bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transforming growth factor‐βs inhibit mitogen‐stimulated proliferation of astrocytes
Authors: Hunter Kim E. , Sporn Michael B. , Davies Alun M. 
Published: January 2005

AbstractWe have studied the influence of three members of the transforming growth factor‐β (TGF‐β) family of multifunctional growth factors on the proliferation of cultured astrocytes isolated from newborn mouse cerebral cortex. Although TGF‐βs 1, 2, and 3 cause only a small reduction in the low level of astrocyte proliferation occurring in chemically defined medium, they each inhibit the effects of five astrocyte mitogens (bFGF, EGF, PDGF, IL‐1α, and IL‐2). Inhibition is observed when astrocytes are exposed to mitogen and TGF‐r3 at the same time and when they are exposed to TGF‐β prior to, and separately from, mitogen. This latter effect appears to be due to the binding of TGF‐βs to astrocyte‐secreted extracellular matrix. These findings raise the possibility that TGF‐β may co‐operate with other growth factors to control astrocyte proliferation in vivo.
Distinct effects of bFGF and PDGF on oligodendrocyte progenitor cells
Authors: McKinnon Randall D. , Smith Carolyn , Behar Toby , Smith Thomas , Dubois‐Dalcq Monique 
Published: January 2005

AbstractWe have compared the effects of platelet‐derived (PDGF) and basic fibroblast (bFGF) growth factors on the shape, migration, and differentiation of oligodendrocyte progenitor cells, the precursors of myelin‐forming cells in the CNS. In the presence of bFGF, oligodendrocyte progenitors purified from rat neonatal brain cultures were stellate, non‐motile, and had a morphological complexity of 1.26 ± 0.03 as measured by fractal dimension (D). These cells expressed transcripts encoding the POU‐homeodomain transcription factor Oct‐6, but not myelin genes. Upon addition of PDGF, bFGF‐treated cells became motile and twofold less complex in shape (D = 1.19 ± 0.03). These changes occurred within 6 ± 4 h and were dependent on de novo transcription and translation, but not DNA synthesis. Upon removal of PDGF the cells reverted to their stellate shape (D = 1.26). Removal of both bFGF and PDGF resulted in oligodendrocyte differentiation after 3 days, with a fourfold increase in complexity of shape (D = 1.55 ± 0.08), loss of Oct‐6 transcripts, and gain of myelin transcripts. Thus PDGF is both necessary and sufficient to induce a motile state in progenitor cells growing in the presence of bFGF. Together with our previous data (McKinnon et al.: Neuron 5:603, 1990), our results suggest that bFGF and PDGF may control distinct phases of proliferation and migration of oligodendrocyte progenitor cells in vivo.
Spinal cord astrocytes in vitro: Phenotypic diversity and sodium channel immunoreactivity
Authors: Black J. A. , Sontheimer H. , Waxman S. G. 
Published: January 2005

AbstractThe expression of sodium channels in morphologically and antigenically distinct astrocytes derived from neonatal rat spinal cords was examined at various times in culture. During the course of this study [2‐40 days in vitro (DIV)], nine morphologies of glial fibrillary acidic protein (GFAP)+ cells were distinguished: (1a) flat, fibroblast‐like; (1b) elongated, with generally few, short processes; (1c) triangular soma with three short, stubby processes; (1d) bipolar with long, slender processes; (1e) bipolar with broad, flared processes; (1f) stellate with radially oriented slender processes extending from a small to moderate‐sized soma; (1g) multiple short, stubby processes extending from a moderate‐sized soma; (1h) flat, roundish shape with either a smooth edge (“pancake”‐like) or numerous very short processes; and (1i) broad, elongated cell body with orthogonally oriented short, spike‐like processes. Not all cell types were present at all times in culture. Each type of astrocyte displayed sodium channel immunoreactivity at some time in culture; however, different types of astrocytes exhibited different patterns, over time, of sodium channel staining. Sodium channel immunoreactivity in all astrocyte types was reduced to low levels by 14 DIV, and was not detectable at 40 DIV. Except for types 1b and 1e, A2B5 staining was present on all astrocyte morphologies at some time in culture, and was generally attenuated with longer times in vitro; in contrast to cultures derived from neonatal rat optic nerve, A2B5 staining does not distinguish unequivocally between the various classes of morphologically different astrocytes derived from spinal cord. O4 immunoreactivity was consistently observed only on bipolar, elongated, and process‐bearing astrocytes, though not all process‐bearing astrocytes were O4+. These results demonstrate that astrocytes derived from neonatal spinal cord are morphologically and antigenically heterogeneous. Moreover, while spinal cord astrocytes express sodium channels, these astrocytes exhibit a time‐course of channel expression that is different from astrocytes derived from several other CNS regions where sodium channel staining is maintained even for extended times in culture, suggesting a regional modulation of astrocyte function.
Independent changes of intracellular calcium and pH in identified leech glial cells
Authors: Deitmer Joachim W. , Schneider Hans‐Peter , Munsch Thomas 
Published: January 2005

