Le rôle du système nerveux central sur les mécanismes de l'oviposition chez Carausius morosus et Clitumnus extradentatus

Cephalic nervous connexions were found necessary for oviposition and normal egg maturation in the two species studied. Neurosecretory cells of A type from the brain, suboesophageal, thoracic, and four abdominal ganglia seem to elaborate a stimulating substance for egg laying. This neurosecretion type is not present in corpora cardiaca, corpora allata, the four last abdominal ganglia, or perisympathetic organs which have no clear-cut effect on oviposition. The circadian rhythm of egg laying appears to be entirely controlled by the liberation of this neurosecretion and by an inhibitory factor localized in the head.In Carausius, egg deposition by the valvulae of the ovipositor is regulated by these two factors whereas egg transit through the common oviduct is a distinct preliminary step under nervous control. This nervous effect from the posterior region does not exist in Clitumnus.     

The distribution and relative potency of diuretic peptides in the house cricket, Acheta domesticus

ABSTRACT Dose-response curves are presented for the diuretic activity in aqueous extracts of brain, retrocerebral complex, and ventral nerve cord ganglia from Acheta domesticus . Diuretic activity is highest in extracts of brain and corpora cardiaca. In comparison with such extracts, those of the suboesophageal ganglia and thoracic ganglia I-III produce truncated responses, whilst abdominal ganglia 1–4 show evidence of an inhibition of the diuretic response at high doses. ED₅₀ values, obtained from Hill plots, are similar for extracts of brain, corpora cardiaca, corpora allata, and abdominal ganglia, but are 3–4 times higher for extracts of suboesophageal and thoracic ganglia.
Separation of aqueous extracts of corpora cardiaca by reversed-phase HPLC yields a number of fractions which stimulate fluid secretion in isolated tubules. Diuretic activity in these fractions is destroyed by treatment with Pronase E, and on this basis is identified as peptidic. In general, diuretic activity is found in the same RP-HPLC fractions prepared from aqueous extracts of brain, suboesophageal ganglia, thoracic ganglia I-III, and abdominal ganglia 1–4.     

Hormonal regulation of proline synthesis and glucose release in the fat body of the Colorado potato beetle, Leptinotarsa decemlineata

In the adult males of the Colorado potato beetle, Leptinotarsa decemlineata, corpora cardiaca extract injected in vivo gives rise to an increase in glucose and a decrease in alanine concentration of the haemolymph. The regulation of proline synthesis and glucose release in the fat body of the Colorado potato beetle was investigated further in vitro. Proline regulates its own synthesis by a feedback inhibition. Moreover, a factor present in extracts from the corpora cardiaca stimulates synthesis in the fat body in vitro. This effect was demonstrated with corpora cardiaca extracts from beetles, locusts and cokroaches. Also, synthetic adipokinetic hormone stimulates proline synthesis in the fat body of the Colorado beetle. In addition, a release of glucose from the fat body of the beetle could be evoked by the addition of locust and beetle corpora cardiaca extracts or synthetic adipokinetic hormone. The physiological significance of both effects is discussed.     

Re-evaluation of the role of corpora cardiaca in calling and oviposition behaviour of giant silk moths

Re-investigation of the role of the corpora cardiaca in the reproductive behaviour of the giant silkmoths, Hyalophora cecropia and Antheraea polyphemus, showed that this pair of glands plays no essential role, either in “calling” behaviour by virgin females or in increased oviposition due to mating. Removal of corpora cardiaca-corpora allata complexes, either from diapausing pupae or from freshly eclosed adult females, had no effect on the calling behaviour or on its timing in either species. Moreover after mating, these operated females laid eggs in the typical mated oviposition pattern. Furthermore, females in which there was only a nervous connection between the brain and the abdomen but no haemolymph circulation called normally and oviposited after mating.Although the corpora cardiaca were not essential for calling behaviour, hormogenates of corpora cardiaca-corpora allata complexes and blood from calling or ovipositing females induced a typical “calling” response in 30–60% of the isolated virgin H. cecropia abdomens tested. This activity was not species-specific as it was also found in Manduca sexta, but the restriction of major activity to corpora cardiaca extracts and haemolymph suggested that a neurosecretory factor may modulate the normal neural control of calling behaviour.     

