Biomedical subjects

L Puelles

Publications and source records attributed to L Puelles.

At least 91 records · Page 5Linked to original sources

PubMed1992

Afferent connections of the habenular complex in the lizard Gallotia galloti.

Afferents to the habenular complex were studied by means of in vitro horseradish peroxidase retrograde labeling and anterograde control experiments in the lizard Gallotia galloti. The medial habenular nucleus was found to receive abundant afferent fibers from the nucleus of the posterior pallial commissure and the nucleus septalis impar. More restricted input comes from the nucleus eminentiae thalami and the nucleus of the stria medullaris. The lateral habenular nucleus is innervated by various fiber groups originating from the bed nucleus of the anterior commissure, the diagonal band nucleus, the lateral preoptic area, the anterior entopeduncular nucleus, the lateral hypothalamic and mammillary areas, the nucleus of the stria medullaris, the area tegmentalis ventralis and a scattered neuronal subpopulation in the large-celled dorsolateral nucleus of the dorsal thalamus. Habenulopetal fibers generally follow the stria medullaris, but hypothalamic, entopeduncular and dorsal thalamic afferents course through the dorsal peduncle of the lateral forebrain bundle in a transthalamic route. Mesencephalic ventral tegmental afferents ascend through the tractus retroflexus.

Afferent Pathways↗

PubMed1992

The pretectal complex of the rabbit: distribution of acetylcholinesterase and reduced nicotinamide adenine dinucleotide diaphorase activities.

The chemoarchitecture of the pretectal complex of the rabbit was examined in sections stained by acetylcholinesterase (AChE) and reduced nicotinamide adenine dinucleotide (NADH) diaphorase in the coronal, horizontal and sagittal plane. Twelve different subdivisions can be identified in the rabbit pretectum on the basis of the distribution of both histochemical markers. According to the standard terminology, the pretectal complex of the rabbit consists of: the nucleus of the optic tract; the anterior, posterior, olivary and medial pretectal nuclei; the nucleus of the posterior commissure; the periventricular subcommissural gray; the suprageniculate and internal suprageniculate nuclei, and the dorsal, lateral and medial terminal nuclei of the accessory optic system. The combined use of several sectioning planes and the histochemical mapping of AChE and NADH diaphorase have been of value in resolving the structural limits within transitional regions of the pretectum.

Acetylcholinesterase↗

PubMed1992

Reduced junctional permeability at interrhombomeric boundaries.

Intercellular communication is considered to have a role during pattern specification processes in early embryonic development. This report analyzes the changing gap junctional communication properties of chick neuroepithelial cells depending on their position relative to the segmental partitions of the rhombencephalon. Intercellular electrical coupling and dye transfer were studied with microelectrode techniques. Neuroepithelial cells were electrically coupled irrespective of their location relative to interneuromeric boundaries. Iontophoretic injection of biocytin or Lucifer Yellow into single cells inside the rhombomeres was followed by transjunctional diffusion to the surrounding cells. In contrast, dye transfer was strictly limited when the diffusion zone contacted the cells forming the interneuromeric limits. Label injected into the boundary cells did not spread to other cells at all. Avian interrhombomeric boundaries are thus sites of reduced junctional permeability during early morphogenesis.

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PubMed1991

Postnatal development of calbindin and parvalbumin immunoreactivity in the thalamus of the rat.

