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J Somogyi

Publications and source records attributed to J Somogyi.

At least 73 records · Page 4Linked to original sources
PubMed1985

Identified axo-axonic cells are immunoreactive for GABA in the hippocampus and visual cortex of the cat.

Chandelier or axo-axonic cells (AACs) are specialized interneurons terminating on the axon initial segments of pyramidal neurons. Two AACs have been localized by Golgi impregnation, one in the CA1 region of the hippocampus and one in the visual cortex of cat, for structural analysis and for the identification of their transmitter. They had 323 and 268 terminal bouton rows, respectively, probably making synapses with an equal number of initial segments. The distribution of the dendrites of the hippocampal cell was strikingly similar to that of pyramidal cells suggesting a similar input. Using an antiserum to GABA and postembedding GABA-immunocytochemistry, developed for Golgi-impregnated neurons, both cells were found to be GABA-immunoreactive. The strategic location of their synapses and the presence of GABA in AACs suggest that in normal cortical tissue they play a major role in GABA-mediated inhibition.

Animals↗
PubMed1985

[Histological changes in the somatosensory thalamus after unilateral coagulation of vibrissa follicles of the muzzle of the newborn mouse].

Light microscopic study of the thalamic ventro-basal complex (VB), after unilateral coagulation of vibrissae follicles in newborn mouse, revealed an excess of neuronal perikarya on the controlateral "deafferented" side as compared to the normal side. The higher density of nerve cells was confined to the vibrissal relay in the medial part of VB nucleus (VBm), whereas the cell number in the non vibrissal-lateral part of this nucleus (VB1) remained on the control level. Electron microscopic investigation of the thalamic vibrissal relay has shown signs of a modified synaptogenesis on the "deafferented" side: (a) the number of specific afferents has diminished and in contrast to the normal side, most of the specific sensory terminals contain small spheroid synaptic vesicles and (b) the number of axon terminals with ovoid pleomorphic vesicles has been doubled.

Afferent Pathways↗
PubMed1985

Epidemiological features of biliary tract cancer incidence in Slovakia.

This descriptive study is based on detailed data of biliary tract cancer incidence in Slovakia in the period 1968-1977. Age-adjusted incidence rates of biliary tract cancer in the given decade decreased in females while in males they showed a slight increase. The study of geographic distribution revealed diminishing incidence rates from west to the east in both sexes with extremely elevated rates in towns and suburban districts in males. Different shapes of age-specific incidence curves together with the identified histological types suggested different epidemiological characteristics of individual subsites within this site. Relatively high incidence rates of biliary tract cancer in Slovakia as well as in whole Czechoslovakia, in comparison with other countries or areas of Europe, could be related to the excessive prevalence of gallstones and high number of surgical interventions upon biliary tract in this country while the decreasing incidence rates in women coincided with elevated number of cholecystectomies. The significance of detailed descriptive data from cancer registries for further analytic and etiologic study of biliary tract cancer according to subsites for a better delimitation of high risk groups and primary prevention strategies is stressed.

Adult↗
PubMed1985

Epidemiologic aspects of malignant skin melanoma in Slovakia.

The trends of age-adjusted incidence rates of malignant skin melanoma in Slovakia from 1968 to 1977 showed important increase with an annual increment of 5.8% in males and 3.2% in females. The mortality rates during this period remained lower and their increase was less expressed. The study of geographic patterns of incidence revealed great variation with highest rates in urban districts. A marked predominance of the primary lesions on trunk in males and on lower limbs in females was observed. The differences in anatomic distribution are demonstrated also in age-specific incidence rates of malignant skin melanoma by main subsites. Intermittent overexposures to the sunlight in connection with rising standard of life and leisure seem to be the most suitable explanation for the rise and subsite distribution and dynamics, as well as the geographic patterns and international position of incidence rates of malignant skin melanoma in this country.

Adolescent↗
PubMed1984

Synaptic reorganization in the lateral geniculate nucleus of the adult cat following chronic decortication.

