Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.23.17 (PCE)
 1,301 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Ester hydrolysis represents an important biotransformation pathway for various parasympatholytic agents. Cleavage of the ciclotropium ester bond results in the formation of alpha-phenylciclopentylacetic acid (PCA). The relevance of this metabolic route for ciclotropium bromide (HIT-PCE, CAS 85166-20-7) including its stereochemical aspects was studied in a preliminary pharmacokinetic study. An enantiospecific assay for biological material was developed that is based on chiral derivatization of PCA with N-ethyl-N'-(3-dimethylaminopropyl)carbodiimide (EDAC) and the primary amine S-FLOPA, a chiral coupling component for carboxylic acids derived from S-flunoxaprofen, followed by HPLC resolution. R-(--)-Ibuprofen was used as internal standard. From plasma or urine PCA can be extracted into n-hexane/ethanol (9:1) at pH 4 under addition of sodium chloride. Derivatization with EDAC/FLOPA was performed under addition of 1-hydroxybenzotriazole in anhydrous dichloromethane that contained trace amounts of pyridine (ambient temperature; 2 h reaction time). The chromatographic separation was performed on a silica gel stationary phase (Zorbax Sil) using n-hexane-chloroform-ethanol (100:10:1, by vol.) as mobile phase (flow rate, 2 ml/min; fluorescence-detection, 305/355 nm; elution order of the derivatives, (-) before (+)). Limit of quantification was 1.0 ng/ml for plasma and 10 ng/ml for urine. In the pharmacokinetic study in two healthy volunteers who received a single i.v. dose of 10 mg ciclotropium race-mate the PCA concentrations in plasma were below the detection limit, but approx. 1.5% of the administered dose were excreted into urine as the respective glucuronides.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Studies on the metabolic clearance of ciclotropium to alpha-phenylciclopentylacetic acid using a new enantiospecific metabolite assay. 149 51

Percutaneous absorption was measured in female hairless guinea pigs dermally exposed for 70 min to very dilute (approximately 10 to 100 ppb) aqueous solutions of 14C-labeled chloroform (CF), trichloroethylene (TCE), or tetrachloroethylene (PCE) in an airtight glass chamber containing no headspace. Similar experiments were conducted using aqueous solutions of TCE at 100,000 ppb. Dermal uptake was estimated by comparing the rate of radiolabel loss from chamber water in systems with and without experimental animals. After each low-concentration dermal-uptake experiment, radiolabel in total urine and feces excreted postexposure was measured and expressed as a fraction of corresponding estimated dermal uptake. For each of the compounds studied, the mean value of these fractions did not differ significantly from that obtained using animals injected with a known dose of that compound, indicating that our experimental system yielded accurate dermal-uptake estimates. The mean permeability coefficients obtained range from 0.13 cm/hr (CF) to 0.37 cm/hr (PCE); those obtained using low- vs high-concentration TCE are not significantly different. The value for CF is very close to one we calculate here from recently published data on CF uptake in human volunteers dermally exposed to aqueous CF while showering with normal tap water. Our results suggest that dermal absorption may be an important route of human exposure to chlorinated volatile organic compounds in domestic water supplies.
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PMID:Dermal absorption of dilute aqueous chloroform, trichloroethylene, and tetrachloroethylene in hairless guinea pigs. 160 Dec 7

1. The effects of palmitoyl carnitine (PC) and novel derivatives were examined on the isolated Langendorff perfused heart of the rat. 2. Bolus injections of PC (1-300 nmol) produced coronary constriction accompanied by a cumulative irreversible depression of contractility. 3. Prior storage of PC in chloroform containing 2% ethanol in heat-sealed ampoules resulted in production of the ethyl ester of the compound (PCE). This compound was isolated and also synthesized (P1E). In contrast to PC, both PCE and P1E exhibited potent vasodilator activity. 4. Increasing the fatty acid chain length from palmitoyl to stearoyl resulted in a significant reduction in coronary dilator activity of the ester compound, whereas different ester groups did not affect the vasodilator action appreciably. Complete removal of the fatty acid chain abolished all vascular effects at the doses used. 5. The vasodilatation produced by these acyl carnitine esters was comparable to that produced by several known vasodilator drugs including verapamil, cromakalim, amyl nitrate and iloprost; however, the duration of the vasodilator response was more prolonged with the carnitate derivatives.
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PMID:The effects of novel vasodilator long chain acyl carnitine esters in the isolated perfused heart of the rat. 169 47

