Metabolism of a synthetic insect juvenile hormone (JH-I) during the development of Tribolium castaneum (herbst) (coleoptera,tenebrionidae)

Metabolites produced from ¹⁴C-labelled C-18 juvenile hormone (JH-I) topically applied to the flour beetle Tribolium castaneum were measured in larvae aged 21 and 28 days, pupae at four stages of development, and newly emerged and mature adults. The hormone was metabolized rapidly, in all stages examined, to form the corresponding diol-ester, acid-epoxide, and acid-diol derivatives, the diol-ester derivative being the major metabolite produced. The metabolism of JH-I was most rapid at the times of the larval/pupal and pupal/adult transformations. The differences in the rate of metabolism appeared to be correlated with changes in the production of the diol-ester derivative. Similar metabolic changes may regulate the levels of endogenous juvenile hormones during development in this species.     

The inhibition of insect juvenile hormone esterase by trifluoromethylketones: Steric parameters at the active site

A rationally designed structure-activity relationship study has been accomplished using trifluoromethylketone inhibitors of insect juvenile hormone esterase from the cabbage looper, Trichoplusia ni (Hubner) (Lepidoptera: Noctuidae). Several α- and α′-substituted derivatives of 3-octylthio-1,1,1-trifluoropropan-2-one have been prepared and assayed for inhibitory potency against juvenile hormone esterase. The results indicate that the sulfur/protein interaction does not occur in a sterically constrained environment. Substitution adjacent to sulfur did not dramatically effect activity. However, substitution adjacent to the carbonyl of the trifluoromethylketone moiety reduced inhibitory potency substantially, indicating that the active site region of juvenile hormone esterase which interacts with the carbonyl is restricted to rather small substrates. A small hydrophobic pocket near the active site has been identified and can serve to increase inhibitory potency by secondary binding of appropriate substituents. The present study has resulted in the preparation of two more effective in vitro inhibitors of juvenile hormone esterase than those previously reported. Evidence that there are two naturally occurring forms of juvenile hormone esterase has also been provided.     

Molecular diagnostic key for identification of single juveniles of seven common and economically important species of root-knot nematode (Meloidogyne spp.)

A molecular protocol is presented for distinguishing seven of the most common and economically important Meloidogyne spp. DNA was extracted from individual second-stage juvenile (J2) nematodes of Meloidogyne spp. and amplified by PCR (polymerase chain reaction). Fifteen PCRs including amplification of rDNA, specific SCAR (sequence characterized amplified region) and RAPD (random amplified polymorphic DNA) fragments were possible from the extracted DNA. This enabled a molecular diagnostic key for M. incognita , M. javanica , M. arenaria , M. mayaguensis , M. hapla , M. chitwoodi and M. fallax to be designed. The key unifies published methods into a single logical schematic using primer combinations that were previously validated and shown to work reliably and specifically. The protocol can be used with single juvenile or adult nematodes and the schematic can readily be expanded to accommodate more species. The use of RAPD amplification to assist with identification of samples which do not yield diagnostic amplification products after the first three steps of the molecular key is also described.     

Comparative inhibition of the juvenile hormone esterases from Trichoplusia ni,Tenebrio molitor, and Musca domestica

Twenty-seven compounds were screened as potential inhibitors of juvenile hormone esterases. Of these compounds O-ethyl-S-phenyl phosphoramidothiolate provided the best inhibition for the cabbage looper, Trichoplusia ni (Hubner), and the yellow mealworm, Tenebrio molitor L., while the juvenile hormone esterases of the house fly, Musca domestica L., were best inhibited by a juvenoid carbamate (1-(m-phenoxy-N-ethyl carbamate)-3,7-dimethyl-7-methoxy-2E-octene). The inhibition patterns of T. ni and T. molitor are similar, while those of M. domestica are relatively different. Further studies on the juvenile hormone and α-napthyl acetate esterases of T. ni showed that they could be differentially inhibited. Diisopropyl phosphorofluoridate and an alkyl trifluoromethyl ketone selectively inhibit the hydrolysis of α-naphthyl acetate and juvenile hormone, respectively, while O-ethyl-S-phenyl phosporamidothiolate inhibits both enzymes. The juvenile hormone esterases of T. ni also appear to be unique enzymes that are selective for juvenile-hormone-like molecules. The in vivo inhibition of T. ni juvenile hormone esterases by O-ethyl-S-phenyl phosphoramidothiolate slows the in vivo hydrolysis of juvenile hormone and results in delayed pupation and malformed larvae that resemble larval-pupal intermediates. Thus, the esterases involved in juvenile hormone metabolism appear to be important in juvenile hormone regulation.     

