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Biomedical subjects

R Vytásek

Publications and source records attributed to R Vytásek.

11 recordsLinked to original sources
PubMed2006

The effect of plant cytokinin hormones on the production of ethylene, nitric oxide, and protein nitrotyrosine in ageing tobacco leaves.

Transgenic plants with genetically increased or decreased levels of cytokinins were used to investigate the effect of cytokinin level on the production of ethylene, a plant hormone with suggested role in senescence, and the production of nitric oxide, potentially important signalling and regulatory molecule. The production of these gases was followed during the course of leaf development and senescence. The production of ethylene and nitric oxide is under genetic control of genes other than those involved in regulation of senescence. The difference in basic ethylene and NO levels in different tobacco cultivars was higher than their changes in senescence. The results of this study did not indicate a direct link between ethylene production and cytokinin levels. However, there was a decreased production of NO in senescent leaves. Low cytokinins level was associated with increased NO production during leaf development. Protein nitrotyrosine proved to be a better indicator of the reactive nitrogen species than measuring of the NO production. Higher nitrotyrosine concentrations were found in insoluble proteins than in the soluble ones, pointing to membrane proteins as the primary targets of the reactive nitrogen species. In plants with elevated cytokinin levels the content of nitrated proteins decreased both in soluble and insoluble fractions. This finding indicates an antioxidative function of cytokinins against reactive nitrogen species.

Cytokinins↗
PubMed2005

Erythrocyte membranes inhibit respiratory burst and protein nitration during phagocytosis by macrophages.

Phagocytosis is associated with respiratory burst producing reactive oxygen and nitrogen species. Several studies imply that erythrocytes can inhibit the respiratory burst during erythrophagocytosis. In this work we studied the mechanisms of this effect using control and in vitro peroxidized erythrocyte membranes. We demonstrated that autofluorescence of peroxidation products can be used for visualization of phagocytozed membranes by fluorescence microscopy. We also found that respiratory burst induced by a phorbol ester was inhibited by control membranes (5 mg/ml) to 63 % (P < 0.001), and to 40 % by peroxidized membranes (P < 0.001). We proved that this effect is not caused by the direct interaction of membranes with free radicals or by the interference with luminol chemiluminescence used for the detection of respiratory burst. There are indications of the inhibitory effects of iron ions and free radical products. Macrophages containing ingested erythrocyte membranes do not contain protein-bound nitrotyrosine. These observations imply a specific mechanism of erythrocyte phagocytosis.

Animals↗
PubMed2004

Hyperoxia attenuated nitrotyrosine concentration in the lung tissue of rats with experimental pneumonia.

Although nitrated proteins have been repeatedly used as markers of lung injury, little is known about their formation and metabolism under hyperoxia. We therefore measured 3-nitrotyrosine (3NTYR) concentrations in lung tissue and serum of rats with carrageenan-induced pneumonia exposed to hyperoxia. Twenty-nine Wistar male rats were assigned to one of 4 groups. Two experimental groups were treated by intratracheal application of carrageenan (0.5 ml of 0.7 % solution) and then one was exposed to hyperoxia for 7 days (FIO2 0.8), the other to air. Rats of two control groups breathed either hyperoxic gas mixture or air for 7 days. At the end of exposure the ventilation was determined in anesthetized, intubated animals in which 3NTYR concentrations were measured in the lung tissue and nitrites and nitrates (NOx) were estimated in the serum. Carrageenan instillation increased 3NTYR concentrations in lung tissue (carrageenan-normoxic group 147+/-7 pmol/g protein, control 90+/-10 pmol/g protein) and NOx concentration in the serum (carrageenan-normoxic group 126+/-13 ppb, control 78+/-9 ppb). Hyperoxia had no effect on lung tissue 3NTYR concentration in controls (control-hyperoxic 100+/-14 pmol/g protein) but blocked the increase of lung tissue 3NTYR in carrageenan-treated rats (carrageenan-hyperoxic 82+/-13 pmol/g protein), increased NOx in serum (control-hyperoxic 127+/-19 ppb) and decreased serum concentration of 3NTYR in both hyperoxic groups (carrageenan-hyperoxic 51+/-5 pmol/g protein, control-hyperoxic 67+/-7 pmol/g protein, carrageenan-normoxic 82+/-9 pmol/g protein, control 91+/-7 pmol/g protein). The results suggest that hyperoxia affects nitration of tyrosine residues, probably by increasing 3NTYR degradation.

Animals↗
PubMed2001

Serum cartilage oligomeric matrix protein reflects the presence of clinically diagnosed synovitis in patients with knee osteoarthritis.

OBJECTIVE: Cartilage oligomeric matrix protein (COMP) is a component of articular cartilage whose serum levels show a strong correlation with radiographic osteoarthritis (OA) status. It has recently been found, however, that COMP is also produced in synovium. To assess the hypothesis that synovitis affects serum COMP levels in patients with knee OA, we collected sera for COMP simultaneous with a clinical examination for synovitis. DESIGN: Sera were collected from OA patients who fulfilled the American College of Rheumatology criteria for knee OA. Radiographs were classified according to the grading system of Kellgren and Lawrence. Synovitis was diagnosed clinically by joint tenderness plus swelling and/or increased warmth over the joint. COMP levels in sera were measured by inhibition ELISA with monoclonal antibody (mAb) 17-C10. RESULTS: Serum COMP levels were significantly correlated with age, synovitis and an interaction of synovitis and OA severity. Synovitis showed the strongest effect on COMP levels (R=0.1587, P< 0.01), in contrast to C-reactive protein, duration of OA and OA severity score which showed no significant effect on COMP levels. Individual signs of synovitis, namely, joint tenderness and warmth had a significant effect on serum COMP levels while swelling alone did not. CONCLUSION: Synovitis exerts a significant effect on serum COMP levels measured with mAb 17-C10 in OA patients. These findings underscore the importance of the clinical joint examination to assess for synovitis, when attempting to apply objective measures, such as COMP, to the clinical setting.

