Median Neurosecretory Cells Research Articles

Three‐dimensional architecture of identified cerebral neurosecretory cells in an insect

The organization of identified neurosecretory cell groups in the larval brain of the tobacco hornworm, Manduca sexta, was investigated immunocytologically. Computer-assisted three-dimensional reconstruction was used to examine the architecture of the neurosecretory cell groups. The group III lateral neurosecretory cells (L-NSC-III) which produce the prothoracicotropic hormone are located dorsolaterally in the protocerebrum and extend axons medially that decussate to the contralateral lobe prior to exiting the brain through the nervi corporis cardiaci I + II. The group IIa2 medial neurosecretory cells (M-NSC IIa2) are located anteriorly in the medial dorsal protocerebrum. The axons of these cells also exit the brain via the contralateral nervi corporis cardiaci I + II. However, their axons traverse a different pathway through the brain from that of the L-NSC III axons. Each of the cell groups possesses elaborate dendrites with terminal varicosities. The dendrites can be classified into specific fields based upon their location and projection pattern within the brain. The dendrites for these two neurosecretory cell groups overlap in specific regions of the protocerebral neuropil. After the axons of these neurosecretory cells exit the brain through the retrocerebral nerve, they innervate the corpus allatum where they arborize to form neurohemal terminals in strikingly different patterns. The L-NSC III penetrate throughout the glandular structure and the M-NSC IIa2 terminals are restricted to the external sheath. A third group of cerebral neurosecretory cells, the ventromedial neurons (VM) which stain with the monoclonal antibody to prothoracicotropic hormone in Manduca, are located anteriorly in the medial region of the brain. The axons of these cells do not exit the brain to the retrocerebral complex, but rather pass through the circumesophageal connectives and ventral nerve cord. These neurons appear to be the same VM neurons that produce eclosion hormone. One dendritic field of the L-NSC III terminates in close apposition to the VM neurons. The distinct morphologies of these neurosecretory cell groups in relation to other cell groups and the distribution of neuropeptides within the neurons suggest that insect neurosecretory cells, like their vertebrate counterparts, may have multiple regulatory roles.

Hormonal control of egg maturation in the corn earworm, Heliothis zea

AbstractAt eclosion, the ovaries of female Corn earworm Heliothis zea do not contain mature eggs. Virgin‐unfed females produced approximately 400 mature eggs in 8 days; mating or feeding doubled this number, and mating plus feeding more than tripled it. Females allatectomized or decapitated at day 0 matured few eggs. Egg production was restored by implantation of active corpora allata (CA) or by treatment with the juvenile hormone (JH) analogue methoprene at day 0. 20‐Hydroxyecdysone, on the other hand, had no effect. Females in which the CA had been denervated or in which the median neurosecretory cells of the brain had been ablated at day 0 produced fewer eggs than sham‐operated animals. These results indicate that egg maturation is controlled by JH and that continuous input from the brain is required for sustained CA activity for maintaining a high rates of egg maturation.The rate of JH biosynthesis by CA in vitro was determined with a radiochemical assay. The major hormones produced were JH‐II and JH‐III with small quantities of JH‐I. The rates of JH synthesis were similar in all experimental groups which may indicate that the in vitro rate of JH synthesis does not reflect the actual state of CA activity in the female.

Immunocytochemical mapping of neuronal pathways from brain to corpora cardiaca/corpora allata in the cockroach Diploptera punctata with antisera against Met-enkephalin-Arg6-Gly7-Leu8

Neuronal circuits in the brain and retrocerebral complex of the cockroach Diploptera punctata have been mapped immunocytochemically with antisera directed against the extended enkephalin, Met-enkephalin-Arg6-Gly7-Leu8 (Met-8). The pathways link median and lateral neurosecretory cells with the corpus cardiacum corpus allatum complex. In females, nerve fibres penetrate the corpora allata and varicosities or terminals, immunoreactive to Met-8, surround the glandular cells. Males differ in having almost no Met-8 immunoreactivity in the corpora allata. The corpora cardiaca of both males and females are richly supplied with Met-8 immunoreactive material, in particular in the 'cap' regions immediately adjacent to the corpora allata. A similarity in the amino-acid sequences of Met-8 and the C-terminus of the recently characterised allatostatins of D. punctata suggests that the pathways identified with the Met-8 antisera may be the same as those by which the allatostatins are transported from the brain to the corpus allatum. In comparative studies on the blowfly Calliphora vomitoria, similar neuronal pathways have been identified except that no sexual dimorphism with respect to amounts of immunoreactive material within the corpus allatum has been observed. These results suggest a possible homology in the neuropeptide regulation of the gland.

