A possible role of SchistoFLRFamide in inhibition of adipokinetic hormone release from locust corpora cardiaca

The distribution and actions of FMRFamide-related peptides (FaRPs) in the corpora cardiaca of the locust Locusta migratoria were studied. Antisera to FMRFamide and SchistoFLRFamide (PDVDHVFLRFamide) label neuronal processes that impinge on glandular cells in the glandular lobe of the corpora cardiaca known to produce adipokinetic hormones. Electron microscopic immunocytochemistry revealed that these FaRP-containing processes form synaptoid contacts with the glandular cells. Approximately 12% of the axon profiles present in the glandular part of the corpus cardiacum contained SchistoFLRFamide-immunoreactive material. Retrograde tracing of the axons in the nervus corporis cardiaci II with Lucifer yellow revealed 25-30 labelled neuronal cell bodies in each lateral part of the protocerebrum. About five of these in each hemisphere reacted with the SchistoFLRFamide-antiserum. Double-labelling immunocytochemistry showed that the FaRP-containing processes in the glandular lobe of the corpora cardiaca are distinct from neuronal processes, reacting with an antiserum to the neuropeptide locustatachykinin. The effect of the decapeptide SchistoFLRFamide and the tetrapeptide FMRFamide on the release of adipokinetic hormone I (AKH I) from the cells in the glandular part of the corpus cardiacum was studied in vitro. Neither the deca- nor the tetrapeptide had any effect on the spontaneous release of AKH I. Release of AKH I induced by the phosphodiesterase inhibitor IBMX, however, was reduced significantly by both peptides. These results point to an involvement of FaRPs as inhibitory modulators in the regulation of the release of adipokinetic hormone from the glandular cells.

Disposition of mirosamicin in honeybee hives

Disposition of mirosamicin, a macrolide antibiotic, to honeybee adults, larvae, honey and royal jelly in the beehive after in-feed administration to adult bees was studied. Treatment was initiated at the end of July when the availability of natural pollen and nectar was poor. The drug was mixed with pollen-substitute paste and administered to honeybee colonies continuously for a week at a dosage of 200 mg/hive/week. High distributions in adult bees, jelly, larvae and a relatively low distribution in honey, of mirosamicin were observed. One day dosing of microsamin in sucrose syrup, a nectar substitute, resulted in a very high and long lasting residue in honey. Both royal and worker jelly, secreted from the jelly glands of adult bees, are acidic, so that a high distribution of a basic drug, such as mirosamicin, in jelly can be expected. This mechanism was considered to be responsible for a high concentration of mirosamicin in honeybee larvae, the host of Paenibacillus-larvae infection (American foulbrood), as primary larval food is jelly.

Cloning of crustacean ecdysteroid receptor and retinoid-X receptor gene homologs and elevation of retinoid-X receptor mRNA by retinoic acid

We report the cloning and analysis of ecdysteroid receptor (bpEcR) and retinoid-X receptor (UpRXR) cDNA homologs from the fiddler crab Uca pugilator. The deduced amino acid sequence of this crustacean EcR most closely resembles the insect EcRs within the DNA binding and ligand binding domains (LBDs). For UpRXR, the DNA binding domain (DBD) shares greatest identity to the insect USPs. The ligand binding domain, however, is closer to vertebrate RXRs but may have a nonfunctional AF-2 domain. Probes derived from these clones were used to examine transcript levels in blastemas during early limb regeneration. Both UpEcR and UpRXR transcripts were detected in low amounts 1 day after limb loss, but increased during the next 4 days. Immersion of crabs in sea water containing all-trans retinoic acid increased the steady state concentrations of UpRXR transcript and altered the pattern of circulating ecdysteroids. These effects correlate with the disruptive effects of retinoic acid on blastemal differentiation observed in earlier studies.

