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PubMed2002

The cDNA-structure of the prothoracicotropic hormone (PTTH) of the silkmoth Hyalophora cecropia.

The structure of the prothoracicotropic neurohormone (PTTH) of the silkmoth Hyalophora cecropia was elucidated at the cDNA level. The identified cDNA of 803 nt, which is over 90% identical with the corresponding part of the Samia cynthia ricini PTTH gene, encodes a preprohormone of 240 amino acids. Presence of proteolytic cleavage sites indicates that the preprohormone is split into a signal peptide, an intercalated peptide (64 residues), and the PTTH monomer (125 residues). Preprohormones of H. cecropia, S. c. ricini, Antheraea pernyi, and Bombyx mori diversified considerably in all these parts, indicating that the evolution of PTTH is unusually fast. Since a similarly rapid, and concerted evolution of the corresponding receptor is unlikely, the PTTH activity probably depends on the conservation of relatively few amino acids allowing proper molecular folding.

Amino Acid Sequence↗
PubMed1986

Farnesoic acid and allatotropin stimulation in relation to locust allatal maturation.

Allatal maturation during the first gonotrophic cycle of adult female Locusta migratoria can be measured in vitro by the competence of these glands to produce juvenile hormone III (JH-III) when maximally stimulated by either farnesoic acid (FA) or allatotropin. Maturation precedes the full activation of the corpora allata (CA) during the first cycle of oogenesis. Basal activity of mature active female CA is highly correlated to stimulated activity. This suggests that between-gland variability reflects the inherent competence of each individual CA, and is not a consequence of a mere pulsatile on/off activation. Older glands may be inactive but their competence is equivalent to that of mature active glands. The kinetics of FA and allatotropic stimulation in vitro are equivalent, suggesting that allatotropin affects rate-limiting steps preceding FA biosynthesis.

Animals↗
PubMed2003

Structural characterization and expression analysis of prothoracicotropic hormone in the corn earworm, Helicoverpa zea.

The cDNA encoding prothoracicotropic hormone (PTTH), the brain neuropeptide that stimulates the prothoracic glands to synthesize ecdysone, was cloned from the corn earworm Helicoverpa zea (Hez). The amino acid sequence deduced from the cDNA indicates a molecular structure that is distinct from the PTTH's reported in other Lepidoptera, but all contain an identical proteolytic cleavage site and the seven cysteine residues that are essential for activity. Northern hybridization shows a single mRNA present in the brain-subesophageal ganglion complex. Using RT-PCR, we observed constant amounts of PTTH mRNA during larval development but large fluctuations at pupation and prior to adult eclosion.

Amino Acid Sequence↗
PubMed1993

Organization of the larval pre-ecdysis motor pattern in the tobacco hornworm, Manduca sexta.

The tobacco hornworm, Manduca sexta, undergoes several larval molts before transforming into a pupa and then an adult moth. Each molt culminates in ecdysis, when the old cuticle is shed. Prior to each larval ecdysis, the old cuticle is loosened by pre-ecdysis behavior, which consists of rhythmic compressions that are synchronous along the abdomen and on both body sides, and rhythmic retractions of the abdominal prolegs. Both pre-ecdysis and ecdysis behaviors are triggered by a peptide, eclosion hormone. The aim of the present study was to investigate the neural circuitry underlying larval pre-ecdysis behavior. The pre-ecdysis motor pattern was recorded in isolated nerve cords from eclosion hormone-treated larvae, and the effects of connective transections and ionic manipulations were tested. Our results suggest that the larval pre-ecdysis compression motor pattern is coordinated and maintained by interneurons in the terminal abdominal ganglion that ascend the nerve cord without chemical synaptic relays; these interneurons make bilateral, probably monosynaptic, excitatory connections with identified pre-ecdysis motor neurons throughout the abdominal nerve cord. This model of the organization of the larval pre-ecdysis motor pattern should facilitate identification of the relevant interneurons, allowing future investigation of the neural basis of the developmental weakening of the pre-ecdysis motor pattern that accompanies the larval-pupal transformation.

