Activation of paraquat in the earthworm Allolobophora chlorotica is mediated by NAD(P)H-cytochrome c reductase activities

This study reports that earthworms, Allolobophora chlorotica, are capable of biotransforming paraquat, a toxic herbicide, resulting in the formation of reactive oxygen species (ROS). We found that in earthworms the reduction of paraquat is mediated by NADPH- and NADH-cytochrome c reductase activities. The formation of superoxide anion (O₂⁻) from the incubation of paraquat with the earthworm extracts was demonstrated by using both Cypridina luciferin analog (CLA) chemiluminescence and the SOD-inhibitable cytochrome c reduction reaction. In addition, in vivo exposure of earthworms to paraquat in solution (24 and 48 h) was performed to investigate whether or not the herbicide affects the levels of the NAD(P)H-cytochrome c reductase activities. Although in vitro NADPH-cytochrome c reductase reduces paraquat more easily than the NADH-dependent activity, after the in vivo exposure an increase of NADH-cytochrome c reductase activity(s) by 12% compared to control values was observed, whereas NADPH-cytochrome c reductase activity was not affected. Xanthine oxidase (XO) is an enzyme implicated in paraquat toxicity, however, no XO was detected in earthworm extracts nor hypoxanthine was a source of electrons for the herbicide reduction. For comparative reasons menadione, a redox cycling quinone, was also incubated with the earthworm extracts. It was found that the incubation of menadione with earthworm extracts formed about two times more (O₂⁻) than with paraquat. It is concluded that the exposure of paraquat to earthworms could elicit radical formation and consequently toxic effects via oxidative stress-mediated mechanisms. The reduction of paraquat by the reductases leads to the formation of paraquat radical, which reacts with molecular oxygen, accounting for the formation of superoxide anion. Further studies are required to conclude that the observed increase of NADH-cytochrome c reductase activity(s) should be used as a biomarker for paraquat exposure in earthworms.     

Effects of Melia azedarach on nutritional physiology and enzyme activities of the rice leaffolder Cnaphalocrocis medinalis (Guenée) (Lepidoptera: Pyralidae)

Laboratory assays were done to evaluate the effect of Melia azedarach L. (Rutales: Meliaceae) seed extract on nutritional indices and gut enzymes acid phosphatases, alkaline phosphatases, adenosinetriphosphatases, and lactate dehydrogenase of the rice leaffolder (RLF) Cnaphalocrocis medinalis (Guenée) (Lepidoptera: Pyralidae). Larvae were fed a treated rice-leaf diet containing the seed extract and their midgut was used for enzyme determination. Laboratory experiments showed that the seed extract suppressed the larval activity of C. medinalis even at a low dose. Gross dietary utilization (efficiency of conversion of ingested and digested food) of RLF decreased after ingesting the treated rice-leaf diet. Food consumption, digestion, relative consumption rate, efficiency of conversion of ingested food, efficiency of conversion of digested food, and relative growth rate values declined significantly. As compared to the control, consumption of the extract containing rice-leaf diet resulted in a 69% reduction of the acid phosphatases activity, a 71% reduction of the alkaline phosphatases activity, a 46% reduction of the adenosine triphosphatases activity, and a 52% inhibition of the lactate dehydrogenase activity.     

Isolation of a novel Carica papaya α-amylase inhibitor with deleterious activity toward Callosobruchus maculatus

Cowpea (Vigna unguiculata) is a subsistence crop for small and poor farmers from Latin America and Africa. This culture is commonly damaged by cowpea weevil (Callosobruchus maculatus), which burrow into stored seeds to fed on. Due to impact of larval predation, several plant defense studies have been developed, indicating that α-amylase inhibitors are able to impede and/or reduce bruchids digestive process. In this report, a novel α-amylase inhibitor from papaya seeds (Carica papaya) with activity against cowpea weevil enzymes was purified and biochemical characterized. Peeled seeds were macerated and extracted with a 0.6 M NaCl and 0.1% HCl solution. Crude extract was precipitated with ammonium sulphate (100%). After dialyses, this rich fraction was applied onto a CM-Cellulose column and retained peak was submitted to an analytic reversed-phase column HPLC (Vydac C-18TP) yielding several peaks. Only one fraction, with molecular mass of 4562 Da, showed significant inhibitory activity against C. maculatus α-amylases. Otherwise, no inhibitory activities against mammalian α-amylases were observed. Bioassays using artificial seeds containing C. papaya α-amylase inhibitor rich fraction (0.5% and 1.0%) were also conduced showing that α-amylase inhibitors were able to increase larval mortality (50%) and also decrease insect fecundity and adult longevity. These results showed the presence of an α-amylase inhibitor from C. papaya seeds with high specificity to insect enzymes, indicating that this inhibitor probably could be used, through genetic engineering, in the construction of transgenic plants with enhanced resistance toward cowpea weevil.     

