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J DeFelipe

Publications and source records attributed to J DeFelipe.

68 records · Page 4Linked to original sources
PubMed1988

A study of tachykinin-immunoreactive neurons in monkey cerebral cortex.

Immunocytochemical methods were used to localize tachykinin-like immunoreactivity within neurons of the monkey cerebral cortex. Three primary antibodies were used: polyclonal antisera raised against fragments of substance P and substance K that excluded the carboxyl termini of these peptides, and a monoclonal antibody that recognized the carboxyl terminus of the tachykinin family. Each antibody stained 2 populations of cortical nonpyramidal neurons: (1) A small number of large, intensely stained cells that give rise to long, coarsely beaded processes; (2) a relatively large number of small, lightly stained cells that are embedded in dense plexuses of stained punctate profiles. The large, dark cells are present in a superficial band that includes layers II and III, and in a deep band that includes layer VI and the subjacent white matter. The smaller, pale cells are present in the middle layers of cortex (layers IV and/or V). Colocalization studies indicate that virtually all the small tachykinin-immunoreactive neurons also display GABA immunoreactivity. The larger cells are not GABA-positive, but display both somatostatin-like and neuropeptide Y-like immunoreactivity. The immunocytochemically stained beaded processes and punctate profiles from plexuses that vary in density and laminar distribution among different areas of monkey cortex. The coarsely beaded processes form a basic quadrilaminar pattern, with relatively dense plexuses in layers I and VI and in 2 middle layers, usually III and V. However, this pattern varies considerably from area to area. Electron microscopically, the large cells contain a rich collection of cytoplasmic organelles, particularly Golgi complex, while the small cells contain relatively few organelles. Both types of cells, including large neurons in the white matter, receive symmetric and asymmetric synaptic contacts on their somata and proximal dendrites. The numbers of these axosomatic contacts are low. Virtually all synaptic contacts formed by immunoreactive terminals possess symmetric membrane thickenings. In 2 areas examined in detail (areas 2 and 4), pyramidal cell somata and dendrites are the major targets of the immunoreactive synaptic terminals.

Animals↗
PubMed1986

A correlative electron microscopic study of basket cells and large GABAergic neurons in the monkey sensory-motor cortex.

Large basket cells were identified in Golgi and horseradish peroxidase labeled material from the sensory-motor cortex of adult monkeys. Their morphology was correlated at the light and electron microscopic level with large comparable cells stained immunocytochemically for glutamate decarboxylase. In Golgi-impregnated material these cells have a very large cell body and dendrites that extend through several layers of the cortex with a predominant vertical orientation. The axon is only stained for a few micrometers. The same cells studied electron microscopically in serial sections after gold-toning show very distinctive ultrastructural characteristics: the cell bodies contain a large number of organelles, the nuclei are rounded with homogeneously dispersed chromatin and synapsing onto the somata are many axon terminals, both symmetrical and asymmetrical but the symmetrical type forms 70-80% of the total; dendrites also receive a large number of both symmetrical and asymmetrical synaptic contacts. All the axons of basket cells become myelinated and the Golgi labeling of the initial segments is interrupted at the commencement of the first myelin internode. The axon initial segments receive several symmetrical synaptic contacts in the proximal one-third of their length. The axonal arborization of a basket cell retrogradely labeled in the somatosensory cortex after intracortical injection of horseradish peroxidase was analyzed in detail. The mainly horizontal axonal collaterals of this cell are myelinated for most of their trajectory and have a preferred orientation in the anteroposterior dimension. These axonal collaterals, although very long (more than 1.8 mm), at intervals give rise to a small number of short unmyelinated terminal branches that bear a series of boutons terminaux forming a multi-terminal ending. The multi-terminal endings surround somata and proximal dendrites of pyramidal and non-pyramidal cells. Dense pericellular terminations (baskets or nests) like those drawn by Ramón y Cajal and Marin-Padilla are not formed by the axon of a single basket cell. Thus, basket formations are presumably formed by converging axons from several basket cells. Immunocytochemical material was stained for glutamate decarboxylase, the enzyme involved in the synthesis of gamma-aminobutyrate (GABA). This shows that large glutamate decarboxylase-positive neurons of the same size as those positively identified as basket cells in the Golgi and horseradish peroxidase material have virtually the same morphological characteristics, at both the light and electron microscope levels, as the basket cells.(ABSTRACT TRUNCATED AT 400 WORDS)

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PubMed1986

Long-range focal collateralization of axons arising from corticocortical cells in monkey sensory-motor cortex.

