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PubMed2003

Physiological differentiation of DH-PBAN-producing neurosecretory cells in the silkworm embryo.

Embryonic diapause of the silkworm, Bombyx mori, is induced by a neuropeptide hormone, the diapause hormone (DH), which is secreted from a limited number of neurosecretory cells in the subesophageal ganglion (SG) at the maternal generation. We examined the developmental fate of the hormone-producing cell (DH-pheromone biosynthesis activating neuropeptide [PBAN]-producing cell) in the embryonic stage at the level of gene expression and cell biology. The DH-PBAN gene expression started at the histogenesis stage and gradually increased toward hatching. DH is an amidated peptide belonging to FXPRLamide family. The immunoreactive somata against anti FXPRLamide antiserum were found in the SG from blastokinesis. Immunoreactive neural processes with varicosites were also found on the corpus cardiacum and the corpus allatum. The implantation of a part of a developing embryo including the SG into the pupae with the SG removed induced diapause eggs in the progeny. These results were obtained from eggs incubated under diapause-averting conditions as well as diapause-inducing conditions. Thus, a neurosecretory system responsible for biosynthesis of FXPRLamide neuropeptides is established as early as histogenesis, although the system to regulate the secretion of neuropeptide hormones has not been fully formed by that time.

Animals↗
PubMed1978

[Cytophysiology of the prothoracic gland of the cricket Acheta domestica L. during the penultimate instar nymph and during the cycle of regeneration (author's transl)].

The cellular kinetic of the prothoracic gland is counted during the penultimate instar nymph of Acheta domestica L. and during the cycle of regeneration, under standard breeding conditions. These experiments show a cycle in the glandular cells in good correlation with the hormonal cycle. Regeneration involves a recovery of phenomenons during the wound-healing and an intense proteosynthesis during the first period of intermue.

Animals↗
PubMed2005

Peptidergic counter-regulation of Ca(2+)- and Na(+)-dependent K(+) currents modulates the shape of action potentials in neurosecretory insect neurons.

Influx of Ca(2+) and Na(+) ions during an action potential can strongly affect the repolarization and the fast afterhyperpolarization (fAHP) if a neuron expresses Ca(2+)- and Na(+)-dependent K(+) currents (K(Ca) and K(Na)). This applies to cockroach abdominal dorsal unpaired median neurons (DUMs). Here the rapid activation of K(Ca) depends mainly on the P/Q-type Ca(2+) current. Adipokinetic hormones (AKHs)-insect counterparts to mammalian glucagon-mobilize energy reserves but also modulate neuronal activity and lead to enhanced locomotor activity. Cockroach AKH I accelerates spiking and enhances the fAHP of octopaminergic DUM neurons, and it is generally held that enhanced release of the biogenic amine from these and other neurons may lead to general arousal. AKH I modulates the voltage-gated Na(+) and P/Q-type Ca(2+) current and the background Ca(2+) current. Upregulation of P/Q-type Ca(2+) current increases the K(Ca) current, whereas enhanced inactivation of Na(+) current decreases the K(Na) current. We quantified the hormone-induced changes in ion currents in terms of Hodgkin-Huxley models and simulated the resulting activity of DUM neurons. Upregulation of P/Q-type Ca(2+) and K(Ca) current enhanced the hyperpolarization but had a weak effect on spiking. Downregulation of Na(+) and K(Na) current decreased hyperpolarization and slightly accelerated spiking. Superposition of these modulations produced an increase in fAHP while the spike frequency remained unchanged. Only when the upregulation of the pacemaking Ca(2+) background current was included in the simulated modulation the model reproduced the experimentally observed AKH-I-induced changes. The possible physiological relevance of this dual effect is discussed in respect to transmitter release and synaptic integration.

Action Potentials↗
PubMed2004

An rxr/usp homolog from the parasitic nematode, Dirofilaria immitis.

Filarial parasites are responsible for several serious human diseases with symptoms such as lymphoedema, elephantiasis, and blindness. An understanding of how these parasites pass through developmental checkpoints may suggest potential targets for intervention. A useful model system for the study of the human parasites is the closely related nematode Dirofilaria immitis, the causative agent of dog heartworm disease. In D. immitis, molting from the third to the fourth larval stage can be induced in vitro by the insect molting hormone, 20-hydroxyecdysone, suggesting that this, or some related steroid, may play a similar role in the development of D. immitis. The holoreceptor of 20-hydroxyecdysone consists of two nuclear receptors (NRs) ecdysone receptor (EcR) and ultraspiracle (USP), USP being the insect orthologue of the vertebrate RXR. We have identified a D. immitis rxr/usp, Di-rxr-1 (NR2B4). Di-RXR-1 can bind in vitro to EcR and DHR38, both known insect USP partners. Like, USP, it activates transcription in Drosophila Schneider S2 cells in a 20-hydroxyecdysone-dependent manner, via its interaction with the endogenous EcR protein. By Northern blot analysis, Di-rxr-1 mRNA is detected in adult females, but not in males. This is the first characterization of a nematode rxr/usp.

