Background-This investigation tested the hypothesis that L-selectin is important in experimental abdominal aortic aneurysm (AAA) formation in rodents. Methods and Results-Rat abdominal aortas were perfused with saline (control) or porcine pancreatic elastase and studied on postperfusion days 1, 2, 4, 7, and 14 (nϭ5 per treatment group per day). Neutrophil (polymorphonucleur leukocyte, PMN) and macrophage counts per high-powered field (HPF) were performed on fixed sections. L-selectin expression and protein levels in aortic tissue were determined by polymerase chain reaction and Western blot, respectively. Elastase-perfused aortic diameters were significantly increased compared with control aortas at all time points except day 1 (PϽ0.05). PMN counts significantly increased in elastase-perfused aortas compared with control aortas at days 1, 2, and 4, reaching maximum levels at day 7 (40.8 versus 0.3 PMNs/HPF, Pϭ0.001). L-selectin mRNA expression in elastase-perfused aortas was 18 (Pϭ0.018), 17 (PϽ0.001), and 8 times (Pϭ0.02) times greater than control aortas at days 1, 2, and 4, respectively. Western blot demonstrated a significant 69% increase in L-selectin protein at day 7 in elastase-as compared with saline-perfused aortas (Pϭ0.005). Subsequent experiments involved similar studies on postperfusion days 4, 7, and 14 of aortas from C57BL/6 wild-type (WT) mice (nϭ21) and L-selectin-knockout (LKO) mice (nϭ19). LKO mice had significantly smaller aortic diameters at day 14 as compared with WT mice (88% versus 123%, Pϭ0.02). PMN counts were significantly greater in elastase-perfused WT mouse aortas as compared with LKO mouse aortas at day 4 after perfusion (12.8 versus 4.8 PMNs/HPF, Pϭ0.02). Macrophage counts were significantly greater at all time points after perfusion in elastase-perfused WT mouse aortas compared with elastase-perfused LKO mouse aortas, with a maximum difference at day 7 after perfusion (13.3 versus 0.5 macrophages/HPF, PϽ0.001). Conclusion-L-selectin-mediated neutrophil recruitment may be a critical early step in AAA formation. (Circulation.2005;112:241-247.)

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The selective estrogen receptor modulator tamoxifen inhibits the development of AAAs in male rats in association with an up-regulation of catalase and inhibition of aortic wall neutrophil infiltration.

Primary aortoenteric fistula (PAEF) is defined as a communication between the native aorta and any portion of the gastrointestinal tract. PAEF differs from secondary aortoenteric fistula (SAEF), which occurs when a pathologic communication develops between a previously placed vascular graft and a portion of the gastrointestinal tract. PAEF is a rare condition, and since its first description in 1817, fewer than 230 cases have been reported worldwide. Although most of these cases involved an abdominal aortic aneurysm (AAA), some involved an aorta without an aneurysm. This case report describes a patient who had a primary aortoduodenal fistula (PADF) and no evidence of an AAA. Possible etiologic mechanisms are discussed, and the literature on cases of PADF without AAA is reviewed. CASE REPORTThe patient was a 74-year-old man who came to our emergency department (ED) with gastrointestinal hemorrhage. While at home, hours before his arrival at the ED, he experienced weakness, diaphoresis, dyspnea, and light-headedness. On arrival at the ED, he passed two large, maroon stools. He reported feeling lightheaded and fatigued, but denied any abdominal pain, nausea, vomiting, diarrhea, fevers, chills, night sweats, or recent travel.His medical history was significant for coronary artery disease. He underwent coronary artery bypass grafting 11 years earlier. He had a history of hypertension and previously asymptomatic diverticulosis. He had no documented history of tuberculosis (TB). One year earlier, he was diagnosed as having transitional carcinoma of the bladder and underwent a course of intravesical bacillus Calmette-Guérin (BCG) instillation with isoniazide (INH) prophylaxis. Shortly after his second course of therapy, he was admitted to the hospital with confusion, chills, high fevers, pancytopenia, and transaminitis. The results of a skin test were negative From the

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