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Biomedical subjects

J Havel

Publications and source records attributed to J Havel.

At least 37 records · Page 2Linked to original sources
PubMed1999

Artificial neural networks for computer-aided modelling and optimisation in micellar electrokinetic chromatography.

The separation process in capillary micellar electrochromatography (MEKC) can be modelled using artificial neural networks (ANNs) and optimisation of MEKC methods can be facilitated by combining ANNs with experimental design. ANNs have shown attractive possibilities for non-linear modelling of response surfaces in MEKC and it was demonstrated that by combining ANN modelling with experimental design, the number of experiments necessary to search and find optimal separation conditions can be reduced significantly. A new general approach for computer-aided optimisation in MEKC has been proposed which, because of its general validity, can also be applied in other separation techniques.

Chromatography, Micellar Electrokinetic Capillary↗
PubMed1999

Determination of platinum (II,IV) and palladium(II) as thiocyanate complexes by capillary zone electrophoresis analysis of carboplatin and similar drugs.

The thiocyanate complexes of Pd(II), Pt(II) and Pt(IV) were studied by capillary zone electrophoresis. Pd(II) can be detected in the form of the thiocyanate complex at 305 nm with higher sensitivity than in the form of its chloro complex (absorption maximum 214 nm). A detection limit equal to 5 ppb for Pd has been finally achieved. The possibility of simultaneous determination of Pd(II) and Pt(IV) in the form of thiocyanate complexes has also been demonstrated. When the method optimized for the determination of Pt(II) was applied to the drugs Cykloplatin and Ribocarbo (containing carboplatin) and Platidiam (containing cisplatin), good agreement of the platinum content with the declared value was obtained. Samples of vehicle exhaust particulates (National Institute for Environmental Studies, Japan, No. 8 reference material) were also analyzed.

Antineoplastic Agents↗
PubMed1999

Prediction of chiral separations using a combination of experimental design and artificial neural networks.

In this work the advantages of using artificial neural networks (ANNs) combined with experimental design (ED) to optimize the separation of amino acids enantiomers, with alpha-cyclodextrin as chiral selector, were demonstrated. The results obtained with the ED-ANN approach were compared with those of either the partial least-squares (PLS) method or the response surface methodology where experimental design and the regression equation were used. The ANN approach is quite general, no explicit model is needed, and the amount of experimental work can be decreased considerably.

Amino Acids↗
PubMed1999

Capillary zone electrophoresis determination of galanthamine in biological fluids and pharmaceutical preparatives: experimental design and artificial neural network optimization.

Galanthamine is a third-generation cholinesterase inhibitor used against Alzheimer's disease. New analytical methods for the determination of galanthamine in pharmaceutical preparatives and biological fluids, such as urine and serum, were developed. An experimental design and artificial neural network approach were used for method optimization. Thirty-five ppb of galanthamine were determined in serum samples (with addition of 10 mM magnesium chloride and using solid-phase preconcentration).

Alzheimer Disease↗
PubMed1998

Capillary zone electrophoretic determination of some drugs against Alzheimer's disease.

A new capillary zone electrophoresis (CZE) method for the determination of tacrine (THA), 7-methoxytacrine (7-MTHA) and their basic metabolites (THAm, 7-MTHAm) in pharmaceutical and biological samples (urine and serum) was developed. Separation of all compounds by CZE was carried out using a 46.6 cm untreated fused-silica capillary applying 20 kV separation voltage using 50 mM phosphate buffer of pH 2.8 for THA and THAm and of pH 7.8 for 7-MTHA and 7-MTHAm as background electrolyte (BGE). Detection was carried out at 240 nm (THA and THAm) and 248 nm (7-MTHA and 7-MTHAm). THA and THAm were separated in less than 4 min while 7-MTHA and 7-MTHAm were separated in less than 7 min. The detection limits (SIN = 3) obtained were 3 ppb for THA and 4 ppb for 7-MTHA in aqueous solutions; 50 ppb for THA and 47 ppb for 7-MTHA for the determination in urine (diluted 1:10); 52 ppb for THA and 56 ppb for 7-MTHA, in deproteinized serum samples. The methods are suitable for therapeutic drug monitoring of the drugs.

