Feeding responses of carabid beetles to dimethoate-contaminated prey

Abstract 1 The feeding responses of Pterostichus madidus Fab., P. melanarius Illiger and Nebria brevicollis Fab. (Coleoptera: Carabidae) to dimethoate‐contaminated prey were investigated in ‘no‐choice’ and ‘choice’ feeding tests. 2 In the no‐choice tests, starved beetles were presented with aphid prey treated with four concentrations of dimethoate. In the choice tests, treated and untreated prey were presented together and the feeding preferences of the starved beetles observed. 3 No avoidance or rejection behaviour was seen in any of the carabids in either of the tests, i.e. no discrimination of the treated and untreated prey was observed. 4 Sufficient dimethoate was consumed with the aphid prey to cause significant mortality levels in the carabids. 5 The concentrations of dimethoate used in these experiments are comparable to field exposure, so carabids feeding in treated fields and field margins could potentially suffer lethal effects via the indirect exposure route of consuming contaminated prey.     

Teratogenicity study of some pesticides in chicken embryos

The use of pesticides involves the risk of poisoning on wild animals. Teratological tests carried out on avian embryos provide useful data for environmental protection and facilitate the development of environment-friendly chemical plant protection techniques. A 30% dimethoate containing insecticide formulation (BI 58 EC) and a 20% benfluralin containing herbicide formulation (Flubalex) and a 960 g/l S-metolachlor containing herbicide formulation (Dual Gold 960 EC) were studied in chicken embryos after single administration by immersion and injection technique. Treatment was done on day 0 of incubation. Applied concentration of pesticides were 0.1% (dimethoate) and 2.05% (S-metolachlor) and 0.375% (benfluralin) corresponding to that used in plant protection practice. Test materials were injected into the air chamber in a volume of 0.1 ml/egg, or eggs were treated by the immersion technique for 30 min. at 37 degrees C. Evaluation was done on day 19 of incubation. Injection treatment: the administration of S-metolachlor and benfluralin did not result a significant decrease in the average body weight of embryos. At the same time the body weight of embryos significantly decreased because of single administration of dimethoate. The embryomortality increased markedly after the administration of test materials (S-metolachlor, benfluralin, dimethoate). Immersion treatment: the administration of S-metolachlor and benfluralin and dimethoate did not result a significant decrease in the average body weight of embryos. The rate of embryomortality was low after the administration of S-metolachlor, benfluralin and dimethoate. After the immersion and the injection treatment the incidences of developmental anomalies were sporadic. In summary it can be established that the injection treatment was more toxic than immersion technique of the test materials in our study.     

Effects of hunger level and nutrient balance on survival and acetylcholinesterase activity of dimethoate exposed wolf spiders

The influence of two nutritional factors (food quantity and quality) on the responses of a wolf spider, Pardosa prativaga (L.K.), to a high dose of the insecticide dimethoate, was investigated in a fully factorial experimental design. Spider groups with different (good and bad) nutrient balance were created by feeding them fruit flies of either high or low nutrient content for 28 days. Both groups were then split into satiated and 14 days starved subgroups. Each of these was further divided into insecticide treated and control halves. Survivorship and acetylcholinesterase (AChE) activity measured on the survivors were used as response variables. Survivorship after topical dimethoate exposure (LD₅₀; 48 h) was influenced by spider body weight, nutrient balance, and starvation. Furthermore, AChE activity was significantly inhibited by dimethoate exposure. A significant interaction between nutrient balance, starvation, and dimethoate exposure revealed synergistic effects of starvation and nutrient imbalance on AChE inhibition by dimethoate in surviving spiders. These results show that the tolerance of non-target arthropods to dimethoate may vary depending on the nutritional history of the animal.     

