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At least 19 recordsLinked to original sources
PubMed1992

Monoclonal antibodies against Nereis virens brain homogenates as probes for isolation and in situ detection of new neurosecretions.

The brain of Nereis contains 26 ganglionic nuclei which produce numerous neurosecretions. Only a few of them have been characterized. The production of monoclonal antibodies was adopted as an approach to discover unknown neurosecretions. Monoclonal antibodies produced against Nereis virens brain homogenates were selected using stepwise ELISA tests first with brain homogenates, then with brain neurosecretions. Eight antibodies specific for Nereis neurosecretions were selected. The results are illustrated with one of these monoclonal antibodies which was directed against a major peak after HPLC purification of brain neurosecretions. This antibody was subsequently used for the in situ detection of recognized epitope(s) in the brain and ventral nerve cord cells.

Animals↗
PubMed1992

Ca(2+)-independent and Ca(2+)-dependent stimulation of quantal neurosecretion in avian ciliary ganglion neurons.

1. Although it is generally agreed that Ca2+ couples depolarization to the release of neurotransmitters, hypertonic saline and ethanol (ETOH) evoke neurosecretion independent of extracellular Ca2+. One possible explanation is that these agents release Ca2+ from an intracellular store that then stimulates Ca(2+)-dependent neurosecretion. An alternative explanation is that these agents act independently of Ca2+. 2. This work extends previous observations on the action of ETOH and hypertonic solutions (HOSM) on neurons to include effects on [Ca2+]i. We have looked for Ca(2+)-independent or -dependent neurosecretion evoked by these agents in parasympathetic postganglionic neurons dissociated from chick ciliary ganglia and maintained in tissue culture. The change in concentration of free Ca2+ in the micromolar range inside neurons ([Ca2+]i) was measured with indo-1 with the use of a Meridian ACAS 470 laser scanning microspectrophotometer. 3. Elevated concentration of extracellular KCl increased [Ca2+]i and the frequency of quantal events. Also, a twofold increase in osmotic pressure (HOSM) produced a similar increase in quantal release and a significant rise in [Ca2+]i; however, the Ca2+ appeared to come from intracellular stores. 4. In contrast, ETOH stimulated quantal neurosecretion without a measurable change in [Ca2+]i. It appears the alcohol exerts its influence on some stage in the process of exocytosis that is distal to or independent of the site of Ca2+ action. 5. The effects of high [KCl]o and osmotic pressure were occlusive. This is explained in part by the observation that hypertonicity reduced Ca2+ current, but an action on Ca2+ stores is also likely.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1979

[Experimental hepatic encephalopathy. The effect of portocaval shunt on the evolution of the anterior hypothalamic neurosecretion in the rat (author's transl)].

The evolution of the anterior hypothalamic neurosecretion is studied in control, sham-operated and portocaval shunt rats. In sham-operated related to control rats, no modification of the anterior hypothalamic neurosecretion is observed. In portocaval shunt rats, the hypothalamic neurosecretion increases. This increase is mainly observed into the median eminence in all the portocaval shunt rats. The hypothesis according to which the modification of neurosecretory acitivity of the hypothalamic structures may be related to a discrepancy between the central monoamines is discussed.

Animals↗
PubMed1978

Histopathology and histochemistry of the insects treated with chemosterilants VI: brain damage including reduced neurosecretion caused by chemosterilants in Periplaneta americana (L).

The brain is damaged and neurosecretion is reduced in the P. americana treated with chemosterilants thio-tepa and bis (dimethylamino) dithiazolium chloride. The damage includes, separation of neurolemma, vacuolisation and chromatolysis in the nuclei of neurons and extensive damage to fibres. Reduced neurosecretion, vacuolisation in the cytoplasm and karyolysis in the nucleus of neurosecretory cells, are also observed. These changes in the brain are of considerable importance to understand the mode of action of the chemosterilants.

Animals↗
PubMed1975

[Distribution of neurosecretion in the neurohypophysis of the cow during and following milking].

Studies by optical microscopy showed that discharge of neurosecretion brought about by the stimulus of milking took place in the zona centralis and also in the transitional and main sectors of the zona terminalis. The zona marginalis, zona metacentralis and the peripheral sector of the zona terminalis were not involved. In pituitary glands fixed at various time intervals after milking, the increase in secretion content and the disappearance of perivascular accumulations of secretion were evidently a result of renewed production and storage of neurosecretion in the hypophysis. The renewed homogeneous distribution of secretion in the zona terminalis had not been completed one hour after milking. The increase in size and number of pituicytes and their frequent appearance in adventitious tissue of vessels and around sinusoid capillaries after the liberation of secretion may be related to degradation processes of neurosecretory material.

Animals↗
PubMed1977

The effect of age and strain on the amount of neurosecretion.

