Biomedical subjects

L Seress

Publications and source records attributed to L Seress.

At least 55 records · Page 3Linked to original sources

PubMed1991

Parvalbumin- and calbindin D28k-immunoreactive neurons in the hippocampal formation of the macaque monkey.

Calcium-binding proteins calbindin D28k (CaBP) and parvalbumin (PV) were localized in neurons of the monkey hippocampal formation. CaBP immunoreactivity is present in all granule cells and in a large proportion of CA1 and CA2 pyramidal neurons, as well as in a distinct population of local circuit neurons. In the dentate gyrus, CaBP-immunoreactive nongranule cells are present in the molecular layer and in the hilar region, but they do not include the pyramidal basket cells at the hilar border. In the Ammon's horn, CaBP-positive, nonpyramidal neurons are more frequent in the CA3 area than in any other parts of the hippocampal formation. They are concentrated in the strata oriens and pyramidale of areas CA1-3, whereas only a few small neurons were found in the strata lucidum and radiatum of CA3 and in the stratum moleculare of the CA1 area. PV is exclusively present in local circuit neurons both in the dentate gyrus and in Ammon's horn. In the dentate gyrus the presumed basket cells at the hilar border exhibit PV immunoreactivity. In the hilar region and molecular layer only a relatively small number of cells are immunoreactive for PV. Most of these PV-positive cell bodies are located in the inner half of the molecular layer, with occasional horizontal cells at the hippocampal fissure. In Ammon's horn, strata oriens and pyramidale of areas CA1-3 contain a large number of PV-positive cells. There are no PV-immunoreactive cells in the strata lucidum, radiatum, or lacunosum moleculare. The CaBP- and PV-containing neurons form different subpopulations of cells in the monkey hippocampal formation. With the exception of a basket cell type in the monkey dentate gyrus, the CaBP- and PV-positive cell types were found to be remarkably similar in rodents and primates.

Animals↗

PubMed1991

The mossy cells of the fascia dentata: a comparative study of their fine structure and synaptic connections in rodents and primates.

In this study the fine structure and synaptic connections of mossy cells in the rat and monkey fascia dentata were analyzed. In order to study commissural connections of identified mossy cells in the rat, hilar neurons were retrogradely labeled by horseradish peroxidase (HRP) or Fast Blue (FB) injections into the contralateral hippocampus. Vibratome sections containing retrogradely HRP-labeled hilar neurons were Golgi-impregnated and gold-toned. Hilar commissural neurons identified by contralateral FB injection were intracellularly labeled with Lucifer Yellow (LY). Lucifer Yellow staining was made electron-dense by photoconversion thereby allowing for an electron microscopic analysis of the retrogradely labeled and intracellularly stained neurons. With these two different approaches, we succeeded in identifying rat mossy cells projecting to the contralateral hippocampus. Mossy cells in the fascia dentata of primates (Papio anubis, Macaca mulatta, Saimiri sciureus) were, like mossy cells of rats, either Golgi-impregnated and gold-toned or intracellularly injected with LY. No major differences were found between mossy cells of rats and monkeys. The mossy cell dendrites originated from the two sides of an ovoid cell body and were mainly oriented parallel to the granule cell layer. In contrast to the rat, dendrites of mossy cells in the primate did not respect the granule cell layer and penetrated frequently into the molecular layer. The occurrence of excrescences on proximal dendrites was a characteristic feature of all mossy cells. These large spines were more complex in the primate than in the rat. In both rats and primates they formed numerous asymmetric synapses with large boutons of mossy fibers. Peripheral dendrites were covered with small, simple spines. Interestingly, these peripheral dendrites lacking excrescences also established asymmetric synapses with mossy fiber boutons as well as asymmetric and symmetric contacts with smaller terminals of unknown origin. These findings indicate that in both rats and primates the thorny excrescences are not the only target of the mossy terminals. While the proximal portions of the mossy cell dendrites appear to be exclusively contacted by the granule cells, a larger number of neuron types may converge on the distal dendrites. The axons of mossy cells, in both rats and primates, although incompletely stained with the present methods, were seen to ramify in the hilar region. Our results demonstrate that, despite minor species differences, the mossy cells of the fascia dentata represent a cell type that is preserved in phylogenetically distant species.

Amidines↗

PubMed1991

Basket cells in the monkey fascia dentata: a Golgi/electron microscopic study.

