András Birinyi

Publications of András Birinyi

• Neurotransmitter systems of commissural interneurons in the lumbar spinal cord of neonatal rats.

  Authors: Ildikó Wéber, Gábor Veress, Péter Szucs, Miklós Antal, András Birinyi

  Brain research. 11/2007; 1178:65-72.

  The circuits that generate rhythmic locomotor activities are located in the ventromedial area of the lumbar spinal cord and comprise commissural interneurons necessary for left-right alternationThe circuits that generate rhythmic locomotor activities are located in the ventromedial area of the lumbar spinal cord and comprise commissural interneurons necessary for left-right alternation during walking movements. In this study we injected biotinylated dextran amine (BDA) into the ventromedial gray matter of the lumbar spinal cord of neonatal rats to label commissural interneurons. Anterogradely labeled axons arose from the site of injection, crossed the midline in the anterior commissure and arborized extensively in the contralateral ventral horn of the spinal cord. The presence of neurotransmitter systems in labeled axon terminals of commissural interneurons was investigated by using antibodies raised against specific transmitter-related proteins. Boutons potentially containing inhibitory amino acids were identified by applying glutamic acid decarboxylase (GAD65/67) and glycine transporter 2 antibodies. Out of 1146 BDA-labeled axon terminals, 663 boutons were assumed on this basis to be inhibitory; 76% of these terminals were immunoreactive for glycine transporter, 53% were immunoreactive for GAD and about 30% of inhibitory boutons might contain both inhibitory amino acids. Boutons potentially containing putative excitatory neurotransmitter were revealed with antibodies raised against vesicular glutamate transporters 1 and 2. Out of 590 BDA-labeled boutons about one fourth (158) were immunoreactive for glutamate transporters. These mammalian commissural interneurons are compared to the glycinergic commissural interneurons in the swimming CPGs of lamprey and the Xenopus tadpole. Our results show that commissural interneurons in the mammalian spinal cord form a heterogeneous group including glutamatergic excitatory and GABAergic and glycinergic inhibitory neurons.

• Quantitative morphological analysis of the motoneurons innervating muscles involved in tongue movements of the frog Rana esculenta.

  Authors: András Birinyi, George Szekely, Krisztina Csapó, Clara Matesz

  The Journal of comparative neurology. 04/2004; 470(4):409-21.

  We give an account of an effort to make quantitative morphological distinctions between motoneurons of the frog innervating functionally different groups of muscles involved in the movements of theWe give an account of an effort to make quantitative morphological distinctions between motoneurons of the frog innervating functionally different groups of muscles involved in the movements of the tongue. The protractor, retractor, and inner muscles of the tongue were considered on the basis of their major action during the prey-catching behavior of the frog. Motoneurons were selectively labeled with cobalt lysin through the nerves of the individual muscles, and dendritic trees of successfully labeled neurons were reconstructed. Each motoneuron was characterized by 15 quantitative morphological parameters describing the size of the soma and dendritic tree and 12 orientation variables related to the shape and orientation of the dendritic field. The variables were subjected to multivariate discriminant analysis to find correlations between form and function of these motoneurons. According to the morphological parameters, the motoneurons were classified into three functionally different groups weighted by the shape of the perikaryon, mean diameter of stem dendrites, and mean length of dendritic segments. The most important orientation variables in the separation of three groups were the ellipses describing the shape of dendritic arborization in the horizontal, frontal, and sagittal planes of the brainstem. These findings indicate that characteristic geometry of the dendritic tree may have a preference for one array of fibers over another.

• Synaptic targets of commissural interneurons in the lumbar spinal cord of neonatal rats.

  Authors: András Birinyi, Kornél Viszokay, Ildikó Wéber, Ole Kiehn, Miklós Antal

  The Journal of comparative neurology. 08/2003; 461(4):429-40.

