bluuebunny/crossref_metadata_2025_split huggingface dataset:
Orthogonal arrays of particles in plasma membranes of Müller cells in the guinea pig retina
Authors: Gotow Takahiro , Hashimoto Paulo H. 
Published: January 2005

AbstractPlasma membranes of guinea pig Müller cells were examined with a freeze‐fracture technique to see how orthogonal arrays are distributed in the avascular retina. Examination of the portion approximately intermediate between the optic disc and equator of the eyeball showed that all end‐feet of Müller cells were provided with arrays. Orthogonal arrays were concentrated on vitreal end‐foot membranes, i.e., membranes that were covered by the basal lamina and contacted the vitreous body, called vitreal membranes here. The arrays were rarely observed in the portions of end‐feet that did not contact the vitreous body, called lateral membranes. The distribution density of arrays in the vitreal membranes was 122.5 ± 45.3/μm2, which was over 10 times higher than that (9.6 ± 9.6/μm2) in the lateral membranes. The arrays became numerous and extended in shape at the periphery of the vitreal membrane, characteristically aligned in rows at the border where vitreal met lateral membrane, but never intruded into the domain of lateral membrane. Some arrays were composed of loosely attached particles and/or rod‐like profiles. Sometimes rod‐like profiles, 9–13 nm wide and 20–50 nm long, called linear structures here, were isolated, and sometimes they appeared in rows. Ordinary intramembrane particles (IMPs) were significantly smaller and less numerous in vitreal than in lateral membranes. IMPs larger than 9 nm in diameter were significantly fewer in the vitreal membranes, which suggests that they have been consumed to form the arrays. Although the distribution of orthogonal arrays is similar to that of K+ channels (Newman: J. Neurosci., 7:2423–2432, 1987), we consider the array an unlikely candidate for the ion channel, because its subunit particles do not protrude onto either the inner or outer surface of the membrane (Gotow and Hashimoto: J. Neurocytol., 17:399–413, 1988). Judging from their unique alignment in rows where the membrane is bent and vitreal and lateral membranes meet, the arrays may contribute to some membrane stability, resisting the physical tension at the interface with mesenchymal tissue.
Müller (glial) cells but not astrocytes in the retina of the goldfish possess orthogonal arrays of particles
Authors: der Emde Karin Berg‐Von , Wolburg Hartwig 
Published: January 2005

AbstractMüller cells as the main glial component of the retina were investigated in the goldfish by means of ultrathin sections and freeze‐fracture replicas. In the optic nerve head, they were directly compared with astrocytes. Whereas astrocytic endfeet bordering the vitreous body can easily be identified by their dense bundles of intermediate filaments, scarce membranous organelles, paravitreous caveolae, and lateral desmosomes, Müller cell endfeet reveal a looser arrangement of intermediate filaments, a characteristic pattern of triangularly shaped endoplasmic reticulum, large and pale mitochondria, and, if at all, very few desmosome‐like junctions. The paravitreous membranes at the cytoplasmic face are covered by a fuzzy coat, which is less marked in astrocytic endfeet. Caveolae are lacking. Considering the freeze‐fracture architecture of the membranes of both glial cell types, the Müller cells reveal orthogonal arrays of particles (OAP), which were predominantly located opposite to the inner limiting membrane; their density (109 ± 33 OAP/μm2) decreases abruptly with the loss of the contact between membrane and vitreous body. In contrast, astrocytes of the optic nerve head in the retina do not show any OAP in their membranes at all and are interconnected by tight junctions and desmosomes. The hypothesis suggesting that OAP might be correlated with K+ channels involved in the spatial buffering of the extracellular space is reconsidered with comparative reference to recent electrophysiological data. Further, the heterogeneity of Müller cell and astrocyte membrane equipment with OAP in the goldfish is briefly discussed.
Glutamine synthetase modulation in astrocyte cultures of different mouse brain areas
Authors: Khelil M. , Rolland B. , Fages C. , Tardy M. 
Published: January 2005

