Studies on glutathione transferase from grasshopper (Zonocerus variegatus)

Glutathione transferase (GST) was purified from the hindgut of grasshopper (Zonocerus variegatus) a polyphagous insect. The purified enzyme had a native molecular weight of 40 kDa and a subunit molecular weight of 19 kDa. The purified enzyme could conjugate glutathione (GSH) with 1-chloro-2,4-dinitrobenzene (CDNB), paranitrobenzylchloride, paranitrophenylacetate, 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole (NBDCl), and 1,2-dichloro-4-nitrobenzene (DCNB) with specific activities of 3.3 ± 0.3, 0.49 ± 0.10, 0.10 ± 0.002, 1.2 ± 0.2, and 1.7 ± 0.4 μmol/min/mg protein, respectively. CDNB appears to be the best substrate with a specificity constant, k_cat/K_m, of 1.8 ± 0.1 × 10⁻⁴ M⁻¹ S⁻¹. The kinetic mechanism of Z. variegatus GST (zvGST) in the conjugation of GSH with some electrophilic substrates appears complex. Conjugation of GSH with DCNB was inhibited by high DCNB concentration, while with NBDCl, as the electrophilic substrates, different values of K_m were obtained at high and low concentrations of the substrates. Cibacron blue, hematin, S-hexylglutathione, and oxidized glutathione inhibited the enzyme with I₅₀ values of 0.057 ± 0.004, 0.80 ± 0.2, 33 ± 2 μM, and 5.2 ± 0.3 mM, respectively. The nature of inhibition by each of these inhibitors is either competitive or non-competitive at varying GSH or CDNB as substrates. NADH and NAD⁺ inhibited the enzyme with an I₅₀ value of 0.4 ± 0.01 and 11 ± 1 mM, respectively. NADH at a concentration of 0.54 mM completely abolished the activity. As part of its adaptation, the flexible kinetic pathway of detoxication by zvGST may assist the organism in coping with various xenobiotics encountered in its preferred food plants.     

Effects of gibberellic acid on ovarian biochemical composition and ecdysteroid amounts in the migratory locust Locusta migratoria (Orthoptera,Acrididae)

Migratory locusts represent the most important crop pests in Africa and Asia. Because environmental damages are associated with the use of synthetic insecticides in locust and grasshopper control, new environmentally acceptable approaches are becoming increasingly important. The effects of gibberellic acid (GA₃), a plant growth regulator, was investigated by topical application and ingestion on the reproductive physiology and ecdysteroids production of the migratory locust Locusta migratoria at concentrations of 125, 625, 3125, 4125, 5125 and 6125 μg/mL. The treatment applied to adult females during the pre-ovipositional phase provokes a significant adverse influence on their reproductive potential. Indeed, GA₃ significantly reduced both fecundity and fertility. Gibberellic acid also caused disturbances in the incorporation of the hemolymph metabolites (proteins, carbohydrates and lipids) in the oocyte resulting in a significant reduction in their concentrations in the ovaries. Ecdysteroid production was measured by an enzymo-immunoassay. GA₃, administered by ingestion to the adult females, significantly reduced the ecdysteroid titers in ovaries and freshly laid eggs.     

