and mitochondrial rat liver aldehyde dehydrogenase toward these compounds was investigated. Both crude and semi-purified preparations of the enzymes were used. Monochloroacetaldehyde was found to be extensively metabolized by this enzyme system. It was metabolized to a greater extent than the standard compound propionaldehyde. Dichloroacetaldehyde was also found to be metabolized by this enzyme, but to a lesser extent than its monochloro-analogue. There was some evidence to suggest, however, that alcohol dehydrogenase and chloral hydrate dehydrogenase may play a significant role in the metabolism of this compound. Chloral hydrate was not metabolized by this enzyme to an appreciable extent.

Polychlorinated biphenyls (PCBs) are resistant to metabolism in most animal species. The dog has the unique ability to metabolize and eliminate certain PCB congeners, as a result of the activity of the cytochrome P450 isozyme PBD-2. An expressible cDNA coding for PBD-2 has been introduced into the genome of tobacco plants. The PBD-2 cDNA coding sequence and a screenable marker gene coding for neomycin phosphotransferase II were introduced into tobacco leaf disks using a binary Agrobacterium tumefaciens vector system. Southern and Western blot analysis have confirmed chromosomal integration of the cDNA and expression of the PBD-2 polypeptide. Differential centrifugation and Western blot analyses have shown the PBD-2 protein to be associated with a membrane fraction in transgenic tobacco leaf homogenates. Measurements of marker enzymes from linear sucrose gradient fractions and Western blotting show the PBD-2 protein to be associated with the endoplasmic reticulum. Our goal is to develop transgenic plants in which the PBD-2 protein metabolizes PCBs, thus providing a novel method for bioremediation of PCB-contaminated soils.

Toxic dinoflagellate Prorocentrum concavum cells (DC) implicated in ciguatera poisoning were lyophilized and mixed with a standard fish food and fed to Domino damsel fish (Dascyllus trimaculatus). Damsel fish fed 50/50-SC/DC and 100% DC diets exhibited physical and behavioral changes as well as death. Feed refusal was apparent among the fish fed 100% DC diet. Toxicity of the control group could be attributed to previous exposure of the fish to other polyether compounds in its natural habitat or even other chemicals. Fish extracts of both control and treatment groups were toxic when tested on the Stick-enzyme immunoassay for ciguatoxin. Okadaic acid was detected in P. concavum, but no okadaic acid was found in any of the fish tissue extracts. Further studies are needed to determine the transfer of toxin to the fish through diet before any conclusion is made.

Resin and fatty acids (RFAs) are the major toxic constituents of pulp and paper mill effluent. RFAs are toxic to aquatic life at low concentrations (2 ppm). The concentration and type of RFAs in the wastewater vary with wood source and mill process. The E-stage effluent contributes only 5-10% of the total plant wastewater discharges, yet most of the total wastewater toxicity and color is attributed to the E-stage. The focus of this research project was to determine which of four Advanced Oxidative Processes (Ozone, Ozone with Hydrogen Peroxide, Ozone with Ultraviolet 254nm light, Ozone with Hydrogen Peroxide and UV254nm light) produces the highest reduction of toxicity for a simulated E-stage wastewater. The treated water was characterized by UV absorbance scans, total organic carbon analysis, Gas Chromatography/Mass Spectroscopy and Microtox toxicity. The highest reduction of toxicity was achieved by 94.4 mg/L (30 minutes contact time) of Ozone transferred.

No description available.

Thesis (Ph.D.)--Brown University, 2008. / Source: Dissertation Abstracts International, Volume: 69-06, Section: B, page: 3556. Adviser: Anatoly Zhitkovich. Includes bibliographical references.

<p> Both infectious and noninfectious disease agents in wildlife impact human health and accurate research, monitoring, and diagnostic methods are necessary. The objectives of the research reported here were to develop and implement novel methods for bacterial and toxicological disease agent surveillance in wildlife. This dissertation begins with a review of tularemia, an important zoonotic disease to the state of Alaska and the Northern hemisphere. In chapter two, I show the development and implementation of broad-based PCR and quantitative PCR (qPCR) surveillance methods for bacterial DNA in tissue samples; 1298 tissue samples were assayed, numerous potential bacterial pathogens were identified and qPCR detection limits were quantified for various tissue matrices. Chapter three describes an investigation into microbial infection as a source of embryo mortality in greater white-fronted geese (<i>Anser albifrons</i>) in Arctic Alaska. This chapter builds upon our previously developed PCR surveillance techniques by which I demonstrated that bacterial infection is responsible for some greater white-fronted goose embryo mortality in Arctic Alaska. Chapter four describes the development and validation of a cellulose filter paper method for quantifying total mercury in whole blood. I determined that filter paper technology is useful for monitoring total mercury in whole blood, with excellent recoveries (82 - 95% of expected values) and R2 values (0.95 - 0.97) when regressed against the concentration of total mercury in whole blood, the technique generally considered as the "gold standard" for mercury detection. These methods will aid in the accurate detection of disease agents in wildlife as demonstrated by our white-fronted goose work. </p>