PubMed Health⌕ Search

Biomedical subjects

F Hajdu

Publications and source records attributed to F Hajdu.

At least 19 recordsLinked to original sources
PubMed1992

Neuronal and synaptic structure of the specific thalamic nuclei.

1. Neuronal organization of the specific thalamic nuclei is rather uniform. The ratio of thalamocortical relay neuron and Golgi II type interneuron is 2:1, as well as 3:1. 2. Interneurons show GABA-immunoreactivity. The presynaptic dendrites (F2-profiles) modify the intrathalamic transmission of the specific afferent impulses. 3. The two principal types of synaptic arrangements were observed in the specific thalamic nuclei: the synaptic glomeruli and the general neuropil. 4. Three different types of axon-terminals could be distinguished in the neuropil of all specific thalamic nuclei: the large RL-boutons are terminals of the specific afferents, the small RS-boutons are mainly the terminals of cortical afferents and the F1-boutons are probably axon-terminals of the Golgi II type interneurons, as well as axon-endings originating from the reticular nucleus of thalamus. 5. Synaptic contacts of the specific afferent fibers have basic importance in the relay nuclei. 6. In associative and anterior thalamic nuclei the RS- and F1-boutons have a significant modification effect on the interneurons (inhibition-disinhibition).

Animals↗
PubMed1991

Organization of the projections from the ventral tegmental area of Tsai to the hippocampal formation in the rat.

The projection from the ventral tegmental area of Tsai (VTA-A10) to the hippocampal formation (HF) has been investigated in the rat by means of the Fink-Heimer technique, after VTA destruction by electrolytic lesions or local injections of 6-hydroxydopamine (6-OHDA, 1 microgram/0.5 microliters). Degenerated axons prevail in the ventral subiculum and adjacent CA1 field. Some degenerated fibers are also observed in the dorsal subiculum and a few in the stratum oriens of the CA3, in the hilus of fascia dentata and in the fimbria. The distribution of VTA neurons projecting to the HF has also been examined by injecting retrograde fluorescent tracers in different combinations (Fast Blue, 2% and Nuclear Yellow, 1%) in several hippocampal areas. The most abundant VTA-HF projections originate from the lower third, the upper and lower edges and the lower half of the VTA. The major terminal fields of VTA projections in the HF (i.e. the ventral subiculum, the adjacent CA1 field and the dorsal subiculum) match with the HF area projecting to the nucleus accumbens. Thus, the dopaminergic meso-limbic pathway could modulate the HF-striatal projection which provides a link between the limbic and motor systems.

Animals↗
PubMed1990

Ultrastructure of neurons and their synaptic contacts in the medial septal nucleus of the rat.

The medial septal nucleus of non-experimentally treated albino rats was investigated electron microscopically. According to former light microscopical findings most of the dendrites in this region are spineless but conspicuously varicose. Besides a striking diminution of the packing density of neurotubules inside the varicosities--compared with the narrow portions of varicose dendrites--some organelles like multivesicular bodies, lamellated bodies and cisterns of the smooth endoplasmic reticulum were found to be characteristic of them. Large neuronal somata rich in RER with a broad rim of cytoplasm around the nucleus and numerous lipofuscin-like granules occur. But there are numerous small cells exhibiting a narrow rim of cytoplasm and pourly developed RER, too. At least six classes of synaptic junctions can be distinguished, three of the asymmetric and three of the symmetric type. Most of axo-somatic contacts are of the symmetric type, at the dendrites asymmetric contacts dominate. Presynaptic profiles with large dense-core vesicles form symmetrical contacts with varicose and non-varicose dendritic profiles.

Animals↗
PubMed1989

Shape and size of synaptic vesicles in different types of presynaptic profiles in the medial septal nucleus of the rat.

Long and short axis diameters of synaptic vesicles were obtained from 6 classes of presynaptic boutons found in the medial septal nucleus (MS) of the rat. The variability of vesicle size and shape was documented in diagrams and discussed with regard to their suitability as criteria of classification and their functional significance. The variability in shape, but not in size, of vesicles in synapses of Gray's type I is lower than of those in Gray's type II synapses.

Animals↗
PubMed1988

Neurons in the basal forebrain complex of the rat: a Golgi study.

