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Radiotracer study on residues and residue distribution of zineb in plant-soil system.

In view of the widespread use of zineb on food plants and the toxicity of one of its metabolites, ETU, a study on the residues and residue distribution of zineb and ETU in plant-soil systems was carried out. The half-life values for total zineb residues on egg-plant leaves and in soil were observed to be over three and two weeks, respectively. Egg-plant skin contained higher amount of zineb residues than the fruit pulp. Washing with water greatly reduced zineb residue levels, especially those in the fruit skin. Compared with zineb, ETU is much easier to be uptaken by plants and to leach into deeper layer of soil due to its high water solubility. Therefore, attention should be paid to the contents of ETU in zineb formulations as impurity and formation of ETU in the environment.

Carbon Radioisotopes

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.

Analysis of Variance

Species-dependent effects of dietary lindane and/or zineb on the activation of aflatoxin B1 into mutagenic derivatives.

Sprague-Dawley rats and Swiss mice were given diets containing lindane, 125 ppm, or zineb, 5200 ppm, or a mixture of both at the above-mentioned concentrations for 2 and 4 weeks. The effect of pesticide ingestion on the ability of liver S9 to metabolize aflatoxin B1 (AFB1) into mutagenic derivatives was tested by the Salmonella (TA100)/microsome test according to Ames. Control mouse-liver S9 was less efficient (13%) than the corresponding preparation from control rat liver. The ingestion of lindane produced a similar increase in the activities of both rat- (68%) and mouse-liver S9 (62%). Pretreatment with zineb inhibited (46%) rat-liver S9 but caused a marked increase (400%) in the activity of mouse-liver S9. Concomitant exposure to both pesticides showed that lindane released the inhibitory action of zineb on rat-liver S9 and reduced the stimulatory effect of zineb on mouse-liver S9. The inducing action of zineb in mice was a function of the dietary concentration of the pesticide. No effect was observed at dietary concentrations of zineb up to and including 500 ppm.

Aflatoxin B1

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.

Age Factors

[Study of the effect of the fungicide zineb on microorganisms].

Changes in yeast cells induced by the fungicide zineb were studied using biochemical, genetic techniques and electron microscopy. The primary changes involved anabolic processes since RNA and protein content increased in the cells. The data were consistent with a larger size of mitochondria. The oxidative-reductive activity of cell extracts did not change under the action of the fungicide. Zineb at a concentration of 0.5 to 50 mg/litre exerted a genetic activity towards indicator microorganisms. The changes in the morphophysiological characteristics of yeast growth under the action of zineb are presumed to be of a protective nature. Zineb traces in soil must be controlled in terms of the microbiological index.

Drug Resistance, Microbial

[Action of a dithiocarbamate (zinebe) on the liver biosynthesis of RNA and proteins in the rat (author's transl)].

Zineb (zinc ethylene bisdithiocarbamate) inhibits the transcriptional activity of an in vitro system functioning with either RNA polymerases of isolated rat liver nuclei or purified E. coli RNA polymerase. Zineb also inhibits the in vitro aminoacid incorporation mediated by a polysomal standard system, by interacting with some pH 5 enzyme components(s). When rats fed a balanced semi-synthetic diet containing zineb (5 200 mg/kg) for ten weeks, one may observe a decrease in the RNA and protein syntheses in liver. The consequences of the ingestion of small but repeated doses of zineb are discussed.

Amino Acids

The effect of maneb, zineb, and ethylenethiourea on the humoral activity of the pituitary-thyroid axis in rat.

Ethylenebisdithiocarbamates (EBDCs) maneb and zineb are widely used fungicides the final metabolite of which is ethylenethiourea (ETU). EBDCs distort the humoral activity of the thyroid gland, and ETU is especially active in this respect. Male Wistar rats were exposed either to exogenous (100 ng i.p.) or endogenous (+4 degrees C) TRH stimulation. ETU (100-500 mg/kg i.p.) caused no changes in serum TSH levels whereas zineb (70-500 mg/kg i.p.) significantly decreased the bursts induced by cold or exogenous TRH. Maneb (20-200 mg/kg i.p.) significantly decreased the cold-induced TSH response while it had no effect on the TRH-stimulated TSH secretion. None of the agents caused significant changes in serum T3 or T4 levels. It seems that maneb, and zineb, but not ETU, inhibit rat TSH secretion through an action on the endogenous TRH at the hypothalamic or pituitary level. The mechanism behind this action may be the inhibition of dopamine-beta-hydroxylase.

