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Biomedical subjects

L Puelles

Publications and source records attributed to L Puelles.

At least 73 records · Page 4Linked to original sources
PubMed1995

Longitudinal organization of the anterior neural plate and neural tube.

Over the last century, several morphological models of forebrain organization have been proposed that hypothesize alternative topological solutions for the relationships of the histogenic primordia. Central to all of these models are their definitions of the longitudinal axis and the longitudinal organization of the neural plate and neural tube. To understand the longitudinal organization of the anterior brain, we have sought to identify molecular properties that are continuous along the entire longitudinal axis of the embryonic CNS. In this essay, we describe studies of the expression of several genes in the mouse between 7.5 (presomite stage) and 10.5 days post coitum (dpc) that provide evidence for the trajectory of the anterior-posterior axis and the longitudinal organization of the anterior CNS. Specifically, we report that the expression of noggin, sonic hedgehog and Nkx-2.2 define longitudinal columns of cells that are present along the entire CNS axis. Within the forebrain, the expression of these genes, as well as that of Nkx-2.1 and BF-1, are in distinct longitudinal regions in the neural plate and tube. We demonstrate that the earliest longitudinal axon pathways of the forebrain are spatially correlated with the longitudinal domain defined by Nkx-2.2. Finally, expression of the former genes, and Otx-1 and Emx-2, suggests that the cephalic neural plate is organized into molecularly distinct domains delimited by longitudinal and transverse borders; these results provide a foundation for defining the mechanisms that pattern the neural plate.

Animals↗
PubMed1995

Oligodendrocytes originate in a restricted zone of the embryonic ventral neural tube defined by DM-20 mRNA expression.

Products of the PLP gene, proteolipid protein and its isoform DM-20, are the most abundant proteins in CNS myelin, and are markers of the oligodendrocyte, the myelin-forming cell in the CNS. The DM-20 transcript has previously been reported to be expressed in newborn oligodendrocyte progenitor cells and during embryonic development. We have therefore used a DM-20 cRNA probe to follow, by in situ hybridization, the oligodendrocyte lineage during embryonic development. DM-20-expressing cells were first detected at E9.5 in the ventricular germinal layer of the laterobasal plate of the diencephalon. At E14.5, DM-20+ cells had largely disappeared from the diencephalic ventricular germinal layer and had colonized the ventral mantle layer at the posterior part of the basal diencephalon. Between E17.5 and P1, the number of DM-20+ cells increased and progressively invaded the major white matter tracts. In the hindbrain, DM-20+ cells appeared at E12.5 in the caudal part of the rhombencephalon, and at E14.5 all along the ventral spinal cord. Between E14.5 and P1, DM-20+ cells progressively colonized, first ventrally then dorsally, all the spinal cord and more extensively the white matter tracts. At E14.5, a large gap separated, rostrally, the medullary columns from the mantle layer cells in the prosencephalon, suggesting that oligodendrocytes in the mid- and forebrain originate from a different pool of precursors than in the rhombencephalon and the spinal cord. Together, these observations suggest that expression of the DM-20 transcript is an early marker of commitment to the oligodendrocyte lineage, and that oligodendrocyte precursors originate in a ventrally restricted region.

Animals↗
PubMed1994

Development of catecholamine systems in the brain of the lizard Gallotia galloti.

For a better insight into general and derived traits of developmental aspects of catecholaminergic (CA) systems in amniotes, we have studied the development of these systems in the brain of a lizard, Gallotia galloti, with tyrosine hydroxylase (TH)- and dopamine (DA) immunohistochemical techniques. Two main groups of TH-immunoreactive (THi) perikarya appear very early in development: one group in the midbrain which gives rise to the future ventral tegmental area, substantia nigra and retrorubral cell groups, and another group in the tuberomammillary hypothalamus. Somewhat later in development, TH/DA-immunoreactive cells are observed in the thalamus, rostrodorsal hypothalamus and spinal cord, and, with another delay, in the suprachiasmatic nucleus, the periventricular organ, and the pretectal posterodorsal nucleus. CA cell groups that appear rather late in development include the cells in the olfactory bulb, the locus coeruleus and the caudal brainstem. As expected, the development of immunoreactive fibers stays behind that of the cell bodies, but reaches the adult-like pattern just prior to hatching. The present study revealed considerable variation in the relation between the state of cytodifferentiation and first expression of TH/DA immunoreactivity between CA cell groups. Catecholamine cells in the midbrain and tuberomammillary hypothalamus are still migrating, immature (absence of dendrites) and express only TH immunoreactivity at the time of first detection. Cells which appear at later developmental stages lie already further away from the ventricle, possess two or more dendritic processes, and generally express both TH- and DA immunoreactivity.