Several types of neurons are coexistent in the basal forebrain nuclear complex of the rat. In the medial septum and vertical limb of the diagonal band 3 classes of neurons occur which are characterized by varicose dendrites. In the horizontal limb of the diagonal band neurons with smooth dendrites and those with varicose dendrites are intermingled. We found 3 classes of neurons in the nucleus preopticus magnocellularis. A giant type with smooth and varicose dendrites occurs in this nucleus, but also in the substantia innominata. In the substantia innominata-nucleus basalis complex 4 classes of neurons with varicose dendrites and 2 classes with spiny dendrites have been observed. Our findings suggest that the nucleus of the vertical limb of the diagonal band forms a unit with the nucleus septi medialis, but is separated from the nucleus of the horizontal limb of the diagonal band by different neuronal composition. The nucleus preopticus magnocellularis is a separate nuclear structure characterized by a content of neurons different from those in the horizontal limb of the diagonal band and in most components also from the substantia innominata-nucleus basalis complex. There is some evidence that the cholinergic neurons have to be searched among those with varicose dendrites.

Animals↗
PubMed1988

An EM and Golgi study on the connection between the nucleus tegmenti pedunculopontinus and the pars compacta of the substantia nigra in the rat.

The present study provides evidence of a synaptic contact between terminals of pedunculopontine neurons and cells of substantia nigra pars compacta (SNPC) in the rat. Three types of projective neurons observed in Golgi stained preparations of the pedunculopontine region might be the source of this afferent pathway to the substantia nigra. These PPN projective neurons were small, medium and large sized cells. After placing a small electrolytic lesion into the pedunculopontine area two types of degenerated terminals were found in the SNPC, a small and a larger one. These degenerated terminals contained round synaptic vesicles, thus suggesting that the pedunculopontine input to the SNPC is monosynaptic and excitatory in nature.

Afferent Pathways↗
PubMed1985

Architectonic differentiation of the lateral geniculate body of the cat.

The cell layers of the lateral geniculate nucleus (LGN) of the cat have been reinvestigated in relation to the localization of the degeneration of optic terminals. After unilateral enucleation the degenerated crossed and uncrossed optic terminals form five continuous alternate strips in all the five layers of the LGN with the Fink-Heimer method. The crossed terminals end in the layers A, B0, and B2, and the uncrossed terminals in the layers A1, and B1 without overlapping. The cyto- and myeloarchitectonic study of complete frontal, sagittal, and horizontal serial sections has shown that the former B layer and the nuclei interlaminares centralis pars ventralis and medialis of Thuma built up three continuous parallel layers, which we propose to call B0, B1, and B2. The layer B0 containing large cells and more single fibers than the layers A and A1, extends on the medial, ventral and caudal side of layer A1. The layer B1 containing smaller cells and less single fibers than the layer B0, surrounds the layer B0 from medial, ventral and caudal. It comprises in the medial part of the ventral extent a pale spot with especially small nerve cells. The layer B2 containing medium-sized cells in less dense arrangement and many small dark fiber bundles split up from optic tract extends medially and ventrally of layer B1. The caudal pole of the LGN is covered cap-like by the layers B0, and B1 and incompletely by B2. This new interpretation of the LGN's layers in the cat is more regular and easier to compare with the stratification of the LGN of other species including primates.

Animals↗
PubMed1983

Neuronal and synaptic arrangements of the lateral geniculate nucleus in night-active primates.

The lateral geniculate nucleus (LGN) of Aotus trivirgatus and Nycticebus coucang shows two types of neurons at the ultrastructural level: a large thalamo-cortical relay neuron (TCR) and a small neuron of Golgi type II, which is considered to be an interneuron. The interneuron contains small aggregations of synaptic vesicles in the perikaryon adjacent to the cell membrane in synaptic contact to a TCR neuron. Only in the perikaryon of the interneurons can cilia have their origin. After unilateral enucleation, neurofilamentous or dark degenerations of large boutons with round vesicles (type RL) occur in the outer layers of the contralateral LGN and in the inner layers of the ipsilateral LGN. The optic terminals establish synaptic contacts in the glomerulus with dendritic spines of the TCR neurons and with presynaptic dendrites (F2) of interneurons.

Animals↗
PubMed1983

Quantitative histological study on the thalamic ventro-basal complex of the cat. Numerical aspects of the transfer from medial lemniscal fibers to cortical relay.

A quantitative analysis was carried out on the thalamic ventrobasal (VB) complex of the cat. The following numerical and metrical parameters of the neuronal elements (cells and fibers) were determined: 1. Volume of nucleus: 27.38 mm3 2. Total number of neurons: 243,000 3. Total number of fibers of medial lemniscus: 26,000 4. Volume of arborization space of one lemniscal fiber: 2.26 X 10(6) micrometers 3. Numerical data of relay neurons and lemniscal fibers and their relations as basic factors in the estimation of the degree of divergence and convergence of lemniscal input were calculated and compared. It was found that the probable degree of convergence is four-fold (1-4) and of divergence 27-fold (1-27) with regard to the relationship of fibers and cells in the VB. The quantitative data obtained in the VB and our considerations on convergence and divergence were compared with analogous values obtained for the lateral geniculate body LGB. The differences between the two sensory relay nuclei reflect differences in their modes of impulse transmission.

