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

The neuroblastoma x glioma hybrid clone NG108-15 is able to release acetylcholine upon depolarization and form cholinergic neuromuscular synapses in culture. Normal functioning of cholinergic synapses is thought to be dependent on the ability of a neuron to take up extracellular choline, since neurons are unable to synthesize choline de novo. For these two reasons it became important to characterize the choline uptake system of NG108-15 cells. The uptake system appears to bear little if any resemblance to the Na+-dependent high-affinity choline uptake system normally associated with cholinergic neurons. Although the cells appear to possess both high- and low-affinity choline uptake systems, neither system is dependent on Na+ and uptake actually is increased about 60% by the substitution of sucrose for NaCl. Acetylcholine synthesis also is not dependent on Na+, since sucrose, substituted for NaCl, also stimulates acetylcholine synthesis. Changes in the concentrations of the other ions in the uptake medium have little effect on uptake, with the exception that elevated Ca2+ or Mg2+ reverses the stimulation of choline uptake produced by substitution of sucrose for NaCl. Choline uptake is inhibited by hemicholinium-3, but only at high concentrations of the drug (IC50 = 30-80 microM). The metabolic poisons cyanide and iodoacetate inhibit uptake by only 30-40%. Growth of the cells in N6,O2' dibutyryladenosine-3',5'-cyclic monophosphate, which promotes functional and morphological differentiation of the cells, decreased slightly the total amount of choline taken up but had no additional effect on the uptake system. Thus, it appears that NG108-15 cells are capable of forming functional cholinergic synapses with muscle cells even though the neuroblastoma does not possess the high-affinity choline uptake system normally associated with cholinergic neurons.
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PMID:Choline uptake by the neuroblastoma x glioma hybrid, NG108-15. 625 99

Chronic treatment of neuroblastoma X glioma NG108-15 hybrid cells with the opiate agonist etorphine resulted in a decrease in both opiate receptor density (receptor down-regulation) and opiate ability to inhibit prostaglandin E1 (PGE1)-stimulated increases in cyclic AMP levels (receptor desensitization). Opiate receptor down-regulation and desensitization were homologous as indicated by the lack of apparent change in muscarinic, alpha 2-adrenergic, and PGE1 receptor binding and also retention, albeit modulation, of the ability of carbachol and norepinephrine to inhibit PGE1-stimulated increases in cyclic AMP levels after 24 hr of etorphine treatment. PGE1-stimulated increases in cyclic AMP levels remained identical in etorphine-treated and control cells. Several lines of evidence indicate that receptor desensitization and receptor down-regulation in NG108-15 cells are two separate cellular adaptation processes. (a) With an agonist which appears to be efficiently coupled, i.e., an agonist whose apparent Kd value is much larger than its apparent IC50 value for regulation of cyclic AMP levels (Ki), the concentration of ligand required to produce half-maximal down-regulation is analogous to its Ki value, whereas the concentration of ligand required to produce half-maximal desensitization is related to its Kd value; (b) receptor desensitization precedes receptor down-regulation; (c) only opiate agonists could produce receptor down-regulation, whereas both opiate agonists and partial agonists could desensitize post-receptor occupancy events. Still further evidence for dissociability of these processes was obtained by incubating NG108-15 cells with etorphine at 30 degrees for 2 hr. Under these conditions, there was a decrease in etorphine's ability to regulate adenylate cyclase while [3H]diprenorphine binding remained unaltered. IC50 values of D-Ala2-D-Leu5-enkephalin's competition for [3H]diprenorphine binding to intact cells increased 19.6-fold after etorphine treatment for 90 min, while naloxone IC50 values remained unaltered. This apparent increase in IC50 values was much lower, about 2-fold, when receptor binding was carried out in membranes isolated from cells treated with etorphine chronically. Furthermore, analysis of [3H]etorphine binding to such membranes in the presence of 10 mM Mg2+ indicated a loss of receptor binding sites with no change in apparent affinity, whereas [3H]diprenorphine binding revealed no significant alteration in either Bmax or Kd values. Therefore, during opiate receptor desensitization, a reduction of agonist high-affinity site occurs with no apparent alteration in total receptor number.
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PMID:Opiate receptor down-regulation and desensitization in neuroblastoma X glioma NG108-15 hybrid cells are two separate cellular adaptation processes. 631 14

