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PubMed2000

Responses of spruce seedlings (Picea abies) to exhaust gas under laboratory conditions--I. Plant-insect interactions.

The effects of motor vehicle exhaust gas on Norway spruce seedlings (Picea abies (L.) Karst) and plant-insect interaction of spruce shoot aphid (Cinara pilicornis Hartig) was studied. The exhaust gas concentrations in the fumigation chambers were monitored and controlled by measuring the concentration of nitrogen oxides (NO(x)) with a computer aided feedback system. The concentrations of major exhaust gas components (black carbon [BC], fine particles, VOCs and carbonyl compounds) in the chamber air were also measured. Responses of Norway spruce seedlings to a 2 and 3-week exhaust gas exposure and subsequent performance of spruce shoot aphid were studied using realistic exposure regimes; 50, 100 and 200 ppb NO(x). The feedback control system based on NO(x) concentrations proved an adequate and practical means for controlling the concentration of exhaust gases and studying plant responses in controlled environment chambers. The exhaust exposure resulted in increased concentrations of proline, glutamine, threonine, aspartic acid, glycine and phenylalanine and decreased concentration of arginine, serine, alanine and glycine in young needles. No changes in soluble N concentrations were observed. The results are interpreted as a stress response rather than use of NO(x) as a nitrogen source. No changes in total phenolics and only transient changes in some individual terpene concentrations were detected. The exhaust gas exposure stressed the exposed seedlings, but had no significant effect on N metabolism or the production of defence chemicals. Aphid performance was not significantly affected. Soluble N, secondary metabolism and aphid performance were not sensitive to exhaust gas exposure during shoot elongation in Norway spruce.

Journal Article↗
PubMed2000

Response of needle sulphur and nitrogen concentrations of Scots pine versus Norway spruce to SO2 and NO2.

The results of two field studies and an open-top chamber fumigation experiment showed that the response of mature Scots pine to SO(2) and NO(2) differed from that of mature Norway spruce. Moreover, the response of pine seedlings to SO(2) and NO(2) differed from that of mature trees. The greater increase in the needle total S concentrations of pine suggested more abundant stomatal uptake of SO(2) compared to spruce. Both pine seedlings and mature trees also seemed to absorb more N from atmospheric deposition. Mature pine was able to assimilate SO(4)(2-) derived from SO(2) into organic S more effectively than mature spruce at the high S and N deposition sites, whereas both pine and spruce seedlings accumulated SO(4)-S under NO(2)+SO(2) exposure. Spruce, in turn, accumulated SO(4)-S even when well supplied with N. Net assimilation of SO(4)(2-) in conifer seedlings was enhanced markedly by elevated temperature. To protect the northern coniferous forests against the harmful effects of S and N deposition, it is recommended that the critical level for SO(2) as a growing season mean be set at 5-10 microg m(-3) and NO(2) at 10-15 microg m(-3), depending on the 'effective temperature sum' and/or whether SO(2) and NO(2) occur alone or in combination.

Journal Article↗
PubMed2000

Screening of bean cultivars for their response to ozone as evaluated by visible symptoms and leaf chlorophyll fluorescence.

Fourteen Italian cultivars of Phaseolus vulgaris were exposed to a single pulse of ozone (O(3), 150 nl l(-1)) or to filtered air (<3 nl l(-1)) for 3.5 h. O(3) sensitivity was assessed by recording the extent of visible symptoms, effects on chlorophyll (Chl) content and changes in Chl a fluorescence parameters. This paper reports the results of an initial screening of 14 bean cultivars that was used to select a small number of cultivars for further work. Seven cultivars showed visible symptoms of injury in the range of 2-60 h after the end of the O(3) fumigation. O(3) significantly depressed total Chl content in most cultivars and a significant correlation was found between Chl content and visible symptoms. Most cultivars showed a significant change in the F(v)/F(m) ratio, even when there were no visual symptoms. There was no relationship between the extent of visual symptoms and quenching coefficients, indicating that these parameters were of no use in the determination of sensitivity to O(3) stress.

