Peptides (v.23, #11)
IFC (editorial board) (IFC).
Invertebrate neuropeptides III by R.J Nachman (1873).
Characterization of an additional molt inhibiting hormone-like neuropeptide from the shrimp Metapenaeus ensis by P.-L Gu; S.S Tobe; B.K.C Chow; K.H Chu; J.-G He; S.-M Chan (1875-1883).
We have identified a second form of the type-II neuropeptide encoding a molt inhibiting hormone-like (MeeMIH-B) neuropeptide. MeeMIH-B showed only a 70% amino acid identity to the MIH-A (formerly MIH) isolated from the same species, suggesting a possible different function of the deduced neuropeptide. Like other neuropeptide members of the CHH family, the MIH-B gene consists of three exons separated by two introns. The levels of MIH-B mRNA transcript in the eyestalk decrease in the initial phase of gonad maturation and increase towards the end of maturation. The drop in MIH-B level suggests an inhibitory role for this neuropeptide in the initiation of vitellogenesis. MIH-B transcripts can also be detected in the brain, thoracic ganglion and ventral nerve cord. Together with the CHH-B peptide that we have previously described, this is the second peptide of the CHH family that can also be identified in the ventral nerve cord and in the XOSG complex. A recombinant MIH-B was produced and a polyclonal antibody against rMIH-B was subsequently generated. Specific anti-rMIH-B antiserum recognized the presence of MIH-B in the sinus gland, X-organs, as well as a giant neuron of the ventral nerve cord. Injection of rMIH-B delayed the molting cycle of the maturing female. Taken together, the results of this study suggest that a drop in MIH-B level may be required for the delay in the molting of the maturing females.
Keywords: Eyestalk; Molt inhibiting hormone; Gene organization; Shrimp reproduction;
Occurrence of insect kinins in the flesh fly, stable fly and horn fly—mass spectrometric identification from single nerves and diuretic activity by Ronald J Nachman; Geoffrey M Coast; Shane E Tichy; David H Russell; J.Allen Miller; Reinhard Predel (1885-1894).
MALDI-TOF mass spectrometric analysis of single lateral abdominal nerves (LANs) demonstrate the presence of the insect kinin Musdo-K in the housefly Musca domestica, and identify heretofore unknown insect kinins in two other Dipteran species as Musdo-K in the stable fly Stomoxys calcitrans and horn fly Haematobia irritans. The insect kinin native to the flesh fly Neobellieria bullata is identified as Drome-K. Musdo-K and Drome-K are identical save for the conservative substitution of Ser for Thr in position 2. The sequences of the insect kinins are, therefore, remarkably conserved throughout Dipterans. The in vitro Malpighian tubule fluid secretion activity of Musdo-K in the stable fly is similar to that in the housefly, whereas that of Drome-K is 30-fold more potent in the flesh fly than in the fruit fly. Given the structural identities of the kinins and CRF-like diuretic hormones of these Dipteran species, the housefly can serve as a model insect for the study of diuretic peptides and their functions in the stable fly and horn fly, both livestock pests.
Keywords: Lateral abdominal nerves (LANs); Malpighian tubule; Musdo-K; Musca domestica;
Four novel PYFs: members of NPY/PP peptide superfamily from the eyestalk of the giant tiger prawn Penaeus monodon by Paisarn Sithigorngul; Jirasak Pupuem; Chatchadaporn Krungkasem; Siwaporn Longyant; Nanthika Panchan; Parin Chaivisuthangkura; Weerawan Sithigorngul; Amorn Petsom (1895-1906).
