Assuntos
Apêndice Atrial/diagnóstico por imagem , Fibrilação Atrial/diagnóstico por imagem , Cardiopatias/diagnóstico por imagem , Implantação de Prótese/efeitos adversos , Trombose/diagnóstico por imagem , Ticlopidina/análogos & derivados , Idoso , Idoso de 80 Anos ou mais , Apêndice Atrial/cirurgia , Fibrilação Atrial/cirurgia , Clopidogrel , Feminino , Cardiopatias/etiologia , Humanos , Masculino , Pessoa de Meia-Idade , Implantação de Prótese/tendências , Trombose/etiologia , Ticlopidina/uso terapêutico , Resultado do Tratamento , UltrassonografiaRESUMO
Abstract Escherichia coli hemolysin is a pore-forming protein belonging to the RTX toxin family. Cysteine scanning mutagenesis was performed to characterize the putative pore-forming domain of the molecule. A single cysteine residue was introduced at 48 positions within the sequence spanning residues 170-400 and labeled with the polarity-sensitive dye badan. Spectrofluorimetric analyses indicated that several amino acids in this domain are inserted into the lipid bilayer during pore formation. An amphipathic alpha-helix spanning residues 272-298 was identified that may line the aqueous pore. The importance of this sequence was highlighted by the introduction of two prolines at positions 284 and 287. Disruption of the helix structure did not affect binding properties, but totally abolished the hemolytic activity of the molecule.
Assuntos
Proteínas de Escherichia coli/química , Proteínas de Escherichia coli/metabolismo , Proteínas Hemolisinas/química , Proteínas Hemolisinas/metabolismo , Porinas/metabolismo , Motivos de Aminoácidos , Animais , Linhagem Celular Tumoral , Membrana Eritrocítica , Humanos , Proteínas Mutantes/química , Proteínas Mutantes/metabolismo , Estrutura Secundária de Proteína , CoelhosRESUMO
Production of a single cysteine substitution mutant, S177C, allowed Escherichia coli hemolysin (HlyA) to be radioactively labeled with tritiated N-ethylmaleimide without affecting biological activity. It thus became possible to study the binding characteristics of HlyA as well as of toxin mutants in which one or both acylation sites were deleted. All toxins bound to erythrocytes and granulocytes in a nonsaturable manner. Only wild-type toxin and the lytic monoacylated mutant stimulated production of superoxide anions in granulocytes. An oxidative burst coincided with elevation of intracellular Ca(2+), which was likely because of passive influx of Ca(2+) through the toxin pores. Competition experiments showed that binding to the cells was receptor-independent, and preloading of cells with a nonlytic HlyA mutant did not abrogate the respiratory burst provoked by a subsequent application of wild-type HlyA. In contrast to a previous report, expression or activation of the beta(2) integrin lymphocyte function-associated antigen-1 did not affect binding of HlyA. We conclude that HlyA binds nonspecifically to target cells and a receptor is involved neither in causing hemolysis nor in triggering cellular reactions.
Assuntos
Eritrócitos/metabolismo , Escherichia coli/metabolismo , Granulócitos/metabolismo , Proteínas Hemolisinas/metabolismo , Superóxidos/metabolismo , Acilação , Substituição de Aminoácidos , Toxinas Bacterianas , Sítios de Ligação , Cálcio/metabolismo , Eritrócitos/citologia , Granulócitos/citologia , Proteínas Hemolisinas/genética , Humanos , Células K562 , Antígeno-1 Associado à Função Linfocitária/metabolismo , Mutagênese Sítio-Dirigida , Mutação , Explosão Respiratória , Deleção de SequênciaRESUMO
PURPOSE: To investigate the effect of septal artery occlusion with transluminally delivered polyvinyl alcohol (PVA) foam particles for the treatment of hypertrophic obstructive cardiomyopathy (HOCM). METHODS: Percutaneous septal artery ablation was performed in 18 symptomatic patients (13 men; mean age 60+/-17 years, range 28-89) with drug-resistant HOCM. PVA foam particles were mixed with contrast medium and injected through an angiographic catheter under fluoroscopic control until complete stasis in the septal branch was achieved. Patients were monitored with echocardiography and cardiovascular magnetic resonance imaging. RESULTS: The septal artery was successfully occluded in all patients; no embolization of other coronary branches occurred after infusion of 3 to 8 mL (5.2+/-0.8) of PVA foam particles. The resting pressure gradient was diminished from 83+/-32 to 31+/-35 mmHg (p<0.05). Over a mean follow-up of 44+/-4 months, all patients had symptomatic improvement of their dyspnea and workload without the need for intensified drug therapy. The average NYHA functional class decreased from 3.3+/-0.5 to 1.3+/-0.7 (p<0.0001), with a significant increase in the area of the left ventricular outflow tract (1.3+/-0.2 to 2.6+/-0.2 cm2, p<0.0001). Three instances of transient atrioventricular block occurred, but no complete heart block was produced by the embolization procedure. CONCLUSIONS: Embolization of the septal artery with PVA foam particles appears effective and safe in this series of patients with hypertrophic obstructive cardiomyopathy. The pure ischemic infarction produced by PVA ablation might be the responsible for the lack of complete heart block and the need for permanent pacing.