Dynamics, following axotomy, of the A1 and A2 median protocerebral neurosecretory cells of the African locust. I. Histophysiological study

In the African locust, the secretory dynamics of the A1 and A2 median protocerebral neurosecretory cells (M-NSC) is evaluated by the product content and the gonadotropic action of these cells. The axotomy of the A1 and A2 M-NSC disturbes their secretory dynamics. The axonal regeneration, if it leads to a reconnexion with the corpora cardiaca (CC), restores a normal secretory dynamics of the M-NSC. Without reconnexion to the CC, the nervi corpori cardiaci interni (NCCI) do note regenerate or regenerate to form new nerve endings. In these cases, the secretory dynamics of the M-NSC remains more or less inhibited specially that of the A2 M-NSC which can be completely suppressed. A functional state of the A2 M-NSC could be necessary for the beginning of the vitellogenesis. In the CC, separated from the regenerating M-NSC, the A1 and A2 neurosecretory products are transformed into large globules which became intensively basophil before disappearance.     

Dynamics, following axotomy, of the A1 and A2 median protocerebral neurosecretory cells of the African locust. II. Ultrastructural study

In the African locust after axotomy of the A1 and A2 median protocerebral neurosecretory cells (M-NSC), the decrease of the basophil neurosecretory products into the pericaryons does not result from an increase of the granulolysis but results from an inhibition of the production. The A1 and A2 neurosecretory products, stored anteriorly and posteriorly to the site of the axonal section, seem destroyed by: 1. a suspected entrance of lytic enzymes into the granule (individual granulolysis); 2. a vacuolar inclusion of small or big cytoplasmic areas rich in granules (partial or total collective granulolysis). The axons of the M-NSC, regenerated without reconnexion to the corpora cardiaca (CC), are not separated by glial elements. This glial deficiency could be at the origin of the inhibition of the neurosecretory dynamics observed in the A1 and A2 M-NSC after axotomy and regeneration without reconnexion to the CC.     

Intervention des cellules neurosecretrices medianes dans la castration parasitaire d'Anacridium aegyptium (Orthoptère)

The median neurosecretory cells (M-NSC) of Anacridium aegyptium were studied by light and electron microscopy during the ovarian diapause (autumn and winter) and the ovarian activity (spring) in normal females and in females infected by a tachinid fly Metacemyia calloti. In spring, the M-NSC contain comparatively much stainable material in normal females than in parasitized ones. This difference results from the ovarian maturity of normal females and the ovarian immaturity of parasitized females.The activity of the M-NSC was assessed in spring using the evolution of the radioactivity of the pars intercerebralis (PI) and corpora cardiaca (CC) after injection of ³⁵S-cysteine. The activity of the M-NSC is impaired in the parasitized females without ovarian development.The ovarian diapause was broken by massive implantations of corpora allata (CA) or electrical stimulations of the PI. Implantations of CA induce in parasitized females the same state of ovarian development than during natural activity in spring. Electrical stimulations of the PI. which increase the activity of the M-NSC. enhance the ovarian development of the parasitized females. A hypoactivity of the M-NSC is involved in the ‘castration’ of the Egyptian grasshopper.     

Experimental evidence for a neuroendocrine control of ecdysone biosynthesis in adult females of Locusta migratoria

The considerable increase in ecdysteroid concentration which occurs in normal Locusta ovaries at the end of each cycle of oöcyte maturation is prevented if the median neurosecretory cells of the pars intercerebralis are cauterized, or if the corpora cardiaca are excised 24 hr before the onset of ecdysone synthesis in normal females. Implantation of additional brain-corpora cardiaca complexes into young vitellogenic females advances the time of ecdysone synthesis by some 12 hr. Oöcyte growth itself is not affected in these different types of experiments.It is inferred from the data of the present study that ecdysone synthesis in the follicle cell epithelium of maturing Locusta ovaries is stimulated by a neurohormone produced in the median neurosecretory cells of the pars intercerebralis and secreted into the blood via the corpora cardiaca.     

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.     

Synthesis, transport, and release of a neurohormone by cultured neuroendocrine glands from the cockroach, Leucophaea maderae

A hindgut-stimulating neurohormone synthesized in vitro by the neurosecretory cells of cultured brains of Leucophaea maderae passes through the nervi corporis cardiaci I into the corpora cardiaca and is released into the culture medium. As much as 90 per cent of the hormone breaks down in the medium during a 3-day incubation period, and the amount recovered represents only a small fraction of the amount actually released.     

