Etude histologique,histochimique et ultrastructurale de la pars intercerebralis chez Locusta migratoria L. (Orthoptere)

Summary A histological, histochemical and ultrastrucutral study of the pars intercerebralis (PI) has been made in Locusta migratoria. The acellular neural lamella is made up of an elastic tissue and collagen fibrils. The cells of the perilemma contain numerous lysosome structures and lipid granules.Three different types of neurosecretory cells (NSC A, B and C) have been distinguished in the PI associated with giant neurons.The cells termed A and B seem not to have an activity cycle during the two last larval instars. At the moment of sexual maturity the NSC A show an important accumulation of neurosecretory material and their number increases at the expense of the NSC B. The NSC A, which are characterized by a highly developped endoplasmic reticulum, contain numerous secretory granules which appear to be individualized in the Golgi complex in three different ways. The NSC B, with a reduced endoplasmic reticulum and an almost quiescent Golgi complex, contain abundant lysosome structures and more seldom some neurosecretory granules. In fact, the study of the fine structure shows different intermediate types, linking in a continuous way typical A cells and typical B cells. NSC A and NSC B might correspond to two opposed stages of secretory activity of one single cell type: the A cell representing the activity stage and the B cell the quiescent stage.NSC C show an accumulation of their neurosecretory products in relation to metamorphosis and sexual maturity. Ultrastructural evidence confirms their neurosecretory activity.A mode of regulating neurosecretion in NSC A and B by internal catabolism of the secretion and formation of lysosome like structures is discussed in the present paper.The giant neurons, which are surrounded by a glial envelope (trophospongium), contain several dense granules originated from Golgi complex.     

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 Cerebral Neurosecretory System,Secretory End-Foot System and Infracerebral Gland—a Probable Neuroendocrine Complex in Nephtys (Annelida; Polychaeta)

Abstract The brain of Nephtys contains four neurosecretory cell types with distinctive cytoplasmic inclusions, a cells are located uniquely in a single pair of ganglionic nuclei and b cells are represented by a single pair of cells, whereas c cells and d cells have a scattered distribution. Their axons form two types of secretory release structure. First, possible axon collaterals synapse upon slender “dentritic twigs” in the core of the brain. Secondly, two tracts descend to the brain floor to form a “neurosecretory neuropile” (or storage and release complex) in contact with the inner surface of the brain capsule. Other neurosecretory fibres penetrate through the capsule, branch extensively, and terminate in contact with its ventral surface in close association with the “infracerebral gland”. The gland is derived from the pericapsular epithelium and exhibits signs of specialization for glandular function. In contrast to certain other polychaetes, it does not contain secretory neuron perikarya. The secretory end-foot system is poorly developed. Its terminals are located adjacent to the neurosecretory neuropile, which they encircle. The cell bodies are probably represented by four e cells which, like the terminals, contain many mitochondria.     

In vitro peptidergic neurons from the adult locust pars intercerebralis: Morphological and immunocytological studies

Primary cell cultures were prepared from a major neurosecretory center of the adult locust brain, the pars intercerebralis, in order to characterize neurosecretory cells growingin vitro. Individual pars intercerebralis could be removed free of surrounding tissue and dissociated by mechanical treatment. Mature neurosecretory neurons of different sizes regenerate new neurites during the initial three daysin vitro in serum-free medium. They show a tendency to sprout one primary neurite from which fine processes develop. By means of electron microscopy, we observed the integrity of the cellular organelles, indicating that cultured neurons are healthy, and we were able to distinguish three types of neurosecretory neurons on the basis of the ultrastructural aspects of the neurosecretory material. These three types have the same ultrastructural characteristics asin situ neuroparsin, ovary maturing parsin and locust insulin related peptide neurons. Immunogold labelling at the electron microscopic level, using the two available specific antibodies, anti-neuroparsin and anti-ovary maturing parsin, confirms the morphological characterization of neuroparsin and ovary maturing parsin cells. These results show for the first time that cultured locust neurosecretory neurons behave like thosein vivo, in terms of their ultrastructure and immunocytochemistry. Moreover, the presence of recently-formed neurosecretory material both in the Golgi zone of the perikaryon and in the neuronal processes indicates that cultured neurons have functional capacity since they are able to synthesizede novo and to transport the neurosecretory material along the neurite. Thus our well-characterized culture system provides a suitable invitro model to investigate the secretory mechanism of locust neurosecretory neurons.     

