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PubMedDate not supplied

[Age-related reactions of the rat hypothalamo-hypophyseal neurosecretory system to physical load].

In two age groups of rats (5 to 6 months--young animals and 10 to 12 months--aging rats) the response of peptidergic Gomori-positive hypothalamic-hypophyseal neurosecretoryoryory (NS) system to moderate exercises (swimming during 30 minutes) was studied. The age differences in histology of NS centers and neurogemnic organs were found immediately after swimming and within 4 subsequent days. More rapid but less significant devastation of neurogemnic regions, combined with sharp intensification of the neurosecret synthesis in NS centers, was seen in the young animals. In the aging rats the response was slower, the neurosecret synthesis and its release from NS centers were not so activated. The anterocommissural group of the NS centers studied (especially in the young animals) and supraoptic nucleus were most closely associated with the response to exercises. The paraventricular nucleus was activated later, that appears to indicate the secondary inclusion of this NS center into elimination of the aftereffects of an upset balance.

Aging↗
PubMed1978

[Electron- and light microscopic study of changes in the structure of the posterior hypophyseal lobe caused by long-term compression of soft tissues].

In 24 dogs light and electron microscopic changes of the neurohypohysis have been studied at early and intermediate periods of the prolonged compressing syndrom. The amount of neurosecrete has been stated to decrease considerably. Increased excretion of neurosecretory material from neurovascular zones is accompanied by mitochondrial swelling. Together with increased permeability of capillaries, disturbances in blood clotting system are demonstrated. With prolonged time of observations (intermediate period), further decrease of neurosecrete in axons and accumulating bodies is taking place. Some necrotic changes occur in endothelium.

Animals↗
PubMed1977

[Effect of lithium chloride on the rat hypothalamus neurosecretory system].

Methods of quantitative cytochemical analysis were applied to the study of the reaction of the hypothalamohypophysial neurosecretory system (HHNS) to single and course administrations of lithium chloride (in doses of 200 mg/kg). Reaction of the HHNS proved to depend directly on the amount of lithium administered and was characteriaed by the activation of the synthesis and elemination of the neurosecretion with a single administration on the preparation, or depression of the hormonopoiesis in the hypothalamus and exhaustion of the neurosecretion stores in the neurohypophysis in its course application. During the restoration (7 to 30 days after stopping the drug administration) the state of the HHNS gradually approached the initial level. The authors came to the conclusion that the changes in the central mechanisms of the neuro-endocrine regulation at the hypothalamic level caused by lithium were significant in the pathogenesis of the side-action of its salts

Animals↗
PubMed1977

[Hypothalamic disturbances in cerebral circulatory disorders (clinico-morphologic studies)].

The authors studied clinical forms of hypothalamic disturbances in 180 patients with disorders of cerebral circulation. The following syndromes of hypothalamic disorders were distinguished: gastro-intestinal, cardio-vascular, endocrinometabolical, vegetative-endocrinological. In 18 deceased the neurosecretion of the hypophysis and hypothalamus was studied. It was possible to establish the form of neurosecretion movement and its existence or absence in the hypothalamus. In patients who died following an acute disorders of cerebral circulation, both factors in the opinion of the authors, play a certain role in the pathogenesis of a cerebral stroke.

Cerebrovascular Disorders↗
PubMed1984

Neurohemal contact in the internal zone of the rabbit median eminence.

The concept of neurosecretion as the mechanism by which neural control of adenohypophyseal function is accomplished was based on the observation that long capillary loops penetrate deeply into the supraopticohypophyseal tract as it passes through the median eminence internal zone. However, neural contact upon these capillary loops has not been demonstrated in the mammalian median eminence. The present transmission electron microscopic investigation of the rabbit median eminence demonstrates neurohemal contact in the median eminence internal zone. Axons containing small lucent vesicles 53.3 +/- 3.28 nm in diameter (mean +/- SEM) or small lucent and large granular vesicles with a mean diameter of 122.4 (+/- 3.28 nm) in their terminals make neurohemal contact with capillary loops in the internal zone and form a cuff about them. These terminals resemble terminals found in the external zone. Intravenous injection of the false neurotransmitter 5-hydroxydopamine (5-OH-DA) renders small lucent vesicles granular in both the external and internal zone. The effect of 5-OH-DA injection is abolished by concurrent reserpine administration. Whereas large granular vesicles in many terminals become lucent after reserpine administration, in others they remained electron dense. Viewed in the light of previous studies our findings suggest that the internal plexus arises from the external plexus and invaginates the neuropil carrying connective tissue and parvicellular axon terminals of aminergic and peptidergic systems from the external zone into the internal zone, that some elements making neurohemal contact with long capillary loops are terminals of the noradrenergic reticular infundibular tract arising outside the hypothalamus in the brainstem, and that long capillary loops form a system of repeating microvascular modules which markedly increase the surface available for neurohemal contact.

