Enhancing the selectivity of prolinamide organocatalysts using the mechanical bond in [2]rotaxanes.

The synthesis of a pair of switchable interlocked prolinamides and their use as organocatalysts in three different enamine-activated processes are reported. A diacylaminopyridine moiety was incorporated into the thread for directing [2]rotaxane formation further allowing the association of complementary small molecules. The rotaxane-based systems were tested as organocatalysts in asymmetric enamine-mediated processes, revealing a significantly improved catalytic ability if compared with the non-interlocked thread. The presence of an electron-withdrawing nitro group at the macrocycle helps to achieve high conversions and enantioselectivities. These systems are able to interact with N-hexylthymine as a cofactor to form supramolecular catalysts displaying a divergent catalytic behaviour. The presence or absence of the cofactor controls the chemoselectivity in competitive reactions.

End-to-end anastomosis in growing vessels using a novel suturing technique: VCS metallic staples.

For pediatric transplants, a suturing technique is needed that allows the vessel to grow along with better healing of the anastomosis, through eliminating exogenous and thrombogenic material in the intimal side, thus minimizing the risk of vascular stenosis. In this study, 12 55-day-old lambs were subjected to end-to-end anastomosis of the right carotid artery and external jugular vein using vascular closure staple (VCS) clips (the vessels from the left side served as controls). Animals were followed up with duplex ultrasound. After 6 months, angiography was performed and animals were euthanized for microscopic study of the vessels. Duplex ultrasonography and angiography showed all vessels to be patent, with no flow disturbances and no stenosis at the anastomotic site at 6 months. Stenotic segments caudal to the anastomosis site were seen in two veins. No significant changes were seen macroscopically in any of the veins, whereas one of the arteries developed a pseudoaneurysm at the anastomotic site. Histological structure was normal in all the studied veins. Arteries showed different degrees of modifications that did not affect patency or flow in any case. Measurements taken after 6 months confirm that this technique allows the vessel to grow. This technique may be useful in vascular pediatric surgery.

Biopsia hepática: visión y control por laparoscopia. 50 casos / Hepactic biopsy: view and control by laparoscopy. 50 cases

La laparoscopia bajo anestesia local y sedación nos permite en forma sencilla y segura, evaluar los órganos intraabdominales, la o las afecciones que los aquejan y la extensión de las patologías. El hígado es uno de los órganos ampliamente visibles por este método. La toma de biopsia hepática, bajo visión y guiada por laparoscopia, descrita en este trabajo, es un procedimiento fácil y sin complicaciones, que nos permite tomar el o los fragmentos necesarios para ser estudiados. El análisis de 50 casos, durante un período de 2 años, en nuestro Servicio de Cirugía IV del Hospital Universitario de Caracas, sin morbilidad ni mortalidad, nos permite aseverar que: la laparoscopia en 100 por ciento segura, fácil y específica en la toma de la biopsia hepática