Effects of juvenile hormone analogues on larval metamorphosis in the barnacle Elminius modestus Darwin (Crustacea: Cirripedia)

Two analogues of insect juvenile hormones (JH) have been shown to interfere with the development of Elminius modestus Darwin larvae when dispersed as acetone solutions in sea water. Stage VI nauplii metamorphosed to morphologically abnormal larvae which were intermediate in size between the nauplius and cypris stages; although these larvae were cypris-like they apparently retained some nauplius characteristics. Cyprids either metamorphosed to non-attached adults or formed larvae which were larger or morphologically abnormal. There was evidence that the effects may be related to the physiological development of the larvae at time of exposure. These observations appear to be the first report of the induction of size and morphological abnormalities in a crustacean species by analogues of insect JH and resemble those arising from the hormonal imbalance which such compounds induce during the development of holometabolous insects.     

Activity of juvenile hormone and juvenile hormone analogues on the growth of Trypanosoma cruzi

The effects of juvenile hormone-III (JH-III) and the juvenile hormone analogues (JHA) methoprene and fenoxycarb on the growth and macromolecular biosynthesis in Trypanosoma cruzi were studied in vitro. It was observed that JH-III and JHA blocked growth and ³H-thymidine incorporation without killing the cells within certain concentrations (≤1 × 10⁻⁴M), but they caused cellular death at concentrations over 1 × 10⁻³M. The inhibitory effect on growth was partially reversible. On the other hand, the inhibitory action of JH-III, methoprene and fenoxycarb was an unspecific effect according to the results obtained with Leishmania mexicana mexicana (promastigotes) and human peripheral blood lymphocytes. The JHA have a good possibility of being used in the control of trypanosomiasis.     

Effects of juvenile non-indigenous Carcinus maenas on the growth and condition of juvenile Cancer irroratus

The Atlantic rock crab, Cancer irroratus, is a commercially fished species and a critical prey item for the American lobster, Homarus americanus, in Atlantic Canada. The recent invasion of European green crab, Carcinus maenas, may have significant effects on the growth and condition of native C. irroratus, because both species overlap spatially and temporally and have similar habitat and dietary requirements. To examine such potential effects, we measured the growth of juvenile C. irroratus in the presence of juvenile C. maenas over a period of 4 months (growing season), under the following species combinations: (1) one C. irroratus (10-25 mm CW); (2) two C. irroratus (10-25 mm CW); (3) one C. irroratus (10-25 mm CW) and one C. maenas (10-15 mm CW). Morphological measurements included pre- and post-molt carapace width, chela height, abdomen width (mm), weight (g), and estimates of molt increment (%) and intermolt duration (days). Analysis of the hepatopancreas for % lipid content at the end of the experiment provided an estimate of physiological condition. The effect of the presence of C. maenas on the growth of C. irroratus shifted from negative to positive, when C. irroratus reached CW of 19-22 mm and gained a presumably significant size advantage over C. maenas. The positive effect resulted from increased energy intake through crab consumption. In the absence of crab consumption, the presence of a second crab (conspecific or C. maenas) had no effect on growth. C. irroratus consumed crabs more frequently when the second individual was a green crab than a conspecific. Consumption of C. maenas had a pronounced effect on the growth rate of C. irroratus, resulting in shorter intermolt periods and larger percent molt increments than in the presence of a conspecific. Therefore, the presence of juvenile C. maenas does not appear to have a prolonged negative effect on the growth of C. irroratus; rather, it may provide an additional food item as rock crabs grow, as long as encounters between the two species occur at high enough rates.     

Effects of a juvenile hormone analogue on the eggs, post-embryonic development, metamorphosis and diapause induction of the Colorado potato beetle, Leptinotarsa decemlineata

The effect of a juvenile hormone analogue, S-71639, was tested on the eggs, four larval instars and adults of the Colorado potato beetle, Leptinotarsa decemlineata Say, by topical application or after treatment of the foodplant. The last larval instar is very sensitive to S-71639. Treatment of this instar delayed the onset of pupation and prevented adult emergence. Treated animals showed severe abnormalities, but they were not immediately killed at the doses used in this study. Treatment of larvae also interfered with the photoperiodic induction of diapause. Adults, kept under diapausing conditions, started to lay eggs after treatment with S-71639. The ovicidal effect of the compound was rather weak. The implications for practical use of S-71639 in control of the Colorado potato beetle are being discussed.

