bluuebunny/crossref_metadata_2025_split huggingface dataset:
Induction of nerve growth factor responsiveness in C6‐2B glioma cells by expression of trk A proto‐oncogene
Authors: Colangelo Anna Maria , Fink Donald W. , Rabin Stuart J. , Mocchetti Italo 
Published: December 2004

AbstractCells that lack the high affinity receptor component (trkA) for nerve growth factor (NGF) are unresponsive to NGF. We investigated whether C6‐2B cells, a rat glioma derived cell line, express trkA and, as a consequence, are responsive to NGF. In these cells, NGF (100 ng/ml) failed to induce the mRNA encoding for c‐fos protooncogene and the low affinity NGF receptor p75NGFR, two NGF‐responsive genes. In contrast, both mRNAs were induced in PC12 cells by NGF. Using a RNase protection assay with a cRNA probe for rat trkA RNA protected fragment was detected in PC12 but not in C6‐2B glioma cells, indicating that C6‐2B cells either do not express the gene or express it only in low amounts. Cross‐linking of 125I‐labeled NGF to PC12 cells identified two major bands with an apparent molecular weight of 158 kDa and 100 kDa corresponding to trkA and p75NGFR, respectively. In contrast, only the 100 kDa band could be detected in C6‐2B cells by cross‐linking analysis. In C6‐2B cells stably transfected with the rat trkA cDNA, NGF increased c‐fos mRNA, induced tyrosine phosphorylation of gp140trk, and SNT (suc‐associated neurotrophic factor‐induced tyrosinephosphorylated target), and caused morphological changes within 72 h. All of these effects of NGF were blocked by the protein kinase inhibitor K‐252a suggesting that NGF signal transduction was restored by trkA expression. Most important, in C6trk+ cells, NGF was a weaker (2‐fold) inducer of [3H]thymidine incorporation when compared to bFGF (5‐fold), suggesting that expression of trkA fails to confer to NGF a strong mitogenic effect. Our findings indicate that C6‐2B glioma cells do not possess high affinity NGF receptor and thus are unresponsive to NGF and that expression of trkA in neuroectoderm derived cells elicits some of the NGF responses characteristic of neuronal cells.
Characterization of C6‐10A glioma cells highly responsive to β‐adrenergic receptor agonist‐induced NGF synthesis/secretion
Authors: Fukumoto Hiroaki , Kakihana Mitsuru , Suno Masahiro 
Published: December 2004

AbstractA subline of rat C6 glioma cells, C6‐10A cells, in which epinephrine can induce nerve growth factor (NGF) synthesis/secretion, was isolated. C6‐10A cells have retained their sensitivity to epinephrine for more than 2 years in a medium containing 0.5% fetal calf serum (FCS) but easily lose it in 10% FCS. C6‐10A cells are S‐100‐ and glial fibrillary acidic protein‐positive, and the doubling time is about 60 h in the medium containing 0.5% FCS and about 20 h in 10% FCS. Epinephrine induced NGF synthesis/secretion prominently in serum‐free cultures of C6‐10A cells and in cultures with a high cell density, but not in serum‐containing cultures. The induction did not occur with parent C6 cells under the appropriate conditions in C6‐10A cells. NGF secretion was induced by catecholaminergic compounds in the following order isoproterenol > epinephrine = norepinephrine » dopamine. The induction caused by epinephrine was blocked by propranolol (α‐blocker) but not by phentolamine (β‐blocker). Various compounds that activate the adenylate cyclase system also induced NGF synthesis/secretion. These results indicate that C6‐10A cells are astrocytes that are highly responsive to β‐adrenergic receptor agonists, which stimulate NGF synthesis/secretion via receptors coupled with adenylate cyclase machinery. These cells may be a useful aid in studying the mechanism of NGF synthesis/secretion.
Expression of BMP‐6, a TGF‐β related morphogenetic cytokine, in rat radial glial cells
Authors: Schluesener Hermann J. , Meyermann Richard 
Published: December 2004

AbstractBone morphogenetic protein‐6 (BMP‐6) is a member of the TGF‐β super‐family of cytokines. The bone morphogenetic proteins and homologous cytokines participate in realization of the genetic body plan by regulating homeotic gene expression, embryonic development, and neurogenesis. Here we demonstrate expression of BMP‐6 in rat radial glial cells which are involved in embryonic organisation of the central nervous system. Thus, morphogenetic cytokines like BMP‐6 might contribute to radial glial cell function in organizing the migration of immature neurons during the development of the CNS cortex.
Intracellular pH regulation in primary rat astrocytes and C6 glioma cells
Authors: Shrode Lamara D. , Putnam Robert W. 
Published: December 2004

