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Bozic I, Savic D, Lavrnja I. Astrocyte phenotypes: Emphasis on potential markers in neuroinflammation. Histol Histopathol 2020; 36:267-290. [PMID: 33226087 DOI: 10.14670/hh-18-284] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Astrocytes, the most abundant glial cells in the central nervous system (CNS), have numerous integral roles in all CNS functions. They are essential for synaptic transmission and support neurons by providing metabolic substrates, secreting growth factors and regulating extracellular concentrations of ions and neurotransmitters. Astrocytes respond to CNS insults through reactive astrogliosis, in which they go through many functional and molecular changes. In neuroinflammatory conditions reactive astrocytes exert both beneficial and detrimental functions, depending on the context and heterogeneity of astrocytic populations. In this review we profile astrocytic diversity in the context of neuroinflammation; with a specific focus on multiple sclerosis (MS) and its best-described animal model experimental autoimmune encephalomyelitis (EAE). We characterize two main subtypes, protoplasmic and fibrous astrocytes and describe the role of intermediate filaments in the physiology and pathology of these cells. Additionally, we outline a variety of markers that are emerging as important in investigating astrocytic biology in both physiological conditions and neuroinflammation.
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Affiliation(s)
- Iva Bozic
- Institute for Biological Research "Sinisa Stankovic", National Institute of Republic of Serbia, University of Belgrade, Belgrade, Serbia
| | - Danijela Savic
- Institute for Biological Research "Sinisa Stankovic", National Institute of Republic of Serbia, University of Belgrade, Belgrade, Serbia
| | - Irena Lavrnja
- Institute for Biological Research "Sinisa Stankovic", National Institute of Republic of Serbia, University of Belgrade, Belgrade, Serbia.
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González-Arnay E, González-Gómez M, Meyer G. A Radial Glia Fascicle Leads Principal Neurons from the Pallial-Subpallial Boundary into the Developing Human Insula. Front Neuroanat 2017; 11:111. [PMID: 29259547 PMCID: PMC5723317 DOI: 10.3389/fnana.2017.00111] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2017] [Accepted: 11/17/2017] [Indexed: 12/29/2022] Open
Abstract
The human insular lobe, in the depth of the Sylvian fissure, displays three main cytoarchitectonic divisions defined by the differentiation of granular layers II and IV. These comprise a rostro-ventral agranular area, an intermediate dysgranular area, and a dorso-caudal granular area. Immunohistochemistry in human embryos and fetuses using antibodies against PCNA, Vimentin, Nestin, Tbr1, and Tb2 reveals that the insular cortex is unique in that it develops far away from the ventricular zone (VZ), with most of its principal neurons deriving from the subventricular zone (SVZ) of the pallial-subpallial boundary (PSB). In human embryos (Carnegie stage 16/17), the rostro-ventral insula is the first cortical region to develop; its Tbr1+ neurons migrate from the PSB along the lateral cortical stream. From 10 gestational weeks (GW) onward, lateral ventricle, ganglionic eminences, and PSB grow forming a C-shaped curvature. The SVZ of the PSB gives rise to a distinct radial glia fiber fascicle (RGF), which courses lateral to the putamen in the external capsule. In the RGF, four components can be established: PF, descending from the prefrontal PSB to the anterior insula; FP, descending from the fronto-parietal PSB toward the intermediate insula; PT, coursing from the PSB near the parieto-temporal junction to the posterior insula, and T, ascending from the temporal PSB and merging with components FP and PT. The RGF fans out at different dorso-ventral and rostro-caudal levels of the insula, with descending fibers predominating over ascending ones. The RGF guides migrating principal neurons toward the future agranular, dysgranular, and granular insular areas, which show an adult-like definition at 32 GW. Despite the narrow subplate, and the absence of an intermediate zone except in the caudal insula, most insular subdivisions develop into a 6-layered isocortex, possibly due to the well developed outer SVZ at the PSB, which is particularly prominent at the level of the dorso-caudal insula. The small size of the initial PSB sector may, however, determine the limited surface expansion of the insula, which is in contrast to the exuberant growth of the opercula deriving from the adjacent frontal-parietal and temporal VZ/SVZ.
