SEARCH · Search PubMed
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
The determination of nicarbazin residues in foodstuffs of animal origin by two different methods, polarography, HPLC with electrochemical detection, is described. By applying pulse polarography at the dropping mercury electrode to acetonitrile extracts of animal tissues and eggs, a detection limit of 50 micrograms/kg and mean recoveries of 79% were obtained. The same extracts were used for the HPLC determination with electrochemical detection. This led to a detection limit of 1 microgram/kg. Additional rapid confirmation can be obtained from HPLC using an internal standard (nifursol) and comparing peak area proportions of both substances at varied polarization voltages. The quantitative determination of nicarbazin in chicken eggs by both polarography and HPLC was found to be in good agreement.
Lipoxygenase activity assayed by differential pulse polarography was found to be more sensitive than that determined by the increase in absorption at 234 nm. The lipoxygenase activity level in the liver cytosol of rats fed oxidized palm oil was significantly higher than that of the control animals fed either saline or fresh palm oil. The effects of flavonoids on the inhibition of lipoxygenase activity level in liver cytosol of rats were in the decreasing order quercetin greater than myricetin greater than morin greater than phloretin. The observed free malonaldehyde (MDA) in liver cytosol of rats determined by high-performance liquid chromatography using malonaldehyde-dinitro-phenylhydrazine complex was 23, 25, and 51.2% for rats fed saline, fresh palm oil, and oxidized palm oil, respectively. A linear relationship between the lipoxygenase activity and the free liver cytosol MDA was shown. The assay of lipoxygenase by differential pulse polarography provides a simple, sensitive, and quantitative method for the study of liver lipid peroxidation.
(1) Cytochromes c3 from Desulfovibrio vulgaris (Hildenborough strain) and Desulfovibrio desulfuricans (Norway strain) have been studied by differential pulse polarography and spectroelectrochemical method. Both cytochromes exhibit two reduction potential values Eh approximately --0.25 and --0.34 V (D. vulgaris), Eh approximately --0.16 and --0.34 V (D. desulfuricans). (2) Titrations by dithionite and controlled potential electrolysis coupled with polarography and spectrophotometry suggest that in both cases electronic exchanges are rapid.
Polyadenylic acid (poly A) was studied under various conditions using both DC polarography and phase sensitive AC polarography and by measuring the time-course of the current during the lifetime of a single drop of the dropping mercury electrode. Under certain conditions the current at potentials of the limiting portion of the DC polarographic wave does not reach its limiting value and in extreme situations peak-shaped curves are observed. This phenomenon is explained in terms of desorption and repulsion from the electrode of neutral poly A due to its polyanionic character. Consequently, the suppression of the current can be enhanced by increasing negative potential of the electrode and by exposing the negative charges of phosphate groups, e.g., by increasing pH and temperature and by decreasing ionic strength and buffer capacity; vice versa, the current suppression can be at least partially eliminated by reversing these conditions. Polyamines which seem to shield the phosphate groups through specific interactions are very effective in eliminating the current suppression. The effectiveness of a polyamine is determined by its chain length and by the density of its amino groups and the geometry of their distribution.
Local choroidal flow has been measured using hydrogen (H2) clearance polarography in dog eyes in vivo and in vitro. The accuracy and reproducibility of the method was checked in the eye in vitro by demonstrating a linear relationship between flow measurements obtained by an absolute method and those obtained by the H2 clearance technique. The H2 electrode was placed through a scleral window and its current response to a bolus injection of H2-saturated saline into a proximal artery was measured. The clearance of H2 from the choroidal circulation in vitro was monoexponential and the reproducibility of the measurements at the same site and in the same eye was good. In vivo the technique was used to measure alterations in local choroidal blood flow produced by acute changes of intraocular pressure. A linear relationship between perfusion pressure and choroidal blood flow was obtained. H2 clearance polarography is shown to be an accurate and reproducible method for determining choroidal flow, with the advantage that localized repeated measurements of flow can be made.
Some fundamental comments are made on cell polarography according to Velázquez and Rosado (Fertil Steril 23:562, 1972). The results which they have obtained cannot be reliable because fundamental mistakes are made against the principles of the electroanalytic techniques used. We comment upon the conductometry, the amperometric titrations, and the alternating-current polarography as carried out by Velázquez and Rosado.
Catalytic currents yielded by cytochrome c in ammoniacal buffers containing cobalt ions at a dropping mercury electrode (Brdicka's catalytic currents) were investigated by means of direct current, differential pulse, normal pulse (NP) and phase-selective alternating current polarography. It was found that Brdicka's catalytic current of cytochrome c, (the more negative part of Brdicka's double wave, wave B) is influenced by the presence of cytochrome c denaturants in the background solution. The wave B rose with the increasing concentrations of urea and sodium perchlorate, and increased in parallel with absorbance changes at 409 and 695 nm measured for identical cytochrome c solutions. The latter absorbance changes reflect unfolding of cytochrome c molecules in the bulk of solution by these denaturants. The results of NP polarography (a technique working with large potential excursion during the drop lifetime) indicate that in Brdicka's solution cytochrome c could extensively be unfolded due to its adsorption at the mercury electrode, polarized to potentials around that of zero charge.
Pulse polarography with anodic stripping has shown the presence of very high levels (2 005 microgram/kg and 6 760 microgram/kg) of bismuth in bone of two patients treated with bismuth, one parenterally and the other orally. The presence of high levels of bismuth in bone of these patients must be considered in the etiology of their athropathies. Pulse polarography with anodic stripping now permits very precise measurement of bismuth impregnating bones.