AbstractWe used the pH‐sensitive fluorescent dye BCECF to study intracellular pH (pHi) regulation in primary cultures of rat astrocytes and C6 glioma cells. Both cell types contain three pH‐regulating transporters: (1) alkalinizing Na+/H+ exchange; (2) alkalinizing Na+ + HCO3 −/Cl− exchange; and (3) acidifying Cl−/HCO3 − exchange. Na+/H+ exchange was most evident in the absence of CO2; recovery from acidification was Na+ dependent and amiloride sensitive. Exposure to CO2 caused a cell alkalinization that was inhibited by DIDS, dependent on external Na+, and inhibited 75% in the absence of Cl− (thus mediated by Na+ + HCO3 −/Cl− exchange). When pHi was increased above the normal steady‐state pHi, a DIDS‐inhibitable and Na+ ‐independent acidifying recovery was evident, indicating the presence of Cl− /HCO3 − exchange. Astrocytes, but not C6 cells, contain a fourth pH‐regulating transporter, Na+ −HCO3 − cotransport; in the presence of CO2, depolarization caused an alkalinization of 0.12 +− 0.01 (n = 8) and increased the rate of CO2‐induced alkalinization from 0.23 ± 0.02 to 0.42 ± 0.03 pH unit/min. Since C6 cells lack the Na+ ‐HCO3 + cotransporter, they are an inferior model of pHi regulation in glia. Our results differ from previous observations in glia in that: (1) Na+ /H+ exchange was entirely inhibited by amiloride; (2) Na+ + HCO3 −/Cl− exchange was present and largely responsible for CO2−induced alkalinization; (3) Cl− /HCO3 − exchange was only active at pHi values above steady state; and (4) depolarization‐induced alkalinization of astrocytes was seen only in the presence of CO2.
Cytokine and insulin regulation of α2 macroglobulin, angiotensinogen, and hsp 70 in primary cultured astrocytes
Authors: Hong‐Brown Ly Q. , Brown C. Randell 
Published: December 2004

AbstractAcute‐phase proteins and heat shock proteins (hsp) are upregulated following exposure to a number of conditions including bacterial infection, tissue injury, or stress. We show here that α2 macroglobulin (α2M), angiotensinogen (AOG), and hsp 70 are regulated by cytokines in primary cultures of astrocytes. In addition, we have found that insulin modulates the effect of cytokines on these proteins. In cells treated with lipopolysaccharide (LPS) conditioned Raw media, interleukin (IL)‐6, or IL‐β for 24 h, there was a significant decrease of α2M secretion below control levels. In the absence of insulin, however, similar treatments resulted in a significant increase in α2M secretion. AOG secretion increased significantly following treatment with individual cytokines either in the presence or absence of insulin, but conditioned media did not cause a response in the absence of insulin. Hsp 73 concentrations also increased following treatment with conditioned media and IL‐β in the presence or absence of insulin. Following IL‐6 treatment, however, hsp levels either decreased (‐insulin) or did not change (+ insulin). To determine whether acute‐phase proteins are regulated similarly to hsp, astrocytes were subjected to elevated environmental temperatures. Cells incubated at 43αC for 90 min showed a marked increase in AOG secretion. However, α2M and hsp 73 levels remained unchanged. In the absence of insulin, heat shock caused a significant increase of α2M and AOG secretion. Thus, in astrocytes, α2M is upregulated by cytokines and heat shock in the absence of insulin, while in the presence of insulin, cytokines function as negative regulators. On the other hand, insulin did not modulate the effects of cytokines on the production of AOG in an inverse manner.
Atrial natriuretic peptide‐like (ANP‐LIR) and ANP prohormone immunoreactive astrocytes and neurons of human cerebral cortex
Authors: McKenzie James C. , Berman Nancy E. J. , Thomas Charles R. , Young John K. , Compton Lisa Y. , Cothran Laval N. , Liu W.‐L. , Klein Robert M. 
Published: December 2004

