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Query: UMLS:C0017638 (glioma)
 30,880 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The previous observation that a continuous chemical depolarization of aggregating rat brain cells with KCl alters the expression of opioid receptors was examined in more detail. In contrast to its significant and converse effect on forebrain and hindbrain cells cultured in serum-containing medium, KCl had only a small and transient effect in serum-free cultures of both types. The basal receptor density in serum-free cultures was similar to the receptor density in KCl-treated serum-containing cultures, but medium conditioned by glial cells restored partially the effect of KCl in serum-free cultures. The effect of KCl in serum-containing forebrain cultures was enhanced by the voltage-dependent calcium channel blocker verapamil, and magnesium and cadmium had a similar, though smaller, effect. The sodium channel activator veratridine had a profound and dose-dependent inhibitory effect on the expression of the receptors in forebrain and hindbrain cultures, and tetrodotoxin blocked the veratridine effect. Information about the selectivity of the effect of neuronal activation on the various opioid receptor subtypes was obtained with the neuroblastoma X glioma hybrid M8 cells that possess only delta type opioid receptors. A Scatchard analysis of [3H]etorphine binding to these cells has shown that depolarization increased the Bmax, but had little, if any, effect on the affinity (KD) of the ligand to the receptors. The significance of depolarization and voltage-dependent sodium and calcium channels on the expression of different opioid receptor subtypes is discussed.
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PMID:Neuronal activation regulates the expression of opioid receptors: possible role of glial-derived factors and voltage-dependent ion channels. 253 11

The effects of toxin II (AaH II) isolated from the scorpion Androctonus australis Hector on sodium current in neuroblastoma X glioma NG 108-15 hybrid cells were analysed under patch clamp conditions in the whole cell configuration. AaH II (70 nM) induced a maintained sodium current, as well as increasing both fast and slow inactivation time constants and the amplitude of the peak current. This latter effect occurred via a shift of the activation-voltage curve towards negative voltage values by about 9 mV. Oleic acid (5 microM), which had no effect on INa under control conditions, decreased the AaH II-induced maintained current. It also reversed, or prevented the increase of the peak current induced by AaH II. However, it neither prevented nor modified the AaH II-induced increase in inactivation time constants. The binding of the toxin to its specific site and the number of binding sites for AaH II were not significantly modified by oleic acid. The oleic acid-induced effects could not be related to the activation of protein kinase C since PMA, a potent activator of this enzyme, did not produce oleic acid-like effects. From these results, it is concluded that AaH II has several independent effects on sodium channels, some of which could be modulated by the lipid environment of sodium channels in the membrane.
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PMID:Effects of toxin II from the scorpion Androctonus australis Hector on sodium current in neuroblastoma cells and their modulation by oleic acid. 253 22

We have studied the ion flux through the sodium channels of low passage number (less than 50 p.) and high passage number (greater than 150 p.) neuroblastoma x glioma hybrid cells using [14C] guanidinium and specific neurotoxins to induce channel opening and closing. The sodium channels of low passage number hybrid cells could be opened by veratridine alone, suggesting the presence of voltage dependent channels in agreement with electrophysiological studies reported in the literature. The sodium channels of the high passage number hybrid cells, however, needed the synergistic action of veratridine and scorpion toxin for activation suggesting that these channels are "silent". The [14C] guanidinium ion flux through the sodium channels of the high passage number hybrid cells was inhibited by significantly lower concentrations of the volatile anesthetics (halothane, isoflurane and enflurane) and the local anesthetics (tetracaine and bupivacaine) than the comparable flux through the sodium channels of the low passage number hybrid cells.
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PMID:The sodium channels of the neuroblastoma x glioma 108 CC 15 hybrid cell change their sensitivity for volatile and local anesthetics upon continuous passage. 254 Feb 63

The actions of brevetoxin (PbTX-3) were studied on single, voltage-dependent sodium channels and whole-cell currents from the neuroblastoma x glioma cell line NG108-15. Purified PbTX-3 shifted the activation of sodium channels to membrane potentials negative to normal. PbTX-3 did not alter the single-channel mean open lifetime, suggesting that the toxin does not change the rate of sodium channel inactivation from the open state. There was also no change in single-channel conductance. These results indicate that brevetoxin increases sodium current at rest by shifting the voltage dependence of channel activation and that the resulting depolarization is limited by channel inactivation.
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PMID:The actions of a red tide toxin from Ptychodiscus brevis on single sodium channels in mammalian neuroblastoma cells. 254 Oct 24

Most antibodies known to interact with beta-adrenergic receptors do not exhibit subtype selectivity, nor do they provide quantitative immunoprecipitation. A monoclonal antibody, G27.1 raised against a synthetic peptide corresponding to the C-terminus of the beta 2-adrenergic receptor of hamster, is selective for the beta 2 subtype. G27.1 provides nearly quantitative immunoprecipitation of the beta 2-adrenergic receptor from hamster lung that has been photoaffinity-labeled and solubilized with sodium dodecyl sulfate. Immunoprecipitation is completely blocked by nanomolar concentrations of the immunizing peptide. This antibody interacts with beta 2-adrenergic receptors from three rodent species, but not with those from humans. When C6 glioma cells, which contain both beta 1- and beta 2-adrenergic receptors, are photoaffinity-labeled in the absence or presence of subtype-selective antagonists, subtype-selective photoaffinity-labeling results. G27.1 can immunoprecipitate beta 2-, but not beta 1-, adrenergic receptors from these cells. Similar results were obtained following subtype-selective photoaffinity-labeling of membranes from rat cerebellum and cerebral cortex. The beta-adrenergic receptors from C6 glioma cells and rat cerebral cortex exist as a mixture of two molecular weight species. These species differ in glycosylation, as shown by endoglycosidase F digestion of crude and immunoprecipitated receptors.
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PMID:Subtype-selective immunoprecipitation of the beta 2-adrenergic receptor. 254 15

