Biomedical subjects

C Hedin-Pereira

Publications and source records attributed to C Hedin-Pereira.

8 recordsLinked to original sources

PubMed2002

Cell migration in the postnatal subventricular zone.

New neurons are constantly added to the olfactory bulb of rodents from birth to adulthood. This accretion is not only dependent on sustained neurogenesis, but also on the migration of neuroblasts and immature neurons from the cortical and striatal subventricular zone (SVZ) to the olfactory bulb. Migration along this long tangential pathway, known as the rostral migratory stream (RMS), is in many ways opposite to the classical radial migration of immature neurons: it is faster, spans a longer distance, does not require radial glial guidance, and is not limited to postmitotic neurons. In recent years many molecules have been found to be expressed specifically in this pathway and to directly affect this migration. Soluble factors with inhibitory, attractive and inductive roles in migration have been described, as well as molecules mediating cell-to-cell and cell-substrate interactions. However, it is still unclear how the various molecules and cells interact to account for the special migratory behavior in the RMS. Here we will propose some candidate mechanisms for roles in initiating and stopping SVZ/RMS migration.

Animals↗

PubMed2001

The 9-O-acetyl GD3 gangliosides are expressed by migrating chains of subventricular zone neurons in vitro.

Neurons from the anterior subventricular zone (SVZ) of the cerebral cortex migrate tangentially to become interneurons in the olfactory bulb during development and in adult rodents. This migration was defined as neuronophilic, independent of a radial glial substrate. The cortical SVZ and the rostral migratory stream to the olfactory bulb were shown to be rich in 9-O-acetyl GD3 gangliosides (9-O-acGD3), which have been previously shown to be implicated in gliophilic migration in the rodent cerebral cortex and cerebellum. In the present study, we performed SVZ explant cultures using rats during their first postnatal week to analyze the expression of these gangliosides in chain migration of neuronal precursors. We characterized migrating chains of these neuroblasts through morphological analysis and immunocytochemistry for the neural cell adhesion molecule. By using the Jones monoclonal antibody which binds specifically to 9-O-acGD3 we showed that migrating chains from the SVZ explants express 9-O-acGD3 which is distributed in a punctate manner in individual cells. 9-O-acGD3 is also present in migrating chains that form in the absence of radial glia, typical of the neuronophilic chain migration of the SVZ. Our data indicate that 9-O-acetylated gangliosides may participate in neuronophilic as well as gliophilic migration.

Animals↗

PubMed2000

Migrating neurons cross a reelin-rich territory to form an organized tissue out of embryonic cortical slices.

In this study we show that the radial migration of neuronal precursors out of cerebral cortex of embryonic brain slices cultured for 4-7 days gives rise to an organized tissue that forms de novo off developing slices. In our in vitro preparations, migrating neuronal precursors overshot the marginal zone, as did the elongation of radial glial processes out of the slices. These cells detached from radial glia at a distance from the cortex and differentiated into pyramidal and nonpyramidal profiles that expressed different neuronal markers. Glial precursors were shown to proliferate in the slice and in the neotissue, and to differentiate into astrocytes. We show that cells expressing reelin in the marginal zone of embryonic cortical slices persist after a week in culture, which implies that neuronal migration is not necessarily hindered by the presumed stop signals provided by reelin in the marginal zone. Furthermore, our results provide a new model for in vitro studies of migration and differentiation during cortical development.

Animals↗

PubMed1997

Callosal neurons in the cingulate cortical plate and subplate of human fetuses.

Given the scarcity of data on the development of the cerebral cortex and its connections in man, four brains of human fetuses at 25, 26, 30, and 32 weeks postovulation were used to investigate the following: 1) the radial distribution of callosal neurons in the cingulate cortex at the immediate postmigratory period; 2) the existence of callosally projecting neurons in the cortical subplate; and 3) the dendritic morphology of developing callosal neurons. The carbocyanine dye (1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate) (DiI) was used as a fluorescent postmortem tracer for the identification and morphological description of callosal neurons, 4-6 months after the insertion of DiI crystals at the callosal midplane. Sixty-one completely labeled neurons were selected for microscopical analysis, drawn by use of a camera lucida and photographed. The main findings were the following: 1) the human cingulate cortex at 25-32 weeks postovulation contains callosally projecting neurons both in the cortical plate and in the subplate; 2) callosal cells in the plate are mostly spiny pyramids with somata distributed uniformly throughout the depth of the plate, irrespective of rostrocaudal position. They have well-differentiated basal dendrites and apical dendrites that consistently ramify within layer 1; 3) subplate callosal cells are smooth neurons of diverse dendritic morphology, distributed widely throughout the subplate depth. They were classified into four cell types according to the dendritic morphology: radially oriented, horizontally oriented, multipolars, and inverted pyramids. These findings extend to the human brain some of the evidence obtained in animals concerning the development of the cerebral cortex, especially those that are relevant to the formation of a transitory circuitry in the subplate.

