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J Sevcík

Publications and source records attributed to J Sevcík.

At least 19 recordsLinked to original sources
PubMed2002

Structures and pathways of the central nervous system are potentially involved in the serotonergic modulation of gastrointestinal activity.

The supposed involvement of rat brain regions in the modulation of rat small intestine serotonergic activity was investigated. Small electrolytic lesions were placed in the areas of medulla oblongata and pons Varoli; one week later, changes in the serotonergic response of the intestine were detected. The contractions mediated by the activation of 5-HT2 receptors in the proximal ileum were investigated. The whole ileum segments were cut and placed into the bath. The preparations were contracted by adding increasing concentrations of 5-hydroxytryptamine (5-HT) (10 nM-1 microM) and noncumulative concentration-response curves (CRCs) were established. The differences between 5-HT responses of preparations from either sham-operated or experimental rats suggest the existence of brainstem regions (dorsal vagal and solitary nuclei, parvocellular reticular nuclei and serotonergic A1,2,5 groups) that either stimulate or inhibit 5-HT modulatory action in the rat gastrointestinal tract.

Animals↗
PubMed2001

Fast analysis of antibacterial isothiazolones by capillary electrophoresis.

Some technical aspects influencing the total time of CE analysis are discussed. A high throughput electrophoretic system based on micellar electrokinetic chromatography (MEKC) is demonstrated as an example. A short capillary, strong electric field, alkaline buffer (pH 9.5) generating strong electroosmotic flow, and parallel hydrodynamic pressure allow the separation of two uncharged isothiazolone derivatives within 45 s.

Anti-Infective Agents↗
PubMed2001

Capillary electrophoresis of methylderivatives of quinolines. I.

Migration behavior of quinoline, isoquinoline and related methylderivatives has been investigated with respect to the influence of running buffer acidity and to the presence of polyethylene glycol (PEG) 2000 as additive. Dissociation constants and ionic mobilities were determined by capillary electrophoresis (CE). Mobility and viscosity measurements in PEG containing buffers show that analyte transport is not in accordance with Walden's rule and microviscosity plays the role in analyte retardation. Variation of pH and PEG concentration provides the optimal conditions for the CE separation of methylquinolines (0.0176 M acetate-Tris buffer, pH 5.5, 10% PEG 2000). Analysis of industrial mixture (isoquinoline fraction from distillation of coal tar) was performed and good agreement with gas chromatographic results was found.

Electrophoresis, Capillary↗
PubMed2001

Purification, crystallization and preliminary X-ray analysis of two crystal forms of ribonuclease Sa3.

RNase Sa3 produced by Streptomyces aureofaciens strain CCM 3239 belongs to the T1 family of microbial ribonucleases. It is closely related both to RNase Sa, studied in detail earlier, and to RNase Sa2 produced by the same microorganism. The most important property of RNase Sa3 is the relatively high cytotoxic activity, which was not observed for RNase Sa and Sa2. Recombinant RNase Sa3 was overexpressed in Escherichia coli and purified to high homogeneity. The hanging-drop vapour-diffusion method was used for crystallization. The two crystal forms are trigonal P3(1)21 and tetragonal P4(1)2(1)2, with unit-cell parameters a = b = 64.7, c = 69.6 A, gamma = 120 degrees and a = b = 34.0, c = 147.2 A, respectively. They diffract to 2.0 and to 1.7 A resolution, respectively, using synchrotron radiation. The asymmetric units of crystal forms I and II contain one molecule of the enzyme, which corresponds to V(M) = 3.8 A(3) Da(-1) with a solvent content of 68% and V(M) = 1.9 A(3) Da(-1) with a solvent content of 37%, respectively.

Crystallization↗
PubMed2001

Determination of anthracycline antibiotics doxorubicin and daunorubicin by capillary electrophoresis with UV absorption detection.

