Mancozeb selectively induces mitochondrial-mediated apoptosis in human gastric carcinoma cells through ROS generation.

Mancozeb (Manganese ethylene bis-dithiocarbamate with zinc salt) is a dithiocarbamate fungicide used to control fungal disease in many fruit plants, flowers and the maintenance of field crops. The effect of mancozeb on cell viability of human gastric adenocarcinoma AGS, SNU-1 cells and human normal FHs 74 Int cells were investigated. This study demonstrated that mancozeb was able to inhibit cell proliferation by 56-82% at 5-10 µM concentrations after 48 h. Mancozeb treatment for 48 h resulted in 33% (P < 0.05) and 61% (P < 0.001) increase in apoptotic cells at 5 and 10 µM concentrations in AGS cells, respectively. Treatment with mancozeb did not cause cell cycle arrest, while modulated the expression level of cleaved caspase-3, and cleavage of poly-(ADP-ribose) polymerase. Furthermore, treatment with mancozeb caused a rapid stimulation of reactive oxygen species (ROS) and loss of mitochondrial transmembrane potential. The results also showed that mancozeb-induced apoptosis was accompanied by up-regulation of Bax and down-regulation of Bcl-2 and Bcl-xL. Overall, our data suggested that mancozeb caused ROS generation which induced significant (P < 0.05) apoptosis in AGS cells that was attenuated with pretreatment of NAC. More importantly, same concentration of mancozeb did not show any considerable effect on cell growth, death, cell cycle arrest and ROS generation in normal FHs 74 Int cells. Overall, for the first time these results suggest that mancozeb has selective anticancer activity at lower concentrations against gastric cancer cells.

Mancozeb impairs the ultrastructure of mouse granulosa cells in a dose-dependent manner.

Mancozeb, an ethylene bis-dithiocarbamate, is widely used as a fungicide and exerts reproductive toxicity in vivo and in vitro in mouse oocytes by altering spindle morphology and impairing the ability to fertilize. Mancozeb also induces a premalignant status in mouse granulosa cells (GCs) cultured in vitro, as indicated by decreased p53 expression and tenuous oxidative stress. However, the presence and extent of ultrastructural alterations induced by mancozeb on GCs in vitro have not yet been reported. Using an in vitro model of reproductive toxicity, comprising parietal GCs from mouse antral follicles cultured with increasing concentrations of mancozeb (0.001-1 µg/ml), we sought to ascertain the in vitro ultrastructural cell toxicity by means of transmission (TEM) and scanning (SEM) electron microscopy. The results showed a dose-dependent toxicity of mancozeb on mouse GCs. Ultrastructural data showed intercellular contact alterations, nuclear membrane irregularities, and chromatin marginalization at lower concentrations, and showed chromatin condensation, membrane blebbing, and cytoplasmic vacuolization at higher concentrations. Morphometric analysis evidenced a reduction of mitochondrial length in GCs exposed to mancozeb 0.01-1 µg/ml and a dose-dependent increase of vacuole dimension. In conclusion, mancozeb induced dose-dependent toxicity against GCs in vitro, including ultrastructural signs of cell degeneration compatible with apoptosis, likely due to the toxic breakdown product ethylenethiourea. These alterations may represent a major cause of reduced/delayed/missed oocyte maturation in cases of infertility associated with exposure to pesticides.

IFN-γ regulates xanthine oxidase-mediated iNOS-independent oxidative stress in maneb- and paraquat-treated rat polymorphonuclear leukocytes.

