Biomedical subjects

J C Dávila

Publications and source records attributed to J C Dávila.

At least 19 recordsLinked to original sources

PubMed2000

Expression of calcium-binding proteins in the diencephalon of the lizard Psammodromus algirus.

This work is a study of the distribution pattern of calbindin-D28k, calretinin, and parvalbumin in the diencephalic alar plate of a reptile, the lizard Psammodromus algirus, by using the prosomeric model (Puelles [1995] Brain Behav Evol 46:319-337), which divides the alar plate of the diencephalon into the caudorostrally arranged pretectum (p1), dorsal thalamus plus epithalamus (p2), and ventral thalamus (p3). Calbindin and calretinin are more extensively expressed in the dorsal thalamus than in the neighboring alar regions, and therefore these calcium-binding proteins are particularly suitable markers for delimiting the dorsal thalamus/epithalamus complex from the ventral thalamus and the pretectum. Conversely, parvalbumin is more intensely expressed in the pretectum and ventral thalamus than in the dorsal thalamus/epithalamus complex. Within the dorsal thalamus, calcium-binding protein immunoreactivity reveals a three-tiered division. The pretectum displays the most intense expression of parvalbumin within the diencephalon. Virtually all nuclei in the three sectors of the pretectum (commissural, juxtacommissural, and precommissural) present strong to moderate expression of parvalbumin. We compare the distribution of calcium-binding proteins in the diencephalon of Psammodromus with other vertebrates, with mammals in particular, and suggest that the middle and ventral tiers of the reptilian dorsal thalamus may be comparable to nonspecific or plurimodal posterior/intralaminar thalamic nuclei in mammals, on the basis of the calcium-binding protein expression patterns, as well as the hodological and embryological data in the literature.

Animals↗

PubMed2000

Light and electron microscopic evidence for projections from the thalamic nucleus rotundus to targets in the basal ganglia, the dorsal ventricular ridge, and the amygdaloid complex in a lizard.

To elucidate the organization and evolution of the tectorotundotelencephalic pathways in birds and reptiles, we reinvestigated at both light and electron microscopic levels the efferent projections of nucleus rotundus in a lizard, using the sensitive tracer biotinylated dextran amine. Our results indicate that nucleus rotundus projects to targets in the basal ganglia (lateral parts of striatum and olfactory tubercle and possibly the globus pallidus), the anterior dorsal ventricular ridge (ADVR), and the amygdaloid complex (the central and possibly lateral amygdaloid nuclei). In these targets, the rotundal axon terminals establish asymmetric, presumably excitatory synaptic contacts, usually with dendrites of local cells. In the ADVR, the rotundal projection terminates in two separate radial regions showing distinct cytoarchitecture: 1) a dorsolateral region that extends radially from the dorsolateral ADVR ventricular surface to the ventral part of the lateral cortex and 2) the lateral part of a ventromedial region that extends radially from the dorsomedial and medial ADVR ventricle to a superficial area interposed between the dorsolateral ADVR and the striatum. These two ADVR regions have different connections with the thalamus and telencephalon, which suggests that they may be involved in different degrees of integration. Our study also suggests that the rotundal projection to the ventromedial ADVR field of lizards may be comparable to the rotundoectostriatal/periectostriatal projection of birds. The connections and pathways involving nucleus rotundus suggest that this nucleus conveys visual information which may play a role in visuomotor, emotional, and visceral functions.

Amygdala↗

PubMed1999

Nucleus accumbens in the lizard Psammodromus algirus: chemoarchitecture and cortical afferent connections.