The incorporation of methionine, lysine, and leucine into protein was studied in Ca2+-depleted and Ca2+-restored preparations of C-6 glial tumor cells in minimal medium. Although incorporation proceeded at linear rates in both preparations for more than 1 h and into the same spectrum of proteins, Ca2+-restored cells incorporated amino acid 5- to 10-fold more rapidly than Ca2+-depleted cells. Addition of approximately 200 microM Ca2+ in excess of chelator was required to achieve maximal rates of incorporation in Ca2+-depleted preparations. Stimulation by Ca2+ was rapid in onset (several minutes) and slowly reversible by chelator. Ca2+ was uniquely potent and specific among physiologically occurring cations in conferring such stimulation. Stimulation of amino acid incorporation by Ca2+ occurred over a broad range of pH and osmolarities and was facilitated by Mg2+. The effects of Ca2+ in stimulating amino acid incorporation were not traceable to changes in cAMP metabolism, amino acid uptake, protein catabolism, cell ATP or GTP content, or aminoacylation of transfer RNA. Actinomycin D (1 microgram/ml) did not block the stimulatory effects of Ca2+ although puromycin and cycloheximide did. The stimulatory effects of Ca2+ on protein synthesis were not restricted to C-6 in minimal medium. Protein synthesis was reduced by ethylene glycol bis(B-aminoethyl ether)-N,N,N',N'-tetraacetic acid 40 to 75% in C-6 glioma, GH3 pituitary tumor, PC-12 adrenal tumor, N2A neuroblastoma, and HeLa cells incubated under simulated growth conditions with various enriched media and sera. Ca2+-depleted S49 lymphoma, CHO ovarian tumor, and normal, dispersed chicken embryo cells in enriched medium responded to Ca2+ restoration with increased rates of protein synthesis as did collagenase-dispersed normal rat liver cells in minimal medium. Protein synthesis in rabbit reticulocyte lysates was also inhibited by Ca2+-selective chelators or by Ca2+ removal by parvalbumin affinity chromatography and the inhibition was reversed by Ca2+. These findings are consistent with the existence of a Ca2+ requirement in the translational phase of protein synthesis in eukaryotic cells.
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PMID:Identification of a Ca2+ requirement for protein synthesis in eukaryotic cells. 631 27

The metabolism of Ca2+ was studied in a neuronal model system, the clonal mouse neuroblastoma x rat glioma hybrid cell line 108CC5. 1. Homogenates of the hybrid cells exhibit a specific activity of Ca2+-ATPase considerably higher than that of homogenates of the parental cells. 2. Uptake and release of 45Ca2+ by the hybrid cells display two and three distinct phases, respectively, and indicate that 40--50% of the cell-associated Ca2+ is located at the cell surface. 3. The influx of 45Ca2+ is insignificantly affected by Mg2+ or Na+, slightly diminished by Ba2+ or Sr2+, strongly inhibited by La3+, Co2+ or prenylamine, and considerably enhanced by high (i.e., depolarizing) concentrations of K+. The efflux of 45Ca2+ is reduced by La3+. 4. The hybrid cells tend to maintain Ca2+ homeostasis with an overall cellular Ca2+ concentration of 0.5--0.7 mM. At 1.8 mM Ca2+ in the medium this implies the necessity of an extrusion pump in the plasma membrane. 5. A reduction in the hybrid cells of the level of ATP is paralleled by a decline in the content of Ca2+. This can only be explained by the existence of energy-dependent intracellular Ca2+ stores that effectively compete for Ca2+ with a Ca2+ pump located in the plasma membrane. The internal stores are not identical with the mitochondria because mitochondrial inhibitors hardly change Ca2+ metabolism. 6. Micromolar concentrations of the ionophore A23187 can switch off the internal Ca2+ stores without affecting considerably the influx of Ca2+ through the plasma membrane. 7. With switched-off Ca2+ stores it is possible to increase the cellular Ca2+ content distinctly and to bring it back again to the control values in an ATP-dependent manner, i.e. to demonstrate the action of a Ca2+-extrusion pump in the plasma membrane. 8. Under some conditions active extrusion of Ca2+ depends not only on ATP but also on the presence of extracellular Na+. 9. Similar results as with hybrid cells are also obtained with rat glioma cells. The methodology of combining energy deprivation with the application of the ionophore A23187 is possibly generally applicable to obtain insight into the Ca2+ metabolism of various cell types.
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PMID:Uptake and energy-dependent extrusion of calcium in neural cells in culture. 644 79

C6 rat glioma cells, like other tumor cells, grow optimally in Ca2+-or Mg2+-depleted 5% serum medium. However, the glucocorticoid hormone hydrocortisone renders these cells dependent on high concentrations of external Ca2+ for growth. Upon Ca2+ deprivation (30-80 microM Ca2+ medium) hydrocortisone-treated C6 cells undergo reversible cell-cycle arrest at G0/G1 phase. This effect is specific for glucocorticoid hormones and occurs at physiological concentrations. Growth restimulation of Ca2+-deprived, hydrocortisone-treated C6 cells by bovine pituitary growth factors or serum growth factors only takes place if the external Ca2+ concentration is increased. On the other hand, C6 cell growth requirement for external Mg2+ was not increased by the glucocorticoid hormone treatment. A minimum of 80 microM of external Mg2+ is required to keep cells adhered and spread in Ca2+-depleted (30 microM) 5% serum medium; in high Ca2+ concentration (1.8 mM), Mg2+ is not required for adhesion or spreading. Thus, the hormone hydrocortisone renders the cell cycle of C6 glioma cells controllable by the levels of external Ca2+, a minimal external Mg2+ being necessary to warrant normal adhesion.
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PMID:Glucocorticoid hormone renders rat glioma cells dependent on high concentrations of external Ca2+ for growth. 683 11

