Sister-chromatid exchanges and thioguanine resistance in V79 Chinese hamster cells after treatment with the aneuploidy-inducing agent carbaryl +/- S9 mix

Carbaryl induced sister-chromatid exchanges (SCEs) but no thioguanine resistance in V79 Chinese hamster cells. Addition of S9 from Aroclor-pretreated rats, or glutathione, reduced the toxic effects of carbaryl. Glutathione or S9 mix reduced the effect of carbaryl on SCE. However, the latter result indicates that carbaryl's effect may be enhanced at a certain compound/S9 ratio. Since treatment with microsomes alone, but not S9 mix, was clastogenic it cannot be excluded that this enhancement of SCE was due to perturbations in the S9 mix by carbaryl rather than to formation of some particular SCE-inducing metabolite from the compound. The effects of carbaryl on chromosomes and chromosomal distribution are comparable to those sometimes reported for TPA. This, in conjunction with the weak indications on carcinogenic activity of carbaryl, makes it of interest that the compound be tested for promotion or co-carcinogenicity in vivo.     

Synergism of toxicity of N,N-diethyl-m-toluamide to German cockroaches (Orthoptera: Blattellidae) by hydrolytic enzyme inhibitors

Various compounds were tested for effects on the toxicity of the insect repellent N, N-diethyl-m-toluamide (DEET) in German cockroaches, Blattella germanica (L.). Organophosphate and carbamate acetylcholinesterase inhibitors carbaryl, DEF, eserine (physostigmine, malathion and pyridostigmine bromide synergized DEET toxicity also synergized the toxicity of the formamidine pesticides. Amitraz and chlordimeform. Results suggest that DEET may have some toxic actions that are similar to those of formamidine pesticides. DEET synergized the toxicity of some acetylcholinesterase inhibitors but not others. Results further suggest that some mechanism other than acetylcholinesterase inhibition was responsible for the toxic interactions observed between DEET and the acetylcholinesterase inhibitors.     

Comparative susceptibility of western corn rootworm (Coleoptera: Chrysomelidae) adults to selected insecticides in Kansas

Susceptibility of adult populations of the western corn rootworm, Diabrotica virgifera virgifera LeConte, to several insecticides was evaluated in seven Kansas counties, including Dickinson, Ford, Finney, Pottawatomie, Republic, Riley, and Stevens, between 1996 and 2002. All populations surveyed were highly susceptible to methyl parathion with the largest difference in susceptibility of only three-fold based on 16 complete bioassays for the populations from six counties over a 5-yr period. Noticeable decreases in carbaryl susceptibility were found in populations collected from Republic County between 1997 and 2001 when the cucurbitacin-carbaryl-based bait SLAM was widely used as an areawide management approach for adult corn rootworm control. However, the lowered carbaryl susceptibility returned to previous levels 1 yr after the use of SLAM was halted in the managed (treated) cornfields. This change implies possible dispersal of insects into the relatively small managed area from surrounding untreated cornfields and / or some fitness cost associated with carbaryl resistance within the population. Relative susceptibility of western corn rootworm adults also was evaluated for seven commonly used insecticides, including bifenthrin, carbaryl, chlorpyrifos, cypermethrin, fipronil, malathion, and methyl parathion. They were tested with corn rootworm adults collected from a single cornfield. Methyl parathion and bifenthrin were highly toxic to corn rootworm adults, and cypermethrin, chlorpyrifos, carbaryl, and malathion were only slightly less toxic. Although fipronil was highly toxic to adult rootworms, its activity was much slower than that of other insecticides. Thus, bifenthrin and methyl parathion were among the most effective in killing corn rootworm adults.     