AbstractThe intracellular Ca2+ (Ca2+i) and the intracellular pH (pHi) were measured in identified neuropile glial cells in the central nervous system of the leech Hirudo medicinalis, using the fluorescent dye fura‐2, and double‐barrelled, neutral carrier, pH‐sensitive microelectrodes. Different stimuli were used to elicit Ca2+i and/or pHi changes, such as application of ammonium, high external K+‐concentration, and low external pH. Ammonium (20 mM) and high external K+ (20 mM), which depolarized the glial membrane by 20–30 mV, evoked rapid and large rises of Ca2+i. In contrast to the Ca2i changes, amplitude and direction of the pHi changes were dependent on the presence of CO2/HCO3− in the saline. The addition of CO2/HCO3−, and the subsequent reduction of external pH from 7.4 to 7.0, had no effect on Ca2+i, but caused significant changes of pHi. The results suggest that the ammonium‐ and K+‐induced Ca2+i rises were due to the membrane depolarization leading to a Ca2+ influx through voltage‐gated Ca2+ channels in the glial membrane, while the pHi changes resulted from movements of ammonia and from the activation or inhibition of the Na+‐HCO3− cotransporter. This indicates that changes of intracellular Ca2+ and pH can occur independently of each other, suggesting that the homeostasis of these ions is not necessarily interrelated in these glial cells.
Oligodendroglial lineage cells express neuroligand receptors
Authors: Kastritsis C. H. , McCarthy Ken D. 
Published: January 2005

AbstractThis study was designed to determine whether cells of the oligodendroglial lineage express neuroligand receptors linked to Ca2+ mobilization. Intracellular Ca2+ levels were monitored with a video‐based imaging system and cells were characterized with immunocytochemical markers. O‐2A progenitor cells (A2B5+/GFAP‐) and mature oligodendroglia (GC+/MBP+) responded to norepinephrine, glutamate, ATP, and histamine with increased intracellular Ca2+ levels. As O‐2A progenitor cells differentiated into mature oligodendroglia, there was an increase in the percentage of cells that responded to ATP and histamine with an increase in intracellular Ca2+ levels. Both O‐2A progenitor cells and mature oligodendroglia were pharmacologically heterogeneous with respect to their ability to respond to neuroligands with an increase in intracellular Ca2+. Treatment with bradykinin, carbachol, and substance P also increased intracellular Ca2+ levels in O‐2A progenitor cells and mature oligodendroglia. Whereas the percentage of cells that responded to bradykinin and substance P increased with differentiation of O‐2A progenitor cells into mature oligodendroglia, the trend was reversed with respect to the percentage of cells responding to carbachol. These results suggest that cells of the oligodendroglial lineage exhibit neuroligand receptors linked to Ca2+ mobilization and that the ability of these cells to respond to neuroligands is developmentally regulated. © 1993 Wiley‐Liss, Inc.
Formation of the myelinated nerve fiber layer in the chicken retina
Authors: Nakazawa Tomoko , Tachi Sumie , Aikawa Eizo , Ihnuma Morio 
Published: January 2005

AbstractOligodendrocytes in the ganglion cell layer, the myelinating cells in the chicken retina, were investigated morphologically and quantitatively. Oligodendroblasts divided in the inner retinal layer around the 14th day of incubation and differentiated into oligodendrocytes. The oligodendrocytes started sheathing an axon in the nerve fiber layer at the 14th day of incubation. The number of myelin lamellae increased rapidly during the first week after chicks had hatched. An immunological reaction of antimyelin basic protein was observed on the myelin sheaths in the nerve fiber layer and on the oligodendrocytes in the ganglion cell layer. These results suggest that the oligodendrocytes form the myelinated nerve fiber layer of the chicken and that they act independently of the Müller cells during myelination. © 1993 Wiley‐Liss, Inc.
Monoamine oxidase‐B in astrocytes
Authors: Ekblom Jonas , Jossan Sukhwinder S. , Bergstrüm Mats , Oreland Lars , Walum Erik , Aquilonius Sten‐Magnus 
Published: January 2005