An immunocytochemical method was used for localization of pancreatic polypeptide (PP) immunoreactive substances in the eyestalk of Penaeus monodon using anti-C-terminal hexapeptide of PP (anti-PP6) antiserum. Approximately 200 neuronal cell bodies were recognized in the ganglia between the medulla interna (MI) and medulla terminalis (MT) and surrounding MT in conjunction with the neuronal processes in medulla externa (ME), MI, MT and sinus gland. About half of the PP immunoreactive neurons were also recognized by a combination of three monoclonal antibodies raised against FMRFamide-like peptides. Isolation of the PP immunoreactive substances from the eyestalk was performed using 7500 eyestalks extracted in methanol/acetic acid/water (90/1/9) followed by five to six steps of RP-HPLC separation. Dot-ELISA with anti-PP6 antiserum was used to monitor PP-like substances in various fractions during the purification processes. Four new sequences of one hexapeptide; RARPRFamide, and three nonapeptides; YSQVSRPRFamide, YAIAGRPRFamide and YSLRARPRFamide were identified, and named as Pem-PYF1–4 due to their structural similarity to the PYF found in squid Loligo vulgaris. Each of the new peptides shares four to seven common residues with the C-terminus of the squid PYF and with the NPFs found in other invertebrates. The NPY/PP superfamily as well as the FMRFamide peptide family may be present throughout vertebrates and invertebrates.
Keywords: Eyestalk; Immunocytochemistry; NPY; NPF; PP; PYF; PYY; Penaeus monodon; Neuropeptides; Primary structure; Purification;
Search for peptidic molecular markers in hemolymph of crowd-(gregarious) and isolated-reared (solitary) desert locusts, Schistocerca gregaria by M.M Rahman; L.Vanden Bosch; G Baggerman; E Clynen; K Hens; B Hoste; K Meylaers; T Vercammen; L Schoofs; A De Loof; M Breuer (1907-1914).
An HPLC analysis of hemolymph extracts was undertaken to uncover differences between desert locusts, Schistocerca gregaria, reared under either crowded or isolated conditions. Some differences in the chromatographic pattern could be detected. One of the major peaks in the hemolymph of crowd-reared adults was found to be a minor one in isolated-reared individuals, whereas other peaks increased after solitarization. The differences became even more pronounced after several generations of isolated rearing. The dominant chromatographic peak in hemolymph extracts of the crowd-reared animals was identified as a novel peptide with a molecular mass of 6080 Da. Edman degradation in combination with enzymatic fragmentation and quadrupole-time of flight (Q-Tof) mass spectrometry revealed the full sequence: DNADEDTICVAADNKFYLYANSLKLYTCYNQLPKVYVVKPKSQCRSSLSDCPTS. This 54 aa-peptide is very abundant in hemolymph of crowd-reared adults. Its concentration in hemolymph amounts to 0.1 mM. To uncover the function, its effects were investigated in several bioassays, so far without positive results. One of the other peaks differentially expressed in the individuals of the two phases was identified as SGPI-2 (MW=3794 Da), which is a serine protease inhibitor in locusts.
Keywords: Locusts; Schistocerca gregaria; Locust phases; Locust phase polymorphism; Locust phase transition; Insect neuropeptides; Hemolymph peptides;
Evidence for crustacean cardioactive peptide-like innervation of the gut in Locusta migratoria by Andrew Donini; Caroline Ngo; Angela B Lange (1915-1923).
Hindguts from female Vth instar larvae, young adults (1–2 days) and old adults (>10 days) are equally sensitive to the crustacean cardioactive peptide (CCAP), with changes in contraction occurring at a threshold concentration of 10−9 M and maximal responses observed at concentrations ranging between 10−7 and 5×10−6 M. An immunohistochemical examination of the gut of Locusta migratoria with an antiserum raised against CCAP revealed an extensive network of CCAP-like immunoreactive processes on the hindgut and posterior midgut via the 11th sternal nerve arising from the terminal abdominal ganglion. Anterograde filling of the 11th sternal nerve with neurobiotin revealed extensive processes and terminals on the hindgut. Retrograde filling of the branch of the 11th sternal nerve which innervates the hindgut with neurobiotin revealed two bilaterally paired cells in the terminal abdominal ganglion which co-localized with CCAP-like immunoreactivity. Results suggest that a CCAP-like substance acts as a neurotransmitter/neuromodulator at the locust hindgut.
Keywords: Crustacean cardioactive peptide; Neurotransmitter; Neuromodulator; Hindgut; Midgut; Locust; Insect;
Central effects of the peptides, SchistoFLRFamide and proctolin, on locust oviduct contraction by Rodney Kwok; Ian Orchard (1925-1932).