Journal Article↗
PubMed1997

Human skin in vitro percutaneous absorption of gaseous ethylene oxide from fabric.

Ethylene oxide, a colourless gas at ordinary room temperature and pressure, is widely used as a fumigant, coming in contact with clothing and human skin. It is genotoxic in somatic and germ cells. [1,2-14C]Ethylene oxide and fabric discs were sealed in a glass container; the fabric discs were then removed and placed on human skin mounted in glass diffusion cells. Percutaneous absorption was 1.3% of the dose when the fabric/skin surface was open to surrounding air, and increased to 46.0% when the surface was occluded with latex glove material. The absorption was rapid, occurring within the first 0-4 hr assay period. Absorbed chemical was confirmed to be unchanged ethylene oxide in the receptor fluid. This study also serves as a model for exposure of fabric/skin to any potentially hazardous gas.

Administration, Cutaneous↗
PubMed1998

Oral teratogenicity studies of methyl bromide in rats and rabbits.

Teratogenicity studies of methyl bromide, a widely used fumigant, were conducted in rats and rabbits. Methyl bromide was dissolved in corn oil and administered orally to groups of 24 copulated female Crj:CD (SD) rats at dose levels of 0 (corn oil), 3, 10 or 30 mg/kg/day on days 6-15 of gestation and to groups of 18 artificially inseminated female Kbl:JW rabbits at 0, 1, 3 or 10 mg/kg/day on days 6-18 of gestation. Maternal rats and rabbits were euthanized on respective days 20 and 27 of gestation. Foetuses were examined for survival, growth and teratological alterations. Maternal toxicity was evident in the high-dose groups for both species. In these groups, maternal body weight gains and food consumption were significantly decreased during the dosing and post-dosing periods. Necropsy of maternal rats also revealed erosive lesions in the stomach and the surrounding organs. However, no treatment-related adverse effects were found in foetuses of the treated groups for both rat and rabbit studies. These results led to the conclusion that methyl bromide was not foetotoxic or teratogenic to rat and rabbit foetuses up to dose levels of 30 and 10 mg/kg/day, respectively, at which maternal toxicity was evident for both species.

Abnormalities, Drug-Induced↗
PubMed2002

Naphthalene toxicity and antioxidant nutrients.

Naphthalene is a bicyclic aromatic compound that has wide industrial and commercial applications. It is used as the starting material for the synthesis of other compounds, as a moth repellent, soil fumigant and lavatory deodorant. Most exposure occurs through low dose chronic inhalation, dermal contact or ingestion through the food chain. The lungs and eyes appear to be most susceptible to toxicity, although biochemical markers of toxicity can be demonstrated in other tissues, such as the kidney, brain and liver. In addition to lens opacification (cataracts) and histological changes associated with pneumotoxicity, other biomarkers of toxic effects include glutathione depletion, lipid peroxidation, DNA fragmentation and the production of the active oxygen species as superoxide anion and hydroxyl radical. In addition, the urinary excretion of lipid metabolites occurs. A role for the tumor suppressor gene p53 has been demonstrated. Toxic manifestations of naphthalene are associated with its oxidative metabolism to various products including quinones. The ability to protect against the toxic effects of naphthalene by using various antioxidants and free radical scavengers has been demonstrated. Studies have been conducted with vitamin E, vitamin E succinate, melatonin, curcumin, various L-cysteine prodrugs, several aldose reductase inhibitors and spin-trapping agents. The ability to prevent the toxic manifestations of naphthalene is dependent on the pharmacokinetic properties of the agents, which have been studied. The appropriate selection of chemoprotectants can be useful in preventing naphthalene toxicity.

Animals↗
PubMed1999

Intravascular hemolysis in aluminium phosphide poisoning.

