In vivo fluctuation of JH,JH acid,and ecdysteroid titer,and JH esterase activity,during development of fifth stadium Manduca sexta

Juvenile hormone (JH), JH acid, and ecdysteroid titer, and JH esterase activity, were measured in hemolymph from synchronous last stadium larvae of Manduca sexta. JH and JH acids were identified and quantified by GC-MS: JH I and II (and the corresponding acids) were the predominant JH homologs detected in males or females. Maximum levels of JHs and JH acids were observed just following ecdysis to the fifth (last) stadium (day 0, 0 hr) and at the prepupal stage (day 6–day 7). JH titer (≥ 1 ng JH I or II/ml) was higher than JH acid titer (∼0.7 ng JH I acid or JH II acid/ml) in very early fifth stadium larvae. However, this was reversed at the prepupal stage when higher titers of JH acids than JH were observed. JH acid titer began to rise prior to JH titer at the prepupal stage. JH esterase activity rose significantly only after JH or JH acid titers had begun to decline; maximum JH esterase activity was observed at day 3 and day 8. Ecdysteroid titer (measured by RIA) decreased during the last larval molt to a low level by day 0 (0 hr) and to undetectable levels at day 0 (12 hr) of the fifth stadium, by which time JH and JH acid levels had also declined substantially. Just prior to wandering, a small ecdysteroid peak was noted and a slightly elevated level of ecdysteroid was maintained for a further 2 days before a surge in ecdysteroid titer occurred at the prepupal stage, in synchrony with JH and JH acid titer maxima. There was no sexual dimorphism in timing or magnitude of JH, JH acid, and ecdysteroid titer or JH esterase activity.     

Juvenile hormone metabolism in the plasma,integument, midgut,fat body,and brain during the last instar of the tobacco hornworm,Manduca sexta (L.)

Juvenile hormone (JH) III esterase and JH III epoxide hydrolase activity was found in the integument, midgut, fat body, and brain during last instar development of the tobacco hornworm, Manduca sexta. JH esterase activity was primarily located in the cytosol in these tissues while the majority of the JH epoxide hydrolase activity was found in the microsomes. A prewandering (on day 3) and postwandering (on day 8) peak in plasma JH III esterase activity occurs in the last instar of gate I M. sexta. The JH esterase activity profile in integument, midgut, fat body, and brain followed a similar pattern to that of the plasma. The only exception to this was the absence of the postwandering, prepupal (on day 8) JH esterase peak in the fat body. The topical application of the juvenoid, (RS)-methoprene, failed to induce fat body JH esterase activity but increased activity in the plasma, integument, midgut, and brain in M. sexta prepupae. These results indicate that the source of plasma JH esterase activity is not always the fat body as previously hypothesized. The developmental profile of tissue JH epoxide hydrolase activity was also similar to that of JH esterase suggesting that both enzymes may be regulated partly by the same factors and that JH epoxide hydrolase may also have an important, previously unrecognized functional role in JH regulation and insect metamorphosis. Multiple isoelectric forms of tissue-specific JH esterases and JH epoxide hydrolases were found in integument, midgut, fat body, and brain. The JH esterases in these tissues had isoelectric points more acidic than that for plasma. Tissue α-naphthyl acetate esterase, developmental profiles, and inhibitor sensitivity to 3-(octylthio)-1,1,1-trifluoropropan-2-one differed significantly from that for JH esterase, suggesting that they represent different enzymes. ©1992 Wiley-Liss, Inc.     

Juvenile hormone titers,juvenile hormone biosynthesis,ovarian development and social environment in Bombus terrestris

The effects of the social environment and age on juvenile hormone (JH) and reproduction were investigated by measuring ovarian development, hemolymph levels of JH III, and rates of JH biosynthesis from the same individual bumble bees (Bombus terrestris). Differences in social environment were associated with differences in rates of JH biosynthesis, JH titer and ovarian development. Young queenless workers had a higher rate of JH biosynthesis, JH titer and ovarian development than queenright (QR) workers of similar age. Dominant workers in QR colonies had a higher rate of JH biosynthesis, JH titer and ovarian development than low ranked workers of similar size. There was a positive correlation between JH titer and ovarian development, but no correlation between rate of JH biosynthesis and ovarian development or between JH biosynthesis and JH titer. Both JH titer and rate of JH biosynthesis increased with age from emergence to 3 days of age, but 6-day-old workers, egg-laying workers, and actively reproducing queens had high JH titers and highly developed ovaries but low rates of JH biosynthesis. These results show that reproduction in B. terrestris is strongly affected by the social environment and the influence of the environment on reproduction is mediated by JH. Our data also indicate that the rate of JH biosynthesis measured in vitro is not a reliable indicator of JH titer or ovarian development in B. terrestris; possible reasons are discussed.     