Small extracellular injections of HRP were placed into a stratum of corticocortical axons situated immediately deep to area 3b of the monkey somatic sensory cortex. This stratum had previously been demonstrated to contain corticocortical fibers linking the cytoarchitectonic fields of the somatic sensory cortex to one another and certain of them to the motor cortex. This method resulted in extremely successful filling of pyramidal cells, their axons, collateral axon branches, and terminations in areas 3b, 1, and 2 posterior to the injection and in areas 3a and 4 anterior to it. The major finding was that cells with somata situated in any one of these fields and with principal axons traversing the injection site have long collaterals, primarily in layers III and V, which can extend throughout their own cytoarchitectonic field and into one or more other fields. In these fields they give off focused, columnlike concentrations of terminal boutons, which can be separated from one another by 800 micron or more. The anterogradely labeled, primary corticocortical fibers, traced forwards into areas 3a and 4, have virtually identical focal terminations. These findings indicate that interareal connectivity in the sensory-motor cortex can be effected by the axon branches of single cells rather than by separate groups of cells, and this may form a basis for the convergence of place and modality information on single cells in the sensorimotor cortex, a convergence that is not seen in the thalamic input to this cortex.

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PubMed1985

Variability in the terminations of GABAergic chandelier cell axons on initial segments of pyramidal cell axons in the monkey sensory-motor cortex.

Chandelier cell axons were studied in the sensory-motor cortex of adult monkeys. The axonal fields of Golgi-impregnated chandelier cells in layer II in motor cortex are flattened sagittally. The vertical terminal portions of the axons varied both in length and in the numbers converging to form terminations of greater or lesser complexity. Golgi-impregnated plexuses were embedded in plastic and resectioned serially at 2.5-3.0 micrograms. A single axonal field could have as many as 400 terminal rows. All lie 3-13 micrograms beneath pyramidal cell somata. These terminations are not randomly distributed but instead, form clusters. Further resectioning the plastic sections for electron microscopy revealed that all the terminations are on the initial axon segments of pyramidal cells and all form symmetric synaptic contacts. In immunocytochemical material stained for glutamic acid decarboxylase (GAD), the enzyme involved in the synthesis of GABA, GAD-positive boutons were found to form symmetric synaptic contacts with a variety of postsynaptic elements including the axon hillocks and axon initial segments of pyramidal cells. Serial reconstructions from electron micrographs revealed GAD-positive terminals synapsing with the axon initial segment of pyramidal cells joined by cytoplasmic bridges and forming vertically oriented rows identical to those of chandelier cell terminals identified positively in the resectioned Golgi material. The GAD-positive terminals forming initial segment synapses were never continuous with GAD-positive terminals forming axo hillock synapses. The latter probably arise from basket cell axons. Initial segments of pyramidal cell axons in layers II and III were contacted by more GAD-positive terminals than the initial segments of pyramidal cell axons in layer V. The largest pyramidal cells in layer III received the most synapses. Many larger pyramidal cells, identified as callosally projecting cells by the retrograde transport of horseradish peroxidase (HRP), were shown in serial electron micrographs to possess large numbers of initial segment synapses, comparable to those seen in the immunocytochemical material. Serial reconstructions of pyramidal cell axons from axon hillock to the first myelin internode in resectioned Golgi, immunocytochemical and HRP material showed that the number of synapses varied from 2 to 52 for layers II and III and from 2 to 26 for layer V. The number of synapses on the axon hillocks varied from zero to 12. The variability in these terminations may be an important factor in the shaping of the functional properties of the pyramidal cells.

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PubMed1985

Vertical organization of gamma-aminobutyric acid-accumulating intrinsic neuronal systems in monkey cerebral cortex.

