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PubMed1986

Physiological and chemical characterization of cyanobacterial metallothioneins.

Techniques have been developed for detection, quantitation, and isolation of bacterial metallothioneins (MTs) from cyanobacterial species. These methods involve differential pulse polarography and reverse-phase high-performance liquid chromatography (HPLC) and have allowed detection of picomole quantities of these high sulfhydryl content proteins. The prokaryotic molecule was found to be induced in the presence of Cd or Zn salts with regulation at the level of transcription. Cu was not found to induce synthesis of the prokaryotic MT. Exposure to the former metals resulted in a growth lag followed by simultaneous induction of MT synthesis and onset of growth. Amino acid analysis and N-terminal sequence analysis indicated that the bacterial MTs from cyanobacteria are unique, having many aromatic and aliphatic residues and no apparent association of hydroxylated or basic amino acids with cysteines. Although the characteristic Cys-X-Cys sequences were present, no apparent amino acid sequence homology with the eukaryotic MTs was found in the first 42 residues.

Amino Acid Sequence↗
PubMed1990

Effect of glucose upon alkaline picrate: a Jaffé interference.

The reactivity of glucose in aqueous alkaline picrate was investigated by spectrophotometry and polarography at 25 degrees C in 0.51 mol/l sodium hydroxide. Thin-layer chromatography and infrared spectroscopy studies have conclusively identified the presence of picramic acid in 5:1 and 10:1 glucose picrate test solutions incubated at 25 degrees C. The polarographic data of an alkaline picrate blank with a concentration of 0.284 mmol/l, show three well-defined nitro group reduction waves with approximate half-wave potentials of -0.62 V, -0.78 V, and -0.93 V and a fourth broad wave appearing near -1.31 V versus a saturated calomel electrode. The addition of glucose to alkaline picrate resulted in a decreased diffusion current for reduction waves 1-3, with little change in reduction wave 4. The reactivity of test solutions containing glucose:picrate in 1:1, 2:1, 5:1 and 10:1 molar ratios was investigated at varied time intervals between 10 and 180 minutes. The absorption spectra of a 10:1 glucose:picrate solution shifted from 356 nm to 375 nm and a broad tailing shoulder absorbance formed in the 450-600 nm region. An orange coloured minor product, separated by thin-layer chromatography, was observed to fluoresce. The maximum excitation and emission wavelengths were 318 nm and 545 nm, respectively. A major, red-coloured product was isolated and identified as picramic acid by infrared spectroscopy. For 10:1 glucose:picrate test solutions incubated at 25 degrees C, picramic acid formed within 10 minutes. Within the first minute, the colour was observed to change from yellow to orange and then to red.

Chemical Phenomena↗
PubMedDate not supplied

On the origin of the non-haemic iron transferrin ESR signal: ESR investigations on histidine-iron-citric acid systems.

The nature of the high spin ferric iron complex located at g = 4.3 has been investigated by means of electron spin resonance spectroscopy and polarography. It could be shown that two complexes each exist in the acid and alkaline pH region, and that the iron is bound to two histidines, three citric acids, and probably to one bicarbonate. These results agree well with previous findings according to which the ligand field of iron should be composed mainly of oxygen and nitrogen atoms. Another low-field signal located at g = 3.6 appears in the pH range from 2 to 7 only and exhibits its maximum where the g = 4.3 signal has its minimum. Its exact nature is still unknown but it seems to represent some intermediate state of the ternary Fe3+-histidine-citric acid complex. When citric acid is used, the spin concentration seems to be always larger than in the case of ascorbic acid. Since the effect obtained with ascorbic acid and citric acid seems to be similar, it may be concluded that the biological function of both of the acids might be somehow related to each other.

Ascorbic Acid↗
PubMedDate not supplied

The effect of glutathion on the reaction of cis-and trans-diamminedichloroplatinum(II) with DNA.

Differential pulse polarography study was used to investigate the influence of glutathion on cis- and trans-DDP induced alterations of DNA structure. Though the applied concentration of glutathion has no effect on the reaction on DNA with cis-DDP, it greatly modifies the reaction with trans isomer. This may be an important reason for the ineffectiveness of the trans-DDP as an antitumor drug.

Animals↗
PubMed2000

Measurement of hypoxia using the comet assay correlates with preirradiation microelectrode pO2 histography in R3327-AT rodent tumors.

