摘要:

AbstractDouble‐barrelled microelectrodes, sensitive to quaternary ammonium ions, were used for simultaneous measurements of the intracellular free concentrations of choline ([Ch]i) or tetramethylammonium [TMAi] as well as membrane potential (Em) in neuropile glial cells of the leech, Hirudo medicinalis. Bath application of Ch or TMA (5 mM, 1 min) resulted in a transient membrane depolarization accompanied by a long‐ lasting (0.5–1 h) intracellular accumulation of these compoundsto levels of between 5 and 15 mM. Changes in [Ch]ior [TMA]iwere used for the calculation of changes in relative cell volume. Elevation of the extracellular K+concentration ([K+]e) from 4 to 9,15,21,27.5, or 40 mM elicited a membrane depolarization and a reversible cell swelling by about 7.5,14, 18.5, 27 and 50%, whereas reduction of [K+]eto 1.5 mM as well as bath application of serotonin (5‐HT) produced a membrane hyperpolarization and a concomitant shrinkage by about 6 and 14.3%, respectively. The measured alterations in cell volume were compared with calculated data based on the assumption of an osmotic equilibrium disturbed by potential‐dependent changes of the intracellular Cl−concentration. The results indicate, that K+‐ and serotonin‐induced changes in the cell volume of the neuropile glial cells are due to passive KCl a

ISSN:0894-1491    

DOI:10.1002/glia.440030302

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

年代:1990

数据来源: WILEY

摘要:

AbstractLabelled histamine was taken up into cultured glial cells of chick embryonic brain by a system with high affinity for histamine and diffusion. The active uptake, occurring at low concentrations of the amine, was Na+dependent and gave an apparent Kmof 0.24 μM and a Vmaxof 0.31 pmol X mg protein−1X min−1. The uptake was completely blocked by desmethylimipramine (Ki= 2.5 μM) and partially by the histamine agonists and histamine‐N‐methyltransferase blockers 4‐methylhistamine and 2‐methylhistamine (I30values obtained were 2 μM and 5 μM). Other psychoactive drugs were either ineffective (imipramine) or they showed moderate inhibitory effects (amitryptyline and cocaine). Ouabain (100 μM) inhibited uptake by ∼50%. Diffusion occurred at high concentrations of the amine, was insensitive to extracellular Na+, and was proportional to histamine concentration up to 1 mM.[3H]‐Histamine, taken up into the cells, was metabolized and/or released. The spontaneous efflux of the radioactivity measured after 10 min of exposure to [3H]‐histamine (when most of it was still unmetabolized), was moderately Ca++dependent, accelerated by both reduced concentrations of extracellular Na+and enhanced concentrations of K+and inhibited by desmethylimipramine. After prolonged (60 min) incubation, histamine metabolites detected in the cells presented 78% of the chromatogram radioactivity and consisted of Nτ‐methylhistamine and Nτ‐methylimidazole acetic acid.These results indicate that at low nM concentrations, histamine is taken up and metabolized by (and released from) glial cells by an Na+‐dependent system, and the intracellular metabolism seems to serve an

ISSN:0894-1491    

DOI:10.1002/glia.440030303

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

年代:1990

数据来源: WILEY

摘要:

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 em

ISSN:0894-1491    

DOI:10.1002/glia.440030304

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

年代:1990

数据来源: WILEY

摘要:

AbstractGlial fibrillary acidic protein (GFAP) and vimentin proteins are known to be component proteins of glial filaments in the CNS of many vertebrates. The nature of the filaments present in the glial cells of the goldfish optic tectum and in the CNS of two members of the Mollusca (Helix pomatiaandOctopus vulgaris) were investigated using immunocytochemical localization of monoclonal antibodies to GFAP and vimentin. Immunoblots visualized by the alkaline phosphatase method showed cross‐reactive protein bands to GFAP and vimentin antibodies in total brain homogenates of the goldfish, octopus, and snail. Immunofluorescence staining of the goldfish optic tectum showed GFAP immunoreactivity, primarily in the ependymal cell processes. Immunogold labelling at the ultrastructural level verified that GFAP antibodies were bound to glial filaments. Immunolabelling of the optic lobe ofOctopus vulgarisand the cerebral ganglia ofHelix pomatiasuggests that a protein exhibiting antigenic properties similar to GFAP is a component protein in the filaments of the protoplasmic and filamentous glia randomly distributed throughout the CNS. Unlike anti‐GFAP antibodies, which stained relatively specific to filaments, vimentin staining in the CNS tissues of the three organisms studied did not appear to be exclusive to filamentous structures. As vimentin protein has been shown, in previous studies as well as our own, to exist in many tissue types, this suggests that it does not appear to be confined to glial filaments but is shared with other subcellular components. The proteins GFAP and vimentin which are thought to be well conserved in vertebrate evolution also appear to be expressed in the nervous system of some lower organi