The corona radiata containing all geniculo-cortical and cortico-geniculate fibers was transected in adult cats. One year after the operation synaptic architecture of laminae A and A1 of the decorticated LGN was investigated utilizing electron-microscopy and Golgi-EM. It was found that synaptic glomeruli became embedded in heavily gliotic neuropile, which contained the dendrites of surviving relay cells in addition to retinal axons and interneuronal processes. In contrast to the intact LGN, where the relay cell dendrites are exclusively postsynaptic, many morphologically identified relay neuronal dendrites of the decorticated LGN also contained large, round synaptic vesicles associated with distinct presynaptic sites. In 60% of all glomeruli, the large presynaptic dendrites of relay neurons occupied a central position and were postsynaptic to retinal axons and interneuronal dendrites/axons, but were presynaptic to other relay dendrites or interneuronal dendritic profiles. Occasional dendro-dendritic synapses between relay cell processes could be observed in the extraglomerular neuropile. Relay cell presynaptic dendrites formed unequivocal Gray I-type synapses, in accordance with the supposed excitatory character of relay cell output. Since sprouting of extrinsic or intrinsic axons could not be observed after decortication, it is proposed that the partial synaptic reorganization of the LGN was primarily due to the compensatory " axonization " of relay cell dendrites. It is further suggested that the electrophysiologically demonstrated expansion of retinal receptive fields in the chronically decorticated LGN was accomplished by the formation of dendro-dendritic synapses between relay cells and interneurons.

Animals↗
PubMed1984

The 'single' section Golgi-impregnation procedure: methodological description.

A method is described which allows the Golgi-impregnation of neurons within a 'single' section or 'slice' of brain tissue 60-200 micron thick. The method may be combined with a variety of histochemical procedures allowing the identification of specific neural elements in the light-microscope and the subsequent examination of their synaptic relationships in the electron-microscope. The technique makes it possible to control visually the extent of the Golgi-impregnation and allows the re-impregnation of single sections. The procedure is illustrated with examples from the cerebellum, cortex, hippocampus, and thalamus of the rat.

Animals↗
PubMed1984

Contributions to the mechanism of action of beta-adrenergic stimulants.

Subcellar localization of ionic Ca was investigated by the Pb-acetate cytochemical method in rat myometrium on the 21st day of pregnancy, following oxytocin and Bricanyl treatment. Following Oxytocin treatment the amount of ionic Ca increased in the muscle cells of the uterus and decreased in the plasma membrane and mitochondria as compared with the control. Tocolytics given in the last four days of pregnancy caused a decrease in the cytoplasmic concentration of ionic Ca and increased the Ca++ content of Ca++ pools (plasma membrane, mitochondrium). The change in the intracellular distribution of Ca++ may be involved in the mechanism of action of tocolytics and in the development of the relaxation of smooth muscle.

Animals↗
PubMed1984

The role of registration in a nationwide cancer control program in Slovakia.

In comparison with the official statistics substantially higher, more reliable and more detailed cancer incidence and mortality rates were ascertained by the National Cancer Registry of Slovakia established in the frame work of a complex cancer control program initiated in Slovakia in 1976. The role of the registry in the evaluation of treatment, planning for material and personal resources, orientation of public education, improved classification of malignancies in childhood, in planning and evaluation of preventive measures as well as its experience with the use of the standard WHO system for cancer registries are described. A more important position for the registry in the continuous evaluation and current orientation of the cancer control program is suggested for the future.

Adolescent↗
PubMed1983

Differentiation of cerebellar mossy fiber synapses in the rat: a quantitative electron microscope study.

