Biomedical subjects

A Sintov

Publications and source records attributed to A Sintov.

26 records · Page 2Linked to original sources

PubMed1989

Sensitive high-performance liquid chromatographic assay using 9-fluorenylmethylchloroformate for monitoring controlled-release lidocaine in plasma.

A sensitive high-performance liquid chromatographic (HPLC) assay using fluorescence detection for quantifying lidocaine levels in plasma (in the ng/ml range) was developed. This novel HPLC assay has made possible the simultaneous monitoring of lidocaine levels in coronary and peripheral plasma obtained after myocardial controlled-release matrix administration (0.92 mg/kg during 4 h) in the arrhythmic dog. The method employed extracts the drug from plasma using 1-chlorobutane and a subsequent derivatization with 9-fluorenylmethylchloroformate in acetonitrile at 110 degrees C. The derivative was chromatographed on a C18 reversed-phase column and measured with fluorescence detection (excitation 254 nm, emission 313 nm). N-Methylephedrine was found to be suitable as an internal standard, post-derivatization. The derivatization product of lidocaine was identified and characterized by mass spectral analysis. It was found to have a unique and reproducible dicarbamate structure, which was stable for at least three days at room temperature. The method was tested with human plasma as well as on dog plasma. Analytical recoveries were 88.6 +/- 3.6 and 77.4 +/- 3.0% (mean +/- S.E.), respectively, at levels ranging from 25 to 200 ng/ml. The lower detection limit was 1 ng/ml lidocaine. In conclusion, this rapid and convenient analysis was found to be suitable for the bioavailability pharmacokinetic assessment of lidocaine following low-dose regional drug administration.

Animals↗

PubMed1988

Pharmacokinetics and protein binding of trichothecene mycotoxins, T-2 toxin and HT-2 toxin, in dogs.

The pharmacokinetics of T-2 toxin, following i.m. and i.v. administration (0.4 mg/kg), were investigated in five dogs. Following i.m. administration, the mean pharmacokinetic parameters for T-2 and HT-2 toxins were, respectively: apparent half-life 21 +/- 5 and 73 +/- 7 min; peak plasma concentration 182 +/- 42 and 74 +/- 16 ng/ml; time to reach peak plasma concentration 9.4 +/- 6.4 and 49 +/- 11 min. Mean residence time calculation, using moment analysis, showed that the terminal slope of T-2 toxin plasma levels following i.m. administration corresponds to the absorption rate constant of the toxin due to the flip-flop phenomenon. T-2 toxin was completely absorbed following i.m. administration and its absolute bioavailability was 1.17 +/- 0.25. A plasma protein binding study showed that in a concentration range of 70-500 ng/ml, T-2 and HT-2 toxins have a mean free fraction of 30.6 +/- 3.1% and 32.6 +/- 3.6% with no concentration dependency. At physiological conditions (temperature and pH), both T-2 and HT-2 toxins were unstable in whole blood and their in vitro stability half-lives were 6.9 and 0.84 hr, respectively. However, under similar conditions, these toxins were stable in plasma for 7 hr. Their instability in whole blood, therefore, may be related to enzymes present in the blood cells.

Animals↗

PubMed1987

T-2 toxin effect on rat aorta: cellular changes in vivo and growth of smooth muscle cells in vitro.

Rats were injected intraperitoneally with T-2 toxin and their aortas were studied by light and electron microscopy. The growth of smooth muscle cell explants taken from the tunica media of aortas of similarly treated animals was observed. A single large dose (2 mg/kg) or four injections of 0.3 mg/kg T-2 toxin caused damage and occasional necrosis of endothelial cells, accumulation of basement membrane-like material in the intima, and swelling and activation of smooth muscle cells in the tunica media. Three or more weeks after the last injection of 0.3 mg/kg T-2 toxin the endothelial cells were normal but an excess of fragmented intimal basement membrane-like material persisted and smooth muscle cells were still activated. Outgrowths from explants of aortic tunica media taken within 1 week of the last dose of T-2 toxin showed marked inhibition of smooth muscle cell growth. Three or more weeks after the toxin, the explants showed significantly increased outgrowths. These findings suggest that T-2 toxin causes early endothelial and smooth muscle cell injury accompanied by inhibition of smooth muscle cell growth in culture. This is followed by stimulation of the proliferative capacity of smooth muscle cells in vitro. If a similar mechanism is operative in vivo, it could explain the chronic vascular changes observed after limited exposure to T-2 toxin.

Animals↗

PubMed1987

Pharmacokinetics of T-2 tetraol, a urinary metabolite of the trichothecene mycotoxin, T-2 toxin, in dog.