AbstractAtrial natriuretic peptide (ANP) represents a family of related peptides originally isolated from cardiac atria that have potent natriuretic, diuretic, and vasorelaxant properties. ANP has previously been localized in neurons of the rat brain in regions subserving cardiovascular functions and fluid/electrolyte balance and has been localized in astroglia of the canine brain. To determine whether ANP is present in astrocytes of the human brain and to validate the canine model for future studies, human brain tissue was obtained from autopsy cases with no brain damage or neurological or vascular disease. Human brains were obtained less than 3 h postmortem, and anterior cingulate and striate cortices were dissected following perfusion or immersion fixation. Immunohistochemical processing utilized antibodies against the processed form of ANP (ANP IV, ANP104–128) and against rat proANP (amino terminus) and the avidin‐biotin‐peroxidase technique. Isolated, strongly ANP‐immunoreactive protoplasmic astrocytes were observed in all layers of the cingulate and striate cortex gray matter. ANP‐positive fibrous astrocytes were observed in the white matter. Additionally, distinctive immunopositive astrocytes were found both within and immediately subjacent to the glia limitans. Antibody against the prohormone stained only protoplasmic astrocytes and sublimitans astrocytes and processes. In addition to the astroglia, ANP was detected in scattered multipolar neurons in the cerebral gray matter. These results provide additional evidence for diversity of peptide localization in astrocytes and suggest roles for ANP in the local regulation of cerebral blood flow, blood‐brain barrier permeability, or cerebrospinal fluid volume.
Glial development in primary cultures established from normal and X‐irradiated neonatal spinal cord
Authors: Sims Terry J. , Davies David L. , Gilmore Shirley Ann 
Published: December 2004

AbstractThe glial population of the lumbosacral spinal cord of the rat can be markedly depleted by exposure to ionizing radiation during the first postnatal week. Identification of specific cell populations which survive the exposure to radiation is difficult in situ; therefore, the present investigation used in vitro approaches to address issues related to specific phenotypes and maturational states of glia in cultures derived from non‐irradiated (control) and irradiated (experimental) lumbosacral spinal cords of 3‐day‐old rats. Cultures were established from the spinal cords 2 to 4 hours following irradiation and were compared to cultures from non‐irradiated, littermate controls. By 4 days in vitro (DIV) the numbers of cells in experimental cultures were profoundly reduced when compared to controls, and this reduction persisted through the termination of the study (8 DIV). In addition to reduction in numbers, astrocyte phenotypes were altered in experimental cultures, with greater proportions of the astrocyte population being constituted by the flat angular, large angular, and pancake types and a lesser proportion by stellate cells. The non‐astrocytic cell types were dramatically reduced as evidenced by the paucity of oligodendrocytes immunoreactive for galactocerebroside and of small, non‐process bearing cells binding the lectin, Griffonia (Bandeiraea) simplicifolia, a marker for microglia. Experimental cultures contained an increased incidence of binucleate astrocytes, an increase not restricted to a particular astrocyte phenotype. This study established the feasibility of utilizing this combined in vivo/in vitro approach in assessment of glial populations in immature spinal cords, and further investigations are in progress using this model.
Strongly GD3+ cells in the developing and adult rat cerebellum belong to the microglial lineage rather than to the oligodendrocyte lineage
Authors: Wolswijk Guus 
Published: December 2004

AbstractA recent study has shown that ramified microglia in the adult rat optic nerve express the ganglioside GD3[Wolswijk Glia 10:244–249, 1994], thereby raising the possibility that some GD3+ in the developing rat central nervous system (CNS) belong to the microglial lineage rather than to the oligodendrocyte lineage, as previously thought. To examine this possibility, sections of postnatal and adult cerebellum were doublelabelled with markers for rat microglia [the B4 isolectin derived from Griffonia simplicifolia (GSI‐B4), the ED1 monoclonal antibody (mAb), and the OX‐42 mAb] and anti‐GD3 mAbs (the mAbs R24 and LB1). These immunolabellings showed that ramified microglia as well as amoeboid microglia are strongly GD3+ in vivo. Moreover, most, if not all, cells that express high levels of GD3 in sections of developing cerebellum appear to belong to the microglial lineage. These observations contradict previous suggestions that the strongly GD3 + cells in the putative white matter regions of the developing brain are oligodendrocyte‐type‐2 astrocyte (0–2A) progenitor cells; the cells that give rise to oligodendrocytes in the CNS. The present study did, however, confirm that some 0–2A progenitor cells in sections of postnatal cerebellum are weakly GD3+ in vivo. Amoeboid microglia are present in areas of the developing cerebellum where newly generated oligodendrocytes are found, suggesting that these cells play a role in the phagocytosis of the large numbers of oligodendrocytes that die as part of CNS development. © 1995 Wiley‐Liss, Inc.
Schwann cell ATP‐mediated calcium increases in vitro and in situ are dependent on contact with neurons
Authors: Lyons Susan A. , Morell Pierre , McCarthy Ken D. 
Published: December 2004

