bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sodium channels in astrocytes of rat optic nerve in situ: Immuno‐electron microscopic studies
Authors: Black J.A. , Waxman S.G. , Friedman B. , Elmer L.W. , Angelides K.J. 
Published: January 2005

AbstractImmuno‐electron microscopic localization of sodium channels within astrocyte somata and processes of adult rat optic nerve was demonstrated with polyclonal antibody 7493. In immunoblots of crude glycoproteins from adult rat optic nerve, antisera 7493, which is directed against purified rat brain sodium channels, recognizes a 260 kDa protein. Antisera 7493 intensely immunostains axon membrane at nodes of Ranvier. Associated perinodal astrocyte processes are also stained with antisera 7493. In addition, astrocyte cell bodies and major processes exhibit immunoreactivity with antibody 7493. Immunostaining with antisera 7493 is heterogeneously distributed within astrocyte cytoplasm and also appears to be associated with some regions of astrocyte plasmalemma. Glial filaments are not immunostained with 7493 antisera. Astrocyte processes forming the glial limitns and surrounding blood vessels display reduced immunoreactivity to 7493 compared to longitudinally oriented or perinodal astrocyte processes. However, some focal regions of the glial limitans exhibit robust 7493 immunostaining. Oligodendrocytes do not display 7493 antisera immunoreactivity. Optic nerve sections incubated with preimmune sera or with 7493 antisera that had been previously adsorbed with purified sodium channel protein, exhibited no immunoreactivity. These results demonstrate localization of sodium channels within astrocytes in situ of rat optic nerve and extend previous electrophysiological and pharmacological findings of sodium channels in cultured astrocytes. Possible functional roles of sodium channels within astrocytes are discussed.
Phosphorylation of myelin basic protein in intact oligodendrocytes: Inhibition by galactosylsphingosine and cyclic AMP
Authors: Vartanian Timothy , Dawson Glyn , Soliven Betty , Nelson Deborah J. , Szuchet Sara 
Published: January 2005

AbstractWe have previously shown that cyclic AMP (cAMP) inhibits the protein kinase C (PKC)‐mediated phosphorylation of myelin basic protein (MBP) in cultured oligodendrocytes (OLGs). Recently, it has been demonstrated that the long chain base sphingosine inhibits PKC by competing with PKC effectors (diacylglycerol and phorbol esters) for a binding site on the kinase (Hannun and Bell: Science 235:670–674, 1987). In this report we define further the mechanism by which cAMP inhibits MBP phosphorylation by comparing the effects of cAMP with that of galactosysphingosine (psychosin), a potential catabolite of galactocerebroside, the major OLG glycosphingolipid. We identify the consequences of psychosine treatment and PKC down‐regulation on OLG morphology and electrophysiology and discuss their relevance. Our results in intact ovine oligodendrocytes are consistent with a mechanism in which cAMP inhibits MBP phosphorylation by interfering with the release of diacylglycerol (DAG) from phosphatidylinositol. First, the effects of cAMP on MBP phosphorylation are reversed with exogenous TPA; and second, cAMP inhibits the incorporation of 1‐[14C]arachidonate into DAG and specifically inhibits the turnover (as judged by 32PO3–4 incorporation) of phosphatidylinositol. Psychosine inhibits MBP phosphorylation, and its action can be reversed by TPA suggesting a mechanism of inhibition similar to that described for other systems. In addition, psychosine has profound effects on OLG morphology; it disintegrates OLG processes while leaving the cell soma intact. Stable hyperpolarized resting potentials were obtained following psychosine treatment, but there was a 66% decrease in membrane capacitance indicating a significant decrement in membrane surface area. The morphological changes induced by psychosine are reversible and can be eliminated by removing the drug but not by the addition of TPA. Whether inhibition of PKC by psychosine plays any role in process dissolution remains an unanswered question. However, current evidence suggests that a PKC‐independent mechanism may be at play. This investigation in conjunction with our previous work emphasizes a role for the interregulation of protein kinase A (PKA) and PKC in the control of OLG somal vs. myelin components. This may have significant implications for central nervous system myelin assembly.
Phosphotyrosine antibodies specifically label ameboid microglia in vitro and ramified microglia in vivo
Authors: Lee Tillotson Meryl , Wood John G. 
Published: January 2005