This study describes non-granule cells in the fascia dentata of rhesus monkeys and baboons. Their cell bodies are located in the molecular layer and at the hilar border of the granular layer. They are called basket cells since their axons give rise to collaterals that branch in the close vicinity of the parent cell body and form symmetric synapses with dendrites and cell bodies of granule cells. These neurons are further classified with regard to the shape and location of their cell bodies and the orientation of their dendrites. Basket cells in the molecular layer are mainly bipolar with dendrites oriented perpendicular to the granular layer. These dendrites are densely innervated by presynaptic boutons forming asymmetric synapses. We have rarely observed molecular layer basket cells with dendrites traversing the granular layer and invading the hilus. We thus conclude that these cells are mainly activated by extrinsic afferents terminating in the molecular layer. Basket cells at the hilar border display pyramidal, fusiform or multipolar cell bodies that give rise to apical dendrites traversing the molecular layer and basal dendrites invading the hilar region. Large boutons establish asymmetric synapses with identified basal dendrites of these neurons. The dendrites of all types of basket cell are smooth, i.e. they had few or no spines. Many of them display varicosities. Cell counts in Cresyl Violet-stained sections revealed a ratio of basket cells to granule cells of 1:500. Essentially, the types of basket cell in the monkey fascia dentata are similar to those described previously for the rat. This contrasts sharply to our recent findings for pyramidal neurons and granule cells of the monkey hippocampus which showed an increased complexity and variability when compared with rodents. These data do not support the hypothesis that only local circuit neurons evolve in phylogeny.

Animals↗

PubMed1991

Septal GABAergic neurons innervate inhibitory interneurons in the hippocampus of the macaque monkey.

The septohippocampal projection was visualized in three Macaca mulatta monkeys by anterograde transport of Phaseolus vulgaris leucoagglutinin. Following injections of the lectin into the medial septal nucleus, P. vulgaris leucoagglutinin-labelled fibres were found in the hippocampal complex, mainly in stratum oriens of the CA1 subfield, throughout the CA3 subfield, and in the hilus and stratum moleculare of the dentate gyrus. The majority of labelled axons were varicose, and formed multiple contacts with cell bodies and dendrites of calbindin D28k- and parvalbumin-immunoreactive non-pyramidal cells. GABA immunoreactivity of P. vulgaris leucoagglutinin-labelled axons and their postsynaptic targets was investigated by sectioning varicose axon segments for correlated light and electron microscopy, and processing alternate ultrathin sections for postembedding immunogold staining for GABA. All P. vulgaris leucoagglutinin-labelled boutons examined were GABA-immunoreactive and the majority of them formed symmetrical synapses with GABA-immunoreactive cell bodies and dendrites. The results demonstrate that a GABAergic septohippocampal pathway exists in the monkey, and, similar to the rat, terminates on different types of GABAergic neurons, including the parvalbumin- and calbindin D28k-containing non-pyramidal cells.

Animals↗

PubMed1990

Proportion of parvalbumin-positive basket cells in the GABAergic innervation of pyramidal and granule cells of the rat hippocampal formation.

Recent studies have indicated that hippocampal GABAergic neurons in both the dentate gyrus and Ammon's horn contain immunoreactivity for the calcium-binding protein parvalbumin (PARV). Although the distribution of PARV-positive neurons has been previously described, detailed quantitative electron microscopic studies of the PARV-positive axon terminals in the hippocampal formation are lacking. In the present study, immunocytochemical methods were used to localize PARV-positive neurons and axon terminals to determine their similarity to GABAergic neurons. The PARV-positive cells and axon terminals are associated closely with the pyramidal and granule cell layers. In agreement with previous studies, the morphology of PARV-positive neurons is similar to that of GABAergic cells, including the basket cells of both the dentate gyrus and Ammon's horn. The PARV-positive axon terminals form exclusively symmetric synapses with somata, dendrites, dendritic spines, and axon initial segments. However, these terminals represent only a portion of the total number of terminals that form symmetric synapses. Quantitative results indicate that only 32-38% of the total number of terminals forming symmetric axosomatic synapses with principal cells of the dentate gyrus and Ammon's horn are PARV positive. Together with previous findings from light microscopic double-labeling studies, these data indicate that the PARV-positive terminals arise from a subpopulation of GABAergic hippocampal neurons. Finally, it is important to note that the terminal plexus of PARV-positive hippocampal axons overlaps at all postsynaptic sites with a plexus of PARV-negative axons.

Animals↗

PubMed1990

Postnatal development of the light and electron microscopic features of basket cells in the hippocampal dentate gyrus of the rat.