Developmental Changes in the Bombyxin-and Insulin-like Immunoreactive Neurosecretory System in the Wax Moth, Galleria mellonella: (prothoracicotropins/corpora cardiaca/regulatory peptides/neurohaemal organs/molting control).

Four medial neurosecretory cells (MNC) and 4 lateral neurosecretory cells (LNC) in each brain hemisphere, and one pair of cells in each thoracic ganglion (TG) of Galleria larva react with antibodies against bombyxin and insulin. Material secreted from the MNC and LNC is released mainly in the corpora allata, and that from the TG through the ventral median nerves. Intrinsic secretory cells of the corpora cardiaca (CC) also contain bombyxin-like, but not insulin-like material. The immunoreactivities all disappear during molts and reappear with resumption of feeding. In the MNC and TG they reappear for less than a day, but in cells of the CC immunoreactivity reappears for the whole feeding period. Before pupation, the LNC become temporarily immunopositive towards the end of feeding period, and the MNC and TG during the wandering period, i.e. at the time of prothoracic gland stimulation. Immunoreactivity disappears during the pupal molt. In pupae it is present in the 4 pairs of MNC and 1-2 pairs of LNC 12-48 hr after ecdysis, and in cells of the CC from 12 hr after ecdysis until the end of the pupal instar. In adult, immunoreactivity is restricted to 2 pairs of the LNC and to CC cells.

Distribution and functional significance of Met-enkephalin-Arg6-Phe7- and Met-enkephalin-Arg6-Gly7-Leu8-like peptides in the blowfly Calliphora vomitoria. I. Immunocytochemical mapping of neuronal pathways in the brain.

Neuronal pathways immunoreactive to antisera against the extended-enkephalins, Met-enkephalin-Arg6-Phe7 (Met-7) and Met-enkephalin-Arg6-Gly7-Leu8 (Met-8), have been identified in the brain of the blowfly Calliphora vomitoria. Co-localisation with other enkephalins in certain neurons suggests that a precursor similar to preproenkephalin A exists in insects and that differential enzymatic processing occurs as in vertebrates. Co-localisations of the extended-enkephalin-like peptides with other vertebrate-type peptides, including cholecystokinin and pancreatic polypeptide, also occur. The enkephalinergic pathways are specific, comprising a few groups of highly characteristic neurons and areas of neuropil. Of special interest is the finding that parts of the antennal chemosensory and the optic lobe visual systems contain Met-8 immunoreactive neurons. Within the median neurosecretory cell groups, some of the giant neurons show immunoreactivity to Met-8 and others to both Met-8 and Met-7. Fibres from these cells project to the corpus cardiacum and also to the suboesophageal ganglion, where arborisations occur in the tritocerebral neuropil. Co-localisation studies of these cells have shown that at certain terminals, one particular type of peptide is the dominant neuroregulator, whilst at other terminals, within the same cell, a different co-synthesised peptide predominates. Several groups of lateral neurosecretory cells show clearly defined enkephalinergic pathways, most of which have connections with the central body. The complex patterns of immunoreactivity seen in terminals in the different parts of the central body, suggest an important role for the enkephalin-like peptides in the integration of multimodal sensory inputs. The physiological functions of the extended-enkephalin-like peptides in the brain of Calliphora is still unknown, but the anatomical evidence suggests they may have a role similar to that in mammals, where they are thought to control aspects of feeding behaviour.

The role of neurosecretion and metabolism in development of an oligophagous feeding habit in Morimus funereus larvae (col., cerambycidae)

1. 1. The effect of an artificial diet (AD) on the activity of median neurosecretory cells (MNC), subtypes Al and A2, and the metabolism in tMorimus funereus larvae has been investigated. 2. 2. Two experimental groups were used: larvae developing under natural conditions (NC, controls) and those continuously reared on the AD at 23°C. 3. 3. Larvae reared on the AD completed their development during 6.5 months. 4. 4. These larvae had an increased number of MNC, i.e. Al by 45%, A2 by 59% and an elevated neurosecretory activity (enlarged cell volumes and greater number of nucleoli). 5. 5. The content of fat body glycogen decreased (0.88 mg glucose/100 mg fat body) and that of haemolymph trehalose increased (28.4 mg/1 ml haemolymph) in larvae bred on the AD when compared to the NC (1.413 and 20.2 mg, respectively). 6. 6. The midgut proteolytic activity raised to 364% and the amylolytic one dropped to 7.5% in comparison with the controls. 7. 7. The results are discussed from the aspect of the dietary effect on the neurosecretory system and metabolism of those oligophagous larvae.