Polarographic determination of tumor oxygenation by Eppendorf histography is currently under investigation as a possible predictor of radiotherapy outcome. Alternatively, the alkaline comet assay has been proposed as a radiobiological approach for the detection of hypoxia in clinical tumor samples. Direct comparisons of these methods are scarce. One earlier study with different murine tumors could not establish a correlation, whereas a weak correlation was reported for a variety of human tumors. Considering the different end points and spatial resolution of the two methods, a direct comparison for a single tumor entity appeared desirable. Anaplastic R3327-AT Dunning prostate tumors were grown on Copenhagen rats to volumes of 1-6 cm(3). Eppendorf histography (100-200 readings in 5 parallel tracks) for 8 different tumors revealed various degrees of oxygenation, with median pO(2) values ranging from 1.1 to 23 mmHg. Within 5 min after an acute exposure to 8 Gy (60)Co gamma rays, tumors were excised from killed animals and rapidly cooled to limit repair, and a single cell suspension was prepared for use with the comet assay. The resulting comet moment distributions did not exhibit two subpopulations (one hypoxic and the other aerobic), and a hypoxic fraction could not be calculated. Instead, the average comet moment distribution was taken as a parameter of overall strand break induction. Corresponding experiments with tumor cells grown in vitro allowed us to derive the relationship between the oxygen enhancement ratio (OER) for the average comet moment and oxygen partial pressure (Howard-Flanders and Alper formula). The validity of this relationship was inferred for cells exposed in situ, and the convolution of a pO(2) distribution with the formula of Howard-Flanders and Alper yielded an array of expected OER values for each tumor. The average expected OER correlated well with the average comet moment (r = 0.89, P < 0.01), and the in situ comet moment distributions could be predicted from the Eppendorf data when 50% repair was taken into account, assuming a 5-min damage half-life. The findings confirm the potential of interstitial polarography to reflect radiobiologically relevant intracellular oxygenation, but also underscore the confounding influence of differences in repair that may occur when cells are prepared from irradiated tissues for use with the comet assay.

Adenocarcinoma↗
PubMed2006

Quantitative analysis of cytochrome C released from rice mitochondria using the adsorptive polarographic wave of guanidine modified Co(II)-cytochrome C complex.

A new, simple and sensitive method for the quantitative analysis of cytochrome C (Cyt C) based on the reduction wave of guanidine modified Co(II)-Cyt C complex at about -1.74 V (vs. SCE) by single sweep polarography in the solution containing 8 x 10(-6) mol L(-1) CoCl2, 0.04 mol L(-1) guanidine hydrochloride, 0.2 mol L(-1) NaOH and 0.5% Na2SO3. The peak height is linearly proportional to the concentration of Cyt C in the range of 0.005 approximately 1.500 mg L(-1) (correlation coefficient 0.999). Common amino acids, saccharide, organic acid and metal ions of appropriate concentrations have no interference on the Cyt C determination. The released Cyt C in the process of mitochondrial permeability transition of Hong-Lian cytoplasmic male sterile line of rice has been measured by the method, and the result is satisfactory.

Amino Acids↗
PubMed1989

Electrochemical characteristics of nitro-heterocyclic compounds of biological interest. II. Nitrosochloramphenicol.

The electrochemical characteristics of nitrosochloramphenicol have been studied in aqueous buffer systems (pH 7.1) using direct current (d.c.) and differential pulse polarography, cyclic voltammetry and coulometric techniques. Up to 4 charge-transfer steps can be identified. The first reduction step is reversible both chemically and electrochemically, the charge-transfer product showing no tendency to undergo further reaction on the electrochemical time-scale. In contrast, the second reduction step is irreversible, with the product undergoing a fast following reaction to yield a redox-active species which was detected by cyclic voltammetry. From the data and by comparison with related systems, two reduction mechanisms are possible and are discussed.

Chloramphenicol↗
PubMed1987

Preparative electrochemical reduction of 2-amino-6-chloropurine and synthesis of 6-deoxyacyclovir, a fluorescent substrate of xanthine oxidase and a prodrug of acyclovir.

D.c. polarography of 2-amino-6-chloropurine in aqueous medium over a broad pH range revealed two diffusion waves, the first of which corresponds to reduction of the C(6)-Cl bond, leading to formation of 2-aminopurine in high yield. Condensation of the sodium salt of 2-aminopurine with (2-acetoxyethoxy)methyl chloride led to the two isomeric 9- and 7-(2-hydroxyethoxymethyl)-2-aminopurines. The 9- isomer, 6-deoxyacyclovir, a prodrug of acyclovir previously synthesized by another route, was readily converted to the latter by xanthine oxidase; the 7-isomer was not a substrate. The intense fluorescence of 6-deoxyacyclovir makes it a convenient fluorescent substrate for xanthine oxidase, although less sensitive than xanthine; it is shown that 2-aminopurine would be a very sensitive fluorescent substrate. The polarographic behaviour of the riboside of 2-amino-6-chloropurine was virtually identical with that of the parent purine, leading to a simple procedure for conversion of 2-amino-6-chloropurine nucleosides and acyclonucleosides to the corresponding 2-aminopurine congeners.

