bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bacterial endotoxin induces [Ca2+]i transients and changes the organization of actin in microglia
Authors: Bader Marie‐France , Taupenot Laurent , Ulrich Gabrielle , Aunis Dominique , Ciesielski‐Treska Jaroslava 
Published: May 2005

AbstractWe have employed amoeboid microglia purified from primary cultures of neonatal rat brain to examine the effect of bacterial lipopolysaccharide (LPS), a potent activator of immune cells, on intracellular calcium concentration ([Ca2+]i) in brain macrophages. In single brain macrophages loaded with indo 1, pulse administration of LPS elicited a rapid and transient increase in [Ca2+]i From a total of 70 cells examined, all responded to LPS with a similar [Ca2+]i transient, indicating a good homogeneity of the cell population with regard to the LPS response. It was concluded that the rise of cytosolic [Ca2+]i originated from intracellular stores because the response to LPS occured similarly in the presence or in the absence of extracellular Ca2+. A second administration of LPS to the same cells resulted in a second but reduced [Ca2+]i transient. In contrast to the first response to LPS, this second response was totally dependent on the presence of Ca2+ in the extracellular medium. The first response to LPS was strongly inhibited by ruthenium red and could be suppressed in a reversible manner by pre incubating the cells with caffeine in the absence of Ca2+ in the extracellular medium. These results indicate that caffeinesensitive intracellular Ca2+ stores may be the major source of Ca2+ in the response of brain macrophages to LPS. The possible release of Ca2+ from phosphatidylinositol(3,4,5)‐trisphosphate (IP3)‐sensitive stores in brain macrophages was also evaluated by stimulating cells with the IP3‐mobilizing agonist histamine. Brain macrophages were heterogeneous with regard to the histamine response since histamine induced a [Ca2+]i rise in only 30% of cells examined.The increase in [Ca2+]i triggered by LPS may in turn activate several intracellular events involved in the transition from one microglial functional state to another. We examined the effect of LPS on the state of organization of actin, which is an essential component of chemoattractant signal transduction. Immunofluorescence staining with anti‐actin antibody which recognizes actin in both filamentous and nonfilamentous configurations, indicated that LPS produced drastic changes in the actin organization. LPS‐treated cells appeared more intensely fluorescent than untreated cells due to the concentration of diffuse fluorescence near the center of the cell. In addition, prominent fluorescent dots were present in the subplasmalemmal region in cells stimulated with LPS. This specific LPS‐induced reorganization of actin was also observed in cells preincubated in the external medium without Ca2+. Thus, it is likely that the LPS‐induced mobilization of Ca2+ from intracellular stores may be responsible for the changes observed in the actin organization. © 1994 Wiley‐Liss, Inc.
Astrocyte‐schwann cell interactions in culture
Authors: Ghirnikar Roopa S. , Eng Lawrence F. 
Published: May 2005

AbstractAfter injury, either as a result of trauma or degenerating/demyelinating diseases, axons of the central nervous system (CNS) normally fail to regenerate. Transplantation of glial cells, particularly Schwann cells, into areas of injury or demyelination has been considered a promising approach to promote recovery. However, the extent of Schwann cell interaction with CNS axons is greatly influenced by the presence of astrocytes which redefine the CNS‐PNS (peripheral nervous system) boundary in a lesioned CNS, thereby preventing invasion of Schwann cells. The molecular basis for this restrictive effect of astrocytes on Schwann cells is not known. In the present study, we have cocultured astrocytes and Schwann cells to develop an in vitro model to characterize this interaction. Astrocytes in contact with Schwann cells appeared hypertrophied and showed increased staining for glial fibrillary acidic protein (GFAP). In cocultures maintained for 2‐3 weeks, segregation of the two cell types was observed, Schwann cells appeared in groups, and each group was surrounded and separated from one another by astrocytic processes. Since the behavior of these two cell types observed in culture is very similar to their interaction seen in vivo, this coculture model may be useful in further studying the relationship between astrocytes and Schwann cells. © 1994 Wiley‐Liss, Inc.
Axons regulate the expression of shaker‐like potassium channel genes in Schwann cells in peripheral nerve
Authors: Chiu S. Y. , Scherer S. S. , Blonski M. , Kang S. S. , Messing A. 
Published: May 2005

