Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “cortical development”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 577 records · Page 32Linked to original sources

Survival of Cajal-Retzius cells after cortical lesions in newborn mice: a possible role for Cajal-Retzius cells in brain repair.

Transient Cajal-Retzius (CR) cells in layer I of the mammalian cerebral cortex are the first postmitotic neurons and they are believed to play a role in neuronal migration and lamination during cortical development. Freezing insults to the cortex of newborn mice produce cortical malformations similar to those observed in human brain disorders. Here we have used calretinin immunostaining to investigate the response of CR cells to freezing lesions of the cortical surface. Shortly after injury, CR cells disappeared from the lesioned zone. Moreover, CR cells located near the lesioned area adopted extremely fusiform shapes. At later postnatal stages (P12), CR cells were still abundant in layer I of the lesioned zone, in contrast to their almost complete loss in control animals. These results show that CR cells survive for longer developmental periods following cortical injury. Furthermore, the initial loss and later re-appearance of CR cells suggest that these neurons might migrate tangentially from the cortical areas surrounding the lesioned zone. These findings imply a role for CR cells in brain repair after cortical injury during development.

Animals↗

Prenatal exposure to thalidomide, altered vasculogenesis, and CNS malformations.

Malformations of cortical development (MCD) result from abnormal neuronal positioning during corticogenesis. MCD are believed to be the morphological and perhaps physiological bases of several neurological diseases, spanning from mental retardation to autism and epilepsy. In view of the fact that during development, an appropriate blood supply is necessary to drive organogenesis in other organs, we hypothesized that vasculogenesis plays an important role in brain development and that E15 exposure in rats to the angiogenesis inhibitor thalidomide would cause postnatal MCD. Our results demonstrate that thalidomide inhibits angiogenesis in vitro at concentrations that result in significant morphological alterations in cortical and hippocampal regions of rats prenatally exposed to this vasculotoxin. Abnormal neuronal development was associated with vascular malformations and a leaky blood-brain barrier. Protein extravasation and uptake of fluorescent albumin by neurons, but not glia, was commonly associated with abnormal cortical development. Neuronal hyperexcitability was also a hallmark of these abnormal cortical regions. Our results suggest that prenatal vasculogenesis is required to support normal neuronal migration and maturation. Altering this process leads to failure of normal cerebrovascular development and may have a profound implication for CNS maturation.

Action Potentials↗

Matching the modules: cortical maps and long-range intrinsic connections in visual cortex during development.

Visual cortical neurons exhibit a high degree of response selectivity and are grouped into small columns according to their response preferences. The columns are located at regularly spaced intervals covering the whole cortical representation of the visual field with a modular system of feature-selective neurons. The selectivity of these cells and their modular arrangement is thought to emerge from interactions in the network of specific intracortical and thalamocortical connections. Understanding the ontogenesis of this complex structure and contributions of intrinsic and extrinsic, experience-dependent mechanisms during cortical development can provide new insights into the way the visual cortex processes information about the environment. Available data about the development of connections and response properties in the visual cortex suggest that maturation proceeds in two distinct steps. In the first phase, mechanisms inherent to the cortex establish a crude framework of interconnected neural modules which exhibit the basic but still immature traits of the adult state. Relevant mechanisms in this phase are assumed to consist of molecular cues and patterns of spontaneous neural activity in cortical and corticothalamic interconnections. In a second phase, the primordial layout becomes refined under the control of visual experience establishing a fine-tuned network of connections and mature response properties.

Animals↗

A small step for the cell, a giant leap for mankind: a hypothesis of neocortical expansion during evolution.

The more than 1000-fold increase in the cortical surface without a comparable increase in its thickness during mammalian evolution is explained in the context of the radial-unit hypothesis of cortical development. According to the proposed model, cortical expansion is the result of changes in proliferation kinetics that increase the number of radial columnar units without changing the number of neurons within each unit significantly. Thus, mutation of a regulatory gene(s) that controls the timing and ratio of symmetric and asymmetric modes of cell divisions in the proliferative zone, coupled with radial constraints in the distribution of migrating neurons, could create an expanded cortical plate with enhanced capacity for establishing new patterns of connectivity that are validated through natural selection.

