RESUMO
The 4-chloro-2-methylphenoxy acid (MCPA) is an herbicide widely used in agriculture, which generates a great concern about contamination of surface water and serious consequences for human health and the environment. In this work, the adsorption of MCPA on an Argentine montmorillonite (MMT) and its organo-montmorillonite product (OMMT) with different dodecyl trimethyl ammonium loading was investigated. MCPA adsorption on OMMT increases at least 3 times, with respect to the amount determined for MMT. X-ray diffraction and zeta potential analyses indicated the inner (interlayer) and outer surface participate as adsorption sites. Changes in surface electric charge and also interlayer expansion suggest that dimethyl amine (MCPA counterion) was also surface-adsorbed. The larger aggregates of OMMT, without and with MCPA, obtained compared to those of MMT samples, generate an improvement in the coagulation efficiency. This property, particularly after MCPA retention, allows an easier separation of the solids from the solution and enables a simple technological process application.
Assuntos
Ácido 2-Metil-4-clorofenoxiacético/química , Bentonita/química , Herbicidas/química , Compostos de Amônio Quaternário/química , Adsorção , Espectroscopia de Infravermelho com Transformada de Fourier , Poluentes Químicos da Água/química , Difração de Raios XRESUMO
In this study, we used primary cultures of fish hepatic cells as a tool for evaluating the effects of environmental contamination. Primary hepatic cell cultures derived from the subtropical fish Metynnis roosevelti were exposed to different concentrations (0.275, 2.75 and 27.5 µg L(-1)) of the herbicides 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-chloro-2-methylphenoxyacetic acid (MCPA). Cellular respiratory activity was evaluated by polarography using three substrates: 0.5 M glucose, 0.5 M succinate and 0.5 M α-ketoglutarate. Significant changes were observed in cellular oxygen consumption with 0.5 M α-ketoglutarate. Even at low concentrations, 2,4-D and MCPA were potent uncouplers of oxidative phosphorylation. Primary cultures of M. roosevelti liver cells may provide a useful tool for the evaluation of environmental contaminant effects. A review of regulations regarding permitted concentrations of these herbicides is needed.
Assuntos
Ácido 2,4-Diclorofenoxiacético/toxicidade , Ácido 2-Metil-4-clorofenoxiacético/toxicidade , Herbicidas/toxicidade , Animais , Células Cultivadas , Characidae/metabolismo , Relação Dose-Resposta a Droga , Hepatócitos/efeitos dos fármacos , Hepatócitos/metabolismo , Ácidos Cetoglutáricos/metabolismo , Fígado/efeitos dos fármacos , Polarografia/instrumentação , Polarografia/métodos , Testes de Toxicidade/métodosRESUMO
The dimorphic fungus Paracoccidioides brasiliensis is the causative agent of the most frequent systemic mycosis in Latin America. In humans, infection starts by inhalation of fungal propagules, which reach the pulmonary epithelium and differentiate into the yeast parasitic phase. Here we describe the characterization of a Dfg5p (defective for filamentous growth) homologue of P. brasiliensis, a predictable cell wall protein, first identified in Saccharomyces cerevisiae. The protein, the cDNA and genomic sequences were analysed. The cloned cDNA was expressed in Escherichia coli and the purified rPbDfg5p was used to obtain polyclonal antibodies. Immunoelectron microscopy and biochemical studies demonstrated the presence of PbDfg5p in the fungal cell wall. Enzymatic treatments identified PbDfg5p as a beta-glucan linked protein that undergoes N-glycosylation. The rPbDfg5p bound to extracellular matrix components, indicating that those interactions could be important for initial steps leading to P. brasiliensis attachment and colonization of host tissues.
