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Query: UMLS:C0027819 (neuroblastoma)
 27,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Functional and optimal activities of the (Na+-K+)ATPase, as determined by ouabain-sensitive K+ influx in intact cells and ATP hydrolysis in cell homogenates respectively, have been measured during the cell cycle of neuroblastoma (clone Neuro-2A) cells. The cells were synchronized by selective detachment of mitotic cells. The ouabain-sensitive K+ influx decreased more than fourfold from 1.62 +/- 0.11 nmoles/min/10(6) cells to 0.36 +/- 0.25 nmoles/min/10(6) cells on passing from mitosis to early G1 phase. On entry into S phase a transient sixfold increase to 2.07 +/- 0.30 nmoles/min/10(6) cells was observed, followed by a rapid decline, after which the active K+ influx rose again steadily from 1.03 +/- 0.25 nmoles/min/10(6) cells in early S phase to 2.10 +/- 0.92 nmoles/min/10(6) cells just prior to the next mitosis. The ouabain-insensitive component rose linearly through the cycle in the same manner as the protein content/cell. Combining total K+ influx values with efflux data obtained previously showed that net loss of K+ occurred with transition from mitosis to G1 phase while net accumulation occurred with entry into S. Throughout mid-S phase net K+ flux was virtually zero, but a large net influx occurred again just before the next mitosis. The (Na+-K+)ATPase activity measured in cell homogenates decreased rapidly from mitosis to G1 phase and increased steadily throughout S phase, but the transient activation on entry into S phase was not observed. Complete inhibition of the (Na+-K+)ATPase mediated K+ influx by ouabain (5 mM) prevents the cells from entering S phase, while partial inhibition by lower concentrations of ouabain (0.2 and 0.5 mM; km = 0.17 mM) causes partial blockage in G1 and, to a lesser extent, a reduced rate of progression through the rest of the cell cycle. We conclude that the transient increase in (Na+-K+)ATPase mediated K+ influx at the G1/S transition is a prerequisite for entry into S phase, while maintenance of adequate levels of K+ influx is necessary for normal rate of progression through the rest of the cell cycle.
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PMID:Modulation of functional and optimal (Na+-K+)ATPase activity during the cell cycle of neuroblastoma cells. 626 Aug 24

Cultures from various normal and neoplastic cell lines exfoliated vesicles with 5'-nucleotidase activity which reflected the ecto-enzyme activity of the parent monolayer culture. The ratio of 5'-nucleotidase to ATPase activity in the microvesicles indicated that cellular ecto-ATPase was conserved in the exfoliative process. Phospholipids of the microvesicles contained significantly increased amounts of sphingomyelin and total polyunsaturated fatty acids. It was concluded that the shedded vesicles constituted a select portion of the plasma membrane. Examination by electron microscopy showed the vesicles had an average diameter of 500 to 1000 nm and often contained a second population of vesicles about 40 nm in diameter. As much as 70% of the plasma membrane ecto-5'-nucleotidase activity of a culture was released into the medium over a 24-h period. Phosphoesterhydrolases from C-6 glioma or N-18 neuroblastoma microvesicles dephosphorylated cell surface constituents when in contact with monolayer cultures. Exfoliated membrane vesicles may serve a physiologic function; it is proposed that they be referred to as exosomes.
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PMID:Exfoliation of membrane ecto-enzymes in the form of micro-vesicles. 626 76

1. Addition of 3.5 mM ATP to mouse neuroblastoma Neuro-2A cells results in a selective enhancement of the plasma membrane permeability for Na+ relative to K+, as measured by cation flux measurements and electro-physiological techniques. 2. Addition of 3.5 mM ATP to Neuro-2A cells results in a 70% stimulation of the rate of active K+ -uptake by these cells, partly because of the enhanced plasma membrane permeability for Na+. Under these conditions the pumping activity of the Neuro-2A (Na+ +K+)-ATPase is optimally stimulated with respect to its various substrate ions. 3. External ATP significantly enhances the affinity of the Neuro-2A (Na+ +K+)-ATPase for ouabain, as measured by direct [3H]ouabain-binding studies and by inhibition studies of active K+ uptake. In the presence of 3.5 mM ATP and the absence of external K+ both techniques indicate an apparent dissociation constant for ouabain of 2 X 10(-6)M. Neuro-2A cells contain (3.5 +/- 0.7) X 10(5) ouabain-binding sites per cell, giving rise to an optimal pumping activity of (1.7 +/- 0.4) X 10(-20) mol K+/min per copy of (Na+ +K+)-ATPase at room temperature.
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PMID:Effect of external ATP on the plasma membrane permeability and (Na+ +K+)-ATPase activity of mouse neuroblastoma cells. 628 92