Animals↗

Migration of cortical neurons is altered by gestational exposure to ethanol.

Rats prenatally exposed to ethanol exhibit a variety of structural anomalies in the central nervous system. One of the key features of experimental fetal alcohol syndrome is microencephaly. Cerebral cortex is particularly susceptible to the effects of prenatal exposure to ethanol. Its total mass is reduced, it is thinner, and it contains fewer neurons and glia. Various studies in rats and humans suggest that chronic early exposure to ethanol leads to a massive reorganization of cortex characterized by heterotopic clusters of neurons. A pulse and chase study with [3H]thymidine autoradiography was used to determine if gestational exposure to ethanol leads to defects in neuronal migration. Rats were fed an ethanol-containing diet between gestational day (G) 6 and G21, pair-fed a liquid control diet, or fed chow. Ethanol delayed the migration of early-generated neurons (those born on G13) to deep cortex by 2 days. Moreover, the migration of late-generated neurons (those born on G21) was delayed 4 to 6 days by ethanol, and often these neurons terminated their migration in ectopic locations. Ethanol significantly decreased the rate of migration and the time postmitotic cells remained in the proliferative zones. On the other hand, ethanol did not have a significant effect on the rate of cortical expansion and the fraction of cells that left the proliferating population in order to migrate to cortex. Thus, the migration of young neurons was profoundly altered by prenatal exposure to ethanol. Such delays may lead to a desynchronization of cortical development that makes it impossible for cortical neurons to establish a normal circuitry.

Animals↗

The role of pattern vision in the development of cortico-cortical connections.

The development of cortico-cortical connections was studied in kittens deprived of vision by binocular eyelid suture during the formation of axonal arbors and synaptogenesis, i.e. between the second postnatal week and the end of the third postnatal month. Axons originating in area 17 and terminating either in ipsilateral or contralateral visual areas were visualized with biocytin. In ipsilateral areas 17 and 18, distinct clusters of branches begin to form, distally from the injection, during the second half of the first postnatal month, independently of pattern vision. More proximal clusters differentiate during the second postnatal month, and this seems to involve elimination of exuberant axonal branches. In kittens deprived of vision for 3 or more months, beginning before natural eye opening, the distal clusters regress and the proximal ones fail to differentiate. In extrastriate areas, distinct clusters of branches have segregated by the end of the second postnatal month, independently of visual experience; however, in kittens deprived of vision for 2 or more months, one of the clusters was selectively eliminated. In contralateral areas 17 and 18, we found stunted terminal arbors in kittens continuously deprived of vision. This was already noticeable at the end of the first postnatal month. Apparently, in the absence of pattern vision, most axons undergo only limited growth and do not form their characteristic terminal columns. Many of these axons are subsequently eliminated. In contrast, 8 days of vision beginning at natural eye opening and followed by visual deprivation caused a nearly normal development of intrahemispheric and interhemispheric connections. In conclusion, pattern vision appears to validate connections at early stages of their development; this validation is necessary for their further growth and differentiation that can then continue autonomously.

Animals↗

Developmental expression of chick cortical GABA(A) receptor alpha1 subunits in vivo and in vitro.

In order to examine the expression of the GABA(A) receptor alpha1 subunit during chick cortical development in vivo and in vitro, we have utilized a polyclonal antibody (RP4) directed against an alpha1(331-381) fusion protein. This antibody exhibits a high titer for precipitation of [3H]flunitrazepam binding sites in chick cortical extracts, no significant cross-reactivity with GABA(A) receptor beta2- or beta4-subunit fusion proteins, and a robust reaction with a single 51-kDa polypeptide on immunoblots of cortical membranes. This indicates monospecificity of the RP4 antiserum for the GABA(A) receptor alpha1 subunit. The alpha1-subunit antibody also showed strong immunocytochemical reactions with neurons in the embryonic mediodorsal cortex and Purkinje cells of the chick cerebellum. The ontogeny of the alpha1 subunit in chick cortex and in derived neuronal cultures was examined by quantitative Western blotting. The level of the alpha1 polypeptide increased from day 2 to day 6 in culture, acquiring 50% of the maximum expression at day 4. Expression of the cortical GABA(A) receptor alpha1 subunit increased in vivo from embryonic day 8 (E8) to day 7 post-hatching, reaching 50% of adult levels at E16. Levels of the corresponding alpha1-subunit mRNA, analyzed from E8 to E20 by quantitative reverse-transcriptase polymerase chain reaction (RT-PCR), showed a corresponding incline. These findings correlated well with previous developmental studies of GABA(A) receptor ligand binding sites both in vivo and in vitro. The parallel increase of the alpha1 subunit transcript and polypeptide with [3H]flunitrazepam binding sites suggests that this subunit may be an important component of GABA(A) receptors early in cortical ontogeny. This was investigated further by quantitative immunoprecipitation. At saturation, the RP4 antiserum consistently precipitated 50-65% of the central [3H]flunitrazepam binding sites in the developing cortex from E12 through P7, despite a 5-fold increase in the binding level. The data suggest that during cortical development the fraction of GABA(A) receptors containing alpha1 subunits remains relatively constant. Furthermore, the alpha1 polypeptide appears to be a major component of GABA(A) receptor oligomers at all stages of cortical maturation.

