摘要:

AbstractWe have studied in cultured rat astroglial cells MAP kinases, known for their role in intracellular signal transduction. The MAP kinase activity was stimulated by growth factors (FGFb, FGFa, EGF, PDGF, and IGF1), by a phorbol ester (TPA) activating‐protein kinase C (PKC), by a neuropeptide (endothelin‐1), and by a neuromediator (carbachol). Astrocytes pretreated for 18 h with TPA were still stimulated by growth factors and endothelin, suggesting that down‐regulated isoforms of PKC are not involved in MAP kinase activation. In contrast, the small effect of carbachol was suppressed by TPA pretreatment. Astrocytes contained two proteins (p41 and p44) recognized by MAP kinase antibody. These proteins were phosphorylated on tyrosine residues in the cytosols of stimulated astrocytes.The kinetics of MAP kinase activation by FGFb and IGF1 were very different. FGFb promoted a rapid activation of MAP kinase (about 10 min) plus a prolonged phase that lasted at least 12 h. IGF1 produced only a rapid transient peak of activation at about 20 min. Hence, extracellular signals might generate different effects in astrocytes by differentially modulating the MAP kinase cascade.On a Mono Q column the growth factor‐stimulated MAP kinase activity was separated into two peaks containing p41 and p44. Stimulation of astrocytes altered the elution pattern of p44 as a result of its phosphorylation.An ATP‐dependent MAP kinase activator (MW = 40–45 kDa) was found in fractions of FGFb‐stimulated cells which were not retained on Mono Q column, indicating the existence of a MAP kinase kinase (MEK) in astrocytes. C‐Raf, identified in other cells as a MAP kinase kinase kinase, was also present in astrocytes.Thus astrocytes contain many components of the MAP kinase cascade activated by growth factors that may also be implicated in the action of neuropeptides and neuromediators. © 1994

ISSN:0894-1491    

DOI:10.1002/glia.440100202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractInjury to the adult brain results in the formation of a glial scar that involves both activated astroglia and microglia/macrophages. Although reactive gliosis has been linked to failure of axonal regeneration in the adult mammalian CNS, the spatio‐temporal pattern of the postlesion responses in morphology and distribution of the major cellular constituents of the gliosis has attracted little attention. In an attempt to define these relationships, we have undertaken a systematic study of astrocytic and microglial/macrophagic responses after stereotactic transection of the postcommissural fornix in rat.To visualize astrocytes, microglia, and macrophages, antibodies against glial fibrillary acidic protein (GFAP), vimentin (VIM), complement receptor type 3 (OX42), and ED1 were used. The cellular responses occurring between 2 h and 1 year postlesion (PL) at various distances distal and proximal to the lesion site were studied.The timing and extension of the sequential glial reactions after postcommissural fornix transection are discussed in relation to the myelin degradation and spontaneous sprouting of injured axons that have previously been observed in this lesion model (Wunderlich et al: Glia 10:49–58, 1994). © 1994 Wiley‐Lis

ISSN:0894-1491    

DOI:10.1002/glia.440100203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractIn the brain of the salamanderPleurodeles waltl, microglial cells were investigated cytochemically with isolectin B4(IB4) ofBandeiraea simplicifoliaafter optic nerve transection and during subsequent regeneration. Double‐labeling with an antibody directed against the glial fibrillary acidic protein of astrocytes revealed no immunoreactivity in microglial cells and confirmed the absence of non‐radial, free astroglial cells in the tectum. After two days, IB4‐labeled microglial cells began to populate the rostral parts of the primary visual system. The origin of these early vimentin‐immunoreactive microglial cells seemed to be mainly IB4‐labeled cells in a perivascular position and meningeal macrophages. After 12 days, microglial cells infiltrated the tectum in four layers: one in the ependyma, one in the outermost periventricular grey, and two in the degenerating visual neuropil where activated microglial cells displayed a ramified mor‐phology. After 3 weeks, microglial cells accumulated within the degenerating neuropil while reducing their processes. After 7 weeks, the number of microglial cells was still increased on the affected side. The subarachnoid space above the neuropil where regenerating retinal afferents arrived was filled with IB4‐labeled macrophages.Only very few microglial cells were seen in co‐existence with Müller cells in the lesioned and intact retinae, whereas microglial cells and macrophages were IB4‐labeled in the optic nerve head and at the ora serrata. © 1

ISSN:0894-1491    

DOI:10.1002/glia.440100204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe release of preloaded radiolabeled taurine (TAU) from cultured rabbit Müller cells [14–21 days in vitro (DIV)] was measured before and after treatment with the following stimuli: (1) isoosmotic 65 mM KCI; (2) a medium made hypoosmotic by uncompensated lowering of Na+by 40–100 mM; and 3) NH4Cl ranging from 0.25 to 5 mM. The same stimuli were tested for their effect on the cell volume by the 3‐0‐methyl‐D‐glucose (OMG) uptake method of Kletzien et al. (Anal Biochem 68:537, 1975). Hypoosmotic media and 65 mM KCl stimulated TAU release, and the release was well correlated with the increase of cell volume. The stimulatory effect of 65 mM KCI was abolished by isotonic removal of Cl−or Na+, and omission of either ion markedly enhanced the basal release of TAU. The results are roughly consistent with the characteristics of the swelling‐induced TAU release reported for cultured astrocytes and neurons of various CNS regions, and also for freshly isolated, nondissociated retina. Taken together, the results are indicative of a significant role of TAU release from Müller cells, in the osmosensory response of the retina.Ammonium chloride stimulated TAU release in a dose‐dependent manner, a significant stimulation being already observed at 0.5 mM, a concentration that is frequently measured in brain during acute hyperammonemia. The effect of NH4Cl was strictly chloride dependent at 0.5–2 mM, but partly Cl−independent at 5mM. The Kletzien's method did not appear to be well suited for measuring cell volume in the presence of ammonium ions. However, data from the literature on other CNS cell types plus our preliminary electron microscopic observations suggest that short‐term treatments with NH4Cl at concentrations up to 1 mM are unlikely to produce cell swelling. An alternative way in which ammonium ions might trigger the “tension sensor” for TAU release is discussed. We propose that in vivo, the outward‐driven TAU could counteract ammoniainduced neuronal disinhibition, according to a putative role for TAU as a gliotran