A two-stage anaerobic-aerobic biofilm reactor successfully degraded a mixture of chlorinated organic compounds to water-soluble metabolic intermediates and carbon dioxide. Reductive dechlorination of hexachlorobenzene (HCB), tetrachloroethylene (PCE), and chloroform (CF) occurred on all tested primary carbon sources such as glucose, methanol, and acetate. However, the extent of dechlorination was maximum when the anaerobic biofilm column was fed acetate as a primary carbon source. HCB, PCE, and CF were dechlorinated to the levels of tri- and dichlorinated products (99, 80, and 32%, respectively) with acetate in the feed. This is important, since these less-chlorinated compounds can be metabolized by the aerobic biofilm. The effluent from the anaerobic biofilm column was fed directly into the aerobic column. After both columns, the total amount transformed into nonvolatile intermediates and carbon dioxide was 94, 96, and 83% for [14C]HCB, [14C]trichloroethylene, and [14C]CF, respectively. This research shows the potential application of this novel two-stage bioreactor system for treating groundwaters and industrial effluents composed of highly chlorinated aliphatic and aromatic hydrocarbons.
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PMID:Complete degradation of polychlorinated hydrocarbons by a two-stage biofilm reactor. 178 18

Permeable reactive barriers (PRBs), such as the Waterloo Funnel and Gate System, first implemented at Canadian Forces Borden facility in 1992, are a passive remediation technology capable of controlling the migration of, and treating contaminated groundwater in situ. Most of the PRBs installed to date have been shallow installations created by backfilling sheet-pile shored excavations with iron filing reactive media. More recently continuous trenchers [R. Puls, Installation of permeable reactive barriers using continuous trenching equipment, Proceedings of the RTDF Permeable Barriers Work Group, Virginia Beach, VA, September 1997] and Caissons [J. Vogan, Caisson installation of a pilot scale, permeable reactive barrier in situ treatment zone at the Sommersworth Landfill, NH, Presented to the RTDF Permeable Barriers Work Group, Alexandria, VA, April 1996], and vertical fracturing emplacements [G. Hocking, Vertical hydraulic fracture emplacement of permeable reactive barriers, Progress Report delivered to the Permeable Reactive Barriers Workgroup of the Remedial Technology Development Forum, Beaverton, OR, April 1998] have been used to create reactive barriers in soil. None of the prior methods are capable of adequately addressing groundwater contamination in deep and fractured bedrock aquifers. The purpose of the RSF pilot study was to install reactive media into an impacted bedrock aquifer, and to evaluate the effectiveness of in situ treatment of chlorinated volatile organic compounds (CVOCs) and metals in that type of aquifer. Three discrete fractures were identified and treated and were subjected to testing before and after treatment. Between 300 and 1700 lb. of 1 mm diameter reactive proppants were injected into each zone to facilitate treatment. Monitoring data obtained from adjacent observation wells verified that fracking fluids reached at least 42 ft from the treatment well following hydrofracturing. The concentrations of many of the CVOCs decreased up to 98% based on the results of pre- and post-RSF treatment analyses. Consistent with other research, concentrations of CVOCs were noted to decrease including trichloroethene (TCE), tetrachloroethene (PCE), 1,1,1-trichloroethane (1,1,1-TCA), 1, 1-dichloroethane (1,1-DCA), and 1,1-dichloroethene (1,1-DCE) and increases were noted in concentrations of cis-1,2-dichloroethene (cis-1,2-DCE) and chloroform suggesting that the rate of transformation of the parent compounds to these daughter products is higher than the rate of destruction of the daughter products. The RSF pilot study demonstrated that: (1) zero valent iron foam proppants have the physical and chemical properties necessary to effectively treat CVOCs and metals in groundwater when inserted under high pressures into fractured bedrock. (2) Iron foam reactive media can be placed in bedrock using high pressure hydraulic fracturing equipment and polysaccharide viscosifiers. (3) The extent of the treatment can be monitored in situ using tracers and pressure transducers. (4) Well capacity is increased by improving hydraulic conductivity through hydraulic fracturing and proppant injection. The approximate cost of all of the effort expended in the pilot study was about US$200,000. Full-scale implementations are projected to cost between US$100,000 and US$1,000,000 and would depend on site specific conditions such as the extent and level of impacted groundwater requiring treatment. This technology can potentially be implemented to create treatment zones for the passive treatment of CVOC and metal impacted groundwater in fractured rock aquifers offering a cost-effective alternative to a pump and treat forever scenario.
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PMID:Results of the reactant sand-fracking pilot test and implications for the in situ remediation of chlorinated VOCs and metals in deep and fractured bedrock aquifers. 1051 68