The maturation of the calcium binding proteins calbindin-D28k (CB) and parvalbumin (PV) during the first 3 postnatal weeks was studied in the rat thalamus using immunohistochemistry. These two proteins display a non-homogeneous distribution in the adult thalamus. In the rat, CB is mainly localized in the neurons and neuropil of the thalamic midline, intralaminar, and ventromedial nuclei, as well as in the posterior complex. At birth, CB-immunoreactive cell bodies were evident in thalamic midline structures, and especially in the nucleus reuniens. The number of thalamic CB-positive cell bodies, as well as the intensity of the neuropil immunostaining, increased progressively in the first postnatal weeks. This quantitative increase was first apparent in the midline structures and then in the other thalamic territories which are CB-positive in adulthood, and followed a mediolateral gradient. The mature pattern was achieved by the end of the third postnatal week. In the adult rat thalamus the neurons of the reticular nucleus display PV-immunostaining and PV-positive fibers densely innervate most of the dorsal thalamic domains. PV-immunoreactivity was clearly evident at birth in the cell bodies of the reticular nucleus. The density of PV-containing fibers increased progressively after birth in the dorsal thalamus, with a lateromedial gradient. At the end of the third postnatal week the ventroposterior (VP) complex appeared heavily innervated by PV-positive fibers, whose density in more medial structures was still lower than in the adult thalamus. A transient hyperinnervation of PV-immunoreactive fibers, displaying a dishomogenous organization in distinct segments, was observed in VP, and especially in the ventroposteromedial nucleus, during the second postnatal week. Altogether these findings indicate that the maturation of CB and PV requires postnatally a relatively prolonged period of time. The possible involvement of these proteins in different functional aspects of thalamic neuronal maturation is discussed.

Animals↗

PubMed1991

Observations on the fate of nucleus superficialis magnocellularis of Rendahl in the avian diencephalon, bearing on the organization and nomenclature of neighboring retinorecipient nuclei.

The cytoarchitectonic development of an. superficialis magnocellularis (dorsal thalamus, posterior parencephalon) was studied from 3 days of incubation up to the mature state after hatching in the chick. A hypothesis of Kuhlenbeck (1937) on a partial transformation or contribution of SM cells into a different neighbouring griseum was tested, in the wider context of divergent interpretations of diencephalic development either within Herrick's (1910) longitudinal columnar theory, or within a modified neuromeric conception (Puelles et al. 1987 a). Nucleus SM develops early within the alar region of the posterior parencephalon, forming an outer mantle stratum over the main telencephalopetal thalamic inner cell mass. Thymidine-labeling data pinpoint its generation period mainly between 3 and 4.5 days of incubation. Throughout its subsequent development, SM remains within the primary interneuromeric limits that separate it from ventral thalamus and pretectum. After 8 days of incubation, SM subdivides into superficial (compact) and deep (disperse) sublaminae. The superficial one becomes much compressed between n. geniculatus ventralis and n. synencephali superficialis. Some of its cells migrate interstitially into the optic tract (12-16 days in ovo) and later disappear. The corresponding mature remnant was called n. interstitialis tractus opticus (ITO). The deep sublamina of SM forms a cap around n. rotundus. It becomes increasingly dispersed due to many passing fibers, and may be recognized in the mature brain as an area perirotundica (ApR). Clarification of the fate of embryonic SM bears on the confused terminology for various visual diencephalic nuclei. It is argued that the terms n. geniculatus dorsalis p. principalis and p. intercalaris, n. superficialis magnocellularis (in its wrong usage), n. lamminaris precommissuralis, n. lentiformis mesencephali p. medialis, p. parvocellularis and p. magnocellularis should be considered obsolete, on various embryological and hodologic grounds. An embryologically consistent terminology is proposed.

Animals↗

PubMed1991

Retinal and tectal connections of embryonic nucleus superficialis magnocellularis and its mature derivatives in the chick.

In a companion paper (Puelles et al, this issue), the cytoarchitectonic development of the thalamic primordium called nucleus superficialis magnocellularis (SM) and its adult configuration in the chick were studied, correcting the misinterpretations that have impeded proper study of this neuronal group. Given its superficial position in the diencephalon, in contact with the optic tract and neighbouring retinorecipient grisea (SS, GV), as well as with the tecto-recipient n. rotundus, SM was suspected to have connections with centers of the visual pathway. In this paper we report the existence of a non-topographic retinal projection over the superficial adult derivate of SM (n. interstitialis tractus opticus, ITO) and a non-topographic, diffuse projection of the whole SM-derived population (area perirotundica, ApR, and ITO) onto the optic tectum. The latter was demonstrated throughout the late embryonic period in which SM loses its embryonic unitary character and becomes dispersed into its ill-defined, definitive adult portions (ITO, ApR). Golgi-like HRP- or DiI-labeling of SM cells showed a protracted immature appearance of their dendrites, expressed coincidently with a capacity to translocate superficially into the optic tract.

