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Biomedical subjects

J Wenzel

Publications and source records attributed to J Wenzel.

At least 73 records · Page 4Linked to original sources
PubMed1977

The phosphorylation of histones in rat liver undergoing malignant transformation.

The incorporation of inorganic phosphate into H1-histones of rat liver was stimulated after the repeated s.c. administration of diethylnitrosamine. This stimulation was observed as early as after the fifth daily injection of the carcinogen and amounts to approximately 3 times the control value on the 60th day of the experiment. The effect was reversible when the application of the carcinogen was not extended beyond 4 weeks. A correlation was observed between these phenomena and alterations in the morphological structure, although the latter required a higher amount of single doses before the first signs of a forthcoming malignant transformation were seen. There was a difference in distribution of phosphate between the individual phosphorylation sites of the H1 molecule as compared to stimulated phosphate incorporation induced by adenosine cyclic 3':5'-monophosphoric acid or liver regeneration. The stimulated phosphorylation was not due to the inflammatory action of the carcinogen.

Animals↗
PubMed1976

[Neuron structure of the rat septum telencephali].

1. The neuronal structure of the septum of adult rats was studied after GOLGI impregnation. On the basis of cytoarchitectonic investigations the septum of the rat was divided into three big nuclei: nuclei septalis lateralis, septalis medialis, and tractus diagonalis (s. ANDY and STEPHAN). 2. The nc. septalis medialis contains cells with pyramidal, oval, round, spindle-shaped, fusiforme or triangular pericarya, while in the nc. septalis lateralis cells with pyramidal pericarya are absent. In the nc. tractus diagonalis four different forms of cells bodies occur: oval, triangular, round, and parymidal ones. 3. The existence of single, characteristic cell forms is not restricted to certain areas within a nucleus; the different kinds of cells are distributed irregularly and arranged ina different distance. 4. Mostly after a dichotome division the dendrites spread into all directions (bipolar to star-shaped dendritic arborisation). An orientation of the dendrites of single neurones into a special direction (i.e. to the ventricle) was not observed. 5. Neurons of the septum have dendritic fields with a mean diameter of 300 mum. The dendritic diameter regularly remains constant in the distance between two branchings and decreases only after the division of the dendrite. 6. The distribution of spines on the dendrites is typical for interneurons. Immediately after their origin from the pericaryon the dividing dendrites have a segment free of spines which extends up to the first outgrowth of a lateral dendrite. In neurons with poorly ramified dendrites this spines-free segment is absent; the first spines are found close by the pericaryon. Bferore and after a ramification of dendrites a different density of spines exists. 7. The neurons of the septum are morphologically and functionally classified as interneurons. Their dendritic fields correspond to those of star cells and are even similar to pyramidal cells. For the cell types described a great structural variability in the dentritic arrangement occurs.

Animals↗
PubMed1976

[Electronmicroscopical and morphometrical study of rat hippocampal synapses].

The neuronal structure and synaptology of the hippocampus of the rat are studied using neurohistological, electron microscopical and morphometrical methods. After Golgi-impregnations the neurons of the hippocampus were classified by reason of special morphological features (pericaryon, dendritic, ramification, course and termination of the axons). The neurons of the hippocampus show from the region CA4 towards the region CA1 an increasing "pyramidalization" which is explained respecting the neuronal structure and synaptic architectonics as the result of a specific presynaptic representation of afferents at the neurons. The high degree of differentiation of the CA1-pyramids speaks for the progressive developmental tendency in the phylogenesis of these pyramids compared to the neocortical neurons. The ultrastructural investigations of the hippocampus show that each individual layer of the regions CA1, CA3 and CA4 has a characteristic synaptic architectonics. In all hippocampal layers the axo-spino-dendritic contacts are the most frequent type of synapses with the structural characteristics of the excitatory synapses; the synaptic contact appears as "Bouton en passage" respectively as "Bouton terminal". The axosomatic synapses of the stratum pyramidale (CA1 to CA3) predominantly are developed as symmetrical contacts with inhibitory function. As the terminals of the basket cells they represent the morphological correlate for the recurrent inhibitation of the pyramids by the inhibitory effecting basket cells. In the supra- and infrapyramidal layers of the regions CA3 and CA4 special contacts are developed for the connection withe the mossy fiber terminals--at the pericarya and the main dendrites as so-called somatic and dendritic protrusions and as micro-dendrites. As has been established for the neocortex, the dendritic spines are the decisive receptive postsynaptic structural characteristic of the hippocampus as well. Pre- and postsynaptic elements show a broad scope of variation in forming their structures. This also applies to the intrahippocampal systems with their highly complex structure which is the morphological expression of an extremely high degree of differentiation. The morphometrical investigations of the ultrastructure of synapses enclose the calculation of the number of synapses per mm3 of the volume of layers, the average individual volume of synapses, the presynaptic portion of volume of the relative volume of cortex of the hippocampal layers as well as the average number and size of the synaptic vesicles. The average number of synapses per mm3 brain tissue runs in CA1 to 5,9 X 10(9), in CA3 to 7,9 X 10(9) andin CA4 to 8,7 X 10(9) synapses per mm3. The average individual volume of synapses amounts to 0,2-0,3 mm3 whereas the average portion of volume of the presynaptic structures per relative cortical volume comes to 14% in CA1, 16-19% in CA3 and 15% in CA4.

Animals↗
PubMed1976

[Spine-distribution of pyramidal neurons of the CAl-region of the rat hippocampus following long-term oral alcohol administration].

