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The role of quorum sensing (QS) in the response of Pseudomonas aeruginosa to UVA radiation was investigated in the PAO1 strain and derivatives defective in the synthesis of the QS signals 3OC12-HSL (lasI strain), C4-HSL (rhlI strain) or both (lasI rhlI strain). Cell viability measurements demonstrated that the double mutant was significantly more sensitive to UVA than single mutants, which in turn showed reduced cell survival with regard to the PAO1 strain. Irradiation under nitrogen atmosphere and chemiluminescence measurements indicated the oxidative nature of the UVA-induced damage. The activity of the antioxidant enzymes catalase and superoxide dismutase was assayed in these strains before and after irradiation, and a strong correlation between catalase levels and UVA sensitivity was observed. When a sublethal UVA dose was applied to PAO1, a growth delay was observed and this mechanism depended on the rhl system. Moreover, low doses of UVA irradiation triplicated the level of C4-HSL in log PAO1 cells. It is concluded that QS is fundamental in the defense against the toxic effects of UVA in P. aeruginosa. The induction of the QS system by UVA independently of cell density could function as an adaptative strategy to withstand this hostile environmental condition., (© 2010 U.S. Government. Journal Compilation. The American Society of Photobiology.)

Prosthetic socket revisions are always difficult and affected by problems such as possible bone-stock losses, leading to an increase in morbidity associated with surgery. These aspects are more important in elderly patients due to their frequently poor health. The bone deficit may be filled in different ways, with techniques that are nevertheless technically demanding and at risk of complications. In the opinion of the Author it is possible to leave a migrated but well-fixed cup/shell in place, simply by loading through the insertion of a second cemented cup alongside. We considered two cases of verticalized sockets: a cemented socket and a non-cemented one which, by demonstrating stability in removal attempts, forced the surgeon to leave them in place and to place a second cemented polyethylene cup alongside. This cheap surgical choice allows to shorten surgical times, to diminish blood losses and to achieve an immediate rigid fixation, aspect of utmost importance in elderly patients, allowing them to walk with a 100% load by the second post-operative day. The unremoved prosthetic cup, that is even better stabilized by the new cement, works as a "support wall" in DeLee and Charnley's zone 3, an acetabular X-ray sector notoriously subordinated to damaging tensile forces which may cause loosening of the original prosthetic cup. Because of the positive clinical and radiographic results demonstrated over time by this "enforced" revision solution, the author proposes to name it as the "Wall-Socket" technique.