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

The purpose of this study was to investigate the genotoxic effects of chronic fluoride exposure on mammalian cells in vivo by use of the mouse bone-marrow micronucleus test and the sperm morphology methodology. Mice of genotype B6C3F1 were obtained at weaning and maintained on a low-fluoride diet (less than 0.2 ppm F) ad libitum throughout the experiment. The animals were randomly assigned to seven groups and given fluoride (as sodium fluoride) in concentrations ranging from 1.0 to 75 ppm in the drinking water. Negative (distilled water) and positive (cyclophosphamide) controls were included. After a 21-week treatment period, the animals were killed by cervical dislocation, and blood was obtained by cardiac puncture. Slides of femur marrow cells were prepared and blindly examined for the frequency of micronucleated polychromatic erythrocytes (MN-PCE). Slides of sperm from the cauda epididymides of the male mice were also prepared and similarly examined for morphological abnormalities. Weight of the testes was recorded, and the plasma, humeri, testes, and carcasses were saved for fluoride analyses. Analyses of bone and plasma fluoride confirmed the effective absorption of fluoride following ingestion. The frequency of MN-PCE, the count of abnormal sperm, and the weight of the testes for mice chronically exposed to fluoride, in doses ranging from approximately 0.3 to 23 mg/kg/day, were not significantly different from those of the negative control animals. The results of this study support the view that fluoride has no genotoxic effects.
 ...
PMID:Genotoxic evaluation of chronic fluoride exposure: micronucleus and sperm morphology studies. 258 20

The kinetics of the previously reported paired basic residue-specific pro-opiomelanocortin-converting enzyme from bovine pituitary intermediate lobe secretory vesicles (Loh, Y. P., Parish, D.C., and Tuteja, R. (1985) J. Biol. Chem. 260, 7194-7205) were studied using human 125I-beta-lipotropin as substrate. The enzyme, at a concentration of 20 ng/100 microliters cleaved human beta-lipotropin to yield gamma-lipotropin, a beta-melanotropin linked to beta-endorphin intermediate and beta-endorphin, whereas at an enzyme concentration of 40 ng/100 microliters, the substrate was completely cleaved to yield beta-endorphin and beta-melanotropin. These products were identified by their immunological properties and size on sodium dodecyl sulfate-polyacrylamide gels. The 125I-beta-endorphin product was further shown by high pressure liquid chromatography to contain two forms; the major form co-eluted with 125I-Arg0-beta h-endorphin and the minor form with 125I-beta h-endorphin. No COOH-terminal shortened forms of beta-endorphin were detected. The products formed indicate cleavages at two of the three pairs of basic residues of human beta-lipotropin, at Lys37-Lys38 and Lys57-Arg58, but not at Lys86-Lys87. The cleavage at Lys57-Arg58 occurred primarily in between these basic residues. The Km values for the cleavage of the Lys37-Lys38 and Lys57-Arg58 pairs were 1.9 and 2.5 microM, respectively. The Vmax values for the cleavage of the Lys37-Lys38 and Lys58-Arg58 pairs were 4.8 nmol/micrograms of enzyme/h and 9.1 nmol/micrograms of enzyme/h, respectively.
 ...
PMID:Kinetic studies on the processing of human beta-lipotropin by bovine pituitary intermediate lobe pro-opiomelanocortin-converting enzyme. 301 55

This study evaluated the effect of hepatic methyl donor status on the ability of sodium arsenite (2.5, 5.0 and 10.0 mg/kg) administered by gavage once or on four consecutive days to induce DNA damage in male B6C3F1 mice. Maintenance on a choline-deficient (CD) diet prior to treatment resulted in mice with hepatic methyl donor deficiency (HMDD) and altered arsenical metabolism, as demonstrated by a decreased total urinary excretion of inorganic and organic arsenicals. The alkaline (pH > 13) Single Cell Gel (SCG) assay was used to evaluate for the induction of DNA damage (single strand breaks, alkali labile sites, DNA crosslinking) in blood leukocytes, liver parenchymal cells, and cells sampled from bladder, lung, and skin, while the bone marrow erythrocyte micronucleus (MN) assay was used to assess for the induction of chromosomal damage in bone marrow cells. Treatment with sodium arsenite once or four times induced a significant decrease in DNA migration (indicative of DNA crosslinking) in bladder and liver parenchymal cells of hepatic methyl donor sufficient (HMDS) mice, but in skin cells of HMDD mice. Both HMDD and HMDS mice exhibited a significant increase in the frequency of micronucleated polychromatic erythrocytes (MN-PCE) in bone marrow following four, but not following one, treatments. However, the positive response occurred at a lower dose for HMDS mice and, in these mice, bone marrow toxicity, as demonstrated by a significant reduction in the percentage of PCE, was present also. These results indicate that hepatic methyl donors deficiency significantly decreases the total urinary excretion of orally administered sodium arsenite and markedly modulates target organ arsenic-induced DNA damage, with an apparent shift from liver and bladder to skin.
 ...
PMID:Effect of hepatic methyl donor status on urinary excretion and DNA damage in B6C3F1 mice treated with sodium arsenite. 921 69

