Juvenile Hormone Release Research Articles

Benzodioxole‐1,3‐benzodioxole derivatives and their effects on the reproductive physiology of insects

AbstractAlkyl ethers of methylenedioxy analogs of obtusastyrene or benzyl‐1,3‐benzodioxole derivatives (BBDs) and related benzylphenols have been shown to interfere with various phases of reproduction in insects. BBDs have also been shown to interfere with sex attractancy, to induce precocious development, and to antagonize juvenile hormone (JH) functions in insects. Because representative BBDs were reported to show low toxicity to mammals and to be negative in assays testing for potential mutagens, these compounds held much promise to be environmentally safe insect chemosterilants. The mode of action of BBDs does not involve blocking or competition for putative JH receptor sites on follicular cells or hemolymph JH binding proteins. However, BBDs were shown to interfere with (1) in vitro biosynthesis and release of JH from corpora allata of Mediterranean fruit fly females, and (2) microtubule assembly in insects. © 1994 Wiley‐Liss, Inc.This article is a US Government work and, as such, is in the public domain in the United States of America.

Changes in the titre of a juvenile hormone III binding lipophorin in the haemolymph of Diploptera punctata during development and reproduction: Functional significance

A monoclonal antibody specific to juvenile hormone binding lipophorin was used in an enzyme-linked immunosorbent assay (ELISA) to determine titre of this protein in the haemolymph during the fourth stadium and the first reproductive cycle of adult female Diploptera punctata. Juvenile hormone binding lipophorin was present in the haemolymph at all times at concentrations between 3.75 and 16 μg/μl and its titre exhibited some changes which were not coincident with those in total haemolymph protein concentration. Three aspects of juvenile hormone binding lipophorin function were examined: (1) Plasma juvenile hormone esterase activity and partially purified juvenile hormone esterase activity was inhibited by exogenous juvenile hormone binding lipophorin in a dose-dependent manner by up to 92%. 10 R-juvenile hormone III was metabolized faster by diluted plasma than racemic juvenile hormone III, both in the presence and absence of exogenous juvenile hormone binding lipophorin. (2) Exogenous juvenile hormone binding lipophorin did not affect the biosynthesis and release of juvenile hormone from the corpora allata of day-2 virgin females in vitro. (3) The amount of juvenile hormone binding lipophorin-immunoreactive material in the ovaries of mated females was determined by ELISA. Juvenile hormone binding lipophorin-immunoreactive material reached a maximum in day-3 mated female ovaries (23 μg/pair) at the start of vitellogenesis and declined rapidly thereafter.

Factors affecting the biosynthesis and release of juvenile hormone bisepoxide in the adult blowfly Calliphora vomitoria

The principal juvenile hormone produced by the corpus allatum of the adult blowfly Calliphora vomitoria has been identified as juvenile hormone bisepoxide. The precursor compounds, methyl farnesoate and juvenile hormone III are also synthesized and released from the isolated gland in vitro, but in small amounts (approx. 1% of the total radiolabelled products of the gland). In females given unrestricted access to sugar, water and meat immediately after eclosion, the rate of juvenile hormone bisepoxide production rises with the initiation of oöcyte development, reaches high levels early in the first gonadotropic cycle and remains consistently high through successive cycles. Mature males on the same diet also produce juvenile hormone bisepoxide at high rates. Flies restricted to a sugar-and-water-only diet synthesize much lower levels of juvenile hormone bisepoxide (less than 50% of meat-fed flies). Partially-purified brain extracts of C. vomitoria contain material that is immunoreactive in an ELISA against the inhibitory neuropeptide, allatostatin 1, of the cockroach Diploptera punctata. This material is able to inhibit significantly the biosynthesis of juvenile hormone bisepoxide in flies, and also has strong inhibitory effects on juvenile hormone III biosynthesis by cockroach corpora allata in vitro. Cockroach allatostatins 1–4 at concentrations of 10 −4–10 −7 M have no significant effect on juvenile hormone bisepoxide release in the blowfly. Also tested at the same concentrations, and shown to have no significant effects on the synthesis and release of juvenile hormone-related compounds in either the blowfly or the cockroach were the vertebrate peptide Met 5-enkephalin-Arg 6-Gly 7-Leu 8 (YGGFMRGL) and its carboxyamidated analogue (YGGFMRGL-NH 2). Similarly, the FMRFamide-related peptides, calliFMRFamides 1 and 5 and their non-amidated analogues, at concentrations of 10 −4–10 −6 M, had no effect on juvenile hormone bisepoxide biosynthesis and release. Forskolin (5 × 10 −5 M) and 8-bromo-cAMP (10 −4 M) appeared not to have an inhibitory influence on juvenile hormone bisepoxide release in the blowfly, suggesting that cAMP may not be the intracellular second messenger in this species. A presumed precursor of juvenile hormone bisepoxide, farnesoic acid, did not stimulate and increased production of juvenile hormone bisepoxide, but resulted in an increase in juvenile hormone III production.