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Affiliation(s)
- Emilio González-Arnay
- Unit of Pathology, Department of Basic Medical Science, Faculty of Medicine, University of La Laguna, San Cristóbal de La Laguna, Spain
| | - Miriam González-Gómez
- Unit of Anatomy, Department of Basic Medical Science, Faculty of Medicine, University of La Laguna, San Cristóbal de La Laguna, Spain
| | - Gundela Meyer
- Unit of Histology, Department of Basic Medical Science, Faculty of Medicine, University of La Laguna, San Cristóbal de La Laguna, Spain
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Ortega JA, Memi F, Radonjic N, Filipovic R, Bagasrawala I, Zecevic N, Jakovcevski I. The Subventricular Zone: A Key Player in Human Neocortical Development. Neuroscientist 2017; 24:156-170. [PMID: 29254416 DOI: 10.1177/1073858417691009] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
One of the main characteristics of the developing brain is that all neurons and the majority of macroglia originate first in the ventricular zone (VZ), next to the lumen of the cerebral ventricles, and later on in a secondary germinal area above the VZ, the subventricular zone (SVZ). The SVZ is a transient compartment mitotically active in humans for several gestational months. It serves as a major source of cortical projection neurons as well as an additional source of glial cells and potentially some interneuron subpopulations. The SVZ is subdivided into the smaller inner (iSVZ) and the expanded outer SVZ (oSVZ). The enlargement of the SVZ and, in particular, the emergence of the oSVZ are evolutionary adaptations that were critical to the expansion and unique cellular composition of the primate cerebral cortex. In this review, we discuss the cell types and organization of the human SVZ during the first half of the 40 weeks of gestation that comprise intrauterine development. We focus on this period as it is when the bulk of neurogenesis in the human cerebral cortex takes place. We consider how the survival and fate of SVZ cells depend on environmental influences, by analyzing the results from in vitro experiments with human cortical progenitor cells. This in vitro model is a powerful tool to better understand human neocortex formation and the etiology of neurodevelopmental disorders, which in turn will facilitate the design of targeted preventive and/or therapeutic strategies.
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Affiliation(s)
- J Alberto Ortega
- 1 Department of Neuroscience, University of Connecticut School of Medicine, Farmington, CT, USA
| | - Fani Memi
- 1 Department of Neuroscience, University of Connecticut School of Medicine, Farmington, CT, USA
| | - Nevena Radonjic
- 1 Department of Neuroscience, University of Connecticut School of Medicine, Farmington, CT, USA.,2 Psychiatry Department, University of Connecticut School of Medicine, Farmington, CT, USA
| | - Radmila Filipovic
- 1 Department of Neuroscience, University of Connecticut School of Medicine, Farmington, CT, USA
| | - Inseyah Bagasrawala
- 1 Department of Neuroscience, University of Connecticut School of Medicine, Farmington, CT, USA
| | - Nada Zecevic
- 1 Department of Neuroscience, University of Connecticut School of Medicine, Farmington, CT, USA
| | - Igor Jakovcevski
- 3 Institute for Molecular and Behavioral Neuroscience, University Hospital Cologne, Center for Molecular Medicine Cologne, Cologne, Germany.,4 Experimental Neurophysiology, German Center for Neurodegenerative Diseases, Bonn, Germany
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Howard BM, Zhicheng Mo, Filipovic R, Moore AR, Antic SD, Zecevic N. Radial glia cells in the developing human brain. Neuroscientist 2008; 14:459-73. [PMID: 18467668 DOI: 10.1177/1073858407313512] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Human radial glia (RG) share many of the features described in rodents, but also have a number of characteristics unique to the human brain. Results obtained from different mammalian species including human and non-human primates reveal differences in the involvement of RG in neurogenesis and oligodendrogenesis and in the timing of the initial expression of typical RG immunomarkers. A common problem in studying the human brain is that experimental procedures using modern molecular and genetic methods, such as in vivo transduction with retroviruses or creation of knockout or transgenic mutants, are not possible. Nevertheless, abundant and valuable information about the development of the human brain has been revealed using postmortem human material. Additionally, a combination and spectrum of in vitro techniques are used to gain knowledge about normal developmental processes in the human brain, including better understanding of RG as progenitor cells. Molecular and functional characterization of multipotent progenitors, such as RG, is important for future cell replacement therapies in neurological and psychiatric disorders, which are often resistant to conventional treatments. The protracted time of development and larger size of the human brain could provide insight into processes that may go unnoticed in the much smaller rodent cortex, which develops over a much shorter period. With that in mind, we summarize results on the role of RG in the human fetal brain.
