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1
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EN
AMP-deaminase from hen stomach smooth muscle was isolated and physico-chemical properties of the purified enzyme were investigated. The enzyme had an activity optimum at pH 6.5, and poorly deaminated the substrate analogues tested. At optimum pH (6.5), in the absence of regulatory ligands (control conditions), the enzyme manifested hyperbolic substrate-saturation kinetics with half-saturation constant (S0.5) of about 4.5 mM. Additions of adenine nucleotide effectors (ATP, ADP) activated the enzyme strongly at all the concentrations tested, diminishing significantly the value of S0.5 constant. In contrast, the regulatory effect of orthophosphate was variable, and depended on the orthophosphate concentration used. The molecular mass of the enzyme subunit determined in SDS/PAG electrophoresis was about of 37 kDa. The obtained results suggest that in different types of hen muscle, similarly as in humans and rats, expression of AMP-deaminase is under the control of independent genes.
3
Content available remote Aldolase A is present in smooth muscle cell nuclei
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EN
Previously we have shown that aldolase (ALD; EC 4.1.2.13) is present in cardiomyocyte nuclei. Now, we focused our attention on ALD localization in smooth muscle cells. Immunocytochemical methods were used to study the subcellular localization of ALD. Aldolase was localized in the cytoplasm as well as in the nuclei. Within the nuclei ALD was located in the heterochromatin region. Native polyacrylamide gel electrophoresis followed by aldolase activity staining in gel was used to study the ALD isoenzyme pattern in porcine smooth muscle cells. Two ALD isoenzymes, A and C, were found in these cells but in the nuclei only the muscle isoenzyme was detected. To support the nuclear localization of ALD, measurement of aldolase activity in the smooth muscle cell nuclei isolated from porcine stomach was performed. The ALD activity in the isolated nuclei was detectable only after preincubation of the nuclear fraction with Triton X-100 and high concentration of KCl.
EN
The mechanical link coupling cytoskeletal and contractile proteins to the sarcolemma of smooth muscle cells is essential for transmitting tension from the cell's interior to exterior. In addition to the well-characterized actin-integrin associations present in adhaerens junctions, our recent work has postulated the existence of a reversible annexin-dependent membrane-cytoskeleton complex, forged in response to a rise in intracellular Ca2+ concentration following smooth muscle cell stimulation (Babiychuk et al., J. Biol Chem. 1999, 274, 35191-35195). Detailed biochemical characterization of the interactions responsible for the formation of this complex revealed that annexins II and VI interact with actomyosin, or detergent-insoluble glycosphingolipid-enriched membrane domains (rafts) purified from smooth muscle, in a concentration- and Ca2+-dependent manner. Annexin II interacted with lipid rafts with high Ca2+-sensitivity, while for annexin VI this interaction required non-physiologically high concentrations of free Ca2+. However, the Ca2+-sensitivity of the latter interaction strongly increased in the presence of purified smooth muscle actomyosin. The detailed biochemical analysis of the interactions occurring between annexin II, annexin VI, actomyosin and rafts suggests that annexins regulate sarcolemmal organization during smooth muscle cell contraction.
EN
AMP-deaminase from hen stomach smooth muscle was isolated and physico-chemi­cal properties of the purified enzyme were investigated. The enzyme had an activity optimum at pH 6.5, and poorly deaminated the substrate analogues tested. At optimum pH (6.5), in the absence of regulatory ligands (control conditions), the enzyme manifested hyperbolic substrate-saturation kinetics with half-saturation constant GS0.5) of about 4.5 mM. Additions of adenine nucleotide effectors (ATP, ADP) activated the enzyme strongly at all the concentrations tested, diminishing sig­nificantly the value of S0.5 constant. In contrast, the regulatory effect of ortho­phosphate was variable, and depended on the orthophosphate concentration used. The molecular mass of the enzyme subunit determined in SDS/PAG electrophore­sis was about of 37 kDa. The obtained results suggest that in different types of hen muscle, similarly as in humans and rats, expression of AMP-deaminase is under the control of independent genes.
6
Content available remote Sensitivity analysis and material identification for activated smooth muscle
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EN
The paper deals with the problem of material identification for smooth muscle tissue in activated, or passive states. In [1] a composite type mathematical model has been proposed describing the complexity of the tissue reduced to the networks of muscle and collagen fibres. The computational model is based on the total Lagrangian formulation with incompressibility of the bulk material. The problem of inflating vessels is considered in order to allow simulation of real experimental conditions and, thus, to determine constitutive parameters of muscle in active state. These parameters are identified also from hysteresis, or relaxation curves. The direct differentiation, or the adjoint systems techniques are applied to the sensitivity analysis. Results of numerical tests are given.