Postembryonic development of leucokinin-like immunoreactive neurons in the moth Spodoptera litura

Antiserum to leucokinin I, a neuropeptide originally isolated from the cockroach Leucophaea maderae, was used for immunocytochemical labeling of neurons in the brain and ventral ganglia of the moth Spodoptera litura during postembryonic development. In the ventral ganglia, leucokinin-like immunoreactivity begins to occur in the abdominal ganglion A3 to A7 of first instar larva. One to two weakly labeled pairs of bilateral LK-LI cell bodies are located in the subesophageal ganglion of fourth to sixth instar larvae and in the abdominal ganglia A1 to A7 of second to sixth instar larvae. The abdominal ganglion A1 of fourth to sixth instar larvae and A8 of sixth instar larva each contain one weakly labeled pair of median LK-LI cell bodies. Two strongly labeled pairs of bilateral LK-LI neurons are found in A3 to A7 of third to sixth instar larvae. Abdominal ganglia A1 to A8 of prepupa, pupa and adult contain one to three weakly labeled pairs of bilateral LK-LI neurons. Two strongly labeled pairs of bilateral LK-LI neurons in each of the abdominal ganglia of larva, prepupa, pupa and adult send axons to the neuropil, and then each axon bifurcates into two axonal branches. Theses axonal branches from two bundles. From each of the two pairs of neurons an axon exits through the posterior ventral nerve (N2) which runs to the transverse nerve of the next posterior segment. In larval brains, 2-16 pairs of bilateral LK-LI cell bodies can be found together with LK-LI processes in the central neuropil. The larval brains show large changes in the number of LK-LI neurons throughout postembryonic development. The number of LK-LI cell bodies are reduced in number from sixth instar larval brain. Therefore, prepupal, pupal and adult brains contain a smaller number of LK-LI cell bodies. Two pairs of LK-LI median neurosecretory cells located immediately beside the pars intercerebralis in larval brains increase to three pairs in the 7-day-old pupal brain. In the adult, however, LK-LI median neurosecretory cells decrease to one pair.

Ecdysteroidostatin from the house fly, Musca domestica

Ovaries from house flies maintained on sucrose secrete large amounts of ecdysteroid when they are cultured with ovarian ecdysteroidogenic hormone, OEH. However, ovarian ecdysteroid secretion is reduced by incubation with both OEH and the ovarian ecdysteroidostatin (OES). A partially purified OES fraction from a semi-preparative reverse phase HPLC C18 column caused a 98% inhibition of ovarian ecdysteroid secretion in vitro at a concentration of 0.8 equivalents per microliter. Ovaries can be activated to produce ecdysteroid in vivo by feeding diet containing protein to flies maintained on sucrose. Ecdysteroid secretion was inhibited when the in vivo stimulated ovaries were cultured with OES. This suggests that OES does not interfere with the OEH activation mechanism, but blocks ovarian ecdysteroid synthesis or release. Furthermore, OES inhibition is reversible and ecdysteroid secretion resumes when OES is removed. Musca OES could explain the decrease in ecdysteroid levels found in flies after mid-vitellogenesis. Both adult male and female abdomens contain OES, but OES was not transferred to females during mating. Evidence is presented that OES is not a trypsin modulating oostatic factor.

Immunocytochemical localization of testis ecdysiotropin in the pupa of the gypsy moth, Lymantria dispar (L.) (Lepidoptera: Lymantriidae)

Antiserum against testis ecdysiotropin isolated from the gypsy moth, Lymantria dispar, reacted with neurons in the protocerebrum, optic and antennal lobes, subesophageal, thoracic and abdominal ganglia, as well as in nerve tracts extending through the optic lobes, tritocerebrum, and interganglionic connectives of the pupal stage of these insects. Testis ecdysiotropin is a peptide required by immature moths to initiate production of testes ecdysteroid, which is necessary for the development of the male reproductive system and initiation of spermatogenesis. Antiserum against testis ecdysiotropin also detected an accumulation of testis ecdysiotripic-like material between the inner and outer testis sheaths of pupae. The localization of this peptide in the imaginal disks of the last larval stage, cells and nerve fibers in the optic and antennal lobes of the pupa of both sexes, as well as in the testes during development of the adult reproductive system indicates that testis ecdysiotropin has a much larger impact on adult metamorphosis than development of the reproductive system and initiation of gametogenesis. Although this peptide may have a modulatory role in the central nervous system (CNS), it may also initiate a cascade of activity required for the development of the adult nervous system, in addition to its role in reproduction.