Animals↗

PubMed1991

Comparative mapping of acetylcholinesterase and reduced nicotinamide adenine dinucleotide diaphorase in the rabbit dorsal thalamus.

The distribution of acetylcholinesterase and reduced nicotinamide adenine dinucleotide (NADH) diaphorase enzymatic activities was mapped histochemically in the dorsal thalamus of the rabbit. A comparison of the resulting patterns helped in the histochemical delimitation of a number of nuclei, as well as in the detection of some subdivisions, that showed differential expression of these enzymes. It was observed that AChE and NADH diaphorase tend to appear in a complementary fashion in many dorsal thalamic neuropiles, so that intense activity of the one was accompanied by low activity of the other. However, coincident expression of both enzymes was also obtained in a small number of areas. The correlation of these patterns with other chemo-architectonic and hodologic data does not yet disclose an explanation of these regularities, which however suggest some functional significance.

Acetylcholinesterase↗

PubMed1990

Acetylcholinesterase-histochemical differential staining of subdivisions within the nucleus rotundus in the chick.

Histochemical mapping of AChE activity in the chick diencephalon shows differential staining of several subregions within the nucleus rotundus. The topography and extent of these subdivisions were studied in transverse, horizontal and sagittal sections. A correlation with rotundic hodologic subdivisions reported in the literature is feasible, whereas several other chemoarchitectonic or functional markers show a homogeneous distribution throughout the n. rotundus. Moreover, cholinergic markers do not detect cholinergic afferents within the rotundic neuropile. Late embryonic appearance of the AChE heterogeneity suggests a modulation of neuropile AChE levels subsequent to synaptogenetic adjustment of differential hodology.

Acetylcholinesterase↗

PubMed1989

Avian nucleus isthmi ventralis projects to the contralateral optic tectum.

Injections of HRP throughout the upper tectal strata led in 4 cases to the appearance of retrogradely labeled neurons within n.isthmi ventralis, contralateral to the experimental side. An additional case proved that this projection courses through the ventral supraoptic commissure. This is the first description of a crossed isthmo-tectal projection in birds.

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PubMed1988

The locus of optic nerve head representation in the retinotopic projection over nucleus geniculatus lateralis ventralis and nucleus griseum tectalis in the chick also lacks a retinal projection.

Recently we have demonstrated the presence of a gap in the avian retinotectal projection, that corresponds with the locus of retinotopic representation of the elongated optic nerve head. The present report describes an equivalent gap in the optic neuropiles of the avian ventral geniculate nucleus and griseum tectalis formation, detected after filling optic terminals anterogradely from the contralateral eye with peroxidase. A projection-less strip appears at the expected retinotopic position in both grisea intersecting radially all the strata of the corresponding neuropiles. It is speculated that a common synaptogenetic mechanism must account for these gaps.

Animals↗

PubMed1987

Segment-related, mosaic neurogenetic pattern in the forebrain and mesencephalon of early chick embryos: I. Topography of AChE-positive neuroblasts up to stage HH18.

Histochemical mapping of AChE-positive neuroblasts in sectioned and whole-mounted preparations of the chick embryo mesencephalon and prosencephalon allows a correlation of early neural tube morphogenesis (segmentation, longitudinal compartmentation) with the heterochronic pattern of neurogenesis. One significant finding is that the initial appearance of neuroblasts in the forebrain does not follow neuromeric segmentation, but evolves in parallel with it. Early neuroblasts appear as separate, distinct groups within specific matrix territories at the center of the transverse neuromeric segments. Neighbouring segments display different spatiotemporal patterns of neurogenesis. Overall gradients of differentiation in the rostrocaudal and ventrodorsal directions are absent, whereas a clear-cut segment-related, mosaic pattern becomes evident. Notwithstanding this, gross regularities of heterochrony in the neurogenetic behavior of the different segments lead to a definition of elemental longitudinal compartments of the forebrain and mesencephalon (floor, paramedian, basal, and alar regions) on the basis of precocious differentiation of the basal region and retarded differentiation of the paramedian and alar regions.

Acetylcholinesterase↗

PubMed1987

The locus of optic nerve head representation in the chick retinotectal map lacks a retinal projection.

