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PubMed1999

Effect of phenylurea herbicides on soil microbial communities estimated by analysis of 16S rRNA gene fingerprints and community-level physiological profiles.

The effect of three phenyl urea herbicides (diuron, linuron, and chlorotoluron) on soil microbial communities was studied by using soil samples with a 10-year history of treatment. Denaturing gradient gel electrophoresis (DGGE) was used for the analysis of 16S rRNA genes (16S rDNA). The degree of similarity between the 16S rDNA profiles of the communities was quantified by numerically analysing the DGGE band patterns. Similarity dendrograms showed that the microbial community structures of the herbicide-treated and nontreated soils were significantly different. Moreover, the bacterial diversity seemed to decrease in soils treated with urea herbicides, and sequence determination of several DGGE fragments showed that the most affected species in the soils treated with diuron and linuron belonged to an uncultivated bacterial group. As well as the 16S rDNA fingerprints, the substrate utilization patterns of the microbial communities were compared. Principal-component analysis performed on BIOLOG data showed that the functional abilities of the soil microbial communities were altered by the application of the herbicides. In addition, enrichment cultures of the different soils in medium with the urea herbicides as the sole carbon and nitrogen source showed that there was no difference between treated and nontreated soil in the rate of transformation of diuron and chlorotoluron but that there was a strong difference in the case of linuron. In the enrichment cultures with linuron-treated soil, linuron disappeared completely after 1 week whereas no significant transformation was observed in cultures inoculated with nontreated soil even after 4 weeks. In conclusion, this study showed that both the structure and metabolic potential of soil microbial communities were clearly affected by a long-term application of urea herbicides.

Bacteria↗

PubMed1977

Comparison of electron-capture and electrolytic conductivity detection for the gas-liquid chromatographic analysis of some perfluoro derivatives of four agricultural chemicals.

The gas chromatographic response of four perfluoro derivatives, of four agricultural chemical [diethylstilbestrol] (DES) clopidol, linuron and carbofuran] was examined. The derivatives varied in fluorine content from 3 to 30 atoms per molecule. The sensitivities of the derivatives were found to be ca. 10-100 times greater by electron-capture detection than by electrolytic conductivity detection (halogen mode). The sensitivity also was found to increase with increasing fluorine content for all derivatives by electrolytic conductivity, whereas by electron capture, DES and clopidol exhibited similar responses with either the penta-, hepta-, or pentadeca-fluoro derivatives. The sensitivity of linuron and carbofuran derivatives by electron capture varied with increasing fluorine content. For detection by electron capture, the hepta-fluorobutyryl derivatives were preferred for DES and clopidol, and either the hepta-fluorobutyryl or the pentadecafluorooctanoyl derivatives for linuron and carbofuran. For detection by electrolytic conductivity, the pentadecafluorooctanoyl derivatives were superior for all four compounds.

Carbofuran↗

PubMed1976

[Hydrolysis of methoxysubstituted phenylureas, acylanilides and phenylcarbamates by a microbial aryl acylamidase (author's transl)].

The phenylurea herbicide linuron is hydrolyzed by Bacillus sphaericus ATCC 12123 quantitatively forming 3,4-dichloroaniline, CO2, and N,O-dimethylhydroxylamine. The inducible enzyme responsible for this hydrolysis was purified to homogeneity as judged by polyacrylamide gel electrophoresis. Its molecular weight was 75 000 +/- 10%. Studies on its substrate specificity showed that either whole cells as the linuron-induced enzyme hydrolyze a large number of herbicidal and fungicidal acylanilides, the methoxysubstituted phenylureas and the phenylcarbamate propham at the carbonyl-aniline bond. This would classify the enzyme as an aryl acylamidase (E.C. 3.5.1). Hydrolysis of phenylamides by whole cells and by the enzyme is inhibited by different methylcarbamate and organophosphorus insecticides. Inhibition of hydrolysis of linuron by the aryl acylamidase by methylcarbamates is a competitive one.