Animals↗
PubMed1989

Juvenile hormone inhibits ecdysone secretion and responsiveness to prothoracicotropic hormone in prothoracic glands of Bombyx mori.

The role of juvenile hormone (JH) in the regulation of prothoracic gland activity was investigated during the early days of the last (fifth) larval instar of Bombyx mori. Allatectomy on the day of larval ecdysis into the fifth instar or 1 day before ecdysis shortened the time between larval ecdysis and gut purge. Prothoracic glands of the freshly ecdysed fifth instar larvae were inactive and did not respond to the prothoracicotropic hormone (PTTH), whereas those larvae that were allatectomized 1 day before ecdysis exhibited secretory activity in vitro and were capable of responding to PTTH. When corpora allata were removed from freshly ecdysed fifth instar larvae, the prothoracic glands became competent to respond to PTTH in 6 hr and exhibited secretory activity in vitro 9 hr after the allatectomy. Treatment of allatectomized larvae with a JH analog resulted in the recovery of the normal inactive state of the glands. These data suggest that JH acts during the early stages of the instar to suppress both the secretory activity of prothoracic glands and also the acquisition of competence to respond to PTTH.

Animals↗
PubMed1997

MALDI-MS as a monitor of the purification and folding of synthetic eclosion hormone.

Analogues of the small protein Manduca sexta eclosion hormone (62 amino acids) were synthesized by Fmoc solid-phase methodology. Matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) was used to analyze the products of the syntheses and this information was used to design an efficient purification scheme. MALDI-MS was used to monitor the target products through purification and it was also used to monitor folding of the purified materials. The folded EH analogues were shown to be biologically active proteins with an in vivo bioassay using pharate adult moths, Heliothis virescens.

Amino Acid Sequence↗
PubMed1987

Developmental endocrinology of larval moulting in the tobacco hornworm, Manduca sexta.

A larval moult in the tobacco hornworm, Manduca sexta, involves an endocrine cascade that begins with the release of a cerebral peptide hormone, the prothoracicotropic hormone (PTTH). The release of PTTH is gated, occurs during the scotophase and appears to be developmentally cued. In fourth instar Manduca larvae, PTTH release into the haemolymph occurs as a single burst over a few hours during the head critical period, i.e. the time during which the head (brain) is needed for the initiation of the moult to the fifth (last) instar. Released PTTH activates the prothoracic glands (PGs), and within a few hours the cumulative effect of this event results in a dramatic increase in the haemolymph ecdysteroid titre, which then elicits the moult. An assessment of the capacity of the corpora allata (CA) to synthesize juvenile hormone (JH) in vitro indicates that the above sequence of endocrine events begins only when JH synthesis has reached a nadir for the instar. Since CA activity is an indirect measure of the haemolymph titre of the hormone, it is conceivable that the developmentally cued release of PTTH is permissively controlled by a decreasing haemolymph titre of JH. With the increase in the ecdysteroid titre which marks the end of this endocrine cascade, the CA again become active, presumably to cause the increase in the JH haemolymph titre which directs the larval moult. This investigation has thus established the temporal and quantitative dynamics of the PTTH-PG axis that drive larval moulting and provides insight into the interendocrine regulatory relationships that may exist between the ecdysteroids and JHs. These possible relationships and the role of the brain in their regulation are discussed.

Animals↗
PubMed1990

Biological effects of synthetic AKH in Manduca sexta and estimates of the amount of AKH in corpora cardiaca.

Dose-response curves were measured with synthetic Manduca adipokinetic hormone (AKH) for glycogen phosphorylase activation in larvae and for lipid mobilization in adults. Both responses are known hormonal functions in Manduca sexta. In ligated larvae, full activation of glycogen phosphorylase was achieved with 0.1 pmol and half-maximal activation with 0.03-0.04 pmol. Maximal lipid mobilization in adults required 10 pmol and half-maximal mobilization 0.15 to 0.2 pmol, respectively. An estimate of AKH content of corpora cardiaca from M. sexta was gained by comparing the dose-response curves for synthetic Manduca AKH with curves from gland extracts. Corpora cardiaca extracts were also quantitated by high performance liquid chromatography. According to both estimates corpora cardiaca of adults contain 10-20 pmol AKH per pair, while a pair of larval corpora cardiaca contains 0.7-2 pmol.