Differential stimulation of juvenile hormone III biosynthesis induced by mevalonate and mevalonolactone in Blattella germanica (L.)

The effects of mevalonolactone and mevalonate on rates of juvenile hormone biosynthesis were studied on corpora allata incubated in vitro, taken from virgin females of Blattella germanica of different ages. The stimulating effects of mevalonolactone were clearly age dependent. In corpora allata from 6-day-old females, a five-fold increase in juvenile hormone biosynthetic rates was induced with a concentration of 0.8 mM. In freshly ecdysed and oötheca-carrying females the most effective concentrations of mevalonolactone were higher: 2 and 10 mM, respectively, and in both cases the compound stimulated juvenile hormone release up to similar levels to that found in untreated 6-day-old corpora allata. Mevalonate also stimulated juvenile hormone biosynthetic rates, but the most effective concentration (40 mM irrespective of the age investigated) was higher than those of mevalonolactone. Furthermore, mevalonolactone and mevalonate were assayed on corpora allata from 6-day-old females previously inhibited with 10 μM of compactin. Both compounds restored the spontaneous rates of juvenile hormone biosynthesis. To elicit this effect, however, the concentration of mevalonate (40 mM) was 40 times that of mevalonolactone (1 mM). These results suggest that enzymes of the juvenile hormone pathway subsequent to mevalonate formation have a low coefficient control on juvenile hormone biosynthesis by corpora allata from freshly ecdysed and oötheca-carrying females.

Juvenile hormone production and accessory reproductive gland development during sexual maturation of male Blattella germanica (L.) (Dictyoptera, Blattellidae)

1. 1. A study of the release of juvenile hormone (JH) by in vitro-incubated corpora allata (CA) and on the development of the accessory reproductive glands (ARG) during sexual maturation of male Blattella germanica has been performed. 2. 2. JH release rates are comparable with those observed in previtellogenic females. 3. 3. The ARG undergo a progressive increase in size and protein content during sexual maturation. 4. 4. After CA removal, ARG protein accumulation is reduced (by 50%) in comparison with controls, and administration of exogenous JH restores normal development. 5. 5. The involvement of JH in ARG growth is discussed.

Biosynthesis and release of juvenile hormone and its precursors in insects and crustaceans: The search for a unifying arthropod endocrinology

It now appears that arthropods produce and release a wider variety of juvenile hormones (JH) and related compounds than previously thought. For instance, in the adult crayfish, Procambarus clarkii, the mandibular organs, the homologous structure to insect corpora allata (CA), release both farnesoic acid (FA) and methyl farnesoate (MF), the immediate precursors of JH III, but not JH III itself. In larvae of the cockroach Diploptera punctata, JH III production ceases during the last half of the 4th stadium, but the CA continue to produce and release FA throughout this period. The embryos of the same species also release JH III and a product that coelutes with MF on HPLC. In adult blowfly, Calliphora vomitoria, the CA release JH III bisepoxide and possibly the 6,7-epoxide, in addition to JH III. In the lepidopteran species Pseudaletia unipuncta, male CA produce and release JH acids I, II, and III as well as a product which we have tentatively identified as homo-(and/or) dihomo-FA. In the females, CA produce and release the three common JH homologues and a product that we believe is the esterified version of the male compound, homo/dihomo-MF. Although the release of JH precursors from their sites of synthesis might result in their conversion to the active hormone in peripheral tissues, there is only limited evidence for such a process. Studies on biological activities of these compounds and on the developmental changes in biosynthesis and its regulation should provide information necessary for the defining of these compounds as hormones or otherwise and should improve our understanding of the evolution of the JH biosynthetic pathway in the phylum Arthropoda.