Evaluation of genotoxic and oxidative stress response to dimethoate in freshwater fish Channa punctatus (Bloch)

Abstract

Dimethoate is one of the organophosphate insecticides widely used in agriculture throughout the world and is an inhibitor of cholinesterase in animals. The objective of the present study was to detect oxidative stress and DNA damage induced by dimethoate in the freshwater fish Channa punctatus (C. punctatus). The LC₅₀-96 h value of technical grade dimethoate was estimated at 19.10 μg L^-1 in a semi-static system and, on the basis of the LC₅₀ value, three concentrations were determined. The fish were exposed to these concentrations of dimethoate for 96 h and samplings were done at 24 and 96 h for assessment of oxidative stress and DNA damage. After exposure to dimethoate, the level of superoxide dismutase declined while lipid peroxidation, glutathione, induction of micronucleus and DNA damage were increased in C. punctatus as the concentration and exposure time increased. Thus our results suggest that dimethoate induces genotoxic effects which invariably accompanied and correlated with oxidative stress.     

Beta 3-adrenergic receptor is involved in feeding regulation in chicks

We examined whether the brain beta 3-adrenergic receptor (B3-AR) is involved in the feeding regulation of chicks. Intracerebroventricular (ICV) injection of BRL37344, a B3-AR agonist, reduced food intake of chicks under ad libitum, but not fasting, feeding conditions. The ICV injection of BRL37344 did not affect chick posture or locomotion activity suggesting that BRL37344 inhibited feeding without induction of sleep-like behavior as caused by norepinephrine. Furthermore, the rectal temperature increased following the ICV injection of BRL37344. Intraperitoneal administration of BRL37344 did not reduce food intake under ad libitum feeding condition. The present study demonstrated that the brain B3-AR is involved in the inhibition of feeding in chicks. We also suggested that activation of the brain affects the energy metabolism in chicks.     

Immunization and Parenteral Chemotherapy for the Control of Cattle Grubs Hypoderma Lineatum

Immunization with two types of warble larvae antigens A and B, the latter treated with tannic acid, and injections of dimethoate, an organic phosphate, were tried for the control of prehypodermic larvae of Hypoderma lineatum De Vill., and H. bovis L., in range calves. In test groups of 20 calves, given intramuscularly, antigen A had no effect, but combined treatment with antigens A and B reduced the number of H. bovis L., larvae by 81 per cent (P<.001), and proved as effective as dimethoate subcutaneously or intramuscularly. H. lineatum De Vill., did not respond to any treatment. Antigen B and dimethoate were free from harmful effects on the host, but antigen A caused anaphylaxis and irritation at the site of injection.     

Upregulation of the immune protein gene hemolin in the epidermis during the wandering larval stage of the Indian meal moth, Plodia interpunctella

Expression of hemolin, which generates an immune protein, was up-regulated in wandering fifth instar larval stage of Plodia interpunctella. The mRNA level peaked in the middle of the wandering stage. Major expression was in the epidermis, rather than in the fat body or gut. To test a possible ecdysteroid effect on hemolin induction we treated with RH-5992, an ecdysteroid agonist, and KK-42, which inhibits ecdysteroid biosynthesis in both feeding and wandering fifth instar larvae. When feeding larvae were treated with RH-5992 the hemolin mRNA level was increased. When wandering larvae were treated with KK-42 its level was reduced. In addition, when KK-42-treated larvae were subsequently treated with RH-5992 the hemolin mRNA level was recovered. These results strongly suggest that ecdysteroid up-regulates the expression of hemolin mRNA. Hormonal and bacterial effects on hemolin induction were further analyzed at the tissue level. Major induction of hemolin mRNA was detected following both RH-5992 treatment and bacterial injection in the epidermis of both feeding and wandering larvae. Minor induction of hemolin was detected in the fat body following a bacterial injection, but not RH-5992 treatment. We infer that in P. interpunctella larvae, the epidermis is the major tissue for hemolin induction in na?ve insects and in insects manipulated with bacterial and hormonal treatments.     