Light and electron microscopic preparations were used to analyze the postnatal development of the basket cells of the rat dentate gyrus. The basket cells, located at the hilar border, were recognized in 2-day-old rats in Golgi preparations, where they displayed immature dendrites and a small axon arbor in the granule cell layer. At 5 days, the basket cells were found to have a large perikaryal cytoplasm, a round nucleus, an axon that forms symmetric synapses with granule cells, and dendrites and somata that are contacted by other axon terminals. The 10-day basket cells display more mature features, such as Nissl bodies and well-developed Golgi complexes. The basket cells from 16-day-old rats are mature in terms of their ultrastructural features, in that the nuclei are highly indented and display intranuclear rods or sheets, the perikaryal cytoplasm is packed with organelles, and the axon has developed an extensive arborization with the somata and dendrites of granule cells at the border with the molecular layer. This arborization will continue to expand as more granule cells are generated and added to the hilar border. These data correlate well with the immunocytochemical and biochemical development of GABAergic neurons in the dentate gyrus. Furthermore, the maturation of the structure of basket cells appears to precede the appearance of adult-like electrical activity in the hippocampus.

Animals↗

PubMed1990

The synaptic connections of basket cell axons in the developing rat hippocampal formation.

Recent studies have indicated that hippocampal basket cells in both the dentate gyrus and Ammon's horn develop their somal and dendritic features during the first two postnatal weeks in rats. Their axon terminals form exclusively symmetric synapses that are found as early as 5 postnatal days in both regions. The present study used Golgi-electron microscopic material from 10 and 16 day old rats to demonstrate that the axon terminals of basket cells form synapses not only with somata, dendrites, and dendritic spines as reported for adult material but also with axon initial segments. However, the terminals forming synapses with axon initial segments and dendritic spines represent only a minor portion of the total number of basket cell terminals. Quantitative results indicate that 36-62% of the total number of these terminals form axosomatic synapses and 32-50% form axodendritic synapses depending on the analyzed cell. These data indicate that hippocampal basket cells have an axonal distribution similar to that found for cortical basket cells.

Animals↗

PubMed1989

Local circuit neurons in both the dentate gyrus and Ammon's horn establish synaptic connections with principal neurons in five day old rats: a morphological basis for inhibition in early development.

Glutamate decarboxylase (GAD)-positive and Golgi impregnated local circuit neurons of the hippocampal formation of five day old rats were examined in light and electron microscopic preparations. The ultrastructural features of these neurons were similar in both the dentate gyrus and CA1 area of Ammon's horn. Somata displayed a perikaryal cytoplasm rich in organelles but lacked organized Nissl bodies. Most nuclei showed intranuclear infoldings of varying degrees but no intranuclear sheets or rods were found. Somata and dendrites were contacted by relatively immature axon terminals that formed mainly symmetric synapses. The axons of local circuit neurons in both the dentate gyrus and Ammon's horn formed symmetric synapses with somata and dendrites of the principal neurons in these regions. Thus, both GAD-positive and Golgi-impregnated terminals of local circuit neurons were observed to form synapses with pyramidal and granule cells. These terminals were usually small and contained relatively few pleomorphic synaptic vesicles. The results show that a circuitry for inhibition is established in the 5 day old dentate gyrus and Ammon's horn, even though the local circuit neurons lack some of the typical adult ultrastructural features at this age.

Animals↗

PubMed1989

Early onset of synapse formation in the human hippocampus: a correlation with Nissl-Golgi architectonics in 15- and 16.5-week-old fetuses.

The developmental status of some potential components of hippocampal circuitry was studied at the time of the emergence of the hippocampal cytoarchitectonic subfields. The laminar distribution of synapses as seen with electron microscopy was correlated with Golgi architectonics in 15- and 16.5-week-old human fetuses. A systematic electron microscopic analysis of the distribution of synapses demonstrated that they were restricted to the two zones bordering the cortical plate, viz. the marginal and subplate zones, which contain dendritic branches of pyramidal and large polymorphous non-pyramidal neurons. The density of synapses (number per unit area) was higher in the marginal zone than in the subplate zone. Most synapses were of the asymmetric axodendritic type, although some were symmetric axodendritic synapses. The possible origins of the axons forming these synapses are discussed. This study demonstrates that the human hippocampus shows an early onset of synapse formation, with a characteristic distribution of synapses in restricted laminae. The finding of early synapse formation is consistent with observations made in other cortical areas during development. The prevalence of synaptogenesis at a superficial level of the cortex seems, however, to be specific to the "archicortex".