Adipose Tissue↗
PubMed1992

Immunocytochemical localization of Bombyx-PTTH-like molecules in neurosecretory cells of the brain of the migratory locust, Locusta migratoria. A comparison with neuroparsin and insulin-related peptide.

Using a monoclonal antibody directed against a synthetic pentadecapeptide corresponding to the N-terminus of the prothoracicotropic hormone (PTTH) of Bombyx mori, we report the presence of immunoreactive molecules in a large number of median neurosecretory cells of the pars intercerebralis of the migratory locust, Locusta migratoria. These cells correspond to the A1 cell type which we show to contain also neuroparsins, a family of predominant neurohormones of the migratory locust. In contrast, PTTH-like molecules are absent from A2 cells of the pars intercerebralis which contain Locusta insulin-related peptide (LIRP). Developmental studies show the presence of PTTH-related substances in neurosecretory cells of Locusta migratoria from late embryogenesis to adult development, including ageing vitellogenic female adults.

Amino Acid Sequence↗
PubMedDate not supplied

Substitution of norleucine for methionine residues in a crustacean pigment-dispersing hormone.

In order to evaluate the structural/functional roles of Met residues in an octadecapeptide pigment-dispersing hormone (PDH: Asn-Ser-Gly-Met-Ile-Asn-Ser-Ile-Leu-Gly-Ile-Pro-Arg-Val-Met-Thr-Glu-Ala- NH2), first described as light-adapting distal retinal pigment hormone (DRPH) from Pandalus, three analogs were synthesized: Nle4-PDH, Nle15-PDH, and Nle4,15-PDH. When tested for melanophore pigment-dispersing activity in destalked Uca, all three Nle-analogs were more potent than unsubstituted PDH. Performic acid oxidation caused a marked loss of potency of PDH, Nle4-PDH, and Nle15-PDH. The analog Nle4,15-PDH was resistant to oxidation and displayed 6-fold higher potency than PDH. Thus Met4 and Met15 are not essential for the PDH activity. The oxidation-induced loss of activity of unsubstituted PDH may result from introduction of oxygen (in methionine sulfone) and a consequent conformational change in the octadecapeptide.

Aminocaproates↗
PubMed1987

Regulation of adipokinetic hormone release from locust neuroendocrine tissue: participation of calcium and cyclic AMP.

In the locust, cyclic adenosine monophosphate (cAMP) mediates at least part of the effects of octopamine, the neurotransmitter which regulates the release of two adipokinetic hormones (AKHs) from the glandular lobe of the corpus cardiacum (CC). We have examined the requirement for extracellular Ca2+ in the process of AKH release mediated by octopamine and by agents which artificially elevate intracellular cAMP levels. Octopamine and the adenylate cyclase activator forskolin elevate the cAMP content of the glandular lobe in normal saline, in normal saline with the Ca2+ channel blocker, methoxyverapamil, and in Ca2+-free saline during 10-min exposure periods. Octopamine, forskolin, and 8-bromo cAMP mediate release of AKHs in vitro in normal saline, but release is prevented in the absence of extracellular Ca2+. When glands are exposed to these agents in normal saline in the presence of methoxyverapamil, AKH release is curtailed in a similar manner. Lanthanum and EGTA dramatically reduce cAMP production elicited by octopamine and forskolin, and lanthanum prevents octopamine-mediated release of AKHs. The phosphodiesterase inhibitor, IBMX, elevates cAMP content in the presence and absence of extracellular Ca2+, and stimulates normal release of AKHs both in the presence and absence of extracellular Ca2+. However, following extensive washing in Ca2+-free saline, IBMX fails to evoke AKH release. Methoxyverapamil has no effect on IBMX-mediated secretion. These results suggest that IBMX may mobilize intracellular stores of Ca2+ to induce release. Extracellular Ca2+ is apparently required for the process of neurotransmitter-evoked release, as has been shown for release of other peptide hormones. Cyclic AMP is intimately associated with Ca2+ in mediating this process. The release of AKHs is more dependent upon extracellular Ca2+ than is cAMP production under the conditions examined in this study. Ca2+ may provide the signal which initiates the secretory response, although cAMP may modulate this signal or the cells' responsiveness to this signal in some way. Support for this hypothesis is provided by experiments with the Ca2+ ionophore, A23187. This agent provokes release of AKHs in a Ca2+-dependent manner, probably by elevating intracellular Ca2+ levels. A23187 does not elevate cAMP levels in the glandular lobe, indicating that cAMP elevation is not a prerequisite for secretion.