Toxicity and residual effectiveness of insecticides on insecticide-treated spheres for controlling females of Rhagoletis pomonella (Diptera: Tephritidae)

This study evaluated the toxicity of five technical-grade insecticides of four different classes to apple maggot females, Rhagoletis pomonella (Walsh), following a 10-min exposure period in insecticide-coated glass jars, with or without a feeding stimulant (sucrose) present. According to LC90 values for toxicity by ingestion and tarsal contact, imidacloprid was 1.5 times more toxic than dimethoate or abamectin, diazinon was less toxic, and phloxine B (a phototoxic dye) least toxic. Based on LC90 values for tarsal contact alone, dimethoate was 2.3, 4.0, and 18.4 times more toxic than imidacloprid, abamectin, and diazinon, respectively. Contact alone with phloxine B caused no mortality. When exposure was assessed using spheres coated with a latex paint mixture containing sucrose and formulated dimethoate (Digon 400 EC) or imidacloprid (Provado 1.6 F) at concentrations ranging from 5 to 70 g (AI)/cm2, both insecticides showed reduced effectiveness compared with toxicities from glass jar tests, with Digon two times more toxic than Provado. After exposure to artificial rainfall and retreatment with sucrose, Digon- and Provado-treated spheres exhibited greatest residual effectiveness, with diazinon-treated spheres less effective. Spheres treated with formulated abamectin (Agri-Mek 0.15 EC) at 1.0% (AI) performed only slightly better than phloxine B-treated spheres, which completely lost effectiveness after exposure to rainfall. Spheres treated with formulated imidacloprid (Merit 75 WP) at 1.5% (AI) showed equal or better residual efficacy in killing apple maggot flies (> 80% mortality, shorter lethal duration of feeding) over a 12-wk exposure period to outdoor weather than spheres treated with Digon at 1.0% (AI) after both types were retreated with sucrose. Our results indicate that imidacloprid is a promising safe substitute for dimethoate as a fly killing agent on lure-kill spheres. Imidacloprid formulated as Merit 75 WP had greater residual efficacy than imidacloprid formulated as Provado 1.6 F.     

Susceptibility of spinosad in Musca domestica (Diptera: Muscidae) field populations

The toxicity of spinosad was determined in one susceptible and five insecticide-resistant laboratory strains of house fly, Musca domestica L. Spinosad was relatively slow-acting, but highly toxic to house flies. In a feeding bioassay, spinosad LC50 at 72 h was 0.51 microg of spinosad per gram of sugar, making it 6.3- and 3.5-fold more toxic to house flies compared with azamethiphos and methomyl, respectively. In topical application bioassay, the LD50 at 48 h of spinosad in susceptible house flies was 40 ng per 20 mg of house fly, making spinosad less toxic than the pyrethroid bioresmethrin synergized by piperonyl butoxide and the organophosphate dimethoate. The insecticide-resistant laboratory strains had resistance factors to spinosad at LC50 in feeding bioassay from 1.5 to 5.5 and at LD50 in topical application bioassay from 2.5 to 4.7, indicating that in house fly cross-resistance to the major insecticide classes will not initially be of major concern for the use of spinosad for house fly control. The toxicity of spinosad was also evaluated against 31 field populations of house flies collected from livestock farms across Denmark. The field populations were 2.2- to 7.5-fold resistant to spinosad at 72 h in feeding bioassay, but based on steep slopes in the bioassay and the limited variation of spinosad toxicity against the various field populations, we consider the field populations to be spinosad-susceptible. We propose a diagnostic dose of 12 microg of spinosad per gram of sugar in feeding bioassay with impregnated sugar for determination of resistant house flies, which is 10x the LC95 of the susceptible strain WHO and approximately = 2x the LD95 of the field populations. Spinosad showed no substantial cross-resistance to the pyrethroid bioresmethrin synergized by piperonyl butoxide, the anticholinesterases dimethoate, azamethiphos, methomyl, and spinosad in house fly field populations.     

Host plant-induced changes in detoxification enzymes and susceptibility to pesticides in the twospotted spider mite (Acari: Tetranychidae)

