Effect of dithiocarbamate pesticide zineb and its commercial formulation, azzurro. II. micronucleus induction in immunophenotyped human lymphocytes

The frequency of micronuclei was measured in human peripheral B-lymphocytes and some T-lymphocyte subpopulations exposed in vitro to 1.0-100.0 microg/ml of the dithiocarbamate pesticide zineb and its commercial formulation azzurro. The peripheral mononuclear lymphocytes were stimulated in vitro with phytohemagglutinin after pesticide treatment and B-lymphocytes and the various T-lymphocyte subsets were classified by the MAC (morphology, antibody, chromosomes) method, which allows the immunological identification of different cell lineages. An increased frequency of micronuclei in CD20(+) (P < 0.01), CD3(+) (P < 0.01), and CD8(+) lymphocytes (P < 0.01) was observed only when 25.0 microg/ml of zineb and azzurro were employed. The frequency of micronuclei in treated CD8(+) cells did not differ from treated CD20(+) lymphocytes (P > 0.05). Lower concentrations of pesticides did not increase the frequency of micronuclei from that observed in control cultures. Furthermore, for both zineb and azzurro cytotoxicity was observed at doses higher than 50.0 microg/ml. Significant increases in the proportion of CD20(+) (P < 0.01) and CD8(+) cells (P < 0.01) among mitotic and interphasic lymphocytes from both zineb- and azzurro-treated cultures were observed only when a concentration of 25.0 microg/ml was employed. In contrast, significant decreases in the proportion of CD3(+) (P < 0.01) and CD4(+) cells (P < 0.01) were found for both mitotic and interphasic lymphocytes from zineb- and azzurro-treated cultures. The MAC methodology revealed that among the different lymphocyte subpopulations analyzed (CD20, CD3, CD4, and CD8), the induction of micronuclei by zineb and its commercial formulation azzurro was restricted to CD20(+) B-cells and T-suppressor/cytotoxic CD8(+) lymphocytes.

Effect of the dithiocarbamate pesticide zineb and its commercial formulation azzurro. I. Genotoxic evaluation on cultured human lymphocytes exposed in vitro

The in vitro cytogenetic effects exerted by the dithiocarbamate fungicide zineb and one of its commercial formulations currently used in Argentina, azzurro, were studied in whole blood human lymphocyte cultures. The genotoxicity of the fungicides was measured by analysis of the frequency of chromosomal aberrations and sister chromatid exchanges (SCEs) and cell cycle progression assays. Both zineb and azzurro activities were tested within the range 0.1-100.0 microg/ml immediately after in vitro lymphocyte stimulation. Only concentrations of 50.0 and 100.0 microg/ml zineb and azzurro induced a significant increase in SCE frequency over control values. Furthermore, this genotoxicity appears to be correlated with its cytotoxicity, measured as cell cycle kinetics, since both a significant delay in cell cycle progression and a significant reduction in proliferative rate index were only observed in those cultures treated with these fungicide concentrations. For both chemicals, a progressive dose-related inhibition of the mitotic activity of cultures was observed when increasing the fungicide concentration. Moreover, only the mitotic activity statistically differed from control values when doses of zineb or azzurro <10 microg/ml were employed. For both fungicides the mitotic index reached the minimal value at doses of 100 microg/ml. Both products induced a significant dose-dependent increase in the number of abnormal cells, chromatid-type and chromosome-type aberrations as well as in the total number of aberrations in the 0.1-100.0 microg/ml dose range. Based on these results, the evaluation of zineb as a controversial genotoxic/non-genotoxic compound for human health should be reconsidered. Instead, we demonstrate that the fungicide induces large DNA alterations and should be considered as a clastogenic mutagen.

Interaction of Dithane M-45 (mancozeb) and lead acetate during a teratogenicity test in rats

The teratogenic effects of lead acetate (Trial 1) and the possible teratogenic effect of this compound administered in combination with a fungicide containing 80% mancozeb (Trial 2) were studied in rats. The test substances were administered by gavage on Days 6-15 of gestation. In Trial 1, five groups were treated with lead acetate administered at doses of 0.1, 0.5, 1.0, 10.0 and 1000.0 mg/kg body weight (bwkg), respectively. In Trial 2, lead acetate was applied at doses of 0.1, 10.0 and 1000.0 mg/bwkg, respectively. In the latter case the dose of the pesticide was 750 mg/bwkg in all treated groups. Lead acetate was not teratogenic after a single administration. Combined administration of lead acetate and mancozeb gave rise to the following toxic effects: average maternal weight decreased during pregnancy, the ratio of live fetuses decreased after the two lowest doses, and fetal mortality increased in the lowest and in the highest dose groups. The ratio of fetal resorption was higher in all the treated groups than in the control group. A significant decrease occurred in average fetal and placental weight in each treated group as compared to the control. Maternal toxicity was expressed in paralysis of the hindlimbs in the two lowest dose groups. Maternal mortality was between 16.7 and 23.3% at the three dose levels. Phocomelia and hernia cerebri occurred as characteristic fetal developmental anomalies in all the treated groups. It is concluded that the joint administration of lead acetate and a mancozeb-containing fungicide can cause maternal toxicity, embryotoxicity and characteristic teratogenic effects.

Transplacental carcinogenic potential of the carbamate fungicide mancozeb

We evaluated the effects of mancozeb (Dithane M4-5), a protective carbamate fungicide, on transplacental carcinogenesis in Swiss albino mice. Mancozeb, a polymeric complex of ethylene bis (dithiocarbamate) manganese with zinc salt, is reported to possess carcinogenic and cocarcinogenic activity in various tumor models. In the present study, pregnant Swiss albino mice were administered mancozeb intraperitoneally on the 14th day of gestation. The first filial generation (F1 progeny) was promoted with a well-known tumor promoter 12-o-tetradecanoyl phorbol-13-acetate (TPA). The results revealed a significantly high tumor incidence (72%) in the F1 progeny of the animals initiated with mancozeb or a well known carcinogen 7,12-dimethyl benzanthracene (DMBA) and promoted with TPA in comparison to animals that were either from mothers given only the vehicle (DMSO) and promoted with TPA in F1 progeny or not promoted with TPA in F1 progeny. No significantly higher tumor incidence was observed in any other experimental groups. These results suggest that mancozeb or its metabolites are capable of crossing the placental barrier and can exert DNA damage and tumor initiating consequences in the fetal cells that, after promotion with TPA, get converted into neoplastic cells.

