摘要:

AbstractThe expression of neurotrophin (NGF, BDNF, and NT‐3) mRNAs in 24 cell lines derived from human malignant gliomas was studied by Northern analysis. Widespread expression of neurotrophin genes was found with BDNF being the most abundantly expressed. Nearly all cell lines expressed BDNF, and about two‐thirds of the cell lines expressed NGF and NT‐3. Half of the cell lines analyzed expressed all three neurotrophins. Secretion of NGF into the medium of several cell lines could be detected by ELISA and a PC12 neurite outgrowth assay. Immuno‐ and bioactive NGF was isolated from conditioned medium of one cell line. No evidence of expression of the neurotrophin receptorstrkandtrkB by Northern analysis was found. Receptor crosslinking with radiolabeled cognate ligands failed to detect functional receptors in all but one cell line. In this cell line a receptor complex for BDNF was found that corresponded to truncatedtrkB receptors that lack the signal transducing tyrosine kinase domain. Neurotrophins did not stimulate mitosis of the glioma cultures. The findings suggest that production of neurotrophins by glioma cells is a general phenomenon, although neurotrophins made by gliomas lacking their receptors may not play an autocrine but rather a paracrine role. © 1993 Wiley

ISSN:0360-4012    

DOI:10.1002/jnr.490340202

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

年代:1993

数据来源: WILEY

摘要:

AbstractWhole cell currents evoked by pain‐inducing agents—bradykinin (Bk), capsaicin (Cap), and reciniferatoxin (RTX), and their modulation of voltage‐activated Ca currents were examined in F‐11 cells using a patch electrode voltage clamp technique. Most F‐11 cells generated action potentials under current clamp if their membrane potentials were held sufficiently negative. Average peak inward Na current (INa) was 100 μA/cm2and theINawas abolished by 10−6M tetrodotoxin. At least two types of Ca currents could be clearly distinguished on the basis of voltage dependency and kinetics; a low threshold transientICa(t)and a high threshold sustainedICa(I). In addition, another high threshold transient Ca current, presumablyICa(n), was observed. About 30% of the cells produced inward current for these pain‐inducing agents, when activated at the membrane holding potential of −70 mV. In some F‐11 cells, the amplitude of action potential was observed to increase during 10−6M Cap‐induced depolarization. Both low and high threshold Ca currents were reduced by 10−6M Bk in the majority of the cells. Similarly, both 10−6M Cap and 10−9M RTX reduced these Ca currents. However, a considerable number of cells showed an initial enhancement followed by reduction in the amplitude of these Ca currents. With higher concentrations of these ligands, all Ca currents were suppressed. Such modulation of voltage‐activated Ca currents by pain‐inducing agents occurred in both the presence and absence of apparent receptor‐activated current flows in the cells. In pertussis toxin (PTX)‐treated cells, the inhibitory modulation of Ca currents by pain‐inducing agents was suppressed. In contrast, in cholera toxin (CTX)‐treated cells, this inhibitory modulation appeared to be enhanced. These data indicate that the inhibitory modulation of Ca channel currents by Cap and RTX, similarly to that of Bk, involves a PTX‐sensitive inhibit

ISSN:0360-4012    

DOI:10.1002/jnr.490340203

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

年代:1993

数据来源: WILEY

摘要:

AbstractIonic channels in human cortical neurons have not been studied extensively. HCN‐1 and HCN‐1A cells, which recently were established as continuous cultures from human cortical tissue, have been shown by histochemical and immunochemical methods to exhibit a neuronal phenotype, but expression of functional ionic channels was not demonstrated. For the present study, HCN‐1 and HCN‐1A cells were cultured in Dulbecco's modified Eagle's medium with 15% fetal calf serum, in some cases supplemented with 10 ng/ml nerve growth factor, 10 μM forskolin, and 1 mM dibutyryl cyclic adenosine monophosphate to promote differentiation. Cells or membrane patches were voltage clamped using conventional patch clamp techniques. In HCN‐1A cells, we identified a tetrodotoxin‐sensitive Na+current, two types of Ca2+channel current, including L‐type current and a second type that in some respects resembled N‐type current, and four types of K+current, including a delayed outward rectifier that showed voltage‐dependent inactivation, two types of noninactivating Ca2+‐activated K+channels with slope conductances of 146 and 23 pS (K+iK+o145 mM/5 mM), and less frequently, a noninactivating, intermediate conductance channel that was not sensitive to internal Ca2+. When HCN‐1A cells were examined after 3 days of exposure to differentiating agents, pronounced morphological changes were evident but no differences in ionic currents were apparent. HCN‐1 cells also exhibited K+and Ca2+channel currents, but Na+currents were not detected in these cells. Our data provide additional evidence indicating a functional neuronal phenotype for HCN‐1A cells, and represent the most comprehensive survey to date of the variety of ionic channels expressed by human cortical neuro