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Résumé L'effet d'un analogue de l'hormone juvénile, S-71639, a été testé sur les oeufs, les quatre stades larvaires et les adultes du doryphore, Leptinotarsa decemlineata Say, par application topique ou après traitement de la plante-hôte. Le dernier stade larvaire est très sensible au S-71639. Le traitement de ce stade retarde le début de la métamorphose et empêche l'émergence adulte. Les animaux traités montrent de graves anomalies, mais ne sont pas immédiatement tués par les doses utilisées dans cette étude. Le traitement des larves perturbe aussi l'induction photopériodique de la diapause. Les adultes placés dans des conditions de diapause, commencent à pondre après traitement au S-71639. L'effet ovicide de la substance est plutôt faible. Les implications pour l'utilisation pratique du S-71639 dans la lutte contre le doryphore sont discutées.

     

Effects of methoprene and juvenile hormone on larval ecdysis,emergence, and metamorphosis of the endoparasitic wasp, Apanteles congregatus

Topical application of juvenile hormone I and III or the hormone analogue methoprene to parasitized Manduca sexta larvae inhibited subsequent emergence of the endoparasitic wasp Apanteles congregatus. Methoprene treatment inhibited wasp emergence in a dose-dependent manner, causing either a delay or total inhibition of emergence. These results were interpreted as reflecting inhibitory effects of juvenile hormone on the second-larval ecdysis of the parasitoid that normally occurs during emergence from the host larva. Parasitoid ecdysis was disrupted even when methoprene was applied to host larvae a few hours prior to the normal expected time of emergence. A correlation between the number of emerging parasitoids and the timing of emergence was seen in methoprene-treated hosts, and few parasitoids emerged after day 9 of the host's fifth-instar. Our findings suggest that the suppression of emergence by juvenile hormone analogues noted in previous studies may be due to a similar inhibitory effect on parasitoid ecdysis. We also observed that parasitoids emerging from hosts treated with a low dose of methoprene (1 μg) later pupated normally but then formed nonviable pupal-adult intermediates. Thus use of this insect growth regulator must be undertaken carefully to prevent possible adverse effects on natural parasitoid populations.     

The onset of metamorphosis in Tenebrio molitor L.: Effects of a juvenile hormone analogue and of 20-hydroxyecdysone

Sensitivity to juvenile hormone and to 20-hydroxyecdysone has been investigated during the last-larval stages of Tenebrio molitor. Topical applications of a juvenile hormone analogue (K-421d) showed that the sensitive period, occurring before apolysis, is relatively short (less than 4 days in a 3-week instar) and divided into two phases. Treatment during the first and longest phase induced a delay in development and then an increase in larval moult percentage. Treatment during the second phase induced several abnormal moults (prothetelic larvae and larval-pupal intermediates).Injections of massive doses of 20-hydroxyecdysone (10 μg per animal) also evidenced a period of disturbance of the morphogenetic programme, beginning before pupal apolysis but continuing several days after.Comparison of the sensitive periods to both hormones suggests that a very important and rapid step of the larval-pupal programme change is controlled hormonally just before pupal apolysis.     

Direct selection of mutants of Drosophila resistant to juvenile hormone analogues

A direct screening technique was devised in which applications of a juvenile hormone analogue (JHA) (RO-20-3600; ENT No. 70357; 6,7-Epoxy-3-methyl-7-ethyl-1-(3,4-[methyl-enedioxy]-(phenoxy)-2-cis/trans-octene), Hoffman-LaRoche) to the food resulted in the death of all the F-1 descendants of mutagenized Drosophila melanogaster males with the exception of those animals which possessed sexlinked mutations affecting the metabolism of JHA. These exceptions would comprise (a), those mutant animals which possess any resistance to the lethal effects of the JHA (JH^R mutants) and/or (b), those mutant animals which have a defective JH metabolism and would normally die but are rescued by the exogenous application of JHA (JH^? mutants). Approximately 95, 850 mutagenized chromosomes were tested in this screen, 99,6% of which were killed by the JHA. Of the surviving 181 fertile males, 6 were found to be JH^R mutants. The statistically significant resistance factors ranged from 1.4X to 21.5X. The analysis of the most resistant mutant strain indicates that it may possibly be a behavioral mutant. The implications of such JH^R mutants are discussed in terms of ‘third generation pesticides’.     

Tissue-specific effects of the juvenile hormone analogue ZR 515 during metamorphosis in Drosophila cell cultures

The juvenile hormone analogue ZR 515 has specific effects on ecdysone-induced metamorphic differentation of Drosophila cells cultured in vitro. The number of vesicles containing imaginal cuticular structures is reduced to 10% of control levels. Similarly, the differentiation of adult fat body is partly inhibited by ZR 515. The differentiation of adult tubular and fibrillar muscles, however, is not affected. ZR 515 does not inhibit cuticle secretion by tracheal cells and larval epidermal cells.     