Toxicity of the dithiocarbamate fungicide mancozeb to the nontarget soil nematode, Caenorhabditis elegans

We have previously shown that the dithiocarbamate fungicide, Mancozeb, strongly induces lacZ reporter expression from an endogenous heat-shock promoter (hsp16) in the PC72 transgenic strain of the nematode Caenorhabditis elegans. Such evidence of organismal stress, in a nontarget species at subapplication concentrations, was much less apparent for the related fungicide, Maneb, which only weakly induced reporter expression. We now show that reporter induction by Mancozeb is marginal (<60%) after a few hours' exposure, but increases substantially (to almost 10-fold) after overnight exposure. In conjunction with our previous results using intermediate exposure periods, this suggests that the factor limiting reporter responses is likely to be a slow rate of uptake and/or metabolism of the fungicide. We confirm that a potentially toxic metabolite of dithiocarbamate fungicides, namely ethylenethiourea (ETU), has minimal toxicity toward C. elegans, even after prolonged exposure at high concentrations. We demonstrate that exposure to Mancozeb (but not ETU) significantly inhibits larval growth in C. elegans, although this parameter is not markedly more sensitive than reporter induction as a toxicological endpoint. Finally, we have used two-dimensional electrophoresis to show that high concentrations of both Maneb and Mancozeb drastically simplify the protein spot profile compared with controls. However, only in the latter case is there evidence of novel proteins being induced. Both fungicides appear toxic to C. elegans, but only Mancozeb induces a strong heat-shock response.

Teratogenic effects of propineb on rat skin

The dithiocarbamates are known to cause dermatitis, conjunctivitis, rhinitis, pharyngitis and bronchitis in humans. The experimental group received Propineb (obtained from Bayer) concentrations of 400 ppm in distilled water five days a week (treatment time three weeks) administered orally by gasric pit. Acute oral LD50 for male rats has been found to be 8,500 mg/kg (Worthing, 1983). The control group (n = 10) received only distilled water. At ultrasonographical examination, there were no resorbed fetuses or stillborns during or after propineb administration. It can be clearly seen that the body weights of the experimental group of litters are lower than those of the control group (p < 0.001). However, the mean length of the experimental litters was identical to the control group of litters (p > 0.05). Under microscopical examination, increased keratinization and hyperplasia were observed in the epidermal cells.

Effects of Acrobat MZ and Tattoo C on Japanese medaka (Oryzias latipes) development and adult male behavior

Exposure of Japanese medaka (Oryzias latipes) embryos and adult males to sublethal concentrations of two commonly used fungicides, Acrobat MZ and Tattoo C, had varying effects on development and adult male behavior. During embryolarval assays, medaka exposed to Acrobat exhibited decreased heart rates throughout embryonic development and were smaller at hatching than controls. Differences in hatching size were not apparent with Tattoo although some decrease in heart rate was observed at higher concentrations. Tail lesions and abnormal spinal development was a problem common to embryos exposed to Acrobat. Neither time to hatch nor early growth was affected by exposure to either fungicide. Adult males that had been exposed to high concentrations of Acrobat or Tattoo over a 28-day period were less likely to approach females during behavioral trials. The absence of other behavioral effects, particularly those related to reproductive performance, may have been due to females being sexually unreceptive during behavioral trials. No other behavioral modifications were apparent for adult males exposed to either fungicide. Information about developmental and behavioral responses to sublethal concentrations of pesticides is important for establishing environmental guidelines concerning their use.

Evaluation of the fungicide manganese-zinc ethylene bis(dithiocarbamate) (mancozeb) for sublethal and acute toxicity to Eisenia fetida (Oligochaeta)

This article describes the outcome of laboratory experiments to determine the acute and sublethal effects of the fungicide mancozeb on the earthworm Eisenia fetida. Apart from a standardized acute test, young worms, 25 days old, were exposed to mancozeb mixed into a urine-free cattle manure substrate. Five groups of 10 worms each were used per concentration level (0, 8, 44 mg/kg substrate). The following life-history parameters were measured: growth in consecutive weeks over a 6-week period, survival rate, maturation time, cocoon production, hatching success of cocoons, number of hatchlings per cocoon, and incubation time of cocoons over another 4 weeks. The results indicated that mancozeb had no significant detrimental effect on either growth or reproduction of E. fetida at the recommended dose (8 mg/kg) or at an estimated environmental concentration (44 mg/kg). The findings do not support the hypothesis that avoidance response to mancozeb could serve as an indication of toxicity.

The toxicity of dithiocarbamate fungicides to soil nematodes, assessed using a stress-inducible transgenic strain of Caenorhabditis elegans

The dithiocarbamate fungicides maneb and mancozeb induce a short-term stress response in a transgenic Caenorhabditis elegans strain (PC72) carrying a reporter lacZ gene under the control of a homologous heat shock (hsp16) promoter. This response can be readily monitored as induced beta-galactosidase activity, either by in situ staining or by a quantitative fluorometric enzyme assay. Particularly strong responses are induced by mancozeb (three- to fivefold above controls at 500 microg mL(-1)), causing acute toxicity at concentrations comparable to those recommended for field application (2 mg mL(-1)). Although much of this fungicide is adsorbed by soil, sufficient (ca. 6%) enters the soil water compartment to cause mild stress in the transgenic worm assay. Among possible metabolites from mancozeb breakdown, neither Mn2+ nor ethylenethiourea (ETU) is particularly toxic even at 10% of the optimum mancozeb dosage. Stress responses to a range of other pesticides are also reported, and in several cases it is clear that a nontarget soil species (here, transgenic C. elegans) may be sensitive to low-level contamination.