Sweeping preconcentration and electrokinetic injection was used for the capillary electrophoretic analysis of trace amounts of biologically active anthracyclines with UV absorption detection. Phosphate buffer (100 mM), pH 2.5, with addition of 40% v/v methanol was used as background electrolyte (BGE). Sodium dodecyl sulfate (150 mM) was added to BGE in the inlet vial as the sweeping agent. The system enables effective separation of anthracyclines as well as cleanup from matrix impurities. Sweeping preconcentration of sample provides an excellent detection limit (1 x 10(-9) mol L(-1)). The method was applied for the determination of therapeutic levels of doxorubicin in real plasma samples.

Antibiotics, Antineoplastic↗
PubMed2000

Past, present and future of psychoneuroimmunology.

Psychoneuroimmunology was for the first time comprehensively described about 20 years ago. The influence of mental status on the course and outcome of a number of diseases, however, was suspected a long time before. Also the links between mental affective disorders and the immune status were repeatedly suggested. The authors in this paper shortly reviewed the most important clinical as well as experimental evidence which at present strongly supports the concept of a close and bidirectional communication between central nervous, neuroendocrine and immune systems. The most important anatomical, physiological as well as pharmacological experimental data, which were obtained by the authors during 20 years of research in this field, are presented. The data strongly suggest that in the very next future we will not only better understand a very complex communication between mind and body, but also completely new types of compounds might become available.

Animals↗
PubMed2000

Capillary electrophoretic determination of sanguinarine and chelerythrine in plant extracts and pharmaceutical preparations.

Capillary electrophoresis was employed to determine the principal quaternary benzo[c]phenanthridine alkaloids, sanguinarine and chelerythrine, in two plant extracts and one oral hygiene product. Phosphate-Tris buffer of pH 2.5 was used as a background electrolyte, limits of detection were 3 micromol/l(-1) (sanguinarine) and 2.4 micromol,l(-1) (chelerythrine) using UV detection at 270 nm. The method, which correlated well with HPLC, is suitable for serial determination of sanguinarine and chelerythrine in plant products and pharmaceuticals.

Alkaloids↗
PubMed2000

MDP and 5-HT receptors. Does MDP interact with 5-HT(7) receptors?

A possible interaction of immunomodulator muramyl dipeptide (MDP) with 5-HT(7) (5-hydroxytryptamine) receptors was investigated. The activation of 5-HT(7) receptors relaxes the guinea-pig distal ileum. The whole ileum segments were, therefore, cut and placed into the bath. The preparations were precontracted by substance P and potently relaxed by adding incremental concentrations of 5-carboxamidotryptamine (5-CT) (0.01-3.2 microM), less potently by 5-hydroxytryptamine (5-HT) (1-100 microM). The preparations most sensitive to 5-CT were also relaxed by MDP (1-100 microM). Noncumulative concentration-response curves (CRCs) for 5-HT or 5-CT were established in the absence or presence of 5-HT antagonist metergoline (320 nM). Metergoline inhibited the relaxations and shifted the CRCs to the right. In the preparations most sensitive to the effects of both 5-CT and metergoline, the latter substance also inhibited the effect of the highest concentration (100 microM) in CRCs for MDP. In another type of experiments, CRCs for 5-HT or 5-CT were constructed in the presence of low concentrations of MDP (5-500 nM). The relaxations evoked by either drug remained unchanged. These results suggest that low concentrations of MDP do not interact with activation of 5-HT(7) receptors. In higher concentrations MDP acts on this receptor type as a very weak partial agonist.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed2000

Potential role of cannabinoids in Parkinson's disease.

Parkinson's disease (PD) is a neurodegenerative disorder caused by a progressive loss of dopaminergic neurons of the substantia nigra, resulting from an oxidative stress. The lack of dopaminergic neurons is reflected by a disturbed balance of the neural circuitry in the basal ganglia. Cannabinoids might alleviate some parkinsonian symptoms by their remarkable receptor-mediated modulatory action in the basal ganglia output nuclei. Moreover, it was recently observed that some cannabinoids are potent antioxidants that can protect neurons from death even without cannabinoid receptor activation. It seems that cannabinoids could delay or even stop progressive degeneration of brain dopaminergic systems, a process for which there is presently no prevention. In combination with currently used drugs, cannabinoids might represent, qualitatively, a new approach to the treatment of PD, making it more effective.