Animals↗

Normal anatomy of the developing fetal brain. Ex vivo anatomical-magnetic resonance imaging correlation.

Fetal brain Magnetic Resonance Imaging (MRI) is a new technique of growing interest, with a high potential to detect prenatal central nervous system abnormalities. This requires an accurate knowledge of the normal morphological sequence of brain development. In this paper we studied the cortical development of post-mortem normal fetal brains, correlating MRI estimations of fetal age with in vitro anatomical and anthropometric measurements. Ten post-mortem fetal heads were submitted to MRI. Maturational state of sulci and gyri and gray-white matter differentiation were analysed in the MRIs and by dissection of the brains. The findings were correlated with the previously estimated ages of the fetuses, which varied between 17 and 38 weeks. Consistency between methods was assessed employing intraclass correlation coefficient and Bland-Altman plots, with a 95% confidence interval. Estimations of fetal age obtained by MRI were very similar to those achieved by anthropometric measurements or by considering anatomical parameters. Gyral development proved to be more precise than gray-white matter differentiation for this purpose. Fetal MRI proved to be as reliable as the macroscopic anatomical examination for depicting normal cortical developmental sequence and age, suggesting that this technique may be a suitable option for achieving precise information about the morphology of human brains along the gestational period.

Aging↗

Developmental expression of the immediate early gene EGR-1 mirrors the critical period in cat visual cortex.

Immediate early gene (IEG) expression in the central nervous system is thought to play a role in coupling extracellular stimulation with the transcriptional events responsible for long-term functional changes in neurons. The goal of the present study was to determine the postnatal developmental profile of EGR-1 protein (also termed zif268, Krox-24, NGFI-A) expression across the layers of cal visual cortex and relate it to the state of visual cortical development and plasticity. Using a polyclonal antibody, EGR-1 immunoreactivity was studied in animals of various postnatal ages (from 0.5 week to adult). In very young animals (0.5 weeks), EGR-1 positive cells were restricted to deep cortical layers (layer VI/Subplate). With the increasing age, EGR-1 immunoreactivity spread across layers of the visual cortex in an inside-outside manner, and by 5 weeks of age, EGR-1 protein was highly expressed in all layers. EGR-1 expression remained high until approximately 10 weeks of age and then gradually began to decline in layer IV with little change in supra- and infragranular layers. In adult animals, EGR-1 was located predominantly in the layers above and below layer IV. This pattern of EGR-1 expression in developing cat visual cortex has both temporal and laminar similarities with the development of visual cortical connectivity, with the development of orientation selective receptive field properties, and with the level of visual cortical plasticity, suggesting an involvement of EGR-1 expression in these processes.

Animals↗

Pax6 controls cerebral cortical cell number by regulating exit from the cell cycle and specifies cortical cell identity by a cell autonomous mechanism.