Adult↗
PubMed2000

A possible role of the oxidant tissue injury in the development of hypoxic pulmonary hypertension.

Chronic sojourn in hypoxic environment results in the structural remodeling of peripheral pulmonary arteries and pulmonary hypertension. We hypothesize that the pathogenesis of changes in pulmonary vascular structure is related to the increase of radical production induced by lung tissue hypoxia. Hypoxia primes alveolar macrophages to produce more hydrogen peroxide. Furthermore, the increased release of oxygen radicals by other hypoxic lung cells cannot be excluded. Several recent reports demonstrate the oxidant damage of lungs exposed to chronic hypoxia. The production of nitric oxide is high in animals with hypoxic pulmonary hypertension and the serum concentration of nitrotyrosine (radical product of nitric oxide and superoxide interaction) is also increased in chronically hypoxic rats. Antioxidants were shown to be effective in the prevention of hypoxia induced pulmonary hypertension. We suppose that the mechanism by which the radicals stimulate of the vascular remodeling is due to their effect on the metabolism of vascular wall matrix proteins. Non-enzymatic protein alterations and/or activation of collagenolytic matrix metalloproteinases may also participate. The presence of low-molecular weight cleavage products of matrix proteins stimulates the mesenchymal proliferation in the wall of distal pulmonary arteries. Thickened and less compliant peripheral pulmonary vasculature is then more resistant to the blood flow and the hypoxic pulmonary hypertension is developed.

Animals↗
PubMed1995

Age-dependent changes in proteoglycan biosynthesis in human intervertebral discs.

Proteoglycans from annulus fibrosus and nucleus pulposus of human intervertebral disc were investigated by electrophoresis in a composite agarose-polyacrylamide gel and immunohistochemically using various monoclonal antibodies against components of extracellular matrix. There were at least five different populations of proteoglycans in both annulus fibrosus and nucleus pulposus. Proteoglycans represented by individual electrophoretic bands differed from each other in hydrodynamic size but all of them contained epitopes present in keratan sulphate. Chondroitin sulphate could be detected in populations with molecular weight above 200,000 daltons. We could postulate that the cleavage of proteoglycan chains starts at the C-terminal end. This is supported by the finding that the globular region G2 on the protein core was detected in the same populations as keratan sulphate. We could confirm these results using tissue cultures of nucleus pulposus, inner and external part of annulus fibrosus. Of interest is the finding that there is de novo synthesis of globular domain G1 only in structures of intervertebral disc from a 16-year-old male and not in the tissue of a 69-year-old male. This might contribute to an explanation of decreased aggregation of proteoglycans during the aging process.

Adolescent↗
PubMed1992

Electrostatic interaction influences cell adhesion?

The effect of electrostatic forces on the adhesion of LEP-19 diploid embryonal fibroblasts, Hep-2 laryngeal carcinoma cells, Raji lymphoblastoma cells and Sp 2/0 myeloma cells was examined in vitro. Adhesivity of all tested cell lines was higher on the cationized glass than on untreated or anionized glass. The negatively charged sialic acids on the cell surface play a role in cell adhesion. The participation of electrostatic interaction is independent of the energy metabolism in serum-free conditions.

Anions↗
PubMed1988

A new cell line, GS, derived from a human renal cell carcinoma.

A new cell line, GS, of human renal cell carcinoma was established and characterized. It was derived from a metastasis of a human renal cell carcinoma, which appeared 6 years after nephrectomy. The GS cells exhibit basic characteristics of renal cell carcinoma: epithelial cell character, PAS and glycogen positivity, typical ultrastructural features. The cells have a pseudotriploid stemline with a modal number of 75 chromosomes and two marker chromosomes. GS cells formed neither colonies in soft agar nor transplantable tumours in nude mice but produced a factor(s) stimulating growth and colony forming activity of indicator cells.

Aged↗
PubMedDate not supplied

Redox regulation of proliferation of lens epithelial cells in culture.

Both oxidants and antioxidants have been shown to modulate cell proliferation. We studied the effects of hydrogen peroxide and two antioxidants on the rate of proliferation of lens epithelial cells in culture. Hydrogen peroxide at concentrations higher than 32 microM caused a significant inhibition of proliferation. However, in the concentration range of 0.01-0.5 microM, hydrogen peroxide stimulated the rate of proliferation. The effect of hydrogen peroxide was dependent on the amount of cells in an individual culture well, indicating decomposition of hydrogen peroxide by cellular enzymes. In order to eliminate the possibility of decomposition of the dose of hydrogen peroxide given as a bolus, we induced continual production of hydrogen peroxide by adding glucose oxidase to the incubation medium. We found that hydrogen peroxide, generated by 1-50 microU x ml(-1) of glucose oxidase significantly increased the rate of cell proliferation. This effect was most apparent at the beginning of the exponential phase of cellular growth. Glucose oxidase alone (100-500 microU x ml(-1)) did not produce any effect. The effects of pro-oxidative hydrogen peroxide were compared with the effects of two biologically important antioxidants, alpha-tocopherol and retinol. Both antioxidants completely inhibited proliferation at concentrations of 30 microM and higher. In contrast to retinol, the effect of alpha-tocopherol was dependent on the amount of cells, indicating cellular decomposition of alpha-tocopherol. The results document the possibility of redox regulation of cellular proliferation at physiologically relevant reactant concentrations.

Anilides↗