The differentiation of cerebellar glomeruli was investigated by quantitative electron microscopy, starting with the period at which mossy fibers made their first appearance. Two developmental stages could be delineated in the maturation of the mossy fiber-granule cell synapse. 1. A primary growth stage (postnatal days 6--15) characterized by the rapid enlargement of mossy rosettes and the intense proliferation of post-synaptic dendrites. The synaptic perimeter of mossy terminals, i.e. percentage of membrane surface occupied by synaptic junctions, exhibited a simultaneous, rapid increase in that stage, reaching a peak at postnatal day 15. 2. Establishment and stabilization of differentiated glomeruli (15th--45th day). Because the size of mossy rosettes did not change in this period, the increase of glomerular size was due exclusively to the continuing multiplication of postsynaptic dendrites. The characteristic feature of this stage was the massive elimination o synaptic junctions. The synaptic perimeter of 14.4% at day 15 decreased to 5.7% by day 30. Since the size of individual synaptic junctions and the size of mossy terminals did not decrease while the number of postsynaptic dendrites even increased during the same period, the elimination of synaptic junctions represents a net loss of the synaptic perimeter of mossy terminals. The quantitative analysis suggests that the stabilization of the synaptic perimeter of mossy rosettes at about 6% is due to the elimination during the second developmental stage of immature synaptic junctions, produced in excess during the first growth phase. Also, the observation that synapse elimination and the subsequent stabilization of synaptic perimeter occurs in spite of a steady increase of available postsynaptic dendrites is indicative that the standard 6% value of synaptic perimeter is defined by the presynaptic mossy terminal itself. On the basis of these observations, it is also proposed that elimination of synaptic junctions may well occur without the concomitant disappearance of presynaptic and/or postsynaptic neuronal processes.

Animals↗
PubMed1983

Fine structural studies on a type of somatostatin-immunoreactive neuron and its synaptic connections in the rat neostriatum: a correlated light and electron microscopic study.

Somatostatin-immunoreactive neurons in the rat neostriatum were studied by correlated light and electron microscopy using the peroxidase-antiperoxidase immunocytochemical technique. Immunoreactivity was localized in neuronal perikarya and processes. The perikarya were of spindle or fusiform shape (average length 16.9 microns) and were found in all parts of the neostriatum. From each neuron there arose two to four straight immunoreactive dendritelike processes, which could frequently be traced as far as about 130 microns from their perikaryon. Immunoreactive varicose axonlike processes were occasionally found, some of which were proximal axons of identified immunoreactive cells. Nine of the light microscopically identified neurons showing somatostatin-immunoreactivity were studied in the electron microscope; two of them had proximal axons with varicosities. Each neuron had an oval or elongated nucleus, which was always indented. These morphological features correspond well to those of certain "medium-size aspiny" neurons classified by Golgi studies. Although the immunoreactive endproduct was diffusely located throughout the neuron, it was characteristically located in the saccules and large granules (diameter 133 nm) of the Golgi apparatus, and large immunoreactive vesicles of similar size to those in the Golgi apparatus frequently occurred in all parts of axon. Very little synaptic input was found on the perikarya and dendrites of somatostatin-immunoreactive neurons. The perikarya and proximal dendrites received both symmetrical and asymmetrical synaptic input, while the distal dendrites usually received boutons that formed asymmetrical contacts. The somatostatin-immunoreactive boutons contained pleomorphic electron-lucent vesicles (diameter 39.3 nm) and a few large immunoreactive granular vesicles; these boutons always formed symmetrical synapses. Their postsynaptic targets were dendritic shafts, spines, and unclassified dendritic profiles. On the other hand, the varicosities of identified proximal axons of somatostatin-positive neurons did not form typical synapses, since they lacked clusters of small vesicles, but some of them were in direct apposition (via membrane specializations) to unlabelled perikarya or dendrites. It is concluded that somatostatin is a useful marker for a particular type of neuron in the neostriatum. The presence of somatostatin immunoreactivity in synaptic boutons is consistent with the view that somatostatin could be a neurotransmitter in the neostriatum.

Animals↗
PubMed1983

Residual neurons in the lateral geniculate nucleus of adult cats following chronic disconnection from the cortex.