  There is strong evidence that commissural interneurons, neurons with axons that extend to the contralateral side of the spinal cord, play an important role in the coordination of left/rightThere is strong evidence that commissural interneurons, neurons with axons that extend to the contralateral side of the spinal cord, play an important role in the coordination of left/right alternation during locomotion. In this study we investigated the projections of commissural interneurons to motor neurons and other commissural interneurons on the other side of the spinal cord in neonatal rats. To establish whether there are direct contacts between axons of commissural interneurons and motor neurons, we carried out two series of experiments. In the first experiment we injected biotinylated dextran amine (BDA) into the lateral motor column to retrogradely label commissural interneurons that may have direct projections to motor neurons. Stained neurons were recovered in the ventromedial areas of the contralateral gray matter in substantial numbers. In the second experiment BDA was injected into the ventromedial gray matter on one side of the lumbar spinal cord, whereas motor neurons were simultaneously labeled on the opposite side by applying biocytin onto the ventral roots. BDA injections into the ventromedial gray matter labeled a strong axon bundle that arose from the site of injection, crossed the midline in the ventral commissure, and extensively arborized in the contralateral ventral gray matter. Many of these axons made close appositions with dendrites and somata of motor neurons and also with commissural interneurons retrogradely labeled with BDA. The results suggest that commissural interneurons may establish monosynaptic contacts with motor neurons on the opposite side of the spinal cord. Our findings also indicate that direct reciprocal connections between commissural interneurons on the two sides of the spinal cord may also exist.

• Ultrastructural organization of lamprey reticulospinal synapses in three dimensions.

  Authors: Jenny S Gustafsson, András Birinyi, John Crum, Mark Ellisman, Lennart Brodin, Oleg Shupliakov

  The Journal of comparative neurology. 09/2002; 450(2):167-82.

  The giant reticulospinal synapse in lamprey provides a unique model to study synaptic vesicle traffic. The axon permits microinjections, and the active zones are often separated from each other,The giant reticulospinal synapse in lamprey provides a unique model to study synaptic vesicle traffic. The axon permits microinjections, and the active zones are often separated from each other, which makes it possible to track vesicle cycling at individual release sites. However, the proportion of reticulospinal synapses with individual active zones ("simple synapses") is unknown and a quantitative description of their organization is lacking. Here, we report such data obtained by serial section analysis, intermediate-voltage electron microscopy, and electron tomography. The simple synapse was the most common type (78%). It consisted of one active zone contacting one dendritic process. The remaining synapses were "complex," mostly containing one vesicle cluster and two to three active zones synapsing with distinct dendritic shafts. Occasional axosomatic synapses with multiple active zones forming synapses with the same cell were also observed. The vast majority of active zones in all synapse types contained both chemical and electrotonic synaptic specializations. Quantitative analysis of simple synapses showed that the majority had active zones with a diameter of 0.8-1.8 microm. The number of synaptic vesicles and the height of the vesicle cluster in middle sections of serially cut synapses correlated with the active zone length within, but not above, this size range. Electron tomography of simple synapses revealed small filaments between the clustered synaptic vesicles. A single vesicle could be in contact with up to 12 filaments. Another type of filament, also associated with synaptic vesicles, emerged from dense projections. Up to six filaments could be traced from one dense projection.

• Location of dye-coupled second order and of efferent vestibular neurons labeled from individual semicircular canal or otolith organs in the frog

  Authors: András Birinyi, Hans Straka, Clara Matesz, Norbert Dieringer

  Brain Research.

  Vestibular nerve branches innervating the sensory epithelia of the three semicircular canals or of the three otolith organs of frogs were selectively labeled in-vitro with biocytin. Labeled afferentVestibular nerve branches innervating the sensory epithelia of the three semicircular canals or of the three otolith organs of frogs were selectively labeled in-vitro with biocytin. Labeled afferent fibers from the semicircular canals, utricle, and lagena were encountered in each of the four vestibular nuclei and their projections overlapped considerably. Saccular afferent fibers projected to the dorsal (acoustic) nuclei and smaller projections to the vestibular nuclei were regionally restricted. Per semicircular canal or otolith organ about equal numbers (11–14) of medium sized vestibular neurons (between 7.5 and 17 μm in diameter) were dye-coupled to afferent fibers. Most of these dye-coupled vestibular neurons were located in the lateral and descending vestibular nuclei between the VIIIth and IXth nerves. The superior vestibular nucleus was relatively free of dye-coupled vestibular neurons. The location of this subpopulation of central vestibular neurons supports the notion that these neurons are part of a particular vestibulospinal pathway. In addition, from each of the canal and/or otolith organs about 3–4 efferent vestibular neurons were labeled retrogradely. These neurons (between 15 and 26 μm in diameter) were located ventral to the vestibular nuclear complex. The branching of efferent vestibular neurons was shown by the presence of neurons that were double labeled by two different fluorescent dyes applied in the same experiment to the anterior and posterior ramus of the same VIIIth nerve, respectively. The branching of these efferent neuron axons explained the presence of collaterals and terminals in the sensory epithelia of a number of untreated ipsilateral endorgans.