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PubMed1994

The lacertidian reticular thalamic nucleus topographically upon the dorsal thalamus: experimental study in Gallotia galloti.

The projection pattern of the ventral thalamic reticular nucleus onto the dorsal thalamus was studied in the lizard Gallotia galloti using in vitro horseradish peroxidase and fluorescent carbocyanine labelling techniques. Localized label deposits at three dorsoventrally spaced sites in the dorsal thalamus elicited retrograde transport into separate, though partly overlapping, medial, dorsolateral and ventrolateral sectors within an extended cytoarchitectonic complex which may be globally identifiable as the reticular nucleus. Neurons found in the dorsolateral and ventrolateral sectors mainly corresponded to the cell group named nucleus ventromedialis (or nucleus of the dorsal supraoptic decussation) in the literature, whereas neurons labelled in the medial sector corresponded to the so-called dorsal hypothalamic nucleus. Sparser cells appear labelled in the superficially placed nucleus suprapeduncularis. Thalamotelencephalic fibers arising from the injected dorsal thalamic nuclei also project to the corresponding retrogradely labeled sectors within the reticular nucleus. These findings reveal a rough topographic organization in the connections of the extended reticular nucleus complex with the whole dorsal thalamus. This supports the hypothesis of hodological homology between this ventral thalamic formation in Gallotia and the mammalian thalamic reticular nucleus.

Animals↗
PubMed1994

New subdivision schema for the avian torus semicircularis: neurochemical maps in the chick.

Chemoarchitectonic subdivisions in the chicken torus semicircularis were mapped by means of acetylcholinesterase histochemistry and immunocytochemical labeling of leucine-enkephalin, choline acetyltransferase, neuropeptide Y, and calbindin/calretinin in adjacent sections. The torus semicircularis was found to consist of three main divisions: intercollicular area, toral nucleus, and preisthmic superficial area. All three appear variously subdivided. The intercollicular area is a mid-mesencephalic ventral periventricular region and appears subdivided into core and shell intercollicular regions. The toral nucleus is formed by a large caudal periventricular cytoarchitectonic complex, consisting of a periventricular lamina subdivided into core and shell regions, a pericentral, diffuse external nucleus, a central nucleus subdivided into core and shell regions, a caudomedial shell nucleus, a paracentral nucleus, and a posterior hiliar nucleus, apart from other minor parcellations. The preisthmic superficial area extends superficially at the caudomedial end of the toral nucleus, reaching the paramedian dorsal brain surface just rostral to the isthmo-optic nucleus. It is subdivided into core and shell regions. This previously unnoticed area is distinguished here from the intercollicular area and from the caudomedial shell and paracentral nuclei, all of which are frequently mixed in the literature under the concept "intercollicular nucleus." The revised terminology and subdivision for the avian torus clarifies many chemoarchitectonic and hodological mappings reported in the literature. It also suggests new research subjects and eliminates some causes of confusion.

Acetylcholinesterase↗
PubMed1994

Patterning of the embryonic avian midbrain after experimental inversions: a polarizing activity from the isthmus.

Rostrocaudal inversions of the prospective midbrain (accompanied in some cases by other adjacent neuroepithelial zones) were performed in the neural tube of 2-day-old chick embryos in the form of autografts or quail/chick chimeras, involving both alar and basal plates. These experiments aimed to analyze causally the histogenetic rostrocaudal patterning of the midbrain, formed normally by diverse neuronal complexes. The experimental embryos were processed for study of the resulting cytoarchitecture or for study of the Engrailed-2 gene expression pattern. The exclusive inversion of the prospective midbrain produced a normal midbrain. Joint inversion of prospective midbrain plus the prospective isthmocerebellar tissue gave rise to an ectopic isthmocerebellar complex plus a symmetric double-caudal midbrain; additionally, the prospective caudal diencephalon was induced to form a polarized isthmomesencephalic phenotype in substitution of the pretectum. All these regulation processes affected both the alar and basal plates. The changes in cytoarchitectural fate were preceded by correlated changes in the gradiental expression of the gene Engrailed-2. These results suggest that the polarized structural pattern of the midbrain is regulated by graded positional information derived from the caudally adjacent isthmocerebellar domain, which is probably a source of morphogens.