The distribution of the dendritic spines in the CA1 hippocampal region of adult rats was investigated by means of lightmicroscopical and statistical methods. The rats received daily equal amounts of aethanol for a period of 52 days. The average number of spines for a part of 50 mum along the apical main dendrite raised from 35 to 36.9 spines. The average spines-density for a part of 1 mum length on the apical dendritic branches raised from 0.71 to 0.94 spines. In a similar way the average spines-density on the basal dendritic branches raised from 0.65 to 0.94 spines. According to our results received after a period of aethanol application the total number of dendritic spines of one rat CA1 hippocampal pyramidal neuron was calculated with 4177 visible spines. The value was compared with the normal value of 3029 dendritic spines. The results were discussed by the aid of additional light- and electronmicroscopical findings.

Alcoholism↗
PubMed1976

[The effect of orotic acid and orotic acid derivatives on the in vitro differentiation of hippocampus neurons-morphometric and electron microscopic studies of ribosomes].

1. By means of electron microscopic and quantitative methods at the explantate cultures of the fetal hippocampus in vitro the influence of the orotic acid, sodium orotate and methylglucamine orotate on the neurogenesis was investigated. 2. After three days of the in vitro cultivation the neuroblasts influenced by these drugs show a smaller respectively not different degree of differentiation compared to the controls. 3. Under the influence of the orotic acid and of its derivatives the neurogenesis is significantly stimulated. The drugs produce a significant increase of the membrane-bound ribosomes and polysomes. The total number of ribosomes increases following the application of orotic acid by 20%, of sodium-orotate by 48% and of methylglucamine-orotate by 23% compared to the controls (alpha = 0,1%). 4. Sodium-orotate shows with reference to the neuronal development the clearest stimulatory effect. After 20 days in vitro the total number of ribosomes is by 60% higher at the treated cultures than in the controls. 5. The results might suggest, that an enlarged supply of the pyrimidine nucleotide via a raising of the RNA- and the protein synthesis might stimulate the development of the neuroblasts even under the in vitro conditions.

Animals↗
PubMed1975

Free and membrane-bound ribosomes and polysomes in hippocampal neurons during a learning experiment.

The ribosomes of the CA1 and CA3 pyramidal cells of hipocampus were investigated by morphometric methods after the acquisition of a shock-motivated brightness discrimination in rats. A significant increase in the total number of ribosomes was observed in CA1 cells of trained animals and in CA3 cells of both active controls and trained rats. A significant increase in membrane-bound ribosomes was obtained in CA1 and CA3 cells after training only. The results confirm the suggestion of an increased protein synthesis in hippocampal neurons during and after the acquisition of a brightness discrimination, as we have concluded from out previous investigations on the incorporation of labeled amino acids under identical experimental conditions. The results lead to the assumption that the protein synthesis in some neuronal cells may probably differ not only quantitatively, but also qualitatively in trained and untrained animals.

Animals↗
PubMed1975

[Quantitative studies on the neuron structure of the rat fascia dentata].

1. In 6 month old male rats the structure of dendrites and the distribution of spines on the apical dendrites of granular cells of the dentate gyrus were investigated by light microscopy and statistical methods. 2. The number of dendrites of the first, second and third order of granular cells increases in this sequence in a ratio of 1:2:3; the total length of the dendrites increases correspondently in a ratio of 1:4:5. 3. The mean number of origin points of dendritic branches is 10, the mean number of free dendritic endings is 12. 4. The number of spines per a 25 mum dendritic segment near to the pericaryon (dendritic segment A), in the middle of the dendrite (dendritic segment B) and in the peripheral dendritic part (dendritic segment C) as well as the distribution of spines in the whole apical dendrite was evaluated. The total mean of spines of granular cell apical dendrites of the dentate gyrus (superior respectively inferior) is 12 respectively 10 for the dendritic segment A, 18 respectively 17 for the dendritic segment B and 17 respectively 15 for the dendritic segment C calculated for a dendritic length of 25 mum. 5. The spine density in each case depends upon the distance pericaryondendritic segment and is in close relation to the adjacent layers with their specific afferents. 6. The averaged total number of spines per 1 mum of dendritic length is 0,62 spines/mum for the dentate gyrus (superior) and 0,57 spines/mum for the dentate gyrus (inferior). 7. The granular cells of the dentate gyrus (superior) have a mean dendritic length of a total of 357 mum with a total of 226 visible spines; the granular cells of the dentate gyrus (inferior) have a mean dendritic length of a total of 450 mum with a total of 258 visible spines.

Animals↗
PubMed1975

[Environmentally affected differentiation of dendrite spines of pyramidal neurons in rat hippocampus (CA 1)].

Three groups of newborn WISTAR-rats were exposed to different environmental influences. The first group was raised in darkness from birth onwards, the second was permanently subjected to noise immediately after birth, while the third group (controls) was reared under normal laboratory conditions. The animals of all three groups were killed on the 15th day after birth and handled by a modified Golgi-Kopsch method. Then the distribution of spines on apical dendrites of CA 1-neurons of the hippocampus was investigated. For apical dendrites of a comparable length the mean number of spines per 50 mum as well as the mean total of spines on the apical dendrite was evaluated. Rats reared in darkness show significantly less spines on the apical dendrites of CA 1-neurons in comparison with the control animals. Rats permanently subjected to noise, on the contrary, have significantly more spines in comparison with the controls (total number of spines on the apical dendrite is 89,8 +/- 10,2 in the control animals, 55,0 +/- 16,6 in the animals reared in darkness, and 125,8 +/- 29,4 in the animals subjected to noise). The changes involve the whole apical dendrite; extreme changes in the individual segments of the apical dendrite were not observed. The results suggest that environmental factors have an influence on the differentiation of central neurons, which is not restricted to the specific analyzer concerned.

Animals↗