Involvement of two plasmids in the degradation of carbaryl by Arthrobacter sp. strain RC100. (1/48)

A bacterium capable of utilizing carbaryl (1-naphthyl N-methylcarbamate) as the sole carbon source was isolated from carbaryl-treated soil. This bacterium was characterized taxonomically as Arthrobacter and was designated strain RC100. RC100 hydrolyzes the N-methylcarbamate linkage to 1-naphthol, which was further metabolized via salicylate and gentisate. Strain RC100 harbored three plasmids (designated pRC1, pRC2, and pRC3). Mutants unable to degrade carbaryl arose at a high frequency after treating the culture with mitomycin C. All carbaryl-hydrolysis-deficient mutants (Cah-) lacked pRC1, and all 1-naphthol-utilization-deficient mutants (Nat-) lacked pRC2. The plasmid-free strain RC107 grew on gentisate as a carbon source. These two plasmids could be transferred to Cah- mutants or Nat- mutants by conjugation, resulting in the restoration of the Cah and Nah phenotypes.  (+info)

Mitotic aberrations induced by carbaryl reflect tyrosine kinase inhibition with coincident up-regulation of serine/threonine protein phosphatase activity: implications for coordination of karyokinesis and cytokinesis. (2/48)

The insecticide carbaryl and its metabolite 1-naphthol cause partial uncoupling of karyokinesis and cytokinesis in V79 Chinese hamster fibroblasts; karyokinesis is blocked in metaphase, the microtubules of the spindle depolymerize and the chromosomes and spindle remnants become displaced to the periphery of the cell. A high frequency of these disturbed cells elongate and a smaller fraction initiate a cleavage furrow. Here, we attempt to determine the potential targets for carbaryl and 1-naphthol in cytokinesis-specific signalling, led by the fact that the potential protein phosphatase inhibitor 1-naphthyl phosphate was previously identified in treated cells. We found that the typical cytological pattern induced by carbaryl and 1-naphthol could be obtained with tyrphostins, specific tyrosine kinase inhibitors, indicating that the carbaryl-induced effects could be due to tyrosine kinase inhibition. This was confirmed by tyrosine kinase assays showing that carbaryl, 1-naphthol and 2-naphthol were equally efficient at inhibiting tyrosine kinase activity as tyrphostin B44(-). As tyrosine kinases can act as regulatory factors in determining dephosphorylation rates, the activities of type-1 (PP1) and type-2A (PP2A) serine/threonine protein phosphatases were also determined. There was a clear up-regulation of the overall PP1/PP2A activities in cells treated with carbaryl, 1-naphthol or tyrphostin B44(-). This stimulation was shown to be indirect because these compounds had no effect on the activity of purified human PP1 in the test tube. 2-Naphthol, which has been found to be less efficient with regard to displacement of chromatin, did not cause up-regulation, but a significant decrease in PP1/PP2A activity. We suggest that a net decrease in tyrosine kinase activity in combination with a net increase in PP1/PP2A activity is a precondition for cell elongation and cytokinesis in mammalian cells and that the corresponding enzymes are targets in the network of activities serving to coordinate karyokinesis and cytokinesis.  (+info)

Predator-induced stress makes the pesticide carbaryl more deadly to gray treefrog tadpoles (Hyla versicolor). (3/48)

Global declines in amphibians likely have multiple causes, including widespread pesticide use. Our knowledge of pesticide effects on amphibians is largely limited to short-term (4-d) toxicity tests conducted under highly artificial conditions to determine lethal concentrations (LC50). We found that if we used slightly longer exposure times (10-16 d), low concentrations of the pesticide carbaryl (3-4% of LC50(4-d)) killed 10-60% of gray treefrog (Hyla versicolor) tadpoles. If predatory cues also were present, the pesticide became 2-4 times more lethal, killing 60-98% of tadpoles. Thus, under more realistic conditions of increased exposure times and predatory stress, current application rates for carbaryl can potentially devastate gray treefrog populations. Further, because predator-induced stress is ubiquitous in animals and carbaryl's mode of action is common to many pesticides, these negative impacts may be widespread in nature.  (+info)

Dermal absorption and distribution of (14)C carbaryl in Wistar rats. (4/48)

The level of (14)C carbaryl was determined in blood (leukocytes, erythrocytes, all blood cells, plasma) and organs (brain, heart, lungs, liver, spleen, skin at the site of exposure) of male Wistar rats after dermal administration. The application liquid was (14)C carbaryl solution in 96% ethyl alcohol. This preparation, possessing an activity of 670 kBq/ml, containing 1.67 mg of carbaryl, was applied to the skin of the tail according to Massmann's method in own modification. The amount of the preparation per 1 cm(2) of the tail skin was 0.19 mg of carbaryl (74.4 kBq). The tails of experimental rats were exposed to (14)C carbaryl by soaking for 4 h daily: once, twice or three times. Beta radiation from (14)C was measured in homogenized organs (brain, heart, lungs, liver, skin) and in blood by computer controlled Wallac scintillation counter Model 1409, using Multi Calc software. The dermal absorption of carbaryl at the site of exposure and in the surrounding area of about 2 cm was observed already during 4 hour exposure. Carbaryl reached plasma within 4 h of a single dermal exposure and penetrated into leukocytes, erythrocytes, heart, liver, lung, kidney and brain. The largest amount of (14)C carbaryl, about 2% of absorbed dose, was detected in liver  (+info)