Intravascular hemolysis is most often secondary to exposure to a variety of drugs or infections, and usually occurs in patients who are deficient in glucose-6-phosphate dehydrogenase (G-6-PD) enzyme. Aluminium phosphide, a fumigant widely used in India, has been reported to produce intravascular hemolysis in only one patient who also had concomitant G-6-PD deficiency. This report describes the occurrence of intravascular hemolysis with aluminium phosphide poisoning in a patient with normal G-6-PD levels. This is of significance as jaundice in patients with this poisoning is often attributed to hepatic damage alone.

Adult↗
PubMed1998

Naphthalene-induced oxidative stress and DNA damage in cultured macrophage J774A.1 cells.

Naphthalene is a bicyclic aromatic compound that is widely used in various domestic and commercial applications including lavatory scent disks, soil fumigants and moth balls. However, little information is available regarding the mechanism of naphthalene toxicity. We have assessed the concentration-dependent in vitro effects of naphthalene on increased lipid peroxidation, cytochrome c reduction, hydroxyl radical production, modulation of intracellular oxidized states by laser scanning confocal microscopy, and DNA fragmentation in cultured macrophage J774A.1 cells. The cells were incubated with 0-500 microM concentrations of naphthalene for 0, 12 and 24 h at 37 degrees C. Concentration- and time-dependent changes were observed. No significant changes were observed with concentrations of naphthalene up to 100 microM. At 24 h, lipid peroxidation increased by 1.8-, 2.4- and 2.9-fold at 200, 300 and 500 microM concentrations of naphthalene. Approximately 2.0-, 3.1- and 4.6-fold increases in cytochrome c reduction were observed at 200, 300 and 500 microM concentrations of naphthalene, respectively, at this time point demonstrating the production of superoxide anion, while under the same conditions approximately 2.4-, 3.2- and 4.9-fold increases in hydroxyl radical production were observed, respectively. Following incubation of these cells with 200 and 500 microM concentrations of naphthalene 2.3- and 4.7-fold increases in fluorescence intensity were observed, respectively, as compared to the untreated cells. At 24 h, approximately 1.8-, 2.3- and 3.0-fold increases in DNA fragmentation were observed following incubation with 200, 300 and 500 microM concentrations of naphthalene, respectively. Naphthalene also produced concentration- dependent decreases in cell viability. At the 12 h time point, significant changes were observed only with 300 and 500 microM concentrations of naphthalene. These results demonstrate that naphthalene may induce toxic manifestations by enhanced production of oxygen free radicals, resulting in lipid peroxidation and DNA damage.

Animals↗
PubMed2003

Spectrum of unnatural fatalities in the Chandigarh zone of north-west India--a 25 year autopsy study from a tertiary care hospital.

A 25 year (1977-2002) autopsy study of 5933 unnatural fatalities from a tertiary care hospital of north-west India revealed an abrupt rise in unnatural deaths (3050; 51.4%) since 1997. 84.2% subjects were between the age group of 16 and 45. Accidental deaths (79.3%) constituted the majority of unnatural fatalities followed by suicidal (13.9%) and homicidal (6%) deaths. Road traffic accidents (RTAs), burn, poisoning, accidental falls from height and firearm injury were responsible for 94.5% of the total unnatural deaths. A male preponderance (73.4%) was seen in all causes of deaths except for burns where females (61%) outnumbered males (39%). The incidence of fatalities due to poisoning and burns had increased from 5.7% and 22.6% to 12% and 24.3%, respectively, whereas due to fire arms and machinery accidents decreased from 4.5% and 1.2% to 1.2% and 0.4%, respectively. The proportion of mortality due to road traffic accidents (50.3%) and accidental fall from height (6.9%) remained almost static. Two-wheeler occupants (motor cycles, etc. 33.3%) were the main victims in road traffic accidents. Pouring of kerosene oil (36% dowry death), malfunctioning and bursting of kerosene oil stove (43.5%) were the most common factors in burn deaths. Between 1977 and 1987 barbiturates (33.3%), organophosphates (23.8%) and copper sulphate (14.3%) and in 1987-1997 organophosphates (45%) and aluminium phosphide (26.5%) were the major fatal poisons. Since 1992 aluminium phosphide (80%), a fumigant pesticide used for wheat preservation was the most common poison. The incidence of suicidal deaths increased from 10.9% (1987-1992) to 15.7% (1997-2002) with a peak incidence of 18.2% in 1992-1997, when this pesticide with no effective antidote was made freely available in the market.

