The Behaviour of Lead in Iodide Medium at the Dropping Mercury Electrode. I. D.C. Polarographic Study

1962 ◽  
Vol 15 (4) ◽  
pp. 729 ◽  
Author(s):  
VS Srinivasan ◽  
AK Sundaram
Keyword(s):  
Mercury Electrode ◽  
Polarographic Study ◽  
Lead Iodide ◽  
Low Concentrations ◽  
Dropping Mercury Electrode ◽  
High Concentrations ◽  
Adsorption Wave ◽  
Second Wave

The polarography of lead in the iodide medium has shown that an irreversible wave is obtained at moderate concentrations of lead, whereas at high concentrations two waves are obtained and at low concentrations a single reversible wave is obtained. This explains the irreversible waves obtained by the earlier workers who have mainly worked in the region of 0.4mM of lead. From a study of the effect of the head of mercury, temperature, etc. it is shown that the second wave is an adsorption wave resulting from the adsorption of lead iodide complexes at the dropping mercury electrode.

The Behaviour of Lead in Iodide Medium at the Dropping Mercury Electrode. II. A.C. Polarographic Study

1962 ◽  
Vol 15 (4) ◽  
pp. 734 ◽  
Author(s):  
VS Srinivasan ◽  
AK Sundaram
Keyword(s):  
Mercury Electrode ◽  
Polarographic Study ◽  
Lead Iodide ◽  
Dropping Mercury Electrode

An a.c. polarographic study of the lead-iodide system is described. Three peaks are obtained. The second and third peaks are proved to be due to a combined tensammetric-polarographic process.

A Polarographic study of some Wurster salts

1958 ◽  
Vol 11 (2) ◽  
pp. 104 ◽  
Author(s):  
JA Friend ◽  
NK Roberts
Keyword(s):  
Aqueous Solution ◽  
Acetic Acid ◽  
Formation Constant ◽  
Platinum Electrode ◽  
Mercury Electrode ◽  
Diffusion Current ◽  
Polarographic Study ◽  
Polarographic Investigation ◽  
Dropping Mercury Electrode ◽  
Hydrolysis Of

Four related Wurster salts are subjected to a polarographic investigation. In the case of Wurster's blue, results from the dropping mercury electrode, stationary platinum electrode, and rotated platinum electrode are compared. The Wurster salt of p-phenylenediamine is unstable in aqueous solution but is fairly stable in a mixture of methanol, acetic acid, and water and the decrease of diffusion current with time indicates a disproportionation. Wurster's red is also unstable in aqueous solution. In the solvent methanol, acetic acid, and water, a wave is observed with the stationary platinum electrode whose E� compares favourably with the potentiometric E?0. Evidence from the three types of electrodes mentioned previously indicates two one-electron waves for Wurster's blue. The semiquinone formation constant qualitatively appears much greater than that reported from potentiometric work. Decrease of diffusion current with time is perhaps due to a disproportionation (the very unstable di-imine has been shown to revert to the radical in aqueous solution). Polarographic waves given by the Wurster salt of diaminodurene suggest that the radical does not exist in aqueous solution. Waves corresponding to the original amine and duroquinone (formed by hydrolysis of the di-imine) are obtained.

Mechanism of 2-quinizarinsulphonic acid reduction on a mercury electrode

1981 ◽  
Vol 59 (8) ◽  
pp. 1201-1204 ◽  
Author(s):  
F. Capitan ◽  
A. Guiraum ◽  
J. L. Vilchez
Keyword(s):  
Mercury Electrode ◽  
Sulphonic Acid ◽  
Kinetically Controlled ◽  
Diffusion Controlled ◽  
Dropping Mercury Electrode ◽  
Reaction Orders ◽  
Second Wave ◽  
Acid Reduction

The reduction of the 1,4-dihydroxyanthraquinone-2-sulphonic acid (quinizarinsulphonic acid) at a dropping mercury electrode has been investigated. The reduction takes place in two monoelectronic steps and show E1/2 values vs. sce (E1/2)1 = −0.380 V and (E1/2)2 = −1.045 V at pH 4.60. The first wave is diffusion controlled, while the second wave is kinetically controlled. The reagent captures one electron and one proton to form the semiquinonic system. The semiquinone is dimerized. The dimer captures one electron and one proton, per molecule, to form the hydroquinone. The reaction orders, together with Tafel's slopes, have been calculated.