Light and electron microscopic methods were used to examine the neurons in the monkey cerebral cortex labeled autoradiographically following the uptake and transport of [3H]-gamma-aminobutyric acid (GABA). Nonpyramidal cell somata in the sensory-motor areas and primary visual area (area 17) were labeled close to the injection site and at distances of 1 to 1.5 mm beyond the injection site, indicating labeling by retrograde axoplasmic transport. This labeling occurred preferentially in the vertical dimension of the cortex. Prior injections of colchicine, an inhibitor of axoplasmic transport, abolished all labeling of somata except those within the injection site. In each area, injections of superficial layers (I to III) produced labeling of clusters of cell somata in layer V, and injections of the deep layers (V and VI) produced labeling of clusters of cell somata in layers II and III. In area 17, injections of the superficial layers produced dense retrograde cell labeling in three bands: in layers IVC, VA, and VI. Vertically oriented chains of silver grains linked the injection sites with the resulting labeled cell clusters. In all areas, the labeling of cells in the horizontal dimension, i.e., on each side of an injection, was insignificant. Electron microscopic examination of labeled neurons confirms that the neurons labeled at a distance from an injection site are nonpyramidal neurons, many with somata so small that they would be mistaken for neuroglial cells light microscopically. They receive few axosomatic synapses, most of which have symmetric membrane thickenings. The vertical chains of silver grains overlie neuronal processes identifiable as both dendrites and myelinated axons, but unmyelinated axons may also be included. The clusters of [3H]GABA-labeled cells are joined to one another and to adjacent unlabeled cells by many junctional complexes, including puncta adherentia and multi-lamellar cisternal complexes. We conclude that groups of GABA-transporting neurons are likely to use GABA as a transmitter and form an inhibitory, bidirectional system of connections that join together cells in superficial and deep layers of functional cortical columns; intrinsic, horizontal GABAergic connections are either far less significant in the organization of the cerebral cortex or are not labeled by this method.(ABSTRACT TRUNCATED AT 400 WORDS)

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PubMed1984

Neuropeptide-containing neurons of the cerebral cortex are also GABAergic.

Neurons in the cat and monkey cerebral cortex were stained immunocytochemically for glutamic acid decarboxylase (GluDCase; L-glutamate 1-carboxy-lyase, EC 4.1.1.15), somatostatin (SRIF), neuropeptide Y (NPY), and cholecystokinin octapeptide (CCK). In all areas of cortex examined (somatic sensory, motor, parietal and visual areas), neurons displaying immunoreactivity for each of these molecules were nonpyramidal cells. Co-localization of GluDCase immunoreactivity with peptide immunoreactivity in the same cells was demonstrated by (i) the antibody elution method, staining the same cells by immunofluorescence, first for a peptide and then for GluDCase; (ii) double staining of the same sections with sheep anti-GluDCase and rabbit anti-peptide antisera, the bound antibodies being localized by rhodamine-conjugated donkey anti-sheep and fluorescein-conjugated swine anti-rabbit secondary antisera. With both procedures, cell bodies immunoreactive for GluDCase and for each of the peptides were found in all areas of cortex examined. With double labeling on single sections, it was found that all CCK-, SRIF-, and NPY-immunoreactive cells in cat cortex and 90%-95% in monkey cortex are also GluDCase positive. Many more cells, however, are immunoreactive for GluDCase alone. GluDCase was co-localized with CCK, SRIF, or NPY not only in cell somata, but also in small punctate structures, which are likely to be axon terminals. From the data gained in previous electron microscopic studies, we postulate that neurons displaying GluDCase- and CCK-like immunoreactivity are a class separate from those displaying GluDCase- and SRIF-like immunoreactivity. NPY, however, is co-localized with SRIF immunoreactivity. These results imply that classes of cortical interneuron contain a conventional neurotransmitter (gamma-aminobutyric acid) and a neuromodulator (one of the peptides).

Animals↗
PubMed1982

A type of basket cell in superficial layers of the cat visual cortex. A Golgi-electron microscope study.