Maneb (MB) and paraquat (PQ) provoke oxidative stress-mediated cell damage. Role of xanthine oxidase (XO) in oxidative stress and its association with nitric oxide (NO)/NO synthase (NOS) have been widely reported. While inducible NOS (iNOS) is implicated in MB+PQ-induced toxicity in rat polymorphonuclear leukocytes (PMNs), role of XO and its alliance with iNOS have not yet been established. The study investigated the role of XO in MB+PQ-induced oxidative stress in rat PMNs and its regulation by iNOS and inflammatory cytokines. MB+PQ-augmented reactive oxygen species (ROS), superoxide, nitro-tyrosine, lipid peroxidation (LPO), and nitrite levels along with the catalytic activity of iNOS, superoxide dismutase (SOD), and XO. XO inhibitor, allopurinol (AP), alleviated MB+PQ-induced changes except nitrite content and iNOS activity. Conversely, an iNOS inhibitor, aminoguanidine, mitigated MB+PQ-induced LPO, nitrite, iNOS, and nitro-tyrosine levels; however, no change was observed in ROS, SOD, and XO. Nuclear factor-κB inhibitor, pyrrolidine dithiocarbamate (PDTC), tumor necrosis factor-alpha (TNF-α) inhibitor, pentoxyfylline, and an anti-inflammatory agent, dexamethasone, attenuated MB+PQ-induced increase in XO, superoxide, and ROS with parallel reduction in the expression of interferon-gamma (IFN-γ), TNF-α, and interleukin-1ß (IL-1ß) in rat PMNs. Exogenous IFN-γ, TNF-α, and IL-1ß enhanced superoxide, ROS, and XO in the PMNs of control and MB+PQ-treated rats; however, IFN- γ was found to be the most potent inducer. Moreover, AP ameliorated cytokine-induced free radical generation and restored XO activity towards normalcy. The results thus demonstrate that XO mediates oxidative stress in MB+PQ-treated rat PMNs via iNOS-independent but cytokine (predominantly IFN-γ)-dependent mechanism.

The fungicide Mancozeb induces metacaspase-dependent apoptotic cell death in Saccharomyces cerevisiae BY4741.

Mancozeb (MZ), a mixture of ethylene-bis-dithiocarbamate manganese and zinc salts, is one of the most widely used fungicides in agriculture. Toxicologic studies in mammals and mammalian cells indicate that this fungicide can cause neurological and cytological disorders, putatively associated with pro-oxidant and apoptotic effects. Yeast adaptation to sub-inhibitory concentrations of MZ has been correlated with oxidative response, proteins degradation, and energy metabolism, and its main effect on yeast has been attributed to its high reactivity with thiol groups in proteins. Herein, we show that acute MZ treatments on aerobic exponentially growing yeast of wild type (BY4741) and deletion mutant strains, coupled with multiplex flow cytometry analysis, conclusively demonstrated that MZ displays the typical features of pro-oxidant activity on Saccharomyces, elevating mitochondrial ROS, and causing hyper-polarization of mitochondrial membranes leading to apoptosis. A drastic reduction of cellular viability associated with the maintenance of cell membrane integrity, as well as phosphatidyl serine externalization on yeast cells exposed to MZ, also supports an apoptotic mode of action. Moreover, abrogation of the apoptotic response in yca1 deficient mutants indicates that metacaspase-1 is involved in the programmed cell death mechanism induced by MZ in yeast.

Changes in the metabolome of lettuce leaves due to exposure to mancozeb pesticide.

This paper describes a proton high resolution magic angle spinning (HRMAS) nuclear magnetic resonance (NMR) metabolomic study of lettuce (Lactuca sativa L.) leaves to characterise metabolic adaptations during leaf growth and exposure to mancozeb. Metabolite variations were identified through multivariate analysis and checked through spectral integration. Lettuce growth was accompanied by activation of energetic metabolism, preferential glucose use and changes in amino acids, phospholipids, ascorbate, nucleotides and nicotinate/nicotinamide. Phenylalanine and polyphenolic variations suggested higher oxidative stress at later growth stages. Exposure to mancozeb induced changes in amino acids, fumarate and malate, suggesting Krebs cycle up-regulation. In tandem disturbances in sugar, phospholipid, nucleotide and nicotinate/nicotinamide metabolism were noted. Additional changes in phenylalanine, dehydroascorbate, tartrate and formate were consistent with a higher demand for anti-oxidant defence mechanisms. Overall, lettuce exposure to mancozeb was shown to have a significant impact on plant metabolism, with mature leaves tending to be more extensively affected than younger leaves.