1. The urinary metabolites of T-2 toxin were identified and analysed quantitatively after i.v. administration to dogs. 2. A new routine assay for T-2 tetraol was developed and a pharmacokinetic study was carried out on this final hydrolytic metabolite of T-2 toxin. T-2 tetraol was excreted in urine for 2-3 days. Its 'sigma minus' plot demonstrated a significantly longer apparent half-life than its precursors (T-2 toxin and HT-2 toxin). This fact was explained by extraplasma binding causing prolongation of the metabolism and excretion of T-2 toxin metabolites. 3. The urinary metabolites of T-2 toxin were: HT-2 toxin, T-2 triol and T-2 tetraol. The metabolites were excreted in free and conjugated forms. In two dogs T-2 toxin was found in the urine in an amount which accounts for 3.2 and 16% of the administered dose respectively. The cumulative amount of the identified metabolites and toxins formed in the urine ranged from 9.7 to 17.3% in four dogs and 44.7% in one dog.

Animals↗

PubMed1987

The feasibility of a Dot enzyme-linked immunosorbent assay (Dot-ELISA) for the diagnosis of Plasmodium falciparum antigens and antibodies.

An enzyme-linked immunosorbent assay for rapid detection of malarial antibodies and antigens was developed. Plasmodium falciparum antigen preparation, obtained from sonicated cultures of the parasite at a parasitemia of 10%-15%, was applied to cellulose filter discs in volumes of 0.1 microliter in 96-well microtiter plates. Antibodies were detected by successive incubations with: bovine serum albumin for blocking, tested serum at different dilutions, peroxidase-conjugated antihuman IgG, and the precipitable substrate 4-chloro-1-naphtol. Positive reactions appeared as blue dots on a white background which are easily read by eye. Pools of sera from patients with recent disease or from individuals with a history of malaria, contained antibodies detectable up to a dilution of 1:64,000. Negative results were obtained when normal RBC were used for dotting the filters. Normal sera showed no reaction at any antigen concentration. P. falciparum antigens were detected by their ability to inhibit the binding of antibody to the filters. RBC infected with P. falciparum in vitro can be detected at a level of 0.001% parasitemia. This report presents the feasibility of an assay for detecting malarial antibodies and antigens in blood samples which is easily applicable to field conditions.

Antibodies↗

PubMed1986

New, sensitive thin-layer chromatographic-high-performance liquid chromatographic method for detection of trichothecene mycotoxins.

Diphenylindenone sulphonyl (Dis) esters of trichothecene mycotoxins when sprayed with sodium methoxide showed fluorescent spots on a thin layer of silica gel when viewed under long-wavelength UV light. The detection limit for trichothecene esters in thin-layer chromatography (TLC) was 20-25 ng per spot for T-2 toxin, HT-2 toxin, diacetoxyscirpenol, T-2 triol, T-2 tetraol and iso-HT-2 toxin. A quantitative high-performance liquid chromatographic (HPLC) analysis of Dis-trichothecene esters was also developed using UV detection at 278 nm. The detection limit for the above esters varied between 30 and 50 ng per injection. This sensitive TLC-HPLC method is very useful for in vivo pharmacokinetic analyses of trichothecenes.

Chromatography, High Pressure Liquid↗

PubMed1985

Gas chromatographic assay with pharmacokinetic applications for monitoring T-2 and HT-2 toxins in plasma.

A gas-liquid chromatographic (GLC) method for monitoring T-2 and HT-2 toxins in plasma was developed. The procedure involved extraction of the toxins with ethyl acetate, chromatography on a C18 reversed-phase column and derivatization with heptafluorobutyric anhydride (HFBA). The T-2 and HT-2 HFBA derivatives were chromatographed on OV-17 at various temperatures and measured with an electron-capture detector. Iso-T-2 toxin and iso-HT-2 toxin were used as internal standards. Recoveries averaged 95.1 +/- 8.6% for T-2 toxin and 102.1 +/- 5.2% for HT-2 toxin at levels ranging from 40 to 120 ng/ml. The limits of detection were 30 and 5 ng/ml of T-2 and HT-2 toxin, respectively. The range of the assay covers plasma concentrations at which toxicity becomes manifest. The pharmacokinetic application of this GLC method is illustrated by simultaneous monitoring of T-2 and HT-2 toxins levels in plasma obtained after intravenous administration of T-2 toxin to a dog.

Animals↗

PubMedDate not supplied

Pharmacokinetics of T-2 toxin and its metabolite HT-2 toxin, after intravenous administration in dogs.

The pharmacokinetics of T-2 toxin and HT-2 toxin were investigated comparatively in five dogs, after iv administration of the toxins (0.4 mg/kg). T-2 toxin was very rapidly and almost completely biotransformed to HT-2 toxin (fm = 83.6 +/- 3.9%). The following mean pharmacokinetic parameters were determined in this study for T-2 toxin and HT-2 toxin, respectively: half-life 5.3 +/- 2.1 and 19.6 +/- 4.7 min, clearance 0.107 +/- 0.056 and 0.167 +/- 0.074 liters/min/kg, and volume of distribution 0.86 +/- 0.63 and 4.47 +/- 1.38 liters/kg. The high clearance values suggest that the metabolism of T-2 toxin and HT-2 toxin is carried out in blood and/or through diffusion by nonspecific carboxyesterases. The results of this study suggest the possibility of a sustenance of T-2 toxin metabolism by its binding to blood cells.

Animals↗