Carbaryl-induced behavioural and reproductive abnormalities in the earthworm Metaphire posthuma: a sensitive model

Carbaryl, an N-methyl carbamate insecticide, is used in India to control foliar insects, but, due to soil contamination, it also adversely affects non-target organisms such as earthworms. This paper deals with the toxic effects of carbaryl on the behavioural and reproductive profiles of the earthworm, Metaphire posthuma. Locomotion and geotaxis were significantly affected, even after a 20-minute exposure to 0.125ppm carbaryl. The hatching of cocoons was altered at 0.5ppm, whereas cocoon production was retarded even at 0.125ppm carbaryl. No cocoon production was observed at 2.0ppm carbaryl. Sperm head abnormalities were reported even at the lowest test concentration of 0.125ppm. Wavy head abnormalities were observed at 0.125ppm carbaryl, whereas at 0.25ppm and 0.5ppm, the sperm heads became amorphous and the head nucleus was turned into granules deposited within the wavy head. It is concluded that the earthworm could be used as an ecosystem model for the initial toxicity testing of environmental pollutants.     

Comparative susceptibility of sweetpotato weevil (Coleoptera: Brentidae) to selected insecticides

The response of sweetpotato weevil, Cylas formicarius (F.) (Coleoptera: Brentidae), to insecticides used for its control was tested in laboratory bioassays. A glass vial bioassay technique was used to determine the susceptibility of two cohorts of sweetpotato weevil to selected insecticides. Vials were treated with methyl parathion, bifenthrin, cyfluthrin, carbaryl, and phosmet. Sweetpotato weevils demonstrated a mortality response to increasing concentrations of all insecticides tested, and our results indicated decreases in susceptibility of the Louisiana cohort of sweetpotato weevil compared with the Texas cohort for all insecticides tested. Methyl parathion was the most toxic chemical tested for both cohorts, followed by the pyrethroids, cyfluthrin and bifenthrin. Phosmet exhibited moderate toxicity compared with other chemicals tested, whereas sweetpotato weevils were least susceptible to carbaryl. Significant differences in lethal concentration (LC)50 and LC90 values for cyfluthrin and bifenthrin, the LC50 values for methyl parathion and phosmet, and the LC90 values for carbaryl were observed between the two cohorts. This study documents baseline toxicological data for five insecticides in two populations of sweetpotato weevil and demonstrates that susceptibility to all insecticides tested is lower for the Louisiana population compared with the Texas population.     

Toxicity of carbaryl and 1-naphthol to four species of freshwater fish

The toxicity of the carbamate insecticide carbaryl (Seven√) and its metabolite, 1-naphthol, to four species of fish was studied. The calculated 96 h LC 60 values of carbaryl forCatla catla (Ham.), Anabas testudineus (Bloch),Mystus cavasius (Ham.) andMystus vittatus (Bloch) are 6.4, 6.6, 4.6 and 2.4 ppm respectively and that of 1-naphthol are 4.3,3, 0.33 and 1.1 ppm respectively. The degradation product of the insecticide was found to be more toxic than the parent compound, to all the four species studied.     

Susceptibility of laboratory-reared northern fowl mites,Ornithonyssus sylviarum (Acari: Macronyssidae), to selected acaricides

Toxicity was determined for 15 acaricides against a laboratory strain of northern fowl mites,Ornithonyssus sylviarum (Canestrini and Fanzago). Adult females were exposed to residues on filter paper for 24 h. Three organophosphorous compounds (monocrotophos, cythioate, and famphur) were more toxic to the northern fowl mite than was carbaryl, the most commonly used pesticide in the poultry industry. The other tested compounds were less toxic to the mite than was carbaryl. Four of these, not used previously for northern fowl mite control, had low LC₅₀'s for northern fowl mites: aldicarb (0.46); pirimiphos-methyl (0.73); exo, exo-2,8-dichloro-4-thiatricyclo [3.2.1.0^3.6]octane-4-oxide (AI3-63182) (0.87); and diazinon (2.48).This article reports the results of research only. Mention of a pesticide or proprietary product does not constitute an endorsement or a recommendation of its use by U.S.D.A.     

