Formation of tetrachloroazobenzene in some Canadian soils treated with propanil and 3,4-dichloroaniline.
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The degradation of xenobiotics was investigated in model experiments in soddy-podzolic soil as a function of their concentration, pH moisture content, temperature, and aeration of the soil, and presence of organic and mineral compounds. The main and secondary factors determining the persistence of xenobiotics in soil were established and approximation formulas for calculating their persistance criteria (ty) were proposed.
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3,4-Dichloropropionaniline (propanil) is an extensively used postemergent herbicide that has been shown to produce toxic and immunotoxic effects. The present report examined if acute exposure to propanil altered in vitro or in vivo cytokine production in response to antigenic stimulation. Studies to determine resistance to infection by the intracellular bacterium Listeria monocytogenes after exposure to propanil were also conducted. Our experiments demonstrate that in vivo exposure to propanil during bacterial infection reduced the subsequent in vitro production of interferon-gamma (IFN-gamma) by splenocytes and liver nonparenchymal cells in response to antigenic and mitogenic stimulation. Additional experiments examined the production of cytokines in vivo after propanil exposure alone or combined propanil exposure and L. monocytogenes infection. It was found that the endogenous levels of cytokines in the liver, spleen, and blood were similar in control and propanil-treated mice. The levels of cytokines were also similar in control and exposed mice that were infected with L. monocytogenes. Initial resistance to the infection was not affected by exposure to propanil. These results demonstrate that in vivo exposure to propanil during a bacterial infection suppresses the subsequent in vitro production of cytokines but that the endogenous levels are not affected during the initial stages of infection.
The herbicide 3,4-dichloropropionanilide (propanil) has several well-documented neurotoxic and immunotoxic effects on mice. We report here a detailed characterization of the effects of propanil exposure on the thymus. We found that at doses of 100-200 mg/kg, propanil induces significant thymic atrophy between 2 and 7 days postexposure. This atrophy is characterized by a decrease in thymus/body ratio and a decrease in cellularity. Flow cytometric analyses of thymuses from propanil- and vehicle-treated mice indicate that the CD4(+) CD8(+) population of immature cells, is most significantly decreased in propanil-exposed mice. We performed cell cycle analysis of thymocyte populations using two-color surface staining and the DNA binding dye 7-aminoactinomycin D to determine whether thymic atrophy was associated with changes in the percentages of cells in the S, G2, and M phases of the cell cycle. We found a high percentage of proliferating CD4(+)CD8(+) thymocytes 4 days after exposure. Thus, recovery of the thymus occurs following increases in thymocyte proliferation, most notably the immature CD4(+) CD8(+) thymocytes. We tested the hypothesis that glucocorticoids play a role in the observed atrophy by examining thymuses in adrenalectomized, propanil-treated mice. No atrophy was observed in those animals. These results suggest that propanil has an immunotoxic effect on the thymus that appears to be mediated, in part, by endogenous glucocorticoids.
This study determined alterations to bone marrow B-cell populations after in vivo exposure to a mixture containing the herbicides 3,4-dichloropropionanilide (propanil) and 2,4-dichlorophenoxyacetic acid (2,4-D) and compared them to the effects of exposure to the individual herbicides. Propanil and 2,4-D are postemergent herbicides that are sold commercially as a mixture. The individual herbicides or the mixture containing propanil and 2,4-D were administered intraperitoneally to C57Bl/6 female mice at doses from 50 to 200 mg herbicide/kg body weight. The mixtures were given in a 1:1 ratio. Flow cytometric analysis was performed to quantitate bone marrow B-cell populations at 1, 2, 7, and 14d posttreatment. Mixture treatment decreased pre-B and immunoglobulin (Ig) M(+) B-cell populations at all doses by 2 d postexposure. The cell populations were still decreased at 7d posttreatment. In contrast, exposure to the individual herbicides only caused decreases in the pre-B and IgM(+) B-cell populations 7d after exposure to the high doses. Previous studies have demonstrated that corticosterone levels are increased by exposure to propanil. Therefore, the glucocorticoid hormone, corticosterone, was investigated as a possible mediator of cell loss in the bone marrow. Treatment with the glucocorticoid receptor antagonist, RU 486, however, did not prevent cell loss in the bone marrow of mice exposed to the mixture of propanil and 2,4-D. This study demonstrates that pre-B and IgM(+) B-cell populations are decreased after exposure to propanil, 2,4-D, or the mixture containing propanil and 2,4-D. Exposure to the mixture had greater toxic effects than the individual herbicides on bone marrow pre-B and IgM(+) B-cell populations, emphasizing the need to study mixture interactions.
Our previous studies demonstrated that both in vivo and in vitro 3,4-dichloro-propionanilide (propanil) exposure inhibited interleukin-6 (IL-6) and tumor necrosis factor (TNF) production by adherent thioglycollate-elicited peritoneal cells (macrophages) after lipopolysaccharide (LPS) stimulation. In this study, we report that IL-6 and TNF-alpha message is reduced by propanil in a concentration-dependent pattern, yet the stability of cytokine mRNA is not affected. In addition, exposure of macrophages to propanil after a relatively short period of LPS stimulation significantly reduced the production of IL-6 and TNF. Determination of the intracellular Ca2+ levels demonstrates that LPS-induced Ca2+ release is abrogated in propanil-treated macrophages. However, the binding of LPS to macrophages is not affected. Measurement of inositol 1,4,5-triphosphate (IP3) demonstrates that propanil significantly increases the level and the duration of IP3 in macrophages. These results suggest that the inhibitory effect of propanil on macrophage cytokine production is associated with the early stages of LPS-mediated signal transduction in macrophages.
