Martin Beranek

Epidemiology of Helicobacter pylori Infection in the Czech Republic

Background:  Prevalence of Helicobacter pylori infection has been estimated to range from 60 to 95% in the former communist countries of Central and Eastern Europe. The aim of this study was to evaluate H. pylori infection prevalence in a representative sample of the Czech population. The second objective was to describe difference of H. pylori prevalence between different social groups of children and adults.

Inhibitory effect of glycation on catalytic activity of alanine aminotransferase

Non-enzymatic glycation is a common post-translational modification of tissue and plasma proteins which can impair their functions in living organisms. In this study, the authors have demonstrated for the first time an inhibitory effect of in vitro glycation on the catalytic activity of alanine aminotransferase (ALT, EC 2.6.1.2), a pyridoxal phosphate enzyme with several lysine residues in the molecule. The porcine heart enzyme was incubated with 50 mmol/l D-fructose, D-glucose, D,L-glyceraldehyde, or D-ribose in 0.1 mol/l phosphate buffer (pH 7.4) at 25°C for up to 20 days. The strongest glycation effect was shown by D,L-glyceraldehyde, which caused complete enzyme inhibition within 6 days. After 20 days of incubation, the ALT activity in samples with D-fructose and D-ribose was less than 7% of the initial enzyme activity. A statistically significant effect of D-glucose on the enzymatic activity of ALT was not found. Incubation of ALT with D-fructose, D,L-glyceraldehyde and D-ribose minimized its catalytic activity both in the glycated and non-glycated fractions of the samples. Markedly higher activity was found in the glycated fraction with glucose. The inhibitory effect of glycation of ALT with D-fructose and D-ribose was found to be more intensive in the presence of L-alanine and weaker in the presence of 2-oxoglutarate. The findings suggest that glycation of the e-amino group of Lys313 as a crucial part of the catalytic site of ALT may contribute to ALT inactivation in the presence of glycating sugars. Nevertheless, glycation of lysine residues outside the active center of ALT seems to be primary.

Steady-state of azathioprine during initiation treatment of pediatric inflammatory bowel disease

BACKGROUND AND AIM Azathioprine (AZA) has a slow onset of action in treatment of pediatric inflammatory bowel disease (IBD). It is anticipated, that this delay correlates to the kinetics of 6-thioguanine nucleotides (6-TGN) accumulation. The aim of this study was to evaluate the time to steady state of 6-TGN concentration in red blood cells. METHODS The inclusion criteria were: a) age 0-19 years b) IBD diagnosis c) AZA treatment initiation. High performance liquid chromatography was used for the 6-TGN analysis. Concentrations of metabolites were studied in weeks 0, 1, 2, 5, and 8 after beginning of treatment. RESULTS The inclusion criteria were matched to 18 patients with IBD. The median time to steady state of 6-TGN was 55.3 days. The mean 6-TGN concentration at the steady state achieved 326 (SD 154) pmol/8.108 erythrocytes. High erythrocyte TPMT activity corresponds to the low steady state 6-TGN concentration and vice versa. This correlation reached statistical significance (p<0.01) for the dose expressed in mg per square meter of body surface area. CONCLUSION The time to steady state of 6-TGN erythrocyte concentration is significantly shorter than would expected according to clinical observation describe earlier.

LUNAR DUST GRAIN CHARGING BY ELECTRON IMPACT: DEPENDENCE OF THE SURFACE POTENTIAL ON THE GRAIN SIZE

The secondary electron emission is believed to play an important role for the dust charging at and close to the lunar surface. However, our knowledge of emission properties of the dust results from model calculations and rather rare laboratory investigations. The present paper reports laboratory measurements of the surface potential on Lunar Highlands Type regolith simulants with sizes between 0.3 and 3 μm in an electron beam with energy below 700 eV. This investigation is focused on a low-energy part, i.e., ≤100 eV. We found that the equilibrium surface potential of this simulant does not depend on the grain size in our ranges of grain dimensions and the beam energies, however, it is a function of the primary electron beam energy. The measurements are confirmed by the results of the simulation model of the secondary emission from the spherical samples. Finally, we compare our results with those obtained in laboratory experiments as well as those inferred from in situ observations.

Dopamine 2 receptor expression in various pathological types of clinically non-functioning pituitary adenomas

Clinically non-functioning pituitary adenomas account for about one-third of pituitary tumors. The majority of them are pathologically classified as gonadotropinomas or null-cell adenomas without hormonal expression. The rest represent silent corticotroph adenomas and plurihormonal tumors. Conservative therapy with dopamine agonists is effective in some cases only depending on the expression of dopamine 2 receptors (D2R). The aim of this study was to quantitatively estimate D2R expression in clinically non-functioning pituitary adenomas and correlate the results with adenoma type according to pathological classification. Out of the 87 adenomas investigated, 63 expressed gonadotropins, 7 were silent corticotroph adenomas, 7 were plurihormonal tumors, and only 6 did not express any pituitary hormone on immunohistochemical investigation. With the use of the reverse transcriptase PCR technique, D2R mRNA was expressed in all adenomas with very heterogeneous quantity. The expression was very low in corticotroph adenomas (relative median quantity after normalization to housekeeping gene 0.01) and lower in plurihormonal tumors (median 0.4) than in gonadotroph (median 1.3) and null-cell adenomas (median 1.9). The difference between corticotroph adenomas and plurihormonal tumors in comparison with other pathological types was statistically significant. The expression of D2R did not depend on the presence or absence of gonadotropins. We conclude that D2R expression is very low in corticotroph adenomas and significantly lower in plurihormonal tumors. The positivity of gonadotropins does not predict the D2R quantity.