两型亚洲小车蝗飞行肌超微结构比较研究

亚洲小车蝗Oedaleus asiaticus B.-Bienko具有长距离迁飞能力,常迁飞为害造成严重损失。掌握其飞行肌结构特征,分析其飞行能力及影响因素,对提高对其监测预警水平具有重要指导作用。本研究采用电子显微镜对群居型和散居型亚洲小车蝗雌成虫背纵肌进行了比较分析。结果表明:群居型和散居型成虫飞行肌具有相似的亚细胞结构,飞行肌的肌原纤维粗细肌丝比例为1∶3,6根细肌丝环绕1根粗肌丝,形成六角形结构。飞行肌的发育和线粒体的形成均是渐进的过程,在不同日龄成虫间存在差异。亚洲小车蝗肌原纤维直径在0.6～1.5μm,群居型成虫的肌原纤维直径多大于散居型。肌节长度为2.6～4.5μm,7日龄肌节长度最短,多数日龄群居型成虫肌节长度小于散居型(2.4～3.8μm)。线粒体在背纵肌内含量占肌纤维线粒体含量的25%～45%,群居型和散居型亚洲小车蝗存在显著差异,群居型7日龄雌成虫线粒体占肌原纤维的比例最高,为52.37%,而散居型的只有32.74%。线粒体含量差异可能是两型亚洲小车蝗成虫飞行能力差异显著的重要原因之一。     

阿维菌素对黄胸散白蚁Reticulitermes speratus的毒效

在室内采用毒土法、滤纸法和毒土柱法测定了0.2%阿维菌素乳油对黄胸散白蚁的毒杀效果。 结果表明,阿维菌素对黄胸散白蚁的触杀作用速度较慢,在处理的96 h内,随时间推移毒性逐渐增强;黄胸散白蚁接触或取食药剂96 h后,其LC50值均低于20 mg/L;在供试条件下,用2.5 mg/L以上的浓度处理土壤,即能阻止黄胸散白蚁在土柱中的穿透,显示阿维菌素是一种值得进一步研究的白蚁预防药剂。     

Biochemical effects of acute phoxim administration on antioxidant system and acetylcholinesterase in Oxya chinensis (Thunberg) (Orthoptera: Acrididae)

The study was undertaken to evaluate the effects of different concentrations of phoxim on acetylcholinesterase (AChE) and esterase (EST) activities, and antioxidant system after topical application to Oxya chinensis. The results showed that phoxim inhibited AChE activity, and did not cause significant changes in the EST activity and the levels of malondialdehyde (MDA) and reduced glutathione (GSH). After phoxim administration, superoxide (SOD) and catalase (CAT) activities showed a biphasic response with an initial increase followed by a decline in their activities. Glutathione reductase (GR) and glutathione peroxidase (GPx) activities were inhibited in comparison with the control. Glutathione S-transferase (GST) activity showed irregular changes. Its activity increased significantly at the concentrations of 0.06 and 0.12 μg/μL and decreased at the concentrations of 0.09 and 0.24 μg/μL compared with the control. Changes in SOD, CAT, GST, GPx, and GR activities indicated that phoxim caused oxidative damage in O. chinensis. However, no significant changes in MDA content suggested that these enzymes played important roles in scavenging the oxidative free radicals induced by phoxim in O. chinensis. The formation of oxygen free radicals might be a factor in the toxicity of phoxim.     

Toxicity,penetration, and metabolism of AC 217,300 (AMDRO) in the tobacco budworm (Heliothis virescens) by various methods of application

Penetration was found to be the major factor in the selective toxicity of AC 217,300 in Heliothis virescens larvae. When applied topically in either acetone or dimethyl sulfoxide solutions, less than 3 and 11%, respectively, of the applied dose penetrated the cuticle after 72 hr. Ingestion resulted in tissue residues of 45–55% of the applied dose, and increased toxicity 40 to 140-fold over topical application. Five primary metabolites were tentatively identified by cochromatography with authentic standards. At least 10 other minor metabolites were detected. The lack of insecticidal activity with any of the known metabolites, as well as the tissue residues and metabolic profile, suggested that AC 217,300 is the actual toxicant.     

白纹雏蝗抗寒特性和高温耐受力及其机制

为阐明白纹雏蝗Chorthippus albonemus抗寒和高温耐受能力及其抵御机制,本研究测定白纹雏蝗过冷却点、冰点值及其对高温的耐受力,并采用生理生化方法测定白纹雏蝗在24、28、32、36、40、44和48℃不同温度下抗逆物质的积累量和变化情况.结果 表明,白纹雏蝗卵的过冷却点值为-22.58℃,冰点值为-30...     

