Comparative ultrastructure of the oesophageal glands of third stage larval hookworms

Smith J. M. 1976. Comparative ultrastructure of the oesophageal glands of third stage larval hookworms. International Journal for Parasitology6: 9–13. The oesophageal glands of the third stage larvae of Necator americanus and Ancylostoma tubaeforme are compared, both before and after penetration through skin. The glands of “infective” larvae of N. americanus are densely packed with secretory granules, contrasting with a reduced gland size in the “penetrated” larvae coupled with the presence of gland secretions in the oesophageal lumen.No difference was observed between the glands of “infective” and “penetrated” larvae of A. tubaeforme. The role of oesophageal gland secretions for penetration of host skin is discussed.     

Effect of repeatedly sensitized bursal extract on the resistance of WLH chickens to experimental infection of Ancylostoma caninum larvae

Goyal P. K. and Johri G. N. 1982. Effect of repeatedly sensitized bursal extract on the resistance of WLH chickens to experimental infection of Ancylostoma caninum larvae. International Journal for Parasitology12: 245–249. Bursal extract from chickens, repeatedly sensitized with Ancylostoma caninum larvae and from normal nonsensitized donor WLH chickens were injected separately into experimental and control groups of isologous recipients of same age and weight. Extract from donors infected with repeatedly high dose (250 + 250 + 500) and low dose (125 + 125 + 250) of A. caninum larvae produced significantly greater acquired immunity in recipients compared to those which received nonsensitized (normal) extract. However, no significant difference was observed between the two experimental groups.     

The fate of multiple doses of infective larvae of Nematodirus battus in 8-month-old lambs and their effect on intestinal enzyme activity

Mapes C.J. and Coop R.L. 1973. The fate of multiple doses of infective larvae of Nematodirus battus in 8-month-old lambs and their effect on intestinal enzyme activity. International Journal for Parasitology3: 363–370. The fate of five daily doses of 60,000 infective larvae of Nematodirus battus was studied in 8-month-old lambs. On 18, 26 and 34 days after the last larval dose 4.0, 3.3 and 1.0 per cent of the total infective dose was recovered. Approximately 50 per cent of the worms recovered on these days were fourth-stage larvae. It is suggested that L5 and adult stages were preferentially lost from the hosts and that male worms were developing at a faster rate than the females. The populations of N. battus were smaller, contained higher proportions of fourth-stage larvae and shorter L5 and adult worms than those developing from similar infective doses in 3-month-old lambs. A transient decrease in alkaline phosphatase and maltase levels was found in the mucosa of the small intestine and was compared with the marked and persistent changes in mucosal enzyme activities found with similar infective doses in 3-month-old hosts.     

Energy cost of locomotory activity in larval hookworms

Lipid changes in the infective third-stage larvae of Ancylostoma tubaeforme following measured periods of activity have been quantified. ‘Excessive’ activity (more than 16 activity régimes, or 8 h in neostigmine bromide) resulted in a significant (> 10%) depletion of the lipid reserves, especially from the anterior region of the intestine.     

Observations on the coiled posture of trichostrongyle infective larvae using a freeze-substitution method and scanning electron microscopy

Wharton D. A. 1982. Observations on the coiled posture of trichostrongyle infective larvae using a freeze-substitution method and scanning electron microscopy. International Journal for Parasitology12: 335–343. A method for the preparation of the infective larvae of Trichostrongylus colubriformis for scanning electron microscopy is described. This involves freeze-substitution with methanol followed by critical-point drying. The method resulted in good preservation and the retention of the coiled posture. The morphology of ensheathed and exsheathed larvae is described and the mechanisms of coil formation discussed. Coiling was also observed in the infective larvae of nine other trichostrongyle species.     