We have developed a semi-intact preparation—consisting of an isolated oviduct with abdominal ganglia VII and VIII intact and attached—with which to characterize the effects on oviduct contraction, of peptides that are bath applied to CNS tissues. The work presented here offers a qualitative analysis of the central effects of SchistoFLRFamide and proctolin upon action potentials recorded from the oviducal nerves and upon oviduct contraction. In the process of this, we hope to demonstrate that a previously characterized putative CNS SchistoFLRFamide receptor [Peptides 23 (2002) 765] is a functional receptor.SchistoFLRFamide (10−6 M), bath applied to abdominal ganglion VII, caused an increase in action potential frequencies recorded from the oviducal nerves, as well as an increase in the frequency of phasic contractions of the oviduct. Although the function of this response is not known, these results further support the possibility that the putative CNS SchistoFLRFamide receptors are functional receptors.Proctolin (10−6 M), bath applied to abdominal ganglion VIII, altered the rhythmic bursting of action potentials recorded from the oviducal nerve and changed the appearance and cycle duration of neurogenic oviduct contractions.
Keywords: Insect; Central nervous system; Abdominal ganglion; Bioassay;
Biological activity of Manduca sexta allatotropin-like peptides, predicted products of tissue-specific and developmentally regulated alternatively spliced mRNAs by Kyeong-Yeoll Lee; Mary E Chamberlin; Frank M Horodyski (1933-1941).
The insect neuropeptide, allatotropin (Manse-AT), exerts multiple functions including the stimulation of juvenile hormone (JH) biosynthesis in adults and the inhibition of active ion transport across the midgut epithelium of feeding larvae. The Manse-AT gene is expressed in multiple regions of the nervous system as three mRNAs that differ by alternative splicing. The specific mRNA isoform present differs in a tissue- and developmental-specific manner thus providing a mechanism for the regulated production of peptides specific to each isoform. These peptides are predicted to include three allatotropin-like (Manse-ATL) peptides that exhibit limited structural identity to Manse-AT and overlapping biological activities.
Keywords: Allatotropin; Manduca sexta; Neuropeptides; Ion transport; Juvenile hormone; Alternative splicing;
Differential expression of CMG peptide and crustacean hyperglycemic hormones (CHHs) in the eyestalk of the giant tiger prawn Penaeus monodon by Paisarn Sithigorngul; Nanthika Panchan; Parin Chaivisuthangkura; Siwaporn Longyant; Weerawan Sithigorngul; Amorn Petsom (1943-1952).
Mouse antiserum against C-terminal amide of Pem-CMG (a peptide in the family of CHH/MIH/GIH) penta-deca peptide (RPRQRNQYRAALQRLamide=CMG-15) was generated and used for localization of the peptide in tissue and extract of the eyestalk of Penaeus monodon by means of immunohistochemistry and dot-ELISA in comparison with anti-T+ antiserum (T+=YANAVQTVamide: the putative C-terminal amide of crustacean hyperglycemic hormone (CHH) of Macrobrachium rosenbergii). The anti-CMG-15 antiserum did not show cross-reactivity to T+ peptide by dot-ELISA and vice versa for anti-T+ antiserum. In dot-ELISA of eyestalk extract of P. monodon after one step separation by RP-HPLC, anti-CMG-15 antiserum recognized different peptide fractions (F38–39) from those recognized by anti-T+ antiserum (F19, 40–41 and 47–51). Most of the T+ immunoreactive fractions (except F19) show higher hyperglycemic activity than the CMG immunoreactive fractions. In immunohistochemical localization, anti-CMG antiserum recognized only 2–3 neurons in medulla terminalis X-organ complex (MTXO) with long processes terminated in the sinus gland. The CMG-immunoreactive neurons were clearly distinct from CHH containing neurons situated in the same area. This evidence confirms the existing of CMG peptide which may play distinct roles from CHHs in hormonal regulation in P. monodon.
Keywords: CMG; CHH/MIH/GIH; Dot-ELISA; Penaeus monodon; Immunohistochemistry;
The different effects of three Drosophila melanogaster dFMRFamide-containing peptides on crop contractions suggest these structurally related peptides do not play redundant functions in gut by Amanda Duttlinger; Kathleen Berry; Ruthann Nichols (1953-1957).