In vitro studies of cellular and molecular developmental toxicity of adjuvants, herbicides, and fungicides commonly used in Red River Valley, Minnesota

Recent epidemiologic studies showed increased frequency of birth defects in pesticide applicators and general population of the Red River Valley, Minnesota. These studies further indicated that this crop growing area used more chlorophenoxy herbicides and fungicides than elsewhere in Minnesota. Based on frequency of use and known biology, certain herbicides, pesticide additives, fungicides, and mycotoxins are suspect agents. To define whether these agents affect developmental endpoints in vitro, 16 selected agrochemicals were examined using the MCF-7 breast cancer cell line. In the flow cytometric assay, cell proliferation in this estrogen-responsive cell line indicates xenobiotic-mediated estrogenic effects. Cell viability, morphology, ploidy, and apoptosis were incorporated in this assay. Data showed that the adjuvants X-77 and Activate Plus induced significant cell proliferation at 0.1 and 1 microg/ml. The commercial-grade herbicides 2,4-D LV4 and 2,4-D amine induced cell proliferation at 1 and 10 microg/ml. The reagent-grade 2,4-D products failed to induce proliferation over the same concentration range, suggesting that other ingredients in the commercial products, presumably adjuvants, could be a factor in these results. The fungicides triphenyltin and mancozeb induced apoptosis at concentrations of 4.1 microg/ml (10(-5) M) and 50 microg/ml, respectively. Triphenyltin also induced aneuploidy (C2/M arrest) at 0.41 microg/ml (10(-6) M). Data provide a mechanistic step to understanding human reproductive and developmental effects in populations exposed to these agrochemicals, and initiative to focusing limited resources for future in vivo animal developmental toxicity studies.

Effect of mancozeb on ovarian compensatory hypertrophy and biochemical constituents in hemicastrated albino rat

Mancozeb a carbamate fungicide was administered orally at doses of 500, 600, 700, and 800 mg/kg/day to normal hemicastrated virgin rats for 15 consecutive days to examine the effect on ovarian hypertrophy. Sham-operated and hemicastrated control rats were administered a similar quantity of olive oil. The vaginal smear and body weight of the rats were recorded daily and rats were sacrificed on the Day 16. The ovary, uterus, kidney, adrenal, spleen, liver, lungs, heart, thymus, and thyroid were removed and weighed. The left ovary from each animal was serially sectioned and stained for histologic studies. The hemicastrated control rats revealed a significant increase in relative ovarian weight with 66.3% hypertrophy. Treatment with 700 and 800 mg/kg/day mancozeb revealed a decrease in ovarian hypertrophy with 28.2 and 22.8% hypertrophy, respectively. There was no significant change in the number of estrous cycles and duration of each phase of the estrous cycle with 500 mg/kg/day mancozeb. However, there was a decrease in the number of estrous cycles, duration of proestrus, estrus, and metestrus with concomitant significant increase in the duration of the diestrus phase with 600, 700, and 800 mg/kg/day mancozeb treatment. There was a significant decrease in the number of healthy follicles with concomitant increase in the number of atretic follicles at higher doses of mancozeb. There were no significant changes in the body and organ weight with 500, 600, 700, and 800 mg/kg/day of mancozeb. The levels of protein, glycogen, total lipid, phospholipid, and neutral lipid were elevated in the liver, uterus, and ovary after hemicastration. Protein, glycogen, total lipid, phospholipid, and neutral lipid were not significantly changed in the liver, uterus, and ovary after 500 mg/kg/day mancozeb. However, treatment with 600, 700, and 800 mg/kg/day mancozeb showed a significant decrease in the levels of protein, glycogen, total lipid, phospholipid, and neutral lipid in the liver, uterus, and ovary, with the exception of liver total lipid and uterine glycogen. In addition to the decrease in the compensatory ovarian hypertrophy, mancozeb treatment reduced the number of healthy follicles with a concomitant increase in the number of atretic follicles. This finding plus disruption of the estrous cycle may be due to a direct effect on the ovary or the hypothalamo-hypophysial-ovarian axis.

Effects of lead(II) nitrate and a dithiocarbamate fungicide on the rat lung

The pulmonary toxicity of two potential environmental pollutants was studied in rats 1, 7 and 30 days after a single intratracheal instillation of lead nitrate and Dithane M-45 (mancoceb), either individually or in various combinations. The cell count, protein, phospholipids and lactate dehydrogenase level were determined in the bronchoalveolar lavage fluid, as were the protein, phospholipids and acid phosphatase contents in the lung tissue. Lead nitrate and Dithane M-45 induced acute inflammation reactions with different features. The effects of mixtures of lead nitrate and Dithane M-45 were found to be different from those of the individual components.

Assessment of toxicological effects of mancozeb in male rats after chronic exposure

Mancozeb, an ethylenebisdithiocarbamate fungicide was administered orally to male rats at doses 0, 500, 1000 and 1500 mg/kg/day for 90, 180 and 360 days produced dose dependent signs of poisoning, loss in body weight gain and mortality. However the signs of toxicity and mortality were more pronounced initially at 0-90 days as compared to 90-360 days of treatment period. A significant increase in the relative weight of liver and slight decrease in the kidney weight were observed in animals exposed to mancozeb (1000 and 1500 mg/kg/day) for 180 and 360 days associated with pathomorphological changes in liver, brain and kidney. Mancozeb has produced significant enzymatic changes in the activities of aspartate aminotransferase (ASAT), alanine aminotransferase (ALAT), alkaline phosphatase (ALP), lactate dehydrogenase (LDH) and acetylcholinesterase (AChE) throughout the period of study in a dose dependent manner. The alterations in the activity of enzymes associated with pathomorphological changes suggest that the chronic exposure of mancozeb produced significant toxicological effects in rats.

The accumulation and histological effects of organometallic fungicides propineb and maneb in the livers of pregnant rats and their offspring

Dithiocarbamate propineb and maneb are organometal fungicides, which are widely used for the control of diseases in plants. Female Wistar rats were exposed orally to 200 and 400 ppm propineb (Zn-containing dithiocarbamate) and 250 ppm maneb (Mn-containing dithiocarbamate), from the 6th day of gestation up to birth. We found that the body weights of both newborn litters and their fungicide-treated mothers were lower than those of controls. Histological examination of the livers of fungicide-treated pregnant females and the offspring showed a variety of histopathological effects. Moreover, the analysis of Zn and Mn concentrations in the livers of pregnant females exposed to organometallic fungicides during pregnancy demonstrated that the metal concentrations in the liver were higher than those of controls. Similarly, the hepatic metal concentrations were significantly increased in the litters, indicating the transplacental passage of the organometallic fungicides.