Synthesis of a homodimer neurohormone precursor of locust adipokinetic hormone studied by in vitro translation and cDNA cloning

The homodimer neurohormone precursor P1, consisting of 41 residue subunits or A-chains, is synthesized by the glandular neurosecretory cells of the corpora cardiaca (CC) of the locust Schistocerca gregaria. Processing of P1 generates two copies of a 10 amino acid peptide neurohormone (AKH I) and one copy of a homodimer peptide (APRP 1). Here we show that the P1 dimer is formed from two independent A-chain translation products. Translation of CC mRNA in vitro produces a prominent 6.4 kd protein, the synthesis of which can be blocked by oligonucleotides hybridizing to mRNA encoding the A-chain. Northern blot experiments suggest that the 6.4 kd protein is produced by an integral of 500 base mRNA. cDNA cloning reveals a pre-A-chain structure in which a single copy of the A-chain is preceded by a 22 amino acid signal peptide. This evidence indicates that the P1 dimer is synthesized by coupling of very small translational products rather than by folding and processing of a larger protein containing more than one copy of the A-chain.     

Release from the brain and acquisition by the corpus cardiacum of a neurohormone in vitro

Hindgut stimulating neurohormone (HSN) was synthesized and stored by cultured brains of the cockroach, Leucophaea maderae. The presence of either HSN or cultured corpora cardiaca in the medium caused the brains to release their accumulated HSN. The corpora cardiaca were able to sequester HSN from the medium when the concentration was above a threshold level. Thus, the corpus cardiacum may provide an homeostatic mechanism for maintaining physiological levels of neurohormone.     

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.     

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.     

Studies on the neurosecretory system of Ranatra elongata fabricius (Hemiptera: Nepidae) with reference to the distal fate of NCC I and II

With the help of PF and PAVB bulk-stained preparations and sections the neurosecretory system of Ranatra elongata has been described. Two medial, each of 9-10 cells, and two lateral, each of 3-4 cells, groups of neurosecretory cells have been observed in the protocerebrum. Only the A-cells have been found to be positive to PAVB histo- and cyto-chemical technique. Axons of the A-cells after traversing the proto- and deuto-cerebrum emerge from the tritocerebrum as the NCC I. The NCC I after bypassing the corpora cardiaca penetrate the aorta wall. There is no physical continuity between the corpora cardiaca and the NCC I and the two are separable. The NSM from the A-cells, transported by their nerve fibers, has been observed in the aorta wall. On the basis of large accumulation on NSM in the aorta wall the latter has been considered as the storage-and-release organ for the A-material. Corpora cardiaca are found to be devoid of A-material. Axons from the B-cells, after emergence from the tritocerebrum as the NCC II, have been observed to penetrate the corpora cardiaca. On the basis of ample amounts of B-material the glands have been considered as the storage-and-release organ for the B-material only. Observations are compared with results on related species and it is concluded that two independent organ complexes constitute the neurosecretory systemt of R. elongata. The A-cells, their pathways, the NCC I, and the aorta wall comprise the first; and the B-cells, their pathways, the NCC II, and the corpora cardiaca the second. The former is concerned with the elaboration, transportion, storage-and-release of the A-material and the latter with the B-material. Finally arguments are presented to include the aorta wall in the neurosecretory system.     

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.

     

The cardiacal neurosecretory system and associated organs of an adult mosquito, Aedes aegypti

Unlike most other insects, mosquitoes do not possess discrete corpora cardiaca composed of neuropile, intrinsic neurosecretory cells and glial cells. Cells homologous with the intrinsic neurosecretory cells of other insects are located at the junction of the neck and thorax of mosquitoes, close to the corpora allata. These cells are named cardiacal neurosecretory cells. Axons run forwards from the cardiacal neurosecretory cells into the allatal nerves. Neurosecretory release sites occur over almost the whole of the nervi corporum cardiacorum, allatal nerves and oesophageal nerves, and these nerves constitute a very extensive neurohaemal organ for many of the cerebral neurosecretory cells. The neurosecretory release sites of the cardiacal neurosecretory cells appear to be in the allatal nerves and possibly also on the perikarya of these cells.     

