Assessment of methomyl-induced adrenal gland disruption in rat fetuses and pups: Potential protective effects of propolis supplementation.

The present study aimed to unravel the possible adverse effects of methomyl on the developing adrenal gland of rat fetuses and pups. Additionally, this study explored the potential improving effects of propolis against these possible hazards induced by methomyl exposure. To achieve that, pregnant rats were divided into four groups: control group, received 1 mL distilled water, propolis group, received 1 mL propolis at a dose of 300 mg/kg, methomyl group, received 1 mL methomyl at a dose of 2 mg/kg, and combined group, received 1 mL methomyl followed by 1 mL propolis, an hour later at the same previous doses. The results revealed that methomyl exposure, during pregnancy and lactation, induced many histological and ultrastructural changes, caused DNA damage and downregulated the expression of steroidogenic acute regulatory (StAR) and CYP11B2 genes in the adrenal glands of both rat fetuses and pups. Interestingly, propolis supplementation demonstrated a remarkable ability to mitigate these deleterious effects and restored the histology and ultrastructure architecture of the adrenal glands of both fetuses and pups, as well as decreased DNA damage and upregulated the expression of StAR and CYP11B2 genes in the adrenal gland of rat fetuses and pups. In conclusion, our study highlights the potential hazardous impact of methomyl exposure during pregnancy and lactation on the development of the adrenal gland in rat fetuses and pups, moreover, the study presents a new approach to alleviate these effects through propolis administration which could be used as a dietary supplement to mitigate the adverse effects of methomyl exposure.

Effect of environmental level of methomyl on hatching, morphology, immunity and development related genes expression in zebrafish (Danio rerio) embryo.

The extensive use of carbamate pesticides has led to a range of environmental and health problems, such as surface and groundwater contamination, and endocrine disorders in organisms. In this study, we focused on examining the effects of toxic exposure to the carbamate pesticide methomyl on the hatching, morphology, immunity and developmental gene expression levels in zebrafish embryos. Four concentrations of methomyl (0, 2, 20, and 200 µg/L) were administered to zebrafish embryos for a period of 96 h. The study found that exposure to methomyl accelerated the hatching process of zebrafish embryos, with the strongest effect recorded at the concentration of 2 µg/L. Methomyl exposure also trigged significantly reductions in heart rate and caused abnormalities in larvae morphology, and it also stimulated the synthesis and release of several inflammatory factors such as IL-1ß, IL-6, TNF-α and INF-α, lowered the IgM contents, ultimately enhancing inflammatory response and interfering with immune function. All of these showed the significant effects on exposure time, concentration and their interaction (Time × Concentration). Furthermore, the body length of zebrafish exposed to methomyl for 96 h was significantly shorter, particularly at higher concentrations (200 µg/L). Methomyl also affected the expression levels of genes associated with development (down-regulated igf1, bmp2b, vasa, dazl and piwi genes), demonstrating strong developmental toxicity and disruption of the endocrine system, with the most observed at the concentration of 200 µg/L and 96 h exposure to methomyl. The results of this study provide valuable reference information on the potential damage of methomyl concentrations in the environment on fish embryo development, while also supplementing present research on the immunotoxicity of methomyl.

Toxicity of methomyl insecticides to testicular cells and protective effect of folic acid.

Methomyl is a carbamate insecticide with confirmed testicular toxicity. This study intended to observe the effect of methomyl on testicular cells and the protective effect of folic acid through in vitro experiments. The GC-1 spermatogonia, TM4 Sertoli cells, and TM3 Leydig cells were treated with methomyl (0, 250, 500, and 1000 µM) with or without folic acid (0, 10, 100, and 1000 nM) for 24 h. It was found that methomyl increased cytotoxicity to testicular cells in a dose-dependent manner. In spermatogonia, methomyl significantly inhibited the expression of proliferation genes Ki67 and PCNA at 1000 µM, and increased the expression of apoptosis genes Caspase3 and Bax at each dose. In Sertoli cells, methomyl dose-dependently inhibited the expression of blood-testis barrier function genes TJP1, Cx43, and N-cadherin, but did not affect Occludin and E-cadherin. In Leydig cells, methomyl inhibited the expression of steroid synthase P450scc, StAR, Hsd3b1 and down-regulated the level of testosterone, but did not affect Cyp17a1 and Hsd17b1. Further, folic acid could basically reduce the damage caused by methomyl. This study provided new insights into the toxicity of methomyl and the protective effect of folic acid.