Embryonic and Fetal Development↗

PubMed1989

Comparative study of glial fibrillary acidic protein (GFAP)--immunoreactivity in the rat and monkey cerebellum.

Vibratome sections of perfusion-fixed rat and monkey cerebella were incubated with an antiserum to glial fibrillary acidic protein (GFAP). Immunolabelled elements showed in both species a principally similar distribution but the presence of long, transverse branches of Bergmann fibres was found to be characteristic to the monkey cerebellum. It is concluded that current methods enable fine interspecies differences of GFAP-localization to be demonstrated. This bears a relevance to the use of GFAP-immunostaining as a diagnostic tool in neuropathology.

Animals↗

PubMed1988

The development of GABAergic neurons in the rat hippocampal formation. An immunocytochemical study.

Recent studies have indicated that hippocampal GABAergic neurons in both the dentate gyrus and Ammon's horn are generated prenatally. Although the adult distribution of GABAergic neurons has been previously described by numerous investigators, the early postnatal appearance of these neurons has not been described. In the present study, immunocytochemical methods were used to localize GABAergic neurons with antisera to both GABA and its synthesizing enzyme, glutamate decarboxylase (GAD). The GABA-positive neurons appeared at the earliest postnatal day (PND) examined, 4 PND. In contrast, GAD-positive cells were not observed until 6 PND, and the number of these neurons remained less than that of the GABA-positive neurons until 14 PND. These findings indicated that immunocytochemically detectable amounts of GAD were not present in many young GABAergic neurons. Both GABA- and GAD-positive hippocampal neurons showed two large increases in number during the 4-8 PND and 12-16 PND time periods, and they reached about 90% of adult levels before 18 PND. The regional distribution of GABA- and GAD-positive neurons throughout the hippocampal formation was homogeneous for all ages examined except 4 PND. At this age, the GABA-positive cells appeared in clusters in the proximal CA3 and the distal CA1 relative to the dentate gyrus. In addition, the number of hippocampal neurons immunostained in adult preparations for both antisera to GABA and GAD showed a similar number and distribution. The data on the developmental appearance of GABA and GAD immunoreactivities are consistent with biochemical data for the development of GABA concentration and GAD activity in the hippocampal formation. Together, these data provide important information about the functional maturation of the hippocampal GABAergic system in the first 3 weeks of rat brain development.

Aging↗

PubMed1988

A Golgi-electron microscopic study of fusiform neurons in the hilar region of the dentate gyrus.

The fusiform cells of the dentate gyrus are located in a portion of the hilus within 100 micron of the granule cell layer. They have ovoid somata and bipolar dendrites that generally run parallel to the granule cell layer. The dendrites of these cells are either spiny or sparsely spiny. The spiny fusiform cell has numerous spines along its dendrites, which are contacted by terminals with the features of granule cell axon collaterals. This cell type also displays somal spines that are contacted by similar terminals. In contrast, the sparsely spiny fusiform cell displays only a few spines, which are contacted by multiple small axon terminals that synapse with both the stalk and end bulb of the spine. Most synaptic input for this cell type is made with the smooth surfaces of the soma and dendrites. A variety of terminals form synapses with the sparsely spiny fusiform cell, including terminals that resemble the fine axon collaterals of mossy fibers. The somata of these two cell types also display differences in the amount of Nissl bodies and the degree of nuclear infolding. The results indicate that spiny fusiform cells are similar to mossy cells, another hilar cell type that receives its major synaptic input from axon collaterals of mossy fibers from granule cells. The distribution of the dendrites of spiny fusiform cells and the pattern of granule cell axon collaterals suggest a high degree of convergence from granule cells. In contrast, the variety of axodendritic synapses for sparsely spiny fusiform cells suggests that more diverse inputs affect this cell's activity. Therefore, the structure and circuitry of these two hilar cell types are probably different. This study adds further evidence to indicate that the hilus contains a large variety of cell types with different neuronal connections.

Animals↗

PubMed1988

Interspecies comparison of the hippocampal formation shows increased emphasis on the regio superior in the Ammon's horn of the human brain.

The cells in the hippocampal formation of rat, cat, rhesus monkey and human have been counted. The results show that there is a continuous increase both in granule and pyramidal cell numbers from rat to human. However, in human there is a disproportionate increase in the number of pyramidal cells of the regio superior. In the dentate gyrus the hilar region accumulates higher number of cells than it might have been expected from the average increase.

Animals↗

PubMed1987

Basal dendrites of granule cells are normal features of the fetal and adult dentate gyrus of both monkey and human hippocampal formations.