Nutritional and developmental factors in larval growth and retrogression of Trogoderma glabrum

Diet is an important determinant of the developmental pattern of Trogoderma glabrum (Herbst). Two nutritionally adequate diets were compared. The average weight of larvae of the same age was greater when cultured on meridic diet than on standard crude diet. The expected pattern of instars, as determined by head capsule widths, was observed for larvae reared on standard diet. On meridic diet, head capsules of each instar were significantly wider, and both sexes pupated after 5 stadia.Survival during retrogression correlated positively with weight at the time of isolation. Larvae reared on meridic diet survived longer than larvae of equal culture age or weight from standard diet. Survival and maintenance of weight were greatly improved by direct contact with nutritional media, some of which were incomplete (powdered cellulose plus 10% lactalbumin, fructose, or glucose). Cellulose alone, however, was more detrimental to survival than no medium.A moult after transfer to isolation tubes produced 3 morphologically distinct forms, determined by the extent of maturation. Immature larvae retromoulted to smaller larvae; fully mature larvae pupated; and larvae that had initiated but not completed pupal differentiation became prothetelic.     

Assays on Rhodnius for juvenile hormone activity

Contrary to expectation the effect of a given quantity of juvenile hormone (JH) topically applied to the abdomen of Rhodnius is greatly reduced if the cuticle is thin; either newly stretched by a large meal or wasted by prolonged starvation. The active substance apparently enters the body too rapidly and is eliminated in metabolism.The activity of the juvenile hormone and the most active JH-mimics is increased ten to fifteenfold if they are topically applied in dilute solution in peanut oil or triolein.Assays of the juvenile hormones of Cecropia at a concentration of 1 : 1000 in peanut oil (suitably diluted with octane) show that synthetic (racemic) C₁₈-JH of Röller (JH-1) is considerably less active than the natural enantiomorph; and the synthetic C₁₇-JH of Meyer (JH-2) has only about two-thirds of the activity of JH-1. Using this method of application, the natural juvenile hormone applied to the fifth instar larva of Rhodnius will cause a 50 per cent suppression of adult characters (grade 10 in the assay) at a dose of about 15 ng.     

Effects of transgenic overexpression of diapause hormone and diapause hormone receptor genes on non-diapause silkworm

Diapause is a state of developmental arrest that is most often observed in arthropods, especially insects. The domesticated silkworm, Bombyx mori, is a typical insect that enters diapause at an early embryonic stage. Previous studies have revealed that the diapause hormone (DH) signaling molecules, especially the core members DH and DH receptor 1 (DHR1), are crucial for the determination of embryonic diapause in diapause silkworm strains. However, whether they function in non-diapause silkworm strains remains largely unknown. Here, we generated two transgenic lines overexpressing DH or DHR1 genes in a non-diapause silkworm strain, Nistari. Our results showed that developmental expression patterns of DH and DHR1 are quite similar in transgenic silkworms: both genes are highly expressed in the mid to late stages of pupae and are most highly expressed in day-6 pupae but are expressed at very low levels in other developmental stages. Moreover, the overexpression of DH or DHR1 can affect the expression of diapause-related genes but is not sufficient to induce embryonic diapause in their offspring. This study provides new insights into the function of DH and DHR1 in a non-diapause silkworm strain.     

Effects of three compounds with anti-juvenile hormone activity and a juvenile hormone analogue on endogenous juvenile hormone levels in the tobacco hornworm, Manduca sexta

The ability of three anti-juvenile hormones and one juvenile hormone analogue to reduce in vivo juvenile hormone levels in Manduca sexta has been investigated. Two compounds. FMev (tetrahydro-4-fluoromethyl-4-hydroxy-2H-pyran-2-one) and ETB (ethyl-4-[2-(tert-butylcarbonyloxy)butoxy]-benzoate) reduced the titres of juvenile hormones I and II to near the levels of detection in topically treated larvae. Precocene III (7-ethoxy-6-methoxy-2,2-dimethylchromene) was inactive but the juvenile hormone analogue hydroprene was as effective as the two anti-juvenile hormones in reducing endogenous juvenile hormone titres in larvae. FMev was also shown to reduce the level of juvenile hormones II and III in pharate adults.     

Studies of growth hormone secretion in juvenile diabetes.

To further investigate the GH secretion in juvenile diabetics, blood glucose (BG) and plasma growth hormone (GH) were determined during controlled exercise performed in basal condition and under glucose infusion, in 7 controls and 22 juvenile diabetics aged 12--35 years, 10 of them with fundal vascular lesions. In controls, glucose infusion significantly lowered the exercise induced GH rise observed under basal conditions. In diabetics, under basal conditions, diabetics with low basal BG (BG less than 100 mg/100ml) had higher GH secretion than those with high basal BG (BG greater than 140 mg/100 ml; p less than 0.05). Under glucose infusion, diabetics with normal BG peak values (not different from controls: BG = 284 +/- (SK) 45 mg/100 ml) had significantly higher plasma GH levels than controls (p less than 0.01). In contrast, in diabetics with BG peak value higher than controls (BG greater than 374 ng/100 ml), plasma GH levels were not different from control values. This study indicates that exercise induced GH secretion in diabetics is mainly related to actual BG levels. Furthermore, we found no relation between the magnitude of GH secretion and the presence of retinopathy in diabetics.     

