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Biomedical subjects

J Bohácek

Publications and source records attributed to J Bohácek.

At least 19 recordsLinked to original sources
PubMed2003

Oxidation behavior of Ru/TiO2 and metallic Ru fine particles on heating in air.

Thermogravimetry (TG) and differential thermal analysis (DTA) were used to investigate the oxidation behavior of Ru/TiO2 and metallic Ru fine particles during heating in air in the range 20-1000 degrees C. Temperature ranges of the oxidation for two samples of Ru/TiO2 with the compositions (92 wt% Ru, 8 wt% TiO2) and (75 wt% Ru, 25 wt% TiO2) and for pure metallic Ru fine particle agglomerates were determined. It was assumed that after the partial oxidation of Ru in the sample containing 75 wt% Ru and 25 wt% TiO2 and in the pure metallic Ru a diffusion barrier was formed, preventing further oxidation of Ru in Ru/RuO2 and Ru/RuO2/TiO2 matrices. XRD and TEM were used for the sample characterization.

Journal Article↗
PubMed2001

The interaction of Prussian blue and dissolved hexacyanoferrate ions with goethite (alpha-FeOOH) studied to assess the chemical stability and physical mobility of Prussian blue in soils.

Colloidal Prussian blue and dissolved hexacyanoferrate ions strongly interact with the surface of goethite (alpha-FeOOH) particles. Whereas Prussian blue is deposited on the surface of goethite as a solid phase with all the properties typical of solid Prussian blue, the hexacyanoferrate ions form initially a layer of surface bound hexacyanoferrate ions, which exhibit properties intermediate between those of free hexacyanoferrate ions and hexacyanoferrate ions bound in Prussian blue. The products of interaction of goethite with Prussian blue and hexacyanoferrate ions were studied by voltammetry of immobilized microcrystals, infrared spectrometry, Vis diffuse reflection spectrometry, transmission electron microscopy, and ESR spectroscopy. The kinetics of Prussian blue destruction was measured by solution Vis spectrometry and also by voltammetry of solid microcrystals. The remarkable stability of Prussian blue in soils can be explained by its strong adherence as a solid phase to iron oxides and oxide hydroxides in soils. This prevents the formation of soluble colloids of Prussian blue. It does not prevent the hydrolysis of Prussian blue to iron oxide hydroxides and hexacyanoferrate(II) ions at elevated pH which proceeds at almost the same rate as that of pure Prussian blue colloid. Even when this hydrolysis of Prussian blue occurs, it is the hexacyanoferrate(II) that is effectively adsorbed on the surface of iron oxide hydroxides, again decreasing the physical mobility of hexacyanoferrate.

Adsorption↗
PubMed1995

Enhancement by carboxymethylglucan of early cellular damage in 1 Gy-irradiated mice.

Our results describe a novel carboxymethylglucan (CMG) activity, namely its radiosensitizing effect on early cellular damage in mice gamma-irradiated with a dose of 1 Gy. An increase of thymidine levels in blood plasma, determined 4 h after irradiation, was used as an indicator of the early cell death. The radiosensitizing effect was observed when administering CMG at time intervals close to irradiation time (1 h before to 1 h after irradiation). Diclofenac (an inhibitor of prostaglandin production) had no modifying effects on elevation of plasma thymidine levels induced by radiation or radiation + CMG. Pentoxifylline (an inhibitor of synthesis of tumour necrosis factor and of phosphodiesterase) administration elevated plasma thymidine to similar levels as CMG alone, combined pentoxifylline + CMG treatment had not additive effects.

Animals↗
PubMed1993

Postirradiation administration of adenosine monophosphate combined with dipyridamole reduces early cellular damage in mice.

The administration of dipyridamole and adenosine 5'-monophosphate (AMP) to mice 5 to 25 min after 1 Gy of total-body gamma irradiation was found to decrease cellular damage, as indicated by the thymidine level in plasma and the amount of saline soluble polynucleotides in the thymus. The drug combination used did not influence similar cytotoxic effects of hydrocortisone. Furthermore, it was shown that the addition of dipyridamole and AMP to in vitro irradiated suspensions of thymocytes enhanced the rejoining processes of DNA strand breaks. Receptor-mediated action of extracellular adenosine may be responsible for the therapeutic effects observed.

Adenosine Monophosphate↗
PubMed1992

Protection of early cellular damage in 1 Gy-irradiated mice by the elevation of extracellular adenosine.

In whole-body 1Gy-irradiated mice a modification of early cellular damage by means of preirradiation dipyridamole and adenosine monophosphate (AMP) treatment was investigated. Both drugs were given either alone or in combination, AMP being administered i.p. at doses of 5, 10 and 15 mg, dipyridamole s.c. at the dose of 2 mg, 20 min before AMP. The thymidine level in plasma and the amount of free polynucleotides in the thymus and spleen, both estimated at the interval of 4 h after irradiation, were used as indices of early cellular damage in vivo. The elevated level of thymidine observed in the plasma of irradiated controls decreased significantly after the administration of AMP (5 mg) alone to 71%, after the combination of dipyridamole and AMP a still deeper significant fall to 60% was observed. Such a protective effect was observed when injecting AMP 15 min before irradiation. Using the interval of 65 min between AMP administration and irradiation, no protection was detected. The higher doses of AMP (10, 15 mg) enhanced the protective effect manifested in plasma thymidine level only moderately. The amount of free polynucleotides, elevated in the thymus and spleen of irradiated mice, was significantly decreased in the thymus of mice pretreated with the combination of dipyridamole and AMP. The results suggest that the treatment used decreases the radiation damage of the sensitive thymocyte population. It is proposed that the joint use of AMP, an adenosine prodrug, and dipyridamole, a drug inhibiting adenosine uptake by cells, leads to an elevation in extracellular adenosine which activates cell surface adenosine receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine↗
PubMed1991

The effect of cyclophosphamide and gamma irradiation on adenosine deaminase and purine nucleoside phosphorylase in mice.