Inhibition of epoxidation of methyl farnesoate to juvenile hormone III by cockroach corpus allatum homogenates

Radiolabeled methyl farnesoate is epoxidized to juvenile hormone III by an NADPH-dependent reaction occurring in corpus allatum homogenates from the cockroach Blaberus giganteus L. Most of the enzymatically produced juvenile hormone has the 10R configuration described for previously isolated natural juvenile hormones. The unnatural 2Z geometrical isomer of methyl farnesoate is epoxidized by the above system faster than the natural 2E isomer. Several series of chemicals known to be inhibitors of mixed-function oxidases were surveyed as inhibitors of methyl farnesoate epoxidation. The anti-juvenile hormone precocene II caused negligible inhibition at 1 · 10^?4M, whereas the best inhibitor was o-bromophenoxymethyl-imidazole with an apparent I₅₀ of 4 · 10^?7M. None of the inhibitors tested were potent morphogenetic agents on Tenebrio molitor pupae, and they failed to cause precocious development of Oncopeltus fasciatus nymphs. The inhibition of in vitro juvenile hormone biosynthesis suggests the possibility of finding an anti-hormone which acts by blocking juvenile hormone biosynthesis.     

Pathomorphological changes in roe deer lungs during ontogenesis of Varestrongylus capreoli (Stroh et Schmid, 1938) Dougherty, 1945

The specification of pathomorphological changes occurring during Varestrongylus capreoli ontogenesis was studied on the basis of different forms of inflammation. The character, course and extent of inflammatory reactions were contingent on the maturity, localization and number of worms. The allergic inflammation accompanying the development of juvenile specimens inside the alveoli was followed by the regeneration of lung tissues providing suitable conditions for further development of the parasite. A prolonged edema occurring during the differentiation of juvenile parasites localized in the bronchioles caused a disposition of the roughen bronchial wall to its miliary necrotic disintegration producing a negative effect on further development of the helminth. The pathomorphological effect of mature productive parasites was characterized by focal changes hatching nodes. Activated epithelial cells of alveoli, phagocytizing disintegrating eggs and not developing 1st-stage larvae together with eosinophilic granulocytes participated in the restoration of the host lung functional ability while tolerating the presence of the parasite. A difficult excretion of sex products from the lungs stimulated the development of proliferative forms of inflammation reducing the number of Varestrongylus specimens.     

保幼激素类似物对红火蚁的作用研究进展

我国发现红火蚁已有4年,但防治技术、产品依然匮乏。为了改善、提高我国红火蚁的防治技术水平,本文就保幼激素类似物(JHA)对红火蚁的作用表现和防治效果进行了总结分析。JHA可以造成蚁后卵巢萎缩、产卵量减少,导致发育畸形和蚁群等级比例失调,如工蚁数量减少、生殖型幼虫比例以及处女蚁后数量增加等,并最终导致整个蚁群死亡。JHA杀虫剂活性高、低残毒、对环境污染小,在田间防治红火蚁效果彻底,并可有效地防止防治区红火蚁种群的再入侵（re invasion）,但JHA毒饵也存在着防治效果缓慢等问题。本文就克服此类问题作了初步的探讨。     

Metabolism of juvenile hormone I by microsomal oxidase,esterase, and epoxide hydrase of Musca domestica and some comparisons with Phormia regina and Sarcophaga bullata

House fly (Musca domestica L.) microsomes prepared from larvae, pupae, or adults contain three enzyme system which can metabolize juvenile hormone I: an esterase, an oxidase, and epoxide hydrase. The presence of the oxidase is indicated by the increased metabolism when microsomes are supplemented with NADPH and by the occurrence of additional metabolites tentatively identified as products arising from oxidation of the 6, 7 double bond. Additional evidence of the activity of the oxidase system is the increased metabolism of juvenile hormone I by the NADPH-dependent system from phenobarbital-induced insects, by inhibition of the oxidation by piperonyl butoxide and carbon monoxide, and by the greater metabolism of the hormone by microsomes from insecticide-resistant (high oxidase) strains. In vivo studies of house fly adults treated with ³H-labeled juvenile hormone I reveal a pattern of metabolism similar to that seen during NADPH-supplemented in vitro metabolism. The three enzymes have somewhat different patterns of activity during the larval stage of the house fly, juvenile hormone esterase and epoxide hydrase beginning at a high level of activity in the young larvae while the juvenile hormone oxidase is low at this stage. In the late larval stage all three enzymes show increased activity followed by declines during the pupal stage and further increases in the adult stage. Comparison of in vitro enzyme levels of the house fly, flesh fly (Sarcophaga bullata Parker), and blow fly [Phormia regina (Meigen)] showed that, although the enzymes were present in the latter two species, their activity on a per insect basis was considerably less than that of the house fly.     

