Autoinhibition of juvenile hormone production. The case of the cockroachBlattella germanica (L.)

In 6-day-old females ofBlattella germanica, the activity of corpora allata (CA) was inhibited in vitro by juvenile hormone III (JH III). Effective doses (281.5 and 375.4 M in the medium) were somewhat higher than (although of the same order of magnitude as) the estimated intraglandular concentration of JH III at this age, and they induced about 45% inhibition of hormonal release and a significant intraglandular accumulation of JH III and methyl farnesoate. The results suggest that autoinhibitory mechanisms operate in the CA to constrain the upper limit of JH III production at the end of the gonadotrophic cycle.     

Juvenile hormone I is the principal juvenile hormone in a hemipteran insect,Riptortus clavatus

Juvenile hormone I (JH I) was identified by combined gas chromatography/mass spectrometry as the predominant JH in the hemolymph of female adults of the bean bug,Riptortus clavatus (Thunberg) (Hemiptera: Alydidae). Among JH I, II, and III, JH I was the most effective hormone for inducing the synthesis of yolk proteins in diapause adults.     

Juvenile hormone titre and regulation in the cockroachDiploptera punctata

Summary Titres of juvenile hormone (JH) have been determined in both hemolymph and whole body extracts of femaleDiploptera punctata during the first gonotrophic cycle using a method employing gas chromatography/mass spectrometry for qualitative and quantitative analysis. JH III is the sole JH found in both adult and last instarD. punctata. Maximum values of 1500 ng/ml (6M) were observed at the middle of the gonotrophic cycle, when basal oocyte growth rate was greatest. Changes in rates of JH release in vitro by corpora allata paralleled closely the changes in JH titre, suggesting that biosynthesis is a major regulator of titre. JH levels per animal were calculated from observed JH titres, and at certain time points in the gonotrophic cycle JH levels obtained from analysis of whole bodies were significantly greater than those predicted from hemolymph titres. These results suggest the existence of a nonhemolymph JH pool inD. punctata. Decay in JH titre after allatectomy of 5 day females has also been studied. Following a rapid initial decline, the rate of decay slowed appreciably 4 h post-operation. Thus, use of a first-order rate constant to estimate half-life of JH significantly underestimated the longevity of the hormone. The apparent persistence of JH following allatectomy may be due to the existence of a nonhemolymph JH pool.     

Differences in the stimulation by calcium ionophore of juvenile hormone III release from corpora allata of solitarious and gregariousLocusta migratoria

Summary Incubation of the calcium ionophore A23187 resulted in an increase in the median rate of juvenile hormone III release by corpora allata (CA) of both gregarious and solitarious adultLocusta migratoria females at 3, 5 and 8 days after fledging. At all 3 datapoints, the enhancement of release rates was highly significant for CA from gregarious females but not significant for CA from solitarious females.     

Forced synthesis of trace amounts of juvenile hormone II from propionate by corpora allata of a juvenile hormone III-producing insect

Summary Corpora allata of the cockroachDiploptera punctata normally synthesize only the isoprenoid juvenile hormone III (JH III). Only under extreme in vitro conditions (absence of carbon sources other than propionate) do they produce trace amounts of the homoisoprenoid JH II in addition to JH III. The specificity of the in vitro synthesis of JH III byD. punctata is thus consistent with the observed lack of homoisoprenoid JHs in this insect.     

Juvenile hormone catabolism inManduca sexta: Homologue selectivity of catabolism and identification of a diol-phosphate conjugate as a major end product

We studied time-dependent metabolism of (10R)-[³H] juvenile hormone (JH) III and (10R, 11S)-[³H]JH I injected intoManduca sexta larvae; the hormones are metabolized to polar metabolites, expecially the JH acid-diol, and an unknown. Products were analyzed using a reversed-phase liquid chromatography assay. (10R)-JH III is metabolized much more rapidly than (10R, 11S)-[³H]JH I, whether injected seperately or as a mixture of hormones. The unknown metabolites of JH I and JH III were identified as phosphate conjugates of JH I and JH III diol by tandem mass spectral analysis of isolated samples. The phosphate conjugate of JH I diol is the principle end product of JH I metabolism.     

Enhancement of boll weevilAnthonomus grandis Boh. (Coleoptera: Curculionidae) pheromone biosynthesis with JH III

Summary The juvenile hormone JH III, when incorporated at 1.0 ppm in the diet of adult male boll weevils (Anthonomus grandis Boh.), increased the biosynthesis of its 4 pheromone compounds by 3 times. The biosynthesis at lower and higher levels of JH III was less. JH I was not active at any of the concentrations tested.In cooperation with the Miss. Agr. and For. Exp. Sta., Miss. State, MS 39762. Mention of a proprietary product does not necessarily imply endorsement of this product by the USDA.     

