Comparative examination on synergistic toxicities of chlorpyrifos, acephate, or tetraconazole mixed with pyrethroid insecticides to honey bees (Apis mellifera L.).

Potential synergistic toxicity of pesticide mixtures has increasingly become a concern to the health of crop pollinators. The toxicities of individual and mixture of chlorpyrifos (CHL), acephate (ACE), or tetraconazole (TET) with nine pyrethroid insecticides to honey bees (Apis mellifera L.) were evaluated to reveal any aggregated interaction between pesticides. Results from feeding toxicity tests of individual pesticides indicated that organophosphate insecticides CHL and ACE had higher toxicities to honey bees compared to nine pyrethroids. Moreover, different pyrethroids exhibited considerable variation in toxicity with LC50 values ranging from 10.05 (8.60-11.69) to 1125 (922.4-1442) mg a.i. L-1 after exposure for 7 days. Among the 12 examined pesticides, a relatively low toxicity to A. mellifera was detected from the fungicide TET. All the binary mixtures of ACE or TET in combination with pyrethroids exhibited synergistic effects. However, TET in combination with pyrethroids showed greater synergistic toxicity to A. mellifera than ACE in combination with pyrethroids. Approximately 50% binary mixtures of CHL in combination with pyrethroids also showed synergistic responses in honey bees. In particular, CHL, ACE, or TET in combination with either lambda-cyhalothrin (LCY) or bifenthrin (BIF) showed the strongest synergy in A. mellifera, followed by CHL, ACE, or TET in combination with either zeta-cypermethrin (ZCY) or cypermethrin (CYP). The findings indicated that the co-exposure of various pesticides in natural settings might lead to severe injury to crop pollinators. Therefore, pesticide mixtures should be applied carefully in order to minimize negative effects on honey bees while maintaining effective management against crop pests.

Impairment of testicular development in rats exposed to acephate during maternal gestation and lactation.

Acephate is an organophosphate insecticide that disrupts the endocrine system and impairs the male reproductive system. Thus, the aim of the present study was to evaluate whether exposure to acephate during maternal gestation and lactation histologically damages the testes of male Wistar rats in adulthood. For this study, adult Wistar rats were divided into the following groups: ACE-mother, (2.5 mg/kg/bw, gestational day (GD) 7 to postnatal day (PND) 21) and oil-mother (corn oil (control), GD 7 to PND 21). The male offspring (PND 90) were euthanized, and the prostates and testes were collected and weighed. The testes were utilized for histopathological analyses and to determine the sperm count. A spermatogenesis kinetic analysis revealed an increased number of seminiferous tubules in stages I-VI in the ACE-mother group. Additionally, we observed a decrease in the epithelium and the diameters of the evaluated seminiferous tubules and in the number of Sertoli cells in the group exposed to acephate. The sperm count analysis showed no difference between the groups. We conclude that maternal exposure to the pesticide acephate did not affect testicular function, but led to the impairment of testicular development and morphology of the tissue in adulthood.

Differential impacts of pesticides on Euschistus heros (Hem.: Pentatomidae) and its parasitoid Telenomus podisi (Hym.: Platygastridae).

Euschistus heros (Fabricius) (Hemiptera: Pentatomidae) primarily attack the pods and seeds of soybean plants, causing severe economic losses in Neotropical Region, and chemical control is essential to avoid these losses. Thus, insecticides more effective against this pest and less toxic to Telenomus podisi Ashmead (Hymenoptera: Platygastridae) - the main biological control agent of E. heros - should be used. In this report, we studied the differential acute impacts of pesticides used in Brazilian soybean against E. heros and T. podisi and evaluated their sublethal effects on the parasitoid to identify effective pesticides towards the pest with less harmful effect to the natural enemy. The LC50 of the insecticides to E. heros ranged from 1.20 to 533.74 ng a.i./cm2; the order of toxicity was thiamethoxam + lambda-cyhalothrin > acetamiprid + fenpropathrin > zeta-cypermethrin > acephate > imidacloprid. All pesticides were classified as slightly to moderately toxic to T. podisi based on the risk quotient. The exposure of T. podisi females to imidacloprid and the insecticide pre-formulated mixtures reduced the emergence of the offspring parasitoids by up to 40% whereas zeta-cypermethrin and the insecticides pre-formulated mixtures reduced offspring survival. The preferred order of choice of insecticides for the management of E. heros according to agronomic, toxicological, and environmental feasibility was the following: thiamethoxam + lambda-cyhalothrin > zeta-cypermethrin > acetamiprid + fenpropathrin > acephate > imidacloprid. Our study provides important and pioneer information to select insecticides for effective control of E. heros with lower impacts on T. podisi.