ISSN:0894-1491    

DOI:10.1002/glia.440030305

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe signals which regulate the proliferation of astrocytes have relevance to normal developmental processes, transformational loss of growth control, and reactive gliosis present in many brain disease states. We have studied, in primary cultures of rat astrocytes, a sequential interaction of two growth factors, epidermal growth factor (EGF) and fibroblast growth factor (FGF), which may be relevant to the brain in these conditions. EGF is a strong mitogen and stimulator of 2 deoxyglucose (2 DG) transport with no effect on plating of cells, and FGF is a lesser mitogen and 2 DG uptake stimulator. However, when FGF is given to the cells as a pretreatment, FGF strongly inhibits the ability of EGF to stimulate both DNA synthesis and 2 DG uptake. The inhibition of EGF stimulation by FGF is across the EGF dose‐response curve, present at high and low culture densities, and stable for at least 3 days. Specificity is indicated by lack of inhibition by PDGF pretreatment and much less inhibition of fetal calf serum‐induced stimulations than EGF‐induced stimulation. Cell counts confirmed that the FGF pretreatment also inhibits EGF stimulation of cell division. Because of FGF brain derivation and angiogenic and neurotropic functions, it may serve as a regulator of EGF‐astrocyte interactions in processes such as development, gliomatous transformation, and neural regen

ISSN:0894-1491    

DOI:10.1002/glia.440030306

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

年代:1990

数据来源: WILEY

摘要:

AbstractStimulation of primary cultures of rat astrocytes with appropriate agents results in the mobilization of arachidonic acid from intracellular lipid pools and the synthesis of eicosanoids. Thromboxane A2is one of the major prostanoids released upon stimulation with calcium ionophore, phorbol esters, and ATP; but a number of other predicted effectors are inactive. In an attempt to understand the pathophysiological significance of eicosanoid release from astrocytes, primary cultures have been derived from human astrocytic glioma biopsies. The majority of cells in the cultures expressed glial fibrillary acidic protein (GFAP), frequently in conjunction with vimentin and fibronectin. Cell sorting revealed that a significant proportion of cells in the cultures from the high‐grade (malignant) tumors expressed epidermal growth factor receptor, indicative of neoplastic cells. Both effective and ineffective agents in rat cultures were tested for their ability to stimulate release of thromboxane from these gliomas, and also from cultures of medulloblastoma and ependymoma which contained significant numbers of GFAP‐positive cells. Only cells from the high‐grade tumors released thromboxane in response to the known effective stimuli. While the muscarinic agonist carbachol was ineffective, norepinephrine evoked thromboxane release from malignant astrocytomas. These data show that cells derived from malignant human gliomas retain the ability to release thromboxane upon stimulation and suggest that a transformation in receptor coupling might accompany neoplasia, such that the cells now respond to a previously ineffective ag

ISSN:0894-1491    

DOI:10.1002/glia.440030307

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe membranes of mammalian astrocytic processes apposed to blood vessels or forming the surface of the brain contain high concentrations of a characteristic intramembrane particle aggregate, termed “assemblies.” In order to identify developmental processes which contribute to this remarkable regional specialization of membrane structure, we have devised culture conditions which support the differentiation of assemblies in secondary cultures of astrocytes derived from neonatal rat forebrain. We report here that different lots of fetal calf serum vary dramatically in their capacity to support the differentiation of assemblies. Fetal calf serum thus appears to exert two distinct influences on astrocyte development: it promotes the differentiation of type 2 astrocytes from bipotential precursor cells, as shown by others, and it influences the density of assemblies in type 1, flat, GFAP‐immunoreactive astrocytes in our secondary cultures. Horse serum and defined media also support the appearance of assemblies in flat, GFAP‐immunoreactive astrocytes. The separate effects of serum supplementation upon cell lineage and membrane differentiation have to be carefully considered in studies designed to examine factors influencing astrocytic development i

ISSN:0894-1491    

DOI:10.1002/glia.440030308

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

年代:1990

数据来源: WILEY

摘要:

AbstractCentral nervous system myelin deficiency is a consistent feature of caprine β‐mannosidosis, and autosomal recessive neurovisceral lysosomal storage disease. To investigate the possibility of an intrinsic oligodendrocyte defect in β‐mannosidosis, oligodendrocyte‐enriched glial cultures from the cerebral hemisphere white matter of two affected and six control goats were compared with respect to culture yield and morphology. Fewer oligodendrocytes were cultured per gram of white matter from affected animals than from control animals. Galactocerebroside‐positive oligodendrocytes from all animals were similar morphologically at all stages of culture by phase contrast and fluorescence microscopy. These findings are consistent with in vivo morphological observations and suggest that differentiated oligodendrocytes from affected animals do not show morphological abnormalities in culture. However, increased numbers of galactocerebroside‐negative bipolar cells, which may be glial progenitor cells, were present in cultures from affected animals. This observation suggests the possibility of a defect in differentiation to mature oligodendrocytes, with persistence of the undifferentiated glia during late stages of

ISSN:0894-1491    

DOI:10.1002/glia.440030309

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

年代:1990

数据来源: WILEY

ISSN:0894-1491    

DOI:10.1002/glia.440030301

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

年代:1990

数据来源: WILEY