The accumulation and histological effects of organometallic fungicides Propineb and Maneb in the kidneys of fetus and female rats during pregnancy

Dithiocarbamate propineb and maneb are organometal fungicides, which are widely used for the control of diseases in plants. Female Wistar rats were exposed orally to 200 and 400 ppm propineb and 250 ppm maneb, from the sixth day of gestation up to birth. We found that the body weights of both one-day old litters and their fungicide-treated mothers were lower than those of controls. Histological examination of the kidneys of fetus and fungicide-treated pregnant females showed a variety of histopathological effects. Moreover, the analysis of zinc (Zn) and manganese (Mn) concentrations (using inductively coupled plasma-atomic emission spectrometry) in the kidneys of pregnant females exposed to organometallic fungicides during pregnancy demonstrated that the metal concentrations in the kidney were higher than those of controls. However, the renal metal concentrations were significantly increased in the litters subjected to the fungicides during gestation, indicating that high levels of the trace metals in the organ of fetus may well be due to the fungicides easily passing the placental barrier.

Dermatotoxicity of agricultural chemicals in the dorsal skin of hairless dogs

Dermatotoxicity of agricultural chemicals (ACs) with or without ultraviolet (UV) irradiation was histologically examined using hairless descendants of Mexican hairless dogs. ACs examined were pentachlorophenol sodium salt, 2,4-dichlorophenoxyacetic acid (DCPAA), Maneb, and Zineb. One day after cessation of the 7-day AC treatment, the skin treated with DCPPA and Maneb indicated only slight histological changes. The UV + AC-treated sites had as much pigmentation as the control sites. Fourteen days after cessation of treatment, dogs treated with Maneb showed marked reactions such as epidermal degeneration, vasodilation, and intradermal infiltration of inflammatory cells. These histological changes were more severe in the UV + AC-treated sites. Zineb induced comedones with well-developed pilosebaceous glands. These results suggest that hairless dogs may be useful laboratory animals for the investigation of dermatotoxicity of ACs in conjunction with UV irradiation.

Studies on rat thyroid after oral administration of mancozeb: morphological and biochemical evaluations

Mancozeb, an ethylenebisdithiocarbamate (EBDC), has been studied for its effects on rat thyroid. Single oral administration of mancozeb at different concentrations (9600, 12,000, 15,000 and 18,750 mg kg(-1) body wt) has derived the oral LD50 value as 15,000 mg kg(-1) body wt. in male rats. Mancozeb at repeated oral doses of 500, 1000 and 1500 mg kg(-1) day(-1) for periods of 30, 90, 180 and 360 days has produced dose-dependent signs of toxicity and death of animals. The fungicide caused a significant increase in thyroid/body weight ratio and histopathological changes. Reduced levels of thyroid radioiodine ([125]I) uptake, serum protein-bound iodine (PB[125]I), thyroxine (T4) and reduced activity of thyroid peroxidase (TPO) have also been observed after exposure to mancozeb. Thus, mancozeb has been shown to produce marked structural and functional changes in thyroid of rats.

Zinc ethylene-bis-dithiocarbamate (Zineb)-mediated inhibition of monooxygenases and lipid peroxidation in bovine liver microsomes

Hepatic bovine microsomes were incubated with Zineb concentrations ranging from 2.5 mM to 2.5 microM. Only the higher concentrations of the fungicide (2.5 and 0.25 mM) elicited a sharp decline in cytochrome P450, cytochrome b5 and total sulphydryl groups content as well as in the activities of NADPH cytochrome c reductase, aminopyrine N-demethylase and aniline 4-hydroxylase. The loss of cytochrome P450 was matched by a concomitant increase in the amount of cytochrome P420, which represents a catalytically inactive form of cytochrome P450. The same concentrations of the fungicide, either alone or in the presence of NADPH 1 mM, failed to increase the amount of thiobarbituric reactive substances with respect to control incubations, thereby excluding the possibility of lipid peroxidation as a contributing factor in the loss of cytochrome P450 and in the inhibition of cytochrome P450-mediated metabolism. It is concluded that Zineb can depress monooxygenase activity in bovine hepatic microsomes mainly through the denaturation of cytochrome P450 and the impaired transfer of reducing equivalents to the complex cytochrome P450-substrate. These mechanisms might also account for the inhibition in lipid peroxidation brought about by the fungicide.

Induction of gonadal toxicity to male rats after chronic exposure to mancozeb

Mancozeb-a fungicide of ethylenebisdithiocarbamate group was orally administered at doses of 500, 1,000 and 1,500 mg/kg body weight/day for 30, 90, 180 and 360 days. Signs of toxicity mortality pattern and loss in body weight were observed in dose dependent manner. However, signs of intoxication and mortality pattern were more pronounced till the exposure of 90 days. A significant increase in testes and decrease in epididymis weight were associated with degeneration in seminiferous and epididymal tubules with loss of sperms. The decrease in gonadal acid phosphatase (ACP), succinic dehydrogenase (SDH) and increase in alkaline phosphatase (ALP), lactate dehydrogenase (LDH) activity were observed with increased serum cholesterol. Sialic acid and protein content of testis and epididymis were also decreased in dose dependent manner. The study has thus indicated marked biochemical and pathological changes in gonads of male rats after chronic exposure to mancozeb.

Toxicity of fungicides containing ethylene-bis-dithiocarbamate in serumless dissociated mesencephalic-striatal primary coculture

Agricultural exposure to the organomanganese fungicide MANEB (manganese-ethylene-bis-dithiocarbamate) may induce an extrapyramidal syndrome resembling parkinsonism. To evaluate the relative role of manganese (Mn) and ethylene-bis-dithiocarbamate (EBDTC) in the hazard of organomanganese fungicides, we studied the effects of MANCOZEB (Mn-Zinc-EBDTC) and ZINEB (Zinc-EBDTC) on serumless dissociated mesencephalic-striatal primary coculture. High affinity 3H-dopamine (DA) and 14C GABA uptakes as well as immunocytochemical staining of tyrosine hydroxylase (TH)-containing cells were used as specific functional markers of DA and GABA neuron viability. Both MANCOZEB and ZINEB, at 10 and 50 microM concentrations, dose dependently reduced DA and GABA viability parameters. These data suggest that EBDTC rather than Mn may be primarily responsible for the cytotoxicity of organomanganese fungicides on neuronal systems relevant to the pathophysiology of parkinsonism.