Influences of acephate and mixtures with other commonly used pesticides on honey bee (Apis mellifera) survival and detoxification enzyme activities.

Acephate (organophosphate) is frequently used to control piercing/sucking insects in field crops in southern United States, which may pose a risk to honey bees. In this study, toxicity of acephate (formulation Bracket®97) was examined in honey bees through feeding treatments with sublethal (pollen residue level: 0.168 mg/L) and median-lethal (LC50: 6.97 mg/L) concentrations. Results indicated that adult bees treated with acephate at residue concentration did not show significant increase in mortality, but esterase activity was significantly suppressed. Similarly, bees treated with binary mixtures of acephate with six formulated pesticides (all at residue dose) consistently showed lower esterase activity and body weight. Clothianidin, λ-cyhalothrin, oxamyl, tetraconazole, and chlorpyrifos may interact with acephate significantly to reduce body weight in treated bees. The dose response data (LC50: 6.97 mg/L) revealed a relatively higher tolerance to acephate in Stoneville bee population (USA) than populations elsewhere, although in general the population is still very sensitive to the organophosphate. In addition to killing 50% of the treated bees acephate (6.97 mg/L) inhibited 79.9%, 20.4%, and 29.4% of esterase, Glutathione S-transferase (GST), and acetylcholinesterase (AChE) activities, respectively, in survivors after feeding treatment for 48 h. However, P450 activity was elevated 20% in bees exposed to acephate for 48 h. Even though feeding on sublethal acephate did not kill honey bees directly, chronic toxicity to honey bee was noticeable in body weight loss and esterase suppression, and its potential risk of synergistic interactions with other formulated pesticides should not be ignored.

Developmental toxicity and neurotoxicity of synthetic organic insecticides in zebrafish (Danio rerio): A comparative study of deltamethrin, acephate, and thiamethoxam.

Synthetic organic insecticides, including pyrethroids, organophosphates, neonicotinoids and other types, have the potential to alter the ecosystems and many are harmful to humans. This study examines the developmental toxicity and neurotoxicity of three synthetic organic insecticides, including deltamethrin (DM), acephate (AP), and thiamethoxam (TM), using embryo-larval stages of zebrafish (Danio rerio). Results showed that DM exposure led to embryo development delay and a significant increase in embryo mortality at 24 and 48 h post-fertilization (hpf). DM and AP decreased embryo chorion surface tension at 24 hpf, along with the increase in hatching rate at 72 hpf. Moreover, DM caused ntl, shh, and krox20 misexpression in a dose-dependent manner with morphological deformities of shorter body length, smaller eyes, and larger head-body angles at 10 µg/L. TM did not show significant developmental toxicity. Furthermore, results of larval rest/wake assay indicated that DM (>0.1 µg/L) and AP (0.1 mg/L) increased activity behavior with different patterns. Interestingly, as an insect-specific pesticide, TM still could alter locomotor activity in zebrafish larvae at concentrations as low as 0.1 mg/L. Our results indicate that different types of synthetic organic insecticides could create different toxicity outcomes in zebrafish embryos and larvae.

Exploring hazards of acute exposure of Acephate in Drosophila melanogaster and search for l-ascorbic acid mediated defense in it.

