The Role of Sialic Acid in Opsonin-Dependent and Opsonin-Independent Adhesion of Listeria monocytogenes to Murine Peritoneal Macrophages

The adhesion of listeriae to host cells employs mechanisms which are complex and not well understood. Listeria monocytogenes is a facultative intracellular pathogen responsible for meningoencephalitis, septicemia, and abortion in susceptible and immunocompromised individuals. Subsequent to colonization and penetration of the gut epithelium, the organism attaches to resident macrophages and replicates intracellularly, thus evading the humoral immune system of the infected host. The focus of these studies was to investigate the attachment of the organism to murine peritoneal macrophages in an opsonin-dependent and opsonin-independent fashion. Assessment of competitive binding experiments by immunofluorescence and enzyme-linked immunosorbent assays showed that adhesion of the organism to macrophages in the presence or absence of opsonins was inhibited (90%) by N-acetylneuraminic acid (NAcNeu). In addition, the lectin from Maackia amurensis, with affinity for NAcNeu-α(2,3)galactose, blocked binding of L. monocytogenes to host cells. Oxidation of the surface carbohydrates on the organism by using sodium metaperiodate resulted in a dose-dependent reduction (up to 98%) in adherence to macrophages. Monoclonal antibody to complement receptor 3 did not prevent listeriae from binding to mouse macrophages or from replicating within the infected cells whether or not normal mouse serum was present. Based on our results, we propose the involvement of NAcNeu, a member of the sialic acid group, in the attachment of L. monocytogenes to permissive murine macrophages.     

Lipoma of the left ventricle

A 36-year-old female was admitted with dyspnea on exertion of one year's duration. Echocardiography revealed a tumor arising from interventricular septum with dynamic left ventricular outflow tract obstruction. On cardiopulmonary bypass with cardioplegic arrest, the tumor was approached through a transverse aortotomy, and excised from the interventricular septum through the aortic valve. Postoperative recovery was uneventful and the patient was asymptomatic with no recurrence at follow-up after one year.     

Impact of coronary collaterals on outcome following percutaneous coronary intervention (from the National Heart, Lung, and Blood Institute Dynamic Registry)

Coronary collateral circulation is beneficial in patients with coronary artery disease, but controversy still exists regarding the association between angiographic collaterals and outcome after percutaneous coronary intervention (PCI). We compared the baseline characteristics and cumulative 1-year event rates of consecutive patients undergoing PCI by target vessel collateral status-no angiographic evidence of collateral circulation (NC; n = 5051), treated artery supplied collaterals (SC; n = 239), and treated artery received collaterals (RC; n = 893)-using the National Heart, Lung, and Blood Institute Dynamic Registry. Patients in the SC group were older and had more previous coronary bypass surgery, myocardial infarction, co-morbid illness, and heart failure than the NC and RC groups and had less often undergone revascularization for acute myocardial infarction (p <0.01 for all). The total angiographic PCI success was comparable for the SC and NC groups but higher than for the RC group (94.1% vs 94.4% vs 83.9%, respectively; p <0.001). Overall stent use was 77.5% and was highest in the SC group (82.4%, p <0.001). At 1 year, significant differences in outcome were observed by collateral status. Compared with the NC group, patients with PCI of a SC artery had higher adjusted mortality (relative risk [RR] 1.95, 95% confidence interval [CI] 1.27 to 3.01, p = 0.002) and death/myocardial infarction (RR 1.75, 95% CI 1.26 to 2.45, p <0.001) rates. Patients with PCI of a RC vessel, conversely, had lower adjusted death/myocardial infarction (RR 0.72, 95% CI 0.54 to 0.96, p = 0.02) and repeat revascularization (RR 0.73, 95% CI 0.59 to 0.91, p = 0.005) rates. In conclusion, our results suggest that PCI on collateralized vessels is warranted, but that patients with PCI in arteries that supply collaterals are a high-risk group that may benefit from closer follow-up and complete revascularization.