Reduced expression of exocytotic proteins caused by anti-cholinesterase pesticides in Brachionus calyciflorus (Rotifera: Monogononta) / Redução da expressão de proteínas de exocitose causados por pesticidas anti-colinesterase em Brachionus calyciflorus (Rotifera: Monogononta)

AbstractThe organophosphate and carbamate pesticides methyl-parathion and carbaryl have a common action mechanism: they inhibit acetylcholinesterase enzyme by blocking the transmission of nerve impulses. However, they can alter the expression of exocytotic membrane proteins (SNARE), by modifying release of neurotransmitters and other substances. This study evaluated the adverse effects of the pesticides methyl-parathion and carbaryl on expression of SNARE proteins: Syntaxin-1, Syntaxin-4 and SNAP-23 in freshwater rotifer Brachionus calyciflorus. Protein expression of these three proteins was analyzed before and after exposure to these two pesticides by Western Blot. The expression of Syntaxin-1, Syntaxin-4 and SNAP-23 proteins in B. calyciflorussignificantly decreases with increasing concentration of either pesticides. This suggests that organophosphates and carbamates have adverse effects on expression of membrane proteins of exocytosis by altering the recognition, docking and fusion of presynaptic and vesicular membranes involved in exocytosis of neurotransmitters. Our results demonstrate that the neurotoxic effect of anticholinesterase pesticides influences the interaction of syntaxins and SNAP-25 and the proper assembly of the SNARE complex.

ResumoOs pesticidas organofosforados e carbamatos metil- paration e carbaril tem um mecanismo de ação comum: eles inibem a enzima acetilcolinesterase, bloqueando a transmissão dos impulsos nervosos. No entanto, eles podem alterar a expressão de proteínas de membrana de exocitose (SNARE), através da modificação da libertação de neurotransmissores e outras substâncias. Este estudo avaliou os efeitos adversos dos pesticidas metil- paration e carbaril sobre a expressão de proteínas SNARE: Sintaxina -1, Sintaxina-4 e SNAP-23 em rotíferos de água doce Brachionus calyciflorus. A expressão destas três proteínas foi analisada antes e depois da exposição a estes dois pesticidas por Western Blot. A expressão das proteínas Sintaxina-1, Sintaxina-4 e SNAP-23 em B. calyciflorus diminui significativamente com o aumento da concentração de ambos os pesticidas. Isto sugere que os organofosfatos e carbamatos têm efeitos adversos sobre a expressão de proteínas de membrana de exocitose, alterando o reconhecimento, de encaixe e fusão de membranas pré-sinápticas e vesiculares envolvidas na exocitose de neurotransmissores. Nossos resultados demonstram que o efeito neurotóxico de pesticidas anticolinesterásicos influencia a interação de sintaxinas e SNAP-25 e a montagem correta do complexo SNARE.

Validation of an electrometric blood cholinesterase measurement in goats

A modified electrometric method was described and validated for measurement of plasma and erythrocyte cholinesterase activities in 6~18 months old goats. The enzymatic reaction mixture contained 3 ml distilled water, 3 ml barbital-phosphate buffer (pH 8.1), 0.2 ml plasma or erythrocytes and 0.1 ml acetylthiocholine iodide (7.5%) as a substrate. The mixture was incubated at 37 degrees C for 40 minutes. The pH of the reaction mixture was determined by a pH meter before and after the incubation. The initial pH was measured before the substrate addition. The enzyme activity was expressed as deltapH/40 min. The coefficients of variation of the described method in measuring plasma and erythrocyte cholinesterase activities were 4 and 2%, respectively. Preliminary reference values (n = 14) of the mean cholinesterase activity (deltapH/40 min) and 95% confidence interval in the plasma were 0.194 and 0.184~ 0.204, respectively, and those of the erythrocytes were 0.416 and 0.396~0.436, respectively. The pseudocholinesterase activity of the plasma cholinesterase was 63.5% as determined by quinidine sulfate inhibition. The organophosphorus insecticides dichlorvos and diazinon at 0.5~4 micrometer and the carbamate insecticide carbaryl at 5~20 micrometer in the reaction mixture significantly inhibited plasma (13.7~85.5%) and erythrocyte (16.4~71.9%) cholinesterases in vitro in a concentration-dependent manner. The results suggest that the described electrometric method is simple, precise and efficient in measuring blood cholinesterase activity in goats.

Study of Serum Cholinesterase levels in fish Clarias batrachus (Linn.) exposed to pesticides carbaryl and phorate.

Study of the Serum Cholinesterase levels (SchE) in the freshwater catfish Clarias batrachus when exposed to sub lethal dose of pesticides phorate and carbamate, was attempted in this paper. SchE levels decreased in the fish exposed to both the pesticides, the depletion being more pronounced with phorate. These results can be due to impairment of nervous system, liver damage as well as myocardial infarction. Similar findings were not only reported in experimental organisms but also found in human beings working in agricultural fields and pesticide manufacturing plants. Hence it is imperative that suitable occupational health and preventive measures need to be undertaken.

Pesticide induced alterations of non-protein nitrogenous constituents in the serum of a fresh water cat fish, Clarias batrachus (Linn.).

