Biomedical subjects

J A de Carlos

Publications and source records attributed to J A de Carlos.

7 recordsLinked to original sources

PubMed2000

Evidence for intrinsic development of olfactory structures in Pax-6 mutant mice.

It has been reported that the arrival of primary olfactory axons is required to induce the development of the olfactory bulb (OB). On the other hand, the Sey(Neu)/Sey(Neu) mutant mouse (Small eye) has been previously described as a model for the absence of olfactory bulbs, owing to the lack of olfactory epithelium (OE). In the present report, we take advantage of this mutant and study a neural structure in the rostral pole of the telencephalon that phenotypically resembles the prospective OB. We named this formation olfactory bulb-like structure (OBLS). We also report the occurrence, in the mutants, of small epithelial vesicles in the malformed craneofacial pits, resembling an atrophic OE, although a mature olfactory nerve was not identified. Axonal tracing, birthdating, immunohistochemistry, and in situ hybridization using antibodies and probes expressed in the olfactory system, indicated that two distinct structures observed in the OBLS correspond to the main and accessory olfactory bulbs of the control mouse. We propose that the OBLS has developed independently of the external influences exerted by the olfactory nerve. The presence of a prospective OB in the mutants, without intervening olfactory fibers, suggests that intrinsic factors could define brain territories even in absence of the proper afferent innervation. The intrinsic mechanisms and environmental cues in the telencephalon could be sufficient to promote axonogenesis in the projection neurons of the OB and guide their axons in a lateral prospective tract, in the absence of olfactory axons.

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PubMed1998

Central olfactory structures in Pax-6 mutant mice.

During the development of the olfactory system, cells located in the olfactory placode/olfactory pit send their axons toward the rostral part of the telencephalic vesicles (TVs). Some of these enter the TV inducing the formation of the olfactory bulbs (OBs), whereas, mitral and tufted cell axons form the lateral olfactory tract (LOT). Our recent studies have shown that the beginning of the central olfactory projections is independent of the arrival of olfactory receptor neuron (ORN) axons to the TV. Here we have used the mouse carrying a mutation in the Pax-6 gene to study whether the nasal olfactory structures intervene in the formation of central olfactory structures. This mutant as well as lacking a nose and eyes, is reported to lack olfactory epithelium and OB. However, we have found an ovoid cellular structure localized in the rostral part of the brain, and some cells in this structure project axons toward the piriform cortex forming a presumptive LOT. We conclude that the referred structure is an OB, which fails to develop because the mutation in the Pax-6 gene affects the formation of nasal structures. As such, fibers of the ORNs are necessary for the protrusion and layered formation of the OB, but these inputs are not necessary for the establishment of the central olfactory projections.

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PubMed1996

Dynamics of cell migration from the lateral ganglionic eminence in the rat.

From previous developmental studies, it has been proposed that the neurons of the ventrolateral cortex, including the primary olfactory cortex, differentiate from progenitor cells in the lateral ganglionic eminence. The objective of the present study was to test this hypothesis. The cells first generated in the forebrain of the rat migrate to the surface of the telencephalic vesicle by embryonic day (E) 12. Using [3H]thymidine, we found that most of these cells contributed to the formation of the deep layer III of the primary olfactory cortex. To study the migratory routes of these cells, we made localized injections of the carbocyanine fluorescent tracers Dil and DiA into various parts of the lateral ganglionic eminence in living embryos at E12-E14 and subsequently maintained the embryos in a culture device for 17-48 hr. After fixation, most migrating cells were located at the surface of the telencephalic vesicle, whereas others were seen coursing tangentially into the preplate. Injections made at E13 and in fixed tissue at E15 showed that migrating cells follow radial glial fibers extending from the ventricular zone of the lateral ganglionic eminence to the ventrolateral surface of the telencephalic vesicle. The spatial distribution of radial glial fibers was studied in Golgi preparations, and these observations provided further evidence of the existence of long glial fibers extending from the ventricular zone of the lateral ganglionic eminence to the ventrolateral cortex. We conclude that cells of the primary olfactory cortex derive from the lateral ganglionic eminence and that some early generated cells migrating from the lateral ganglionic eminence transgress the cortico-striatal boundary entering the preplate of the neocortical primordium.

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PubMed1989

Vasoactive intestinal polypeptide-immunoreactive neurons in the main olfactory bulb of the hedgehog (Erinaceus europaeus).