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Abstract
Radial glial (RG) cells have been demonstrated to be a major neural progenitor cell type, but in the human fetal brain, neither their molecular nor their spatiotemporal characteristics are well known. We used glial and neuronal-specific antibodies to determine the antigen characteristics and distribution of RG cells and other neuronal progenitors in the human brain during the first half of intrauterine development. Proliferating RG (4A4+) cells in the ventricular zone (VZ) showed clear caudorostral and ventrodorsal gradients, spreading from the spinal cord to the ventral rhombencephalon, at embryonic stages (4.5-5.5 gestational weeks [gw]). However, in the same embryo, other dividing cells expressed the neuronal marker SMI-31 and were present throughout the entire CNS, including the rostral prosencephalon. At the beginning of cortical neurogenesis (6 gw), proliferating VZ cells labeled either with neuronal markers (SMI-31, MAP2, beta-III-tubulin), double-labeled 4A4(+)/SMI-31+ cells, or cells not labeled with these antibodies, were in close proximity to each other. At midgestation (17-24 gw), RG divisions were less frequent, but were spread throughout the entire cerebral cortex, including the subventricular and intermediate zones and the subpial granular layer. Several subtypes of RG were co-labeled with vimentin and other glial markers (BLBP, GFAP, or GLAST) and quantified in vitro. In conclusion, the diversity of cortical progenitors in the human brain may, in part, explain the unique complexity of the human cerebral cortex.
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Affiliation(s)
- Brian Howard
- Department of Neuroscience, University of Connecticut Health Center, Farmington, CT 06030-3401, USA
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Furuta A, Takashima S, Yokoo H, Rothstein JD, Wada K, Iwaki T. Expression of glutamate transporter subtypes during normal human corticogenesis and type II lissencephaly. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 2005; 155:155-64. [PMID: 15804404 DOI: 10.1016/j.devbrainres.2005.01.005] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2004] [Revised: 01/24/2005] [Accepted: 01/26/2005] [Indexed: 10/25/2022]
Abstract
Glutamate transporters are thought to have an important role in central nervous system (CNS) development. We investigated the expression of the sodium-dependent high-affinity glutamate transporters EAAT1, EAAT2, and EAAT3 in 11 human autopsied cases without neurological disorders and in four cases with type II lissencephaly including Walker Warburg's syndrome (WWS) and Fukuyama-type congenital muscular dystrophy (FCMD), both of which are classified as migration disorders of the human brain. Expression of glutamate transporter subtypes was differentially regulated during normal human corticogenesis. Although EAAT1 and EAAT2 were mainly localized to the cortical astrocytes in the postnatal brain, EAAT1 was enriched in the proliferative zones and radial glia from 13 gestational weeks (GW) to 20 GW. EAAT2 was abundant in the intermediate zone until 23 GW, and transiently expressed in the radial fibers of the transitional form of radial glia into mature astrocytes as well as partly in the corticofugal axonal bundles. EAAT3 immunoreactivity was robust in the apical dendrites of the pyramidal neurons in the marginal zone and cortical plate during corticogenesis, and decreased postnatally. In the individuals with type II lissencephaly, glutamate transporters were expressed in the extrusion of neuroglial tissue. Bundles of EAAT2-immunoreactive radial fibers were prominent in the specimens at 20 GW. Thus, glutamate transporters are differentially regulated during normal and impaired corticogenesis. Altered glutamate transporter expression in type II lissencephaly suggests that glutamate metabolism is involved in the formation of the normal cortex and contributes to the disorganized cortex seen in migration disorders.
