bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of glial subpopulations in cultures of the ovine central nervous system
Authors: Elder Gregory A. , Potts Barbara J. , Sawyer Mary 
Published: January 2005

AbstractThe cellular composition and in vitro development of glial cultures derived from the rat CNS has been well studied. However, less information is available on similar cultures from other species, particularly higher mammals. To study ovine glial development in vitro, cultures from 50‐day fetal to adult animals were characterized with various immunocytochemical markers, which are frequently used to define neural cell subsets in rat cultures. As in rats, both A2B5+ and A2B5− astrocytes can be identified in ovine cultures. However, ovine A2B5+ and A2B5− could not be reliably differentiated by their morphology, which was more influenced by whether the cells were in serum‐free or serum‐containing media than by their A2B5‐positive or ‐negative status. In addtion, ovine A2B5 + astrocytes were present in cultures from early fetal brain before the development of identifiable oligodendrocytes, unlike rat type II astrocytes, which develop only after the appearance of oligodendrocytes. An A2B5 + cell, morphologically similar to the rat 02‐A cell, can be found in cultures from fetal ovine cerebrum or cerebellum. A2B5 +/ glial fibrillry acidic protein (GFAP)– cells in cultures from 100‐ to 115‐day ovine cerebellum appeared to differentiate into A2B5 + astrocytes in serum‐containing media. However, in serum‐free media, although the A2B5 + cells assumed a more “oligodendroglial‐like” morphology, they did not express galactocerebroside or myelin basic protein, suggesting that these cells may not be bipotential as is the rat 02‐A cell. Oligodendroglial differentiation was not induced by treatment with dibutyryl cyclic AMP or insulin‐like growth factor I. Many cells in cultures from a variety of fetal ages did not label with any of the immunocytochemical markers used, suggesting the need for more cell‐type‐specific markers to identify neural cell subsets in higher mammals.
Astrocytes regulate GFAP mRNA levels by cyclic AMP and protein kinase C‐dependent mechanisms
Authors: Shafit‐Zagardo Bridget , Kume‐Iwaki Akiko , Goldman James E. 
Published: January 2005

AbstractGlial fibrillary acidic protein (GFAP) mRNA and protein levels in rat astrocyte cultures and in the human astrocytoma line U‐373MG were examined in order to determine the effects of agents that regulate cAMP‐dependent kinase and protein kinase C. Treatment of cells with dibutyryl cAMP or forskolin and 3‐isobutyl‐1‐methylxan‐thine increased steady‐state GFAP mRNA levels. Short‐term treatment of cells with phorbol‐12‐myristate‐13‐acetate (PMA) increased GFAP mRNA levels, but prolonged treatment of cells with PMA or 1‐oleoyl‐2‐acetyl‐rac‐glycerol produced a dramatic decrease in GFAP mRNA; 4‐beta‐phorbol had no effect. Thus, both cAMP‐dependent kinase and protein kinase C may exert regulatory roles in determining GFAP mRNA levels. Nuclear run‐off studies showed no change in GFAP mRNA synthesis after cAMP or PMA treatment, suggesting post‐transcriptional mechanisms. Western blot analysis revealed that the effect of PMA on U‐373MG cells shows specificity in that GFA protein levels decline, while those of other major cytoskeletal proteins were unaltered.
Functions of glial cells in the retina of the honeybee drone
Authors: Coles Jonathan A. 
Published: January 2005

AbstractIn the retina of the honey bee drone, Apis mellifera ♂, physiological interactins between glial cells and neurons (the photoreceptors) are exceptionally clearcut and amenable to investigation. The principal glia (outer pigment cells) contribute to the homeostasis of extracellular [K+] and [Na+] by (1) spatial buffering of K+ and (2) net uptake fo K+ and Cl−. The glia supply carbohydrate metabolic substrate to the neurons; only the glia take up and phosphorylate glucose. Neuronal activity (1) modifies glycogen metabolism in the glia, and (2) can be signalled to the glia in the absence of elevated extracellular [K+].
Release of taurine from astrocytes during potassium‐evoked swelling
Authors: Pasantes‐morales Herminia , Schousboe Arne 
Published: January 2005