1-Methyl-3-isobutylxanthine↗
PubMed1995

Action of linoleic acid on phospholipase C activity at the rectal level of the African locust under the control of protein kinase C.

Linoleic acid (18:2n-6), linolenic acid and eicosatrienoic acid stimulated fluid reabsorption in locust rectum. Only 18:2n-6 was able to enhance phospholipase C activity, inositol(1,4,5) trisphosphate production and to increase cytosolic free Ca2+ concentrations in epithelial cells via the opening of L-type Ca2+ channels. These effects resemble those exerted by neuroparsin, an antidiuretic neuronal hormone extracted from the storage lobes of the locust corpora cardiaca. As for neuroparsin, the effects of 18:2n-6 were abolished after pre-treatment with the protein kinase C inhibitor, polymyxin B. The results were consistent with a regulation of neuroparsin-sensitive phospholipase C activity by 18:2n-6 under control of protein kinase C, possibly by increasing membrane fluidity. Cyclooxygenase inhibitors attenuated the effects of 18:2n-6. This demonstrated that the results should be produced via the metabolites of 18:2n-6 HODEs rather than the PUFA itself.

8,11,14-Eicosatrienoic Acid↗
PubMed1997

Regulation of ecdysis-triggering hormone release by eclosion hormone.

Ecdysis behavior in the tobacco hornworm Manduca sexta (Lepidoptera: Sphingidae) is triggered through reciprocal peptide signaling between the central nervous system and the epitracheal endocrine system. Recent evidence indicates that eclosion hormone may initiate endocrine events leading to ecdysis through its action on epitracheal glands to cause the release of ecdysis-triggering hormone (ETH). Here, we report that direct exposure of epitracheal glands to eclosion hormone in vitro leads to secretion of ETH. The threshold concentration of eclosion hormone needed to evoke release of ETH is approximately 3 pmol l-1. Eclosion hormone also induces elevation of cyclic GMP, but not cAMP, concentration in epitracheal glands at concentrations similar to those causing release of ETH. Both cGMP and 8-Br-cGMP mimic the secretory action of eclosion hormone. The sensitivity of the secretory response to eclosion hormone occurs during a narrow window of development, beginning approximately 8 h prior to pupal ecdysis. However, eclosion hormone can cause elevation of cGMP levels in epitracheal glands long before they acquire competence to release ETH, showing that the initial portion of the signal transduction cascade is in place early in development, but that the absence of a downstream step in the cascade prevents secretion. Measurements of cGMP levels in epitracheal glands during the ecdysis sequence show a sudden elevation some 30 min after the onset of pre-ecdysis, well after ETH secretion has been initiated. ETH secretion can therefore be viewed as a two-step process, beginning at pre-ecdysis when cGMP levels are relatively low, followed by a massive release resulting from a logarithmic elevation of cGMP levels.

Animals↗
PubMed1985

Primary structures of locust adipokinetic hormones II.

Adipokinetic hormones II from corpora cardiaca of the locusts Schistocerca gregaria and Locusta migratoria, respectively, have been isolated and their primary structures elucidated. Both octapeptides are N-terminally blocked by a 5-oxoproline (pyroglutamate) residue and had to be cleaved by 5-oxoprolyl-peptidase to make them available for the Edman degradation method carried out with a gas-phase sequencer. The C-termini are blocked as both peptides are not cleaved by carboxypeptidase A; the presence of C-terminal amide groups is very likely. AKHII (S. gregaria) Glu-Leu-Asn-Phe-Ser-Thr-Gly-Trp-NH2 AKHII (L. migratoria) Glu-Leu-Asn-Phe-Ser-Ala-Gly-Trp-NH2.