AbstractSchwann cells freshly isolated from the sciatic nerves of neonatal rats respond to exogenously applied ATP with a rapid increase in cytosolic calcium. This increase in [Ca2+]i is mediated by a P2Y‐purinergic pathway (Lyons et al.: J. Neurochem. 63:552–560, 1994) and was measured using the calcium indicator dye, fura‐2/AM, and a video‐enhanced calcium imaging system. The ability to respond to ATP with increases in intracellular calcium is lost over a period of several days in culture; this loss can be prevented or reversed by application of cAMP analogs in a defined medium. We now demonstrate that the direct contact of Schwann cells with neurons also induces and stabilizes this ATP responsiveness. The induction of ATP responsiveness was observed among all Schwann cells contacting neurites, including those forming myelin, and regardless of whether the source of neurons was dorsal root ganglion neurons or superior cervical ganglion neurons. Approximately 85% of Schwann cells responded to ATP over the time studied (72 d in coculture). Addition of axolemma to Schwann cell cultures did not induce ATP responsiveness. We also examined the ATP responsiveness of Schwann cells in situ (excised nerves) using laser‐scanning confocal microscopy and the calcium indicator dye, fluo‐3/AM. Schwann cells in intact sciatic nerve segments isolated from neonatal and 16–day‐old rats exhibited ATP‐mediated [Ca2+]i increases. We conclude that neuronal contact is necessary for the expression of the ATP‐mediated calcium responses in Schwann cells and that these responses are independent of myelin formation or maintenance. Copy 1995 Wiley‐Liss, Inc.
Immunolocalization of vgr (BMP‐6, DVR‐6), a TGF‐β related cytokine, to Schwann cells of the rat peripheral nervous system: Expression patterns are not modulated by autoimmune disease
Authors: Schluesener Hermann J. , Meyermann R. , Jung S. 
Published: December 2004

AbstractThe transforming growth factors type β (TGF‐β) have been implicated in regulation of peripheral nervous system inflammation and regeneration. Here we demonstrate expression of a TGF‐β‐related bone morphogenetic protein, the vgr (BMP‐6, DVR‐6) in Schwann cells of the rat peripheral nervous system. The expression of vgr in the peripheral nervous system suggests that this factor and probably other TGF‐β‐related bone morphogenetic proteins might participate in Schwann cell function during aspects of peripheral nervous system physiology and pathology. However, we did not observe changes in expression patterns in response to autoimmune inflammation (experimental autoimmune neuritis) of the peripheral nervous system. © 1995 Wiley‐Liss, Inc.
Laser cytometric analysis of FIV‐induced injury in astroglia
Authors: Zenger Elisabeth , Collisson Ellen W. , Barhoumi Rola , Burghardt Robert C. , Danave Indrani R. , Tiffany‐Castiglioni Evelyn 
Published: December 2004

AbstractGlia are the predominant brain cells infected by the lentiviruses human immunodeficiency virus (HIV) and feline immunodeficiency virus (FIV). The importance of astrocytes in maintenance of central nervous system homeostasis suggests that astrocytes are likely to play a strategic role in the progression of neurological disease in lentiviral‐infected patients. In consideration of this postulate, the ability of FIV to cause injury by infection of cultured feline astroglia was examined via vital fluorescence assays. Intracellular Ca2+homeostasis, plasma membrane permeability and fluidity, and cytosolic glutathione (GSH) levels were evaluated. Although basal intracellular Ca2+was not significantly different between groups, FIV‐infected astroglia displayed both a significant delay in development of peak Ca2+levels following ionophore application and a decrease in the amount of Ca2+released from intracellular stores. Plasma membrane lipid mobility was increased in FIV‐infected cells within 24 h of infection. Glutathione levels were affected in a dose dependent fashion. With a standard viral inoculum there was a decrease in GSH which became significant after 8 days postinfection. With a high inoculum dose there was rapid loss of cell viability with an increase in GSH in surviving cells. We have identified several cellular processes altered in FIV‐infected astroglia and our findings suggest that FIV‐infection of feline astroglia affects cellular membranes, both structurally and functionally. © 1995 Wiley‐Liss, Inc.
Phagocytic microglia during delayed neuronal loss in the facial nucleus of the rat: Time course of the neuronofugal migration of brain macrophages
Authors: Angelov D. N. , Gunkel A. , Stennert E. , Neiss W. F. 
Published: December 2004

