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C Nitsch

Publications and source records attributed to C Nitsch.

At least 73 records · Page 4Linked to original sources
PubMed1981

Ultrastructure of mossy fiber endings in in vitro hippocampal slices.

0.2 to 0.4 mm thick slices of guinea pig hippocampus were studied morphologically after varying periods of incubation at 36 degrees C in Krebs-Ringer solution. Prior to fixation, the slices were tested for the presence of synaptically driven discharges of CA 3 neurons following mossy fiber (mf) stimulation because tissue preservation was satisfactory only in slices in which electrical responses were obtained. The fine structure of the MF layer in slices was compared with the ultrastructure of this region in hippocampal tissue fixed by transcardial perfusion or immersion of the tissue in the fixative. In the central part of the slices many intact neuronal structures of the mf layer could be seen even after 4 h of incubation. In the outer parts of the slices, neurons were swollen and vacuolated. These alterations were not observed in hippocampal tissue fixed by transcardial perfusion or by immersion. In all parts of the slices dark neurons and processes were found. Since dark neurons were also numerous in tissue blocks immersed in the fixative but were rare in perfused material, these changes were obviously caused by damage to unfixed tissue and fixation by immersion.

Animals↗
PubMed1981

[Effects of 3-methylcholanthrene and 3-methylcholanthrene plus piracetam on the gamma-amino-butyric acid (GABA) content of several cerebral regions (author's transl)].

Chronic application of Piracetam decreases 3-methylcholanthrene-induced increased GABA content in the brains of rats and delays tumor appearance. The most active inhibitor of GABA-transaminase, amino oxyacetic acid (AOAA), increases the GABA content in the brain and appears to increase the tumor rate in 3-MC rats. Despite some reservations in view of results derived from investigations of only two compounds (3-MC and Piracetam) we suppose that a relation exists between effects on central nervous system and peripheral carcinogenesis. We will try to support our hypothesis further by using other compounds influencing the GABA-content of the brain.

Aminooxyacetic Acid↗
PubMed1981

Large dense-core vesicle exocytosis and membrane recycling in the mossy fibre synapses of the rabbit hippocampus during epileptiform seizures.

The ultrastructure of the hippocampal mossy fibre layer was studied in ultrathin sections and freeze-fracture preparations of rabbits under deep Nembutal anaesthesia, after recovery from ether anaesthesia, and 40 min after a single injection of methoxypyridoxine, that is, during the second generalized seizure discharge. The giant mossy fibre boutons contain two types of vesicles: evenly distributed, small round clear vesicles (50 nm) and a few scattered large dense-core vesicles (100 nm). In rare instances fusion of dense-core vesicles with the presynaptic membrane was observed. No differences in the morphology of the mossy fibre synapses were found between anaesthetized and unanaesthetized animals. During epileptiform seizures, however, the size and shape of clear and dense-core vesicles varied greatly. The active synaptic zones were covered with large, core-containing omega profiles or bumps and indentations. Only dense-core vesicles seem to undergo exocytosis. A fusion of clear vesicles with presynaptic membrane was not observed. Various explanations for the fact that only dense-core vesicles seem to undergo exocytosis are discussed. The hypothesis is put forward that in the mossy fibre bouton two morphologically and functionally distinct populations of synaptic vesicles exist and that only one of them undergoes visible irreversible exocytosis, whereas the majority, that is, the small vesicles discharge their transmitter by reversible fusion. After MP injection features of membrane retrieval were also prominent. Frequently, at the borders of the active synaptic zones coated membrane convolutes of both pre- and postsynaptic membranes had invaded the terminals as well as the postsynaptic spine. Thus, in contrast to electrical stimulation, the self-sustained seizures allows energy-expensive processes such as extensive membrane internalization to take place during the interictal pauses.

Animals↗
PubMed1981

Factors in the reproducibility of the gravimetric method for evaluation of edematous changes in the brain.