Endocrine regulation of female contact sex pheromone production in the German cockroach, Blattella germanica

ABSTRACT The amount of the major component of the cuticular sex pheromone, 3, 11‐dimethyl‐2‐nonacosanone, on individual female German cockroaches, Blattella germanica (L.), as a function of age was determined by gas‐liquid‐chromatographic analysis. Accumulation of phermone increased with age in both virgin and mated females. During the first gono‐trophic cycle, the pheromone accumulated most rapidly when oocyte growth rates were maximal (days 5–10), and least rapidly while the female carried an ootheca (days 11–32). Pheromone accumulation was similar in virgin and mated females when the same physiological stages (determined by oocyte maturation) were considered. Inhibition of Juvenile Hormone release, through allatectomy, chemicals (precocene or fluoromevalonate), or through mechanical egg case implants, suppressed or delayed pheromone production and oocyte growth. The Juvenile Hormone analogue ZR512 induced allatectomized or head‐ligated females and females with chemically or mechanically inhibited corpora allata to produce pheromone and enlarge their basal oocytes. Finally, ZR512 applied to intact females stimulated pheromone production in a dose‐dependent manner.

Corpora allata activity, a prime regulating element for caste-specific juvenile hormone titre in honey bee larvae ( Apis mellifera carnica)

Corpora allata activity of queen and worker larvae of the honey bee in late larval development was studied in vitro by a radiochemical assay. Prospective queens showed a high peak of corpora allata activity in the fourth and early fifth larval stadium. This peak coincides with a queen-specific maximum in juvenile hormone titre, demonstrating that modulation of juvenile hormone release is of prime importance in the regulation of the caste-specific juvenile hormone titre. In both castes, hormone release is strictly correlated with juvenile hormone synthesis. The conversion of the precursor methyl farnesoate to juvenile hormone may be regulated caste-specifically, since only in queens but not in workers a linear correlation between intraglandular contents of juvenile hormone and methyl farnesoate could be found.

Juvenile Hormone biosynthesis and release during oocyte development in Phormia regina Meigen

AbstractA radiochemical assay for Juvenile Hormone (JH) biosynthesis and release by the corpus allatum (CA) was used to assess the effects of diet on CA activity of adult female Phormia regina (Meigen) fed either sugar‐water or sugar‐water‐liver. CC‐CA complexes were incubated in L‐methionine‐free medium 199 supplemented with 3H‐L‐methionine.The rate of JH release by the CC‐CA complexes is linear for 3 h and declines slightly thereafter. JH III appears to be one of the major components of the isooctane‐extractable product from incubated CC‐CA. High pressure liquid chromatographic analysis indicates that 10% of the released radiolabelled product is JH III. Rates of JH release show a strict dependence on L‐methionine concentration in the incubation medium, with optimal rates occurring between 100 and 150 μM L‐methionine. JH release is at a low level (<0.02pmolh‐1 per pair of CC‐CA) in flies fed only sugar‐water, but increases dramatically in flies fed sugar‐water‐liver (average release rate of 0.2pmolh‐1 per pair of CA, 24h after a liver meal). The rate of JH release increases steadily to more than 1.2pmolh‐1 per pair at 128h of age (i.e. 56h after a liver meal) at which time oocytes are mature. Elevated rates of JH release in vitro appear to be correlated in vivo with the appearance of vitellogenin in the haemolymph and its uptake by the developing oocytes.

