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Biomedical subjects

A Csiba

Publications and source records attributed to A Csiba.

At least 19 recordsLinked to original sources
PubMed1998

Determination of endogenous formaldehyde in plants (fruits) bound to L-arginine and its relation to the folate cycle, photosynthesis and apoptosis.

A very powerful nucleophilic reagent, hydralazine(1-hydrazino-phtalazine) proved to be suitable for determination of the endogenous formaldehyde level in biological samples. It was found that in different plants (vegetables, fruits, especially in red beet, cauliflower, kohlrabi, grapes) is a large amount of releasable endogenous formaldehyde (0.5-1.0 mM) bound to L-arginine mainly in the form of N(G)-trihydroxymethyl-L-arginine (TriHMA). N(G)-hydroxymethyl-L-arginines (HMA) were proved to transfer their hydroxymethyl groups to tetrahydrofolic acid producing N5,N10-methylene-tetrahydrofolate, the coenzyme of thymidylate synthase. HMA was found to inhibit the cell proliferation of HT-29 cell culture (human colon adenocarcinoma ATCC HT-B 38) causing apoptosis. Photosynthetic experiments produced confirmatory evidences that 14CH2O could be formed in photosynthesis already after 10 seconds of 14CO2 fixation in the seedlings of Zea mays L. (single cross) and the 14CH2O was immediately trapped by L-arginine mainly as TriHMA.

Adenocarcinoma↗
PubMed1998

The hydrazine derivative aminoguanidine inhibits the reaction of tetrahydrofolic acid with hydroxymethylarginine biomolecule.

UNLABELLED: Aminoguanidine (AG), a hydrazine derivative is known to inhibit the formation of Advanced Glycosylation Endproducts (AGE) and AG has been proposed as an agent in prophylaxis of diabetic complications. However, treatment with hydrazine produced liver and lung tumors by formation of N7- and O6-methylguanine in the DNA of rodents. The hydrazine derivative, isonicotinic acid hydrazide induced pulmonary tumors in mice. N(G)-hydroxymethyl-arginine (HMA) was synthesized by our research group and it showed anticancer effect against experimental tumors. HMA was found earlier in human blood and urine, and recently in many plants (in fruits and vegetables). We could demonstrate a reaction (pH = 7.5, 37 degrees C, 1h) between HMA and tetrahydrofolate (THF) producing N5,N10-methylene-tetrahydrofolate (CH2-THF), the coenzyme of thymidylate synthase (TS). In model experiments AG proved to react with formaldehyde (HCHO) and to eliminate the C1-fragment of HMA, but not that of CH2-THF. In the presence of AG burst chemiluminescence and a higher speed of the formylation and methylation reactions were found in the AG, HCHO, hydrogen peroxide (H2O2) and L-lysine system than without AG. CONCLUSIONS: HMA as a biomolecule is one of the compounds which are responsible for the endogenous HCHO level. The biochemical function of HMA may be the direct supply of C1-fragment for the folate cycle. AG can disturb the above function of HMA. The reaction between AG and HCHO seems to be dangerous for biological systems because of the possible presence of L-lysine and H2O2. The burst chemiluminescence indicates excited molecules with extreme high energy producing uncontrolled formylation and methylation reactions. Considering the results of the experiments with AG its use as a medicament seems to be questionable.

Animals↗
PubMed1998

Analogies and differences in the excited reactions of formaldehyde and D-glucose.

The investigations proved that D-glucose (as reducing sugar) can easily be activated in a ternary system (L-lysine: D-glucose: H2O2) similarly to formaldehyde at 20 degrees C, in pH = 7.4 forming chemiluminescence (CL) and singlet oxygen. The kinetic investigation showed that: CL lasted many hours (permanent emission) and had no bell-shaped curve differently from other aldehydes e.g. formaldehyde. The reason of the effect is that D-glucose exists mainly in ring form in water solution (Haworth ring form) and the open form (the aldehyde group) is slowly liberated during the excited reaction. These excited reactions may be important in human organism, because D-glucose and lysyl residues of proteins occur permanently in human body and endogenous formaldehyde and H2O2 may be liberated there, too.

Chromatography, High Pressure Liquid↗
PubMed1996

A high-performance liquid chromatographic (HPLC) method for the simultaneous determination of nitrite and formaldehyde from foods.

A high-performance liquid chromatographic (HPLC) procedure with fluorometric detector has been developed for the determination of nitrite and formaldehyde from foods by the use of hydralazine. Hydralazine reacts with nitrite and formaldehyde under acidic conditions in boiling water-bath for 15 min to form tetrazolo-(5,1-a)-phthalazine (Tetra-P) and triazolo-(3,4-a)-phthalazine (Tri-P) quantitatively. Without extraction, the determination of Tetra-P and Tri-P was simple, specific, sensitive and reliable over the range of 0.003-0.3 ppm of sodium nitrite and 0.02-0.4 ppm of formaldehyde. This procedure using hydralazine is one of the most useful methods for routine analysis of nitrite and formaldehyde in foods, biological fluids and ambient waters.

Animals↗
PubMed1995

[Scanning electron microscopy of the resorption surface of deciduous teeth].

Based on a study of ten deciduous human teeth, (front teeth and molars) under a Scanning Electron Microscope type Tesla BS 300 we could observe that the differences of the mineralization levels are more striking in the peritubular dentin, then in the intertubular structures. The structural transformation increases by approaching the resorption surface. Near the enamel the resorption surface shows a two-edged demineralization. The mineralized part near the enamel is probably the result of the protecting processes of the human organism.

