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T Szabo

Publications and source records attributed to T Szabo.

At least 73 records · Page 4Linked to original sources
PubMed1979

On the course and origin of cranial nerves in the teleost fish Gnathonemus determined by ortho- and retrograde horseradish peroxidase axonal transport.

By horseradish peroxidase (HRP) labelling the course and origin of the II-X cranial nerves are identified in the teleost fish Gnathonemus petersii. Roots as well as motor and sensory nuclei in the viscero- and somatomotor and somatosensory areas are localised. Earlier data of comparative and experimental anatomical observations are completed, partly confirmed or corrected.

Animals↗
PubMed1979

Development of the gigantocerebellum of the weakly electric fish Pollimyrus.

The morphogenesis of the "hypertrophied" mormyrid cerebellum was investigated in Pollimyrus (Pisces). Two adults and 36 larvae and young fish raised in captivity were used. Two Gnathonemus petersii adults were taken for comparison. The ontogenetic development of the various cerebellar structures was analysed in inverse chronological order with the aid of serial sagittal and frontal brain sections. Special attention was given to the trilobed corpus cerebelli (C1, C2, C3), the lobi transitorii et caudales, the valvula, the crista cerebelli, the eminentia granularis and the lobus lineae lateralis. 1. The cerebellar structures are of bilateral origin; they develop from the cerebellar and acoustico-lateral "anlage" of the rhombencephalon behind the rhombomesencephalic fissure, either through budding or individualisation and appear between the 4th and 11th day after spawning. The midline fusion of the symmetrical structures is accomplished somewhat later, between the 8th and 23rd days. 2. The cerebellar structures acquire their definitive spatial organisation within 38 days, except for the valvula whose development takes much longer. Recognisable from the 11th day, the valvula upon which ridges are visible from the beginning continues to grow after the 38th day beyond the mesencephalic ventricle, finally overlying the telencephalon frontally and the different rhombencephalic structures caudally. This development, which includes a large antero-lateral folding of the valvula, takes 240 days. 3. Cytological differentiation is just as complex as the general development of the cerebellar structures. Cortical stratification first begins on the 8th to the 11th day in the corpus cerebelli and in the valvula from day 21 to 23 onwards. This differentiation is characterised throughout almost the entire cerebellum by a downward migration of the superficial undifferentiated cells which then constitute the granular layer. In the valvula, the majority of the undifferentiated cells leave the ridges to form a continuous granular layer at the base of the ridges. 4. A differentiation gradient was observed on the antero-posterior axis. 5. In spite of its complexity, the mormyrid cerebellum develops much more rapidly than the cerebellum of the trout.

Aging↗
PubMed1979

Electrosensory systems in the mormyrid fish, Gnathonemus petersii : special emphasis on the fast conducting pathway.

1. Rhombencephalic and mesencephalic structures involved in electroreception were investigated by electrophysiological methods in the weakly electric fish Gnathonemus petersii. 2. The existence of a synchronous response to electric field stimulation of the fish in the mesencephalic exterolateral nucleus (n.ext.-lat.mes) with 2.5-3 ms latency was confirmed. The lateral line lobe nucleus (nLLL) is identified as the rhombencephalic relay for the mesencephalic responses because of the short latency synchronous response in the nLLL obtained by threshold stimulation of the posterior lateral line nerve. Responses in both the nLLL and the n.ext.-lat.mes. appear and their amplitudes increase simultaneously with increasing stimulus intensity. 3. Comparison of latencies supports a three-neuron pathway hypothesis which also agrees well with the various functional properties described. 4. The nLLL-n.ext.-lat.mes. pathway is blocked sharply for a period of 1 ms occurring 3 ms after the electric organ discharge (EOD). This inhibitory period is phase-related to the Mesencephalic Command Associated Signal (MCAS) of Aljure (1946) ; The phase relation is such that no response is observed to the fish's own EOD. 5. Long-lasting responses of 10-12 ms duration to higher stimulation intensities were obtained in the ganglionic layer of the lateral line lobe (LLL). Intensities evoking maximal responses in the nLLL and n.ext.lat.mes. are still threshold stimulation for lateral line lobe responses. 6. Long-lasting responses (of the same order as in the LLL) to the fish' own EOD were observed in the mesencephalic lateral nucleus. Responses to artificial electric pulses were obtained only if delivered in a certain phase realtion to the MCAS. The MCAS displays a facilitating effect on the slow conducting electrosensory system. 7. Results indicate the existence in mormyrids of a double, fast and slow conducting, electrosensory system similar to that of gymnotid fish. The mormyrids can control both of these electrosensory systems by means of the MCAS, the effect of which is opposite for the same time period on the two systems.