AbstractWe examined potassium channel gene expression of two members of the Shaker subfamily, MK1 and MK2, in sciatic nerves from rats and mice. In Northern blot analysis, MK1 and MK2 probes detected single transcripts of ∼8 kb and ∼9.5 kb, respectively, in sciatic nerve and brain from both species. Polymerase chain reaction amplification of a cDNA library of cultured rat Schwann cells using MK1‐ and MK2‐ specific primers produced DNA fragments that were highly homologous to MK1 and MK2. To determine whether these channel genes were axonally regulated, we performed Northern blot analysis of developing, permanently transected, and crushed rat sciatic nerves. The mRNA levels for both MK1 and MK2 increased from P1 to P15 and then declined modestly. Permanent nerve transection in adult animals resulted in a dramatic and permanent reduction in the mRNA levels for both MK1 and MK2, whereas normal levels of MK1 and MK2 were restored when regeneration was allowed to occur following crush injury. In all cases, MK1 and MK2 mRNA levels paralleled that of the myelin gene P0/sb. Elevating the cAMP in cultured Schwann cells by forskolin, which mimics axonal contact but not myelination, did not induce detectable leveles of MK1 and MK2 mRNA by Northern blot analysis. Further, the level of MK1 mRNA in the vagus nerve, which contains relatively fewer myelinating Schwann cells and relatively more non‐myelinating Schwann cells than the sciatic nerve, is reduced relative to the sciatic nerve. In conclusion, we have identified two Shaker‐like potassium channel genes in sciatic nerves whose expressions are regulated by axons. We suggest that MK1 and MK2 mRNA are expressed in high levels only in myelinating Schwann cells and that these Shaker‐like potassium channel genes have specialized roles in these cells.
Postmitotic oligodendrocytes generated during postnatal cerebral development are derived from proliferation of immature oligodendrocytes
Authors: Skoff Robert P. , Ghandour M. Said , Knapp Pamela E. 
Published: May 2005

AbstractThe phenotype of proliferating glia is examined during postnatal rodent development by combining immunocytochemistry (ICC) with 3H‐thymidine autoradiography (ARG) to identify cells in the S phase of the cell cycle. Antibodies (ABs) which are specific for cells in the oligodendrocyte (OL) lineage were utilized, with emphasis placed upon the proliferation of OLs as it remains unclear whether this cell type divides in situ. The results show that proliferating cells stain with ABs which are specific for OLs and myelin glycolipids. The proliferating OLs (oligodendroblasts), although they do not appear to have formed myelin sheaths, have quite elaborate and distinctive morphologies. These oligodendroblasts give rise to very long, thin processes which in turn have additional branches. Their cytoarchitecture corresponds closely to cells described as oligodendroblasts with electron microscopy and whose processes often appear to be in the initial phase of myelination (Skoff et al: J. Comp. Neurol. 169:291‐312, 1976a). These proliferating OLs are still quite immature because the expression of myelin specific proteins is only occasionally observed in 3H‐thymidine labeled cells. The phenotype of the oligodendroblasts is quite different from that of proliferating astrocytes (astroblasts). As shown in previous studies (Skoff; Dev. Biol. 139:149‐163, 1990), the astroblasts, which are identified by the presence of glial fibrillary acidic protein (GFAP), usually have thick, stubby processes, and both their nucleus and cytoplasm are larger and of lighter density than those found in oligodendroblasts.In early myelinating regions of the cerebrum, glycolipid positive cells account for the majority of the 3H‐thymidine labeled cells. This data, when combined with the quantification of proliferating astrocytes (ASs) from previous immunocytochemical and electron microscopic studies, indicate that oligodendroblasts and astroblasts constitute the vast majority of the proliferating glia in the brain and in optic nerve at times when ASs and OLs are being generated. In normal postnatal cerebral development, the immature ASs and OLs which proliferate are the direct, immediate precursors for most postmitotic ASs and OLs.
Osmoregulatory changes in Myo‐inositol content and Na+/Myo‐inositol contransport in rat cortical astrocytes
Authors: Strange Kevin , Emma Francesco , Paredes Ana , Morrison Rebecca 
Published: May 2005

