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Biomedical subjects

P Barták

Publications and source records attributed to P Barták.

At least 19 recordsLinked to original sources
PubMed2006

[Pigmented tumors of the skin and anoikis].

Nevocellular nevus can develop by two mechanisms: 1. after the chronic solar irradiation of the skin which impairs barrier lipids' homeostais and keratinocytes together with melanocytes undergo apoptosis; 2. Apoptosis can arise in melanocytes during phylogenetic development from the neural crest to epidermis when it migrates through the "enemy" territory of dermis. Apoptosis can be thus stopped by enzymatic process which results in anoikis and the endangered melanocyte would further proliferate. The later is the path of nevocellular nevi.

Anoikis↗
PubMed2003

[Sun photoaging].

Only in the last years the recognition of the solar radiation danger has been glowing. The rising curve of the skin cancer makes it obvious mainly for the medical experts and it is the high time to warn the endangered laymen. There is a great quantity of the contemporary "photopathological" knowledge but there is still a long way to go. This short synopsis of the very last publications intends to renew the ultraviolet comprehension of the medical professionals in order to share it with their patients.

Humans↗
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

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↗
PubMed2001

Electrochemical behavior and voltammetric determination of the herbicide metribuzin at mercury electrodes.

The electrochemical behavior of the herbicide metribuzin (4-amino-6-tert-butyl-4,5-dihydro-3-methylthio-1,2,4-triazin-5-one) at mercury electrodes was studied in aqueous solutions by direct current (DC) and tast polarography, differential pulse (DPV) and cyclic voltammetry (CV), and controlled-potential coulometry. The electrolysis products were separated and identified by chromatographic techniques combined with mass spectrometric detection. The reduction process in acid media includes two irreversible steps. In the first four-electron step the N-NH2 and the 1,6-azomethine bonds are reduced. The second step leads to the formation of 5-tert-butyl-2,3,4,5-tetrahydroimidazol-4-one at the mercury-pool electrode. The first reduction step combined with adsorptive accumulation of the herbicide molecule at the mercury electrode surface was used for its determination by differential pulse adsorptive stripping voltammetry (DPAdSV). Calibration curves were linear in the range 1-30 microg L(-1) with a detection limit of 0.27 microg L(-1) (1 nmol L(-1)) under the conditions used (buffer pH 4.5, Eacc = -0.45 V relative to Ag/AgCl and tacc = 10 s). Preconcentration on solid-phase extraction columns (SPE-phenyl) was used for the determination of very small amounts of metribuzin in river water samples. Recovery was approximately 97%. The reproducibility of the analytical procedure including SPE treatment and DPV determination was expressed as relative standard deviations of 2.53 and 3.66% for 2 and 6 microg L(-1) metribuzin, respectively.

Chromatography, High Pressure Liquid↗
PubMed2001

[The epidermal permeability barrier and its function in immune reactions].

Epidermal barrier represents one of the essential conditions of life on Earth. However, our present understanding of its function is still insufficient. The role of water incorporated in stratum corneum has not been yet studied enough. Till recently, both the stratum corneum et granulosum were considered to be "dead" layers. It turned out that these layers form very active part of epidermis and they have a secretory function. Their rigid anhydrotic consistency, complex intercellular spaces, and lipid bilayers produced by lamellar bodies form the defense barrier against both the loss of fluids and ions and protecting against the hostile external environment. Important stabilizing function in the barrier has ceramides and urea. The Langerhans' dendritic cells and macrophages induce production of cytokines in keratinocytes by means of calcium signals. That triggers the inflammatory cascade, which is accompanied by formation of pathological types of T-cells and by activation of apoptosis. Last but not least, the impairment of epidermal barrier has an important role in the physiological aging of the skin.

Aging↗
PubMed2000

Determination of dissociation constants of cytokinins by capillary zone electrophoresis.

A method for the pKa determination, based on mobility data measured by capillary zone electrophoresis, was applied to cytokinins and their analogs. The combination of charged mobility standards with an uncharged electroosmosis marker, injected in the uncoated capillary simultaneously with the measured substances, allows one to minimize the number of runs, reduce their duration and, in addition, to inform on the run-to-run stability of electroosmosis and on contingent side-effects. pKa values of investigated cytokinins and their analogs ranged from 2.8 to 4.0 at 25 degrees C in the phosphate and acetate buffers of ionic strength 0.015 M. Standard deviations of the constants, obtained by the non-linear fitting of equations for the pKa calculation, were 3-5-times lower than standard deviations from the linear fitting or from the point-to-point calculation utilizing the Hendersson-Haselbalch equation. The equation of Boltzman sigmoid offers two checks on reliability of effective mobilities that serve as the raw data in the pKa calculation.

Cytokinins↗
PubMed2000

Determination of phenols using simultaneous steam distillation-extraction.