AbstractCultured astrocytes superfused with isosmotic solutions containing high concentrations of potassium, i.e., 25, 56, 75, and 100 mM, showed a proportional increase in cell volume corresponding to 25, 36, 57, and 75% greater than the cell volume in physiological solutions. This volume increase was abolished in low chloride or hypertonic solutions.The release of 3H‐taurine previously accumulated by astrocytes was stimulated by potassium at all concentrations examined. During 4‐minute exposure to 25, 56, 75, or 100 mM of potassium, cells released 13.5, 15.6, 20.2, or 36.2%, respectively, of the total labeled taurine accumulated during the preloading period. The potassium‐stimulated release of 3H‐taurine was calcium‐independent and insensitive to BaCl2 and bumetanide. Substitution of chloride by gluconate to concentrations necessary to maintain the K+ × Cl− product constant abolished the potassium‐stimulated release of 3H‐taurine. Superfusion with solutions made hypertonic with sucrose also decreased the potassium‐elicited efflux of 3H‐taurine. In both conditions, the depolarizing effect of potassium measured with 3H‐TPP+ was unchanged. High potassium concentrations and hyposmotic solutions released 3H‐taurine by a nonadditive mechanism. These results indicate that in cultured astrocytes high concentrations of potassium produce both swelling and depolarization, but only swelling elicits the release of taurine. These observations suggest an involvement of taurine in cell‐volume regulation in astrocytes.
Vulnerability of rat and mouse brain cells to murine hepatitis virus (JHM‐strain): Studies in vivo and in vitro
Authors: van Berlo M.F. , Warringa R. , Wolswijk G. , Lopes‐Cardozo M. 
Published: January 2005

AbstractThe pathogenicity and cell tropism of mouse hepatitis virus (MHV‐JHM‐strain) in the developing mouse (Balb/c) and rat (Wistar and Lewis) brain were analysed. Intracranial infection of Balb/c mice at postnatal day 5 induced a lethal encephalitis in all animals. Of Wistar rats infected at day 2 or 5 after birth, 30 to 70%, respectively, survived. The distribution of viral antigen was studied in frozen brain sections of animals that died after infection; astrocytes were found to be the major virus‐infected cell type throughout the central nervous system. More than 75% of the surviving rat pups developed paralysis, but viral antigen was detected in only few brain cells and not in astrocytes. The cell tropism of MHV‐JHM was examined further in virus‐infected glial cell cultures derived from brains of rats or mice. In the glial cultures derived from Wistar rats, only oligodendrocytes were infected, whereas in cultures derived from mouse or Lewis rat brain viral antigen was detected in both astrocytes and oligodendrocytes. Infection of astrocytes led to the formation of syncytia and degradation of the cytoskeleton. Infected rat oligodendrocytes gradually disappeared from the cultures because of cell death. These phenomena indicate that, besides an indirect autoimmune response triggered by infected astrocytes, direct virus‐induced injury to astrocytes or to oligodendrocytes can have a dominant role in the neuropathogenicity of mouse hepatitis virus. The present results underscore the importance of species and developmental stage of experimental animals in the neurotropism and pathogenicity of MHV‐JHM.
Evidence that glutamate mediates Axon‐to‐Schwann cell signaling in the squid
Authors: Lieberman Edward M. , Abbott N. Joan , Hassan Sami 
Published: January 2005

AbstractHigh‐frequency stimulation (100 Hz) of isolated giant axons of the small squid Alloteuthis subulata and the large squid Loligo forbesi caused the periaxonal Schwann cell resting potential (Em = ‐40 mV) to hyperpolarize up to 11 mV in direct proportion to train duration and action potential amplitude. In both species, the Schwann cell also hyperpolarized up to 17 m V with the application of L‐glutamate (10−9 to 10−6 M), in a dose‐dependent manner. By contrast, in the presence of 10−8 M d‐tubocurarine (d‐TC) to block the cholinergic component of the Schwann cell response, Schwann cells depolarized 8–9 mV during electrical stimulation of the axon or application of L‐glutamate. In the presence of 10−5 M 2‐amino‐4‐phosphonobutyrate (2‐APB), the hyperpolarization to glutamate and to axon stimulation was blocked, whereas the cholinergic (carbacholinduced) hyperpolarization was unaffected. In experiments with Alloteuthis, L‐aspartate (10−7 M) also caused a Schwann cell hyperpolarization, but this was not blocked by 2‐APB. In tests with glutamate receptor agonists and antagonists, quisqualate (10−5 M) produced a hyperpolarization blocked by 10−4 M L‐glutamic acid diethylester (GDEE), which also blocked the response to axonal stimulation. Kainic acid (10−4 M) also caused a hyperpolarization, but n‐methyl‐D‐aspartate (NMDA; 10−4 M), ibotenate (10−5 M), α‐amino‐3 hydroxy‐5‐methyl‐isoxazole proprionate (AMPA; 10−4M), and isethionate (10−5M) had no effect. The results suggest that glutamate is a mediator of communication between the active axon and its surrounding Schwann cells and, by acting on quisqualate/kainate (i.e., non‐NMDA) glutamate receptors, causes depolarization of the Schwann cell membrane. This depolarization in turn appears to activate cholinergic mechanisms in the Schwann cell that result in a secondary, long‐lasting Schwann cell hyperpolarization. The function of the hyperpolarization is presently not well understood, but a contribution to regulation of the [K+] in the periaxonal microenvironment is proposed.
Activation of substance P receptors leads to membrane potential responses in cultured astrocytes
Authors: Wienrich Marion , Kettenmann H. 
Published: January 2005

