bluuebunny/crossref_metadata_2025_split huggingface dataset:
Regulation of an oligodendrocyte progenitor cell line by the interleukin‐6 family of cytokines
Authors: Kahn M. A. , de Vellis J. 
Published: December 2004

AbstractWe report pleiotropic actions of the interleukin‐6 family of cytokines on a rat cerebral cortical oligodendrocyte cell line, Central Glia‐4 (CG‐4). This is a bipotential oligodendrocyte type‐2 astrocyte (O‐2A) progenitor cell line that can be manipulated in vitro to become either a type‐2 astrocyte or to follow a linear sequence of events into becoming a mature oligodendrocyte. Using Northern and Western analyses in conjunction with immunocytochemistry we have demonstrated that ciliary neurotrophic factor (CNTF), leukemia inhibitory factor (LIF), and interleukin‐6 (IL‐6) cause a transient increase in glial fibrillary acidic protein (GFAP) in oligodendrocyte type‐2 astrocyte (O‐2A) progenitor cells. At maximal cytokine concentrations, the largest increase in GFAP protein levels were observed for CNTF and LIF; albeit, IL‐6 did increase GFAP but the order of magnitude was 6‐7 times less. Moreover, in trophic factor deprived medium, CNTF and LIF protected immature (O4+/MBP−) and mature (MBP+) oligodendrocytes from the apoptotic mode of cell death, while IL‐6 had no effect in enhancing oligodendrocyte cell survival. Analysis of the cytokine‐induced early response genes (ERGs) revealed a strong degree of overlap for CNTF and LIF. The effect of IL‐6 was different in the degree to which the ERGs were up‐regulated and in their temporal patterns of expression. These findings suggest that ERGs may be important, at least in part, for determining the extent of functional overlap observed within this cytokine family. Our findings clearly demonstrate differential regulation of oligodendrocyte survival and differentiation by the IL‐6 family of cytokines.
Denervated skeletal muscle stimulates migration of Schwann cells from the distal stump of transected peripheral nerve: An in vivo study
Authors: Dubový Petr , Svíženská Ivana 
Published: December 2004

AbstractWe have tested the stimulation of Schwann cell migration from the distal stump of a 1 week transected sciatic nerve of adult rats by denervated skeletal muscle. Migrating Schwann cells were distinguished by the presence of non‐specific cholinesterase (nChE) activity and glial fibrillary acidic protein (GFAP) at a distance of about 6 mm among denervated muscle fibres 4 weeks after insertion of the distal stump. In addition, the distal stump was introduced into the open end of a silicone chamber packed with artificial fibrin sponge (Gelaspon®) soaked in homogenate from intact or denervated muscles. A larger amount of migrated Schwann cells was observed in the chambers filled with homogenate from denervated muscles. An alteration in the amounts of Schwann cells migrating into the silicone chambers observed after histochemical staining (nChE or GFAP) was supported by biochemical measurements of the nChE activity. The biochemical assessment of the nChE activity revealed the increased amounts of migrated Schwann cells in proportion to the protein contents of homogenates from the denervated muscles. In addition, heating of homogenate from the denervated muscles resulted in a diminution of Schwann cell migration. Bromodeoxyuridine incorporation did not show an increased proliferation of Schwann cells inside the chambers following application of homogenate from the denervated muscles in comparison with the homogenate from the innervated muscles. Our results suggest a stimulation of Schwann cell migration from the distal stump of the transected sciatic nerve by soluble factor(s) produced by denervated skeletal muscles.
Ryanodine‐induced intracellular calcium mobilisation in cultured astrocytes
Authors: Langley David , Pearce Brian 
Published: December 2004