To better understand the organization and evolution of the basal ganglia of vertebrates, in the present study we have analyzed the chemoarchitecture and the cortical input to the nucleus accumbens in the lacertid lizard Psammodromus algirus. The nucleus accumbens contains many gamma-aminobutyric acid (GABA)-positive neurons and calbindin-positive neurons, the majority of which may be spiny projection neurons, and a few dispersed neuropeptide Y-positive neurons that likely represent aspiny interneurons. The nucleus accumbens contains two chemoarchitectonically different fields: a rostromedial field that stains heavily for substance P, dopamine, GABA(A) receptor, and a caudolateral field that stains only lightly to moderately for them, appearing more similar to the adjacent striatum. Injections of biotinylated dextran amine were placed in either the medial, dorsomedial, or dorsal cortices of Psammodromus. The medial and the dorsal cortices project heavily to the rostromedial field of the accumbens, whereas they project lightly to moderately to the caudolateral field. Cortical terminals make asymmetric, presumably excitatory, synaptic contacts with distal dendrites and the head of spines. Our results indicate that the hippocampal-like projection to the nucleus accumbens is similar between mammals and reptiles in that cortical terminals make mainly excitatory synapses on spiny, putatively projection neurons. However, our results and results from previous investigations indicate that important differences exist between the nucleus accumbens of mammals and reptiles regarding local modulatory interactions between cortical, dopaminergic, and cholinergic elements, which suggest that the reptilian nucleus accumbens may be as a whole comparable to the shell of the mammalian nucleus accumbens.

Afferent Pathways↗

PubMed1999

Calcium-binding proteins in the dorsal ventricular ridge of the lizard Psammodromus algirus.

The aim of the present work was to study further the intrinsic organization of the dorsal ventricular ridge of lizards. For that purpose, the morphology and distribution of cells and fibers containing the calcium-binding proteins calbindin-D28k, parvalbumin, and calretinin were investigated by using immunohistochemical methods. Colocalization of calcium-binding proteins with the neurotransmitter gamma-aminobutyric acid (GABA) was also studied because they are shown to coexist in many areas of the telencephalon where they define distinct subpopulations of GABAergic local circuit neurons. Neurons containing calcium-binding proteins are limited to the anterior part of the dorsal ventricular ridge (ADVR), whereas the posterior or caudal portion of the ridge is devoid of immunoreactive cells. This result gives further evidence for defining both regions of the dorsal ventricular ridge. Calcium-binding proteins mark three distinct populations of neurons within the ADVR. Two of them, parvalbumin- and calretinin-expressing cells, are GABAergic. On the other hand, calbindin-containing neurons do not express GABA, and the possibility is discussed that these cells are projection neurons. The distribution and overall density of fibers immunoreactive to calcium-binding proteins suggests that most fibers are of extrinsic origin, the thalamic nuclei projecting to the ADVR and the lateral amygdala being good candidates for their origin. The comparison of data on the populations of calcium-binding protein-containing neurons in the reptilian ADVR with those of mammals illustrate the difficulty in finding a mammalian homologue for this controversial region of the reptilian telencephalon.

Animals↗

PubMed1999

Calbindin-D28k in cortical regions of the lizard Psammodromus algirus.

The morphology, distribution, and ultrastructural features of calbindin-D28k-immunoreactive neurons and fibers in the cortical regions of the lizard Psammodromus algirus, considered homologues to the mammalian hippocampal formation, were analyzed by using the peroxidase anti-peroxidase technique at the light and electron microscopic level. On the basis of staining properties and localization, two distinct populations of calbindin-D28k-immunoreactive neurons were observed in both the medial and dorsal cortices. Those located in the cell layer, namely principal neurons, were weakly immunostained, whereas a number of Golgi-like stained neurons were observed in plexiform layers. Double immunocytochemistry showed that all calbindin immunoreactive neurons in the deep plexiform layers were also gamma-aminobutyric acid immunoreactive. We consider them as a population of nonprincipal neurons different from those containing the calcium-binding proteins parvalbumin and calretinin. Two types of immunoreactive Boutons were revealed by electron microscopy on the basis of the synaptic specialization: Boutons making asymmetrical synapses were generally smaller in size and contacted on small dendritic profiles or cell bodies, whereas larger boutons established symmetrical synapses mainly on dendritic shafts. We propose that the first type of boutons arises from principal neurons and that the second type arises from nonprincipal ones. Finally, the staining pattern, localization, and the circuit in which nonprincipal calbindin-immunoreactive neurons and other neurochemically defined neurons could be involved in cortical regions of Psammodromus are compared with those of mammalian hippocampus.

Animals↗

PubMed1999

GABAergic cell types in the lizard hippocampus.

