Biomedical subjects
Publications and source records attributed to G Somogyi.
The Golgi architecture of the Fascia dentata and hippocampus is described in the cat. The main cell types are like those found in other species. The initial collaterals of granule cell axons were demonstrated and are commented on. The interneurons proved to be of several types and subtypes not observed in lower species. The intrinsic fibers and few of the afferents -- both in the dentate fascia and in the hippocampus -- are discussed.
Electron microscopical studies of the thalamic AV-AM nuclei substantiated the presence of two main types of neurons, i.e. principal (or relay) cells and Golgi type II interneurons. Characteristic synaptic islands are found in abundance in the AV-AM. Four different types of synaptic terminals have been identified in these islands: RL-boutons = large axonal terminals with round synaptic vesicles; RS-boutons = small axonal terminals with round synaptic vesicles; F1-boutons = small axonal profiles containing flattened synaptic vesicles, and F2-profiles interpreted as presynaptic dendrite appendages, bearing pleomorphic vesicles, both belonging to the Golgi type II interneurons. --The synaptic relations were studied in normal preparations and after lesions in the mamillary body, limbic cortex and hippocampus. The specific afferents (RL-boutons)--originating from the medial mamillary nucleus--are presynaptic to both relay cell dendrites and "presynaptic" dendrite profiles of Golgi type II interneurons, which in turn are presynaptic to the same relay dendrites (synaptic triads). RS-boutons originate mainly from limbic cortex and hippocampus.
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Retrograde axonal transport of horseradish peroxidase was used to identify the afferent projection systems of the anterior thalamic nuclei in the cat. The results indicate that fibres projecting to the three anterior nuclei of the thalamus arise from the hippocampal region, septum and cingulate cortex unilaterally and from the hypothalamus (mamillary nuclei) both bilaterally and unilaterally. The cells of the medial mamillary nuclei send their axons to the ipsilateral AV and AM nuclei whereas the lateral mamillary nucleus projects bilaterally to the AD nuclei.
The numerical data, gained both from the quantitative histology and Golgi stained material was completed with those of optic fibers. The number of X and Y fibers was estimated on the basis of our results, on the data of literature and from the ratio of the large and medium size relay neurons. The crossed and uncrossed fibers were counted and compared with the number of relay neurons in layer A and A1. Knowing the different numerical and metrical counts of neuronal elements in LGN of cat some calculations were carried out on the overlaping of optic fiber arborizations, on the intersections of dendritic ramification points of relay neurons and on the spatial arrangement of both the optic terminals and the relay neurons. The comparison of the neumerical data on relay neurons and optic fibers and their relations were the basic factors of considerations on divergence and convergence of retinal input.
Numerical data of neuron and fiber elements were observed and measured on Golgi preparations. The aim of the quantitative Golgi analysis was to obtain data on the spatial arrangement of arely neurons, their relations to the interneurons, on the spatial architecture of the arborizations of optic fibers and their relations to the main neuron types. The quantitative data on arely neurons include numbers of dendrites, of their chief points of ramification as the main targets of the optic afferents, geometric data on the "specific active sphere" of the dendritic tree; on the arborization of initial collaterals. The data on interneurons refer both to numeric and geometric parameters of their axonal arborizations, and to those of various characteristics of their dendritic processes. The data on optic fibers include the size of their arborization space, the numbers of bouton clusters and preterminal bouquets per arborization.
In the cat lateral geniculate nucleus all cells of all types were counted: their absolute numbers, their densities and their relative distribution. The nuclear volume and the volume of each layer was measured. The data of volume was applied on living material. The average densities of cells were calculated from the volume of LGN. The density of the cells was combined with the "specific active dendritic sphere" of relay neurons and it could be estimated that there may be a large number of spatially overlaping of ramification points around the cell body of relay neurons.
An attempt is made on the definition of proportional distribution of the different types of neurons in the layers of LGN by means of quantitative method. On the basis of nuclear volume, nuclear and cell diameters the different types of neurons were separated according to their size and shape. The ratio of relay and interneurons proved to be 2:1 in all layers of LGN of cat. The proportional distribution of further subgroups of neurons was also defined. The bilateral connections between the relay and interneurons based on initial axon collateral of TCR neurons and on axon terminals and dendritic appendages of INs, are also calculated. The interneurons--in the LGN--have widespread contacts with both types of relay neurons, similarly the relay neurons contact the interneurons. The numerical data of morphological observations are accord with the results of physiologists.
The ultrastructure of mossy fibre terminals, granule cells, and pyramidal neurons was studied in cat material. The average of the mossy terminals and the density of the synaptic vesicles were analysed. The large mossy terminals establish mainly axo-spiny synapses on the apical dendrites of pyramidal neurons in the CA3 area, but some axo-dendritic synapses were also observed. Mossy fibre endings were found in the subgranular layer, and also on the dendrites of interneurons.
The ultrastructure and synaptic organization of the anterodorsal nucleus (AD) of the thalamus were investigated under normal and experimental conditions. The large glomeruli are composed of an extensive central dendrite, probably arising from a projecting neuron, and of various terminal boutons. Besides the typical small bouton (RS) filled with round vesicles, two specializations of the large bouton (RL) containing round vesicles are found. The larger one (RL1) is characterized by a looser arrangement of synaptic vesicles and many mitochondria; it undergoes dark degeneration following unilateral lesions of the mamillary body in both AD. The intermediate type (RL2) is distinguished by a denser arrangement of vesicles; it undergoes dark degeneration following lesions of the midline nuclei of the thalamus. The two types of terminal boutons (F1 and F2) which contain flattened or pleomorphic vesicles do not degenerate following lesions of the mamillary body and midline nuclei; they belong to Golgi type II interneurons.
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The nucleus lateralis posterior-pulvinar complex of the thalamus displays an integrative function. The efferent connections of this nuclear group were examined by the authors in the cat. In their work, they utilized also the earlier observations on the afferent connections of the nucleus. The nuclear complex projects to the associative fields encompassed by the visual- and the acoustic cortex without intruding into the primary cortical areas. On the other hand, its afferent connections are, apart from the associative field, also yielded by the primary visual and acoustic cortex. All this is completed by the reciprocal connections of the LP-pulvinar complex with the visual- and acoustic system, as well as between the associative areas of the cortex.
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One week's administration of phenobarbital does not affect the disappearance of a single dose of digitalis glycosides from the serum of man. The increase of bile flow and of liver weight produced by phenobarbital in the rat is not further enhanced by glycosides. In case of acute digitalization, the enzyme inducing effect of barbiturates has probably no clinical significance.