This study reveals protective role of l-ascorbic acid (25, 50 and 100µg/mL) against toxic impacts of acute sub-lethal exposure of Acephate (5µg/mL) in a non-target organism Drosophila melanogaster. Organismal effect was evident from increased impairment in climbing activities (9 folds) of treated individuals who also manifested altered ocular architecture. These anomalies were reduced with l-ascorbic acid (l-AA) supplementation. Acephate induced apoptotic lesions in eye imaginal discs and gut confirmed tissue damage that also reduced with l-AA co-treatment. Reduction in viability of fat body cells (∼41%), neural cells (∼42%) and hemocytes (3 folds) indicates cytotoxic and immunotoxic potential of Acephate, which were significantly mitigated with l-AA co-administration. The sub-cellular toxic impacts of Acephate treatment became obvious from enhancement in activities of antioxidant enzymes (CAT by ∼1.63 folds, SOD by ∼1.32 folds), detoxifying enzymes (Cyp450 by ∼1.99 folds and GST by ∼1.34 folds), 2.1 times boost in HSP 70 expression, and inhibition of cholinesterase activity (by ∼0.66 folds). DNA breaks evident through comet assay confirmed Acephate triggered genotoxicity which could also be prevented through co-administration of. L-AA Furthermore, the study proposes the use of Drosophila as a model to screen chemicals for their protective potential against pesticide toxicity.

Acephate exposure during a perinatal life program to type 2 diabetes.

Acephate has been used extensively as an insecticide in agriculture. Its downstream sequelae are associated with hyperglycemia, lipid metabolism dysfunction, DNA damage, and cancer, which are rapidly growing epidemics and which lead to increased morbidity and mortality rates and soaring health-care costs. Developing interventions will require a comprehensive understanding of which excess insecticides during perinatal life can cause insulin resistance and type 2 diabetes. A Wistar rat animal model suggests that acephate exposure during pregnancy and lactation causes alterations in maternal glucose metabolism and programs the offspring to be susceptible to type 2 diabetes at adulthood. Therapeutic approaches based on preventive actions to food contaminated with insecticides during pregnancy and lactation could prevent new cases of type 2 diabetes.

Lethal and sublethal effects of seven insecticides on three beneficial insects in laboratory assays and field trials.

Lethal and sublethal effects of insecticides on target and non-target arthropods are a concern of pest management programs. Cycloneda sanguinea, Orius insidiosus and Chauliognathus flavipes are important biological control agents for aphids, whitefly, lepidopterus eggs, thrips and mites. All three test species were subjected to a toxicity study using the insecticides acephate, bifenthrin, chlorantraniliprole, chlorpyrifos, deltamethrin, imidacloprid, and thiamethoxam. Experiments were done in the lab and field. In the laboratory we evaluated the mortality and sublethal effects of the concentration that killed 20% of the population (LC20) on feeding, repellence and reproduction of the species tested. The lethal effects of these insecticides at the recommended doses was evaluated in the field. Concentration-response bioassays indicated chlorantraniliprole had the lowest toxicity, while chlorpyrifos and acephate were the most toxic. Test species exposed to filter paper surfaces treated with pyrethroids, neonicotinoids and organophosphates were repelled. On the other hand, test species were not repelled from surfaces treated with chlorantraniliprole. Chlorantraniliprole therefore seemed to be the least dangerous insecticide for these three beneficial arthropod test species.

Amphibian (Euphlyctis cyanophlyctis) in vitro ovarian culture system to assess impact of aquatic agrochemical contaminants on female reproduction.

The present study is an attempt to screen impacts of aquatic agrochemical contaminants (acephate, atrazine and cypermethrin) on development and growth of follicles, in in vitro-cultured ovarian fragments of frog (Euphlyctis cyanophlyctis). Ovarian lobes removed surgically from gravid females were cut into small pieces and cultured in vitro in presence of graded (0.01 or 0.1 µg/ml of culture medium) concentrations of test chemicals or estradiol-17ß (positive controls) or culture medium alone (controls) in quadruplicate sets at 23 ± 1 °C temperature for 20 days in a humidified sterile chamber. On 21st day, they were fixed in Bouin's fluid and used for differential follicle counting (n = 3 sets) and histology (n = 1 set). In vitro exposure of ovarian fragments to test chemicals caused a decline in previtellogenic follicles, maintenance of large yolky follicles, incorporation of brown granules into early vitellogenic follicles and decrease in follicular atresia compared to corresponding controls. These results suggest that ovarian follicles are greatly sensitive to chemical exposure during their transition from previtellogenic to vitellogenic growth phase and in vitro ovarian culture system may be used as a tool to assess the effects of aquatic agrochemical contaminants on ovarian function.