The corpus allatum in relation to sexual behaviour and aggressiveness in male Supella supellectilium (Serville) (Blattoidea: Blattellidae)

Histological signs of the secretory cycle of the corpus allatum in the adult males of Supella supellectilium correlate well with sexual maturity, behaviour and aggressiveness. Cauterisation of the median neurosecretory cells, allatectomy and implantation of active corpora allata into the allatectomised and cauterised insects suggest that the corpus allatum is primarily responsible for normal sexual behaviour and aggressiveness in the male insect.

Immunohistochemical investigation of locust neuroparsin-like substances in several insects, in some other invertebrates, and vertebrates

Anti-neuroparsin serum was immunohistochemically tested on brain and/or neurohemal organ from 40 insect species belonging to 13 orders, and from 8 non-insect invertebrate and 5 vertebrate representatives using the peroxidase-antiperoxidase procedure. In insects, immunostaining of only the A1 type of the protocerebral median neurosecretory cells was revealed in all species tested of Odonata, Dictyoptera, Isoptera and Orthoptera and in 2 species from the 9 other orders out of 13 orders tested. No immunostaining was detected in vertebrate and non-insect invertebrate species except in 2 annelid species out of 4 tested. The distribution of neuroparsin-like products in Coelomata appears to be restricted mainly to 4 phylogenetically close insect orders.

Role of endocrines in water balance in the coconut palm beetleOryctes rhinoceros—Ultrastructural and electrophoretic studies

Ultrastructural observations on the brain median neurosecretory cells of the hydrated larvae (third instar) ofOryctes rhinoceros showed a well developed granulated endoplasmic reticulum and golgi bodies, indicating active state. The dehydrated animal on the other hand revealed inactive brain median neurosecretory cells with broken and swollen endoplasmic reticulum and underdeveloped golgi bodies. The axonal endings of the median neurosecretory cells in the corpus cardiacum of the dehydrated animal showed retention of secretory granules. Polyacrylamide gel electrophoretic studies also showed accumulation of neurosecretory materials in corpus cardiacum and brain samples of the dehydrated animal than those of the hydrated animal. The above results provide additional evidence that the brain median neurosecretory cells are involved in the regulation of water balance by secreting a diuretic hormone in response to hydration stress.

FMRFamide- and adipokinetic hormone-like immunoreactivity in the nervous system of the mosquito, Aedes aegypti.

As demonstrated with immunocytochemistry, specific cells and axons in the nervous system of female Aedes aegypti contain antigens immunologically related to FMRFamide (phenylalanine-methionine-arginine-phenylalanine-amide) and locust adipokinetic hormone I (AKH). In the supra-esophageal ganglion, including some medial neurosecretory cells, and in all ganglia of the ventral nerve cord, there are 100-120 cells immunoreactive to a FMRFamide antiserum. The same cells cross-react with a bovine pancreatic polypeptide antiserum, but when the latter antiserum is preabsorbed with FMRFamide, immunoreactivity is lost. However, immunoreactivity is maintained when FMRFamide antiserum is preabsorbed with pancreatic polypeptide, suggesting that the immunoreactive peptide is more closely related to FMRFamide. There are 6-12 cells in the supra- and subesophageal ganglia immunoreactive to an AKH antiserum, and some of the same cells are reactive to the FMRFamide antiserum. As well, unpaired cells in each of the abdominal ganglia are positive for both AKH and FMRFamide. Although the function of the FMRFamide- and AKH-like peptides in mosquitoes is unknown, this study, combined with previous reports on the localization of FMRFamide-like peptides in midgut endocrine cells, supports the concept of a brain-midgut neuroendocrine axis in this insect.

Production and characterization of antibodies to neuroparsins A and B isolated from the corpora cardiaca of the locust

Antisera were raised in rabbits against neuroparsins A and B which were purified to near homogeneity using electroelution from 7,5% polyacrylamide electrophoresis gels. They were characterized using immunohistochemical, enzyme-linked immunosorbent assay (ELISA), and protein-blotting methods. The antineuroparsin A and the antineuroparsin B sera have different titers and sensitivities (higher titer for antineuroparsin A, higher sensitivity for antineuroparsin B). They exhibit very good specificity. The immunohistochemical study of the entire central nervous system using either antineuroparsin A or antineuroparsin B sera shows that only the A1 type of the protocerebral median neurosecretory cells are immunostained. Moreover, among the numerous proteins of the median region of the brain and of the corpora cardiaca, each immune serum recognized only neuroparsin A or neuroparsin B. Displacement curves obtained for each immune serum by competition between either neuroparsin A or neuroparsin B demonstrate that the neuroparsin A is recognized as well as neuroparsin B, with both antisera supporting the concept that these two proteins are chemically related. The nonspecific binding of neuroparsins to an antisomatostatin immune serum used at 1 100 dilution indicates thay any cross-reactivities of invertebrate molecules obtained with very low dilutions of antisera to vertebrate molecules must be considered carefully before concluding any immunological relation between invertebrate and vertebrate products.