3,4-Dichloropropionanilide-(14)C (propanil) labeled in either the C-1 or C-3 carbon atoms of the propionic acid moiety was applied to the roots of pea (Pisum sativum L.) and rice (Oryza sativa L.) plants in nutrient solution (0.1 mm-0.28 mm). Radioactivity was detected throughout the treated plants, but the greatest labeling was found in the roots. None of the products that contained aniline were radioactive, suggesting that the plants split the propionic acid moiety from propanil. The fate of the propionate moiety of propanil was determined by recovery of (14)CO(2) from plants exposed to propanil-(14)C. The time-course of the (14)CO(2) production demonstrated that the intact propionic acid was cleaved from the propanil and subsequently catabolized by the beta-oxidation catabolic sequence. The appearance of radioactivity in the shoots was attributed to the incorporation of products of propionate metabolism. Both the susceptible pea plants and the tolerant rice plants converted a high percentage of the administered propanil-(14)C to (14)CO(2).
Studies to elucidate the fate of 3,4-dichloropropionanilide (propanil) in rice (Oryza sativa L. var. Nato) plants have shown that the propanil molecule is cleaved and the propionic acid moiety metabolized. To ascertain the fate of the 3,4-dichloroaniline moiety of propanil, rice plants were exposed to propanil in liquid culture. The roots and shoots of treated rice plants were extracted and quantitatively assayed for four aniline-containing metabolites. One of the four metabolites proved to be 3,4-dichloroaniline, while the remaining three metabolites contained complexed 3,4-dichloroaniline. N-(3,4-dichlorophenyl)-glucosylamine was identified as one of the complexes. A time-course study of the four metabolites indicated the appearance of the 3,4-dichloroaniline-containing metabolites within 6 hours. After 14 days of treatment, the complexed aniline metabolites amounted to only 10 percent of the total propanil administered to the rice plants.
Fluorescent pseudomonads were a major component [log (10) 4.2-6.1 colony-forming units mL-1] of the culturable heterotrophic gram-negative bacterioplankton observed in three Mississippi Delta oxbow lakes in this study. Pure cultures of fluorescent pseudomonads were isolated from three Mississippi Delta oxbow lakes (18 per lake), using selective media S-1. Classical physiological tests and Biolog GN plates were used in criteria for taxonomic identification. Most isolates were identified as biotypes of Pseudomonas fluorescens 55% (II), 7% (III), and 25% (V). About 7% of the isolates were identified as P. putida and 7% as non-fluorescent Pseudomonas-like. Cell suspensions of these isolates were tested for their ability to metabolize/co-metabolize six 14C-radiolabeled herbicides (2,4-dichlorophenoxyacetic acid (2,4-D), cyanazine, fluometuron, metolachlor, propanil, and trifluralin) that are commonly used for crop production in this geographical area. Almost all (53 of 54) isolates transformed trifluralin via aromatic nitroreduction. Most isolates (70%) dechlorinated metolachlor to polar metabolites via glutathione conjugation. About 60% of the isolates hydrolyzed the amide bond of propanil (a rice herbicide) to dichloroaniline, with the highest frequency of propanil-hydrolyzing isolates observed in the lake from the watershed with rice cultivation. All propanil-hydrolyzing isolates were identified as P. fluorescens biotype II. No metabolism of cyanazine or fluometuron was observed by any isolates tested, indicating little or no potential for N-dealkylation among this group of bacterioplankton. No mineralization of 2,4-D labeled in either the carboxyl or ring position was observed. These results indicate that reductive and hydrolytic pathways for herbicide co-metabolism (aromatic nitroreduction, aryl acylamidase, and glutathione conjugation) are common in Mississippi Delta aquatic fluorescent pseudomonads; however, the potential for certain oxidative transformations (N-dealkylation, cyano group oxidation) may be rare in this group of bacterioplankton.