Morphogenetic and gonadotrophic effects of a juvenile hormone analogue ((7S)‐hydroprene) in last instar female larvae of Diploptera punctata

ABSTRACT. The effect of treatment of last instar female larvae of Diploptera punctata with a Juvenile Hormone (JH) analogue, (7S)‐hydroprene, has been determined with respect to the ability of the analogue to alter the duration of the stadium and the nature of the ensuing ecdysis. We have also investigated the effects of the analogue on JH release, the growth of the basal oocytes, as well as ecdysteroid titres during the fourth stadium. Analogue treatment prior to day 10 of the stadium results in prolongation of the stadium and desynchronization of ecdysteroid release. Thereafter, treatment with the analogue has little effect. Analogue treatment results also in the formation of supernumerary larvae and intermediates, in a dose‐dependent fashion, provided that animals are treated on day 10 or earlier. Thus, the ‘critical’ period for metamorphosis in last instar D. punctata is between days 0 and 10.Treatment with (7S)‐hydroprene produces profound effects also on both JH release, and basal oocyte growth. At a dose of 500μg administered on day 1, JH release is stimulated significantly at a time when JH release is normally undetectable. Significant growth of basal oocytes is observed in such treated animals, and appears to precede the peak in JH release. We suggest that the growth of the basal oocytes, as a result of analogue treatment, stimulates the production of JH by CA in these last instar larvae.

In vitro juvenile hormone biosynthesis in adult virgin and mated female brown-banded cockroaches, Supella longipalpa

The in vitro radiochemical assay for juvenile hormone biosynthesis by pairs of corpora allata has been employed in the adult female brown-banded cockroach, Supella longipalpa. [2- 14C]acetate and the methyl moiety of l-[methyl- 3H]methionine were incorporated into juvenile hormone in a 9:1 ratio. The corpora allata of 9-day mated females release juvenile hormone at a linear rate for 5 h and maximal release rates occur at l-methionine concentrations greater than 30 μM. The juvenile hormone homologue was identified as juvenile hormone-III by HPLC analysis of the radiobiosynthesized corpora allata product. The release of juvenile hormone by the corpora allata closely parallels oöcyte development in both mated and virgin females over two gonotrophic cycles. The corpora allata exhibit rapid, nonoverlapping cycles of activity. Mating further activates the corpora allata and accelerates ovulation. The depression of corpora allata activity when the basal oöcytes exceed a critical volume of 0.9 mm 3 suggests a negative feedback mechanism.

Stimulatory activity of cysteamine on juvenile hormone release in adult females of the cockroach, Blattella germanica

1. 1. A study of the activity of cysteamine in relation to juvenile hormone (JH) production in adult females of Blattella germanica was carried out. 2. 2. In vivo assays showed that cysteamine stimulates protein synthesis in the left colleterial gland and, in some instances, enhances oocyte growth. 3. 3. In vitro assays demonstrated that cysteamine enhances JH release by incubated corpora allata (CA), and that this effect is more pronounced when using CA from 10-day-old females (period of ootheca transport), either connected to the corpora cardiaca (CC) or to the CC and to the brain. 4. 4. Possible antiallatostatic effects of cysteamine are discussed.

Stimulating action of methyl 12, 12, 12‐trifluorofarnesoate on in vitro juvenile hormone III biosynthesis in blattella germanica

AbstractMethyl 12, 12, 12‐trifluorofarnesoate (MTFF) at a dose of 10 μM, stimulated in vitro juvenile hormone (JH) release in corpora allata (CA) from 6‐day‐old, freshly ecdysed, and 8‐day‐old (period of ootheca transport) adult virgin females of Blattella germanica. In addition, MTFF also induced intraglandular accumulation of JH and MF in treated CA. Trifluorofarnesoic acid (TFFA) and trifluorofarnesol (TFF) exhibited the same properties, although to a lesser extent than MTFF. The detection of MTFF in TFFA‐treated CA suggested that TFFA and TFF were biotransformed into MTFF by the CA enzymatic system and that this ester might be responsible for the activity observed. Equivalent experiments carried out with farnesoic acid (FA) resulted in a more significant stimulation of JH production. This is not surprising, because exogenous FA is readily epoxidized at C10‐C11 double bond and methylated to afford JH. Conversely, analytical data have shown that the C6‐C7 double bond of MTFF is epoxidized by the CA enzymatic system, whereas that at C10‐C11 remains practically unaltered.