AbstractAstroglial cells from mouse cerebral hemispheres, cerebellum, olfactory bulbs, and medulla oblongata were grown in the presence of either hormones (hydrocortisone, insulin) or cell second messengers (dBcAMP, dBcGMP). Glutamine synthetase (GS) specific activity, GS protein level, and GS translation were investigated under the effect of these factors. Hydrocortisone produced a simultaneous increase in GS translation, GS level, and activity. This increase was observed in the astrocytes cultured from the four brain areas but at a variable magnitude depending on the area. The hydrocortisone effect appeared at the transcriptional level. Inversely, insulin decreased both the GS activity and the in vitro translated GS. This effect was seen only in the olfactory bulbs and the medulla. DBcAMP increased the GS biological activity only in the cerebral hemisphere cultures. It raised, however, the level of translated GS and GS protein in astrocytes from all the areas, suggesting a post‐translational effect for intracellular cAMP. DBcGMP only affected GS in the astrocytes from cerebral hemispheres and the medulla modulating either the GS transcription or the messenger RNA stability.These results suggest specific regulation for GS expression, depending on the brain area from which the cells were dissociated or on the astroglial cell population present in these cultures affecting either the transcription, the mRNA stability, or the biological activity of the protein.
Myelination requirements of central nervous system glia in vitro: Statistical validation of differences between glia from adult and immature mice
Authors: Stanhope Gail B. , Billings‐Gagliardi Susan , Wolf Merrill K. 
Published: January 2005

AbstractGila from adult optic nerve, like those from immature nerve, have been shown to colonize and myelinate cerebellar axons in combined cultures. Preliminary experiments suggested, however, that the glia from adults might require the added nutrients and/or chemical signals present in a serum and embryo extract containing medium to produce myelin, whereas glia from immature animals could form myelin in a chemically defined medium described by Hendelman et al. (1985). This observation demanded rigorous confirmation, since it depended on the meaning of a negative result (the absence of myelin), which could produced by many factors other than the composition of the medium in this complex culture system. Here we report an extensive series of experiments, with controls for all other factors, that provide unquestonable statistical validation of the additional myelination requirements of the glia from adult nerves. The cultures can now be used to identify these required substances, which may be limiting factors for central nervous system myelin regeneration in situ.
Proliferation and differentiation of a transfected schwann cell line is altered by an artificial basement membrane
Authors: Yoshino Jun E. , Neuberger Timothy J. , Cornbrooks Carson J. , Tennekoon Gihan I. , Eng Larry F. , Devries George H. 
Published: January 2005

AbstractRapidly dividing transfected Schwann cells were grown on MatrigelTM, a reconstituted basement membrane gel. Matrigel decreased the proliferation of the cells by 75% when compared to sister cultures that were grown on an untreated plastic substrate. Some transfected cells plated onto a Matrigel substrate formed colonies similar to that observed when the cells were plated on a plastic substrate. Additionally, many cells on Matrigel assembled themselves into fascicles projecting away from the colonies. These fascicles were composed of transfected Schwann cells that had assumed a bipolar appearance reminiscent of quiescent secondary Schwann cells in culture. Transfected cells grown on Matrigel contained approximately 10‐fold less glial fibrillary acidic protein when compared to sister cultures grown on an untreated plastic substrate. By indirect immunofluorescence laminin immunoreactivity appeared as globules within the cytoplasm of the cells which were cultured on a plastic substrate. However, cells that were grown on the Matrigel substrate appear to organize laminin in a linear array around themselves. These results demonstrate that the presence of an artificial basement membrane alters the morphology, rate of proliferation, and state of differentiation of a transfected Schwann cell line.
The excitatory neurotransmitter glutamate causes filopodia formation in cultured hippocampal astrocytes
Authors: Cornell‐Bell Ann H. , Thomas Prem G. , Smith Stephen J. 
Published: January 2005