Vasoactive intestinal polypeptide (VIP) immunoreactivity was localized by the indirect antibody enzyme method (PAP technique) in the main olfactory bulb of the hedgehog. Most VIP-immunoreactive cells were located in the glomerular layer and throughout the external plexiform layer. Fewer cells were observed in the granule cell layer. At the morphological level they exhibit the characteristics of periglomerular, external tufted, superficial short axon, horizontal and Van Gehuchten cells. It should be mentioned that another specific neuronal type was found in the inner third of the external plexiform layer, which is not described in other animals. These results revealed that a high number of intrinsic neuronal types of the olfactory bulb of the hedgehog display a strong VIP immunoreactivity.

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PubMed1989

Layers I and VI of the visual cortex in the rabbit. A correlated Golgi and immunocytochemical study of somatostatin and vasoactive intestinal peptide containing neurons.

Immunocytochemical and Golgi staining techniques were used to correlate the morphology of neurons in layers I and VI of the rabbit's visual cortex. Antisera against somatostatine (SOM) and vasoactive intestinal peptide (VIP) were employed in the immunocytochemical investigation. In layer I, SOM-positive cells were multipolar and situated in the lower part of the layer. Some had long horizontal axons like those of the Cajal-Retzius cells when observed by the Golgi method. Most VIP-positive cells were bipolar and some had axons throughout this layer. In layer VI, SOM-positive cells were of multipolar, bitufted, or pyramidal-like morphology. Frequently, they presented a thicker and more prominent dendrite with various collaterals and axons with ascending, horizontal and sometimes descending courses. Cells with recurrent axon were occasionally observed. Either the dendrite or the axonal characteristics are similar to some Golgi-impregnated non-pyramidal cells of our material, including the inverted pyramidal neurons. In this study, we have described peptidergic cells in these layers and correlate them with Golgi impregnated neurons and with those described in the literature.

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PubMed1986

Neocortical layers I and II of the hedgehog (Erinaceus europaeus). II. Thalamo-cortical connections.

This study examines the thalamo-cortical projections to the most superficial neocortical layers in the hedgehog (Erinaceus europaeus) after small injections of horseradish peroxidase and horseradish peroxidase conjugated to wheat germ agglutinin in the somato-sensory cortex. The injections were limited to layers I, II and upper parts of layer III/IV. Retrogradely labeled cells were plotted in serial sections through the thalamus. Injections in the somato-sensory cortex gave a pattern of elongated columns of labeled cells, extending rostro-caudally in the nucleus ventralis thalami. In the neocortex, labeled fibers extended for considerable distances running horizontally in layer I. Complementary observations demonstrate the thalamic origin of certain, coarse ascending bundles observed previously in Golgi preparations of the hedgehog. It is concluded that a major cortical input to layer I originates in the hedgehog in the principal thalamic (relay) nuclei. After injections in the somato-sensory cortex, retrogradely labeled cells were also found in the nucleus ventro-medialis thalami and very few in a zone medial to the nucleus ventralis thalami corresponding to the intralaminar thalamic nuclei. The contributions of this latter system seem to be limited in comparison with other mammals.

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PubMedDate not supplied

Further studies on cortical tangential migration in wild type and Pax-6 mutant mice.

In this study we present new data concerning the tangential migration from the medial and lateral ganglionic eminences (MGE and LGE) to the cerebral cortex during development. We have used Calbindin as a useful marker to follow the itinerary of tangential migratory cells during early developmental stages in wild-type and Pax-6 homozygous mutant mice. In the wild-type mice, at early developmental stages, migrating cells advance through the intermediate zone (IZ) and preplate (PP). At more advanced stages, migrating cells were present in the subplate (SP) and cortical plate (CP) to reach the entire developing cerebral cortex. We found that, in the homozygous mutant mice (Pax-6(Sey-Neu)/Pax-6(Sey-Neu)), this tangential migration is severely affected at early developmental stages: migrating cells were absent in the IZ, which were only found some days later, suggesting that in the mutant mice, there is a temporal delay in tangential migration. We have also defined some possible mechanisms to explain certain migratory routes from the basal telencephalon to the cerebral cortex. We describe the existence of two factors, which we consider to be essential for the normal migration; the first one is the cell adhesion molecule PSA-NCAM, whose role in other migratory systems is well known. The second factor is Robo-2, whose expression delimits a channel for the passage of migratory cells from the basal telencephalon to the cerebral cortex.

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