Neutrophil Elastase Potentiates Cathepsin G-lnduced Platelet Activation

1992 ◽  
Vol 68 (05) ◽  
pp. 570-576 ◽  
Author(s):  
Mary A Selak
Keyword(s):  
Neutrophil Elastase ◽  
Cell Activation ◽  
Thromboxane A2 ◽  
Creatine Phosphate ◽  
Dense Granule ◽  
Cathepsin G ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Low Concentrations ◽  
High Concentrations

SummaryWe have previously demonstrated that human neutrophil cathepsin G is a strong platelet agonist that binds to a specific receptor. This work describes the effect of neutrophil elastase on cathepsin G-induced platelet responses. While platelets were not activated by high concentrations of neutrophil elastase by itself, elastase enhanced aggregation, secretion and calcium mobilization induced by low concentrations of cathepsin G. Platelet aggregation and secretion were potentiated in a concentration-dependent manner by neutrophil elastase with maximal responses observable at 200 nM. Enhancement was observed when elastase was preincubated with platelets for time intervals of 10–60 s prior to addition of a low concentration of cathepsin G and required catalytically-active elastase since phenylmethanesulphonyl fluoride-inhibited enzyme failed to potentiate cell activation. Neutrophil elastase potentiation of platelet responses induced by low concentrations of cathepsin G was markedly inhibited by creatine phosphate/creatine phosphokinase and/or indomethacin, indicating that the synergism between elastase and cathepsin G required the participation of ADP and thromboxane A2. On the other hand, platelet responses were not attenuated by the PAF antagonist BN 52021, signifying that PAF-acether did not play a role in elastase potentiation. At higher concentrations porcine pancreatic elastase exhibits similar effects to neutrophil elastase, demonstrating that the effect of elastase was not unique to the neutrophil protease. While neutrophil elastase failed to alter the ability of cathepsin G to hydrolyze a synthetic chromogenic substrate, preincubation of platelets with elastase increased the apparent affinity of cathepsin G binding to platelets. In contrast to their effect on cathepsin G-induced platelet responses, neither neutrophil nor pancreatic elasatse potentiated aggregation or dense granule release initiated by ADP, PAF-acether, arachidonic acid or U46619, a thromboxane A2 mimetic. Moreover, unlike its effect on cathepsin G, neutrophil elastase inhibited thrombin-induced responses. The current observations demonstrate that elastase can potentiate platelet responses mediated by low concentrations of cathepsin G, suggesting that both enzymes may function synergistically to activate platelets under conditions where neutrophil degranulation occurs.

In Vitro Effects of Ethanol on Rabbit Platelet Aggregation, Secretion of Granule Contents, and Cyclic AMP Levels in the Presence of Prostacyclin

1989 ◽  
Vol 61 (02) ◽  
pp. 254-258 ◽  
Author(s):  
Margaret L Rand ◽  
Peter L Gross ◽  
Donna M Jakowec ◽  
Marian A Packham ◽  
J Fraser Mustard
Keyword(s):  
Cyclic Amp ◽  
Inhibitory Effect ◽  
Rabbit Platelet ◽  
Inhibitory Effects ◽  
Low Concentrations ◽  
Rabbit Platelets ◽  
High Concentrations ◽  
In Vitro Effects ◽  
Aggregation Of Platelets

SummaryEthanol, at physiologically tolerable concentrations, inhibits platelet responses to low concentrations of collagen or thrombin, but does not inhibit responses of washed rabbit platelets stimulated with high concentrations of ADP, collagen, or thrombin. However, when platelet responses to high concentrations of collagen or thrombin had been partially inhibited by prostacyclin (PGI2), ethanol had additional inhibitory effects on aggregation and secretion. These effects were also observed with aspirin- treated platelets stimulated with thrombin. Ethanol had no further inhibitory effect on aggregation of platelets stimulated with ADP, or the combination of ADP and epinephrine. Thus, the inhibitory effects of ethanol on platelet responses in the presence of PGI2 were very similar to its inhibitory effects in the absence of PGI2, when platelets were stimulated with lower concentrations of collagen or thrombin. Ethanol did not appear to exert its inhibitory effects by increasing cyclic AMP above basal levels and the additional inhibitory effects of ethanol in the presence of PGI2 did not appear to be brought about by further increases in platelet cyclic AMP levels.

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