AbstractUsing an affinity‐purified, polyclonal antibody to phosphotyrosine (Wang: Molecular and Cellular Biology 5:3640–3643, 1985) we have previously demonstrated that phosphotyrosine immunoreactivity is restricted to a population of multipolar GFAP‐negative neuroglia in adult rat brain (Tillotson and Wood: Journal of Comparative Neurology 282:133–141, 1989) and retina (Tillotson and Wood: Journal of Cell Biology 107:724a, 1988). In this study, we show that the phosphotyrosine‐immunoreactive cells are microglia. This conclusion is supported by numerous morphological and ultrastructural similarities between the phosphotyrosine‐immunoreactive cells and microglia. Furthermore, phosphotyrosine co‐localizes with the microglial‐specific B4 isolectin of Bandeiraea simplifolia‐1 lectin. Phosphotyrosine antibodies also stain ameboid microglia in primary cultures of neonatal rat brain. In addition, after 7 days in vitro, microglia are the only phosphotyrosine‐immunoreactive element in the cultures. This temporal pattern of staining in vitro mimics the developmental progression of phosphotyrosine immunoreactivity in situ, in which a variety of structures stain during postnatal neural development (Tillotson and Wood: Journal of Comparative Neurology 282:133–141, 1989), but only microglia stain in mature brain. The significance of phosphotyrosine‐containing proteins potentially expressed in a microglial‐specific manner is discussed.
Visualization of oligodendrocytes and astrocytes in the intact rat optic nerve by intracellular injection of lucifer yellow and horseradish peroxidase
Authors: Butt Arthur M. , Ransom Bruce R. 
Published: January 2005

AbstractThe morphology of glial cells in the intact rat optic nerve, a central nervous system (CNS) white matter tract, was analysed by filling over 500 macroglial cells intracellularly with horseradish peroxidase (HRP) or Lucifer yellow (LY). Two main cell types were distinguished: fibrous astrocytes and cells presumed to be oligodendrocytes. Intracellularly stained astrocytes were highly complex, with 50–60 long branching processes which passed radially from the cell body and terminated in end‐feet at the pial surface or on blood vessels; some processes ended freely in the nerve parenchyma. Astrocytes filled with LY were usually dye‐coupled to other astrocytes after the first week of life. Filled oligodendrocytes had a unique appearance that unmistakably distinguished them from astrocytes and were occasionally dye‐coupled to nearby oligodendrocytes. These cells had 20–30 longitudinally oriented processes 150–200 μm long, which passed exclusively along the long axis of the nerve parallel to axons; the longitudinal processes were connected to the cell body by thin branches 15–30 μm long. The longitudinal processes probably represent the tongue processes of the internodal myelin sheaths, and thus each oligodendrocyte appears to myelinate 20–30 axons with sheaths that are 150–200 μm in length.
Human chromogranin A‐like immunoreactivity in the bergmann glia of the rat brain
Authors: McAuliffe W. Geoffrey , Hess Arthur 
Published: January 2005

AbstractA mouse monoclonal antibody to human chromogranin A (LK2H10) selectively stains the Bergmann glia (Golgi epithelial cells) of the rat cerebellum, while rabbit antibodies to bovine or porcine chromogranin A do not. Chromogranin A immunostaining in the cell bodies and processes reveals the characteristic candelabra morphology seen in Golgi preparations of these cells. Immunostaining adjacent sections with antibodies to glial fibrillary acidic protein shows that a relatively small number of the glial cell processes in the molecular layer are chromogranin A positive. Recent reports indicate that the metabolites of chromogranin A play a regulatory role in endocrine and neuroendocrine systems but the function of chromogranins in neurons and glia is unknown.
Transection of the rat olfactory nerve increases glial fibrillary acidic protein immunoreactivity from the olfactory bulb to the piriform cortex
Authors: Anders Juanita J. , Johnson Julie A. 
Published: January 2005

