Relation of local platelet glycoprotein IIb/IIIa independent activation during coronary angioplasty in acute myocardial infarction to recovery of left ventricular function

We assessed glycoprotein (GP) IIb/IIIa independent platelet activation in coronary sinus and peripheral blood from patients who underwent angioplasty for acute myocardial infarction and stable angina. Despite complete blockade of the activated GP IIb/IIIa receptor with abciximab in patients with acute myocardial infarction, unsuppressed local GP IIb/IIIa independent activation was associated with a lack of recovery of left ventricular function.     

The pulmonary bioprosthetic heart valve: its unsuitability for use as an aortic valve replacement

BACKGROUND AND AIM OF THE STUDY: The porcine pulmonary bioprosthetic heart valve represents an alternative means of aortic valve replacement (AVR), though knowledge of its biomechanical function and characteristics is limited. The valve has potential advantages over the aortic bioprosthesis; notably, it lacks the muscular shelf of the right coronary cusp of the latter bioprosthesis. The study aim was to investigate the suitability of the porcine pulmonary bioprosthetic valve for AVR. METHODS: Porcine pulmonary and aortic roots were zero pressure-fixed with 0.5% buffered glutaraldehyde, characterized, and compared with fresh porcine pulmonary and aortic roots. The in-vitro analysis included assessment of mechanical properties, hydrodynamic function, geometry of the pulmonary root, and durability. RESULTS: The fixed pulmonary roots and fresh aortic roots were similar in certain aspects of mechanical response, notably leaflets in the radial direction and the root wall. The fixed pulmonary root was slightly more compliant than the fixed aortic root, and this led to an improvement in forward flow hydrodynamic function. The reverse flow hydrodynamic function of the pulmonary roots was poor; fresh pulmonary roots exhibited a trivial closed valve regurgitant volume. On fixation, this characteristic was aggravated, leading to a gross closed valve regurgitant volume in 50% of all fixed pulmonary roots. The cause of leakage was identified as a prolapsed anterior leaflet. Durability of the fixed pulmonary root was also inferior to that of the fixed aortic root; three fixed pulmonary roots subjected to accelerated fatigue testing showed signs of leaflet macroscopic damage. CONCLUSION: Overall, the performance of the porcine pulmonary bioprosthesis was far inferior to that of the currently used porcine aortic bioprosthesis. Hence, the porcine pulmonary bioprosthetic valve was deemed unsuitable for AVR.     

Molecular basis of altered red blood cell membrane properties in Southeast Asian ovalocytosis: role of the mutant band 3 protein in band 3 oligomerization and retention by the membrane skeleton

Southeast Asian ovalocytosis (SAO) is an asymptomatic trait characterized by rigid, poorly deformable red cells that resist invasion by several strains of malaria parasites. The underlying molecular genetic defect involves simple heterozygous state for a mutant band 3 protein, which contains a deletion of amino acids 400 through 408, linked with a Lys 56-to-Glu substitution (band 3-Memphis polymorphism). To elucidate the contribution of the mutant SAO band 3 protein to increased SAO red blood cell (RBC) rigidity, we examined the participation of the mutant SAO band 3 protein in increased band 3 attachment to the skeleton and band 3 oligomerization. We found first that SAO RBC skeletons retained more band 3 than normal cells and that this increased retention preferentially involved the mutant SAO band 3 protein. Second, SAO RBCs contained a higher percentage of band 3 oligomer-ankyrin complexes than normal cells, and these oligomers were preferentially enriched by the mutant SAO protein. At the ultrastructural level, the increased oligomer formation of SAO RBCs was reflected by stacking of band 3-containing intramembrane particles (IMP) into longitudinal strands. The IMP stacking was not reversed by treating SAO RBCs in alkaline pH (pH 11), which is known to weaken ankyrin-band 3 interactions, or by removing the cytoplasmic domain of band 3 from SAO membranes with trypsin. Finally, we found that band 3 protein in intact SAO RBCs exhibited a markedly decreased rotational mobility, presumably reflecting the increased oligomerization and the membrane skeletal association of the SAO band 3 protein. We propose that the mutant SAO band 3 has an increased propensity to form oligomers, which appear as longitudinal strands of IMP and exhibit increased association with membrane skeleton. This band 3 oligomerization underlies the increase in membrane rigidity by precluding membrane skeletal extension, which is necessary for membrane deformation.     

Frequency of small-colony variants and antimicrobial susceptibility of methicillin-resistant Staphylococcus aureus in cystic fibrosis patients

Background

Small-colony variants (SCVs) are a distinct phenotype of Staphylococcus aureus, known for their role in chronic, difficult to treat infections, including cystic fibrosis (CF) lung disease. The goal of this study was to characterize SCV MRSA infection in an adult and pediatric CF population and to identify antibiotic susceptibility patterns unique to SCV MRSA.