A Drosophila melanogaster dFMRFamide gene product, TPAEDFMRFamide, decreased crop contractions. However, DPKQDFMRFamide and SDNFMRFamide, also encoded in dFMRFamide, did not affect crop motility, which suggests these peptides are not functionally redundant in the crop and their unique N-terminal structures are important for activity. TPAEDFMRFamide-specific antisera did not stain the crop, which suggests it acts as a hormone. TDVDHVFLRFamide (DMS), encoded in D. melanogaster myosuppressin, stops crop contractions. TPAEDFMRFamide and DMS each contains a RFamide C-terminus; however, their effects on crop contractions differ, which suggests that unique receptors or different ligand:receptor binding requirements exist for these structurally related peptides.
Keywords: Peptides; Ligand; Receptor; Brain–gut peptide; FaRP;
Structural and functional diversities of the Aplysia Mytilus inhibitory peptide-related peptides by Kosei Sasaki; Yoriko Shimizu; Genbu Abe; Yuko Fujisawa; Fumihiro Morishita; Osamu Matsushima; Yasuo Furukawa (1959-1965).
Aplysia Mytilus inhibitory peptide-related peptides (AMRPs) are multiple hexapeptides coded on a single precursor. By comparing the AMRP precursors of two species of Aplysia (Aplysia californica and Aplysia kurodai), we found that there are substantial numbers of species-specific AMRPs. We next compared the function of AMRPs on the anterior aorta between A. kurodai and Aplysia juliana. In A. juliana, AMRPs inhibited the contractile activity of the aorta (EC50=10−9 to 10−8 M), whereas the peptides had no obvious action in A. kurodai up to 10−7 M. These results indicate that AMRPs are both structurally and functionally diverse neuropeptides even among closely related species.
Keywords: Neuropeptide; Aplysia; Anterior aorta; Immunohistochemistry;
Evidence for CRF-like and kinin-like peptides as neurohormones in the blood-feeding bug, Rhodnius prolixus by V.A Te Brugge; I Orchard (1967-1979).
In Rhodnius prolixus, the rapid post-feeding diuresis is under neurohormonal control. While serotonin has been demonstrated to be a diuretic neurohormone [J Exp Biol 156 (1991) 557], a peptide is also known to be involved. Previously, we have demonstrated the presence of corticotropin releasing factor (CRF)-like and kinin-like peptides in the central nervous system (CNS) of 5th instar Rhodnius [J Exp Biol 202 (1999) 2017; Peptides 22 (2001) 161]. These peptides are present in neurohemal sites of the corpus cardiacum and are co-localized in neurohemal sites on abdominal nerves. While various CRF-like peptides have been demonstrated to increase Rhodnius Malpighian tubule secretion the kinin-like peptides do not [Peptides 23 (2002) 671]. The kinin-like peptides do however, increase hindgut contraction which may contribute to the rapid post feeding diuresis by the mixing of hemolymph and/or hindgut contents and the removal of wastes. The presence of these peptides in neurohemal sites suggests that they could be released into the hemolymph and act as neurohormones.We have used immunohistochemical techniques and radioimmunoassay (RIA) to demonstrate qualitative and quantitative changes of CRF-like and kinin-like peptides in the CNS associated with feeding. As well we have examined Malpighian tubule secretion in response to assays of hemolymph from unfed and fed insects. Hemolymph was also partially purified by Sep-Pak and HPLC and the fractions assayed for kinin-like immunoreactivity and the ability to stimulate Malpighian tubule secretion. The results suggest that both kinin-like and CRF-like peptides are neurohormones in Rhodnius, released in response to feeding.
Keywords: Malpighian tubule; Insect; RIA; Diuresis; Immunohistochemistry;
Methyl farnesoate and juvenile hormone production in embryos of Diploptera punctata in relation to innervation of corpora allata and their sensitivity to allatostatin by B Stay; J.R Zhang; S.S Tobe (1981-1990).
Corpora allata (CA) of embryos of Diploptera punctata have been previously shown to produce JH III. We have re-examined sesquiterpenoid biosynthesis throughout embryonic development and have found that early embryos produce both methyl farnesoate (MF) and JH III; as development proceeds, less MF and more JH is produced. The cockroach allatostatin peptide Dippu-allatostatin (AST) 7 inhibits sesquiterpenoid production by CA of mid to late embryos whereas it exerts a dose-dependent stimulatory effect in early embryos. This stimulatory effect is particularly apparent on MF biosynthesis. CA become innervated by allatostatin-containing nerves in early embryos (35% development). Shortly thereafter, the allatostatin-containing innervation of the CA appears complete.