Regulation of JH epoxide hydrolase versus JH esterase activity in the cabbage looper, Trichoplusia ni, by juvenile hormone and xenobiotics

JH III esterase and JH III epoxide hydrolase (EH) in vitro activity was compared in whole body Trichoplusia ni homogenates at each stage of development (egg, larva, pupa and adult). While activity of both enzymes was detected at all ages tested, JH esterase was significantly higher than EH activity except for day three of the fifth (last) stadium (L5D3). For both enzymes, activity was highest in eggs. Adult virgin females had 4.6- and 4.0-fold higher JH esterase and EH activities, respectively, than adult virgin males. JH III metabolic activity also was measured in whole body homogenates of fifth stadium T. ni that were fed a nutritive diet (control) or starved on a non-nutritive diet of alphacel, agar and water. With larvae that were starved for 6, 28 and 52 h, EH activity per insect equivalent was 48%, 5% and 1%, respectively, of the control insects. At the same time points, JH esterase activity levels in starved T. ni were 29%, 4% and 3% of that of insects fed the nutritive diet. Selected insect hormones and xenobiotics were administered topically or orally to fifth stadium larvae for up to 52 h, and the effects on whole body EH and JH esterase activity analyzed. JH III increased the JH III esterase activity as high as 2.2-fold, but not the JH III EH activity. The JH analog, methoprene, increased both JH esterase and EH activity as high as 2.5-fold. The JH esterase inhibitor, 3-octylthio-1,1,1-trifluoropropan-2-one (OTFP), had no impact on EH activity. The epoxides trans- and cis-stilbene oxide (TSO and CSO) in separate experiments increased the EH activity approximately 2.0-fold. TSO did not alter JH esterase levels when topically applied, but oral administration reduced activity to 70% of the control at 28 h, and then increased the activity 1.8-fold at 52 h after the beginning of treatment. CSO had no effect on JH esterase activity. Phenobarbital increased EH activity by 1.9-fold, but did not change JH esterase levels. Clofibrate and cholesterol 5alpha,6alpha-epoxide had no effect on EH. JH esterase activity also was not affected by clofibrate, but cholesterol 5alpha,6alpha-epoxide reduced the JH esterase activity to 60-80% of the control. The biological significance of these results is discussed.     

Recombination events near the immunoglobulin Cmu gene join variable and constant region genes, switch heavy-chain expression, or inactivate the locus

Immunoglobulin heavy-chain expression is initiated by recombination between a variable region (VH) gene and one of several joining region (JH) genes located near the mu constant region (Cmu) gene, and the active VH gene can subsequently switch to another CH gene. That the general mechanism for CH switching involves recombination between sites within the JH-Cmu intervening sequence and the 5' flanking region of another CH gene is supported here by Southern blot hybridization analysis of eight IgG- and IgA-secreting plasmacytomas. An alternative model requiring successive VH linkage to similar JH clusters near each CH gene is shown to be very unlikely since the mouse genome appears to contain only one complement of the JH locus and no JH gene was detectable within large cloned sequences flanking germline C gamma 3 and C gamma 1 genes. Thus, VH-JH joining and CH switching are mediated by separate regions of "the joining-switch" or J-S element. In each plasmacytoma examined, the J-S element had undergone recombination within both the JH locus and the switch region and was shown to be linked to the functional CH gene in an IgG3, and IgG1, and three IgA secretors. Both JH joining and CH switching occurred by deletion of DNA. Switch recombination occurred at more than one site within the J-S element in different lines, even for recombination with the same CH gene. Significantly, although heavy-chain expression is restricted to one allele ("allelic exclusion"), all rearranged in each plasmacytoma. Some rearrangements were aberrant, involving, for example, deletion of all JH genes from the allele. Hence, an error-prone recombination machinery may account for allelic exclusion in many plasmacytomas.     

Juvenile hormone catabolism and oviposition in the codling moth, Cydia pomonella, as functions of age, mating status, and hormone treatment.