Different susceptibility of two aquatic vertebrates (Oncorhynchus mykiss and Bufo arenarum) to azinphos methyl and carbaryl

We studied the effect of two insecticides azinphos methyl and carbaryl on two resident aquatic species (Oncorhynchus mykiss and Bufo arenarum). Juvenile trout and larval stages of toad were used for exposure and recovery assays. O. mykiss was more sensitive to azinphos methyl exposure than B. arenarum larvae, with a mean 96-h LC50 of 0.007 mg/l. Carbaryl is markedly less toxic than the organophosphate and the differences in potency, expressed as LC50, for both species varies only by five-fold. The relationship between cholinesterase (ChE) inhibition and lethality is not straightforward: O. mykiss survives with an almost complete inhibition of the brain enzyme when exposed to azinphos methyl and carbaryl. Their IC50 values are one or two orders of magnitude lower than the corresponding 96-h LC50 value. In B. arenarum larvae, the IC50 values for azinphos methyl and carbaryl are one half and one third of their 96-h LC50s, respectively. The time courses of enzyme inhibition and recovery also points out differences between both types of pesticides and species. Identifying the key features conferring species selectivity can be exploited to minimize the incidence and severity of intoxication of non-target organism. The data presented here highlight the necessity of including several species and endpoint analyses in the pesticide risk evaluations of aquatic ecosystems.     

Relationship between the phagocytic inhibition of the rat reticuloendothelial system and the anticholinesterasic effect of an insecticide, Carbaryl (author's transl)]

Phagocytic activity of the reticuloendothelial system (RES) and blood cholinesterase activity were determined in male rats after veinous administrations of carbaryl and 1-naphthol, a carbaryl metabolite. The various parameters were measured 1, 24, 48 and 72 hours after administration of the following four doses per 100 g body weight : 1.875, 3.75, 7.5 and 15 mumol. 1. Results showed an inhibition of the RES phagocytic activity (clearance of colloidal carbon) after carbaryl administration; although 1.875 mumol/100 g had no effect, the other doses inhibited RES activity, blockade time being a function of the dose given. The phagocytic function had returned to normal 72 hr after carbaryl administration. 2. Reductions in spleen weight and protein content were observed together with the RES blockade. 3. At all four doses, the anticholinesterase effect was already apparent one hour after carbaryl administration. 4. 1-naphthol, one of carbaryl's chief metabolites, had no effect either on the RES or on the different parameters studied. These results show a relationship between the phagocytic inhibition of the reticuloendothelial system and the anticholinesterasic effect by carbaryl. They suggest an inhibition of some esterases of macrophages interfering with the phagocytosis.     

Spindle disturbances in mammalian cells. II. Induction of viable aneuploid/polyploid cells and multiple chromatid exchanges after treatment of V79 Chinese hamster cells with carbaryl. Modifying effects of glutathione and S9

Treatment of V79 cells with carbaryl increased the frequency of cells with elevated chromosome numbers (greater than 22). This effect of carbaryl was inhibited by simultaneous addition of glutathione or S9. Although selective forces seemed to act against cells with increased chromosome numbers, such cells were still significantly more frequent in treated compared with control cultures 74 h after treatment. In addition, a high adaptive value for these remaining aneuploid/polyploid cells was indicated because they were able to go through 2 successive rounds of replication immediately before fixation to the same extent as cells with chromosome numbers considered normal (21/22) for this cell line. Multiple chromatid exchanges were also observed after carbaryl treatment. The lack of single exchange events indicates that the effect may be systemic. However, additional experiments are required before this hypothesis can be confirmed or discarded. Considering the results obtained and the possible importance of gene dosage for tumor promotion, it is suggested that carbaryl should be tested for tumor promotion in vivo.     

Laboratory studies to elucidate the residual toxicity of eight insecticides to Anystis baccarum (Acari: Anystidae)

