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Dithiocarbamates form a large group of chemicals that have numerous uses in agriculture and medicine. It has been reported that dithiocarbamates, including thiuram (tetramethylthiuram disulfide), cause wavy distortions of the notochord in zebrafish and other fish embryos. In the present study, we investigated the mechanism underlying the toxicity of thiuram in zebrafish embryos. When embryos were exposed to thiuram (2-1000 nM: 0.48-240 microg/L) from 3 h post fertilization (hpf) (30% epiboly) until 24 hpf (Prim-5), all embryos develop wavy notochords, disorganized somites, and have shortened yolk sac extensions. The thiuram response was specific and did not cause growth retardation or mortality at 24 hpf. The thiuram-dependent responses showed the same concentration dependence with a waterborne EC50 values of approximately 7 nM. Morphometric measurements revealed that thiuram does not affect the rate of notochord lengthening. However, the rate of overall body lengthening was significantly reduced in thiuram-exposed animals. Other dithiocarbamates, such as ziram, caused similar malformations to thiuram. While expression of genes involved in somitogenesis was not affected, the levels of notochord-specific transcripts were altered after the onset of malformations. Distortion of the notochord started precisely at 18 hpf, which is concomitant with onset of spontaneous rhythmic trunk contractions. Abolishment of spontaneous contractions using tricaine, alpha-bungarotoxin, and a paralytic mutant sofa potato, resulted in normal notochord morphology in the presence of thiuram. These results indicate that muscle activity is necessary to reveal the underlying functional deficit and suggest that the developmental target of dithiocarbamates impairs trunk plasticity through an unknown mechanism.

The activity of glutathione system enzymes exposed to nitroso-compound (NC) precursors in small doses for 12 months and preliminary injection of vitamin A have been studied. The histo- and biochemical examinations have revealed a pronounced increase in the enzyme activity exposed of NC precursors and a slight increase when injecting preliminary vitamin A.

A single i.p. dose (120 mg/kg) of thiram given to male Sprague-Dawley rats caused a significant increase in the activity of SGOT and SGPT 24 hr post-treatment indicating liver damage. A considerable diminution in the serum cholinesterase activity was also noted in the treated rats as against the control animals. Additional evidence for thiram-induced liver toxicity is provided by the observation that there was approximately 50% inhibition of the activity of hepatic microsomal benzphetamine N-demethylase with a concomitant decrease in the concentration of cytochrome P-450, an important component of the mixed-function oxidase system. Although not significant, hepatic glutathione levels were also depleted by thiram, probably making the liver susceptible to toxic injury.

The results of a chronic 2-years experiment of thiram on Wistar-rats are given. On the basis of clinical, biochemical and pathomorphological investigations a Noel of 5 mg/kg bw were proposed.

In rats, a single oral dose of 30 mg or 1 g thiram per kilogram produced a significant prolongation of the hexobarbital sleeping time or zoxazolamine paralysis time, respectively, a depression of hepatic microsomal O-demethylation of p-nitroanisole to p-nitrophenol, and a decrease in the microsomal cytochrome P-450 content. In addition, incorporation of 14C activity from glucose, glycerol, and palmitic acid into phospholipids (PLs) decreased in most of the components, showing a compensatory increase in only a few of them. Fatty acid (FA) concentrations in phosphatidylcholine (PC) or phosphatidylethanolamine (PE) molecules were increased or decreased from one FA class to the other. This alteration of the FA concentrations in PC and PE, respectively, was virtually exclusively in position 2 of the two PL molecules. The total content of saturated FAs in PC and PE was significantly decreased only after 1 g/kg thiram; this was associated with an increase in total unsaturated FAs. The multiple changes in the bioformation and composition of microsomal membrane PLs suggest a disturbance of the monooxygenase system. It is conceivable that there is an interrelationship between the observed impairment and the inhibitory effect of thiram on the microsomal monoxygenases (MMs).