Propanil (3,4-dichloropropionanilide) and 2,4-D (2,4-dichlorophenoxyacetic acid) are commonly used herbicides that have toxic effects on the immune system. The present study determined the effect of exposure to these chemicals on the immune response to a bacterial vaccine. The antibody responses to the T-independent type 2 antigen, phosphorylcholine (PC) and the T-dependent antigen, pneumococcal surface protein A (PspA) were characterized in C57BL/6 mice after heat-killed Streptococcus pneumoniae (HKSP) immunization and single or mixture herbicide exposure. Propanil exposure significantly increased the number of PC-specific IgM, IgG2b, and IgG3 antibody-secreting B cells (ASC) in the spleen 4-6-fold over control animals in a dose-dependent manner. However, the number of ASC in the bone marrow and serum titers were comparable in control and propanil-treated mice. In contrast, 2,4-D exposure decreased the number of PC-specific IgM and IgG bone marrow ASC 2-3-fold from control animals. The decrease in bone marrow ASC in 2,4-D-treated mice corresponded to a 3-4-fold decrease in PC-specific IgM, IgG2b, and IgG3 serum titers compared to control mice. The number of ASC in the spleens of 2,4-D-treated mice was, however, comparable to control mice. The antibody response to PspA was not affected by any of the treatments. There were no mixture interactions between the two herbicides in any of the responses measured. These results characterize the primary PC-specific antibody response in the bone marrow, spleen, and serum after HKSP vaccination and herbicide exposure. The differential effects of propanil and 2,4-D on the antibody response to a bacterial vaccine demonstrate the potential of chemical exposure to augment or suppress immune responses to vaccines and infectious diseases.
Propanil (3',4'-dichloropropionanilide) was a potent inhibitor of the nitrogenase activity of blue-green algae (cyanobacteria) in flooded soil, but the herbicide at comparable concentrations was not toxic to rice, protozoa, and nitrogen-fixing bacteria. Ethanol-amended flooded soils treated with propanil exhibited higher rates of nitrogenase activity than those not treated with the herbicide. The enhanced nitrogenase activity in propanil-treated soils was associated with a rise in the population of purple sulfur bacteria, especially of cells resembling Chromatium and Thiospirillum. By employing propanil and a means of excluding light from the floodwater to prevent the development of phototrophs during rice growth under lowland conditions, the relative activities of blue-green algae, photosynthetic bacteria, and the rhizosphere microflora were determined. The results suggest that the potential contribution of photosynthetic bacteria may be quite high.
Herbicide antagonism is defined as the reduction of control of certain weeds as the result of applying mixtures of two or more herbicides. Cyhalofop-butyl, a graminicide used for postemergence grass weed control in rice, is antagonized by some rice herbicides when applied simultaneously. The result of this type of antagonism usually results in decreased control of grass weeds. Research has shown that herbicide antagonism between graminicides and other herbicides may be caused by different mechanisms as the result of activity of the tank-mix partner. Using HPLC, the objective of this experiment was to analyze the fate of cyhalofop-butyl in barnyardgrass tissue when applied alone and in combination with halosulfuron, propanil, or triclopyr. Results indicated that absorption of cyhalofop-butyl and hydrolysis to its phytotoxic metabolite, cyhalofop-acid, was rapid and that halosulfuron and triclopyr had no effect. Because of a likely interaction of propanil with an apoplastic esterase enzyme, increased levels of cyhalofop-butyl and cyhalofop-acid were detected in barnyardgrass tissue, indicating that cyhalofop-butyl metabolism was hindered by propanil.
The health effects of two pesticides, chlordimeform and propanil, are discussed. Chlordimeform and 2-methyl-4-chloroaniline, a major metabolite of chlordimeform, cause severe hemorrhagic cystitis in humans. In cats, however, only a mild effect on the bladder was noted. The herbicide propanil has produced chloracne in humans, and along with 3,4-dichloroaniline, hyperkeratosis in rabbits. The contaminants 3,4,3',4'-tetrachloroazobenzene and 3,4,3',4'-tetrachloroazoxybenzene are responsible for the chloracnegenic characteristics of propanil, 3,4-dichloroaniline, and methazole.
3,4-Dichloropropionanilide (propanil) and 2,4-dichlorophenoxyacetic acid (2,4-D) are two commonly used herbicides that are marketed as a chemical mixture. It was hypothesized that the interaction between these two herbicides, when administered as a mixture, would result in a greater effect on the immune system than the individual components of the mixture. The present study demonstrates in a murine model that a mixture of propanil and 2,4-D, when compared to single herbicide exposures, exacerbates decreases in thymocyte populations 2 d postexposure and inhibits the repopulation of T-cells in the thymus 7 d postexposure. Exposure to 150 mg herbicide/kg body weight of propanil or 2,4-D alone had no effect on thymus weight. In contrast, decreases in the ratio of thymus weight to body weight (TW:BW) occurred 2 d after treatment with the mixture of 150 mg propanil/kg body weight + 150 mg 2,4-D/kg body weight (150/150). Thymic atrophy was associated with a decrease in the double-positive thymocyte population (CD4+CD8+) and correlated with sera corticosterone levels from 600 to 1000 pg/ml. Therefore, the hypothesis was tested that glucocorticoids, induced after exposure to herbicides, were responsible for the thymic atrophy and depletion of thymocytes. However, similar levels of corticosterone were induced after exposure to 50, 100, or 150 mg propanil/kg body weight, and 50/50 or 100/100 mixture treatments, doses that did not produce thymic atrophy or cell loss. In addition, RU 486, a glucocorticoid receptor blocker, only partially abrogated the thymic atrophy in mice exposed to the 150/150 mixture of herbicides. These results suggest that glucocorticoids are only partially responsible for herbicide-induced thymic atrophy. This study demonstrates that the effects of exposure to a mixture of chemicals cannot always be predicted based on single exposure data and emphasizes the importance of mixture-based studies.