High-efficiency degradation of methomyl by the novel bacterial consortium MF0904: Performance, structural analysis, metabolic pathways, and environmental bioremediation.

Methomyl is a widely used carbamate pesticide, which has adverse biological effects and poses a serious threat to ecological environments and human health. Several bacterial isolates have been investigated for removing methomyl from environment. However, low degradation efficiency and poor environmental adaptability of pure cultures severely limits their potential for bioremediation of methomyl-contaminated environment. Here, a novel microbial consortium, MF0904, can degrade 100% of 25 mg/L methomyl within 96 h, an efficiency higher than that of any other consortia or pure microbes reported so far. The sequencing analysis revealed that Pandoraea, Stenotrophomonas and Paracoccus were the predominant members of MF0904 in the degradation process, suggesting that these genera might play pivotal roles in methomyl biodegradation. Moreover, five new metabolites including ethanamine, 1,2-dimethyldisulfane, 2-hydroxyacetonitrile, N-hydroxyacetamide, and acetaldehyde were identified using gas chromatography-mass spectrometry, indicating that methomyl could be degraded firstly by hydrolysis of its ester bond, followed by cleavage of the C-S ring and subsequent metabolism. Furthermore, MF0904 can successfully colonize and substantially enhance methomyl degradation in different soils, with complete degradation of 25 mg/L methomyl within 96 and 72 h in sterile and nonsterile soil, respectively. Together, the discovery of microbial consortium MF0904 fills a gap in the synergistic metabolism of methomyl at the community level and provides a potential candidate for bioremediation applications.

Appraisal of sub-chronic exposure to lambada-cyhalothrin and/or methomyl on the behavior and hepato-renal functioning in Oreochromis niloticus: Supportive role of taurine-supplemented feed.

The existing study was designed to inspect the toxicological consequences of two pesticides; lambda-cyhalothrin (LCT) and methomyl (MTM) and their combination on Nile tilapia (Oreochromis niloticus) behaviors, oxidative stress, hepato-renal function indices and microarchitectural alterations. In addition, the efficiency of taurine (TUR) to rescue their toxicity was also considered. Juvenile O. niloticus were assigned into eight groups. The control and TUR groups were fed on a basal diet and TUR-enriched (10 g kg1) diet, respectively. The other groups were fed on a basal diet, and exposed to LCT (0.079 µg L-1), MTM (20.39 µg L-1 and (LCT + MTM). The last three groups were (LCT + TUR), (MTM + TUR), and (LCT + MTM + TUR) and fed on a TUR-enriched diet during exposure to LCT and/or MTM for 60 days. The exposure to LCT and/or MTM resulted in several behavioral alterations and stress via enhanced cortisol and nor-epinephrine levels. A significant elevation of serum 8-hydroxy-2- deoxyguanosine, aspartate and alanine aminotransferases, lactate dehydrogenase, Alkaline phosphatase, urea, creatinine was also observed in these groups. Furthermore, reduced antioxidant enzymes activities, including (catlase, glutathione peroxidase, and superoxide dismutase) with marked histopathological lesions in both liver and kidney tissues were detected. The up-regulated Bax and down-regulated Bcl-2 proteins were expressed in the liver and kidney tissues of LCT and/or MTM -exposed groups. Interestingly, all the observed alterations in behaviors, biochemical indices, and histo-architecture of renal and hepatic tissues were mitigated by TUR supplementation. The findings suggest that feeding O. niloticus dietary TUR may help to reduce the negative effects of LCT and/or MTM, and can also support kidney and liver health in O. niloticus, making it a promising aquaculture feed supplement.