Keywords: Juvenile hormone; Methyl farnesoate; Allatostatin; Cockroach; Diploptera punctata; Embryonic development;
Aplysia cardioactive peptide (NdWFamide) enhances the L-type Ca2+ current of Aplysia ventricular myocytes by Kazunori Kanemaru; Fumihiro Morishita; Osamu Matsushima; Yasuo Furukawa (1991-1998).
NdWFamide is a d-amino acid containing tripeptide purified from Aplysia heart. Although the cardioexcitatory action of NdWFamide is well established, little is known about how the excitatory action is induced. To examine the action of the peptide on the ion channels expressed in the Aplysia heart muscles, we carried out whole cell clamp experiments in the isolated Aplysia ventricular myocytes. We found that the high voltage-activated (HVA) Ca2+ current of Aplysia ventricular myocytes is mostly a nifedipine-sensitive L-type current, and that the current was enhanced by NdWFamide via the activation of G proteins.
Keywords: Cardioexcitatory peptide; The high voltage-activated Ca2+ current; G protein; Nifedipine; Bay K 8644; GTP-γ-S; GDP-β-S;
Functional analysis of synthetic insectatachykinin analogs on recombinant neurokinin receptor expressing cell lines by Herbert Torfs; Karl E. Åkerman; Ronald J. Nachman; Hendrica B. Oonk; Michel Detheux; Jeroen Poels; Tom Van Loy; Arnold De Loof; Rob H. Meloen; Gilbert Vassart; Marc Parmentier; Jozef Vanden Broeck (1999-2005).
The activity of a series of synthetic tachykinin-like peptide analogs was studied by means of microscopic calcium imaging on recombinant neurokinin receptor expressing cell lines. A C-terminal pentapeptide (FTGMRa) is sufficient for activation of the stomoxytachykinin receptor (STKR) expressed in Schneider 2 cells. Replacement of amino acid residues at the position of the conserved phenylalanine (F) or arginine (R) residues by alanine (A) results in inactive peptides (when tested at 1 μM), whereas A-replacements at other positions do not abolish the biological activity of the resulting insectatachykinin-like analogs. Calcium imaging was also employed to compare the activity of C-terminally substituted tachykinin analogs on three different neurokinin receptors. The results indicate that the major pharmacological and evolutionary difference between tachykinin-related agonists for insect (STKR) and human (NK1 and NK2) receptors resides in the C-terminal amino acid residues (R versus M). A single C-terminal amino acid change can turn an STKR-agonist into an NK-agonist and vice versa.
Keywords: Agonist; Calcium; Evolution; Insect; Neurokinin; Neuropeptide; Peptide; Pharmacology; Tachykinin; Receptor;
Extracellular peptidases of imaginal discs of Drosophila melanogaster by Claire L Wilson; Alan D Shirras; R.Elwyn Isaac (2007-2014).
The imaginal discs of Drosophila melanogaster give rise to the adult epidermis during metamorphosis. During this developmental period several peptidase genes are expressed in disc cells, but there is a paucity of biochemical information regarding substrate specificity. We have used peptides and peptidyl 7-amino-4-methylcoumarin (AMC) substrates to detect several peptidases either positioned on the surface of wing discs or secreted by the imaginal cells. Using [Leu5]enkephalin as a substrate, a captopril sensitive dipeptidyl carboxypeptidase (angiotensin I-converting enzyme) and an amastatin-sensitive aminopeptidase were detected as prominent activities associated with intact discs. The formation of [Leu5]enkephalin-derived Phe was attributed to the concerted action of the D. melanogaster angiotensin I-converting enzyme (Ance) and a dipeptidase. The disc Ance also showed endopeptidic activity towards locust tachykinin-1 (LomTK-I) by cleaving the Gly–Val peptide bond, but this enzyme was not the sole endopeptidase activity associated with discs. Complete inhibition of the endopeptidic hydrolysis of the LomTK-1 by a disc homogenate required a combination of captopril and the neprilysin inhibitor, phosphoramidon, providing biochemical evidence for a neprilysin-like peptidase, in addition to Ance, in imaginal discs of D. melanogaster. Peptidyl AMC substrates for furin, prohormone convertase and tryptase provided evidence for trypsin-like serine endopeptidases in addition to the metalloendopeptidases. We conclude that imaginal discs are endowed with a variety of peptidases from different families that together are capable of hydrolyzing a broad range of peptides and proteins. Some of these peptidases might be responsible for the metabolic activation/inactivation of signaling peptides, as well as being involved in the production of dipeptides and free amino acids required for protein synthesis and osmotic balance during adult morphogenesis.