Juvenile hormone titre and regulation in the cockroach Diploptera punctata

Titres of juvenile hormone (JH) have been determined in both hemolymph and whole body extracts of female Diploptera punctata during the first gonotrophic cycle using a method employing gas chromatography/mass spectrometry for qualitative and quantitative analysis. JH III is the sole JH found in both adult and last instar D. punctata. Maximum values of approximately 1500 ng/ml (approximately 6 microM) were observed at the middle of the gonotrophic cycle, when basal oocyte growth rate was greatest. Changes in rates of JH release in vitro by corpora allata paralleled closely the changes in JH titre, suggesting that biosynthesis is a major regulator of titre. JH levels per animal were calculated from observed JH titres, and at certain time points in the gonotrophic cycle JH obtained from analysis of whole bodies were significantly greater than those predicted from hemolymph titres. These results suggest the existence of a nonhemolymph JH pool in D. punctata. Decay in JH titre after allatectomy of 5 day females has also been studied. Following a rapid initial decline, the rate of decay slowed appreciably 4 h post-operation. Thus, use of a first-order rate constant to estimate half-life of JH significantly underestimated the longevity of the hormone. The apparent persistence of JH following allatectomy may be due to the existence of a nonhemolymph JH pool.     

Forced synthesis of trace amounts of juvenile hormone II from propionate by corpora allata of a juvenile hormone III-producing insect

Corpora allata of the cockroach Diploptera punctata normally synthesize only the isoprenoid juvenile hormone III (JH III). Only under extreme in vitro conditions (absence of carbon sources other than propionate) do they produce trace amounts of the homoisoprenoid JH II in addition to JH III. The specificity of the in vitro synthesis of JH III by D. punctata is thus consistent with the observed lack of homoisoprenoid JHs in this insect.     

Hormonal control of sexual receptivity in cockroaches

Many animals exhibit specific behaviors associated with sexual receptivity only when they are reproductively competent. In insects with gonadal maturation cycles, these behaviors usually coincide with ovarian matruation. In the cockroachBlattella germanica, juvenile hormone (JH), produced by the corpora allata (CA), regulates female reproductive physiology. Various experimental manipulations, including ablation of the CA, therapy with JH analogs, CA denervation, ovariectomy, and changing nutrient quality, coupled with time-lapse video recording, support the hypothesis that JH also controls female sexual receptivity. A re-examination of the role of the CA in the maturation of male sexual readiness shows that, while sexual behavior develops in the absence of JH in bothB. germanica andSupella longipalpa, JH accelerates the expression of sexual readiness.     

In vitro biosynthesis of juvenile hormone III by the corpora allata ofCalliphora vomitoria and its role in ovarian maturation and sexual receptivity

Summary JH III is the only JH detected by GLC-MS in medium from in vitro incubations of corpora allata of adult females ofCalliphora vomitoria. When corpora allata were removed from females at various times during the reproductive cycle and the JH III produced by the glands in vitro measured by a JH III radioimmunoassay, an increase in the level of synthesis was found to occur before previtellogenesis (0–24 h). A second increase appeared at the onset of vitellogenesis (72–83 h) and continued until the end of vitellogenesis (96 h) and the occurrence of chorionation (120 h). Since sexual receptivity develops with vitellogenesis, the significantly higher levels of JH III biosynthesis in vitro at this time supports a possible role for JH in the acquisitive of receptivity.     

Reversible juvenile hormone inhibition of ecdysteroid and juvenile hormone synthesis by the ring gland ofDrosophila melanogaster

Juvenile hormone bisepoxide (JHB₃) and juvenile hormone III (JH III) both inhibited the in vitro production of ecdysteroids by ring glands and brain-ring gland complexes from third instar post-feeding larvae ofDrosophila melanogaster in a reversible manner, although JHB₃ had greater efficacy. The JH III and JHB₃ precursor, methyl farnesoate, did not affect ecdysteroid production. The in vitro synthesis of total detectable JH (JHB₃+JH III+methyl farnesoate) by the corpus allatum portion of the isolated ring gland was also inhibited reversibly in the presence of exogenous JHB₃ and JH III, but not by methyl farnesoate. These data indicating negative feedback are in agreement with the accepted dogma of endocrine gland regulation.     

Phosphoramidon enhances allatostatin-mediated inhibition of juvenile hormone biosynthesis in the corpora allta of the cockroach,Diploptera punctata

Use of the enkephalinase inhibitor phosphoramidon in the in vitro radiochemical assay for juvenile hormone biosynthesis enhanced allatostatin-mediated inhibition of hormone production by corpora allata of the cockroach,Diploptera punctata. Significant increases in inhibition in day 2 virgin female CA by AST 1 (at 10^–7 M) and AST 4 (10^–8–10^–7 M) were observed in the presence of phosphoramidon (10^–5M or greater). No significant increases in inhibition were seen in CA from day 6 mated females with AST 4 (10^–9–10^–7M) and phosphoramidon combined. Phosphoramidon alone had no effect on JH biosynthesis. Analysis of allatostatin content of the CA, as determined by ELISA, revealed that addition of phosphoramidon to the medium increased the endogenous allatostatin conten in CA of virgin and mated females. The similarity in primary structure between allatostatins and enkephalin-like peptides and their similar distribution makes it probable that phosphoramidon acts by preventing breakdown of allatostatins within the CA.     