Animals↗
PubMed1994

DLX-2, MASH-1, and MAP-2 expression and bromodeoxyuridine incorporation define molecularly distinct cell populations in the embryonic mouse forebrain.

Recently, the Dlx family of homeobox genes have been identified as candidates for regulating patterning and differentiation of the forebrain. We have made a polyclonal antiserum to the protein product of the Dlx-2 gene. Using this antiserum, we have characterized the spatial and temporal pattern of DLX-2 protein expression during murine development and in the adult mouse brain. These studies demonstrate that, like the mRNA from the Dlx-2 gene, DLX-2 protein is expressed in mouse embryonic forebrain, limbs, tail, genital tubercle, and branchial arches. Within the embryonic forebrain, DLX-2 protein is expressed within specific transverse and longitudinal domains. Analysis of expression within the wall of the forebrain shows that DLX-2 is expressed in proliferative regions including the ventricular and subventricular zones. DLX-2 is expressed in the same cells as MASH-1, a marker of relatively undifferentiated cells, but in a reciprocal fashion to MAP-2, a marker of terminal neuronal differentiation. A number of DLX-2-expressing cells, but not all, can be labeled with bromodeoxyuridine (BrdU). Using the patterns of DLX-2, MASH-1, MAP-2 expression, and bromodeoxyuridine incorporation, we identify four molecularly distinct populations of cells that may correspond to different stages of neuronal differentiation in the mouse basal forebrain, in which DLX-2 is expressed at the transition from proliferation to terminal differentiation.

Animals↗
PubMed1993

Distribution of choline acetyltransferase immunoreactivity in the brain of the lizard Gallotia galloti.

The aim of the present study is to provide a complete description of the distribution of choline acetyltransferase (ChAT) immunoreactivity (i) in the brain of the lizard Gallotia galloti, on the basis of two different primary antisera: rat anti-ChAT and rabbit anti-chicken ChAT. Considering that the brain is a segmented structure, we have analysed our data with respect to transverse segmental domains (or neuromeres), which have been previously described by several authors in the brain of vertebrates. In the telencephalon, ChATi neurons are seen in the cortex, anterior dorsal ventricular ridge, basal ganglia, diagonal band, and bed nucleus of the stria terminalis. Further caudally, ChATi cell bodies are located in the preoptic area, hypothalamus, habenula, isthmus, and all motor efferent centers of the brainstem and spinal cord. Plexuses of ChATi fibers are observed in the areas containing cholinergic cell bodies. In addition, distinct plexuses are found in the cortex, the posterior dorsal ventricular ridge, the neuropiles of all primary visual centers of the diencephalon and mesencephalon, and several non-visual nuclei of the brainstem. The distribution of ChAT immunoreactivity in the brain of G. galloti resembles in many respects that of other vertebrates, and differences are mainly observed in the pretectum and midbrain tectum. Transverse segmental domains were identified in the brainstem and forebrain of Gallotia when the cranial nerve roots and fiber tracts were used as a reference, and most cranial motor nuclei were found to occupy the same segmental positions as have been reported in the chick.

Animals↗
PubMed1993

Expression patterns of homeobox and other putative regulatory genes in the embryonic mouse forebrain suggest a neuromeric organization.

The molecular mechanisms that control regional specification, morphogenesis and differentiation of the embryonic forebrain are not known, although recently several laboratories have isolated homeobox, Wnt and other genes that are candidates for playing roles in these processes. Most of these genes exhibit temporally and spatially restricted patterns of expression within the forebrain. However, analysis of the spatial patterns has been complicated because an understanding of the organization of the embryonic forebrain has been lacking. This article describes a neuromeric model of the forebrain that is consistent with the expression patterns of these genes, and that provides a framework for understanding the morphological relationships within this complex structure.

Animals↗
PubMed1993

The mouse Dlx-2 (Tes-1) gene is expressed in spatially restricted domains of the forebrain, face and limbs in midgestation mouse embryos.

The pattern of RNA expression of the murine Dlx-2 (Tes-1) homeobox gene is described in embryos ranging in age from E8.5 through E11.5. Dlx-2 is a vertebrate homologue of the Drosophila Distal-less (Dll) gene. Dll expression in the Drosophila embryo is principally limited to the primordia of the brain, head and limbs. Dlx-2 is also expressed principally in the primordia of the forebrain, head and limbs. Within these regions it is expressed in spatially restricted domains. These include two discontinuous regions of the forebrain (basal telencephalon and ventral diencephalon), the branchial arches, facial ectoderm, cranial ganglia and limb ectoderm. Several mouse and human disorders have phenotypes which potentially are the result of mutations in the Dlx genes.

