Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027819 (neuroblastoma)
 27,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A method for quantitative evaluation of transmembrane electrical potential and pH gradients across a subcellular compartment in an intact cell is presented. This approach has been applied in studies of mouse neuroblastoma C-1300 clone NB41A3, in which the transmembrane electrical potential and pH gradients and the mitochondrial volume percent have been determined. Membrane potentials and pH gradients were measured by two different methods. Equilibrium distributions of [(3)H]triphenylmethyl phosphonium and [(14)C]-thiocyanate ions gave calculated apparent membrane potentials of -77.0 and -29.6 mV, respectively, at 20-25 degrees C; a value of -60.8 mV was obtained from microelectrode measurements. Equilibrium distributions of weak acids ([(14)C]trimethylacetic acid and 5,5-di[(14)C]methyl-2,4-oxazolidine-dione) and of weak bases ([(14)C]dimethylamine and [(14)C]trimethylamine) gave calculated upper and lower limits of the pH gradient (Delta pH = pH(e) - pH(i)) of -0.14 and -0.21 pH unit, respectively. The microelectrode measurements showed that the intracellular pH is within 0.1 of a pH unit or less of the extracellular pH over the extracellular pH range of 7.35-6.85. The mitochondrial volume percent calculated on the basis of the measured cytochrome c content is 5.6 +/- 1.2% and compares well with estimates of 5.4 +/- 1.1% obtained from 25 electron micrographs. Measurements of the cellular energetic parameters gave values within the range found in other cells and perfused organs. Comparison of the results of the microelectrode and equilibrium measurements permits estimates of the electrical potential and pH gradients across the mitochondrial membrane (mitochondria-to-cytoplasm gradients) to be made and suggests that the trans-mitochondrial membrane protonmotive force in the intact cell cannot be greater than -143 mV.
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PMID:Cellular energy metabolism, trans-plasma and trans-mitochondrial membrane potentials, and pH gradients in mouse neuroblastoma. 3 13

N-bromosuccinimide-cytochromes c (Myer, Y. P. (1972), Biochemistry 11, 4195) and formyl-cytochrome c (Aviram, I and Schejter, A. (1971), Biochim. Biophys. Acta 229, 113) have been chromatographically purified, and the resulting components have been characterized in terms of their structure, conformation, and function. The activity measurements are considered in terms of the oxidizability, as the transference of an electron to solubilized cytochrome c oxidase, and reducibility, as the tendency to accept an electron from NADH-cytochrome c reductase. Conformational characterization has been carried out by absorption measurements, pH-spectroscopic behavior, circular dichroism, thermal denaturation, ionization of phenolic hydroxyls, the tendency to form the CO complex, and autoxidation with molecular oxygen. NBS-cytochrome c yields two major components, the relative proportions of which, with increasing modification of the protein, exhibit a pattern typical of the formation of the two in a consecutive manner. The first product contains the modification of the Trp-59 and Met-65 side chains, and the second contains the added modification of Met-80. The former in both valence states of iron is more or less like the native protein, except for an apparently slightly loosened heme crevice; the latter, as in other modifications involving modification of centrally coordinated Met-80, was found to be in a conformational state characteristic of the native protein with a disrupted central coordination complex, a loosened heme crevice, and small, but finite derangement of the polypeptide conformation. Functionally, the first component reflected 55% of the reducibility property and an unimpaired oxidizability property, while the latter exhibited derangement of both aspects of cytochrome c activity. Formyl-cytochrome c yielded a single component with modification of Trp-59. Conformationally, in both valence states, it is a molecular form with a disrupted central coordination complex, a loosened heme crevice, and gross derangement of the overall protein conformation. It exhibits a minimal reducibility property, 12%, whereas it retains a native-like tendency to transfer an electron to cytochrome c oxidase. The data from the NBS-cytochrome c components are analyzed with reference to the two forms in the earlier studies of the unpurified preparations. The results are found to be in agreement with one another. The selectivity between the reducibility and the oxidizability exhibited by the first NBS component and formyl-cytochrome c, irrespective of significant differences in the conformational and coordinational configurations of the two, has been viewed in light of a two-path, two-function model for oxidoreduction, as well as with reference to conformational and structural requirements for the oxidizability and reducibility properties of the molecule.
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PMID:Conformational and functional studies of chemically modified cytochromes: N-bromosuccinimide- and formyl-cytochromes c. 16 5

The expression of receptors for nerve growth factor (NGF) on the cell surface was assayed by rosette formation with ligand-coated sheep red blood cells (SRBC). Cell clones derived from the murine C1300 neuroblastoma and from hybrids between a neuroblastoma clone and L cell clones showed a wide variation in the capacity to form rosettes with NGF-coated SRBC. All the neuroblastoma, L cell and hybrid clones formed rosettes with phytohemagglutinin-coated SRBC and none formed rosettes with cytochrome c- or ferritin-coated SRBC or with SRBC not coated with ligand.
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PMID:Differences between murine C1300 neuroblastoma clones detected by rosette formation with nerve growth factor-coated sheep red blood cells. 18 19