Effects of arachidonic acid on cellular metabolism, cation content, lipid peroxidation, sodium pump activities and release of labeled arachidonic acid were studied in C-6 glioma cells and N18TG2 neuroblastoma cells. Arachidonic acid caused a significant increase in intracellular sodium levels concomitant with a decrease in intracellular potassium in both cell lines. Both (Na+ + K+)-ATPase and p-nitrophenyl phosphatase of glioma cells were inhibited by arachidonic acid whereas only the p-nitrophenyl phosphatase of neuroblastoma cell was inactivated. Low concentrations of arachidonic acid stimulated lactic acid release whereas high concentrations had an opposite effect. In addition, the lipid peroxide content of glioma cells was increased abruptly by 50 microM arachidonic acid whereas only a slight increase of malondialdehyde was observed in neuroblastoma cells. When the cultured cells of both cell lines were incubated with exogenous labeled arachidonic acid, 78-95% of the label was incorporated into membrane phospholipids. Only a very small fraction of prostaglandin E2 and prostaglandin F2 alpha was synthesized. Exogenous arachidonic acid and free radicals generated with xanthine-xanthine oxidase caused a significant release of endogenous labeled arachidonic acid from cellular membrane phospholipids. These data further support our hypothesis that the arachidonic acid and its oxygen radical metabolites induce pathological alterations in membrane permeability and cellular volume.
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PMID:Alterations of membrane integrity and cellular constituents by arachidonic acid in neuroblastoma and glioma cells. 628 88

In this study the effects of experimental modifications of plasma membrane lipid lateral mobility on the electrical membrane properties and cation transport of mouse neuroblastoma cells, clone Neuro-2A, have been studied. Short-term supplementation of a chemically defined growth medium with oleic acid or linoleic acid resulted in an increase in the lateral mobility of lipids as inferred from fluorescence recovery after photobleaching of the lipid probe 3,3'-dioctadecylindocarbocyanide iodide. These changes were accompanied by a marked depolarization of the membrane potential from -51 mV to -36 mV, 1.5 h after addition, followed by a slow repolarization. Tracer flux studies, using 86Rb+ as a radioactive tracer for K+, demonstrated that the depolarization was not caused by changes in (Na+ + K+)-ATPase-mediated K+ influx or in the transmembrane K+ gradient. The permeability ratio (PNa/PK), determined from electrophysiological measurements, however, increased from 0.10 to 0.27 upon supplementation with oleic acid or linoleic acid. This transient rise of PNa/PK was shown by 24Na+ and 86Rb+ flux measurements to be due to both an increase of the Na+ permeability and a decrease of the K+ permeability. None of these effects occurred upon supplementation of the growth medium with stearic acid.
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PMID:Effect of fatty acids on plasma membrane lipid dynamics and cation permeability in neuroblastoma cells. 629 65