Retinotopic representation of the optic nerve head of the contralateral eye lies at the rostrodorsal face of the avian tectum. Since the homologous mammalian retino-collicular map shows an optic disc gap, the present anterograde HRP transport experiments were designed to detect an equivalent gap in the avian tectal retinorecipient strata. Sections tangential to the tectum at the locus of pecten representation displayed a thin, elongated, projection-less strip, crossing radially all retinorecipient laminae. Histochemical demonstration of NADH-diaphorase on similar sections showed low activity of this enzyme along an equivalent, elongated strip.

Animals↗

PubMed1987

Solitary magnocellular neurons in the avian optic tectum: cytoarchitectonic, histochemical and [3H]thymidine autoradiographic characterization.

Solitary magnocellular neurons are described in the adult chick optic tectum on the basis of their large size, polygonal shape, intensely basophilic perikarya, characteristic position at the border between the stratum griseum centrale and the stratum album centrale, decreasing density along a rostrocaudal gradient, and intense activity of NADH-diaphorase. These characteristics distinguish this population from the adjacent ganglion cells of the stratum griseum centrale, which are more numerous, smaller, paler staining and have background levels of NADH-diaphorase. Moreover, the solitary magnocellular neurons appear unlabeled after tritiated-thymidine administration after stage 17+, and are thus born before the stratum griseum centrale neurons, which are generated after stage 19. These large cells may correspond to a class of stellate ganglion cells with thick spiny dendrites described by Ramón (1943).

Animals↗

PubMed1987

Location of the rostral end of the longitudinal brain axis: review of an old topic in the light of marking experiments on the closing rostral neuropore.

The rostral end of the forebrain was classically defined on the basis of descriptive data. Different assumptions on the mode of closure of the rostral neuropore caused three different theories of the rostral end of the forebrain to be formulated (His 1893a; von Kupffer, '06; Johnston, '09). Some recent descriptive and experimental data have put these theories into question. A piece of black nylon thread was inserted through the rostral neuropore of chick embryos and was fixed to its ventral lip. These operations were done at all intermediate stages during the process of closure of the rostral neuropore. The embryos were sacrificed at a later stage, by which time the neuropore had disappeared. In the cleared specimens the threads always lay at the same site, namely the upper border of lamina terminalis, irrespective of the stage at which the marker was inserted. These results stand against His's conception (1893a,b) of a sutura terminalis and support the single mechanism of sutura dorsalis during closure of the rostral neuropore. The marking data therefore imply that the topologic rostral end of the forebrain lies at the upper limit of lamina terminalis, as proposed by von Kupffer, '06).

Acetylcholinesterase↗

PubMed1987

Autoradiographic and Golgi study on the early development of n. isthmi principalis and adjacent grisea in the chick embryo: a tridimensional viewpoint.

Neurogenesis, cell migration and early histogenesis of the isthmic nuclear complex in chick embryos were investigated in autoradiographic and Golgi material. The aim of the experimental observations was to detect whether the apparent origin of different grisea of this complex at separate matrix territories (neuromeres) was accompanied by peculiar generation patterns, consistent with predictions of neuromeric theory. Differential birthday patterns were indeed obtained for a) n. semilunaris--born in the rh1 a rhombomere, b) n. isthmi principalis pars parvocellularis, nn. lemnisci lateralis dorsalis and ventralis, and n. isthmi ventralis--born in the isthmic rhombomere, and c) n. isthmi principalis pars magnocellularis--born at the m1 mesomere. Only the nuclear group at (b) shows a clear-cut gradient of generation. The morphological analysis aimed to describe isthmic neuroblast cell form before, during and immediately after migration into the mesencephalic optic lobe. Golgi data indicate that isthmic neuroblasts emerge as free cells from the matrix and aggregate into a dense superficial mantle layer. Between stages HH26 and 30, the whole mass of cells translocates tangentially in a rostrolateroventral direction, invading the m2 mesomere. The individual migrating neuroblasts have a leading axonal process which rapidly grows into the tectum in advance of the cell body, which follows at a slower pace. As the migration runs to an end the neuroblasts start to differentiate, sprouting dendritic processes. A joint origin in the isthmic mantle primordium is proposed for the nuclear group at (b) (above), whereas n. isthmi principalis pars magnocellularis is formed separatedly from the rest, and shows no tangential migratory behaviour of its neuroblasts. The complex histogenetic and morphogenetic processes at the isthmo-mesencephalic boundary may be explained on the basis of these new data, but this requires a tridimensional viewpoint that is exposed in the Discussion.

