Effect Of Nickel Ions Research Articles

Nickel-induced substrate inhibition of bovine liver glutamate dehydrogenase.

The effects of nickel ions on reductive amination and oxidative deamination activities of bovine liver glutamate dehydrogenase (GDH) were examined kinetically by UV spectroscopy, at 27 degrees C, using 50 mM Tris, pH 7.8, containing 0.1 M NaCl. Kinetic analysis of the data obtained by varying NADH concentration indicated strong inhibition, presumably due to binding of the coenzyme to the regulatory site. In contrast, almost no inhibition was observed in the forward reaction. The fact that nickel ions have the capacity to enhance binding of NADH to the enzyme was confirmed by an electrochemical method using a modified glassy carbon electrode. Use of NADPH instead of NADH showed only a weak substrate inhibition, presumably related to lower affinity of NADPH for binding to the regulatory site. Lineweaver-Burk plots with respect to alpha-ketoglutarate and ammonium ions indicated substrate and competitive inhibition patterns in the presence of nickel ions, respectively. ADP at 0.2 mM concentration protected inhibition caused by nickel. These observations are explained in terms of formation of a nickel-NADH complex with a higher affinity for binding to the regulatory site in GDH, as compared with the situation where nickel is not present. Such effects may be important for regulation of GDH and other NADH-utilizing enzymes.

Effect of nickel ions on sensitivity of In 2O 3 thin film sensors to NO 2

The effect of Ni 2+ ions on the properties of sol–gel obtained In 2O 3 thin film sensors under detection of low concentrations of NO 2 had been investigated. Doping of In 2O 3 thin films with Ni 2+ ions leads to the increase of their sensitivity to NO 2. According to electron microscopy, electron and X-ray diffraction results, Ni 2+ ions substitute In 3+ ions in the cationic sites of In 2O 3 crystal lattice with the formation of In 2− x Ni x O 3 solid solution containing higher In 2+ ions concentration as compared with In 2O 3. At exposure of In 2O 3 and In 2O 3–Ni 2+ surfaces with NO 2 oxidation of In 2O 3, lattice defects (i.e., In 2+ ions) occur. Thus, interaction with NO 2 leads to changes of oxide stoichiometry and electric conductivity conformably, causing In 2O 3 and In 2O 3–Ni 2+ sensors response. Higher In 2O 3–Ni 2+ sensitivity to NO 2 correlates with higher In 2+ ions concentration as compared with In 2O 3.

State-dependent nickel block of a high-voltage-activated neuronal calcium channel.

Effect of nickel ions (Ni2+) on noninactivating calcium channels in squid giant fiber lobe (GFL) neurons were investigated with whole cell voltage clamp. Three different effects of Ni2+ were observed to be associated with distinct Ca2+ channel activation states. 1) Nickel ions appear to stabilize closed channel states and, as a result, slow activation kinetics. 2) Nickel ions block open channels with little voltage dependence over a wide range of potentials. 3) Block of open channels by Ni2+ becomes more effective during an extended strong depolarization, and this effect is voltage dependent. Recovery from this additional inhibition occurs at intermediate voltages, consistent with the presence of two distinct types of Ni2+ block that we propose correspond to two previously identified open states of the calcium channel. These results, taken together with earlier evidence of state-dependent block by omega-agatoxin IVA, suggest that Ni2+ generates these unique effects in part by interacting differently with the external surface of the GFL calcium channel complex in ways that depend on channel activation state.

A quantitative study of the enhancing effect of nickel ions on the taste response to sodium ions of single fibers of the frog glossopharyngeal nerve: competitive inhibition by calcium ions of the nickel-enhanced response to sodium ions.