Many cerebral cortical neurons and glia are produced by apical progenitors dividing at the ventricular surface of the embryonic dorsal telencephalon. Other neurons are produced by basal progenitor cells, which are derived from apical progenitors, dividing away from the ventricular surface. The transcription factor Pax6 is expressed in apical progenitors and is downregulated in basal progenitors, which upregulate the transcription factor Tbr2. Here we show that Pax6(-/-) cells are under-represented in the cortex of Pax6(+/+)<-->Pax6(-/-) chimeras early in corticogenesis, indicating that Pax6 is required for the production of normal numbers of cortical cells. We provide evidence that this underproduction is attributable to an early depletion of the progenitor pool caused by greater than normal proportions of newly divided cells exiting the cell cycle. We show that most progenitor cells dividing away from the ventricular surface in Pax6(-/-) embryos fail to express the transcription factor Tbr2 and that Pax6 is required cell autonomously for Tbr2 expression in the developing cortex of Pax6(+/+)<-->Pax6(-/-) chimeras. Transcription factors normally expressed ventrally in the telencephalic ganglionic eminences (Mash1, Dlx2 and Gsh2) are upregulated cell autonomously in mutant cells in the developing cortex of Pax6(+/+)<-->Pax6(-/-) chimeras; Nkx2.1, which is expressed only in the medial ganglionic eminence, is not. These data indicate that early functions of Pax6 in developing cortical cells are to repress expression of transcription factors normally found in the lateral ganglionic eminence, to prevent precocious differentiation and depletion of the progenitor pool, and to induce normal development of cortical basal progenitor cells.

Animals↗

Microdysgenesis in epilepsy.

Microdysgenesis is a microscopic malformation of cortical development characterized by heterotopic neurones and abnormal cortical architecture. It has been described in primary generalized and partial epilepsy. Its significance in epileptogenesis is controversial, partly due to lack of consensus of diagnostic criteria. Different terms have also been used for the malformation. Several quantitative studies have been performed of the histopathological aberrations associated with microdysgenesis. A majority of the studies have revealed an increased number of heterotopic neurones in specimens from epilepsy patients. However, the quantitative values given for abnormal numbers of white matter neurones vary greatly between studies and there is no consensus yet on quantitative criteria for microdysgenesis. There have also been conflicting results from studies correlating microdysgenesis with clinical data. Both favourable and worse outcome after epilepsy surgery have been reported in patients with increased numbers of white matter neurones and microdysgenesis. While some studies have shown earlier seizure onset and increased frequency of mental retardation in patients with microdysgenesis, others have not. Differences in inclusion criteria and definition might contribute to the contradictory results. There is some evidence that microdysgenesis could be important in epileptogenesis, but the mechanisms involved remain unknown and difficult to investigate. A consensus on what histopathological criteria to use for the diagnosis of microdysgenesis is needed to explore this further and enable comparisons between centres. There are advantages and disadvantages both with quantitative stereological and with qualitative assessments. It is necessary to evaluate these in the decision on diagnostic criteria, if possible taking both qualitative and quantitative aspects into account.

Cerebral Cortex↗

Development of AChE-positive neuronal projections from basal forebrain to cerebral cortex in organotypic tissue slice cultures.

Development of the innervation of the cerebral cortex by acetylcholinesterase (AChE)-stained basal forebrain neurons was studied in vitro using the roller tube technique. Slice cultures were maintained from 3 days to 4 weeks either in serum based medium or in chemically defined medium, each supplemented in some cases with nerve growth factor (NGF). The distribution of AChE and choline acetyltransferase (CAT)-containing neurons was investigated using histo- and immunocytochemical techniques. Slice cultures of basal forebrain revealed the presence of large and medium sized AChE-positive neurons. Within one week of cultivation, numerous AChE-labeled fibers could be seen growing out from the basal forebrain toward the cortex. After entering cortical tissue most of the afferent basal forebrain fibers projected either radially or obliquely into the cortical layers. Many afferent axons initially also travelled tangentially within the white matter, and turned then to grow into the cortical layers. Cerebral cortex tissue maintained a coarse laminar organization. Ramifications of basal forebrain fibers were visible within the subplate region, the deep and superficial cortical layers, and within the marginal zone; greatest density occurred in the subplate region and in marginal zones. Many of these processes exhibited branching patterns markedly similar to those observed during cortical development in vivo. Cortex slices placed with the pial surface adjacent to the basal forebrain revealed AChE-stained fibers that entered the cortical tissue through the marginal surface and gave off ramifications within the superficial layers and, less frequently, the deeper cortical layers. CAT-immunostaining revealed labeled cell bodies and neurites only in the basal forebrain, not in the cortex tissue. Control experiments with co-cultures of basal forebrain and cerebellum slices showed no AChE-positive fiber ingrowth into the cerebellum tissue. The results of these studies demonstrate that basal forebrain projections to cerebral cortex in vitro appear similar to the projections that develop in vivo, and indicate that organotypic co-cultures provide a valuable model for studies of developing cortical afferents.