Afferent Pathways↗
PubMed1976

Complement consumption in fresh blood sera by double culture of Paramecium caudatum and Aerobacter cloacae compared with survival and stage of disease in some malignant tumors in man.

Using the complement consumption test by double culture of Paramecium caudatum and Aerobacter cloacae (DPA) as antigen we examined blood sera and compared survival rates and stage of disease in 124 patients with carcinoma of cervix uteri, corpus uteri, ovaries and breast. The evidence suggests that bacteria Aerobacter cloacae constitute the proper antigenically effective substances of DPA. The intensity of reaction and therapy the relative titres of antibodies detected by the test were expressed by the amount of complement consumed in the reaction and designated by the abbreviation "NMHD", i. e. number of minimum haemolytic doses of complement fixed by antigen in the reaction. Patients with NMHD above 8 (i. e. with an intensive reaction corresponding to a high level of antibodies) exhibited partly higher three-year survival rates -- starting from the time of diagnosis, partly more often the clinical stages of disease I or II as compared with patients with NMHD below 4. The best survival rates were found in patients with NMHD above 8 and clinical stage I or II. NMHD values in patients with the initial period of disease and in healthy women did not differ substantially.

Animals↗
PubMed1975

An electrotonically coupled pathway in the central nervous system of some teleost fish, Gymnotidae and Mormyridae.

Morphological and physiological results indicate that the magnocellular mesencephalic nucleus (MMN) is characteristic of all species of weakly electric fish, so far investigated. The potentials recorded from this nucleus are due to the fish's own electric organ discharge (EOD). After abolition of the EOD by curare the mesencephalic potential is suppressed, but it can still be obtained by artificial electric stimulation. After injection of curare the medullary pacemaker activity responsible for the EOD remains undisturbed. The results, therefore, let us exclude the hypothesis that the mesencephalic response is evoked by recurrent pacemaker activity. The very short delay (1 msec) of the mesencephalic potential is explained by the existence of a rapid conduction electrosensory pathway where the peripheral, rhombencephalic and mesencephalic elements are electrotonically coupled. This kind of transmission provides a constant synaptic delay and a one-to-one input-output ratio. The fish can receive, by means of this electrosensory pathway, a binary signal for each electrical event whether it comes from its own electric organ or from neighbouring fish.

Animals↗
PubMed1975

Morphological correlates of electrotonic coupling in the magnocellular mesencephalic nucleus of the weakly electric fish Gymnotus carapo.

The magnocellular mesencephalic nucleus (MMN) of Gymnotus carapo was studied by electron microscopy. This particular nucleus, characteristic of weakly electric fish, contains two principal classes of neuron. (1) Large neurons (25-35 mum): these are rounded unipolar cells, with the perikaryon partially covered by a sheath of compact myelin. The axon leaves the neuron as a short thick unmyelinated process not resembling the initial segment of multipolar neurons. The axon branches profusely and becomes myelinated very close to its origin. The perikaryal surface not covered by the myelin sheath receives abundant club endings. The synaptic interface between club endings and large neurons is characterized by alternating gap junctions and attachment plaques. In addition, at the periphery of the club endings, "active" zones are generally present, and this synapse is therefore a "mixed" synapse. (2) Small neurons (5-12 mum): these are uni- or bipolar cells, scattered throughout the nucleus, and occasionally, grouped in small clusters. Gap junctions were not observed between neuronal perikarya in such clusters. The synaptic investment of small neurons is formed by long cup endings which almost completely encircle the perikarya. The synaptic interface between cup endings and the perikarya of small neurons is characterized by large areas of gap junctions. A single cup ending establishing gap junctions with two small neurons within the plane of the section was frequently observed and this arrangement provides a morphological basis for electrotonic coupling between small neurons by way of presynaptic fibres. In the neuropil of the MMN, there are abundant synaptic islands constituted by a large axon terminal in synaptic contact with small unidentified profiles; both synaptic elements are surrounded by numerous thin glial lamellae. At the synaptic interface, in the islands, both gap junctions and "active" zones are present. The synaptic islands must also be considered as "mixed" synapses. The morphological results presented here correlate with electrophysiological data (Szabo et al., 1975). The very short delay (0.8-1.3 ms) of the MMS response to the fish's own electric organ discharge can only be explained by the existence of electrotonic transmission along the neuronal chain of the electrosensory pathway. The presence of gap junctions between club endings and large neurons provides a morphological basis for electrotonic transmission at the mesencephalic level of the electrosensory pathway.

Animals↗