ISSN:0360-4012    

DOI:10.1002/jnr.490340204

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe neuroprotective effects of the platelet‐activating factor (PAF) antagonists BN 52020 and BN 52021 were determined in a temperature‐controlled model of transient forebrain ischemia in the rat (occlusion of both common carotid arteries combined with lowering of the mean arterial blood pressure to 40 mm Hg for 10 min). After 7 days of recirculation, the ischemic neuronal damage was evaluated histologically within the hippocampus and neocortex. Combined pre‐ and post‐treatment with the PAF antagonists (2 × 25 mg/kg, s.c.) significantly reduced the resulting neuronal damage of the CA1 and CA3 hippocampal subfields and of the occipital and parietal cerebral cortex. The two PAF antagonists were also tested for their neuroprotective activity in primary neuronal cultures isoalted from embryonic chick telencephalon. Since an excessive activation of excitatory amino acid receptors is discussed to be of importance for the ischemic brain damage, the cultured neurons were exposed to the excitatory amino acid L‐glutamate (1 mM) for a period of 60 min. Twenty hours after the excitotoxic insult, BN 52020‐ and BN 52021‐ treated cultured (1–100 μM) showed both a better preserved morphology, as well as a dose‐dependent increase in cell viability and protein content compared to the control cultures. Our results demonstrate that the PAF antagonists BN 52020 and BN‐52021 have the capacity to protect brain tissue against ischemic neuronal damge independent of hypothermic effects and are also capable of reducing excitotoxic damage of telencephalic neurons from chick embryos cultured in the absence of glial or endothelial cells. We thus propose that PAF plays an important role in the pathophysiology of ischemic/excitotoxic neuronal injury via a direct action on neurons.

ISSN:0360-4012    

DOI:10.1002/jnr.490340205

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe insulin‐like growth factor are postulated to play a role during brain development. Because they are believed to act in a paracrine/autocrine manner, the production of insulin‐like growth factor‐I (IGF‐I) by cultured astroglial cells was examined. Quantities of IGF‐I in conditioned media were determined by RIA after separation of IGFs from IGF‐binding proteins by high‐pressure liquid chromatography. Astrocytes from 1‐day‐old rats and the rat glioma cell line (C6) both secreted 7.5‐kDa IGF‐I. A peak of immunoreactivity with an apparent mol wt of 12,000 was additionally present in media conditioned by C6 cells. Exposure to epidermal growth factor (EGF) increased media content of immunocreactive IGF‐I slightly (60%) in C6 cells but more than 2‐fold in normal astrocytes. Fibroblast growth factor also increased the amount of IGF‐I contained in media conditioned by normal astrocytes. To determine whether the secreted IGF‐I was biologically active, media IGFs were immunoneutralized with a monoclonal antibody (Sm 1.25). In the presence of the antibody, EGF‐stimulated astrocyte replication was blocked. These data indicate that IGF‐I secretion by rodent astrocytes is stimulated by factors thought to be important for brain growth and development and that the IGFs are likely intimate participants in EGF‐induced astro

ISSN:0360-4012    

DOI:10.1002/jnr.490340206

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

年代:1993

数据来源: WILEY

摘要:

AbstractSpecific binding sites for neuropeptide Y could be demonstrated in primary cultures of astrocytes from neonatal rat brain. Neuropeptide Y binding was saturable, reversible, and temperature dependent as revealed by saturation studies and kinetic experiments. Scatchard analysis of equilibrium binding data indicated a single population of high‐affinity binding sites with respective KDand Bmaxvalues of 0.43 nM and 6.9 fmol/2.7 × 105cells. Physiological responses induced by neuropeptide Y could be detected in a distinct subpopulation of cultured astrocytes on the basis of two criteria: (1) electrophysiological responses and (2) single cell measurements of changes in [Ca2+]i. In that fraction of cells responding (20–70%, varying among cultures from different preparations), brief application of neuropeptide Y led to a membrane potential depolarization, lasting several minutes. When the membrane was clamped close to the resting membrane potential using the whole‐cell patch‐clamp technique, neuropeptide Y induced an inward current with a similar time course as the neuropeptide Y‐induced membrane depolarization. As detected by single cell microfluorimetric (fura‐2) measurements neuropeptide Y induced an increase of [Ca2+]iwhich was caused by the entry of extracellular Ca2+. Both the [Ca2+]iincrease and the electrophysiological responses were unaffected by pretreatment of the astrocytes with pertussis toxin. © 1993 Wi