Amino Acid Sequence↗
PubMed2004

Juvenile hormone-dependent motor activation in the adult locust Locusta migratoria.

Abdominal motoneurones of the locust Locusta migratoria were investigated in immature, mature and allatectomised females to compare their response characteristics during reproductive development. These motoneurones were chosen because they control muscles which are involved in extreme lengthening during egg-laying behaviour. The study focused on changes in motoneurone firing activity and its possible regulation by juvenile hormone. In isolated nerve-muscle preparations, increased resting motor activity was found in mature (>14 days) but not in immature females (<5 days). Removing the corpora allata, the gland producing juvenile hormone in insects, prevented increased motor activity. Stimulus evoked activation of the motor system led to a characteristic burst of action potentials which lasted for a few seconds. The time-course and amount of activation changed significantly during reproductive development. Mature females displayed longer lasting and higher activity than immature or allatectomised females, but only those segments involved in egg-laying were found to express the altered firing properties. Single cell analysis of motoneurone dendritic morphology or membrane properties revealed no evidence that could be causative for the activity changes seen during reproductive development. The results suggest that altered motoneurone activity serves to adapt females to the neuromuscular requirements of egg-laying behaviour.

Action Potentials↗
PubMed2002

Cardioacceleratory effects of Manduca sexta allatotropin in the true armyworm moth, Pseudaletia unipuncta.

Manduca sexta allatotropin (Manse-AT), a peptide originally isolated on the basis of its ability to stimulate juvenile hormone (JH) biosynthesis in the tobacco hornworm, is a potent in vitro stimulator of the corpora allata (CA) in Pseudaletia unipuncta (Lepidoptera: Noctuidae). At 10(-6)M, Manse-AT stimulated in vitro rates of JH biosynthesis by CA of day 0 and 6 adult females 15- and 10-fold respectively. Both Manse-AT and serotonin were also shown to be dose-dependent stimulators of heart rate in day 0, 3 and 6 adult males and females. Furthermore, analysis suggests that there are differences in both resting and Manse-AT-stimulated heart rates depending on age and rearing conditions.

Animals↗
PubMed1994

Structure and expression of the gene for the prothoracicotropic hormone of the silkmoth Bombyx mori.

We cloned and characterized two allelic variants of the gene for the Bombyx mori prothoracicotropic hormone (PTTH), a homodimeric 30-kDa brain secretory protein. These PTTH genes contain five exons that encode a precursor protein consisting of 224 amino acid residues whose C-terminal 109 residues represent the PTTH subunit. The Bombyx haploid genome contains a single copy of the PTTH gene. The major site of PTTH expression is the brain but expression at a very low level occurs in the gut. One Bombyx brain at day 0 of the fifth larval instar contained 2.4-2.8 pg PTTH mRNA, and this amount did not change markedly during larval-pupal development.

Amino Acid Sequence↗
PubMed1987

A monoclonal antibody against a synthetic fragment of bombyxin (4K-prothoracicotropic hormone) from the silkmoth, Bombyx mori: characterization and immunohistochemistry.

Monoclonal antibodies were produced by immunizing mice with a synthetic decapeptide corresponding to the N-terminal portion of the A-chain of bombyxin, a peptide from Bombyx mori which activates the prothoracic glands of the saturniid moth, Samia cynthia ricini, and was previously called 4K-PTTH. We obtained a hybridoma clone secreting an antibody that recognized specifically bombyxin after treatments for disulfide-bond reduction but did not when untreated. Immunoblotting studies demonstrated the presence of highly heterogeneous immunoreactive components in Bombyx brain homogenates. Immunohistochemistry using this antibody indicated that bombyxin was produced by four pairs of mid-dorsal neurosecretory cells of the brain and transferred to and released from the corpora allata of Bombyx.

Animals↗