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Affiliation(s)
- Akiko Furuta
- Department of Degenerative Neurological Diseases, National Institute of Neuroscience, National Center of Neurology and Psychiatry, 4-1-1, Ogawahigashi, Kodaira, Tokyo 187-8502, Japan.
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Jakovcevski I, Zecevic N. Sequence of oligodendrocyte development in the human fetal telencephalon. Glia 2005; 49:480-91. [PMID: 15578660 DOI: 10.1002/glia.20134] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Oligodendrocytes (OL), cells that myelinate axons in the CNS, differentiate from early to late oligodendrocyte progenitor cells (OPC) to become mature OL. Unlike the case in the rodent brain, myelin formation starts prenatally in the human brain, but the sequence of OL development and the onset of myelination are not well understood. We studied the human fetal forebrain at midgestation (17-23 gestational weeks, g.w.) using OL lineage-specific antibodies and mRNA probes. Early OPC were present in a gradient from the subventricular zone to the cortical plate. Their close apposition to radial glia fibers suggests a possible role of these fibers in OPC migration. Late OPC reached peak density in the subplate layer, whereas multipolar cells with the morphology of mature OL were restricted to the emerging white matter. At 20 g.w., myelinated axons were observed in the diencephalon, but not in the telencephalon, consistent with caudal-to-rostral progression of myelination. Interestingly, in organotypic slice cultures of the same gestational ages, the subventricular zone contained a considerably greater number of the mature OL cells, suggesting the presence of inhibitory signals in vivo. Overall, in addition to considerable similarities with rodents, important differences in temporal and spatial distribution and regulatory signals for OL differentiation exist in the human brain.
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Affiliation(s)
- Igor Jakovcevski
- Department of Neuroscience, University of Connecticut Health Center, Farmington, CT 06030-3401, USA
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Ulfig N, Briese M. Evidence for the presence of the sphingosine-1-phosphate receptor Edg-8 in human radial glial fibers. Acta Histochem 2004; 106:373-8. [PMID: 15530552 DOI: 10.1016/j.acthis.2004.08.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2004] [Revised: 07/20/2004] [Accepted: 08/01/2004] [Indexed: 02/02/2023]
Abstract
The distribution pattern of Edg-8 immunostaining in the human developing brain has been investigated with special reference to radial glial fibers. At 24 weeks of gestation, fragments of radial glial fibers are Edg-8-positive within the cortical plate and subplate of allocortical areas. These Edg-8-positive fragments often appear enlarged as varicosities and some of them terminate at blood vessels. Between 28 and 30 weeks of gestation, all iso- and allocortical areas contain Edg-8-immunolabelled radial glial fibers revealing curvature next to sulci. After 32 weeks of gestation, radial glial fibers gradually disappear; instead Edg-8-positive transitional stages between radial glia and astrocytes were found. The findings indicate that sphingosine-1-phosphate may play a regulatory role in the transformation of radial glial cells into astrocytes and may affect proliferative activity of these cells.
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Affiliation(s)
- Norbert Ulfig
- Department of Anatomy, Neuroembryonic Research Laboratory, University of Rostock, Gertrudenstrasse 9, D-18055 Rostock, Germany.