Dentin↗
PubMed1994

[Clinico-pharmacologic studies on pefloxacin].

The impact of liver impairment, renal insufficiency and age-related changes on the pharmacokinetics of pefloxacin was studied in 55 patients. The elderly patients were stratified into three age groups (61-70, 71-80 and above 81 years). The patients suffering from various infections were treated with oral or intravenous pefloxacin in a dose of 400 mg bid. Blood samples were withdrawn on the first and seventh day of therapy. The pharmacokinetics of pefloxacin was characterized by marked interindividual differences that became even more pronounced during multiple dosing. The elimination rate of pefloxacin during therapy slowed down, presumably due to its decreased metabolism. In elderly patients, the rate of cumulation is greater than in the young ones, but no significant differences could be detected among the elderly age-groups. Pefloxacin elimination also decreased in renal and hepatic impairment. There was no correlation between serum concentrations of pefloxacin and the development of adverse effects. In elderly subjects and in patients with renal or hepatic impairment, dose reduction might be considered. In mild or moderate infections or in urinary tract infections smaller doses of pefloxacin also could assure good therapeutic results. However, in severe infections especially caused by less susceptible pathogens, routine dose reduction is not recommended because of the significant interindividual differences in serum concentrations of pefloxacin.

Administration, Oral↗
PubMed1989

A new staining and evaluating procedure for protein gel electropherograms based on the pyrogallol red-molybdate complex.

A new method is reported for staining and evaluating gel electropherograms of proteins. With pyrogallol red-molybdate reagent the gel-embedded proteins are transformed into a derivative of blue colour. After destaining, the blue-coloured proteins are well visible against a colourless background and can be quantified by densitometry with high reliability. The quantity of the coloured protein is directly proportional to the height of peaks in the densitogram. Colour intensity is concentration dependent. The measurement range of serum albumin was 1 to 50 micrograms/tube and 10 to 100 micrograms/slab in polyacrylamide gel disc electrophoresis and agar gel electrophoresis, respectively.

Electrophoresis↗
PubMed1989

[Colorimetric determination of isoniazid in aqueous solutions and biological fluids].

Method has been developed for determination of tuberculostatic isoniazid in aqueous solutions and biological fluids. The principle of the method is that hydrazine group of isoniazid reacts with 1-fluoro-2,4-dinitrobenzene forming a red chromophor in alkaline medium. The absorbency maximum of the chromophor is at 530 nm. Biological fluids were deproteinized and diluted with acetonitrile then adjusted to pH = 8.2 with trometamol-hydrochloric acid buffer and reacted with 1-fluoro-2,4-dinitrobenzene dissolved in acetonitrile. The chromphore was measured colorimetricaly against a blank solution which did not contain isoniazid. The method was calibrated in the range of 1-30 mg/l isoniazid and reproducibility was checked with recovery % determinations.

Body Fluids↗
PubMed1988

The effect of ciprofloxacin on antipyrine metabolism.

The effect of multiple-dose ciprofloxacin on antipyrine metabolism was studied in patients suffering from bacterial infections. The patients were given antipyrine 15 mg/kg intravenously before and after ciprofloxacin treatment. The dosage of ciprofloxacin was 500 mg bd by mouth for 8-10 days. Blood samples were taken at 0, 2, 4, 6, 10 h. Antipyrine total clearance was significantly decreased after ciprofloxacin treatment (0.85 +/- 0.45 vs. 0.52 +/- 0.24 ml/min/kg): elimination rate constants for antipyrine were decreased in all patients after ciprofloxacin, whereas no change in volume of distribution was observed. The average half-life of antipyrine was increased from 9.45 +/- 3.74 h to 14.92 +/- 3.32 h. In two males with advanced chronic hepatic failure the antipyrine half-lives were extremely prolonged. Our results support the hypothesis that ciprofloxacin inhibits intrinsic hepatic drug-metabolizing capacity and may be a source of clinically important drug interactions, particularly in patients with liver disease.

Adult↗
PubMed1988

Pharmacokinetics of cefotaxime and desacetylcefotaxime in elderly patients.

This study was undertaken to determine the effect of age on the pharmacokinetics of cefotaxime and desacetylcefotaxime after intravenous administration of 1 g cefotaxime. 30 elderly patients suffering from acute infection were enrolled in the study. They were divided into 3 subgroups (group I aged 60 to 70 years, group II aged 71 to 80 years, group III aged over 80 years) with 5 men and 5 women in each. The elimination of cefotaxime in patients aged between 60 and 80 years was slightly slower than that in young people: elimination half-lives (in men and women, respectively) in group I were 1.2 and 1.58 hours, in group II, 1.45 and 1.57 hours and in group III, 2.56 and 2.59 hours. The change in elimination of desacetylcefotaxime was similar to that of cefotaxime, but less marked. The slower elimination of cefotaxime in patients over 80 years of age may allow reduction in the dose without jeopardizing the efficacy of therapy, whereas in patients under 80 years of age the normal dosage is required.

Age Factors↗
PubMed1986

[Serum level of antibiotics in burn patients].

Antibiotic serum levels were recorded from 100 patients with burns. Antibiotic doses to ensure effective serum levels were found to be in excess of maximum values quoted as necessary by manufacturers, provided that serum creatinine was normal. These findings were in agreement with literature data. This was the first instance to check on serum levels, following oral administration of antibiotics. Differences between individual patients may be considerable, probably due to variable renal blood supply and other factors. Individual dosage with control of serum levels is, therefore, recommended. Specific dosage recommendation for patients with burns would be desirable for hospital practice.

Adult↗