Assuntos
Parede Celular/metabolismo , Proteínas Fúngicas/metabolismo , Paracoccidioides/crescimento & desenvolvimento , Paracoccidioides/metabolismo , Ácido 2-Metil-4-clorofenoxiacético , Sequência de Aminoácidos , Sequência de Bases , DNA Complementar/genética , DNA Fúngico/genética , Dicamba , Combinação de Medicamentos , Fluorenos , Proteínas Fúngicas/genética , Regulação Fúngica da Expressão Gênica , Genes Fúngicos , Genoma Fúngico , Humanos , Dados de Sequência Molecular , Paracoccidioides/genética , Paracoccidioides/ultraestrutura , Paracoccidioidomicose/sangue , Paracoccidioidomicose/imunologia , Ligação ProteicaRESUMO
A Mg/Al layered double hydroxide (LDH) was intercalated with the anionic herbicides 2,4-D, MCPA, and picloram by using three different methodologies: (i) direct synthesis (DS), (ii) regeneration (RE), and (iii) ion exchange (IE). The resulting complexes were characterized and assayed by batch release and column leaching tests, aiming at the controlled release of these herbicides. All the tested LDH-herbicide complexes displayed similar slow herbicide release properties in water, although the IE method seemed to result in complexes with a greater fraction of herbicide in a readily available form. Apparently, the LDH-herbicide complexes released most of the active ingredient present in the complexes at the end of the batch release experiment. This was attributed to the replacement of the intercalated herbicide by carbonate and hydroxyl anions from the aqueous solution. Compared to the free herbicides, the application of the three LDH-herbicide complexes (RE) to soil columns resulted in reduction in the maximum herbicide concentration in leachates and led to the retardation of herbicide leaching through the soil. All LDH-herbicide complexes presented an herbicidal efficacy similar to that of the free (technical) herbicides. Our results indicated the potential applicability of LDHs as supports for the preparation of slow release formulations of acid herbicides such as 2,4-D, MCPA, or picloram.
Assuntos
Herbicidas/administração & dosagem , Herbicidas/química , Hidróxidos/química , Ácido 2,4-Diclorofenoxiacético/administração & dosagem , Ácido 2,4-Diclorofenoxiacético/química , Ácido 2-Metil-4-clorofenoxiacético/administração & dosagem , Ácido 2-Metil-4-clorofenoxiacético/química , Ânions , Preparações de Ação Retardada , Herbicidas/análise , Cinética , Picloram/administração & dosagem , Picloram/química , Solo/análiseRESUMO
Phenoxyalkanoic compounds are used worldwide as herbicides. Cupriavidus necator JMP134(pJP4) catabolizes 2,4-dichlorophenoxyacetate (2,4-D) and 4-chloro-2-methylphenoxyacetate (MCPA), using tfd functions carried on plasmid pJP4. TfdA cleaves the ether bonds of these herbicides to produce 2,4-dichlorophenol (2,4-DCP) and 4-chloro-2-methylphenol (MCP), respectively. These intermediates can be degraded by two chlorophenol hydroxylases encoded by the tfdB(I) and tfdB(II) genes to produce the respective chlorocatechols. We studied the specific contribution of each of the TfdB enzymes to the 2,4-D/MCPA degradation pathway. To accomplish this, the tfdB(I) and tfdB(II) genes were independently inactivated, and growth on each chlorophenoxyacetate and total chlorophenol hydroxylase activity were measured for the mutant strains. The phenotype of these mutants shows that both TfdB enzymes are used for growth on 2,4-D or MCPA but that TfdB(I) contributes to a significantly higher extent than TfdB(II). Both enzymes showed similar specificity profiles, with 2,4-DCP, MCP, and 4-chlorophenol being the best substrates. An accumulation of chlorophenol was found to inhibit chlorophenoxyacetate degradation, and inactivation of the tfdB genes enhanced the toxic effect of 2,4-DCP on C. necator cells. Furthermore, increased chlorophenol production by overexpression of TfdA also had a negative effect on 2,4-D degradation by C. necator JMP134 and by a different host, Burkholderia xenovorans LB400, harboring plasmid pJP4. The results of this work indicate that codification and expression of the two tfdB genes in pJP4 are important to avoid toxic accumulations of chlorophenols during phenoxyacetic acid degradation and that a balance between chlorophenol-producing and chlorophenol-consuming reactions is necessary for growth on these compounds.