Modulation of juvenile hormone release and oocyte growth following (RS)‐hydroprene treatment in virgin female Diploptera punctata

ABSTRACT. The effect of (flS)‐hydroprene treatment (2, 20, 200 μg) on JH release was assessed in virgin females of D. punctata (Eschscholtz) during the first 10 days of adult life as was basal oocyte length and number of cells in the CA. At a dose of 2 μg hydroprene, JH release was stimulated slightly and, on days 4 and 6, oocyte growth was significantly greater than that of acetone‐treated controls. A similar but more striking enhancement of JH release and basal oocyte growth was observed at a dose of 20 μg and a significant inhibition of JH release, in concert with a rapid growth of basal oocytes, was observed at a dose of 200 μg. During the observation period, the mean number of cells in the CA decreased in a dose‐dependent fashion, with a highly significant reduction in numbers in 20 and 200 μg‐treated animals. Reimplantation of vitellogenic ovarioles (three or six) into ovariectomized virgin females also resulted in an enhancement of JH release; this indicates that virgin female CA can respond to the stimulatory action of the ovary and is consistent with a model for (RS)‐hydroprene action in which the ‘positive feedback’ effect (stimulation of JH release) observed with low doses of the analogue occurs as a consequence of the action of the analogue on the ovary. (RS)‐hydroprene treatment stimulates basal oocyte growth to the point at which the previously unstimulatory virgin oocytes are able to enhance JH release by a feedback loop involving the CA and probably the brain.

In vivo and in vitro effects of compactin in liposome carriers on juvenile hormone biosynthesis in adult females of Blattella germanica

A study on the in vitro and in vivo effects of compactin, a known inhibitor of juvenile hormone biosynthesis, either free or encapsulated into liposomes, on virgin females of Blattella germanica (Dictyoptera, Blattellidae) is reported. Encapsulation efficiency and stability were higher for liposomes with low compactin (1.6 to 10%) and cholesterol content. In vitro incubations (2 hr) of corpora allata from 6-day-old females with compactin showed an estimated ID 50 = 10 −7 M for juvenile hormone biosynthesis and the inhibition persisted during the 2-hr posttreatment incubation period. For the case of liposomes containing compactin, significant values of inhibition of juvenile hormone release were only induced after prolonged incubation periods (14 hr). However, persistence of the inhibition during the corresponding 2-hr posttreatment period was higher in comparison with that showed by the nonencapsulated compound. These results constitute the first example of a direct corpora allata response to the action of an encapsulated inhibitor. Results from in vivo short-term experiments showed that compactin is only moderately active as inhibitor of oocyte growth. Administration of the compound in fractionated doses, 3 or 5 × 5 μg, from the third day on the first gonotrophic cycle led to 43 or 28% inhibition, respectively, on Day 6. Similar results were obtained for encapsulated compactin, although in this case a single dose of 5 μg administered on Day 3 elicited 26% inhibitory activity. However, long-term experiments showed that neither compactin nor liposomes were able to inhibit the formation of the first ootheca, although the encapsulated compound induced a significant delay in the gonotrophic cycle when administered at fractionated doses (5 × 5 and 3 × 5 μg).