The neurochemical classification of GABAergic cells in the lizard hippocampus resulted in a further division into four major, non-overlapping subtypes. Each GABAergic cell subtype displays specific targets on the principal hippocampal neurons. The synaptic targets of the GABA/neuropeptide subtype are the distal apical dendrites of principal neurons. Calretinin- and parvalbumin-containing GABAergic cells synapse on the cell body and proximal dendrites of principal cells. Calbindin is expressed in a distinct group of interneurons, the synapses of which are directed to the dendrites of principal neurons. Finally, another subtype displays NADPH-diaphorase activity, but its synaptic target has not been established.

Animals↗

PubMed1998

The birth of intracardiac surgery: a semicentennial tribute (June 10, 1948-1998)

On June 10, 1948, Charles Philamore Bailey, of Philadelphia, auspiciously performed the first anatomically conceived and digitally guided operation inside the heart: the first successful intracardiac operation. The patient, Claire Ward, was a 24-year-old woman afflicted with severe mitral stenosis. Dwight E. Harken and Russell C. Brock performed their own mitral operations very soon after Bailey, using new variations of methods that had been discarded about two decades earlier; they soon adopted the logical anatomic approach. This threesome, with the added contributions of Robert P. Glover--Bailey's partner at the time, in the role of respected and convincing teacher--opened the floodgates upon a decade of so-called closed heart surgery. These accomplishments, added to the earlier successes with the patent ductus, aortic coarctation, and "blue babies," justified and strengthened the demand for precise diagnosis in cardiology--at that time a languishing specialty--and brought to the fore the indisputable requirement to operate inside the heart with maximal control. This essay calls attention to the semicentennial of that seminal event and reviews the origins of surgery for mitral stenosis.

Cardiac Surgical Procedures↗

PubMed1998

Cholecystokinin innervation of the cerebral cortex in a reptile, the lizard, Psammodromus algirus.

We used light and electron microscopic and immunohistochemical methods to map the distribution of cholecystokinin (CCK) in the cerebral cortex of a lizard, Psammodromus algirus. At light microscopy, the CCK immunoreactivity was limited to fibers and terminals densely innervating all cortical regions except for the lateral (pyriform) cortex which was very slightly immunostained. The CCK-positive terminals were almost restricted to the cell layers in every cortical region where they surrounded immunonegative cell bodies and proximal dendrites of neurons within the layer. No CCK-containing neurons were observed within the cerebral cortex. At the electron microscopic level, most positive structures were presynaptic boutons contacting cell bodies and proximal dendrites. All contacts appeared to form symmetric junctions, both the distribution and type of synaptic contacts of CCK fibers in the cerebral cortex of Psammodromus are very similar to the corresponding features in the hippocampus of mammals, although in this lizard the CCK cortical innervation, unlike that in mammals, is probably of extrinsic origin. Double HRP-retrograde labeling and CCK immunohistochemistry show that part of the CCK in the cerebral cortex of Psammodromus arises from the hypothalamic supramammillary nuclei.

Animals↗

PubMed1997

Calretinin immunoreactivity in the cerebral cortex of the lizard Psammodromus algirus: a light and electron microscopic study.

The present study describes the distribution and structural features of calretinin-immunoreactive neurons and fiber plexuses in the cerebral cortex of a lacertid lizard, at the light and electron microscopic levels, and also examines the colocalization of calretinin with parvalbumin and gamma-aminobutyric acid (GABA) in certain cortical regions. Calretinin-immunoreactive neurons are present throughout the cerebral cortex of Psammodromus and can be classified according to morphological and neurochemical criteria. Neurons in the medial cortex are small, spine-free and lack parvalbumin, whereas in the lateral cortex, calretinin-immunoreactive neurons display sparsely spiny dendrites and also lack parvalbumin. The dorsomedial and dorsal cortices contain most of the calretinin cortical neurons, which were located almost exclusively in the deep plexiform layer. These neurons are large, with an extensive spine-free dendritic tree. Most of the calretinin-immunoreactive neurons of dorsomedial and dorsal cortices are GABAergic and contain parvalbumin. Calretinin-immunoreactive fibers form two main afferent systems in the cortical areas. One probably intrinsic inhibitory system, arising from the calretinin and parvalbumin GABAergic neurons in the dorsomedial and dorsal cortices, makes symmetrical synapses on the soma and proximal dendrites of neurons located in the cell layers of the same cortical areas. The other system is formed by extremely thin axons running within the superficial plexiform layers of the medial, dorsomedial and dorsal cortices. These axons make asymmetrical synapses on dendrites or dendritic spines. We suggest that this system, probably extrinsic excitatory, arises from neurons located in the basal forebrain.

