Biomedical subjects

R Anadón

Publications and source records attributed to R Anadón.

At least 55 records · Page 3Linked to original sources

PubMed1995

The nitric oxide synthase (NOS)-like immunoreactive extrahypophysial projections of the neurosecretory preoptic nucleus of the electric ray (elasmobranchs) suggest a neuroregulatory role for this nucleus.

The extrahypohysial projections of the neurosecretory preoptic nucleus (PON) of the electric ray were studied with the aid of an antibody against nitric oxide synthase (NOS). PON neurons were the only NOS-like-immunoreactive (NOS-ir) cells in the brain. These neurons gave rise to both hypophysial and extrahypophysial NOS-ir projections. Some fibres coursed from the PON to the neurointermediate lobe in the preoptic-hypophysial tract. Other NOS-ir fibres coursed either rostrally or caudally forming terminal fields in the telencephalon (subpallial region), diencephalon (preoptic nucleus, ventrolateral thalamus and posterior recess nucleus), tuberal region (area tegmentalis ventralis and substantia nigra), mesencephalon (lateral tegmentum), rhombencephalon (isthmal nucleus, vagal viscerosensory column and ventrolateral reticular area) and the spinal cord (intermediate horn). The possible involvement of the extrahypophysial PON projections in neuroregulation of visceral centres is discussed.

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PubMed1995

Neurons of the olfactory organ projecting to the caudal telencephalon and hypothalamus: a carbocyanine-dye labelling study in the brown trout (Teleostei).

The caudal extrabulbar projections and their neurons of origin in the trout were studied after carbocyanine-dye (DiI) labelling in either the olfactory organ or the caudal telencephalon. DiI application to the caudal telencephalon labelled bipolar neurons in the olfactory epithelium, where they were sparsely distributed throughout the olfactory lamellae. Labelled fibres ran scattered in the olfactory nerve without forming bundles. DiI application to the olfactory organ labelled extrabulbar projections to the ventral telencephalon, preoptic region and tuberal hypothalamus. These results confirm that primary sensory fibres running in the medial olfactory tract of trout have an olfactory origin.

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PubMed1995

Marginal cells in the spinal cord of four elasmobranchs (Torpedo marmorata, T. torpedo, Raja undulata and Scyliorhinus canicula): evidence for homology with lamprey intraspinal stretch receptor neurons.

This study reports for the first time the presence of marginal cells, probably with stretch receptor function, in the spinal cord of four elasmobranch species, two electric rays, Torpedo marmorata and T. torpedo, the skate Raja undulata and the dogfish Scyliorhinus canicula. In all four species, the marginal cells were located close to the lateroventral surface of the cord and possessed thick dendrites which formed part of characteristic glomerular structures. In vitro retrograde labelling of the spinal cord of the dogfish with horseradish peroxidase (HRP) showed that some of these cells have contralateral projections. Ultrastructural study of normal and retrograde HRP-labelled material showed that the glomerular dendrites of marginal cells give rise to numerous fingerlike structures and are associated with a rich plexus of nerve terminals. Characteristically, these dendrites contain numerous mitochondria. Immunocytochemical studies revealed a rich plexus of somatostatin- and GABA-immunoreactive fibres in the glomeruli. These results strongly suggest that the marginal cells of the elasmobranch spinal cord are stretch receptors homologous to lamprey edge cells and to the marginal nucleus cells of the spinal cord of urodeles and snakes. We discuss the possible role of these cells in the modulation of swimming movements.

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PubMed1995

GABAergic neuronal circuits in the cerebellum of the dogfish Scyliorhinus canicula (Elasmobranchs): an immunocytochemical study.