AbstractChanges in intracellular Ca2+ concentration were monitored in cultured cortical astrocytes challenged with ryanodine and ATP. Ryanodine elicited a modest, in comparison to ATP, increase in cytosolic Ca2+ concentration in approximately 60% of the cell fields examined. This effect was evident and, in fact, was augmented when incubations were performed in Ca2+ concentration were dose dependent, desensitised rapidly, and could not be mimicked by caffeine. Exposure to ryanodine was without effect on eicosanoid release from these cells nor did it influence Ca2+ mobilisation and eicosanoid release in response to ATP. In contrast, caffeine attenuated part of the ATP‐evoked increase in intracellular Ca2+ concentration in the majority of cells tested and abolished its effect on eicosanoid release.
Regulation of metallothionein‐I+II levels in specific brain areas and liver in the rat: Role of catecholamines
Authors: Gasull Teresa , Giralt Mercedes , Garcia Agustina , Hidalgo Juan 
Published: December 2004

AbstractThe role of the catecholamines noradrenaline, adrenaline and dopamine on metallothionein (MT) levels of specific areas of the rat brain has been studied. MT‐I or MT‐I+II levels were measured by radioimmunoassay using specific antibodies that cross‐react only slightly with human MT‐III (growth inhibitory factor, GIF). The inhibition of tyrosine hydroxylase with α‐methyl‐p‐tyrosine (MPT), which depletes brain dopamine, noradrenaline, and adrenaline, increased MT levels in all brain areas studied (frontal cortex, cortex, medulla oblongata plus pons, midbrain, striatum, hippocampus, hypothalamus, and cerebellum) when considering the results of two separate experiments. The α‐ and β‐receptor blockers, phentolamine, and propranolol, alone or together, did not increase brain MT levels in any area of the brain, suggesting that the effect of MPT in vivo is related to inhibition of the synthesis of dopamine rather than of noradrenaline and adrenaline. Dopamine, noradrenaline, and serotonin increased MT‐I levels in primary cultures of neurons, whereas decreased them in astrocyte‐enriched primary cultures. Since MT‐I levels are about ten times higher in astrocytes than in neurons, the increased brain MT levels induced by MPT may reflect the supperssion of the normal inhibitory effect of dopamine on astrocyte MT levels. The increase in MT concentrations induced in most parts of the brain by immobilization stress was not prevented by MPT, phentolamine, or propranolol, suggesting that it was not mediated by the central monoamines.
Type II sodium channels in spinal cord astrocytes in situ: Immunocytochemical observations
Authors: Black Joel A. , Westenbroek Ruth , Ransom Bruce R. , Catterall William A. , Waxman Stephen G. 
Published: December 2004

AbstractThe expression of sodium channel α‐subunit isoforms in astrocytes in adult rat spinal cord and optic nerve was examined utilizing immunocytochemical methods with antibodies generated against conserved and subtype‐specific sequences of the sodium channel. In adult rat spinal cord, astrocytes within the dorsal and ventral funiculi were immunolabelled with antibody SP20, which recognizes a conserved sequence within sodium channel types I, II, and III. In addition, astrocytes within these spinal cord white matter tracts were immunostained with antibody SP11‐II, which recognizes sodium channel type II. Antibodies SP11‐I and SP32‐III, which are directed against subtype‐specific sequences in sodium channel types I and III, respectively, did not label astrocytes in the dorsal and ventral funiculi of the spinal cord. In optic nerves, astrocytes were immunostained with antibody SP20. However, no detectable labelling of cells within the optic nerve was observed with antibodies SP11‐I, SP11‐II, and SP32‐III. These observations demonstrate that sodium channel II is expressed by astrocytes in spinal cord white matter. Moreover, these data suggest that regional factors regulate the level of sodium channel isoform expression in astrocytes.
Blood monocytes and spleen macrophages differentiate into microglia‐like cells on monolayers of astrocytes: Morphology
Authors: Sievers Jobst , Parwaresch Reza , Wottge Hans‐Ulrich 
Published: December 2004