EN
Heme oxygenase-1 (HO-1), an inducible enzyme degrading heme to biliverdin, iron and carbon monoxide, is involved in regulation of inflammation and angiogenesis. Tin protoporphyrin (SnPPIX) and zinc protoporphyrin (ZnPPIX) are commonly used as competitive inhibitors of HO-1. We aimed to compare the effects of SnPPIX and ZnPPIX on the production of vascular endothelial growth factor (VEGF), activity of in­ducible nitric oxide synthase (iNOS) and cell viability. All experiments were per­formed on rat vascular smooth muscle cells and murine RAW264.7 macrophages treated with 3-10 ,uM protoporphyrins. Some cells were additionally stimulated with IL-1β or with lipopolysaccharide. After a 24 h incubation period SnPPIX and ZnPPIX significantly reduced the generation of VEGF in vascular smooth muscle cells and RAW264.7, both in resting and stimulated cells. The inhibitory potentials of both protoporphyrins on VEGF synthesis were very similar. In contrast, analysis of iNOS activity revealed that results obtained with different HO-1 inhibitors are discrepant.
EN
Several chimeric peptides consisting of the N-terminal fragment of galanin (GAL) and C-terminal fragments of other bioactive peptides (e.g. substance P, bradykinin, neuropeptide Y, mastoparan) have been synthesized and reported as high-affinity galanin receptor antagonists. Recently we have synthesized a new chimeric peptide, GAL(1-13)-[Ala10,11]ET-1(6-21)-NH2, consisting of the N-terminal fragment of GAL and the C-terminal fragment of endothelin-1 (ET-1) analogue. This chimera was previously shown to be a moderate-affinity ligand to hypothalamic galanin receptors with a KD value of 205 nM. However, its biological action has been unknown so far. In our studies we characterized the biological properties of this new chimeric analogue, investigating its action on rat isolated gastric smooth muscles and influence on insulin secretion from rat isolated islets of Langerhans. Data acquired in the course of our studies suggest that analogue GAL(1-13)-[Ala10,11]ET-1(6-21)-NH2 does not seem to be a potent galanin receptor antagonist in the gastrointestinal tract.
10
Content available remote Flavonoids and nitric oxide synthase
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EN
Induction of NOS-2 in macrophages and smooth muscles within vascular wall with concomittant suppression of endothelial NOS-3 activity is considered to be a hallmark of vascular inflammation that triggers atherogenesis. Accordingly, drugs designed to reverse these changes should not only support vaning function of NOS-3 but also suppress proinflammatory NO production by NOS-2. It means that using selective inhibitors of induction of NOS-2 (they spare ex definitione constitutive activity of NOS-3) is a more rational approach than using isselectivel. inhibitors of activity of previously induced NOS-2. First of all, those drugs are never sufficiently selective. In our work we tried to identify inhibitors of NOS-2 induction within the group of flavonoids, known stimulators of NOS-3 with putative antiatherogenic effects. Representatives of four main groups of flavonoids: flavonols (kaempferol, quercetin, rutin), flavones (apigenin, primuletin), flavanols (catechine) and flavanones (hesperetin, hesperidin, naringenin) were tried on NOS-2 induction and activity in the in vitro model of LPS-treated macrophages (cell line J774.2). While none of these compounds inhibited activity of NOS-2, all with unexpectedly scattered potencies inhibited induction of NOS-2 protein in LPS-treated J774.2 cells, as evidenced by Western blotting technique. Subsequently, RT-PCR and Northern blotting methods revealed that so far the most potent compounds, kaempferol and apigenin, at micromolar concentrations did inhibit NOS-2 induction at the level of NOS-2 gene transcription. We conclude that some of flavonoids are potent inhibitors of NOS-2 induction. At the same time they may increase endothelial NOS-3 activity. Could these flavonoids become natural parents of future drugs, which will be used for reversal of inflammatory component of atherothrombosis?
EN
The aim of this study was to investigate whether apamin-sensitive K+ channels play a role in the NO induced relaxation of the human pregnant myometrium. Concentration-response curves for sodium nitroprusside (SNP) (10-9 – 10-4 M) were constructed in the absence and presence of 10-8 M apamin and 10-7 M charybdotoxin (CTX). Preincubation with apamin resulted in a significant attenuation of the relaxation caused by SNP, while pre-treatment with CTX insignificantly decreased the SNP induced relaxation. Our findings suggest that apamin-sensitive K+ channels exist in the human pregnant myometrium and play a role in modulation of the myometrium response to NO donors.
