Morphology of neurosecretory cells delineated with cobalt applied extracellularly to the cephalic aorta of the insect Rhodnius prolixus

Cobalt applied extracellularly to the cephalic aorta in Rhodnius prolixus filled neurosecretory cells (NSCs) located in the brain, the retrocerebral complex, and the suboesophageal ganglion (SOG). Axons of these cells converged over the corpora cardiaca and corpus allatum and merged into a large tract before travelling posteriorly along the ventral side of the aorta. Cobalt-filled cells in the posterior margins of the brain and the retrocerebral complex lacked extensive dendritic arborizations, suggesting that their cell bodies and/or axonal processes in the retrocerebral complex are directly involved with integrative processes determining hormone release. Cobalt-filled cell bodies in the anterior region of the brain were closely associated with the ocellar nerve, and the cobalt-filled cells in the SOG formed extensive dendritic arborizations in the neuropile, suggesting the involvement of sensory cells in regulation of their electrical activity. The ability to fill NSCs with cobalt applied to the aorta demonstrates that the cephalic aorta of R. prolixus is an important neurohaemal region.     

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.     

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.     

Neurosecretory system of the earwig Labedura riparia, and the rôle of the aorta as a neurohaemal organ

The neurosecretory system of Labedura riparia has been described from sections and whole mounts using a variety of techniques. The pars intercerebralis contains two clusters of medial neurosecretory cells (MNC), each cluster consisting of 8 to 10 A-cells and occasional B-cells. The lateral sides of the brain have a few B-cells. The axons of the median neurosecretory cells terminate in the cephalic aorta (AO), whereas the axons of the lateral neurosecretory cells (LNC) terminate in the corpora cardiaca (CC). It appears that the neurosecretory material (NSM) elaborated in the MNC is stored in the cephalic aorta and that elaborated in the LNC is stored in the corpora cardiaca, which are two oval or elongate bodies composed of large chromophobe and small chromophil cells. Posteriorly there is the oval or elongate corpus allatum (CA) attached to the CC by thick nerves. The CA consists of one cell type only. Both CC and CA contain no A-cell neurosecretory material. It has been suggested that the neurosecretory system of L. riparia is composed of two complexes. One is formed by the medial neurosecretory cells for which the aorta functions as a neurohaemal organ, and the other is formed by lateral neurosecretory cells-lateral neurosecretory pathways-nervi corporis cardiaci-II in which the corpora cardiaca function as a neurohaemal organ.     

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.     

The release of a pheromonotropic neuropeptide, PBAN, in the turnip moth Agrotis segetum, exhibits a circadian rhythm

In the female turnip moth, Agrotis segetum, a pheromone biosynthesis activating neuropeptide (PBAN) stimulates sex pheromone biosynthesis which exhibits a daily rhythm. Here we show data supporting a circadian rhythm in PBAN release from the corpora cardiaca, which we propose regulates the endogenous rhythm in sex pheromone biosynthesis. This conclusion is drawn as the observed daily rhythm in PBAN-like immunoreactivity in the hemolymph is persistent in constant darkness and is phase-shifted by an advanced light:dark cycle. PBAN-like immunoreactivity was found in the brain, the optic lobe, the suboesophageal ganglion and in the retrocerebral complex. In each hemisphere ca. 10 immunopositive neurons were observed in the pars intercerebralis and a pair of stained somata in the dorso-lateral protocerebrum. A cluster of cells containing PBAN-like immunoreactive material was found in the tritocerebrum and three clusters of such cells were found in the SOG. Their processes reach the corpora cardiaca via nervi corporis cardiaci and the dorsal surface of the corpora allata via the nervi corporis allati.     

Myoinhibitory neuropeptides in the American cockroach

A large number of myostimulatory neuropeptides from neurohaemal organs of the American cockroach have been described since 1989. These peptides, isolated from the retrocerebral complex and abdominal perisympathetic organs, are thought to be released as hormones. To study the coordinated action of these neuropeptides in the regulation of visceral muscle activity, it might be necessary to include myoinhibitors as well, however, not a single myoinhibitory neuropeptide of the American cockroach has been described so far. To fill this gap, we describe the isolation of LMS (leucomyosuppressin) and Pea-MIP (myoinhibitory peptide) from neurohaemal organs of the American cockroach. LMS was very effective in inhibiting phasic activity of all visceral muscles tested. It was found in the corpora cardiaca of different species of cockroaches, as well as in related insect groups, including mantids and termites. Pea-MIP which is strongly accumulated in the corpora cardiaca was not detected with a muscle bioassay system but when searching for tryptophane-containing peptides using a diode-array detector. This peptide caused only a moderate inhibition in visceral muscle assays. The distribution of Pea-MIP in neurohaemal organs and cells supplying these organs with Pea-MIP immunoreactive material, is described. Additionally to LMS and Pea-MIP, a member of the allatostatin peptide family, known to exhibit inhibitory properties in other insects, was tested in visceral muscle assays. This allatostatin was highly effective in inhibiting spontaneous activity of the foregut, but not of other tested visceral muscles of the American cockroach.     