Animals↗
PubMed1993

Spatially restricted expression of Dlx-1, Dlx-2 (Tes-1), Gbx-2, and Wnt-3 in the embryonic day 12.5 mouse forebrain defines potential transverse and longitudinal segmental boundaries.

The expression patterns of four genes that are potential regulators of development were examined in the CNS of the embryonic day 12.5 mouse embryo. Three of the genes, Dlx-1, Dlx-2 (Tes-1), and Gbx-2, encode homeodomain-containing proteins, and one gene, Wnt-3, encodes a putative secreted differentiation factor. These genes are expressed in spatially restricted transverse and longitudinal domains in the embryonic neural tube, and are also differentially expressed within the wall of the neural tube. Dlx-1 and Dlx-2 are expressed in two separate regions of the forebrain in an identical pattern. The Gbx-2 gene is expressed in four domains, two of which share sharp boundaries with the domains of the Dlx genes. One boundary is in the basal telecephalon between deep and superficial strata of the medial ganglionic eminence; the other boundary is in the diencephalon at the zona limitans intrathalamica. The Wnt-3 gene is expressed in a dorsal longitudinal zone extending from the hindbrain into the diencephalon, where its expression terminates at the zona limitans intrathalamica. Reciprocal patterns of expression are found within the dorsal thalamus for the Gbx-2 and Wnt-3 genes. These findings are consistent with neuromeric theories of forebrain development, and based upon them we suggest a model for forebrain segmentation.

Animals↗
PubMed1993

A chemoarchitectonically similar internal extension connects the rabbit intergeniculate leaflet to midline dorsal thalamaic nuclei.

The adscription of the intergeniculate leaflet to the ventral thalamus or to the dorsal thalamus has remained undecided due to the absence of specific evidence supporting either possibility. This report describes a thin retroreticular band of dorsal thalamic neurons, innervated selectively by Substance-P and L-enkephalin immunoreactive fibers, that extends from the medial end of the intergeniculate leaflet to the lateral border of the midline dorsal thalamic nuclei and abuts on the caudal aspect of the reticular nucleus. The area of the band contains small basophile fusiform neurons, but no immunoreactive cell bodies were observed. NADH-diaphorase histochemistry shows that this band is sharply distinct from ventral thalamic grisea, as well as from the neighboring ventrobasal complex of the dorsal thalamus. Our data suggest that, in the rabbit, the substance-P and L-enkephalin immunoreactive band forms together with the intergeniculate leaflet a chemoarchitectonically distinct structural unit of the dorsal thalamus, constituting a thin mediolateral lamina that bounds other dorsal thalamic nuclei from the ventral thalamus.

Animals↗
PubMed1992

Distribution of neuropeptide Y-like immunoreactivity in the brain of the lizard Gallotia galloti.

The distribution of neuropeptide Y (NPY)-like immunoreactivity was studied in the brain of the lizard Gallotia galloti, in order to gain insight into the comparative topography of this peptide. Antisera against both NPY and its C-terminal flanking peptide (C-PON) were used, demonstrating a general coexistence of both peptides, as described in other vertebrates. Most NPY-like immunoreactive (NPY-LI) cell bodies were observed in the telencephalon, specifically in various olfactory structures, all cortices, septum, basal ganglia (except for the globus pallidus), the nucleus of the diagonal band of Broca, the amygdaloid complex, and the bed nucleus of the anterior commissure. NPY-LI cells were also seen in the preoptic and hypothalamic regions and the dorsal thalamus (mainly in the perirotundal belt), as well as in the mesencephalic tegmentum (in the ventral tegmental area, the substantia nigra, and the retrorubral area). NPY-LI fibers and terminals were widely distributed in the brain. All visual and auditory neuropiles were densely innervated. Specially dense plexuses were seen in the nucleus accumbens, the ventral pallidum, the suprachiasmatic and ventromedial hypothalamic nuclei, the nucleus medialis thalami, the left habenula, and the central nucleus of the torus semicircularis. Our analysis shows that the distribution of NPY-like immunoreactivity in the forebrain of Gallotia largely resembles that of other vertebrates, whereas differences are mainly observed in the brainstem. The widespread distribution of NPY in the lizard brain suggests several modulatory functional roles, either in local-circuit systems of the forebrain, or in various limbic, neuroendocrine, and sensory pathways.