Animals↗
PubMed1992

Ultrastructure of the neurohypophysis.

This review summarizes our current knowledge of the ultrastructure of the human neurohypophysis and includes comments on its anatomy, physiology, and embryology. The neurohypophysis represents a unique tissue having neural and endocrine characteristics and possessing ultrastructural features distinct from those of conventional endocrine organs such as the anterior pituitary, thyroid, pancreatic islets, etc. In contrast to these glands, the neurohypophysis is composed of the processes of mature neurons. As such, it is not capable of synthesizing hormones but only of their storage and release. Neurosecretion is one of the most exciting areas of neuroendocrinology and, although spectacular progress has been achieved in elucidating the process, a number of aspects are incompletely understood. Recent evidence indicates that the magnocellular nuclei of the hypothalamus, the anatomic origin and functional basis of the neurohypophysis, produce not only vasopressin and oxytocin, the so-called "neurohypophyseal hormones," but a number of other biologically active peptides as well. The physiologic function of these substances is largely unknown but they may be of profound importance in endocrine homeostasis. Based on these novel findings, the role of the neurohypophysis in endocrine regulation has to be re-evaluated.

Exons↗
PubMed1980

Fine structure of an octopaminergic neuron and its terminals.

The large octopaminergic dorsal unpaired median neuron of the locust that innervates the extensor tibiae muscle, DUMETi, was examined electronmicroscopically. Its soma contains many Golgi complexes apparently making dense-core vesicles similar to those found in peripheral branches and terminals. There are also larger stores of the dense material in the soma, especially near the exit of the principal neurite, that are not in vesicular form. Since the neurons can be penetrated and stimulated by microelectrodes, they form favorable subjects for direct studies of the control of neurosecretion. Preterminal fine branches of the neuron were located in proximal outer bundles of muscle fibers into which they had been traced electrophysiologically. They contain numerous large dense-core vesicles arrayed in rows near microtubules. These fine branches have a thick layer of collagenous connective tissue between the axon and the muscle fiber. Final terminals have varicosities containing many vesicles, lying inside the outer layers of the sarcolemmal complex of muscle fibers. They do not form synaptic structures. Terminals of another DUM neuron, one that innervates the dorsal longitudinal flight muscles (DUMDL), were similar in detail to those of DUMETi. DUMETi swelled about 20-fold in cross-sectional area above a ligature, in a 12-hr period, indicating that there is an extensive centrifugal flow of material in it, and sprouted a branch.

Animals↗
PubMed1994

Dynamic changes in LHRH neurovascular terminals with various endocrine conditions in adults.

Luteinizing hormone-releasing hormone (LHRH) release is required for ovulation in mammals. Although evidence for the direct action of gonadal steroids on LHRH neurons has been minimal, their importance in inducing the preovulatory surge of LHRH is unequivocal. We have identified a subgroup of LHRH neurons with progestin receptors in guinea pigs. Given their central position, these neurons may constitute foci of initial activity, which are amplified throughout the population of LHRH neurons, resulting in increased LHRH neurosecretion on the afternoon of proestrus. Additionally, gonadal steroids may regulate LHRH secretion at the level of the terminals. Using immunoelectron microscopy and image analysis, we have illustrated the dramatic influence of gonadal steroids on individual LHRH terminals in the median eminence of rats. Indirectly, gonadal steroids may modulate LHRH release by modulating glial elements. Using double-label fluorescence confocal microscopy, we illustrate that LHRH terminals in the median eminence are encased by end-feet of tanycytes. Acting on glial elements, gonadal steroids may regulate access of LHRH terminals to the basal lamina and influence the amount of the neuropeptide reaching the portal vessels. We propose that during the preovulatory surge, LHRH release is coordinated by synergistic mechanisms operating at the level of particular subgroups of neuronal perikarya and/or discrete regions of the median eminence. These synergistic actions may ensure that LHRH is released in a precipitous fashion, to induce the surge of LH from the pituitary, required for ovulation.

Animals↗
PubMed1982

Ultrastructure of the rat median eminence after superfusion.