Expression of dynamin immunoreactivity in experimental pancreatic tumors induced in rat by mancozeb-nitrosomethylurea

Dynamins are GTPases which support receptor-mediated endocytosis and bind to several tyrosine kinase receptor-associated proteins known to mediate cell proliferation and differentiation. We have recently established that dynamin expression correlates with normal neuronal (Torre et al., J. Biol. Chem., 269 (1994) 32411-32417) and acinar pancreatic cell differentiation (Cook et al., Mol. Biol. Cell, 6 (1995) 405a). To begin to understand the role of dynamin in neoplastic pancreatic cell differentiation, we have followed the expression of this protein by immunohistochemistry during the development of pancreatic tumors in a mancozeb-nitrosomethylurea (NMU)-based carcinogenesis model recently developed in our laboratory (Monis and Valentich, Carcinogenesis, 14 (1993) 929-933). After a single intraperitoneal injection (50 mg/g body wt) of this carcinogen, rats fed with mancozeb develop pancreatic focal acinar hyperplasia (FACH), dysplastic foci (DYF) displaying acinar-like and ductular-like structures, and ductular-like carcinoma in situ (CIS). After histochemical staining using a monoclonal anti-dynamin antibody, high levels of this protein are consistently observed in well-differentiated acinar tumors (FACH). In contrast, dynamin immunoreactivity is almost undetectable in more advanced lesions showing a ductular-like phenotype (ductular-like DYF and CIS). This change in the expression pattern of dynamin during the progression of acinar into ductular-like DYF and CIS lesions correlates with recent findings from our laboratory showing a differential expression pattern for dynamin in pancreatic cells during embryonic development, with ductular-like precursor cells expressing low levels of this protein. Based upon these results, we conclude that more advanced ductular-like neoplastic cells induced by the carcinogen NMU in rat pancreas behave phenotypically like pancreatic precursor cells in their pattern of expression for dynamin.

Fungitoxic action of dithanes in presence of surfactant micelles

A rationale of arriving at the concentration of surfactant additives in the pesticidal formulations has been discovered. Fungitoxic activity of each of the two dithanes, Dithane M-45 (maneb) and Dithane Z-78 (zineb) has been estimated in the presence of various concentrations of three surfactants namely sodium lauryl sulphate, cetyl pyridinium chloride and Tween 80. Data reveal that the concentration of the surfactant additives in the pesticidal formulations should be at least equal to its critical micelle concentration (CMC) for enhanced biological activity. This rationale for the concentration of surfactant additives in the pesticidal formulation has so far not been clearly brought out in the literature. Since biological activity of the pesticides is enhanced in the presence of surfactant additives the present study is relevant to the reduction of environmental pollution due to pesticide residues.

Effect of Ziram, Thiram, and Dithane M-45 on bone marrow cells of mice-assessed by micronucleus test

Micronucleus test is an extensively used protocol to assess the mutagenicity of environmental chemicals. This was developed by Schmid and his co-workers (Matter and Schmid, 1971; Ledebur and Schmid, 1973). The micronucleus test is simple, quick and as sensitive as the chromosome aberration analysis. It is based on the principle that during anaphase, acentric chromatid and chromosome fragments lag behind, where as centric elements move towards the spindle pole. After telophase both the undamaged chromosomes and the centric fragments give rise to the daughter nuclei. The lagging elements are transferred into one or several secondary nuclei, which are as a rule much smaller than the main nucleus, and therefore called micronucleus (Schmid, 1973). The clastogenic effect of various chemicals is measured by micronucleus test. Erythrocytes are two types, the younger ones are polychromatic erythrocytes (PCE), which stain bluish and the older, the normo chromatic erythrocytes (NCE) which stain reddish. A few hours after the completion of last mitosis the erythroblasts expel their nucleus for unknown reasons and the micronucleus alone remains in the cytoplasm of the Polychromatic erythrocytes, and they are easily recognisable. Erythrocyte micronucleus represents the consequence of chromosomal aberrations induced during preceding mitotic division of erythrocytes (Matter and Grauwiler, 1974).

Ameliorating effect of vitamin C on murine sperm toxicity induced by three pesticides (endosulfan, phosphamidon and mancozeb)

The ameliorating effect of vitamin C (injected intraperitoneally) was evaluated against changes in sperm count and sperm head morphology in mice fed either 3, 6 or 1000 mg/kg body wt/day endosulfan, phosphamidon or mancozeb, respectively. The animals received aqueous preparations of the pesticides and/or vitamin C once daily for 35 consecutive days. All three pesticides, irrespective of their chemical nature, significantly decreased the sperm count, as well as increased the frequency of sperm with aberrant head morphology. Out of the three doses of vitamin C used the middle and higher ones (20 and 40 mg/kg body wt/day, respectively) afforded comparatively more significant amelioration. The lower dose (10 mg/kg body wt/day) of this vitamin (quantitatively equivalent to the human therapeutic dose according to body weight) was least efficacious in both the tests. However, amelioration was never up to the control level in any case. Vitamin C doses, when administered alone, did not produce any adverse effect on sperm count and sperm head morphology.

Biochemical and genetic interactions of two commercial pesticides with the monooxygenase system and chlorophyllin

Two commercial preparations of atrazine and zineb were tested on a diploid D7 strain of the yeast Saccharomyces cerevisiae using cells from logarithmic growth phase (with a high level of cytochrome P-450) and from stationary growth phase. The compounds induced marked increases of both gene conversion and point mutation frequencies in the logarithmic phase cells, while in the stationary phase no genotoxic effect was observed. The results obtained employing TA98 and TA100 strains of Salmonella typhimurium (Ames test) confirmed that neither atrazine nor zineb were mutagenic. The interaction between zineb and chlorophyllin, a known antimutagen in several biological systems, has been evaluated in yeast cells from logarithmic growth phase. The results showed that chlorophyllin seems to have a protective role against the genotoxic effects of zineb. The in vivo effects on cytochrome P-450 content (Cyt. P-450) and on monooxygenase activities were examined in hepatic microsomes of induced animals (rat, pig, and rabbit) 24 hrs after acute treatment. The results obtained with atrazine showed that it caused different effects in the three animal species. Preliminary data with zineb indicated that it can act both as an inducer or as an inhibitor of the monooxygenase system, depending on the dose used.