Allatotropic activity of the median neurosecretory cells ofGalleria mellonella (lepidoptera) larval brain

The brain allatotropic hormone (ATTH) is released inGalleria mellonella from the Median neurosecretory cells located in the pars intercerebralis. These cells show the ability to elicit supernumerary larval molts upon implantation into sensitive host larvae, and the ability to in vitro stimulate the juvenile hormone synthesis in corpora cardiaca-corpora allata glands ofG. mellonella.

Nutrition and reproduction in haematophagous arthropods

Hosts of haematophagous arthropods range from amphibians to mammals. Blood meal is essential for egg production. Quantity and quality of ingested blood are important in realization of optimum reproductive potentials. In terms of egg production, the lowest nutritive value is for human blood. This inequality is probably based on differences in proteins and their constituent amino acids. Carbohydrates in the diet have no direct contribution to reproduction. Very little is known about sterol, lipid, vitamin and salt requirements for reproduction. In the mosquitoAedes aegypti some substance from the blood meal is thought to initiate vitellogenesis and is sustained by a complex hormonal mechanism in which median neurosecretory cells, corpus allatum, fat body and ovary participate. Mechanical stimuli from gut distension also has a role in hormone induction.

Evidence for neurosecretory control of the optic gland in terrestrial pulmonates

The optic gland in terrestrial pulmonates secretes gonadotropic hormone. The present study investigates the fine structure of the optic gland to clarify the control of secretion. Animals used were the slug, Limax marginatus, and the snail, Euhadra peliomphala. The optic gland cell has a process and the cytoplasm is filled with large granules about 750–1300 nm in diameter with a thin corfex in L. marginatus and 800–1700 nm delimited by a thick peripheral layer in E. peliomphala. These gland cells are characterized by well-developed granular endoplasmic reticulum. Granule formation was seen in the region of the Golgi apparatus. During the breeding season, the medial neurosecretory cells of the brain are active in the production and release of secretory materials. Although no neurosecretory cell bodies occur in the tentacular ganglion, neurosecretory axons penetrate into the optic gland cells. Cobalt filling reveals that axons of the medial neurosecretory cells project to the tentacular ganglion, near the optic gland. These results suggest that the optic gland is controlled by a neurohormone originating from the medial neurosecretory cells of the brain.

Role of the fat body in the regulation of host-seeking behaviour in the mosquito, Aedes aegypti

Following a blood meal that initiates oöcyte development, the host-seeking behaviour of Aedes aegypti mosquitoes is inhibited by a haemolymph-borne factor that is released in response to a humoral signal from a vitellogenic ovary. This inhibition is accompanied by a decrease in the sensitivity of the peripheral lactic acid receptors. Implantation of corpora allata, medial neurosecretory cells, or terminal abdominal ganglia from blood-fed donors could not induce the inhibition in sugar-fed recipients. However, fat body transplanted from blood-fed into sugar-fed females suppressed host-seeking behaviour as well as the sensitivity of lactic acid receptors, suggesting that the source of the behavioural inhibitor is the fat body. Resting-stage ovaries from other mosquito species inhibited host-seeking after the A. aegypti host was fed on blood only if the fat body was activated by the donor ovary.

Anti-juvenile effect of neuroparsin A, a neuroprotein isolated from locust corpora cardiaca

Neuroparsin A, a sulfur-containing protein synthesized by the medial part of the brain of Locusta and transported to the corpora cardiaca (CC) via the nervi corporis cardiaci I (Girardie et al., 1987), was satisfactorily isolated using electro-elution. A specific immune serum against electro-eluted neuroparsin A was generated. On serial histological sections of the brain treated with the immune serum, only the median neurosecretory cells [stained in blue following the double staining Victoria blue-paraldehyde fuchsin (Al type)] were revealed using peroxidase-antiperoxidase technique. Inactivation of neuroparsin A by antigen-antibody complex formation following injections of immune serum induced green pigmentation, intermediary forms and precocious sexual maturation. These symptoms also follow juvenile hormone (JH) injections. Injections of immune serum antineuroparsin A or the electro-eluted neuroparsin A produced opposite effects on oocyte growth but had no effect on the rate of JH biosynthesis evaluated by radiochemical assay. The neurohormone neuroparsin A could be the median humoral inhibiting factor of the JH system which was previously demonstrated (Girardie, 1966, 1967) in the central area of the pars intercerebralis.