Rat C6 glioma cells were cultured for 4 days in MEM medium supplemented with 10% bovine serum and Na+, K+-ATPase activity was determined in homogenates of harvested cells. Approximately 50% of enzyme activity was attained at 1.5 mM K+ and the maximum (2.76 +/- 0.13 mumol Pi/h/mg protein) at 5 mM K+. The specific activity of Na+, K+-ATPase was not influenced by freezing the homogenates or cell suspensions before the enzyme assay. Ten minutes' exposure of glioma cells to 10(-4) or 10(-5) M noradrenaline (NA) remained without any effect on NA+, K+-ATPase activity. Neither did the presence of NA in the incubation medium, during the enzyme assay, influence the enzyme activity. The nonresponsiveness of Na+, K+-ATPase of C6 glioma cells to NA is consistent with the assumption that alpha (+) form of the enzyme may be preferentially sensitive to noradrenaline. Na+, K+-ATPase was inhibited in a dose-dependent manner by vanadate and 50% inhibition was achieved at 2 x 10(-7) M concentration. In spite of the fact that Na+, K+-ATPase of glioma cells was not responsive to NA, the latter could at least partially reverse vanadate-induced inhibition of the enzyme. Although the present results concern transformed glial cells, they suggest the possibility that inhibition of glial Na+, K+-ATPase may contribute to the previously reported inhibition by vanadate of Na+, K+-ATPase of the whole brain tissue.
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PMID:Na+, K+-ATPase activity in cultured C6 glioma cells. 254 85

The aim of this work was to determine if the total (Na+ + K+)-ATPase of the plasma membrane of a cell population could be assayed without cell homogenization and partial purification of the enzyme. Several types of intact cells that were placed in an assay medium containing MgATP, Na+, and K+ hydrolyzed little or none of the added ATP. When the cells were pretreated with the ionophore alamethicin and then placed in the assay medium, they exhibited an ouabain-sensitive (Na+ + K+)-ATPase activity that increased and reached a limiting value with increasing alamethicin concentration. Since alamethicin did not increase the activity of the purified membrane-bound (Na+ + K+)-ATPase, its effects on the intact cells are probably due to the formation of large channels within the plasma membrane that allow the free access of the components of the assay medium to the intracellular domains of (Na+ + K+)-ATPase. Utilizing whole cells treated with alamethicin, total (Na+ + K+)-ATPase activity was determined in clonal pheochromocytoma cells (PC12), neuroblastoma x glioma hybrid cells (NG108-15), and myocytes isolated from adult and neonatal rat hearts. With the use of this whole-cell assay, the ouabain sensitivities of the enzymes in adult and neonatal rat heart myocytes were determined and found to be the same as those that have been determined with the use of partially purified enzymes.
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PMID:Determination of total (Na+ + K+)-ATPase activity of isolated or cultured cells. 256 Mar 48

We have investigated the effect of pharmacological agents on [14C]guanidinium ion influx through sodium channels in C6 rat glioma and N18 mouse neuroblastoma cells. The sodium channels of the N18 cells can be activated by aconitine alone, indicating that they are voltage-dependent channels. In contrast, sodium channels in the C6 cells require the synergistic action of aconitine and scorpion toxin for activation and are therefore characterized as so-called silent channels. The general anesthetic halothane used at clinical concentrations, specifically inhibited the ion flux through the silent sodium channel of C6 rat glioma cells. The voltage-dependent channels of the N18 cells were insensitive to halothane at the concentrations tested.
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PMID:Halothane inhibits the neurotoxin stimulated [14C]guanidinium influx through 'silent' sodium channels in rat glioma C6 cells. 257 48

Gd(DO3A), a member of a new family of nonionic MRI contrast agents, was evaluated in vivo in a rat model. In 10 animals, enhancement of an intracerebral glioma was studied following Gd(DO3A) injection. Correlation with tissue pathology was obtained in all cases. Comparative studies of renal enhancement were performed in 15 animals, utilizing disodium Gd(DTPA)2-, sodium-Gd(DOTA)-, and Gd(DO3A). With the glioma model, Gd(DO3A) administration provided enhancement of tissue with an altered blood brain barrier, thus permitting identification of the bulk of the neoplastic lesion. Comparative studies revealed that enhancement of normal renal medulla was equal or superior with Gd(DO3A).
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PMID:Experimental trials with Gd(DO3A)--a nonionic magnetic resonance contrast agent. 260 11

The transport of glycine in C6 glioma cells takes place mainly in a heterogeneous Na+-dependent manner which can be resolved into different components. A Na+- and Cl(-)-dependent component with high affinity for glycine is pH-sensitive and inhibited by sarcosine, all these characteristics corresponding to System Gly. The low-affinity component of the transport of glycine can be discriminated as two components, namely System A and System ASC. The main proportion of glycine transport through the low-affinity system is carried out by the ASC System, which appears to be constitutively expressed by the cells. The adaptive response of the low-affinity Na+-dependent transport of glycine to amino acid deprivation was identified with System A on the basis of its ion-dependency, pH-sensitivity and by inhibition analysis. The possible physiological role of the high- and low-affinity components of the transport system for glycine in glial cells is discussed.
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PMID:Characteristics and adaptive regulation of glycine transport in cultured glial cells. 270 91


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