Hormone stimulated lipolysis and proline synthesis in the fat body of the adult tsetse fly, Glossina morsitans

G. morsitans fat cells incubated in vitro with l-[U-¹⁴C]-leucine incorporated the radiolabel, mainly into triglycerides. Aqueous extracts of corpora cardiaca, midbrain, or thoracic ganglion stimulated the release of radiolabelled material from prelabelled fat cells in vitro. Corpora cardiaca extracts were the most active, approx. 1 × 10^?3 gland pairs/μl elicited the maximal response. At concentrations above 1 × 10^?3 gland pairs/μl the activity of corpora cardiaca extracts was inhibited by a substance which could be removed by gel filtration. The stimulatory factor in nervous-tissue extracts was destroyed by proteolytic enzymes and was recoverable in a single peak by Sephadex G15 gel filtration. Results suggest that it is a peptide hormone produced mainly by the median neurosecretory cells of the midbrain with the corpora cardiaca being the site of storage and release. No hormone was detectable in fresh haemolymph, but it was found at high concentration in boiled haemolymph, implying the presence of a heat labile inhibitor.Under the in vitro conditions used the hormone stimulated the synthesis of proline from alanine and the hydrolysis of triglycerides to free fatty acids. The probable functions of the hormone are to stimulate proline synthesis in response to demand for flight and/or to mobilise lipid for larval nutrition. The relative importance of these apparent functions in vivo could not be determined.     

Isolation, physiological characterization, release and sequence elucidation of a hypertrehalosaemic neuropeptide from the corpus cardiacum of the stick insect, Sipyloidea sipylus

ABSTRACT. The corpora cardiaca of the stick insect, Sipyloidea sipylus Westwood, contain peptidic material which elevates blood lipids in migratory locusts, blood carbohydrates in American cockroaches, and activates glycogen phosphorylase in the fat body of the cockroach in a time- and dose-dependent manner. The active principle is found in appreciable amounts only in the corpora cardiaca; slight hyperlipaemia is caused by extracts made from corpora allata and abdominal ganglia, whereas brain, suboesophageal and thoracic ganglia are not active. The adipokinetic activity is already present in corpora cardiaca from second instar (first day) nymphs. The factor retains its adipokinetic activity after boiling for up to 1 h. Conspecific injections of extracts from corpora cardiaca of S.sipylus cause hypertrehalosaemia in ligated stick insects and activate glycogen phosphorylase in non-ligated S.sipylus. After incubation of corpora cardiaca in vitro in saline with high concentrations of potassium and calcium, one fraction with adipokinetic (in locusts) and hypertrehalosaemic (in stick insects) activity can be isolated from the medium by RP-HPLC. Fractionation of a methanolic extract of corpora cardiaca from S.sipylus by RP-HPLC shows that active compounds are confined to apparently three absorbance peaks. The material of the highest absorbance peak was purified to homogeneity by RP-HPLC, and its amino acid composition determined after acid hydrolysis with HCl and with methanesulfonic acid revealed the residues Asx, Thr₍₃₎, Glx, Pro, Gly, Leu, Phe and Trp. The primary structure of this hypertrehalosaemic factor is assigned as a blocked decapeptide, pGlu-Leu-Thr-Phe-Thr-Pro-Asn-Trp-Gly-Thr-NH₂, from its FAB spectrum and metastable scans of its FAB spectrum. The structure is confirmed by synthesis; the synthetic and natural peptide co-chromatograph, and the synthetic peptide elevates blood carbohydrates in ligated stick insects and activates fat body phosphorylase in non-ligated S.sipylus.     