Journal Article↗
PubMed2001

Genotoxic effects of methyl isothiocyanate.

Aim of the study was to investigate the genotoxic effects of methyl isothiocyanate (MITC), a compound widely distributed in the environment as a constituent of certain vegetables, a soil fumigant and breakdown product of carbamate pesticides. MITC caused only marginal mutation induction in reversion assays with Salmonella strains TA100 and TA98 and, the maximum effect (<2-fold increase over the background rate) was seen at 100microg/ml. In differential DNA-repair assays with E. coli (strains 343/763 uvrB/recA and 343/765 uvr(+)/rec(+)), a pronounced dose-response effect (induction of repairable DNA-damage) was seen at low concentrations (>/=4microg/ml). In both bacterial assays, addition of activation mix (rat liver S-9) led to a reduction of the genotoxic effects. In micronucleus assay and in single cell gel electrophoresis assay with human hepatoma cells (HepG2), clear cut positive results were obtained at exposure concentrations of <5microg/ml. On the contrary, only marginal effects were seen in differential DNA-repair host-mediated assays where E. coli indicator cells were recovered from different inner organs of mice that had been treated orally with a high dose (90mg/kg bw) of the test compound. Further in vitro experiments showed that MITC is inactivated by body fluids (saliva, gastric juice) and that its DNA-damaging properties are attenuated by non-enzymatic protein binding. Since exposure of HepG2 cells to MITC led to formation of thiobarbituric acid reactive substances, it is likely that its DNA-damaging effects involve lipid peroxidation processes. Overall, our findings show that MITC induces only marginal effects at extremely high (almost lethal) doses in inner organs in vivo, but it causes DNA-damage at low concentrations in vitro.

Adult↗
PubMed1998

In vitro and in vivo genotoxic activity of miral, an organophosphorus insecticide used in Colombia.

Miral 500 CS (CAS# 42509-80-8), an organophosphorus insecticide, has been widely used in Columbia to fumigate coffee plantations. Therefore, there is extensive human exposure to this pesticide. Miral's mutagenic and genotoxic activities, however, are not known. In this study, such activities of the pesticide were evaluated using the Salmonella TA98/S9 test and the chromosome aberration assay in bone marrow cells of Swiss albino CD1 male mice. All doses tested with Salmonella in the presence of S9 mix (3.2, 16, 80, 400 and 2000 micrograms/plate) induced a mutagenic response that was three times the spontaneous mutation frequency. The mutagenic response without S9 was twice the spontaneous frequency. Based on a 4-day treatment (i.p.) of mice with Miral, the median lethal dose (LD50) and the maximum tolerated dose (MTD) were 912.5 mg/kg and 730 mg/kg, respectively. A significant dose-dependent cell cycle delay (r2 = 0.85, p < 0.01) was observed in bone marrow cells when mice were treated for 24 h with 73, 146, 219, 292, 365, 438, 511, 584, 657 and 730 mg/kg. Significant increase in mitotic indices (p < 0.02) and chromosome aberrations (p < 0.05) were induced in bone marrow cells, when mice were treated for 18 h with the highest dose 511 mg/kg. Our results indicate that Miral is a mutagenic compound in Salmonella and is capable of inducing chromosome aberrations at high doses in mice. Additional genotoxicity studies in farmers exposed to Miral should be conducted to determine the potential human health risk resulting from chronic low-dose exposures to this pesticide.

Animals↗
PubMed1998

Genotoxicity in workers exposed to methyl bromide.

