摘要:

AbstractConfocal fluorescence microscopy was used to study the bradykinin‐induced calcium signals in the neuro‐blastoma × glioma cell line NG 108–15. We found that bradykinin induced a rise in free calcium, not only in the cytoplasm but also in the nucleus. The nuclear and cytosolic calcium concentrations were not significantly different and rose to about 1.2 :μM. The signal was mediated by the B2‐receptor subtype as confirmed using the specific antagonist Hoe 140. Both the onset and the intensity of the calcium signals were concentration‐dependent. The rise of nuclear calcium level was independent of extracellular calcium and suppressed by thapsigargin which is known to deplete inositol 1,4,5‐trisphosphate‐sensitive calcium stores. Bradykinin‐induced calcium increase desensitizes rapidly. This desensitization was shown not to involve activation of protein kinase C. © 19

ISSN:0360-4012    

DOI:10.1002/jnr.490400502

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

年代:1995

数据来源: WILEY

摘要:

AbstractThe potential role of certain important immunoregulatory and effector cytokines in autoimmune neuroinflammation have been studied. We have examined the expression of mRNA, with in situ hybridization, of interferon ‐γ (IFN‐γ), interleukin 4 (IL‐4) and transforming growth factor β (TGF‐β) both in sections of spinal cords and the antigen‐induced expression of these cytokines by lymphoid cells after stimulation with a dominant encephalitogenic peptide of MBP (MBP 63–88) during the course of actively induced experimental autoimmune encephalomyelitis (EAE) in Lewis rats.In spinal cords, the target organ in EAE, cells expressing mRNA for IFN‐γ, first appeared at the onset of clinical signs, i.e., day 10 postimmunization (p.i.), peaked at the height of disease (day 13 p.i.), and then gradually decreased concomitant with recovery. Very few IL‐4 mRNA‐expressing cells appeared in the spinal cord with no clear relation to clinical signs or histopathology. In contrast, expression of mRNA for TGF‐β did not increase until day 13 p.i., at height of the disease, shortly preceding recovery. These data are consistent with a disease upregulating role of IFN‐γ, while TGF‐β may act to limit central nervous system (CNS) inflammation.In lymphoid organs, primed MBP 63–88 reactive T cells showed an interesting time‐dependent evolution of their cytokine production in vitro. Thus, early after immunization there was a conspicuous MBP 63–88‐induced production of both IFN‐γ and IL‐4. Such cells may act in the initiation and promotion of the disease. Later, in the recovery phase, MBP 63–88 induced lymphoid cells to TGF‐β production. Thus, an autoantigen‐specific production of TGF‐β occurred during EAE and hypothetically such a mechanism may serve to downregulate aggres

ISSN:0360-4012    

DOI:10.1002/jnr.490400503

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

年代:1995

数据来源: WILEY

摘要:

AbstractCultured oligodendrocyte progenitor cells derived from the developing central nervous system (CNS) express a pattern of ion channels that is distinct from mature oligodendrocytes and other cell types of the CNS. In the present study, we used the whole‐cell patch‐clamp technique and the fura‐2‐based Ca++imaging system to study the ion channel expression of oligodendrocyte progenitor cells derived from the optic nerves of adult rats. We found that the adult oligodendrocyte progenitor cell membrane is dominated by K+currents, both delayed outward and inward rectifying. The inwardly rectifying K+currents were often as large as the outward delayed rectifying K+currents. The delayed rectifying outward currents were partially blocked by 50 mM tetraethylammonium or 1 mM 4‐aminopyridine, but not by 2 or 5 mM BaCl2. This suggests that the delayed rectifier channels expressed by adult progenitor cells are different from those expressed by perinatal cells. Most adult oligodendrocyte progenitor cells showed no or only small A‐type K+currents. Both Ca++and Na+channels were also detected in these cells. Furthermore, adult progenitor cells responded to the neurotransmitters GABA and kainate and the pharmacology of these responses indicated that these cells express GABAAreceptors and kainate receptors that are Ca++‐permeable. Our study suggests that adult oligodendrocyte progenitor cells are electrophysiologically distinct and that these cells share electrophysiological characteristics with both perinatal progenitor cells and immature oligodendrocytes. © 1995 W

ISSN:0360-4012    

DOI:10.1002/jnr.490400504

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

年代:1995

数据来源: WILEY

摘要:

AbstractWe had earlier found that the numbers of mouse muscle nicotinic receptors expressed on the surface of individual cells of a stably transfected clonal line of quail fibroblasts varied from cell to cell (Kopta and Steinbach: J Neurosci 14:3922–3933, 1994). We have now used repeated selective passages of these clonal cells to produce a population of cells which expresses a greater and more uniform number of surface receptors per cell. The increased level is stable over many cell divisions, and over many half‐lives for the metabolic degradation of the surface receptors. Selection was performed by adhesion to a surface coated with a monoclonal antibody to a surface epitope on the muscle receptor, followed by expansion of the most tightly attached population of cells. Studies of the selected cells show that the surface receptors contain all four subunits of the muscle nicotinic receptor, and the functional properties of the receptors appear normal. The metabolic stability of the surface receptors is not altered, while the amount of mRNA for the subunits is increased in the selected population of cells. These observations indicate that the more likely reason for increased expression is a transcriptional effect, and that translational or posttranslational changes are unlikely. © 1995 Wiley‐Lis

ISSN:0360-4012    

DOI:10.1002/jnr.490400505

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

年代:1995

数据来源: WILEY

摘要:

AbstractThe effect of verapamil on resting and depolarization‐induced monoamine release was investigated in rat hippocampal synaptosomes prelabeled with [3H]‐5‐hydroxytryptamine (HT) or [3H]‐norepinephrine (NE) and rat striatal synaptosomes prelabeled with [3H]‐dopamine (DA). Verapamil (50 μM) completely abolishes high K+‐induced [3H]‐NE release, but paradoxically facilitates high K+‐induced [3H]‐5‐HT and [3H]‐DA release. All these high K+‐evoked responses were Ca2+dependent. Verapamil does not modify [3H]‐NE baseline release, but increases dose dependently [3H]‐5‐HT and [3H]‐DA baseline release. Verapamil (10 μM, for 5 min) increases endogenous DA release (70%) and endogenous 5‐HT release (40%) independently on the presence of external Ca2+. The total amount of these monoamines (released plus retained by the preparation) and their metabolites (DOPAC and 5‐HIAA) was similar in control and verapamil‐treated synaptosomes. Verapamil displaces [3H]‐spiroperidol specific binding (Kiof 2.4 × 10−6M) and [3H]‐SCH‐23390 specific binding (Kiof 9 × 10−6M) from striatal synaptosomal membranes, and [3H]‐5‐HT specific binding (Kiof 3 × 10−5M) from hippocampal synaptosomal membranes. It is concluded that in addition to the Ca2+antagonistic properties of verapamil on the Ca2+‐dependent, depolarization‐induced release of some neurotransmitters [gamma aminobutyric acid (GABA and NE)], another mechanism probably mediated by presynaptic receptors underlies the effects of verapamil on DA and 5

ISSN:0360-4012    

DOI:10.1002/jnr.490400506

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

年代:1995

数据来源: WILEY

摘要:

AbstractPossible differentiation mechanisms were investigated in a glioblastoma multiform cell line (GL15) presenting an undifferentiated phenotype with weak glial fibrillary acidic protein (GFAP) and strong vimentin (VIM) expression. Serum‐free conditions induced time‐dependent increases of GFAP‐mRNA and GFAP protein levels, associated with a process‐bearing astrocytic morphology.Activation of protein kinase C (PKC) by tumor promoter phorbol 12‐myrystate 13‐acetate (PMA) induced a rapid morphological differentiation and a decrease in GFAP mRNA, whereas the GFAP level remained unchanged. Such parameters were shown to characterize a physiological differentiation stage in astroglial cultures. Treatment of process‐bearing GL15 cells with dibutyryl cyclic AMP (dbcAMP), a protein kinase A (PKA) activator, induced a timedependent decrease in the GFAP mRNA and GFAP protein levels and reverted morphological changes induced by serum‐free conditions. Neither PMA nor dbcAMP influenced the VIM mRNA expression.In GL15 cells, PKC and PKA activation have opposite effects. Understanding the role of these kinases in malignant transformation and in the in vitro differentiation process is of both basic and clinical interest. © 1995

ISSN:0360-4012    

DOI:10.1002/jnr.490400507

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

年代:1995

数据来源: WILEY

摘要:

AbstractGlutamate‐induced currents were recorded from cultured trout astrocytes with the whole‐cell variation of the patch‐clamp technique. Ninety percent of the tested cells were directly depolarized by the amino acid neurotransmitter in a concentration‐dependent manner. The depolarizing effect was due to an inward current that reversed near 0 mV and was accompanied by a noise increase, indicating the opening of an ion channel. Ion substitution experiments revealed that the glutamate‐induced current was mainly carried by sodium ions but not chloride or calcium ions. The glutamate‐induced response could be mimicked by the neuronal glutamate receptor subtype agonists kainate and quisqualate, whileN‐methyl‐D‐aspartate was without detectable effect. © 19

ISSN:0360-4012    

DOI:10.1002/jnr.490400508

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

年代:1995

数据来源: WILEY

摘要:

AbstractSeizure activity induced by kainic acid (KA) and subsequent neuronal death are thought to be associated with an increase in cytoplasmic free calcium ([Ca2+]i) and can be prevented byN‐methyl‐D‐aspartate (NMDA) antagonists. In addition to influx through receptor operated Ca2+channels the increase in [Ca2+]imay be the result of an increased influx through voltage‐operated calcium channels and/or release from intracellular deposits. It was therefore investigated whether compounds other than NMDA antagonists with known actions on the intracellular Ca2+homeostasis had any protective effect against KA‐induced neuronal death. Voltage‐operated calcium channels in the cell membrane were blocked with the L‐type ion channel antagonist, Nimodipine (1.0 mg/kg), and release of Ca2+from internal stores was prevented with Dantrolene (10 mg/kg). Animals from two control groups injected with kainate (8 mg/kg) exhibited a survival rate of 67 and 53%, respectively. Countings of neurons in dorsal hippocampus showed subtotal or total loss in the CA1 and CA3 subregions. There were no significant differences concerning seizure and survival rates in the groups injected with kainate and treated with Dantrolene or Nimodipine and the control groups. The group treated with Dantrolene showed no neuropathological changes in the hippocampal CA3 region and only slight changes in the CA1 region, while the neuron loss in the Nimodipine group did not differ from that of its control group. The results emphasize the importance of Dantrolene‐sensitive Ca2+release from intracellular stores for the development of seizureinduced neuronal death. © 1995

ISSN:0360-4012    

DOI:10.1002/jnr.490400509

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

年代:1995

数据来源: WILEY

摘要:

AbstractTo study injury‐induced astrocytic responses associated with regrowth of axons and regeneration of myelin, the method of Collins and colleagues was used to make focal cryogenic lesions in spinal cords of adult rats (Collins et al.: J Neuropathol Exp Neurol 45:742–757, 1986). The duration of cryogenic injury (CI), the size of the cryode, and its temperature were chosen to destroy all myelin sheaths and axons without producing cavities or hemorrhages. Messenger RNA and peptide distributions of insulin‐like growth factor I (IGF‐I), IGF‐I receptor (IGFR‐I), IGF binding protein 2 (IGFBP‐2), glial fibrillary acidic protein (GFAP), and myelin basic protein (MBP) were studied 3–56 days after CI by in situ hybridization and immunocytochemistry. At 3 days, vimentin‐positive, GFAP‐negative astrocyte‐Iike cells in the lesion expressed IGF‐I mRNA and peptide and 7 days after CI, both were expressed by typical GFAP‐positive, hypertrophic astrocytes, many of which also were vimentin‐positive. Levels of IGF‐I, IGFBP‐2, and GFAP mRNA and peptide were higher in lesion astrocytes after 14 days. They attained maximum levels at 21–28 days before declining to near control levels at 56 days. Decreasing relative levels of oligodendroglial MBP mRNA were found in and around lesions 7–14 days after CI; subsequently, rising levels accompanied remyelination. At 28 and 56 days after CI, some transferrin‐positive, oligodendroglia‐like cells also were immunostained by anti‐IGFR‐I. Our findings suggest that early astrocytic production of IGF‐I and IGFBP‐2 may be involved in the myelin regeneration which occurs in this model of spinal cord injury. © 1995 Wiley‐Liss, Inc.This article is a US Government work and, as such, is in

ISSN:0360-4012    

DOI:10.1002/jnr.490400510

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

年代:1995

数据来源: WILEY

摘要:

AbstractIn vivo microdialysis of the rabbit hippocampus was used to study the effects ofN‐methyl‐D‐aspartate (NMDA) receptor stimulation on dialysate concentrations of thromboxane B2(Tx B2)‐ and 6‐keto prostaglandin F1α(6‐keto PGF1α)‐immunoreactive materials that are stable metabolites of biologically active thromboxane A2and prostacyclin. All pharmacological substances were applied in the dialysis medium. The application of 1 mM NMDA for 20 min resulted in five‐ and eightfold increases in Tx B2and 6‐keto PGF1αconcentrations, respectively. An increase in NMDA concentration to 2.5 mM did not potentiate a peak eicosanoid release, but significantly prolonged this effect. Either 10μM MK‐801 or the extrusion of Ca2+from the dialysis medium inhibited the release by about 50%. Quinacrine, a phospholipase A2inhibitor (250 μM), decreased the NMDA‐evoked eicosanoid release by 30%, whereas 10μM indomethacin, a cyclo‐oxygenase inhibitor, completely suppressed the release. One hundred micromolar furegrelate, an inhibitor of thromboxane synthase, reduced by 75% Tx B2release with concomitant 100% increase in 6‐keto PGFμ formation. Thus, stimulation of NMDA receptors induces calcium‐dependent formation of thromboxane A2and prostacyclin in the hippocampus, which may have pathophysiological implications. The neuronal site of their formation seems probable, although a transcellular mechanism of their synthesis should be also

ISSN:0360-4012    

DOI:10.1002/jnr.490400511

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

年代:1995

数据来源: WILEY