Vitellogenin and ecdysteroid titers in Ixodes scapularis during vitellogenesis

Ecdysteroids are the only hormones unequivocally identified thus far in ticks. We found a positive correlation between ecdysteroid concentration and vitellogenin synthesis in female Ixodes scapularis. Vitellogenin (Vg) synthetic activity was measured by an in vitro assay for Vg, involving incubations of the fat body with 35S-methionine and immunoprecipitation collected on a solid-phase matrix, protein A. Vitellogenin synthetic activity in the fat body was undetectable in unfed females but was detected after tick attachment to the host. Vitellogenin production in the fat body remained low from attachment until 2 days prior to detachment from the host. Vitellogenin synthesis in the fat body peaked 2 days after detachment and declined to a level 2-3 times above background from 6 days after dropping from the host through oviposition. A peak of ecdysteroids in females 6 days after attachment preceded an increasing rate of Vg synthesis, suggesting a positive correlation between these parameters. Ecdysone and 20-hydroxyecdysone, the 2 major ecdysteroids present during vitellogenesis, could not be detected in females prior to feeding or 2 days after attachment to the host; however, concentrations began to increase 4 days after attachment, peaked during rapid engorgement, and subsequently declined.

Quantification of Locusta diuretic hormone in the central nervous system and corpora cardiaca: influence of age and feeding status, and mechanism of release

Locusta-DH is known to have a hormonal function in the control of post-feeding diuresis in the migratory locust. This study has quantified Locusta-DH in tissues from V(th) instar nymphs and adults, and investigated the K+-induced release of the peptide from corpora cardiaca. Locusta-DH is present in thoracic and abdominal ganglia, but the amounts are small (25-200 fmol) compared with brain (approximately 1 pmol) and corpora cardiaca ( > 5 pmol) from 14-day old locusts. About 50% of the immunoreactive material in corpora cardiaca coelutes with Locusta-DH on reversed-phase HPLC. An earlier eluting fraction is also biologically active, suggesting locusts have a second, previously undetected, CRF-related peptide. The amount of peptide stored in corpora cardiaca varies with age and physiological status. Reductions on day 1 of the adult instar and immediately after feeding suggest Locusta-DH controls post-eclosion as well as post-feeding diureses. Locusta-DH is released by a Ca2+-dependent mechanism from corpora cardiaca held in salines containing > or =40 mM K+. This is blocked by verapamil, implicating L-type Ca2+ channels. Release is most rapid shortly after transfer to a high K+ saline, and more peptide is released from glands allowed to recover in normal saline between successive K+ depolarisations.

Radioimmunoassay determination of tachykinin-related peptide in different portions of the central nervous system and intestine of the cockroach Leucophaea maderae

A radioimmunoassay was developed for insect tachykinin-related peptides with the use of an antiserum raised to the locust neuropeptide locustatachykinin I (LomTK I). Determination of tachykinin-related peptide was performed in different tissues of the cockroach Leucophaea maderae. The largest amounts of LomTK-like immunoreactivity (LomTK-LI) reside in the brain and in the midgut. Relatively large amounts were also found in the suboesophageal ganglion and throughout the ganglia of the ventral nerve cord, whereas smaller amounts of LomTK-LI were detected in the corpora cardiaca, foregut and hindgut. Extracts of unfused abdominal ganglia and midguts, respectively, were analysed by a combination of reversed phase high performance liquid chromatography, and radioimmunoassay for LomTK-LI. The extracts of abdominal ganglia and midguts both contain LomTK-LI material which separates in at least two major components. This LomTK-LI material had retention times corresponding approximately to those of synthetic LomTK I and II. Since the cellular source of LomTK-LI material in the foregut and hindgut was not known from earlier studies, we investigated these tissues by immunocytochemistry. We found that the LomTK-LI material associated with the foregut was in arborizing fibres in the oesophageal and gastric nerves and in the ingluvial ganglion. In the hindgut the muscle layer was innervated by immunoreactive fibres derived from cell bodies in the terminal ganglion. The amount of LomTK-LI material in other portions of the nervous system correlates well with previous immunocytochemical data. We conclude that L. maderae have two or more isoforms of tachykinin-related peptides in the nervous system and intestine and that these are present in various amounts in different parts of the central nervous system and intestine. The relative large amounts of LomTK-LI material in the suboesophageal ganglion, oesophageal nerve and associated ganglia and intestine indicate important roles of tachykinin-related peptides in feeding and digestion.