AbstractIn the present report we describe the astrocytic localization and content of monoamine oxidase‐B (MAO‐B) by means of a 3H‐L‐deprenyl emulsion autoradiography in primary cultures of rat astrocytes, in cryosectioned astrocytoma surgical specimen, and in cryosections of human spinal cords from patients dying in amyotrophic lateral sclerosis (ALS) and controls.The occurrence of MAO‐B enzyme protein depends on the degree of cellular differentiation as demonstrated by studies on astrocytes in primary cultures analyzed at two different stages of maturation. Highly differentiated cells exhibited high relative enzyme concentration whereas glioblasts lacked or showed very low contents of MAO‐B enzyme. This was further substantiated by studies performed on human astrocytoma tissue using 3H‐L‐deprenyl emulsion autoradiography in combination with immunohistochemical detection of glial fibrillary acidic protein (GFAP).Regional increases of MAO‐B concentration were found in ALS lumbar sections with quantitative 3H‐L‐deprenyl autoradiography. On the basis of results obtained from double staining for GFAP and MAO‐B, the increase in MAO‐B seemed to be due to an increased number of astrocytes as well as an increased content of MAO‐B in reactive species of astrocytes. A cell culture model has been used that produces cells with morphology and GFAP‐content similar to reactive cells. These astrocytes exhibited high relative content of the MAO‐B enzyme protein.In the light of the presented data, taking into account the finding that a subpopulation of reactive cells contained low levels of MAO‐B, a heterogeneity among reactive astrocytes was observed. © 1993 Wiley‐Liss, Inc.
Coexpression of PMP22 gene with MBP and P0 during de novo myelination and nerve repair
Authors: Kuhn G. , Lie A. , Wilms S. , Müller H. W. 
Published: January 2005

AbstractThe recently cloned PMP22 gene, the rat variant of the murine growth arrest‐specific gene gas3, encodes a new 22 kD integral membrane glycoprotein of peripheral myelin. By means of in situ hybridization and immunohistochemistry, we have (1) analyzed PMP22 expression in myelinated and nonmyelinated peripheral nerves, and (2) compared the spatio‐temporal changes in the expression of PMP22 mRNA with the expression of the myelin genes P0 and MBP (myelin basic protein) in developing as well as degenerating and regenerating sciatic nerve of rat. (3) We further investigated the expression of PMP22 mRNA by Northern blot in cultured Schwann cells maintained under different conditions of cell growth and arrest. Expression of PMP22 mRNA is restricted to Schwann cells of myelinated peripheral nerve. Transection of sciatic nerve in adult rat leads to a simultaneous and rapid decline in both PMP22 and P0 mRNA to nondetectable levels in the degenerating distal stump. When a demyelinated and axon‐free distal stump, as indicated by the lack of MBP and neurofilament immunoreactivity, was reanastomosed to its proximal counterpart, the coordinated reexpression of PMP22 and MBP succeeded axonal regeneration through the distal segment with a delay of 1‐2 weeks. As in regenerating nerve, a striking synchrony of expression of PMP22 and P0 transcripts, as well as MBP immunoreactivity, could be observed during sciatic nerve development. Further, in vitro evidence suggests that, unlike NIH3T3‐fibroblasts, expression of PMP22/gas3 is not strictly growth arrest‐specific in Schwann cells. In conclusion, the spatio‐temporal pattern of PMP22 gene expression in developing, injured, and regenerating peripheral nerve very closely resembles P0 and MBP expression, indicating a mechanism of PMP22 gene regulation in Schwann cells that is similar or identical to that of established myelin genes. © 1993 Wiley‐Liss, Inc.
Expression of janusin (J1–160/180) in the retina and optic nerve of the developing and adult mouse
Authors: Bartsch Udo , Pesheva Penka , Raff Martin , Schachner Melitta 
Published: January 2005

