In vitro activation and substrates of recombinant, baculovirus expressed human protein kinase C mu

To investigate whether thromboxane and/or platelet activating factor (PAF) mediate the pulmonary vasoconstrictive response to antigen in vivo, we intra-arterially injected human erythrocytes as antigen into sensitized rabbits after administration of putative inhibitors: a cyclooxygenase synthetase inhibitor (indomethacin, 5 mg.kg-1), a thromboxane synthetase inhibitor (OKY 046, 10 mg.kg-1 + 100 micrograms.kg-1.min-1), and a PAF blocker (CV6209, .1 mg.kg-1). Pulmonary artery and airway pressures significantly increased after the antigen challenge in sensitized rabbits, but did not in nonsensitized rabbits. Both indomethacin and OKY046 significantly inhibited the increase in pulmonary artery pressure after the antigen challenge, while CV6209 did not. CV6209 significantly attenuated the decrease in femoral artery pressure after the antigen challenge, while neither indomethacin nor OKY046 did. There were no significant differences in the increase in airway pressure among the groups. We conclude that thromboxane rather than PAF mediates the pulmonary vasoconstriction after the antigen challenge and that mediators other than thromboxane and PAF mediate bronchoconstriction after the antigen challenge in sensitized rabbits.     

Activity of immobilized lipoxygenase used for the formation of perhydroxyacids

Lipoxygenase-produced oxidized fatty acids may serve as intermediates in chemical and pharmaceutical syntheses. For practical applications the enzyme should be immobilized to prevent its loss at product retrieval and to enable a continuous process. In this study the immobilization of soybean lipoxygenase on various neutral and charged supports was investigated. The best results were obtained using cellulose-based anion exchangers. The activity of the immobilized lipoxygenase was lower than the activity of the free enzyme, which was possibly caused by diffusion limitation of the fatty acids to or from the support beads.     

Modelling of severe wear: a survey of the contributions of the Technical University of Zittau to tribology

In the year from 1974 to 1992 members of the Technical University of Zittau investigated problems of analytical modelling in the field of tribology. Most of the questions and suggestions came from difficulties in the practice of technology. Therefore the application of general knowledge to different concrete situations was adopted as the governing principle for this research. Thus modelling and generalizing became the favoured means of investigation. First of all erosive blasting wear became of interest because damage in coal and energy plants were studied. Later on sliding wear developed as a phenomenon which could be described by stochastic fields surprisingly well. One-, two- and three-body abrasive wear patterns were handled. Also the effect of lubrication on mechanical contacts was included in this study. Eventually droplet impact erosion and erosion by cavitation were objects of investigation, the former because of its appearance in the last stages of steam turbines, and the latter because of similarities to droplet impact.     

Experimental determination and simulation of explosion limits of benzene-inert gas-air mixtures

In this work, the influences of inert diluents, N₂ and CO₂, on the explosion limits of benzene-air mixtures were investigated at two different initial temperatures. The model of constant flame temperature was tested for the simulation of the experimental data. It was seen that the model fitted the data of the lower explosion limits, but didn't correlate with the data of the upper explosion limits.     

Phase separation phenomena in aqueous solutions of amphiphilic poly(ethylene oxide) star polymers

Three- and four-armed star polymers with poly(ethylene oxide) arms capped with hydrophobic end-groups were synthesized from nonylphenoxypoly(ethylene glycol)s and well defined tri- and tetraisocyanates. The latter were hydrosilylation products of m-isopropenyl-,-dimethylbenzyl isocyanate (m-TMI). In aqueous solution the arm ends associate, and above a critical star concentration the mixture phase separates into a dilute phase and a condensed gel phase. Their respective polymer concentrations remain constant as long as the two phases coexist, their volume fractions being proportional to the total polymer concentration. Brookfield viscosity measurements confirm the formation of the gel phase which resembles an amphiphilic hydrogel. It exhibits a high affinity for hydrophobic compounds.     

Determining Repeater Margin with a Stub and Attenuator

The margin of a high-speed digital regenerative repeater can be determined easily by adding a misterminated stub at the repeater input. The stub adds an interfering signal which, if large enough, will cause the repeater to make errors. The amplitude of the interfering signal is determined by the termination, so the termination impedance at which errors begin is a good measure of repeater margin. No calibration procedure is required.