Oxidative stress induced by methomyl exposure reduces the quality of early embryo development in mice.

Methomyl is a widely used carbamate insecticide and environmental oestrogen that has adverse effects on the reproductive system. However, there have been no reports on the effect of methomyl on early embryos in mammals. In this study, we explored the effect of methomyl exposure on the quality of early embryonic development in mice and the possible mechanisms. During in vitro culture, different concentrations of methomyl (10, 20, 30 and 35 µM) were added to mouse zygote medium. The results showed that methomyl had an adverse effect on early embryonic development. Compared with the control group, the addition of 30 µM methomyl significantly reduced the rate of early embryo blastocyst formation. Methomyl exposure can increase oxidative stress and impair mitochondrial function, which may be the cause of blastocyst formation. In addition, we found that methomyl exposure promoted apoptosis and autophagy in mouse blastocysts. The toxic effect of methomyl on early embryos may be the result of oxidative stress induction. Taken together, our results indicate that methomyl can cause embryonic development defects in mice, thereby reducing the quality of early embryo development.

Subacute and subchronic methomyl exposure induced toxic effects on intestines via oxidative stress in male albino rats: biochemical and histopathological study.

The aim of the present study was to estimate the potential toxic effects of a subacute and a subchronic exposure to methomyl (MET) on some parts of the digestive system in male albino rats. Wistar rats were exposed daily by oral gavage to 4 mg/kg body weight (b.w.) of MET over 28 days in subacute experiments and to 1 mg/kg b.w. of MET for 90 consecutive days in subchronic exposure. Plasma levels of liver function indicators (ALT, AST, ALP and LDH) were significantly elevated after administration of MET to rats. MET had significant pro-oxidative effects on the intestines, as indicated by decreases in nonenzymatic (GSH) and enzymatic antioxidant (GPx, GST and CAT) parameters and significant increases in TBARS levels in both the duodenum and colon of rats. Microscopically, the duodenum and colon of rats exposed to MET showed severe pathological changes. It could be concluded that MET profoundly altered the structure and antioxidant status of intestinal rat tissue, which might lead to intestinal and digestive dysfunctions.

Toxic effects of methomyl on mouse oocytes and its possible mechanisms.

Methomyl is a broad-spectrum carbamate insecticide that has a variety of toxic effects on humans and animals. However, there have been no studies on the toxicity of methomyl in female mammalian oocytes. This study investigated the toxic effects of environmental oestrogen methomyl exposure on mouse oocyte maturation and its possible mechanisms. Our results indicated that methomyl exposure inhibited polar body extrusion in mouse oocytes. Compared with that in the control group, in the methomyl treatment group, superoxide anion free radicals in oocytes were significantly increased. In addition, the mitochondrial membrane potential of metaphase II stage oocytes in the methomyl treatment group was significantly decreased, resulting in reduced mouse oocyte quality. After 8.5 h of exposure to methomyl, metaphase I stage mouse oocytes displayed an abnormal spindle morphology. mRNA expression of the pro-apoptotic genes Bax and Caspase-3 in methomyl-treated oocytes increased, which confirmed the apoptosis. Collectively, our results indicated that mouse oocyte maturation is defective after methomyl treatment at least through disruption of spindle morphology, mitochondrial function and by induction of oxidative stress.

Carbamate C-N Hydrolase Gene ameH Responsible for the Detoxification Step of Methomyl Degradation in Aminobacter aminovorans Strain MDW-2.