Production sites of the three neurosecretory proteins characterized in the corpora cardiaca of the migratory locust

The sites of production of three cysteine and/or cystine-rich neurosecretory proteins (a monomer, a dimer and a trimer) partially characterized by us previously (Girardie et al., 1985) were determined by slab gel autoradiography using both intact locusts and locusts in which the corpora cardiaca (CC) were disconnected from the brain before injection of [ 35S]cysteine. The dimer is synthesized by the glandular cells of the CC and we propose the name cardiacin for this protein. The trimer is synthesized by the protocerebral median neurosecretory cells (A1 and/or A2 types) and we propose the name neuroparsin A for this molecule. The monomer, which appears only in nervous CC results from a transformation of neuroparsin A and we thus propose the name neuroparsin B. The mechanism of this transformation, which also occurs in vitro with the isolated oligomer is, as yet, unknown but neuroparsin B could be a releasable form of neuroparsin A.

Morphology of identified neurosecretory and non-neurosecretory cells in the cockroach pars intercerebralis.

Electrophysiologically identified cells of the cockroach pars intercerebralis (Periplaneta americana) were injected with the dye Lucifer Yellow for morphological examination and with horseradish peroxidase for ultrastructural marking. In addition to this, uninjected cells were also studied to elaborate the findings from the injected material. The two electrophysiologically distinct classes of cells (type I and type II) correspond to two distinct morphological and ultrastructural classes. Type I cells are the medial neurosecretory cells of the pars intercerebralis, which project their axons to the retrocerebral neuro-hemal complex. Their cell bodies have a mean diameter of 17 microns, and they contain neurosecretory granules 200 nm in diameter. Arborizations emanate from the axon in the anterior part of the protocerebral neuropil. The type II cell bodies are larger (38 microns in diameter). Their axons project into the contralateral circumesophageal connective. These cells were usually multipolar, having somatic arborizations in the anterior portocerebral neuropil. The cell bodies contain vesicles 40 nm in diameter, numerous trophospongia, and a multi-layered glial envelope.

Brain neurosecretory cell and ecdysiotropin activity of the non-diapausing, pre-diapausing and diapausing southwestern corn borer, Diatraea grandiosella Dyar

The location and number of brain neurosecretory cells were studied in the larval southwestern corn borer. One posterior, two median and two lateral groups of paraldehyde-fuchsin positive cells were found in each cerebral hemisphere. Implantation of brain parts containing different groups of neurosecretory cells revealed that the median neurosecretory cells contained higher ecdysiotropic activity than the other cell groups. In vitro culture of ecdysial gland with brain or brain-parts extract showed also that the median neurosecretory cells contained much higher ecdysiotropic activity than other neurosecretory cells. To estimate the ecdysiotropic activity of pre-diapausing 6th instar larvae, their brain or brain extract was incubated in culture medium containing an ecdysial gland from a day-4 last-instar non-diapausing larva. Data showed that the ecdysiotropic activity in the pre-diapausing larvae was far lower than in non-diapausing and diapausing larvae.

Characterization of three neurosecretory proteins from the [formula omitted] median neurosecretory cells of Locusta migratoria by coupled chromatographic, electrophoretic and isoelectrofocusing methods

Proteins from the nervous corpora cardiaca (N-CC) of Locusta migratoria were analysed using a combination of chromatography, electrophoresis and electrofocusing. Three major cysteine or/and cystine-rich proteins were identified as neurosecretory proteins of the median neurosecretory cells (M-NSC) by comparing the pattern of separated proteins of (1) intact N-CC and (2) depleted N-CC after intracerebral axotomy of the M-NSC. These three neurosecretory proteins are: a trimer, a dimer and a monomer. The trimer and the monomer are composed of apparent 18,000 subunits and 9000 polypeptide chains. The dimer is composed of apparent 7000 subunits composed of putative 4000 polypeptide chains. The three neurosecretory proteins are acidic (pH i approx. 5.6 for the trimer, 5.1 for the monomer and 4.0 for the dimer). Their relationship to the neurophysins and to the neurosecretory protein isolated from brain and corpora cardiaca of the locust by Friedel et al. (1980) ( Gen. comp. Endocr. 41, 487–498) is discussed. The role of these three neurosecretory proteins (carrier protein, neurohormone or precursor of neurohormone) is as yet unknown.