Cerebral Cortex↗

PubMed1992

Bicommissural neurones in the cerebral cortex of developing hamsters.

The trajectory, developmental time course, and origin of callosal fibres that recross through the anterior commissure were studied in developing hamsters, using carbocyanines in fixed brains on different ages. The bicommissural fibres were found in hamsters from E15 through P7, but disappeared after P7. By double labelling it was found that the neurones of origin of these bicommissural fibres were located in the lateral cortex within the region where the callosal zone of origin overlaps that of the anterior commissure. From these experiments, it was concluded that the axons of a group of cells in the lateral cortex of developing rodents are branched and grow transiently through both the callosum and the anterior commissure.

Animals↗

PubMed1990

Neurogenesis and development of callosal and intracortical connections in the hamster.

The developmental time-course of callosal and ipsilateral corticocortical projections was studied in embryonic and postnatal hamsters, from the time of neurogenesis until the appearance of adult patterns. Callosal neurogenesis was determined by combining the incorporation of [3H]thymidine injected on specific embryonic days with retrograde labelling of callosal neurons in the adult animal. The development of both callosal and corticocortical projections was studied by the transport of wheat germ agglutinin conjugated to horseradish peroxidase. Despite a significant radial disperson of postmigratory neurons born on the same day, it was found that the birthdates of callosally-projecting neurons in the frontal cortex were not restricted to a short period of time, but extended between embryonic days 13 and 15. This period covers the neurogenesis of cells in cortical layers III-V. Elongation of callosal axons (and possibly also of corticocortical fibres) started a couple of days before birth in the frontal cortex, and continued through the first postnatal days. After a "waiting period" of a few days, axons from both sets of projections were seen innervating restricted target sectors of the cortex. The zones of origin of these projections were initially exuberant, but were subsequently trimmed to overlap completely with the corresponding terminal fields. It is concluded that callosal and ipsilateral corticocortical projections undergo similar sequences of ontogenetic stages, suggesting that the development of neocortical connectivity as a whole may be governed by one and the same set of rules.

Animals↗

PubMed1988

The development of callosal and corticocortical innervation in the neocortex of the hamster.

The development of cortical afferentation by callosal and ipsilateral corticocortical fibers was studied in hamsters by transport of wheat germ agglutinin conjugated to horseradish peroxidase. Elongation of callosal axons (and possibly also of corticocortical fibers) started a couple of days before birth and extended through the first postnatal days. After a "waiting" period of a few days, axons were seen innervating restricted target sectors of the cortex. The zones of origin of these projections were initially exuberant, but they were subsequently trimmed down to overlap with the corresponding terminal fields.

Afferent Pathways↗

PubMedDate not supplied

Morphogenesis of callosal arbors in the parietal cortex of hamsters.

The morphogenesis of callosal axons originating in the parietal cortex was studied by anterograde labeling with Phaseolus lectin or biocytin injected in postnatal (P) hamsters aged 7-25 days. Some labeled fibers were serially reconstructed. At P7, some callosal fibers extended as far as the contralateral rhinal fissure, with simple arbors located in the homotopic region of the opposite cortical gray matter, and two or three unbranched sprouts along their trajectory. From P7 to P13, the homotopic arbors became more complex, with branches focused predominantly, but not exclusively, in the supra- and infragranular layers of the homotopic region. Simultaneously, the lateral extension of the trunk axon in the white matter became shorter, finally disappearing by P25. Arbors in the gray matter were either bilaminar (layers 2/3 and 5) or supragranular. A heterotopic projection to the lateral cortex was consistently seen at all ages; the heterotopic arbors follow a similar sequence of events to that seen in homotopic regions. These observations document that callosal axons undergo regressive tangential remodeling during the first postnatal month, as the lateral extension of the trunk fiber gets eliminated. Radially, however, significant arborization occurs in layer-specific locations. The protracted period of morphogenesis suggests a correspondingly long plastic period for this system of cortical fibers.

Animals↗