Keywords: Peptide metabolism; Angiotensin I-converting enzyme; Aminopeptidase; Dipeptidase; Dipeptidyl peptidase IV; Neprilysin;
Degradation of Manduca sexta allatostatin and allatotropin by proteases associated with the foregut of Lacanobia oleracea larvae by Neil Audsley; Robert J Weaver; John P Edwards (2015-2023).
The degradation of synthetic Manduca sexta allatostatin (Manse-AS) and allatotropin (Manse-AT), by enzymes of the foregut of larvae of the tomato moth, Lacanobia oleracea was investigated using reversed-phase high performance liquid chromatography (RP-HPLC) together with matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) and Edman sequencing. Metabolism of 1 nmol Manse-AS by foregut extract (1 μg protein) was rapid, t 1/2≈5 min, with two major products produced. Mass spectrometry of HPLC fractions identified cleavage products Manse-AS-(4-15) and Manse-AS-(6-15), which indicates enzymatic cleavage at the C-terminal side of arginine residues (R3 and R5). This degradation of Manse-AS could be inhibited by up to 80% by the serine protease inhibitor aprotinin, but not PMSF, pepstatin, E64, EDTA, or 1,10-phenanthroline. M. sexta allatotropin was also rapidly degraded when incubated with foregut extract, t 1/2≈8 min, producing two metabolic products, one of which was identified as Manse-AT-(1-11), showing enzymatic cleavage at the C-terminal side of arginine (R11). The second product was identified as Manse-AT-(1-8). Hydrolysis of Manse-AT could only be partially inhibited by high doses of aprotinin (30%).
Keywords: Neuropeptide; Metabolism; MALDI-TOF; Mass spectrometry; Insect; Protease inhibitor;
Peptidyl dipeptidases (Ance and Acer) of Drosophila melanogaster: major differences in the substrate specificity of two homologs of human angiotensin I-converting enzyme by Richard J Siviter; Ronald J Nachman; M.Paulina Dani; Jeffrey N Keen; Alan D Shirras; R.Elwyn Isaac (2025-2034).
Drosophila melanogaster angiotensin converting enzyme (Ance) and angiotensin converting enzyme related (Acer) are single domain homologs of mammalian peptidyl dipeptidase A (angiotensin I-converting enzyme) whose physiological substrates have not as yet been identified. We have investigated the in vitro substrate specificities of the two peptidases towards a variety of insect and mammalian peptides. Ance was generally much better than Acer at hydrolyzing peptides of 5–13 amino acids in length. Only two of the peptides, [Leu5]enkephalinamide and leucokinin-I were cleaved faster by Acer. Increasing NaCl concentration had opposite affects on the cleavage of [Leu5]enkephalin and [Leu5]enkephalinamide by Acer, decreasing the activity towards [Leu5]enkephalin but increasing the activity towards [Leu5]enkephalinamide. Of the insect peptides tested, the tachykinin-related peptide, Lom TK-1, proved to be the best substrate for Ance with a k cat/K m ratio of 0.122 s−1 μM−1. However, in comparison, the D. melanogaster tachykinins, DTK-1, DTK-2, DTK-3 and DTK-4 were poor Ance substrates. DTK-5 was the best substrate of this family, but the apparent high K m for hydrolysis by Ance suggested that this peptide would not be a natural Ance substrate. This low affinity for DTK-5 is the likely reason why the peptide was not rapidly degraded in D. melanogaster hemolymph, where Ance was shown to be a major peptide-degrading activity.