新烟碱类等杀虫剂对葱蝇的毒力及其对生长发育和繁殖的影响

采用定量滴加法和浸渍法测定了8种药剂对葱蝇1龄和3龄幼虫的毒力,用噻虫胺和噻虫嗪等新烟碱类杀虫剂的亚致死浓度分别处理葱蝇1龄和3龄幼虫,观察其对葱蝇生长发育和繁殖的影响,并进行了田间药效试验。结果表明,噻虫胺和噻虫嗪对3龄幼虫48 h的LC₅₀分别为14.7839 mg/L和13.3055 mg/L,毒力为毒死蜱的0.41倍和0.50倍。但LC_30-40剂量处理葱蝇3龄幼虫后,第6天存活幼虫体重分别较对照降低35.47%和36.34%,幼虫发育历期延长3.68天和3.98天,化蛹率降低71.91%和78.65%,雌蛹重降低13.36%和14.72%,雄蛹重降低15.97%和18.32%,羽化率降低12.50%和17.86%,单雌产卵量降低47.71%和51.68%。噻虫胺和噻虫嗪处理1龄幼虫,对其生长发育也有显著不利影响。田间药效试验结果显示,1 200 g/hm²噻虫胺和噻虫嗪处理后7天防效分别达98.16％和92.46％,表明这两种药剂对葱蝇防治效果高、推广应用价值大。     

Toxicity and neurophysiological effects of selected insecticides on the mole cricket, Scapteriscus vicinus (Orthoptera: Gryllotalpidae)

Mole crickets (Scapteriscus spp.) are severe subterranean pests of turfgrasses, commonly targeted with neurotoxic insecticides. Ideally insecticides used against mole crickets should induce quick knockdown or mortality to minimize damage caused by their tunneling. However, neurophysiological effects of insecticides on mole crickets are mostly unknown. The aims of this study were to investigate neurophysiological and toxic effects of several insecticides on tawny mole cricket (Scapteriscus vicinus Scudder) adults and nymphs, and potential synergy between pyrethroid and neonicotinoid insecticides. Bifenthrin, fipronil, and the combination of bifenthrin + imidacloprid provided the fastest median mortality when injected. The combination of bifenthrin + imidacloprid elicited faster toxicity than either active ingredient alone. Imidacloprid, bifenthrin, and bifenthrin + imidacloprid caused immediate knockdown, whereas fipronil immobilized mole crickets within 1-2 h. Acephate, bifenthrin, fipronil, imidacloprid, and bifenthrin + imidacloprid caused significant neuroexcitation. Bifenthrin + imidacloprid resulted in greater increases of spontaneous neural activity than the additive effects of imidacloprid and bifenthrin alone. Excitatory compounds acting at sodium and chloride channels (bifenthrin and fipronil) were the most toxic against S. vicinus. Combining a sodium channel toxin (bifenthrin) and a synaptic toxin (imidacloprid) led to greater than additive neurophysiological and toxic effects, which to our knowledge provides the first documented evidence of synergistic neurological “potentiation”.     

5株绿僵菌对东亚飞蝗的毒力测定

在室内用点滴法测定了 5株绿僵菌对东亚飞蝗的毒力 ,结果表明 ,其毒力效果与菌株种类 ,接种剂量和温度有密切关系 ,菌株对东亚飞蝗的毒力为LA06>LB08>LC11>LF07>LD04。接种LA06菌株孢子量在 2.6×10⁴个/头下 ,对 4龄蝗蝻的LT₅₀为 3.91d。用不同剂量LA06接种 4龄蝗蝻时 ,发现其LD₅₀仅为26.67个/头。在设定剂量下 ,低龄蝻比高龄蝻和成虫更敏感 ,死亡较快。不同菌株在不同温度下的毒力不同 ,LA06在 30℃下比在 24℃下毒力强 ,而LD04和LF07在 24℃下比在30℃下毒力强。     

