Ultrastructure of retrocerebral complex of the earwig, Euborellia annulipes, and rôle of aorta as a neurohaemal organ

The ultrastructure of the retrocerebral endocrine-aortal complex of the earwig, Euborellia annulipes has been studied. The space between the inner and outer stromal layers of the aorta is occupied by numerous axon terminals and pre-terminals containing large electron dense granules (NS-I) of approximately 100 to 220 nm and a few axon terminals having small granules (NS-II) of approximately 40 to 90 nm; the former appear to belong to medial neurosecretory A-cells, and the latter to the B-cells of the brain. The corpora cardiaca consist of intrinsic cells with mitochondria and multivesicular bodies. Granules of type NS-II and NS-III are observed in the axon terminals and pre-terminals in the corpora cardiaca. The NS-II are identical to those found in the aorta and are probably the secretions of the lateral B-cells. Granules of type NS-III are 40 to 120 nm and electron dense, and are intrinsic in origin. Similar granules occur in the intrinsic cells of the corpora cardiaca. E M studies have confirmed the rôle of the aorta as a neurohaemal organ for the medial neurosecretory cells, and the corpora cardiaca for the lateral neurosecretory cells of the brain. The corpora cardiaca also act as a reservoir for the intrinsic secretion. The corpus allatum is a solid body consisting of parenchymal cells with prominent nuclei, mitochondria, and endoplasmic reticulum. In between its cells are occasional glial cells and also neurosecretory as well as non-neurosecretory axons. The gland is devoid of A-cell NSM.     

Ultrastructural differences of neurosecretion granules in the corpora cardiaca of the honeybee with and without infection by Nosema apis

Axons of corpora cardiaca in the Nosema infected honeybees contained numerous tightly packed neurosecretion granules. These granules invariably possessed high electron densities. Neurosecretion granules of similar size were also observed in the axons of corpora cardiaca in the healthy honeybees. But these granules were shown to possess various electron densities. Image analysis revealed that some of these granules possessed an electron dense core, and the electron densities decreased gradually from the core, to the fringe of the granule. Some granules appeared to be completely broken down into fine granular substances, while others appeared to be completely broken down into finer particles. It is suggested that in the healthy honeybees, the releasing of neurosecretion from the corpora cardiaca had taken place normally, whereas in the diseased bee, the releasing mechanism had been blocked. The blockage is probably due to the infection.     

Variations de la tendance au vol soutenu du criquet Pélerin Schistocerca gregaria après implantations de corpora cardiaca

An attempt has been made to determine the influence of the corpora cardiaca on sustained flight tendency shown by Schistocerca gregaria male imagos reared in dense groups or in isolation, taking into consideration the presence or absence of the corpora allata. Corpora cardiaca either whole or in part (glandular or neurohaemal lobe) from either good or poor flyers were inserted into the abdomen of either good or poor flyers. A small amount of extra corpora cardiaca or neurohaemal lobe from good flyers favours sustained flight. A large amount from good or poor flyers inhibits flight. Allatectomized recipients react like intact animals, but locusts isolated for several generations scarcely react. Glandular lobes are without effect and so are corpora cardiaca taken from good fliers about 15 days after their connexions with the brain have been cut. Organs taken from good fliers just after a long flight are also of little effect. It is concluded that factors are elaborated by the pars intercerebralis, then stored and activated in the neurohaemal part of the corpora cardiaca: these organs alone do not control flight tendency.     

Neurosecretion XVII. Experimentally induced release of neurosecretory material by exocytosis in the insect Leucophaea maderae

Summary In the corpora cardiaca of the insect Leucophaea the administration of serotonin elicits ultrastructural features indicative of the extrusion of neurosecretory material by exocytosis. The response to the stimulus and the process of extrusion seem to occur at considerable speed. Nearly all of the 30 test animals, fixed at various intervals starting as early as 3 min after the injection of the drug, show granules captured at the moment of leaving the axon as well as fully exteriorized secretory material. The fact that many of these granules are much smaller than the typical neurosecretory type speaks for intracellular fragmentation of the latter prior to the discharge of this cellular product. After 25 min or more the extruded electron dense structures show signs of breakdown. The apparent speed of these phenomena accounts for the dearth of omega-type configurations observed in unstimulated specimens of this species. The possible relationship between the membrane phenomena involved in exocytosis and the transient protrusions of bounding membranes of neurosecretory granules described in earlier papers remains to be clarified.Supported by N.S.F. research grant BMS 74-12456     