AbstractAstrocytic glial fibrillary acidic protein (GFAP) immunoreactivity in response to retrograde changes of motoneurons after axotomy has been the subject of a number of reports. In contrast, this study examined the astrocytic GFAP immunoreactivity in response to axotomy in a sensory system, the adult rat olfactory system. The purpose of this study was to determine, by immunolabeling GFAP, the extent and transience of astrocytic reactivity in the olfactory system. Unilateral transection of the olfactory nerve fascicles was performed intracranially at the level of the cribriform plate. Rats were allowed to survive from 24 hours to 1 month after axotomy. GFAP immunolabeling was examined throughout the rat olfactory system using the peroxidase–anti‐peroxidase method. After axotomy, a transient increase occurred in the astrocytic GFAP immunore‐activity in the ipsilateral olfactory system. The greatest enhancement of GFAP immuno‐reactivity in the olfactory system occurred at 48 hours post‐axotomy. Increased GFAP immunoreactivity occurred not only along the axons and synaptic endings of the injured primary olfactory neurons, but also along the dendrites, cell bodies, axons, and synaptic endings of the secondary sensory neurons. The increased GFAP immunoreactivity was specifically associated with the anatomical distribution pathways of the primary and secondary olfactory neurons. Increased GFAP immunoreactivity was not altered until 14 days post‐axotomy. At 1 month post‐axotomy, GFAP immunoreactivity returned to control levels. The time course and transience of increased GFAP immunoreativity closely correlates with the time course of rat primary olfactory neuronal degeneration and regeneration after axotomy. The increase in astrocytic GFAP immunoreactivity along the secondary olfactory neurons suggests the existence of a transsynaptic effect that is directly related to the state of degeneration and regeneration of the primary olfactory neurons.
Expression of glial fibrillary acidic protein (GFAP) in goldfish optic nerve following injury
Authors: Stafford C. A. , Shehab S. A. S. , Nona S. N. , Cronly‐Dillon J. R. 
Published: January 2005

AbstractBy using an antibody to goldfish glial fibrillary acidic protein (GFAP), the reaction of goldfish optic nerve to injury has been studied by immunoblotting and immunohistochemical methods. Goldfish optic nerve, which normally lacks GFAP immunoreactivity (Nona et al.: Glia, 2:189–200, 1989), expresses GFAP following injury. This immunoreactivity, which is observed as early as 10 days after crush and which is still evident at 30 days after crush, all but disappears by 150 days after crush. Since it is well established that functional restoration of synaptic connections and the recovery of vision takes place in goldfish following optic nerve injury, our results indicate that reactive astrocytes do not represent an impediment to regeneration in goldfish visual system.
A functional parameter to study heterogeneity of glial cells in rat brain slices: Cyclic guanosine monophosphate production in atrial natriuretic factor (ANF)‐responsive cells
Authors: De Vente J. , Manshanden C. G. , Sikking R. A. , Ramaekers F. C. S. , Steinbusch H. W. M. 
Published: January 2005

AbstractStimulation of guanylate cyclase in vitro by atrial natriuretic factor (ANF) or sodium nitroprusside was studied in rat brain tissue slices biochemically as well as by means of cyclic guanosine monophosphate (cGMP) immunocytochemistry. The ANF‐responsive, cGMP‐producing cells were studied in the olfactory bulb, the septal area, the hippocampus, the medial amygdala, and the medial preoptic area. These cells, having the ANF‐stimulated particulate guanylate cyclase, were characterized as astroglial cells on the basis of their glial fibrillary acidic protein (GFAP) immunostaining, although not all astroglial cells in these areas could be identified as cGMP‐immunoreactive cells. Sodium nitroprusside‐stimulated soluble guanylate cyclase activity was demonstrated in neuronal cell bodies and varicose fibers and was associated with blood vessel walls.Upon maturation, a significant decrease in cGMP production was found after stimulation by 100 nM ANF‐(103–126) in the olfactory bulb, the medial amygdala, and the hippocampus, but not in the septal area; no change was found in these areas in cGMP content after stimulation of cGMP production by 10 μM sodium nitroprusside. Via cGMP immunocytochemistry, no qualitative differences were seen in the ANF‐responsive, cGMP‐producing cells upon maturation.
Region‐ and sex‐related differences in maturation of astrocytes in dissociated cell cultures of embryonic rat brain
Authors: Beyer C. , Epp B. , Fassberg J. , Reisert I. , Pilgrim C. 
Published: January 2005