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9
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Abstract
Phenotypic characteristics of cells in the developing human telencephalic wall were analyzed using electron microscopy and immunocytochemistry with various glial and neuronal cell markers. The results suggest that multiple defined cell types emerge in the neocortical proliferative zones and are differentially regulated during embryonic development. At 5-6 weeks gestation, three major cell types are observed. Most proliferating ventricular zone (VZ) cells are labeled with radial glial (RG) markers such as vimentin, glial fibrillary acidic protein (GFAP), and glutamate astrocyte-specific transporter (GLAST) antibodies. A subpopulation of these RG cells also express the neuronal markers beta III-tubulin, MAP-2, and phosphorylated neurofilament SMI-31, in addition to the stem cell marker nestin, indicating their multipotential capacity. In addition, the presence of VZ cells that immunoreact only with neuronal markers indicates the emergence of restricted neuronal progenitors. The number of multipotential progenitors in the VZ gradually decreases, whereas the number of more restricted progenitors increases systematically during the 3-month course of human corticogenesis. These results suggest that multipotential progenitors coexist with restricted neuronal progenitors and RG cells during initial corticogenesis in the human telencephalon. Since the multipotential VZ cells disappear during the major wave of neocortical neurogenesis, the RG and restricted neuronal progenitors appear to serve as the main sources of cortical neurons. Thus, the diversification of cells in human VZ and overlying subventricular zone (SVZ) begins earlier and is more pronounced than in rodents.
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Affiliation(s)
- Nada Zecevic
- Department of Neuroscience, University of Connecticut School of Medicine, Farmington, Connecticut 06030-3401, USA.
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Fayol L, Baud O, Monier A, Pellerin L, Magistretti P, Evrard P, Verney C. Immunocytochemical expression of monocarboxylate transporters in the human visual cortex at midgestation. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 2004; 148:69-76. [PMID: 14757520 DOI: 10.1016/j.devbrainres.2003.10.010] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Lactate and the other monocarboxylates are a major energy source for the developing brain. We investigated the immunocytochemical expression of two monocarboxylate transporters, MCT1 and MCT2, in the human visual cortex between 13 and 26 post-ovulatory weeks. We used immunoperoxidase and immunofluorescence techniques to determine whether these transporters co-localized with markers for blood vessels (CD34), neurons (microtubule-associated protein 2 [MAP2], SMI 311), radial glia (vimentin), or astrocytes (glial fibrillary acidic protein [GFAP], S100beta protein). MCT1 immunoreactivity was visible in blood vessel walls as early as the 13th week of gestation mainly in the cortical plate and subplate. At this stage, less than 10% of vessels in the ventricular layer expressed MCT1, whereas all blood vessels walls showed this immunoreactivity at the 26th gestational week. Starting at the 19th week of gestation, sparse MCT1 positive cell bodies were detected, some of them co-localized with MAP2 immunoreactivity. MCT2 immunoreactivity was noted in astrocytic cell bodies from week 19 and spread subsequently to the astrocyte end-feet in contact with blood vessels. MCTs immunoreactivities were most marked in the subplate and deep cortical plate, where the most differentiated neurons were located. Our findings suggest that monocarboxylate trafficking between vessels (MCT1), astrocytes (MCT2) and some postmitotic neurons (MCT1) could develop gradually toward 20 gestational weeks (g.w.). These data suggest that lactate or other monocarboxylates could represent a significant energy source for the human visual cortex at this early stage.
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Affiliation(s)
- Laurence Fayol
- INSERM E9935, Hôpital Robert Debré, 48, Bd Sérurier 75019, Paris, France
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deAzevedo LC, Fallet C, Moura-Neto V, Daumas-Duport C, Hedin-Pereira C, Lent R. Cortical radial glial cells in human fetuses: depth-correlated transformation into astrocytes. JOURNAL OF NEUROBIOLOGY 2003; 55:288-98. [PMID: 12717699 DOI: 10.1002/neu.10205] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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.