ISSN:0360-4012    

DOI:10.1002/jnr.490340207

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe axolemma membrane forms a stable and reproducible monomolecular layer at the air‐aqueous interface. The major lipids and proteins are present in this monolayer in molar ratios similar to the original membrane. Acetylcholinesterase and Na‐K‐ATPase activities are preserved in the monolayer to levels of 64% and 25%, respectively. The total lipid fraction forms a homogeneously mixed phase. The presence of proteins in the monolayer introduces surface inhomogeneties. Among other features, this is revealed by the presence of two values of lateral pressure at which the monolayer shows partial or total collapse: a broad partial collapse at surface pressures between 13 to 30 mN/m and a sharp collapse point at 46 mN/m. The average molecular areas, the broad collapse point, and the variation of the surface potential per molecule suggest the relocation of protein components at surface pressures between 13 to 30 mN/m. The behavior is consistent with the extrusion and exposure of proteins toward the aqueous medium that depends on the lateral pressure.Schwann cells grown on coverslips coated with axolemma monolayers at 13 mN/m (beginning of the broad collapse) and 34 mN/m (above the broad collapse) recognize the difference in the surface organization of axolemma caused by the lateral pressure which affects their proliferation, morphology, and spatial pattern of organization. Our results show for the first time that response of Schwann cells depends on the intermolecular organization of the axolemma surface with which they interact. These results suggest that the local expression of putative surface molecules of axolemma that may mediate membrane recognition and the signalling of morphological and proliferative changes can be modulated by long range supramolecular properties. © 1993 Wiley‐L

ISSN:0360-4012    

DOI:10.1002/jnr.490340208

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

年代:1993

数据来源: WILEY

摘要:

AbstractCultured rat cerebellar granule neurons exposed to solutions of reduced osmolarity, responded initially by swelling followed by a regulatory volume decrease (RVD) which is completed within 15 min. Increasing external osmolarity lead to cell shrinking but no evidence of volume regulation was observed within 1 hr. Replacing Na+by choline did not affect RVD whereasN‐methyl‐D‐glucamine accelerated the volume recovery and K+suppressed it completely. The blockade of RVD in high extracellular K+was only observed when chloride and nitrate but not sulfate or gluconate were the accompanying anions. Replacing intracellular Cl−, by long incubations with gluconate, markedly inhibited RVD. Removal of extracellular Ca2+or addition of dantrolene which blocks Ca2+released from intracellular stores had no effect on RVD. Increasing extracellular taurine prevented RVD. These results indicate that membrane permeability to K+, Cl−, and taurine is increased by hyposmolarity and suggest the involvement of these molecules in RVD in granule neurons. © 1993 Wiley

ISSN:0360-4012    

DOI:10.1002/jnr.490340209

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

年代:1993

数据来源: WILEY

摘要:

AbstractInterleukin‐1β (IL‐1) stimulates by about fivefold NGF secretion from rat neonatal cortical astrocytes in primary culture. We investigated the possible intracellular second messenger mechanisms involved in the IL‐1 induced NGF secretion. Basal NGF secretion did not require extracellular Ca2+, whereas Ca2+was necessary for the maximal NGF secretion stimulated by IL‐1 (10 units/ml). The protein kinase C activator TPA stimulated by sixfold NGF secretion, but in this case, TPA acted synergistically with IL‐1 to increase NGF secretion. Treatment of cells with the phospholipase A2inhibitor mepacrine (30 μM) inhibited basal (by 50%) and IL‐1 stimulated (by 80%) NGF secretion. Indomethacin, a cyclooxygenase inhibitor, produced a slight increase in basal NGF secretion at low concentrations, while PGE2(10 μM) inhibited basal and IL‐1 stimulated NGF secretion. In contrast, treatment of cells with nordihydroguaiaretic acid (NDGA), a lipoxygenase inhibitor, blocked in a concentration‐dependent manner (IC50= 10 μM) IL‐1 stimulation of NGF secretion. The leukotriene LTB4increased basal NGF secretion and this effect was not additive with IL‐1 when both agents were added at saturating concentrations, indicating a common mechanism of action for these two agents. Thus, one possible mechanism by which IL‐1 stimulates NGF secretion from astrocytes is by activation of the phospholipase A2‐lipoxygenase path

ISSN:0360-4012    

DOI:10.1002/jnr.490340210

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

年代:1993

数据来源: WILEY

摘要:

AbstractBrain catalase was continuously depleted throughout the life span starting with a large population of initially young and old frogs. Free radical‐related parameters were measured in the brain tissue once per year after 2.5, 14.5, and 26.5 months of experimentation. Brain lipofuscin accumulation was observed after 14.5 and 26.5 months, and survival was continuously followed during 33 months. The age of the animal did not decrease endogenous antioxidants nor increase tissue peroxidation either in cross‐sectional or longitudinal comparisons. Continuous catalase depletion similarly affected young and old animals, inducing glutathione reductase, tending to decrease oxidized glutathione/reduced glutathione (GSSG/GSH) ratio, decreasing lipofuscin accumulation in the brain, and increasing survival from 46% to 91% after 14.5 months. At 26.5 months of experimentation the loss of the glutathione reductase induction in catalase‐depleted animals was accompanied by the presence of higher lipofuscin deposits than in controls and was followed by a great increase in mortality rate. Even though the maximal life span (7 years) was the same in the control and treated animals which were already old (4.2 years) at the beginning of the experiment, the treated animals showed a strong reduction in the rates of early death. It is proposed that the maintenance of a high antioxidant/prooxidant balance in the vertebrate brain greatly increases the probability of the individual to reach the final segments of its species‐specific life span. © 1993 Wiley

ISSN:0360-4012    

DOI:10.1002/jnr.490340211

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

年代:1993

数据来源: WILEY