Identification of the juvenile hormone from the cricket, Teleogryllus commodus, and juvenile hormone titre changes

In the cricket, Teleogryllus commodus, eggs, haemolymph of 7th and 8th (last)-larval instars, and haemolymph of adults of both sexes contain only juvenile hormone III. While in the male the hormone titre is independent of previous mating experience, juvenile hormone concentration in haemolymph taken from females 36–38 hr after mating (an event which is followed by oviposition) is at a level 5 times higher than that of virgin females. Based on data gleaned from several research groups the identification of juvenile hormone III as the exclusive juvenile hormone in the Order Orthopteroidea is discussed.     

Effects of ecdysone and juvenile hormone on DNA metabolism of imaginal disks of Drosophila melanogaster

Imaginal disks of Drosophila melanogaster isolated en masse and incubated in Robb's tissue culture medium incorporate ³H-thymidine into nuclear DNA. Both α- and β-ecdysone stimulate the rate of ³H-thymidine incorporation into disk DNA. Concentrations of ecdysone that induce complete evagination of disks in vitro cause the initiation of DNA synthesis in some disk cells. Juvenile hormone has no effect on DNA synthesis in control disks. However, juvenile hormone blocks the ecdysone stimulation of DNA synthesis. It is proposed that juvenile hormone and ecdysone act in a balanced fashion to regulate DNA synthesis in imaginal disks.     

保幼激素类似物对白蚁的作用研究进展

本文介绍了保幼激素类似物对白蚁的影响,包括诱导前兵蚁、兵蚁和一些中间品级(形态畸形)的产生、抑制白蚁的取食、减少或消除白蚁的共生原生动物群、对白蚁产生不同水平的急性和慢性毒性、抑制工蚁蜕皮以及繁殖蚁建立新群体等方面的影响,其中最主要影响是诱导前兵、兵蚁和一些中间品级的产生破坏了白蚁群体品级比例的平衡性或完整性.因此,保幼激素类似物可用于白蚁的防治,并在田问防治散白蚁和乳白蚁均取得了较好的防治效果,并探讨了应用保幼激素类似物防治白蚁的潜力与前景.     

Effects of decapitation and ovariectomy on the regulation of juvenile hormone synthesis in the cockroach, Diploptera punctata

Corpora allata from Diploptera punctata females at adult ecdysis or at the end of the last-larval stadium, when implanted into decapitated females, underwent a cycle of juvenile hormone synthesis similar in timing and magnitude to that of glands implanted into control animals which had been starved and allatectomized. Starvation did not alter the cycle in rates of juvenile hormone synthesis of sham-operated animals.Decapitation of ovariectomized animals resulted in no cycle in rates of juvenile hormone synthesis by implanted adult corpora allata; however, implantation of an ovary along with the corpora allata into decapitated, ovariectomized hosts resulted in a cycle of juvenile hormone synthesis. In control animals, which retained their heads but were starved and allatectomized as well as ovariectomized, the implanted corpora allata showed a cycle of juvenile hormone synthesis only when implanted with an ovary. The maximal rates of juvenile hormone synthesis by the corpora allata in both experimental and control conditions were lower than normal, likely due to the repeated trauma of surgery. However, at no time from eclosion to the end of the first gonotrophic period was the brain necessary for the cyclic response of the corpora allata to the presence of the ovary.     

Effects of juvenile hormone analogs and 20-hydroxyecdysone on diapause termination in eggs of Locusta migratoria and Oxya yezoensis

To understand the hormonal control of embryonic diapause, juvenile hormone analogs (JHAs), methoprene and hydroprene, and 20-hydroxyecdysone (20E) were applied onto diapause eggs of Locusta migratoria and Oxya yezoensis. These insects enter diapause at the mid-stage of embryogenesis prior to blastokinesis. Topical application of JHAs significantly facilitated diapause termination in both species but JHA-treated embryos underwent abnormal morphogenesis, pigmentation and sclerotization without dorsal closure. The Locusta eggs immersed in the 20E solution for 24h terminated diapause in a dose-dependent manner. We also investigated phosphorylation of extracellular signal-regulated kinase (ERK), a member of mitogen-activated protein kinase (MAPK), during diapause-terminating process of Locusta migratoria and found that ERK was activated either by cold exposure or JHA treatment. The possible involvement of the hormones and ERK in embryonic diapause and the possibility of ecdysteroids synthesis by prothoracic glands of diapause embryo were proposed.