Median Neurosecretory Cells Research Articles

The role of endocrines in flight-muscle degeneration in Dysdercus cingulatus (Heteroptera: Pyrrhocoridae)

In Dysdercus cingulatus, extirpation of the median neurosecretory cells inhibits flight-muscle breakdown. However, implantation of median neurosecretory cells or corpus allatum into females lacking these neurosecretory cells induces muscle histolysis. Median neurosecretory cells stimulate the corpus allatum to produce juvenile hormone which in turn induces muscle degeneration. Topical application of kinoprene induces muscle breakdown, even in males and starved virgin females. The direct participation of juvenile hormone in muscle degeneration is further confirmed by observations on the effect of precocene II which inhibits muscle histolysis in many individuals. The endocrine basis of vitellogenesis and flight-muscle degeneration could be identical; vitellogenesis however appears to require a higher threshold concentration of juvenile hormone.

Differences in the sensitivity of protocerebral neurosecretory cells arising from the effect of different factors in Morimus funereus larvae

1. 1.The combined effect of different factors (temperature, starvation, potassium saline, cerebral complex extract) on the activity of protocerebral neurosecretory cells (A1, A2, L2) in Morimus funereus larvae has been studied. 2. 2.Our results show that the most sensitive cells to the effect of the factors studied are A1 cells, and the least sensitive ones are those of L2 type. The latter respond mainly to the effect of potassium saline as well as to the cerebral complex extract, changing the affinity of the cytoplasm and neurosecretory granules from paraldehyde fuchsin positive into orange G positive, in addition to other parameters. 3. 3.Variability among larvae regarding the activity of medial neurosecretory cells, particularly of the most sensitive ones (A1 types), has been observed, both under natural and experimental conditions.

Immunohistochemical localization of dopamine in the brain of the insect Locusta migratoria migratorioides in comparison with the catecholamine distribution determined by the histofluorescence technique

As part of a follow-up study to our previous investigation of the catecholaminergic neurosecretory cells in the brain of adult female locusts (Locusta migratoria migratorioides) by means of the formaldehyde-induced fluorescence method, we have attempted to specify the identity of the amines present in these cells by an immunohistological technique. Using a recently developed anti-dopamine serum, we have demonstrated that the majority of the catecholaminergic median neurosecretory cells contain dopamine. Moreover, dopamine is present in some cell bodies of other zones of the brain, i.e. the median subocellar neurosecretory cells, perikarya in external areas of the protocerebrum, below the calyces, around the pedunculus, in the optic lobes (between the lobula and the medulla, between the medulla and the lamina), and in external zones of the tritocerebrum. Among the structured neuropils, which were particularly fluorescent in the formaldehyde-induced fluorescence method, only the pedunculus, the posterior part of the central body, the external zones of the alpha- and beta lobes and the proximal part of the lamina contain little dopamine.

The stomatogastric nervous system of the house cricket Acheta domesticus L. II. Iontophoretic study of neuron anatomy.

The anatomy of neurons of the stomatogastric nervous system of Ascheta domesticus was studied using heavy metal iontophoresis through cut nerve ends followed by silver intensification. Nineteen categories of neuron are described and compared with neurons known from the stomatogastric nervous system of other insects. Possible functions for the neurons are suggested. Motor neuron candidates are suggested for all parts of the gut served by the stomatogastric nervous system, and axons of sensory neurons of the anterior pharynx are located. There are four neuron types that cannot readily be assigned motor, sensory, or interneuron functions: large dorsal cells of the frontal ganglion; the two neurons of the nervus connectivus, and two categories of neurons in the median neurosecretory cell group of the pars intercerebralis, the axons of which are contained in the stomatogastric nerves.

Control of corpus allatum activity inDiploptera punctata: roles of the pars intercerebralis and pars lateralis

Control of the corpora allata (CA) ofDiploptera punctata is maintained by at least 2 factors. The glands are directly inhibited by an allatostatin arriving at the CA via the nervi corporis cardiaci I (NCC I). Destruction of the putative source (median neurosecretory cells, MNC) of the allatostatin by radio-frequency (RF) cautery relieved the inhibition imposed on the CA of virgin females, and the glands became active. Similarly, destruction of the lateral neurosecretory cells (LNC) also relieved the inhibition. We propose that the LNC stimulated the MNC to release allatostatin. RF-cautery did not result in the activation of CA of pregnant or ovariectomized females. Activation of the CA may therefore require not only absence of the inhibitory factor but also the presence of a stimulatory one (perhaps from the ovary).

Immunocytochemical identification of alpha-endorphin-like material in neurones of the brain and corpus cardiacum of the blowfly, Calliphora vomitoria (Diptera).