Animals↗

PubMed1996

Intrinsic connections in the anterior dorsal ventricular ridge of the lizard Psammodromus algirus.

We have studied the intrinsic connections of the anterior dorsal ventricular ridge (ADVR) in the lacertid lizard Psammodromus algirus by means of retrograde transport of horseradish peroxidase (HRP) and fluorescent labeling with the lipophilic carbocyanine dye DiI. We injected HRP into different regions in the ADVR arrayed in a medial-to-lateral sequence, with each consisting of three distinct superficial-to-deep zones. When HRP was injected into a given region, many labeled neurons (always located ipsilateral to the injection site) were found at all mediolateral regions of ADVR in locations rostrally distant from the injection site. DiI crystals were applied on different superficial-to-deep zones within each region. Two patterns could be recognized: DiI crystals applied on the periventricular (most superficial) zone resulted in a labeling of cells widely distributed throughout the ADVR independently of the mediolateral region of the application site, whereas DiI crystals applied on deeper zones resulted in a staining of cells mostly restricted to a narrow radial area. Results from both types of labeling confirm that the ADVR has a prominent radial component in its intrinsic organization, but they also demonstrate that some areas of the ADVR receive projections from distant, rostrally located neurons in every ipsilateral region of the ridge itself, which establishes a clear non-radial component. This organization may have important functional properties with regard to a putative integration of different sensory modalities conveyed by thalamic afferent fibers to the ADVR. Last, we analyzed some evolutionary implications of our results.

Animals↗

PubMed1996

Multivariate statistical analysis of Golgi stained neurons.

The multivariate statistical analysis provides a useful method to study neuronal populations. It allows both the objective classification of neuronal types and the study of the morphological variation within a neuronal population. We report a particular example of the use of these techniques on a Golgi study of a complex telencephalic structure, the reptilian anterior dorsal ventricular ridge (aDVR). We present a R-mode factor analysis and a cluster analysis on the results of the factor analysis. Sixteen original variables were chosen for the study in order to obtain the greatest information about the cell body, the dendritic field and the location of 96 Golgi-stained cells. Six factors were obtained after the R-mode factor analysis, the interpretation of which was clear in five of them. This contributed to explain the morphological variation of the neuronal types within the aDVR. The cluster analysis classified the 96 cells into eight groups. Some groups could be ascribed to specific regions of the aDVR.

Animals↗

PubMed1995

NADPH diaphorase-positive neurons in the lizard hippocampus: a distinct subpopulation of GABAergic interneurons.

We analyzed the distribution and light-microscopic features of the NADPH diaphorase-containing structures in the lizard hippocampus, likely to correspond to nitric oxide synthase-containing cells and fibers, and thus likely to release nitric oxide. We also studied co-localization of NADPH diaphorase with the neurotransmitter GABA, the calcium-binding protein parvalbumin, and the neuropeptide somatostatin, in order to examine whether putative nitric oxide-synthesizing neurons represent a different subpopulation of GABA cells, on which the authors recently reported in lizards. We also studied co-localization of NADPH diaphorase with parvalbumin or somatostatin in mice to ascertain whether the characteristics of this population in reptiles parallel the situation in mammals. Most of the positive NADPH diaphorase neurons were stained in a Golgi-like manner and were in the plexiform layers of the lizard hippocampus with morphologies ranging from bipolar to multipolar. Co-localization with GABA was 100%, and NADPH diaphorase-positive neurons in the lizard hippocampus did not contain parvalbumin or somatostatin. The results indicate that putative nitric oxide-synthesizing neurons represent a distinct subpopulation of GABA interneurons in the lizard hippocampus. Two different types of fibers were described in the plexiform layers: one type bearing thick varicosities, and the other thinner ones. We discuss the possibility that at least part of the positive fibers arise from a hypothalamic aminergic nucleus contacting the third ventricle, the periventricular hypothalamic organ. Most radial glia were stained almost completely and formed typical end-feet both at the pia and around capillaries. The results of this study confirm that the capacity for synthesizing nitric oxide is linked to a determined set of neuronal markers depending on the specific brain region, and they provide new resemblances between hippocampal regions in different classes of vertebrates.