The role of cytochrome P450 monooxygenase in the different responses to fenoxaprop-P-ethyl in annual bluegrass (Poa annua L.) and short awned foxtail (Alopecurus aequalis Sobol.)

Herbicide resistance or tolerance in weeds mediated by cytochrome P450 monooxygenase is a considerable problem. However, cytochrome P450 mediated resistance or tolerance in weeds was less studied. Thus, in this work, the role of the cytochrome P450 monooxygenase in the different responses of Poa annua and Alopecurus aequalis to fenoxaprop-P-ethyl was studied. We found that the effect of fenoxaprop-P-ethyl could be synergized by piperonyl butoxide (PBO) in P. annua, but not by malathion. After being treated with fenoxaprop-P-ethyl (containing mefenpyr-diethyl), the contents of cytochrome P450 and cytochrome b₅ in P. annua increased significantly compared to plants treated with mefenpyr-diethyl only or untreated plants. However, the increase was less in A. aequalis, which was susceptible to fenoxaprop-P-ethyl. The activities of ρ-nitroanisole O-demethylase (PNOD), ethoxyresorufin O-deethylase (EROD), ethoxycoumarin oxidase (ECOD) and NADPH-dependent cytochrome P450 reductase mediated by cytochrome P450 monooxygenase increased in P. annua after treatment with fenoxaprop-P-ethyl, especially the activities of ECOD and cytochrome P450 reductase. Besides this, cytochrome P450 monooxygenase activity toward fenoxaprop-P-ethyl in P. annua increased significantly compared to untreated or treated with mefenpyr-diethyl plants and treated or untreated A. aequalis. Cytochrome P450 monooxygenase may play an important role in the different responses to fenoxaprop-P-ethyl in P. annua and A. aequalis.     

渐狭蜡蚧菌Lecanicillium attenuatum产几丁质酶的活性及对南方根结线虫卵孵化的抑制作用

为探究卵寄生真菌产生的几丁质酶对南方根结线虫卵孵化的抑制作用,采用分离自黑龙江大豆孢囊线虫孢囊上的菌株CGMCC5328,利用NAG和pNP法测定其几丁质降解酶系和外切酶的活性,分析几丁质酶粗酶液对南方根结线虫卵的孵化抑制效果.结果表明,菌株CGMCC5328经形态学和ITS序列分析鉴定为渐狭蜡蚧菌Lecanicillium attenuatum;在几丁质酶诱导培养基中培养第4天时其分泌的几丁质降解酶系达酶活高峰,为16.90 U/mL;第6天外切酶达酶活高峰,为0.59 U/mL,之后酶活趋于稳定持续至第14天;几丁质酶分子量分别为79.6、65.6、54.1、42.1和32.9 kDa;其中培养第7天的几丁质酶粗酶原液对南方根结线虫卵孵化的抑制率为83.17%;第6天菌株CGMCC5328对卵的寄生率为85.10%.表明高效产几丁质酶的卵寄生真菌渐狭蜡蚧菌菌株CGMCC5328对南方根结线虫卵孵化具有明显的抑制效果.     