The presence of GABAergic cells and fibres in the corpus cerebelli and auricles of a dogfish, Scyliorhinus canicula, was studied with immunocytochemistry. In both locations, two types of GABA-immunoreactive (GABA-ir) neurons were observed: stellate cells in the molecular layer and Golgi cells in the granular layer. Stellate cell axons gave rise to numerous GABA-ir boutons distributed throughout the molecular layer and a smaller number of boutons which contacted Purkinje cell perikarya. No GABA-ir baskets around Purkinje cells were observed. Golgi cells of the granular layer gave rise to numerous GABA-ir boutons which were located around cerebellar glomeruli. Purkinje cell perikarya and their axon terminals in the cerebellar nucleus were not GABA-immunoreactive. These findings are discussed in terms of the phylogeny of cerebellar circuits.

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PubMed1995

The thymosin beta 4 gene is strongly activated in neural tissues during early postimplantation mouse development.

We studied the temporal and spatial distribution of the mRNA encoding for thymosin beta 4 (T beta 4), a small acidic actin-sequestering peptide, during the early postimplantation mouse development. Analysis of total embryo RNA demonstrated a strong activation of T beta 4 gene after gastrulation and coincident with neurulation. In situ hybridization showed that T beta 4 mRNA was strongly expressed in the central nervous system and peripheral ganglia, paralleling the gradient of neuronal differentiation. An intense signal was also observed in intraventricular macrophages and blood vessels. The role of T beta 4 in mammalian neuroembryogenesis is discussed.

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PubMed1995

Ontogeny of somatostatin-immunoreactive systems in the brain of the brown trout (Teleostei).

The development of somatostatin-immunoreactive neurons and fibres was studied, using immunocytochemistry, in the brain of the brown trout. Somatostatinergic perikarya were found in many regions including several telencephalic areas, the preoptic nucleus, anterior tuberal and lateral tuberal nuclei, the lateral recess nucleus, dorsal tuberal nucleus, the pre- and pseudoglomerular nuclei, central thalamic nucleus, optic tectum, interpeduncular nucleus, several isthmal and reticular nuclei and the solitary fascicle nucleus. The ventrolateral area of the telencephalon and the nucleus lateralis tuberis are the first immunoreactive nuclei to appear in ontogeny, and cells of some telencephalic areas and of the lateral optic recess nucleus, the latest. Somatostatin-immunoreactive fibre tracts innervate the hypophysis and different regions of the brain. The most richly innervated areas in adults are the dorsolateral telencephalic area and the organon vasculosum laminae terminalis. Two patterns of production of somatostatinergic cells were observed: that of populations in which cell numbers increase over the lifetime of the fish, and that of populations whose cell number is established early in development or even diminishes in adulthood. These results provide interesting contrasts to those previously reported in birds and mammals.

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PubMed1995

Early development and organization of the retinopetal system in the larval sea lamprey, Petromyzon marinus L. An HRP study.

Development of the retinopetal system of the larval sea lamprey, Petromyzon marinus, was investigated following labelling of this system by injection of horseradish peroxidase into the orbit. This study extends our previous report on larval stages and provides a detailed description of the development of this system. We present quantitative and qualitative evidence suggesting that the retinopetal nuclei of Schober's M2-M5 nucleus, the mesencephalic reticular area and the tectum arise sequentially in that order, that the three retinopetal nuclei originate from a common anlage in the ventricular zone of the mesencephalic tegmentum and that the retinopetal cell population increases throughout the larval period. No neuronal death was observed. We also describe and discuss the significance of a transitory phase of retinopetal cell differentiation characterized by the presence of ventricular dendrites. Finally, we compare the development of retinopetal and retinofungal systems.

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PubMed1994

Primary olfactory fibres project to the ventral telencephalon and preoptic region in trout (Salmo trutta): a developmental immunocytochemical study.