In vitro catabolism of juvenile hormone (JH) in haemolymph of adult female Cydia pomonella was ascribed mainly to juvenile hormone esterase (JHE) activity. No significant differences were noted between virgin and mated females 0-96 h post-emergence. Changes in JHE activity did not appear dependent upon fluctuations in JH titre; conversely, changes in JHE activity could not explain the changes in JH titres. Maximal JHE activity was recorded at 24 h (331.47 +/- 47.25 pmol/h/microl; 355.93 +/- 36.68 pmol/h/microl, virgin; mated insects, respectively) and preceded the peak in JH titres at 48 h. Topical application of JH II (10 ng-10 microg) or fenoxycarb (50 ng) enhanced JHE activity up to 640 and 56%, respectively. Treatment upon emergence with 10 microg JH II induced enzymic activity for less than 24 h, and when 10 microg JH II or 50 ng fenoxycarb were applied, circulating JH titres returned to control levels within 24 h. Oviposition was highly sensitive to exogenous JH and declined significantly with dosages >100 pg. To allow a degree of oocyte maturation before JH treatment, the hormone was administered at 6, 12, 24, or 48 h post-emergence and/or females were mated. Neither measure "protected" the system; oviposition declined immediately after JH application.     

Juvenile hormone synthesis, metabolism, and resulting haemolymph titre in Heliothis virescens larvae parasitized by Toxoneuron nigriceps

Last instar larvae of the tobacco budworm, Heliothis virescens F., fail to pupate and have little 20-hydroxyecdysone when parasitized by Toxoneuron nigriceps (Viereck). In this paper, we extend these observations to juvenile hormone (JH) to determine if parasitism by this wasp affects other endocrine systems. To this end, we compared the production of JH by corpora cardiaca-corpora allata complexes (CC-CA), the metabolism of JH by haemolymph enzymes, and the haemolymph titre of JH in parasitized and non-parasitized control larvae of H. virescens during the last larval instar. CC-CA from parasitized and control larvae had similar peaks of JH synthesis on day 1 of the fifth instar, with JH II accounting for more than 90% of total JH in both groups. On subsequent days, JH synthesis dropped to undetectable levels more quickly in non-parasitized controls than in parasitized larvae. JH metabolism by haemolymph of parasitized and control animals increased from low levels on day 1 of the fifth instar to high levels on days 2 and 3 of the instar. JH metabolism was significantly higher in control larvae than in parasitized larvae. After day 3, JH metabolism decreased in both groups, but was significantly higher in parasitized larvae. The major metabolite of JH in both groups was JH acid, though traces of JH diol and JH acid diol were also detected. The haemolymph titre of JH in both groups peaked on day 1 of the fifth instar and, similar to the synthesis of JH by CC-CA, decreased more rapidly in control larvae. As a result, non-parasitized animals had significantly lower JH titres on day 2. The higher JH titres observed in parasitized larvae during the early fifth instar may contribute to their developmental arrest. The possible role of these JH alterations in the host developmental and metabolic redirection is discussed and a more comprehensive physiological model accounting for host-parasitoid interactions is proposed.     

Detection of juvenile hormone I,II and III in adult monarch butterflies (Danaus plexippus)

Hemolymph of Danaus plexippus (monarch butterfly) was analyzed for juvenile hormone titer by gas liquid chromatography-mass spectrometry (GC-MS) in the selected ion monitoring mode. Laboratory reared, reproductively active, adult males and females contained JH I, II and III. JH II predominated with titers ranging from 2.3 to 11 ng/ml hemolymph. Titers of JH I and JH III were approx. 1 order of magnitude lower than those of JH II. JH I, II and III acids were also detected, but at levels generally lower than the corresponding JHs. JH titers in field collected reproductively inactive, gregarious adult monarchs, were 1–2 orders of magnitude lower than those of laboratory reared reproductively active monarchs. JH II was again the predominant JH in these animals.     