Anystis baccarum (L.) [=Anystis agilis (Banks)] (Acari: Anystidae) is a common predatory mite recently identified in apple (Malus spp.) orchards and in vineyards (Vitus spp.) in Québec, Canada. Studies of its susceptibility to pesticides used in these crops need to be carried out to encourage integrated pest management programs. A laboratory evaluation of methoxyfenozide, acetamiprid, thiamethoxam, imidacloprid, spinosad, phosmet, carbaryl, and lambda-cyhalothrin showed that residues of lambda-cyhalothrin, phosmet, and carbaryl were highly toxic in 48-h petri dish bioassays. The field rate of lambda-cyhalothrin is 0.0184 g (AI) /liter, which is 26-fold the estimated LC50 of 0.0007 g (AI) /liter) for this predator. The field rate for phosmet is 0.6000 g (AI) /liter, which is 118-fold the LC50 for phosmet, which is 0.0051 g (AI) /liter), and the field rate for carbaryl is 1.960 g (AI) /liter, which is 784-fold the estimated LC50 of 0.0025 g (AI) /liter). Five other insecticides, methoxyfenozide, acetamiprid, thiamethoxam, imidacloprid, and spinosad, were evaluated and found to be nontoxic.     

Spindle disturbances in mammalian cells II. Induction of viable aneuploid/polyploid cells and multiple chromatid exchanges after treatment of V79 Chinese hamster cells with carbaryl modifying effects of glutathione and S9

Treatment of V79 cells with carbaryl increased the frequency of cells with elevated chromosome numbers (> 22). This effect of carbaryl was inhibited by simultaneous addition of glutathione or S9. Although selective forces seemed to act against cells with increased chromosome numbers, such cells were still significantly more frequent in treated compared with control cultures 74 h after treatment. In addition, a high adaptive value for these remaining aneuploid/polyploid cells was indicated because they were able to go through 2 successive rounds of replication immediately before fixation to the same extent as cells with chromosome numbers considered normal (21/22) for this cell line.Multiple chromatid exchanges were also observed after carbaryl treatment. The lack of single exchange events indicates that the effect may be systemic. However, additional experiments are required before this hypothesis can be confirmed or discarded. Considering the results obtained and the possible importance of gene dosage for tumor promotion, it is suggested that carbaryl should be tested for tumor promotion in vivo.     

Toxicity assessment of insecticides commonly used in rice pest management to the fry of common carp, Cyprinus carpio, a food fish culturable in rice fields

Toxicity of four insecticides commonly used in rice pest management, chlorpyrifos, dimethoate, carbaryl and carbosulfan, to the fry of common carp was assessed through median lethal concentrations (LC₅₀) and in vivo inhibition of the brain acetylcholinesterase (AChE) enzyme at sublethal concentrations. The 96‐h LC₅₀ values for these four insecticides were determined to be 0.008, 26.11, 7.85 and 0.60 mg L^?1 respectively. Exposure of fish to a series of sublethal concentrations (0.5–5% LC₅₀) of each insecticide for 14 days resulted in concentration‐dependent inhibition in AChE activity in comparison with the controls. AChE activity was greatly inhibited in the fish exposed to sublethal concentrations of chlorpyrifos. Upon transfer to insecticide‐free water, AChE activities in fry exposed to 0.5 and 1% LC₅₀ concentrations of carbaryl and carbosulfan were restored to the control level within 7–21 days whereas the fish exposed to chlorpyrifos or dimethoate did not fully recover from the insecticide‐induced anticholinesterase action. Of the four insecticides tested, chlorpyrifos was the most toxic for the fry of common carp. Although dimethoate was least toxic for the fish under acute exposure, the restoration level of normal AChE activity was slower under chronic exposure in comparison with carbaryl and carbosulfan. Hence, the use of carbamates, especially carbaryl, to control insect pests of rice in rice‐cum‐carp culture systems is recommended when considering survival, restoration of the normal AChE activity and stamina of the cultured fish.     

Growth and development of larval green frogs (Rana clamitans) exposed to multiple doses of an insecticide

Our objective was to determine how green frogs (Rana clamitans) are affected by multiple exposures to a sublethal level of the carbamate insecticide, carbaryl, in outdoor ponds. Tadpoles were added to 1,000-l ponds at a low or high density which were exposed to carbaryl 0, 1, 2, or 3 times. Length of the larval period, mass, developmental stage, tadpole survival, and proportion metamorphosed were used to determine treatment effects. The frequency of dosing affected the proportion of green frogs that reached metamorphosis and the developmental stage of tadpoles. Generally, exposure to carbaryl increased rates of metamorphosis and development. The effect of the frequency of carbaryl exposure on development varied with the density treatment; the majority of metamorphs and the most developed tadpoles came from high-density ponds exposed to carbaryl 3 times. This interaction suggests that exposure to carbaryl later in the larval period stimulated metamorphosis, directly or indirectly, under high-density conditions. Our study indicates that exposure to a contaminant can lead to early initiation of metamorphosis and that natural biotic factors can mediate the effects of a contaminant in the environment.     