We studied the development of the primary olfactory system of a teleost, the brown trout, with the aims of clarifying whether the caudal projection pertains to the olfactory or to the terminal nerve system, of identifying the brain regions receiving this projection, and of investigating its possible functional significance. As olfactory markers (OMs) we used two polyclonal antibodies (to substance P and to alpha-melanocyte-stimulating hormone) that were found to label the olfactory projection strongly after preadsortion of the antibody with the corresponding antigen (OMs), and as a terminal nerve marker we used an antiserum to FMRF-amide peptide. OM labelling was observed in both perikarya and axons of olfactory neurons. In adults, olfactory neurons projected not only to olfactory glomeruli in the olfactory bulb but also, as has been reported previously, to more caudal targets in the forebrain through the medial olfactory tract. Our results show that these targets include the ventral and commissural nuclei of the area ventralis telencephali, the periventricular preoptic region, and the organum vasculosum laminae terminalis. Glomeruli were not observed before hatching, and the extrabulbar olfactory projections appear late in development. Extensive periventricular preoptic olfactory plexuses and olfactory innervation of the organum vasculosum laminae terminalis did not appear until adulthood. The cells of the ganglion nervus terminalis, which form ganglionic groups along the olfactory nerves, were not stained with these olfactory markers at any developmental stage studied, nor was the medial olfactory tract FMRP-amide peptide immunoreactive. Our results thus confirm the existence of primary olfactory projections to extrabulbar targets in trout. The target regions identified in this study are implicated in sexual behaviour: We discuss the related possibility that, in teleosts, these extrabulbar olfactory projections (rather than projections of the terminal nerve, as is widely held) are the primary mediators of neuroendocrine response to pheromones.

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PubMed1994

Are the dopaminergic cells of the lamprey retina interplexiform cells? A dopamine, tyrosine hydroxylase and dopamine beta-hydroxylase immunocytochemical study.

The distribution of dopaminergic cells in the retina of sea lamprey Petromyzon marinus L. was studied with antisera against dopamine and tyrosine hydroxylase. Both antisera consistently labelled cells and processes located in the inner nuclear and inner plexiform layers. No dopamine-immunoreactive processes were observed in the external retina. The ellipsoids of photoreceptors and small bodies close to the external limiting membrane were also labelled with the tyrosine hydroxylase antiserum. It is concluded that the dopaminergic cells of the lamprey retina are amacrine cells. In addition, the presence of dopamine-beta-hydroxylase-like-immunoreactive fibres of central origin is reported for the first time.

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PubMed1994

The structure and development of dopaminergic interplexiform cells in the retina of the brown trout, Salmo trutta fario: a tyrosine hydroxylase immunocytochemical study.

The organisation and development of the dopaminergic (DA) system in the retina of the adult brown trout were studied with tyrosine hydroxylase immunocytochemical techniques. Adult DA cells are rather homogeneous in appearance and possess thick dendritic processes running to the ganglion cell layer and thinner axonal processes which run to the horizontal cell layer, where they form a rich plexus of varicose fibres closely associated with the surface of these cells. Contact of DA fibres with photoreceptor processes was not observed. We therefore consider this DA population to consist mainly of interplexiform cells. These cells appear late in development, being first observed in prehatching (16 mm) embryos (after photoreceptors have begun to differentiate). DA cells increased in number throughout the fry and juvenile stages, but even in the largest juveniles studied (30-35 mm) the size of the DA cell population was only about 20% of that in adults. DA cells appear to arise in the marginal retina. In developing stages (embryos and fry) only inner nuclear layer processes were observed, the horizontal cell layer DA plexus appearing late in development (28 mm juveniles).

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PubMed1993

Neural projections of the pineal organ in the larval sea lamprey (Petromyzon marinus L.) revealed by indocarbocyanine dye tracing.

The distribution of the central neural connections of the pineal organ of the larval sea lamprey was investigated by means of anterograde and retrograde tracing with the fluorescent lipophilic dye, DiI (1,1'-dioctadecyl 3,3,3',3'-tetramethylindocarbocyanine perchlorate). Pinealofugal projections are well developed in larvae, extending from the posterior commissure into the diencephalon and mesencephalon. Small numbers of neurons were retrogradely labelled in the transition zone between the diencephalon and the mesencephalic tegmentum. These cells may constitute the first pinealopetal system described in anamniotes.