Effects of fenoxycarb on the secretory activity of the prothoracic glands in the fifth instar of the silkworm, Bombyx mori

Effects of fenoxycarb on the secretory activity of the prothoracic glands (PGs) of the silkworm, Bombyx mori, were investigated. Fenoxycarb inhibited the secretory activity of PGs in vitro throughout the fifth instar. Incubation of PGs in the presence of 1 microgram of fenoxycarb resulted in a approximately 50% inhibition of their secretory activity. This inhibition of fenoxycarb was dose dependent. Stimulation of the PGs by recombinant prothoracicotropic hormone (rPTTH) reached a high activation ratio of 15.9. Simultaneous presence of fenoxycarb and 1 ng rPTTH significantly decreased the stimulatory effect of rPTTH on the PGs, and the activation ratio never exceeded 3.65. Early in the fifth instar, fenoxycarb strongly inhibited the secretory activity of the PGs and induced a developmental arrest as well. After the onset of pupal commitment, its action toward the PG secretory activity was inhibitory. However, fenoxycarb treatment was not able to induce a developmental arrest in intact animals after the pupal commitment although it could do so in head-ligated animals. On the contrary, application of fenoxycarb after the wandering behavior resulted in a significantly increased secretory activity by the PGs of both intact and head-ligated larvae.

Ovarian and hemolymph ecdysteroids in the terrestrial isopod Armadillidium vulgare (Malacostracan Crustacea)

Ovarian and hemolymph ecdysteroids in Armadillidium vulgare were analyzed at four stages of ovarian maturation through the reproductive molt cycle using high-performance liquid chromatography and radioimmunoassay. The major ecdysteroids in the ovaries and hemolymph of A. vulgare were 20-hydroxyecdysone and ecdysone in free and conjugated forms. The concentration of ovarian ecdysteroids reached a maximal level in maturing ovaries during stage D (premolt period) of the molt cycle. At the end of stage D, a high level of ecdysteroids was detected in fully matured ovaries. On the other hand, hemolymph ecdysteroid titers in reproductive females showed a peak during stage D and declined rapidly to a low level at the end of stage D. No appreciable differences in the amounts of hemolymph ecdysteroids and in molecular species of them were apparent in females in reproductive and nonreproductive molt cycles. The amounts of hemolymph ecdysteroids were about fivefold higher in females than those in males. These ecdysteroids may have a role in controlling ovarian development in female A. vulgare.

Immunolocalization of the oostatic and prothoracicostatic peptide, Neb-TMOF, in adults of the fleshfly, Neobellieria bullata

The hexapeptide Neb-TMOF (H-NPTNLH-OH, trypsin modulating oostatic factor of the gray fleshfly, Neobellieria bullata)2 occurs in vitellogenic ovaries and is involved in negative feedback regulation of trypsin biosynthesis in the gut of late vitellogenic females. Polyclonal antisera were raised against the synthetic peptide and were used to identify and immunolocalize Neb-TMOF epitopes in different fleshfly tissues. Neb-TMOF-immunoreactive material first appears in the cortical layer of young vitellogenic oocytes and later spreads over the yolk granules. This suggests a pinocytosis with the three yolk polypeptides (vitellogenins). Controls treated with the preimmune sera or with anti-Neb-TMOF antiserum preadsorbed to Neb-TMOF peptide coupled to a solid phase support did not stain. There was no immunostaining in the central nervous system (brain and ventral nerve cord), the retrocerebral complex, the fat body, or the testes. Western blot analysis showed that the anti-Neb-TMOF antisera specifically recognize a putative hormone precursor polypeptide (Mr 75 kDa) from vitellogenic ovaries. This protein is virtually absent from the hemolymph. It is not immunologically related to the three yolk polypeptides, since it is not recognized by yolk polypeptides antisera. In adult females the ovary appears to be the only site of synthesis of Neb-TMOF and of its precursor. Immunopositive staining is found in the apical areas of ovarian follicle cells, suggesting these cells as a site of hormone precursor biosynthesis. This is the first demonstration that a protein colocalized with yolk proteins might act as a precursor for a folliculostatic hormone.