AbstractThe injection of Fluoro‐Gold (FG) into the whisker pad of rats yields a stable fluorescent labeling of the motoneurons in the lateral facial subnucleus. Following resection of 8–10 mm of the facial nerve, the microglia phagocytose the FG‐preloaded neurons and assume the label. Employing this vital labeling of microglia in situ we studied the fate of same after completion of phagocytic activity. Starting at 56 days post resection (DPR) the FG‐labeled microglia spread out from the lateral facial subdivision and invaded the entire facial nucleus. The quantitative analysis of this redistribution of the fluorescent marker revealed a prolonged increase in the number of labeled microglia strictly proportional to the delayed loss of neurons. The differentiation between microglia and shrunken neurons was performed with the new method of immunoquenching: the staining of vibratome sections with anti‐rat neuron‐specific enolase (NSE) combined with an ABC‐HRP kit and DAB as detector totally extinguished (quenched) all fluorescence from the pre‐labeled facial motoneurons. The fluorescent microglia were additionally stained with GSA I‐B4 and OX–42, which should completely quench all fluorescence in the section. However, a few small round cells, always closely opposed to neuronal perikarya, still fluoresced. These NSE‐negative, GSA I‐B4 and OX–42 negative, but fluorescent cells may represent a new, immunologically uncharacterized microglial cell type, that participates in neuronophagia. (c) 1995 Wiley‐Liss, Inc.
Elevated intracellular levels of cAMP induce olfactory ensheathing cells to express GAL‐C and GFAP but not MBP
Authors: Doucette R. , Devon R. 
Published: December 2004

AbstractThe primary olfactory pathway contains non‐myelinating glial cells, called ensheathing cells, that exhibit a variety of phenotypes depending on their immediate environment. In vivo, these cells normally possess a mixture of astrocyte‐ and Schwann cell‐specific phenotypic features. When co‐cultured with dorsal root ganglion neurons, their phenotype can become more like that of a myelinating Schwann cell. The objective of this study was to determine whether ensheathing cells would express a myelinating phenotype in culture in the absence of neurons but in the presence of cAMP analogues that are known to induce the expression of myelin associated molecules in Schwann cell cultures. The ensheathing cell cultures were initiated using the nerve fiber layers of Theiler stage 23 rat olfactory bulb primordia and were fed for 1 day to 3 weeks with serum containing (1% or 10% FBS) or serum‐free media to which was added different concentrations of dBcAMP (0.1 to 1 mM) or forskolin (10 M). These cultures were double‐labelled with a rabbit polyclonal antibody to S100 in combination with mouse anti‐GAL‐C (01 and BRD1 hybridomas) or anti‐MBP monoclonal antibodies. The remaining cultures were double‐labeled with a rabbit polyclonal antibody to GFAP in combination with the BRD1 antibody. Treatment with dBcAMP or forskolin failed to induce ensheathing cells to express MBP regardless of the concentration. On the other hand, the treatment induced approximately one tenth of the cells to express GAL‐C, and virtually all of the cells to express GFAP. These results indicate that although ensheathing cells can synthesize myelin associated molecules, the cAMP second messenger system appears to play a lesser role in controlling the expression of a myelinating phenotype in ensheathing cells than it does in Schwann cells. © 1995 Wiley‐Liss, Inc.
Expression of NMDA 2B receptor subunit mRNA in bergmann glia
Authors: Luque Juan M. , Richards J. Grayson 
Published: December 2004

AbstractN‐methyl‐D‐aspartate (NMDA)‐activated glutamate receptor subunits are invariably expressed in neurons, although NMDA‐activated currents have been recently described in Bergmann glia. To date, the NMDA receptor subunit 2B (NMDAR2B) was thought not to be expressed in adult cerebellum. In the present study we provide evidence, from in situ hybridization histochemistry, that Bergmann glial cells in rat brain express mRNA encoding the NMDAR2B subunit, most probably co‐expressed with the ubiquitous NMDAR1 subunit, while transcripts for other NMDAR2 subunits (A,C,D) were either not resolved or detected. Our findings suggest that Bergmann glial cells contain the molecular machinary to synthesize the NMDA receptor 2B subunit. The role of physiological NMDA receptors in the interaction between Bergmann glia and Purkinje neurons is not yet known. © 1995 Wiley‐Liss, Inc.