Animals

Studies on the mechanism of nabam- and zineb-induced inhibition of the hepatic microsomal monooxygenases of the male rat.

In vitro effects of the ethylene bis-dithiocarbamate fungicides, nabam and zineb, on the hepatic microsomal monooxygenases of male rats were examined. Incubation of nabam and zineb with hepatic microsomes, without NADPH, leads to an inhibition of the metabolism of aminopyrine and aniline and to a denaturation of cytochrome P-450 into cytochrome P-420; in addition nabam causes the destruction of cytochrome P-450. Addition of NADPH into the incubation medium increases the inhibition of the monooxygenases, principally the inhibition of the metabolism of aniline induced by nabam. We studied the in vitro effects of three of the chief breakdown products of these fungicides: ethylene bis-isothiocyanate sulfide (EBIS), ethylene thiourea (ETU), and carbon disulfide (CS2). EBIS appears to be the only metabolite affecting directly (without NADPH) the hepatic monooxygenases activity. EBIS accounted partly for nabam-induced inhibition of the hepatic microsomal monooxygenases. The data suggest that the decrease of monooxygenases activity seen on incubation of nabam with hepatic microsomes may be due to the denaturation and destruction of cytochrome P-450 resulting from covalent binding of the compounds with cysteine sulfhydryl groups in cytochrome P-450. Inhibition of monooxygenase activity induced by zineb seems to be due to the reaction with the sulfhydryl groups of cytochrome P-450 and to another mechanism, probably related to its lipophilic character.

Aminopyrine N-Demethylase

Uptake, distribution and retention of zineb and ziram in rainbow trout (Salmo gairdneri).

In short-term static bioaccumulation experiments with 14C-labelled zinc ethylenebisdithiocarbamate (zineb) and zinc dimethyldithiocarbamate (ziram) both compounds were rapidly disseminated through the tissues. Whole-body accumulation was low, with bioconcentration factors less than 100. Whole-body elimination was rapid with 45% and 25% of the initial radioactivity from ziram and zineb, respectively, being retained by the end of the 16-day depuration period. Pigmented tissues appeared to be major distribution sites as well. This may be related to the affinity of the compounds and/or their degradation products to melanin or to complexation with phenoloxidase, a copper-containing enzyme involved in melanin synthesis. Autoradiography also revealed a high labelling of thyroid follicles. The results show that dithiocarbamates are selectively localized in various tissues, reported to be the target organs for their toxic action. The observed differences in toxicokinetics between zineb and ziram may, in part, explain the differences in toxicity to fish between ethylenebisdithiocarbamates and dialkyldithiocarbamates.

Animals

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.

3T3 Cells

Acute central nervous system changes due to intoxication by Manzidan (a combined dithiocarbamate of Maneb and Zineb).

A 42-year old man sprayed Manzidan (a combined dithiocarbamate of Maneb and Zineb) on a cucumber plantation, twice during a week. Behavioural changes appeared after the first application, and loss of consciousness, convulsions and right hemiparesis after the second application with diffuse slow rhythm in the EEG. Both the behavioural and CNS symptomatology disappeared spontaneously after a few days. The previous history of the patient, the sudden appearance and spontaneous disappearance of the symptoms and a dose-response relationship strongly suggest that Maneb and Zineb were the cause of the illness.

Adult

Genotoxicity of zineb detected through the somatic and germ-line mosaic assays and the sex-linked recessive-lethal test in Drosophila melanogaster.

The genotoxicity of zineb, a carbamate fungicide, has been tested through eye, wing and female germ line mosaic assays and the sex-linked recessive-lethal test in Drosophila melanogaster. Larvae of different instars, heterozygous for appropriate recessive genetic markers, were exposed to the fungicide in food for different durations of time. The adult eyes and wings were screened for induction of mosaic spots and the eggs laid by the females were checked for induction of female germ-line mosaicism. It is concluded that zineb is genotoxic to both somatic and germ-line cells of Drosophila.

Animals

The measurement of ethylenethiourea and ethyleneurea in the rat and common marmoset Callithrix jacchus after zineb (zinc ethylenebisdithiocarbamate) dosing.

The metabolism of the fungicide zineb, (zinc ethylenebisdithiocarbamate), has been studied in the rat and the marmoset. 2. It was found in both species that a relatively large proportion (21-22%) of the original zineb administered was detectable in the excreta as ethylenethiourea (ETU) a known mutagen, teratogen and carcinogen. 3. A further proportion (2-5%) was determined to be ethyleneurea which is a metabolite of ETU. 4. Results of comparative experiments in marmosets revealed that ETU was photolabile in the presence of excreta, thus showing the importance of conducting the studies in the dark.