Untersuchungen zum circadianen Sekretionszyklus der neurosekretorischen Kerngebiete der Maus*

Abstract Investigations on the circadian cycle of secretion in the neurosecretory nuclei of mouse. The circadian cycle of secretion of both hypothalamic neurosecretory nuclei N. supraopticus and N. paraventricularis in mice was studied by histological, histochemical, biochemical and electron-microscopical methods. Both areas undergo a circadian secretion cycle (24 h-rhytm). The activity of metabolism increases at the beginning of night, whereas by day the cells are considered to be in a phase of restitution and transportation of the secretion. Especially increases the volume of the cell nuclei (synthesis of RNA and proteins) and the activity of the extralysosomal unspecific esterase rises to maximal values. From midnight till the beginning of the light-phase the cells show a maximal volume of the nuclei and an increased secretion as well as higher activity of acid phosphatase and lactate dehydrogenase. Unspecific esterase activity, on the other hand, diminished. There was a noticable increase in the quantity of neurosecretion in both areas, it reached a maximum at the beginning of the light-phase, whereas the volume of the nuclei and the activity of acid phosphatase and thiamine pyrophosphatase diminished. The neurosecretion is more and more transported to the hypophysis. The cells restitute during the light-phase and reach their starting level.     

Brain-derived neurotrophic factor-like neuropeptide is secreted as a neurohormone from specific brain neurons into the corpus allatum in the silkworm Bombyx mori

The aim of this study was to investigate the secretion of brain‐derived neurotrophic factor (BDNF)‐like neuropeptide in the silkworm, Bombyx mori , by using immunocytochemical techniques on the brain and retrocerebral complex of fifth instar larvae. In the brain, four pairs of median neurosecretory cell (MNC) bodies and six pairs of lateral neurosecretory cell (LNC) bodies had distinct immunoreactivities to this peptide, suggesting that this peptide is produced from two types of brain neuron. These reactivities were much stronger in the MNC than in the LNC. Labeled MNC projected their axons into the contralateral corpora allata, to which axons of labeled MNC were eventually innervated, through decussation in the median region, contralateral nerve corporis cardiaci I and nerve corpora allata I. Labeled LNC extended their axons into the ipsilateral corpora allata to be innervated through the ipsilateral nerve corporis cardiaci II and nerve corpora allata I. These results suggest that BDNF is secreted as a neurohormone from MNC and LNC of the brain into the corpora allata.     

Electron microscopical and histochemical observations on the relation between medio-dorsal bodies and neurosecretory cells in the basommatophoran snails Lymnaea stagnalis,Ancylus fluviatilis,Australorbis glabratus and Planorbarius corneus

Summary In Basommatophora medio-dorsal bodies (MDB) are closely attached to the cerebral ganglia, in which, just underneath the bodies, groups of Gomori-positive neurosecretory cells (MDC) occur. It has been suggested that the MDB-cerebral ganglion complex should be regarded as a neuro-endocrine association.In the present study the morphological relation between MDB and the ganglion is histochemically and ultrastructurally investigated in Lymnaea stagnalis, Ancylus fluviatilis, Australorbis glabratus and Planorbarius corneus.Histochemical tests showed the paraldehyde-fuchsin positive material of fibers in the MDB to be different from the neurosecretory material (NSM) in the MDC. At the ultrastructural level no penetration of nerve cell processes through the perineurium, separating the MDB from the ganglion, into the medulla of the MDB was observed. However, excepting for Lymnaea, the perineurium at these places shows particular differentiations. In the medulla of the MDB granule laden profiles (granule ø 700–900 Å) occur. They appeared to be processes of MDB cells.From these results it is concluded that the medulla of the MDB should not be regarded as a neurosecretory neuropile. Apparently, the MDB-cerebral ganglion complex is no neuroendocrine association. Probably the MDB is an endocrine organ. The small electron dense granules of the profiles in the medulla were also found in the MDB cell bodies. They are thought to represent a secretion product. The close morphological relation between MDB and cerebral ganglion may be connected with the origin of the MDB cells from perineural elements.     