JH III production, titers and degradation in relation to reproduction in male and female Anthonomus grandis

Juvenile hormone (JH) is necessary for the production of vitellogenin (Vg) in the boll weevil, Anthonomus grandis. Occurrence of Vg in this species is typically restricted to reproductively competent females, and is not detected in untreated males. However, the JH analog, methoprene stimulates Vg production in intact males and in the isolated abdomens of both male and female boll weevils (where in each case no Vg is detected without treatment), suggesting that males are competent to produce Vg but are normally not stimulated to do so. Preliminary work indicating that male boll weevil corpora allata (CA) produced little or no JH in vitro suggested that failure of males to produce Vg might be due to very low JH levels compared to females. This study re-examines the question of JH in male boll weevils by determining in vitro production of JH III by male CA during the first 10 days after adult emergence, determining hemolymph JH esterase activity during this same time period and hemolymph JH III titers in adults of both sexes. We also re-examine the ability of isolated male abdomens to produce Vg in response to hormonal stimulation, analyzing the effect of a wide range of methoprene and JH III dosages. Results indicate that male A. grandis have circulating JH titers and JH production similar to females. JH esterase activity is slightly but significantly higher in males than females. Vg production by isolated abdomens of both sexes after stimulation with methoprene or JH III was confirmed. Dose response studies indicated that high levels of methoprene were less effective than intermediate doses in stimulating Vg synthesis in both sexes. We conclude that the sexually dimorphic effect of JH on Vg synthesis is not due to differences in JH production or differences in JH titer between the sexes.     

Antenna contact and agonism in the male lobster cockroach, Nauphoeta cinerea

On any given day, about 35% of 80- to 85-day-old socially na?ve male (SNM) lobster cockroaches (Nauphoeta cinerea) spontaneously adopted an aggressive posture (AP) without encountering another male [spontaneous AP (SAP)]. Although SAP SNMs showed significantly higher release of the pheromone 3-hydroxy-2-butanone (3H-2B) than non-SAP SNMs, there was no significant difference in hemolymph juvenile hormone (JH) III titer. When different body parts were tested for induction of the attack behavior, the antenna was found to be the most effective. After 1 min of contact with an antenna from another SAP SNM, attack behavior was induced in 100% of SAP and 76.2% of non-SAP SNMs, and the JH III titer was significantly increased in all responders. Among the non-SAP SNMs, the JH III titer before antenna contact was significantly lower in the non-responders than in the responders, and, although the JH III increase induced by 1 min antenna contact was similar between responders and non-responders, the final JH III titer of the non-responders was significantly lower. A similar attack response, JH III titer change, and 3H-2B release were seen when the individual's own antenna was used. After 5 min of contact with an antenna from another SAP SNM, attack behavior was induced in 100% of SAP and 82% of non-SAP SNMs; in the former, 3H-2B release was similar before and after antenna contact, but the JH III titer was significantly increased after antenna contact, while, in the latter, both 3H-2B release and JH III titer were significantly increased after antenna contact. Among the non-SAP SNMs, JH III titer in the non-responders was not elevated after 5 min antenna contact, and was significantly lower than that in the responders. A pentane-washed antenna did not induce attack behavior or increase the hemolymph JH III titer, and a pentane-washed antenna coated with 3H-2B also failed to induce attack behavior. These results indicate that N. cinerea male-male agonistic interactions, to which the vertebrate challenge hypothesis can be applied, are due to contact pheromone on the antenna, resulting in the concomitant expression of attack behavior and an increase in 3H-2B release and JH III titer.     

Development changes in juvenile hormone and juvenile hormone acid titers in the hemolymph and in-vitro juvenile hormone synthesis by corpora allata of the silkworm,Bombyx mori

A simple method was developed to quantify hemolymph juvenile hormone (JH) and JH acid in hemolymph extracts from Bombyx mori with an established radioimmunoassay (RIA) for JH I. When various organic solvent extracts of hemolymph were assayed by RIA, levels of non-specific binding of the labeled ligand in the assay were determined to be greater than 50% of the maximum amount of the label bound by the antiserum. When hemolymph was diluted with methanol:water:8.4N ammonium hydroxide (10:9:1) and extracted with isooctane, non-specific binding was only 50% higher than control levels obtained with the assay buffer alone. The organic phase contained only JH and aqueous phase, JH acid. Consequently, this extraction method was used to prepare samples for RIA and enabled the separate measurement of JH and JH acid in hemolymph. With this method, changes in the hemolymph titers of JH and JH acid were determined from the third instar through early pupal stage of Bombyx mori. Changes in the in vitro secretory activity of corpora allata and brain-corpora cardiaca-corpora allata complexes from fifth instar larvae were also determined by using JH I RIA of the incubation medium.     