黏虫保幼激素环氧水解酶基因MsJHEH2的克隆与生物学功能

保幼激素环氧水解酶（juvenile hormone epoxide hydrolase,JHEH）是调控保幼激素（juvenile hormone,JH）滴度的重要降解酶。本文在黏虫体内克隆得到一条具有EHN环氧水解酶超家族结构域的保幼激素环氧水解酶MsJHEH2基因cDNA序列（GenBank登录号：MT802192）,长度1533 bp,开放阅读框（ORF）为1389 bp,编码462个氨基酸,推测分子量和等电点分别为52.42 kDa和7.07。表达模式分析发现,MsJHEH2在黏虫各个龄期与组织中均有表达,其中在蛹期和中肠中表达量最高。RNA干扰处理4龄幼虫6 h后的基因沉默效率最高,为64.86%,此时黏虫体内JH滴度上升为对照的1.58倍。该基因沉默后对黏虫无明显致死作用,但导致其蛹历期延长、羽化率降低。本研究表明MsJHEH2可以通过调节JH含量进而影响黏虫生长发育进程。     

The effect of 2,2-dimethylchromene derivatives and some other compounds on the development of Oncopeltus fasciatus (dallas) and Locusta migratoria migratorioides (R&F)

As an adjunct to biochemical studies on the action of juvenile hormone antagonists (‘antijuvenile hormones’), a study has been made of the effects on insect development of 71 compounds based on the 2,2-dimethylchromene structure, and 30 other compounds, including especially chemicals containing acetylenic and 1,3-benzodioxole (methylenedioxyphenyl) groups, that were expected to inhibit microsomal mixed function oxidases. The ageratochromenes, 7-methoxy-2,2-dimethylchromene and 6,7-dimethoxy-2,2-dimethylchromene (precocene I and precocene II, respectively), were used for comparison. With the jar deposit method used for Oncopeltus fasciatus, and the topical application method used for Locusta migratoria, only derivatives of 2,2-dimethylchromene and 2-(3-methylbut-2-enyl)phenol, the alkene double bonds of which were activated by an alkoxy group, exhibited characteristic antijuvenile hormone actions. In the whole life-cycle exposure test on O. fasciatus, a number of other compounds had non-specific effects on development, especially at the fifth instar. Some of the compounds, including certain derivatives of 2,2-dimethylchromene with ester side-chains, had juvenile hormone agonist actions. The scope for structural optimization for antijuvenile hormone action in the 2,2-dimethylchromene series appears to be limited, and structure-activity relationships are obscured, especially for O. fasciatus, by an overlap between the prothetelic morphogenetic and lethal effects. The results are discussed in relation to the mode of action of the 2,2-dimethychromenes.     

Inhibition of neurotoxic esterase and acetylcholinesterase by organophosphorus compounds in selected ectothermic vertebrates

The sensitivity of brain acetylcholinesterase and neurotoxic esterase to inhibition by several organophosphorus compounds was studied in selected ectothermic vertebrates. These enzymes are associated with organophosphorus compound acute and delayed toxicity, respectively. In addition, the susceptibility of several of these species to delayed neurotoxicity induced by organophosphorus compounds was studied. Larvae of the gray treefrog, Southern leopard frog, and narrow-mouthed toad were exposed dermally to tri-o-tolyl phosphate or phenyl saliginen cyclic phosphate (PSCP); no symptoms of delayed neurotoxicity were observed in any of these animals up to 2 weeks after metamorphosis. No symptoms of delayed neurotoxicity were seen in juvenile bullfrogs exposed to multiple ip doses of PSCP. The specific activity of neurotoxic esterase was highest in the larval bullfrog, with juvenile channel catfish and adult mosquitofish demonstrating intermediate levels. The larval Southern leopard frog, adult Northern leopard frog, juvenile green treefrog, and adult marine toad exhibited extremely low activities. The specific activity of acetylcholinesterase was highest in the juvenile channel catfish. Neurotoxic esterase in the larval bullfrog was more sensitive to organophosphate inhibition than that in either fish. PSCP was a more potent neurotoxic esterase inhibitor than leptophos-oxon. The juvenile channel catfish had the acetylcholinesterase most sensitive to organophosphate inhibition. Under the conditions tested, no evidence of in vivo sensitivity to the organophosphate-induced delayed neurotoxicity phenomenon was observed.     