Amino Acid Sequence↗
PubMed1996

Evidence for the involvement of 3-oxo-delta 4 intermediates in ecdysteroid biosynthesis.

Although the involvement of 3-oxo-delta 4 compounds as intermediates in arthropod ecdysteroid biosynthesis has been postulated for a long time, it has not yet been directly demonstrated. In the present study, 3-oxo-delta 4-steroids have been synthesized and incubated in vitro with dissociated moulting gland cells from the crab Carcinus maenas. The tritiated compounds were converted into 3-dehydroecdysone, ecdysone and/or 25-deoxyecdysone, i.e. final ecdysteroids. This means that the 3-oxo-delta 4 compounds had undergone a 5 beta-reduction, to give the 5 beta-conformation of ecdysteroids. Our results suggest that the 3-oxo-delta 4-steroid 4,7-cholestadien-14 alpha-ol-3,6-dione may be an intermediate in the biosynthetic pathway. The 5 beta-reduction reaction involves a cytosolic enzyme which requires NADPH as electron donor and seems specific for 3-oxo-delta 4 substrates. This reaction was the most active in crab Y-organs, as compared with other tissues. The characteristics of the 5 beta-reductase (subcellular localization, substrate and cofactor requirements) appear similar to those of the vertebrate 3-oxo-delta 4-steroid 5 beta-reductase involved in steroid hormone catabolism and bile acid biosynthesis.

Animals↗
PubMed2005

Quantitative real-time RT-PCR analysis in desert locusts reveals phase dependent differences in neuroparsin transcript levels.

In different parts of the world, locust swarms cause severe ecological and economic damage. However, the physiological mechanisms underlying this gregarization process remain elusive. In this study, we present a detailed quantitative analysis of two neuroparsin precursor (Scg-NPP1 and Scg-NPP2) transcripts in the brain, fat body, gut, gonads and accessory glands of male and female, gregarious and solitarious desert locusts (Schistocerca gregaria). These transcripts are generally more abundant in solitarious than in gregarious animals. In contrast to their gregarious congeners, solitarious locusts contain detectable Scg-NPP1 and Scg-NPP2 transcript levels in the fat body. Moreover, our data reveal temporal changes of neuroparsin mRNA levels in the brains and fat bodies of adult isolated-reared locusts. This paper provides the first scientific evidence for phase-dependent transcriptional regulation of neuropeptide hormone encoding genes.

Animals↗
PubMed1979

[Hormonal stimulation and in vitro cellular differentiation in the integument of the desert locust Schistocerca gregaria (author's transl)].

Spontaneous cellular differentiation (glandular units appearance with a well-defined duct) is observed in larval integument of Schistocerca cultured in an hormone free medium. Hormonal stimulations modify the expression of this phenomenon, particularly the frequency of new elaborated duct cells belonging to secretory units. The most effective factor is supplied by the prothoracic glands. Complete secretory units can be observed but the glandular cells are in an undifferentiated and unfunctional state. They appear active if the corpora allata act after the prothoracic glands. Corpora allata alone or synthetic juvenile hormones have an inhibitory effect. The addition of alpha-ecdysone permits only cellular divisions, a preliminary and indispensable condition for ulterior differentiation. Between cuticles deposited with beta-ecdysone, new formed ducts take place in the theorical imaginal exuvia. These observations prove that the elaboration and the activity of imaginal glandular units are conditioned by the larval hormonal context: by contrast, sex dimorphism is only a genetic dependant process.

Animals↗
PubMed1998

Juvenile hormone acid: evidence for a hormonal function in induction of vitellogenin in larvae of Manduca sexta.

In the tobacco hornworm (Manduca sexta), vitellogenin (Vg), the major yolk protein precursor, and its mRNA are first detectable in the prepupal stage; and production of both can be enhanced by methoprene, a juvenile hormone (JH) analog. Competence to respond to methoprene is acquired after ecdysteroid-initiated commitment for metamorphosis. Here we show that acquisition of competence requires prior exposure to JH-II acid in addition to ecdysteroid. Application of 20-hydroxyecdysone or RH5992, an ecdysteroid analog, to isolated abdomens from feeding larvae (precommitment) results in exposure of the dorsal vessel (EDV), a sign of metamorphic commitment--but such abdomens do not make Vg in response to methoprene. However, injection of JH-II acid along with 20-hydroxyecdysone into isolated abdomens causes Vg production in response to methoprene. Methoprene acid similarly induces competence to respond to methoprene. Northern blot analysis confirmed that Vg transcripts are present in fat body only if isolated abdomens were pretreated with both ecdysteroid, and JH-II acid or methoprene acid. The latter two can induce competence even in precocious prepupae resulting from removal of the corpora allata (the glands that produce JH) from early penultimate larvae. JH-III acid and related metabolites such as farnesol, farnesoic acid, and methyl farnesoate do not induce competence. Hitherto, JH acids have been regarded as precursors or catabolites of JHs. Here we show for the first time that JH acid has a hormonal function that cannot be performed by JH itself.