Binding of thrombin to monolayer cultures of human umbilical vein endothelium is studied. Binding is measured as inhibition by unlabeled ligand of the binding of 125I-thrombin to the cells. Radioactivity bound to cultures at equilibrium is measured after draining but not washing the cells. To correct for unremoved supernatant, 131I-albumin is included as a second label in the medium. Equilibrium between bound and free thrombin is attained within 1 min, and Scatchard analysis indicates a population of approximately 3 x 10(3) sites/cell with a dissociation constant of 10(-10) M, and a larger population with a dissociation constant greater than 10(-8) M. The two populations of sites are also indicated by a biphasic dissociation of bound label. Thrombin inactivated with diisopropyl fluorophosphate binds to the same receptor, with an affinity similar to that of active thrombin. Binding is unaffected by albumin (an acidic protein) and cytochrome c (a basic protein). Cultures of umbilical cord smooth muscle and fibroblasts bind thrombin at least 100 times more weakly than endothelium, and no binding to erythrocytes or a monolayer culture of mouse neuroblastoma is detected.
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PMID:Binding of human thrombin to cultured human endothelial cells. 43 77

A trypsin-degradable nerve growth factor (NGF) receptor associated with the phospholipid component of the surface membrane has been detected on F98 anaplastic glioma cells. NGF also bound to the nucleus of F98 cells. Bound NGF was not displaceable by insulin, cytochrome C, growth hormone, or bovine serum albumin. Specific binding of NGF occurred with a Kd of 8.79 X 10(-12) M as determined by Scatchard analysis with approximately 34,000 receptors per cell. Specific NGF binding was also evident to C6 rat glioma cells and IMR-32 human neuroblastoma cells, but not to 3T3 mouse fibroblasts. These observations coupled with previous findings suggest that the NGF receptor may be a marker found on cells of neural derivation. As little as 1 ng/ml NGF caused an increase in the adhesiveness of F98 cells to culture flasks. Increased adhesiveness could be observed in as little as 5 min and was apparent for at least 45 min. At 25 min in NGF-containing medium, 24 +/- 3% of the cells adhered to the flasks compared to 13 +/- 1% of control cells. The NGF-induced increase in adhesiveness was not duplicated by epidermal growth factor, insulin, cytochrome c, bovine serum albumin, dibutyryl cyclic AMP, or sodium butyrate. Oxidized NGF blocked the effect of native NGF, but had little or no adhesion-promoting activity itself. Pretreatment of the cells with NGF was also effective in promoting adhesion, even though nerve growth factor was not added to the binding medium. The effect of this pretreatment was reversible; when NGF-pretreated cells were grown in medium without supplemental NGF, the adhesiveness of the cells returned to control levels or lower.
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PMID:Increased adhesion response of anaplastic glioma cells to nerve growth factor and the presence of specific receptors. 631 24

Sixteen synthetic or plant-derived coumarins of dietary importance with different patterns of substitution were tested for their capacity to scavenge superoxide and for their cytotoxicity. Superoxide was generated by human polymorphonuclear leukocytes stimulated by phorbol myristate acetate and was measured using the reduction of ferricytochrome c or of nitrobule tetrazolium (NBT). Eleven of the coumarins, all lacking dihydroxy substitution, did not scavenge superoxide. Of the remaining five, the most potent scavenger was fraxetin (7,8-dihydroxy-6-methoxycoumarin) with an IC50 (concentration producing 50% inhibition) of 2.3 microM in the cytochrome assay and 5.8 microM using NBT. The other four coumarins (all containing ortho-dihydroxy catechol functions, and found previously to be pro-oxidant in cell-free systems by virtue of reduction of ferric to ferrous ions), themselves rapidly reduced cytochrome c. Therefore their effects on superoxide were measured using NBT, yielding IC50 values in the range 8.5 to 82.0 microM. Fraxetin and the other active and inactive coumarins were not directly cytotoxic at 100 microM to leukocytes or to erythrocytes, as shown by their failure to cause release of cytosolic lactate dehydrogenase or to cause haemolysis, respectively. However, all five dihydroxylated pro-oxidant coumarins were toxic to NS20Y neuroblastoma cells in 24 hr culture, whereas the other eleven coumarins were nontoxic. We conclude that 7,8-dihydroxylated coumarins such as fraxetin are agents which are not themselves directly cytotoxic and are capable of direct scavenging of superoxide anion radicals, an action which might be protective at sites of leukocyte activation during inflammation. However, in the presence of free ferric ions they may exert potentially damaging pro-oxidant actions, including cytotoxicity. This series of compounds provides a useful basis for structure-activity studies designed to achieve separation or combination of these properties.
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PMID:Superoxide scavenging activity in leukocytes and absence of cellular toxicity of a series of coumarins. 806 31

