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

1. Membrane current responses to focal application of bradykinin (BK) were recorded in voltage-clamped NG108-15 neuroblastoma x glioma hybrid cells. 2. BK produced sequential outward and inward currents at clamp potentials between -60 and -30 mV, designated IBK(out) and IBK(in), respectively. 3. The outward current IBK(out) was accompanied by an increased membrane conductance. Ramp current-voltage (I-V) curves yielded a reversal potential (VBK) of -80 +/- 5.6 mV (mean +/- S.D., n = 9) in 5.4 mM [K+]o. VBK showed a positive shift on raising [K+]o, compatible with a primary increase in K+ conductance. Subtracted I-V curves indicated that the underlying conductance was not strongly voltage dependent between -120 and -40 mV. 4. IBK(out) was inhibited by d-tubocurarine (dTC, 0.1-0.5 mM) but was insensitive to tetraethylammonium (TEA) below 5 mM. 5. The inward current IBK(in) was accompanied by a fall in membrane conductance. This was associated with the inhibition of a time- and voltage-dependent K+ current, IM. In consequence, IBK(in) was strongly voltage dependent and dissipated, usually without reversal, on hyperpolarizing the cell beyond -70 mV in 5.4 mM [K+]o. Reversal to an outward current negative to -40 mV could be obtained on raising [K+]o to 54 mM. 5. Both IBK(in) and IBK(out) persisted when ICa was blocked with Co2+ or Cd2+. IBK(out) slowly diminished in Ca2+-free, Mg2+-substituted solution. 6. The Ca2+ spike current ICa and the Ca2+-activated K+ current IAHP were inhibited during IBK(out) or after Ca2+ injections. BK did not affect the voltage-activated K+ current IK(V) recorded in Co2+ solution. 7. It is concluded that the dual response to BK results from opposing effects on two different species of K+ current. IBK(out) results from activation of a Ca2+-dependent, voltage-insensitive K+ conductance, probably mediated by a transient rise in intracellular Ca2+. It is suggested that the Ca2+ is released from an intracellular store. IBK(in) results primarily from inhibition of the Ca2+-independent, voltage-gated K+ current, IM. This effect is not replicated by a rise of intracellular Ca2+ and must therefore be generated by another mechanism.
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PMID:Membrane current responses of NG108-15 mouse neuroblastoma x rat glioma hybrid cells to bradykinin. 245 96

Metallothioneins are a class of cysteine-rich and low molecular weight, metal-binding proteins that are inducible by a wide variety of agents, including metal ions, such as cadmium and zinc, glucocorticoid hormones, interferon, and tumor promoters. In an effort to delineate the regulation of the synthesis of the recently identified brain metallothionein-like protein, a study was undertaken to compare the induction of metallothionein in human neuroblastoma IMR-32 cells by zinc, cadmium, and dexamethasone using the human Chang liver cells as a control. Both cadmium (1 microM) and zinc (100 microM) significantly enhanced the incorporation of [35S]cysteine into metallothioneins isolated from both neuroblastoma and Chang liver cells. Dexamethasone in concentrations of 10 microM stimulated the synthesis of metallothionein in the Chang cells, whereas it had no effects on the synthesis of metallothionein in the neuroblastoma cells at concentrations ranging from 2.5--100 microM. The degree of stimulation of metallothionein synthesis in the Chang cells by cadmium and zinc was significantly higher than seen in neuroblastoma cells. The neuroblastoma IMR-32 exhibited less tolerance to the toxicity of both cadmium and zinc than the Chang cells, which may correlate with the inherent ability of these ions to induce metallothioneins in these dissimilar cells. The results of these studies are interpreted to indicate that the factors regulating the synthesis of metallothioneins in the Chang and neuroblastoma cells are not identical, suggesting also of the presence of dissimilar regulatory mechanisms in the liver and brain.
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PMID:The stimulation of metallothionein synthesis in neuroblastoma IMR-32 by zinc and cadmium but not dexamethasone. 248 8