Keywords: Insect tachykinin; Insect peptides; Peptide metabolism; Peptidases; Tachykinin-related peptides;
Enhanced oral availability/pheromonotropic activity of peptidase-resistant topical amphiphilic analogs of pyrokinin/PBAN insect neuropeptides by Ronald J Nachman; Peter E.A Teal; Allison Strey (2035-2043).
The peptide bond between active core residues Pro and Arg is the primary site of susceptibility for the pyrokinin/PBAN neuropeptides to insect tissue-bound peptidases, and incorporation of modified Pro residues can enhance resistance to peptidase hydrolysis. An Hyp-containing amphiphilic analog (Hex-FT[Hyp]RLa) is shown to operate as a topically active tissue-bound peptidase-resistant analog of the pyrokinin/PBAN class of insect neuropeptides in adult Heliothis virescens moths. An Oic amphiphilic analog (Hex-FT[Oic]RLa) is ineffective topically, but proves to be a superior tissue-bound, peptidase-resistant pyrokinin/PBAN analog for oral administration; outperforming both the Hyp analog and the orally inactive natural hormone PBAN in the moths. The Oic analog is effective in penetrating an isolated, ligated foregut preparation, but less successful in transmigrating an isolated midgut preparation; whereas the opposite behavior is observed for the Hyp analog. The success of the Oic analog via oral administration may be related to its ability to effectively penetrate the foregut, thereby bypassing the hostile environment of the midgut region.
Keywords: Oral availability; Heliothis virescens; Amphiphilic analog;
Approaches to radioiodination of insect neuropeptides by Joe W Crim; Stephen F Garczynski; Mark R Brown (2045-2051).
High quality radioiodinated neuropeptides are essential to radioimmunoassays (RIA) and receptor binding assays. Approaches of direct and indirect labeling of neuropeptides with 125 Iodine ( 125 I ) are compared. An HPLC equipped with an in-line gamma detector and UV absorbance detector was used to evaluate selected labeling methods and products. Treatment of [Y1]-adipokinetic hormone-I ([Y1]-AKH-I) with chloramine-T caused oxidative damage, whereas enzymatic labeling with lactoperoxidase in the presence of H2O2 produced a good yield of intact, apparently monoiodinated peptide. Labeling of the FMRFamide-related peptide (YGGFMRFa), with chloramine-T apparently formed the methionine sulfoxide, which subsequently could be reduced with dithiothreitol. Products of high specific activity typically are achievable.
Keywords: Adipokinetic hormone; Chloramine-T; Insect; Radiolabel; YGGFMRFa;
Neuropeptides in flatworms by M.K.S Gustafsson; D.W Halton; N.D Kreshchenko; S.O Movsessian; O.I Raikova; M Reuter; N.B Terenina (2053-2061).
The use of well-characterized antibodies raised to neuronal signal substances and their application through immunocytochemistry and confocal scanning laser microscopy has revolutionized studies of the flatworm nervous system (NS). Data about flatworm neuropeptides and the spatial relationship between neuropeptides and other neuronal signal substances and muscle fibers are presented. Neuropeptides form a large part of the flatworm NS. Neuropeptides are especially important as myoexcitatory transmitters or modulators, controlling the musculature of the attachment organs, the stomatogastric and the reproductive systems.
A review of the involvement of proctolin as a cotransmitter and local neurohormone in the oviduct of the locust, Locusta migratoria by Angela B Lange (2063-2070).
The pentapeptide proctolin, originally identified in the cockroach, has been shown to be widely distributed in many insects and to have a broad range of physiological functions. In the oviduct of the locust, Locusta migratoria, proctolin’s role as a neurotransmitter/neuromodulator has been well documented; however, a neurohormonal role in the locust is less certain. This review will examine the various roles of proctolin in locust oviduct contraction and will present evidence that a substance chromatographically, immunologically and physiologically indistinguishable from proctolin is present in the hemolymph of the locust, L. migratoria. This material is concentrated in the plasma, rather than the hemocytes, and is present at concentrations ranging from 0.1 to 0.2 nM. This review extends the role of proctolin in insects, and suggests that proctolin may play a neurohormonal role in the locust.
Keywords: Visceral muscle; Spermathecae; Skeletal muscle; Second messengers; Neural substrate;