Effect of celangulin V on detoxification enzymes in Mythimna separata and Agrotis ypsilon

Celangulin V (CA-V), a β-dihydroagrofuran sesquiterpene polyol ester, is extracted from the root bark of Chinese bittersweet, Celastrus augulatus Maxim. It exhibited selective toxicity against different insects. By CO-difference spectral and biochemical method, the effects of CA-V on two kinds of detoxification enzymes, cytochrome P450 (P450 and NADPH-cytochrome P450 reductase) and glutathione S-transferase, were investigated in oriental armyworm, Mythimna separata and black cutworm, Agrotis ypsilon. CA-V showed higher induction against P450 of M. separata than that of A. ypsilon. Treated by CA-V, the maximum absorption of M. separata increased 1.2 and 0.8 nm than the control, respectively. Meanwhile, compared with the control, the P450 content and NADPH-P450 reductase activity in treated M. separata larvae increased 1.46-, 2.26- and 1.26-, 2.56-fold, respectively. But in treated A. ypsilon larvae, they all increased a little more than those of control. So far as M. separata and A. ypsilon, whether there is exposure of CA-V or not, the P450 content and GST activity in A. ypsilon were obviously higher than those in M. separata. It suggested that the content or activity difference of these two kinds of detoxification enzymes may have important roles in the selective toxicity of CA-V in M. separata and A. ypsilon.     

The effects of Saw palmetto on flumethrin-induced lipid peroxidation in rats

In the present study, 40 male Wistar albino rats were used and divided into 4 groups. The first group served as the control group; the second group was administered Saw palmetto extract at the dose of 20 mg/kg/bw; the third group was administered flumethrin at the dose of 15 mg/kg/bw; and the fourth group was administered a combination of 20 mg/kg/bw Saw palmetto extract and 15 mg/kg/bw flumethrin, for 21 days, orally. After the trial period, blood and tissue (liver, kidney and brain) samples were taken from the rats. Saw palmetto extract did not cause significant alterations in plasma and tissue malondialdehyde (MDA) levels, serum and tissue nitric oxide (NO) levels, erythrocyte and tissue superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) activities when compared to the controls (p > 0.05). Flumethrin led to increased plasma and tissue MDA levels, serum and tissue NO levels, tissue GSH-Px activities and decreased erythrocyte and tissue SOD and CAT activities, and erythrocyte GSH-Px activity, compared to the controls (p < 0.05). The flumethrin and Saw palmetto extract combination increased erythrocyte SOD activity and decreased brain GSH-Px activity as compared to flumethrin (p < 0.05). In conclusion, it was determined that Saw palmetto extract did not cause any negative effect on the prooxidant-antioxidant balance. While flumethrin stimulated lipid peroxidation; Saw palmetto extract at the dose of 20 mg/kg/bw did not exhibit enough antioxidant effect in rats.     

苏云金杆菌亚致死浓度对美国白蛾及其寄生蜂生长发育的影响

为阐明苏云金杆菌Bacillus thuringiensis(Bt)与白蛾周氏啮小蜂Chouioia cunea Yang的协同作用,分别用103~108孢子/m L的6个Bt浓度处理美国白蛾Hyphantria cunea 2龄幼虫后,通过室内试验测定了Bt对其致死、亚致死效应,及亚致死浓度Bt对寄生蜂子代出蜂的影响。结果表明,浓度106孢子/m L处理组美国白蛾均未能化蛹;而106孢子/m L处理组均能化蛹并羽化,且幼虫发育历期随Bt浓度的增加而延长,平均蛹重在74.92~92.18 mg之间,均高于对照的68.66 mg,但蛹重不呈线性规律变化。当Bt对美国白蛾平均校正死亡率低于17.17%时,幼虫发育历期延迟不明显,但平均蛹重为101.11~124.34 mg,均高于对照;接蜂后能够正常出蜂,出蜂率为33.13%~51.25%,每蛹出蜂量为117.43~143.42头,均显著高于对照。表明用平均校正死亡率低于20%的Bt处理对白蛾周氏啮小蜂的寄生有利,2种生防措施协同作用存在增效潜力。     

Effects of Artemisia annua L. (Asteracea) on nutritional physiology and enzyme activities of elm leaf beetle, Xanthogaleruca luteola Mull. (Coleoptera: Chrysomellidae)