Interactions of carbaryl with estuarine bacterial communities

The addition of carbaryl (100g/ml) to a model estuarine ecosystem did not affect the number of bacteria in the sediment, but reduced the diversity (as measured by the rarefaction technique) of the microbial community as compared with a control model ecosystem. Two carbaryltolerant strains of bacteria were isolated from the carbaryl-treated system, but none were isolated from the control system. Bacterial growth and filter paper decomposition in mixed cultures was prevented by 100g/ml carbaryl, but this amount had no effect on the extracellular cellulase of an estuarine isolate. Increasing the amount of organic matter in the medium attenuated the toxicity of carbaryl to pure cultures of an estuarine isolate. The addition of 1, 10, or 100g/ml carbaryl to field plots had no effect on bacterial numbers, diversity, or filter paper decomposition. The amount of carbaryl in sediments exposed to 100g/ml fell below the limit of detection by thin-layer chromatography within 12 hours. In sterile and nonsterile model systems, carbaryl rapidly adsorbed to sediment, and hydrolyzed to 1-naphthol in both sediment and water. Although carbaryl may be toxic to bacteria under some conditions, the amounts that might enter and persist in an estuary are insufficient to have a significant impact on the sediment microbial community.     

Rainfastness and residual activity of insecticides to control Japanese beetle (Coleoptera: scarabaeidae) in Grapes

Field-based bioassays and residue profile analysis were used to determine the relative toxicity, rainfastness, and field degradation over time of five insecticides from five insecticide classes on adult Japanese beetles, Popillia japonica Newman (Coleoptera: Scarabaeidae), in grapes, Vitis labrusca L. Bioassays assessed Japanese beetle condition as alive, knockdown, or immobile when exposed for 24 h or 7-d field-aged residues of phosmet, carbaryl, bifenthrin, thiamethoxam, or indoxacarb after 0, 12.7, or 25.4 mm of rain had been simulated. We found that the two most toxic insecticides to Japanese beetle were phosmet and carbaryl, followed by bifenthrin, thiamethoxam, and then indoxacarb. The efficacy of phosmet decreased because of rainfall, but not because of field aging. The efficacy of carbaryl decreased because of rainfall and field aging. The efficacies of bifenthrin and thiamethoxam were not affected by rainfall but decreased because of field aging. The efficacy of indoxacarb was not affected by rainfall or field aging. This study will help vineyard managers make informed decisions on when reapplications of insecticides are needed with the aim of improving integrated pest management programs.     

Muscular and brain cholinesterase sensitivities to azinphos methyl and carbaryl in the juvenile rainbow trout Oncorhynchus mykiss

The organophosphate azinphos methyl (AzMe) and the carbamate carbaryl are the insecticides mostly used in the irrigated valley of Río Negro and Neuquén, Patagonia, Argentina. Juvenile rainbow trout were exposed to AzMe and carbaryl and the sensitivity of skeletal muscular cholinesterase (ChE) and the time course of inhibition and recovery were evaluated. EC50 values demonstrated that AzMe was a stronger in vivo inhibitor of muscular ChE (1.05+/-0.23 microg/L) than carbaryl (270+/-62.23 microg/L). Muscular ChE was significantly less sensitive to both insecticides than brain ChE. EC50 values obtained for muscular ChE were closer than those for brain ChE to the respective pesticide lethal concentrations, pointing out the relevance of the muscular enzyme in determining acute toxicity. The recovery process of ChE activity after carbaryl exposure (500 microg/L) was fast, whereas no significant recovery was observed with AzMe (1 microg/L) after 21 days in uncontaminated media. Brain and muscular ChE were inhibited and showed a significant but not complete recovery after three consecutive 48-h exposures to AzMe (1 microg/L) followed by a recovery period of 7 days. This scheme mimics the periodical application of the insecticides in the region and suggests a certain probability of a sustained ChE inhibition under field conditions, affecting fish development and survival.     