To address the genotoxicity of in vivo methyl bromide (CAS 74-83-9) exposure in humans, we collected blood and oropharyngeal cells as part of a cross-sectional morbidity study of methyl bromide-exposed fumigation workers and their referents. Micronuclei were measured in lymphocytes and oropharyngeal cells, and hypoxanthine-guanine phosphoribosyl transferase gene (hprt) mutations were measured in lymphocytes. A total of 32 workers and 28 referents provided specimens. Among current non-smokers, mean hprt variant frequencies (Vfs) were found to be elevated among workers compared to referents (geometric mean: workers=4.49x10(-6), referents=2.96x10-(6); two-sided p=0.22); this difference was more pronounced among workers with 4 h or more of recent methyl bromide exposure compared to referents (geometric mean: workers=6.56x10(-6), referents=2.96x10(-6); two-sided p=0.06). Mean oropharyngeal cell micronuclei were higher among workers compared to referents (mean: workers=2.00, referents=1.31; two-sided p=0.08); the results were similar when workers with 4 h or more of recent methyl bromide exposure were compared to referents (mean: workers=2.07, referents=1.31; two-sided p=0.13). No consistent differences between workers and referents were observed for frequencies of kinetochore-negative lymphocyte micronuclei, or kinetochore-positive lymphocyte micronuclei. The study was limited by a sample size sufficient only for detecting relatively large differences, absence of a reliable method to measure the intensity of workplace methyl bromide exposures, and relatively infrequent methyl bromide exposure (e.g., the median length of exposure to methyl bromide during the 2 weeks preceding the survey was 4 h). In conclusion, our findings provide some evidence that methyl bromide exposure may be associated with genotoxic effects in lymphocytes and oropharyngeal cells. Further study on the genotoxicity of methyl bromide exposure in humans is warranted.

Adult↗
PubMed1999

Glutathione activation of chloropicrin in the Salmonella mutagenicity test.

Chloropicrin (CCl3NO2) is a major soil fumigant for control of fungi, insects and nematodes and may by formed by chlorination of drinking water. It is also a strong lacrimator and induces sister chromatid exchanges in cultured human lymphocytes. Mutagenicity assays of CCl3NO2 in Salmonella typhimurium TA100 establish that it is toxic but not mutagenic at 500 nmol/plate but becomes mutagenic but not toxic on addition of S9 (previous work) or 1-2 molar equivalents of glutathione (GSH) (this study). The preincubation assay is superior to the plate incorporation test giving 2-4-fold higher revertants/nmol. Using the preincubation assay with GSH at 5 mM (a biomimetic level) in the top agar gives linear dose-response relationships for CCl3NO2 and its dechlorination products CHCl2NO2 and CH2ClNO2 with 0.56, 0.56 and 1.8 revertants/nmol, respectively. The mutagenicity values for CHCl2NO2 and CH2ClNO2 are the same in the presence and the absence of GSH, which only improves the linearity at high levels by reducing toxicity to the bacteria. GSH activation of CCl3NO2 mutagenicity may be due to reductive dechlorination of the trichloro compound to the more active CHCl2NO2 and CH2ClNO2. Alternatively, the mutagenicity may result from an intermediate GSH conjugate such as GSCCl2NO2 or GSCHClNO2. In comparison, the mutagenicity of CH2Br2 and CH2I2 is affected little if any by addition of GSH and these dihalomethanes are much less active than the halonitromethane series. It therefore appears that CCl3NO2 is not mutagenic in the absence of activation and that the dechlorinated metabolites CHCl2NO2 and CH2ClNO2 are moderately potent bacterial mutagens, consistent with the possible genotoxicity of CCl3NO2 in mammals.

Animals↗
PubMed2006

Susceptibility of Plodia interpunctella (Lepidoptera: Pyralidae) developmental stages to high temperatures used during structural heat treatments.

