Connecting genomic patterns of local adaptation and niche suitability in teosintes.

The central abundance hypothesis predicts that local adaptation is a function of the distance to the centre of a species' geographic range. To test this hypothesis, we gathered genomic diversity data from 49 populations, 646 individuals and 33,464 SNPs of two wild relatives of maize, the teosintes Zea mays ssp. parviglumis and Zea. mays. ssp. mexicana. We examined the association between the distance to their climatic and geographic centroids and the enrichment of SNPs bearing signals of adaptation. We identified candidate adaptive SNPs in each population by combining neutrality tests and cline analyses. By applying linear regression models, we found that the number of candidate SNPs is positively associated with niche suitability, while genetic diversity is reduced at the limits of the geographic distribution. Our results suggest that overall, populations located at the limit of the species' niches are adapting locally. We argue that local adaptation to this limit could initiate ecological speciation processes and facilitate adaptation to global change.

The effects of cimetidine and ranitidine on the pharmacokinetics of cifenline.

Twelve healthy subjects completed an open single dose study to evaluate the effect of co-administration of cimetidine and ranitidine on the pharmacokinetics of cifenline. Each subject received a single 160 mg dose of cifenline alone, in combination with cimetidine (300 mg four times daily), and with ranitidine (150 mg twice daily). The H2-receptor antagonists were given with breakfast 1 h prior to cifenline dosing and continuing for 48 h. Co-administration of cimetidine significantly increased Cmax (27%) and AUC (44%) and prolonged the half-life (30%) of cifenline. There were no differences in these parameters when ranitidine was co-administered with cifenline. The results of this study suggest that cimetidine, but not ranitidine, lowers the clearance of cifenline by inhibition of hepatic oxidative metabolism.

Continued propranolol administration following coronary bypass surgery. Antiarrhythmic effects.

One hundred consecutive patients requiring propranolol hydrochloride before undergoing isolated aortocoronary bypass procedures were examined. In half the patients, propranolol therapy was discontinued, whereas the other half continued to receive intraoperative and postoperative propranolol regardless of clinical events. Although there were no preoperative differences in the apparent degree of coronary arterial disease or left ventricular function in the two groups, postoperative supraventricular arrhythmias were less frequent in the propranolol-treated group, most noticeably in those receiving less than 320 mg preoperatively. In patients who had received large preoperative doses (greater than or equal to 320 mg/day), there were no significant differences in postoperative supraventricular tachycardias. Continued propranolol therapy following isolated coronary bypass surgery appears to be a safe and efficacious method of decreasing the incidence of postoperative supraventricular tachycardias.