In vitro study of the neuropathic potential of the organophosphorus compounds trichlorfon and acephate.

Organophosphorus-induced delayed neuropathy (OPIDN) is a central and peripheral distal axonopathy characterized by ataxia and paralysis. Trichlorfon and acephate are two organophosphorus compounds (OPs) used worldwide as insecticide and which cause serious effects to non-target species. Despite that, the neuropathic potential of these OPs remains unclear. The present study addressed the neurotoxic effects and the neuropathic potential of trichlorfon and acephate in SH-SY5Y human neuroblastoma cells, by evaluating inhibition and aging of neuropathy target esterase (NTE), inhibition of acetylcholinesterase (AChE), neurite outgrowth, cytotoxicity and intracellular calcium. Additionally, the effects observed were compared to those of two well-studied OPs: mipafox (known as neuropathic) and paraoxon (known as non-neuropathic). Trichlorfon and mipafox presented the lowest percentage of reactivation of inhibited NTE and the lowest ratio IC50 NTE/IC50 AChE. Moreover, they caused inhibition and aging of at least 70% of the activity of NTE at sub-lethal concentrations. All these effects have been associated with induction of OPIDN. When assayed at these concentrations, trichlorfon and mipafox reduced neurite outgrowth and increased intracellular calcium, events implicated in the development of OPIDN. Acephate caused effects similar to those caused by paraoxon (non-neuropathic OP) and was only able to inhibit 70% of NTE activity at lethal concentrations. These findings suggest that trichlorfon is potentially neuropathic, whereas acephate is not.

The plasma metabolic profiling of chronic acephate exposure in rats via an ultra-performance liquid chromatography-mass spectrometry based metabonomic method.

This study aimed to investigate the toxic effects of long-term, low-dose acephate administration on rats using ultra-performance liquid chromatography-mass spectrometry. A total of 120 male Wistar rats were randomly assigned to different groups: control; low-dose acephate (0.5 mg kg(-1) bw(-1)); middle-dose acephate (1.5 mg kg(-1) bw(-1)); and high-dose acephate (4.5 mg kg(-1) bw(-1)). The rats continuously received acephate via drinking water for 24 weeks. Rat plasma samples were collected at different time points to measure metabonomic profiles. Liver tissues were subjected to histopathological examination. The results showed that 10 metabolites in the plasma were significantly changed in the treated groups compared with those in the control group (P < 0.05 or P < 0.01). Exposure to acephate resulted in increased lysoPC (15 : 0), lysoPC (16 : 0), lysoPC (O-18 : 0), lysoPC (18 : 1(9Z)), lysoPC (18 : 0), lysoPC (20 : 4(5Z, 8Z, 11Z, 14Z)), arachidonic acid, and 12-HETE as well as decreased tryptophan and indoleacrylic acid in rat plasma. Moreover, the contents of high-density lipoprotein, low-density lipoprotein, triglyceride, total cholesterol, free fatty acids, and malondialdehyde, as well as the activities of superoxide dismutase and phospholipaseA2 in the serum, were significantly changed in the middle- and high-dose groups compared with those in the control group (P < 0.05 or P < 0.01). Histopathological examination results revealed that exposure to acephate may induce vacuolar degeneration in the liver cell cytoplasm, fat degeneration, and liver cell necrosis. These results indicated that exposure to acephate disrupted metabolism of lipids and amino acids, induced oxidative stress, caused neurotoxicity, and resulted in liver dysfunction.

Toxicopathological evaluation in Wistar rats (Rattus norvegicus) following repeated oral exposure to acephate.