AbstractExposure of cortical astrocytes to 325, 350, or 390 mosM culture media for 48 h caused a 1.4‐, 2.1‐, and 3.5‐fold increase, respectively, in cellular content of the compatible osmolyte myo‐inositol. Elevated myo‐inositol levels accounted for ∼56‐100% of the solute needed by the cells for complete volume regulation under hypertonic conditions. Myo‐inositol accumulation was associated with 4‐5‐fold (peak rate) and 1.8‐2‐fold (steady‐state rate) increases in the rate of Na+ ‐dependent myo‐inositol uptake when cells were acclimated to 390 mosM culture medium for 12 h or 24‐96 h, respectively. When medium osmolality was elevated by 25 mosM, peak and steady‐state increases in myo‐inositol uptake of 1.7‐fold and 1.3‐fold, respectively, were observed. Exposure to 390 mosM medium for 12‐48 h induced a 3‐8‐fold increase in cotransporter mRNA levels suggesting that the increase in myo‐inositol uptake is brought about by increased cotransporter gene expression. Abrupt return of hypertonic cells to an isotonic medium induced a rapid increase in myo‐inositol efflux and a return of cotransporter mRNA to control values in <2 h. In contrast, the cotransporter remained fully activated at hypertonic levels for 16 h. Between 16‐24 h after the transfer, the rate of myo‐inositol uptake returned to control values. The remarkable sensitivity of the cotransporter to hypertonic stress indicates that upregulation of myo‐inositol transport in glial cells is likely to occur in a variety of disease states that cause an elevation of plasma osmolality. Slow downregulation of the cotransporter may be responsible in part for the slow loss of myo‐inositol and cerebral edema that occurs with too rapid correction of chronic plasma hypertonicity.
Transitory disappearance of microglia during the regeneration of the lizard medial cortex
Authors: Lopez‐Garcia C. , Nacher J. , Castellano B. , de la Iglesia J. A. Luis , Molowny A. 
Published: May 2005

AbstractIn normal lizards, microglial cells populate the medial cortex (a zone homologous to the hippocampal fascia dentata), with a preferential distribution along the border between the granular cell layer and the plexiform layers.Intraperitoneal injection of the neurotoxin 3‐acetylpyridine (3AP) induces a selective lesion in the medial cortex with a rapid degeneration of the granular layer and its zinc‐enriched axonal projection. Within 6‐8 weeks, the granular layer is, however, repopulated by a new set of neurons generated in the subjacent ependyma and the cell debris is removed. The aim of this study was to determine to what extent microglia were involved in the scavenging processes during the regeneration process. To this end we studied the brains of regenerating lizards at different times after 3AP lesion, visualising microglial cells by the nucleoside diphosphatase (NDPase) histochemical reaction.Surprisingly, we found that stained microglial cells disappeared 6–8 hours after 3AP injection and remained absent until 10–15 days after injection. One month postlesion an increased population of microglial cells was found scattered throughout all plexiform layers of the cortex. Thorough examination of semithin and ultrathin sections confirmed the absence of microglia in the medial cortex of recent lesioned animals but the presence of an exuberant population after 1 month postlesion. In the tissue, phagocytotic scavenging was carried out by radial ependymocytes, not by microglia.
Immunocytochemical demonstration of glycogen phosphorylase in Müller (glial) cells of the mammalian retina
Authors: Pfeiffer Brigitte , Grosche Jens , Reichenbach Andreas , Hamprecht Bernd 
Published: May 2005

AbstractGlycogen phosphorylase (GP) was immunocytochemically detected in Müller cells of the rabbit and rat retina using a monoclonal antibody raised against bovine brain GP. Immunofluorescence and immunoenzymatic procedures were applied on isolated, Müller cells and sections of paraformaldehyde‐fixed, paraffin‐embedded retinas. All methods used revealed positive immunostaining. GP immunoreactivity was most intense in the Müller cell endfeet and the pericarya, corresponding to the nerve fibre layer and the inner nuclear layer in the retina. The presence of GP in Müller cells stresses the important role of these glial cells in the energy metabolism of the mammalian retina.
Astrocyte and microglial motility in vitro is functionally dependent on the hyaluronan receptor RHAMM
Authors: Turley E. A. , Hossain M. Z. , Sorokan T. , Jordan L. M. , Nagy J. I. 
Published: May 2005

AbstractRHAMM (Receptor for Hyaluronic Acid Mediated Motility) has been identified as a receptor for the extracellular matrix component hyaluronan (HA) and was recently shown to be essential for the locomotion of normal and transformed peripheral cells. Until now the potential role of RHAMM in the motility of neural‐derived cells has not been investigated. Here, we report that cultured primary astrocytes, astrocyte cell lines, and microglia express this receptor and exhibit RHAMM‐dependent motility. Immunocytochemical localization of RHAMM showed that it was often present as aggregates at the periphery of cells in contact with one another or concentrated on protruding processes of isolated cells. Glial cells contained 50 and 72 kDa forms of RHAMM, and both of these forms were found to have HA binding capacity. Time lapse imaging of cell locomotion revealed a significant inhibition of motility and process elongation by neutralizing anti‐RHAMM antibodies and by peptides corresponding to the HA binding domains of RHAMM. These results demonstrate that RHAMM serves a role in glial cell locomotion in vitro and provide the basis for investigations of the motile behavior of glial cells in vivo after CNS injury.
Evidence for an NGF‐induced autocrine neurotrophic potential of glial cells in nervous system development
Authors: Zimmermann Astrid , Sutter Arne , Stephani Ulrich 
Published: May 2005