Abdomen↗
PubMed2000

Triple co-localisation of two types of allatostatin and an allatotropin in the frontal ganglion of the lepidopteran Lacanobia oleracea (Noctuidae): innervation and action on the foregut.

The triple co-localisation of peptidergic material immunoreactive to antisera raised against allatostatins of the Y/FXFGL-NH2 type, Manduca sexta allatostatin (Mas-AS), and allatotropin has been demonstrated in a single pair of anterodorsal neurones in the frontal ganglion of the tomato moth, Lacanobia oleracea (Noctuidae). Another pair of posterior neurones contain only Y/FXFGL-NH2-type allatostatin immunoreactivity. The neurites of all four cells trifurcate, and axons project to the brain in the frontal connectives and to the foregut in the recurrent nerve. Axons from the anterior neurones, within the recurrent nerve, have prominent lateral branches supplying muscles of the crop, and axons from both anterior and posterior cells show profuse branching and terminal arborisations in the region of the stomodeal valve. The brain contributes Y/FXFGL-NH2-immunoreactive material, but not allatotropin or Mas-AS, to the recurrent nerve via NCC 1+2 and NCC 3. All three peptides have a reversible effect on the spontaneous (peristaltic) contractions of the foregut (crop) in vitro. Thus, both types of allatostatin are inhibitory at 10(-12) to 10(-7) M, whereas allatotropin is strongly myostimulatory at 10(-14) M. This is the first demonstration of the gut myoinhibitory effects of Mas-AS and, taken together with the effects of Y/FXFGL-NH2-type allatostatins and allatotropin, reveals a different functional aspect to that normally attributed to these three peptides, i.e. control of juvenile hormone synthesis by the corpus allatum.

Amino Acid Sequence↗
PubMed1990

Relationships among hormonal changes, cuticular hydrocarbons, and attractiveness during the first gonadotropic cycle of the female Calliphora vomitoria (Diptera).

Attractiveness in adult females of Calliphora vomitoria is correlated with ovarian development and there is a marked increase during the previtellogenic and vitellogenic periods. The development of attractiveness may result from the combined actions of ecdysteroids and juvenile hormone. A rise in total hydrocarbons parallels the first increase in levels of these hormones during the previtellogenic stage. Cuticular hydrocarbons subsequently fall, along with the disappearance of hemolymphatic ecdysteroids, and then rise again during the vitellogenic phase of JH production. Increasing and decreasing of some cuticular hydrocarbons, some hydrocarbons implicated in the attractiveness, are correlated with variation of the titer of these hormones, especially JH III.

Animals↗
PubMed1975

The control of diuresis in the tsetse fly Glossina austeni: a preliminary investigation of the diuretic hormone.

The rate of secretion of the Malpighian tubules of Glossina austeni is controlled by a diuretic hormone. This hormone is present in the nervous tissue of the fly together with a degradative enzyme that can be activated by boiling. It is demonstrated that the Malpighian tubules are able to destroy the diuretic hormone; they may therefore participate in the control of diuresis. The diuretic hormone appears to be a heat-stable, non-dialysable, alcohol-soluble molecule, containing amino acid, glucose and sialic acid residues.

Animals↗
PubMed1984

Isolation and amino-acid composition of the adipokinetic hormone of Manduca sexta.

An adipokinetic hormone was purified from corpora cardiaca of au adult Manduca sexta (tobacco hornworm)by reversed-phased high performance liquid chromatography. The following amino-acid composition was determined: 2 Thr, 2 Ser, Glx, Gly, Leu, Phe, Trp. The adipokinetic activity was tested in adult Manduca. In a bioassay in which activation of fat body glycogen phosphorylase was measured in ligated larvae, the hormone elicited a maximal response at the same concentration as it did in the bioassay for hyperlipaemic activity.

Amino Acids↗
PubMed1995

Effect of cycloheximide on eclosion hormone sensitivity and the developmental appearance of the eclosion hormone and cGMP regulated phosphoproteins in the CNS of the tobacco hornworm, Manduca sexta.