Methomyl {bis[1-methylthioacetaldehyde-O-(N-methylcarbamoyl)oximino]sulfide} is a highly toxic oxime carbamate insecticide. Several methomyl-degrading microorganisms have been reported so far, but the role of specific enzymes and genes in this process is still unexplored. In this study, a protein annotated as a carbamate C-N hydrolase was identified in the methomyl-degrading strain Aminobacter aminovorans MDW-2, and the encoding gene was termed ameH A comparative analysis between the mass fingerprints of AmeH and deduced proteins of the strain MDW-2 genome revealed AmeH to be a key enzyme of the detoxification step of methomyl degradation. The results also demonstrated that AmeH was a functional homodimer with a subunit molecular mass of approximately 34 kDa and shared the highest identity (27%) with the putative formamidase from Schizosaccharomyces pombe ATCC 24843. AmeH displayed maximal enzymatic activity at 50°C and pH 8.5. Km and kcat of AmeH for methomyl were 87.5 µM and 345.2 s-1, respectively, and catalytic efficiency (kcat/Km ) was 3.9 µM-1 s-1 Phylogenetic analysis revealed AmeH to be a member of the FmdA_AmdA superfamily. Additionally, five key amino acid residues (162, 164, 191, 193, and 207) of AmeH were identified by amino acid variations.IMPORTANCE Based on the structural characteristic, carbamate insecticides can be classified into oxime carbamates (methomyl, aldicarb, oxamyl, etc.) and N-methyl carbamates (carbaryl, carbofuran, isoprocarb, etc.). So far, research on the degradation of carbamate pesticides has mainly focused on the detoxification step and hydrolysis of their carbamate bond. Several genes, such as cehA, mcbA, cahA, and mcd, and their encoding enzymes have also been reported to be involved in the detoxification step. However, none of these enzymes can hydrolyze methomyl. In this study, a carbamate C-N hydrolase gene, ameH, responsible for the detoxification step of methomyl in strain MDW-2 was cloned and the key amino acid sites of AmeH were investigated. These findings provide insight into the microbial degradation mechanism of methomyl.

Can Toxicities Induced by Insecticide Methomyl be Remediated Via Soil Bacteria Ochrobactrum thiophenivorans and Sphingomonas melonis?

The research study was about revealing the biochemical response of Gammarus pulex related to insecticide methomyl before and after bioremediation by two soil bacteria species, Ochrobactrum thiophenivorans and Sphingomonas melonis. Catalase (CAT), glutathione S-transferase.(GST), cytochrome. P4501A1 (CYP1A1) activities in G. Pulex related to methomyl solution were investigated in 24 h and 96 h. ELISA method was used for test studies. CAT enzyme was decreased in Gammarus pulex that was exposed to methomyl after all exposure period (P < 0.05). CAT activities were returned to control results after bioremediation assays. GST enzyme activity was decreased depending on methomyl exposure during 24 h but increased during 4 days (P < 0.05). After 8 days of bioremediation period, GST activity increased again during 24 h while decreased during 4 days (P < 0.05). CYP1A1 activity increased in Gammarus pulex that was exposed to methomyl after all exposure period (P > 0.05). After bioremediation, statistically significant changes were not revealed in CYP1A1 activities (P > 0.05). According to the results of our study, CYP1A1, CAT, and GST activities in G. pulex sanctioned the capability of Ochrobactrum thiophenivorans and Sphingomonas melonis in methomyl bioremediation. Isolated and enriched Ochrobactrum thiophenivorans and Sphingomonas melonis that were added to 2.5 ppb concentrations of methomyl for 8 days. Each day, chemical oxygen demand (COD) and biochemical oxygen demand (BOD5), pH and dissolved oxygen parameters were monitored. At the final phase of the bioremediation step, it was determined that these bacteria have efficient methomyl bioremediation properties in a mixed corsortia at a rate of 86%. These results show that these bacteria can be used for bioremediate the receiving environments that are polluted by these kinds of insecticides.

Current Approaches to and Future Perspectives on Methomyl Degradation in Contaminated Soil/Water Environments.

