Increase In Metal Ion Concentration Research Articles

Metal ion concentrations in retrieved polyethylene total hip inserts and implications for artifactually high readings in tissue.

Although there are many studies which document high metal ion concentrations in clinically retrieved tissues surrounding total joint replacements, most investigations have remained cautious in their interpretation due to the artifactual influences of metal particulate. The possible contribution of polyethylene wear debris to artifactually high periprosthetic metal ion concentration readings has not been previously considered. This study documents the potential role of polyethylene particulate contamination in causing artifactually high metal concentration readings in tissues. The data showed metal ion contamination in the polyethylene was progressive at each stage of exposure to metal: from bar stock preparation, to manufacturing, to in vivo ambulation. The manufacturing and machining processes showed a statistically significant (P < or = .05) increase in metal ion concentrations in the nonarticulated acetabular inserts over bar stock. The results of this study demonstrate that periprosthetic tissue and synovial fluid metal ion concentration data must be interpreted with caution due to possible artifactual problems associated with metal ion contaminated polyethylene particulate.

The biosorpnon of copperod byC. vulgarisand Z.ramigera

Abstract The adsorption of copper(II) ions to dead cells of Chlorella vulgaris and Zoogloea ramigera was investigated. Optimum initial pH of the adsorption medium was found to be 4.0–4.5 for both microorganisms. In general, higher adsorptive uptake was observed at 25°C. The initial adsorption rate of metal ion increased by increasing metal ion concentration for C. vulgaris and Z. ramigera up to 150–200 mg l‐1 and 100–125 mg l‐1, respectively. Freundlich constants were determined from the Freundlich adsorption isotherms of two microorganisms.

Pectin methylesterase, metal ions and plant cell-wall extension. The role of metal ions in plant cell-wall extension.

The study of pectin methylesterase and wall-loosening enzyme activities in situ, as well as the estimation of the electrostatic potential of the cell wall, suggest a coherent picture of the role played by metal ions and pH in cell-wall extension. Cell-wall growth brings about a decrease of local proton concentration because the electrostatic potential difference (delta psi) of the wall decreases. This in turn activates pectin methylesterase, which restores the initial delta psi value. This process is amplified by the attraction of metal ions in the polyanionic cell-wall matrix. The amplification process is basically due to the release of enzyme molecules that were initially bound to 'blocks' of carboxy groups. This increase of metal-ion concentration also results in the activation of wall-loosening enzymes. Moreover, the apparent 'inhibition' of pectin methylesterase by high salt concentrations may be considered as a device which prevents the electrostatic potential from becoming too high.

A comparative study of the adsorption of chromium(VI) ions toC. vulgarisandZ. ramigera

Abstract The adsorption of chromium(VI) ions to dead cells of Chlorella vulgaris and Zoogloea rssalgera was investigated in this study. Optimum initial pH of the adsorption medium was found as pH 2.0 for both microorganisms. Maximum adsorption rates of metal ions to Cvulgaris and Zramigera were obtained at temperatures ranging from 25 to 50 °C. The adsorption rate of metal ion increased by increasing metal ion concentration for Cvulgaris and Zramigera up to 200 and 75 mg 1−1. respectively. Freundlich constants were determined from Freundlich adsorption isotherms of two microorganisms.

The oxidative modification of lens proteins.

In summary, in vitro oxidation of lens crystallins mimics many of the post-translational modifications observed with age and in cataracts These results lend further support to earlier proposals that oxidation is a key factor in cataract formation. The extent to which ascorbate contributes to the oxidation reactions in vivo is not known. In addition to the data presented here that ascorbate can produce these effects in vitro, other observations support the possibility that under certain conditions ascorbate may be involved in the generation of reactive oxygen species in the lens. Using electron spin resonance the ascorbyl radical can be detected early in nuclear cataract formation, and there appears to be a decrease in total ascorbic acid (reduced and oxidized), suggesting further oxidation of ascorbate. Iron and copper are both present in mammalian lenses, and there are reports of increased copper levels in the lens with age and in cataracts. Increased metal ion concentrations would facilitate these oxidative processes.

Simultaneous determination of titanium, zirconium, and hafnium in aqueous solution by phosphorus-31 nuclear magnetic resonance spectrometry

In acidic solution, the group 4A elements form ternary heteropoly complexes with molybdophosphate, e.g., molybdotitanophosphate, molybdozirconophoaphate, and molybdohafnophosphate. Each ternary heteropoly molybdate gives a different chemical shift in its /sup 31/P NMR spectra, respectively, and its relative peak area increases with increasing metal ion concentration. Simultaneous determination of these elements was found to be possible within accuracies of 1 to 5% and detection limits for Tl, Zr, and Hf were 20, 40, and 60 ppm, respectively, under the proposed experimental condition. The small amounts of these ternary heteropoly molybdates in aqueous solution are extracted quantitatively with cyclohexanone. The optimum acidity for extraction was found to be in the pH range between 1.5 and 2.5 and its recovery in cyclohexanone was more than 95%. 14 references, 3 tables, 4 figures.