Cannabinoids↗
PubMed1999

The evolution of starch-binding domain.

Amylolytic enzymes belonging to three distinct families of glycosidases (13, 14, 15) contain the starch-binding domain (SBD) positioned almost exclusively at the C-terminus. Detailed analysis of all available SBD sequences from 43 different amylases revealed its independent evolutionary behaviour with regard to the catalytic domains. In the evolutionary tree based on sequence alignment of the SBDs, taxonomy is respected so that fungi and actinomycetes form their own separate parts surrounded by bacteria that are also clustered according to taxonomy. The only known N-terminal SBD from Rhizopus oryzae glucoamylase is on the longest branch separated from all C-terminal SBDs. The 3-dimensional (3-D) structures of fungal glucoamylase and bacterial CGTase SBDs are compared and used to discuss the interesting SBD evolution.

Amino Acid Sequence↗
PubMed1999

[New, modern, centrally active antihypertensive agents in the treatment of essential hypertension].

It was recently found that the rise of blood pressure leads to the excitation of a vasomotor centre in the brain stem and that the accompanying decrease in brain cortex excitability results in the reduced sensitivity to various adverse stimuli. Centrally acting antihypertensives, moxonidine and rilmenidine, do not impair circulatory reflexes and therefore do not deprive the patient of a chance to resist the pressure; thus the compliance of the patient might be increased. Both drugs activate I1-imidazoline receptors on the neurons of the rostral ventrolateral medulla oblongata. The reduction of neuronal firing rate results in the decrease of sympathetic activity and arterial pressure. Beside other advantages, centrally acting antihypertensives might be more promising than peripherally acting drugs due to their possible more favourable psychopharmacological profile; this component of their action might be underestimated at present.

Adrenergic alpha-Agonists↗
PubMed1999

Determination of adenosine deaminase activity in human erythrocytes by on-column capillary isotachophoresis-capillary zone electrophoresis in the presence of electroosmotic flow.

Transient capillary isotachophoresis (CITP)-capillary zone electrophoresis (CZE) in presence of electroosmotic flow (EOF) was utilized for the measurement of adenosine deaminase activity in human erythrocytes. Phosphates, dominant anions of the sample matrix, were used as leading ions for transient isotachophoresis, and borates (0.3 M, pH 10) were used as terminating ions and background electrolyte for CZE. Final experimental conditions made it possible to inject 70% of the total capillary volume (1.45 microL) with the sample. Enzymatic conversion products (inosine and hypoxanthine), present in the sample in the low-micromolar range, were determined using optimized conditions. The limit of detection was 28 nM using UV detection at 202 nm. The presented data shows that CITP-CZE can be performed in uncoated capillaries in the presence of strong EOF.

Adenosine Deaminase↗
PubMed1999

The interaction of immunomodulatory muramyl dipeptide with peripheral 5-HT receptors: overview of the current state.

Immunomodulator muramyl dipeptide (MDP) exerts also pronounced neuropharmacological activities which are probably mediated by an interaction with 5-HT receptors. Some of these effects are considered as undesirable by its clinical use. More precise information concerning MDP effects on 5-HT receptors with respect to their many subtypes could result from studies using isolated organs in vitro. Earlier conducted studies of this type provided data that are concisely overviewed and reinterpreted here from the view of current 5-HT receptor classification. Since new 5-HT receptor types have emerged recently, new studies are under way. The results might contribute to the development of novel immunomodulatory drugs devoid of adverse effects.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1999

Capillary electrophoresis for detection of inherited disorders of purine and pyrimidine metabolism.