Corpora Cardiaca-Allata Complex of the Larvae of the Pink Bollworm,Pectinophora gossypiella. An Ultrastructural Study in Relation to Diapause

Raina, A. K., Borg, T. K. 1980. Corpora cardiaca-allata complex of the larvae of the pink bollworm, Pectinophora gossypiella. An ultrastructural study in relation to diapause. (Department of Entomology, North Dakota State University of South Carolina, School of Medicine, Columbia, U.S.A.) — Acta zool. (Stockh.) 61(2): 65–77. The corpora cardiaca (CC) and corpora allata (CA) of the pink bollworm, Pectinophora gossypiella, were studied at the ultrastructural level during induction maintenance, and termination of larval diapause. The CC is composed of 5–6 intrinsic secretory (IS) cells, glial cells, and axons that carry electron dense (ED) and electron lucent (EL) granules from the brain. The IS cells produce ED granules with an average diameter of 110 ± 26 nm. During diapause, the axons with ED granules showed large accumulations of neurosecretory granules, but the axons with the EL granules contained lesser amounts. The CA is made up of approximately 25 large cells and axons that pass through the CC from the brain. Most of the axons take up a peripheral position. A characteristic feature of CA cells during diapause was the presence of stacks of convoluted tubules of the smooth endoplasmic reticulum (SER) that may be associated with juvenile hormone synthesis. The IS cells of the CC appeared to be inactive during diapause.     

Ultrastructural localization of unique neurosecretory granules in the corpora cardiaca of the stable fly,Stomoxys calcitrans,and the Tsetse Fly,Glossina morsitans

Ultrastructural analysis of the corpora cardiaca of the stable fly, Stomoxys calcitrans, and the tsetse fly, Glossina morsitans, revealed the presence of elementary neurosecretory granules (ENG) unique to the intrinsic neurosecretory cells (INC) of these species. In addition to electron‐dense spheres, the INC of the corpus cardiacum of the stable fly contain electron‐dense angular granules, either square or rectangular in shape, while the INC of the tsetse fly contain electron‐dense spindle‐shaped ENG. The distinctive granules of these INC can be traced within nerves to their sites of storage and release, eliminating the need for labeling with artificial probes. Although the INC of the corpus cardiacum of most species have been found to be fuchsinophilic, neither the INC of the stable fly nor the tsetse fly are aldehyde‐fuchsinophilic. These peptigenic cells offer neuroendocrinologists a unique opportunity to study the physiology and biochemistry of neurosecretory cells. J. Morphol. 240:155–168, 1999. Published 1999 Wiley‐Liss, Inc.     

Studies on the neurosecretory system and retrocerebral endocrine glands of Nezara viridula Linn. (Heteroptera: Pentatomidae)

The neurosecretory system and retrocerebral endocrine glands of Nezara viridula Linn. have been described on the basis of in situ preparations and histological sections employing the paraldehyde fuchsin (PF) and performic acid-victoria blue (PAVB) techniques. In the brain of N. viridula, there are two medial groups–each consisting of five neurosecretory cells which belong to A-type. The lateral neurosecretory cells are absent. The axons of the two groups of medial neurosecretory cells (MNC) compose the two bundles of neurosecretory pathways (NSP) that decussate in the anterodorsal part of the protocerebrum. The two pathways, after the cross-over, run deep into the protocerebrum and deutocerebrum and emerge as NCC-I from the tritocerebrum. The nervi corporis cardiaci-I (NCC-I) of each side which are heavily loaded with NSM terminate in the aorta wall. Thus, the neurosecretory material (NSM), elaborated in the medial neurosecretory cells of the brain, is stored in the aortic wall and nervi corporis cardiaci-I (NCC-I). The NCC-II are very short nerves that originate from the tritocerebrum and terminate in the corpora cardiaca (CC) of their side. Below the aorta, but dorsal to the oesophagus, lie two oval or spherical corpora cardiaca. A corpus allatum (CA) lies posterior to the corpora cardiaca (CC). The corpora cardiaca do not contain NSM; only the intrinsic secretion of their cells has been occasionally observed which stains orange or green with PF staining method. The corpus allatum sometimes exhibits PF positive granules of cerebral origin. A new connection between the corpus allatum and aorta has been recorded. The suboesophageal ganglion contains two neurosecretory cells of A-type which, in structure and staining behaviour, are similar to the medial neurosecretory cells of the brain. The course and termination of axons of suboesophageal ganglion neurosecretory cells, and the storage organ for the secretion of these cells have been reported. It is suggested that the aortic wall and NCC-I axons function as neurohaemal organ for cerebral and suboesophageal secretions.     