We have attempted to elucidate the mechanism of apoptotic cell death induced by hypoxia (very low oxygen conditions) in neuronal cells. Human neuroblastoma SK-N-MC cells under hypoxic conditions resulted in apoptosis in a time-dependent manner estimated by DNA fragmentation assay and nuclear morphology stained with fluorescent chromatin dye. Pretreatment with Z-Asp-CH2-DCB, a caspase inhibitor, suppressed the DNA ladder in response to hypoxia in a concentration-dependent manner. An increase in caspase-3-like protease (DEVDase) activity was observed during apoptosis, but no caspase-1 activity (YVADase) was detected. To confirm the involvement of caspase-3 during apoptosis, Western blot analysis was performed using anti-caspase-3 antibody. The 20- and 17-kDa proteins, corresponding to the active products of caspase-3, were generated in hypoxia-challenged lysates in which processing of the full length form of caspase-3 was evident. With a time course similar to this caspase-3 activation, hypoxic stress caused the cleavage of PARP, yielding an 85-kDa fragment typical of caspase activity. In addition, caspase-2 was also activated by hypoxia, and the stress elicited the release of cytochrome c into the cytosol during apoptosis. These results suggest that caspase activation and cytochrome c release play roles in hypoxia-induced neuronal apoptosis.
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PMID:Hypoxia induces apoptosis in human neuroblastoma SK-N-MC cells by caspase activation accompanying cytochrome c release from mitochondria. 984

It is well known that caspases are produced as proforms, which are proteolytically cleaved and activated during apoptosis or programmed cell death. We report here that caspases are activated during apoptosis by treatment with NOC18, a nitric oxide (NO) donor. Our present experiments have examined the way in which NO induces neuronal cell death, using a new type of NO donor that spontaneously releases only NO without enzymatic metabolism. NOC18 induced apoptosis in human neuroblastoma SH-SY5Y cells in a concentration- and time-dependent manner as estimated by DNA fragmentation assay, FACScan analysis, and nuclear morphology. Oxyhemoglobin, an NO trapper, suppressed NOC18-triggered DNA fragmentation, indicating that NO from NOC18 is a real activator in this study. Upon the induction of apoptosis, an increase in caspase-3-like protease activity, but not caspase-1, was observed. Procaspase-2 protein, an inactive form of caspase-2, decreased dramatically. In addition, NOC18 also resulted in poly (ADP-ribose) polymerase (PARP) cleavage, yielding an 85-kDa fragment typical of caspase activity. Oxyhemoglobin blocked the decrease of procaspase-2 and the cleavage of PARP by NOC18 in a concentration-dependent manner. Moreover, NO elicited the release of cytochrome c into the cytosol during apoptosis. These results suggest that both stimulation of caspase activity and cytochrome c release are partly involved in NO-induced neuronal apoptosis.
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PMID:Caspase activation accompanying cytochrome c release from mitochondria is possibly involved in nitric oxide-induced neuronal apoptosis in SH-SY5Y cells. 988 70

Apoptosis and aging share common mechanisms in oxidative stress and mitochondrial involvement. Treatment of cultured neuroblastoma cells with a radical initiator induced apoptosis; raise in hydrogen peroxide and release of cytochrome c from mitochondria preceded collapse of mitochondrial potential and cell death. In rat hepatocytes treated with adriamycin incubation with exogenous Coenzyme Q10 counteracted the drug-induced increase of hydrogen peroxide and the fall of the mitochondrial potential, thus demonstrating the quinone antioxidant effect. Complex I activity and its rotenone sensitivity decreased in brain cortex non-synaptic mitochondria from old rats; a 5 kb mitochondrial DNA deletion was found only in the old rats. A similar behavior was found in human platelets from old individuals. The postulated energy decline was confirmed by the inhibitor sensitivities of platelet aggregation and lactate production. The lack of the 5 kb deletion in platelets throws doubts on mitochondrial DNA lesions as the only causes of mitochondrial dysfunction in aging.
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PMID:Oxidative stress, antioxidant defences and aging. 991 19

Amplification of the MYCN gene is found in a large proportion of neuroblastoma and considered as an adverse prognostic factor. To investigate the effect of ectopic MycN expression on the susceptibility of neuroblastoma cells to cytotoxic drugs we used a human neuroblastoma cell line harboring tetracycline-controlled expression of MycN. Neither conditional expression of MycN alone nor low drug concentrations triggered apoptosis. However, when acting in concert, MycN and cytotoxic drugs efficiently induced cell death. Apoptosis depended on mitochondrial permeability transition and activation of caspases, since the mitochondrion-specific inhibitor bongkrekic acid and the caspase inhibitor zVAD-fmk almost completely abrogated apoptosis. Loss of mitochondrial transmembrane potential and release of cytochrome c from mitochondria preceded activation of caspase-8 and caspase-3 and cleavage of PARP. CD95 expression was upregulated by treatment with cytotoxic drugs, while MycN cooperated with cytotoxic drugs to increase sensitivity to CD95-induced apoptosis and enhancing CD95-L expression. MycN overexpression and cytotoxic drugs also synergized to induce p53 and Bax protein expression, while Bcl-2 and Bcl-X(L) protein levels remained unchanged. Since amplification of MYCN is usually associated with a poor prognosis, these findings suggest that dysfunctions in apoptosis pathways may be a mechanism by which MycN-induced apoptosis of neuroblastoma cells is inhibited.
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PMID:MycN sensitizes neuroblastoma cells for drug-induced apoptosis. 1005 Aug 84


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