Identification of ecdysis-triggering hormone from an epitracheal endocrine system
ABSTRACT Developing insects repeatedly shed their cuticle by means of a stereotyped behavior called ecdysis, thought to be initiated by the brain peptide eclosion hormone. Here an ecdysis-triggering hormone, Mas-ETH, is described from the tobacco hornworm Manduca sexta. Mas-ETH contains 26 amino acids and is produced by a segmentally distributed endocrine system of epitracheal glands (EGs). The EGs undergo a marked reduction in volume, appearance, and immunohistochemical staining during ecdysis, at which time Mas-ETH is found in the hemolymph. Injection of EGs extract or synthetic Mas-ETH into pharate larvae, pupae, or adults initiates preecdysis within 2 to 10 minutes, followed by ecdysis. Sensitivity to injected Mas-ETH appears much earlier before ecdysis and occurs with shorter latency than that reported for eclosion hormone. The isolated central nervous system responds to Mas-ETH, but not to eclosion hormone, with patterned motor bursting corresponding to in vivo preecdysis and ecdysis. Mas-ETH may be an immediate blood-borne trigger for ecdysis through a direct action on the nervous system.
- SourceAvailable from: Carlos L Cespedes
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- "In this study, analysis of the test insect fed with C. microphylla extracts, revealed a developmental disruption in which the insects died (between 10 and 25 ppm) during pharate conditions after initiation of molting (the apolysis step), without completion of morphogenesis . During a molt, ecdysteroid levels first rise to stimulate onset of apolysis and cuticle synthesis, but then must fall to facilitate the release of eclosion hormone (EH) (Truman et al., 1983; 2002) and the ecdysis-triggering hormone (ETH) (Zitnan et al., 1996, 1999). These last substances act in concert to trigger insect ecdysis during the final stages of the molt. "
ABSTRACT: Extracts obtained from a common shrub that occurs as part of vegetative species growing on arid lands of North-Central Chile and adjacent central Argentina known as “piquilin” Condalia microphylla (Rhamnaceae) showed insect growth inhibitory activity against the fall armyworm Spodoptera frugiperda, yellow meal worm Tenebrio molitor and fruit fly Drosophila melanogaster larvae in artificial diet feeding assays. The effects of these extracts on mortality, antifeedancy and growth inhibition were examined. The phytochemical profile of the most active extract was examined with conventional chromatographic and spectroscopic procedures. This n-hexane extract showed a high percentage of hentriacontane and triacontane. The observed mortality strongly correlates with the contents of these long-chain n-alkanes compounds, the LD50 for n-hexane, ethyl acetate and methanol extracts against S. frugiperda, were 3.89, 9.4, and 9.7 ppm; against T. molitor 5.2, 14.2, and 20.4 ppm, and against D. melanogaster 3.23, 7.65 and 17.9 ppm, respectively. © 2012 Elsevier B.V. All rights reserved.Industrial Crops and Products 03/2013; 42(1):78-86. DOI:10.1016/j.indcrop.2012.05.002 · 2.84 Impact Factor
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- "Instead, neurosecretory cells that send axons to a release site are located mainly in the pars intercerebralis, but some are also located in the pars lateralis or tritocerebrum, in the suboesophageal and/or ventral ganglia. Non-neuronal Inka cells that produce the releasing hormone ecdysis-triggering hormone (ETH) are located on the surface of insect tracheae . The gut is also a site of synthesis and release (into the hemolymph) of some brain-gut peptides. "
ABSTRACT: Vertebrate releasing hormones include gonadotropin releasing hormone (GnRH), growth hormone releasing hormone (GHRH), corticotropin releasing hormone (CRF), and thyrotropin-releasing hormone (TRH). They are synthesized in the hypothalamus and stimulate the release of pituitary hormones. Here we review the knowledge on hormone releasing systems in the protostomian lineage. We address the question: do insects have peptides that may be phylogenetically related to an ancestral GnRH, GHRH, TRH, and CRF? Such endocrine archeology has become possible thanks to the growing list of fully sequenced genomes as well as to the continuously improving bioinformatic tool set. It has recently been shown that the ecdysozoan (nematodes and arthropods) adipokinetic hormones (AKHs), the lophotrochozoan (annelids and mollusks) GnRHs as well as the protochordate GnRHs are structurally related. The adipokinetic hormone precursor-related peptides (APRPs), in locusts encoded by the same gene that contains the AKH-coding region, have been forwarded as the structural counterpart of GHRH of vertebrates. CRF is relatively well conserved in insects, in which it functions as a diuretic hormone. Members of TRH-receptor family seem to have been conserved in some arthropods, but other elements of the thyroid hormone signaling system are not. A challenging idea is that in insects the functions of the thyroid hormones were taken over by juvenile hormone (JH). Our reconstruction suggests that, perhaps, the ancestral releasing hormone precursors played a role in controlling energy metabolism and water balance, and that releasing hormone functions as present in extant vertebrates were probably secondarily acquired.General and Comparative Endocrinology 03/2012; 177(1):18-27. DOI:10.1016/j.ygcen.2012.02.002 · 2.67 Impact Factor
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- "in Manduca sexta   and Drosophila melanogaster  . Blood-borne ETHs initiate the ecdysis sequence through direct actions on the central nervous system (CNS)  . Discovery of ETH receptor genes in Drosophila   and Manduca  facilitated identification of many neuronal targets of ETH within the CNS. "
ABSTRACT: Ecdysis triggering hormones (ETHs) from endocrine Inka cells initiate the ecdysis sequence through action on central neurons expressing ETH receptors (ETHR) in model moth and dipteran species. We used various biochemical, molecular and BLAST search techniques to detect these signaling molecules in representatives of diverse arthropods. Using peptide isolation from tracheal extracts, cDNA cloning or homology searches, we identified ETHs in a variety of hemimetabolous and holometabolous insects. Most insects produce two related ETHs, but only a single active peptide was isolated from the cricket and one peptide is encoded by the eth gene of the honeybee, parasitic wasp and aphid. Immunohistochemical staining with antiserum to Manduca PETH revealed Inka cells on tracheal surface of diverse insects. In spite of conserved ETH sequences, comparison of natural and the ETH-induced ecdysis sequence in the honeybee and beetle revealed considerable species-specific differences in pre-ecdysis and ecdysis behaviors. DNA sequences coding for putative ETHR were deduced from available genomes of several hemimetabolous and holometabolous insects. In all insects examined, the ethr gene encodes two subtypes of the receptor (ETHR-A and ETHR-B). Phylogenetic analysis showed that these receptors fall into a family of closely related GPCRs. We report for the first time the presence of putative ETHs and ETHRs in genomes of other arthropods, including the tick (Arachnida) and water flea (Crustacea). The possible source of ETH in ticks was detected in paired cells located in all pedal segments. Our results provide further evidence of structural and functional conservation of ETH-ETHR signaling.Peptides 11/2009; 31(3):429-41. DOI:10.1016/j.peptides.2009.11.022 · 2.61 Impact Factor