Methanolic extract of Artemisia annua L., a weed collected around paddy fields in north of Iran, was investigated for its toxic effects on: feeding, growth, fecundity, fertility including the biochemical characteristics of elm leaf beetle Xanthogaleruca luteola Mull. The toxicity tests indicate that insecticidal effect was 2.4-fold higher in 3rd instar larvae than in adults. The LC₅₀ was 48% and 43.77% of a methanolic leaf extract at 24 and 48 h, respectively. The feeding deterrence was highest at 10% concentration and lowest at 0.625% for 3rd instar larvae and adults during the first 24 h and decreased thereafter. Larval duration significantly increased at higher concentrations. Larval treatment with 10% methanolic extract resulted in deformed adults (adultoids) with drastic changes in gross morphology of female reproductive system. Food digestion and assimilation significantly decreased in adults. Larval duration and adult fecundity and fertility were also significantly reduced. Twenty-four hours after treating 3rd instar larva with the extract the levels of glucose, protein, urea, uric acid, α-amylase, alkaline phosphatase, alanine amino transferase and aspartate amino transferase significantly changed. However, at 48 h the extract lost its potency. The extract did not effect the level of cholesterol in treated larva. These results indicate that Artemisia annua L. extract contains inhibitors of key metabolic pathways that may be useful in future control of the elm leaf beetle.     

Effects of N-acetylcysteine on oxidative responses in the liver of fenthion exposed Cyprinus carpio

The aim of this study was to evaluate the effects of different N-acetylcysteine doses on the tolerance to fenthion-induced oxidative stress, alterations in glutathione metabolism and cholinesterase specific activities in the liver by using freshwater fish Cyprinus carpio (Cyprinidae) as a model organism. An acute toxicity study was carried out to determine 96-h median lethal concentration of fenthion for this species (2.16 mg/L) and 80% of this concentration was applied in toxicity studies. Four groups, each containing eight fish were constituted as follows: Control group, fenthion treated group, 0.5 or 400 mg/kg NAC-injected + fenthion-treated groups. Biochemical analyses were carried out spectrophotometrically. Fenthion treatment significantly decreased total glutathione and glutathione levels, glutathione/glutathione disulfide ratio together with glutathione reductase and γ-glutamylcysteine synthetase specific enzyme activities. The higher dose of N-acetylcysteine increased the toxic effects of fenthion and γ-glutamyl transpeptidase specific activity while decreasing glutathione S-transferase specific activity. However, injection of the lower dose provided a limited protection against fenthion toxicity. In all exposure groups, lipid peroxidation increased and total protein levels decreased, while protein depletion was prevented by low dose of N-acetylcysteine application. Acetylcholinesterase and butyrylcholinesterase activities were at similar levels in the liver of C. carpio. A dose-dependent inhibition was observed in butyrylcholinesterase activity by N-acetylcysteine application. The results showed that fenthion had a significant oxidative stress inducing potential through the reduction of glutathione redox capacity. The critical point for overcoming oxidative stress by N-acetylcysteine in fenthion toxicity was the selection of the dose; N-acetylcysteine exerted its toxic effects by means of oxidative stress in fish liver at the higher dose.     

Effect of pesticides on phosphate solubilization by Bacillus sphaericus and Pseudomonas cepacia

Intensive screening of phosphate solubilizing bacteria with genetic potential for increased tolerance to high salt, high pH and high temperature could enhance production of food and forage in semi-arid regions. Emphasizing particularly on this hypothesis 165 phosphate solubilizing bacteria was isolated. Among these, two cultures Bacillus sphaericus and Pseudomonas cepacia were selected on the basis of salt tolerance property and PS activity with different forms of phosphates. In the present investigation both these culture were assessed for the effect of six different pesticides, to confirm its successful realistic application as microbial inoculants in actual farm conditions. Both cultures showed better phosphate solubilizing activity with phosphate containing pesticides. Among these two isolates P. cepacia was a better performer in terms of phosphate solubilizing activity with different pesticides. It may be due to its well documented extra ordinary, versatile metabolic activity. The present study may prove them to be potential candidates to be used as microbial inoculants.     