Amidohydrolases↗

PubMed1999

Expression of a soybean cytochrome P450 monooxygenase cDNA in yeast and tobacco enhances the metabolism of phenylurea herbicides.

A strategy based on the random isolation and screening of soybean cDNAs encoding cytochrome P450 monooxygenases (P450s) was used in an attempt to identify P450 isozymes involved in herbicide metabolism. Nine full-length (or near-full-length) P450 cDNAs representing eight distinct P450 families were isolated by using PCR-based technologies. Five of the soybean P450 cDNAs were expressed successfully in yeast, and microsomal fractions generated from these strains were tested for their potential to catalyze the metabolism of 10 herbicides and 1 insecticide. In vitro enzyme assays showed that the gene product of one heterologously expressed P450 cDNA (CYP71A10) specifically catalyzed the metabolism of phenylurea herbicides, converting four herbicides of this class (fluometuron, linuron, chlortoluron, and diuron) into more polar compounds. Analyses of the metabolites suggest that the CYP71A10 encoded enzyme functions primarily as an N-demethylase with regard to fluometuron, linuron, and diuron, and as a ring-methyl hydroxylase when chlortoluron is the substrate. In vivo assays using excised leaves demonstrated that all four herbicides were more readily metabolized in CYP71A10-transformed tobacco compared with control plants. For linuron and chlortoluron, CYP71A10-mediated herbicide metabolism resulted in significantly enhanced tolerance to these compounds in the transgenic plants.

Cloning, Molecular↗

PubMed1998

Application of an androgen receptor assay for the characterisation of the androgenic or antiandrogenic activity of various phenylurea herbicides and their derivatives.

The potency of different substances for [3H]dihydrotestosterone ([3H]DHT) displacement from the bovine androgen receptor was tested. The phenylurea herbicide linuron and its derivative 3,4-dichloroaniline (3,4-DCA), which are found in sediments and surface waters, are known to displace bound testosterone from the rat androgen receptor. Because 3,4-DCA is rapidly taken up by fish and metabolised into 3,4-dichloroacetanilide (3,4-DCAc), it was investigated whether the displacement effects are attributable to 3,4-DCA or to 3,4-DCAc. The potency of 3,4-DCAc androgen receptor binding was compared with that of several phenylurea compounds. In a radioreceptor assay with calf uterus cytosol as androgen receptor preparation, the specific binding of [3H]DHT, the endogenous ligand, was completely displaceable by increasing concentrations of 3,4-DCAc. The relative binding affinities (RBA) of the various compounds were about 1/10(4) to 1/10(5) of that of DHT. 3,4-DCAc had the relative highest affinity (1.31 x 10(-4)), followed by linuron, 3,4-dichlorophenylurea, flutamide, 3,4-DCA and diuron with the lowest RBA (2.4 x 10(-5)). Hence the metabolism of xenobiotic compounds has to be considered to estimate potential ecotoxiocological effects. This test not only can be used to screen for androgen- and antiandrogen-like substances in environmentally relevant samples such as surface waters, but might also be applied for drug testing and for residue monitoring.

Acetanilides↗

PubMed1976

A comparison of electron-capture GLC, electrolytic-conductivity GLC and UV-absorption HPLC for the analysis of some herbicides in foods.

A comparison of gas chromatography with electron-capture or electrolytic-conductivity (nitrogen mode) detection, and high-pressure liquid chromatography (HPLC) with UV-absorption detection (254 nm) was carried out for the analysis of several herbicides in foods. Linuron, propanil, terbacil, benzoylprop-ethyl, and the fungicide DCNA in samples of cabbage, corn, potato, and wheat spiked at 2 and 0.2 ppm were examined. The pesticides were extracted with acetone, partitioned into petroleum ether-methylene chloride, and cleaned up on a 2% deactivated Florisil column before direct chromatographic analysis. Electron-capture gas-liquid chromatography (GLC) was most suitable for DCNA and benzoylprop-ethyl while UV-absorption HPLC was best for terbacil analysis. Linuron and propanil gave similar results for both electron-capture GLC and HPLC. Electrolytic-conductivity GLC could detect all pesticides at the 0.2 ppm level and exhibited the least number of extraneous peaks in the chromatograms.