• A mozgató működésekért felelős gerincvelői neuronhálózatok morfológiai, fiziológiai vizsgálata és számítógépes szimulációja = Morphological, physiological investigations and computer simulation of spinal neuronal network involved in locomotion.

  Authors: András Birinyi, Miklós Antal, Zoltán Király, Zita Puskár, György Székely, Péter Szűcs, Ildikó Wéber, Ervin Wolf

  1. Fiziológiai kísérletekben jelentős különbségeket találtak propriospinalis axon - motoneuron (MN) kapcsolatokban a MN-ból elvezetett EPSP amplitúdójában a béka gerincvelőben. Modellkísérletekkel1. Fiziológiai kísérletekben jelentős különbségeket találtak propriospinalis axon - motoneuron (MN) kapcsolatokban a MN-ból elvezetett EPSP amplitúdójában a béka gerincvelőben. Modellkísérletekkel bizonyítottuk, hogy a kapcsolatok között mért eltéréseket több tényező magyarázhatja: a szinapszisok elhelyezkedése, a dendrit kitüremkedések, nem-lineáris PSP szummáció illetve a PSP-ok szómára érkezéséhez szükséges késési idők eltérései. 2. A Xenopus embrió úszómozgásáért felelős központi ritmusgeneráló hálózatában azt vizsgáltuk, hogyan vezethet egy rövid inger hosszú ideig tartó úszó mozgáshoz. Az utóagy-gerincvelő határának populációs modelljében azt találtuk, hogy az utóagyi neuronok közötti reciprok serkentő kapcsolatok felelősek lehetnek az említett jelenségért. Elképzelésünket a kísérletes eredmények megerősítik. 3. Patkány gerincvelőben vizsgáltuk a cink kolokalizációját gátló aminosavakkal. Eredményeink azt mutatták, hogy a gerincvelőben a cink tartalmú terminálisok elsősorban gátló karakterűek, amelyekben a GABA és glicin is megtalálható. 4. Újszülött patkány gerincvelőben elemeztük a commissuralis interneuronok (CIN) neurokémiai sajátságait és szinaptikus kapcsolatait. A jelölt CIN terminálisok több mint fele tartalmazott gátló aminosavat, míg a glutamátot tartalmazó terminálisok aránya 27% volt. A jelölt CIN terminálisok közvetlen kapcsolatot képeztek az ellenoldali motoneuronokkal és CIN-okkal. | 1. We investigated the postsynaptic factors that may contribute the high variability of synaptic efficacy in monosynaptically connected propriospinal axon-motoneuron pairs in the spinal cord of frog. We proved that differences in location of these synapses, dendritic protrusions, non-linear summation of PSPs, sizes of time windows for effective temporal summation and differences in delays of arrivals of PSPs to soma are all factors that may differentiate between high and low efficacy single fiber propriospinal connections found experimentally. 2. The central pattern generator for swimming in the Xenopus tadpole was investigated to find out how a brief stimulus can lead to prolonged swimming. By using large-scale population model of the hindbrain-spinal cord junction we found that reciprocal excitatory connections among hindbrain neurons may be responsible for this phenomenon. Our proposal has strong experimental support. 3. Colocalization of zinc with inhibitory neurotrasmitters was investigated in the rat spinal cord. 70% of zinc-containing terminals showed immunoreactivity for GABA and glycine. 4. In neonatal rats we investigated the axonal projection and neurotransmitter properties of spinal commissural interneurons (CIN). About half of the labelled CIN terminals contained GABA or glycine and one third proved to be excitatory. Many of CIN terminals made close appositions with motor neurons and also with CINs on the opposite side of the spinal cord.