哈茨木霉菌与啶酰菌胺联用对番茄灰霉病菌的增效机制

为验证哈茨木霉菌与啶酰菌胺联用对番茄灰霉病菌的增效作用,采用显微镜观察法观察了菌药联用后哈茨木霉菌和番茄灰霉病菌的菌丝形态,用菌丝生长速率法和圆盘滤膜法测定了菌药联用后哈茨木霉菌挥发性物质、非挥发性物质和粗酶液对番茄灰霉病菌的抑菌活性.结果显示:啶酰菌胺对哈茨木霉菌的菌丝基本无影响,但能使灰霉病菌的菌丝发生间断性溶解;菌药联用后哈茨木霉菌挥发性物质对灰霉病菌的最高抑菌活性为61.17％,而哈茨木霉菌和啶酰菌胺单独对灰霉病菌的抑菌活性分别为48.79％、0.97％,表现增效作用;菌药联用后哈茨木霉菌非挥发性物质和粗酶液对番茄灰霉病菌的抑菌活性未明显增强.研究表明,啶酰菌胺与哈茨木霉菌联用的增效机制是啶酰菌胺导致灰霉病菌的菌丝部分溶解,同时增强了哈茨木霉菌挥发性物质对灰霉病菌的抑菌活性.     

生防菌Alternaria amaranthi-3对反枝苋的防治效果

反枝苋Amaranthus retroflexus是一种世界性恶性杂草。为了确定微生物除草剂候选菌Alternaria amaranthi-3防除反枝苋的潜力,通过盆栽试验研究了接种浓度、露期和水乳剂型对A.ama-ranthi-3菌株致病力的影响。结果显示,接种浓度显著影响菌株的致病力,在48h露期条件下,接种孢子浓度为105个/mL时,菌株水剂对反枝苋幼苗生长抑制率为35.55%;浓度为107个/mL时,生长抑制率达到75.25%。露期对该菌株的致病力也有较大影响,在不保湿条件下,菌株水剂对反枝苋的生长抑制率为26.43%,而保湿48h处理的生长抑制率达到77.96%。Span80∶Tween80=1∶3的复配乳化剂和大豆油制备的水乳剂可显著降低露期对菌株防效的影响和提高菌株的致病力,无露期时,菌株水乳剂对反枝苋的生长抑制率达到88.35%,显著高于水剂;48h露期条件下,菌株水乳剂处理的生长抑制率为90.59%,而菌株水剂处理为77.96%。表明通过剂型的改进菌株Alternaria amaranthi-3能有效防除反枝苋。     

Bio-potency of serine proteinase inhibitors from Acacia senegal seeds on digestive proteinases, larval growth and development of Helicoverpa armigera (Hübner)

Proteinase inhibitors (AsPIs) with high activity against serine proteinases were purified from seeds of the tree legume, Acacia senegal by ammonium sulfate precipitation followed by DEAE-Sephadex A-25 column and evaluated against Helicoverpa armigera larvae by in vitro and in vivo methods. The molecular weight of AsPIs was found to be approximately 19.58 ± 1.00 and 21.23 ± 1.00 kDa for PI and 18.16 ± 1.00 kDa for PII on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The AsPIs (5 μg/ml) inhibited approximately 70% of midgut trypsin and 61% of elastase-like chymotrypsin. In vitro studies showed that AsPIs have remarkable inhibitory activity towards total gut proteolytic enzymes followed by trypsin and chymotrypsin. The IC₅₀ of AsPIs for midgut trypsin was 0.1 μg/ml and for chymotrypsin was 2.0 μg/ml. The inhibition of gut proteinase enzymes was of the non-competitive type. In larval feeding studies, AsPIs were found to retard growth and development of H. armigera and also affects the fecundity of the pest. The results advocate the use of AsPIs in transgenic technology to develop plant resistance to H. armigera.     