ISSN:0894-1491    

DOI:10.1002/glia.440100205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe development of a nerve bank as a source of donor material to repair large defects in peripheral nerve injuries requires an understanding of the influence of cold storage on cell viability and function in these potential nerve grafts. Segments of peripheral nerves from both human and rat were stored in University of Wisconsin Cold Storage Solution (UW) at 4°C for<12 h, 3 days, and 1, 2, or 3 weeks. Cellular viability was initially assessed by the degree of cellular outgrowth from explants of the stored nerves placed in culture, and then further quantitated by dissociating the cultured nerve explants and calculating the type and number of cells per milligram of peripheral nerve. Rat Schwann cells (SCs) obtained from the stored (control and 1 and 2 weeks) nerves were tested for their functional ability to myelinate dorsal root ganglion (DRG) neurons in culture. Our findings indicate that human and rat peripheral nerves contain few viable SCs and fibroblasts after 3 weeks of cold storage with the quantity of viable cells within the human cold stored peripheral nerves decreasing significantly after 1 week of cold storage. Despite their reduced number, some SCs from rat nerves stored up to 2 weeks are capable of myelinating DRG axons in culture. These results suggest that short intervals (<1 week) of cold storage will result in potential peripheral nerve grafts containing large populations of functional cells, while long‐term (≥ 3 weeks) cold stored peripheral nerves will contain few viable cells. © 1994 Wiley‐Li

ISSN:0894-1491    

DOI:10.1002/glia.440100206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe distribution of octadecaneuropeptide (ODN)‐like immunoreactivity (LI) and its relationship to γ‐aminobutyric acid (GABA)‐LI were investigated in the cerebellar cortex of adult rats with electron microscopy. At the electron microscopic level, ODN‐LI was found exclusively in glial cells. In addition to Bergmann glia and its processes, cerebellar astrocytes were also labelled, encapsulating unlabelled neuronal elements of the cerebellum. These ODN‐LI glial processes were observed in close apposition to synaptic junctions, but immunoreactivity could not be found in the synaptic cleft or in association with neuronal membranes. Since GABA‐LI is always associated with neuronal elements, the colocalization of GABA‐ and ODN‐LI could not be confirmed in the cerebellar cortex. Our results do not support the assumption that ODN is a neuron‐specific processing product of diazepam binding inhibitor. © 1

ISSN:0894-1491    

DOI:10.1002/glia.440100207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe present series of experiments demonstrate that a polypeptide activity present in rat serum induces a proliferative response in cultured rat Schwann cells. Schwann cells in multi‐well tissue culture plates were incubated in medium containing 10% heat‐inactivated fetal bovine serum and serial dilutions of normal rat serum, and control preparations were incubated in the same culture medium without rat serum. Rates of cell proliferation were assayed by measuring DNA incorporation of tritiated thymidine using liquid scintillation counting. A prominent dose‐dependent proliferative response was observed among Schwann cells incubated with rat serum and rat plasma dilutions as compared to controls; this activity is abolished by heat inactivation and by proteolytic digestion, and was not affected by dialysis against a cellulose ester membrane that excludes molecules larger than 10,000 daltons. In contrast, no increase in DNA uptake of tritiated thymidine was observed when astrocyte and oligodendrocyte cultures were incubated with serial dilutions of rat serum. No proliferative effect was observed when rat Schwann cells were incubated with a dilution of standard adult bovine serum. These results suggest there is an intravascular plasma polypeptide with a molecular weight greater than 10,000 daltons that specifically stimulates Schwann cell proliferation, and it is proposed that this factor may be the mitogen responsible for the Schwann cell proliferative response known to occur after nerve injury. © 1994 Wiley‐L

ISSN:0894-1491    

DOI:10.1002/glia.440100208

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractOligodendrocyte progenitor cells (O‐2A) express both kainate‐preferring and AMPA‐preferring glutamate receptors (Gallo et al., Soc. Neurosci. Abstr., 18:653, 1992b; Gallo et al., 1994). The expression and regulation of the GluR‐4c, AMPA‐preferring subunit by growth factors was studied by Northern blot analysis of total RNA from purified rat cortical O‐2A progenitors. Differently from cortical neurons, O‐2A progenitors only expressed two high molecular weight GluR‐4c transcripts (6.2 and 4.2 kb), as observed also in cultured astrocytes. Basic fibroblast growth factor (bFGF) increased GluR‐4c transcript levels in O‐2A progenitors and its effects were not mimicked by platelet derived growth factor (PDGF) or fetal calf serum. Therefore, bFGF may regulate O‐2A progenitor responsiveness to glutamate during development through the expression of glutamate receptor subunits.

ISSN:0894-1491    

DOI:10.1002/glia.440100209

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

ISSN:0894-1491    

DOI:10.1002/glia.440100210

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

ISSN:0894-1491    

DOI:10.1002/glia.440100201

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY