Allatotropin is a cardioacceleratory peptide in Manduca sexta

Biogenic amines evoke heartbeat reversal in larvae of the sweet potato hornworm, Agrius convolvuli

The sweet potato hornworm, Agrius convolvuli, possesses a pair of anterior cardiac nerves innervating the dorsal vessel. The anterior cardiac nerves branch off the visceral nerve that arises posteriorly from the frontal ganglion. Heartbeat reversal from anterograde heartbeat to posterograde heartbeat is triggered by the anterior cardiac nerves. Application of octopamine (OA) during the anterograde heartbeat phase reverses the anterograde heartbeat to the posterograde heartbeat, while application of OA during the phase of posterograde heartbeat accelerates heartbeat. The heartbeat reversal from anterograde heartbeat to posterograde heartbeat evoked by stimuli applied to the visceral nerve is blocked by application of the octopaminergic antagonists, phentolamine and chlorpromazine. The results suggest that OA may be a neurotransmitter for the anterior cardiac nerve. The alary muscle of the second segment receives excitatory innervation from the posterior cardiac nerve and from the nerve which extends from the second abdominal ganglion. Activation of the alary muscle results in acceleration of posterograde heartbeat. Other neurotransmitters, besides OA, may take part in the resultant acceleration.

Enhanced haemolymph circulation by insect ventral nerve cord: hormonal control byPseudaletia unipunctaallatotropin and serotonin

The ventral diaphragm (VD) in many insects is a muscular membrane that essentially partitions a perineural sinus from the rest of the abdomen. In the true armyworm moth Pseudaletia unipuncta (Lepidoptera: Noctuidae) we describe how the VD is characterized by a series of aliform muscles inserted into a tissue matrix that is fused to the dorsal surface of the ventral nerve cord (VNC) itself. Because of this arrangement, the abdominal VNC can attain high rates of lateral oscillation, and is capable of directing haemolymph flow. We have previously demonstrated Manduca sexta allatotropin(Manse-AT)-like immunoreactivity throughout the central nervous system (CNS)in P. unipuncta, and that both Manse-AT and serotonin (5-HT) are dose-dependent stimulators of the dorsal vessel. Here we describe both Manse-AT- and 5-HT-like immunoreactivity associated with the VD. Furthermore,both Manse-AT and 5-HT are dose-dependent stimulators of the rates of VNC oscillation, and together are capable of maintaining highly elevated rates of VNC oscillation for extended periods of time. These data indicate that both the dorsal vessel and the VD/VNC are similarly modulated by both Manse-AT and 5-HT, and that VNC oscillations play a more active role in overall haemolymph circulation than previously recognized.

Neuropeptides in the nervous system of Drosophila and other insects: multiple roles as neuromodulators and neurohormones

Neuropeptides in insects act as neuromodulators in the central and peripheral nervous system and as regulatory hormones released into the circulation. The functional roles of insect neuropeptides encompass regulation of homeostasis, organization of behaviors, initiation and coordination of developmental processes and modulation of neuronal and muscular activity. With the completion of the sequencing of the Drosophila genome we have obtained a fairly good estimate of the total number of genes encoding neuropeptide precursors and thus the total number of neuropeptides in an insect. At present there are 23 identified genes that encode predicted neuropeptides and an additional seven encoding insulin-like peptides in Drosophila. Since the number of G-protein-coupled neuropeptide receptors in Drosophila is estimated to be around 40, the total number of neuropeptide genes in this insect will probably not exceed three dozen. The neuropeptides can be grouped into families, and it is suggested here that related peptides encoded on a Drosophila gene constitute a family and that peptides from related genes (orthologs) in other species belong to the same family. Some peptides are encoded as multiple related isoforms on a precursor and it is possible that many of these isoforms are functionally redundant. The distribution and possible functions of members of the 23 neuropeptide families and the insulin-like peptides are discussed. It is clear that each of the distinct neuropeptides are present in specific small sets of neurons and/or neurosecretory cells and in some cases in cells of the intestine or certain peripheral sites. The distribution patterns vary extensively between types of neuropeptides. Another feature emerging for many insect neuropeptides is that they appear to be multifunctional. One and the same peptide may act both in the CNS and as a circulating hormone and play different functional roles at different central and peripheral targets. A neuropeptide can, for instance, act as a coreleased signal that modulates the action of a classical transmitter and the peptide action depends on the cotransmitter and the specific circuit where it is released. Some peptides, however, may work as molecular switches and trigger specific global responses at a given time. Drosophila, in spite of its small size, is now emerging as a very favorable organism for the studies of neuropeptide function due to the arsenal of molecular genetics methods available.

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.

Molecular characterization of a cDNA from the silk moth Bombyx mori encoding Manduca sexta allatotropin peptide

Allatotropin is a 13-residue amidated neuropeptide isolated from pharate adult heads of the tobacco hornworm, Manduca sexta and strongly stimulates biosynthesis of juvenile hormones in adults, but not larval, lepidopteran corpora allata. From a Bombyx mori midgut cDNA library, a cDNA that encodes a 130-amino-acid polypeptide containing M. sexta allatotropin sequence was isolated. The B. mori allatotropin cDNA consists of 1196 nucleotides. The encoded allatotropin peptide is identical to that isolated from M. sexta and that predicted from Pseudaletia unipuncta, with 84% and 81% identity in the amino acid sequence of the allatotropin peptide precursor, respectively. M. sexta allatotropin is flanked by two different endoproteolytic cleavage sites within the precursor of the B. mori allatotropin peptide. Evidence from northern blotting of B. mori tissues showed that the allatotropin gene is expressed in the cells of midgut, head and integument with different transcription amount, but not in the fat body and silk gland. Midgut has also a number of allatotropin-immunoreactive cells and nerve fibers. These results will provide valuable information in understanding the AT gene of insects.

Immunolocalization and possible effect of a moth allatotropin-like substance in a fly, Phormia regina (Diptera: Calliphoridae)

Insect allatotropin upregulates the biosynthesis of juvenile hormones by the corpus allatum. We raised two rabbit antisera against the allatotropin of Manduca sexta (Mas AT) using a synthetic, multiple-antigenic-peptide that contains a branching heptalysine core and eight Mas AT molecules. Both antisera recognized specifically the same neurons in the larval brain, frontal ganglion and terminal abdominal ganglion of M. sexta as previously reported by others. Immunoassay showed reactivity specific to the Mas AT. Very low or nearly no cross-reactivity was found for two Mas AT-like peptides, a myotropin from Locusta migratoria and a Mas AT-like peptide deduced from the DNA sequence of Aedes aegypti, respectively. Immunopositive neurons also were identified in adult Phormia regina, Dacus dorsalis, Oncopeltus fasciatus, and Mythimna loreyi, and in larval M. loreyi, Bombyx mori, and Andraca bipunctata. At 20 pmol per 25 µl incubation medium (i.e. 8x10(-7) M), synthetic Mas AT significantly stimulated in vitro juvenile hormone biosynthesis by the corpus allatum of adult, sugar-fed females of P. regina to 2.64-fold that of controls. Thus, this study provides the first demonstration that at the higher end of the physiological concentration range, the Mas AT has allatotropic effect in vitro to CA of non-lepidopterans. However, in vivo functions of Mas AT and/or Mas AT-like peptide in P. regina remain to be defined.

Flights of fancy: possible roles of allatostatin and allatotropin in migration and reproductive success of Pseudaletia unipuncta

Many invertebrate neuropeptides have recently been identified and there is evidence that the same compound may serve different roles in different species and/or multiple functions within a given species. However, until the relevant receptors or 'knock out' animals, lacking the neuropeptide of interest, become available it will be difficult to clarify the precise inter- and intraspecific functions of these neuropeptides. In the present paper, we argue that until these tools are available a more meaningful understanding of the roles of neuropeptides could be obtained by carrying out experiments within an ecological context. Furthermore, this approach would allow us to generate hypotheses that could be rigorously tested when more sophisticated techniques are developed. We discuss these ideas using our interdisciplinary research on the reproductive biology of the true armyworm, Pseudaletia unipuncta, as a case study.

The role of allatostatic and allatotropic neuropeptides in the regulation of juvenile hormone biosynthesis in Lacanobia oleracea (Lepidoptera: Noctuidae)

In the sphinghid moth Manduca sexta, two allatoactive neuropeptides appear to be responsible for regulating juvenile hormone (JH) production by the corpora allata (CA). These peptides (M. sexta allatostatin, Mas-AS, and M. sexta allatotropin, Mas-AT) respectively inhibit and stimulate in vitro JH biosynthesis by CA in this insect. However, although Mas-AS inhibits CA in both larval and adult insects, Mas-AT is active only in adult M. sexta. The situation in other lepidopteran species is less clear-cut and, although both peptides have been detected (usually by immunologic and/or molecular techniques) in several other moths (including noctuids), their function as regulators of JH production remains uncertain. In the tomato moth Lacanobia oleracea (Lepidoptera: Noctuidae), we have previously demonstrated the occurrence of Mas-AS and/or Mas-AT in extracts of CA, brain and other organs, and have shown that both peptides are present in larval and adult forms. However, in L. oleracea, although Mas-AS inhibits larval and adult CA in vitro, it does so only at relatively high concentrations, and to a maximum of only approximately 70%. By contrast, Mas-AT (which is also present in larval and adult L. oleracea) stimulates larval and adult CA, but is substantially more potent ( approximately 100 fold) than the allatostatin. In this paper we present the results of paired, concurrent measurements (using ELISA) of levels of Mas-AS and Mas-AT in brains, CA and hemolymph (plasma and hemocytes) of L. oleracea at times when there are marked changes in JH titers. We also present data on the in vitro rates of JH biosynthesis by isolated CA, and on hemolymph JH esterase activity measured at the same critical developmental times, and discuss all of these data in relation to the putative allatoregulatory roles of the M. sexta allatotropic and allatostatic neuropeptides in L. oleracea.

Alternative splicing of transcripts expressed by the Manduca sexta allatotropin (Mas-AT) gene is regulated in a tissue-specific manner

The Manduca allatotropin (Mas-AT) gene is expressed as at least three mRNA isoforms that differ from each other by alternative splicing. The location at which the alternative exons are included in the mature mRNAs occur within the open reading frame, so that three different propeptides are predicted as translation products. In the pharate adult insect, the major mRNA isoform expressed in the brain and frontal ganglion differs from that expressed in the nerve cord. Examination of the deduced translations of the alternative exons reveals the presence of three additional Mas-AT-like sequences that are flanked by basic amino acid residues. Therefore, the Mas-AT-like sequences present within the gene may be derived from a duplication of an ancestral Mas-AT-like sequence followed by divergence.

Two orcokinins and the novel octapeptide orcomyotropin in the hindgut of the crayfish Orconectes limosus: identified myostimulatory neuropeptides originating together in neurones of the terminal abdominal ganglion

The tridecapeptides Asn(13)-orcokinin and Val(13)-orcokinin, two known members of the orcokinin neuropeptide family native to crustaceans, and a novel octapeptide, orcomyotropin, FDAFTTGFamide, have been identified from extracts of hindguts of the crayfish Orconectes limosus using an isolated hindgut contractility bioassay, high-performance liquid chromatography, microsequencing and mass spectrometry. All three peptides display strong inotropic actions on crayfish hindguts. Orcomyotropin showed higher potency than the two orcokinins. Threshold concentration was approximately 5 × 10(−12)mol l(−1)versus 10(−10)mol l(−1) for the two orcokinins. An approximately fivefold increase in contraction amplitude was observed with 10(−9)mol l(−1) orcomyotropin and 10(−7)mol l(−1) of the orcokinins. Asn(13)- and Val(13)-orcokinin did not differ significantly with regard to their biological effects. Semi-isolated crayfish hearts and locust oviducts did not respond to the three peptides. Immunocytochemistry using antisera against Asn(13)-orcokinin and orcomyotropin showed that these neuropeptides are co-localized in approximately 80–90 neurones of the terminal abdominal ganglion that have been shown to innervate the entire hindgut muscularis via the intestinal nerve. The neurones form elaborate terminal branches preferentially on longitudinal hindgut muscles. Orcomyotropin is a novel crustacean member of the GF-amide family of myotropic and/or allatotropic neuropeptides from annelids, molluscs and insects.

Molecular characterization of a cDNA from the true armyworm Pseudaletia unipuncta encoding Manduca sexta allatotropin peptide(1)

Allatotropin (AT) is an insect neuropeptide isolated from the tobacco hornworm, Manduca sexta, stimulates juvenile hormone (JH) biosynthesis by the corpora allata. A cDNA isolated from the true armyworm, Pseudaletia unipuncta, encodes a 135 amino acid AT precursor peptide which contains the AT peptide, with processing sites necessary for its endoproteolytic cleavage and amidation, plus two additional peptides of unknown function. The encoded AT peptide is identical to that isolated from M. sexta and Agrius convolvuli. Southern blot analysis indicated that AT is a single copy gene per haploid genome and is present in two allelic forms. A single transcript of approximately 1.5 kilobases was detected by northern blot analysis. The expression of the AT gene was analyzed during development from sixth instar larvae to five day-old moths. Initial expression was observed in late pupae and this expression was maintained throughout the adult stages in both sexes. In one day-old moths, expression was at its lowest level of the stages that express AT mRNA but levels increased in day 3 and day 5 adults. This pattern of AT expression in adult P. unipuncta moths mirrors that of JH biosynthesis and supports the notion that AT may act in the adult stages. Immunohistochemistry and in situ hybridization revealed that AT expression was localized to numerous structures of the nervous system, suggesting that AT may have functions distinct from regulation of JH biosynthesis.

A review of the role of neurosecretion in the control of juvenile hormone synthesis: a tribute to Berta Scharrer

In the 1950s, Berta Scharrer predicted that neurosecretions from the brain regulated corpus allatum activity based upon the observation of the change in localization of neurosecretory material in the brain and change in gland activity after severance of nerves between the brain and corpus allatum. Isolation and characterization of neuropeptide regulators of juvenile hormone production by the corpora allata in the late 1980s has confirmed this prediction. Both a stimulatory allatotropin and an inhibitory allatostatin have been isolated from moth brains. Two families of allatostatins, both quite different from each other and that of moths, have been isolated from cockroaches and crickets. The wide distribution of these peptides in the nervous system, in nerves to visceral muscle, in endocrine cells of the midgut and in blood cells, indicate multifunctions in the insects in which they are allatoregulatory. Some of these other functions have been demonstrated in these insects and in insects in which these neuropeptides occur but do not act as corpus allatum regulators. For the latter group, the neuropeptide regulators of the corpora allata have yet to be isolated. The families of neurosecretory regulators will continue to grow.

Juvenile hormone biosynthesis in larval and adult stick insects, Carausius morosus

Corpora allata (CA) from adult egg-carrying Indian stick insects, Carausius morosus, synthesise and release juvenile hormone (JH) III in vitro. No JH biosynthesis was observed in larvae, young adults, and old adult females that do not carry sclerotised eggs. In females, which bear sclerotised eggs, a consistent JH biosynthesis was observed. Supplementation of precursors of JH biosynthesis (farnesol, mevalonic acid lactone) greatly enhanced JH biosynthesis in a stage-, age-, and dose-dependent manner, but CA from the last larval instar retained the biosynthesised JH within the gland. Elevated calcium concentration in the incubation medium stimulated JH biosynthesis by CA from older adults but had either no or a poor effect on CA from young adults and larvae. The results obtained with farnesol, mevalonic acid lactone, and calcium indicate that the rate-limiting steps of JH biosynthesis very likely occur before the formation of mevalonic acid and that these early steps cannot be stimulated by elevated calcium concentrations in larvae and young adults. In older adults, in which spontaneous JH biosynthesis occurs, elevated calcium concentration can markedly stimulate JH biosynthesis. A pre-purified extract from brains of adult females had a stimulating effect on JH biosynthesis by CA from adult females. The results indicate that JH biosynthesis in C. morosus may require food-derived farnesol and may be regulated by allatotropic signals from the brain, possibly triggered by sclerotised oocytes in the ovary.

Neuropeptides in insect sensory neurones: tachykinin-, FMRFamide- and allatotropin-related peptides in terminals of locust thoracic sensory afferents

Sensory afferents in the thoracic ganglia of the locust Locusta migratoria were labelled with antisera to different neuropeptides: locustatachykinins, FMRFamide and allatotropin. The locustatachykinin-immunoreactive (LTKIR) sensory fibres were derived from the legs and entered the ventral sensory neuropil of each of the thoracic ganglia via nerve 5. In the thoracic neuropil, the LTKIR sensory fibres formed a distinct plexus of terminations ventrally in the ipsilateral hemisphere. The peripheral cell bodies of the sensory neurones could not be revealed, but lesion experiments indicated that origin of the LTKIR fibres was the tarsus of each leg. Possibly the thin fibres are from tarsal chemoreceptors. Double labelling immunocytochemistry revealed that all the LTKIR sensory fibres contained colocalized FMRFamide immunoreactivity. A larger population of sensory fibres reacted with antiserum to moth (Manduca sexta) allatotropin. By means of double labelling immunocytochemistry, we could show that the LTKIR fibres constituted a subpopulation of the larger set of allatotropin-like immunoreactive fibres. Thus some sensory fibres may contain colocalized peptides related to locustatachykinins, FMRFamide-related peptide(s) and allatotropin-like peptide. A separate non-overlapping small set of sensory fibres in nerve 5 reacted with an antiserum to serotonin. Sensory fibres of the other nerves of the ventral nerve cord, including the abdominal ganglia, did not react with the peptide antisera. Since acetylcholine is the likely primary neurotransmitter of insect sensory fibres, it is possible that the peptides and serotonin are colocalized with this transmitter and serve modulatory functions in a subset of the leg afferents.

Structure, distribution, and biological activity of novel members of the allatostatin family in the crayfish Orconectes limosus

In the central and peripheral nervous system of the crayfish, Orconectes limosus, neuropeptides immunoreactive to an antiserum against allatostatin I (= Dipstatin 7) of the cockroach Diploptera punctata have been detected by immunocytochemistry and a sensitive enzyme immunoassay. Abundant immunoreactivity occurs throughout the central nervous system in distinct interneurons and neurosecretory cells. The latter have terminals in well-known neurohemal organs, such as the sinus gland, the pericardial organs, and the perineural sheath of the ventral nerve cord. Nervous tissue extracts were separated by reverse-phase high-performance liquid chromatography and fractions were monitored in the enzyme immunoassay. Three of several immunopositive fractions have been purified and identified by mass spectroscopy and microsequencing as AGPYAFGL-NH2, SAGPYAFGL-NH2, and PRVYGFGL-NH2. The first peptide is identical to carcinustatin 8 previously identified in the crab Carcinus maenas. The others are novel and are designated orcostatin I and orcostatin II, respectively. All three peptides exert dramatic inhibitory effects on contractions of the crayfish hindgut. Carcinustatin 8 also inhibits induced contractions of the cockroach hindgut. Furthermore, this peptide reduces the cycle frequency of the pyloric rhythms generated by the stomatogastric nervous system of two decapod species in vitro. These crayfish allatostatin-like peptides are the first native crustacean peptides with demonstrated inhibitory actions on hindgut muscles and the pyloric rhythm of the stomatogastric ganglion.

Isolation and identification of a peptide and its cDNA from the mosquito Aedes aegypti related to Manduca sexta allatotropin

Immunocytochemistry revealed that an allatotropin-immunoreactive peptide is produced by several neuroendocrince cells in the abdominal ganglia of the mosquito Aedes aegypti. The immunoreactive peptide was isolated and its structure determined to be Ala-Pro-Phe-Arg-Asn-Ser-Glu-Met-Met-Thr-Ala-Arg-Gly-Phe-amide. A cDNA clone encoding this novel neuropeptide was shown to encode a single copy of this peptide. The cDNA is unusual in that the first seven ATGs are not used for translation initiation.

Molecular characterization of a cDNA from Pseudaletia unipuncta encoding the Manduca sexta allatostatin peptide (Mas-AST)

A 15-residue neuropeptide, Manduca sexta allatostatin (Mas-AST), strongly inhibits juvenile hormone (JH) biosynthesis in vitro by corpora allata (CA) from Manduca fifth-stadium larvae and adult females as well as Helicoverpa zea adult females (Kramer et al., 1991 Proc. Natl. Acad. Sci (USA) 88, 9458-9462). In contrast, this study found that 1.0 microM Mas-AST has no JH biosynthesis inhibitory activity in Pseudaletia unipuncta sixth instar larvae or newly-emerged (day 0) adults but inhibited CA of 5-day-old adult females by 60%. From a P. unipuncta brain cDNA library, was isolated a cDNA that encodes a 125 amino acid polypeptide containing the Mas-AST sequence. Within the precursor, Mas-AST is situated at the carboxy terminus and is flanked by different dibasic proteolytic cleavage signals. The Pseudaletia gene specifying the Mas-AST peptide is present as a single copy per haploid genome. Expression of this gene was low in Pseudaletia sixth instar larvae, prepupae and early pupae but was relatively high in late pupae, and day 1 and 3 adults of both sexes. In day 5 adults, the relative transcript level appears to be maintained in females but declines in males. This pattern of Mas-AST expression does not correlate well with the profile of JH biosynthesis in Pseudaletia, which increases during the first 5 days of adult life, suggesting additional or alternative functions for this peptide.

Molecular characterization and expression analysis of Manduca sexta allatotropin

Juvenile hormones (JH) are a class of regulatory sesquiterpenoids that control metamorphosis in immature insects and reproduction in adult insects. The regulation of JH synthesis by the corpora allata (CA), a pair of endocrine glands with nervous connections to the brain, is achieved by a complex interplay of stimulatory and inhibitory factors mediated in part by the brain. The neuropeptide, allatotropin (Mas AT), was recently isolated and sequenced from the brain of the tobacco hornworm Manduca sexta. Mas AT is a 13-residue amidated peptide that activates JH synthesis in adult, but not larval, lepidopteran CA. A 23-nucleotide degenerate oligonucleotide was designed based on the peptide sequence and was used to isolate the Mas AT genomic clone. The Mas AT gene is expressed as three mRNAs which differ from one another by alternative splicing. These mRNAs are predicted to encode three distinct prohormones, each containing Mas AT. A restriction fragment from the genomic clone was then used to isolate the cDNA clone. In situ hybridization and immunohistochemistry studies show that Mas AT is expressed in both the central and enteric nervous systems. Cells expressing Mas AT were identified in the brain, frontal ganglion and terminal ganglion.

Immunohistological localization of regulatory peptides in the midgut of the female mosquito Aedes aegypti

The midgut of the female mosquito Aedes aegypti was studied immunohistologically with antisera to various regulatory peptides. Endocrine cells immunoreactive with antisera to perisulfakinin, RFamide, bovine pancreatic polypeptide, urotensin 1, locustatachykinin 2 and allatostatins A1 and B2 were found in the midgut. Perisulfakinin, RFamide and bovine pancreatic polypeptide all react with the same, about 500 endocrine cells, which were evenly distributed throughout the posterior midgut, with the exception of its most frontal and caudal regions. In addition, these antisera recognized three to five neurons in each ingluvial ganglion and their axons, which ran longitudinally over the anterior midgut, as well as axons innervating the pyloric sphincter. The latter axons appear to be derived from neurons located in the abdominal ganglia. Antisera to two different allatostatins recognized about 70 endocrine cells in the most caudal area of the posterior midgut and axons in the anterior midgut whose cell bodies were probably located in either the brain or the frontal ganglion. Antiserum to locustatachykinin 2 recognized endocrine cells present in the anterior midgut and the most frontal part of the posterior midgut, as well as about 50 cells in the most caudal region of the posterior midgut. Urotensin 1 immunoreactivity was found in endocrine cells in the same region as the perisulfakinin-immunoreactive cells, but no urotensin-immunoreactive axons were found in the midgut. Double labeling experiments showed that the urotensin and perisulfakinin immunoreactivities were located in different cells. Such experiments also showed that the locustatachykinin and allatostatin immunoreactivities in the most caudal area of the posterior midgut were present in different cells. No immunoreactivity was found in the mosquito midgut when using antisera to corazonin, allatropin or leucokinin IV. Since these peptides have either been isolated from, or can reasonably be expected to be present in mosquitoes, it was concluded that these peptides are not present in the mosquito midgut.

Amino acid sequence of CAP2b, an insect cardioacceleratory peptide from the tobacco hawkmoth Manduca sexta

The primary structure of a novel insect neuropeptide, Cardioacceleratory Peptide 2b (CAP2b), from the tobacco hawkmoth Manduca sexta has been established using a combination of mass spectroscopy, Edman degradation microsequencing, amino acid analysis, and biological assays. The sequence of CAP2b, pyroGlu-Leu-Tyr-Ala-Phe-Pro-Arg-Val-amide, has a molecular weight of 974.6 and is blocked at both the amino and carboxyl ends. Examination of several national computer protein data bases failed to reveal other peptides or proteins with any sequence homology to CAP2b indicating that this is likely to be a novel insect neuropeptide. This peptide may be a general activator of insect viscera since it causes an increase in heart rate in Manduca and in Drosophila, and has also been implicated in the regulation of fluid secretion by the Malphigian tubules of Drosophila.

A novel gut tetradecapeptide isolated from the earthworm, Eisenia foetida

A novel bioactive tetradecapeptide, GFKDGAADRISHGFamide, was isolated from the gut of the oligochaete annelid, Eisenia foetida, using the isolated anterior gut (crop-gizzard) as a bioassay system. A highly homologous peptide, GFRDGSADRISHGFamide, was also purified from the whole body of another species of earthworm, Pheretima vittata. These peptides were termed Eisenia tetradecapeptide (ETP) and Pheretima tetradecapeptide (PTP), respectively. Both the peptides showed a potent excitatory action on spontaneous contractions of the anterior gut with a threshold as low as 10(-10)-10(-9) M. These peptides were significantly homologous to molluscan tetradecapeptides and, to a lesser extent, to arthropodan tridecapeptides that have been reported to date. All these peptides seem to be evolutionally related to each other.