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PubMed1993

Golgi study of the telencephalon of the small-spotted dogfish Scyliorhinus canicula L.

The telencephalon of the small-spotted dogfish, Scyliorhinus canicula L., was examined by Nissl and Golgi-aldehyde techniques. On the basis of differences in perikaryal and dendritic morphology and size, several cell types were distinguished in pallial and subpallial regions, most of them reported here for the first time in elasmobranchs. In the pallium, the pallium dorsalis is the richest in cell types (eight types of neurons), whereas the neuron population of the pallium medialis is the most homogeneous. Dendrites of most neuron types in the pallium are smooth or sparsely thorny. Interestingly, the pallium dorsalis and pallium lateralis contain a type of primitive pyramidal cell characterized by the dense appearance of its thorny dendrites. In the subpallium, the area superficialis basalis contains a heterogeneous population (six types of neurons): large radial cells are the most characteristic cell type. Dendrites of these cell types are smooth or sparsely thorny. The cell populations of the nucleus N are roughly similar to those of the area superficialis basalis, but they lack the large radial cells characteristic of this area. The area centralis subpallialis and striatum consist of populations of small neurons. The regio septalis contains a rather homogeneous population of small cells. The populations in the nucleus entopeduncularis and the nucleus interstitialis of the basal forebrain bundle are the least varied and consist of large radial cells and bipolar cells similar to those of the area superficialis basalis. This investigation reveals important differences in cytoarchitecture that should be useful in the interpretation of immunocytochemical, tracing, and electrophysiological studies of the telencephalon of elasmobranchs.

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PubMed1993

Prominent expression of the actin-sequestering peptide Fx gene in the hippocampal region of rat brain.

We have analyzed by in situ hybridization the distribution of Fx (an actin-sequestering peptide) mRNA in the brain of young and old rats. The strongest Fx mRNA-specific hybridization signal was located in the hippocampo-entorhinal cortex; this mRNA was also found in the piriform cortex, amygdala, lateral septum and neocortex. Northern blot analysis confirmed the prominent expression of the Fx transcript in the hippocampus and showed a notably lower amount of this mRNA in the hippocampus of old rats suggesting an influence of aging on the expression of this gene. The possible implication of Fx in synaptic plasticity and in long-term potentiation is discussed.

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PubMed1993

Distribution of types of neurons in the optic tectum of the small-spotted dogfish, Scyliorhinus canicula L. A Golgi study.

The distribution of neuronal types in the six layers of the optic tectum of the small-spotted dogfish, Scyliorhinus canicula, was studied using Golgi methods. The eight types of neurons have a variable distribution, some of them represented in all six tectal layers. Most neurons of the optic tectum have a radial orientation, and a small portion are disposed horizontally. The relative ratios of the different neuronal types in the six layers indicate that about 80% of the tectal neurons are intermingled with the optic nerve axon terminals in the superficial layers of the tectum. These results corroborate previous reports that the tectum of this selachian species is more specialized than formerly supposed, in spite of the differences in degree of neuropil lamination with other non-mammalian vertebrates.

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PubMed1993

Organization of catecholaminergic systems in the hypothalamus of two elasmobranch species, Raja undulata and Scyliorhinus canicula. A histofluorescence and immunohistochemical study.