Distribution of allatostatin in the adult cockroach,Diploptera punctata and effects on corpora allata in vitro

Direct radiochemical measurements of juvenile hormone synthesis showed that corpora allata from adult female Diploptera punctata can be inhibited in vitro by neuropeptides extracted from several ganglia of the central nervous system of females at many stages of the reproductive cycle. Extracts of protocerebra, corpora cardiaca, suboesophageal, thoracic and ventral ganglia all elicited dose-depedent reductions in juvenile hormone synthesis. On a ‘per organ’ basis, the protocerebrum contains the most extractable material. Inhibitory activity of extracts of suboesophageal, thoracic and 6th abdominal ganglia, like that of protocerebra (Rankin et al., 1986) was trypsin sensitive.Glands of high activity were less sensitive to protocerebral extract than those of low activity. The inhibitory effect on glands of low activity was maximal within 1 h, persisted in the presence of protocerebral extract for at least 46 h, and was abolished within 1 h after corpora allata were placed in normal medium. The inhibitory effect of protocerebral extract was not altered by the addition of magnesium to the medium. The extract had a specific effect on synthetic step(s) prior to methylation and epoxidation as demonstrated by enhanced juvenile hormone synthesis in the presence of inhibitory factor and the juvenile hormone precursor, farnesoic acid.     

In vivo and in vitro photoperiodic induction of diapause using isolated brain-suboesophageal ganglion complexes of the silkworm,Bombyx mori

By use of a bivoltine silkworm race which shows a long-day photoperiodic response after induction during the last (5th) instar, we tried to programme photoperiodic induction in the isolated brain-suboesophageal ganglion complex in vivo and in vitro. A pair of the complexes from a newly ecdysed 5th-instar female was transplanted into the abdomen of a late 5th-instar larva and exposed to long-day (20 h light: 4 h dark) or short-day (8 h light: 16 h dark) conditions for 3 cycles. The short-day-exposed complexes elicited the production of diapause eggs in the recipient silkworms destined to become non-diapause egg producers, whereas the long-day-exposed brain complexes produced non-diapause eggs. Transplant experiments of the brain-suboesophageal ganglion complex using isolated abdomens showed a similar result. The brain complexes from newly ecdysed females of the 5th-instar were cultured in Grace's insect medium under 20 h light: 4 h dark or 8 h light: 16 h dark for 4 cycles, respectively. After in vitro culture, a pair of complexes was implanted into the abdomen of a late 5th-instar larva destined to become a non-diapause egg producer, and the diapause incidence in the resultant moths was examined. The brain complexes which received the short-day cycles induced a large portion of diapause eggs, whereas those which received the long-day conditions induced non-diapause eggs. The connection of corpora cardiaca and corpora allata with the brain complex had no influence on the result. Suboesophageal ganglia which had been cultured in vitro and implanted elicited a remarkable production of diapause eggs, but cultured brains were ineffective in producing diapause eggs, regardless of the photoperiod experienced. These results demonstrate that photoperiodic induction of the silkworm can be programmed in in vivo and in vitro culture systems, and that components of the photoperiodic clock (photoreceptor, clock, and counter system) are located in the brain-suboesophageal ganglion complex, possibly in the brain itself.     

An active principle from the corpora cardiaca,corpora allata and suboesophageal ganglion of the locust,inducing egg diapause in Bombyx mori

The activity of the substance(s) which are contained in the cephalic endocrine organs of the locust which induce egg diapause in Bombyx mori was examined by implantation and injection of saline extracts of these organs. Extracts from the median and lateral neurosecretory parts of the locust brain were not effective in inducing egg diapause. Extracts of the corpora cardiaca, corpora allata, and suboesophageal ganglion of the locust induced diapause eggs in Bombyx pharate adults from which the suboesophageal ganglion had been removed. The first two extracts could induce egg diapause even in isolated abdomens of pharate adults of Bombyx. In the locust corpora cardiaca, the activity was present only in the glandular lobe and not in the nervous region. This activity decreased when the nervi corporis cardiaci I and II and of nervi corporis allati I were cut. Allatectomy also brought about a decrease in the activity in the glandular lobe which could not be restored by the injection of juvenile hormone. The activity in the corpora allata was enhanced slightly by the disconnection though not significantly.From these results, it is assumed that the corpora cardiaca, corpora allata and suboesophageal ganglion of the locust contain and active principle(s) capable of inducing egg diapause in Bombyx mori. The nervous connections between the brain, corpora cardiaca, and corpora allata are essential for the accumulation of the active substance(s) in the glandular lobes of the corpora cardiaca.     