Animals↗

PubMed1994

Immunocytochemical localization of the GABAA receptor in the cerebral cortex of the lizard Psammodromus algirus.

This study examined the distribution and localization of the gamma-aminobutyric acid (GABA)A receptor in the brain cortex of a reptile by light and electron microscopy, to test whether cortical GABA inhibition is mainly mediated through the GABAA receptor complex. We used preembedding immunocytochemistry and a monoclonal antibody, raised against the receptor complex, that recognizes the beta 2 and beta 3 subunits of the receptor. GABAA receptors were distributed throughout the entire cerebral cortex except the dorsomedial cortex. The immunostaining consisted of fine granules restricted to the plexiform layers of the cortex as seen by light microscopy. This granular aspect of the immunoreactivity most likely corresponds to the immunopositive dendritic and axonal profiles observed under the electron microscope. Some neurons in the medial and lateral cortices displayed patches of immunoreactivity along the cell body and processes, and as a result their morphology was outlined. We discuss the possibility that these neurons were GABAergic as well. The immunocytochemical data demonstrate that the distribution and localization of GABAA receptors in discrete regions of the reptilian cerebral cortex resemble that of parts of the hippocampal formation of humans and rats, suggesting that the basic configuration of the GABA system in these regions is conserved.

Animals↗

PubMed1994

Monoaminergic innervation patterns in the anterior dorsal ventricular ridge of a lacertid lizard, Psammodromus algirus.

In contrast to the view of a diffuse monoaminergic innervation of the telencephalon, studies on the monoaminergic innervation in certain mammalian isocortical regions have shown a high degree of regional and laminar specificity. The present study was designed to examine the distribution patterns of dopamine, noradrenaline and serotonin in a telencephalic structure, the anterior dorsal ventricular ridge, of the sand lizard Psammodromus algirus (Lacertidae) using specific antibodies against each monoamine. The anterior dorsal ventricular ridge receives an abundant monoaminergic innervation compared to that of cortical telencephalic regions. The distribution of the different monoamines presented zonal and regional patterns throughout the ridge. The cell cluster zone was profusely innervated by catecholamines, whereas no serotoninergic fibers innervated the cell bodies in the cluster zone. On the other hand, the periventricular zone was heavily innervated by serotonin, but catecholaminergic fibers were almost lacking. With regard to regional patterns, dopamine exhibited major differences in the mediolateral axis of the anterior dorsal ventricular ridge: dopaminergic innervation was densest in the lateral region, which in other reptiles is described as a target of visual thalamic projections. Whereas the zonal pattern of the monoaminergic innervation of the anterior dorsal ventricular ridge seems to be a constant feature in the reptiles studied to date, the regional pattern varies among reptilian groups, especially taking into account the density of monoaminergic innervation.

Animals↗

PubMed1993

Subpopulations of GABA neurons containing somatostatin, neuropeptide Y, and parvalbumin in the dorsomedial cortex of the lizard Psammodromus algirus.

Different subpopulations of GABA neurons containing the neuropeptides somatostatin and neuropeptide Y, and the calcium binding protein parvalbumin were studied by immunocytochemistry using light and electron microscopy in the dorsomedial cortex of the lizard Psammodromus algirus to investigate the connectivity of different subsets of GABA neurons in the lizard dorsomedial cortical circuitry and to compare cortical regions of reptiles and mammals. GABA neurons were classified into different subsets by using the peroxidase anti-peroxidase immunohistochemical method on adjacent Araldite-embedded semithin sections. GABA neurons in the dorsomedial cortex fall into three major subsets: 1) neurons with somatostatin (and neuropeptide Y), which accounted for about 44% of the GABA population; 2) neurons with parvalbumin, which accounted for about 13% of the GABA neurons; and 3) neurons without parvalbumin or neuropeptides, which represented 40% of all GABA cells. This division of GABA neurons in non-overlapping subpopulations of neuropeptide- and parvalbumin-containing cells is similar to that found in the mammalian hippocampal formation. On the basis of the nerve terminal fields, somatostatin- and parvalbumin-immunoreactive neuronal populations appear to be functionally different, acting on different portions of the projection neurons. Parvalbumin-immunoreactive neurons inhibit the pyramidal neurons at the cell body level, whereas somatostatin-immunoreactive neurons inhibit them on distal dendrites. The results of the present study add more similarities between the lizard dorsomedial cortex and parts of the mammalian hippocampus.