AbstractWe have analyzed the expression of the oligodendrocyte‐derived extracellular matrix molecule janusin (previously termed J1–160/180) in the retina and optic nerve ofdeveloping and adult mice using indirect light and electron microscopic immunocytochemistry, immunoblot analysis, and enzyme‐linked immunosorbent assay. In the optic nerve, janusin is not detectable in neonatal and only weakly detectable in 7‐day‐old animals. Expression is at a peak in 2‐ or 3‐week‐old animals and subsequently decreases with inceasing age. In the retina, expression inceases until the third postnatal week and then remains at a constant level. In immunocytochemical investigations at the light microscopic level, janusin was found in the myelinated regions of the nerve with spots of increased immunoreactivity possibly corresponding to an accumulation of the light microscopic level, janusin was found in the myelinated regions of the nerve with sports of increased immunoreactivity possibly corresponding to an accumulation of the molecule at the nodes of Ranvier. At the electron microscopic level, contact sites between unmyelinated axons, between axons, and glial cells, and between axons and processes of myelinating oligodendrocytes were immunoreactive. Cell surfaces of astrocytes at the periphery of the nerve and forming the glial‐limiting membrane, in contrast, were only weakly immunopositive or negative. In cell cultures of young postnatal mouse or rat optic nerves, oligodendrocytes and type‐2 astrocytes, but not type‐1 astrocytes were stained by janusin antibodies. In the oligodendrocyte‐free retina, janusin was detectable in association with neuronal cell surfaces, but not with cell surfaces of Muller cells or retinal astrocytes. Our observations indicate that expression of janusin in the optic nerve and in the retina is developmentally differentially regulated and that other cell types, in addition to oligodendrocytes, express the molecule. Since the time course of janusin expression in the optic nerve coincides with the appearance of oligodendrocytes and myelin and since janusin is associated with cell surfaces of oligodendrocytes and outer aspects of myelin sheaths and is concentrated at nodes of Ranvier, we suggest that janusin is functionally involved in the process of myelination. © 1993 Wiley‐Liss, Inc.
Microglial response to degeneration of serotonergic axon terminals
Authors: Wilson Mary Ann , Molliver Mark E. 
Published: January 2005

AbstractThe neurotoxic drug p‐chloramphetamine (PCA) causes widespread de‐generation offine, unmyelinated serotonergic (5‐HT) axons in the forebrain. PCA toxicity is selective for 5‐HT axon terminals; preterminal axons and cell bodies are spared. Degeneration is followed by slowly progressive axonal sprouting and partial reinnervation. PCA is injected subcutaneously; this route of administration avoids mechanical disruption of the blood brain barrier. The present study analyzed the response of microglia and astrocytes in rat brain to selective ablation of 5‐HT axons by PCA. Several microglial markers were analyzed with immunocytochemical methods. An increase in the number of microglial processes and in immunoreactive staining was observed with antibodies directed against CR‐3, MHC‐I, CD4, and rat LCA. The microglial response was maximal 3 weeks after PCA treatment, became less evident 6 weeks after treatment, and by 9 weeks no difference was observed between treated and control rats. No change was detected in MHC‐II or the macrophage marker ED1, nor in expression of GFAP by astrocytes. Thus, degeneration of 5‐HT axon terminals affects only a subset of the micro‐glial markers examined; in comparison, retrograde reaction to facial nerve transection causes a robust increase in all of these markers and in GFAP. The microglial response to PCA‐induced axon loss is slow in onset and small in magnitude. These findings indicate that CNS microglia are activated by degeneration of fine, unmyelinated 5‐HT axon terminals; furthermore, sensitive microglial markers can detect a subtle axonal lesion that provokes no detectable increase in GFAP expression by astrocytes. © 1994 Wiley‐Liss, Inc.
FGF‐2 in the MPTP model of parkinson's disease: Effects on astroglial cells
Authors: Otto Dörte , Unsicker Klaus 
Published: January 2005

AbstractFibroblast growth factor (FGF) is synthesized and stored by astroglial cells and regulates their proliferation and differentiation in vitro. Its implication in the transformation of quiescent astrocytes into reactive astroglia has been discussed. Using a mouse model of Parkinson's disease, in which FGF‐2 has been shown to exert marked neuroprotection of nigrostriatal dopaminergic neurons, we have studied striatal levels of glial fibrillary acidic protein (GFAP), an established marker for astrocytes, and the distribution and morphologies of GFAP‐immunoreactive cells following treatments with the neurotoxic drug 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP), the growth factor FGF‐2, and the non‐trophic control protein cytochrome C (cyt C). Systemic injections of MPTP (30 mg/kg) on 3 consecutive days, which we have previously shown to cause profound and long‐lasting damage to the nigrostriatal system, induced an approximate 20% transient increase in striatal GFAP, determined by enzyme‐linked immunosorbent assay (ELISA), 1 day after the final MPTP injection (= day 4), with subsequent normalization at day 7, which lasted until the end of the experiment (day 18). Morphologically, MPTP elicited a marked increase in number, size, arborization, and stainability of GFAP‐immunoreactive cells at day 4 in a striatal area adjacent to the corpus callosum, which was evaluated throughout all experiments. Even on day 18, astrocytes were still apparently larger and more branched than in unlesioned controls. Administration of 4 μg of either FGF‐2 or cyt C (soaked into a piece of Gelfoam unilaterally to the right striatum in either MPTP‐ or saline‐injected controls) increased striatal GFAP levels bilaterally about 2‐ to 2.5‐fold at 14 days, when FGF‐2 showed marked protection of dopaminergic parameters. Likewise, GFAP immunocytochemistry revealed increased numbers of intensely immunoreactive astrocytes under any experimental situation. Differences in the morphologies of astrocytes in FGF‐2‐ and cyt C‐treated animals were very subtle and only noted at greater distances away from the site of application of the factors. We conclude that FGF‐2, a potent neurotrophic factor for the neurotoxically lesioned nigrostriatal system, does not cause a marked astrogliotic reaction, which might be expected from previous in vitro and in vivo studies in other neural systems. This may limit concerns regarding potential applicability of FGF‐2 to the parkinsonian striatum. © 1994 Wiley‐Liss, Inc.
Roles for protein kinases in the induction of nitric oxide synthase in astrocytes
Authors: Simmons Martha L. , Murphy Sean 
Published: January 2005