Alzheimer Disease↗
PubMed1998

Humic acid capillary zone electrophoresis adsorption on capillary walls, separation in metal ion supplemented buffer and the fingerprints.

Capillary zone electrophoresis (CZE) in quartz tubes is often being used for the separation and characterization of humic acids (HA). A method was found to follow adsorption (and kinetics) of humic acids on a fused-silica capillary wall. It was shown that the adsorption of humic acids on an uncoated capillary wall is high. The effect on sorption of additives to the background electrolyte (BGE) was studied. Sorption can be eliminated by adding magnesium(II) salts (14-50 mM) to the BGE (pH 3.40) with resultant highly reproducible electropherograms as well as detailed and expressive fingerprints for HA of different origin.

Adsorption↗
PubMed1998

Capillary electrophoresis separation of the new anti-AIDS agents 9-(2-phosphonylmethoxyethyl)adenine and 9-(2-phosphonylmethoxyethyl)-2,6-diaminopurine in mixtures with some monoribonucleotides or the most common deoxynucleotides.

The present work describes an electrophoretic method for the separation and determination of the new antivirals, 9-(2-phosphonylmethoxyethyl)adenine (PMEA) and 9-(2-phosphonylmethoxyethyl)-2,9-diaminopurine (PMEDAP) in model mixtures with some monoribonucleotide isomers (3'-AMP, 2'-CMP, 3'-CMP, 3'-GMP, 2'-GMP, 3'-UMP, 5'-GMP, and 5'-UMP) or with the most common deoxynucleotides (dCMP, dCDP, dCTP, dTMP, dTDP, dTTP, dGMP, dGDP, dGTP, dAMP, dADP, dATP). A fused-silica capillary tube, 75 microm ID, 67.8 cm total length (60.3 cm length to the detector), with detection at 210 nm was employed. A hydrodynamic injection for 10 s (1.5 psi vacuum) was utilized to introduce the sample, and 30 kV voltage was applied for the separation. The complete separation of PMEA and PMEDAP from the mononucleotide isomers and deoxynucleotide mixtures is possible in less that 10 min and 25 min, respectively, using 20 mM borate buffer, pH 9.9, with the addition of 10 mM beta-cyclodextrin. Efficiencies of more than 120 000 and resolution higher than 1.9 were reached for each of the compounds studied. This capillary electrophoretic procedure opens the possibility for future determination of PMEA and PMEDAP in cell pool samples.

Adenine↗
PubMed1997

Direct determination of procainamide and N-acetylprocainamide by capillary zone electrophoresis in pharmaceutical formulations and urine.

In this work a new sensitive capillary zone electrophoresis method for the direct determination of procainamide (PA) and N-acetylprocainamide (NAPA) in pharmaceutical formulations and urine samples without any extraction and/or preconcentration steps has been developed. The determination was carried out in a fused-silica capillary of 43.5 cm (35.9 cm length to the detector) x 0.75 micron J.D. Phosphate 0.05 M buffer was used as the background electrolyte and 10 kV separation voltage was applied. The separation of PA and NAPA is possible in a wide range of pH from 1.7 to 9.7. However, in order to avoid the effect of the urine matrix, it is optimal to work at pH 7.7. The determination of PA and NAPA takes less than 5 min while high resolution is achieved. The detection limits obtained, 1.235 micrograms/ml and 0.359 microgram/ml for PA and NAPA respectively, are lower than those for GC method normally reported.

Acecainide↗
PubMed1996

Separation of aracytidine and cytidine by capillary electrophoretic techniques.