麻疯树萜醇I对家蚕的毒性及作用机理研究

研究了从麻疯树种子中分离的麻疯树萜醇I对3龄家蚕的毒性及其对家蚕中肠蛋白酶和组织结构的影响。结果显示:麻疯树萜醇I对家蚕无接触毒性,其急性毒性主要表现为胃毒作用,处理后48、72和120 h的LC50值分别为0.579、0.220和0.158 mg/mL。家蚕对麻疯树萜醇I处理 叶片的取食量显著少于对照组,24 h和 48 h的拒食中浓度(AFC50)分别为0.160和0.145 mg/mL。 取食麻疯树萜醇I后,家蚕体重增长显著被抑制,这一抑制作用具有明显的时间效应和浓度效应,即随着处理浓度的增高和处理时间的延长而逐渐增大。取食麻疯树萜醇I还导致家蚕中肠蛋白酶的比活力随时间逐渐下降,48 h时最低,0.25、0.125及0.062 5 mg/mL处理组蛋白酶比活力分别仅为对照的32.94%、43.35%、71.45%;处理浓度越大,蛋白酶比活力越低。石蜡切片显示,麻疯树萜醇I主要影响了中肠细胞的组织结构,引起细胞从基底膜上脱落,细胞破裂,使脂肪体消融等。表明麻疯树萜醇I对消化系统的破坏是其导致试虫中毒的重要机制之一。     

稻田中华稻蝗发生动态、危害损失及防治指标

系统地研究了中华稻蝗发生动态与危害损失。结果表明,中华稻蝗在浙江年发生1代,主要危害早稻和早播单季晚稻。水稻分蘖期接入虫量10～50头/m2,叶被害率为52.61%～78.81%,叶被害指数为14.51～25.00,产量损失率为2.31%～27.42%,孕穗至破口期接入虫量1～17头/m2,叶被害率为56.63%～88.00%,叶被害指数为14.69～31.32,产量损失率为1.28%～32.74%,随着虫口密度增加,危害程度上升,产量损失率加大,两者具有密切相关性,建立了危害损失关系式。水稻叶片受害、光合能力减弱、幼穗分化不良、实粒减少、秕谷增加和粒重下降是导致水稻减产的主要原因。模拟测试表明,随着水稻受害生育期推迟损失增大,且分蘖期危害具有一定的补偿能力。在现有生产条件下,经济允许损失水平为2.5%～3.0%;2～3龄蝗蝻为防治适期,氟虫腈、三唑磷等有较好防治效果。提出水稻分蘖期和孕穗至破口期防治指标分别为10头/m2和5头/m2。     

微量氯氰菊酯对家蚕的毒性

在桑园中喷施微量氯氰菊酯,用该桑叶连续喂饲2龄起蚕,调查一个龄期的死亡率。结果表明:喷施过1.08 μg/L氯氰菊酯的桑叶在经过63 d后,对家蚕依然存在致死作用;喷施过108.00 μg/L氯氰菊酯的桑园中,10 d后新生长桑叶未见对家蚕的致死作用。对家蚕3龄起蚕进行连续喂饲染毒桑叶的试验结果表明:0.11 ng/L氯氰菊酯将引起家蚕幼虫死亡率显著上升(P＜0.05)和眠蚕体重显著下降(P＜0.05);1.08 ng/L将引起幼虫死亡率的极显著上升(P＜0.01),以及眠蚕体重和全茧量的极显著下降(P＜0.01);10.80 ng/L将引起茧层率的极显著下降(P＜0.01)。     

Characterizations of general esterases in relation to malathion susceptibility in two field populations of the oriental migratory locust, Locusta migratoria manilensis (Meyen)