Adult female twospotted spider mites, Tetranychus urticae Koch, reared on lima bean plants were moved to cucumber, maize, or new lima bean plants (the latter being a control) and evaluated after 24 h or 7 d for changes in susceptibility to three pesticides and in levels of related detoxification enzymes. The largest and most consistent changes were observed in mites feeding on cucumber. Susceptibility of mites on cucumber to the synthetic pyrethroids bifenthrin and lambda-cyhalothrin was greater than that of mites reared on lima bean and maize after only 24 h on the plants, and remained higher after 7 d. Mites on cucumber also were more susceptible to the organophosphate dimethoate than were mites on lima bean, but only after 7 d on the host. Susceptibility was inversely related to activities of both general esterase and glutathione S-transferase (GST) in mites on cucumber; general esterase and GST activities were 60 and 25% lower, respectively, than activities of twospotted spider mite on lima bean after 7 d of feeding. Mites on maize were slightly but significantly more susceptible than those on lima bean to bifenthrin, but not to lambda-cyhalothrin, after 7 d and to dimethoate after 24 h but not after 7 d. General esterase and GST activities in twospotted spider mite fed on maize for 24 h were 20 and 16% higher, respectively, than activities in twospotted spider mite on lima bean, but general esterase activity was 30% lower than lima bean-fed mites and GST was not different after 7 d. Thus, plant-induced changes in general esterase activity, perhaps in combination with GST activity, in twospotted spider mite appear to be inversely related to, and possibly responsible for, changes in susceptibility of twospotted spider mite to several pesticides, particularly the synthetic pyrethroids. General esterases appear to play less of a role in the detoxification of the organophosphate insecticide dimethoate.     

Circadian intervention of obesity development via resting-stage feeding manipulation or oxytocin treatment

The obesity pandemic can be viewed as a result of an imbalanced reaction to changing environmental factors. Recent research has linked circadian arrhythmicity to obesity and related diseases; however, the underlying mechanisms are still unclear. In this study, we found that high-fat diet (HFD) feeding strikingly promoted daytime rather than nighttime caloric intake in mice, leading to feeding circadian arrhythmicity. Using scheduled feeding with a defined amount of daily HFD intake, we found that an increase in the ratio of daytime to nighttime feeding promoted weight gain, whereas a decrease of this ratio rebalanced energy expenditure to counteract obesity. In identifying the underlying mechanism, we found that hypothalamic release of anorexigenic neuropeptide oxytocin displayed a diurnal rhythm of daytime rise and nighttime decline, which negatively correlated with the diurnal feeding activities of normal chow-fed mice. In contrast, chronic HFD feeding abrogated oxytocin diurnal rhythmicity, primarily by suppressing daytime oxytocin rise. Using pharmacological experiments with hypothalamic injection of oxytocin or oxytocin antagonist, we showed that daytime manipulation of oxytocin can change feeding circadian patterns to reprogram energy expenditure, leading to attenuation or induction of obesity independently of 24-h caloric intake. Also importantly, we found that peripheral injection of oxytocin activated hypothalamic oxytocin neurons to release oxytocin, and exerted metabolic effects similar to central oxytocin injection, thus offering a practical clinical avenue to use oxytocin in obesity control. In conclusion, resting-stage oxytocin release and feeding activity represent a critical circadian mechanism and therapeutic target for obesity.     

Effects of recombinant human interleukins on food intake of previously food-deprived rats

The effects of intracerebroventricular injection of recombinant human interleukin 1 beta (rhIL-1 beta), 1 alpha (rhIL-1 alpha), and 2 (rhIL-2) on feeding behavior were examined in previously food-deprived rats for 18 hr. At doses of 2-17 ng/rat, rhIL-1 beta significantly reduced food intake in a dose-dependent manner and the feeding suppression continued about 4 hr later. Only 17 ng/rat rhIL-1 beta reduced body weight gain for 8 hr after the injection. However, rhIL-1 alpha at dose of 17 ng/rat did not show any significant change of food intake and body weight gain during the whole observation period. At both doses of 8 and 40 ng/rat, rhIL-2 also failed to suppress overfeeding after food deprivation. In adrenalectomized rats, feeding suppression by rhIL-1 beta appeared at the 1- to 2-hr time period. The present studies suggest that rhIL-1 beta may be, at least in part, involved in feeding suppression on various inflammatory processes and that adrenal hormones may not play an important role in the induction of feeding suppression by rhIL-1 beta.     