Differential host utilisation by different life history stages of the fish ectoparasite Argulus foliaceus (Crustacea: Branchiura)

In this study we examine differences in the occurrence of life history stages of the destructive fish ectoparasite Argulus foliaceus (L., 1758) on eight fish species (stickleback, rudd, roach, gudgeon, bream, tench, crucian carp and common carp) sampled from a mixed-species recreational fishing lake on nine occasions during late spring and summer. Total numbers ofA. foliaceus, as well as the number of larval, juvenile and adult parasite stages, from each fish were recorded along with the fish species. Lice generally exhibited an aggregated distribution approximating a negative binomial distribution. Significant differences in the prevalence, intensity and intensity frequency distribution were observed between life history stages and between host species. In general, all life history stages of A. foliaceus exhibited an over-dispersed distribution. However, larval lice did show some degree of aggregation particularly within the stickleback samples. Infection data for parasite larval stages suggested that sticklebacks are more likely to be infected than other host species. For adult lice, however, carp appeared to be the main host. We propose that A. foliaceus infection characteristics are predominantly determined by the level of host exposure to the parasite and its life history stages (larval, juvenile and adult) rather than by an innate difference in host susceptibility related to individual host factors such as immune responses. We conclude that host exposure is determined by the parasite-host behavioural interplay related to species-specific ecology and behavioural traits such as microhabitat preference and normal swimming speed.     

Action of some aromatic juvenogen esters on insects

New types of juvenogens, which are biochemically activated juvenoid esters, have been assayed for juvenile hormone activity in three species of insects. The hormonally active component, liberated from the juvenogen substrate by carboxylesterase enzymes within the insect's body, was a secondary juvenoid alcohol related to the well-known group of juvenile hormone analogs derived from 4-substituted (7-alkoxygeranyloxy)benzenes. Juvenogen esters obtained by acylation of this juvenoid alcohol with a homologous series of C₂ to C₁₈ straight-chain monocarboxylic acids retain the juvenile hormone activity of the parental alcohol. The corresponding formyl derivative, as a first member of the series, was inactive and the activity of esters with longer acyl radicals than C₁₈ also successively diminished. Such a weak dependence for juvenile hormone activity on the size of the molecule has not previously been encountered in juvenoid esters which do not yield biologically active hydrolysis products. These findings favor an assumption that juvenogens may represent selective, nontoxic, hormonally acting pesticides whose physicochemical properties (volatility, lipophility, stability) can be adjusted to suit practical requirements by simple alterations of the biologically unimportant acyl component. Moreover, this can be done without affecting the species-specific properties in the juvenile hormone activity of the built-in juvenoid product.     

褐飞虱寄生性天敌两索线虫生活史的研究

两索线虫(Amphimermis sp.)的幼虫寄生于褐飞虱、灰飞虱等害虫的体内,使宿主产生一系列的病理变化,直至死亡。本文较详细地报导了湖北省褐飞虱寄生性天敌两索线虫的生活史。在实验室内用感染期幼虫作感染褐飞虱的试验获得成功。根据该虫的生活史和生态习性,在汉阳县的两索线虫孳生田里,采用与水稻高产栽培相结合的保护线虫措施,可以在褐飞虱中等发生量的年份,有效地控制褐飞虱的危害。     

7种常用药物对扁吻鱼幼鱼的急性毒性试验

在常温静水条件下,以1月龄的扁吻鱼幼鱼为实验对象,进行高锰酸钾、硫酸铜、甲醛、敌百虫、溴氯海因、聚维酮碘、氯化钠7种药物的急性毒性试验,计算出半致死浓度和安全浓度。结果表明,扁吻鱼幼鱼对这7种药物的敏感性:敌百虫硫酸铜高锰酸钾溴氯海因甲醛聚维酮碘氯化钠,安全浓度(特伦堡公式)分别为0.043 mg/L,0.376 mg/L,0.436 mg/L,1.64 mg/L,14.2 mg/L,18.8 mg/L和3 480 mg/L。     

Albumin and cytochrome P450 binding characteristics of juvenile hormone and its analogs

