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At least 793 records · Page 44Linked to original sources
PubMed1979

[Electrochemical analysis of microsomal cytochromes].

The electrochemical behaviour of the electron transfer proteins -- cytochromes b5, c and P-450 was studied by classical polarography and electrolysis with spectrophotometric monitoring. It was shown electrons are directly transferred from the electrode to oxidized cytochromes c and b5. Cytochrome P-450 is not reduced on the electrodes. However, the reduced inactivated from of cytochrome P-420 was detected at high potential values (-1,5 v).

Animals↗
PubMed1990

[Polarographic evaluation of oxygen metabolism in the transplant after esophagogastroplasty].

Oxygen metabolism of a tube graft formed from the greater curvature of the stomach in esophagoplasty for carcinoma of the thoracic esophagus was studied by polarography. The study was conducted during the stages of treatment: in the early postoperative period and before the formation of a postponed extracavitary esophagogastric anastomosis. Oxygen tension (pO2) and the rate of oxygen consumption (ROC) by the graft tissue were studied. The pO2 for the isoperistaltic grafts was 65.3 +/- 2.31 mm Hg in the zone of the nutrient vessel and 51.68 +/- 11.6 mm Hg in the zone of the mechanical suture. A favourable postoperative period corresponded with a ROC of 0.1-0.2 units. The results of the study coincided with the clinical result in 86.3% of cases.

Adult↗
PubMed1989

[Dynamics of oxygen tension in the tissues of patients with post-thrombophlebitic syndrome].

With the use of the methods of percutaneous contact polarography, roentgeno-contrast phlebography, Doppler ultrasound, 83 patients with different location and stage of the post-thrombophlebitic syndrome were examined. The significant alteration of the indices of polarographic curve versus the norm was defined. The most pronounced disorders were revealed in occlusion of the deep veins of the lower extremities.

Adult↗
PubMedDate not supplied

Methods of analysis for toxic elements in food products. 2. Review of USSR standards on determinations of heavy metals and arsenic.

Methods of analysis prescribed by USSR standards for Hg, Pb, Zn, As, Cd, Cu, Fe, and Sn in foods are described: for Hg--colorimetry of tetraiodide mercurate and atomic absorption spectroscopy (AAS); for Pb, Cd, Zn, and Cu--polarography; for Cu--colorimetry with sodium diethyldithiocarbamate and zinc dibenzyldithiocarbamate; for As--colorimetry with silver diethyldithiocarbamate; for Sn--colorimetry with quercetin; and for Fe--colorimetry with o-phenanthroline. All of the methods have the necessary metrological characteristics, including intralaboratory repeatability value (r), interlaboratory reproducibility value (R), minimum quantity of the element to be determined in the analytical test portion (MQSM), and the coefficients that account for mercury and arsenic losses during analysis. Establishing constant r- and R-values for the methods under consideration is expedient because (a) the methods suggested are used for safety purposes; and (b) the optimum amount of the element studied in the test sample is determined, to a certain degree, by the mass of the test portion.

Arsenic↗
PubMed1989

[Disorders of oxygenation and skin capillary blood flow rate in psoriasis and correction of them with ethacizine].

Oxygen and hydrogen polarography has revealed functional changes of the oxygen regimen and hemoperfusion of both involved and apparently intact skin in patients with common psoriasis. These changes developed by stages and their intensity varied. Ethacizine therapy has been effective in 91% of the patients, improving the parameters of the skin capillary blood oxygenation and volumetric rate both during the stationary and progressive forms of the disease.

Adult↗
PubMed1989

Some aspects of the copper(II)-DNA interaction.

The Cu(II) ion interaction with calf-thymus DNA was studied by means of differential pulse polarography and sweep voltammetry as well as chromatography and viscosimetry. Most of the complexes formed at high ionic strength (0.2 M) and lower Cu(II) concentrations are of a nondenaturing nature. Their formation has but a minor effect on unwinding process of the DNA double helix. The excess of Cu(II) (P = 5) leads, however, to distinct denaturation of the DNA structure. Metal ions have little effect on the denaturation induced by the polarographic reduction of DNA on the mercury electrode. This conclusion is consistent with the character of the polarographic process and with the fact that Cu(II) ions are not very effective in the interaction with AT pairs. Cupric ions have no renaturing ability towards thermally denatured DNA at 0.2 M ionic strength but distinct renaturation was observed at low ionic strength (0.05 M).

Chromatography, Liquid↗
PubMed1978

A new procedure for estimation of nitrovin and carbadox residues and their metabolites in food of animal origin.

