The preemptive use of extracorporeal membrane oxygenation to facilitate high risk percutaneous cardiac interventions: left main percutaneous coronary interventions and percutaneous balloon aortic valvuloplasty

As percutaneous cardiac interventions continue to evolve, high-risk procedures are being performed on patients deemed too ill for surgery. What were once considered lower-risk procedures compared with open cardiac interventions may no longer be so because of the complex nature of the interventions and the complex comorbidities of the patients on whom these are being performed. We present a case involving high-risk percutaneous cardiac interventions (left main coronary angioplasty and aortic balloon valvuloplasty), facilitated by the use of extracorporeal membrane oxygenation in a critically ill patient with severe aortic stenosis, left main coronary disease, and ischemic cardiomyopathy.

Mutational analysis of the group A streptococcal operon encoding streptolysin S and its virulence role in invasive infection

The pathogen group A Streptococcus (GAS) produces a wide spectrum of infections including necrotizing fasciitis (NF). Streptolysin S (SLS) produces the hallmark beta-haemolytic phenotype produced by GAS. The nine-gene GAS locus (sagA-sagI) resembling a bacteriocin biosynthetic operon is necessary and sufficient for SLS production. Using precise, in-frame allelic exchange mutagenesis and single-gene complementation, we show sagA, sagB, sagC, sagD, sagE, sagF and sagG are each individually required for SLS production, and that sagE may further serve an immunity function. Limited site-directed mutagenesis of specific amino acids in the SagA prepropeptide supports the designation of SLS as a bacteriocin-like toxin. No significant pleotrophic effects of sagA deletion were observed on M protein, capsule or cysteine protease production. In a murine model of NF, the SLS-negative M1T1 GAS mutant was markedly diminished in its ability to produce necrotic skin ulcers and spread to the systemic circulation. The SLS toxin impaired phagocytic clearance and promoted epithelial cell cytotoxicity, the latter phenotype being enhanced by the effects of M protein and streptolysin O. We conclude that all genetic components of the sag operon are required for expression of functional SLS, an important virulence factor in the pathogenesis of invasive M1T1 GAS infection.

Regulated assembly of the Toll signaling complex drives Drosophila dorsoventral patterning

In Drosophila, the Toll pathway establishes the embryonic dorsoventral axis and triggers innate immune responses to infection. The transmembrane receptor Toll acts through three death domain-containing proteins, the kinase Pelle and the adapters Tube and MyD88, in signaling to downstream NF-kappaB-like transcription factors. Here, we delineate the critical events in the earliest stages of Toll signaling. Mutational studies based on structural modeling reveal that the direct interaction of the bivalent Tube death domain with MyD88 is critical for signaling in vivo. The complex of MyD88 and Tube forms prior to signaling and is localized to the embryonic plasma membrane by MyD88. Upon Toll homodimerization, this complex is rapidly recruited to Toll. Binding of Pelle to the MyD88-Tube complex promotes Pelle activation, leading to degradation of the IkappaB-like inhibitor, Cactus. Together, these experiments convert a linear picture of gene function into a dynamic mechanistic and structural understanding of signaling complex assembly and function.