General esterases were characterized and compared from two populations of the oriental migratory locust, Locusta migratoria manilensis, collected from Huanghua and Pingshan Counties, Hebei Province, China. General esterases were most concentrated in the thorax and abdomen, which contained 46.1 and 36.1% of total esterase activity in females, and 42.7 and 36.0% in males, respectively, when α-naphthyl acetate was used as a substrate. There was no distinct difference in esterase banding patterns in different body regions for the substrates α-naphthyl acetate and β-naphthyl acetate on non-denaturing polyacrylamide gel electrophoresis (PAGE). However, the general esterase activities in the Huanghua population were 1.8-fold higher than those in the Pingshan population in both females and males. Increased esterase activity in the Huanghua population appeared to be mainly due to several additional esterase bands detected on non-denaturing PAGE. Inhibition studies of general esterases using four inhibitors, including paraoxon, malaoxon, eserine, and carbaryl, indicated that most general esterases in the two populations were B-type. The increased esterase activity in the Huanghua population appeared to be associated with a 1.8-fold decreased susceptibility to malathion. Such differences may attribute to the difference in control practices for the locust between Huanghua and Pingshan Counties.     

用无菌苗法鉴定油菜对菌核病的抗(耐)病性

快速、准确、有效的抗病性鉴定方法是抗病育种的基础和保障.目前,国内外鉴定油菜菌核病的抗(耐)病性的方法归纳起来主要有草酸鉴定法、人工气候室盆栽苗接种鉴定、大田成株期人工辅助接种鉴定和大田病圃或非病圃自然侵染鉴定法等.草酸鉴定法对鉴定材料的破坏性大,育种中应用仅供筛选抗草酸的单株或材料,且不能鉴定抗菌核病菌侵入的材料.人工气候室盆栽苗接种鉴定受空间或成本的限制,难以用于大量的筛选工作,大田成株期人工辅助接种鉴定和大田自然侵染鉴定既受季节的限制,也受环境因素的影响.因此,探寻更高效、准确的抗(耐)病性鉴定方法,仍是抗病育种的迫切需要.本文介绍了一种准确、快速、高效的鉴定新方法.     

Increased activity and reduced sensitivity of acetylcholinesterase associated with malathion resistance in a field population of the oriental migratory locust, Locusta migratoria manilensis (Meyen)

The susceptibility to malathion, and the activity and sensitivity of acetylcholinesterase (AChE, EC 1.1.1.7) were compared between two populations of the oriental migratory locust, Locusta migratoria manilensis (Meyen) collected from Wudi County of Shandong Province in East China and Huangliu County of Hainan Province in South China. Huangliu population showed 8.5-fold resistance to malathion compared with Wudi population. AChE from Huangliu population showed 4.8-fold higher activity than that from Wudi population toward the model substrate acetylthiocholine (ATC). Kinetic studies indicated that AChE from Huangliu population had 2.6-fold lower affinity, but 5.0-fold higher catalytic activity toward ATC than AChE from Wudi population. Significantly increased activity of AChE in Huangliu population was also confirmed by non-denaturing polyacrylamide gel electrophoresis. Inhibition kinetics revealed that AChE from Huangliu population was 9.8-, 2.4-, 8.0- and 7.7-fold less sensitive to inhibition by paraoxon, malaoxon, chlopyrifos oxon, demeton-S-methyl, respectively, than that from Wudi population. Our studies revealed that a mild resistance to malathion in Huangliu population was associated with reduced sensitivity and increased catalytic activity of AChE. Our results suggest that alterations of AChE may play an important role conferring or contribute to malathion resistance in Huangliu population of the locust.     