AbstractPrevious studies using dissociated cell cultures of fetal rat brain have revealed considerable regional diversity as well as sex steroid‐independent sex differences in developmental schedules of dopaminergic neurons. Because these phenomena might be related to glial heterogeneity, cultures of dissociated male and female diencephalon, mesencephalon, and rhombencephalon of gestational day 14 rats were investigated with respect to the development of astrocytic markers. Cultures were incubated for 3–8 days in vitro (DIV) in serum‐supplemented or serum‐free medium. Vimentin and glial fibrillary acidic protein (GFAP) were quantified by counting of immunolabeled cells and immunoblotting. Vimentin and GFAP content rose from DIV 3 to 6 in all cultures. Regional variation of vimentin content was low, but large differences occurred in amounts of GFAP. GFAP reached high levels in rhombencephalon, especially when supplemented with serum, but remained very low or not detectable in mesencephalon. Simultaneous immunostaining for both cytoskeletal proteins revealed the presence of large numbers of vimentin single‐labeled and small numbers of vimentin/GFAP double‐labeled cells. Numbers of cells expressing GFAP showed similar regional variations as GFAP contents in both serum‐free and serum‐supplemented medium. They rose steeply from DIV 3 to 8 in rhomb‐ and diencephalon but not in mesencephalon. Transiently, female diencephalic cultures contained slightly more GFAP‐immunoreactive cells than male cultures. The results thus demonstrate considerable regional heterogeneity of astrocytic maturation. However, neither the regional nor the sex differences show a consistent correlation with previous data on development of dopaminergic and other monoaminergic neurons in vitro. It seems likely that the dependence of neurons on glial environment for realization of an inherent developmental program varies among neuronal phenotypes.
Intracellular pH shifts capable of uncoupling cultured oligodendrocytes are seen only in low HCO3− solution
Authors: Kettenmann H. , Ransom B. R. , Schlue W.‐R. 
Published: January 2005

AbstractElectrical coupling between cultured mouse oligodendrocytes was transiently blocked when pHi was decreased below about 6.5 using the NH4+ prepulse method. This uncoupling could, however, only be achieved if the dominant pHi regulating mechanism in these cells, the Na+/HCO3− cotransporter, was blocked by lowering bath [HCO3−]. Under this condition, an NH4+ prepulse caused pHi to decrease toward the passive distribution for H+ (i.e., about pH 6.2). In the presence of normal bath [HCO3−] an NH4+ prepulse did not decrease pHi below 6.5 even when the second pHi regulating mechanism, the Na+/H+ exchanger, was blocked by amiloride, and consequently oligodendrocytes could not be uncoupled. Increasing CO2, which uncouples glial cells in situ (Connors et al: J. Neurosci. 4:1324–1330, 1984), did not uncouple cultured oligodendrocytes in the presence of normal bath [HCO3−], but did cause uncoupling in low [HCO3−] solution. These results indicate that electrical coupling between cultured oligodendrocytes is sensitive to pHi; in normal bath [HCO3−], however, the pHi regulation of these cells is so effective that standard techniques for intracellular accidification are unable to lower pHi to levels which cause the closure of oligodendrocyte gap junctions.
Schwann cells depleted of galactocerebroside express myelin‐associated glycoprotein and initiate but do not continue the process of myelination
Authors: Owens Geoffrey C. , Bunge Richard P. 
Published: January 2005

AbstractTwo peripheral myelin components, galactocerebroside (GalC) and myelin‐associated glycoprotein (MAG), are known to be expressed early in Schwann cell differentiation, prior to the formation of definitive myelin segments containing compacted membrane. To discern the relative roles of these myelin components, cultures of Schwann cells and dorsal root ganglion neurons were treated with antigalactocerebroside mAbs in order to remove GalC from the Schwann cell surface (Ranscht et al., 1987). In the continuous presence of anti‐GalC antibodies and in a medium containing serum plus ascorbic acid, Schwann cells assemble a basal lamina and progress to the one:one stage of Schwann cell:axon interaction but do not differentiate further. Immunostaining with anti‐MAG antibodies revealed that GalC‐depleted Schwann cells expressed high levels of MAG. Double staining with anti‐MAG and anti‐Po antibodies showed that there was essentially no Po immunoreactivity in the same cells. In those Schwann cells that had attained a one:one association with large‐diameter axons, the inner‐axon‐related cytoplasmic process had passed under the outer mesaxon but had not completed a full turn around the axon. The expression of MAG on the single cytoplasmic process apposed to the axon in Schwann cells depleted of GalC further implicates MAG in the initial envelopment of the axon during myelination.
Neuronal‐glial interactions: Complexity of neurite outgrowth correlates with substrated adhesivity of serotonergic neurons
Authors: Lieth Erich , McClay David R. , Lauder Jean M. 
Published: January 2005