Aniline Compounds↗

PubMed1975

Inhibition of phenylamide hydrolysis by Bacillus sphaericus with methylcarbamate and organophosphorus insecticides.

The degradation of the phenylamide herbicides monolinuron, linuron, and solan by cultures of Bacillus sphaericus ATCC 12123 was inhibited by the methylcarbamate insecticides metmercapturon, aldicarb, propoxur, and carbaryl and by the organophosphorus insecticides fenthion and parathion. The extent of inhibition was largest with metmercapturon and smallest with parathion inhibition of hydrolysis of the two phenylurea herbicides was greater than of the acylanilide compound. Tests with crude enzyme preparations of aryl acylamidase derived from B. sphaericus showed that the inhibition of the hydrolysis of linuron with methylcarbamates is a competitive one. The insecticides tested did induce the enzyme, nor could they serve as its substrate.

Amidohydrolases↗

PubMed1977

Response of soil microbiota to selected herbicide treatments.

Recommended concentrations of paraquat alone and its combination with each of linuron, diuron, atrazine, simazine, and simazine plus diuron exerted little effect on total populations of bacteria, actinomycetes, and fungi in Fox sandy loam under laboratory and simulated field conditions in 66 and 77 days, respectively. Respiration of the total microbiota in soil suspension was afeected by the combinations as well as individual herbicides in various concentrations. Yet, the inhibition of the O2 uptake by any of these herbicides, including some extreme concentrations, was not permanent, indicating adaptation, or suppression of specific organisms. Only linuron in concentrations up to 20 microng/ml stimulated respiration of the soil.

Actinomycetales↗

PubMed1978

A method for the detection and analysis of growth patterns of microorganisms in soil.

A fluorescence-staining technique using the magnesium salt of 8-anilino-1-naphthalene sulfonic acid is described and used to follow the changes in the distribution patterns of microorganisms in soils. A statistical procedure was used to determine the occurrence of significant differences in clumping of bacteria (i.e., production of colonies) in different regions of artificial soil-aggregate systems treated with nutrient solutions and also with a herbicide, Linuron. The response of soil microorganisms to glucose amendment was most marked in the aerobic, outer zone of aggregates. Linuron inhibited colony formation in aggregates treated with the herbicide. The method allows continued observations to be made on the same soil sample at intervals during incubation and os can be used to determine growth rates, inhibitory effects of chemicals, distribution patterns in soils, effects of added nutrients, and other effects where growth in situ is important.

Anilino Naphthalenesulfonates↗

PubMed1982

[Microbial side chain splitting of phenylurea and carbonic acid anilides].

A Gram- negative rod-shaped bacterium 28/1 isolated by enrichment cultures is able to hydrolyze the amide bond of some phenylurea herbicides and acid anilide herbicides by an inducible amidase. 7.5% of 0.3 mumol.ml-1 linuron (3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea) are hydrolyzed after 16 hours. 1,1-Dimethylphenylureas are not degraded. Acid anilides are hydrolyzed at a higher rate, 80% of 0.5 mumol.ml-1 N-(4-chlorophenyl)-propionamide and N-(4-nitrophenyl)-propionamide are transformed after 6 hours. The 1-methoxy-1-methyl phenylureas are effective inducers. Linuron-induced cells have a specific activity of 3-4 nmol per mg dry weight per min on the substrate N-(3,4-dichlorophenyl)-propionamide (Propanil). The rate of hydrolysis is influenced by substituents of the aniline ring and by the structure of the side chain of the acid anilides.

Amidohydrolases↗

PubMed1997

Effect of the nature of exogenous organic matter on pesticide sorption by the soil.

