Cortical Mantle (cortical + mantle)

Distribution by Scientific Domains

Selected Abstracts

Cortical radial glial cells in human fetuses: Depth-correlated transformation into astrocytes

Leonardo C. deAzevedo
Abstract In the human brain, the transformation of radial glial cells (RGC) into astrocytes has been studied only rarely. In this work, we were interested in studying the morphologic aspects underlying this transformation during the fetal/perinatal period, particularly emphasizing the region-specific glial fiber anatomy in the medial cortex. We have used carbocyanine dyes (DiI/DiA) to identify the RGC transitional forms and glial fiber morphology. Immunocytochemical markers such as vimentin and glial fibrillary acidic protein (GFAP) were also employed to label the radial cells of glial lineage and to reveal the early pattern of astrocyte distribution. Neuronal markers such as neuronal-specific nuclear protein (NeuN) and microtubule-associated protein (MAP-2) were employed to discern whether or not these radial cells could, in fact, be neurons or neuronal precursors. The main findings concern the beginning of RGC transformation showing loss of the ventricular fixation in most cases, followed by transitional figures and the appearance of mature astrocytes. In addition, diverse fiber morphology related to depth within the cortical mantle was clearly demonstrated. We concluded that during the fetal/perinatal period the cerebral cortex is undergoing the final stages of radial neuronal migration, followed by involution of RGC ventricular processes and transformation into astrocytes. None of the transitional or other radial glia were positive for neuronal markers. Furthermore, the differential morphology of RGC fibers according to depth suggests that factors may act locally in the subplate and could have a role in the process of cortical RGC transformation and astrocyte localization. The early pattern of astrocyte distribution is bilaminar, sparing the cortical plate. Few astrocytes (GFAP+) in the upper band could be found with radial processes at anytime. This suggests that astrocytes in the marginal zone could be derived from different precursors than those that differentiate from RGCs during this period. © 2003 Wiley Periodicals, Inc. J Neurobiol 55: 288,298, 2003 [source]

Therapeutic effects of complex rearing or bFGF after perinatal frontal lesions

Wendy Comeau
Abstract We investigated the effects of an enriched environment and/or basic fibroblast growth factor (bFGF) on recovery from neonatal frontal injury in rats. Rats received medial frontal lesions, or sham surgery, on postnatal day (P) 2/3. In the first set of experiments (Experiments 1 and 2), rats were housed in enriched environments that consisted of a large enclosure with multiple objects (or standard housing) for 90 days beginning at weaning (P22) or in adulthood (P110). In Experiment 3, the rats either received 7 days of subcutaneous bFGF beginning on the day after surgery or bFGF plus enriched housing beginning at weaning. After the 90-day housing period, the animals were tested on a spatial navigation task and a skilled reaching task. Early lesions of the medial frontal cortex caused severe impairments in spatial learning but this deficit was markedly reduced with enriched housing, bFGF, or a combination of both, with the latter being most effective. The housing effects varied with age, however: the earlier the experience began, the better the outcome. Enriched housing increased dendritic length in cortical pyramidal neurons, an effect that was greater in the lesion than the control animals, and enriched housing reversed the lesion-induced decrease in spine density. Enriched environment increased the thickness of the cortical mantle in both lesion and controls whereas bFGF had no effect. Experience thus can affect functional and anatomical outcome after early brain injury but the effects vary with age at experience and may be facilitated by treatment with bFGF. © 2008 Wiley Periodicals, Inc. Dev Psychobiol 50: 134,146, 2008. [source]