A group of the 24-26 paraldehyde fuchsin-positive median neurosecretory cells (MNC) in the pars intercerebralis of the brain of the blowfly, Calliphora vomitoria, has shown immunoreactivity towards three different antibodies to alpha-endorphin, a peptide that corresponds to the amino acid sequence present between residues 61 and 76 of the precursor molecule, beta-lipotropin (beta-LPH). The immunoreactive material could be followed in axons within the median bundle, the tract through which neurosecretory material from the MNC is passed down to the corpus cardiacum (CC). The alpha-endorphin-immunoreactive material was observed leaving the CC in the cardiac-recurrent nerve, dorsal to the proventriculus, in the direction of the abdomen. The cells that contain the alpha-endorphin-like material are different from those of the MNC that contain insulin-, pancreatic polypeptide-, and gastrin/CCK-like peptides. This finding demonstrates the considerable complexity and peptidergic nature of the MNC and constitutes further evidence that morphinomimetic-like peptides are present in the nervous system of invertebrates.

Control of corpus allatum activity during the imaginai diapause in females ofLocusta migratoriaL

In the Savio strain of Locusta migratoria an imaginai diapause is induced by long daylength. In diapausing females, the haemolymph level of juvenile hormone (JH) was undetectable during the first 3-wk of imaginai life and later rose only slightly to about 20 ng/JH3IR per ml. Only peripheral cells of the corpora aliata (CA) were active. In nondiapausing animals, or after the termination of diapause, the JH level was high (140–200 ng/ml) and the ultrastructure of the gland exhibited signs of activity. CA severance in 3-wk-old diapausing females terminated diapause as a result of activation of the CA. CA disconnection in the fifth larval instar or at the imaginai moult in long daylength animals did not break diapause and the CA stayed inactive. The lateral cells of the protocerebrum exert a jdual effect: at the end of larval life they bring about CA maturation and render them active, whereas during the imaginai diapause they inhibit CA activity. The median neurosecretory cells of the pars intercerebralis sup...

Anatomy and electrophysiology of individual neurosecretory cells of an insect brain.

The structure and electrophysiological properties of individual neurosecretory cells of the pars intercerebralis, medial neurosecretory cells (MNSCs), in the brain of an insect, the cricket Teleogryllus commodus, were investigated by means of intracellular injections of the dye Lucifer Yellow and electrophysiological recordings. Action potentials recorded from these cells were of long duration, 8-50 msec. In the pars intercerebralis there are both neurosecretory cells with axons that join one of the tracts of the nervi corpori cardiaci I (NCC I) and cells without an axon or collateral that leaves the brain, local neurosecretory cells. MNSCs with axons that join NCC I and terminate in the anterior corpus cardiacum arborize extensively in the protocerebrum and to a lesser degree in the deutocerebrum. Other MNSCs have axons that pass through the corpus cardiacum and hypocerebral ganglion and join one of the oesophageal nerves. These MNSCs have sparse collateral arborizations in the protocerebrum but do have extensive terminal arborizations in the tritocerebrum. This type of cell is dye-coupled to other MNSCs. Among the local MNSCs, some have an unusual loop shape. These cells branch extensively in the protocerebrum and have massive terminal arborizations in a posterior ventromedial region of the brain. Both the long curved axons of the loop-shaped cells and their ventromedial branches are of large diameter, suitable for storage of neurosecretory material.

Interaction of the neuroendocrine system and ovaries in sheep blowflies, Lucilia sericata, sterilized with tepa

ABSTRACT. Female Lucilia sericata Mg. fed a reproductive diet of meat were sterilized by injection of 10μg of tepa. Light microscopy revealed that the medial neurosecretory cells of the brain of sterilized flies were highly active compared with the same cells in untreated flies of similar age and nutritional status. The corpora allata of sterilized flies were also greatly enlarged. The evidence suggests that developing oocytes secrete a substance that inhibits the corpora allata hormone, thereby suppressing brain neurosecretory cell activity and preventing oogenesis in the subsequent oocytes.

Ovulation in Rhodnius prolixus Stal is induced by an extract of neurosecretory cells

The injection of an extract of 10 identified median neurosecretory cells from the pars intercerebralis into gravid mated females previously deprived of these cells by surgery induces ovulation and oviposition during the ensuring 24 h. Injection of an extract of ocellar nerves has no effect. These observations support the hypothesis that ovulation and oviposition are controlled by a myotropin released from neurosecretory cells in the brain.