The ATP signaling mechanism in neuroblastoma x glioma hybrid NG108-15 cells differentiated by exposure to dibutyryl-cAMP was characterized. In cells loaded with fura-2, ATP rapidly raised the cytosolic Ca2+ concentration ([Ca2+]i); the magnitude of the rise was inversely proportional to the extracellular Na+ concentration. Large increases in cytosolic Na+ concentration, measured with the fluorescent Na+ indicator sodium-binding benzofuran isophthalate, were dose-dependently elicited by ATP. ATP also evoked the entry of ethidium bromide into cells, and this process was inhibited by Mg2+. Inositol-1,4,5-trisphosphate (IP3) generation induced by ATP was totally blocked by removal of extracellular Ca2+, but residual IP3 generation still remained in nondifferentiated cells. In addition, ATP produced a concentration-, time-, and Mg(2+)-dependent biphasic uptake of 45Ca2+. A range of nucleotides and ATP analogues, including CTP, UTP, and GTP, induced only 9-29% of the ATP response. However, adenosine 5'-thiotriphosphate evoked 79% of ATP-induced 45Ca2+ uptake. 45Ca2+ uptake elicited by ATP could be potently blocked by purinoceptor antagonists, but other tested reagents less effectively blocked the action of ATP. When bradykinin was used as an agonist, the [Ca2+]i rise was transient and was insensitive to the extracellular Na+ concentration. Na+ influx, entry of ethidium bromide, and 45Ca2+ uptake were unaffected by bradykinin. Furthermore, bradykinin-evoked IP3 generation was insensitive to extracellular Ca2+. Neither ATP nor bradykinin had any effect on cAMP levels within cells. These data suggest that ATP induces a [Ca2+]i rise in differentiated NG108-15 cells via two distinct Ca2+ influx mechanisms, i.e., a receptor-operated cation channel and pores formed by ATP4-. These mechanisms are distinct from those elicited by bradykinin.
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PMID:Two distinct ATP signaling mechanisms in differentiated neuroblastoma x glioma hybrid NG108-15 cells. 751 80

The changes in ionic permeability induced by the application of alpha-latrotoxin to NG108-15 neuroblastoma x glioma cells were examined using the nystatin perforated-patch technique for whole-cell recording. Complex single channel activity appeared in the plasmalemmas after delays that ranged from 1-20 min in Krebs' solution. The conductance of a channel fluctuated among at least three broad, approximately equispaced bands, the maximum conductance being about 300 pS, and the reversal potential approximately 0 mV. The channels were permeable to Na+, K+, Ca2+ and Mg2+, poorly permeable to glucosamineH+ and Cl-, and were blocked by La3+. The channels stayed fully open in Ca(2+)-free solutions with 4 mM Mg2+, in solutions with no divalent cations and in solutions with 2 mM Ca2+ and 96 mM Mg2+. They opened infrequently if both internal and external Cl- were replaced by glutamate-. If alpha-latrotoxin opened similar channels in nerve terminals, the flux of ions through them could account for the massive release of neurotransmitter induced by the toxin.
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PMID:Alpha-latrotoxin channels in neuroblastoma cells. 751 70