Acetylcholinesterase↗

Visual deprivation effects on the s100beta positive astrocytic population in the developing rat visual cortex: a quantitative study.

After birth, exposure to visual inputs modulates cortical development, inducing numerous changes of all components of the visual cortex. Most of the cortical changes thus induced occur during what is called the critical period. Astrocytes play an important role in the development, maintenance and plasticity of the cortex, as well as in the structure and function of the vascular network. Dark-reared Sprague-Dawley rats and age-matched controls sampled at 14, 21, 28, 35, 42, 49, 56 and 63 days postnatal (dpn) were studied in order to elucidate quantitative differences in the number of positive cells in the striate cortex. The astrocytic population was estimated by immunohistochemistry for S-100beta protein. The same quantification was also performed in a nonsensory area, the retrosplenial granular cortex. S-100beta positive cells had adult morphology in the visual cortex at 14 dpn and their numbers were not significantly different in light-exposed and nonexposed rats up to 35 dpn, and were even higher in dark-reared rats at 21 dpn. However, significant quantitative changes were recorded after the beginning of the critical period. The main finding of the present study was the significantly lower astroglial density estimated in the visual cortex of dark-reared rats over 35 dpn as well as the lack of difference at previous ages. Our results also showed that there were no differences when comparing the measurements from a nonsensory area between both groups. This led us to postulate that the astrocytic population in the visual cortex is downregulated by the lack of visual experience.

Animals↗

Immunological characterization of cortical rod proteins of kuruma prawn, Marsupenaeus japonicus.

The penaeid shrimp develops cortical rods (CRs) in the oocyte after completing yolk accumulation during ovarian maturation. In this study, CRs from the mature ovary of the kuruma prawn (Marsupenaeus japonicus) were isolated and their proteins were characterized. Under reducing conditions of SDS-PAGE, the CR demonstrated five major bands of approximately 210, 150, 140, 130 and 30 kDa. Of 32 clones of monoclonal antibodies raised against the CR proteins, 21 were found to be immunoreactive by Western blotting, demonstrating 150, 140 and 130 kDa proteins simultaneously. This result suggested that the proteins were post-translational or post-transcriptional products from the same gene, or that they originated from the same gene family. CRs were identified by immunohistochemical analysis by 31 clones of monoclonal antibodies in paraffin sections and by 26 clones in cryostatic ones. Most of the antibodies also stained the yolk in both developing and mature oocytes, suggesting that CR proteins accumulated in developing oocytes, then assembled to form the CR structure.

Animals↗

Multiple defects in the formation of rat cortical axonal pathways following prenatal X-ray irradiation.

Prenatal X-ray irradiation is known to result in severe defects of neuronal migration and laminar formation in the cerebral cortex. We examined the formation of cortical afferent and efferent pathways in rats that had been exposed to X-ray irradiation (1.0 Gy) at embryonic day 14 (E14), by birthdating with bromodeoxyuridine (BrdU) and axonal labeling with 1-1'-dioctodecyl-3,3,3',3'- tetramethyl-indocarbocyanine perchlorate (DiI), in addition to immunohistochemical staining for various axonal markers including neurofilament, and cell adhesion molecules L1 and TAG-1. The results obtained were as follows. (i) The neuroepithelium formed germinal rosettes and concavities in the cortical anlage from 2 days after irradiation. Neurons generated in the neuroepithelium accumulated to form subcortical heterotopia and obstructed pathway formation in the intermediate zone, resulting in an aberrant trajectory of TAG-1-immunoreactive cortical efferent axons. (ii) In rats exposed to X-ray irradiation at E14, cystic cavities were formed in the cortex-striatum boundary region between E15 and E17, probably because of delayed cell death of neurons generated at E14. These cavities transiently interrupted both cortical afferent (L1-positive) and efferent (TAG-1-positive) axons. (iii) X-ray irradiation at E14 partially destroyed subplate neurons (transient targets of thalamic afferent axons) and disturbed the arrangement of the subplate layer. This resulted in a misrouting of neurofilament- and L1-immunoreactive thalamocortical axons that obliquely traversed the cortical plate to run up to the superficial layer. The present study demonstrates for the first time that X-ray irradiation during initial cortical development causes multiple defects in the formation of cortical afferent and efferent pathways.