AbstractCultured astrocytes from rat cortex and spinal cord responded with different types of membrane potential changes upon brief (10 seconds) applications of the natural neurokinin agonists substance P and neurokinin A. The most prominent type of response was a long‐lasting membrane depolarization. In some cells, an initial rapid depolarization followed by a partial repolarization preceded the slow depolarizing event. Few astrocytes responded with a hyperpolarization of the membrane. Selective agonists at the NK‐1 receptive site, substance P‐methyl ester (SP‐OME) and septide, mimicked the response to the natural neurokinins as did DiMe‐C7, a selective NK‐3 receptor agonist. A putative neurokinin antagonist, (D‐Arg1,D‐Pro2,D‐Trp7,9,Leu11)SP (DADPDT) partially blocked membrane potential responses induced by substance P, SP‐OME, septide, DiMe‐C7, and NKA. The authors conclude that astrocytes express NK‐1 and NK‐3 receptors, which upon activation affect the electrical properties of these cells.
An endogenous lectin found in rat astrocyte cultures has a role in cell adhesion but not in cell proliferation
Authors: Kuchler Sabine , Perraud Frédéric , Sensenbrenner Monique , Vincendon Guy , Zanetta Jean‐Pierre 
Published: January 2005

AbstractThe presence of an endogenous cerebellar soluble lectin (CSL) has been demonstrated in cultured rat astrocytes by using immunocytochemical techniques. In these cells, the location of lectin CSL was found intracellularly as well as on the external surface of the plasma membrane of the cell bodies and processes, especially in the zones of contact between cells. This suggested that CSL could have a role in adhesion of astrocytes to sister cells. Kinetics of adhesion of astrocytes to culture dishes precoated with CSL showed a rapid binding of these cells. In confluent astrocyte cultures, anti‐CSL Fab fragments affected the shape and organization of astrocytes (retraction of the cytoplasm), but they did not detach cells from the substratum. These results indicated that CSL has adhesive properties for astroglial cells and is probably involved (1) in adhesion of astrocytes to sister cells; (2) in binding of protoplasmic regions of astrocyte membrane to the substratum. Further support for these roles came from demonstration of the presence in cultures of glycoprotein ligands recognized by this lectin. The problem of the mitogenic properties of the lectin was also questioned. The addition of CSL to confluent astroglial cultures was able to stimulate only by 40% the proliferation of these cells at an optimal concentration of 5 μg CSL lectin/ml of culture medium. This indicated that CSL is not a powerful growth factor for astrocytes.
Electrical coupling, without dye coupling, between mammalian astrocytes and oligodendrocytes in cell culture
Authors: Ransom B. R. , Kettenmann H. 
Published: January 2005

AbstractEvidence of electrical and dye coupling between oligodendrocytes and astrocytes was sought in cultures of mouse spinal cord. Cell identity was verified using cell specific antigenic markers. In most experiments current was injected into oligodendrocytes while recording voltage in nearby astrocytes. Nine of 17 oligodendrocyteastrocyte cell pairs showed weak electrical coupling; the average estimated coupling ratio was 0.03 ± 0.06 (cf. 0.11 for oligodendrocyte‐oligodendrocyte and 0.44 for astrocyteastrocyte pairs; Kettenmann and Ransom: Glia, 1: 64–73, 1988). Application of 0.5 mM BaCl2 or 44.6 mM CsCl depolarized astrocytes and oligodendrocytes and was estimated to increase the coupling ratio between these cells 3–5‐fold; these effects were rapid in onset and completely reversible. In 5 of 7 cases, oligodendrocyte‐astrocyte pairs that appeared uncoupled in normal solution exhibited coupling during Ba++ or Cs+ exposure. The actions of these cations are believed to be mediated by blockade of glial K+ channels. Depolarization, per se, as induced by increasing [K+]o, did not increase coupling ratio. The fluorescent dye lucifer yellow (LY) was injected into 10 oligodendrocytes, 8 of which were electrically coupled to nearby astrocytes, and never passed into astrocytes in detectable quantities. Likewise, astrocytes injected with LY stained other astrocytes, but never oligodendrocytes. These findings document the presence of weak electrical coupling between astrocytes and oligodendrocytes, in the absence of dye coupling. Weak coupling of this sort could subserve metabolic interactions between these cells mediated by the passage of small but important molecules such as cyclic AMP, but would not allow strong electrical interactions. If such coupling among glial cells is widespread, it would constitute a “metabolic syncytium” that could serve to coordinate glial behavior.
Experimental inhibition of peroxisomal β‐oxidation in rats: Influence on brain myelination
Authors: Van Den Branden Christiane , Leeman Jan , Dacremont Georges , Collumbien Robert , Roels Frank 
Published: January 2005