cis-Dichloroethene (DCE) and vinyl chloride (VC) often accumulate in contaminated aquifers in which tetrachloroethene (PCE) or trichloroethene (TCE) undergo reductive dechlorination. "Dehalococcoides ethenogenes" strain 195 is the first isolate capable of dechlorinating chloroethenes past cis-DCE. Strain 195 could utilize commercially synthesized cis-DCE as an electron acceptor, but doses greater than 0.2 mmol/L were inhibitory, especially to PCE utilization. To test whether the cis-DCE itself was toxic, or whether the toxicity was due to impurities in the commercial preparation (97% nominal purity), we produced cis-DCE biologically from PCE using a Desulfitobacterium sp. culture. The biogenic cis-DCE was readily utilized at high concentrations by strain 195 indicating that cis-DCE was not intrinsically inhibitory. Analysis of the commercially synthesized cis-DCE by GC/mass spectrometry indicated the presence of approximately 0.4% mol/mol chloroform. Chloroform was found to be inhibitory to chloroethene utilization by strain 195 and at least partially accounts for the inhibitory activity of the synthetic cis-DCE. VC, a human carcinogen that accumulates to a large extent in cultures of strain 195, was not utilized as a growth substrate, and cultures inoculated into medium with VC required a growth substrate, such as PCE, for substantial VC dechlorination. However, high concentrations of PCE or TCE inhibited VC dechlorination. Use of a hexadecane phase to keep the aqueous PCE concentration low in cultures allowed simultaneous utilization of PCE and VC. At contaminated sites in which "D. ethenogenes" or similar organisms are present, biogenic cis-DCE should be readily dechlorinated, chloroform as a co-contaminant may be inhibitory, and concentrations of PCE and TCE, except perhaps those near the source zone, should allow substantial VC dechlorination.
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PMID:Reductive dechlorination of cis-1,2-dichloroethene and vinyl chloride by "Dehalococcoides ethenogenes". 1135 22

Reductive dechlorination of chlorobenzene (PhCl), trichloroethylene (TCE), tetrachloroethylene (PCE), 1- and 2-chlorobutanes, chloroform, carbon tetrachloride, and 1,1,1- and 1,1,2-trichloroethanes adsorbed on molecular sieve 13X was investigated. The molecular sieve adsorbing the organic chlorides was irradiated with gamma-rays, heated, or allowed to stand at room temperature in a sealed ampule and was then soaked in water. The dechlorination yields were determined from the Cl- concentrations of the supernatant aqueous solutions. It was found that the chlorinated alkanes adsorbed on the molecular sieve are readily dechlorinated on standing at room temperature. The dechlorination at room temperature was limited for TCE and PCE. PhCl was quite stable even at 200 degrees C. gamma-Radiolysis was examined for PhCl, TCE, and PCE at room temperature. The radiation chemical yields of the dechlorination, G(Cl-), were 1.9, 40, and 30 for PhCl, TCE, and PCE, respectively. After 5 h of heating at 200 degrees C, the dechlorination yields for TCE and PCE were 24.5 and 4.3%, respectively. TCE is much more reactive than PCE in the thermal dechlorination, whereas their radiolytic dechlorination yields are comparable. The pH of the supernatant solutions decreased along with the dechlorination.
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PMID:Radiolytic and thermal dechlorination of organic chlorides adsorbed on molecular sieve 13X. 1139 96