2-Aminopurine↗
PubMed1999

[Hypotensive and anti-ischemic efficiency of estulic in course treatment of myocardial infarction complicated by essential hypertension].

AIM: To assess hypotensive and antiischemic activity of estulik (Sandos, Switzerland) in patients with myocardial infarction (MI) complicated by essential hypertension (EH). MATERIALS AND METHODS: 23 MI patients with moderate EH (diastolic blood pressure up to 110 mm Hg) and 25 patients with manifest EH (diastolic blood pressure 115-120 mm Hg) of group 1 and 2, respectively, have received single doses and a 10-day course of estulik in a dose 0.5-1.0 mg/day. Hemodynamic and antiischemic activities were evaluated at echocardiography, coupled veloergometry, Holter monitoring, myocardial scintigraphy, polarography. In 31% of the patients selective coronarography was made. RESULTS: Clinical condition and hemodynamics of group 1 patients have improved by 30-40%, microcirculation has improved by 25-35%. In group 2 patients the drug was found ineffective. CONCLUSION: Estulik is a drug of choice in moderate EH with manifest angina pectoris.

Adrenergic alpha-Agonists↗
PubMed1999

Separation of structurally related flavonoids by GC/MS technique and determination of their polarographic parameters and potential carcinogenicity.

The present study deals with the investigation of the naturally occurring derivatives of the benzo[b]pyran-4-one - flavonoids - chrysin, tectochrysin and galangin, and with the effect of minor changes in their chemical structure on their separation using GC/MS. In the relation to their close chemical structure, their basic polarographic parameters were also investigated. Their potential carcinogenicity index tg alpha was determined by DC polarography experiments in the presence of alpha-lipoic acid. The tg alpha values for chrysin, tectochrysin and galangin were all under 0.180. This indicates a very minor carcinogenic potential that does not prevent the use of the investigated flavonoids in human.

Carcinogens↗
PubMed2000

Application of electroanalytical methods to the characterization of metallothioneins and related molecules.

Electroanalytical methods have been applied to the characterization and to the study of complexing properties of several Cd,Zn metallothioneins (MT) of different mammalian origin, rabbit and rat liver and horse kidney and human foetal liver and adult kidney. Differential pulse polarography (DPP) has been selected as the most suitable technique for distinguishing the chemical form of compounds and, assuming a diffusion controlled mechanism, monitoring the evolution of different species as a function of parameters, such as the solution pH and the gradual addition of cations, cadmium and/or zinc, initially contained in the studied molecules. Due to the fact that the metallothioneins structure is complex and often not perfectly known, the peptidic fragment Lys-Cys-Thr-Cys-Cys-Ala (56-61) MT-1 (FT) of the mouse liver has been taken as a model for MT characterization. The study of FT alone and in the presence of Cd and/or Zn, using several electroanalytical methods has been very useful for the investigation of adsorption-diffusion processes and for the identification and elucidation of electrochemical systems. The interpretation of voltammetric data is very often not easy. For some cases, proper interpretation can be made using chemometric techniques. Multivariate factor analysis has been applied to the electroanalytical investigation of the complexing properties between cadmium and/or zinc and FT, using results obtained by DPP and linear sweep voltammetry. For more complex systems, like MT, the application of chemometry becomes more complex.

Adult↗
PubMed2000

[In vitro and in vivo physicochemical study of depot formation of cinchocaine in an atelocollagen matrix].

The paper presents an introductory physicochemical study dealing with the preparation of atelocollagen felt saturated with local anesthetics, with the modelling of the release of the anesthetic from the collagen matrix in vitro, and with the checking of the corresponding analytical procedures (dc-polarography and UV-VIS spectrophotometry) for the determination of cinchocaine. The study is supplemented with experiments in vivo that confirm the usability of the new material for the depot formation of local anesthetics.

Anesthetics, Local↗
PubMed2000

Potential carcinogenic and inhibitory activity of compounds isolated from Lilium candidum L.