Assuntos
Ácido 2,4-Diclorofenoxiacético/metabolismo , Ácido 2-Metil-4-clorofenoxiacético/metabolismo , Burkholderiaceae/enzimologia , Herbicidas/metabolismo , Oxigenases de Função Mista/genética , Plasmídeos/genética , Ácido 2,4-Diclorofenoxiacético/farmacologia , Ácido 2-Metil-4-clorofenoxiacético/farmacologia , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Biodegradação Ambiental , Burkholderiaceae/genética , Burkholderiaceae/crescimento & desenvolvimento , Clorofenóis/metabolismo , Herbicidas/farmacologia , Oxigenases de Função Mista/metabolismo , Especificidade por SubstratoRESUMO
We investigated the developmental toxicity in mice of a common commercial formulation of herbicide containing a mixture of 2,4-dichlorophenoxyacetic acid (2,4-D), mecoprop, dicamba, and inactive ingredients. Pregnant mice were exposed to one of four different doses of the herbicide mixture diluted in their drinking water, either during preimplantation and organogenesis or only during organogenesis. Litter size, birth weight, and crown-rump length were determined at birth, and pups were allowed to lactate and grow without additional herbicide exposure so that they could be subjected to additional immune, endocrine, and behavioral studies, the results of which will be reported in a separate article. At weaning, dams were sacrificed, and the number of implantation sites was determined. The data, although apparently influenced by season, showed an inverted or U-shaped dose-response pattern for reduced litter size, with the low end of the dose range producing the greatest decrease in the number of live pups born. The decrease in litter size was associated with a decrease in the number of implantation sites, but only at very low and low environmentally relevant doses. Fetotoxicity, as evidenced by a decrease in weight and crown-rump length of the newborn pups or embryo resorption, was not significantly different in the herbicide-treated litters.
Assuntos
Ácido 2,4-Diclorofenoxiacético/efeitos adversos , Ácido 2-Metil-4-clorofenoxiacético/análogos & derivados , Ácido 2-Metil-4-clorofenoxiacético/efeitos adversos , Dicamba/efeitos adversos , Implantação do Embrião/efeitos dos fármacos , Fertilidade/efeitos dos fármacos , Morte Fetal , Herbicidas/efeitos adversos , Animais , Animais Recém-Nascidos , Peso ao Nascer , Relação Dose-Resposta a Droga , Feminino , Camundongos , GravidezRESUMO
Two racemic herbicides, mecoprop (R,S-MCPP) and dichlorprop (R,S-DCPP), as well as their enantiopure R-forms, were incubated in three calcareous soils at 15 degrees C and 80% of their field capacity to try to elucidate their behaviour in soil and compare the dissipation rates when racemic and enantiopure compounds are used. Quantitation of pesticides is made by HPLC and the R/S ratio by GC-MS. The inactive S-enantiomer from the racemic forms persists longer than the R-forms in silt and sandy loam soils, but for shorter time in the clay loam soil. The pure R-enantiomers, both for MCPP and DCPP, after incubation in soil, are partially converted into their S-forms. In all cases, the dissipation of racemic and pure enatiomeric forms is lower in the clay loam soil than in the silt and sandy loam soils. The R-forms' peristence, in the three soils, is approximately two times lower when they are incubated alone than when they are incubated as racemic compounds. When peat is added, the persistence of these herbicides in the silt and sandy loam soils increases, while in the clay loam soil it decreases. Besides, in the clay loam soil, the enantiomeric ratio (ER) changes from its S-preferential degradation to a preferential degradation of its R-form, so an increase in the persistence of the inactive S-form occurs.
Assuntos
Ácido 2,4-Diclorofenoxiacético/análogos & derivados , Ácido 2,4-Diclorofenoxiacético/farmacocinética , Ácido 2-Metil-4-clorofenoxiacético/análogos & derivados , Ácido 2-Metil-4-clorofenoxiacético/farmacocinética , Herbicidas/farmacocinética , Poluentes do Solo/farmacocinética , Meia-Vida , SoloRESUMO
Leaching studies of mecorprop (R,S)-2-(4-chloro-2-methylphenoxy)propanoic acid, and dichlorprop, (R,S)-2-(4-chloro-2,4-dichlorophenoxy) propanoic acid, under saturated conditions were conducted in unamended and amended soil columns. The purpose of the study was to investigate the leaching of these herbicides in three type of soils and the exogen organic matter effect on this process. The leaching patterns could be related to variation in the soil texture and diffusion processes of the herbicides into micropores within the walls of conducting pore. The leaching rate in the amended soil columns decreased with the addition of organic matter. The breakthrough curves (BTC) of these herbicides in the leachates of the amended soil columns were wider and more diffused than the BTC obtained for the corresponding unamended soil. The theoretical BTC overestimated the pore volume required for the displacement of these pesticides from the soil column. This may be due to the differences in the adsorption process between the bacth and soil columns methods.