Degradative solidification/stabilization (DS/S) is a novel remediation technology that combines chemical degradation with conventional solidification/stabilization. The applicability of the Fe(II)-based DS/S to treating chlorinated alkanes was tested by characterizing degradation reactions of carbon tetrachloride (CT) and its daughter products in cement slurries containing Fe(II). Degradation kinetics of CT and chloroform (CF) were generally very rapid with reaction rates comparable to rates that can be obtained with zero-valent iron. Dechlorination reactions of CT proceeded primarily via a hydrogenolysis pathway, which yielded CF and methylene chloride (MC) as major products and chloromethane and methane as minor products. However, reaction pathways other than hydrogenolysis also appeared to be important at very high pH conditions. MC apparently was resistant to dechlorination reactions over a period of about two months. Kinetics of CT and CF transformation were strongly dependent on pH with an optimal value around 13, which was higher than found previously for PCE. When the initial CF concentration varied between 0.01 and 1 mM, and the Fe(II) dose was 104 mM, pseudo-first-order kinetics generally described the degradation reactions of CF. However, there was also some indication of substrate saturation kinetics in these experiments. This suggests that a saturation model would better describe the kinetics in systems with higher concentration of substrates or lower concentration of the reactive surfaces.
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PMID:Reductive dechlorination of chlorinated methanes in cement slurries containing Fe(II). 1222 6

The widespread use and storage of volatile organic compounds (VOCs) in the United States has led to releases of these chemicals into the environment, including groundwater sources of drinking water. Many of these VOCs are commonly found in public drinking water supplies across the nation and are considered by state or federal agencies to be potentially carcinogenic to humans. In this paper, we evaluate the detection frequencies, detected concentrations, and relative cancer risks of six VOCs in drinking water sources in California from 1995 to 2001. We find that during this 7-year period, the most frequently detected VOCs in sampled drinking water sources were chloroform (12-14%), PCE (11-13%), and TCE (10-12%). Detection frequencies in water were lower for 1,1-DCE (3-6%), MTBE (1-3%), and benzene (<1%). Mean detected concentrations were also consistently above California's primary maximum contaminant level for some VOCs, including benzene, PCE, and TCE. Although none of the six VOCs necessarily poses a significant public health threat from drinking water exposures, 1,1-DCE and benzene werefound to pose the greatest cancer risk relative to the other VOCs. However, after adjusting for the occurrence of each VOC in drinking water, chloroform and PCE were found to pose the greatest relative cancer risk. Despite media reports about significant MTBE contamination of drinking watersupplies in California, MTBE detections were infrequent and this chemical was found to pose the least cancer risk relative to the other VOCs.
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PMID:Comparative risk analysis of six volatile organic compounds in California drinking water. 1248 91

Reductive dechlorination of carbon tetrachloride (CT) and tetrachloroethylene (PCE) by zerovalent silicon (ZVS, Si0) and the combination of Si0 with metal iron (Fe0) was investigated as potential reductants for chlorinated hydrocarbons. The X-ray photoelectron spectroscopy (XPS) was used to identify the surface characteristics of Si0. CT and PCE can be completely degraded via sequential reductive dechlorination to form lesser chlorinated homologues by Si0. Productions of chloroform (CF) and trichloroethylene (TCE) accounted for 80% of CT and 65% of PCE dechlorination, respectively. The degradation of CT and PCE by Si0 at pH 8.3 followed pseudo-first-order kinetics, and the normalized surface rate constants (k(sa)) were 0.288 and 0.003 L m(-2) h(-1), respectively, which react more efficiently than zerovalent iron in CT and PCE dechlorination. A linear relationship was also established between pH and the k(sa) value. The XPS results showed that the hydrogenated silicon surface and silicon oxides on the silicon surface were removed during the dechlorination processes, thus providing a relatively clean silicon surface for dechlorination reactions. The combination of zerovalent silicon with iron influences both the dechlorination rate and the distribution of products. Sequential reductive dechlorination was still the main reaction for CT dechlorination by Si0/Fe0, while reductive dechlorination and beta-elimination were the dominant reaction pathways for PCE dechlorination with ethane and ethene as the major end products. Also, the combination of silicon and iron constitutes a buffer system to maintain the pH at a stable value. A 0.3 unit of pH changed upon increasing the amount of Fe by a factor of 35 was observed, depicting that Si0 serves as a pH buffer in Si0/Fe0 system during dechlorination processes.
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PMID:Reductive dechlorination of carbon tetrachloride and tetrachloroethylene by zerovalent silicon-iron reductants. 1283 Oct 46


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