Single water fibers of the frog glossopharyngeal nerve respond to relatively high concentrations of NaCl ( > 80 mM). NiCl2 at 1 mM enhanced the Na+ response and reduced the threshold concentration for NaCl to 20 mM. CaCl2 at 0.5-1 mM induced an inhibition of the Ni2+ -enhanced response to Na+ ions. A quantitative explanations for these results is provided by the hypothesis that Ni2+ ions secondarily affect a sodium receptor or channel (designated XNa*) that is responsible for the Na+ response and that Ca2+ ions inhibit the Ni2+ -enhanced response to Na+ ions by competing with Na+ ions for XNa*. Double-reciprocal plots of the experimental data indicate that the affinity of XNa* for both Na+ ions (agonist) and Ca2+ ions (competitive antagonist) in the presence of 1 mM NiCl2 was five times higher than the previously reported values obtained in the absence of NiCl2 (Kitada, 1991). Ni2+ ions at 1 mM enhanced the maximal response to Na+ ions by 190%. It appears that a sodium receptor (or channel) interacts with a Ni2+ -binding element that is affected by Ni2+ ions and, thus, Ni2+ ions can induce both an increase in the affinity of the sodium receptor for the respective cations and an enhancement of the Na+ response.

Effects of nickel ions on polymerase activity and fidelity during DNA replication in vitro

Nickel is a genotoxic carcinogen. However, the mechanisms of nickel-induced genotoxicity are not well understood. We have investigated the effects of Ni 2+ ions on DNA polymerase activity and the fidelity of DNA replication in vitro. The effect of Ni 2+ on different DNA polymerases is quite variable. The amount of enzyme inhibition and degree of alteration in replication fidelity induced by Ni 2+ are dependent both on the polymerase and its associated 3′-5′ exonuclease activity. Some polymerases, such as E. coli DNA polymerase I, AMV reverse transcriptase and human DNA polymerase α, can utilize Ni 2+ as a weak substitute for Mg 2+ during DNA replication. Other polymerases are very sensitive to inhibition by Ni 2+ and the IC 50 can vary by an order of magnitude. T4 polymerase is relatively insensitive to inhibition by Ni 2+, although the sensitivity is enhanced in the absence of added Mg 2+, and Ni preferentially inhibits the 3′-5′ exonuclease function of T7 DNA polymerase. The fidelity and processivity of DNA polymerases may be either increased or decreased by Ni ions in a polymerase dependent manner. The inhibition DNA polymerase activity and altered replication fidelity may contribute significantly to Ni-induced mutagenesis and genotoxicity in vivo.

Nickel as an accelerator of biogas production in water hyacinth ( Eichornia crassipes solms.)

The effect of nickel ions on biogas production has been investigated in 3-litre fermenters. It was observed that nickel is stimulatory up to 5 ppm, with an optimum at 2·5 ppm, in a water hyacinth-bovine excreta substrate. A similar effect with nickel was also observed at 5 ppm in bovine excreta.

The effect of nickel on the mechanism of the initial stages of zinc electrowinning from sulphate electrolytes. Part I. Investigations on a spectrally pure aluminium cathode

The effect of nickel ions on the mechanism of the initial stages of zinc electrowinning was studied using scanning electron microscopy (SEM) and cyclic voltammetry. It is shown that nickel ions are deposited simultaneously onto the zinc crystals which are being formed and onto the still exposed aluminium cathode. As a result of the catalytic activation of the hydrogen ion discharge during the initial stages of the process, conditions are created for the formation of hydrogen bubbles on the uncovered aluminium cathode.

Mössbauer study of Ni0.01Fe0.99S.

The effects of nickel ions on crystallographic and spin-flip transitions in FeS have been studied using the M\ossbauer effect. It is found that only 1% impurity of ${\mathrm{Ni}}^{2+}$ in FeS causes hysteresis of such large temperature widths as 13 K in the crystallographic \ensuremath{\alpha} transition and 20 K in the spin-flip transition, whereas no appreciable hysteresis is found in ${M}_{0.025}$${\mathrm{Fe}}_{0.975}$S (M=Sc, Ti, Cr, Mn, Co, Cu). The above Ni impurity also causes a hysteresis in the temperature of coexistence of two crystallographic phases.