A study was carried out on the sorption of two sparingly water-soluble pesticides (diazinon and linuron) by a sandy loam soil modified with different exogenous organic materials (EOMs) containing humic-like substances: city refuse compost (CRC), peat (P), commercial "humic" acid (HA), liquid "humic" acid (LHA), and two (nonhumic) model compounds (surfactants), tetradecyltrimethylammonium bromide (TDTMA) and sodium dodecyl sulphate (SDS), before and after 2- and 8-month incubation periods with the soil. In all cases, the isotherms fitted the Freundlich sorption equation (x/m = KCen), generally with r2 values greater than 0.99. The value of the sorption constant K for the natural soil was 8.81 for diazinon and 2.29 for linuron. These values increased significantly for EOM modified soils with respect to natural soil, with the exception of the samples modified with SDS and LHA, in which cases they decreased, possibly due to the micellar properties of these compounds. Incubation of EOMs with soil increased their sorption capacity: the Koc values were increased proportionally to the incubation time for both pesticides and for all treatments carried out. Accordingly, the sorption capacity of hydrophobic pesticides increases with the degree of evolution in the soil of EOMs with "humic"-type compounds, possibly due, among other causes, to the increase in the EOMs' colloidal properties and the modifications occurring in the hydrophobic-hydrophilic characteristics of the soil surfaces. The main conclusion is that application to the soil of carbon-rich wastes, especially those with a high degree of maturity, may offer an important strategy for reducing pesticide leaching and for eliminating pesticide residues from soil with the use of anionic surfactants.

Adsorption↗

PubMed1995

Trace determination of herbicides in estuarine waters by liquid chromatography-high-flow pneumatically assisted electrospray mass spectrometry.

High-flow pneumatically assisted electrospray (ESP) was applied to the characterization of triazine (atrazine, simazine, ametryne, cyanazine, deethylatrazine and deisopropylatrazine), phenylurea (chlortoluron++, isoproturon, diuron, linuron and diflubenzuron) and other priority herbicides (alachlor, metolachlor). In LC-ESP-MS the [M+Na]+ ion was used as the base peak in most cases, with the exception of chlorotriazines, which showed [M+H]+ as the base peak. When LC-TSP-MS was used, [M+H]+ was the base peak for many of the pesticides, with the exception of linuron and diflubenzuron, which showed [M+NH4]+ as the base peak. The ESP results were compared with those obtained with thermospray (TSP). LC-TSP-MS offered greater sensitivity for triazines than phenylurea herbicides, whereas the use of LC-ESP-MS offered an enhancement in sensitivity for phenylurea herbicides. As regards the fragmentation obtained using both techniques, ESP offered a considerable amount of structural information for the different chlorotriazines studied when the extraction voltage was increased from 20 to 40 V. Liquid-liquid extraction with dichloromethane was used for the trace enrichment of the different herbicides in estaurine water samples from the Elorn river (France). The presence of the different triazine metabolites, atrazine, simazine, metolachlor, isoproturon and diuron was confirmed by both LC-MS techniques.

Chromatography, High Pressure Liquid↗

PubMed2000

Indirect analysis of urea herbicides from environmental water using solid-phase microextraction.

We described here a solid-phase microextraction procedure used to extract six urea pesticides-- chlorsulfuron, fluometuron, isoproturon, linuron, metobromuron and monuron--from environmental samples. Two polydimethylsiloxanes and a polyacrylate fiber (PA) are compared. The extraction time, pH control, addition of NaCl to the water and the influence of organic matter such as humic acid on extraction efficiency were examined to achieve a sensitive method. Determination was carried out by gas chromatography with nitrogen-phosphorus detection. The proposed method requires the extraction of 2 ml of sample (pH 4, 14.3%, w/v, NaCl) for 60 min with the PA fiber. The limits of detection range from 0.04 for linuron to 0.1 microg/l for fluometuron and monuron and the relative standard deviations at the 1 microg/l level are between 15% and 9%. The apparent fiber-water distribution constants (Kfw) calculated in the proposed conditions were in the order of 10(3). Phenylurea herbicides were indirectly determined in the form of their derived anilines and chlorsulfuron in the form of an aminotriazine as confirmed by gas chromatography-mass spectrometry. Natural waters were utilized to validate the final procedure. However, a unequivocal identification in unknown environmental samples should be done by LC-MS. The presence of dissolved organic matter such as humic acid produces losses during the extraction step. Adding sodium chloride to the sample compensates for this effect.

