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Toxicity profiles in mice treated with hepatotumorigenic and non-hepatotumorigenic triazole conazole fungicides: Propiconazole, triadimefon, and myclobutanil.

Conazoles comprise a class of fungicides used in agriculture and as pharmaceutical products. The fungicidal properties of conazoles are due to their inhibition of ergosterol biosynthesis. Certain conazoles are tumorigenic in rodents; both propiconazole and triadimefon are hepatotoxic and hepatotumorigenic in mice, while myclobutanil is not a mouse liver tumorigen. As a component of a large-scale study aimed at determining the mode(s) of action for tumorigenic conazoles, we report the results from comparative evaluations of liver and body weights, liver histopathology, cell proliferation, cytochrome P450 (CYP) activity, and serum cholesterol, high-density lipoprotein and triglyceride levels after exposure to propiconazole, triadimefon, and myclobutanil. Male CD-1 mice were treated in the feed for 4, 30, or 90 days with triadimefon (0, 100, 500, or 1800 ppm), propiconazole (0, 100, 500, or 2500 ppm) or myclobutanil (0, 100, 500, or 2000 ppm). Alkoxyresorufin O-dealkylation (AROD) assays indicated that all 3 chemicals induced similar patterns of dose-related increases in metabolizing enzyme activity. PROD activities exceeded those of MROD, and EROD with propiconazole inducing the highest activities of PROD. Mice had similar patterns of dose-dependent increases in hepatocyte hypertrophy after exposure to the 3 conazoles. High-dose exposures to propiconazole and myclobutanil, but not triadimefon, were associated with early (4 days) increases in cell proliferation. All the chemicals at high doses reduced serum cholesterol and high-density lipoprotein (HDL) levels at 30 days of treatment, while only triadimefon had this effect at 4 days of treatment and only myclobutanil and propiconazole at 90 days of treatment. Overall, the tumorigenic and nontumorigenic conazoles induced similar effects on mouse liver CYP enzyme activities and pathology. There was no specific pattern of tissue responses that could consistently be used to differentiate the tumorigenic conazoles, propiconazole, and triadimefon, from the nontumorigenic myclobutanil. These findings serve to anchor other transcriptional profiling studies aimed at probing differences in key events and modes of action for tumorigenic and nontumorigenic conazoles.

Animals↗

Method validation for strobilurin fungicides in cereals and fruit.

Strobilurins are a new class of fungicides that are active against a broad spectrum of fungi. In the present work a GC method for analysis of strobilurin fungicides was validated. The method was based on, extraction with ethyl acetate/cyclohexane, clean-up by gel permeation chromatography, (GPC) and determination of the content by gas chromatography (GC) with electron capture (EC-), nitrogen/phosphorous (NP-), and mass spectrometric (MS-) detection. Three strobilurins, azoxystrobin, kresoxim-methyl and trifloxystrobin were validated on three matrices, wheat, apple and grapes. The validation was based on recovery tests at three or four spiking levels, determined as double determinations and repeated three times (n = 6). The mean recoveries for the three detectors were in the range of 70-114%, and the LODs were between 0.004 mg/kg and 0.014 mg/kg, for all three strobilurins. The values for repeatability and reproducibility were within the limits for repeatability and reproducibility given by the Horwitz equation. Validation was not accepted for azoxystrobin in grapes on all three detectors and for azoxystrobin in apple for the MS-detector. A comparison of matrix-matched standards versus standards in solvent showed varying differences between the two calibration curves.

Acrylates↗

Screening of grapes and wine for azoxystrobin, kresoxim-methyl and trifloxystrobin fungicides by HPLC with diode array detection.

The Quinone outside Inhibitors (QoI) are one of the most important and recent fungicide groups used in viticulture and also allowed by Integrated Pest Management. Azoxystrobin, kresoxim-methyl and trifloxystrobin are the main active ingredients for treating downy and powdery mildews that can be present in grapes and wines. In this paper, a method is reported for the analysis of these three QoI-fungicides in grapes and wine. After liquid-liquid extraction and a clean-up on commercial silica cartridges, analysis was by isocratic HPLC with diode array detection (DAD) with a run time of 13 min. Confirmation was by solid-phase micro-extraction (SPME), followed by GC/MS determination. The main validation parameters for the three compounds in grapes and wine were a limit of detection up to 0.073 mg kg(-1), a precision not exceeding 10.0% and an average recovery of 93% +/- 38.