AbstractNGF receptor bearing peripheral glial cells, purified from chicken embryo dorsal root ganglia, were found to secrete neurite growth promoting activity (NGPA) but no NGF (detection limit 1 pM). If, however, minute concentrations of NGF (2 pM) were added to the glial cultures, an autocrine response was observed. Levels of NGF‐like activity in the medium rose up to 50‐fold. Induction of this autocrine response occured within a narrow range of NGF concentrations. NGPA production was not affected by addition of NGF. Coculture with neurons influenced the neurotrophic factor production. The data suggest that glial cells can “sense” traces of NGF and regulate its availability during neural development.
Expression of myelin transcription factor I (MyTI), a “Zinc‐Finger” DNA‐binding protein, in developing oligodendrocytes
Authors: Armstrong Regina C. , Kim Jin G. , Hudson Lynn D. 
Published: May 2005

AbstractThe production of myelin by oligodendrocytes requires the coordinated, massive synthesis of myelin components, a program that is dependent on transcriptional controls. Myelin transcription factor I (MyTI) was named for its ability to recognize the proteolipid protein (PLP) gene, the most abundantly transcribed central nervous system myelin gene (Kim and Hudson: Mol. Cell Biol. 12:5632, 1992). MyTI is a zinc‐dependent, DNA‐binding protein of the Cys2‐His‐Cys class. The pattern of MyTI expression, documented in the present study, suggests that MyTI may be instrumental in early stages of oligodendrocytic development and myelin production. MyTI mRNA transcripts are more highly expressed in oligodendrocyte progenitors than in differentiated oligodendrocytes. In vitro and in vivo analyses show that MyTI immunoreactivity is stronger in oligodendrocytic progenitors than in mature oligodendrocytes which have already accumulated PLP. In oligodendrocyte progenitors, MyTI immunoreactivity appears as speckles within the nucleus, suggestive of an association of MyTI with a function that is spatially segregated into discrete nuclear domains. MyTI continues to be expressed in cells transcribing PLP. However, as oligodendrocytes accumulate PLP, MyTI immunoreactivity becomes restricted to the cytoplasm and progressively diminishes. Since MyTI has two widely separated sets of DNA‐binding domains and initial MyTI expression markedly precedes PLP expression, we hypothesize the following model: MyTI may play a role in assembling transcriptionally active complexes of PLP, perhaps by bending the DNA of the promoter region to induce an appropriate conformation to enable subsequent binding the DNA of the promoter region to induce an appropriate conformation to enable subsequent binding of additional regulatory proteins. © 1995 Wiley‐Liss, Inc.
Astrocytes modulate retinal vasculogenesis: Effects on endothelial cell differentiation
Authors: Jiang Baoen , Alibezhadian M. , Caldwell Ruth B. 
Published: May 2005

AbstractIn the developing retina, the microvessels form by differentiation of endothelial precursor cells in a process referred to as vasculogenesis. Experiments using in vivo and in vitro model systems were designed to determine the specific influence of astrocytes on this process. Immunolocalization analyses of retinal vasculogenesis in vivo showed that astrocytes spread within the nerve fiber layer of the neonatal rat retina just ahead of the forming vessels. Then, endothelial precursor cells align themselves in register with the astrocytes. In contact with astrocytes, precursor cells differentiate as vascular endothelium, as indicated by lumen formation and patency to red blood cells. Experiments in vitro using cell culture and conditioned medium approaches showed that cell‐cell contact between rat brain astrocytes and bovine retinal endothelial cells results in release of soluble factors, inhibiting endothelial cell growth and inducing morphological differentiation in capillary‐like structures. Thus, it is suggested that astrocytes lay down the pattern for vasculogenesis and induce the elongation and alignment of endothelial precursor cells into a prevascular meshwork. In contact with astrocytes, precursor cells differentiate as vascular endothelium. Furthermore, this cell‐cell contact with astrocytes apparently inhibits endothelial cell growth and stimulates their elongation, alignment, and morphogenic differentiation by means of the release or activation of soluble, growth factor‐like substances. © 1995 Wiley‐Liss, Inc.
Characterization of a voltage‐dependent potassium channel in quid Schwann cells reconstituted in planar lipid bilayers
Authors: Noceti F. , Ramírez A. N. , Possani L. D. , Prestipino G. 
Published: May 2005