Changes in ADA and PNP activities in the spleens and thymuses of mice were studied after a single administration of cyclophosphamide (CY, 200 mg/kg) and after whole-body gamma irradiation (5.5 Gy), applied alone or three days after CY application. In the first days after the treatment the enzyme activities were significantly depressed (p less than 0.01) with the exception of ADA in the spleen, where a high elevation (220-380%) in relation to controls was observed. During the regeneration period a pronounced rise of PNP activity in the spleen occurred mainly after a combined application of CY and irradiation (270%). In the thymus the regeneration was manifested by a mild increase of both ADA and PNP activities towards control values. The findings suggest that the expressive changes of ADA and PNP activities, participating in the purine salvage pathway, may, after a cytotoxic treatment, influence the nucleotide pool and DNA synthesis in lymphoid organs.

Adenosine Deaminase↗
PubMed1989

Purine metabolizing enzyme activities in radiosensitive tissues of mice after sublethal whole-body irradiation.

The activities of adenosine deaminase (ADA) and purine nucleoside phosphorylase (PNP) were determined between days 1-14 in the spleen, thymus and femoral bone marrow of mice subjected to whole-body gama irradiation with a dose of 5.5 Gy. In control animals, the highest activity of ADA (as related to 10(6) cells) was recorded in the thymus (58.9 pmol.s-1), the lowest one in the femur (34.8 pmol.s-1), the PNP activity was the lowest in the thymus (14.5 pmol.s-1) and the highest in the femur (96.0 pmol.s-1). In the spleen, an elevation of ADA activity (up to 379%) was observed during the first postirradiation days; PNP activity was reduced (to 58%) on postirradiation day 3, followed by the return and even elevation on day 14 (265%). In the thymus, a parallel reduction of the activities of both enzymes appeared during the first postirradiation days, with a subsequent increase during the regeneration phase. In the femoral bone marrow, ADA and PNP activities were increased on postirradiation day 1 (275% and 201%, respectively). Reference is made to the possible relationship between the observed characteristic changes in activities and the degree of damage and/or renewal of cell population in the hemopoietic tissues after irradiation.

Adenosine Deaminase↗
PubMed1988

Determination of adenosine deaminase and purine nucleoside phosphorylase activities using high-performance liquid chromatographic and radiochromatographic methods.

Two methods for the determination of adenosine deaminase and purine nucleoside phosphorylase activities were compared. The high-performance liquid chromatographic (HPLC) technique used separation on a reversed-phase silica column and exhibited adequate sensitivity and a markedly higher rate of analysis compared with that of the paper radiochromatographic method. Correlation analysis of the results obtained by the two methods on a set of lymphoid cells from 25 patients with lympho-proliferative disorders confirmed the utility of the HPLC technique in clinical investigations.

Adenosine Deaminase↗
PubMed1986

The effect of hypoxia on the activity of purine nucleoside phosphorylase in rats.

The activity of purine nucleoside phosphorylase (PNP) in rat erythrocytes fractionated by centrifugation in microhematocrit capillaries was studied. After seven-day hypoxia (54 kPa) the PNP activity was increased by 67 +/- 4% (S.E.M.) in the lightest fraction of erythrocytes; on the fifth day after hypoxia PNP activity did not differ from control values.

Animals↗
PubMed1976

Actinobacilli in domestic fowl.

Reports on haemolytic rods from salpingitis in hens and from organs of died chicks may be found since the year 1950 (Kjos-Hanssen). Correct systematic classification on these microorganisms is still lacked because not all relations to the nearest pasteurellae were known as well as the clear differences in the Pasteurella-Actinobacillus group. The authors have isolated 34 suspected strains from 14 localities; 25 strains were from salpingitis or internal organs of died fowl inclusively chicks, and 9 strains from choanas of pullets clinically healthy. Bacteriological, serological, chemical and biological tests gave the results as follows: 1) All strains exhibit fundamental properties of Pasteurella-Actinobacillus group, and moreover, they show ability to grow on MacConkey agar with crystal violet (BioQuest) being a significant feature of the genus Actinobaccillus (Mráz, 1975). 2) From the nearest species Actinobacillus haemolyticus (Newsom and Cross, 1932) Mráz, 1969, they differ with expressive haemolysis on agar with sheep blood, single haemolytic zone on agar with lamb blood according to Smith (1962), structure of somatic antigen, with natural hosts (gallinaceous birds) and pathogenicity for 5-day-old chicks. The GC content in DNA was determined in the range 39,6-42,9% (mean value 41,5%). 3) The first who presumed an independent state of these microorganisms, was Kohlert (1968), from the work of which the epithet for correct name, i.e. Actinobacillus salpingitidis (Kohlert, 1968) comb. nov., was accepted.

Actinobacillus↗