Acetates↗

The effect of home processing on postharvest fungicide residues in citrus fruit: residues of imazalil, 2-phenylphenol and thiabendazole in 'home-made' marmalade, prepared from late Valencia oranges.

The effects of domestic marmalade-making procedures on residues of imazalil, 2-phenylphenol and thiabendazole in 'sweet' oranges were investigated by comparing residue levels in raw fruit and in marmalades, prepared by heating the oranges with water and sugar for about 4 h in a preserving pan on a gas ring or for about 1 h in a microwave oven. Determination of residues in raw oranges and in marmalades was carried out by extraction with dichloromethane, followed by clean-up and reversed phase HPLC with UV detection for imazalil and fluorescence detection for 2-phenylphenol and thiabendazole. Residue analysis showed that the extent of carry-through of imazalil, 2-phenylphenol and thiabendazole residues into the marmalades depended on the method of marmalade-making and the nature of the fungicide. Persistence of fungicides was higher in the marmalade prepared in the microwave oven than in that prepared in the preserving pan. An increase (about 50%) in levels of imazalil in the fruit portions of marmalades compared with raw fruit residue levels indicated that imazalil was more readily extracted from oranges after processing. Comparison of 2-phenylphenol levels in raw fruit and fruit portions of marmalades showed that the longer exposure to heat, needed for marmalade-making in a preserving pan, reduced residue levels more severely (48%) than cooking in the microwave oven (13%). Thiabendazole levels in the fruit portion of marmalade prepared in the microwave oven stayed the same as in the raw fruit, but cooking in the preserving pan decreased residue levels by about 22%.

Biphenyl Compounds↗

[Toxicity of commercial fungicides in relation to the larvae of Drosophila melanogaster Meigen (Diptera, Drosophilidae) and effect on the sex ratio].

Bouillie bordelaise, Benlate, Euparène and Dithane M45 had no effects on Drosophila eggs. However, a post-hatching mortality was observed and, in all cases, a "dose effect" was established. There was a quick effect with Bouillie bordelaise, a slow and continued one with Benlate and Euparène, and the effect was delayed until the pupal stage with Dithane. Bouillie bordelaise, Benlate and Euparène slowed down the larval development and the emergence period was longer, according to the doses. Bouillie bordelaise was always the most toxic fungicide and Dithane the least one. The sex-ratio was not disturbed with Bouillie bordelaise. With Benlate and Euparène, the females were more sensitive than the males, while Dithane was more toxic towards males. Considering a same fungicide, a difference was exhibited according to the chosen criterion: Benlate caused an effect on larval mortality which was more important than its effect on the developing-time. Moreover, both carbamates, Benlate and Dithane, acted differently whatever their toxicity level.

Animals↗

[Ovarian activity of Drosophila melanogaster Meigen (Diptera), during a chronic intoxication with four fungicides: anatomical and cytological study].

Two types of reactions were observed on the alteration of Drosophila vitellogenesis by the four fungicides used in this study. Dithane M45 resulted in stimulation associated with egg retention. However, the other three fungicides (Benlate, Bouillie bordelaise and Euparène) resulted in inhibition to a varying degree. Although the inhibition was comparatively limited due to Benlate it induced an egg retention. The inhibition was very high due to Bouillie bordelaise and Euparène. With Bouillie bordelaise an egg retention occured together with the reduction of vitellogenesis and caused an increase in the rate of the follicle resorption. The latter depended on the duration of treatment. With Euparène, no egg retention was observed and the toxicity was only noticed on vitellogenesis.

Aniline Compounds↗

Evaluation of entomopathogenic fungus Metarhizium anisopliae against soil-dwelling stages of cabbage maggot (Diptera: Anthomyiidae) in glasshouse and field experiments and effect of fungicides on fungal activity.