Methomyl is a broad-spectrum oxime carbamate commonly used to control arthropods, nematodes, flies, and crop pests. However, extensive use of this pesticide in agricultural practices has led to environmental toxicity and human health issues. Oxidation, incineration, adsorption, and microbial degradation methods have been developed to remove insecticidal residues from soil/water environments. Compared with physicochemical methods, biodegradation is considered to be a cost-effective and ecofriendly approach to the removal of pesticide residues. Therefore, micro-organisms have become a key component of the degradation and detoxification of methomyl through catabolic pathways and genetic determinants. Several species of methomyl-degrading bacteria have been isolated and characterized, including Paracoccus, Pseudomonas, Aminobacter, Flavobacterium, Alcaligenes, Bacillus, Serratia, Novosphingobium, and Trametes. The degradation pathways of methomyl and the fate of several metabolites have been investigated. Further in-depth studies based on molecular biology and genetics are needed to elaborate their role in the evolution of novel catabolic pathways and the microbial degradation of methomyl. In this review, we highlight the mechanism of microbial degradation of methomyl along with metabolic pathways and genes/enzymes of different genera.

Degradation of methomyl by the combination of Aminobacter sp. MDW-2 and Afipia sp. MDW-3.

Methomyl (S-methyl N-(methylcarbamoyloxy) thioacetimidate) is a kind of oxime carbamate insecticide. It is considered to be extremely toxic to nontarget organism. To date, no pure culture or consortium has been reported to have the ability to degrade methomyl completely. In this study, a methomyl-degrading enrichment E1 was obtained by using the sludge from the wastewater-treating system of a pesticide manufacturer as the original inoculant. Two bacterial strains named MDW-2 and MDW-3 were isolated from this enrichment, and they were preliminarily identified as Aminobacter sp. and Afipia sp. respectively. Strains MDW-2 and MDW-3 could coexist and degrade 50 mg l-1 methomyl completely within 3 days by the cooperative metabolism. Methomyl was first converted to methomyl oxime and methylcarbamic acid by strain MDW-2, and the latter could be used as the carbon source for the growth of strain MDW-2. But methomyl oxime could not be sequentially degraded by strain MDW-2. However, it could be degraded and used as the carbon source by strain MDW-3. SIGNIFICANCE AND IMPACT OF THE STUDY: This study presents a bacterial combination of Aminobacter sp. MDW-2 and Afipia sp. MDW-3, which could degrade methomyl completely by biochemical cooperation. This study also proposes the biodegradation pathway of methomyl for the first time and highlights the application potential of a bacterial combination in the remediation of methomyl-contaminated environments.

Removal of carbamates and detoxification potential in a biomixture: Fungal bioaugmentation versus traditional use.

The use of fungal bioaugmentation represents a promising way to improve the performance of biomixtures for the elimination of pesticides. The ligninolyitc fungus Trametes versicolor was employed for the removal of three carbamates (aldicarb, ALD; methomyl, MTM; and methiocarb, MTC) in defined liquid medium; in this matrix ALD and MTM showed similar half-lives (14d), nonetheless MTC exhibited a faster removal, with a half-life of 6.5d. Then the fungus was employed in the bioaugmentation of an optimized biomixture to remove the aforementioned carbamates plus carbofuran (CFN). Bioaugmented and non-bioaugmented systems removed over 99% ALD and MTM after 8d of treatment, nonetheless a slight initial delay in the removal was observed in the bioaugmented biomixtures (removal after 3d: ALD 87%/97%; MTM 86%/99%, in bioaugmented/non-bioaugmented systems). The elimination of the other carbamates was slower, but independent of the presence of the fungus: >98% for MTM after 35d and >99.5% for CFN after 22d. Though the bioaugmentation did not improve the removal capacity of the biomixture, it favored a lower production of transformation products at the first stages of the treatment, and in both cases, a marked decrease in the toxicity of the matrix was swiftly achieved along the process (from 435 to 448 TU to values <1TU in 16d).

Responses and recovery pattern of sex steroid hormones in testis of Nile tilapia (Oreochromis niloticus) exposed to sublethal concentration of methomyl.