In vitro activity of levamisole on the infective larvae, microfilariae and adult worms of Breinlia Sergenti

In vitro activity of levamisole on the infective larvae, microfilariae and adult worms of Breinlia sergenti. International Journal for Parasitology4: 207–210. Levamisole shows in vitro activity against the infective larvae, microfilariae and adult worms of Breinlia sergenti. The polygraph studies using the adult worms indicate that levamisole causes an increase in the muscle tone; this action being dose related. The adult worms are more sensitive to the drug than the infective larvae and microfilariae. In vitro, levamisole is more potent compared with diethylcarbamazine against all the three stages of B. sergenti.     

Gonadal hormones in experimental Ancylostoma caninum infections in male Swiss albino mice

Ismail Bhai and Pandey A. K. 1982. Gonadal hormones in experimental Ancylostoma caninum infections in male Swiss albino mice. International Journal for Parasitology12: 589–591. Orchiectomy in mice increased their resistance to Ancylostoma caninum infection. Testosterone propionate increased the susceptibility of castrated animals to infection and also increased the survival of larvae in muscles, compared with sham-operated placebo-treated controls with intact testes. Estradiol benzoate increased the resistance of castrated mice as demonstrated by differential larval recoveries. The possible involvement of the small intestine as a barrier to infection and the influence of testosterone on host susceptibility to infection is discussed.     

The initiation of coiling behaviour prior to desiccation in the infective larvae of Trichostrongylus colubriformis

Wharton D.A.1981. The initiation of coiling behaviour prior to desiccation in the infective larvae of Trichostrongylus colubriformis. International Journal for Parasitology11: 353–357. Infective larvae of Trichostrongylus colubriformis coil during the evaporation of water films. Decreasing the depth of the liquid film does not initiate coiling but enclosure in capillary tubes of similar diameter to the track width of actively swimming or crawling larvae results in a marked stimulation of coiling behaviour. It is suggested that larvae coil in response to the progressive restriction of lateral movement in an evaporating water film. The behavioural flexibility of the infective larvae of T. colubriformis maximizes both their survival and their chances of infection.     

Reversible inhibition of hatching of infective eggs of Ascaris suum (Nematoda)

Hurley L. C. and Sommerville R. I. 1982. Reversible inhibition of hatching of infective eggs of Ascaris suum (Nematoda). International Journal for Parasitology12: 463–465. Dilute solutions of an oxidising agent, iodine, reversibly inhibit hatching of infective eggs of Ascaris suum. The capacity to hatch is restored by exposure to reducing agent, hydrogen sulphide. These observations add to known similarities between hatching of infective eggs and exsheathment of infective larvae. It is proposed that the regulatory mechanisms for both processes are similar.     

The fate of large infective doses of Nematodirus battus in young lambs

Mapes C.J., Coop R.L. and Angus K.W. 1973. The fate of large infective doses of Nematodirus battus in young lambs. International Journal for Parasitology3: 339–347. The fate of 300,000 and 5 × 60,000 infective larvae of Nematodirus battus during the 2–3 weeks after patency was studied in 3-month-old lambs. The proportions of the infective doses recovered after 18, 26 and 34 days were 37, 6 and 3.5 per cent in the single dose and 29,12 and 4.7 in the multiple dose groups. Fifth-stage larvae and adults, especially females, were preferentially lost from the hosts. The numbers of worms present and the percentage of fourth-stage larvae present were similar in both the single and multiple dose groups.     

Synthesis and biological evaluation of novel tris-chalcones as potent carbonic anhydrase,acetylcholinesterase, butyrylcholinesterase and α-glycosidase inhibitors