Precocene sensitivity of corpora allata in adult female Locusta migratoria after electrocoagulation of the pars intercerebralis neurosecretory cells

Destruction, by electrocoagulation, of the median neurosecretory cells of the pars intercerebralis of 2-day old adult female Locusta migratoria completely suppressed normal juvenile hormone-biosynthetic activity of the corpora allata in most animals. For example, 6 days after electrocoagulation the rates of spontaneous juvenile hormone biosynthesis, measured by radiochemical assay of freshly isolated glands, showed a median value of less than 1 100 that of the corresponding sham operated controls, which were then in mid-vitellogenesis. Injection of graded doses (200–1600 μg) of precocene I at this time, followed by assays five days later, resulted in a similar decline of both corpus allatum volume and precocene epoxidase activity (measured by radiochemical assays of precocene I dihydrodiol formation in vitro) in pars intercerebralis-coagulated and sham-operated animals, when expressed as a percentage of their own zero precocene controls. Electrocoagulation of the pars intercerebralis largely prevented the normal increase in both corpus allatum volume and its epoxidase activity, so that by age 13 days these parameters were about 2.5-fold lower in coagulated vs control (sham operated) animals. In fact, electrocoagulation had no marked effect on the value of epoxidase activity per unit corpus allatum volume. It is concluded that the corpora allata from this species and stage are sensitive to precocene irrespective of whether they are active in biosynthesis of juvenile hormone.

Neurosecretory regulation of the haemolymphatic titre of a vasopressin-like substance in the migratory locust

The multihormonal regulation of the release of a vasopressin-like factor, synthetized into the suboesophageal ganglion of the locust, is shown by means of electrical stimulations. Stimulation of the brain median neurosecretory cells induces a decrease of the release while stimulation of the brain median subocellar neurosecretory cells induces an increase. These results allow us for the first time to relate different neurosecretory centres up to now separatively involved in locust diuresis, in a single regulatory pattern.

Co-localization of amines and peptides in the same median neurosecretory cells of locusts

Two different techniques, the Falck and Hillarp method and paraldehyde fuchsin staining, have been used on freeze-dried adjacent sections. The co-existence of catecholamines and peptidergic neurosecretions has been demonstrated in the same pars intercerebrals neurons of the insect Locusta migratoria.

The neurosecretory system of the adult Melanogryllus desertus Pall. (Orthoptera, Gryllidae) : III. Crystalline pattern of neurosecretory material

Crystalline structures occur in median neurosecretory cells of Melanogryllus desertus. A unit membrane surrounds smaller structures but does not enclose the larger aggregates. They are probably formed in the Golgi complexes.

Light and electron microscopic localization of substance P-like immunoreactivity in the cerebral ganglion of locust with a monoclonal antibody.

The occurrence of substance P-like immunoreactivity was studied in the locust brain at light and electron microscopic level using monoclonal IgG fraction to substance P. Small immunoreactive perikarya have been found beside the medial neurosecretory cells in horizontal brain sections. Widespread immunoreactivity was also observed in the protocerebral neuropil notably in the central body and bordering on the corpora pedunculata. The reaction endproduct appeared as fine, more or less round particles in the central body, and as coarse varicosities and wavy fibres bordering the peduncles. The roundish particles probably represent nerve terminals, while the wavy fibers correspond to neural processes. In the vicinity of the beta lobe immunoreactivity was not observed. Electron microscopically, a number of immunoreactive terminals were found in the protocerebral neuropil. The reaction endproduct was accumulated mostly in large dense core granules/average diameter 80 nm/however reaction endproduct was also observed on the external surface membranes of clear vesicles and mitochondria. Our results suggest the widespread occurrence of a substance-P immunoreactive neuropeptide in the cerebral ganglia of the migratory locust.

Enhancement of juvenile hormone biosynthesis in locusts following electrostimulation of cerebral neurosecretory cells

Electrostimulation of the medial neurosecretory cells of day-1 adult female Locusta migratoria resulted in a significant enhancement of juvenile hormone biosynthesis by the corpora allata within 2–3 days of the operation, as determined by a radiochemical assay for juvenile hormone biosynthesis. This elevation in the rate of juvenile hormone biosynthesis was also reflected in basal oöcyte length, with the oöcytes of stimulated animals significantly larger than the sham-operated animals. Radio-frequency cautery of the cerebral axonal tracts of the medial neurosecretory cells prevented this enhancement in juvenile hormone biosynthesis and in basal oöcyte growth in both stimulated and sham-operated animals. Stimulation of the lateral neurosecretory cells resulted in a slight elevation in rates of juvenile hormone biosynthesis 2 days after the operation. However, after cautery of the medial cell tracts, a significant elevation in juvenile hormone biosynthesis was observed 1 and 2 days after stimulation. Basal oöcyte length in stimulated animals differed significantly from sham-operated animals only on day 6. Cautery of the medial cell tracts again attenuated oöcyte growth. Our results suggest that the medial neurosecretory cells are the source of an allatotropin that can be released by electrostimulation. This substance appears to operate directly on the corpus allatum, causing a change in the juvenile hormone biosynthetic machinery.