Hormonal control of lipid synthesis in the fat body of the adult female tsetse fly, Glossina morsitans

Aqueous extracts of brain, thoracic ganglion or corpora cardiaca of female Glossina morsitans were shown to contain a substance which inhibited the synthesis of lipid from l[U-¹⁴C] leucine by fat cells incubated in vitro. The highest concentration of this substance was found in the corpora cardiaca; approximately 1 × 10^?6 gland pairs μl^?1 were required for maximum inhibition. At concentrations greater than 1 × 10^?4 gland pairs μl^?1 the lipid synthesis inhibiting factor (hereafter referred to as the LSIF) was inactivated by the presence of a substance which could be removed by gel filtration. The concentration of LSIF in the corpora cardiaca and midbrain varied throughout the reproductive cycle of the female. Net release of LSIF from the midbrain occurred between the 2nd and 7th day of the 9-day reproductive cycle. Net release from the corpora cardiaca began on day 5 and continued until the end of the interlarval period on day 9. Results are consistent with the hypothesis that LSIF is synthesised mainly in the medial neurosecretory cells of the midbrain whereas the corpora cardiaca are the site of storage and release into the haemolymph. LSIF was present in midbrain and corpora cardiaca extracts from male G. morsitans but at lower concentrations than in females. No variation in LSIF concentration could be correlated with the feeding cycle. LSIF activity was not detected in fresh haemolymph but was found at high concentration in boiled haemolymph, suggesting the presence of an inhibitor which was inactivated at high temperature. Preliminary investigations into the nature of LSIF have shown it to be inactivated by proteolytic enzymes and to be recoverable in a single peak from a Sephadex G15 column.Results support the view that LSIF is a peptide hormone which, in conjunction with an inhibitor, controls the lipid synthetic ability of the fat cells of the adult female tsetse fly throughout the reproductive cycle.     

Diuresis or clearance: Is there a physiological role for the “diuretic hormone” of the desert beetle Onymacris?

Malpighian tubules of Namib Desert tenebrionid beetles of the genus Onymacris are strongly stimulated by homogenates of the corpora cardiaca. The corpora cardiaca of other arid-adapted tenebrionids also contain diuretic material. Biogenic amines, which could be released during the preparation of corpora cardiaca extracts, do not stimulate fluid secretion in tubules of Onymacris rugatipennis. The diuretic factor in corpora cardiaca extracts is stable to boiling and to incubation with pronase. HPLC separation of the corpora cardiaca of O. rugatipennis gives a single region with diuretic activity in both secretory and electrical bioassays. Diuretic activity can not be detected in the haemolymph of Onymacris, and injection of corpora cardiaca extracts into the beetles does not cause diuresis. Simultaneous injection of corpora cardiaca and the dye amaranth shows that the most of the dye transported by the Malpighian tubules moves anteriorly into the midgut, indicating fluid recycling by this route. The most likely function for this “diuretic hormone” is clearance of metabolic wastes from the haemolymph.     

Induction of egg diapause in Bombyx mori by some cephalo-thoracic organs of the cockroach, Periplaneta americana

Induction of egg diapause in the silkworm, Bombyx mori by some cephalo-thoracic organs of the cockroach, Periplaneta americana was examined. All tissues tested such as brain, corpora cardiaca, corpora allata, suboesophageal and thoracic ganglia and nerve cords between thoracic ganglia were able to produce diapause eggs in non-diapause egg producers both by transplantation and injection of their crude homogenates. The homogenate of thoracic ganglia was effective even in pharate adults with the suboesophageal ganglion removed or in isolated abdomens of pharate adults.From these results, it was surmised that some endocrine organs, as well as the central nervous system in the cephalo-thorax of Periplaneta americana, contained the active principle responsible for egg diapause in Bombyx mori.     