Plasmid-mediated dimethoate degradation in Pseudomonas aeruginosa MCMB-427

AIMS: To investigate the genetics of dimethoate degradation in Pseudomonas aeruginosa MCMB-427. METHODS AND RESULTS: Pseudomonas aeruginosa MCMB-427 demonstrated the ability to degrade dimethoate, a synthetic organophosphate insecticide. Total DNA preparation of MCMB-427 revealed the presence of a 6.6 kbp plasmid (designated as pDMD427). Escherichia coli NovaBlue transformed with plasmid pDMD427 subsequently acquired the ability to degrade dimethoate. Curing of the plasmid by plumbagin or ethidium bromide resulted in the loss of ability of MCMB-427 to degrade dimethoate. Plasmid pDMD427 was stable in MCMB-427 over 20 passages without selection. Genes encoding resistance to norfloxacin and cobalt were also located on plasmid pDMD427. CONCLUSION: The ability of Ps. aeruginosa MCMB-427 to degrade dimethoate is plasmid-mediated and transferable to other strains. SIGNIFICANCE AND IMPACT OF THE STUDY: As far as is known, this is the first report of plasmid-mediated dimethoate biodegradation. This study contributes significantly towards an understanding of the genetics of bacterial dimethoate degradation.     

Dissipation Pattern,Processing Factors,and Safety Evaluation for Dimethoate and Its Metabolite (Omethoate) in Tea (Camellia Sinensis)

Residue levels of dimethoate and its oxon metabolite (omethoate) during tea planting, manufacturing, and brewing were investigated using a modified QuEChERS sample preparation and gas chromatography. Dissipation of dimethoate and its metabolite in tea plantation followed the first-order kinetic with a half-life of 1.08–1.27 d. Tea manufacturing has positive effects on dimethoate dissipation. Processing factors of dimethoate are in the range of 2.11–2.41 and 1.41–1.70 during green tea and black tea manufacturing, respectively. Omethoate underwent generation as well as dissipation during tea manufacturing. Sum of dimethoate and omethoate led to a large portion of 80.5–84.9% transferring into tea infusion. Results of safety evaluation indicated that omethoate could bring higher human health risk than dimethoate due to its higher hazard quotient by drinking tea. These results would provide information for the establishment of maximum residue limit and instruction for the application of dimethoate formulation on tea crop.     

STUDIES ON SELECTIVE TOXICITY OF SIX INSECTICIDES BETWEEN GREEN PEACH APHID AND LADYBIRDS

Abstract  The selective toxicity of six kinds of insecticides, including imidacloprid, imidacloprid + synergist (SV1), fenvalerate, endosulfan, methomyl and dimethoate, between the green peach aphid ( Myzus persicae Sulzer) and two species of ladybirds ( Coccinella septempunctata Linnaeus and Propylaea japonica Thunbery), was investigated in the laboratory. The reults showed that both imidacloprid WP and imidacloprid + synergist (SVl) EC possessed the highest toxicity to the aphids. Between C. septempunctata and M. persicae and between P. japonica and M. persicae , the selective toxicity ratios (STRs) of imidacloprid WP, imidacloprid+ synergist (SV1) EC and endosulfan EC were 37.6 and 13.0, 9.84 and 7.75, 54.0 and 7.28 respectively. All of them showed rather high selective toxicity. The STRs of fenvalerate EC, dimethoate EC and methomyl EC were all very low, ranging from 0.02 to 0.21, indicating their low degree of safety to the two species of ladybids. The results demomarated that imidacloprid WP and imidacloprid + SVl EC not only had rather high toxicity to the aphids, but also reduced strikingly the reproduction rate and fecundity of the survival aphids. Insecticides can induce the relative fitness of insects decrease. Among the six insecticides tested with M. persicae , the following were insecticides and the order of induction was: imidacloprid + SV1 imidacloprid endosulfan methomyl fenvalerate > dimethoate.     