Animals

Acute intoxication due to exposure to maneb and zineb. A case with behavioral and central nervous system changes.

The dithiocarbamates are considered chemicals of low toxicity. They are known to cause dermatitis, conjunctivitis, rhinitis, pharyngitis, and bronchitis in humans. Central nervous system effects in humans have not been found, but some cases have been reported in experimental animals. This case report concerns a 42-year-old man previously in good health, who sprayed a combined dithiocarbamate of maneb and zineb on a cucumber plantation twice during a week, the second time with a more concentrated solution than the first. Behavioral changes appeared after he walked through the sprayed area following the first application, and loss of consciousness, convulsions, and right hemiparesis with diffuse slow rhythm in the electroencephalogram occurred after the second exposure. Both the behavioral and central nervous system symptomatology disappeared spontaneously after a few days. An electroencephalogram was normal two weeks later. The absence of a positive previous history of the patient, the sudden appearance and spontaneous disappearance of the symptoms, and the apparent dose-response relationship strongly suggested that maneb and zineb were the cause of the illness.

Acute Disease

[Diminution of activity of liver microsomal oxygenase in a rat fed with a diet with added zineb].

Young Wistar CF male rats were fed with diets containing 6,15,60,600,3600 p.p.m of zineb (a zinc thiocarbamate used as fongicide). Four weeks after the beginning of the treatment, a calcic precipitation method is used for obtaining a preparation of liver microsomes from these animals. The microsomes are then used for measuring the activity of both aminophenazone demethylase and aniline hydroxylase as well as the liver concentration of cyt. P 450 and cyt. b5. The weight growth was reduced by the highest dose of zineb, which corresponds to about a daily intake of twentieth of the LD 50 per os. The fongicide brings down the activity of the microsomal monoxygenases and reduces the P 450 quantity. The lessening of the aminophenazone demethylation is apparent starting from a dose between 60 and 600 p.p.m...

Aminopyrine

[Effect of methyl parathion and zineb administration on the activity of some hepatic enzymes in rats].

Male albinos rats were fed diets containing parathion-methyl or Zineb so that the average daily intake is 1/10 or 1/20 lethal dose 50, for a period of 4 or 8 weeks. The activity of hepatic microsomal enzymes, namely :aminopyrine N-demethylase, BHT oxidase, aniline hydroxylase, Butter Yellow & Amaranth reductases, NADPH-cyt. c reductase, G6P phosphatase, were measured. The activities of G6P & 6PG deshydrogenases were also determined. With the application of the parathion-methyl doses, the only effect showed is the lowering of the microsomal protein concentration.

Aminopyrine N-Demethylase

Simple method for distinguishing maneb, zineb, mancozeb, and selected mixtures.

Maneb, zineb, mancozeb, and arbitrarily selected mixtures of those can be differentiated by a simple method. Compounds are differentiated on the basis of colors produced after treatment of saturated solutions of the fungicides in n-propanol-acetone mixture (1 + 1 v/v), first with dithizone and then with monosodium dihydrogen phosphate solution in the same solvent. The color depends on the type and concentration of metal present in the sample.

Colorimetry

[Effect of perocin (zineb) on the quality of ovine seminal fluid].

The fungicide perocin , an analogue of the preparation Zineb ( ditiocarbamate ) was applied orally with the feed to 11 rams divided into two test groups of three animals each and one control group of five rams. The preparation was administered at the rate of 1/50 and 1/100 of DL50 per kg body mass to the first and second test group, respectively, in the course of 4 months. During both the preparatory and the experimental period semen was sampled twice a week with the use of an artificial vagina, and investigations were carried out to evaluate the qualitative properties of the semen, the level of Na ions, the redoxi -potential and the activity of the alkaline phosphatase (APh). Apparently, the preparation triggered a trend toward increasing the number of pathologic spermatozoa (20-30 per cent) and decreasing to a lower extent the concentration of the sodium ions and the values of the redoxi -potential. The motility of spermatozoa was lowered by 4.3 per cent for the animals that were treated with 1/50 DL50 per kg body mass, and by 2.1 per cent for those that were offered 1/100 DL50 per kg body mass. There were certain differences between the values obtained although these were statistically insignificant so far as the alkaline phosphatase was concerned. They pointed to the fact that perocin contributed to the increase in the value relationships of some of the forms of this enzyme. The same applied also to the APh1 which is believed to have certain bearing upon preserving the activity of spermatozoa.

Alkaline Phosphatase