Herbicides↗

PubMed1996

Evaluation of the genotoxicity potential (by Mutatox test) of ten pesticides found as water pollutants in Cyprus.

Ten pesticides: aldicarb, aldicard sulfone, aldicarb oxide, carbofuran, propoxur, methomyl, diuron, linuron, alachlor and parathion-methyl, found as water pollutants in Cyprus, were evaluated for their genotoxicity potential with the Mutatox test, both directly and after exogenous activation with S9 hepatic enzymes. A dark variant (M 169) of the Photobacterium phosphoreum was used as the test organism. Trials were undertaken in triplicate using ground-water spiked with pesticides solutions at testing concentration theoretically corresponding to acute effects of 0.004%, up to a maximum of 2%. All tested pesticides were found to be 'suspect genotoxic' directly and after S-9 activation, except for Alachlor which after S-9 activation was found to be 'genotoxic' at 30 micrograms/l. Among the ten pesticides Linuron was found to be 'suspect genotoxic' after S-9 activation at the lowest concentration, i.e. 2 micrograms/l. Genotoxicity after activation with S-9 was demonstrated at a concentration 1-3 orders of magnitude lower than the respective concentration for direct genotoxic effects. Moreover, genotoxicity after S-9 was developed at levels where the acute toxic effects (Microtox) were 'non measurable' to 'negligible'. The investigation of possible genotoxic effects provides essential information on the impacts of pesticides on the Ecosystem and can contribute to the selection of pesticides with the least possible effects.

Animals↗

PubMed1998

Alternative methods for mechanistic studies in toxicology. Screening of hepatotoxicity of pesticides using freshly isolated and primary cultured hepatocytes and non-liver-derived cells, SIRC cells.

We constructed a screening battery for the evaluation of hepatotoxicity using freshly isolated and primary cultured rat hepatocytes (abbreviated to FIH and PCH, respectively) and rabbit eye derived cell line, SIRC cells. Effects on cell viability and drug metabolizing enzyme activities were examined by several pesticides and compared to those of in vivo. Among the pesticides studied, prometryn and ametryn showed cytotoxicity on PCH at lower concentration than on SIRC cells. Cytotoxicities of these chemicals on FIH were inhibited by metyrapone. They also increased rat serum AST in vivo. On the other hand, cytotoxicities of IBP, erusan, alanicarb, benfuracarb, and swep in PCH were observed at similar concentration to those in SIRC cells. Linuron, nitrofen, and chlomethoxifen increased ethoxycoumarin O-deethylation activities by almost similar concentration to those of benzo[a]pyrene. Linuron also induced ethoxycoumarin O-deethylation activity in vivo. These findings indicated that a battery of in vitro tests consisting of FIH, PCH and SIRC cells was useful to screen the hepatotoxicity of pesticides.

Animal Testing Alternatives↗

PubMedDate not supplied

Removal of herbicides from liquid media by fungi isolated from a contaminated soil.