AbstractAn affinity column prepared with noxiustoxin (NTx), a K+ channel blocker from the venom of the Mexican scorpion Centruroides noxius, was used to purify a functional channel from a detergent extract of Schwann cell membrane of the giant axon of the squid Loligo vulgaris. The purified protein was reconstituted as a functional unit in a planar lipid bilayer and tested with a sequence of potentials to obtain information about single‐channel amplitude and kinetics. The reconstituted channel showed delayed rectifier behavior with a slope conductance of 10 pS under 5:1 asymmetric KCl concentrations and a clear tendency to open under negative potentials. The zero‐current potential was +36 mV, which fitted well with the Nernst equation for the CIS/TRANS K+‐concentration ratio of 5:1. The channel also showed a strong sensitivity to tetraethylammonium and its activity was inhibited by NTx, as expected from the purification procedure. The behavior of this protein in the presence of 0.5 mM ATP (cis side) was also tested, significantly increasing current fluctuations across the membrane. In order to compare the modulation of the Schwann cell K+ channel with that of the axonal K+ channel, a purified protein from the squid axon membrane was also tested in the presence of ATP. This 10–11 pS, delayed rectifier channel from the squid giant axon (Prestipino et al., FEBS Lett. 250:570–574, 1989) was also tested in the presence of ATP and showed a similar rise in activity. © 1995 Wiley‐Liss, Inc.
Cytokine‐induced expression of type II nitric oxide synthase in astrocytes is downregulated by ATP and glutamate
Authors: Murphy Sean , Lin Hsin Lee , Park Song Kyu 
Published: May 2005

AbstractCombinations of cytokines and/or phorbol ester induce expression of Type II nitric oxide synthase (NOS) mRNA in astrocyte cultures via protein kinase mediated pathways (Simmons and Murphy: GLIA 11:227, 1994; Feinstein et al.: J Neurochem 62:811,1994). Agonists that activate receptors linked to protein kinases did not reproduce this effect of cytokines in astrocytes. On the contrary, ATP and glutamate treatment of astrocytes prior to a combination of interleukin‐1ß and interferon‐γ markedly reduced (30–50%) subsequent NOS mRNA expression. The effect was not seen if treatment coincided with or followed cytokine activation, suggesting that ATP and glutamate were not destabilizing NOS mRNA. The effects of ATP and glutamate were additive and could be mimicked by selective receptor agonists, but were insensitive to a specific inhibitor of protein kinase C. The inhibition of cytokine‐induced NOS mRNA expression caused by these agents was not the result of interference with the activation/translocation of nuclear factor‐ϰB by interleukin‐1ß. These results suggest that exposure of astrocytes to ATP and glutamate, both of which increase markedly in a variety of neuropathologies, could modulate the subsequent responsiveness of these cells to NOS‐inducing stimuli. As such, this may be an important regulatory mechanism in the expression of Type II NOS in vivo. © 1995 Wiley‐Liss, Inc.
Relationship between astrocytic processes and “Perineuronal nets” in rat neocortex
Authors: Blümcke Ingmar , Eggli Peter , Celio Marco R. 
Published: May 2005

Abstract“Perineuronal nets” (PNs) ensheath a subtype of inhibitory neurons in the mammalian neocortex. In the light of the proposal that PNs consist of glial processes, we have analyzed the relationship between intracellularly injected glial cells and PNs in the rat neocortex. Glial cells were injected iontophoretically with Lucifer Yellow in lightly fixed tissue slices and PNs were visualized with the lectin from Vicia villosa. Using confocal laser scanning microscopy, glial processes and PNs were identified as distinct structures. Lectin labeling was consistently associated with the extracellular space interposed between LY‐labeled astrocyte processes and neurons. Of the different types of glial cells injected, only the densely‐ramifying protoplasmic astrocytes extended processes which could be traced to contact PNs. These protoplasmic astrocytes also sent out processes to adjacent neurons not ensheathed by PNs, and to capillaries. The present data strongly suggests that PNs do not consist of glial processes but rather support the idea that PNs represent specialized extracellular material interposed between the surface of some inhibitory interneurons and astrocytic processes. © 1995 Wiley‐Liss, Inc.