Heating the ambient air of a whole, or a portion of a food-processing facility to 50 to 60 degrees C and maintaining these elevated temperatures for 24 to 36 h, is an old technology, referred to as heat treatment. There is renewed interest in adopting heat treatments around the world as a viable insect control alternative to fumigation with methyl bromide. There is limited published information on responses of the Indian meal moth, Plodia interpunctella (Hübner), exposed to elevated temperatures typically used during heat treatments. Time-mortality relationships were determined for eggs, fifth-instars (wandering-phase larvae), pupae, and adults of P. interpunctella exposed to five constant temperatures between 44 and 52 degrees C. Mortality of each stage increased with increasing temperature and exposure time. In general, fifth-instars were the most heat-tolerant stage at all temperatures tested. Exposure for a minimum of 34 min at 50 degrees C was required to kill 99% of the fifth-instars. It is proposed that heat treatments aimed at controlling fifth-instars should be able to control all other stages of P. interpunctella.

Animals↗
PubMed2006

Experimental airborne transmission of Salmonella Agona and Salmonella Typhimurium in weaned pigs.

This study tested the hypothesis of airborne transmission of Salmonella Agona (Trial I) and Salmonella Typhimurium (Trial II) in weaned pigs. The trials were performed using stainless-steel/glass isolation cabinets connected by air ducts to permit an unidirectional airflow from cabinet 1 (two control pigs) to cabinet 3 (two sentinel pigs), passing through cabinet 2 (two inoculated pigs). Air samples, pooled faecal samples from the floor and rectal swabs were collected daily and assessed by culture and PCR. A fumigation chamber and rubber gloves coupled to the cabinets allowed sampling without opening the system. Trials I and II lasted 15 and 19 days respectively. The recovery of S. Agona and S. Typhimurium and detection of seroconversion in sentinel pigs indicate that airborne Salmonella transmission in weaned pigs over short distances is possible. Further studies on the role of aerosols in the epidemiology of Salmonella in intensive pig production should be performed.

Aerosols↗
PubMed1990

Metabolic activation of 1,2-dibromo-3-chloropropane: evidence for the formation of reactive episulfonium ion intermediates.

The nematocide and soil fumigant 1,2-dibromo-3-chloropropane (DBCP) is a carcinogen and a mutagen and displays target-organ toxicity to the testes and the kidney. It has been proposed that both cytochrome P-450 mediated activation and glutathione (GSH) conjugation pathways are operative in DNA damage and organotropy induced by DBCP. To determine the chemical mechanisms involved in the bioactivation of DBCP and to assess a role for an episulfonium ion intermediate, the mechanism of formation of GSH conjugate metabolites of DBCP was investigated. Five biliary GSH conjugates of DBCP were isolated from rats and identified by fast atom bombardment tandem mass spectrometry: S-(2,3-dihydroxy-propyl)glutathione (I), S-(2-hydroxypropyl)glutathione (IIA), S-(3-chloro-2-hydroxypropyl)glutathione (III), 1,3-di(S-glutathionyl)propan-2-ol (IV), and 1-(glycyl-S-cysteinyl)-3- (S-glutathionyl)propan-2-ol (V). The mechanisms of conjugate formation were addressed by assessing deuterium retention in conjugates derived from [1,1,2,3,3-2H5] DBCP (D5-DBCP). GSH conjugates I, III, IV, and V displayed quantitative retention of deuterium, an observation consistent with the formation of an episulfonium ion intermediate. GSH conjugate IIA, however, retained three atoms of deuterium, thus invoking a P-450 mechanism in its genesis. The involvement of glutathione transferase (GST) and sequential episulfonium ion intermediates in the formation of metabolites I, III, and IV was demonstrated in vitro. Upon incubation of DBCP with GST, metabolites I, III, and IV were identified by tandem mass spectrometry and were found to arise with quantitative retention of deuterium when D5-DBCP was employed as a substrate. An additional GSH conjugate, 1,2,3-tri(S-glutathionyl)propane (VI), was observed as the major metabolite in incubations of GST with DBCP. When the incubations of DBCP with GST were performed in H2(18)O, metabolite I incorporated two atoms of 18O, and metabolites III and IV incorporated one atom of 18O. The ability of GST to catalyze the formation of the four GSH conjugates observed in vivo, with quantitative retention of deuterium and incorporation of 18O from H2(18)O, may be rationalized by a mechanism invoking the initial formation of S-(2-bromo-3-chloropropyl)glutathione. Rearrangement of this unstable conjugate via several reactive episulfonium ions, with either hydrolysis by water or alkylation of GSH at various stages, would account for the pattern of metabolites and their status of isotopic enrichment observed under various incubation conditions.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2003