AbstractCan neurons induce surrounding glia to provide a more favorable microenvironment? Synapses and nerve growth cones have been shown to release neurotransmitters (Hume et al. Nature 1983;305:632–634; Kater et al. Trends Neurosci. 1988;11:315–321; Young and Poo Nature 1983;305:634–637) providing a possible mechanism for this type of control. The excitatory neurotransmitter glutamate induces an increase in the number of filopodia on the surface of astrocytes cultured from the neonatal rat hippocampus. This seems to be associated with a receptor‐mediated event that is activated to a lesser degree by the quisqualate and kainate, but not NMDA receptors. In addition, time‐lapse video recordings have revealed a rapid extension of filopodia from the apical margins of cells treated with glutamate. The apical margins of glutamate‐treated cells studied with electron microscopy contained dense cortical actin networks that are devoid of microtubules. Coated pits are often seen to invaginate from the the apical membrane in the vicinity of filopodia. A receptor‐binding step may be followed by a rapid reorganization of cortical actin resulting in actin‐containing filopodia. This process may be mediated by inositol lipid hydrolysis. Pyramidal neurons settled on glial cultures induced filopodia to form around the entire margin of growth cones and neurite tips suggesting that these events might occur in situ.
Astrocytic reactions in spinal gray matter following sciatic axotomy
Authors: Gilmore Shirley Ann , Sims Terry J. , Leiting Jane E. 
Published: January 2005

AbstractAstrocytic responses following unilateral sciatic nerve axotomy were examined in the spinal gray matter. Using an antiserum to glial fibrillary acidic protein (GFAP), immunoreactive astrocytes were studied in both dorsal and ventral gray matter at intervals from 2 days through 34 days post‐axotomy. In all axotomized animals, increased numbers of strongly immunoreactive astrocytes were present in the gray matter ipsilateral to the surgery. Such astrocytes were absent from the contralateral intact side and from gray matter bilaterally in adjacent spinal segments not involved in formation of the sciatic nerve. These GFAP‐positive astrocytes occurred not only in association with large motor neurons in the ventral gray matter but also in association with central processes of dorsal root ganglion neurons in the dorsal gray matter. The response was quite rapid, being discernible both dorsally and ventrally as early as the second post‐operative day. This increased GFAP immunoreactivity persisted throughout the entire observation period, with the perikarya of large ventral motor neurons appearing to become surrounded or encapsulated by the immunoreactive processes. A further alteration noted at the longest post‐operative intervals was the presence in the ventral gray matter of astrocytes appearing to be binucleate. The data obtained indicate that the astrocytic response is not related solely to reactions in motor neurons and, furthermore, the rapidity with which it develops in the dorsal gray matter suggests that its induction is not dependent upon transganglionic degeneration, which others have reported to occur weeks after peripheral nerve injury.
Substance P modulation of the membrane potential of the Schwann cell of the squid giant nerve fibre
Authors: Evans Peter D. , Reale Vincenzina , Merzon Rosa Maria , Villegas Jorge 
Published: January 2005

AbstractSubstance P produced a dose‐dependent, logn‐lasting hyperpolarization of the membrane of the Schwann cells of the giant nerve fibre of the tropical squid. A survey of the effectiveness of a range of other naturally occurring tachykinin agonists suggested that the receptors present on the squid Schwann cell belong to the subtype SP‐P or NK1, for which substance P is the preferred agonist. A survey of the effectiveness of a range of substance P fragments indicated that the direct hyperpolarizing effects of the substance P molecule were mediated by peptides with an intact amidated C‐terminal. However, a second subset of receptors that can be activated by N‐terminal fragments and analogues lacking an amidated C‐terminal was also present in this preparation. The non‐subtype‐specific antagonist D‐Arg1, D‐Trp7,9, Leu11 substance P (spantide) was a potent blocker of the effects of substance P in this preparation. Activation of the substance P receptors did not interact with the effects induced by activation of either the nicotinic cholinergic receptors or octopaminergic receptors present in this preparation. However, it did potentiate the effects of activation of the receptors for vasoactive intenstinal peptide (VIP), either in response to bath application of the peptide or due to their activation by the release of an endogenous VIP‐like peptide after stimulation of the giant axon.
Laminin and s‐laminin are produced and released by astrocytes, schwann cells, and schwannomas in culture
Authors: Chiu Arlene Y. , Espinosa De Los Monteros A. , Cole Ruth A. , Loera Sofia , De Vellis Jean 
Published: January 2005