Effects of the subchronic administration of zinc ethylene-bis-dithiocarbamate (zineb) to rabbits

The effects of subchronic administration (90 d) of zineb were studied in male New Zealand White rabbits. Rabbits were allotted to 3 groups of 8 animals each and offered diets containing 0, 0.3 or 0.6% zineb. A marked decline in weight gain, hemoglobin concentration, hematocrit, and erythrocyte and leucocyte counts occurred at the highest zineb dosage. There was a dose-related depression in circulating thyroid hormones, whereas serum lipid concentration, particularly that of cholesterol and triglycerides, increased. Hepatic lipid concentration was considerably reduced in rabbits exposed to 0.6% zineb. Neither serum testosterone nor the activities of selected testicular enzymes showed changes suggestive of testicular involvement. Pathological changes were in agreement with biochemical findings; there was a marked dose-related enlargement of the thyroid showing histological colloid struma. An increase in relative weight and moderate glycogenosis were detected in liver, whereas no lesions occurred in testes. It was concluded that thyroid and liver are the main targets for zineb toxicity in the rabbit. Unlike the results from previous studies conducted on other food-producing species, repeated exposure of rabbits to zineb failed to cause testicular damage. This might be related to the inability of zineb to significantly accumulate in the testes.

In vitro transforming effect of the fungicides metalaxyl and zineb

The cytotoxic effects and the transforming properties of two fungicides, metalaxyl and zineb, whose mutagenic or carcinogenic activity has not been clarified yet, were analyzed in the in vitro BALB/c 3T3 cell transformation test both in the presence and in the absence of an exogenous metabolizing system. Zineb was completely detoxified when the exogenous metabolizing system was added to the target cells to increase their inherent metabolic capacity. Metalaxyl induced cell transformation at any assayed dosage, i.e., 500, 250, and 50 micrograms/ml, in the presence of bioactivation, and at the highest dosage (500 micrograms/ml) in the absence of bioactivation. The transforming effect was detectable only in the level-II transformation cultures and it was likely linked to the induction of additional cell proliferation which allowed obtaining the transformation amplification in these experimental conditions.

Genotoxicity of dithiocarbamates and their metabolites

Dithiocarbamate fungicides are widely used in agriculture for protection of vegetable crops and seeds. The mutagenicity spectra of ziram, thiram, zineb S-65 and ETU were determined by employing a battery of test systems included the bacterium Salmonella typhimurium (strains TA98, TA100, TA102, TA104, TA1535, TA1538), the yeast Saccharomyces cerevisiae (strain D61.M) and the shallot Allium ascalonicum somatic cells. Plate incorporation assay with S. typhimurium demonstrated direct mutagenicity of ziram in TA100 and thiram in TA100 and TA98 whereas zineb S-65 and ETU were ineffective. Tests for mitotic chromosome malsegregation in S. cerevisiae D61.M gave positive results with thiram, zineb S-69 and ETU. In shallot somatic root-tip cells ziram, thiram and ETU induced different genetic damages e.g. mitotic disturbance, polyploidy and micronuclei.

Dominant lethals induced by Dithane M-45 in silkworm Bombyx mori

Dithane M-45, a ethylenebis(dithiocarbamate) fungicide widely used in agriculture, including moriculture and sericulture, was tested for its efficacy in inducing dominant lethals in Bombyx mori. A polyvotine race of Pure Mysore was used for the studies and the topical application method was employed. After treatment with sublethal concentrations of 5, 10, and 20 g/50 larvae, the results have revealed that all of the concentrations could induce significant dominant lethals in a dose-dependent manner compared to controls. The results are discussed in the light of precautionary measures in the use of Dithane M-45 in the sericulture industry.

In vivo cytogenetic analyses of the carbamate pesticides Dithane M-45 and Baygon in mice

Two carbamate pesticides, Dithane M-45 and Baygon, were analysed for their cytogenetic effects using meiotic chromosome analysis and the micronucleus test in Swiss albino male mice. The three sub-lethal doses of 1687.5, 3375 and 5962.5 mg/kg bw of Dithane M-45 and 1250, 2500 and 3750 mg/kg bw of Baygon were employed in all the experiments. The results demonstrate that neither Dithane M-45 nor Baygon could induce a significant (P > 0.05) increase in the number of chromosomal aberrations in the germ cells or in the percentage of micronuclei in erythrocytes.

Impact of higher doses of vitamin C in modulating pesticide genotoxicity

The modulatory effect of higher doses of vitamin C (ascorbic acid) on the genotoxicity of the three pesticides (endosulfan, phosphamidon, and mancozeb) was assessed in the in vivo micronucleus test in Swiss albino mice. Concurrent administration of the vitamin in a dose (20 mg/kg bwt/day) equivalent to double the human therapeutic one, along with each of the three pesticides, was most effective as an antimutagen. The therapeutic dose (10 mg/kg bwt/day) was comparatively less so, and the quadruple (40 mg/kg bwt/day) of it did not show any further amelioration.

Toxic interactions between copper sulphate and some organic agrochemicals

Groups of rats were treated with graded doses of zineb or aldicarb solely or in association with copper sulphate for nine consecutive weeks. Body weight gain was retarded and thymus gland weight was decreased in all treated groups. A pronounced synergism between copper sulphate and zineb was noticed in lowering the weights of thymus, testes, and adrenal glands. Various degrees of reduction in hemoglobin concentration, red blood cells and platelet counts occurred after treatment with the above-mentioned agrochemical regimen. Copper sulphate synergised the elevation of serum alkaline phosphatase (AP) activity, and bilirubin concentration as well the reduction of hemoglobin concentration by zineb. Alanine aminotransferase (ALT) activity was significantly increased, while cholinesterase (ChE) activity was decreased in all treated groups. Serum triglycerides (TGs) were lowered in rats treated with medium or high doses of zineb or aldicarb.

Carcinogenic potential of some pesticides in a medium-term multi-organ bioassay in rats

The carcinogenic potential of 5 pesticides was analyzed using a medium-term multi-organ bioassay for carcinogenicity. Male F344 rats were initially treated with 3 known carcinogens (diethylnitrosamine, N-methyl-N-nitrosourea and N-bis(2-hydroxypropyl)nitrosamine) during a period of 4 weeks to induce neoplastic changes in a variety of organs, and then given one of 5 pesticides in the diet for a further 16 weeks. Neoplastic and pre-neoplastic lesions were found in the thyroid, kidney and urinary bladder with propineb, in the forestomach, kidney and thyroid with captan and folpet. The number of glutathione S-transferase placental-form-positive liver-cell foci was significantly increased in the captan- and phosmet-treated groups. Based on these findings, captan and propineb can be considered as carcinogens and carcinogenicity is suspected for folpet and phosmet. These results are in concordance with reported long-term carcinogenicity for captan, folpet and propineb. Daminozide was considered not to be carcinogenic. Thus, the present assay of 20 weeks' duration is useful for the prediction of potential carcinogens.