Three clones of neuroblastoma-glioma cells that contain low amounts of calmodulin were selected from the NG108-15 cells after several treatments with high concentrations of chlorpromazine. Purified membranes of the three clones had decreased numbers of both alpha-adrenergic and opiate receptors, monitored with [3H]yohimbine and [3H,D-Ala2]methionine encephalinamide, respectively. No changes were observed in the affinity of these radioactive ligands to the receptors of the selected cells as compared to the parent cells. Addition of bovine brain calmodulin did not affect the binding of [3H,D-Ala2]methionine encephalinamide to the membranes of the selected cells and they had the same number of acetylcholine receptors, determined with 1-quinuclidinyl-[phenyl-4-3H]-benzilate, as the parent NG108-15 cells. The basal ATPase activity in the membranes of the selected cells was 35-50% of the parent cells, with a decreased V value and no significant change in the affinity constant Ka to ATP. Addition of Ca2+ to the purified membranes increased the V of the ATPase in the selected as well as the parent cells but the V of the selected cells remained lower than that of the parent cells. Ca2+ had no effect on the Ka to ATP in either cell type. The Ca2+-dependent ATPase activity of both the parent and the selected cells was also calmodulin-dependent dependent since it was blocked in vitro by chlorpromazine. The co-regulation of opiate and adrenergic receptors and their interaction with calmodulin and Ca2+-ATPase is discussed in view of recent observations indicating biochemical and physiological association between opiates, Ca2+ and adrenergic compounds.
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PMID:A genetic approach to reveal the action of the opiate receptor in selected neuroblastoma-glioma cells. Interaction with alpha-adrenoceptors, calmodulin and Ca2+-ATPase. 629 58

Mouse neuroblastoma cells (clone N1E-115) differentiate in culture upon withdrawal of serum growth factors and acquire the characteristics of neurons. We have shown tht exponentially growing N1E-115 cells possess functional epidermal growth factor (EGF) receptors but that the capacity for binding EGF and for stimulation of DNA synthesis is lost as the cells differentiate. Furthermore, in exponentially growing cells, EGF induces a rapid increase in amiloride-sensitive Na+ influx, followed by stimulation of the (Na+-K+)ATPase, indicating that activation of the Na+/H+ exchange mechanism in N1E-115 cells [1] may be induced by EGF. The ionic response is also lost during differentiation, but we have shown that the stimulation of both Na+ and K+ influx is directly proportional to the number of occupied receptors in all cells whether exponentially growing or differentiating, thus only indirectly dependent on the external EGF concentration. The linearity of the relationships indicates that there is no rate-limiting step between EGF binding and the ionic response. Our data would suggest that as neuroblastoma cells differentiate and acquire neuronal properties, their ability to respond to mitogens, both biologically and in the activation of cation transport processes, progressively decreases owing to the loss of the appropriate receptors.
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PMID:Loss of EGF binding and cation transport response during differentiation of mouse neuroblastoma cells. 630 14

The pumping activity of the plasma membrane-bound Na+,K+-ATPase shows considerable variation during the cell cycle of mouse neuroblastoma Neuro-2A cells. Addition of external ATP at millimolar concentrations, which selectively enhances the plasma membrane permeability of Neuro-2A cells for sodium ions, stimulates the Na+,K+-ATPase pumping activity at all phases of the cell cycle from a factor of 1.05 in mitosis up to 2.2 in G1 phase. Determination of the number of Na+,K+-ATPase copies per cell by direct 3H-ouabain binding studies in the presence of external ATP shows a gradual increase in the number of pump sites on passing from mitosis to the late S/G2-phase by approximately a factor of 2. From these data the pumping activity per copy of Na+,K+-ATPase, optimally stimulated with respect to its various substrate ions, has been determined during the various phases of the cell cycle. This optimally stimulated pumping activity per enzyme copy, which is a reflection of the physicochemical state of the plasma membrane, is high in mitosis, almost twofold lower in early G1 phase, and increases gradually again during the other phases of the cell cycle. This shows that the observed regulation of Na+,K+-ATPase activity during the cell cycle is caused by a combination of three independent factors--namely variation in intracellular substrate availability (Na+), changes in number of enzyme copies per cell, and modulation of the plasma membrane environment of the protein molecules. The modulation of the optimal pumping activity per enzyme copy shows a good correlation (rho = 0.96) with the known modulation of protein lateral mobility during the cell cycle, such that a high protein lateral mobility correlates with a low enzyme activity. It is concluded that changes in plasma membrane properties take place during the Neuro-2A cell cycle that result in changes in the rate of protein lateral diffusion and Na+,K+-ATPase activity in directly correlated way.
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PMID:Membrane regulation of the Na+,K+-ATPase during the neuroblastoma cell cycle: correlation with protein lateral mobility. 630 15