Modulation by somatostatin of juvenile hormone release in a cockroach

Modulation by somatostatin of juvenile hormone release in a cockroach

Effect of high potassium concentrations on juvenile hormone release in vitro from corpora allata of Locusta migratoria

ABSTRACT. Incubation of corpora allata (CA) from adult females of Locusta migratoria (L.) in vitro in medium with a potassium concentration of 50 mM results in an elevation of the rate of juvenile hormone (JH) release. This elevation is however delayed, becoming apparent after the glands have been returned to low concentration of potassium but it is also prolonged, lasting up to 270 min. The elevation is initially modest but becomes more marked with time. The response of glands to high concentration of potassium is heterogeneous and appears to some extent to be a function of the initial rate of JH release of the glands. Glands starting with low rates of JH release are stimulated strongly by potassium, those with high rates of JH release much less so. Co‐incubation of glands with high concentration of potassium and with calcium channel blockers (both organic and ionic) prevents the elevation of release rates otherwise consequent on high concentrations of potassium.

The effect of a calcium ionophore, a calcium channel blocker and calcium-free medium on juvenile hormone release in vitro from corpora allata of Locusta migratoria

Prolonged incubation of corpora allata (CA) of Locusta migratoria in calcium-free medium in vitro did not result in a significant reduction in juvenile hormone (JH) release; however, high rates of juvenile hormone release were precluded. Incubation with the ionic calcium channel blocker, lanthanum, also did not effect a reduction, and, in this case, high release rates were not precluded. In contrast, incubation with the ionophore A23187 resulted in a substantial stimulation of juvenile hormone release which lasted for up to 3 h. This stimulation appeared to be attributable specifically to the influx of calcium ions since it did not occur in calcium-free medium. Measurement of juvenile hormone content of stimulated and unstimulated glands revealed that the increase in release reflected an increase in juvenile hormone biosynthesis. Calcium influx was not associated with a change in the cyclic AMP content of glands and incubation with forskolin and cyclic AMP analogues did not result in a stimulation of juvenile hormone release.

In vitro inhibition of juvenile hormone III biosynthesis by precocene II and 3,4-dihydroprecocene II on Blattella germanica

In vitro incubations of corpora allata from 6-day old females of B. germanica with precocene II showed that the glands are intrinsically sensitive to the action of this allatocidin. However, irreversible cytotoxic effects on corpora allata were only obtained after 9h of incubation at 10 −3 M. Measurement of intraglandular juvenile hormone III and methyl farnesoate contents of treated and control corpora allata showed a depletion of juvenile hormone III contents which was parallel to the inhibition of juvenile hormone release. Conversely, methyl farnesoate levels of treated glands were not different from those found in controls which suggested that a specific inhibition of the epoxidase did occur in addition to the general inactivation of the glands. Finally, results from incubations with 3,4-dihydroprecocene II showed that this compound is also a juvenile hormone inhibitor and the effects elicited are comparable with those observed for precocene II.

Calcium as a regulator of juvenile hormone biosynthesis and release in the cockroach Diploptera punctata

The role of calcium in the modulation of juvenile hormone (JH) biosynthesis and release by the corpora allata (CA) of Diploptera punctata was examined using an in vitro radiochemical assay. JH production showed a dose dependence on extracellular calcium in the incubation medium. Rates of JH release were maximal between calcium concentrations of 3–5 mM and were almost totally inhibited in its absence. Upon return to medium containing 5 mM calcium, CA exhibited a rapid increase in JH release, although rates of release remained slightly below normal. Blockers of voltage-dependent calcium channels (verapamil, nifedipine), at physiological doses, were able to modulate JH production whereas non-specific calcium channel blockers such as lanthanum effectively inhibited JH release. The calcium ionophore A23187 caused a rapid and irreversible decline in JH release. The calcium dose-response for A23187 showed 50% inhibition of JH release at about 1 mM calcium and maximal inhibition (93%) at 6 mM calcium. Treatment with lanthanum or A23187 did not result in an accumulation within the CA of either JH or methyl farnesoate and accordingly, these compounds appeared to reduce overall JH biosynthesis rather than inhibiting release. Inhibition of JH release by A23187 was dramatically attenuated by coincubation with cobalt, although cobalt alone was found to stimulate JH release significantly. Intracellular calcium levels thus appear to be important in the regulation of JH biosynthesis and release.