A novel class of fluoro-substituted tris-chalcones derivatives (5a-5i) was synthesized from phloroglucinol and corresponding benzaldehydes. A three step synthesis method was followed for the production of these tris-chalcone compounds. The structures of the newly synthesized compounds (5a-5i) were confirmed on the basis of IR, ¹H NMR, ¹³C NMR, and elemental analysis. The compounds’ inhibitory activities were tested against human carbonic anhydrase I and II isoenzymes (hCA I and hCA II), acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and α-glycosidase (α-Gly). These chalcone derivatives had K_i values in the range of 19.58–78.73 nM for hCA I, 12.23–41.70 nM for hCA II, 1.09–6.84 nM for AChE, 8.30–32.30 nM for BChE and 0.93 ± 0.20–18.53 ± 5.06 nM against α-glycosidase. These results strongly support the promising nature of the tris-chalcone scaffold as selective carbonic anhydrase, acetylcholinesterase, butyrylcholinesterase, and α-glycosidase inhibitor. Overall, due to these derivatives’ inhibitory potential on the tested enzymes, they are promising drug candidates for the treatment of diseases like glaucoma, leukemia, epilepsy; Alzheimer’s disease; type-2 diabetes mellitus that are associated with high enzymatic activity of carbonic anhydrase, acetylcholine esterase, butyrylcholinesterase, and α-glycosidase.     

Bioactivity of semisynthetic eugenol derivatives against Spodoptera frugiperda (Lepidoptera: Noctuidae) larvae infesting maize in Colombia

The anti-acetylcholinesterase, larvicidal, antifeedant activities and general toxicity of 15 semisynthetic eugenol derivatives based on clove oil (including the own oil), were evaluated against the maize armyworm, Spodoptera frugiperda (J.E. Smith). Therefore, promising eugenol molecules were classified with larvicidal, anti-acetylcholinesterase and antifeedant activities for controlling this pest. During structure–activity relationship studies and physicochemical profile analysis, it was found that among tested molecules 1–15, eugenol 1, prenyl eugenol 4, isoeugenol 8 and isoeugenol acetate 11 exhibited lethal effects LD₅₀ at concentrations <1 mg/g of insect. On the other hand, eugenol 1, metallyl eugenol 3, isoeugenol 8 and isoeugenol acetate 11 showed a good antifeedant activity (CE₅₀ = 158–209 µg/mL) with a high antifeedant index (70–78%) at concentration 1000 µg/mL, possessing a weak anti-acetylcholinesterase activity (IC₅₀ = 21–31 μg/mL). According to their ecotoxicological profiles (LC₅₀ = 2033.1–6303.8 µg/mL on Artemia salina larvae), isoeugenol 8 and its acetate derivative 11 could be potential used in control of the growth, feeding, or reproduction of S. frugiperda larvae, acting as moderate insecticidal acetylcholinesterase inhibitors and/or antifeedant molecules. Such structure–activity relationship studies could stimulate the identification of lead structures from natural sources for the development of larvicidal and deterrent products against S. frugiperda and related insect pests.     

棉铃虫乙酰胆碱酯酶(AChE)的体躯分布及部分纯化

该文研究了棉铃虫Helicoverpa armigera乙酰胆碱酯酶(AChE)的体躯分布及部分纯化技术。在幼虫和成虫体内均以头部AChE活性最高;AChE在成虫和幼虫头、胸、腹部的活性分布分别为78.2%、3.9%、17.9%和90.3%、6.5%和3.2%。通过用Sepharose 4B和Sephadex G-200纯化后,AChE的最高纯化倍数为3.66和17.74倍。样品和洗脱液中含有Triton X-100时,纯化倍数明显高于无Triton X-100的处理组。     

New sense organ in larval hookworms.

A new ciliary sense organ is described which is bilaterally arranged, one in each lateral cord. It is just posterior to the nerve ring and adjacent to the excretory duct. The cilium is closely associated with another structure which is itself connected to the cuticle beneath the lateral alae. A nervous circuit is proposed which links this receptor via the hemizonid to the nerve ring. The receptor and associated structures are in the infective larvae of Necator americanus and Ancylostoma tubaeforme.     