Animals↗
PubMed1982

Neuronal and synaptic organization of the lateral geniculate nucleus of the tree shrew, Tupaia glis.

The ultrastructural study of the lateral geniculate nucleus (LGN) of the tree shrew (Tupaia glis) revealed two types of neurons: (1) a large thalamocortical relay cell (TCR), which may bear cilia, and (2) a small Golgi type-II interneuron (IN) with an invaginated nucleus. The narrow rim of pale cytoplasm of the IN contains fewer lysosomes and fewer Nissl bodies than the cytoplasm of the TCR. The IN perikarya, which in some cases establish somatosomatic contacts, frequently contain flattened or pleomorphic synaptic vesicles. The ratio of TCR to IN is 3:1. Three types of axon terminals were observed in the LGN. Two of them contain round synaptic vesicles but differ in size. The large RL boutons undergo dark degeneration after enucleation; they are the terminals of retino-geniculate fibers. The smaller RS boutons show dark degeneration after ablation of the visual cortex; they are the terminals of the cortico-geniculate fibers. The third type of bouton (F1) does not degenerate after either intervention. The boutons of this type are filled with flattened vesicles and are believed to be intrageniculate terminals. F2-profiles were interpreted as presynaptic dendrites of the IN. The characteristic synaptic glomeruli found in the LGN contain in their center an optic terminal. These optic terminals establish synaptic contacts with dendrites or spine-like dendritic protrusions of TCRs as well as with presynaptic dendrites. Synaptic triads were also seen. The distribution of the individual types of synaptic contacts in layers 3 and 4 were determined. Layer 4 contains only one third of the retino-geniculate synapses and of the synaptic contacts of F1-terminals.

Animals↗
PubMed1982

The distribution of crossed and uncrossed optic fibers in the different layers of the lateral geniculate nucleus in the tree shrew (Tupaia glis).

The laminar distribution of crossed and uncrossed optic fibers was studied in the lateral geniculate nucleus (LGN) in the tree shrew (Tupaia glis) following unilateral enucleation. For the investigation of the termination of optic fibers the transneuronal degeneration method and experimental EM were employed. By using formvar film-coated slot grids, all six layers of the LGN could be studied in a single ultrathin section. Degeneration of crossed optic fibers was observed in layers 1, 3, 4 and 5 of the contralateral LGN. The uncrossed retinofugal fibers supply layers 2 and 6 of the LGN. The degeneration in layer 4 was less pronounced than that in the other layers. Ipsilateral and contralateral optic fibers were well separated. Filamentous as well as dark types of degeneration were found in the LGN after enucleation. The optic terminals (RL boutons) were seen only in the synaptic glomeruli.

Animals↗
PubMed1979

A combined horseradish peroxidase and Golgi study on the afferent connections of the ventrobasal complex of the thalamus in the cat.

Afferent connections to the ventrobasal complex (VB) of the thalamus were studied by means of retrograde transport of horseradish peroxidase (HRP) and by the Golgi-method. After HRP-injection into the VB, peroxidase-positive cells were observed contralaterally in the dorsal column nuclei (DCN), in the trigeminal nuclei and in the lateral cervical nucleus (LCN), and ipsilaterally in the somatosensoty I (SI) and II (SII) cortical areas. Labeled cells of different shape and size were compared with neurons impregnated by the Golgi-technique. On tn size and shape even within one region and that they correspond to the relay or efferent neurons observed in the Golgi-material.

Animals↗
PubMed1979

Types of thalamo-cortical relay neurons in the anteroventral nucleus of the cat. A combined horseradish peroxidase--Golgi study.

Neurons displaying a thalamo-cortical projection were marked by means of the retrograde transport of horseradish peroxidase (HRP), and the labeled elements were compared with neurons impregnated by the Golgi technique. Injections of HRP into the posterior area of the limbic cortex resulted in its uptake by various anterior thalamic nuclei, especially the anteroventral nucleus. HRP-positive cells are characterized by their position, dendritic orientation, and the shape and size of their somata. On the basis of the combined HRP-and Golgi-analysis three different types of thalamo-cortical relay neurons can be distinguished.

Animals↗
PubMed1978

Golgi study on cat hippocampal formation.

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.

Animals↗
PubMed1978

Ultrastructure of the anterior ventral and anterior medial nuclei of the cat thalamus.

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.

Animals↗
PubMed1978

Limbic projections to the cat thalamus. A horseradish peroxidase study.

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.

Afferent Pathways↗