AbstractLipopolysaccharide (LPS) or a combination of interferon (IFN)‐γ and interleukin (IL)‐1β can induce a calcium‐independent nitric oxide synthase (iNOS) in astrocyte cultures (Simmons and Murphy: J Neurochem 59:897, 1992; Eur J Neurosci 5:825,1993; Galea et al: Proc Natl Acad Sci USA 89:10945,1992). This induction can be measured by assaying cyclic GMP levels in the cultures, which correlates with, but is more sensitive than, measurement of nitrite accumulation. To study potential second‐messenger systems involved in the induction of iNOS, phorbol 12‐myristate 13‐acetate (PMA), a protein kinase C (PKC) activator, and various protein kinase inhibitors were employed. PMA induced a time‐, dose‐, and L‐arginine‐dependent increase in cyclic GMP, which could be inhabited by dexamethasone or actinomycin D. This induction could be dramatically increased by concurrent treatment with IFN‐y. The presence of iNOS mRNA could be demonstrated by hybridization with a specific cDNA probe. H7 (a non‐specific serine/threonine kinase inhibitor) but not H89 (a more specific PKA inhibitor) prevented induction by all agents. However, downregulation of PKC or pretreatment with the PKC inhibitor calphostin C did not prevent the induction by LPS or cytokines, suggesting that PKC is not necessary for iNOS induction by these mediators. Additionally, genistein (a nonspecific tyrosine kinase inhibitor) could prevent induction by all agents, but the more specific inhibitor, tyrphostin, attenuated only NOS induction by LPS. These results suggest that activation ofPKC can lead to, but is not necessary for, the induction of NOS in astrocytes and that there is a potential role for tyrosine kinases in NOS induction by LPS. This complex control of induction of iNOS, seemingly requiring activation of multiple pathways for maximal effect, might represent a safeguard to prevent production of potentially toxic nitric oxide (NO) under normal physiological conditions. © 1994 Wiley‐Liss, Inc.
Mobilization of intracellular calcium by substance p in a human astrocytoma cell line (U‐373 MG)
Authors: Bordey A. , Feltz P. , Trouslard J. 
Published: January 2005

AbstractVariations in intracellular free calcium concentration (Δ[Ca2+]i) were measured in intact and isolated human astrocytoma cells (U373 MG) loaded with fura‐2 acetoxymethylester. Microperfusion of 50 nM substance P (SP), applied for 1 s, increased [Ca2+]i by 351 nM from a stable basal level of [Ca2+]i of 26 nM. The peak Δ[Ca2+]i induced by SP was dose dependent with a threshold of 10‐3 nM, an ED50 of 1.3 nM and a maximal effect for concentrations of SP greater than 100 nM. The NKI receptor agonist, [Sar9Met(O2)11]SP, mimicked the effect of SP, while the NK2 and NK3 selective receptor agonists, [N110]NKA(4‐10) and senktide, respectively, had no effect. The Δ[Ca2+]i induced by SP was unaffected by 100 μM cadmium or by removal of extracellular calcium ions. Caffeine up to 30 mM had no effect on [Ca2+]i. In contrast, thapsigargin increased resting [Ca2+]i by 92 nM and reduced the Δ[Ca2+]i induced by SP. A pertussis treatment (500 ng/ml‐24 h) did not modify the Δ[Ca2+]i induced by SP.We conclude that SP, acting on a NK1 receptor, mobilizes cytosolic calcium from an intracellular calcium pool which can be partially depleted by thapsigargin. © 1994 Wiley‐Liss, Inc.