Marked differences in foraging area use and susceptibility to predation between two closely-related tropical seabirds

Ecological theory predicts that closely-related species must occupy different niches to coexist. How marine top predators achieve this during breeding, when they often gather in large multi-species colonies and are constrained to central-place foraging, has been mostly studied in productive temperate and polar oceans with abundant resources, but less so in poorer, tropical waters. Here, we track the foraging movements of two closely-related sympatric seabirds—the white-tailed and red-tailed tropicbirds Phaethon lepturus and P. rubricauda—breeding on Aldabra Atoll, Seychelles, to investigate potential mechanisms of niche segregation and shed light on their contrasting population trends. Combining data from GPS, immersion, depth and accelerometry loggers, we show that the two species have similar behaviour at sea, but are completely segregated spatially, with red-tailed tropicbirds flying further to feed and using different feeding areas than white-tailed tropicbirds. Using nest-based camera traps, we show that low breeding success of both species—which likely drives observed population declines—is caused by high nest predation. However, the two species are targeted by different predators, with native avian predators mainly targeting red-tailed tropicbird nests, and invasive rats raiding white-tailed tropicbird nests when they leave their eggs unattended. Our findings provide new insight into the foraging ecology of tropicbirds and have important conservation implications. The extensive range and spatial segregation highlight the importance of considering large-scale protection of waters around tropical seabird colonies, while the high level of nest predation provides evidence in support of rat eradication and investigating potential nest protection from native avian predators

An ex-vivo quantitative assessment to determine the optimal aortotomy closure technique

BACKGROUND: After performing an aortotomy, there are a variety of techniques utilized for suture closure. There is no published data comparing the efficacy of various suture techniques. The goal of this study is to provide an ex-vivo quantitative assessment of resistance to leakage and dehiscence for three aortotomy closure techniques. MATERIALS AND METHODS: An ex-vivo model was developed utilizing explanted porcine aorta. Aortotomies were closed using one of three techniques: 1) single layer baseball stitch 2) double layer baseball stitch 3) horizontal mattress stitch with a top layer baseball stitch. The aorta was pressurized with saline using an apparatus which captured all leaked fluid. The intra-aortic pressure was adjusted over 8 increments from 110 to 375 mmHg. Leakage rates were determined at each pressure level. Ten aortotomies were performed for each technique, resulting in 240 calculated leakage rates. RESULTS: At all pressures, the horizontal mattress group was measured to have significantly less leakage when compared to single or double layer baseball stitch closures (p < 0.005). There was a trend towards a lower leakage rate in the double layer baseball compared to the single layer baseball stitch. However, this difference is statistically significant only at 300 and 335 mmHg. There were no instances of rupture. CONCLUSION: This study provides the first quantitative comparison of three commonly used aortotomy closure techniques. The running horizontal mattress stitch combined with a baseball stitch provides the greatest resistance to leakage at all pressures. This technique may be superior in clinical scenarios with challenging hemostasis

Repair of Bicuspid Aortic Valve in the Presence of Endocarditis and Leaflet Perforation

Aortic valve repair can be a good option in younger patients who have severe aortic regurgitation. A systematic, disease-directed approach can simplify repair. This case report describes how a simplified approach can be successfully applied to complex pathologic conditions of the aortic valve. A 49-year-old man with a bicuspid aortic valve and a history of endocarditis presented with severe aortic regurgitation and evidence of recurrent infection. Intraoperatively, we found congenital and degenerative aortic anatomy with endocarditis and perforation. We performed aortic valve repair to enable leaflet coaptation and to adjust the coaptation height. After 24 months, the patient remained well, with an intact repair and trivial aortic regurgitation. We describe our systematic repair approach and rationales for targeting repairs to identified lesions. To our knowledge, this is the first description of complex aortic valve repairs in a patient who had simultaneous congenital, degenerative, and infectious conditions

Human Blood Vessel–Derived Endothelial Progenitors for Endothelialization of Small Diameter Vascular Prosthesis

BACKGROUND:Coronary bypass graft failure as a result of acute thrombosis and intimal hyperplasia has been the major challenge in surgical procedures involving small-diameter vascular prosthesis. Coating synthetic grafts with patients' own endothelial cells has been suggested to improve the patency rate and overall success of bypass surgeries. METHODOLOGY/PRINCIPAL FINDINGS:We isolated endothelial progenitor cells (EPCs) from leftover pieces of human saphenous vein/mammary artery. We demonstrate that EPCs can be expanded to generate millions of cells under low-density culture conditions. Exposure to high-density conditions induces differentiation to endothelial cell phenotype. EPC-derived endothelial cells show expression of CD144high, CD31, and vWF. We then assessed the ability of differentiated endothelial cells to adhere and grow on small diameter expanded polytetrafluoroethylene (ePTFE) tubings. Since ePTFE tubings are highly hydrophobic, we optimized protocols to introduce hydrophilic groups on luminal surface of ePTFE tubings. We demonstrate here a stepwise protocol that involves introduction of hydrophilic moieties and coating with defined ECM components that support adhesion of endothelial cells, but not of blood platelets. CONCLUSION/SIGNIFICANCE:Our data confirms that endothelial progenitors obtained from adult human blood vessels can be expanded in vitro under xenoprotein-free conditions, for potential use in endothelialization of small diameter ePTFE grafts. These endothelialized grafts may represent a promising treatment strategy for improving the clinical outcome of small-caliber vascular grafts in cardiac bypass surgeries