Histological and ultrastructural studies of rats exposed to carbaryl. (5/48)

The aim of the study was to assess the general toxic effects of dermally applied carbaryl, based on histological and ultrastructural examinations of internal organs and to relate these effects to earlier own studies where 14C carbaryl was used for determining the pesticide penetration. The pesticide was applied in doses of 1/5 and 1/10 LD50, administered to the tail skin of male Wistar rats 4 hours daily, for 4 weeks except Saturdays and Sundays. After the experiment, the animals were anaesthetized and the following organs were taken for histological study: brain, lung, heart, liver, kidney, skin from the site of exposure and skin from a place at least 2 cm distant from the exposure site. Lung, liver, kidney, heart and skin were used for ultrastructural studies. Dermal application of carbaryl resulted only in slight histological changes in skin, liver, brain and lung. Even in brain and liver, where large amounts of 14C carbaryl, compared to other organs (lung, kidney, heart), where the intensity of histologic changes was earlier stated to below. Ultrastructural changes were observed in skin, liver, lung, heart and kidney.  (+info)

Nucleotide sequence and genetic structure of a novel carbaryl hydrolase gene (cehA) from Rhizobium sp. strain AC100. (6/48)

Rhizobium sp. strain AC100, which is capable of degrading carbaryl (1-naphthyl-N-methylcarbamate), was isolated from soil treated with carbaryl. This bacterium hydrolyzed carbaryl to 1-naphthol and methylamine. Carbaryl hydrolase from the strain was purified to homogeneity, and its N-terminal sequence, molecular mass (82 kDa), and enzymatic properties were determined. The purified enzyme hydrolyzed 1-naphthyl acetate and 4-nitrophenyl acetate indicating that the enzyme is an esterase. We then cloned the carbaryl hydrolase gene (cehA) from the plasmid DNA of the strain and determined the nucleotide sequence of the 10-kb region containing cehA. No homologous sequences were found by a database homology search using the nucleotide and deduced amino acid sequences of the cehA gene. Six open reading frames including the cehA gene were found in the 10-kb region, and sequencing analysis shows that the cehA gene is flanked by two copies of insertion sequence-like sequence, suggesting that it makes part of a composite transposon.  (+info)

The use of the radioisotope method in studies of pesticide penetration into the eyeball. (7/48)

The studies concerning the effects of pesticides on the human body focused mainly on their local action or chronic poisoning of the organism. In this study we examine the pesticide penetration into the eyeball resulting from direct contact with the eye. We used an isotope-labelled carbamate pesticide -- carbaryl. The determinations of the amount and concentration of this substance in the cornea, aqueous humour, vitreous humour and retina were performed using the method measuring beta radiation emitted by radioactive carbon. The results revealed measurable concentrations of labelled carbamate in the cornea and aqueous humour 10 and 30 min after application. The levels of this pesticide in the vitreous humour and retina were very low and difficult to analyse statistically. The described method appears to be useful in determining the range and rate of eye penetration by environmental toxins having direct contact with the eyeball.  (+info)

Urinary levels of insecticide metabolites and DNA damage in human sperm. (8/48)

BACKGROUND: Members of the general population are exposed to non-persistent insecticides at low levels. The present study explored whether environmental exposures to carbaryl and chlorpyrifos are associated with DNA damage in human sperm. METHODS: Subjects (n=260) were recruited through a Massachusetts infertility clinic. Individual exposures were measured as spot urinary metabolite concentrations of chlorpyrifos [3,5,6-trichloro-2-pyridinol (TCPY)] and carbaryl [1-naphthol (1N)], adjusted using specific gravity. Sperm DNA integrity was assessed by neutral comet assay and reported as comet extent, percentage DNA in comet tail (Tail%) and tail distributed moment (TDM). RESULTS: A statistically significant increase in Tail% was found for an interquartile range (IQR) increase in both 1N [coefficient=4.1; 95% confidence interval (CI) 1.9-6.3] and TCPY (2.8; 0.9-4.6), while a decrease in TDM was associated with IQR changes in 1N (-2.2; -4.9 to 0.5) and TCPY (-2.5; -4.7 to -0.2). A negative correlation between Tail% and TDM was present only when stratified by comet extent, suggesting that Tail% and TDM may measure different types of DNA damage within comet extent strata. CONCLUSIONS: Environmental exposure to carbaryl and chlorpyrifos may be associated with increased DNA damage in human sperm, as indicated by a change in comet assay parameters.  (+info)

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