Tilapia were exposed to sublethal methomyl concentrations of 0, 0.2, 2, 20 or 200 µg/L for 30 days, and then transferred to methomyl-free water for 18 days. The sexual steroid hormones 17ß-estradiol (E2), testosterone (T), and 11-ketotestosterone (11-KT) in tilapia testes were examined at 0, 6, 12, 18, 24 and 30 days after methomyl exposure, and at 18 days after fish were transferred to methomyl-free water. There were no significant changes in the hormone parameters in testes of tilapia exposed to low concentration 0.2 and 2 µg/L methomyl compared with the controls. However, high concentration 20 and 200 µg/L methomyl had the potential to disrupt the endocrine system of male tilapia, as shown by an increase in E2 and a decrease in T and 11-KT in the testes. Thus, it would appear that the 2 µg/L methomyl might be considered the no-observed-adverse-effect level. Recovery data showed that the effects produced by the lower concentration of 20 µg/L were reversible but the effects were not reversible at the higher concentration of 200 µg/L.

Assessment of genotoxicity of Lannate-90® and its plant and animal metabolites in human lymphocyte cultures.

This study evaluated direct and metabolic genotoxic effects caused by Lannate-90®, a methomyl-based formulation (90 % active ingredient), in human lymphocyte cultures using sister chromatid exchange assay (SCE). Two processes were used for the plant promutagens evaluation: in vivo activation, applying the insecticide systemically in plants for 4 h and subsequently adding plant metabolites containing extracts to lymphocyte cultures; and in vitro activation, where the insecticide was incubated with Vicia faba S10 mix plus human lymphocyte culture. Direct treatment with the insecticide significantly increased SCE frequency in human lymphocytes (250-750 mgL-1), with cellular death observed at 1000 mgL-1 concentration. Using the extracts of Vicia faba treated with Lannate-90® to treat human lymphocytes, a dose-response relationship was observed. In lymphocyte cultures treated directly with the insecticide for 2 h, a negative response was obtained. When S10 mix was added, SCE frequency did not change significantly. Meanwhile, a mixture of S9 mammalian metabolic mix and Lannate-90® increased the SCE frequency, with an observed concentration-dependent response. Although Lannate-90® induced cellular death at the highest concentrations, it did not cause a delay in cell proliferation in any of the treatments, confirming its genotoxic action. This study is one of the first to evaluate and compare the direct effect of Lannate-90® in two bioassays, animal and vegetal, and the effect of plant and animal metabolism on its genotoxic potential.

Fate of thiodicarb and its metabolite methomyl in sandy loam soil under laboratory conditions.

Fate of thiodicarb and its major metabolite in sandy loam soil were studied by applying thiodicarb (Larvin 75 WP) at 500 and 1000 g a. i. ha(-1) under laboratory conditions. Samples drawn periodically were analysed on GC-FTD equipped with capillary column. The average initial deposits of total thiodicarb (thiodicarb and methomyl) were 0.025 and 0.035 mg kg(-1) at single and double dosages, respectively. Residues of thiodicarb reached below the determination level (BDL) of 0.005 mg kg(-1) after 15 days. Half-life periods for total thiodicarb were calculated to be 5.90 and 8.29 days at two doses, respectively, following first-order kinetics.

Different enzymatic activities in carp (cyprinus carpio L.) as potential biomarkers of exposure to the pesticide methomyl.

This study investigated the influence of the pesticide methomyl on different enzymatic activities in carp. The fish were exposed to a sub-lethal concentration (0.34 mg L-1) of methomyl for 15 days. On days 4 and 15, catalase (CAT) and glutathione-S-transferase (GST) activities were measured in the liver and gills. Acetylcholinesterase (AChE) activity in brain and muscle was also determined. Liver catalase activity slightly increased in exposed fish when compared to controls, but it was statistically significant only at the beginning of the experiment. No changes in CAT activity in the gills of exposed and control animals were observed (mean values were in the range 10.7-11.7 nmol min-1 per mg of protein). Liver GST activity was slightly inhibited in the exposed animals at the beginning of the study; however, it was significantly inhibited in the gills. Brain AChE activity was diminished throughout the experiment and significantly decreased after 96 h of exposure compared to controls (0.041 vs. 0.075 nmol min1 per mg of protein; p<0.001). Our findings suggest that CAT, GST, and AChE are reliable biomarkers of effect after exposure to methomyl.