Total and nonsedimented activities of lysosomal proteinases were studied in rat liver and kidney tissues after administration of silimarine simultaneously with tetramethylthiuram disulfide (TMTD). Silimarine did not affect the pattern of alterations in total activity of lysosomal proteinases, caused by the TMTD treatment, but the nonsedimented activity of the enzymes studied was normalized. Silimarine appears to exhibit the membrane-stabilizing effect.

The dimethylthiocarbamate fungicide thiram has been found to be a potent and direct inducer of point mutations at the hypoxanthine-guanine phosphoribosyl transferase (HGPRT) locus in Chinese hamster cells in vitro. It also increased the incidence of micronuclei in polychromatic erythrocytes in the bone marrow of mice given a single ip dose of 100 mg/kg. Both the in vitro and the in vivo mutagenic responses were observed with doses of thiram that were cytotoxic.

Rats were fed diets containing various amounts of added thiram, a dithiocarbamate fungicide. As thiram feeding resulted in decreased appetite, control rats not receiving thiram were pair-fed to the experimental ones. On d 30 of the experiment the animals were weighed and sacrificed, and the following organs were weighed: liver, kidneys, heart, epididymal and perirenal fat pads, testes, seminal vesicles, tibia, adrenals, and thyroid. Liver concentrations of lactate, pyruvate, beta-hydroxybutyrate, acetoacetate, ATP, and ADP were determined by enzymatic-spectrofluorimetric assay. For each parameter studied and each thiram dosage, values for treated rats were compared to those for control rats and the probability under the null hypothesis was computed. These probabilities were transformed into probits, logits, or "Weibull transforms" and plotted against the logarithms of the respective doses. Models were fitted to the data by linear regression techniques. Finally, the dose inducing the least significant difference (LSD dose), and the dose considered "safe" at P = 0.95, 0.99, and 0.999 were calculated. Significant pesticide-induced changes in the following parameters were found: food intake; weights of the whole body, kidneys, epididymal and perirenal fat pads, testes, and seminal vesicles; and liver beta-hydroxybutyrate/acetoacetate and lactate/pyruvate ratios. As the models did not differ in fit to the experimental data or in computed LSD doses, they were discriminated on the grounds of their underlying theoretical assumptions and their prediction of safe doses in a long-term study. The log-probit model was rejected for the former reason, and it was shown that the Weibull model foresees a nonnegligible risk of change, with thiram feeding at low doses, for too many parameters. The analysis resulted in the selection of the log-probit model for further use. Weight of fatty tissues was the most sensitive parameter and, using the log-probit model, the predicted no-effect dose at the 95 percent confidence level was 38 ppm thiram in the diet.

A pesticide tetramethylthiuram disulfide, administered per os at doses of 1/10 and 1/5 LD50 within 5 days, inhibited the activity of proteolytic system in liver and kidney lysosomes as well as impaired the lysosomal membrane structure in these tissues. Glucagon, injected simultaneously with the pesticide, prevented its inhibitory effect on lysosomal proteinases but did not affect the enzymatic activity in unsedimented fraction and in blood serum.

In recent years data have accumulated regarding genotoxic properties of dithiocarbamic acid derivatives. The results from the present work indicate that the mutagenicity of these compounds depends on an indirect effect via oxygen radicals. Mutagenicity of tetramethylthiuram disulfide ( TMTD ), that was used as a model substance, was established with both frameshift and base substitution sensitive strains of Salmonella typhimurium. Addition of copper ions resulted in a decreased survival at low dithiocarbamate doses. The dose response curves seem to correlate with the formation of two types of metal dithiocarbamate complexes. At low doses charged complexes are formed, while the formation of uncharged complexes is favoured at higher dosages. The data suggest that this formation of uncharged metal complexes implies a decreased toxicity but at the same time an increased mutagenicity. The mutagenicity of both TMTD and its ethyl analogue TETD was enhanced by oxygen. Furthermore, TMTD potentiates the mutagenic action of menadione, a substance that produces O(2) and H2O2 by redox cycling with molecular oxygen. Interaction of uncharged metal dithiocarbamate complexes with both production and detoxification of reactive forms of oxygen is suggested to be responsible for the direct mutagenic effects via oxidative damage to DNA. A further enhancement of the oxygen radical content of the cells by adding microsomes that produce oxygen radicals via autoxidation of cytochrome P-450 is proposed as the mechanism for the 'metabolic activation of TMTD '.