Morphofunctional basis of neurosecretory cell plasticity

Mass accumulation and storage of neurosecretory products are typical only for nonapeptidergic elements, as it has been shown by our study of the structure and function in neurosecretory cells of different nature. All liberinergic, statinergic and monoaminergic neurosecretory cells keep constancy in the state of high functional activity of extrusive processes at normal conditions. Morpho-functional features of these elements principally differ from those of nonapeptidergic neurosecretory cells, which are characterized by remarkable secretory cycles. The extremely large size of elementary secretory granules, maximum development of the Herring bodies, various modes of secretion, secretory and extrusive cycles in neurosecretory function, and massive accumulation of neurosecretory granules occurring in neurosecretory terminals finally, all these characters are considered to be the primary features of a high plasticity of the nonapeptidergic neurosecretory cell. A high reactivity of nonapeptidergic neurosecretory cells has been demonstrated here by the quantitative ultrastructural research of the dynamics of functional activity of neurosecretory terminals at both experimental and physiological stressful states. The highest plasticity of nonapeptidergic neurosecretory cells compared to all other neurosecretory cell types may be provided by their ability to restore the initial law level of functional activity, referred to as "functional reversion".     

The praeoptico-hypophysial system,Nucleus tuberis lateralis and the subcommissural organ of Gasterosteus aculeatus after changes in osmotic stimuli

Summary The histology and cytology of the praeoptico-hypophysial system, nucleus tuberis lateralis and subcommissural organ in Gasterosteus aculeatus were analyzed after the fishes had been put in waters of different salinity (see Tables 1–4).These three structures are all identical in fishes which are accustomed to fresh water and to 32 salt-water. A transference to hypertonic water causes changes in the neurosecretory system which suggest the existence of an antidiuretic principle in the neurosecretory substance. No such relationship is found when the fishes are put into hypotonic water. Further, no connection is found between either the secretion production in nucleus tuberis lateralis or in the subcommissural organ and variations in osmotic value.Aided by grants from the Swedish Natural Science Research Council.     

Neuroendocrine control of oocyte development in Poecilocera picta (Insecta: Orthoptera)

The neuroendocrine control of oocyte development in Poecilocera picta Fab. has been described. The secretory activity of the A type of neurosecretory cells has been correlated with ovarian development. In P. picta during the first four days after emergence the neurosecretory material is seen passing down the axons but the cells are largely devoid of neurosecretory material. When the oocytes are developed the A type cells are with stored neurosecretory material.
In P. picta the mature males do not appear to accelerate the process of maturation in females. The females which are reared without males or with castrated males also mature at the same time as the females which are reared with males. The corpus allatum also enlarges and decreases at the same period. The number of resorptive bodies is much more in the females which are reared with castrated males or without males. There appears to be some correlation in the secretion of the neurosecretory material, copulation, and the appearance of resorptive bodies. In P. picta the role of the mature male is only in copulation which very likely allows the cell to synthesize and secrete and release a large amount of neurosecretory material whose discharge in the haemolymph enables a successful development of the oocyte. Corpus allatum appears to be controlled by a precursor from the brain.
Cautery of the cerebral neurosecretory cells, allatectomy and sectioning of the nerves have been done to find out the role of neurosecretory material.     

Histochemical studies on the neurosecretory system of the common garden lizard Calotes versicolor (Daudin) under experimental condition

Summary Histochemical localizations of various substances in the hypothalamic neuro-secretory cells as well as neurohypophysis of the normal and stressed (scalded) garden lizards, Calotes versicolor suggest that the neurosecretory materials, secreted by the hypothalamic neurones may be a mucoprotein-lipoprotein complex which is finally stored in the neuro-hypophysis. Only the proteinaceous fraction of this complex appears to be released by the nerve terminals in the neurohypophysis under the stressed condition. Such suggestion implies a chemical transformation of neurosecretory substances after leaving the neurosecretory cell body.     