Diapause of the southwestern corn borer, Diatraea grandiosella: Further evidence showing juvenile hormone to be the regulator

Further evidence is presented to demonstrate the involvement of juvenile hormone (JH) in regulating diapause in the final larval stage of the southwestern corn borer. Diatraea grandiosella. JH titres in the haemolymph were measured throughout the entire diapause period. Additional results showed that actively secreting corpora allata are necessary to maintain diapause because allatectomized larvae terminated diapause prematurely. A topical application of JH mimic 2 days after the allatectomy prevented this premature termination of diapause. Intact nervous connections between the brain and the corpora allata were necessary for the maintenance of JH secretion. Other surgical work showed that the brains of nondiapausing larvae exhibited a higher ecdysiotropic activity than those of pre-, early-or mid-diapausing larvae.A single application of a JH mimic was more effective in maintaining a diapause-like state in nondiapausing larvae than were repeated topical applications of C₁₈-JH or an implantation of active corpora allata, suggesting that JH was more rapidly metabolized than was the JH mimic. The oxygen consumption of diapausing larvae which had received repeated topical applications of JH mimic was not significantly elevated over that of the controls indicating that treated larvae maintained a low metabolic rate even though they reverted to the spotted morph. A single application of 0.03 μg JH mimic/larva was sufficient to prolong diapause, thereby confirming that JH is necessary for diapause maintenance.     

The interactions between juvenile hormone (JH), lipophorin, vitellogenin, and JH esterases in two cockroach species

For the cockroach species Leucophaea maderae and Periplaneta americana two major juvenile hormone (JH)-binding proteins have been identified: lipophorin (Lp) and vitellogenin (Vg). Each of these macromolecules binds JH with an approximate affinity of K(d) of 10 nM. In Leucophaea the concentration of Lp is augmented by JH during vitellogenesis at the same time when Vg is induced de novo. The circulating levels of each of Lp and Vg at mid-vitellogenesis are in the 10 microM range. Similar values have been determined for Periplaneta. Total JH concentrations (bound and free) can be as high as micromolar in Leucophaea. However, because of the large quantities of the two major JH-binding proteins and their high affinity for JH, we can assume that the amount of free (unbound) JH in circulation is extremely low (the actual values are not know).The JH esterases (JHEs) of the hemolymph in both cockroach species have been isolated by anion exchange chromatography. The JHEs of Leucophaea bound to the anion exchange resin more tightly than the JHE of Periplaneta. The V(max) of the Leucophaea esterases fluctuated by a factor of 2 to 3 during vitellogenesis. The K(m) values for the two distinct esterases of Leucophaea were similar (about 0.15x10(-6) M). On the other hand, k(cat) of the JHEs for Leucophaea at ovulation time was two to three times higher than earlier during vitellogenesis, i.e. 23.30 min(-l) compared to 6.20 min(-1). The JHE of Leucophaea is shown to bind JH III with high affinity: K(d)=3x10(-9) M. However, since there are only very small amounts of JH available for degradation (due to the binding to Lp and Vg), the quantitative removal of JH from circulation, and this includes the release of bound JH, is indeed slow, with a measured half-life of 6-8 h. Classical kinetic assumptions are not met in conditions where the enzyme concentrations exceed by far that of the available substrate. Nonetheless, we attempted to determine the initial velocity of JH hydrolysis under natural conditions, i.e. for undiluted hemolymph, by measuring the initial velocities of JH hydrolysis in serially diluted hemolymph and extrapolating to zero dilution. For in vivo conditions we estimated an initial velocity of JH hydrolysis of <0.1 fmol microl hemolymph(-1) min(-1), i.e. four to five orders of magnitude lower than that measured at substrate saturation in vitro.     