Quercetin protected isolated human erythrocytes against mancozeb-induced oxidative stress.

Mancozeb is a fungicide belonging to the ethylene-bisdithiocarbamate group and is widely used in agriculture. The aim of this study was to examine the protective effect of quercetin (QRN) against oxidative stress induced by mancozeb in human erythrocytes. In order to verify this, 5 ml of venous blood was collected and the erythrocytes were separated and divided into equal parts. One part was incubated with different concentrations of mancozeb (0, 10, 30, 100 µM) for 4 h at 37°C. The other part was preincubated with QRN (40 and 80 µM) for 30 min, followed by mancozeb (0, 10, 30, 100 µM) incubation for 4 h. We found reduction in the levels of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione (GSH) along with elevated levels of lipid peroxide (LPO) in erythrocytes incubated with 30 and 100 µm of mancozeb. Pre-incubation with QRN (80 µM) reversed oxidative stress induced by mancozeb (30 µM) and inhibited LPO induced at 100 µM by 64.36%. QRN also reduced the haemolytic effect on erythrocytes but could not prevent the induction of haemolysis by mancozeb. Therefore, these results suggest that QRN may play a role in preventing the oxidative stress induced by mancozeb in human erythrocytes.

The ethylene bis-dithiocarbamate fungicide Mancozeb activates voltage-gated KCNQ2 potassium channel.

Mancozeb (manganese/zinc ethylene bis-dithiocarbamate) is an organometallic fungicide that has been associated with human neurotoxicity and neurodegeneration. In a high-throughput screen for modulators of KCNQ2 channel, a fundamental player modulating neuronal excitability, Mancozeb, was found to significantly potentiate KCNQ2 activity. Mancozeb was validated electrophysiologically as a KCNQ2 activator with an EC50 value of 0.92±0.23µM. Further examination showed that manganese but not zinc ethylene bis-dithiocarbamate is the active component for the positive modulation effects. In addition, the compounds are effective when the metal ions are substituted by iron but lack potentiation activity when the metal ions are substituted by sodium, signifying the importance of the metal ion. However, the iron (Fe(3+)) alone, organic ligands alone or the mixture of iron with the organic ligand did not show any potentiation effect, suggesting as the active ingredient is a specific complex rather than two separate additive or synergistic components. Our study suggests that potentiation on KCNQ2 potassium channels might be the possible mechanism of Mancozeb toxicity in the nervous system.

Quantitative modeling of the Saccharomyces cerevisiae FLR1 regulatory network using an S-system formalism.

In this study we address the problem of finding a quantitative mathematical model for the genetic network regulating the stress response of the yeast Saccharomyces cerevisiae to the agricultural fungicide mancozeb. An S-system formalism was used to model the interactions of a five-gene network encoding four transcription factors (Yap1, Yrr1, Rpn4 and Pdr3) regulating the transcriptional activation of the FLR1 gene. Parameter estimation was accomplished by decoupling the resulting system of nonlinear ordinary differential equations into a larger nonlinear algebraic system, and using the Levenberg-Marquardt algorithm to fit the models predictions to experimental data. The introduction of constraints in the model, related to the putative topology of the network, was explored. The results show that forcing the network connectivity to adhere to this topology did not lead to better results than the ones obtained using an unrestricted network topology. Overall, the modeling approach obtained partial success when trained on the nonmutant datasets, although further work is required if one wishes to obtain more accurate prediction of the time courses.

Qualitative modelling and formal verification of the FLR1 gene mancozeb response in Saccharomyces cerevisiae.