The work carried on 4 groups of guinea pigs, each group consisting of five animals showed, that the age and strain may influence the amount of neurosecretion, with the older (except 6 month old animals which passed maturing stage) secreting more than that of younger. And the amount of neurosecretion in animals of the black strain is somehow lower than the ones of the grey.

Age Factors↗
PubMed1992

An electron microscopic study of neurosecretion in the cerebral ganglion of the earthworm.

Non-synaptic, exocytotic release of neurosecretory granules in cerebral ganglion neurons was observed electron microscopically in 3 species of the oligochaete annelids Aporrectodea caliginosa, Octolasion cyaneum and Lumbricus terrestris. In addition to the features indicating exocytotic release of neurosecretory granules into perineuronal space, possible features of neurosecretion into blood vessels were seen within the cerebral ganglion. Axon terminals in synaptic contact with perikaryal profiles of cerebral ganglion neurons were also found.

Animals↗
PubMed1975

[Distribution of neurosecretion in the supraoptic and paraventricular nuclei of the cow before and following milking].

Distribution of neurosecretion and enzymes in the nuclei was studied by optical microscopy and histochemical methods. The stimulus of milking had no effect on the amount of secretion in the supraoptic nucleus, but synthesis of secretion in the paraventricular nucleus was stimulated by oxytocin liberation associated with milking, and it was still present 60 minutes after milking. It seems that each nuclear region is a functionally independent unit.

Animals↗
PubMed1991

Ca(2+)-dependent phosphorylation of synapsin I as a possible regulatory mechanism of neurosecretion.

Phosphorylation of homogeneous synapsin I isolated from human brain by Ca2+, phospholipid-dependent protein kinase (protein kinase C) from the same source was studied. The inhibitory effect of calmodulin on this process was demonstrated. The kinetics of activation of synapsin I phosphorylation by acidic phospholipids, phosphatidylserine and phosphatidylinositol, in the absence and presence of phosphatidylinositol-4,5-bisphosphate and diacylglycerol was compared. The proteolytic effect of degradation of the synapsin I molecule phosphorylated by Ca2+, calmodulin-dependent protein kinase II was revealed. No proteolysis of synapsin phosphorylated under similar conditions either by protein kinase C or cAMP-dependent protein kinase was detected. In view of the process specificity, the physiological significance of the observed effect is suggested. The inter-relationship between two ways of neurosecretion regulation is discussed: an earlier known, conventional way, mediated by synapsin I phosphorylation by Ca2+, calmodulin-dependent protein kinase II, and another one, mediated by synapsin I phosphorylation by protein kinase C. The modulating role of polyphosphoinositides in the PK C-dependent way of regulation is considered.

Brain↗
PubMed1990

Tetrahydroaminoacridine (tacrine) stimulates neurosecretion at mammalian motor endplates.

1. Tacrine (20 microM) induced, like 4-aminoquinoline (4-AQ, 200 microM), the appearance of a population of miniature endplate potentials (m.e.p.ps) with more than twice the normal amplitude or time-to-peak. The times-to-peak of nerve impulse-evoked endplate potentials were not similarly affected. 2. Cholinesterase inhibition by edrophonium (25 microM) did not prevent tacrine or 4-AQ from inducing this population of m.e.p.ps. 3. Nerve-muscle preparations in which the normal calcium-sensitive quantal release of acetylcholine had been blocked by botulinum neurotoxin type A also responded to tacrine by an increase in the frequency of giant or slow m.e.p.ps. 4. Reduction of the temperature from 30 degrees to 14 degrees C reduced the frequency of giant or slow m.e.p.ps induced either by tacrine or by 4-AQ. A similar effect was obtained by colchicine (5 mM). This supports the idea that proximo-distal axonal transport is required for the secretory activity. 5. The neurosecretion evoked by tacrine could explain the therapeutic effects of the drug claimed in the treatment of Alzheimer's type of dementia.

Acetylcholine↗
PubMed1978

Neurosecretion. XVII. Experimentally induced release of neurosecretory material by exocytosis in the insect Leucophaea maderae.

In the corpora cardiaca of the insect Leucophaea the administration of serotonin elicits ultrastructural features indicative of the extrusion of neurosecretory material by exocytosis. The response to the stimulus and the process of extrusion seem to occur at considerable speed. Nearly all of the 30 test animals, fixed at various intervals starting as early as 3 min after the injection of the drug, show granules captured at the moment of leaving the axon as well as fully exteriorized secretory material. The fact that many of these granules are much smaller than the typical neurosecretory type speaks for intracellular fragmentation of the latter prior to the discharge of this cellular product. After 25 min or more the extruded electron dense structures show signs of breakdown. 3the apparent speed of these phenomena accounts for the dearth of omega-type configurations observed in unstimulated specimens of this species. The possible relationship between the membrane phenomena involved in exocytosis and the transient protrusions of bounding membranes of neurosecretory granules described in earlier papers remains to be clarified.