AbstractSeveral morphological and functional properties of microglial cells, the resident immunoeffector cells of the central nervous system (CNS), differ from those of monocytes/macrophages in other tissues. Microglia are assumed to derive from the myelomonocytic lineage, possibly as a distinct subpopulation that diverges from a common cell line early in ontogeny, invades the CNS, proliferates, and differentiates into ameboid and then ramified microglia. We tested the hypothesis that some morphological and functional properties of microglia are induced in myelomonocytic cells by nervous tissue, specifically astrocytes. In the present in vitro studies we compared the differentiation of microglia, blood monocytes, and spleen macrophages on acellular substrates and on monolayers of astrocytes and fibroblasts.On acellular substrates, microglial cells at first acquire an ameboid morphology; later they show a few short, unbranched processes. On monolayers of pure astrocytes, microglial cells at first also differentiate inot ameboid cells, but after 5 to 7 days they start to develop processes with large lamellopodial tips. These lengthen and branch continuously during the next 2 weeks in vitro, demarcating a round to oval territory around the small ellipsoid cell body. By contrast, on monolayers of fibroblasts the microglial cells develop an ameboid morphology, but do not grow the typical long branched processes of the ramified form. Blood monocytes and spleen macrophages behave indistinguishably from microglia both on acellular and cellular substrates, i.e., on astroglia they develop the ramified form, while on fibroblasts they retain the ameboid shape. When microglia, macrophages, or monocytes are cultured on coverslips on top of astrocytic monolayers, i.e., physically separated from the astroglia, but exposed to the medium conditioned by astrocytes, a significant proportion of them also develop the ramified shape. These findings indicate that the ramified shape of microglia is induced by astrocytes. Since this morphology can also be induced in blood monocytes and macrophages, we take this to be further evidence for the proposition that microglial cells are derived from the myelomonocytic lineage, and, moreover, that properties of resident macrophages are largely determined by tissue components of their host organ.
Ca2+ influx into leech glial cells and neurones caused by pharmacologically distinct glutamate receptors
Authors: Hoschstrate Peter , Schlue Wolf‐Rüdiger 
Published: December 2004

AbstractThe effect of glutamatergic agonists on the intracellular free Ca2+ concentration ([Ca2+]i) of neuropile glial cells and Retzius neurones in intact segmental ganglia of the medicinal leech Hirudo medicinalis was investigated by using iontophoretically injected fura‐2. In physiological Ringer solution the [Ca2+]i levels of both cell types were almost the ssame (glial cells: 58 ± 30 nM, n = 51; Retzius neurones: 61 ± 27 nM, n = 64).In both cell types glutamate, kainate, and quisqualate induced an increase in [Ca2+]i which was inhibited by 6,7‐dinitroquinoxaline‐2,3‐dione (DNQX). This increase was caused by a Ca2+ influx from the extracellular space because the response was greatly diminished upon removal of extracellular Ca2+.The glutamate receptors of neuropile glial cells and Retzius neurones differed with respect to the relative effectiveness of the agonists used, as well as with regard to the inhibitory strenght of DNQX. In Retzius neurones the agonist‐induced [Ca2+]i increase was abolished after replacing extracellular Na+ by organic cations or by mM amounts of Ni2+, whereas in glial cells the [Ca2+]i increase was largely preserved under both conditions. It is concluded that in Retzius neurones the Ca2+ influx is predominantly mediated by voltage‐dependent Ca2+ channels, whereas in neuropile glial cells the major influx occurs via the ion channels that are associated with the glutamate receptors.
Normal and pathological expression of GFAP promoter elements in transgenic mice
Authors: Galou M. , Pournin S. , Ensergueix D. , Ridet J.‐L. , Tchélingérian J.‐L. , Lossouran L. , Privat A. , Babinet C. , Dupouey P. 
Published: December 2004