BACKGROUND: Qualitative models allow understanding the relation between the structure and the dynamics of gene regulatory networks. The dynamical properties of these models can be automatically analysed by means of formal verification methods, like model checking. This facilitates the model-validation process and the test of new hypotheses to reconcile model predictions with the experimental data. RESULTS: The authors report in this study the qualitative modelling and simulation of the transcriptional regulatory network controlling the response of the model eukaryote Saccharomyces cerevisiae to the agricultural fungicide mancozeb. The model allowed the analysis of the regulation level and activity of the components of the gene mancozeb-induced network controlling the transcriptional activation of the FLR1 gene, which is proposed to confer multidrug resistance through its putative role as a drug eflux pump. Formal verification analysis of the network allowed us to confront model predictions with the experimental data and to assess the model robustness to parameter ordering and gene deletion. CONCLUSIONS: This analysis enabled us to better understand the mechanisms regulating the FLR1 gene mancozeb response and confirmed the need of a new transcription factor for the full transcriptional activation of YAP1. The result is a computable model of the FLR1 gene response to mancozeb, permitting a quick and cost-effective test of hypotheses prior to experimental validation.

Insights into the mechanisms of toxicity and tolerance to the agricultural fungicide mancozeb in yeast, as suggested by a chemogenomic approach.

Abstract Saccharomyces cerevisiae was used to uncover the mechanisms underlying tolerance and toxicity of the agricultural fungicide mancozeb, linked to cancer and Parkinson's disease development. Chemogenomics screening of a yeast deletion mutant collection revealed 286 genes that provide protection against mancozeb toxicity. The most significant Gene Ontology (GO) terms enriched in this dataset are associated to transcriptional machinery, vacuolar organization and biogenesis, intracellular trafficking, and cellular pH regulation. Clustering based on physical and genetic interactions further highlighted the role of oxidative stress response, protein degradation and carbohydrate/energy metabolism in mancozeb stress tolerance. Mancozeb was found to act in yeast as a thiol-reactive compound, but not as a free radical or reative oxygen species (ROS) inducer, leading to massive oxidation of protein cysteins, consistent with the requirement of genes involved in glutathione biosynthesis and reduction and in protein degradation to provide mancozeb resistance. The identification of Botrytis cinerea homologues of yeast mancozeb tolerance determinants is expected to guide studies on mancozeb mechanisms of action and tolerance in phytopathogenic fungi. The generated networks of protein-protein associations of yeast mancozeb tolerance determinants and their human orthologues share a high degree of similarity. This toxicogenomics analysis may, thus, increase the understanding of mancozeb toxicity and adaptation mechanisms in humans.

Insights into yeast adaptive response to the agricultural fungicide mancozeb: a toxicoproteomics approach.

Toxicogenomics has the potential to elucidate gene-environment interactions to identify genes that are affected by a particular chemical at the early stages of the toxicological response and to establish parallelisms between different organisms. The fungicide mancozeb, widely used in agriculture, is an ethylene-bis-dithiocarbamate complex with manganese and zinc. Exposure to this pesticide has been linked to the development of idiopathic Parkinson's disease and cancer. Given that many signalling pathways and their molecular components are substantially conserved among eukaryotic organisms, we used Saccharomyces cerevisiae to get insights into the molecular mechanisms of mancozeb toxicity and adaptation based on expression proteomics. The early global response to mancozeb was analysed by quantitative proteomics using 2-DE. The target genes (e.g. TSA1, TSA2, SOD1, SOD2, AHP1, GRE2, GRX1, CYS3, PRE3, PRE6, PRE8, PRE9, EFT1, RPS5, TIF11, HSP31, HSP26, HSP104, HSP60, HSP70-family) and the putative main transcription activators (e.g. Yap1, Msn2/Msn4, Met4, Hsf1, Aft1, Pdr1, Skn7, Rpn4p, Gcn4) of the complex mancozeb-induced expression changes are related with yeast response to stress, in particular to oxidative stress, protein translation initiation and protein folding, disassembling of protein aggregates and degradation of damaged proteins. Our results also suggest that this study provided powerful indications that may be useful to expand the knowledge obtained in yeast not only to the global response to mancozeb toxicity in phytopathogenic fungi but also to humans.

Different responses of biochemical markers in frogs (Rana ridibunda) from urban and rural wetlands to the effect of carbamate fungicide.