In the gravimetric method for estimation of water content in brain tissue, four factors that may affect specific gravity (SG) measurements are described and evaluated. These factors are: (1) the purity of kerosene (K) and monobromobenzene (MBB), (2) duration of interaction of MBB with tissue and/or standard solutions, (3) the size of tissue samples, and (4) the temperature. A water-soluble contaminant in K, which can be effectively extracted by water treatment, may significantly decrease SG values. Conversely, in MBB, the SG of tissue samples tends to increase in proportion with time. The SG of the tissue samples appears to be influenced by their size, the smaller pieces registering higher SG values. Also, the temperature of the column affects the SG, with higher temperatures resulting in higher SG values; a difference of 5 degrees C produces a significant difference in SG (p less than 0.05). A standardized procedure providing highly reproducible SG values is presented in which the size of the tissue samples, the recording time, and the temperature of the column consisting of water-treated K and MBB are kept strictly constant.

Animals↗
PubMed1981

Glutamate as a transmitter of the hippocampal commissural system.

In rabbits, after unilateral hippocampus extirpation, glutamate level decreased in the contralateral hippocampal fields CA1, CA3 and area dentata. No change in aspartate content was observed. A detailed analysis of glutamate level in single layers of the dentate area revealed that, after removal of the contralateral hippocampus, glutamate content decreased in those layers receiving normally a dense input of commissural terminals. If, however, deafferented layers border innervation zones of other glutamergic systems, such as of the entorhinal perforant path, their glutamate concentration will normalize after longer survival times. It is concluded that glutamergic fibers of different origin proliferate into the decommissurated areas. As a reflection of this activity, glutamate level rises in those layers where the sprouting originates.

Animals↗
PubMed1980

Changes in acetylcholine in caudate nucleus tissue isolated in situ detected by gas chromatography mass spectrometry selected ion monitoring.

Acetylcholine neurons in the striatum are believed to be primarily intrinsic. In cats a cylinder of caudate tissue was isolated unilaterally from all afferent and efferent connections while preserving the blood supply through the base of the cylinder. Cats were decapitated two and four weeks after operation. Dorsal, intermediate and ventral portions of the viable isolated cylinder, and corresponding tissue from the contralateral hemisphere serving as control, were removed, weighed and frozen. Deuterated internal standards at concentrations approximating those of acetylcholine and choline in the tissue were added and acetylcholine and choline extracted, reacted with propionyl chloride and demethylated with sodium benzenethiolate. The derivatives were separated by gas chromatography, and the acetylcholine and choline concentrations in the tissue evaluated using selected ion monitoring of m/z 58, 60 and 64. The observed decrease in the acetylcholine concentration in the dorsal portion could be due either to the interruption of the cholinergic thalamic input or to the more severe ischemia in this portion. The increase in the acetylcholine concentration in the ventral portion, where blood circulation is normal, may reflect accumulation of acetylcholine in inactive intrinsic neurons after severance of their input, or indicate sprouting of intrinsic acetylcholine neurons.

Acetylcholine↗
PubMed1980

Selected ion monitoring determination of acetylcholine during methoxypyridoxine seizures.

The neurotransmitter gamma-aminobutyric acid is known to decrease preictally after administration of the potent convulsant methyoxypyridoxine, a competitive inhibitor of glutamate decarboxylase. An attempt was made to determine the effect of this gamma-aminobutyric acid decrease on the cholinergic system. Rabbits were immobilized and artificially ventilated in order to avoid hypoxidosis. Seizures were induced by intravenous injection of 100 mg kg-1 methoxypyridoxine; 40 minutes later the animals were decapitated and discrete brain areas removed. Tissue contents of acetylcholine and choline were estimated by gas chromatographic mass spectrometric analysis of the beta-dimethylaminoethyl acetate and propionate derivatives using deuterated internal standards. Gas chromatographic column optimization resulted in a considerable sensitivity gain. Computerized selected ion monitoring was carried out on the dimethylmethyleneimmonium ions using voltage switching. The use of a computer controlled solvent dump valve was implemented to increase precision. No significant difference was observed in the concentration of acetylcholine in the frontal cortex, cerebellar cortex, septum, hippocampus, or caudate of seizure versus control animals; septal choline increased, however. This suggests that the acetylcholine turnover could be increased during seizure.