AbstractThe expression of the glial fibrillary acidic protein (GFAP), a component of astroglial intermediate filaments, is regulated under developmental and pathological conditions. In order to characterize DNA sequences involved in such regulations, we produced transgenic mice bearing 2 kb of the 5′ flanking region of the murine GFAP gene linked to the Escherichia coli β‐galactosidase (β‐gal) reporter gene. Seven transgenic lines were obtained. We observed that the regulatory elements present in the transgene GFAP‐nls‐LacZ direct an expression in the neural and non‐neural tissue and target in vivo an unexpected subpopulation of astrocyte. In the developing brain, β‐gal activity and GFAP appeared simultaneously and in the same region, on embryonic day 18 (E18), suggesting that the 2 kb of the promoter contains the regulatory sequences responsible for the perinatal vimentin/GFAP switch. In addition, we demonstrated that the 2 kb sequence of the GFAP promoter used in the transgene possess elements which are activated after a surgical injury, thus permitting to study some aspects of reactive gliosis in these transgenic mice. These transgenic lines provide a useful tool by enabling further studies of astroglial and, probably, neuronal physilogies.
GM‐CSF promotes proliferation of human fetal and adult microglia in primary cultures
Authors: Lee Sunhee C. , Liu Wei , Brosnan Celia F. , Dickson Dennis W. 
Published: December 2004

AbstractProliferation of microglia/macrophages is a common finding in many central nervous system diseases. To identify mitogenic signals for human microglia, we examined primary cultures of human fetal and adult microglia after stimulation with cytokines, colony stimulating factors (CSFs), or LPS, using proliferating cell nuclear antigen (PCNA) expression as an index of cell proliferation. The results showed that both M‐CSF and GM‐CSF induced microglial proliferation in fetal and adult human cultures, but that GM‐CSF provided a much stronger stimulus. At 96 h post‐stimulation, the mean PCNA labeling index was 2.4 for M‐CSF and 13.3 for GM‐CSF in fetal microglia; in adult microglia, the PCNA labeling index was 4.7 for M‐CSF and 9.0 for GM‐CSF. The effect of GM‐CSF on fetal microglia was dose dependent and synergistic with M‐CSF. LPS abolished the basal level of PCNA labeling in adult microglia, but in fetal microglia, caused a slight increase in PCNA labeling (1.9) at 96 h and consistently enhanced microglial cell survival and differentiation into highly branched cells. The production of GM‐CSF in purified human fetal astrocyte and microglial cultures was examined after stimulation with LPS, TNF‐α, or IL‐1β. Unlike M‐CSF, neither cell type produced GM‐CSF in unstimulated cultures; however, when stimulated with IL‐1β, astrocytes expressed GM‐CSF mRNA and protein, which accumulated in the culture through 72 h. In microglia, LPS was the only effective inducing agent. An immunocytochemical study performed to identify in vivo sources of GM‐CSF revealed selective labeling of reactive astrocytes in active lesions of multiple sclerosis and senile plaques of Alzheimer's disease. Our data demonstrate that both fetal and adult human microglia are capable of proliferation in response to CSFs, GM‐CSF being the more effective stimulus.
Cultured rat astrocytes possess Na+‐Ca2+ exchanger
Authors: Takuma Kazuhiro , Matsuda Toshio , Hashimoto Hitoshi , Asano Shoichi , Baba Akemichi 
Published: December 2004