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

Cd2+ and other divalent metals mobilized cell Ca2+ in human skin fibroblasts. The divalent metals produced a large spike in cytosolic free Ca2+ and strikingly increased net Ca2+ efflux similarly to bradykinin. One-tenth microM Cd2+ half-maximally increased 45Ca2+ efflux. The potency order of the Ca2+ mobilizing metals was: Cd2+ greater than Co2+ greater than Ni2+ greater than Fe2+ greater than Mn2+. Cd2+ probably acts at an extracellular site because loading the cells with a heavy metal chelator only slightly inhibited Cd2+-evoked 45Ca2+ efflux. Cd2+ increased [3H]inositol polyphosphates; [3H]inositol trisphosphate increased 4-fold in 15 s. Zn2+ reversibly blocked 45Ca2+ efflux evoked by Cd2+ but not that produced by bradykinin. Zn2+ competitively (Ki = approximately 0.4 microM) inhibited net Ca2+ efflux produced by Cd2+. Cd2+ also evoked Ca2+ mobilization in umbilical artery muscle, endothelial, and neuroblastoma cells, and the divalent cation agonist and antagonist specificities were similar to those in the fibroblasts. The divalent metals appear to trigger Ca2+ mobilization via a reversible interaction with an external site on the cell surface, which may be considered a "Cd2+ receptor."
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PMID:Cadmium evokes inositol polyphosphate formation and calcium mobilization. Evidence for a cell surface receptor that cadmium stimulates and zinc antagonizes. 254 Jan 74

The action of several ligands on the low- (LVA,T) and high-threshold (HVA,L and N) Ca channels of adult rat sensory neurons and human neuroblastoma IMR32 cells has been investigated. In both cell types, 40 microM Cd2+ and 6.4 microM /omega-Conotoxin (omega-CgTx) selectively blocked the HVA channels, sparing the majority of LVA channels that were antagonized by amiloride and Ni2+. In 50% of the cells, however, /omega-CgTx spared also a 15% of HVA channels that proved to be sensitive to BAY K 8644. The agonistic action of BAY K 8644 on [omega-CgTx-resistant HVA channels caused a large Ba current increase, prolonged current deactivation and acceleration of HVA channels inactivation that was particularly evident in adult rat DRG.
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PMID:Action of Ca2+ agonists/antagonists in mammalian peripheral neurons. 256 66

1. The role of inositol 1,4,5-trisphosphate (InsP3) and diacylglycerol (DAG) as possible mediators of the membrane current responses of NG108-15 neuroblastoma x glioma hybrid cells to bradykinin (BK, Brown & Higashida, 1988b) has been tested using intracellular ionophoresis of InsP3 and external application of phorbol dibutyrate (PDBu) and 1-oleoyl-2-acetylglycerol (OAG). 2. Intracellular ionophoresis of InsP3 into cells clamped at -30 to -50 mV produced (i) a transient outward current, (ii) a transient outward current followed by an inward current, or (iii) an inward current. All currents were accompanied by an increased input conductance. 3. The transient outward current reversed at between -80 and -90 mV. The reversal potential was shifted to more positive potentials on raising extracellular [K+], suggesting that it resulted from an increased K+ conductance. 4. The outward current was inhibited by apamin (0.4 microM) or d-tubocurarine (0.2-0.5 mM); these drugs also inhibit the outward current produced by BK or by intracellular Ca2+ injections (Brown & Higashida, 1988 a, b). The outward current was also slowly reduced in 0 mM [Ca2+] or 0.5 mM [Cd2+] plus 2 mM [Co2+] solution. 5. Ionophoretic injection of inositol 1,3,4-trisphosphate and inositol 1,3,4,5-tetrakisphosphate, guanosine trisphosphate or inorganic phosphate did not evoke an outward current but produced only an inward current with an increased conductance, reversing at between -10 and -20 mV. 6. Bath application of PDBu (10 nM-1 microM) or OAG (1-10 microM) produced an inward current with a fall in input conductance. The inward current was voltage dependent and was accompanied by an inhibition of the time-dependent current relaxations associated with activation or deactivation of the voltage-dependent K+ current, IM. 7. PDBu did not clearly reduce the Ca2+ current or the Ca2+-dependent K+ current recorded in these cells. During superfusion with PDBu, the outward current produced by intracellular ionophoresis of InsP3 was greatly enhanced. 8. The results support the view that the two membrane current responses to BK might both result from accelerated membrane phosphatidylinositide hydrolysis. One product, InsP3, releases Ca2+ and activates an apamin-curare-sensitive outward K+ current; this effect is imitated by intracellular InsP3 ionophoresis. The second product, DAG; activates protein kinase C to inhibit the voltage-dependent K+ current IM and generate an inward current; this effect is imitated by external application of PDBu or OAG.
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PMID:Inositol 1,4,5-trisphosphate and diacylglycerol mimic bradykinin effects on mouse neuroblastoma x rat glioma hybrid cells. 326 93