The effect of two isolates of the entomopathogenic fungus Metarhizium anisopliae (Metchnikoff) Sorokin (389.93 and 392.93) on root-feeding stages of cabbage root fly, Delia radicum (L.), was studied under glasshouse and field conditions. In glasshouse studies, the effect of drenching a suspension of conidia (concentration 1 x 10(8) m(-1), 40 ml per plant, applied on four occasions) onto the base of cabbage plants infested with D. radicum eggs was compared with mixing conidial suspension into compost modules (concentration 1 x 10(8) ml(-1), 25 ml per plant) used to raise seedlings. Drench application reduced the mean number of larvae and pupae recovered per plant by up to 90%, but the compost module treatment had no statistically significant effect. Both application methods reduced the emergence of adult flies from pupae by up to 92%. Most conidia applied as a drench application remained in the top 10-cm layer of compost. Applications of the fungicides iprodione and tebuconazole, which are used routinely on brassica crops, were compatible with using M. anisopliae 389.93 against D. radicum under glasshouse conditions, even though these fungicides were inhibitory to fungal growth on SDA medium. In a field experiment, drench applications of M. anisopliae 389.93 to the base of cauliflower plants at concentrations of 1 x 10(6) to 1 x 10(8) conidia ml(-1) did not control D. radicum populations, although up to 30% of larval cadavers recovered supported sporulating mycelium. Drench applications often exhibited considerable lateral movement on the soil surface before penetrating the ground, which may have reduced the amount of inoculum in contact with D. radicum larvae.

Animals↗

Sub-lethal effects of a copper sulfate fungicide on development and reproduction in three coccinellid species.

Copper-based fungicides reliably control various foliar diseases in citrus production, although they are suspected to exacerbate mite problems through various mechanisms. Studies have shown negative effects of various copper formulations on entomopathogenic fungi, nematodes, and parasitoids, but few have sought to measure its impact on the biology of predatory insects. We exposed the larvae of three species of ladybeetle (Coleoptera: Coccinellidae) to field rates of copper sulfate in combination with petroleum oil, a formulation commonly applied in Florida citrus. First instar larvae of Curinus coeruleus Mulsant, Harmonia axyridis Pallas, and Olla v-nigrum Mulsant received a 24 h exposure to residues on Petri dishes, and another 24 h exposure in the third instar. Treated larvae of all three species survived to adulthood at the same rate as control larvae, but larvae of O. v-nigrum experienced a significant increase in developmental time. Female adults of C. coeruleus and H. axyridis receiving copper sulfate exposures as larvae did not differ from control adults in pre-reproductive period, fecundity or fertility over ten days of reproduction. Treated O. v-nigrum females had significantly longer pre-reproductive periods than control females and laid significantly fewer eggs, although egg fertility was equivalent. We conclude that copper-sulfate fungicides are unlikely to disrupt biological control processes in citrus groves that are mediated by these coccinellid beetles.

Animals↗

The genetic and non-genetic toxicity of the fungicide Vinclozolin.

The mutagenic/cocarcinogenic potential of the fungicide Vinclozolin was assessed by a comprehensive examination of toxicity mechanisms at both the genetic and the metabolic level. Vinclozolin did not induce any significant increase in chromosomal aberrations in human pheripheral blood lymphocytes cultured in vitro, both in the presence and in the absence of metabolic activation. However, significant dose-related increases in micronucleated erythrocytes (up to 4-fold over the control) were found in the bone marrow cells of mice 24 h after treatment with the fungicide over a range of concentrations from 312.5 to 1250 mg/kg. The morphology and the size of micronuclei induced was suggestive of a predominantly clastogenic mode of action. Several cytochrome P450 (CYP)-dependent reactions have been monitored in liver, kidney and lung microsomes of male and female Swiss Albino CD1 mice in order to ascertain certain toxic non-genetic properties (related to carcinogenesis) of Vinclozolin. It was found to be a selective inducer towards CYP 3A (liver, kidney) and 2E1 (liver), as exemplified by the significant increases of the demethylation of aminopyrine (APND, up to 2.3-fold, female liver), and hydroxylation of p-nitrophenol (pNPH, up to 5.6-fold, male liver). In general, however, Vinclozolin has a complex pattern of induction and suppression of CYP-dependent enzymes, as shown from the reduced expression of various monooxygenases depending upon dose, sex or organ considered. For example, pNPH activity was suppressed in kidney (up to 48% loss, averaged between male and female), whereas ethoxycoumarin O-deethylase was reduced in lung up to 53% in male (at the highest dose). These data were sustained by means of Western immunoblotting using rabbit polyclonal antibodies anti-CYP 3A and 2E1. Northern blotting analysis using CYP 3A1/2 and 2E1 cDNA biotinylated probes showed that the expression of such isozymes is regulated at the mRNA level. Taken together, the findings indicate the clastogenic activity and the possible cotoxic, cocarcinogenic and promoting potential of Vinclozolin.