Effect of nickel ions on the cardiac transmembrane potentials andcurrents

Effect of nickel ions on the cardiac transmembrane potentials andcurrents

The effects of nickel ions on articular chondrocyte growth in monolayer culture.

Monolayer cultures of lapine articular chondrocytes were used to study the effects of nickel ions (Ni++) on chondrocyte proliferative capacity, proteoglycan synthesis and cellular morphology. Nickel depressed chondrocyte proliferation at the highest concentration tested (100 mumol/l; P less than 0.01) and also exerted a dose-dependent inhibition of proteoglycan synthesis (50 and 100 mumol/l; P less than 0.01). Despite both these effects, no evidence of chondrocyte damage was detectable at the light-microscopical level. The possible significance of the nickel-induced reduction of articular chondrocyte proteoglycan synthesis for the functional integrity of the residual cartilage following hemiarthroplasty operations is discussed.

Effect of nickel ions on ultrastructure of isolated perfused rat heart

The effect of NiCl 2 on ultrastructure of the myocardium was studied in isolated rat hearts perfused by the modified Langendorff technique. Ultrastructural localization of Ni was carried out by the dimethylglyoxim electron cytochemical method. After 15 min perfusion with Krebs-Henseleit solution (K-H), containing 10 −6 m NiCl 2, mitochondria showed swelling and the amount of cytosolic glycogen increased. Perfusion at 15 min with K-H containing 10 −4 m NiCl 2 resulted in focal vacuolization and partial lysis of mitochondria, significant increase of cytosolic glycogen and glycogen accumulation in the dilated vesicles of sarcoplasmic reticulum (SR), T-tubules and in the outer compartment of damaged mitochondria. Following dimethylglyoxim treatment, electrondense deposits were observed in the lumen of the capillaries, in the capillary endothel, in the cytosol and mitochondria of myocardial cells. The presence of Ni in these electrondense deposits was verified by electron probe X-ray micro-analysis.

Effects of nickel ion on the conduction of action potentials in non-myelinated nerve fibre of crayfish.

Effects of NiCL2 and PCMB (p-chloromercuribenzoate) on the action potential were examined by the method of extra- and intracellular electrodes, using a single nerve fibre of crayfish. The results obtained were as follows : The conduction of the action potential was blocked by treating the nerve fibre with Ni ion or PCMB. The blockade was easily recovered by replacement with cysteine. The process of the blockade and recovery, which could be repeated several times, was fairly characteristic such that the more repetition led the sooner blockade and the harder recovery. No conduction block was observed by treatment with Ni-cysteine mixed solution nor with PCMB-cysteine solution. The critical concentration for blocking was 1.1 x 10(-4)M for NiCL2 and 5.6 x 10(-6) M for PCMB. The action potential was disappeared without any change in the resting potential by treatment with the chemicals, which gave significant effects on the rising and falling phases of the action potential before the blockade.

Copper Nuclear Magnetic Resonance in Cu-Ni and Cu-Mn Alloys

The 63Cu resonance has been observed in copper-nickel alloys containing up to 9.2% Ni, at 3 Mc/s and 7 Mc/s in the temperature range 20°K to 290°K. The resonance shows a reduction in intensity and a shift to lower frequencies which are larger at the lower frequency and substantially independent of temperature. The line width is not much greater than in pure copper. These effects are interpreted as due to an interaction between the electric quadrupole moment of the 63Cu nucleus and electric field gradients resulting from the difference in size between copper and nickel ions. Any magnetic effect of nickel ions is negligible. The resonance in copper-manganese alloys containing up to 6.1% Mn at the same frequencies and temperatures has a width proportional to the applied field and inversely proportional to the absolute temperature. The direct magnetic interaction with manganese ions is insufficient to account for the broadening. If the results are interpreted in terms of an indirect interaction through the conduction electrons, of the form proposed by Behringer and Yosida, an s-d exchange constant six times the Mn free atom value must be assumed. A large decrease in width on heat treatment is tentatively attributed to clustering of Mn ions.