Aracytidine (cytarabine, 1-beta-D-arabinofuranosylcytosine) is a synthetic analog of cytidine in which ribose is substituted by arabinose; it is used as a drug for the treatment of leukemia. A fast and reliable capillary electrophoretic method for the analysis of cytarabine and cytidine is described. The procedure utilizes the interactions with sodium dodecyl sulfate (SDS) micelles and borate, present in the background electrolyte, for the mobilization and selective separation of the analytes. The detection is carried out by UV absorbance at 275 nm. The method was applied both to pharmaceutical preparations and human serum. Analysis of an untreated serum requires 15 min; the detection limit is 0.8 microgram/mL and the relative standard deviation (RSD) is 5.3%.

Boric Acids↗
PubMed1996

Influence of chlorobenzoates on the utilisation of chlorobiphenyls and chlorobenzoate mixtures by chlorobiphenyl/chlorobenzoate-mineralising hybrid bacterial strains.

Chlorobenzoates (CBA) arise as intermediates during the degradation of polychlorinated biphenyls (PCBs) and some chlorinated herbicides. Since PCBs were produced as complex mixtures, a range of mono-, di-, and possibly trichloro-substituted benzoates would be formed. Chlorobenzoate degradation has been proposed to be one of the rate-limiting steps in the overall PCB-degradation process. Three hybrid bacteria constructed to have the ability to completely mineralise 2-, 3-, or 4-monochlorobiphenyl respectively, have been studied to establish the range of mono- and diCBAs that can be utilised. The three strains were able to mineralise one or more of the following CBAs: 2-, 3-, and 4-monochlorobenzoate and 3,5-dichlorobenzoate. No utilisation of 2,3-, 2,5-, 2,6-, or 3,4-diCBA was observed, and only a low concentration (0.11 mM) of 2,4-diCBA was mineralised. When the strain with the widest substrate range (Burkholderia cepacia JHR22) was simultaneously supplied with two CBAs, one that it could utilise plus one that it was unable to utilise, inhibitory effects were observed. The utilisation of 2-CBA (2.5 mM) by this strain was inhibited by 2,3-CBA (200 microM) and 3,4-CBA (50 microM). Although 2,5-cba and 2,6-cba were not utilised as carbon sources by strain jhr22, they did not inhibit 2-cba utilisation at the concentrations studied, whereas 2,4-cba was co-metabolised with 2-cba. The utilisation of 2-, 3-, and 4-chlorobiphenyl by strain JHR22 was also inhibited by the presence of 2,3- or 3,4-diCBA. We conclude that the effect of the formation of toxic intermediates is an important consideration when designing remediation strategies.

Biodegradation, Environmental↗
PubMed1995

The influence of physicochemical effects on the microbial degradation of chlorinated biphenyls.

The influence of different forms of substrate administration (either through the vapour phase or the liquid phase) on growth of two bacterial strains on biphenyl, 2-chlorobiphenyl, and 3,5-dichlorobiphenyl has been investigated. During growth with all three compounds, the availability of the substrate for the cells turned out to be the growth-limiting factor, even in liquid culture with excess substrate supplied to the medium. Growth on biphenyl and 2-chlorobiphenyl could be greatly enhanced if the substrate was distributed on a folded filter providing a large surface, which was placed in the vapour phase of the culture flask. This was not possible in the case of 3,5-dichlorobiphenyl. Here growth accelerated after accumulation of a yellow meta cleavage product. Through measurement of the surface tension it was shown that this yellow compound possessed detergent-like activities, increasing the amount of 3,5-dichlorobiphenyl dissolved in the medium.

Biodegradation, Environmental↗
PubMed1995

Development and validation of an LC/MS/MS method for the determination of L-hyoscyamine in human plasma.

A sensitive and specific LC/MS/MS method for the determination of L-hyoscyamine was developed and validated over the linearity range 20-500 pg ml-1 with 1.0 ml of plasma using scopolamine as the internal standard. The API III-Plus LC/MS/MS was operated under the multiple reaction monitoring mode using the atmospheric pressure chemical ionization technique. The instrument parameters were optimized to obtain 1.8 min run time with baseline separation of the internal standard from L-hyoscyamine. The between-run precision and accuracy of the calibration standards were 1.2 to 5.0% RSD and -4.5 to +2.5% relative error (RE). The within-run precision and accuracy of quality controls (60, 150 and 350 pg ml-1) were 1.9-3.4% RSD and -3.3 to +5.1% RE. Stability of L-hyoscyamine in human plasma and processed samples has been established.

