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Background: So far studies showing the role of the plasmin system in airway remodelling have been conducted using in vitro models. The aim of the present study was to determine plasmin system regulation in an in vivo rat model of asthma. Methods: Asthma in Wistar rats was induced by ovalbumin (OVA) sensitization followed by an OVA challenge (OVA/OVA, n = 6). Control groups were saline-sensitized challenged with OVA (VEH/OVA, n = 6) and OVA-sensitized challenged with saline (OVA/VEH, n = 6). Plasmin system components were determined in the plasma by ELISA. Plasminogen activator inhibitor-1 (PAI-1) was localized by an immunohistochemical reaction. Results: Sensitization and challenge with OVA caused thickening of the airway wall, hypertrophy of smooth muscle cells, infiltration of inflammatory cells, subepithelial fibrosis, epithelial and endothelial lesions.Serum total IgE was significantly higher in OVA-sensitized rats as compared to VEH-sensitized control groups. Tissue plasminogen activator activity was significantly decreased in asthmatic animals (4.48 ± 0.4 vs. 6.7 ± 0.3 ng/ml for OVA/OVA and OVA/VEH; p < 0.05), and PAI-1 activity was statistically significantly higher in asthma rats (0.8 ± 0.05 vs. 0.5 ± 0.03 ng/ml for OVA/OVA vs. OVA/VEH; p < 0.05). α2-Antiplasmin was higher in rats receiving OVA sensitization than in those that were sham sensitized (p < 0.05). Immunohistochemical staining for PAI-1in the lungs of asthmatic animals showed very strong PAI-1 expression in lung inflammatory cells. Conclusions: We have demonstrated for the first time the existence of PAI-1 in lung inflammatory cells of rats with asthma. This finding was consistent with the superiority of plasmin system inhibition over activation in plasma. Copyright © 2008 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

The carburisation of nanocrystalline iron with ethylene has been studied. The carburisation processes were carried out under atmospheric pressure, under the flow of pure ethylene or ethylene-hydrogen mixture at a constant temperature in the range of 310-550 °C. The process was controlled using a spring thermobalance and cathetometer, with the accuracy of 0,1 mg. The phase composition of the samples after carburisation was determined by means of X-ray diffraction (XRD). As a result of the carburisation of nanocrystalline iron with ethylene, the formation of iron carbide Fe3C occurs, followed by the formation of carbon deposits. Under a C2H4/H2 gas mixture, these two reaction steps can be separated, while under pure ethylene the reactions are much faster and the simultaneous formation of iron carbide and carbon deposits is observed. Depending on temperature and on the carburisation degree, various forms of carbon deposits can be observed using TEM: spherical, helicoidal, and nanotubes. The diameter of these carbon forms is below 100 nm. [ABSTRACT FROM AUTHOR]

Ferromagnetic resonance (FMR) and ac conductivity have been applied to study a polymer composite containing as filler a binary mixture of magnetite (Fe3O4) and cementite (Fe3C) nanoparticles (30–50 nm) dispersed in a diamagnetic carbon matrix, which was synthesized by the carburization of nanocrystalline iron. Ac conductivity measurements showed thermally activated behavior involving a range of activation energies and power law frequency dependence at high frequencies similar to conducting polymer composites randomly filled with metal particles. Ferromagnetic resonance measurements revealed a relatively narrow FMR line at high temperatures indicating the presence of ferromagnetic nanoparticles, where thermal fluctuations and interparticle interactions determine the FMR temperature variation. An abrupt change of the FMR spectra was observed at T<81 K (ΔT<=1 K) coinciding with a sharp anomaly resolved in the temperature derivative of the ac conductivity. This behavior is attributed to the Verwey transition of Fe3O4 nanoparticles, where the concurrent skin depth variation unveils the FMR of large magnetite conglomerates and thus allows discriminating their contribution from relatively isolated nanoparticles. [ABSTRACT FROM AUTHOR]

Three powder samples with different content of iron carbide in a carbon matrix have been synthesised by carburisation of nanocrystalline iron with methane. The samples have been characterised by XRD and TEM methods. The mean crystallite size of the obtained iron carbide has been found to be in the range from 41 to 67 nm. The magnetic resonance measurements of these samples have been performed at room temperature. Very intense magnetic resonance lines have been recorded for each of the samples.A resonance field, an integral intensity and a linewidth strongly depend on the concentration of iron carbide. The observed magnetic resonance lines have been fitted with two Lorentzian-shape lines, one centred at lower and the other at higher magnetic fields. Strong magnetic anisotropy was observed for all the samples and for the sample with lower concentration of iron carbide it is more intense. The resonance absorption signal arises from the agglomerates of iron carbide nanoparticles interacting strongly among themselves. The observed shift of the resonance field is connected with a strong ferromagnetic interaction between agglomerates of nanoparticles. [Copyright &y& Elsevier]