Biological and biochemical parameters of Biomphalaria alexandrina snails exposed to the plants Datura stramonium and Sesbania sesban as water suspensions of their dry powder

Four plant species, as a dry powder of their leaves, were tested against Biomphalaria alexandrina snails, the intermediate host of Schistosoma mansoni. The bioassay tests revealed the plants Datura stramonium and Sesbania sesban to be more toxic to the snails than the other two ones. Therefore, they were tested against snails’ fecundity (M_x), reproduction rate (R_o) and their infection with S. mansoni miracidia. In addition, total protein concentration and the activities of the transaminases (AsT and AlT) and phosphatases (AcP and AkP) enzymes in hemolymph and tissues of snails treated with these plants were determined. As well, glucose concentration in snails’ hemolymph was evaluated.Exposure of snails for 4 weeks to LC₁₀ and LC₂₅ of the plants D. stramonium and S. sesban dry powder markly suppressed their M_x and R_o. The reduction rates of R_o for snails exposed to LC₂₅ of these plants were 62.1% and 76.4%, respectively. As well, a considerable reduction in the infection rates of snails exposed to these plants either during, pre- or post-miracidial exposure was recorded. Thus, infection rates of snails treated during miracidial exposure with LC₁₀ of D. stramonium and S. sesban were 41.7% and 52.2%, respectively, compared to 92.6% for control group (P < 0.01). These plants, also, reduced the duration of cercarial shedding and cercarial production/snail. So, snails exposed to LC₂₅ of these plants shed 372.8 and 223.2 cercariae/snail, respectively, compared to 766.3 cercariae/infected control snail (P < 0.01).The results, also, revealed that glucose and total protein concentrations in hemolymph of snails treated with LC₁₀ and LC₂₅ of these plants were decreased, meanwhile, the activities of the enzymes AsT, AlT, AcP and AkP were elevated (P < 0.01). However, the activity of AcP in tissues of treated snails was decreased compared to that of control ones. It is concluded that LC₂₅ of the plants D. stramonium and S. sesban negatively interferes with biological and physiological activities of B. alexandrina snails, consequently it could be effective in interrupting and minimizing the transmission of S. mansoni.     

Mosquito larvicidal activity of alkaloids from Zanthoxylum lemairei against the malaria vector Anopheles gambiae

Four alkaloids, 10-O-demethyl-17-O-methylisoarnottianamide 1, 6-acetonyl-N-methyl-dihydrodecarine 2, nitidine 3, and chelerythrine 4 were isolated from the plant Zanthoxylum lemairei (Rutaceae) and evaluated for mosquito larvicidal activity against the malaria vector Anopheles gambiae. The mortalities of the larvae were determined after 24 h. The results of the larvicidal tests demonstrated that compounds 1 and 2 were the most potent with mortality rates of 96.7% and 98.3% at a concentration of 250 mg/L, respectively. Compound 3 was less potent with a mortality of 28.3% at the same concentration. The percent mortality of 100% was observed at a concentration of 500 mg/L. The least potent of the four alkaloids was compound 4, which achieved 100% mortality at 1000 mg/L. These findings could be useful in the research for newer more selective, biodegradable and natural larvicidal compounds or can be used as lead compounds for the development of larvicides.     

椰心叶甲人工饲料的研制及应用效果评价

为了获得入侵害虫椰心叶甲Brontispa longissima(Gestro)的人工饲料,在分析其天然寄主叶片水分和营养成分基础上,借鉴其它鞘翅目昆虫人工饲料配方,进行椰心叶甲人工饲料的配制和筛选,并评价人工饲料饲养的椰心叶甲对其寄生蜂椰甲截脉姬小蜂Asecodes hispinarum和椰心叶甲啮小蜂Tetrastichus brontispae的适合性。人工饲料配方的成分:蔗糖4%、椰子粉2%、大豆粉2%、椰树叶粉10%、酵母2%、维生素E 0.3%、抗坏血酸0.2%、对羟基苯甲酸甲酯0.2%、琼脂4%、链霉素0.03%和水75%。用所配制的人工饲料饲养椰心叶甲初孵幼虫,其蛹成活率可达36%,蛹羽化率与对照无显著差异,均在90%以上;雌成虫占52.4%,与对照无显著差异。表明人工饲料饲养所得的椰心叶甲可用于其幼虫寄生蜂椰甲截脉姬小蜂和蛹寄生蜂椰心叶甲啮小蜂的扩繁。     

Elevated α-esterase levels associated with permethrin tolerance in Aedes aegypti (L.) from Baja California, Mexico

