Characterization of Genome-Wide Association-Identified Variants for Atrial Fibrillation in African Americans

Despite a greater burden of risk factors, atrial fibrillation (AF) is less common among African Americans than European-descent populations. Genome-wide association studies (GWAS) for AF in European-descent populations have identified three predominant genomic regions associated with increased risk (1q21, 4q25, and 16q22). The contribution of these loci to AF risk in African American is unknown.We studied 73 African Americans with AF from the Vanderbilt-Meharry AF registry and 71 African American controls, with no history of AF including after cardiac surgery. Tests of association were performed for 148 SNPs across the three regions associated with AF, and 22 SNPs were significantly associated with AF (P<0.05). The SNPs with the strongest associations in African Americans were both different from the index SNPs identified in European-descent populations and independent from the index European-descent population SNPs (r(2)<0.40 in HapMap CEU): 1q21 rs4845396 (odds ratio [OR] 0.30, 95% confidence interval [CI] 0.13-0.67, P = 0.003), 4q25 rs4631108 (OR 3.43, 95% CI 1.59-7.42, P = 0.002), and 16q22 rs16971547 (OR 8.1, 95% CI 1.46-45.4, P = 0.016). Estimates of European ancestry were similar among cases (23.6%) and controls (23.8%). Accordingly, the probability of having two copies of the European derived chromosomes at each region did not differ between cases and controls.Variable European admixture at known AF loci does not explain decreased AF susceptibility in African Americans. These data support the role of 1q21, 4q25, and 16q22 variants in AF risk for African Americans, although the index SNPs differ from those identified in European-descent populations

Bioclimates, aridity and végétation stages mapping in Morocco

L’objectif de cet article est l’analyse comparative de l’extension spatiale et de la localisation géographique de l’aridité et des étages bioclimatiques du Maroc et de leurs limites en utilisant différents indices utilisés en Afrique du Nord et ailleurs en Méditerranée. L’analyse a été orientée vers l’utilisation des données issues de la base données WorldClim, la spatialisation moyennant les techniques SIG et l’étude de la répartition des différentes espèces végétales. Ainsi, les étages bioclimatiques ont été caractérisés moyennant une approche spatiale en utilisant le diagramme pluviothermique d’Emberger (Sauvage, 1963). Les résultats obtenus montrent que les zones hyperarides au Maroc représentent 45 à 55% du territoire en fonction des différents indices d’aridité. La répartition spatiale des pluies indique que 48% du territoire Marocain reçoit moins de 100mm annuellement, alors que les régions où il pleut plus de 600mm ne dépassent pas les 6%. Les zones arides, semi-arides et subhumides potentiellement concernées par la désertification sont de l’ordre de 42%. La comparaison des différents indices utilisés montre que l’indice d’aridité de De Martonne, le plus facile à calculer, reste satisfaisant pour les études à caractère régional. La dérivation de la carte des étages bioclimatiques, en se basant sur le diagramme d’Emberger, (Q2 et Tmin) montre l’existence au Maroc de 5 grands types de climats allant de humide jusqu’au peraride. L’étage perhumide n’existant que sous forme insignifiante au niveau des crêtes de la chaine du Rif (<5Km²). Les variantes thermiques allant du « Tempéré » à « Très chaud » y représentent plus que 70%

Investigations of the availability and survival of submersed aquatic vegetation propagules in the tidal Potomac River

The establishment of submersed aquatic vegetation (SAV) at unvegetated sites in the freshwater tidal Potomac River was limited primarily by factors other than propagule availability. For two years, traps were used to quantify the amount of plant material reaching three unvegetated sites over the growing season. The calculated flux values provided a gross estimate of the flux of propagules that could potentially survive if other site factors were suitable. The mean flux ofHydrilla verticillata and all other species (?0.01 gdw m?2 d?1) appeared sufficient to favor the establishment of vegetation, particularly considering the high viability (70–100%) of whole plants and fragments under controlled conditions. However, median water clarity values (i.e., for light attenuation, Secchi depth, total suspended solids, and chlorophylla) were below SAV restoration goals at all unvegetated sites. Additionally, sediments from unvegetated sites showed a potential for nitrogen limitation of the growth ofH. verticillata. Our findings support the hypothesis that in the tidal Potomac River, water clarity and nutrient (especially nitrogen) levels in sediment are key to plant community establishment

Thirty-day vein remodeling is predictive of midterm graft patency after lower extremity bypass

ObjectiveSuccessful adaptation of a vein graft to an arterial environment is incompletely understood. We sought to investigate whether early vein graft remodeling is predictive of subsequent patency.MethodsA prospective longitudinal study was conducted of 67 patients undergoing lower extremity bypass with autogenous vein between February 2004 and April 2008. Preoperative blood samples were drawn for biomarkers. During the bypass operation, a 5-cm index segment of the graft was registered for serial lumen diameter measurements at 0, 1, 3, 6, 9, and 12 months using duplex ultrasound imaging. The imaging substudy analysis included patients with at least two ultrasound assessments.ResultsPatients (55% male) were a median age of 70 years (interquartile range [IQR], 59-76 years), 40% had diabetes mellitus, 49% had critical limb ischemia, 75% were taking a statin, and 91% were taking an antiplatelet medication. Median follow-up was 32 months (IQR, 15-47 months). The median baseline high-sensitivity C-reactive protein level (hsCRP) was 3.2 mg/L (IQR, 1.4-9.7 mg/L). The average intraoperative, postimplantation vein lumen diameter was 3.9±1.0 mm, increasing to 4.7±1.1 mm at 1 month, an average 24%±27% change per patient. By 3 months, the average lumen diameter was 5.1±1.6 mm, with little subsequent change observed to 12 months. Nonwhite race, baseline hsCRP ≥5 mg/L, statin use, and initial lumen diameter were significantly associated with early (0- to 1-month) vein remodeling in a multivariable regression model. The primary patency rate for the cohort was 60%±6.3% at 2 years. Initial lumen diameter of the index segment was not associated with primary patency, whereas larger lumen diameter achieved at 1 month (≥5.1 mm) was positively associated with primary patency (log-rank, P=.03). Early (30-day) remodeling behavior was used to divide patients into "poor remodelers" (&lt;-5% lumen diameter change, n=6), "modest remodelers" (-5% to 25% change, n=29), and "robust remodelers" (&gt;+25% change, n=30). Early remodeling category was significantly associated with primary patency rate at 2 years (log-rank, P=.02). A multivariable Cox proportional hazards model showed that modest remodelers (hazard ratio, 3.9; 95% confidence interval, 1.02-15; P=.04) and poor remodelers (hazard ratio, 13; 95% confidence interval; P=.008) had significantly higher hazard ratios for graft failure than robust early remodelers.ConclusionsEarly remodeling of the arterialized vein appears to predict midterm bypass graft patency. In addition to baseline diameter, race, inflammation, hsCRP, and statin use are associated with early adaptive remodeling, but the mechanisms for these observations are not understood