We examined the organization of catecholaminergic neurons in the hypothalamus of the painted ray, Raja undulata, and the small-spotted dogfish, Scyliorhinus canicula, with the use of formaldehyde-induced fluorescence (FIF) methods and tyrosine hydroxylase (TH) immunohistochemistry. In both species we identified distinct populations of catecholamine-containing neurons differing in a) their immunoreactivity to antibodies against the enzyme tyrosine hydroxylase (TH), b) their fluorescence in response to FIF methods for the detection of catecholamines, and c) their relationship with the third ventricle. One population is made up of FIF-positive and TH-negative neurons (most of which are CSF [cerebrospinal fluid]-contacting) and located in two circumventricular organs, the preoptic recess organ and the organon vasculosum hypothalami. Another population comprises TH-immunoreactive (TH-IR), FIF negative neurons that are located in the suprachiasmatic nucleus and the posterior tuberculum and are not related to the third ventricle recesses. A third population of TH-IR, CSF-contacting neurons is also present in the organon vasculosum hypothalami. The existence of three catecholaminergic populations suggests differences in the metabolism of catecholamines and/or different functions. The circumventricular neurons are not associated with the hypophysis and appear to accumulate catecholamine (dopamine) obtained from exogenous sources. In both Raja and Scyliorhinus the neurointermediate lobe is innervated by TH-IR fibres originating from dopamine-synthesizing neurons of the second catecholaminergic population.

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PubMed1993

Fine structure and development of ionocyte areas in the labyrinth of the trout (Salmo trutta fario).

The distribution of ionocyte areas in the trout labyrinth (in the semicircular canal ampullae, crus communis and utricular vesicle) is very similar to that of areas of dark cells in mammals. In all 3 regions, ionocytes begin to develop after hatching, and are cuboid at fry stages and prismatic in juveniles and adults. On electron microscopy, 3 types of cell can be seen in adult ionocyte areas: ionocytes, associate cells and basal cells. Ionocytes possess many mitochondria, occupying approximately 28% of the cytoplasmic volume, and a well-developed tubulomembranous system which opens on the basal surface at some points. These ultrastructural features, very similar to those of chloride cells, strongly suggest that ionocytes are involved in ion transport. Unlike mammalian dark cells, there are no basal or lateral infoldings of the plasma membrane in trout ionocytes. Trout associate cells have a well developed vacuolar system, few mitochondria and bundles of cytoplasmic filaments. Although less specialised than ionocytes, they may be involved in endolymph secretion.

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PubMed1992

The origin of trochlear motoneurons in the larval sea lamprey, Petromyzon marinus L. An HRP study.

The origin of trochlear motoneurons in larval lampreys was studied by injection of HRP into the orbit. Immature motoneurons had ventricular attachments, the position of which with respect to the ventricular sulci was used to study their regions of origin. Motoneurons originate from the region between the sulcus intermedius dorsalis and the sulcus intermedius ventralis, which in other parts of the brain were identified as the visceromotor and viscerosensory columns. Both ipsilateral and contralateral immature motoneurons were found. The significance of these findings is discussed in relation to the origins of the trochlear nerve and its nucleus in vertebrates.

Aging↗

PubMed1992

Central projections of the vagus nerve in Chelon labrosus Risso (Teleostei, O. Perciformes).

The primary projections of the vagus nerve and its nuclei in a perciform teleost, Chelon labrosus, are described after application of hoseradish peroxidase (HRP) labeling and Nissl and silver staining methods. The vagus nerve has three peripheral roots, rostral, medial and caudal, which are formed from viscerosensory and visceromotor rootlets. In addition to viscerosensory and visceromotor rootlets, the caudal root has a cutaneous root and a 'descending' root. Dorsally in the caudal root, a fiber bundle enters the medulla from the retroocular and opercular skin region; this bundle joins the descending trigeminal root and courses with it rostrally and caudally. Fibers from another rootlet, which enters dorsolaterally, course caudally towards the spinal cord. This rootlet has not been described in other fishes. The vagal viscerosensory nucleus, where most of the viscerosensory fibers terminate, forms a column in which two types of neurons can be distinguished. The most caudal part of the nucleus is continuous with the commissural nucleus, into which vagal nerve projections also enter. No vagal projections were found in the area postrema. In the visceromotor column, two types of neurons are seen lateroventral to the IV ventricle.

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