Reactions of trans-3-chloroacrylic acid dehalogenase with acetylene substrates: consequences of and evidence for a hydration reaction.

Various soil bacteria use 1,3-dichloropropene, a component of the commercially available fumigants Shell D-D and Telone II, as a sole source of carbon and energy. One enzyme involved in the catabolism of 1,3-dichloropropene is trans-3-chloroacrylic acid dehalogenase (CaaD), which converts the trans-isomers of 3-bromo- and 3-chloroacrylate to malonate semialdehyde. Sequence analysis suggested a relationship between the heterohexameric CaaD and the bacterial isomerase, 4-oxalocrotonate tautomerase (4-OT), thereby distinguishing CaaD from a number of dehalogenases whose mechanisms proceed through an alkyl- or aryl-enzyme intermediate. In this study, the genes for the alpha- and beta-subunits of CaaD have been synthesized using a polymerase chain reaction-based strategy, cloned into separate plasmids, and the proteins expressed and purified as the functional heterohexamer. Subsequently, the product of the reaction was confirmed to be malonate semialdehyde by (1)H and (13)C NMR spectroscopy, and kinetic constants were determined using a UV spectrophotometric assay. In view of the proposed hydrolytic nature of the CaaD-catalyzed reaction, three acetylene compounds were investigated as substrates for the enzyme. One compound, 2-oxo-3-pentynoate, a potent active site-directed irreversible inhibitor of 4-OT, is a substrate for CaaD, and was processed to acetopyruvate with kinetic constants similar to those determined for the trans-isomers of 3-bromo- and 3-chloroacrylate. The remaining two compounds, 3-bromo- and 3-chloropropiolic acid, were transformed into potent irreversible inhibitors of CaaD. The inactivation observed for 3-bromopropiolic acid is due to the covalent modification of Pro-1 of the beta-subunit. The results provide evidence for a hydratase activity and set the stage to use the 3-halopropiolic acids as ligands in inactivated CaaD complexes that can be studied by X-ray crystallography.

Acetylene↗
PubMed2001

Fate and origin of 1,2-dichloropropane in an unconfined shallow aquifer.

A shallow aquifer with different redox zones overlain by intensive agricultural activity was monitored for the occurrence of 1,2-dichloropropane (DCP) to assess the fate and origin of this pollutant. DCP was detected more frequently in groundwater samples collected in aerobic and nitrate-reducing zones than those collected from iron-reducing zones. Simulated DCP concentrations for groundwater entering an iron-reducing zone were calculated from a fate and transport model that included dispersion, sorption, and hydrolysis but not degradation. Simulated concentrations were well in excess of measured values, suggesting that microbial degradation occurred in the iron-reducing zone. Microcosm experiments were conducted using aquifer samples collected from iron-reducing and aerobic zones to evaluate the potential for microbial degradation of DCP and to explain field observations. Hydrogenolysis of DCP and production of monochlorinated propanes in microcosm experiments occurred only with aquifer materials collected from the iron-reducing zone, and no dechlorination was observed in microcosms established with aquifer materials collected from the aerobic zones. Careful analyses of the DCP/1,2,2-trichloropropane ratios in groundwater indicated that older fumigant formulations were responsible for the high levels of DCP present in this aquifer.

Agriculture↗