AbstractComponents of the extracellular matrix (ECM) have been implicated in the regulation of neuronal migration, axonal growth, and synaptogenesis. We have examined cultures of glial cells, Schwann cells, and schwannomas for the expression of two components of the ECM, laminin and s‐laminin, using immunohistochemical and Western blot techniques. Laminin is a potent promotor of neurite outgrowth in cultures of both central and peripheral neurons, and is present in all ECMs. In contrast, s‐laminin (for synaptic laminin), a recently described homolog of laminin, is highly localized at the neuromuscular synaptic cleft (Sanes and Chiu, Cold Spring Harbor Symp. Quant. Biol. 1983;48:667–678; Chiu and Sanes, Dev. Biol. 1984;103:456–467) and shows selective adhesivity for motor neurons (Hunter et al. Cell 1989;59:905–913). While the distribution of these ECM components have been well documented in situ, the sources of these extracellular molecules are unclear. We report that astrocytes cultured in serum‐free medium maintain an organized ECM that only bears laminin immunoreactivity; s‐laminin appears to be sequestered intracellularly. However, both molecules are found in the astrocyte conditioned medium. Thus, under these growth conditions, astrocytes produce and release laminin and s‐laminin, but only incorporate the former into an ECM. In contrast, neither molecule is present in comparable cultures of oligodendrocytes. Although no established ECM is seen in cultures of Schwann cells or schwannomas, laminin and s‐laminin immunoreactivity are present within cells and in the conditioned media. These results indicate that certain populations of non‐neuronal support cells and cell lines can produce and release both synaptic and extrasynaptic components of the ECM. The assembly of these different molecules into an organized basal lamina may require the presence of additional factors or interaction with neurons.
Gap junctional intercellular communication between cultured ependymal cells, revealed by lucifer yellow CH transfer and freeze‐fracture
Authors: Bouillé Christian , Mesnil Marc , Barriere Helene , Gabrion Jacqueline 
Published: January 2005

AbstractIn order to analyze intercellular communication between ependymal cells in mammalian brain, we have studied gap junctional communication of ependymal and glial cells in long term primary cultures derived from fetal mouse or rat hypothalamus and choroid plexus obtained in serum supplemented media with two complementary methods: (1) dye transfer of Lucifer Yellow CH after intracellular microinjection of the different cellular types, and (2) freeze‐fracture of the same cultured ependymal cells. In our culture conditions, we have shown that the GJIC capacity to transfer dye was very different according to cellular types microinjected with Lucifer Yellow CH in the following respects: (1) in ependymal cells, GJIC was always important: ciliated ependymal cells, which are numerous in hypothalamic ependymal cultures (10–120 coupled cells), choroidal ependymocytes in plexus cultures (15–250 coupled cells), and non‐choroidal ependymocytes in diencephalic roof cultures (10–30 coupled cells), and (2) in astroglial cells found in these primary cultures, no GJIC was observed in spite of the presence of well‐differentiated gap junctions revealed by freeze‐fracture replicas. All these results show a strong GJIC in ependymal cells and indicate the very good functional state of these cells in vitro.
Assembly, disassembly, and exchange of glial fibrillary acidic protein
Authors: Nakamura Yu , Takeda Masatoshi , Angelides Kimon J. , Tada Kunitoshi , Hariguchi Shiro , Nishimura Tsuyoshi 
Published: January 2005