We found in cultured glioma (C6BU-1) cells that excitatory amino acids (EAAs) such as glutamate, N-methyl-D-aspartate (NMDA), aspartate, and metabotropic glutamate receptor agonist trans-(+/-)-1-amino-1,3-cyclopentanedicarboxylate caused an increase in the inositol 1,4,5-trisphosphate formation and the intracellular Ca2+ concentration ([Ca2+]i) in the absence of extracellular Mg2+ and Ca2+. Pertussis toxin treatment abolished this glutamate-induced [Ca2+]i increase. Various antagonists against NMDA receptor-ion channel complex, such as Mg2+, D-2-amino-5-phosphonovalerate (D-APV), HA-966, and MK-801, also inhibited the increase in [Ca2+]i induced by glutamate. These results indicate that these metabotropic EAA receptors coupled to pertussis toxin-susceptible GTP-binding protein and phospholipase C system in C6BU-1 glioma cells have the pharmacological properties of NMDA receptor-ion channel complexes. We also found that in the presence of Mg2+ these metabotropic receptors resemble the NMDA receptor-ion channel complex interacted with 5-hydroxytryptamine2 (5-HT2) receptor signaling. EAAs inhibited 5-HT2 receptor-mediated intracellular Ca2+ mobilization and inositol 1,4,5-trisphosphate formation in a concentration-dependent manner. The inhibitory effect of glutamate was reversed by various NMDA receptor antagonists (D-APV, MK-801, phencyclidine, and HA-966), but L-APV failed to block the inhibitory effect of glutamate. The same result was observed in the absence of extracellular Ca2+. In addition, this inhibitory effect on 5-HT2 receptor-mediated signal transduction was abolished by treatment of C6BU-1 cells with pertussis toxin, whereas 5-HT2 receptor-mediated [Ca2+]i increase was not abolished by pertussis toxin treatment. We can, therefore, conclude that the inhibitory effect of glutamate is not a result of the influx of Ca2+ through the ion channel and that it operates via metabotropic glutamate receptors, having NMDA receptor-ion channel complex-like properties and being coupled with pertussis toxin-sensitive GTP-binding protein and phospholipase C.
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PMID:Metabotropic glutamate receptor in C6BU-1 glioma cell has NMDA receptor-ion channel complex-like properties and interacts with serotonin2 receptor-stimulated signal transduction. 752 90

In the present study, we have attempted to clarify whether neuroblastoma glioma hybrid NG 108-15 cells (NG cells) possess the NMDA receptor complex using [45Ca2+]influx and [3H]MK-801 binding as functional measures. Glutamate and NMDA dose-dependently increased [45Ca2+]influx and these increases were further enhanced by glycine. Scatchard analysis revealed the presence of a high-affinity binding site for [3H]MK-801 with a KD of 18.8 nM and a Bmax of 0.328 pmol/mg protein. This [3H]MK-801 binding was also increased by NMDA in a dose-dependent manner and this increase was further enhanced by glycine. Both ketamine and MK-801 inhibited glutamate- and NMDA-induced [45Ca2+]influx as well as the increase of [3H]MK-801 binding in a dose-dependent manner. Similarly, Mg2+ and Zn2+ dose-dependently reduced both glutamate-induced [45Ca2+]influx and [3H]MK-801 binding. Spermine, one of the polyamines, showed a biphasic stimulatory effects on glutamate-induced [45Ca2+]influx and [3H]MK-801 binding. These results indicate that NG cells possess a pharmacologically distinct NMDA receptor complex and suggest that these cells may be useful for the analyses on pharmacological and biochemical characteristics of the NMDA receptor complex.
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PMID:Presence of N-methyl-D-aspartate (NMDA) receptors in neuroblastoma x glioma hybrid NG108-15 cells-analysis using [45Ca2+]influx and [3H]MK-801 binding as functional measures. 791

Clones of neuroblastoma x glioma hybrid, NH108-15, cells expressing differing levels of the human beta 2 adrenoceptor were isolated. Two clones were examined in detail, beta N22 which expressed some 4000 fmol/mg of membrane protein and clone beta N17 which expressed approx. 300 fmol/mg of membrane protein of the receptor. In beta N22 cells 'basal' adenylate cyclase activity measured in the presence of Mg2+ was significantly greater than that in wild-type NG108-15 or beta N17 cells. Both isoprenaline and iloprost were able to stimulate adenylate cyclase activity in each of beta N22 and beta N17 membranes. However, the EC50 for isoprenaline stimulation of adenylate cyclase in membranes of beta N22 cells (6 nM) was significantly lower than that in membranes of beta N17 cells (80 nM), whereas the EC50 for iloprost stimulation of adenylate cyclase (approx. 25 nM) was the same in the two clones and in parental NG108-15 cells. The high basal adenylate cyclase activity of beta N22 cell membranes was not a reflection of higher levels of expression of the adenylate cyclase catalytic unit, as adenylate cyclase activity measured in the presence of Mn2+ was equivalent in membranes of each of wild-type NG108-15 cells and clones beta N22 and beta N17. Basal adenylate cyclase activity measured in the presence of Mg2+ in clone beta N22 was significantly reduced, however, by the beta-receptor antagonist propranolol, whereas this agent was without effect on basal adenylate cyclase activity in membranes of wild-type NG108-15 cells. These data indicate that the elevated basal adenylate cyclase cascade in NG108-15 cells expressing high levels of the beta 2 adrenoceptor represents empty receptor activation of the signalling cascade.
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PMID:Regulation of basal adenylate cyclase activity in neuroblastoma x glioma hybrid, NG108-15, cells transfected to express the human beta 2 adrenoceptor: evidence for empty receptor stimulation of the adenylate cyclase cascade. 798 Apr 49


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