BACKGROUND: Measurement of purine and pyrimidine metabolites presents complex problems for separations currently performed by HPLC and thin-layer chromatography in clinical practice. We developed a novel capillary electrophoresis method for this purpose. METHODS: Separations were performed in 60 mmol/L borate-2-amino-2-methyl-1-propanol-80 mmol/L sodium dodecyl sulfate (pH 9.6) at 35 degrees C. RESULTS: The conditions reported allowed separation of all diagnostic metabolites from major urinary constituents in an analysis time of 3 min and with a separation efficiency of 220 000 theoretical plates/m. The clinically important metabolites were detectable at concentrations of 0.85-4.28 micromol/L. The method was linear over the range 5-500 micromol/L (r >0.99). The within-run and intra- and interday imprecision (CV) was <5%. Characteristic abnormalities were detected in the electropherograms of urine samples from patients with purine and pyrimidine enzyme deficiencies. We provide the electrophoretic and spectral characteristics of many intermediates in purine and pyrimidine metabolism and describe common artifacts from medication and ultraviolet-absorbing compounds. CONCLUSION: Capillary electrophoresis is a valuable screening tool in the detection of inborn errors of purine and pyrimidine metabolism.

Adenine Phosphoribosyltransferase↗
PubMed1998

Structure of glucoamylase from Saccharomycopsis fibuligera at 1.7 A resolution.

The yeast Saccharomycopsis fibuligera produces a glucoamylase which belongs to sequence family 15 of glycosyl hydrolases. The structure of the non-glycosyl-ated recombinant enzyme has been determined by molecular replacement and refined against 1.7 A resolution synchrotron data to an R factor of 14.6%. This is the first report of the three-dimensional structure of a yeast family 15 glucoamylase. The refinement from the initial molecular-replacement model was not straightforward. It involved the use of an unrestrained automated refinement procedure (uARP) in combination with the maximum-likelihood refinement program REFMAC. The enzyme consists of 492 amino-acid residues and has 14 alpha-helices, 12 of which form an (alpha/alpha)6 barrel. It contains a single catalytic domain but no starch-binding domain. The fold of the molecule and the active site are compared to the known structure of the catalytic domain of a fungal family 15 glucoamylase and are shown to be closely similar. The active- and specificity-site residues are especially highly conserved. The model of the acarbose inhibitor from the analysis of the fungal enzyme fits tightly into the present structure. The active-site topology is a pocket and hydrolysis proceeds with inversion of the configuration at the anomeric carbon. The enzyme acts as an exo-glycosyl hydrolase. There is a Tris [2-amino-2-(hydroxymethyl)-1,3-propanediol] molecule acting as an inhibitor in the active-site pocket.

Amino Acid Sequence↗
PubMed1998

Recognition of RNase Sa by the inhibitor barstar: structure of the complex at 1.7 A resolution.

We report the 1.7 A resolution structure of RNase Sa complexed with the polypeptide inhibitor barstar. The crystals are in the hexagonal space group P65 with unit-cell dimensions a = b = 56.9, c = 135.8 A and the asymmetric unit contains one molecule of the complex. RNase Sa is an extracellular microbial ribonuclease produced by Streptomyces aureofaciens. Barstar is the natural inhibitor of barnase, the ribonuclease of Bacillus amyloliquefaciens. It inhibits RNase Sa and barnase in a similar manner by steric blocking of the active site. The structure of RNase Sa is very similar to that observed in crystals of the native enzyme and its complexes with nucleotides. Barstar retains the structure found in its complex with barnase. The accessible surface area of protein buried in the complex is about 300 A2 smaller and there are fewer hydrogen bonds in the enzyme-inhibitor interface in RNase Sa-barstar than in barnase-barstar, providing an explanation of the reduced binding affinity in the former. Previous studies of barstar complexes have used mutants of the inhibitor and this is the first structure which includes wild-type barstar.

Amino Acid Sequence↗
PubMed1998

Methamphetamine--properties and analytical methods of enantiomer determination.

Methamphetamine is one of the most frequently abused drugs of today. Due to its stereogenic center, it can exist as single enantiomer. Like many other chiral compounds, methamamphetamine enantiomers exhibit different pharmacological effects on living organisms. For this reason, it is necessary to develop enantioselective and sufficiently sensitive methods of determination. This review focuses on methamphetamine with an accent on analytical chemistry and especially on chiral separations of this toxicologically important compound.

Animals↗