decapentaplegic overexpression affects Drosophila wing and leg imaginal disc development and wingless expression

We have used the GAL4-UAS expression system to increase the level of expression of the Drosophila gene decapentaplegic (dpp) in a pattern approximating its normal pattern in leg and wing imaginal discs. Intermediate increases of dpp expression have little effect in wing discs but high levels of dpp overexpression lead to reduction of the scutellum and duplication of posterior wing structures. In leg discs intermediate increases cause supernumerary outgrowths of ventral leg structures in the anterior-ventral region. Greater increases of dpp expression cause the loss of ventral leg structures with the concomitant fusion of left and right dorsal forelegs. The defects observed in both legs and wings appear to arise through dose-dependent effects of dpp on wingless (wg) expression. A high level of dpp overexpression in the wing disc causes reduction of wg expression in the presumptive scutellar region, consistent with the subsequent reduction of the scutellum. An intermediate increase of dpp expression in leg discs induces the expansion of wg expression into the ventral outgrowths. At higher dpp expression levels, ventral wg expression in leg discs is eliminated, consistent with the loss of ventral leg cuticle. In the leg disc end knob and in the wing margin primordium, where wg and dpp cooperate in producing distal outgrowth, dpp overexpression has no detectable effect either on patterning or on wg expression. We propose that a critical role for dpp in other regions of the leg and wing discs is to reduce or block the expression of wg. This role of dpp is supported by the observation that ectopic wg expression is detected in imaginal discs where dpp signaling is compromised by lowering the activity of one of its receptors, tkv. This antagonism between dpp and wg expression may be critical to assigning only one disc region as the distal organizer.

Dual function of the region-specific homeotic gene spalt during Drosophila tracheal system development

We report that the region-specific homeotic gene spalt affects the Drosophila tracheal system at two different stages of embryonic development. Both lack-of-function and gain-of-function experiments show that blastodermal spalt activity restricts tracheal development to 10 bilaterally positioned pairs of tracheal placodes in the trunk region by repressing placode formation in parasegments 2, 3 and 14. The results suggest that the activity of the zinc-finger type transcription factor encoded by spalt suppresses the molecular pathway that establishes tracheal development. spalt function is also necessary for the directed migration of the dorsal trunk cells, a distinct subset of tracheal cells. This process is a prerequisite for the formation of the dorsal trunk generated by fusion of adjacent tracheal metameres into a common tubular structure. The directed cell migration, in which spalt gene function participates, seems to be independent of branch fusion and general tracheal cell migration processes.

Distribution of Dip-allatostatin I-like immunoreactivity in the brain of the locust Schistocerca gregaria with detailed analysis of immunostaining in the central complex

The distribution and morphology of neurons containing allatostatin-related substances in the brain of the locust Schistocerca gregaria was investigated using an antiserum against Diploptera punctata allatostatin I (Dip-allatostatin I, APSGAQRLYGFGL-amide). In each brain hemisphere, about 550 neurons in the midbrain and 500 neurons in the optic lobe exhibit Dip-allatostatin I-like immunoreactivity, including about eight lateral neurosecretory cells with processes to the retrocerebral complex. All major brain areas except the antennal lobe, the mushroom body, and large parts of the lamina, are innervated by Dip-allatostatin I-immunoreactive processes. Immunostaining in the central complex was studied in detail. The central complex is innervated by more than 260 Dip-allatostatin I-immunoreactive neurons belonging to six different cell types, four sets of tangential neurons and two sets of columnar neurons. These neurons give rise to intense immunostaining in the protocerebral bridge, in several layers of the upper division of the central body, and in the dorsalmost layer of the lower division of the central body. Double-label experiments show colocalization of Dip-allatostatin I- and serotonin-like immunoreactivities in one type of columnar and one type of tangential neurons of the central complex. The similar patterns of Dip-allatostatin I- and galanin message-associated peptide-like immunoreactivities result from cross-reactivity of the anti-galanin message-associated peptide antiserum with Dip-allatostatin I. The results provide further insight into the anatomical and neurochemical organization of the locust central complex and suggest a prominent neuroactive role for Dip-allatostatin I-related peptides in this brain area.