Acetylcholine↗
PubMed1980

Aspartate, glutamate and GABA levels in pallidum, substantia nigra, center median and dorsal raphe nuclei after cylindric lesion of caudate nucleus in cat.

Aspartate, glutamate and GABA levels were determined in afferent and efferent projection nuclei of the striatum after unilateral cylindric lesion in the head of the caudate nucleus in cats. Two and four weeks after operation, GABA content was significantly reduced in substantia nigra and pallidum ipsilateral to the lesion. Glutamate (GLU) level was decreased in substantia nigra and pallidum only 4 weeks after lesion, whereas aspartate content in substantia nigra decreased significantly already after 2 weeks. No changes in the contents of these amino acids were detected in the dorsal raphe nucleus, which receives a projection from the caudate, as well as in the center median nucleus, which projects to the striatum. These experiments using longer survival times substantiate the role of GABA in caudato-pallidal and caudatonigral projections. The possibility is discussed that aspartate (ASP) could function as transmitter of cortico-nigral fibers.

Animals↗
PubMed1979

Distribution of glutamate in layers of the rabbit hippocampal fields CA1, CA3, and the dentate area.

The distribution of L-glutamic acid in single layers dissected from freeze-dried sections of the rabbit hippocampus was estimated by means of an enzymatic cycling procedure. Although the regional variation in glutamate content is less than that of other transmitter candidates, there were present significant differences in it between the projection fields of certain fiber connections. Glutamate concentration was highest in the termination areas of commissural fibers and Schaffer's collaterals.

Animals↗
PubMed1979

Effect of hippocampus extirpation in the rat on glutamate levels in target structures of hippocampal efferents.

Twenty days after complete uni- or bilateral hippocampus extirpation in rats, a 25% decrease in glutamate concentration was observed in the septum. Glutamate content also decreased in other terminal structures of the hippocampo-subicular system, i.e. entorhinal cortex, nucleus accumbens septi, mammillary bodies and contralateral hippocampus. It is concluded that the fall in glutamate content which is absent in caudate nucleus is specific for target regions of the hippocampal efferents, adding further support to the suggested transmitter role of glutamate in the limbic system.

Animals↗
PubMed1977

Calcium-induced displacement of membrane-associated particles upon aggregation of chromaffin granules.

Isolated chromaffin granules incubated in 10 millimolar calcium chloride aggregated, forming contact sites with a pentalaminar membrane structure. These circular attachment sites were free of membrane-associated particles, which accumulated at the periphery. Incubation in 20 millimolar ethylenediaminetetraacetic acid reversed these changes, which are regarded as initial events in the membrane fusion reaction.

Adrenal Medulla↗
PubMed1976

Antivitamin B6 induced ultrastructural changes in the hippocampus of the convulsant rabbit and its biochemical correlates.

In rabbits epileptiform seizures were induced by systemic application of methoxypyridoxine, an antimetabolite of vitamin B6. The regional distribution of GABA was measured in 11 brain structures, before the onset of the seizure and during the generalized convulsions. In brain regions with a high GABA level the GABA content drops already preictally, in contrast to the GABA poor structures where no preictal decrease takes place. From this it is concluded that there exist two GABA pools, a functional one containing the GABA for chemical transmission, which is exhausted already preictally giving rise to the seizure discharges, and a metabolic one, which is utilized as an additional energy-source during the convulsions. Due to the decrease of the hippocampal GABA the endings of the dentate gyrus granule cells, the giant boutons contacting the apical dendrites of the pyramidal cells of CA3 and CA4, can discharge unrestrained. An ultrastructural correlate of the increased excitation is demonstrated. The dense-core vesicles of the giant boutons fuse in an omega-shaped form with the presynaptic membrane of the spines. This fusion-phenomenon is observed in ultrathin sections as well as in freeze-fractured replicas of this region.

Animals↗