A neurosecretory hormone-releasing factor from ovaries of mosquitoes fed blood

In mosquitoes, a hormone (egg development neurosecretory hormone or EDNH), produced by the medial neurosecretory cells and stored in the corpus cardiacum soon after eclosion, is released after a blood meal, and vitellogenesis begins a few hours later. When either the ovaries or the neurosecretory cells and corpus cardiacum are removed before the blood meal, vitellogenin is not synthesized. Therefore, we tested the hypothesis that the release of EDNH from the corpus cardiacum is dependent on the secretion of a releasing factor from the ovaries. Using a bioassay for EDNH in the corpus cardiacum, we found that the gland of an ovariectomized female remained active after blood feeding, and therefore, has not released EDNH. When an ovary was implanted before the blood meal, the corpus cardiacum was inactive, and therefore, had released EDNH. We concluded that the ovaries secrete an EDNH-releasing factor, and that this factor and EDNH must both be in circulation before vitellogenesis can begin. Although releasing factor alone did not stimulate vitellogenesis, it was the rate limiting process that controlled the onset of vitellogenesis. Using a bioassay for the EDNH-releasing factor from the ovaries and using rocket-immuno-electrophoresis, we showed that a Culex ovary, but not an Anopheles ovary, could replaces Aedes ovaries as a source of the releasing factor. In Ae. aegypti, EDNH-releasing factor was required again after oviposition in order to reinitiate the vitellogenic process in females that took a second blood meal. Thus, the releasing factor is part of the mechanism regulating cyclic egg maturation in mosquitoes.

20-Hydroxy-ecdysone as a modulator of electrical activity in neurosecretory cells of Rhodnius prolixus

Ovariectomy of the adult female Rhodnius results in a reduction of the electrical activity of the corpus cardiacum. Injection of 20-hydroxy-ecdysone into ovariectomized animals increases the activity to control values. Incubation of heads isolated from ovariectomized females in 1.0 × 10 −7 M 20-hydroxy-ecdysone elicits a recruitment of large-amplitude spikes and the appearance of bursting activity in the corpus cardiacum of mated females which is characteristic of neurohormone release. Simultaneous recordings from the median neurosecretory cells and the corpus cardiacum demonstrate that the action neurosecretory cells.

Hormone stimulated lipolysis and proline synthesis in the fat body of the adult tsetse fly, Glossina morsitans

G. morsitans fat cells incubated in vitro with l-[U- 14C]-leucine incorporated the radiolabel, mainly into triglycerides. Aqueous extracts of corpora cardiaca, midbrain, or thoracic ganglion stimulated the release of radiolabelled material from prelabelled fat cells in vitro. Corpora cardiaca extracts were the most active, approx. 1 × 10 −3 gland pairs/μl elicited the maximal response. At concentrations above 1 × 10 −3 gland pairs/μl the activity of corpora cardiaca extracts was inhibited by a substance which could be removed by gel filtration. The stimulatory factor in nervous-tissue extracts was destroyed by proteolytic enzymes and was recoverable in a single peak by Sephadex G15 gel filtration. Results suggest that it is a peptide hormone produced mainly by the median neurosecretory cells of the midbrain with the corpora cardiaca being the site of storage and release. No hormone was detectable in fresh haemolymph, but it was found at high concentration in boiled haemolymph, implying the presence of a heat labile inhibitor. Under the in vitro conditions used the hormone stimulated the synthesis of proline from alanine and the hydrolysis of triglycerides to free fatty acids. The probable functions of the hormone are to stimulate proline synthesis in response to demand for flight and/or to mobilise lipid for larval nutrition. The relative importance of these apparent functions in vivo could not be determined.

Influence of a baculovirus infection on molting and food consumption by Spodoptera litura

The effect of a baculovirus (nuclear polyhedrosis virus) infection on molting, neurosecretory activity, and food consumption of the tobacco leaf eating caterpillar. Spodoptera litura, is studied. The virus was administered by allowing the larvae to feed on castor leaves contaminated with purified polyhedral suspension (5.57 × 10 8/ml). Host larvae failed to molt more than once after infection. Infected last-instar larvae failed to pupate and had prolonged larval stage. Activity of median neurosecretory cells (MNC) of brain increased during disease development. However, the larval—pupal molt was inhibited, possibly due to lack of release of neurosecretion from the MNC. The surface area of corpus allatum of last-instar larvae increased during infection indicating high activity. Infected larvae continued to feed almost until death. The indices of digestion and utilization were significantly lowered due to disease development.