AbstractNa+‐Ca2+ exchange activity in its reverse mode was demonstrated in cultured rat astrocytes. Combination of ouabain (1 mM) and monensin (20 ±M) caused a marked increase in 45Ca2+ uptake in astrocytes. 45Ca2+ uptake was also stimulated by lowering the external Na+ concentration. Ouabain plus monensin‐stimulated 45Ca2+ uptake was blocked by 3,4‐dichlorobenzamil (IC50, 16 ±M), an inhibitor of Na+‐Ca2+ exchanger, but not by nifedipine (0.1 ±M). The stimulated‐45Ca2+ uptake was observed even in K+‐free medium, and external K+ at 5‐10 mM caused a 2.2‐fold increase in the uptake. Microspectrofluorimetry using the Ca2+‐sensitive dye fura‐2 showed that ouabain plus monensin increased intracellular Ca2+ concentration in single astrocytes. The Ca2+ signal was dependent on external Ca2+ (EC50, 1.4 mM), and blocked by 20 ±M 3,4‐dichlorobenzamil, but not by Ca2+ channel blockers (Cd2+, 20 ±M; Ni2+, 100 ±M). Antiserum of cardiac Na+‐Ca2+ exchanger recognized 160 and 120‐135 kDa proteins on SDS‐polyacrylamide gel electrophoresis of astrocyte homogenate. Northern blot analysis revealed the presence of mRNA for the exchanger protein in astrocytes. These findings indicate that Na+‐Ca2+ exchanger which is modulated by K+ is present in cultured rat astrocytes.
Subcellular heterogeneity of voltage‐gated Ca2+ channels in cells of the oligodendrocyte lineage
Authors: Kirischuk S. , Scherer J. , Möller T. , Verkhratsky A. , Kettenmann H. 
Published: December 2004

AbstractWe studied the distribution of voltage‐gated Ca2+ channels in cells of the oligodendrocyte lineage from retinal and cortical cultures. Influx Of ca2+ via voltagegated channels was activated by membrane depolarization with elevated extracellular K+ concentration ([K+]e) and local, subcellular increases in cytosolic free Ca2+ concentration ([Ca2+]in) could be monitored with a fluometric system connected to a laser scanning confocal microscope. In glial precursor cells from both retina and cortex, small depolarizations (with 10 or 20 mM K+) activated Ca2+ transients in processes indicating the presence of low‐voltage‐activated Ca2+ channels. Larger depolarizations (with 50 mM K+) additionally activated high‐voltage‐activated Ca2+ channels in the soma. An uneven distribution of Ca2+ channels was also observed in the mature oligodendrocytes; Ca2+ trasients in processes were considerably larger. Recovery of Ca2+ levels after the voltage‐induced influx was achieved by the activity of the plasmalemmal Ca2+ pump, while mitochondria played a minor role to restore2+ levels after an influx through voltageoperated channels. During the development of white matter tracts, cells of the oligodendrocyte lineage contact axons to form myelin. Neuronal activity is accompanied by increases in [K+]e; this may lead to Ca2+ changes in the processes and the Ca2+ increase might be a signal for the glial precursor cell to start myelin formation. © 1995 Wiley‐Liss, Inc.
Transformation of type 1 astrocytes with N‐ethyl‐N‐nitrosourea: Establishment of an in vitro system and the role of the p53 gene
Authors: Hiraga Shoju , Arita Norio , Ohnishi Takanori , Izumoto Shuichi , Taki Takuyu , Yamamoto Hiroshi , Higuchi Masahide , Hayakawa Toru 
Published: December 2004

AbstractN‐ethyl‐N‐nitrosourea (ENU)‐induced gliomas, animal models of human gliomas, are most frequently oligodendrocytic, while human gliomas tend to be astrocytic. To facilitate a detailed study of human glial carcinogenesis, we developed an in vitro system using type 1 astrocyte transformation with ENU. Type 1 astrocytes from fetal Wistar rat brain were treated by a single dose of ENU. Transformed colonies appeared 50 days after exposure to single doses of ENU greater than 150 μg/mL. Cloned cells from these colonies retained the immunohistochemical characteristics of type 1 astrocytes. They showed rapid growth and high saturation densities, colony formation in low (2%) serum medium and gave rise to tumors when injected into nude mice. When p53 expression was studied at each passage, a single cell positive for mutant p53 protein emerged 40 days after ENU treatment. In the next 1–3 passages, the mutant p53 positive cell formed piled‐up colonies and exhibited dominant growth. Northern blot analysis showed markedly increased accumulations of p53 mRNA in transformed cells. This in vitro transformation system of type 1 astrocytes provides a valuable tool for further investigations of astrocyte carcinogenesis. © 1995 Wiley‐Liss, Inc.
Glial cell transplants that are subsequently rejected can be used to influence regeneration of glial cell environments in the CNS
Authors: Blakemore W. F. , Crang A. J. , Franklin R. J. M. , Tang K. , Ryder S. 
Published: December 2004