Animals↗

Prochloraz: an imidazole fungicide with multiple mechanisms of action.

Prochloraz is an imidazole fungicide that is widely used in Europe, Australia, Asia and South America within gardening and agriculture. Screening studies have shown that prochloraz elicits multiple mechanisms of action in vitro, as it antagonizes the androgen and the oestrogen receptor, agonizes the Ah receptor and inhibits aromatase activity. In vivo prochloraz acts as an antiandrogen in the Hershberger assay by reducing weights of reproductive organs, affecting androgen-regulated gene expressions in the prostate and increasing luteinizing hormone levels. In order to investigate the developmental effects of prochloraz, pregnant Wistar dams were dosed perinatally with 30 mg/kg prochloraz. Results showed that prochloraz significantly reduced plasma and testicular testosterone levels in gestational day 21 male foetuses, whereas testicular progesterone was increased. Gestational length was increased by prochloraz. In male pups a significant increase in nipple retention was found, and the weight of the bulbourethral glands was decreased. Behavioural studies showed that the activity level and sweet preference of adult males were significantly increased, indicating that exposure during gestation and lactation causes permanent effects in adulthood. Overall, these results indicate that prochloraz feminizes the male offspring after perinatal exposure, and that these effects are due, at least in part, to diminished fetal steroidogenesis. Thus, a novel endocrine disruptor has been identified that is mechanistically interesting as it elicits dual mechanisms of action and acts as an antiandrogen both by blocking the androgen receptor and by inhibiting fetal steroidogenesis. That a fungicide with such effects is so widely used is a cause for concern, and its use should be reduced, thereby minimizing the risk of human exposure.

Androgen Antagonists↗

Interactions between yeasts, fungicides and apple fruit russeting.

The effect of inoculations with yeasts occurring on apple surfaces and fungicide treatments on the russeting of Elstar apples was studied. Captan, dithianon and a water treatment were implemented to study the interaction between the fungicides, the inoculated yeast species and Aureobasidium pullulans, and the development of russet. All yeast inoculations aggravated russet, but Rhodotorula glutinis, Sporidiobolus pararoseus and A. pullulans did so to a greater extent than the other species. Both captan and dithianon significantly reduced russeting. Denaturing gradient gel electrophoresis analysis showed that inoculations with R. glutinis and S. pararoseus seemed to suppress other yeast species present on the apple surface.

Anthraquinones↗

Contact dermatitis due to a new fungicide used in the tulip bulb industry.

We describe an outbreak of contact dermatitis in a tulip bulb processing company. Shortly after the introduction of a new pesticide, the fungicide fluazinam, employees started to complain of dermatitis of the arms and the face. 8 employees were investigated and showed positive patch tests to fluazinam. The dermatitis disappeared quickly when they stopped work, but returned as soon they restarted. Subsequent investigations showed that the fungicide had not been used according to the manufacturer's recommendations. Fluazinam was shown to be a strong sensitizer under these circumstances.

Adult↗

Allergic contact dermatitis from the newly introduced fungicide fluazinam.

In spring 1992, several farmers in the western part of The Netherlands developed dermatitis on their hands, forearms and face. In some, the legs, trunk and genitals were also affected. Complaints ranged from a mildly itchy, papular rash to a painful, weeping and blistering dermatitis. Medical aid was needed by 5/9 of them. Some of the farmers grew seed potatoes, the others cultivated lilies. All of them had in common that their complaints emerged after repeated application of a new fungicide over several weeks. The fungicide was Shirlan, with fluazinam as its active ingredient. 9 farmers were patch tested with a concentration range of the whole formulation (aq.) and of the active ingredient (pet.). In 7 of 9 farmers, positive patch tests were scored with both the whole formulation (down to 0.01% aq.) and fluazinam itself (down to 0.1% pet.). Patch tests in consecutive control patients (n = 10) were all negative. As it was impossible to substitute fluazinam as the active ingredient, farmers are now supplied with detailed information as to how to avoid skin contact as much as feasible.

Adult↗

Cytotoxicity of the dicarboximide fungicides, vinclozolin and iprodione, in rat hepatoma-derived Fa32 cells.

