György Szekely

Publications of György Szekely

• Dendrodendritic and dendrosomatic contacts between oculomotor and trochlear motoneurons of the frog, Rana esculenta.

  Authors: Tímea Bacskai, Gabor Veress, Gabor Halasi, Adam Deak, Eva Racz, György Szekely, Clara Matesz

  Brain research bulletin. 04/2008; 75(2-4):419-23.

  Gaze fixation requires very fast movements of the eye during body displacement. The morphological and physiological background of the very fine and continuous tuning of gaze fixation is not yet fullyGaze fixation requires very fast movements of the eye during body displacement. The morphological and physiological background of the very fine and continuous tuning of gaze fixation is not yet fully understood. In a previous study we have shown that the dendrites of oculomotor neurons form bundles which invade the trochlear nucleus, and vice versa, trochlear dendritic bundles invade the oculomotor nucleus. Earlier physiological observations demonstrating electrotonic coupling between dendrites of spinal motoneurons in the frog suggest a similar mechanism between the oculomotor and trochlear motoneurons. We studied a possible morphological basis of gaze fixation. The experiments were carried out on common water frogs, Rana esculenta. The trochlear and oculomotor nerves were cut, and their proximal stumps were labeled simultaneously with different retrograde fluorescent tracers. Using confocal laser scanning microscope we detected a large number of close contacts in both nuclei, the majority of them were dendrodendritic apposition. The distance between the adjacent profiles suggested close membrane appositions without intercalating glial or neuronal elements. At the ultrastructural level, the dendrodendritic and dendrosomatic contacts did not show any morphological specialization; the long membrane appositions may provide ephaptic interactions between the neighboring profiles. This electrotonic coupling between the oculomotor and trochlear nerve motoneurons may promote the co-activation of the muscles responsible for vertical eye movements.

• Extracellular matrix molecules and their possible roles in the regeneration of frog nervous system.

  Authors: Clara Matesz, Laszlo Modis, Gabor Halasi, Zsuzsa M Szigeti, Szabolcs Felszeghy, Timea Bacskai, György Szekely

  Brain research bulletin. 10/2005; 66(4-6):526-31.

  Recent biochemical and histochemical analyses explored different components of the extracellular matrix (ECM) in the nervous system, and either permissive or non-permissive roles in neuronalRecent biochemical and histochemical analyses explored different components of the extracellular matrix (ECM) in the nervous system, and either permissive or non-permissive roles in neuronal development and regeneration were suggested. The aim of this study was to detect the distribution pattern of a few of these molecules in the nervous system of intact frogs and during nerve regeneration. The hyaluronan (HA) and tenascin C reactions were negative in the peripheral nerves, but appeared in their entry zones. In the CNS, different populations of neurons were surrounded with HA and tenascin C-positive material, forming a perineuronal net (PN). The phosphacan reaction was weakly positive in the PNS, and a moderate intensity was detected in the entry zone and in the PN. Laminin and fibronectin immunoreactivity was strong in the PNS, but laminin could not be detected in the CNS. In animals with cut and regenerating vestibulocochlear nerve, the distribution of the ECM molecules in the CNS and PNS characteristically changed from that of the normal pattern. Our results showed a non-homogenous distribution of ECM components in the frog nervous system that could be associated with their different roles in physiological and pathological processes.