Simultaneous distillation-extraction was proposed as a preconcentration step for the determination of phenol and its derivatives in aqueous and soil samples. Detection limits of 0.01 mg l(-1) (water) and 0.1 mg kg(-1) (soil) were achieved by gas chromatography-flame ionization detection. The described preconcentration procedure was applied for the primary study of the adsorption equilibrium in a water-soil system serving as a model of phenol behaviors in the environment.

Chromatography, Gas↗
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

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↗
PubMed1997

Determination of purine nucleoside phosphorylase activity in human erythrocytes by capillary electrophoresis.

Purine nucleoside phosphorylase (EC 2.4.2.1) activity in human erythrocytes was measured using capillary electrophoresis. Enzyme samples were directly loaded into the capillary without preconcentration or purification. The electrophoretic separations were carried out in an uncoated fused-silica capillary (75 microm internal diameter, effective length of 45 cm, total 72 cm) at an electric field of 415 V/cm at ambient temperature (25 degrees C). UV detection at 200 nm was used. Borate buffer (100 mmol/l, pH 9.5) was used as background electrolyte. The results obtained by CE compared favourably (r=0.989) with those of standard HPLC methods. The method presented is reliable, slightly faster and less expensive than the routinely performed HPLC method.

Electrophoresis, Capillary↗
PubMed1997

[Apoptosis in the morphology of Lyme borreliosis].

BACKGROUND: Morphological, mainly ultrastructural changes in borreliosis has been the matter of contemporary interest indeed and it seems to be more and more clear that they are the product of an immunologic reaction. The aim of this study is to find out the epidermal changes of erythema migrans and acrodermatitis chronica on the ultrastructural level. METHODS AND RESULTS: There were 14 cases of erythema migrans and 5 acrodermatitis examined and many apoptotic keratinocytes, but also Langerhans cells and melanocytes were the dominant findings. Considering the very short time needed for apoptosis there is a good reason to take our findings as an important component of the borreliosis pathogenesis. CONCLUSIONS: The presence of many apoptotic cells in Lyme disease epidermis emphasises the importance of the immunology in the borreliosis pathogenesis. The striking number of apoptotic melanocytes suggests the higher affinity of the borrelia to the neuroectodermal tissue.

Apoptosis↗
PubMed1996

[Is the sun our friend?].

Since the beginning of the 19th century the scientific knowledge concerning the effect of the sun rays upon the human organism, mainly on the skin, has been studied and the components of the sun spectrum were specified. During the last years the ozone layer was seriously damaged due to the so called civilization and the very harmful UVC component of the spectrum has entered the earth atmosphere. The accumulation of the unhealthy human habits and the new sun aggression threaten the human skin. The result is the growing number of the skin cancer, incl. melanoma of young people. The whole world dermatologists common opinion is that only the proper knowledge of this sun danger and the daily behaviour change combined with adequate dress and reliable sunscreen are able to prevent the serious damage in not very distant future.

Humans↗
PubMed1996

[Langerhans cells and cutaneous immune reactions].

The epidermis is a metabolically highly active organ where in addition to other substances important cytokines are formed which play a key role in many physiological and pathophysiological reactions. They are produced in the epidermis but influence not only keratinocytes but also other epidermal cells among which for immune reactions the Langerhans cells are most important. The complexity of immune reactions anywhere in the organism greatly hampers research of this vitally important important function. The best experimental model is, however, allergic contact eczema and irritant reactions. Experimental investigations of both provide and certainly will provide findings which will clarify in an important way immune cascades of all types and thus will have a substantial impact on knowledge of the pathogenesis and will make possible quite new approaches to treatment not only of allergic diseases but also viral diseases, and last not least, also new approaches to the treatment of malignant tumours. The authors make the reader familiar with the most recent findings, their own and published ones, from the sphere of immune dermal skin reactions in conjunction with the cells of Langerhans and cytokines.

Animals↗
PubMed1995

[Langerhans dendritic cells in atopic dermatitis: present status of knowledge].

There are still many "white spots" on the ethiopathogenetic map of atopic dermatitis. Are there is also no doubt that the contemporary ecological horror upregulates the number of atopic patients. This review article demonstrates some up-to-date highlights of atopic dermatitis research concerning mainly the Langerhans antigen-presenting cell part.

Dermatitis, Atopic↗
PubMed1994

Comparative sensitivity of the immunoelectronmicroscopy test and ELISA with intact virions in detecting HPV-1 antibodies and age distribution of these antibodies among general population and in children's homes.

A high degree of concordance between the results of immunoelectronmicroscopy and ELISA tests with purified human papillomavirus (HPV-1) particles was observed. The prevalence of HPV-1 antibodies in children living in children's homes was higher than in the general population.

Adolescent↗