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The leaf‐cutting ant Atta texana Buckley (Formicidae: Attini) forages on new leaves of live oak, Quercus fusiformis (Fagaceae), each spring in a central Texas habitat. The ants repeatedly attack one individual tree while nearby live oaks are ignored. Field bioassays showed that: 1) mature leaves remained palatable to the ants throughout the year, but that foragers were deterred by leaf toughness, and 2) the ants preferred mature leaf discs from the forage tree to those from the non‐forage trees. Intraspecific preference appeared to be related to leaf toughness. Ants cut significantly more mature live oak leaves when leaves were sugar‐coated, indicating that there is a toughness x palatability threshold that inhibits attack by the ants. RÉSUMÉ Les fourmis coupeuses de feuilles et le chêne‐vert: importance de la dureté des feuilles dans le choix saisonnier et intraspécifique La fourmi coupeuse de feuilles, Alta texana Buckley (Formicidae; Attini), fourrage sur des végétaux vivants dont elle alimente des champignons symbiotiques. Les fourmis fourragent tout au cours de l'année sur une succession prévisible de plantes hôtes. Au printemps, les fourmis récoltent les feuilles jeunes des chênes‐verts dans l'habitat du Texas central. Un vieil arbre est régulièrement attaqué, tandis que des chênes‐verts tout proches et plus petits sont ignorés. Dans cette étude, j'ai examiné les bases des préférences intraspécifiques et du choix de nouvelles feuilles, en utilisant un dispositif de terrain conçu pour séparer les effets de la dureté et du goùt des feuilles comme dissuadants de fourrager. L'expérience consistait à proposer pour le transport des feuilles entières et des disques foliaires de deux tailles à des fourmis actives. Lorsque les fourmis enlevaient les petits disques mais ne coupaient pas les gros disques, les feuilles étaient supposées appétissantes mais trop dures pour être coupées. De plus, j'ai mesuré ta dureté de feuilles d'arbres semblables à celles utilisées dans l'expérience et aux charges de feuilles portées par les femelles fourrageuses. Les résultats montrent que les feuilles de tout âge sont appétissantes pour les fourmis tout au cours de l'année, mais que les feuilles mûres sont trop dures pour être coupées. En mai, les fourmis portaient des charges de feuilles qui étaient généralement plus molles que les feuilles mûres sur les arbres fourrages. Les fourmis cueillaient significativement plus de feuilles mûres dans les expériences où elles avaient été enduites de sucre, ce qui indique que les fourmis réagissent à un seuil combiné dureté‐appétence. Dans les expériences, les fourmis coupaient significativement plus de feuilles mûres sur les arbres fourrages que sur les négligés, bien que les feuilles des deux origines paraissaient aussi appétissantes d'après les transports de petits disques. Les choix intra‐spécifiques et de feuilles jeunes étaient tous les deux fortement influencés par la dureté des feuilles, bien que les effets de la dureté des feuilles pouvaient être surmontés quand les feuilles avaient ét...
ImportanceIn patients with severe aortic valve stenosis at intermediate surgical risk, transcatheter aortic valve replacement (TAVR) with a self-expanding supra-annular valve was noninferior to surgery for all-cause mortality or disabling stroke at 2 years. Comparisons of longer-term clinical and hemodynamic outcomes in these patients are limited.ObjectiveTo report prespecified secondary 5-year outcomes from the Symptomatic Aortic Stenosis in Intermediate Risk Subjects Who Need Aortic Valve Replacement (SURTAVI) randomized clinical trial.Design, Setting, and ParticipantsSURTAVI is a prospective randomized, unblinded clinical trial. Randomization was stratified by investigational site and need for revascularization determined by the local heart teams. Patients with severe aortic valve stenosis deemed to be at intermediate risk of 30-day surgical mortality were enrolled at 87 centers from June 19, 2012, to June 30, 2016, in Europe and North America. Analysis took place between August and October 2021.InterventionPatients were randomized to TAVR with a self-expanding, supra-annular transcatheter or a surgical bioprosthesis.Main Outcomes and MeasuresThe prespecified secondary end points of death or disabling stroke and other adverse events and hemodynamic findings at 5 years. An independent clinical event committee adjudicated all serious adverse events and an independent echocardiographic core laboratory evaluated all echocardiograms at 5 years.ResultsA total of 1660 individuals underwent an attempted TAVR (n = 864) or surgical (n = 796) procedure. The mean (SD) age was 79.8 (6.2) years, 724 (43.6%) were female, and the mean (SD) Society of Thoracic Surgery Predicted Risk of Mortality score was 4.5% (1.6%). At 5 years, the rates of death or disabling stroke were similar (TAVR, 31.3% vs surgery, 30.8%; hazard ratio, 1.02 [95% CI, 0.85-1.22]; P = .85). Transprosthetic gradients remained lower (mean [SD], 8.6 [5.5] mm Hg vs 11.2 [6.0] mm Hg; P < .001) and aortic valve areas were higher (mean [SD], 2.2 [0.7] cm2 vs 1.8 [0.6] cm2; P < .001) with TAVR vs surgery. More patients had moderate/severe paravalvular leak with TAVR than surgery (11 [3.0%] vs 2 [0.7%]; risk difference, 2.37% [95% CI, 0.17%- 4.85%]; P = .05). New pacemaker implantation rates were higher for TAVR than surgery at 5 years (289 [39.1%] vs 94 [15.1%]; hazard ratio, 3.30 [95% CI, 2.61-4.17]; log-rank P < .001), as were valve reintervention rates (27 [3.5%] vs 11 [1.9%]; hazard ratio, 2.21 [95% CI, 1.10-4.45]; log-rank P = .02), although between 2 and 5 years only 6 patients who underwent TAVR and 7 who underwent surgery required a reintervention.Conclusions and RelevanceAmong intermediate-risk patients with symptomatic severe aortic stenosis, major clinical outcomes at 5 years were similar for TAVR and surgery. TAVR was associated with superior hemodynamic valve performance but also with more paravalvular leak and valve reinterventions.
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