AbstractOral administration of thioridazine, an inhibitor of peroxisomal β‐oxidation, to normal rats from weaning till day 60 causes a small increase of the very long chain fatty acid C26 in brain lipids. Myelination in the brain is decreased. In the genu of the corpus callosum the ratio of non‐myelinated/myelinated axons is increased. In the commissura anterior the myelin sheaths of the axons are significantly thinner in treated than in control animals. Undernourishment caused by the drug is minimal in this experiment. Area and total DNA of glial nuclei are unaltered in both the genu and the commissura anterior of treated rats. The distribution of chromatin (texture), however, shows small differences in the corpus callosum.
Isoproterenol selectively releases endogenous and [14C]‐labelled taurine from a single cytosolic compartment in astroglial cells
Authors: Waniewski Robert A. , Martin David L. , Shain William 
Published: January 2005

AbstractTaurine is stored in and released from astroglial cells. We have investigated whether taurine is stored in multiple subcellular compartments and whether taurine is released from a distinct pool. Taurine compartmentation was examined by determining the subcellular distribution of labelled taurine and by comparing the specific radioactivities of taurine in cells with that of the taurine released into the superfusion medium during receptor stimulation. Three observations indicate that taurine is found in a single subcellular pool. First, labelled taurine was localized exclusively within a freely exchangeable pool and not sequestered in membrane‐bound compartments. Second, endogenous and newly acquired [14C]taurine was released identically by the β‐adrenergic agonist isoproterenol (IPR). Third, measurements of the specific radioactivity of taurine indicate that accumulated [14C]taurine mixes homogeneously with endogenous taurine and both are simultaneously released from the same pool. Chemical analysis revealed net uptake of taurine from the medium during loading and a net loss during IPR‐stimulated release. Taurine was selectively released by IPR; five other amino acids found in the superfusion medium were unaffected. One possible mechanism capable of explaining these results is that receptor‐mediated taurine release from astroglia occurs by a selective transporter moving taurine from a single cytoplasmic pool to the extracellular space.
Accumulation of extracellular glutamate and neuronal death in astrocyte‐poor cortical cultures exposed to glutamine
Authors: Rosenberg Paul A. 
Published: January 2005

AbstractThe function of astrocytes in cerebral cortex may be studied by comparing the properties of conventional, astrocyte‐rich cultures with astrocyte‐poor cultures in which astrocyte proliferation has been stringently suppressed. Exposure of astrocytepoor, but not astrocyte‐rich, cultures to fresh medium containing 2 mM glutamine resulted in the death of most neurons within 24 h. This study was undertaken to understand the basis for the apparent toxicity of glutamine in astrocyte‐poor cultures. The toxicity of glutamine was found to be mediated by glutamate, which demonstrated an LD50 as a neurotoxin in astrocyte‐poor cultures of 2 μM. Exposure of astrocyte‐poor (but not astrocyte‐rich) cultures to fresh medium containing glutamine for 17.5–24 h resulted in the accumulation of substantial quantities of glutamate (255 ± 158 μM; mean ± standard deviation) coincident with the death of neurons in the cultures. Exposure of astrocyte‐poor cultures to glutamate in the absence of glutamine did not result in the accumulation of extracellular glutamate. Both the neuronal death and the extracellular glutamate accumulation in astrocyte‐poor cultures exposed to glutamine could be blocked by N‐methyl‐D‐aspartate (NMDA) antagonists. These observations suggest that astrocytes as well as glutamine may play an important role in the pathogenesis of glutamate neurotoxicity in the central nervous system.
Division of astroblasts and oligodendroblasts in postnatal rodent brain: Evidence for separate astrocyte and oligodendrocyte lineages
Authors: Skoff Robert P. , Knapp Pamela E. 
Published: January 2005

