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PubMed1978

[Circadian rhythm of neurosecretion of the macrocellular hypothalamic nuclei under different lighting conditions].

Parameters of diurnal changes in the diameter of neuronal nuclei of the supraoptical and paraventricular nuclei in the hypothalamus of hybrid mice F1 (CBA X C57BL/6) depend on the duration of illumination and dark periods. Biwave character of variations is preserved at changing the illumination regime from 6C + 18T to 18C + 6T. Certain specificity in diurnal changes of neurosecretory activity of the nuclei under investigation is noted.

Animals↗
PubMed1980

Neurosecretion in the central nervous system of an Indian spider Oxyopes sakuntale Tikader (Araneidae: Oxyopidae).

Neurosecretory cells have been observed in the entire central nervous system of an adult Indian spider Oxyopes sakuntale Tikader. These cells are present in groups at various locations in the central nervous system. They can be divided into two types on the basis of their shape, size and cytomorphic properties. Unlike insects here the median group of pars intercerebralis has very few cells. All the neruosecretory cells have similar staining reaction and can not be differentiated into types on the basis of their staining property. Majority of the cells are circular in shape, bigger in size and dark staining. In between there are few cells which are elleptical in shape, smaller in size and light staining. They all stain green with PAF (As modified by Ewen 1962) light blue with CHP (Gomori 1941) and red with HEIDENHAINS Azan stain.

Animals↗
PubMed1995

Characterization of presynaptic calcium channels with omega-conotoxin MVIIC and omega-grammotoxin SIA: role for a resistant calcium channel type in neurosecretion.

The peptide Ca2+ channel antagonists omega-conotoxin (omega-CTX) MVIIC and omega-grammotoxin (omega-GTX) SIA were studied by measuring their effects on the release of [3H]glutamate from rat brain synaptosomes. The pseudo-first-order association constant for omega-CTX MVIIC (1.1 x 10(4) M-1 sec-1) was small, relative to that for omega-GTX SIA (3.6 x 10(5) M-1 sec-1). Equilibrium experiments showed that omega-CTX MVIIC blocked approximately 70% of Ca(2+)-dependent glutamate release evoked by 30 mM KCl (IC50 approximately 200 nM), whereas omega-GTX SIA virtually eliminated release, with lower potency (IC50 approximately 700 nM). At stronger depolarizations (60 mM KCl), neither toxin (at 1 microM) showed significant block of release, but when these or other Ca2+ channel antagonists (omega-CTX GVIA or omega-agatoxin IVA) were used in combination a substantial fraction of release was blocked. [3H]Glutamate release that was resistant to omega-CTX MVIIC was characterized with respect to its sensitivity to block by omega-GTX SIA and the inorganic blocker Ni2+. Both omega-GTX SIA and Ni2+ were relatively weak blockers of the resistant release. These results suggest that a previously uncharacterized Ca2+ channel exists in nerve terminals and can be distinguished on the basis of its resistance to omega-CTX MVIIC and its weak sensitivity to omega-GTX SIA and Ni2+. Thus, at least three channel types (P, N, and a "resistant" type) contribute to excitation-secretion coupling in nerve terminals.

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PubMed1976

[Variations in cerebral neurosecretion during the reproductive cycle of a viviparous insect, Glossina fuscipes fuscipes (Diptera, Muscidae)].

The neurosecretory A cells of the pars intercerebralis of the viviparous fly Glossina fuscipes fuscipes present important changes during the genital cycle. A slight release of neurosecretory products occurs at the moment of the first ovulation and at the hatching. An important discharge takes place just before the larviposition and the second ovulation.

Animals↗
PubMedDate not supplied

[Morphofunctional state of the rat supraoptico-neurohypophyseal system in hypoparathyroisis].

Volumes of nuclei and nucleoli of neurosecretory cells of the hypothalamic supraoptic nucleus were investigated morphometrically, and the amount of neurosecretion in the posterior hypophyseal lobe was determined photometrically in rats at varying time of parathyroprivic hypocalcemia. The data obtained were indicative of increased function of the hypothalamic supraoptic nucleus on the 5th day of parathyroprivic hypocalcemia and a decrease in the amount of neurosecretion in the posterior hypophyseal lobe that can be interpreted as a sign of an increased discharge of neurosecretion into the blood flow. A decrease in function of neurosecretory cells of the supraoptic nucleus in parallel with an increase in the amount of neurosecretion in the posterior hypophyseal lobe on days 15 and 30 of development of parathyroprivic hypocalcemia indicated retention of a discharge of neurosecretion. Return of neurosecretion to normal tended to occur on day 60.

Animals↗
PubMed1975

[Morphometric studies on the cells of the supraoptic and the paraventricular nuclei of milked and unmilked cows].