Promoting effects of mancozeb on pancreas of nitrosomethylurea-treated rats

Rats were treated with a single i.p. injection of the carcinogen nitrosomethylurea (NMU, 50 mg/kg b.w.) at day three of age. The treatment induced hyperplastic and atypical acinar cell proliferation [focal acinar cell hyperplasia (FACH)]. In this investigation, NMU treated rats were fed AIN-76 diet containing mancozeb (MZ; 100 mg/kg diet), a polymeric complex of ethylene bis (dithiocarbamate) manganese with zinc salt, which is an agricultural fungicide.

EXPERIMENTAL DESIGN

Group one was treated with NMU plus MZ (MZ-NMU), group 2 received NMU alone (NMU), group 3 was fed MZ and saline injected (MZ-SAL) and group 4 was the saline injected control (SAL). Rats were killed at week 24 of age. In MZ-NMU group pancreas there were FACH, dysplastic foci (DYF) and carcinomas in situ (CIS). FACH were larger, coalescent and may show areas of undifferentiated cells (focus within focus). DYF contain proliferative acinar and ductular structures with loss of polarity but no malignant traits. CIS had medullary appearance or consisted of irregularly shaped acini and ducts in stromal framework. Cell had scant cytoplasm and large hyperchromatic, pleomorphic nuclei. DYF and CIS were not seen in MZ group pancreas. The MZ-NMU group had increased mitotic index and greater number of apoptotic cells. There was no pathologic change in MZ-SAL group. Our data indicated that MZ did not cause pancreatic cell proliferation in normal rats whereas it had distinct promoting and progressor effects on NMU initiated pancreatic cells. Thus, a two-stage protocol of pancreatic carcinogenesis was achieved. It is suggested that the NMU protocol may be useful for testing promoter, progressor or inhibitory effect of chemical and physical agents on cell proliferation and transformation of rat pancreas.

Relationship between poly(ADP-ribose) polymerase activity and DNA damage induced by zinc dithiocarbamates in mouse and rat liver

The genotoxic effects due to in vivo treatment with zinc dithiocarbamates were evaluated in rat and mouse liver. The two pesticides Zineb and Ziram, belonging to this chemical class, induced an increase in single-strand DNA breaks, as measured by the alkaline elution technique. The nuclear enzyme poly(ADP-ribose) polymerase (pADPRP), a chromatin-bound catalytic protein, utilizing NAD+ as a substrate, was tested by a radiometric procedure. A close relationship between the increased extent of DNA damage and the enhanced level of endogenous pADPRP activity was obtained in rat liver, whereas both parameters remained unchanged in mouse liver.

Toxicological effects of ziram, thiram, and dithane M-45 assessed by sperm shape abnormalities in mice

The three commonly used dithiocarbamate fungicides ziram, thiram, and dithane M-45 were investigated for their mutagenic and carcinogenic potency using sperm shape abnormalities in mice. The fungicides were administered intraperitoneally in single and cumulative doses. All three of the fungicides tested were found to induce significant increase in the frequency of abnormal sperm at all the doses, and a linear dose effect was observed.

Status of ornithine decarboxylase activity and DNA synthesis in mancozeb-exposed mouse skin

The effect of mancozeb, a fungicide, on mouse skin ornithine decarboxylase (ODC) activity and DNA synthesis was studied. ODC activity was induced after topical application of mancozeb and exhibited a peak level at 5 h. This ODC induction was dependent on the dose of mancozeb applied. Cycloheximide, an inhibitor of protein synthesis, inhibited the mancozeb-caused ODC induction, indicating the effect on enzyme protein synthesis. The rate of DNA synthesis was also increased by mancozeb, as indicated by increased [3H]thymidine incorporation into skin DNA. Induction of ODC activity and DNA synthesis are among the events probably involved in the tumorigenic action of mancozeb on mouse skin.

[Toxicologic evaluation of propyneb on the Wistar rat]

This experiment was performed in Wistar rats of both sexes exposed subchronically to 1:100, 1:500, 1:1000 and 1:1500 LD50. The evaluation was based on endpoints measured on the 30th and 90th after starting exposure and after a recovery period of 30 days: these included clinical signs, functional changes, hematological parameters, urine analysis, biochemical, histochemical, immunomorphological endpoints, electron microscopy of internal organs, chromosome examination of bone marrow. A high lethality was shown to occur with a characteristic clinical picture: interruption of weight gain, behavioural changes, leucopenia mainly involving neutrophil leucocytes, biochemical changes characteristic of liver, cardio-vascular system (myocardium and aorta) together with pathologic, biochemical, histochemical and ultrastructural changes in liver, brain, thyroid gland, myocardium, spleen and bone marrow. Endpoints were shown to be clearly dose-dependently related with small variations with the low dose, i.e. 1:1500 LD50 (5 mg/kg-1 bw).

Pathologic changes, tissue distribution, and extent of conversion to ethylenethiourea after subacute administration of zinc ethylene-bis-dithiocarbamate (zineb) to calves with immature rumen function

The toxicity of zinc ethylene-bis-dithiocarbamate (zineb), a widely used fungicide, was studied in four 4-week-old Friesian calves with immature rumen function. Calves were first subjected to liver biopsy, and thereafter, 3 of them were orally administered 200 mg of zineb/kg of body weight daily for 80 days, whereas the fourth calf served as control and remained untreated. Clinical, hematologic, and pathologic (including ultrastructural) findings were recorded. The distribution in body fluids and tissues of the parent compound and one of its main metabolites, ethylenethiourea (ETU), also was examined. Treated calves had unthrifty appearance and reduction in weight gain. They also had remarkable impairment of thyroid function, as reflected by reduction in serum concentrations of triiodothyronine and thyroxine and increase in weight of the thyroid gland associated with epithelial vacuolization and foci of hyperplasia. Moderate increase in liver glycogen content and impairment in maturation of germ cells were recorded consistently. Whereas zineb was widely distributed in body tissues, ETU accumulated mainly in the liver and the thyroid gland, although noticeable concentrations also were attained in muscle. Data were consistent with involvement of ETU mainly in the pathogenesis of thyroid gland lesions, and indicate that unweaned calves given zineb develop a clinicopathologic syndrome that does not differ qualitatively from that already described in adult cattle exposed to zineb.