State of the hypothalamo-hypophyseal neurosecretory system of rabbits in anaphylactic shock]

With the aid of morphometric and histochemical methods a study was made of the hypothalamo-hypophyseal neurosecretory system of rabbits in anaphylactic shock. The following occurred in rabbits which survived the shock: an enlargement of the perikarions and reduction in the size of the nuclei and nucleoli of the neurosecretory cells; the content of the neurosecretory substance was increased in the whole neurosecretory system. In rabbits which perished from shock the nuclei and the nucleoli of the neurosecretory cells diminished to a lesser extent, perikarion measurements remained unchanged and the content of the neurosecretory substance in the posterior lobe of the hypophysis fell. Thus, in the animals which survived the shock the processes of synthesis of the neurohormones by the neurosecretory cells were sharply activated, but the secretion of the neurohormones from the posterior lobe of the hypophysis was inhibited; in animals which perished from shock the activation of the hormone formation in the neurosecretory cells was less pronounced, but the processes of the secretion of the neurohormones from the posterior lobe were apparently intensified.     

Paraneuronal pseudobranchial neurosecretory cells in scorpion catfish Heteropneustes fossilis: an environment scanning electron microscope and transmission electron microscope study

Yadav, L., Sengar, M., Zaccone, D. and Gopesh, A. 2011. Paraneuronal pseudobranchial neurosecretory cells in scorpion catfish Heteropneustes fossilis: an environment scanning electron microscope and transmission electron microscope study. —Acta Zoologica (Stockholm) 00 : 1–8. Pseudobranchial neurosecretory system (PNS), found in the gill region of certain groups of teleosts, falls under the category of the ‘diffuse neuroendocrine system’ (DNES). The cells belonging to the system share morpho‐functional features with the paraneuronal cells observed in respiratory tract and airway surfaces of higher vertebrates. On the basis of the experimental observations, a role in condition of hypoxia has been recorded for this system. In an attempt to elucidate the ultrastructure of pseudobranchial neurosecretory cells, present investigation was undertaken using environment scanning electron microscope (ESEM) and TEM in an air‐breathing catfish, Heteropneustes fossilis. The external morphology of PNS under ESEM appeared as a mass of cells supplied with nerves and blood capillaries. Each cell mass is made up of numerous pear‐shaped neurosecretory cells, confirmed by neurosecretion‐specific acid violet stain. The TEM investigation of the cells revealed the presence of different sizes of dense‐cored vesicles in the cytoplasm, which was observed as granular cytoplasm under light microscope. Presence of large number of mitochondria in the cytoplasm confirmed active involvement of these cells in the physiology of fishes. Although lacuna prevails regarding the exact function of this system of fish, its probable role in hypoxic condition and surfacing behavior are speculated.     

Membrane potential of the corpus cardiacum neurosecretory cells of the blowfly, Calliphora erythrocephala

The corpus cardiacum neurosecretory cells (c.n.c.) of Calliphora are unipolar cells with slender projections (axonal length: 50 to 110 μ; diameter: 0·25 to 1·75 μ).The cell body, where production of neurosecretory material occurs, is electrically inexcitable (resting potential about 36 mV, inside negative), whereas the axon—responsible for controlled neurohormone release—is excitable. Spike potentials with a duration of 3 to 7 msec occur in volleys the number and duration of which are supposed to determine the amount of secretion released. Electrical activity may be stimulated via the brain. Resting and action potentials are compared with recordings from other cell types of the blowfly.     