Atropine↗
PubMed1993

Degradation of Aroclor 1221 in soil by a hybrid pseudomonad.

The hybrid Pseudomonas cepacia strain JHR22 was tested for its ability to degrade Aroclor 1221 in soil. The influence of supplements--mineral salts and trace elements--on the degradation was investigated. Disappearance of Aroclor 1221 congeners, occurrence of metabolites, and release of chloride were measured under different conditions. After 45 days the hybrid organism, strain JHR22, was still present at high numbers in soil, independently of whether the soil had been sterilized prior to inoculation or not. There was only a minor difference in degradation efficiency between sterilized and untreated soil with about 70% release of chloride when 10(7) cells/g soil were inoculated. The whole hybrid pathway, originating from three different strains, was found to be stable under the conditions tested. Mineral salts did not significantly affect the degradation rate or survival of the hybrid strain.

Aroclors↗
PubMed1993

Microbial degradation of chlorinated acetophenones.

A defined mixed culture, consisting of an Arthrobacter sp. and a Micrococcus sp. and able to grow with 4-chloroacetophenone as a sole source of carbon and energy, was isolated. 4-Chlorophenyl acetate, 4-chlorophenol, and 4-chlorocatechol were identified as metabolites through comparison of retention times and UV spectra with those of standard substances. The proposed pathway was further confirmed by investigation of enzymes. The roles of the two collaborating strains were studied by growth experiments and on the level of enzymes. If transient accumulation of 4-chlorophenol was avoided either by the use of phenol-absorbing substances or by careful supplement of 4-chloroacetophenone, the Arthrobacter sp. was able to grow as a pure culture with 4-chloroacetophenone as a sole source of carbon and energy. Several mono-, di-, and trichlorinated acetophenones were mineralized by the Arthrobacter sp.

Acetophenones↗
PubMed1991

Total degradation of various chlorobiphenyls by cocultures and in vivo constructed hybrid pseudomonads.

Cocultures consisting of strains converting chlorobiphenyls to the respective benzoates or catechols and of chlorobenzoate degraders were investigated for the mineralization of chlorobiphenyls. Stable mixed cultures were obtained with 4-chlorobiphenyl, while those with 2-chloro- or 3-chlorobiphenyl were found to be unstable and released only low yields of chloride. When both sets of enzyme sequences were combined in one organism, Pseudomonas cepacia strain JH230, by conjugative transfer of genes of the biphenyl degradation sequence, the total degradation of 2-chloro-, 3-chloro-, 4-chloro-, 2,4-dichloro-, and 3,5-dichlorobiphenyl was achieved.

Aroclors↗
PubMed1991

[Preservation surgery in splenic injuries at a type II hospital].

In 1986-1989 in the surgical department of the Pelhrimov hospital nine casualties were treated injuries of the spleen by preserving operations of the latter. In three patients the operation formed part of comprehensive treatment in the abdominal cavity and further treatment because of multiple injuries. In two patients the rupture was treated by a stitch with Gelaspon, in one instance by Gelaspon only. Six times splenectomy was performed with subsequent implantation of the tissue into omentum. All patients with the implantations recovered, except one, with out complications on the part of the implant. The authors present the case-history of a patient where on the 13th day day after operation the implant incl. the omentum had to be removed by relaparotomy. The authors did not encounter this complication in the literature. They ascribe it to the greatly reduced immunity of the patient due not only to the splenectomy but also to associated injuries, and thus healing processes facilitating incorporation of the spleen in the new environment were lacking. Despite this in the authors' opinion implantation of lienal tissue into the omentum, corresponding to one third of the original spleen, is a suitable therapeutic method even in district hospitals.

Adult↗