Age Factors↗

Developmental changes in integrin beta-subunits in rat cerebral cortex.

The present study was carried out to characterize the developmental expression of beta 1-, beta 5- and beta 6-integrin subunits in rat cerebral cortex. Using reverse transcriptase-polymerase chain reaction, mRNA of the three beta-subunits were shown to be present at all developmental stages. Based on immunoblots, beta 1-subunit expression was decreased during cortical development from embryonic stages to adults. beta 6-subunit expression appeared only in adult cortex. beta 5-subunit expression did not change during development. These beta-subunits were expressed in cortical embryonic cells as revealed by immunological studies in vitro. beta 5 and beta 6 were also present in neuronal cells and in oligodendrocytes in adult cortex. Altogether, these results demonstrate that rat cerebral cortex expresses distinct integrin beta-subunits with different developmental profiles. This switch of beta-subunits may be an important mechanism for the regulation of cell behaviour during development.

Animals↗

Expression of coiled-coil protein 1, a novel gene downstream of FGF2, in the developing brain.

Fibroblast growth factor 2 (FGF2) plays an important role in cortical development. However, the genes downstream of FGF2 that mediate its effect are largely unknown. We have performed a microarray screening of genes regulated by FGF2 using primary cortical neuron culture derived from embryonic day 14.5 (E14.5) mouse forebrains. In this study, we have analysed a previously uncharacterised gene encoding a 180-amino acid protein, hereby named 'coiled-coil protein 1 (ccp1)', that showed a modest up-regulation upon FGF2 stimulation. Northern blots and RT-PCR showed specific expression of ccp1 in multiple tissues including adult and embryonic brains. In situ hybridizations revealed that ccp1 was expressed in the cortical plate between Reelin and Tbr1-positive layers in the dorsal cortex at E15.5. Furthermore, the expression pattern of ccp1 at E13.5-E14.5 reflected some of the aspects of tangential migration of cortical progenitors during the early phase. We observed that the expressed ccp1 protein was localised to endo/lysosomal compartment in the cell body as well as to vesicles present in the processes of primary cortical neurons and oligodendrocyte cell line.

Amino Acid Motifs↗

Cerebral cortex thickness in 15-year-old adolescents with low birth weight measured by an automated MRI-based method.

Infants with low birth weight are at increased risk of perinatal brain injury. Disruption of normal cortical development may have consequences for later motor, behavioural and cognitive development. The aim of this study was to measure cerebral cortical thickness, area and volume with an automated MRI technique in 15-year-old adolescents who had low birth weight. Cerebral MRI for morphometric analysis was performed on 50 very low birth weight (VLBW, birth weight </=1500 g), 49 term small for gestational age births (SGA, birth weight <10th percentile at term) and 58 control adolescents. A novel method of cortical surface models yielded measurements of cortical thickness and area for each subject's entire brain and computed cross-subject statistics based on cortical anatomy. The cortical surface models demonstrated regional thinning of the parietal, temporal and occipital lobes in the VLBW group, whereas regional thickening was demonstrated in the frontal and occipital lobes. The areas of change were greatest in those with the shortest gestational age at birth and lowest birth weight. Cortical surface area and cortical volume were lower in the VLBW than in the Control group. Within the VLBW group, there was an association between surface area and estimation of the intelligence quotient IQ (IQ(est)) and between cortical volume and IQ(est). Furthermore, cortical grey matter as a proportion of brain volume was significantly lower in the VLBW, but not in the SGA group compared with Controls. This observed reorganization of the developing brain offers a unique opportunity to investigate any relationship between changes in cortical anatomy and cognitive and social impairments, and the increase in psychiatric disorders that have been found in VLBW children and adolescents.

Adolescent↗