The secretion of the systemic insecticides dimethoate and phorate into nectar

In pot experiments, root applications of dimethoate and phorate were made to plants of fuchsia, nasturtium and bean. Twenty-five mg dimethoate applied to a 5-in pot made nectar from fuchsia and nasturtium and nectaries of beans toxic to bees and Drosophila melanogaster. Similar amounts of phorate and disulfoton did not cause toxicity. Gas chromatography showed that 4 days after treatment there was at least 100 times more dimethoate than phorate in the nectar of fuchsia and nasturtium. The dimethoate in nectaries taken from bean plants treated at rates between 0·5 and 50 mg dimethoate per pot was assayed by gas chromatography. The concentration of dimethoate in the nectaries depended on the applied dose: it was greatest 4 days after treatment. Loss was more rapid with larger doses than with smaller doses.     

Effects of cypermethrin and deltamethrin on the feeding behaviour of Aphis craccivora and transmission of cowpea aphid-borne mosaic virus

The effects of two synthetic pyrethroids, cypermethrin and deltamethrin, on the feeding behaviour of Aphis craccivora and its transmission of the nonpersistent cowpea aphid-borne mosaic virus (CAMV) were compared to those of an organophosphate (dimethoate) and carbamate (pirimicarb) in greenhouse and laboratory tests. Cypermethrin at 100, 150 and 200 mg a.i. litre^-1 and deltamethrin at 75, 100 and 150 mg a.i. litre^-1 restricted the acquisition and inoculation of CAMV, whereas dimethoate and pirimicarb had no significant effect. Cypermethrin protected against transmission of CAMV longer after application than deltamethrin and there was a strong interaction between The duration of the first probe was shorter on pyrethroid-treated plants than on dimethoate-or pirimicarb-treated plants, and on pyrethroid-treated plants aphids probably did not probe long enough to acquire or inoculate CAMV. It is concluded that the use of synthetic pyrethroids is potentially valuable in controlling CAMV in the field until resistance against the virus has been bred into cultivars.     

乐果对菠菜叶片POD、SOD、CAT活性及MDA含量的影响

研究了喷施乐果后不同时间及不同施用量对菠菜(Spinacia oleracea)叶片POD、SOD和CAT活性及MDA含量的影响;同时检测了喷药后不同时间菠菜中乐果的残留量。结果表明,喷施乐果可促使菠菜叶片中POD和CAT活性增强以及MDA含量明显增加,而SOD活性在部分乐果处理中呈下降趋势;随着喷药后时间的延长,乐果在菠菜中的残留量亦随之减少。     

Specifically induced suppression of T cell and NK-like cytolytic activity by ingested soluble antigens

The effect of feeding xenoserum (xs) on cytolytic cell activity induced by parenteral injection was examined in C3H/N mice. Spleen cells were cultured with xs and then assayed for cytolytic activity against a panel of 51Cr-labeled YAC-1, AKR-A, or P815 target cells. Prior feeding resulted in significant suppression of responses stimulated by injection and culture. The induction of these responses was antigen specific for xs whereas the effector stage represented polyclonal activation of cytolytic cells. Some effector cells were lysed by either anti-Lyt 2 or anti-NK- 1.2 and complement and some were blocked by anti-Lyt 2 or anti-T200 in the cytotoxicity assay. Thus, both cytolytic T and NK-like cells were suppressed by antigen feeding. Activity of TH cell-derived factors which enhance cytolytic activity ("promoter" factor, interferon, and interleukin 2) also was diminished in culture supernatants of cells from mice fed soluble antigens. The conclusion that polyclonal cytolytic responses induced by soluble antigen can be regulated by prior enteric stimulation is made.     

Neuropeptide Y: A potent inducer of consummatory behavior in rats

Neuropeptide Y (NPY) is a 36 amino acid peptide with potent cardiovascular effects. In the present study, intraventricular injection of NPY was shown to markedly stimulate feeding and drinking during the illuminated period of the light/dark cycle, a time when rats ingest small amounts of food. It also enhanced nocturnal food and water intake following a 24 hour period of food deprivation and during nocturnal feeding. The NPY induction of food intake was suppressed by the opiate antagonist, naloxone, and by the dopamine antagonist, haloperidol. Phentolamine, an alpha adrenergic antagonist, failed to suppress NPY-induced feeding. Based on the maximum quantity of food which was ingested following central administration of NPY, this peptide appears to represent one of the most potent stimulators of feeding yet to be described.