Determination of methomyl in the stomach contents of baited wildlife by gas chromatography-mass spectrometry.

The poisoning of wildlife with fly-bait containing the active ingredient methomyl is an intentional and illegal act in many jurisdictions. A case of 2 animals poisoned by methomyl through consumption of tainted bait at multiple stations is described. Although thermally and ultraviolet-labile, methomyl can be identified by gas chromatography-mass spectrometry and is detected in abundance in bait samples; however, it is not readily observed in tissues, owing to its rapid metabolism and elimination. The application of derivatizing functionalities, such as trimethylsilyl groups, stabilizes the methomyl-oxime metabolite to facilitate its detectability during exposure to the relatively harsh conditions of gas chromatography. This brief communication reports on the analytical detection of methomyl in baits and biological samples from poisoned wildlife. Essential to the case were the added determination of a fly-bait coactive ingredient, (Z)-9-tricosene, and identification of a chemical indicator, caffeine, to confirm both the type of pesticide product involved in the poisoning incident and the vehicle used to perpetrate its delivery.

Dynamic plant uptake model applied for drip irrigation of an insecticide to pepper fruit plants.

BACKGROUND: Drip application of insecticides is an effective way to deliver the chemical to the plant that avoids off-site movement via spray drift and minimizes applicator exposure. The aim of this paper is to present a cascade model for the uptake of pesticide into plants following drip irrigation, its application for a soil-applied insecticide and a sensitivity analysis of the model parameters. RESULTS: The model predicted the measured increase and decline of residues following two soil applications of an insecticide to peppers, with an absolute error between model and measurement ranging from 0.002 to 0.034 mg kg fw(-1). Maximum measured concentrations in pepper fruit were approximately 0.22 mg kg fw(-1). Temperature was the most sensitive component for predicting the peak and final concentration in pepper fruit, through its influence on soil and plant degradation rates. CONCLUSION: Repeated simulations of pulse inputs with the cascade model adequately describe soil pesticide applications to an actual cropped system and reasonably mimic it. The model has the potential to be used for the optimization of practical features, such as application rates and waiting times between applications and before harvest, through the integrated accounting of soil, plant and environmental influences.

Potential use of the oligochaete Limnodrilus profundicola V., as a bioindicator of contaminant exposure.

Cholinesterase (ChE) and ethoxyresorufin-O-deethylase (EROD) were of special interest to this study as these biochemical tools have been widely used for the determination of exposure to pollutants. In this study, the freshwater oligochaete Limnodrilus profundicola was tested for its potential as a bioindicator of freshwater pollution. For this purpose, the ChE and EROD activities of L. profundicola and the level of polycyclic aromatic hydrocarbons (PAH) of water samples collected from different sites along the Curuksu stream on the Menderes River (the ancient Meander) running through south-western Turkey were studied. First, these activities were characterized using, as model substrates, acetylthiocholine (ATC), propionylthiocholine (PTC), and butyrylthiocholine (BTC). Then, the in vivo effects of insecticides and pollutants on these activities were investigated. L. profundicola were exposed to various doses of methyl-parathion, methomyl, and deltamethrin. Although significant inhibition of ChE was detected with each of the insecticides, the highest level of inhibition was observed with methyl-parathion. In addition to the inhibition of ChE, the activity of EROD was induced by exposure to oil-contaminated sediments. Thus, although L. profundicola has a reputation for being very resistant to pollution (although it is not insensitive to it), we demonstrated that it may potentially be used as a bioindicator species for contaminant exposure when ChE and EROD are used as biomarkers.