The axonal arborizations of the basket cells in the cerebral neocortex have long been considered as the source of the presynaptic terminals contacting the cell bodies of pyramidal cells. Given that the concept of the cortical basket cell is based upon indirect evidence only, it was deemed worthwhile to re-investigate this problem using the Golgi-EM technique. This approach permits one to trace the presynaptic terminals back to their parent cell body, so that it allows for a positive identification of basket cells, i.e. cells which produce axosomatic synapses by preference. A type of interneuron in layer II-III of the cat visual cortex is described. Its axon treminals form multiple synaptic contacts, of the symmetrical type, on cell bodies and proximal dendrites of pyramidal and non-pyramidal cells. On the basis of this efferent synaptic pattern, this interneuron is considered to be a basket cell. The possible correspondence of this interneuronal type with other putative basket cells described in previous Golgi studies is discussed. In addition, a simple re-section method for semithin sections is described, which has been used to identify individual Golgi-impregnated axonal boutons in electron microscopy.

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PubMedDate not supplied

Synaptic relationships of serotonin-immunoreactive terminal baskets on GABA neurons in the cat auditory cortex.

Correlative light and electron microscopic immunocytochemical methods were used to analyze the 5-HT innervation of the primary auditory area (AI) of the cat cerebral cortex and to examine the synaptic relationships of 5-HT basket terminations on target neurons in that area. Three morphological types of 5-HT-immunoreactive fibers are present: type I, which is very thin and very finely beaded; type II, which is thin and coarsely beaded; and type III, which has a relatively thick main shaft and very few beads. Type I is the most abundant, type II is relatively less common, and type III is the least abundant type. The 3 types of fibers are present through the thickness of AI and in the subjacent white matter, but the densest plexus is found in layers I-III. One of the most characteristic features of type II fibers is that they commonly form small, dense clusters that resemble baskets apposed to the somata and primary dendrites of unstained neurons. The basket formations are more frequently found in layers I and II, and they vary in complexity. Simultaneous immunostaining for GABA and 5-HT reveals that many 5-HT baskets surround the somata and dendrites of GABA neurons. In 2-microns-thick plastic sections, each basket formation can be seen surrounding 1 or a group of 2 or 3 cells. In the latter case, one cell is much larger and at the electron microscope level is identified as a neuron, while the other cells are neuroglial cells. Reconstructions were made from serial electron micrographs of 135 5-HT-immunoreactive boutons. Of these boutons, 110 belonged to basket formations, 14 to type I axons located in the neuropil, and the remaining 11 to type II fibers located in the white matter. Only 4 of the 135 boutons made conventional synaptic contacts. These were of the asymmetrical type. Most of the boutons made very small, indistinct membrane specializations or none at all. The present results therefore suggest a strong interaction between 5-HT axon terminals and specific GABA neurons, which may be mediated by release sites that are not associated with morphologically distinct synaptic contacts.

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PubMedDate not supplied

Selective changes in the microorganization of the human epileptogenic neocortex revealed by parvalbumin immunoreactivity.

The microanatomy of the human lateral temporal cortex removed from patients with intractable temporal lobe epilepsy was studied using correlative light and electron microscopic immunocytochemical methods for the localization of the calcium-binding protein parvalbumin (PV). PV immunostaining was mainly used to label a subpopulation of powerful cortical inhibitory interneurons that have been shown to be lost at epileptic foci in certain animal models of epilepsy. In the human neocortex with normal appearance, we identified the same local neuronal circuitry as in the normal monkey cortex, but in some regions of the same cortex, a fine disorganization of neuronal circuits (loss of inhibitory neurons and presumptive thalamocortical terminals) was found. This abnormal circuitry may interfere with normal cerebral activity in epileptic patients. These results also indicate that PV immunoreactivity can be a useful tool to study normal and abnormal synaptic circuits in the human cerebral cortex.

Adolescent↗
PubMedDate not supplied

Neocortical neuronal diversity: chemical heterogeneity revealed by colocalization studies of classic neurotransmitters, neuropeptides, calcium-binding proteins, and cell surface molecules.