Nutrition, hormones and life history in burying beetles

Nutrition, hormones and the allocation of physiological resources are intricately related. To investigate these inter-relationships in female burying beetles (Nicrophorus spp.), we examined the effect of diet quality on juvenile hormone (JH) levels and reproduction, and the effect of JH supplementation on reproduction and resistance to starvation. Nicrophorus orbicollis adult females fed a less preferred mealworm larvae diet gained less body mass, had smaller ovaries and had lower titers of JH in their hemolymph than females fed a preferred blowfly diet. When presented a carcass for breeding, females on a less preferred diet oviposited 33% fewer eggs, and eggs were of 18% less mass. Females on the less preferred diet also took longer to begin oviposition as indicated indirectly by the time when their eggs hatched. To investigate the effects of JH, independent of nutrition, JH was topically applied to single and paired females of Nicrophorus tomentosus. When presented a carcass, JH-treated paired females oviposited more eggs (28%-year 1, 44%-year 2) than control females, and also showed a trend toward faster oviposition. JH supplementation had a greater effect on single females. JH treatment increased the proportion of single females attempting reproduction (at least one viable larva), increased the number of eggs (69%-year 1, 123%-year 2), and increased the proportion of females ovipositing early. In separate experiments, treatment with JH or a JH analog negatively affected resistance to starvation in three species. Treatment with JH reduced starvation survival by 10.3% days in N. tomentosus females. Treatment with the JH analog methoprene reduced starvation survival 17.8% in N. orbicollis females and by 18% in Ptomascopus morio females. These results suggest that JH has positive and negative effects on different components of life history.     

Pheromone, juvenile hormone, and social status in the male lobster cockroach Nauphoeta cinerea

In this study, the major pheromone component, 3‐hydroxy‐2‐butanone (3H‐2B), released by dominants was measured during early scotophase. Both the JH III titer in the hemolymph and the 3H‐2B content of the sternal glands of the dominants and subordinates were then measured during late scotophase and late photophase. These investigations were performed on encounter days 1, 2, 3, 5, 7, 9, 12, and 20. The results showed that, for non‐aggressive posture (AP)‐adopting socially naïve males (SNMs), both the 3H‐2B release and the hemolymph JH III titer were maintained at a low level. Once a fight occurred, 3H‐2B release was raised significantly in the AP‐adopting dominants, but not in non‐AP‐adopting subordinates, and remained raised throughout the entire experimental period. At 30 min after the first encounter, the hemolymph JH III titer was significantly increased in dominants, but not in subordinates. A significantly higher hemolymph JH III titer was observed in dominants during late scotophase on days 3, 5, 12, and 20 and during late photophase on days 3, 5, and 20. After fighting, the sternal gland 3H‐2B content of the dominants or subordinates was significantly lower than in SNMs. In dominants, the sternal gland 3H‐2B content during late scotophase was significantly lower than that during late photophase in the first 9 domination days, while, in the subordinates, the 3H‐2B content during late scotophase was either similar to, or significantly higher than, that in late photophase. In the dominants, 3H‐2B release and JH III titer were positively correlated. In rank switchers, the switched social status was positively correlated with both 3H‐2B release and JH III titer. Comparison of 3H‐2B release and JH III titer in 1‐time, 3‐time, or 5‐time dominants showed that, although winning significantly increased both 3H‐2B release and JH III titer, there is no significant difference in 3H‐2B release between 3‐ and 5‐time winners, while the JH III titer was most significantly increased in the 3‐time winners. The possible relationship between pheromone release, JH III titer, and social status is discussed. Arch. Insect Biochem. Physiol. 2008. © 2008 Wiley‐Liss, Inc.     

Characterization and the developmental role of plasma juvenile hormone esterase in the adult cabbage looper,Trichoplusia ni

Juvenile hormone (JH) esterase was characterized from the plasma of adult females of the cabbage looper, Trichoplusia ni, and compared with that present in 4th and 5th instar larvae. Ester hydrolysis was the principal route of JH metabolism. Gel filtration of plasma resolved a single peak of JH esterase which was distinct from that of the α-naphthyl acetate (α-NA) esterase activity. The JH esterase apparent molecular weight was 62,000 in prepupae and virgin, female adults and 69,000 in 2-day-old 4th instar larvae. Broad range isoelectric focusing of plasma of prepupae and adults resolved a major peak of activity at pH 5.5 with a minor peak of activity at pH 6.1 and in 4th instar larvae at pH 5.45 and 5.8, respectively. By this method JH esterase was resolved from the α-NA esterase activity. The plasma of prepupae and adults metabolized JH I at about twice the rate of JH III. JH esterase activity from adult plasma was more stable than the α-NA esterase activity. Adult JH esterase activity was insensitive to inhibition by O,O-diisopropyl phosphorofluoridate in contrast to that of the α-NA esterase activity. Mated females oviposited 8 times more eggs than virgin females to 10 days after emergence. The total haemolymph protein content of virgin females remained high throughout the period of study whereas mated females showed a significant decline beginning on day 4. JH esterase activity remained unchanged in virgins whereas it declined drastically in mated females. The α-NA esterase activity declined to low levels shortly after emergence in both groups. JH and α-NA esterase activity was not affected by the application of the juvenoid, (RS)-methoprene. The present study provides evidence of a functional role for JH esterase in JH metabolism and reproduction in adult T. ni. JH esterases in the adult were identical to that of prepupae by the methods described above.     