Animals↗
PubMed1992

Tangential neuronal migration in the avian tectum: cell type identification and mapping of regional differences with quail/chick homotopic transplants.

This paper is a sequel to a previous report, using quail/chick chimeras with partial tectal transplants, in which a tangential invasion of host (chick) tectal territories by cells originating in the quail graft was demonstrated. The cells displaying this secondary tangential migration appeared restricted to two strata (stratum griseum centrale (SGC) and stratum griseum et fibrosum superficiale (SGFS)). Here we describe the morphology of the tangentially displaced neurons, as well as their overall distribution in the host tectal lobe, by means of an antibody that specifically recognizes quail cells, staining them in a Golgi-like manner. Neurons that migrated into the SGC are identified as multipolar projection neurons, typical of this stratum. The majority of cells that migrated into the SGFS correspond to horizontal neurons, as was also corroborated by observations in Golgi-impregnated material. These horizontal cells are concentrated in laminae b, d and f, where their processes form well delimited axonal plexuses. In confirmation of previous results, SGC neurons have a limited range of migration, whereas SGFS cells translocate across much longer distances. In reconstructions of appropriate cases, a remarkable polarity was noted. Significant invasion of chick tectum by quail cells mostly occurred in the rostral half of the host tectum. The long-range migration of superficial horizontal cells frequently reached, but did not cross, the rostral tectal boundary. Conversely, tangential migration in the caudal half of the host tectum was scarce and coincided with a typical arrangement of quail-derived radial columns interdigited with chick-derived columns. These findings are discussed in relation to existing data on immature neuronal populations, molecular marker distribution and polarity of the avian optic tectum.

Animals↗
PubMed1992

Prenatal development of calbindin immunoreactivity in the dorsal thalamus of the rat.

The distribution of calbindin immunoreactivity was studied in the developing rat dorsal thalamus at embryonic days 14, 16, 18 and 20. At early stages (days 14-16), calbindin is expressed throughout the dorsal thalamic cell mass. Most intense labeling occurs in cells adjacent to the ventricular surface, in a spatial gradient reflecting the well-known outside-in generation pattern. Between days 16 and 20, calbindin-positive periventricular cells are redistributed in the dorsal thalamus according to two different patterns. They first become oriented tangentially within the periventricular layer, and diminish in number at the central locus where midline thalamic fusion occurs at 18 days. Periventricular calbindin immunoreactivity becomes restricted to a ring of late-born cells surrounding the gray commissure. Recognizable portions of this ring-shaped primordium will mature forming n.paratenialis, n.reuniens, n.paraventricularis, and n.subparafascicularis magnocellularis. Simultaneously, a massive contingent of radially-oriented, fusiform, calbindin-positive young neurons extends from the periventricular ring-shaped aggregate to the lateral brain surface at the caudoventral pole of the dorsal thalamus at embryonic days 17/18. These cells surround the primordium of the medial geniculate body, participating in the constitution of its marginal zone, and invade the lateral posterior nucleus, accumulating within its caudomedial part. Other portions of this stream form the parvocellular subparafascicular nucleus and the peripeduncular nucleus. The observed patterns of calbindin expression suggest that dorsal thalamic postmitotic neurons transiently express the marker during initial phases of axogenesis, whereas a specific, late-born population expresses calbindin continuously into adulthood. This late subpopulation displays migratory behavior, and finally subdivides into several nuclei of the mature midline, superficial and posterior thalamus.

Animals↗
PubMed1992

In vitro HRP-labeling of the fasciculus retroflexus in the lizard Gallotia galloti.

In order to test the usefulness of the in vitro HRP-labeling technique in the brains of small lizards, the fasciculus retroflexus was labeled in isolated brains of young specimens of the lizard Gallotia galloti by means of HRP applied with the tip of a micropipette located approximately midway along the descending course of the tract. Cells in the medial and lateral habenular nuclei were labeled retrogradely. Anterograde transport showed the course of the fasciculus retroflexus, first dorsoventrally into the paramedian prerubral tegmentum and then longitudinally into the isthmic nucleus interpeduncularis. Some fibers spread dorsally into the mesencephalic and isthmic tegmental fields. A substantial bundle continues caudally into nucleus raphe parvocellularis. Other fibers diverge rostral-wards from the point of inflexion of the fasciculus, coursing longitudinally in the medial forebrain bundle into the basal telencephalon. Some fibers course rostrally from the nucleus habenularis lateralis in the stria medullaris and could be followed to the dorsal septum.

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