Juvenile hormone and reproduction in the cricket. II. Effect of rearing temperature on corpus allatum activity (in vitro) in adult females

Summary In the Mediterranean field cricket,Gryllus bimaculatus, reproduction is controlled by temperature and the corpus allatum (CA) hormone JH III. In CA of females reared at 24°12°C(168 h) (high reproduction rate) a first peak in JH III synthesis is reached about 4 days earlier than in those of 20°C females (low reproduction rate). Furthermore, in 20°C animals CA activity is low during the entire oviposition period, whereas at 24°12°C high CA activity is found during this period of adult life. The results indicate a stimulation of CA activity and reproduction by thermoperiods around a constant low temperature.Supported by the DFG (SFB 87 A 4).     

Relationship between the absolute configuration and the biological activity of juvenile hormone III

Summary The activity of the pure 10R (=natural) and 10S enantiomers of juvenile hormone III (JH III) was determined in 3 different bioassays, and the relative binding affinity of the 2 enantiomers to the haemolymph JH-binding protein of the cockroachNauphoeta cinerea was measured. In theGalleria wax test, a local morphogenetic assay, the 10R enantiomer was 5240 times more active than, the 10S enantiomer, 1Galleria unit corresponding to 0.42 pg of 10R-JH III as compared to 2.2 ng for 10S-JH III. In a systemic morphogenetic assay with the cockroachNauphoeta cinerea 380 times less 10R enantiomer was necessary in order to induce detectable juvenilisation (58 ng 10R and 22 g 10S) and in a systemic gonadotropic assay withNauphoeta cinerea 255 times less 10R was needed to induce vitellogenin synthesis in 50% of the insects (6.7 ng 10R and 1710 ng 10S). In the JH-binding protein assay 10R-JH III had an affinity for the JH-binding protein (lipophorin) which was approximately 46 times higher than that of 10S-JH III.     

Reversible juvenile hormone inhibition of ecdysteroid and juvenile hormone synthesis by the ring gland of Drosophila melanogaster

Juvenile hormone bisepoxide (JHB3) and juvenile hormone III (JH III) both inhibited the in vitro production of ecdysteroids by ring glands and brain-ring gland complexes from third instar post-feeding larvae of Drosophila melanogaster in a reversible manner, although JHB3 had greater efficacy. The JH III and JHB3 precursor, methyl farnesoate, did not affect ecdysteroid production. The in vitro synthesis of total detectable JH (JHB3 + JH III + methyl farnesoate) by the corpus allatum portion of the isolated ring gland was also inhibited reversibly in the presence of exogenous JHB3 and JH III, but not by methyl farnesoate. These data indicating negative feedback are in agreement with the accepted dogma of endocrine gland regulation.     

Identification of JH III as the princpal juvenile hormone inLocusta migratoria

Summary JH titers in the hemolymph of nymphal and adult femaleLocusta migratoria migratorioides (R. and F.) were determined using a selective mass spectrosc opic detection technique. Only JH III could be found in either stage, with no detectable JH I (or II). Titers observed were 10–1000-fold lower than those found via a recently reported radioimmunoassay procedure.     

Juvenile hormones inThermobia domestica females: Identification and quantification during biological cycles and after precocene application

Summary JH I and JH III immunoreactive substances were detected in the hemolymph of imaginal females of the primitive insectThermobia domestica. Periodic changes in the levels of these hormones were investigated in correlation with molting and reproductive cycles in inseminated, virgin and precocene-treated females. The presumed influence of JH III on the various phases of vitellogenesis is discussed, also taking into account the periodic changes of the hemolymphatic ecdysteroid levels.     

Insect anti-juvenile hormone and juvenile hormone activity from plants in the genusNama

Summary The insect anti-juvenile hormones precocene I and II (7-methoxy-2,2-dimethyl-2H-1-benzopyran and 6,7-dimethoxy-2,2-dimethyl-2H-1-benzopyran) were identified in three of nineNama (Hydrophyllaceae) species. Precocene I occurred inN. lobbii while precocene II occurred inN. hispidum, N. lobbii andN. sandwicense. N. hispidum contained the highest concentration (ca 0.5% dry weight) of precocene II, which was found in the leaves, stems, seed capsules, corolla, glandular trichomes, and seeds. In addition to the anti-juvenile hormone, insect juvenile hormone activity was detected in the organosoluble extracts ofN. rothrockii andN. sandwicense. N. sandwicense is the first plant discovered to contain compounds with both anti- and juvenile hormone activity.     

The transfer of juvenile hormone from male to female during mating in the Cecropia silkmoth

Summary The juvenile hormone (JH) stored in the accessory sex glands (ASG) of adult maleHyalophora cecropia (L.) originates both from sequestration of circulating hormone and from JH synthesized de novo in the ASG from JH acid taken up from the hemolymph. The secretions present in the lumina of the ASG contain most of the accumulated JH. During mating, endogenous JH, labeled biosynthetically via injected [³H-methyl]-methionine, is transferred along with the other seminal material to the bursa copulatrix of the female. The physiological significance of the JH transfer remains unknown.Research was supported by a grant from the National Science Foundation (PCM72-01892) and Organized Research Funds from Texas A&M University.This work was done as partial fulfillment for the degree of Doctor of Philosophy.