Animals↗

PubMed1991

Distribution of neuropeptide Y (NPY) in the cerebral cortex of the lizards Psammodromus algirus and podarcis hispanica: co-localization of NPY, somatostatin, and GABA.

The aim of the present study was to analyze the distribution and characteristics of NPY immunoreactive structures in the cerebral cortex of lizards and to investigate the degree of co-existence of this neuropeptide with somatostatin and GABA. The immunoperoxidase method was applied to vibratome sections as well as to semithin sections. NPY neurons are multipolar or fusiform and were unevenly distributed throughout the brain cortex. Within the medial, dorsomedial and dorsal cortices, most NPY perikarya were located in the plexiform layers, especially in the deep one. This suggests that these cells could be regarded as interneurons. In the lateral cortex, NPY neurons were found throughout all layers. The dorsomedial cortex displayed the highest NPY cell density. Here, neuronal perikarya projected many immunoreactive processes toward two distinct zones: the deep plexiform layer of the medial cortex and the superpositio medialis. The NPY neurons of the dorsomedial cortex differed from the other NPY cortical immunoreactive cells in that the latter displayed very few immunoreactive processes. A high degree of co-existence among NPY, somatostatin, and GABA (approx. 80%) was found. This co-existence rate is very similar to that reported in mammals and suggests that co-localization is a phylogenetically ancient phenomenon.

Animals↗

PubMed1989

Serotonin innervation of the cerebral cortex in lizards.

The serotonin (5-HT) innervation of the cerebral cortex in two species of lizards has been studied. Results show no differences between both species. Most of the cerebral cortex of these lizards is innervated by serotoninergic fibers, which are fine and varicose. Their density varies greatly from one cortical region to another: the areas with higher density of serotoninergic fibers and terminals are parts of the medial and dorsal cortices. There is a laminar pattern of distribution of serotoninergic fibers. In the medial cortex, 5-HT fibers are found preferentially in both plexiform layers just above and below the cellular layer. In the dorsomedial cortex, there is an immunoreactive plexus in the outermost third of the superficial plexiform layer and another in the depth of the layer, whereas 5-HT fibers are distributed evenly in the deep plexiform layer of this cortex. In the pars medialis of the dorsal cortex, serotoninergic fibers are abundant in all layers, whereas in the pars lateralis, fibers are found predominantly in the external third of the superficial plexiform layer. The lateral cortex is almost devoid of immunoreactive fibers. These results show a different organization of the cortical serotonin innervation between lizards and turtles.

Animals↗

PubMed1988

Immunocytochemical localization of somatostatin in the cerebral cortex of lizards.

The distribution of somatostatin-like immunoreactivity in the cerebral cortex of two lizards has been studied. Results are similar in both species. Somatostatin-positive neurons show variable morphology; they are bipolar, multipolar or pyramidal cells. Their distribution within the cerebral cortex is not homogeneous: they tend to be found in the innermost cortical layer, the deep plexiform layer, where they constitute a constant population in the region of the dorsomedial cortex. All immunoreactive processes observed in the cerebral cortex belong to somatostatin cortical neurons since no immunoreactive fiber is found to reach or leave the telencephalic cortex. Most of the dendrites are smooth or sparsely spinous. Axons are abundant in the deep plexiform layer; in the dorsomedial cortex a prominent terminal field appears in the outermost region of the superficial plexiform layer, which may arise from the neuronal somatostatin immunoreactive population found deeper in the same cortex.

Animals↗