Animals↗

PubMed1987

Two modes of free migration of amacrine cell neuroblasts in the chick retina.

The migration of amacrine neuroblasts toward the prospective amacrine cell layer in the chick embryo retina has been studied, in Golgi-stained sections, between days 5 and 9 of embryogenesis. Two distinct populations of presumptive amacrine neuroblasts have been identified on the basis of their shape and migratory behavior. One population (smooth amacrine neuroblasts) display smooth, monopolar or bipolar contours, moving freely across the retina without major changes in the original postmitotic shape, and give processes only after reaching the primitive inner plexiform layer. The second population (multipodial amacrine neuroblasts) includes multipolar neuroblasts with abundant filiform and/or lamelliform processes sprouting in various directions; these highly plastic cells begin modifying their shapes at the time of release from the ventricular lining and continue to do so as they move toward their definitive location. Thus, the well-known heterogeneity of adult amacrine cells seems to be preluded by differences in neuroblastic migratory patterns, suggesting the existence of at least two different subsets of amacrine cell precursors.

Animals↗

PubMed1981

A golgi study on the early sequence of differentiation of ganglion cells in the chick embryo retina.

An examination of retinal structure in chick embryos, impregnated with the Golgi-Stensaas method between 2 and 6 days of incubation, discloses, on the one hand, a uniform typology of the proliferating ventricular cells, the pre- and postmitotic forms of which were tentatively identified; on the other hand, postmitotic neuroblasts are evidenced in the stages of differentiation previous to the growth of their neurites. In the earliest embryos (up to 5 1/2 days of incubation), all cells that detach from the ventricular lining to differentiate as neurons do so while the ventricular cell precursor has an interphasic configuration. This means that, although they free themselves from the scleral attachment site, they keep for a while a vitreal attachment. The vitreally-attached endfeet subsequently transform into axonal growth cones, sprouting filopodia and lamellipodia. While the axons grow towards the optic nerve head, cell bodies and remaining scleral processes are progressively retracted inwards, leading to the appearance of typical ganglion cells. After 5 1/2 days of incubation, a great number of postmitotic neuroblasts detach while still in the G1 phase of the ventricular cell cycle. Those of them that show the longest leading processes become also ganglion cells, after their leading tip has acquired a growth cone configuration and has bent into the optic fiber layer. These results on early mechanisms of ganglion cell genesis are discussed in relation to data in the literature, and a simple hypothesis is offered which explains the biphasic pattern in which presumptive ganglion cells detach from the ventricular lining of the chick retina.

Animals↗

PubMed1978

A Golgi-study of oculomotor neuroblasts migrating across the midline in chick embryos.

The Golgi-Stensaas impregnation technique was employed at appropriate stages of development to study the morphology of the oculomotor neuroblasts as these migrate across the midline. Data reported in previous publications were confirmed, such as the timing of the migration (occurring between the 4th and the 9th days of inoculation), the fact that the migrating cells carry their axons across the midline as trailing processes, and the absence of pre-existing fibrillar structures able to provide contact guidance for this migration. The most striking new fact discovered is that the leading processes of the oculomotor neuroblasts are often branched, and that all these branches are uniformly oriented towards the midline. This seems to indicate the existence of a non-random growth process. It is argued in the discussed that this can be explained through the presence of an orienting neurotropic influence. This one could have its source in certain non-oculomotor neuroblasts which were detected within the midline ventricular zone. On morphological grounds, this group of cells may be tentatively identified as the avian counterpart of the midventral mesencephalic proliferation described in several mammals. This proliferative zone is known to contain dopamine at early stages of development. A hypothetic casual mechanism of the oculomotor migration is therefore advanced, wherein dopamine, diffusing out of the non-oculomotor midline neuroblasts, induces at short range oriented outgrowth of oculomotor leading processes across the midline.

Animals↗