Hormonal basis of adult eclosion in the gypsy moth (Lepidoptera: Lymantriidae)

Eclosion hormone was found to control the stereotypic adult eclosion behaviour of Lymantria dispar, the gypsy moth. A bioassay for hormonal activity was developed utilizing pharate adult females, and comparisons were made with the Manduca wing assay. The distribution of eclosion hormone activity was confined to the central nervous system tissues including the protocerebrum, corpora allata/corpora cardiaca complex, thoracic and the last abdominal ganglion. Haemolymph ecdysteroid titres were determined daily throughout pupal-adult development, and the peak activity period was found in 3–4 day pupae. Eclosion hormone activity in the brain and corpora allata/corpora cardiaca complex started to increase when the ecdysteroid titre dropped to background levels. Eclosion hormone in the brain peaked in the pharate adult stage, was released in the haemolymph 1 h prior to eclosion, which coincides with the depletion of activity in the retrocerebral complex, and fell to undetectable levels after the adult emerged.     

Feeding effects on the neuroendocrine regulated development of fat body mitochondria in the cockroach Blaberus discoidalis

Fat body mitochondria in male Blaberus discoidalis showed a stepwise three-fold development in succinoxidase activity during the first 10 days of adult life. Long-term corpora cardiaca deficiency or prevention of feeding by oral blockage prevented the third step in succinoxidase development. Starvation alone did not prevent the complete development. Administration of corpora cardiaca extracts to orally blocked animals stimulated the final development of succinoxidase activity. It is speculated that the mechanical acts of feeding stimulate neurosecretory activity which increases the metabolic capacity of the fat body through effects on mitochondriogenesis.     

Ecdysteroid regulation of the onset of cuticular melanization in allatectomized and Black mutant Manduca sexta larvae

The absence of juvenile hormone at the time of head cap slippage during the last-larval moult of the tabacco hornworm, Manduca sexta, causes deposition of premelanin granules into the outer regions of the newly forming endocuticle beginning 13 h later. These granules were found to contain an inactive phenoloxidase which becomes activated about 9 h later, 4 h before body melanization begins. The onset of melanization was not accelerated by melanization and reddish colouration hormone from Bombyx heads, extracts of pharate-adult corpora cardiaca or pharate-larval ventral nerve cords (sources of eclosion hormone), or extracts of pharate-larval suboesophageal ganglia or corpora cardiaca-corpora allata complexes. Instead the fall of the ecdysteroid titre to below 250 ng/ml 20-hydroxyecdysone equivalents appeared to be the cue that allowed melanization about 4.5 h later. Up to, but not after, this time both melanization and ecdysis could be delayed by exogenous 20-hydroxyecdysone in a dose-dependent fashion above 0.1 μg per larva. In vitro studies published elsewhere indicate that 20-hydroxyecdysone prevents the activation of the premelanin granules. Thus the granules can be deposited at the proper time in the newly forming endocuticle but their melanization is regulated by the declining ecdysteroid titre and it thus synchronized with other events occurring just before ecdysis.     

A quantitative study of adipokinetic hormone of the firebug,Pyrrhocoris apterus

The development of an enzyme-linked immunoassay (ELISA) for the adipokinetic neuropeptide hormone, Pya-AKH, from the firebug Pyrrhocoris apterus L. is described. The ELISA measures as little as 20 fmol of Pya-AKH. Tested against a range of synthetic peptides, the assay has a high sensitivity for peptides containing the C-terminal motif FTPNWamide. The amounts of Pya-AKH in the brain, corpora cardiaca, suboesophageal ganglia, and fused thoracic and abdominal ganglionic mass are very small, with only the corpora cardiaca containing appreciable levels of the hormone (ca. 4 pmol per bug). Preliminary estimates of the persistence of the hormone in the haemolymph are consistent with values determined for AKHs in other insects, and suggest that Pya-AKH has a rapid turnover with a half-life of ca. 18 min. Measurements of circulating titres of AKH in Pyrrhocoris are only possible in the ELISA described here by using pooled samples of haemolymph, and after preliminary clean-up of the haemolymph samples. The titre of Pya-AKH in resting reproductive female Pyrrhocoris is ca. 1 fmol/μl.     