Synthesis and bioassay of isoprenoid 3-alkylthio-1,1,1-trifluoro-2-propanones: Potent,selective inhibitors of juvenile hormone esterase

Four 3-alkylthio-1,1,1-trifluoro-2-propanones with juvenile hormone-like side chains were prepared from citronellol and homogeraniol. These substrates were designed as possible transition-state analogs for the juvenile hormone (JH)-specific esterases present in insects. These four isoprenoid trifluoromethyl ketones were assayed in vitro with JH esterase and general esterases from larvae of the cabbage looper, Trichoplusia ni (Lepidoptera, Noctuidae), and with eel acetylcholinesterase and bovine chymotrypsin. JH esterase inhibition I₅₀ values were in the nanomolar range for all four compounds, while the other esterases had I₅₀'S which were 10³ to 10⁵ higher. The high selectivity of these inhibitors is believed to be due to their similarity in size and functionality to natural JH III. Treatment of T. ni larvae in vivo with solutions of the most active analog, 3-[(E)-4,8-dimethyl-3,7-nonadienylthio]-1,1,1-trifluoro-2-propanone (DNTFP) causes a dose-dependent delay in pupation and a concurrent selective inhibition of JH esterase. These data support the hypothesis that the reduction in in vivo JH titer in larval T. ni is due, in part, to hydrolysis of the hormone by selective esterases. DNTFP appears to be competing with JH for the active site of JH esterase.     

A Biochemical Evidence of the Inhibitory Effect of Diflubenzuron on the Metamorphosis of the Silkworm,Bombyx mori

Diflubenzuron (DFB) has been known to prevent metamorphosis of silkworm, Bombyx mori, from larval to pupal stage at low dose exposure. To explain this inhibitory action of DFB, a hypothesis was raised that DFB acts like juvenile hormone (JH) or DFB inhibits JH esterase to increase endogenous JH titer. A JH bioassay using isolated abdomen clearly indicates that DFB does not act as JH analog because DFB did not induce vitellogenesis in the isolated female abdomen, while endogenous JHs did significantly. General esterase activities in hemolymph were lower in DFB-treated fifth instar larvae than in the control larvae, but there was no difference between fat body esterase activities in both groups. Two hemolymph esterases (‘E1’ and ‘E2’) of the fifth instar larvae were separated and visualized by α-and β-naphthyl acetate. From in vitro incubation experiment, the cathodal esterase (‘E1’) was sensitive to DFB at its nanomolar range. Considering the fact that early fifth instar larvae have high level of JH esterase in the hemolymph, these results suggest that DFB inhibit larval to pupal metamorphosis by blocking JH degradation, which increases endogenous JH titer especially at the critical period when the larvae determine metamorphic development at the following molt.     

二化螟对杀螟硫磷产生抗性的机理

本文就二化螟Ckilo suppressalis Walker对杀螟硫磷抗性发生的机理进行了较为全面的研究。活体增效作用研究表明,脱叶磷(DEF)和氧化胡椒基丁醚(PBO)对抗性种群可分别增效1.3和34.8倍。这表明了多功能氧化酶(MFO)活性增强,而似乎与水解酶的活性无关。对寓体解毒酶的进一步研究表明,抗性和敏感种群的非特异性酯酶活力无明显差异,但羧酸酮酶(CarE,加入10^-4mol/L的毒扁豆碱)和MFO的活力在抗性种群中有所增高。R种群幼虫CarE活力分别是s的2.42和2.92倍(以a-和β-乙酸萘酯为底物);R种群幼虫MFO的O-脱甲基作用的活力为s幼虫的1.43倍(以对硝基茴香醚为底物);R幼虫乙酰胆碱酯酶(AChE)对乙酰胆碱的活力是s的1.3倍,两者相差不大。但从米氏常数K_m)和最大反应速度(V_max)看,R幼虫是s幼虫的1.9和1.6倍;以对氧磷为抑制剂的R幼虫150是s幼虫的2倍。这些表明了R和s的AChE是不同的。研究结果还表明,二化螟对杀螟硫磷抗性的机理至少包括：(1)CarE活性的增高;(2)MFO的O-脱甲基活力的增高和(3)AChE敏感性的降低等。     