The present study was carried out to evaluate the effects of exposure at different doses of acephate on hematology, blood biochemistry, oxidative stress and immune system of Wistar rats. The experiment was carried out on 40 Wistar rats, which were divided in four groups. Animals of the three treatment groups were given with different sublethal doses (1/40th, 1/20th, 1/10th of lethal dose 50 value) of acephate by oral gavage. The hematology, blood biochemistry, oxidative stress marker, humoral immune response and cell-mediated immunity were evaluated following acephate exposure. Significant alteration in hematological parameters was not observed following different doses of acephate; however, significant alteration in alkaline phosphatase, gamma glutamyl transferase, acetyl cholinesterase, lipid peroxidase and superoxide dismutase was observed in medium- and high-dose group animals. Nonsignificant decrease in antibody titer in animals exposed to high dose has been observed compared with animals of control group. However, significant alteration in cell-mediated immunity was not observed in animals treated with acephate at different doses.

Effect of repeated applications of buprofezin and acephate on soil cellulases, amylase, and invertase.

The impact of repeated applications of buprofezin and acephate, at concentrations ranging from 0.25 to 1.0 kg ha(-1), on activities of cellulases, amylase, and invertase in unamended and nitrogen, phosphorous, and potassium (NPK) fertilizer-amended soil planted with cotton was studied. The nontarget effect of selected insecticides, when applied once, twice, or thrice on soil enzyme activities, was dose-dependent; the activities decreased with increasing concentrations of insecticides. However, there was a rapid decline in activities of enzymes after three repeated applications of insecticides in unamended or NPK-amended soil. Our data clearly suggest that insecticides must be applied judiciously in pest management in order to protect the enzymes largely implicated in soil fertility.

Key amino acid associated with acephate detoxification by Cydia pomonella carboxylesterase based on molecular dynamics with alanine scanning and site-directed mutagenesis.

Insecticide-detoxifying carboxylesterase (CE) gene CpCE-1 was cloned from Cydia pomonella. Molecular dynamics (MD) simulation and computational alanine scanning (CAS) indicate that Asn 232 in CpCE-1 constitutes an approximate binding hot-spot with a binding free energy difference (ΔΔGbind) value of 3.66 kcal/mol. The catalytic efficiency (kcat/km) of N232A declined dramatically, and the half inhibitory concentrations (IC50) value increased by more than 230-fold. Metabolism assay in vitro reveals that the acephate could be metabolized by wild CpCE-1, whereas N232A mutation is unable to metabolize the acephate, which suggests that the hot-spot Asn 232 is a crucial residue for acephate metabolism. Mutation detection suggests that low frequency of Asn 232 replacement occurred in Europe field strains. Our MD, CAS, site-directed mutagenesis, and metabolism studies introduce a new amino acid residue Asn 232 involved in the metabolism of the acephate with CpCE-1, and this method is reliable in insecticide resistance mechanism research and prediction of key amino acids in a protein which is associated with specific physiological and biochemical functions.

Duplication of acetylcholinesterase gene in diamondback moth strains with different sensitivities to acephate.

This study examined the acetylcholinesterase 1 gene (AChE1) in Plutella xylostella strains with different sensitivities to acephate. Multiple haplotypes of the gene were found in the field-collected strains including distinct haplotypes carrying one or both previously reported mutations (A298S and G324A). Moreover, sequencing results indicated the presence of duplicated copies of the gene in the field-collected strains. No correlation was found between copy numbers of AChE1 and levels of resistance to acephate suggesting that extensive AChE1 duplication is not a major resistance factor at least in some P. xylostella strains. Proportions of the A298S and G324A mutations showed no correlation with levels of resistance to acephate. This suggests that acephate resistance of P. xylostella is complex and cannot be evaluated based on the AChE1 copy number or proportions of the resistance mutations alone.

Diphenyl diselenide protects against metabolic disorders induced by acephate acute exposure in rats.