Laboratory studies were conducted to determine the effects of carbamate fungicide TATTU (mixture of propamocarb and mancozeb, 0.091 mg L(-1)) on biochemical markers of exposure in Rana ridibunda from clean (reference) and polluted sites. The untreated animals from the polluted site had lower Cu,Zn- and Mn-superoxide dismutase (SOD) and acetylcholinesterase activity, the levels of lipid peroxidation products (TBARS) and protein carbonyls in the liver and vitellogenin-like proteins (Vtg-LP) in the serum, but higher levels of glutathione in the liver in comparison with untreated frogs from the reference site. Catalase activity, superoxide anion and metallothionein levels were the same in both groups. The animals from two sites demonstrate different response on the effect of TATTU during 14 days. In the frogs from polluted site the oxidative damage (the decrease of Mn-SOD activity, lipids and protein oxidative destruction), neurotoxicity (depletion of acetylcholinesterase activity), and endocrine disruption (increase of Vtg-LP level) were revealed. On the other hand, the part of the indices in the animals from the reference site was unchanged after the treatment and the level of metallothionein was elevated demonstrating the satisfactory ability for the adaptation to unfavourable conditions.

Suitability of two laboratory testing methods to evaluate the side effects of pesticides on Typhlodromus pyri Scheuten (Acari: Phytoseiidae).

BACKGROUND: Laboratory results of the French ANPP/CEB guideline No. 167 and IOBC/WPRS Ring Testing Group methods for testing the side effects of pesticides on the predatory mite Typhlodromus pyri Scheuten were compared with respect to their suitability to evaluate the toxicity of three pesticides. RESULTS: Results obtained with the ANPP/CEB guideline allow the demonstration of significant differences between two slightly toxic products, a dichlofluanid 500 g kg(-1) kWP (Euparen) 50WP) and a quinoxyfen 250 g L(-1) SCC (Legend), and a highly toxic cymoxanil 60/mancozeb 200/folpet 275 g kg(-1) WP [Remiltine F Pepite) (RFP)], on the basis of bioassays conducted in the laboratory. In contrast, results obtained with the IOBC/WPRS method classified all three as harmful. CONCLUSION: The evaluation of the toxicity of RFP revealed that the concentration, the quantity of the wet deposit and the food source used in the IOBC/WPRS method maximise the toxicity, in comparison with those used in the ANPP/CEB protocol. Valid criteria in controls were all respected in the ANPP/CEB tests but not in the IOBC/WPRS samples. This result revealed difficulties related to the use of the IOBC/WPRS method in laboratories.

Melatonin inhibits maneb-induced aggregation of alpha-synuclein in rat pheochromocytoma cells.

Melatonin, a secretory product of the pineal gland, is involved in the regulation of circadian and seasonal rhythms, in oncostasis, and in inducing osteoblast differentiation. Furthermore, melatonin is a scavenger of a number of reactive oxygen and reactive nitrogen species both in vitro and in vivo. In this study, the antioxidant nature of melatonin was shown to prevent cultured neural cells from apoptosis induced by endocrine-disrupting chemical, maneb. The neurotoxicity of the fungicide, maneb (1 microg/mL), on the PC12 cells was elicited through apoptotic cell death, concomitant with aggregation of alpha-synuclein, a feature of Parkinson's disease. Activation of caspase-3/7 was associated with this process. A fluorescence rationing technique using a mitochondrial dye revealed that maneb altered the mitochondrial membrane potential of the neural cells. However, melatonin (1 nm) largely prevented the neural cells from the neural toxicant by inhibition of both caspase-3/7 activation and disruption of the mitochondrial transmembrane potential. Furthermore, aggregation of alpha-synuclein by maneb was also inhibited by melatonin. Thus, melatonin prevents maneb-induced neurodegeneration at a nighttime physiological blood concentration, most likely by inhibiting the aggregation of alpha-synuclein as well as preventing mitochondrial dysfunction in PC 12 cells.

Fungicidal activity of volatile oil from eucalyptus Citriodora Hook. against Alternaria triticina.