Studies on Vinyl Polymerization: Polymerization of Acrylonitrile by Permanganate-Glucose Initiator System

Abstract Aqueous polymerization of acrylonitrile initiated by the permanganate-glucose system has been studied under atmospheric conditions at 35 to 45°C. The rate of polymerization (Rp) is maximum at an optimum concentration of activator, but directly proportional to the concentration of monomer. Rp increases with an increase of metal ion concentration to a certain value and then decreases with a further increase of metal ion concentration. The effects of various water-soluble salts and solvents have been investigated. The end group of the polymer has been characterized by IR spectra. A suitable kinetic scheme has been proposed, appropriate rate expressions have been derived, and they are explained in the light of the experimental findings.

7Li and 23Na Nuclear Magnetic Relaxation in Poly(acrylic Acid) Solutions Containing a Paramagnetic Mn(II) Salt

AbstractLarge enhancements are observed for the 7Li and 23Na relaxation in solutions of poly(acrylic acid), containing Mn(II). The effect is explained by the evaluation of the increased metal ion concentrations near the polyion. — Using the cell model for polyelectrolyte solutions and the Poisson‐Boltzmann equation to obtain the distribution of the mobile ions with respect to the polymer, the calculated magnitudes of the enhancements and the dependences of the relaxation rates on the polymer charge density are found to be in agreement with the experimental data. — The condensation concept and other current two‐phase models are shown to be inadequate to account for the observed enhancements.

Interaction of cis- and trans-dichlorodiammineplatinum(II) with synthetic polydeoxyribonucleotides: Effect on equilibrium buoyant densities

Equilibrium buoyant densities in Cs 2SO 4 of four synthetic double-stranded polydeoxyribonucleotides were compared following reaction with either cis-Pt(NH 3) 2Cl 2, trans-Pt(NH 3) 2Cl 2 or PtCl 4. While both Pt(NH 3) 2Cl 2 isomers caused significant increases in the buoyant densities (ϱ) of the two G + C polymers, the cis- isomer increased the ϱ of poly[d(G−C)] and the trans- isomer increased the ϱ of poly(dG) · poly(dC) more sharply than the corresponding isomer at low molar ratios of metal ion to polymer. Chloroplatinic acid was without effect. Only cis-Pt(NH 3) 2Cl 2 produced substantial increases in the ϱ of poly[d(A−T)] and poly(dA) · poly(dT) with increasing metal ion concentrations. These increases were accompanied by a proportional decrease in the thermal transition temperature (T m) of poly(dA)-poly(dT) and a sharp increase in the T m of poly[d(A−T)]. Our results indicate that the cis- isomer reacts with all four polymers to produce ϱ changes clearly distinct from those values observed after reaction with either the trans- isomer or PtCl 4. These results help explain the observation by others that the cis- isomer produces greater ϱ changes in native DNA than the trans- isomer. On the basis of our data and the published results of others, one may rationalize the quantitative differences between the cis- and trans- compounds on the buoyant densities of naturally occurring DNA; however, additional studies are clearly needed.

The facilitated transport of carbon dioxide through bicarbonate solutions

The facilitated transport of CO 2 through thin layers of bicarbonate solution has been investigated. Mathematical models of the steady-state transport process have been analyzed and compared with experimental results. The results have been obtained using a new experimental technique which permits flux studies on immobilized films as thin as 100 μ. With no added catalysts, the augmentation of the CO 2 flux was found to be reaction-rate limited. The magnitude of the augmentation increases with increasing metal ion concentration and with increasing liquid film thickness. On the addition of the enzyme carbonic anhydrase which catalyzes the hydration/dehydration reaction, unexpected results were obtained. At small metal ion concentrations, the enzyme increased the flux to a value predicted for reaction equilibrium. For high metal ion concentrations and for enzyme concentrations approaching those found in the red blood cell, the flux remained reaction-rate limited with the extent of reaction apparently independent of enzyme concentration.

Aspects of Chemical Conversion Coating Processes

SummaryThe mechanisms for the formation of conversion coatings on metals in acidic solutions have been studied and individual reactions for the production of crystalline and amorphous phosphate coatings, oxalate coatings, fluoride coatings and Chromate coatings on a variety of metals have been deduced from the compositions of the coatings and other evidence. It is postulated that, apart from direct oxidation, the initial reaction in all cases is attack by acid on the metal which can lead to local rise in pH, to hydrogen evolution and reducing conditions or to a local increase in metal ion concentration, any or all of which can bring about the precipitation of insoluble compounds.