AbstractTo study the interactions between neurons of known transmitter phenotype and non‐neuronal cells of glial or fibroblastic origin, serotonergic (5‐HT) neurons were tested for their strength of adhesion and neurite outgrowth patterns on substrates of astrocytes or fibroblasts using a cell adhesion assay for transmitter‐identified neurons, and morphometry of immunocytochemically stained neurons in dissociated cell cultures. Both the strength of adhesion and the rate and complexity of neurite outgrowth by 5‐HT neurons were significantly greater on substrates of astrocytes compared to fibroblasts. These results provide evidence that 5‐HT neurons can interact selectively with glia via cell surface determinants, and that this process may be important for the development of complex (dendrite‐like) neuritic arbors. The methods developed in this study will be useful for future studies of interactions between transmitter‐identified neurons and glial cells during ontogeny of the embryonic brain.
Growth of adult rat retinal ganglion cell neurites on astrocytes
Authors: Baehr M. , Bunge R. P. 
Published: January 2005

AbstractAstrocytes, as well as Schwann cells (SC), can provide suitable substrata for embryonic neurites during development, but their abilities to support adult regenerating neurites have not been directly compared. The aim of the present study was to determine the ability of astrocytes to promote adult rat retinal ganglion cell (RGC) regeneration in vitro and to compare this to previously determined growth on the surface of Schwann cells. We prepared Type I astrocytes (Raff et al: J. Neurosci. 3:1289–1300, 1983) from perinatal rats. These were subcultured and maintained in either a serum‐free medium for at least 2 weeks (stellate astrocytes with little immunoreactivity for laminin) or in serum containing medium for 7 to 10 days (flat and polygonal astrocytes with immunoreactivity for laminin). Stellate astrocytes might therefore represent mature astrocytes in vivo (Ard and Bunge: J. Neurosci. 8:2844–2858, 1988), while flat astrocytes might resemble immature brain astrocytes (Liesi et al: J. Cell Biol. 96:920–924, 1983). Adult RGC survival and axonal regrowth on these glia populations was compared to that observed on different SC populations, as previously reported (Baehr and Bunge: Exp. Neurol. 106:27–40, 1989). Both astrocyte populations (either flat or stellate astrocytes) did not enhance RGC survival. Stellate astrocytes were less effective in supporting RGC axon regeneration than flat astrocytes. When these date were compared to RGC survival and axon growth on SC (Baehr and Bunge: Exp. Neurol. 106:27–40, 1989) only “ctivated” mature SC populations were superior to astrocytes in enhancing RGC survival and neurite regrowth. These results suggest 1) that astrocytes and “immature” SC are similar in their ability to support RGC survival; 2) “activated” mature SC populations are significantly better than astrocytes and “immature” SC in enhancing RGC survival and neurite growth; 3) stellate (“mature”) astrocytes, although permissive for regrowing axons, are not a favorable substrate for regenerating adult RGC neurites, nor do they effectively support RGC survival.
Dark‐rearing retards the maturation of astrocytes in restricted layers of cat visual cortex
Authors: Müller Christian M. 
Published: January 2005

AbstractThe cat visual cortex develops its mature appearance, i.e., its circuitry and neuronal morphology, during a limited period of postnatal development under the influence of visual experience. The critical period for cortical plasticity, which normally extends from the third to seventh postnatal week, can be prolonged by raising animals in total darkness. The prolongation of the critical period by dark‐rearing is restricted to the cortical layers except layer IV. Besides the influence of afferent activity on the physiology of cortical cells and on the interconnectivity of thalamo‐cortical afferents, visual experience has also been shown to affect the development of glial cells. The present study investigates the effects of dark‐rearing on astroglial characteristics as determined by immunostaining for glial fibrillary acidic protein (GFAP) and the S‐100 protein. The data reveal a retardation of astrocytic maturation in dark‐reared animals, shown by a reduced presence of GFAP immunoreactivity compared to light‐experienced animals. The density of astrocytic cell bodies positive for S‐100 is unaffected by dark‐rearing, suggesting that astroglial proliferation does not rely on afferent activity. However, punctate S‐100 staining in the neuropil, which has been shown to reflect astrocytic processes, was also reduced in certain cortical layers in dark‐reared animals. The effects of dark‐rearing on the expression of GFAP and S‐100 were restricted to the cortical layers except layer IV, i.e., those layers that reveal a prolongation of the critical period for cortical plasticity following dark‐rearing. It is concluded that astrocytic maturation in the visual cortex is influenced by neuronal activity. The coincidence of the location of retarded astrocytic maturation and the prolongation of the critical period for cortical plasticity is discussed in the light of the recent evidence that immature astrocytes may be involved in activity‐dependent plasticity of the visual cortex.