Binding data were gathered for the cecropia juvenile hormone (methyl(E, E cis)-10,11-epoxy-7-ethyl-3,11-dimethyl-2,6-tridecadienoate) and two of its analogs {isopropyl(2E, 4E)-11-methoxy-3,7,11-trimethyl-2,4-dodecadienoate; (E)-4-[(6,7-epoxy-3,7-dimethyl-2-nonenyl)-oxyl]-1,2-(methylenedioxy)benzene} with bovine serum albumin and rat hepatic microsomal cytochrome P₄₅₀. The proteins were found to bind the juvenile hormone and juvenile hormone analogs with affinity constants ranging from 10⁵ to 10⁶M^?1. Thermodynamic calculations suggest that the binding of all three compounds is electrostatic in nature and that the size of the ether and ester substituents can greatly influence the binding to proteins. The juvenile hormone and its analogs all formed spectrally apparent Type I complexes with oxidized cytochrome P₄₅₀; one of the juvenile hormone analogs formed a spectrally observable product adduct with reduced cytochrome P₄₅₀. The product complex may contribute many of the hormonal effects observed for this compound.     

Selective inhibition of JH esterases from cockroach hemolymph

Juvenile hormone III was tritium labeled on the methyl ester and utilized with other substrates in an investigation of inhibition and substrate specificity of hemolymph esterases from the cockroach, Blaberus giganteus. The structure of labeled juvenile hormone III was supported both chemically and biochemically. Forty-two potential inhibitors were examined, and the best inhibitors included phosphoramidothiolates and S-phenylphosphates. One of these inhibitors was found useful in hormone biosynthesis studies dealing with the enzymatic conversion of methyl farnesoate to juvenile hormone in corpora allata homogenates. Several commonly used inhibitors of carboxyesterases caused only weak inhibition of JH esterases. Gel filtration elution patterns, inhibitor relationships, and specific activities of the hemolymph esterases indicate that juvenile hormones I and III are degraded by similar if not identical enzymes. In some cases, α-naphthyl acetate and juvenile hormone esterase activity could be differentially inhibited. Hemolymph esterases were not capable of degrading ethyl or isopropyl conjugated esters of two juvenoids or three model substrates.     

Juvenile hormonal activity of mono- and polyenehomobenzenes in Drosophila virilis, Spodoptera frugiperda and Araschnia levana

A series of mono- and polyenehomobenzenes was synthesised by a highly regioselective palladium-catalysed allylic alkylation of substituted and unsubstituted benzylic Grignard reagents employing catalytic amounts of catalyst and tested for juvenile hormone activity on the fruit fly Drosophila virilis Sturtevant (Diptera: Drosophilidae), on an important agricultural pest species, the fall armyworm Spodoptera frugiperda JE Smith (Lepidoptera: Noctuidae), and on the map butterfly Araschnia levana L. (Lepidoptera: Nymphalidae). In D. virilis only polyenehomobenzenes with a geranyl chain and a methyl, methoxy or isopropyl group at the para position of the aromatic ring displayed significant juvenile hormonal activity at low doses. A monoenehomobenzene and polyenehomobenzenes with longer allylic chains or without a substituted aromatic ring were not active. In S. frugiperda and in A. levana, a mono-, a di- and a tetraene displayed juvenile hormonal activity. In the lepidopteran species, a trend for the necessity of a substitution at position 4 of the phenyl group for high juvenile hormonal activity was also found.     

山东泰安地区小麦禾谷孢囊线虫幼虫孵化特性初步研究

为大量获得研究所需的小麦禾谷孢囊线虫2龄幼虫,在室内离体条件下研究了预处理条件、孵化温度、低温预处理时间以及田间采样时期对山东泰安地区小麦禾谷孢囊线虫幼虫孵出量的影响.结果表明:5℃低温预处理条件下,孢囊浸水处理有利于幼虫孵出;低温预处理后,孵化温度为15℃处理的2龄幼虫孵出率高于20℃处理的孵出率;低温预处理时间为8周的2龄幼虫孵出率最高;6月和8月田间采集的孢囊幼虫孵出率显著高于7月和9月,其中8月采集的孢囊幼虫孵出率最高,为最佳采集时间.     

Some Problems Posed by the Heterodera avenae Complex1

Cyst nematodes are sedentary parasites with limited host ranges and co-evolution with circumscribed host groups is believed to result in species complexes. A scheme for this process is given. The Heterodera avenae group is such a complex parasitising cereals and grasses. Although the group includes ten nominal species, only H. mani, H. avenae and H. avenae pathotype 3 present taxonomic problems of immediate relevance in agriculture. Application of a multivariate technique, principal co-ordinate analysis, to second-stage juvenile characters indicates that H. avercae pathotype 3 is as distinct from H. avenae as H. arenaria, an accepted species in the H. avenae group. In contrast there are difficulties with juvenile and cyst morphology in distinguishing H. mani from H. avenae.