The purpose of this investigation was to examine the potential genotoxic influence of sodium fluoride (NaF) on mammalian cells by means of a mouse bone-marrow micronucleus test. Mice of genotype B6C3F1 were obtained at about eight weeks of age and maintained on a low-fluoride diet (< 0.2 ppm F) and distilled water ad libitum throughout the experiment. At approximately 12 weeks of age, the animals were randomly assigned to seven groups, with multiple sampling schedules. The animals were intubated with various doses of NaF, ranging from 0.1 mg/kg to the Maximum Tolerable Dose (MTD), with sampling at 30, 48, and 72 hours after treatment. Negative (distilled water) and positive (cyclophosphamide) controls were included. Coded slides of femur marrow cells were prepared and examined, without identification as to treatments, for the frequency of micronucleated polychromatic erythrocytes (MN-PCE). The humera were analyzed for fluoride for monitoring of the absorption of fluoride following oral intubation. The results indicated that doses of NaF up to the MTD did not significantly increase the frequencies of MN-PCE when compared with the negative controls, although the bone fluoride content increased as the dose of NaF was increased.
 ...
PMID:Lack of genotoxic effects of fluoride in the mouse bone-marrow micronucleus test. 1087 8

The effects of surfactants, sodium dodecyl sulfate (SDS) and Triton X-a00 (TX), and alcohols (methanol, ethanol, and propanol) on the dehalogenation of TCE and PCE by zero-valent iron were examined. Surface concentrations of PCE and TCE on the iron were dependent on aqueous surfactant concentrations. At concentrations above the CMC, sorbed halocarbon concentrations declined and concentrations associated with solution phase micelles increased. The anionic surfactant SDS ([SDS] < CMC) did not affect reduction rates, until the CMC was exceeded after which reactivity decreased, possibly due to sequestering of the TCE and PCE in mobile micelles. The nonionic TX showed a mixed effect on reactivity, increasing the PCE reduction rate, but not affecting TCE removal. Production of TCE from PCE increased in the presence of TX. Similar experiments showed that methanol, ethanol, and propanol inhibited reduction of TCE and PCE by metallic iron. Zero-valent iron may be useful in recycling soil washing effluents contaminated with TCE and PCE.
 ...
PMID:Effects of alcohols, anionic and nonionic surfactants on the reduction of PCE and TCE by zero-valent iron. 1131 92

Tetrachloroethene (PCE) dense nonaqueous-phase liquid (DNAPL) can act as a persistent groundwater contamination source for decades. Biologically enhanced dissolution of pure PCE DNAPL has potential for reducing DNAPL longevity as indicated previously (Environ. Sci. Technol. 2000, 34, 2979). Reported here are expanded studies to evaluate donor substrates that offer different remediation strategies for bioenhanced DNAPL dissolution, including pentanol (soluble substrate, fed continuously), calcium oleate (insoluble substrate, placed in column initially by alternate pumping of sodium oleate and calcium chloride), and olive oil (mixed with PCE and placed in column initially). Compared with a no-substrate column control, the DNAPL dissolution rate was enhanced about three times when directly coupled with biological transformation. The major degradation product formed was cDCE, but significant amounts of VC and ethene were also found with some columns. Extensive methanogenesis, which reduced PCE transformation, occurred in both the pentanol-fed and oleate-amended columns, but not in the olive-oil-amended column, suggesting that methanogens managed to colonize column niches where PCE DNAPL was not present. Detrimental methane production in the pentanol-fed column was nearly eliminated by presaturating the feed solution with PCE. These results suggest potential DNAPL remediation strategies to enhance dehalogenation while controlling competitive methanogenic utilization of donor substrates.
 ...
PMID:Comparison between donor substrates for biologically enhanced tetrachloroethene DNAPL dissolution. 1283 Oct 52