Thiram, a dithiocarbamate fungicide, is known to evolve to dimethylnitrosamine (DMNA) when associated with nitrites. Conditions of appearance of that carcinogenic compound have been studied in short-term experiments by association of the fungicide, nitrates or nitrites, and species representative of freshwater biota. DMNA has been estimated by GLC equipped with a specific detector. Chlorella vulgaris can rapidly produce nitrites from nitrates and DMNA is obtained in presence of thiram. Daphnia magna can also synthesize DMNA but nitrites have to be added to the medium. Increased toxicity of thiram is observed. The same results are obtained on Cyprinus carpio and for a part on Brachydanio rerio. When the species are associated in a 15-day experimental food chain, and intoxicated algae feed the two other levels, no significant transfer is observed. Nevertheless, some DMNA hazard may exist for particular species exposed to thiram associated with nitrites or even nitrates if algae are present.

Single oral doses of ferbam, thiram, zineb, or maneb produced central nervous system stimulation followed by depression and alopecia. Ferbam and thiram were more toxic on the basis of weight than zineb; maneb was relatively nontoxic. There was no species difference in acute toxicity between rats and mice. In 13- and 80-wk feeding studies, the toxic effects of ferbam and thiram in rats were similar; however, thiram was more toxic on the basis of weight than ferbam. During the 80-wk feeding study, weight gain was reduced in ferbam-treated rats starting at daily doses of 8 mg/kg in males and 37 mg/kg in females and in thiram-treated rats staring at daily doses of 5 mg/kg in males and 26 mg/kg in females. Food consumption was reduced in proportion to the reduced weight gain. Death occurred in males fed 109 or 331 mg/kg.d ferbam and in males fed 58 or 132 mg/kg.d thiram. Female rats fed 96 mg/kg.d ferbam or 67 mg/kg.d thiram developed alopecia and ataxia, which led to paralysis of the hind limbs. Male rats fed ferbam or thiram had a more severe incidence of squamous metaplasia in the thyroid and fatty infiltration in the pancreas than control males. Ferbam or thiram reduced the incidence of spontaneous nephritis in both males and females. The male rats that were fed 109 or 331 mg/kg.d ferbam and died betweeen 1 and 5 wk had golden pigment in the reticuloendothelial cells of the spleen and in the enlarged mesenteric lymph nodes, associated with hemosiderosis. Moderate tubular degeneration of the testes with atypical spermatids in the epididymis occured in some rats fed 132 mg/kg.d thiram for 13 wk but not in rats fed up to 52 mg/kg.d for 80 wk. Periodic hematologic examination and terminal clinical blood tests did not reveal any severe changes. Ferbam and thiram did not alter the occurrence or latent period of the spontaneous tumors seen in control rats.

Tetramethylthiuramdisulfide (TMTD), the active ingredient in Arasan, fed to broiler breeder hens at 10, 20, or 40 ppm depressed egg production, reduced hatchability, and resulted in soft-shelled eggs. The progeny of these hens had anomalies manifested by bilaternal medial deviation of the toes, exophthalmia, and shortened femurs. Broiler breeder hens that consumed a ration containing 80 ppm of TMTD produced only soft-shelled eggs.

Combined action of Thiuram with Carbaryl, Propoxur, Pirimor, Chlorfenvinphos, Malathion, Lindane, and Carbendazine was investigated in rats. The effects induced by Thiuram containing combinations were stronger in females than in males. The type of response was differentiated in each individual case. In rats receiving Chlorfenvinphos or Carbendazine with Thiuram the effects were on the borderline between more than additive and potentiated toxicity in males, while in females potentiation was observed. In the case of the combination with Propoxur the effects appeared to be less than additive in males and strictly additive in females. Other tested combinations exerted additive action in males, while in females effects ranged from additive to potentiating toxicity. It is evident, that combined action of Thiuram with some pesticides might have resulted in potentiation of toxicity. Hence, this fact ought to be considered in evaluation of Thiuram containing multicomponent pesticidal preparations that are to be introduced into practical use.