Cognitive function, P3a/P3b brain potentials, and cortical thickness in aging

Anders M. Fjell
Abstract The purpose of the study was to assess the relationship between the P3a/P3b brain potentials, cortical thickness, and cognitive function in aging. Thirty-five younger and 37 older healthy participants completed a visual three-stimuli oddball ERP (event-related potential)-paradigm, a battery of neuropsychological tests, and MRI scans. Groups with short vs. long latency, and low vs. high amplitude, were compared on a point by point basis across the entire cortical mantle. In the young, thickness was only weakly related to P3. In the elderly, P3a amplitude effects were found in parietal areas, the temporoparietal junction, and parts of the posterior cingulate cortex. P3b latency was especially related to cortical thickness in large frontal regions. Path models with the whole sample pooled together were constructed, demonstrating that cortical thickness in the temporoparietal cortex predicted P3a amplitude, which in turn predicted executive function, and that thickness in orbitofrontal cortex predicted P3b latency, which in turn predicted fluid function. When age was included in the model, the relationship between P3 and cognitive function vanished, while the relationship between regional cortical thickness and P3 remained. It is concluded that thickness in specific cortical areas correlates with scalp recorded P3a/P3b in elderly, and that these relationships differentially mediate higher cognitive function. Hum Brain Mapp 2007. © 2007 Wiley-Liss, Inc. [source]

In Vivo Visualization of Senile-Plaque-Like Pathology in Alzheimer's Disease Patients by MR Microscopy on a 7T System

Tsutomu Nakada MD
ABSTRACT BACKGROUND Microscopic application of magnetic resonance imaging (MRI) has entered the era of clinical application. One of the most important targets is the visualization of pathological findings such as senile plaques (SP), in vivo, in patients with Alzheimer's disease (AD). Such an application provides not only the most accurate diagnostic tool for clinicians but also a solid basis for scientists for developing effective treatment and preventive strategies for AD. METHODS Focused microscopic studies were performed on parietal association cortex at the level of the centrum semiovale identified on conventional axial slices using a system constructed based on General Electric Signa LX (Waukesha, WI) equipped with a 900-mm clear bore superconducting magnet operating at 7.0 T in 10 patients (67-83-year old, five males, five females) who fulfilled the NINCD and the SADRDA criteria for probable AD, 10 age-matched controls (71-85-year old, five males, five females), and 20 young adults (22-35-year old, 10 males, 10 females) using a susceptibility weighted imaging (SWI) algorithm. RESULTS SWI microscopy consistently provided images with SP-like pathology extending within the entire parietal cortex in all cases of AD and 2 out of 10 age-matched volunteers. CONCLUSIONS Although the precise mechanisms leading to the higher susceptibility rendering SP-like pathology observable within the cortical mantle are not totally understood, the study unambiguously demonstrated that MR microscopy is capable of directly visualizing cortical pathology in AD patients in vivo. [source]

Origins and migratory routes of murine Cajal-Retzius cells

Fernando García-Moreno
Abstract The first layer that appears in the cortical neuroepithelium, the preplate, forms in the upper part of the cortex immediately below the pial surface. In mice, this layer exists between embryonic days (E) 10 and 13, and it hosts different cell populations. Here, we have studied the first cell population generated in the preplate, the Cajal-Retzius cells. There is considerable confusion regarding these cells with respect to both their site of generation and the migratory routes that they follow. This perhaps is due largely to the different opinions that exist regarding their characterization. We have studied the site of origin of these cells, their migratory routes, and the molecular markers that may distinguish them by injecting tracers into early embryos, culturing them in toto for 24 hours, and then performing immunohistochemistry. We found that the Cajal-Retzius cells are most likely generated in the cortical hem by comparing with other cortical or extracortical origins. These cells are generated mainly at E10 and E11, and they subsequently migrate tangentially to cover the whole cortical mantle in 24 hours. From their site of origin in the medial wall of the telencephalon, they spread in a caudorostral direction, following an oblique migratory path toward the lateral part of the neuroepithelium. Prior to the splitting of the preplate, a percentage of the Cajal-Retzius cells that can be distinguished by the expression of reelin do not contain calretinin. Furthermore, there were no early-migrating neurons that expressed calbindin. J. Comp. Neurol. 500:419,432, 2007. © 2006 Wiley-Liss, Inc. [source]