The aim of this study was to analyze the granule cell population of the dentate gyrus both in healthy rhesus monkeys and in humans free of mental and neurological disorders. Brains of neonatal and adult rhesus monkeys as well as brains of fetal, neonatal and adult humans were impregnated with Golgi methods. The results show that a significant population of granule cells have basal dendrites in primates. Some basal dendrites curve up into the molecular layer where they have similar morphology as the apical dendrites. In contrast, other basal dendrites protrude into the hilus and they are shorter, thinner and have only a few side branches. The frequency of granule cells with basal dendrites in the human dentate gyrus is twice as much as that of the rhesus monkey. Most of these human granule cells have their basal dendrites in the hilus. This observation confirms the fact that discrepancies occur in the normal morphology of individual neurons between the rodent and primate hippocampal formations. The results indicate that basal dendrites of granule cells are not pathological as previously suggested.

Animals↗

PubMed1987

Electron microscopic localization of acetylcholinesterase in the dentate gyrus of young and adult rats.

Acetylcholinesterase (AChE) histochemical staining occurred in neurons of the dentate gyrus at the day of birth and steadily increased in intensity and distribution during the first 3 postnatal weeks until the adult pattern was reached. Granule cells failed to display AChE staining; however, the somata of most non-principal cells in these regions showed AChE activity. It is interesting that most hilar neurons in the dentate gyrus were AChE-positive, but molecular layer local circuit neurons and pyramidal basket cells associated with the granule cell layer did not display AChE staining. AChE reaction product was localized to the nuclear envelope and cisternae of the granular endoplasmic reticulum in the labeled neuronal somata. In addition, the neuropil in the dentate gyrus displayed AChE staining associated with membranes. The possible cholinoceptive role of the AChE somata in the hilus is discussed.

Acetylcholinesterase↗

PubMed1986

A GABAergic inhibitory component within the hippocampal commissural pathway.

Previous results from immunocytochemical and retrograde transport studies indicated that some GABAergic neurons in the hilus of the dentate gyrus may have axonal projections through the hippocampal commissure. This study has utilized a combined immunocytochemical and retrograde transport method as well as 2 anterograde electron-microscopic methods to determine the existence of this projection in rats. Combined tracer and immunofluorescence studies showed several double-labeled GABAergic neurons in the hilus contralateral to the injection site. The electron-microscopic studies revealed both degenerating and HRP-labeled commissural axons that formed symmetric synapses, the type shown to be formed by GABAergic terminals in the hippocampus. These data demonstrate a GABAergic component within the hippocampal commissural pathway and add further evidence that cortical GABAergic terminals are not derived exclusively from intrinsic neurons.

Animals↗

PubMed1985

A substantial number of asymmetric axosomatic synapses is a characteristic of the granule cells of the hippocampal dentate gyrus.

The types of axosomatic synapses for pyramidal neurons of the Ammon's horn and granule cells of the dentate gyrus were investigated in the rat hippocampus. Local circuit neurons in both of these regions were also included. The mean number of axosomatic synapses was higher for pyramidal neurons than granule cells. Practically all of these synaptic contacts were symmetric for the pyramidal neurons of the CA1 area, whereas the percentage of asymmetric axosomatic synapses for granule cells and local circuit neurons was 21% and 26%, respectively. This finding is interesting because granule cells appear to be the only known projection neuron type to possess such a high percentage of asymmetric axosomatic synapses.

Animals↗

PubMed1985

A combined Golgi-electron microscopic study of non-pyramidal neurons in the CA 1 area of the hippocampus.

Non-pyramidal neurons of the CA 1 area of the rat hippocampus were identified with a combined Golgi-electron microscopic method. They were observed to have distinctive light and electron microscopic characteristics that are different from those of pyramidal cells. These features included smooth dendrites, locally arborizing axons, infolded cell nuclei with intranuclear rods or sheets, and a well-developed perikaryal cytoplasm with many organelles. In addition, the axon terminals that contact the somata and dendrites of local circuit neurons may form asymmetric as well as symmetric synapses. The axons of these cells form symmetric synapses with dendrites and somata of pyramidal cells. Some of these features were utilized to identify non-pyramidal neurons of the CA 1 area for studies of connectivity. Degenerating commissural terminals were found to form synapses with the dendrites and somata of non-pyramidal neurons. These results indicate that these neurons are a significant population of hippocampal neurons that may provide feed-forward inhibition of pyramidal neurons.

Animals↗