Secondary Emission From Glass Grains: Comparison of the Model and Experiment

The surface potential of dust grains immersed in surrounding plasma results from the balance of many charging processes such as photoemission, electron/ion attachments, and secondary and field emissions. Since hot electrons are often present in space as well as laboratory plasmas, the understanding of the secondary electron (SE) emission process for small dust grains is of great interest because their size effects modify well-known characteristics of large samples. This paper compares the measured surface potential of SiO2 spherical dust grains with the results of the Monte Carlo model of secondary emission developed for metallic samples. It was found that 1) the model can be used for description of the secondary emission process from cosmic dust, 2) the backscattering of primary beam electrons is the most important factor for the charging of small grains, and 3) the actual value of the surface grain potential is given by the energy spectrum of SEs

A Relationship between K-ras Gene Mutations and Some Clinical and Histologic Variables in Patients with Primary Colorectal Carcinoma

Abstract Mutations in the Kirsten ras 2 (K-ras) gene were described as early events in the process of colorectal carcinogenesis. The aim of this study was to find a possible relationship between the presence of K-ras mutation in samples of primary colorectal carcinomas and the clinico-pathological data of the investigated patients. Mutation in codon 12 of the K-ras gene was determined in 18 of 53 colorectal carcinomas (34 %) in our group of patients. The presence of K-ras gene mutations was not related to gender, age of subject at diagnosis, staging or cancer location (p > 0.05). Sixteen of the 42 (38 %) moderately differentiated carcinomas, and two of the eight (25 %) well differentiated carcinomas contained K-ras mutation in codon 12, but none of the three poorly differentiated carcinomas contained the mutation. Moderately differentiated tumours contained an aspartate code GAT (in eight cases), a valine code GTT (in six cases), an alanine code GCT (in one case) and a serine code AGT (in one case) in codon 12. Well differentiated tumours contained only the valine code GTT (two cases). Our results show that the frequency of mutations in the K-ras gene in carcinomas in Central Europe is not different from the frequencies found in other parts of the world. The homogeneous incidence of K-ras mutation does not seem to be related to ethnic factors, dietary habits, or the composition of the diet.

SECONDARY EMISSION FROM NON-SPHERICAL DUST GRAINS WITH ROUGH SURFACES: APPLICATION TO LUNAR DUST

Electrons impinging on a target can release secondary electrons and/or they can be scattered out of the target. It is well established that the number of escaping electrons per primary electron depends on the target composition and dimensions, the energy, and incidence angle of the primary electrons, but there are suggestions that the targets shape and surface roughness also influence the secondary emission. We present a further modification of the model of secondary electron emission from dust grains which is applied to non-spherical grains and grains with defined surface roughness. It is shown that the non-spherical grains give rise to a larger secondary electron yield, whereas the surface roughness leads to a decrease in the yield. Moreover, these effects can be distinguished: the shape effect is prominent for high primary energies, whereas the surface roughness predominantly affects the yield at the low-energy range. The calculations use the Lunar Highlands Type NU-LHT-2M simulant as a grain material and the results are compared with previously published laboratory and in situ measurements.

Venous Thromboembolism in Young Female While on Oral Contraceptives: High Frequency of Inherited Thrombophilia and Analysis of Thrombotic Events in 400 Czech Women:

Oral contraceptive use is a common risk factor for venous thromboembolism in women of reproductive age. The presence of inherited thrombophilia further increases this risk. Methods: We analyzed a large group of 400 Czech women with venous thromboembolism in association with oral contraceptive with regard to duration of use at the time of manifestation of venous thromboembolism, the frequency of inherited and acquired thrombophilia, the frequency of eliciting risk factor for thrombosis including immobilization, surgery, administration of plaster cast, long travel, and so on, and the type of thrombosis. The mean age of the women was 26 years, and the average duration of use was 45 months at the onset of thrombosis. Results: Venous thrombosis solely due to the pill occurred in 57% of the women, and in the other 43%, an additional transient eliciting factor was recognized. Among the clinical manifestation, distal thrombosis prevailed (N = 231, 58%) followed by proximal deep vein thrombosis (N = 65, 16%), pulmonary embolism (N = 21, 5%), and thrombosis in unusual sites (N = 20, 5%). Inherited or acquired thrombophilia was diagnosed in 195 (49%) women: factor V Leiden mutation in 35%, congenital deficiency of antithrombin in 1.8%, protein C in 0.8%, protein S in 1%, F IIG20210A in 5%, and antiphospholipid syndrome (APS) in 5.3%. Among the most common risk factors were immobilization of lower limb, minor and major surgery, and trauma. Conclusion: The results confirm that venous thromboembolism is a multifactorial disease in which thrombophilia screening is needed in young symptomatic women on the pill with thrombosis. The results also emphasize the value of proper thromboprophylaxis in women while on oral contraceptive in situations of increased risk for venous thromboembolism.

Dust as a Gas Carrier

Dust in space can collect particles from surrounding plasma and transport them over long distances. Release of the implanted particles can then change the mass composition in a particular place of the space. The depth of ion penetration into the dust body strongly depends on an initial mutual energy and differs with ion species as well as with the grain composition. The same holds for diffusion constant of implanted ions (already neutralized) exiting back to the free space. We have used our measurements of the release of Ar ions implanted into glassy carbon dust grains for determination of the diffusion coefficient. Our calculations provide the limits for the amount of gas that can be dissolved in the grain as well as its release rate. We discuss the influence of the dust sputtering and dust temperature on the aforementioned quantities.