Dicarboximide fungicides are widely used to control various fungal species. Their primary action is not known, due to a lack of knowledge concerning the mechanism of action of the dicarboximide group. The cytotoxicities of vinclozolin and iprodione in rat hepatoma-derived Fa32 cells were investigated. Cytotoxicity was measured by neutral red uptake inhibition after treatment for 24 hours. Iprodione was more toxic than vinclozolin. Vinclozolin was less toxic in glutathione-depleted cells than in control cells. This was also true for iprodione at lower concentrations, but iprodione became more toxic at higher concentrations. Both the fungicides increased the endogenous glutathione content by 20% after 1 hour. After 24 hours, the glutathione content was doubled by vinclozolin, but was not affected by iprodione. No effect on glutathione S-transferase activity or reactive oxygen species formation could be observed. Cytochrome P450-dependent ethoxyresorufin-O-deethylase and pentoxyresorufin-O-depentylase activities were moderately activated by iprodione and strongly activated by vinclozolin. A glutathione-related cytochrome P450-dependent metabolic attack of vinclozolin and iprodione could be responsible for their cytotoxicity in Fa32 cells. Further research is needed to fully elucidate these (or other) mechanisms.

Aminoimidazole Carboxamide↗

The fungicide procymidone alters sexual differentiation in the male rat by acting as an androgen-receptor antagonist in vivo and in vitro.

Procymidone is a dicarboximide fungicide structurally related to the well-characterized fungicide vinclozolin. Vinclozolin metabolites bind to mammalian androgen receptors (AR) and act as AR antagonists, inhibiting androgen-dependent gene expression in vivo and in vitro by inhibiting AR-binding to DNA. The current study was designed to determine if procymidone acted as an AR antagonist in vitro and to describe the dosage levels of procymidone that alter sexual differentiation in vivo. In vitro, procymidone inhibited androgen from binding the human AR (hAR) in COS (monkey kidney) cells transfected with hAR at 3.16 microM. In vitro, procymidone acted as an androgen antagonist, inhibiting dihydrotestosterone (DHT)-induced transcriptional activation at 0.2 microM in CV-1 cells (cotransfected with the hAR and a MMTV-luciferase reporter gene). In vivo, maternal procymidone exposure at 0, 25, 50, 100, or 200 mg kg-1 day-1 during gestation and early lactation (gestational day 14 to postnatal day 3) altered reproductive development of male offspring at all dosage levels tested. Male offspring exhibited shortened anogenital distance (at 25 mg kg-1 day-1 and above), permanent nipples, reduced weight of several androgen-dependent tissues (levator ani and bulbocavernosus muscles, prostate, seminal vesicles, Cowper's gland and glans penis), and malformations (hypospadias, cleft phallus, exposed os penis, vaginal pouch, hydronephrosis, occasional hydroureter, epididymal granulomas, and ectopic, undescended testes). In addition, perinatal procymidone treatment had a marked effect on the histology of the lateral and ventral prostatic and seminal vesicular tissues of the offspring (at 50 mg kg-1 day-1 and above). These effects consisted of fibrosis, cellular infiltration, and epithelial hyperplasia. This constellation of effects is similar to that produced by perinatal exposure to vinclozolin. However, procymidone appears to be slightly less potent in inducing malformations than vinclozolin by a factor of about two. In summary, the antiandrogenic activity of procymidone was demonstrated in vivo and in vitro in cell lines transfected with hAR. Since the role of androgens in mammalian sexual differentiation is highly conserved, it is likely that humans would be adversely affected by procymidone in a predictable manner if the human fetus was exposed to sufficient levels during critical stages of intrauterine and neonatal life.

Androgen Receptor Antagonists↗

Synthesis of 1-triazolyl-4-trimethylsilyl-2-butanol and 1-triazolyl-5-trimethylsilyl-2-pentanol derivatives and an investigation of their fungicidal activities.

A new series of azole derivatives of 1-triazolyl-4-trimethylsilyl-2-butanol and 1-triazolyl-5-trimethylsilyl-2-pentanol were synthesized and evaluated for fungicidal activities against rice blast, sheath blight, and powdery mildew on barley. The derivatives of 2,4-difluorobenzene exhibited high antifungal activities when applied by spray, but exhibited no fungicidal activity by submerged application.

Ascomycota↗