We show here that a protein tyrosine phosphatase inhibitor, sodium orthovanadate, induces rat pheochromocytoma cells to express neurites, a prominent morphological marker of neuronal phenotype. Vanadate-induced differentiation and neurite outgrowth in pheochromocytoma cells was not as extensive as that induced by the positive control employed, nerve growth factor. However, neurite outgrowth responses were comparable between nerve growth factor-treated pheochromocytoma cells and cells primed and then restimulated with vanadate. In the human neuroblastoma cell line, SH-SY5Y, a single exposure to vanadate induced neurite extension in this cell line equal to that initiated by nerve growth factor. In both cell lines vanadate treatment resulted in tyrosine phosphorylation of several high-molecular-weight proteins and using anti-phosphotyrosine antibodies, intense fluorescence was observed in the cell body and neurites of pheochromocytoma cells exposed to vanadate. Vanadate mediated differentiation and neurite outgrowth in pheochromocytoma cells could be ablated by the tyrosine kinase inhibitor erbastatin, whereas nerve growth factor-induced neurite outgrowth was only partially inhibited. In SH-SY5Y cells, erbstatin mediated partial inhibition of both vanadate and nerve growth factor-induced neurite elongation with similar kinetics. In contrast, K252b, a trk tyrosine kinase inhibitor, exhibited only a 30% reduction of neurite outgrowth in vanadate treated pheochromocytoma cells but an 80% reduction in nerve growth factor-treated cells. In SH-SY5Y cells, K252a did not have a statistically significant effect on neurite elongation induced by vanadate in contrast to a 60% reduction in nerve growth factor-treated cells. The membrane impermeable analogue K252b, had no effect on neurite elongation induced with either vanadate or nerve growth factor in these cells. The effects of vanadate were not mimicked by ouabain (0.1-50 microM) indicating that vanadate does not induce differentiation and/or neurite extension by inhibiting ion channel Na,K-ATPase, which is one of its other well-characterised inhibitory activities. Evidence for the selective action of vanadate on some but not all neuronal cell lines comes from the fact that it did not induce neurite extension in the human neuroblastoma cell line SK-N-MC. These data imply that vanadate-induced neurite outgrowth responses in pheochromocytoma and SH-SY5Y cells can be induced by the inhibition of tyrosine phosphatases and appears not to simply mimic nerve growth factor signals. The target(s) of vanadate action in the two cell lines are currently being sought.
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PMID:Vanadate stimulates differentiation and neurite outgrowth in rat pheochromocytoma PC12 cells and neurite extension in human neuroblastoma SH-SY5Y cells. 752 Oct 24

The effects of ouabain, ATP, and vanadate on palytoxin induction of ion channels were examined with the aim of elucidating the role of Na,K-ATPase in palytoxin action. Palytoxin-induced membrane depolarization of crayfish giant axons and single channel currents of frog erythrocytes and mouse neuroblastoma N1E-115 cells were examined using the intracellular microelectrode and patch-clamp techniques. External application of palytoxin in nanomolar concentrations induced depolarization in the crayfish giant axons, and the depolarization was inhibited by pretreatment of the axon with ouabain (10 microM). Internally perfused axons were less sensitive to palytoxin unless ATP (6 mM) was added internally. In patch-clamp experiments, picomolar palytoxin in the patch electrode induced single channels in both cell-attached and inside-out patches of erythrocytes and neuroblastoma cells. The induced channels had a conductance of about 10 pS, reversed near 0 mV in physiological saline solution, and was permeable to Na+, K+, Cs+, and NH4+, but not to choline. Single channel activities induced by palytoxin were inhibited by ouabain (10 microM) and vanadate (1 mM), but promoted by ATP (1 mM). The modulating effects of ouabain, vanadate, and ATP on palytoxin action suggest that the Na,K-ATPase is involved in the induction of single channels by palytoxin. Palytoxin-induced and ouabain-inhibitable single channels were observed in planar lipid bilayer incorporated with purified Na,K-ATPase. The results indicate that an interaction between palytoxin and Na,K-ATPase leads to opening of a 10-pS ion channel. They further raise the possibility that a channel structure may exist in the sodium pump which is uncovered by the action of palytoxin.
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PMID:Involvement of the Na,K-ATPase in the induction of ion channels by palytoxin. 754 78


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