EN
The overall size and shape of the chicken gizzard calponin (CaP) h1 molecule was investigated by dynamic light scattering (DLS) measurements. From the DLS experiments, a z-averaged translational diffusion coefficient is derived (5.75 0.3) 10-7cm2s-1, which corresponds to a hydrodynamic radius of 3.72 nm for calponin. The frictional ratio (1.8 for the unhydrated molecule and 1.5 for the hydrated one) suggests a pronounced anisotropic structure for the molecule. An ellipsoidal model in length 19.4 nm and with a diameter of 2.6 nm used for hydrodynamic calculations was found to reproduce the DLS experimental data. The evaluation of the secondary structure of CaP h1 from the CD spectra by two independent methods has revealed that it contains, on average, 23% helix, 19% beta-strand, 18% beta-turns and loops, and 40% of remainder structures. These values are in good agreement with those predicted from the amino-acid sequence. Predictions used for CaP h1 were applied to other isoforms of known sequences and revealed that all calponins share a common secondary structure. Moreover, the predicted structure of the calponin CH domain is identical to that found by X-ray studies of the spectrin, fimbrin and utrophin CH domains.
EN
Kinetics of the smooth muscle calponin-F-actin interaction was studied by stopped- flow measurements of light scattering and fluorescence intensity of pyrene-labelled F-actin. The intensity and character of the changes in light scattering, and thus the mode of calponin binding to actin filaments leading to changes in their shape and bun­dling, depend on the molar ratio of the two proteins. Parallel measurements of pyrene-fluorescence quenching upon calponin binding revealed that intrinsic conformational changes in actin filaments are delayed relative to the binding process and are not markedly influenced by the mode of calponin binding. Bundling of actin filaments by calponin was not correlated with fluorescence changes and thus with al­terations in the structure of actin filaments.
EN
Prostaglandin E2 (PGE2) can interact with at least four cell surface receptors (EP1-EP4) in smooth muscle, which evokes a variety of intracellular responses depending on the G protein to which the cell surface receptors are coupled. The activation of G protein-coupled receptors and receptor tyrosine kinases can lead to the phosphorylation of tyrosine residues of various cellular proteins. The aim of this study was to examine the role of tyrosine phosphorylation in PGE2, vanadate and carbachol-evoked contractions. PGE2, vanadate, and carbachol induced contractile motor responses in the longitudinal smooth muscle of rabbit duodenum. PGE2-evoked contractions decreased in the presence of genistein or tyrphostin B44. PGE2-evoked contractions increased in the presence of vanadate. Vanadate-evoked contractions decreased in the presence of genistein. In contrast, tyrphostin 47 increased the vanadate-evoked contractions. Vanadate-evoked contractions were reduced in the presence of Ca2+-free solutions, verapamil, or indomethacin. U-73122 decreased PGE2-evoked contractions. Carbachol-evoked contractions decreased in the presence of genistein, tyrphostin B44 or tyrphostin 47. Our results suggest that PGE2, vanadate or carbachol-evoked contractions are mediated by protein tyrosine phosphorylation. Protein tyrosine phosphorylation might cause an increase in calcium influx through voltage-dependent channels and the release of prostaglandins in the longitudinal smooth muscle of the rabbit duodenum.
EN
The research was conducted on 5 inter-breed hybrid sheep, at the age of 10 to 24 months and of the body mass of 30-45 kg, which had bipolar electrodes implanted to uterus horns and shank. The registration of uterus myoelectric activity was performed on sheep 24 and 48 hours after sensitising with Stilboestrol, by the use of Reega Duplex TR XVI electroencephalograph. After recording the output activity, the sheep were applied intravenously in continuous injection: adrenaline – 0,12-0,18 μg ˇ kg-1 ˇ min-1, oxytocin – 0,25-0,4 i.u., propranolol – 1mg ˇ kg-1, isoprenaline – 0,4-1,5 μg ˇ kg-1 ˇ min-1, salbutamole – 0,4-0,8 μg ˇ kg-1 ˇ min-1. The experiment results are presented in the inclosed drawings. The conducted research revealed that the stimulation of beta-adrenergic receptors causes the decrease or inhibition of uterus myoelectric activity of sheep sensitised with Stilboestrol.
EN
Seven highly conserved regions were found in caldesmon molecules from various sources using the multiple sequence alignment method. Their localization coincides with regions where the binding sites to other proteins were postulated. Less conserved and highly divergent regions of the sequences are described as well. These results could refine the planning of caldesmon gene manipulations and accelerate the precise localization of binding sites in the caldesmon molecule and, as a consequence, this could help to elucidate its function in smooth muscle contraction.
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