Search results for "Fascia dentata"
showing 9 items of 9 documents
A Golgi study of the principal projection neurons of the medial cortex of the lizardPodarcis hispanica
1997
The medial cortex of lizards is a simple three-layered brain region displaying many characteristics that parallel the hippocampal fascia dentata of mammals. Its principal neurons form a morphologically diverse population, partly as a result of the prominent continuous growth of this nervous center. By using the classic Golgi impregnation method, we describe here the morphology of the principal neurons populating the medial cortex of Podarcis hispanica. These were projection neurons giving off descending axons. These axons displayed deep collateral branches provided with prominent axonal boutons, while the main axonal branch reached adjacent cortical areas and the bilateral septum. According…
Delayed postnatal neurogenesis in the cerebral cortex of lizards
1988
Labelled cells were consistently observed in the medial cortex of the lizard brain after i.p. injections of tritiated thymidine (5 microCi/g b. wt.), 1, 7, 18 or 28 days of survival and posterior autoradiographic evaluation. In 3 groups of specimens (postnatal, young and adult) of the species Podarcis hispanica, after one day of survival, labelled cells were located in the ependymal cell layer underlying the medial cortex. After intermediate survival times (7, 18 days), labelled cells were found in 3 zones: the ependymal layer, the inner plexiform layer and the granular layer. After one month of survival, most labelled cells were observed in the granular layer. In the granular layer, these …
Long-spined polymorphic neurons of the medial cortex of lizards: a Golgi, Timm, and electron-microscopic study.
1988
The morphology, ultrastructure, and principal synaptic input of longspined neurons located in the inner plexiform layer of the medial cortex in three related species of lizards is described. Golgi impregnations have been used to define the external morphology of these neurons and their axonal trajectories. Their most striking characteristic is the presence of very long spines or “microdendrites” especially abundant on the distal dendritic segments. Axons have ascendent trajectories, pass through the cell layer, and ramify in the outer plexiform layer. Combined Golgi-electron microscopy as well as standard electron microscopy permitted the definition of the ultrastructure of these neurons. T…
Photoperiod-temperature and neuroblast proliferation-migration in the adult lizard cortex.
1997
The lizard medial cortex (a zone homologous to the mammalian fascia dentata) shows delayed postnatal neurogenesis throughout the lifetime of these animals. Experimental lesioning of this area is followed by neuronal regeneration, a unique phenomenon in the adult amniote telencephalon. The differential effects of temperature and photoperiod on postnatal neurogenetic activity were studied using tritiated thymidine pulses and posterior autoradiography as well as proliferating cell nuclear antigen (PCNA) immunostaining. Long (summer) photoperiods increased the number of proliferating neuroblasts in the ependymal neuroepithelium. Cold (winter) temperature prevented migration of the newly generat…
A Golgi study of the short-axon interneurons of the cell layer and inner plexiform layer of the medial cortex of the lizardPodarcis hispanica
1997
The medial cortex of lizards is a three-layered brain region displaying cyto- and chemoarchitectonical, connectional, and ontogenetic characteristics that relate it to the hippocampal fascia dentata of mammals. Three interneuron types located in the cell layer and ten others in the inner plexiform layer (six in the juxtasomatic zone and four in the deep zone) are described in this study. The granuloid neurons, web-axon neurons, and deep-fusiform neurons lay within the cell layer. These neurons were scarce; they were probably gamma-aminobutyric acid (GABA)-, and parvalbumin-immunoreactive and presumably participated in feed forward as well as in feed back inhibition of the principal projecti…
Reactive neurogenesis during regeneration of the lesioned medial cerebral cortex of lizards
1995
Abstract This study reports that lesion of the adult lizard medial cortex (lizard hipocampal fascia dentata) induces a short period of intensive neurogenesis which we have termed reactive neurogenesis; a cell proliferation event that occurs in the subjacent ependyma. Specific lesion of the medial cortex was achieved by intraperitoneal injection of the neurotoxin 3-acetylpyridine and proliferating cells were detected using tritiated thymidine or 5-bromodeoxiuridine pulse labelling. After lesion, granule neurons in the lizard medial cortex cell layer appeared pyknotic and died; they were then removed and progressively replaced by a set of new neurons. These neurons were mostly generated from …
Transitory disappearance of microglia during the regeneration of the lizard medial cortex
1994
In normal lizards, microglial cells populate the medial cortex (a zone homologous to the hippocampal fascia dentata), with a preferential distribution along the border between the granular cell layer and the plexiform layers. Intraperitoneal injection of the neurotoxin 3-acetylpyridine (3AP) induces a selective lesion in the medial cortex with a rapid degeneration of the granular layer and its zinc-enriched axonal projection. Within 6-8 weeks, the granular layer is, however, re- populated by a new set of neurons generated in the subjacent ependyma and the cell debris is removed. The aim of this study was to determine to what extent microglia were involved in the scavenging processes during …
Neuronal circuitry in the medial cerebral cortex of lizards
1997
The medial cortex of lizards is a simple three-layered brain region displaying many characteristics which parallel the hippocampal fascia dentata of mammals. Its principal neurons form a morphologically diverse population, partly as a result of the prominent continuous growth of this nervous centre. By using the classical Golgi impregnation method we describe here the morphology of the principal neurons (8 types) and the short-axon interneurons (18 types) populating the medial cortex of Podarcis hispanica as well as the connections between them.
The lizard cerebral cortex as a model to study neuronal regeneration
2002
The medial cerebral cortex of lizards, an area homologous to the hippocampal fascia dentata, shows delayed postnatal neurogenesis, i.e., cells in the medial cortex ependyma proliferate and give rise to immature neurons, which migrate to the cell layer. There, recruited neurons differentiate and give rise to zinc containing axons directed to the rest of cortical areas, thus resulting in a continuous growth of the medial cortex and its zinc-enriched axonal projection. This happens along the lizard life span, even in adult lizards, thus allowing one of their most important characteristics: neuronal regeneration. Experiments in our laboratory have shown that chemical lesion of the medial cortex…