Restricted specificity of a hyperglycaemic factor from the corpus cardiacum of the stick insect Carausius morosus

Extracts of the corpora cardiaca of the stick insect Carausius morosus elevate the haemolymph carbohydrate concentration in adult and 6th-instar larvae which are ligated behind the first pair of legs, but not in non-ligated (intact) insects. The increase in haemolymph sugars is due to trehalose elevation, is time dependent (with a maximal effect about 90–120 min after injection), and is dose dependent (needing 0.005 gland equivalents for a significant effect and a tenfold higher dose for a maximal response). The hyperglycaemic factor is localised entirely in the corpora cardiaca and appears to be specific to stick insects; corpora cardiaca extracts of two lepidopteran species (Acherontia atropos and Aglais urticae) and of Locusta migratoria have no effect, whereas corpora cardiaca extracts of the stick insects Cuniculina impigra and Sipyloidea sipylus have similar activity to those from C. morosus. This specificity is also shown when S. sipylus is used as the recipient. Synthetic adipokinetic hormone and red pigment concentrating hormone possess no hyperglycaemic activity in the stick-insect system. Two peaks of hyperglycaemic activity were obtained after column chromatography of corpora cardiaca extract of C. morosus on Sephadex G-25 and Sephadex LH-20. The factor seems to act via activation of fat-body glycogen phosphorylase, which, although 60% active in the control insects, is significantly increased to approx. 85% upon corpora cardiaca injection. However, the activation is demonstrated in ligated and intact insects. No significant decrease in the glycogen level of the fat body is observed after corpora cardiaca injection.     

The glycogenolytic effect of the corpus cardiacum on the cockroach nerve cord

Aqueous extracts of corpora cardiaca cause glycogenolysis in the ventral nerve cord of the cockroach. The duration of the glycogenolytic response is shorter than in fat body and requires a higher concentration of extract for its initiation. The evidence suggests that glycogenolysis is accelerated in the presence of extract because of the activation of phosphorylase caused by an increase in the level of cyclic AMP. The activation of nerve cord phosphorylase by the cardiaca factor in vitro is completely inhibited by 1×10^?4 M 5-hydroxytryptamine.     

The catabolism of glucose in Tenebrio molitor: The effects of corpora cardiaca

During the development of the mealworm Tenebrio molitor, the effects of corpora cardiaca (CC) extracts on glucose catabolism were tested. In control insects and in insects receiving CC extracts, the activity of the pentose cycle and the glycolytic-citric acid cycle, were evaluated in vivo by a radiorespirometric method using [1-¹⁴C] glucose and [6-¹⁴C] glucose as substrates. The CC extracts strongly divert glucose from the pentose phosphate pathway, which is very active in Tenebrio molitor. Glucose oxidation is reduced by the CC extracts in pupae and adults but is increased in last instar larvae. It seems that the effects of CC extracts vary depending upon the state of carbohydrate reserves.     

Spatial and temporal distribution of pheromone biosynthesis-activating neuropeptide in Helicoverpa (Heliothis) armigera using RIA and in vitro bioassay.

A [3H]-PBAN (pheromone biosynthesis-activating neuropeptide) analog was synthesized, and binding of the radioligand to a specific PBAN-antiserum was achieved. The inhibition of binding of the radioligand by unlabeled PBAN, several PBAN analogs, and other competitors was studied and a specific radio-immunoassay was developed. Using this radioimmunoassay we found PBAN-like immunoreactivity in methanol extracts of hemolymph and neural tissues from females. Higher levels of PBAN-like immunoreactivity in extracts of brain-suboesophageal ganglion complexes, corpora cardiaca, thoracic ganglia, and abdominal ganglia were observed during the 4-5th h scotophase when compared to the PBAN-like immunoactivity levels during the 6-11th h photophase. On the other hand, the concentrations of PBAN-like immunoreactivity, in the terminal abdominal ganglion were higher during the photophase relative to minimal levels observed during the scotophase, indicating an accumulation before the onset of pheromone production. These differences in concentrations of PBAN were also reflected in the stimulation of in vitro pheromone glands, whereby significant stimulations were obtained by scotophase and photophase brain extracts, scotophase thoracic ganglia extracts, and photophase terminal abdominal ganglia extracts. No detectable levels of PBAN were found in hemolymph extracts during the sampling periods.