Residual neurons following chronic surgical disconnection from the cortex were studied by light and electron microscopy in the dorsal Lateral Geniculate Nucleus (LGN) of adult cats. One year after operation the volume of the decorticated LGN had shrunken to approximately half that of the control LGN. The number of nerve cells decreased at the same time, to 13-15% of the control, with relatively higher cell loss in A and A1 laminae than in lamina C. The Golgi, Golgi-EM and EM analysis of the residual neurons revealed that they contain two distinct nerve cell types. (1) 55% of all surviving neurons were identified as geniculo-cortical relay cells, while (2) 45% of the persisting nerve cells were interneurons. These data suggest that in the normal LGN of adult cat 7% (or more) of all nerve cells are local interneurons. Finally, those factors which might contribute to the unexpected survival of many relay neurons to the axotomy-caused retrograde degeneration, are considered and discussed.

Animals↗
PubMed1983

Subcellular localization of bioactive cholecystokinin-like peptides in the rat cerebral cortex.

The subcellular distribution of cholecystokinin (CCK), especially its exact localization within the synaptosome, was studied in the rat cerebral cortex. Highest CCK-like bioactivity was measured in the synaptic membrane fractions, paralleling the distribution of (Na+ + K+)-dependent ATPase. In the synaptic vesicles, which were characterized by high acetylcholine content and by the absence of (Na+ + K+)-ATPase, only minimal quantities of CCK were detected.

Animals↗
PubMed1983

Formation of new synaptic contacts by Purkinje axon collaterals in the granular layer of deafferented cerebellar cortex of adult rat.

In addition to (i) mossy terminals, (ii) Golgi axons, (iii) granule cell dendrites and (iv), occasionally, Golgi cell dendrites, a third axonal profile identified by morphological criteria as the collateral of Purkinje axons, has been found in 2% of all cerebellar glomeruli. These infrequent components of a few glomeruli, however, were never seen in normal cerebellar cortex to establish specialized synaptic contact with glomerular dendrites. Two to four weeks after surgical isolation of the cerebellar cortex, i.e. following the destruction of both efferent and afferent fibres, the number of glomeruli containing (hypertrophic) axonal branches of Purkinje cells has increased to 13% of all surveyed glomeruli. In addition, the Purkinje axon terminals in the mossy fibre-deprived glomeruli were observed to establish numerous Gray II-type synaptic contacts with surrounding granule cell dendrites. It is suggested that the development of heterologous synapses between hypertrophic, or even intact, Purkinje axon collaterals on the one hand and the mossy fibre-vacated granule cell dendrites on the other, is a compensatory, reactive process to the synaptic "desaturation" of granule neurons, which demonstrate a dormant potential of Purkinje cells to form new synaptic contacts in the adult cerebellum.

Animals↗
PubMed1983

Incidence of childhood tumors in Slovakia.

During the decade 1968-1977 a total of 1488 cases of neoplasms were registered in Slovakia in children aged 0-14 years giving an average annual age-specific rate of 120.7 per million. Tumors prevailed in boys with 131.2 in comparison with girls showing 109.7 incidence rate/10(6). The most common malignancies were leukemias (28.2%), tumors of nervous system (23.9%), lymphomas (14.9%) and Wilm's tumors of kidney (6.7%). The proportion of remaining histologic types was lower. The necessity of the use of standard international classification based on morphology for mutual international comparison of childhood tumors incidence rates as well as for other epidemiological investigations is emphasised.

Adolescent↗
PubMed1983

Vanadate inhibition of Na+K+. ATPase and K+-dependent p-nitrophenylphosphatase: a kinetic analysis.

Vanadate in redox state +5 inhibited the Na+K+-activated ATPase as well as the potassium-stimulated p-nitrophenylphosphatase (p-NPPase) activities of plasma membrane fragments prepared from rat brain. Vanadate exhibited a mixed type inhibition on the Na+K+-ATP-ase activity. The same type of inhibition was observed when the p-NPPase activity of the enzyme preparation was measured either in the presence of 20 mM K+ or with 5 mM Na+ + 1 mM K+. When the reaction mixture contained 50 microM ATP, 5 mM Na+ and 1 mM K+, inhibition of p-NPP hydrolised by vanadate displayed a noncompetitive character. Higher noradrenalin concentration was required for counteracting, the inhibition of p-NPPase by vanadate in the presence of ATP than in its absence.

4-Nitrophenylphosphatase↗