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.     

Contribution à l'étude infrastructurale du système neurosécréteur rétrocérébral chez Locusta migratoria migratorioides (R. et F.)

Résumé L'étude infrastructurale des corpora cardiaca de Locusta révèle l'existence de 3 types de fibres neurosécrétrices (portion neurohémale) et d'un seul type de cellules glandulaires (portion endocrine intrinsèque). Elle permet également d'envisager les modalités du rejet des sécrétions exogènes et endogènes.

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Ultrastructural study of the retrocerebral neurosecretory system in Locusta migratoria migratorioides (R. et F.)I. The corpora cardiaca

Summary An ultrastructural study of the corpora cardiaca of Locusta migratoria migratorioides shows three neurosecretory fiber types in the neurohaemal part of these organs; only one cellular type constitutes the intrinsic glandular part of the corpora cardiaca. This study also shows sites of release of stored extrinsic neurosecretory material and of products elaborated by intrinsic glandular cells of the corpora cardiaca.

     

New features of the brain-retrocerebral neuroendocrine complex of the locust Schistocerca vaga (scudder)

Summary The techniques of axonal iontophoresis and cobalt sulfide precipitation were used to elucidate the relationships of the brain's neurosecretory cell groups and the retrocerebral complex of the locust Schistocerca vaga. The axons of the nervi corporis cardiaci I (NCC I) arise (1) from the medial neurosecretory cells of the protocerebrum, showing only limited branching, looping or spiraling; and (2) from a cell group previously undescribed for this species, located in the tritocerebrum. The axons project into the neurohemal and the glandular portions of the corpora cardiaca and into the hypocerebral ganglion, but not into the corpora allata. Axons of the NCC II arise from the lateral neurosecretory cells of the protocerebrum and project into the center of the corpora allata via the nervi corporis allati I (NCA I), as well as into the neurohemal and glandular portions of the corpora cardiaca. Axons of the NCC III arise from another newly described cell group in the tritocerebrum and end in both the corpora cardiaca and corpora allata. Axons of the NCA II arise from cells in the subesophageal ganglion and also end in the corpora allata.Supported by NIH Predoctoral Fellowship No. 5 F 01 GM 43816-03, NSF Grant GB-23033 and NIH Grant CA-05045 to H. A. Bern and USPHS Grant 1 R 01 NS09404 to C.H.F. Rowell.I wish to express my gratitude to Professors H.A. Bern and C.H.F. Rowell for unending encouragement and advice. I am indebted to Dr. Mick O'Shea for instruction in the cobalt/axonal iontophoresis method, and to Ms. Bea Bacher for excellent technical assistance.     

Neural control of rhythmic pheromone gland exposure in Utetheisa ornatrix (Lepidoptera: Arctiidae)

The rhythmic exposure of the sex pheromone gland during calling in female Utetheisa ornatrix (L.) (Lepidoptera: Arctiidae) is under neural control. Two lines of evidence support this conclusion. (1) Bisection of the ventral nerve cord of adult females prevented calling while sham-operations had little effect. (2) Brief electrical stimulation of the ventral nerve cord in isolated abdomens elicited extended trains of regularly spaced gland exposures indistinguishable from normal calling behaviour. The coordination of calling behaviour is localized in the terminal abdominal ganglion and the peripheral structures that it innervates. Removal of the corpora allata and corpora cardiaca, neurohaemal organs previously implicated in calling control, did not affect calling behaviour.     

Identification of neuronal pathways between the stomatogastric nervous system and the retrocerebral complex of the cockroach Periplaneta americana (L.)

Summary The neuronal pathways connecting the stomatogastric nervous system with the retrocerebral complex of the cockroach, Periplaneta americana, were investigated by means of axonal cobalt chloride iontophoresis. Somata in the hypocerebral ganglion and in the nervus recurrens sending their axons to different parts of the stomatogastric nervous system were traced. Some axons in the oesophageal nerve arise from large perikarya in the anterior part of the pars intercerebralis and pass via the NCCI to the corpora cardiaca and the oesophageal nerve. They form a profuse dendritic tree in the protocerebrum. Fibers of the NCC I and NCC II as well as the NCA I and NCA II enter the stomatogastric nervous system via the hypocerebral ganglion.     