Changes in vulnerability of Daphnia to an insecticide application depending on the population phase

1. Laboratory populations of cloned Daphnia pulex at three population phases (growing phase, density peak, declining phase) were exposed to the insecticide carbaryl at 15 μg L^?1, which killed juveniles but not adults. 2. The population decline was largest and recovery was slowest when the chemical was applied at the density peak, indicating that the population was most sensitive to the chemical at that stage. Populations in the declining phase were least affected by the treatment. 3. We propose that food condition, which varies with population density, was a major factor affecting vulnerability to carbaryl. In that case, Daphnia populations in lakes would be most vulnerable to toxic chemicals during food‐limited condition such as the spring clear‐water phase.     

Experimental studies on reproductive toxicologic effects of lamotrigine in mice

BACKGROUND: Virtually all antiepileptic drugs (AED) tested so far have been found to be teratogenic. The second generation AED possess a number of therapeutic advantages over the older ones. There are, however, very little data on their effects on embryonic development. A recent report suggests that lamotrigine (LTG) can be teratogenic to human fetuses. With only a few cases of prenatal exposure to LTG in the record, however, it has not been possible to establish a recognizable pattern of malformations in the infants of LTG‐treated mothers. OBJECTIVES: The objectives of the present study were to evaluate the reproductive toxic effects of LTG RESULTS: Single (50–200 mg/kg) or multiple doses (25, 50, 75 mg/kg) of LTG were administered by intraperitoneal (i.p.) injection (note that the therapeutic administration is oral) to groups of TO mice on gestation day (GD) 7 or 8. Fetuses were collected on GD 18. Maternal toxic effects including a dose‐related mortality, a high incidence of abortion, embryo lethality, congenital malformations and intrauterine growth retardation (IUGR) were observed in the LTG‐treated group. Administration of LTG in multiple low doses resulted in a better maternal survival and increased incidence of embryonic resorption and malformations with increasing dose; IUGR was significant but not dose‐dependent. The malformations characteristic of the LTG multiple low dose group fetuses included maxillary‐mandibular hypoplasia, exencephaly, cleft palate, median facial cleft, urogenital anomalies and varying degrees of caudal regression. Skeletal malformations and developmental delay of the skeleton were observed both in single and multiple dose groups. CONCLUSIONS: The results of this study indicate that LTG administered i.p. at high doses can induce intrauterine growth retardation and at low multiple doses causes a dose‐dependent increase in embryonic resorption, craniofacial and caudal malformations as well as maternal toxicity in the mouse. Previous studies in other laboratories have used oral route of exposure and concluded that there are no teratogenic effects of LTG at dose levels that are not maternally toxic. Birth Defects Res B 68:428–438, 2003. © 2003 Wiley‐Liss, Inc.     

Toxicity of Piperonyl Butoxide — Carbaryl Synergism on the Snail Lymnaea acuminata

Effects of piperonyl butoxide and carbaryl synergism were studied on the metabolism of the snail Lymnaea acuminata. Snails were exposed to 40 % and 80 % of the 48 h LC₅₀ of carbaryl or carbaryl + piperonyl butoxide mixture (1:5). The amount of carbaryl present in the LC₅₀ mixture was only 0.23 % of the LC₅₀ of carbaryl alone. The treatments caused a dose-dependent decrease in glycogen and protein levels and acetylcholinesterase (AChE) and alkaline phosphatase activity; simultaneously, there was an increase in levels of lactic acid, reducing sugars and amino acid and the activity of acid phosphatase. Significant differences in AChE and phosphatase activity were also observed between the effects of equivalent concentrations of carbaryl and carbaryl-synergist.