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Despite all the benefits of drug-eluting stents (DES), concerns have been raised over their long-term safety, with particular reference to stent thrombosis. In an effort to address these concerns, newer stents have been developed that include: DES with biodegradable polymers, DES that are polymer free, stents with novel coatings, and completely biodegradable stents. Many of these stents are currently undergoing pre-clinical and clinical trials; however, early results seem promising. This paper reviews the current status of this new technology, together with other new coronary devices such as bifurcation stents and drug-eluting balloons, as efforts continue to design the ideal coronary stent.
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No abstract is provided for this article.
Chronic obstructive pulmonary disease (COPD) involves disease of small airways with an increase in airway smooth muscle sensitivity to spasmogens and with structural changes described as airway remodeling. We investigated the effect of tobacco smoke (TS) exposure on the structure and function of small airways in rats and the role of IL-13 in this response. Precision-cut lung slices (230-280 microm) were prepared from male Sprague-Dawley rats after acute (3 d) or chronic (8 or 16 wk) daily exposure to TS or air. Carbachol (CCh) and 5-hydroxytryptamine (5HT) concentration responses were performed on airways (50-400 microm diameter). The effect of IL-13 in vitro on small airway sensitivity to CCh and 5HT was also determined. Acute exposure to TS did not affect the sensitivity of the intrapulmonary airways to either spasmogen. After 8 weeks of TS exposure, airway hyperresponsiveness (AHR) to CCh was evident (log EC(50) CCh: air = 0.22 microM; TS = -0.12 microM; P = 0.019); AHR to 5HT was also observed after the 16-week exposure to TS (air = -0.85 microM; TS = -1.06 microM; P = 0.038). Chronic TS exposure increased airway wall SMA content, which correlated with increased expression of IL-13 and transforming growth factor (TGF)-beta(1) in the lung tissues. In vitro incubation with IL-13, but not TGF-beta(1), induced changes in small airway sensitivity to CCh and 5HT. Chronic TS exposure induces increased responsiveness in intrapulmonary airways of rats that may be mediated in part by an increase in IL-13.
When tubular members are in bending, they tend to flatten towards the axis of bending, thus reducing their second moment of area. Eventually, a limit point is reached whereupon the initial stability of the system is lost and unstable equilibrium prevails, thus reducing the load carrying capacity of the member. This effect was originally described by Brazier (1927) for circular tubular members. In the present study, the analysis of Brazier is adapted for elliptical hollow section members, taking into account the additional geometric complexities inherent in ellipses. An analytical method is presented whereby the initial geometry and the displacement functions of the system are replaced by Fourier series, thus reducing the analytical complexity of the problem. After formulating the potential energy functional, use of a variational method allows for the amplitudes of the constituent harmonics of the Fourier approximations of the displacement functions to be solved for, providing estimates of the deformed geometry of the cross-section and the associated moment. In keeping with the analogy of Brazier for circular sections, a limit point is observed. These analytical predictions are then compared with the results of a complementary finite element analysis, whereupon it is found that for smaller longitudinal curvatures there is close agreement between the analytical and numerical methods. For larger curvatures and moments beyond the limit point some divergence is observed between the predictions of the two methods, which can be attributed to the lower-order approximations assumed in formulating the potential energy functional in the analytical method