The distribution of pheromone-biosynthesis-activating neuropeptide (PBAN) immunoreactivity in the central nervous system of the corn earworm moth,Helicoverpa zea

Summary Production of sex pheromone in several species of moths has been shown to be under the control of a neuropeptide termed pheromone-biosynthesis-activating neuropeptide (PBAN). We have produced an antiserum to PBAN from Helicoverpa zea (Lepidoptera: Noctuidae) and used it to investigate the distribution of immunoreactive peptide in the brain-suboesophageal ganglion complex and its associated neurohemal structures, and the segmental ganglia of the ventral nerve cord. Immunocytochemical methods reveal three clusters of cells along the ventral midline in the suboesophageal ganglion (SOG), one cluster each in the presumptive mandibular (4 cells), maxillary (12–14 cells), and labial neuromeres (4 cells). The proximal neurites of these cells are similar in their dorsal and lateral patterns of projection, indicating a serial homology among the three clusters. Members of the mandibular and maxillary clusters have axons projecting into the maxillary nerve, while two additional pairs of axons from the maxillary cluster project into the ventral nerve cord. Members of the labial cluster project to the retrocerebral complex (corpora cardiaca and cephalic aorta) via the nervus corpus cardiaci III (NCC III). The axons projecting into the ventral nerve cord appear to arborize principally in the dorsolateral region of each segmental ganglion; the terminal abdominal ganglion is distinct in containing an additional ventromedial arborization in the posterior third of the ganglion. Quantification of the extractable immunoreactive peptide in the retrocerebral complex by ELISA indicates that PBAN is gradually depleted during the scotophase, then restored to maximal levels in the photophase. Taken together, our findings provide anatomical evidence for both neurohormonal release of PBAN as well as axonal transport via the ventral nerve cord to release sites within the segmental ganglia.Abbreviations A aorta - Br-SOG brain-suboesophageal ganglion complex - CC corpus cardiacum - PBS phosphate-buffered saline - PLI PBAN-like immunoreactivity - TAG terminal abdominal ganglion - VNC ventral nerve cord     

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.     

Anatomy of the neurosecretory cells in the cerebral and subesophageal ganglia of the female European corn borer moth,Ostrinia nubilalis (Hübner) (Lepidoptera: Pyralidae)

The anatomy of the neurosecretory cells in the brain-subesophageal ganglion complex of female European corn borer moth Ostrinia nubilalis (Lepidoptera: Pyralidae) was studied using histological and cobalt backfilling techniques. Histological staining revealed the presence of 2 median and one lateral neurosecretory cell groups in the brain. These brain neurosecretory cells are made up of mainly type A cells with a few type B cells in the median group. Three type C neurosecretory cell clusters occupy the apparent mandibular, maxillary, and labial neuromeres at the ventral median aspect of the subesophageal ganglion. Axonal pathways of the neurosecretory cell groups were delineated by retrograde cobalt filling from the corpora cardiaca. Fibers of the 3 brain neurosecretory cell groups merged to form a distinct axonal tract that exits the brain via the fused nervi corporis cardiaci-1 + 2. Cobalt backfilling from the corpora cardiaca filled 4 groups of cell bodies in the subesophageal ganglion. The presence in the subesophageal ganglion of extensive dendritic arborizations derived from the brain suggests interactions between neurosecretory cell groups in the 2 head ganglia.     

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.     

Substances resembling peptides of the vertebrate gonadotropin system occur in the central nervous system of Periplaneta americana L.: Immunocytological and some biological evidence

Cockroach cerebrum, retrocerebral complex and suboesophageal ganglion were studied by immunocytochemistry to detect the presence of luteinizing hormone (LH), follicle stimulating hormone (FSH), gonadoliberin (LHRF), thyroid stimulating hormone (TSH) and thyrotropin releasing hormone (TRH) immunoreactive neurons. Gonadotropin system (LH, FSH, LHRF) immunoreactive perikarya and/or nerve fibres were encountered in various regions. In contrast, no labeling could be observed with antisera to either hormone of the vertebrate thyrotropin system (TSH, TRH). Preliminary data indicate that extracts of corpora cardiaca, which by immunocytochemical methods are shown to contain abundant immuno-LH-like material, are capable of stimulating testosterone secretion in mouse Leydig cells (positive LH bioassay). Functional and evolutionary aspects of the presence of vertebrate peptides in insects are discussed.     

A comparative ultrastructural and physiological study on melanophores of wild-type and periodic albino mutants of Xenopus laevis

Summary The central and visceral nervous systems of the cockroach Periplaneta americana were studied by means of the peroxidase-antiperoxidase immunocytochemical method, with the use of antibody to bovine pancreatic polypeptide (PP). PP-like immunoreactive neuron somata are most numerous in the brain; at least 6 pairs of cell groups occur in clearly defined regions. Three pairs of cells each are also present in the suboesophageal ganglion and the thoracic ganglia, one pair of a single cell each in the first abdominal and the frontal ganglia, and 4 to 6 pairs of single cells in the terminal ganglion. No reactive cells were found in the retrocerebral complex and the second to the fifth abdominal ganglia. The axons containing PP-like immunoreactivity issue many branches that are distributed in the entire brain-retrocerebral complex, ventral cord, and visceral nervous system. PP-like immunoreactive material produced in the brain seems to be transported by three routes: protocerebrum to corpora cardiaca (-allata) through the nervi corporis cardiaci, tritocerebrum to visceral nervous system through frontal commissures, and to ventral cord through circumoesophageal connectives.A possible homology between the mammalian brain-GEP (gastro-enteropancreatic) system and the brain-midgut system of this insect is discussed.     

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.