Isolation and structure of two novel 6-kDa dimeric peptides from the corpora cardiaca of the insect Locusta migratoria. Molecular mass determination by mass spectrometry

We have isolated two major 6-kDa peptides from extracts of corpora cardiaca of adult females of Locusta migratoria. These peptides have been characterized by peptide sequencing and liquid secondary-ion mass spectrometry. They are structurally related dimers, one (6278.5 Da) being a homodimer (A-A chains), the other (6280.5 Da) being a heterodimer (A-B chains). A 60% similarity exists between the A and B chains. Both peptides have been chemically synthesized and the synthetic compounds appeared to be identical to the native ones. Polyclonal antibodies raised against each of these peptides demonstrated that they were contained within the secretory granules of the intrinsic cells of the glandular lobes of the corpora cardiaca. The physiological significance of these two peptides is unknown but, using the synthetic peptides, we are currently probing their biological role.     

Adipokinetic hormone controls lipid metabolism in adults and carbohydrate metabolism in larvae of Manduca sexta

The peptide hormone which controls activation of fat body glycogen phosphorylase in starving larvae of Manduca sexta was isolated from larval corpora cardiaca and sequenced by FAB tandem mass spectrometry. It was found to be identical with Manduca AKH. This, together with earlier observations, demonstrates that in M. sexta AKH controls glycogen phosphorylase activation in starving larvae while in adults it controls lipid mobilization during flight. Larval corpora cardiaca contain about 10 times less AKH than the corpora cardiaca of adults. The corpora cardiaca of M. sexta appear to contain only one AKH.     

Cytophysiology of the glandular lobe of the corpora cardiaca: ergastoplasmic granules and their significance

The number of ergastoplasmic granules in the glandular lobe of the corpora cardiaca is counted in Locusta migratoria migratorioides R. and F. and Schistocerca gregaria Forsk., male adults of different ages, grouped or isolated, having flown or not, and reared in various conditions of hygrometry and temperature. A good correlation was found between the number of ergastoplasmic granules and the utilization of the adipokinetic hormone. Ergastoplasmic granules may représent an original mechanism of hormonal storage used in view of heavy metabolic requirements.     

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.     

Production of Monoclonal Antibodies Against Corpora Cardiaca Extracts of Locusta Migratoria: A Potential Tool for the Isolation of Insect Neurohormones

Summary

Corpora cardiaca of Locusta migratoria, contain the axon endings of the neurosecretory cells of the brain and store in neurosecretory granules a variety of mostly unidentified neurohormones. Homogenates of corpora cardiaca served to generate a battery of monoclonal antibodies screened by their immunoreactivity to antigenic determinants present in the neurosecretory cells of the pars intercerebralis in the brain. The results are illustrated with three selected monoclonal antibodies which recognize antigens located within the neurosecretory granules of the pericarya of the pars intercerebralis, the cerebro-cardiac axon tracts and the axonic endings in the neurohaemal part of the corpora cardiaca. The apparent molecular weights of these antigenes were determined by Western blotting. We discuss the potential of these monoclonal antibodies for the isolation and structure determination of neuropeptides.     

Effect of endocrine glands on the unfixed total haemocyte counts of the bug Halys dentata

Changes in total haemocyte counts in relation to the endocrine glands have been studied in Halys dentata. Unfixed total haemocyte counts were taken after extirpation and implantation of three endocrine structures. It is concluded that haemocyte count decreases after the extirpation of the corpora allata in the early life span of adults, while an abrupt increase was noted after the 7th day. When both the corpora allata and corpora cardiaca are extirpated, the count was significantly decreased throughout the life span of adults. However, when only the corpora cardiaca were removed there was no significant variation up to the 7th day, but later on the count gradually decreased. The implantation of brain, corpora cardiaca and allata is followed by a significant rise in the haemocyte count throughout the life span. Total haemocyte count also fluctuated after the implantation of corpora allata and brain, separately. After implantation of corpora cardiaca of one-day-old adult insects there was no variation in the total haemocyte count while the corpora cardiaca of 6-day-old adults when implanted in one-day-old adults cause a significant rise in the total haemocyte count. Therefore, it is concluded that the corpora cardiaca influences the total haemocyte count after a critical period.     