In order to establishe the length of the protective period for which the animals are given food without chemical growth stimulators before slaughter two methods are proposed permitting wide use in sanitary control: 1/ A highly sensitive method of pulse-polarography has been worked out for the estimation of widely used growth stimulator nitrovin residues/ 1.5-bis/5-nitro2-furyl/1.4-pentadiene-3-on amidinohydrazone / and its metabolites. In the tissues of the experimental animals examined were found residues at a level of about 50 ppb. The limit of sensitivity of the procedure used is 10 ppb. 2/ Based upon double-electron reduction of the quinoxaline circle a simple and sufficiently sensitive polarographic method was worked out for the estimation of carbadox residues / quinoxaline-1.4-N-dioxide-2-methylcarbazate/and its main metabolite / quinoxaline-2-carboxylic acid/. With the sensitivity of the method of 0.1 ppm excretion curves were designed and residue levels were determined in tissues of pigs fed up to 56 days of age by feed containing 20 - 50 ppm of carbadox.

Animals↗
PubMed1978

[Process of fumigatin and spinulosin formation by Aspergillus fumigatus Fres and polarographic assay of these toxins (author's transl)].

A strain of Aspergillus fumigatus (Fresenius) isolated from a milk food for calves was grown on a culture medium containing added saccharose. The purpose was to study the synthesis of two recently discovered mycotoxins, fumigatin and spinulosin. The work was performed under many different conditions of temperature, pH and inoculum. These mycotoxins were measured by analytical differential pulse polarography. Correlations were observed between the growth rate of A. fumigatus and variation in pH of the medium and the formation of fumigatin, which is only possible when pH falls to less than 4.0. Fumigatin appears promptly at the beginning of the growth phase of the fungus but quickly disappears. The production of metabolite depends on limited conditions of culture. Spinulosin, very similar to fumigatin, is substituted for fumigatin in slightly different conditions. During growth, the fungus degrades both metabolites. The nature of the substitution and the reason of these modifications have not been investigated. Fumigatin and spinulosin formation is observed in both toxigenic and non-toxigenic strains.

Animal Feed↗
PubMedDate not supplied

[Polarographic evaluation of extra-intracranial microvascular anastomoses in the early postoperative period].

Dynamic recording of the brain oxygen level by means of polarography during test with clamping of the superficial temporal artery in the early postoperative period in patients with an extra-intracranial microvascular anastomosis (EICMA) makes it possible to judge whether the anastomosis in patient or occluded. Patent anastomoses were marked by two types of changes occurring on the polarograms in clamping of the donor artery of the anastomosis. They reflect the relations between the EICMA and the natural channels of the collateral blood supply of the brain, correlate to a great measure with the localization of the occluding lesions in the cerebral vessels, and allow the efficacy of the operative intervention to be predicted.

Anastomosis, Surgical↗
PubMed1988

[The pharmacokinetics of 2-methyl-4-nitroimidazole-1-ethanol (isometronidazole) in man].

2 and 4 g isometronidazole, respectively, were administered to two groups of 6 healthy male volunteers (21-29 years, 62-93 kg). The unchanged compound and its nitro group containing metabolites were measured by HPLC and polarography. Isometronidazole was absorbed rapidly, distributed slowly into peripheral compartments and eliminated with half lives of about 12 h. It was not bound to plasma proteins. On an average 70% (2 g) and 80% (4 g), respectively, were excreted into urine within 48 h both unchanged and in form of at least two more polar and/or water soluble metabolites. Distribution and excretion of isometronidazole were not proportional to dose.

Adult↗
PubMed1986

Polarographic studies on the conformation of some platinum complexes: relations to anti-tumour activity.

Conformational alterations induced in DNA by the binding of various bivalent and tetravalent platinum complexes were characterized by means of differential pulse polarography and circular dichroism spectroscopy. It was found that at low levels of binding the platination of DNA markedly influenced its polarographic behaviour. The results indicated that the binding of the active anti-tumour complexes resulted in minor conformational changes in DNA when the double-stranded structure remained conserved. On the other hand, the attack by inactive anti-tumour compounds induced more severe alterations which had the character of denaturation of longer regions of the DNA molecule. It was also demonstrated that active anti-tumour tetravalent platinum complexes could react with DNA, without their prior reduction to the bivalent state, and may induce in DNA conformational changes similar to those produced by bivalent cisplatin.

Antineoplastic Agents↗
PubMedDate not supplied

Determination of sulfur dioxide in foods by modified Monier-Williams distillation and polarographic detection.