By morphometric methods the quantitative changes of cell, cytoplasm, nucleus, nucleolus and also of the contents of secretes from the neurosecreting cells of the N.S.O. (Pars parvocellularis and Pars magnocellularis) and N.P.V. from unmilked and milked cows was investigated. This single parameters change in N.S.O. and N.P.V. approximately in the same rhythm. The nucleus-plasma-relation is only unessential influenced. The cytoplasm of the neurosecreting cells of the N.P.V. from unmilked and milked cows is greater ca 6 once, than the nucleus of this. The cytoplasm of the neurosecreting cells of the N.S.O. is greater ca 5 once. A maximal increase of the size of the single parameters and so the greatest activity were observed in the neurosecreting cells of the N.S.O. and N.P.V. of cows, which were prepared 15 min after milking. 60 min after milking of the cows they reach the initial value. The reaction to the milking stimulus is maximal 3 once greater in the neurosecreting cells of the N.P.V. than in the N.S.O. To the same time after the milking stimulus the contents of secretes is maximal diminished about 10 once in the N.P.V. and about 8 once in the N.S.O. The conception that in the N.P.V. the hormon oxytocin is synthetized, is anew supported.

Animals↗
PubMed2002

Neuronal and glial response in the rat hypothalamus-neurohypophysis complex with streptozotocin-induced diabetes.

This study was aimed to examine the neuronal and glial response in the hypothalamus and neurohypophysis of rats with streptozotocin-induced diabetes. At various time intervals after induction of diabetes the neurons in the paraventricular- (PVN) and supraoptic- (SON) nucleus showed upregulated arginine vasopressin (AVP) and oxytocin (OXT) immunoexpression, being most pronounced at 2 weeks. Concomitant to this was the hypertrophy of PVN and SON neurons. NMDAR1, which was constitutively and moderately expressed in normal rats, was markedly augmented, being most intense at 4 months. This coincided with the expression of neuronal nitric oxide synthase (nNOS). Contrary to this, the expression of GluR2/3 was progressively downregulated, so that it was hardly detected at 4 months. Both astrocytes and microglia marked by anti-GFAP and OX-42, respectively, appeared activated. In pars nervosa, the projection target of the axon terminals of PVN and SON neurons, massive axons and terminals (Herring bodies) laden with neurosecretions were observed in diabetic rats. Colocalization study showed that the neurosecretions were internalized by activated pituicytes and microglia associated with the axons. The present results suggest that the neurosecretion of PVN and SON neurons is enhanced in diabetes. This is coupled by upregulation of NMDAR1 and nNOS but downregulation of GluR2/3. It is speculated that the glutamate receptors and NO are linked to overactivation of PVN and SON neurons leading ultimately to cell death of some of them. The pituicytes and microglia in pars nervosa would help to modulate the release of neurosecretion.

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PubMed2003

Cadmium effect on the structure of supra- and subpharyngeal ganglia and the neurosecretory processes in earthworm Dendrobaena veneta (Rosa).

Cadmium effects on the supra- and subpharyngeal ganglia, neurosecretion and RNA content in the neurosecretory cells were tested in earthworms Dendrobaena veneta exposed to 10 and 50 mg Cd kg(-1) in soil after 20 days of the experiment. Accumulation of cadmium in the ganglia of nervous system was also measured using AAS method. Cadmium was accumulated in the nervous system. The accumulated amount was proportional to Cd soil concentration and the exposure time. A considerable fall in neurosecretion and RNA content in the neurosecretory cells and neurosecretion in the neuropile (the axons) of both tested ganglia was induced by 50 mg Cd kg(-1). It seemed that neurosecretion synthesis and its axonal transport could be suppressed. Cadmium caused degenerative changes as vacuolization of the neurosecretory cells and neuropile in both tested ganglia.

Animals↗
PubMed2001

Hyperosmolarity reduces facilitation by a Ca(2+)-independent mechanism at the lobster neuromuscular junction: possible depletion of the releasable pool.

1. At the crustacean neuromuscular junction, action potential-evoked neurosecretion increases in proportion to stimulation frequency, a process termed frequency facilitation. In the present study we examined how frequency facilitation is affected by osmotic pressure. 2. Hypertonic solution (HS) was applied by local superfusion of the synaptic area. Quantal release was monitored by focal extracellular recordings of postsynaptic potentials. Several stimulation frequencies (f) in the range from 1 to 10 Hz were employed, and quantal content (m) together with the number of releasable units (n) and release probability (p) was evaluated for each frequency. 3. Osmotic pressure enhanced quantal release at the lowest f tested (1 Hz) but suppressed neurosecretion at higher f (7-10 Hz). Thus, hyperosmolarity enhanced action potential-evoked release but suppressed frequency facilitation. 4. Chelation of intracellular calcium by BAPTA showed that the effect of HS was calcium independent. 5. Binomial analysis of quantal content revealed that HS suppressed the increase in the number of releasable units, which was very pronounced during facilitation under control conditions. Since HS also stimulated asynchronous quantal release, the observed effect of HS on facilitation can be explained by the depletion of the releasable pool of quanta caused by the asynchronous neurosecretion. 6. To test this hypothesis we increased the available pool of vesicles using serotonin and demonstrated that the suppressing effect of HS on facilitation was reversed. 7. The observed effects of HS on facilitated neurosecretion could be described quantitatively using our model for mobilization of vesicles into the releasable pool enhanced by action potentials.

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