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.     

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.     

On the structure of the peptidoglycan of cell walls from Myxobacter AL-1 (Myxobacterales)

Basically the peptidoglycan of Myxobater AL-1 consists of alternating β-1,4-linked N-acetylglucosamic-N-acetylmuramic acid chains. After splitting the aminosugar backbone with a specific algal enzyme three subunits arise: a monomer, a dimer and a trimer. Investigation of the monomer with specific enzymes and comparison of the degradation products to standards derived from other bacterial peptidoglycans suggest the following structure of the monomer peptide: l-alanyl-d-glutamic-l-meso-diaminopimelic-d-alanine. A d-alanyl-d-meso-diaminopimelic acid bond is the bridgebond between the peptides of the subunits.     

Immunochemical analysis of the distribution of the new ovary maturating neurohormone during development of the African locust,Locusta migratoria

Summary Following our prior identification of a gonadotropic neurohormone isolated from the neurosecretory lobe of the corpora cardiaca of the African locust, we have raised a polyclonal antiserum against this new molecule. In the present paper, we characterize this antiserum using enzyme-linked immunosorbent assay and Western blotting. The latter procedure reveals that the immune serum specifically recognizes the neurohormone, which we have termed ovary maturating parsin. Immunohistochemistry, enzyme-linked immunosorbent assay and Western blotting were used to analyze the distribution of this gonadotropic neurohormone throughout the central nervous system during development. It is produced only by the type-B neurosecretory cells of the pars intercerebralis-corpora cardiaca system and is present both in males and females throughout life from embryo to adult. This permanent expression suggests that the neurohormone may have functions other than its primary direct gonadotropic role in females.     

Comparative immunocytochemical study of release sites of insulin,glucagon and AKH-like products in Locusta migratoria,Periplaneta americana,and Carausius morosus

Summary Insulin, glucagon and adipokinetic hormone antisera were applied to the corpora cardiaca, perisympathetic organs, neurohemal areas and peripheral neurosecretory cells of three insect species, the locust Locusta migratoria, the cockroach Periplaneta americana, and the stick insect Carausius morosus. The neurohemal part of the corpora cardiaca was shown to be immunoreactive to both insulin and glucagon antisera while the glandular cells reacted to adipokinetic hormone antisera. The perisympathetic organs seem to be devoid of these three substances, but certain peripheral neurohemal areas contained AKH and glucagon immunoreactive products. The latter were found to originate in the peripheral neurosecretory cells.     

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.     

Système endocrine et physiologie de la diapause imaginale chez le criquet égyptien, Anacridium aegyptium

The Egyptian locust, Anacridium aegyptium, has four protocerebral neurosecretory centres: the A to B neurosecretory cells of the pars intercerebralis (the A cells are rich in fuchsinophil material and the B cells are devoid of fuchsinophil neurosecretion), the voluminous C neurosecretory cells poor in neurosecretion, and the median sub-ocellar neurosecretory cells.From September to the beginning of January, imaginal diapause is characterized by an accumulation of the median neurosecretion in the pars intercerebralis-corpora cardiaca system, by small corpora allata, and, in the female, by a stop in oöcyte development although the male's sexual activity is still not altered. Allatectomy suppresses neither the male's sexual behaviour nor its fecundity. From January, the increase of the photoperiod causes a release of the median neurosecretion in both sexes, an increase of the volume of the corpora allata, and breaks ovarian diapause.In autumn, the implantation of the male's or female's corpora allata of Anacridium does not stimulate ovarian growth of diapausing females. On the contrary, the implantation of corpora allata or of pars intercerebralis or of corpora cardiaca of Locusta migratoria migratorioides (locust without diapause) causes ovarian development of the diapausing females of Anacridium. Thus, in the two sexes of the Egyptian locust, the corpora allata are inactive during the female ovarian diapause. The imaginal diapause of Anacridium affects both sexes (stocking of median neurosecretion, arrest of the corpora allata). If diapause does not seem to affect the male's development, it is because its sexual activity is free from the pars intercerebralis and corpora allata.The corpora allata of Anacridium show a sexual dimorphism in the active adult: they are smaller in the male and have more mitosis in the female. An explanation of this dimorphism is advanced.