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Affiliation(s)
- Leonardo C deAzevedo
- Departamento de Anatomia, Instituto de Ciências Biomédicas, C.C.S. Bl. F, Universidade Federal do Rio de Janeiro, 21941-590, R.J., Brazil
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Rezaie P, Ulfig N, Male D. Distribution and Morphology of GFAP-Positive Astrocytes in the Human Fetal Brain at Second Trimester. ACTA ACUST UNITED AC 2003. [DOI: 10.1159/000071021] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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13
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Ulfig N. The Functional Organization of the Developing Human Brain in Relation to Motor Deficits, Cognitive Impairment and Psychotic States. ACTA ACUST UNITED AC 2003. [DOI: 10.1159/000071024] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Ganat Y, Soni S, Chacon M, Schwartz ML, Vaccarino FM. Chronic hypoxia up-regulates fibroblast growth factor ligands in the perinatal brain and induces fibroblast growth factor-responsive radial glial cells in the sub-ependymal zone. Neuroscience 2002; 112:977-91. [PMID: 12088755 DOI: 10.1016/s0306-4522(02)00060-x] [Citation(s) in RCA: 99] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
A number of signaling molecules have been implicated in the acute response to hypoxia/ischemia in the adult brain. In contrast, the reaction to chronic hypoxemia is largely unexplored. We used a protocol of chronic hypoxia in rat pups during the first three postnatal weeks, encompassing the period of cellular plasticity in the cerebral cortex. We find that the levels of fibroblast growth factor 1 (FGF1) and FGF2, two members of the FGF family, increase after 2 weeks of chronic hypoxia. In contrast, members of the neurotrophin family are unaffected. FGF2 is normally expressed in the nucleus of mature, glial fibrillary acidic protein (GFAP)-containing astrocytes. Under hypoxia, most FGF2-containing cells do not express detectable levels of GFAP, suggesting that chronic low O(2) induces their transformation into more immature glial phenotypes. Remarkably, hypoxia promotes the appearance of radial glia throughout the sub-ventricular and ependymal zones. Most of these cells express vimentin and brain lipid binding protein. A subset of these radial glial cells expresses FGF receptor 1, and are in close contact with FGF2-positive cells in the sub-ventricular zone. Thus, FGF receptor signaling in radial glia may foster cell genesis after chronic hypoxic damage. From the results of this study we suggest that after the chronic exposure to low levels of oxygen during development, the expression of radial glia increases in the forebrain periventricular region. We envision that astroglia, which are the direct descendants of radial glia, are reverting back to immature glial cells. Alternatively, hypoxia hinders the normal maturation of radial glia into GFAP-expressing astrocytes. Interestingly, hypoxia increases the levels of expression of FGF2, a factor that is essential for neuronal development. Furthermore, chronic hypoxia up-regulated FGF2's major receptor in the periventricular region. Because radial glia have been suggested to play a key role in neurogenesis and cell migration, our data suggests that hypoxia-induced FGF signaling in radial glia may represent part of a conserved program capable of regenerating neurons in the brain after injury.
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Affiliation(s)
- Y Ganat
- Child Study Center, Yale University, 230 South Frontage Road, New Haven, CT 06520, USA
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15
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Ulfig N. Ganglionic eminence of the human fetal brain--new vistas. THE ANATOMICAL RECORD 2002; 267:191-5. [PMID: 12115267 DOI: 10.1002/ar.10104] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
This review deals with recent findings concerning the complex functions of the ganglionic eminence (GE), which represents a conspicuous domain of the telencephalic proliferative zone and persists nearly throughout fetal life. The GE not only contains precursor neurons of the basal ganglia, it also contributes significantly to the population of interneurons in the cerebral cortex and to a population of thalamic neurons. The latter migrate through a distinct transient structure, the gangliothalamic body (GTB). The GE also represents an intermediate target for growing thalamic axons (on their way to the cerebral cortex) and cortical axons (on their way to the thalamus). In developmental neuropathology the GE plays an important role in prematurely born infants. The pathogenesis of GE bleedings is discussed with regard to the abundant expression of interleukin-6 (IL-6) receptors on GE cells. The consequences of such bleedings are discussed in view of cellular responses, such as the induction of leukemia inhibitory factor (LIF) expression in GE cells after hemorrhage.