Heterogeneous effects of ethylenebisdithiocarbamate (EBDC) pesticides on oxidative metabolism of xenobiotics

Comparative evaluation of the acute effects of ethylenebisdithiocarbamate (EBDC) fungicides, mancozeb and zineb on microsomal mixed function oxidases (MFO) revealed marked substrate-dependent inhibition of oxidative metabolism of aminopyrine, p-nitroanisole and aniline in rats sacrificed 4 hr after oral administration of 100 mg mancozeb or zineb/kg body weight. Mancozeb inhibited p-nitroanisole O-dealkylase and aniline hydroxylase to a greater degree than zineb, whereas the inhibition of aminopyrine N-demethylase by the two fungicides was quantitatively comparable. Interestingly, aryl hydrocarbon hydroxylase (AHH) which exhibited maximum inhibition with mancozeb, remained unaffected following zineb administration. The time-course and dose-dependence of MFO inhibition examined 1 and 4 hr after a single oral dose of 100 mg or 250 mg zineb/kg was expressed as a dose-dependent decline in the rate of xenobiotic biotransformation at 4 hr. In vitro interaction of zineb with MFO resulted in slightly greater inhibition of aminopyrine, p-nitroanisole and aniline while AHH exhibited more pronounced decrease with mancozeb. The magnitude of inhibition of aminopyrine N-demethylase and AHH was independent of the time of preincubation of fungicides with the enzyme. Kinetic studies indicated the non-competitive nature of AHH inhibition. Chronic oral treatment with mancozeb and zineb at a dose of 250 mg/kg for 4 weeks did not modify xenobiotic biotransformations except for a slight induction of aminopyrine N-demethylase by mancozeb.

Genotoxic effects of dithane M-45 on the bone marrow cells of mice in vivo

Genotoxic effects of dithane M-45 were studied on the bone marrow cells of male albino mice (Lacca strain) in vivo. Different doses (30 mg, 40 mg and 300 mg/kg b.wt) of dithane M-45 were injected intraperitoneally and their effects were investigated after time intervals of 1, 2, 5 and 10 days. The chromosomal aberrations observed in the bone marrow cells of male mice after treatment with dithane M-45 were fragments, rings, dicentric chromosomes, terminal chromatid deletions, chromatid gaps and breaks. In addition to these chromosomal aberrations, physiological effects such as uneven stretching of chromatin material, end-to-end chromosomal associations, exchange configurations, clumping, stickiness and centromeric associations were also observed.

Effect of mancozeb on hydrolytic metabolism of xenobiotics

The present investigation reports the effect of chronic oral administration of mancozeb, a fungicide, on hepatic microsomal carboxylesterases/amidases or B-esterases responsible for hydrolytic metabolism of aspirin (acetylsalicylic acid or ASA) at pH 5.5 and 7.4, 2-acetylaminofluorene (AAF), acetanilide and p-nitrophenylacetate (NPA) and cholinesterase in rat. Oral administration of mancozeb (250 mg/kg/day) for 30 days caused significant stimulation of ASA esterase I (pH 5.5), ASA esterase II (pH 7.4), AAF N-deacetylase and acetanilide N-deacetylase in liver. However, the activities of NPA esterase and cholinesterase remained unaffected. Evaluation of induction kinetics demonstrated that the pattern and magnitude of responses of these microsomal hydrolases to mancozeb treatment for 7 days were comparable to those obtained after treatment for 30 days. The activities of hydrolases were not altered in animals killed 4 hr after an oral dose of mancozeb. Mancozeb did not affect these hydrolases in vitro.

Analysis of chromosome aberrations and sister-chromatid exchanges in peripheral blood lymphocytes of workers with occupational exposure to the mancozeb-containing fungicide Novozir Mn80

Chromosome aberrations and sister-chromatid exchanges (SCEs) were analyzed in short-term cultures of peripheral lymphocytes of 44 workers occupationally exposed to mancozeb during the production of the pesticide Novozir Mn80 and 30 control persons. The results suggest that mancozeb exposure was associated with a significant increase in the frequencies of cells with structural chromosome aberrations (2.07% vs. 1.10% in the controls), and the number of SCEs per cell (9.19 +/- 1.81 vs. 7.82 +/- 1.04 in the controls).

Effect of pesticides on the growth of aquatic hyphomycetes

The effect of two herbicides (paraquat and 2,4-dichlorophenoxybutyric acid) and two fungicides (mancozeb and captafol) was studied on the growth of Flagellospora penicillioides, Lunulospora curvula and Phalangispora constricta using the poisoned-food technique. The pesticides did not produce any inhibition of growth at concentrations up to 5 mg/l. The required concentration to bring about total inhibition of growth varied among the chemicals and the cultures. The herbicides produced a slight enhancement of culture growth at concentrations ranging from 1 to 25 mg/l.

Subacute toxicological examination of Dithane M-45

A subacute toxicological study of the effects of the ethylene-bisdithiocarbamate-containing fungicide Dithane M-45 (80% mancozeb) was carried out in male Wistar rats. The rats were given Dithane mixed in the feed at doses of 0, 10, 50, 75, 113, 169, 253 or 379 mg/kg body weight for 12 wk. One-third of the rats given 379 mg Dithane/kg body weight died, and doses of greater than or equal to 169 mg/kg decreased the growth of the rats as well as the nutrient utilization. The relative weights of the liver and thyroid were significantly increased in rats given greater than or equal to 75 mg Dithane/kg body weight, and those of the kidneys, adrenals and testes were significantly increased in the two highest dose groups. The serum cholesterol level was increased significantly in groups given greater than or equal to 75 mg/kg, and doses of 113, 169 or 253 mg/kg caused the elevation of the triglyceride content of the liver. The two highest doses of Dithane decreased the detoxicating capacity of the liver. The function of the thyroids was impaired even by very small doses of Dithane: at a dose of 10 mg/kg body weight the quantity of iodine stored in the thyroids was decreased by 20%. At doses of greater than or equal to 50 mg/kg statistically significant decreases in thyroid iodine content were observed. Histological examination of the thyroids showed dose-dependent hyperplasia in rats treated with Dithane.