AbstractWhat precursor cells are the source of the macroglia generated during postnatal development? In order to answer this question, we studied the expression of glial specific antigens in proliferating neuroglia in postnatal rodent brain and optic nerve. Immunocytochemistry using antibodies to oligodendrocyte (OL) specific markers (sulfatide and galactocerebroside) and an astrocyte (AS) specific marker (glial fibrillary acidic protein) was combined with thymidine autoradiography. During the first week of postnatal development when most ASs are being generated, one third to one half of the proliferating cells in the optic system are positive for glial fibrillary acidic protein after a 1 h injection of thymidine (Skoff, Dev. Biol., 139:149–168, 1990). During the second postnatal week when OLs are being generated, 30 to 100% of the proliferating cells in presumptive white matter tracts are sulfatide positive and at least 10% are galactocerebroside positive. This finding demonstrates that ASs and OLs divide during postnatal development. These results confirm previous electron microscopic autoradiographic studies showing that the vast majority of proliferating cells in postnatal rat optic nerve have the morphologic characteristics of differentiating ASs or OLs (Skoff, J. Comp. Neurol., 169:291–312, 1976). Since proliferating ASs (astroblasts) and OLs (oligodendroblasts) constitute the majority of the dividing cells at the time that ASs and OLs are being generated, these glioblasts must be the major source for the macroglia generated postnatally.The findings strongly suggest that separate lineages exist for ASs and OLs during postnatal development. There is no compelling in vivo evidence for a bipotential progenitor cell that generates the majority of OLs and certain ASs in postnatal rodent brain. There may, of course, be distinct lineages for the subtypes of ASs and possibly even for subtypes of OLs. We review the concepts of commitment and plasticity and apply these terms to glial differentiation. In situ, the presence of oligodendrobalsts and astroblasts demonstrates the COMMITMENT of proliferating cells to a specific glial lineage during normal development. Culture conditions may provide an environment that permits proliferating glial cells to vacillate in their selection of a specific lineage. This situation demonstrates developmental PLASTICITY and the ability of glia to adapt to an altered environment. Whether committed glial cells in situ can be induced to switch their lineage when normal CNS conditions are altered is an intriguing question that remains to be answered.
Characterization of glutamate uptake systems in astrocyte primary cultures from rat brain
Authors: Flott Berenike , Seifert Wilfried 
Published: January 2005

AbstractThe dependence of 3[H]‐L‐glutamate uptake on the presence of sodium, chloride, or calcium ions or on a combination of the three was investigated in astrocyte primary cultures. A stimulating effect on glutamate uptake by each of the ions tested was found. In addition to the comparably small effect by calcium alone, calcium exhibits a synergistic effect on the sodium‐ and chloride‐dependent uptake. The sodium‐dependent transport accumulates the glutamate analogue D‐aspartate as well as L‐glutamate. L‐aspartate is taken up by about 50% of the values observed for L‐glutamate transport. Sodium‐dependent glutamate uptake is strongly inhibited by aspartate‐beta‐hydrox‐amate (AβH) and threo‐beta‐hydroxyasparatate (TβH). Quisqualate is less potent in inhibiting this uptake.In contrast, the chloride‐ and the calcium‐dependent uptake systems do not handle D‐ and L‐aspartate as substrates. AβH and TβH are only poor inhibitors of these transporters while quisqualate reduces glutamate uptake almost completely. Kinetic data of all uptake systems were estimated. High and low affinity components of each individual system are demonstrated by Eadie‐Hofstee analysis. Hill plots indicate that high and low affinity uptake may be due either to two respective uptake sites for Na+‐, Cl−‐, and Ca++‐dependent glutamate transport, or to two glutamate binding sites for each single transport system with negative cooperativity.
Contact spacing among astrocytes in the central nervous system: An hypothesis of their structural role
Authors: Distler Claudia , Dreher Zofia , Stone Jonathan 
Published: January 2005

AbstractAstrocytes are found throughout the central nervous system. They interact closely with surrounding structures, their processes contributing to the glia limitans of the neural tube, and to the glial investment of blood vessels, and of the somas, axons, and synaptic structures of neurones. This paper presents evidence that astrocytes in the central nervous system also interact with each other in a dual way, adhering to their neighbours via their processes, and repelling the somas of those neighbours. We suggest that this interaction, which has been termed contact spacing, distributes astrocytes through the central nervous system, and forms the basis of their structural role.