The use of immunocytochemical and histochemical methods to study colocalization of two or more chemical compounds in the same neuron has revealed that there is a great diversity of neocortical neurons. Neurons double stained for two or more substances are found in all layers, except in layer I, in all cortical areas and species studied so far, but there seem to be differences in the proportions and numbers of neurons double stained for a particular combination of substances between different species, and between cortical layers and cortical areas of the same species. With few (though important) exceptions, the majority of classic neurotransmitters, neuropeptides, calcium-binding proteins, and cell surface molecules currently known to be present in the neocortex are localized mainly, if not exclusively, in smooth nonpyramidal cells. Therefore, chemical diversity of neurons in the neocortex is mainly a feature of the population of nonpyramidal cells. It seems clear that no combinations of double staining are found exclusively in a single morphological type of nonpyramidal neuron. However, in some species, certain combinations are found selectively in particular groups of smooth nonpyramidial neurons. Conversely, the same morphological type of neuron can display a variety of chemical characteristics depending on the species and cortical area and layer in which it is located. These studies have so far proved useful to characterize and identify cortical neuronal subpopulations and cortical circuits anatomically, but they probably have functional significance as well.

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PubMedDate not supplied

Nitric oxide-producing neurons in the neocortex: morphological and functional relationship with intraparenchymal microvasculature.

Nitric oxide is a ubiquitous intercellular messenger involved in particular functions in the cardiovascular, immunological and nervous systems. In the cerebral cortex, nitric oxide is synthetized by endothelial cells and by a discrete population of neurons and glial cells expressing nitric oxide synthase. Nitric oxide of endothelial and neuronal origin is involved in the regulation of cerebral blood flow. In this review, we have tried to combine morphological data providing information on the chemical nature of nitric oxide synthase-containing neurons and their arrangement, especially in relation to intracortical blood vessels, with functional results suggesting the participation of these neurons in the coupling between local cortical blood flow and synaptic activity.

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PubMedDate not supplied

Estimation of the number of synapses in the cerebral cortex: methodological considerations.

In the present work we discuss several sampling procedures commonly used for counting synapses in the cerebral cortex. We compare, within the same tissue, two frequently used sterereological methods for determining the numerical density of synapses per unit volume, using as an example the estimation of the number of types of synapses by layers in the neuropil of the adult human temporal neocortex. These two methods are a size-frequency method (formula N(A)/d) and the disector method (sigmaQ-/a x h). Since the size-frequency method is assumption-based and the disector method is considered to be an unbiased method, the latter is often recommended for the quantification of synapses and other objects. We obtained, however, similar estimates for the numerical density of the different types of synapses using both methods, although they presented different technical difficulties and statistical properties. In addition, we show that the size-frequency method is more efficient and easier to apply than the disector method. Nevertheless, there are other methods for quantification which may also be valid, depending on the aim of the research; but the data reported in many articles are often complicated, which makes it very difficult for the reader to follow all the steps of the calculation. If certain basic information were given, this would facilitate the interpretation and sharing of important information with other laboratories, regardless of the method used for quantification. Finally, based on our present results and previous literature, we propose a simple general protocol for estimating the numerical synaptic density by volume in the neuropil of the cerebral cortex.

Adult↗
PubMedDate not supplied

[Pharmacoresistant temporal-lobe epilepsy. Exploration with foramen ovale electrodes and surgical outcomes].

AIM: To report our experience in the surgical treatment of temporal-lobe epilepsy. PATIENTS AND METHODS: An analysis was performed of the outcomes of 137 patients submitted to surgery between 1990 and 2001, with a follow-up of more than two years. A study was conducted of the percentages of successful detection by the different complementary tests--MRI, EEG, interictal SPECT, video-EEG with foramen ovale electrodes (FOE), neuropsychological study (NPS)--and the precision with which they reported the epileptogenic focus. RESULTS AND CONCLUSIONS: Successful surgical outcomes (Engel grades I-II): 73.4%. No surgical mortality occurred, although some mild, reversible morbidity was observed. Surgical outcomes were not affected by sex, age, age of onset and the length of time the patient had had the disease, or the frequency of the seizures. No association was found between seizures in the immediate post-operative period and a poorer long term control of the epilepsy. MR images were normal in 25% of patients; in these cases the surgical outcomes (Engel grades I-II at two years: 62%) were significantly poorer than in cases of tumours/cavernomas (86%); RMI studies of other types of lesions gave intermediate results (72%). With respect to the capacity of the different tests to lateralise/locate the epileptogenic focus, video-EEG-FOE proved to be the best, followed by MRI, SPECT, EEG and NPS.

Adolescent↗