A comparative immunocytochemical study using an antiserum against a synthetic analogue of the corpora cardiaca peptide Pea-CAH-I (MI, neurohormone D) of Periplaneta americana

An antiserum against the octapeptide Pea-CAH-I, a member of the adipokinetic hormone/red pigment-concentrating hormone family, has been produced for immunocytochemical staining in insects and various other invertebrate species. The anti-Pea-CAH-I serum stains the glandular corpora cardiaca cells of those insect species that synthesize identical or structurally similar peptides. In the corpora cardiaca of species producing peptides with a different C-terminus, these cells remain unstained. Pea-CAH-I-like immunoreactivity has also been found in neurons of the central nervous system of all invertebrate orders studied. The antiserum recognizes the C-terminal sequence Pro-Asn-Trp-NH2 of the Pea-CAH-I molecule as established by enzyme immunoassay. The widespread Pea-CAH-I-like immunoreactivity in all nervous systems of the studied animals probably does not reflect the presence of Pea-CAH-I but the occurrence of peptides carrying similar epitopes.

Binding of APC to the human homolog of the Drosophila discs large tumor suppressor protein

The adenomatous polyposis coli gene (APC) is mutated in familial adenomatous polyposis and in sporadic colorectal tumors, and its product binds to the adherens junction protein beta-catenin. Overexpression of APC blocks cell cycle progression. The APC-beta-catenin complex was shown to bind to DLG, the human homolog of the Drosophila discs large tumor suppressor protein. This interaction required the carboxyl-terminal region of APC and the DLG homology repeat region of DLG. APC colocalized with DLG at the lateral cytoplasm in rat colon epithelial cells and at the synapse in cultured hippocampal neurons. These results suggest that the APC-DLG complex may participate in regulation of both cell cycle progression and neuronal function.

Localization of myosuppressinlike peptides in the hypocerebral ganglion of two blood-feeding flies: horn fly and stable fly (Diptera:Muscidae)

The insect peptides leucomyosuppressin (pEDVDHVFLRFamide) and dromyosuppressin (TDVDHVFLRFamide) have identical chemical sequences with the exception of the N-terminal amino acid; both inhibit spontaneous contraction of insect visceral muscles. Neurons in the hypocerebral ganglion of horn fly, Hematobia irritans (L.), and stable fly, Stomoxys calcitrans (L.), were found to contain material immunoreactive to antiserum produced against the C-terminal of leucomyosuppressin, but not to the N-terminal of dromyossuppressin. Two large lateral clusters containing 8 cells, linked dorsally and ventrally by 2 chains of 6 cells, encircled the anterior surface of the proventriculus and were immunoreactive of leucomyosuppressin and FMRFamide antisera. Axons from these cells were traced to the wall of the aorta and over the surface of the proventriculus. Ultrastructural analysis revealed these cells contained a singular type of elementary secretory granule that contained material of relatively low electron density, both in the cell body and at the axon terminals.

The GAGA factor is required in the early Drosophila embryo not only for transcriptional regulation but also for nuclear division

The GAGA protein of Drosophila was first identified as a stimulatory factor in in vitro transcription assays using the engrailed and Ultrabithorax promoters. Subsequent studies have suggested that the GAGA factor promotes transcription by blocking the repressive effects of histones; moreover, it has been shown to function in chromatin remodeling, acting together with other factors in the formation of nuclease hypersensitive sites in vitro. The GAGA factor is encoded by the Trithorax-like locus and in the studies reported here we have used the maternal effect allele Trl13C to examine the functions of the protein during embryogenesis. We find that GAGA is required for the proper expression of a variety of developmental loci that contain GAGA binding sites in their upstream regulatory regions. The observed disruptions in gene expression are consistent with those expected for a factor involved in chromatin remodeling. In addition to facilitating gene expression, the GAGA factor appears to have a more global role in chromosome structure and function. This is suggested by the spectrum of nuclear cleavage cycle defects observed in Trl13C embryos. These defects include asynchrony in the cleavage cycles, failure in chromosome condensation, abnormal chromosome segregation and chromosome fragmentation. These defects are likely to be related to the association of the GAGA protein with heterochromatic satellite sequences which is observed throughout the cell cycle.