Use of plant products for the management of phytopathogenic fungi is fast becoming an important component of Integrated Disease Management (I.D.M.) programme. The natural plant products are bio-degradable and thus eco-friendly, are catching the attention of the scientist worldwide. Such products from higher plants are relatively broad spectrum, bio-efficacious, economical and environmentally safe. Among these essential oils from higher plants because of their greater inhibitory action are being explored preferably worldwide. In this context, a study was undertaken to explore the effect of volatile oil from Eucalyptus citriodora against Alternaria triticina. The radial growth, dry weight and spore germination of pathogen were drastically reduced in response to the different concentrations of volatile oil. A complete inhibition of radial growth, dry weight and spore germination were observed at 1500, 1000 and 100 ppm, respectively. In contrast, similar complete inhibition of test pathogen was observed at very high concentration (6500, 6500 and 1000 ppm) of mancozeb--a commercially available synthetic fungicide. Based on these observations, it was therefore concluded that eucalypt volatile oil has potential to suppress the phytopathogenic fungi.

[WITHDRAWN] Overexpression of superoxide dismutase or glutathione peroxidase protects against the paraquat + maneb-induced Parkinson disease phenotype.

Oxidative stress has been implicated in the pathogenesis of Parkinson disease based on its role in the cascade of biochemical changes that lead to dopaminergic neuronal death. This study analyzed the role of oxidative stress as a mechanism of the dopaminergic neurotoxicity produced by the combined paraquat and maneb model of the Parkinson disease phenotype. Transgenic mice overexpressing either Cu,Zn superoxide dismutase or intracellular glutathione peroxidase and non-transgenic mice were exposed to saline, paraquat, or the combination of paraquat + maneb twice a week for 9 weeks. Non-transgenic mice chronically exposed to paraquat + maneb exhibited significant reductions in locomotor activity, levels of striatal dopamine and metabolites, and dopaminergic neurons in the substantia nigra pars compacta. In contrast, no corresponding effects were observed in either Cu,Zn superoxide dismutase or glutathione peroxidase transgenic mice. Similarly, the increase in levels of lipid hydroperoxides in the midbrain and striatum of paraquat + maneb-treated non-transgenic mice was not detected in either Cu,Zn superoxide dismutase or glutathione peroxidase transgenic mice. To begin to determine critical pathways of paraquat + maneb neurotoxicity, the functions of cell death-inducing and protective mechanisms were analyzed. Even a single injection of paraquat + maneb in the non-transgenic treated group modulated several key pro- and anti-apoptotic proteins, including Bax, Bad, Bcl-xL, and upstream stress-induced cascade. Collectively, these findings support the assertion that protective mechanisms against paraquat + maneb-induced neurodegeneration could involve modulation of the level of reactive oxygen species and alterations of the functions of specific signaling cascades.

Effects of mancozeb on the activities of murine peritoneal macrophages in vitro and ex vivo.

Mancozeb (MCZ) is known to have detrimental effects on the reproductive system, but the toxicity of MCZ on immune responses has not been systematically investigated. We investigated the effects of MCZ exposure on the activities of murine peritoneal macrophages through evaluation of MCZ-induced alteration of nitric oxide (NO) production and tumor necrosis factor-alpha (TNF-alpha) synthesis. Macrophages were examined ex vivo from mice orally treated with various doses of MCZ for 5 consecutive days per week for 4 weeks (subacute exposure, 250, 1000, 1500 mg/kg/day) followed by culture for 2 (TNF-alpha) or 3 days (NO) in the presence of LPS plus IFN-gamma. Macrophages from naive mice were also cultured with various concentrations of MCZ (0.05, 0.25, 0.5, 1 and 2 microg/mIL in the presence of LPS plus IFN-gamma for 2 (TNF-alpha) or 3 days (NO) in vitro. NO production was decreased with the in vitro exposure to all concentrations of MCZ. However, the amount of NO production by peritoneal macrophages from MCZ-subacutely exposed mice was increased in comparision with that of control group. In vitro, MCZ suppressed TNF-alpha secretion with significant reduction at 2 microg/mL MCZ. Conversely, TNF-alpha release was enhanced ex vivo. This study provides the substantial evidence on MCZ-induced alternation in macrophage activity. In order to clearly understand the contrasting effect of MCZ on peritoneal macrophage activity, it is necessary to further investigate the influence of major metabolite of MCZ (ETU) exposure on the NO production and TNF-alpha synthesis.