二化螟对杀螟硫磷产生抗性的机理

本文就二化螟Ckilo suppressalis Walker对杀螟硫磷抗性发生的机理进行了较为全面的研究。活体增效作用研究表明,脱叶磷(DEF)和氧化胡椒基丁醚(PBO)对抗性种群可分别增效1.3和34.8倍。这表明了多功能氧化酶(MFO)活性增强,而似乎与水解酶的活性无关。对寓体解毒酶的进一步研究表明,抗性和敏感种群的非特异性酯酶活力无明显差异,但羧酸酮酶(CarE,加入10^-4mol/L的毒扁豆碱)和MFO的活力在抗性种群中有所增高。R种群幼虫CarE活力分别是s的2.42和2.92倍(以a-和β-乙酸萘酯为底物);R种群幼虫MFO的O-脱甲基作用的活力为s幼虫的1.43倍(以对硝基茴香醚为底物);R幼虫乙酰胆碱酯酶(AChE)对乙酰胆碱的活力是s的1.3倍,两者相差不大。但从米氏常数K_m)和最大反应速度(V_max)看,R幼虫是s幼虫的1.9和1.6倍;以对氧磷为抑制剂的R幼虫150是s幼虫的2倍。这些表明了R和s的AChE是不同的。研究结果还表明,二化螟对杀螟硫磷抗性的机理至少包括：(1)CarE活性的增高;(2)MFO的O-脱甲基活力的增高和(3)AChE敏感性的降低等。     

转Bt基因抗虫玉米对亚洲玉米螟幼虫几种主要酶系活性的影响

研究了表达Cry1Ab杀虫蛋白的转Bt基因抗虫玉米对亚洲玉米螟Ostrinia furnacalis (uenée) 幼虫解毒酶、保护酶和中肠蛋白酶活性的影响,测定比较了取食转Bt基因玉米后幼虫体内α-乙酸萘酯酶、乙酰胆碱酯酶、谷胱甘肽S-转移酶、过氧化氢酶、超氧化物歧化酶、中肠总蛋白酶、类胰蛋白酶和类胰凝乳蛋白酶的活力。结果表明,取食转Bt基因玉米48 h后亚洲玉米螟幼虫体内的α-乙酸萘酯酶、谷胱甘肽S转移酶活力明显低于对照;而乙酰胆碱酯酶活力显著高于对照,在取食48 h、60 h和72 h的活力分别是对照的2.00、1.50和2.50倍。保护酶系、中肠总蛋白酶、弱碱性类胰蛋白酶和类胰凝乳蛋白酶的活性在取食48 h后明显受到抑制;但强碱性类胰蛋白酶的活性显著高于对照,取食48 h、60 h和72 h的活力分别是对照的4.00、1.67和1.33倍。乙酰胆碱酯酶和强碱性类胰蛋白酶可能与亚洲玉米螟对Bt的抗性有关。     

In vitro maintenance of nematode parasites assayed by acetylcholinesterase and allergen secretion.

A comparison was made of the ability of Nippostrongylus brasiliensis and Necator americanus to synthesize and secrete acetylcholinesterase when they were maintained in different in vitro culture media. The amount of allergen released by N. brasiliensis was also studied. The adult and fourth stage larval stages (but not the infective larvae) of Necator and adult N. brasiliensis secreted from their anterior glands up to 40 times as much acetylcholinesterase as they contained at the outset of culture. In contrast, allergen, which is less easy to quantitate, was secreted into the same media at about one-third the rate of secretion of acetylcholinesterase. Acetylcholinesterase was synthesized and released by both worms in media containing protein and the enzyme did not lose activity when kept for several days at 37 C. The secretion of this enzyme by nematodes kept in culture provides a simple, sensitive, rapid, and quantitative assay for measuring the ability of these nematodes to synthesize and secrete antigens in culture.