A freshwater cat fish was exposed to sublethal concentrations of two pesticides--carbaryl, a carbamate and phorate, an organophosphorus pesticide for 24, 72, 120 and 168 hr. The alterations in the serum profile of non protein nitrogen compounds demonstrated an increase in urea, uric acid and creatinine throughout the experimental period.

Development of cellular slime mould, Dictyostelium discoideum treated with a carbamate pesticide.

Dictyostelium cells when treated with 100 ppm carbaryl or placed on 20 ppm carbaryl agar showed profound changes in the developmental stages. The treated cells showed larger aggregate formations, inhibition of cAMP-chemotaxis and cAMP dependent extracellular phosphodiesterase activity. The fruiting body formations were also scarce. The developing Dictyostelium cells when placed on carbaryl agar showed aberrant morphogenesis with larger aggregates, abnormal slugs and large fruiting bodies. In all cases the development of the treated cells showed considerable delay when compared with controls.

Elevation of C-reactive protein in serum of Channa punctatus as an indicator of water pollution.

Effect of some pollutants like heavy metals, non-metals and pesticides on the circulating level of C-reactive protein (CRP) which is an acute phase plasma protein was studied in a freshwater murrel C. punctatus. Fish was exposed to nonlethal doses of these xenobiotics which were apparently safe. But the level of CRP detected by sensitive single radial immunodiffusion (SRID) technique showed that within 12 hr of exposure the nonlethal doses of xenobiotics could initiate the acute phase response in terms of elevated CRP titre. Heavy metals caused the acute phase within 24 hr, nonmetals and Metacid-50 within 48 hr exposure. The carbamate compound, carbaryl demonstrated a biphasic response to CRP level which may be correlated with the reversible type of anticholinesterase property of this compound while Metacid-50 is an irreversible type of anticholinesterase agent. The assessment of the CRP level in the serum of fish may be utilized as a primary bioindicator of a contaminated environment toxic enough to mount an acute phase response.

Effects of carbamates on the hemodynamic parameterns of rats treated or not with (alpha) - Pyridylaldoxime methylsulfomethylate (P2S)

O objetivo da presente investigaçäo foi determinar os efeitos de doses tóxicas de agentes anticolinesterasicos carbamatos, fisostigmina e carbaril, na pressäo arterial e freqüência cardíaca de ratos, bem como a açäo protetora do reativador de colinesterase, a pralidoxima, contra estes efeitos. A acetilcolina injetada intravenosamente, em ratos, causou uma imediata queda dose-dependente na Pressäo Arterial Média (PAM), seguida por um aumento na PAM que apresentava duraçäo maior que a queda. Houve também uma queda na Freqüência Cardíaca (F.C). Injeçäo intravenosa de carbaril em rato normal causou uma queda na PAM dentro de 5 segundos, seguida pelo aumento significante na mesma em relaçäo ao valor do controle, 5 minutos após a injeçäo Carbaril näo provocou nenhum efeito na F.C. Quando o carbaril foi precedido pela injeçäo de pralidoxima, as alteraçöes na PAM foram similares àquelas observadas após a injeçäo de carbaril isoladamente, porém a F.C. diminuiu de maneira significante nos grupos que receberam doses maiores. Fisostigma injetada intravenosamente em ratos normais näo apresentou efeito imediato (5 segundos) na PAM, porém ocorreu um aumento significante na PAM 5 minutos após a injeçäo. Nenhuma alteraçäo significante ocorreu na F.C. Em animais previamente tratados com pralicoxima, a fisostigmina causou uma queda imediata na PAM que foi seguida por um aumento significante em relaçäo ao controle, 5 minutos após a injeçäo. Uma queda na F.C. também ocorreu. Administraçäo prévia de pralitoxima potenciou os efeitos cardiovasculares causados pela fisostigmina, porém näo os efeitos do carbaril.

Behavioral and biochemical changes following reapeted administration of carbaryl to aging rats

Motor, sensory and thermoregulatoty function were examined in aging rats (12 months) following two schedules of repated po adminstration of the carbamate insecticide carbaryl and these effects were assessed in terms of blood cholinesterase activity. Administration of carbaryl (50 mg/Kg) by gavage daily for 30 days resulted in a resultad in a reduction of locomotor activity in thre open-field and an inhibition of cholinesterase activity within 30 min after the last treatment. Twenty-for h later, only the locomotor effect was evident. After 90 days of exposure to carbaryl in drinking water, no significant effects were observed. These findings suggest that repeated administration of carbaril to aging rats can induce an impairment of motor function and a reduction of cholinesterase activity, while tolerance develops in some other parameters

Toxicological studies of four insecticides against Musca domestica L.

Toxicological studies of four insecticides (malathion, carbaryl, bioresmethrin, and GH 74) against Musca domestica vicinia (Ampang strain) were undertaken with particular reference to age, sex and posttreatment temperature. It was found that bioresmethrin and GH 74, both with a negative temperature coefficient, have great potential for use against houseflies. In vitro inhibitory studies of head and body esterases showed that unlike malathion and carbaryl, bioresmethrin had only negligible effect on these enzymes. The possibilities of using bioresmethrin and GH 74 for controlling the housefly problem in the Cameron Highlands, West Malaysia are discussed.