Isolated medio-basal hypothalami of adult rats were continuously superfused in a chamber with controllable inputs and outputs, for periods from 30 to 240 min. The median eminence was prepared for transmission electron microscopy under carefully controlled conditions by immersion fixation with osmium tetroxide. The ultrastructure of superfused median eminence was compared with that of directly fixed, non-superfused median eminence. Even after 4h of superfusion, the median eminence displays remarkably well preserved histological and cytological patterns; cytomembranes, cell organelles, intercellular relationships, and extracellular spaces were remarkably similar in superfused and non-superfused tissues. As a consequence of osmium tetroxide fixation, microtubules were not observable. The ultrastructural information obtained from unstimulated rat median eminence superfused in vitro provides a basis for future morphofunctional correlations in the study of neurosecretion.

Animals↗
PubMed1975

Regulation of neurosecretory activity in the freshwater pulmonate Lymnaea stagnalis (L.) with particular reference to the role of the eyes: a quantitative electron microscopical study.

The process of neurosecretion in the Caudo-Dorsal Cells (CDC) of the freshwater snail Lymnaea stagnalis, which produce an ovulation hormone, shows a diurnal rhythmicity. Synthesis, transport and release of the neurosecretory material (NSM) is high during the evening and the early night and low during the rest of the day, while storage of NSM mainly occurs during the daytime. In the present study the role of the eyes in the regulation of the CDC-rhythm was investigated. During a 24-hr period, at time intervals of 6 hrs, cerebral ganglia, which contain CDC, of blinded and control snails (5 per group) were fixed and the CDC were studied with quantitative electron microscopical methods. The CDC of the controls showed a distinct diurnal thythmicity. Blinding, on the other hand, clearly affected this rhythmicity. The results indicate that after blinding the circadian CDC-rhythms of individual snails are no longer synchronous with each other ("interanimal desynchronization"). It is suggested that the rhythm of CDC neurosecretory activity is synchronized by the natural light/dark cycle via the eyes. The information from the eyes probably reaches the CDC via a nervous pathway. True snyapses and three types of synapse-like structures were found on the CDC. Their role in the regulation of CDC-activity is discussed. The effect of blinding is specific for the CDC; blinding does not influence the diurnal rhythmicity of another type of cerebral neurosecretory cells, the Light Green Cells (LGC). The CDC within a cluster act synchronously. This synchrony does not depend upon the presence of the eyes. Some structures which may be involved in establishing this synchrony, such as subsurface cisterns, desmosome-like structures and "specific release sites", are described.

Animals↗
PubMed1978

The frontal ganglion of Periplaneta americana L. (Insecta): an electron microscopic and immunohistochemical study.

The frontal ganglion, part of the stomatogastric nervous system, contains about 60 to 80 neurons, 25 to 30 micron in diameter. A well developed Golgi system, producing dense-core vesicles, lysosomes, multivesicular bodies and dense bodies are abundant. Glia elements are sparsely distributed. Many nerve fibres contain granules of different size and electron density. Five groups of fibres can be distinguished: Fibres with granules of about 200 nm (type A), fibres with granules of about 160 to 170 nm (type B), fibres with granules of about 80 to 100 nm (type C) and those with synaptic vesicles of 50 nm (type D) respectively. A fifth very small type contains neither vesicles nor granules. Special attention was paid to synaptic contacts. The divergent dyad seems to be the main type in the frontal ganglion. Frequently, neurosecretory endings are observed in presynaptic position. Immunocytochemical "staining" of neurosecretory material closely corresponds to the distribution of type A fibres, as observed electron microscopically. Immunoelectrophoresis of extracts from frontal ganglia with polyspecific anti-neurosecretion-serum reveals a single precipitation line, indicating that the immunocytochemical localization of neurosecretory material is due to reaction with a specific as well as a cross-reagent anitbody.

Animals↗
PubMed1975

Functional correlates of low molecular weight peptide synthesis in Aplysia neurons.

An attempt was made to determine whether the synthesis of low molecular weight proteins by certain neurons of Aplysia could be correlated with either pacemaker activity or neurosecretion. Electrophysiological tests indicated that the spontaneous generation of action potentials in cells L8 and L9 is due to an endogenous pacemaker mechanism. Gel electrophoresis of proteins synthesized by these neurons showed no evidence of low molecular weight material. The non-neurosecretory interneuron L10 synthesizes a 12,000 dalton protein, whereas the silent neurosecretory cell L5 synthesizes a lower molecular weight peptide. Taken with previous findings, these results indicate that there is no correlation between pacemaker activity and the synthesis of these peptides. There is, however, a strict correlation between neurosecretory activity and the synthesis of proteins of molecular weights lower than 12,000 daltons.

Action Potentials↗
PubMed1980

Electrical activity of neurosecretory axons from the brain of Rhodnius prolixus: relation of changes in the pattern of activity to endocrine events during the moulting cycle.