Identification of adenohypophysiotropic neurohormone producing neurosecretory cells in Rana temporaria

Summary Electron microscopic investigation of neural isolated and normal pars ventralis of the tuber cinereum showed the presence, in Rana temporaria, of a tubero-hypophysial neurosecretory system. A striking structural resemblance between this parvicellular, aldehydefuchsin negative, tubero-hypophysial neurosecretory system and the magnocellular, aldehydefuchsin positive, hypothalamo-hypophysial neurosecretory system was observed. Six different neurosecretory cell types are described, characterized by different shape and size of their respective secretory granules. The nature of the secretory product of these cells is briefly discussed.Of the results of this investigation, a preliminary note has been published (Dierickx, 1971).The authors wish to thank Prof. Dr. H. Steyaert and Dr. W. Moerdijk of the Laboratory for Mathematical Statistics, Ghent University, for invaluable advice and assistance with their computers. They thank Dr. G. De Waele for his help with the scanning electron microscopy.     

Neurosecretory system of the American dog tick,Dermacentor variabilis (Acari: lxodidae). I. Diversity of cell types

An arbitrary classification scheme is presented for the thirteen distinct types of secretory cells distinguished within the central nervous system of Dermacentor variabilis by several specific and general neurosecretory staining techniques. Comparisons to classic arthropod neurosecretory cell types are made and the histochemical implications of the chromophilic response of various secretory products are discussed. Dermacentor cells of Types I, VII, IX and X may be considered neurosecretory on the basis of intracellular elaboration and discharge of secretory product. Type II, III, IV, V, VI, XI and XII cells are considered as putative neurosecretory cells although secretory products were detected only within the perikarya. The large Type XII cells are also similar to motor neurones reported from other arachnids. Cells of Types VIII and XIII appear to be glial elements. The secretory products of Type XIII_A are distributed within trabecular processes in the subperineurium. These products may play a trophic role or they may have some endocrine function as a form of “gliosecretion”.     

Annual changes in the brain neurosecretory profile of the Indian freshwater Leech,Poecilobdella viridis (Blanchard) in relation to reproduction

Annual changes in the brain neurosecretory profile of Poecilobdella viridis in relation to reproductive activity have been investigated. The changes in A cell neurosecretory activities were found to be in strong correlative correspondence with the reproductive programme. Heavy accumulation of neurosecretory material was observed in A cells perikarya during the reproductive period i.e. from March to June, 1975, with enlarged nuclei and during reproductive quiescence i.e. from August, 1974 to January 1975, the neurosecretory activity was low.     

Ultrastructural changes of the hypothalamo-hypophysial neurosecretory system in the magnesium deficient rats.

A magnesium deficient diet caused transient but marked degenerative changes in the rat hypothalamo-hypophysial neurosecretory system which strongly resembled in many ultrastructural respects those induced by a prolonged administration of aldosterone as previously reported by us. The possible mechanism for this selective alteration in the neurosecretory neurons has been briefly discussed with regard to aldosterone secretion.     

Neurosecretory cells in the central nervous system of the adult blowfly, Phormia regina Meigen (Diptera: Calliphoridae)

• 1 Neurosecretary cells in the central nervous system of the adult blowfly, Phormia regina Meig., have been examined histologically using the parparaldehyde-fuchsin and Gomori's staining method. Six groups of the neurosecretory cells occur in each hemisphere of the brain, the medial, frontal, lateral A, lateral B, posterior I and posterior II groups. In the subesophageal ganglion, four B-cells and two A-cells are present. In the thoracico-abdominal ganglion, ten A-cells are found in the thoracic region and a total of about 50 A- and B-cells in the hind part of the abdominal region.
• 2 A comparison with the neurosecretory system of two other species of blowfly, Calliphora erythrocephala Meig., Sarcophaga bullata Parker, and the housefly, Musca domestica L., showed similar arrangements and grouping.
• 3 Neurosecretory granules have been observed along the axons originating from the medial neurosecretory cells of the brain, and the thoracico-abdominal ganglion. The granules originating from the medial groups can be traced directly to the corpus cardiacum from which they move to the aorta, crop duct and cardia through axons.
• 4 There is with advancing age a gradual increase in the size of cell bodies and nuclei of the median neurosecretory cells in both females and males of Phormia regina, and also a decrease in stainable granules. This increase in size is dependent on nutrition, with no increase in water alone, a slight increase on sugar, and a maximum increase on sugar and liver. Corresponding increases in size occur in the ovaries in connection with feeding the same substances.