Biotransformation of clomazone in rice (Oryza sativa) and early watergrass (Echinochloa oryzoides)

Rice (Oryza sativa), a relatively tolerant species, and early watergrass (Echinochloa oryzoides; EWG), a relatively susceptible species, were exposed to ¹⁴C-labeled clomazone to determine accumulation, biotransformation, and mass balance. On a total mass basis, rice absorbed more clomazone than EWG (p < 0.05), but on a nmol/g basis, there was no significant difference between the two species (p > 0.05). Rice contained more extractable ¹⁴C residues (7.7 ± 0.5 vs. 4.8 ± 0.5 nmol in rice vs. EWG, respectively; p < 0.5), but the concentration in EWG was significantly higher (4.2 ± 0.5 vs. 1.8 ± 0.1 nmol/g in EWG vs. rice, respectively; p < 0.01). More metabolized residue was measured in EWG compared to rice (84.1% vs. 67.9%; p < 0.01). Both species produced hydroxylated forms, β-d-glucoside conjugates, and several other unidentified polar metabolites, but EWG generally produced higher metabolite concentrations. The concentration of the suspected active metabolite, 5-ketoclomazone, was significantly higher in EWG vs. rice (21 ± 2 vs. 5.7 ± 0.5 pmol/g, respectively; p < 0.01). Differences in sensitivity to clomazone between rice and EWG appear to be due to differential metabolism, but in this case the more susceptible EWG qualitatively and quantitatively metabolized more clomazone than the more tolerant rice. This is consistent with the action of a metabolically activated herbicide. This metabolic difference could be exploited to develop herbicide safeners for use with clomazone.     

美国白蛾性信息素(9Z,12Z)-十八碳二烯醛及(9Z,12Z,15Z)-十八碳三烯醛的合成

采用仿生合成法制备了美国白蛾Hyphantria cunea性信息素的两个主要成分,(9Z,12Z)-十八碳二烯醛和(9Z,12Z,15Z)-十八碳三烯醛。其结构均经IR、1H NMR、GC-MS波谱分析确证。     

镧素对镰刀菌Fusarium solani及其致病酶的影响

采用琼脂平板生长速率法及液体培养基培养测定了La对镰刀菌Fusarium solani的抑制作用和毒力,并测定了其对病菌胞外的果胶酶、蛋白酶和纤维素酶等几种致病酶活性的影响。结果表明,随着La2O3浓度升高,对病菌菌丝生长的抑制作用增强,对病菌的EC50和EC95分别为278.2和552.0 mg/L;在一定浓度范围内,La提高了单位量菌丝所产生3种致病酶的活性,但由于菌丝生长受到抑制,除蛋白酶外,病菌胞外致病酶果胶酶和纤维素酶的总量或总活性受到了抑制,降低了病菌的致病力。     

Acephate toxicity,metabolism, and anticholinesterase activity in Heliothis virescens (F.) and Anthonomus grandis grandis (Boheman)

The toxicity (72 hr) of acephate and methamidophos to fourth-instar larvae of the tobacco budworm, Heliothis virescens (F.), was nearly equivalent. In contrast, toxicity (72 hr) of methamidophos to adult boll weevils, Anthonomus grandis grandis (Boheman), was substantially greater than that of acephate. The internal accumulation of acephate was greater for A. grandis grandis than for H. virescens at 24 and 48 hr post-treatment, as was excretion. Acephate was metabolized to methamidophos both in vivo and in vitro by H. virescens but not by A. grandis grandis. In vitro acetylcholinesterase inhibition by methamidophos was greater than that of acephate, but less than that of paraoxon for H. virescens, A. grandis grandis, and the electric eel. Treatment of H. virescens larvae with acephate resulted in increased in vivo acetylcholinesterase inhibition between 24 and 72 hr post-treatment, which was associated with a large increase in mortality. H. virescens treated with methamidophos showed greater mortality and greater acetylcholinesterase inhibition at earlier time periods than those treated with acephate. However, by 72 hr post-treatment, in vivo acetylcholinesterase inhibition by LD₅₀ doses of acephate and methamidophos were approximately equivalent. These results indicate that, for H. virescens, toxicity of acephate is directly related to its metabolism to methamidophos and subsequent acetylcholinesterase inhibition. Likewise, the differential toxicity of acephate and methamidophos to A. grandis grandis adults appears to be due to their inability to metabolize acephate to methamidophos.