Ongoing electrical activity was recorded from the axons of neurosecretory cells from the brain of 5th instar Rhodnius prolixus throughout the moulting cycle. Dramatic changes in both the frequency and pattern of electrical activity occur at specific times during the cycle, enabling the timing of release of neurohormones from the brain to be inferred. The level of transport of stainable secretion appears to be closely coupled to the electrical activity at all times. Activity is low in unfed Rhodnius, but within minutes of the insect taking a blood meal, there is a rapid appearance of bursting activity from a number of units, in conjunction with apparently continuous firing components. The bursting activity declines at about 2 h remaining low for the following 5 days, at which time there is a resurgence in the bursting pattern for a few hours. Both peaks of bursting activity immediately precede increases in haemolymph titer of ecdysones, suggesting that release of prothoracotropic hormone occurs on these two occasions. The continuously firing components initiated at feeding maintain a high level for 5 days indicating release of other brain neurosecretions. Intense electrical activity in the form of bursting activity and high apparently continuous pattern resumes shortly before ecdysis and continues until 12 h after. The relationship of neurohormone release at this time to bursicon and ecdysis behavior is discussed.

Animals↗
PubMed1984

Dose-dependent influence of fentanyl on prolactin, growth hormone, and mood.

The effect of Fentanyl (FE), an opioid agonist, on neurosecretion and mood was investigated in normal volunteers using doses of 0.1, 0.2, 0.25 mg/70 kg. FE caused a strong dose-dependent increase in prolactin (PRL) secretion in every subject. In contrast, growth hormone (GH) was stimulated significantly at the highest dose only. Additionally, FE induced a significant increase in feeling of wellbeing measured by the Visual Analogue Scale (VAS).

Adult↗
PubMed1986

Growth hormone neurosecretory dysfunction.

The basis for understanding clinical disorders in the neuroregulation of GH secretion is derived from the complexity of the CNS-hypothalamic-pituitary axis. Studies in animals and humans demonstrate an anatomic, physiological and pharmacological evidence for neurosecretory control over GH secretion including neurohormones (GRH, somatostatin), neurotransmitters (dopaminergic, adrenergic, cholinergic, serotonergic, histaminergic, GABAergic), and neuropeptides (gut hormones, opioids, CRH, TRH, etc). The observation of a defect in the neuroregulatory control of GH secretion in CNS-irradiated humans and animals led to the hypothesis of a disorder in neurosecretion, GHND, as a cause for short stature. We speculate that in this heterogeneous group of children a disruption in the neurotransmitter-neurohormonal functional pathway could modify secretion ultimately expressed as poor growth velocity and short stature.

Amino Acid Sequence↗
PubMed1989

Neurosecretory-like material in 3rd- and 4th-stage Dirofilaria immitis larvae (Nematoda: Filarioidea).

Phase-interference microscopic examination of the infective, post-infective 3rd-stage and 4th-stage larvae of Dirofilaria immitis has identified a single cell body in each of the paired lateral amphidial nerves which undergoes characteristic morphological change during the development from 3rd- to 4th-stage larvae. Acetaldehyde-fuchsin staining of worm sections revealed fuchsinophilic material in the precise location of the amphidial nerve-cell bodies observed by phase-interference microscopy. This material was found in 70% of infective larvae recovered from mosquitoes and in 100% of larvae recovered from micropore chambers 24 h after implantation into BALB/C mice. In pre-moult larvae recovered at 42 h (Experiment 1) and at 48 h (Experiment 2) fuchsinophilic material was demonstrable, but no staining was observed in those larvae in which separation of the 3rd- and 4th-stage cuticles had occurred. No such material was observed in 4th-stage larvae recovered from chambers after 74 h, and in these larvae the amphidial nerve-cell bodies were not discernible. These cytological observations are consistent with a cycle of elaboration and release of neurosecretion associated with moulting in D. immitis.

Animals↗
PubMedDate not supplied

[Mechanism of hyocorticosteronemia action of Strongyloides ratti in the rat].

In order to explain the hypocorticosteronemia which establishes itself in rats with Strongyloides ratti parasites, we are proceeding with a functional exploration of the hypothalamo-hypophyso-corticosurrenal axis in experimentally infested rodents. The adreno-cortico-tropic-hormone test (A.C.T.H.), stress to ether and the Lysin-8-Vasopressin and Metopirone tests lead to concordant results: -- the hypothalamo-pituitary-corticosurrenal present a functional integrity which allows it to react normally to direct stimulation or to feed-back; -- the deficiency seems to relate to the hypothalamic secretion of the cortico-releasing factor; -- the cause would stem from an inhibition of the nervous mechanism which regulates this neurosecretion.

Adrenal Cortex Hormones↗