AbstractTransplantation of glial cells into demyelinating lesions in CNS offers an experimental approach which allows investigation of the complex interactions that occur between CNS glia, Schwann cells, and axons during remyelination and repair. Earlier studies have shown that (1) transplanted astrocytes are able to prevent Schwann cells from participating in CNS remyelination, but that they are only able to do so with the cooperation of cells of the oligodendrocyte lineage, and (2) transplanted mouse oligodendrocytes can remyelinate rat axons provided their rejection is controlled by immunosuppression. On the basis of these observations, we have been able to prevent the Schwann cell remyelination that normally follows ethidium bromide demyelination in the rat spinal cord by co‐transplanting isogeneic astrocytes with a potentially rejectable population of mouse oligodendrocyte lineage cells. Since male mouse cells were used it was possible to demonstrate their presence in immunosuppressed recipients using a mouse Y‐chromosome probe by in situ hydridisation. When myelinating mouse cells were rejected by removal of immunosuppression, the demyelinated axons were remyelinated by host oligodendrocytes rather than Schwann cells, whose entry was prevented by the persistence of the transplanted isogeneic astrocytes. The oligodendrocyte remyelination was extensive and rapid, indicating that the inflammation associated with cell rejection did not impede repair. If this host oligodendrocyte remyelination was prevented by local X‐irradiation, the lesion consisted of demyelinated axons surrounded by processes from the transplanted astrocytes. By this approach, it was possible to create an environment which resembled the chronic plaques of multiple sclerosis. Thus, these experiments demonstrate that in appropriate circumstances the temporary presence of a population of glial cells can alter the outcome of damage to the CNS. © 1995 Wiley‐Liss, Inc.
GFAP‐positive hippocampal astrocytes in situ respond to glutamatergic neuroligands with increases in [Ca2+]i
Authors: Porter James T. , McCarthy Ken D. 
Published: December 2004

AbstractIt is becoming increasingly clear that astrocytes play very dynamic and interactive roles that are important for the normal functioning of the central nervous system. In culture, astrocytes express many receptors coupled to increases in intracellular calcium ([Ca2+]i). In vivo, it is likely that these receptors are important for the modulation of astrocytic functions such as the uptake of neurotransmitters and ions. Currently, however, very little is known about the expression or stimulation of such astrocytic receptors in vivo. To address this issue, confocal microscopy and calcium sensitive fluorescent dyes were used to examine the dynamic changes in astrocytic [Ca2+]i, within acutely isolated hippocampal slices. Astrocytes were subsequently identified by immunocytochemistry for glial fibrillary acidic protein. In this paper, we present data indicating that hippocampal astrocytes in situ respond to glutamate, kainate, α‐amino‐3‐hydroxy‐5‐methylisoxazole‐4‐propionic acid (AMPA), 1‐aminocyclopentane‐trans‐1,3‐dicarboxylic acid (t‐ACPD), N‐methyl‐D‐aspartate (NMDA), and depolarization with increases in [Ca2+]i. The increases in [Ca2+]i occurred in both the astrocytic cell bodies and the processes. Temporally the changes in [Ca2+]i were very dynamic, and various patterns ranging from sustained elevations to oscillations of [Ca2+]i were observed. Individual astrocytes responded to neuroligands selective for both ionotropic and metabotropic glutamate receptors with increases in [Ca2+]i. These findings indicate that astrocytes in vivo contain glutamatergic receptors coupled to increases in [C2+]i and are able to respond to neuronally released neurotransmitters. (c) 1995 Wiley‐Liss, Inc.