This paper deals with determination of potential carcinogenic and inhibitory activity of 10 compounds isolated from the ethanolic extract of Lilium candidum L. perfonned by DC polarography. The series of investigated compounds consisted of two spirostanol saponins, two pyroline derivatives, jatropham and its glucoside, flavonol kaempferol, 2-fenylethyl-alpha-L-arabinopyranosyl-(1-->6)-beta-D-glucopyranoside, 2-phenylethylpalmitate and methylsuccinic acid. Carcinogenic, resp. mutagenic activity data for these compounds, with the exception of kaempferol, are not available in scientific literature. All tested compounds were reduced in N,N-dimethylformamide in one or two well defined steps. They also fonned a reversible complex with alpha-lipoic acid, a compound serving as an indicator of carcinogenic activity. The marginal diffuse current values of these complexes served as a criterion of a very low potential carcinogenicity. The inhibitory activity of isolates were studied in the presence of 12-O-tetradecanoylphorbol-13-acetate, a specific tumor promoter for an epidermal carcinogenesis, and in the presence of a polyaromatic substance 7,12-dimetylbenz(a)anthracene known as a carcinogen. The spirostanol saponins possessed the highest inhibitory activity (> 70%) and jatropham (66%). The inhibitory activity of jatropham glucoside was significantly lower (49%). Practically zero inhibitory activity was measured for the 2-phenylethylpalmitate and methylsuccinic acid.

9,10-Dimethyl-1,2-benzanthracene↗
PubMedDate not supplied

Voltammetric determination of benazepril and ramipril in dosage forms and biological fluids through nitrosation.

A simple and highly sensitive voltammetric method was developed for the determination of benazepril (I) and ramipril (II). The compounds were treated with nitrous acid, and the cathodic current produced by the resulting nitroso derivatives was measured. The voltammetric behavior was studied by adopting direct current (DCt), differential pulse (DPP), and alternating current (ACt) polarography. Both compounds produced well-defined, diffusion-controlled cathodic waves over the whole pH range in Britton-Robinson buffers (BRb). At pH 3 and 5, the values of diffusion-current constants (Id), were 5.90 +/- 0.40 and 6.66 +/- 0.61 for I and II, respectively. The current concentration plots for I were rectilinear over the range of 1.5-40 and 0.1-30 microg/mL in the DCt and DPP modes, respectively; for II, the range was 2-30 and 0.1-20 microg/mL in the DCt and DPP modes, respectively. The minimum detectabilities (S/N = 2) were 0.015 microg/mL (about 3.25 x 10(-8)M) and 0.012 microg/mL (about 2.88 x 10(-8)M) for I and II, respectively, adopting the DPP mode. Results obtained for the proposed method when applied to the determination of both compounds in dosage forms were in good agreement with those obtained using reference methods. Hydrochlorthiazide, which is frequently co-formulated with these drugs, did not interfere with the assay. The method was also applied to the determination of benazepril in spiked human urine and plasma. The percentage recoveries adopting the DPP mode were 96.2 +/- 1.21 and 95.7 +/- 1.61, respectively.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1997

[Polarographic behavior of latamoxef sodium and its trace determination].

In the medium of HCl-KCl (pH 1-2) by means of cyclic voltammetry and differential pulse polarography (DPP), the mechanism of the electrode reaction for latamoxef sodium (Shiomarin) at static mercury drop electrode (SMDE) and hanging mercury drop electrode (HMDE) has been proposed. A sensitive method for the determination of nanomolar concentration of latamoxef sodium by DPP was developed. The peak potential was -0.62 V (vs Ag/AgCl). The linear range was from 1 x 10(-8) to 8 x 10(-4) mol.L-1, the detection limit was ca. 4 x 10(-9) mol.L-1(tac = 90 s). The method was applied to the determination of latamoxef sodium in injection with satisfactory results. The possibility for the direct determination of latamoxef sodium in mimic urine sample was also studied.

Moxalactam↗
PubMed1975

Effects of papaverine, chloracyzine, and bencyclane on local blood flow and oxygen tension in cat brain.

In experiments on 100 cats with multichannel recording, the effects of three vasodilators - papaverine, chloracyzine, and bencyclane (Halidor) - on the volume velocity of the blood flow (by microthermistor technique) and on oxygen tension (by polarography) in the carotid artery, the cerebral cortex, the thalamus, and in white matter were tested. Considerable differences were found in the effects of the drugs mentioned, although all of them augment the total and local blood flow in the brain, and in most instances elevate the oxygen tension in arterial blood and cerebral tissue. Characteristic of papaverine is a uniform augmentation of blood supply to the cerebral cortex, the thalamus, and white matter, whereas chloracyzine, and especially bencyclane, primarily augment the blood supply to the cerebral cortex. In an analogous way the drugs tested influence the cerebral blood flow and oxygen tension in experimental cerebral ischaemia induced by intracarotid infusion of a serotonin solution.

Animals↗