A discriminating dose for permethrin for Aedes aegypti from Baja California, Mexico was determined, and was used to select individuals. Mosquitoes were collected from four different municipalities located in the north and south end of the Baja California Peninsula. Individuals were chosen for further study based on their similar response to the insecticide. We exposed 10 groups of 90 Ae. aegypti females to the discriminating dose (172 μg/ml) and after producing 50% mortality, individuals were divided into two categories: killed and survivors. Each of these groups was dissected to separate the head, thorax, and abdomen. Biochemical tests were performed on the head and thorax to determine resistance-related enzyme activities including: α- and β-esterases, glutathione S-transferase, acetyl cholinesterase, insensitive acetyl cholinesterase, and mixed-function oxidases. The results were compared with those for the susceptible New Orleans strain of Ae. aegypti. All the populations studied showed the consistent presence of α-esterases, with elevated levels in permethrin-selected populations. Although β-esterases and GST levels were present in high proportions, they did not reveal a clear pattern in relation to resistance.     

Biological and biochemical responses of Biomphalaria alexandrina to some extracts of the plants Solanum siniacum and Artemisia judaica L.

The molluscicidal activity of cold water, boiled water, methanol, ethanol, acetone and chloroform extracts of Solanum siniacum and Artemisia judaica L. plants against Biomphalaria alexandrina snails was carried out. The tests revealed plant’s ethanol extract was more toxic to the snails than the other tested extracts. Therefore, it was tested against snails’ fecundity (M_x), reproduction rate (R₀) and their infection with Schistosoma mansoni miracidia. In addition, biochemical parameters and the activities of some enzymes in tissues of snails treated with the two tested plants were determined. As well, glucose concentration in snails’ hemolymph was evaluated. Exposure of B. alexandrina snails to plant’s ethanol extract led to a significant reduction in their survival and snails’ fecundity, reproduction rate. In addition, it caused a considerable reduction in the infectivity of S. mansoni miracidia to the snails. Also, it caused a reduction in number of cercariae per snail during the patent period and in the period of cercarial shedding. The results revealed that the glucose concentration in hemolymph and Lactate level in soft tissues of treated snails were increased (P < 0.001) while glycogen, total protein, the lipid content and the pyruvate level in snail’s tissues decreased (P < 0.001). The activities of lactic dehydrogenase (LDH), pyruvatekinase (PK) and cytochrome oxidase (CY) enzymes in homogenate of snail’s tissues were reduced (P < 0.001) in response to treatment with the two tested plants while protease (PR) activity increased (P < 0.001). It is concluded that the application of LC₂₅ of ethanol extract of S. siniacum and A. judaica L. may be helpful in snail control as it interferes with the snails’ biology and physiology.     

Methylparathion- and carbofuran-induced mitochondrial dysfunction and oxidative stress in Helicoverpa armigera (Noctuidae: Lepidoptera)

The cotton bollworm, Helicoverpa armigera is a polyphagous pest of several crops in Asia, Africa, and the Mediterranean Europe. Organophosphate and carbamate insecticides are used on a large-scale to control Helicoverpa. Therefore, we studied the effect of methylparathion and carbofuran, an organophosphate and carbamate insecticide, respectively, on oxidative phosphorylation and oxidative stress in H. armigera larvae to gain an understanding of the different target sites of these insecticides. It was observed that state III and state IV respiration, respiratory control index (RCI), and P/O ratios were inhibited in a dose-dependent manner by methylparathion and carbofuran under in vitro and in vivo conditions. Methylparathion and carbofuran inhibited complex II by ∼45% and 30%, respectively. Lipid peroxidation, H₂O₂ content, and lactate dehydrogenase (LDH) activity increased and glutathione reductase (GR) activity decreased in a time- and dose-dependent manner in insecticide-fed larvae. However, catalase activity was not affected in insecticide-fed larvae. Larval growth decreased by ∼64% and 67% in larvae fed on diets with 100 μM of methylparathion and carbofuran. The results suggested that both the insecticides impede the mitochondrial respiratory functions and induced lipid peroxidation, H₂O₂, and LDH leak, leading to oxidative stress in cells, which contribute to deleterious effects of these insecticides on the growth of H. armigera larvae, along with their neurotoxic effects.