The neuropeptide, eclosion hormone (EH), triggers ecdysis behavior at the end of each molt in Manduca sexta. Previous studies have shown that the action of EH is mediated by an increase in cGMP and is associated with the phosphorylation of two proteins, named the EGPs. The ability of insects to respond to EH is developmentally regulated with sensitivity being first seen at about 8 hr prior to the normal time of ecdysis. The EGPs are also first detectable in the CNS at 8 hr prior to ecdysis, suggesting that it is their synthesis which determines EH sensitivity. The protein synthesis inhibitor, cycloheximide was used to study the development of the events leading to pupal ecdysis in Manduca. The results of these experiments suggest that protein synthesis is necessary about 10 hr before ecdysis for both the development of EH sensitivity and for the appearance of the EGPs.

Animals↗
PubMed2004

[Ecdysteroids of Silene italica ssp. nemoralis, novel approaches of ecdysteroid therapy].

Ecdysteroids are known as insect moulting hormones. They have the basic steroid structure, although their physiological effects on mammalians do not show the thymolytic and androgenic side effects of vertebrate type steroid hormones. At the same time, phytoecdysteroids can be used utilizing their anabolic and adaptogenic effects. Ecdysteroids also have a tremendous potential in the most modern therapy. Recently, the biotechnology started to employ ecdysteroids as powerful inducers for gene-switch systems with insertion of modified insect receptor into the malignant cells. Nineteen ecdysteroids were isolated with combined chromatographic methods from the herbs of Silene italica ssp. nemoralis (Waldst. and Kit.) Nyman. The chemical structure of the isolated compounds have been elucidated using spectroscopic methods (x-ray, UV, CD, IR, MS, 1D-, 2D-NMR, HMQC, HMBC, COSY, TOCSY, NOESY, ROESY). Structural determination of two of the five new ecdysteroids is detailed here.

Ecdysteroids↗
PubMed1997

Effects of estrogenic xenobiotics on molting of the water flea, Daphnia magna.

The effects of five xenobiotics, 2,4,5-trichloribiphenyl (PCB29), the polychlorinated biphenyl (PCB) Aroclor 1242, diethyl phthalate, lindane, and 4-octylphenol, on molting of Daphnia magna were investigated. All except PCB29 are known to have unexpected estrogenicity in vertebrates. Daphnids exposed to PCB29, Aroclor 1242, and diethyl phthalate took significantly more time to complete four molts than did the controls. The inhibitory effects of these ortho-chlorinated PCBs suggest that certain structural features, most probably including ortho-chlorination, are related to the ability of a PCB to affect molting. Agents with multicyclic structures, such as PCBs, are more effective in inhibiting molting than are single-ringed xenobiotics, such as diethyl phthalate, which suggests that hydrophobicity may be a requirement for binding to the ecdysteroid receptor. These molt-inhibiting agents with multiple rings appear to bear more structural resemblance to the steroidal molting hormones of arthropods, the ecdysteroids, than do the single-ringed ones. While the possibility of alternative mechanisms, such as impairment of ecdysteroidogenesis exists, the results obtained herein support the hypothesis that some xenobiotics which disrupt endocrine processes in vertebrates can also interfere with the hormonally regulated molting process in arthropods through acting as antagonists of endogenous ecdysteroids by binding to and thereby blocking the ecdysteroid receptor.

Animals↗
PubMed1986

Developmental changes in choline uptake and acetylcholine metabolism in the larval brain of the tobacco hornworm, Manduca sexta.

The larval brain of the tobacco hornworm, Manduca sexta, was maintained in vitro and the uptake of labelled and unlabelled choline as well as their subsequent metabolism were measured by high-voltage paper electrophoresis. Significant levels of choline lipid metabolites, phosphorylcholine and acetylcholine (ACh) were noted. Unbound choline reached equilibrium after 6-8 h of incubation, while ACh accumulation continued to increase after 24 h indicating that the rate of synthesis exceeded the rate of breakdown. An apparent Km could not be determined for these whole-organ studies; however, the Vmax for ACh accumulation for days 5 (70 pmol/brain/h) and 6 (105 pmol/brain/h) of the last larval instar did vary significantly while the level of unbound choline in the brain did not change. The level of choline uptake was dependent upon the presence of Na+ and Ca2+, while the amount of ACh accumulated was affected specifically by the presence of Mg2+, the latter ion activating acetylcholinesterase. The determination of levels of unbound choline and ACh accumulation in the developing brain during the last two larval instars demonstrated increases in acetylcholine accumulation at previously reported times of the release of the hormone that initiates the molting process, prothoracicotropic hormone. These changes in the patterns of ACh accumulation occur during 4-8 h time intervals; this is the first report of such short-range changes in neurotransmitter metabolism in whole brains. The intensity of the ACh accumulation shift is equivalent to the intensity of the hormone burst. Other fluctuations in the levels of ACh accumulation and free choline correlate with the development of the brain.

Acetylcholine↗