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Affiliation(s)
- Norbert Ulfig
- Neuroembryonic Research Laboratory, Department of Anatomy, Faculty of Medicine, University of Rostock, Rostock, Germany.
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Ciccarelli R, Ballerini P, Sabatino G, Rathbone MP, D'Onofrio M, Caciagli F, Di Iorio P. Involvement of astrocytes in purine‐mediated reparative processes in the brain. Int J Dev Neurosci 2001; 19:395-414. [PMID: 11378300 DOI: 10.1016/s0736-5748(00)00084-8] [Citation(s) in RCA: 178] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Astrocytes are involved in multiple brain functions in physiological conditions, participating in neuronal development, synaptic activity and homeostatic control of the extracellular environment. They also actively participate in the processes triggered by brain injuries, aimed at limiting and repairing brain damages. Purines may play a significant role in the pathophysiology of numerous acute and chronic disorders of the central nervous system (CNS). Astrocytes are the main source of cerebral purines. They release either adenine-based purines, e.g. adenosine and adenosine triphosphate, or guanine-based purines, e.g. guanosine and guanosine triphosphate, in physiological conditions and release even more of these purines in pathological conditions. Astrocytes express several receptor subtypes of P1 and P2 types for adenine-based purines. Receptors for guanine-based purines are being characterised. Specific ecto-enzymes such as nucleotidases, adenosine deaminase and, likely, purine nucleoside phosphorylase, metabolise both adenine- and guanine-based purines after release from astrocytes. This regulates the effects of nucleotides and nucleosides by reducing their interaction with specific membrane binding sites. Adenine-based nucleotides stimulate astrocyte proliferation by a P2-mediated increase in intracellular [Ca2+] and isoprenylated proteins. Adenosine also, via A2 receptors, may stimulate astrocyte proliferation, but mostly, via A1 and/or A3 receptors, inhibits astrocyte proliferation, thus controlling the excessive reactive astrogliosis triggered by P2 receptors. The activation of A1 receptors also stimulates astrocytes to produce trophic factors, such as nerve growth factor, S100beta protein and transforming growth factor beta, which contribute to protect neurons against injuries. Guanosine stimulates the output of adenine-based purines from astrocytes and in addition it directly triggers these cells to proliferate and to produce large amount of neuroprotective factors. These data indicate that adenine- and guanine-based purines released in large amounts from injured or dying cells of CNS may act as signals to initiate brain repair mechanisms widely involving astrocytes.
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Affiliation(s)
- R Ciccarelli
- Department of Biomedical Sciences, Section of Pharmacology, Via del Vestini Pal. B, 66013, Chieti, Italy.
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Abstract
BACKGROUND The confusing term "gestational age" is generally either not defined or is used for menstrual "age," postovulatory age, or postfertilizational age. The designation (post)menstrual weeks and/or days is very useful in obstetrics but, because prenatal age extends from fertilization to birth, menstrual "age" is a misnomer. The term "stage" has a specific morphological meaning in embryology and should not be used either for ages or for lengths. METHODS Embryonic age is best assessed, when possible, from the 23 internationally recognized morphological stages. A morphological staging system is not available for the fetal period, and fetal age is assessed mainly from measurements. RESULTS Among these, the unsatisfactory designation crown-rump length (CRL) should be replaced, in ultrasonic biometry as well as in embryology, by the greatest length (GL), exclusive of the lower limbs. These points are discussed in detail, and justification for the views expressed is provided. CONCLUSIONS The continuing confusion concerning prenatal age is shown to be unnecessary once the ambiguous and superfluous term "gestational age" is abandoned.
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Affiliation(s)
- R O'Rahilly
- Institut d'Embryologie Spéciale, Université de Fribourg, Fribourg, Switzerland
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