Hydrophobic dyes have been used to visually distinguish dense non-aqueous phase liquid (DNAPL) contaminants from background aqueous phases and soils. The objective of this study was to evaluate the effects of a dyed DNAPL, 0.5 g Oil-Red-O/l of PCE, on the physical properties of remedial solutions: water, co-solvents (50, 70, and 90% (v/v) ethanol), and surfactants (4% (w) sodium dihexyl sulfosuccinate). This study compared the densities, viscosities, and interfacial tensions (IFTs) of the remedial solutions in contact with both dyed and undyed PCE. The presence of the dye in PCE substantially alters the IFTs of water and ethanol solutions, while there is no apparent difference in IFTs of surfactant solutions. The remedial solutions saturated with PCE showed higher viscosities and densities than pure remedial solutions. Solutions with high ethanol content exhibited the largest increases in liquid density. Because physical properties affect the flow of the remedial solutions in porous media, experiments using dyed DNAPLs should assess the influence of dyes on fluid and interfacial properties prior to remediation process analysis.
 ...
PMID:Effects of pure and dyed PCE on physical and interfacial properties of remedial solutions. 1240 43

The partitioning tracer technique is among the DNAPL source-zone characterization methods being evaluated, while surfactant in-situ flushing is receiving attention as an innovative technology for enhanced source-zone cleanup. Here, we examine in batch and column experiments the magnitude of artifacts introduced in estimating DNAPL content when residual surfactants are present. The batch equilibrium tests, using residual surfactants ranging from 0.05 to 0.5 wt.%, showed that as the surfactant concentrations increased, the tracer partition coefficients decreased linearly for sodium hexadecyl diphenyl oxide disulfonate (DowFax 8390), increased linearly for polyoxyethylene (10) oleyl ether (Brij 97), and decreased slightly or exhibited no observable trend for sodium dihexyl sulfosuccinate (AMA 80). Results from column tests using clean sand with residual DowFax 8390 and Tetrachloroethylene (PCE) were consistent with those of batch tests. In the presence of DowFax 8390 (less than 0.5 wt.%), the PCE saturations were underestimated by up to 20%. Adsorbed surfactants on a loamy sand with positively charged oxides showed false indications of PCE saturation based on partitioning tracers in the absence of PCE. Using no surfactant (background soil) gave a false PCE saturation of 0.0004, while soil contacted by AMA 80, Brij 97, and DowFax 8390 gave false PCE saturations of 0.0024, 0.043, and 0.23, respectively.
 ...
PMID:Influence of residual surfactants on DNAPL characterization using partitioning tracers. 1524 Jan 67

This study reports on a surfactant-based flood for tetrachloroethylene (PCE) removal from a control test cell at the Dover National Test Site. The surfactant formulation (sodium dihexyl sulfosuccinate (Aerosol-MA or AMA), isopropanol and calcium chloride) was able to achieve a high concentration of PCE in swollen micelles (supersolubilization) without vertical PCE migration. The hydraulic system included eight screened wells that were operated in both vertical circulation and line drive configurations. After 10 pore volumes of flushing, the overall PCE removal was 68% (65% of which corresponded to the surfactant flooding alone). In addition, the residual PCE saturation was reduced from 0.7% to 0.2%, and the concentration of PCE in the groundwater was reduced from 37-190 mg/L before the flushing to 7.3 mg/L after flooding. Recycling the surfactant solution reduced the required surfactant mass (and thus cost, and waste) by 90%. Close to 80% of the total PCE removal was obtained during the first five pore volumes which were operated in an upward vertical circulation flow scheme. No free oil phase was observed during the test. Further analysis of multilevel sampler data suggests that most of the trapped oil remaining in the cell was likely localized in secluded regions of the aquifer, which helps explain the lower PCE groundwater concentration after remedial activities. In summary, this field study demonstrated the feasibility of surfactant-enhanced remediation to reduce the mass in the source zone and significantly reduce the PCE aqueous concentration and therefore the risk associated with the contaminant plume.
 ...
PMID:Field demonstration of surfactant-enhanced solubilization of DNAPL at Dover Air Force Base, Delaware. 1623 35

Effects of surfactants and natural organic matter (NOM) on the sorption and reduction of tetrachloroethylene (PCE) with zero valent iron (ZVI) were examined in this study. PCE reduction by ZVI depended on the ionic type of the surfactants. The removal of PCE and production of TCE with non-ionic Triton X-100 and cationic hexadecyltrimethyl-ammonium (HDTMA) at one-half and two times the critical micelle concentration (CMC) were 1.2-1.8 times higher than without surfactants because of the enhanced PCE partitioning and surface concentration by the sorbed surfactants. When anionic sodium dodecyl benzene sulfonate (SDDBS) at one-half and two times CMC and NOM at 20 mg l(-1) and 50 mg l(-1) concentrations were used, the removal of PCE doubled and TCE production decreased. In the presence of SDDBS, TCE production by ZVI was lower than with HDTMA and Triton X-100 while PCE removal was higher than with the other surfactants.
 ...
PMID:Sorption and reduction of tetrachloroethylene with zero valent iron and amphiphilic molecules. 1648 31


1 2 3 Next >>