The present study investigated the effect of diphenyl diselenide [(PhSe)2 ] on metabolic disorders induced by acephate acute exposure in rats. We also investigated a possible mechanism of action of (PhSe)2 against hyperglycemia induced by acephate. (PhSe)2 was administered to rats at a dose of 10 or 30 mg/kg by oral gavage (p.o.) 1 hour prior to acephate administration (140 mg/kg; p.o.). Glucose and corticosterone levels as well as the lipid status were determined in plasma of rats. Cardiovascular risk factors and the atherogenic index were calculated. Glycogen levels as well as tyrosine aminotransferase (TAT) and glucose-6-phosphatase (G6Pase) activities were determined in livers of rats. Cerebral acetylcholinesterase (AChE) activity was assayed. Acephate induced an increase in glucose and corticosterone levels as well as in TAT and G6Pase activities. AChE activity was inhibited by acephate. Triglyceride (TG) levels and the cardiovascular risk factor TG/high-density lipoprotein-cholesterol (HDL) were increased by acephate. (PhSe)2 was effective against the metabolic disorders induced by acephate acute exposure in rats.

Entomotoxicity and biosafety assessment of PEGylated acephate nanoparticles: a biologically safe alternative to neurotoxic pesticides.

This is a report of an experimental study on a nanoencapsulation of the organophosphate acephate. Acephate was encapsulated in polyethylene glycol, using a simple, easy-to-replicate method that required no special equipment or conditions. The nanoencapsulation (nanoacephate) was characterized and its bioefficacy as compared to the regular commercial acephate was tested. The biosafety of the new compound was also tested on a murine model. Our new nanoencapsulation scored over the regular variety on all counts. It was found to successfully incorporate the active pesticidal component, acephate and this compound retained greater functional integrity over time as a nanoencapsulation. It was significantly more efficacious than the regular variety. It was biosafe when tested on murine model. We have reason to believe that this nanoencapsulation would allow the use of an organophosphate in a more targeted manner, thereby making it a cost-effective and eco-friendly alternative to the regular variety in use now.

Characterization of acetylcholinesterase in Hong Kong oyster (Crassostrea hongkongensis) from South China Sea.

Acetylcholinesterase (AChE) activity has been used to evaluate the exposure of mollusk bivalves to organophosphates, carbamate pesticides, and heavy metals. Crassostrea hongkongensis is a Hong Kong endemic oyster, and has a high commercial value along the coastal area of South China. The use of this species as a bio-indicator of the marine environment, and the use of AChE activity measurements in tissues of C. hongkongensis require prior characterization of AChE in this species. Here, we report that gill tissue contains the highest AChE activity in C. hongkongensis, and that the molecular form of AChE is most likely to be a dimeric form. In addition, the effect of the pesticide acephate on AChE activity in the gill of C. hongkongensis was analyzed, and the mean inhibition concentration (IC50) value was determined. This study suggests that AChE activity in the gill tissue of C. hongkongensis might be used as a biomarker in monitoring organophosphate contamination in the marine fauna of South China.

In vitro induction/inhibition of germinal vesicle breakdown (GVBD) in frog (Euphlyctis cyanophlyctis) oocytes by endocrine active compounds.

Oocyte maturation is transformation of oocytes into a fertilizable egg. This study examined the effects of four classes of chemicals: 1) acephate (organophosphate); 2) atrazine (herbicide); 3) cypermethrin and fenvalerate (synthetic pyrethroids); and 4) carbaryl (carbamate) on in vitro germinal vesicle breakdown (GVBD) of Euphlyctis cyanophlyctis oocytes. Follicles were isolated and defolliculated from surgically removed ovaries of E. cyanophlyctis and exposed to either progesterone (1 µM/mL) or graded concentrations (1, 5, 10, 15, and 20 µg/mL) of test chemicals. GVBD was evident by the presence of a white spot in the animal pole as well as the absence of germinal vesicles in sectioned heat-fixed oocytes. Percent GVBD was scored every 4 hours until 24 hours. Progesterone induced 77-84% GVBD, compared to 29-33% in controls, at 24 hours. Acephate induced 46-67% GVBD, whereas atrazine elicited 58-77% of GVBD. In cypermethrin or carbaryl- or fenvalerate-exposed oocytes, GVBD was limited to 22-28, 17-29 and 18-24%, respectively. The study infers that some chemical contaminants in the aquatic system may interfere with GVBD in amphibians. Because oocyte maturation is a prerequisite for the production of fertilizable eggs, any alteration in this process potentially impairs the fecundity of females.