Endothelin-1 levels and conduit artery mechanical properties in end-stage renal disease

BACKGROUND: Endothelial cell (EC) dysfunction markers are increased in end-stage renal disease (ESRD). The present study focused on the relationship between EC markers, conduit artery wall mechanics and hemodynamics in ESRD. METHODS: In 29 ESRD patients and 16 controls, brachial artery diameter, distension, and wall thickness was measured and circumferential wall stress (CWS) calculated. Shear stress was determined with a shear rate-estimating system. Furthermore, von Willebrand factor antigen (vWF) and endothelin-1 (ET-1) levels were measured. RESULTS: vWF (p = 0.002) and ET-1 (p < 0.001) were higher in ESRD patients and vWF was related to ET-1 (r = 0.70, p = 0.005). Peak (p = 0.001) and mean shear stress (p = 0.003) were significantly lower in ESRD patients, and ET-1 showed an inverse log linear relation with both (peak: r = -0.59, p = 0.016; mean: r = -0.64, p = 0.007). Also, ET-1 was log linearly related to CWS (r = 0.58, p = 0.014). CONCLUSION: These results indicate that, in ESRD, conduit artery shear stress is lower, which might be secondary to an increased peripheral vascular resistance caused by higher ET-1 levels

The effect of flow changes on the arterial system proximal to an arteriovenous fistula for hemodialysis

Arterial remodeling in response to flow changes is controlled by the endothelium, sensing wall shear stress (SS) changes. The present study focuses on the remodeling capacities of the brachial (BA) and radial artery (RA) of 16 renal failure patients after arteriovenous fistula creation. Pre- and postoperatively at predetermined time-points, diameter, wall thickness and peak and mean SS were assessed. After arteriovenous fistula creation, acute increases in BA SS (p = 0.018) and lumen diameter (p = 0.028) were observed. The diameter further increased in the next year (p = 0.023), whereas BA SS remained unchanged. RA SS and diameter increased acutely (p = 0.005) and remained unaltered after 1 y. RA wall thickness tended to decrease acutely (p = 0.059) and increased steadily during 1 y (p = 0.008). BA and RA diameter acutely increased after an acute SS rise and remained augmented after 1 y. Also, the RA vessel wall thickness enlarged, indicating structural remodeling. After 1 y, however, these changes did not result in SS restoration. (E-mail: )

Evaluating 4 years of atmospheric ammonia (NH3) over Europe using IASI satellite observations and LOTOS-EUROS model results

Monitoring ammonia (NH3) concentrations on a global to regional scale is a challenge. Due to the limited availability of reliable ground-based measurements, the determination of NH3 distributions generally relies on model calculations. Novel remotely sensed NH3burdens provide valuable insights to complement traditional assessments for clear-sky conditions. This paper presents a first quantitative comparison between Atmospheric Sounding Interferometer (IASI) satellite observations and LOTOS-EUROS model results over Europe and Western Russia. A methodology to account for the variable retrieval sensitivity of the measurements is described. Four years of data (2008-2011) highlight three main agricultural hot spot areas in Europe: the Po Valley, the continental part of Northwestern Europe, and the Ebro Valley. The spatial comparison reveals a good overall agreement of the NH3 distributions not only in these source regions but also over remote areas and over sea when transport is observed. On average, the measured columns exceed the modeled ones, except for a few cases. Large discrepancies over several industrial areas in Eastern Europe and Russia point to underestimated emissions in the underlying inventories. The temporal analysis over the three hot spot areas reveals that the seasonality is well captured by the model when the lower sensitivity of the satellite measurements in the colder months is taken into account. Comparison of the daily time series indicates possible misrepresentations of the timing and magnitude of the emissions. Finally, specific attention to biomass burning events shows that modeled plumes are less spread out than the observed ones. This is confirmed for the 2010 Russian fires with a comparison using in situ observations. ©2014. American Geophysical Union. All Rights Reserved