The carcinogenic potential of tetramethylthiuram disulfide (thiram) was examined in F344 rats. Groups of 50 male and 50 female rats were given thiram in their diet at concentrations of 0.1% and 0.05% for 104 weeks. Similar numbers of male and female rats received the basal diet throughout the experiment. All surviving rats were sacrificed at week 112. The rats given the chemical at 0.1% showed reduced body weight gain, especially in females, and liver dysfunction in biochemical examination of blood in males. Histopathologically, however, no significant lesions or tumor induction attributable to the treatment were observed in any tissue except for dose-dependent reduction of spontaneous leukemia in both sexes and slightly reduced incidences of pituitary and thyroid adenomas in females. Under the present experimental conditions, thiram was not carcinogenic in F344 rats.

Embryonal lethality (EL) in rats was examined after administration of the rubber accelerators (RA), captax, altax, santocure, santocure-mor and thiurams D and E. Administration of RA to non-pregnant females caused the increase in the estrous cycle and diminished the rate of conception. The total EL increased after administering all the RA, while the postimplantation one only after altax administration. The index of altax mutagenicity is comparable with those of cancerogens or alkylating agents. Administration of RA to pregnant females leads to the increase in the total EL, with altax being the single agent that produces the rise in all the types of lethality. Inhibition of reproduction function of white rats is a consequence of mutagenic, embryotic and gonadotropic actions of RA, with altax being found the most active agent.

Two experiments were conducted to determine the effect of dietary addition of 30 ppm of thiuram or disulfiram on the development of tibial dyschondroplasia (a large mass of cartilage in the proximal end of the tibia) in chicks in the presence and absence of trace element supplementation: B, Ni, Al, Sr, Br, V, Si, Sn, Cr, F, Mo, Li, Mn, Zn, Fe, Cu and I. In two experiments, the incidence and severity of tibial dyschondroplasia were lower in chicks fed the diet containing the trace element supplement than in those fed the basal diet. Adding thiuram or disulfiram to the diet caused a significantly higher incidence and severity of tibial dyschondroplasia in chicks regardless of the presence or absence of the trace element supplement. In a third experiment not involving thiuram or disulfiram the addition of trace elements had no significant effect on tibial dyschondroplasia. Adding thiuram or disulfiram to the diet in a fourth experiment lowered the absorption of 47Ca from the gastrointestinal tract but did not influence the biological half-life of 47Ca in the chick.

The cytotoxic and mutagenic effects of the fungicides mancozeb and thiram were studied using human peripheral blood lymphocytes cultured in vitro with or without an S-9 mix microsomal metabolizing system. The results obtained suggested that the chemicals caused dose-dependent inhibition of thymidine uptake and unscheduled DNA synthesis on both resting and proliferating lymphocytes in the absence of the S-9 mix. In the presence of the S-9 mix, only thiram showed mutagenic activity by eliciting unscheduled DNA synthesis and a significantly higher frequency of sister chromatid exchanges than did controls.

Simultaneous feeding to rats of thiram with sodium nitrite was carried out to assess the possibility of formation of carcinogenic N-nitroso derivatives in vivo. Following the administration of feed containing 500 ppm thiram plus 2000 ppm sodium nitrite for 104 w, a high incidence of tumors of the nasal cavity was found in both sexes, 18 of 24 males and 15 of 24 females. No nasal-cavity tumors were seen in untreated rats, or those given 500 ppm of thiram or 2000 ppm of sodium nitrite alone. A 20% incidence of papillomas of the forestomach was also seen in the rats of both sexes given the combined treatment. The other significant difference in incidence of tumors between the rats given thiram with or without nitrite was a decreased number of animals with monocytic leukemia, which is a common neoplasm in untreated F344 rats.