A screening method for determination of cadmium, lead, and copper in foods was developed. The sample (1-3 g) is digested with HNO3-H2SO4-HClO4 in a centrifuge tube attached to a straight glass tube that prevents loss of HNO3 by volatilization. After digestion, potassium iodide, H2SO4, and MIBK (4-methyl 2-pentanone) are added, and the metals are extracted with MIBK as metal iodides. The MIBK solution is injected and the metals are determined by flame polarized Zeeman atomic absorption spectrometry using a discrete nebulization technique. Recoveries of metals from fortified milk powder, unpolished rice, fish, beef, peanut butter, apple, and cabbage were satisfactory. The analytical results for NBS Oyster Tissue and NIES Pepperbush, Chlorella, and Mussel agreed with certified or reference values except lead in Pepperbush. The limits of quantitation for cadmium, lead, and copper were 0.01, 0.09, and 0.02 ppm, respectively. This method is simple and safe for routine analysis of high levels of cadmium, lead, and copper in foods.
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PMID:Screening method for determination of high levels of cadmium, lead, and copper in foods by polarized Zeeman atomic absorption spectrometry using discrete nebulization technique. 341 11

Neurotoxicity of long-term exposure to lead, aluminum and cadmium has been studied in vitro on the human neuroblastoma cell line IMR32 by measuring cytotoxicity, and the effects on neuronal-specific characteristics such as nitrite outgrowth and expression of cholinergic receptors as parameters of toxicity. Cytotoxicity was highest with cadmium, intermediate with lead and lowest with aluminum exposure. Lead, but not cadmium and aluminum, interfered with neurite growth. The expression of alpha-bungarotoxin binding sites and muscarinic receptors was markedly increased by cadmium and not affected by aluminum exposure. Lead induced only an increase of toxin binding sites. These in vitro modifications are discussed in relation to the possible use of neuronal cell lines for detecting neurotoxic effects of heavy metals.
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PMID:Effects of long-term in vitro exposure to aluminum, cadmium or lead on differentiation and cholinergic receptor expression in a human neuroblastoma cell line. 350 65

Results are reported for an interlaboratory study conducted to assess the reproducibility of analyses for lead, copper, cadmium, and zinc. The 10 participating laboratories analyzed 2 samples of freeze-dried clam tissue and 1 disguised sample of NBS Oyster Tissue. Interlaboratory variations were observed for all metals, although the methods yielded reproducible data for Cu and Zn with average interlaboratory coefficients of variation of 15 and 11%, respectively. The performance of methods used for Cd and, more so, for Pb was less than satisfactory. Cadmium levels in the 3 samples ranged from about 0.7 to 3.7 ppm with an average interlaboratory coefficient of variation (CV) of 24%. Lead levels in the 3 samples were about 0.5 ppm with an interlaboratory CV of 68%. Some laboratories' results were consistently high or low but data were insufficient to relate these trends to one particular variable. Results from this study were compared with 5 other studies reported in the literature since 1980. Coefficients of variation from all studies were comparable for samples with similar metal concentrations.
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PMID:Interlaboratory comparison of analyses for heavy metals in clam tissue. 377 59

A simple, automated wet digestion procedure was developed for the quantitative determination by atomic absorption spectroscopy (AAS) of arsenic, cadmium, copper, mercury, lead, selenium, and zinc in animal tissue. A commercial digestion block system with automated temperature programming was used. Recoveries of all elements from spiked bovine liver and kidney samples exceed 95%. The analytical results obtained for samples of NBS Bovine Liver (No. 1577a) agree well with certified values. The procedure is safe and requires minimum analyst time.
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PMID:Simple automated wet digestion of animal tissues for determination of seven elements by atomic absorption spectroscopy. 398 99


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