Hydrolysis of juvenile hormone in diapausing and non-diapausing larvae of the southwestern corn borer,Diatraea grandiosella

Summary The role of juvenile hormone (JH) esterases in relation to the diapause state of the southwestern corn borer,Diatraea grandiosella, was examined. The facultative larval diapause of this insect is dependent upon the presence of JH. Plasma, fat body, midgut, and body wall extracts metabolized [³H]JH I and [³H]JH III to JH-acid in vitro. JH-diol, JH-acid-diol, or conjugated polar metabolites were not detected. A longer half life of [³H]JH I was found in vitro in the plasma of diapausing larvae than in that of non-diapausing larvae. Although JH hydrolytic activity was relatively low in the plasma of pre-diapausing and diapausing larvae, systematic changes were observed suggesting that JH esterases may be involved in regulating the JH titer during this period. The JH hydrolytic activity found in the plasma of diapausing larvae was 3 to 5 times lower than that found in the plasma of mid-last instar non-diapausing larvae. Gel filtration profiles obtained from the plasma of diapausing and non-diapausing larvae suggested that JH esterases and -naphthyl-acetate esterases are different enzymes. Multiple overlapping peaks of JH hydrolytic activity with an apparent molecular weight range of 43,000 to 75,000 were detected, whereas 2 separate peaks of -naphthyl-acetate hydrolytic activity (apparent mol. wt. ca. 54,000, and 120,000) were detected. Gel filtration of supernatants of fat body indicated that JH was hydrolyzed at a lower rate by the fat body of pre-diapausing larvae than by that of non-diapausing larvae.     

Disturbance of Adult Eclosion by Fenoxycarb,a Juvenile Hormone Mimic,in the Beet Armyworm,Spodoptera exigua

Effect of exogenous juvenile hormones (JHs) on pupal development was assayed in the beet armyworm, Spodoptera exigua. Fenoxycarb, a potent JH mimic, was applied topically to different ages of the pupae, and showed significant inhibition of normal adult eclosion even at 0.1 μg dose when it was applied at the early pupal stage (day 0). As the pupal development underwent, the susceptibility of the pupae fenoxycarb decreased. RH5992, a potent ecdysteroid mimic, did not, however, any similar inhibitory effect on the pupae. Natural JH types (JH I, JH II, and JH III) were applied on day 0 pupae to compare their inhibitory effects on adult eclosion. Both JH I and JH II significantly inhibited adult eclosion at 1.0 μg dose, but JH III did not even at 10.0 μg dose. It was noted that fenoxycarb-treated pupae showed little rectum development. Fenoxycarb did not, however, show any negative effect on the development of compound eye and wing imaginal discs, and on the pupal hemolymph protein pattern. These results suggest that there should be a commitment period requiring an absence of JH for a normal adult metamorphosis during early pupal development and that the endogenous type of JH in S. exigua is JH I or JH II or both JHs like other lepidopteran species.     

Starvation influences allatotropin gene expression and juvenile hormone titer in the female adult oriental armyworm, Mythimna separata

The first day of adult life is the sensitive stage for shifting migrants into the resident morphs of the oriental armyworm (OAW), Mythimna separata (Walker). The juvenile hormone (JH) titer, expression of the allatotropin (AT) gene, and their relationship were investigated in adult female migrants starved in the sensitive stage, to understand the underlying mechanism of changing migrants into resident OAWs. Haemolymph JH titers of the starved female adults were mostly elevated earlier than in controls, although not all differences were statistically significant. JH I titers in the starved moths were significantly higher than those in the controls on 1, 2, and 5 days after treatment (DAT), respectively. JH II titers in the starved moths were significantly higher than the controls through the period tested except on 5 DAT. JH II is the most likely regulator in changing migrants into resident morphs. The relative quantities of AT expression in the starved moths were higher through the period tested except on 5 DAT. AT expression and JH titers appear to be positively correlated, especially for those in earlier days of the adult life. We infer that AT is the important regulator of JH levels. A model for the shifting of migrants into resident morphs in the OAW is proposed.