A rapid, sensitive polarographic method is presented for determining sulfiting agents in foods and beverages. The method is based on the modified Monier-Williams distillation followed by polarographic detection by differential pulse polarography or square wave voltammetry. A clearly defined wave is obtained by both techniques, with a current maximum at a potential (E) of about -600 mV vs an Ag/AgCl reference electrode. The reaction is based on the reduction of sulfur dioxide at a dropping mercury electrode. Peak current was linear over the range 0-20 micrograms/mL. Quantitation is done by linear regression analysis of standard addition data or by using a standard calibration graph. Screening levels of less than 1 ppm total SO2 were easily achieved in the foods analyzed, which had levels from less than 1 ppm (cereals) to thousands of parts per million (dried fruit). Recoveries from fortified samples ranged from 70 to 108% at fortification levels of 20, 100, and 1000 micrograms/g.

Animals↗
PubMed1986

[Polarographic determination of patulin].

The polarographic behaviour of the mycotoxin patulin is described with special reference to its analytical determination. The analysis of extracts is possible with the help of differential puls polarography and acetonitril as solvent. The analytical method needs a prepurification of the ethyl-acetate extracts like in the case of TLC analysis.

Chromatography, Thin Layer↗
PubMed1987

[Postnatal development of zinc levels in the epididymis and testis in rats under normal and experimental conditions].

Postnatal testicular and epididymal zinc concentration in the rat was investigated by means of differential pulse polarography. The zinc concentration increased gradually from birth to day 90 in the testis and up to day 60-90 in the epididymis with an abrupt increase on day 21. No marked variation in the zinc content was observed all along the epididymal duct. Experimental castration and efferent duct ligation were carried out in order to assess the influence of blood-borne and luminal androgens on epididymal zinc content. In prepubertal rats, unilateral castration and efferent duct ligation did not affect the zinc content of the epididymis. Moreover, zinc concentration was not affected by bilateral castration which induced very low plasma testosterone levels. These results suggested that epididymal zinc content did not depend upon endocrine testicular secretions, especially androgens. On the other hand, in adult rats efferent duct ligation and cryptorchidism resulted in about 50 and 70% reduction, respectively of the testicular and epididymal zinc content. A correlation was found between the absence of testicular fluid and spermatozoa or the alteration of germ cells and the decrease in epididymal and testicular zinc content.

Aging↗
PubMed1987

Electrochemical study of the reduction of toyocamycin and sangivamycin in aqueous media.

The redox behaviour of two antibiotics, toyocamycin and sangivamycin, structurally related pyrrolopyrimidine nucleosides, and their reduction products in buffered aqueous media, have been examined by direct current polarography and cyclic voltammetry. Both compounds exhibit one 3-electron polarographic wave in the pH range 1-6. Macroscale electrolysis at the crest of the polarographic wave was followed electrochemically and by UV spectroscopy. The photochemical transformation of the reduction products on UV irradiation has been examined. It was found that the reduction of both compounds occurs in the pyrimidine ring, leading to two reduction products. One of these (lambda max = 306 nm) is photochemically reversible to the parent compound.

Aminoglycosides↗
PubMed1979

Accelerating effect of ascorbic acid on N-nitrosamine formation and nitrosation by oxyhyponitrite.

The reaction of nitrite ion with ascorbic acid and its effect on the rate of nitrosation of secondary amines have been investigated by differential pulse polarography in aqueous acidic solution. Ascorbic acid shows nonuniform behavior: it accelerates the nitrosation of N-methylaniline between pH 1.00 and 1.95, allows the nitrosation of diphenylamine and iminodiacetonitrile, but inhibits the nitrosation of secondary amines, such as dimethylamine, diethylamine, proline, hydroxyproline, N-methylaminoacetonitrile, N-methylaminopropionitrile, and sarcosine. The nitrosating agent generated by the reaction between ascorbic acid and nitrite ion appears to be oxyhyponitrite ion (N2O3-2).

Ascorbic Acid↗
PubMed1985

[Pulse polarographic determination of piperacillin (Pipril) in serum and urine].

Two pulse polarographical methods for determination of the half-synthetic penicillin derivate piperacillin in serum and in urine are described. 3.7 X 10(-5) mol/l (20 micrograms/ml) can yet been proved in serum with the direct pulse polarographical determination. 1.85 X 10(-6) mol/l (1 microgram/ml) can quantitatively be determined after preceded hydrolysis. Both the methods are diffusion standards being well developed which can be evaluated in an adequate manner. The piperacillin concentrations determined by pulse polarography agree to the levels of the agar diffusion test. The precision is some reduced by the separations incorporated. Inspite of the hydrolysis, the pulse polarographical method of determination will offer more prompt and reliable results.

Chromatography, Thin Layer↗