Animals↗
PubMed1977

"Gomori-positive" neurosecretion in the rat after deafferentation of the medial basal hypothalamus.

A portion of the "Gomori-positive" peptidergic neurosecretory (NS) cells in the paraventricular and especially in the supraoptic and postoptic nuclei degenerate three weeks after deafferentation of the medial basal hypothalamus. Most of the remaining NS cells show signs of high activity. Regenerating NS fibres form "muffs" around the blood vessels laterally from the lesion; some of them enter the "isolated" area or persist there if a thin layer of the brain tissue is left somewhere untouched under the basal end of the cut. The regenerating NS fibres are also found outside the nervous tissue: within the scar tissue, in the proliferating connective tissue of the brain sheet below the basal end of the cut and in the mantel plexus area. The NS fibres make close contact with blood vessels invading or penetrating the vascular wall. It is suggested that peptide neurohormones discharged from the "Gomori-positive" NS terminals enter the general blood circulation as well as the portal blood at the site of these newly formed axovasal contacts. It is supposed that under these conditions monoaminergic terminals do not discharge monoamines because no stimulation of monoamine-producing NS cells occurs with deafferentation.

Animals↗
PubMed1975

Correlations between brain catecholamines, neurosecretion, and serum corticoid levels in osmotically stressed mallard ducks (Anas platyrhynchos).

The effects of depleting brain catecholamines with a combined treatment of reserpine and alpha-methyl-p-tyrosine on serum corticosterone levels and release of immunoreactive neurophysin from the median eminence, in osmotically stressed and unstressed mallard ducks, were studied. Corticoid levels in salt loaded birds were more than three times that of unstressed birds. The combined treatment of reserpine and alpha-methyl-p-tyrosine significantly decreased the concentration of brain monoamines in all experimental groups and raised serum corticoid levels in non-stressed birds to the same level found in the osmotically stressed animals. Immunoreactive neurophysin in the zona externa of the median eminence was depleted in all birds subjected to either osmotic stress and/or reserpine treatment but not in unstressed control birds. These preliminary data indicate that catecholamines may exert an inhibitory influence on both ACTH release from the anterior pituitary and neurophysin from the median eminence and that these two events may in some way be interrelated in the duck.

Animals↗
PubMed1977

Neurosecretion. XVI. Protrusions of bounding membranes of neurosecretory granules.

Protrusions of bounding membranes of neurosecretory granules, comparable to those demonstrated by Castel (1977) in the mammalian neurohypophysis, were observed under various experimental conditions in the corpora cardiaca of the insects Leucophaea maderae and Periplaneta americana. Electrical stimulation in vitro of the nervus corporis cardiaci I, which elicited a marked rise in the amount of neurohormone discharged, as determined by bioassay, also yielded a significantly larger number of membrane protrusions than were observed in unstimulated controls. However, no comparable response was obtained in glands subjected to stimulation of hormone release by exposure to serotonin or high potassium concentrations. On the other hand, membrane protrusions were numerous under certain conditions not expected to stimulate neurohormone release, i.e., in tissue exposed to a zinc iodide mixture without prior fixation. The present results support the conclusion drawn by Castel that these configurations appear to be related to the process by which neurosecretory material is discharged. Too transient to be much in evidence under physiological condition, they become more prominent not only after appropriate acceleration of the rate of release, but also when such membrane arrangements are "frozen" by procedures that interfere with the regular milieu.

Animals↗
PubMed1977

An ultrastruct study of the innervation of the musculature of the pond snail Lymnaea stagnalis (L.) with reference to peripheral neurosecretion.

The ultrastructure of nerve endings in the musculature of Lymnaea stagnalis was studied. Seventeen different types of axon ending were distinguished according to the size and morphology of the granules or vesicles they contain. Nine types of axon endings form neuromuscular synapses. Some of these types also form axo-somatic synapses on peripheral neurones. One axon may innervate several muscle cells. Furthermore more than one type of axon may innervate one muscle cell. One type of axon ending forms axo-axonic synapses on the presynaptic part of neuromuscular junctions. In the connective tissue near muscle cells seven types of free axon endings were found. These seem to be peripheral neurosecretory endings. Some of these are probably derived from known types of neurosecretory cells in the central nervous system, whereas others appear to originate from peripheral neuronal perikarya. Body wall muscles appear to be innervated by neuromusculatur synapses, whereas in the visceral musculature both neuromuscular junctions and free axon endings are found.

Animals↗
PubMed1975

Neurosecretion in the sinus gland of the fiddler crab, Uca pugnax.

The ultrastructure of the sinus gland of the fiddler crab, Uca pugnax, was investigated and found to be similar to that in other crustaceans. Five types of neurosecretory axon terminals were tentatively identified on the basis of the size, shape, and electron density of granules within the axons. Release of neuro-secretory material appears to be by exocytosis.

Animals↗