AbstractThe kinetics and dynamics of glial fibrillary acidic protein (GFAP) assembly was explored by a fluorescence energy transfer assay method. Purified GFAP was stoichiometrically labeled at a single cysteine residue with fluorescein‐maleimide. Soluble labeled GFAP in a low ionic strength buffer was assembled into 10 nm filaments by rapidly increasing the ionic strength, and the kinetics of GFAP assembly was monitored by the reduction in fluorescence due to self‐quenching of fluorescein. The extent of fluorescence quench correlated with both the formation of 10 nm filament morphology and the amount of protein pelleted at 12,000g. The assembly of GFAP is critically dependent upon both protein and magnesium ion concentration, and at the critical concentration for GFAP assembly is ∼ 40 μg/ml. Disassembly of GFAP filaments was also observed as a relief of fluorescence quenching after dilution of labeled GFAP filaments. When labeled GFAP filaments were mixed with an excess of unlabeled filaments, a rapid increase of fluorescence was observed, which is due to an exchange of subunits between labeled and unlabeled GFAP filaments. These results indicate that GFAP filaments are dynamic structures and that a small pool of kinetically active unassembled GFAP subunits are in a dynamic equilibrium with assembled GFAP filaments. The ability of GFAP to assemble, disassemble, and undergo subunit exchange has important implications for the organization and dynamics of astroglia cell cytoskeleton during development and in response to injury.
Enteric glia
Authors: Gershon Michael D. , Rothman Taube P. 
Published: January 2005

AbstractThe structure of the enteric nervous system (ENS) is different from that of extraenteric peripheral nerve. Collagen is excluded from the enteric plexuses and support for neuronal elements is provided by astrocyte‐like enteric glial cells. Enteric glia differ from Schwann cells in that they do not form basal laminae and they ensheath axons, not individually, but in groups. Although enteric glia are rich in the S‐100 and glial fibrillary acidic proteins, it has been difficult to find a single chemical marker that distinguishes enteric glia from non‐myelinating Schwann cells. Nevertheless, two monoclonal antibodies have been obtained that recognize antigens that are expressed on Schwann cells (Ran‐1 in rats and SMP in avians) but not enteric glia. Functional differences between enteric glia and non‐myelinating Schwann cells, including responses to gliotoxins and in vitro proliferative rates, have also been observed. Developmentally, enteric glia, Schwann cells, are derived from the neural crest. In both mammals and birds the precursors of the ENS appear to migrate to the bowel from sacral as well as vagal levels of the crest. These crest‐derived emigrés give rise to both enteric glia and neurons; however, analyses of the ontogeny of the enteric innervation in a mutant mouse (the ls/ls), in which the original clolonizing waves of crest‐derived precursor cells are unable to invade the terminal colon, suggest that enteric glia can also arise from Schwann cells that enter the gut with the extrinsic innervation. When induced to leave back‐transplanted segments of avian bowel, enteric crest‐derived cells migrate into peripheral nerves and form Schwann cells. Enteric glia and Schwann cells thus appear to be different cell types, but ones that derive from lineages that diverge relatively late in ontogeny.
Astroglia in CNS injury
Authors: Hatten Mary E. , Liem Ronald K. H. , Shelanski Michael L. , Mason Corol A. 
Published: January 2005

AbstractThe astroglial response to CNS injury is considered in the context of neuron‐glial relationships. Although previous models suggested that astroglial cells present in “scars” impede axon regrowth owing to irreversible changes in the glial cell following injury, recent in vivo and in vitro studies indicate that astroglial cells exhibit considerable plasticity, elevating expression of the glial filament protein and altering expression of properties which support axons, including extracellular matrix components and cell surface adhesion systems. Both in vivo and in vitro studies on neuron‐glia interactions in different brain regions suggest that glia express region‐specific properties, including ion channels, neurotransmitter uptake and receptor systems, and cell surface adhesion systems. Together these findings suggest that a more detailed analysis of glial response to injury in different brain regions will lead to an appreciation of the diversity of the astroglial response to injury, and its regulation by neuron‐glia relationships.