Juvenile and sublethal effects of selected pesticides on the leafminer parasitoids Hemiptarsenus varicornis and Diglyphus isaea (Hymenoptera: Eulophidae) from Australia.

The pest leafminers Liriomyza huidobrensis (Blanchard), Liriomyza sativae (Blanchard), and Liriomyza trifolii (Burgess) (Diptera: Agromyzidae) have spread into South East Asia and Oceania, and they are likely to reach Australia in the near future. Two translaminar pesticides, cyromazine and abamectin, currently provide effective chemical control of these pests, but because parasitoids can play an important role in controlling and preventing leafminer outbreaks, understanding the impact of pesticides on leafminer parasitoids is vital. Here, we tested larval and pupal mortality and sublethal effects of abamectin, cyromazine, and the widely used fungicide mancozeb on two common Australian leafminer parasitoids, Hemiptarsenus varicornis (Girault) and Diglyphus isaea (Walker). Abamectin caused significant mortality to larvae and pupae of both parasitoid species but cyromazine and mancozeb did not. Progeny production and longevity of H. varicornis were not affected by adult exposure to cyromazine and mancozeb, nor did direct pupal exposure decrease number of progeny produced by either parasitoid. Mortality of H. varicornis females emerging from leaves treated with abamectin was high for up to 72 h after eclosion but those surviving beyond 72 h did not differ from control females in the number of progeny produced. Mancozeb did not influence leaf residence time or parasitism by H. varicornis females. Cyromazine and the fungicide mancozeb were concluded to be compatible with the parasitoids tested and suitable for integrated pest management of leafminers should outbreaks of pest species occur in Australia. Abamectin should be used with caution because it caused significant mortality in both parasitoids tested here.

Dithiocarbamate pesticides affect glutamate transport in brain synaptic vesicles.

Dithiocarbamate compounds are widely used agricultural fungicides that display low acute toxicity in mammals and that may become neurotoxic after prolonged exposure. Mancozeb, among other dithiocarbamates tested, proved to be the most potent (Ki= 0.27 microM) at noncompetitively inhibiting the in vitro ATP-dependent uptake of [3H]glutamate in rat cortical vesicles. Furthermore, mancozeb partially (20%) inhibited the ATP-dependent uptake of [14C]methylamine, used as an index for the vesicular transmembrane proton gradient (DeltapH), and evoked its efflux from organelles previously incubated with the 3H-labeled marker. Meanwhile, the vesicular uptake of 36chloride- anions whose concentrations regulate the transmembrane potential gradient (DeltapsiSV) was not impaired. The dithiocarbamate effects on the vesicular transport of [3H]glutamate thus appeared to involve mainly the DeltapH gradient rather than the potential gradient. Dithiocarbamate metabolites, the potent neurotoxin carbon disulfide included, did not affect the uptake process, thus implying the relevance for inhibition of the persistence, if any, of parent compounds in the brain. The present novel and potent in vitro interferences of selected dithiocarbamate pesticides with the vesicular transport of glutamate, if representative of in vivo alterations, may play some role in the probably complex origin of dithiocarbamate neurotoxicity.

Inhibition of growth and mycotoxin production of Alternaria alternata inhabiting decayed fruits by pesticides.

The effect of the two pesticides, cuprosan and sumi oil, on growth and mycotoxin production by two strains of Alternaria alternata isolated from decayed fruits was studied. Mycelial biomass of the two strains was significantly inhibited with most applied doses, however, cuprosan was most effective. Sumi oil exhibited significant inhibitory effect on the Alternaria strain isolated from decayed lemons, whereas, it suppressed mycelial biomass of that isolated from decayed tomatoes at only higher doses (250 ppm). Mycelial respiration of the two tested strains was mainly inhibited by most used does. However, CO2 evolution was occasionally promoted. Synthesis of alternariol (AOH) and its monomethyl ether (AME) by the examined strains was mainly inhibited by pesticide application in a manner similar to that of mycelial growth.