Isolation and partial structure of a unique lipophilic peptide, VAP peptide, from the heads of male silkworm moths

A new lipophilic peptide was isolated from the MeOH-CH2Cl2 extract of adult heads of the male silkworm, Bombyx mori, by monitoring the diapause egg-inducing activity. Partial amino acid sequencing (1-55) revealed this peptide to be a unique type having a high content of lipophilic amino acids, Val, Ala, and Pro, and many repeating sequences. The compound was thus named VAP peptide.

Structural characterization and location of disulphide linkages of a potent vasodilatory peptide, recombinant maxadilan, by a multiple mass spectrometric approach

A multiple mass spectrometric strategy using fast-atom bombardment (FAB) and matrix-assisted laser desorption/ionization (MALDI) has been used to confirm the sequence and to locate the disulfide linkages of recombinant maxadilan (r-maxadilan) (average molecular mass 7422.5 Da), a potent vasodilatory peptide from Lutzomyia longipalpis. MALDI measurements of intact r-maxadilan, its reduced form and its pyridylethylated form (p-maxadilan) indicated the presence of four Cys residues without major post-translational modifications. FAB and FAB-tandem mass spectrometry measurements of chymotryptic digests of p-maxadilan were sufficient to map the primary structure of p-maxadilan, though the complementary use of MALDI was necessary for complete mapping using Asp-N digestion due to a strong suppression observed in FAB. Assignment of the Cys-5-Cys-9 linkage was achieved by comparison of FAB mass spectra before and after reduction of tryptic digests of r-maxadilan. Since the molecular weight of the peptide fragment containing the Cys-18-Cys 55 linkage is more than 4000, MALDI measurement was indispensable for assignment of this linkage. The results fully support the value of the multiple mass spectrometric strategy in the structural characterization of peptides and proteins.

Isolation and characterization of a kettin-like protein from crayfish claw muscle

A 540 kDa protein was isolated from crayfish claw muscle (closer). The secondary structure mainly consisted of beta-sheet (70%). The rotary shadowed images were long filaments, 300-360 nm long. It is localized in the sides of the Z-lines extending to the I band and elongatable upon stretch of muscle. Immunological crossreactivities strongly suggested that this protein corresponds to kettin (500-700 kDa) of insect striated muscle. In view of molecular shape and secondary structure, and immunological crossreactivities, it is suggested that this kettin-like protein belongs to connectin/titin family of striated muscle.

Immunocytochemical mapping of serotonin and neuropeptides in the accessory medulla of the locust, Schistocerca gregaria

Accumulating evidence suggests that pigment-dispersing hormone-immunoreactive neurons with ramifications in the accessory medulla of the insect brain are involved in circadian pacemaking functions. We have used immunocytochemical techniques to investigate the neurochemical organization of the accessory medulla in the locust Schistocerca gregaria. Local neurons with arborizations largely restricted to the accessory medulla are immunoreactive with antisera against serotonin, Manduca sexta allatotropin, and Diploptera punctata allatostatin 7. Projection neurons with arborizations in the accessory medulla and fibers to the lamina and/or several areas in the midbrain including the posterior optic tubercles, the inferior and the superior protocerebrum show Phe-Met-Arg-Phe (FMRF)amide-, gastrin/cholecystokinin-, crustacean cardioactive peptide-, and substance P immunoreactivities. A unique neuron with tangential ramifications in the medulla and lamina and varicose terminals in the accessory medulla contains a peptide related to locustatachykinin I/II. Double-label experiments show colocalization of pigment-dispersing hormone-immunoreactivity with substances related to gastrin/cholecystokinin, FMRFamide, substance P, or crustacean cardioactive peptide in certain projection neurons of the accessory medulla. The results suggest that neuropeptides and biogenic amines play major neuroactive roles in the accessory medulla of the locust. The abundance and extensive colocalization of neuropeptides in the locust accessory medulla is discussed with respect to the possible involvement of this brain area in circadian pacemaking functions.