Fungi were isolated from soil samples corresponding to pesticide-contaminated soil (CS) and noncontaminated soil (NCS) in the Annaba vicinity (Algeria) and identified. The number of isolates obtained from CS and NCS were 263 and 288, respectively. The most frequent species (Aspergillus fumigatus, A. niger, A. terreus, Absidia corymbifera, and Rhizopus microsporus var microsporus) were not sensitive to the pesticides. The growth of the genus Trichoderma was inhibited by the pesticides, while genera Absidia and Fusarium were stimulated. The 53 species isolated were assayed for their ability to remove metribuzin from liquid medium. Only Botrytis cinerea from NCS and Sordaria superba and Absidia fusca from CS removed more than 50% of the compound after 5 d. Metamitron was very resistant. Among the 21 species tested, only Alternaria solani (from NCS), Drechslera australiensis (from CS and NCS), and Absidia fusca (from CS) reduced the concentration in the medium more than 10% (10-16%). Twelve species were grown with linuron, seven of them were inefficient in removing this compound. The two strains of Sordaria macrospora yielded 22 to 25% depletion, while Botrytis cinerea depleted linuron almost completely. Among the 31 species assayed for their ability to eliminate metobromuron, Botrytis cinerea (from CS and NCS) depleted almost completely the chemical from the medium. Rhizopus oryzae and Absidia fusca from CS removed 40 and 47% of the compound, respectively. No systematic relationships were observed between the soil contamination and herbicide elimination capacities of soil fungi. Absidia fusca and Botrytis cinerea were particularly interesting for bioremediation purposes because they were able to transform efficiently three of the four compounds assayed.

Biodegradation, Environmental↗

PubMedDate not supplied

Glutathione depletion induced in rat liver fractions by seven pesticides.

Glutathione (GSH) plays a central role in the chemical detoxication. Xenobiotics which induce GSH depletion, either via GSH conjugation or via oxidation of GSH to glutathione disulfide (GSSG), alter the mechanism of natural cellular defence against toxicants. The aim of this study was to evaluate the ability of seven widely used pesticides (Alachlor, Atrazine, Benomyl, Captan, Linuron, Methyl Parathion and Propanil) and/or of their metabolites to deplete GSH in rat liver fractions. In our experimental conditions, Atrazine, Linuron and Propanil failed to interact with rat liver GSH. Conversely, Alachlor, Benomyl and Methyl Parthion were able to deplete GSH in rat liver, probably by forming GSH conjugates. The fungicide Captan rapidly reduced the rat liver concentration of GSH by converting it to the oxidized form GSSG. But a longer incubation of Captan with rat hepatic enzymes produced the formation of metabolites which depleted GSH via conjugation. Our results suggest that exposure to the pesticides Alachlor, Benomyl, Captan and Methyl Parathion may induce an alteration of natural mechanisms of defence against toxicants in mammals, including humans.

Amino Acid Sequence↗

PubMed1995

Segment specificity of the cytological response in rainbow trout (Oncorhynchus mykiss) renal tubules following prolonged exposure to sublethal concentrations of atrazine.

Cytopathological alterations in proximal (PS I, PS II) and distal segments (DS) of rainbow trout (Oncorhynchus mykiss) renal tubules following exposure to 0, 10, 20, 40, 80, and 160 micrograms/liter atrazine for 4 weeks were investigated by means of electron microscopy. Cellular responses were clearly dose-dependent with a gradual increase in variability and intensity of effects. Ultrastructural modifications in PS I and II were observed from 10 micrograms/liter atrazine, in DS from 20 micrograms/liter. In PS I, major changes included proliferation of smooth endoplasmic reticulum, atypical mitochondria and lysosomes, as well as gradual alterations of the apical plasmalemma. Typical changes in PS II cells were a proliferation of peroxisomes and ring- and cup-shaped mitochondria, as well as alterations in the basal labyrinth; DS cells were characterized by a proliferation of atypical mitochondria with longitudinally oriented cristae, disorganization of Golgi fields and vacuolization of the cell base. Results document that different segments of the renal tubule in rainbow trout react not only with different levels of sensitivity to atrazine exposure, but also in a segment-specific way. Moreover, comparison of effects induced by atrazine with those resulting from chronic exposure to the herbicide linuron revealed a distinct substance specificity in the reaction of different tubular segments.

Animals↗