Evidence for a crustacean hyperglycemic hormone-like molecule in the nervous system of the stick insect,Carausius morosus

Summary Histological sections of the brain, suboesophageal ganglion, and the corpora cardiaca/corpora allata complex were examined for the presence of crustacean hyperglycemic hormone-like immunoreactive material. With the use of an antiserum directed against the hyperglycemic hormone of Carcinus maenas, immunofluorescence was found in the median portion of the pars intercerebralis, and the corpora cardiaca. Extracts of corpora cardiaca were examined by radioimmunoassay for competitive binding to the antiserum; one pair of corpora cardiaca contains at least 7 pg crustacean hyperglycemic hormone-like material.     

Anchorage of secretion-competent dense granules on the plasma membrane of bovine platelets in the absence of secretory stimulation

The ultrastructural changes in electropermeabilized bovine platelets that accompany the Ca2(+)-induced secretion of serotonin were investigated in ultra-thin sections of chemically fixed cells. Such preparations permitted us to study both the localization of and the structures associated with serotonin-containing dense granules. Localization of dense granules within cells was examined by measuring the shortest distances between the granular membranes and the plasma membrane. About 40% of total granules were located close to the plasma membrane at an average distance of 10.8 +/- 1.6 nm. 71% of the total number of granules were localized at a similar average distance of 12.5 +/- 2.7 nm in intact platelets. The percentage of granules apposed to the plasma membrane corresponded closely to the percentage of total serotonin that was maximally secreted after stimulation of the permeabilized (38 +/- 4.9%) and the intact platelets (72 +/- 3.6%). Furthermore, the percentage of granules anchored to the membrane, but not of those in other regions of permeabilized cells, decreased markedly when cells were stimulated for 30 s by extracellularly added Ca2+. The decrease in the numbers of granules in the vicinity of the plasma membrane corresponded to approximately 22% of the total number of dense granules that were used for measurements of the distances between the two membranes and corresponded roughly to the overall decrease (15%) in the average number of the granules per cell. Most dense granules were found to be associated with meshwork structures of microfilaments. Upon secretory stimulation, nonfilamentous, amorphous structures found between the plasma membrane and the apposed granules formed a bridge-like structure that connected both membranes without any obvious accompanying changes in the microfilament structures. These results suggest that the dense granules that are susceptible to secretory stimulation are anchored to the plasma membrane before stimulation, and that the formation of the bridge-like structure may participate in the Ca2(+)-regulated exocytosis.     

Number and size of intracisternal granules in the adipokinetic hormone-secreting cells of locusts: a phase-dependent characteristic

Abstract.The intracisternal (= ergastoplasmic) granules in the adipokinetic hormone-secreting cells of the glandular lobes of the corpora cardiaca in Locusta migratoria migratorioides represent accumulations of adipokinetic prohormones within cisternae of the rough endoplasmic reticulum. Solitary locusts have more and larger intracisternal granules than gregarious locusts. This coincides with the general locomotor activity and thus the energy metabolism in solitary locusts being quite different from that of gregarious locusts, which apparently has consequences for the amounts of adipokinetic hormones synthesized and/or released and, consequently, for the storage of these hormones in the intracisternal granules. These granules apparently function as supplementary stores of secretory material.     

The Corpus Cardiacum Neurosecretory Cells of Schistocerca gregaria. Electron Microscopy of Resting and Secreting Cells

The corpora cardiaca of Schistocerca consist of a neurohaemal part containing mainly extrinsic neurosecretory axons coming from the brain, and of a glandular part consisting mainly of intrinsic neurosecretory cells. Some extrinsic axons penetrate into the glandular region, and innervate intrinsic corpus cardiacum neurosecretory cells. The fine structure of the latter has been examined and related to other neurosecretory cell types. Secretion occurs by exocytosis. Omega-profiles are more frequently observed in corpora cardiaca stimulated electrically or by acetylcholine than in the controls.     

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.     

Peptidomics of the pars intercerebralis-corpus cardiacum complex of the migratory locust, Locusta migratoria.

The pars intercerebralis-corpora cardiaca system (PI-CC) of insects is the endocrinological equivalent of the hypothalamus-pituitary system of vertebrates. Peptide profiles of the pars intercerebralis and the corpora cardiaca were characterized using simple sampling protocols in combination with MALDI-TOF and electrospray ionization double quadrupole time of flight (ESI-Qq-TOF) mass spectrometric technologies. The results were compared with earlier results of conventional sequencing methods and immunocytochemical methods. In addition to many known peptides, several m/z signals corresponding to putative novel peptides were observed in the corpora cardiaca and/or pars intercerebralis. Furthermore, for a number of peptides evidence was provided about their localization and MALDI-TOF analysis of the released material from the corpora cardiaca yielded information on the hormonal status of particular brain peptides.     

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.