RESUMO
Torsade de pointes is a well-established toxic effect of sotalol hydrochloride. In a patient presenting with torsade de pointes and a long QTc interval of unknown cause, a serum sotalol level was used to secure an otherwise difficult diagnosis.
Assuntos
Antiarrítmicos/intoxicação , Eletrocardiografia , Síndrome do QT Longo/induzido quimicamente , Sotalol/intoxicação , Torsades de Pointes/induzido quimicamente , Adulto , Antiarrítmicos/administração & dosagem , Antiarrítmicos/sangue , Overdose de Drogas , Feminino , Humanos , Síndrome do QT Longo/diagnóstico , Sotalol/administração & dosagem , Sotalol/sangue , Torsades de Pointes/diagnósticoRESUMO
Cardiac arrhythmias are common in the perioperative period. Most arrhythmias are clinically benign. Occasionally, cardiac arrhythmias and conduction disturbances can pose a major additional risk to the patient in the perioperative and postoperative periods. The current availability of a wide array of techniques for controlling serious arrhythmias--pharmacologic, electrical, and interventional--enable the physician to manage most arrhythmias and conduction disturbances successfully. The added risks posed by arrhythmias and conduction disturbances in the perioperative period now can be minimized.
Assuntos
Arritmias Cardíacas/etiologia , Complicações Pós-Operatórias , Amiodarona/uso terapêutico , Fibrilação Atrial/tratamento farmacológico , Flutter Atrial/tratamento farmacológico , Procedimentos Cirúrgicos Cardíacos , Desfibriladores Implantáveis , Humanos , Marca-Passo Artificial , Fatores de Risco , Taquicardia/tratamento farmacológico , Taquicardia Supraventricular/tratamento farmacológico , Procedimentos Cirúrgicos TorácicosRESUMO
Transgenic mice are increasingly being utilized for understanding cardiac electrophysiologic abnormalities. However, little is known about the normal atrioventricular nodal and infraHisian physiology in the mouse because of the prior inability to record a His-bundle deflection. We present the first comprehensive examination of the murine atrioventricular nodal and His-Purkinje systems employing His-bundle recordings. Normal, healthy, male C57BL/6J mice (n = 48) underwent an in vivo electrophysiology study using a 2 F octapolar electrode catheter. Effective refractory periods were determined during premature atrial and ventricular stimulation. The PR interval measured 44 +/- 6 ms with a mean sinus cycle length of 185 +/- 42 ms. Baseline AH intervals were 36 +/- 5 ms and HV intervals were 10 +/- 2 ms. At a pacing cycle length of 140 ms the atrioventricular nodal effective refractory period (AVNERP) and atrial effective refractory period (AERP) were 86 +/- 19 ms and 57 +/- 17 ms, respectively. The mean AV Wenckebach and 2:1 paced cycle length were 103 +/- 14 ms and 84 +/- 13 ms, respectively. Premature atrial stimulation curves were asymptotic without discontinuity. A subset of nine mice was studied after administration of isoproterenol. The sinus cycle length, AVNERP and AERP decreased significantly from baseline measurements. This method establishes a practical and feasible technique to record in vivo His-bundle electrograms in the mouse to assess atrioventricular nodal and infraHisian physiology. Use of this model will allow for the examination of abnormalities of atrioventricular nodal and infraHisian conduction in transgenic murine models.
Assuntos
Nó Atrioventricular/fisiologia , Agonistas Adrenérgicos beta/administração & dosagem , Animais , Nó Atrioventricular/efeitos dos fármacos , Fascículo Atrioventricular/efeitos dos fármacos , Fascículo Atrioventricular/fisiologia , Eletrofisiologia , Frequência Cardíaca/efeitos dos fármacos , Injeções Intraperitoneais , Isoproterenol/administração & dosagem , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Ramos Subendocárdicos/efeitos dos fármacos , Ramos Subendocárdicos/fisiologia , Estimulação QuímicaRESUMO
The Nun protein of phage HK022 blocks the expression of genes that lie downstream of the nut sites of phage lambda. Nun is believed to act by promoting premature termination of transcription at or near these sites. To test this hypothesis and to facilitate mapping the sites of termination, we inserted a gene encoding a suppressor tRNA immediately downstream of the lambda nutL site and determined the effect of Nun on tRNA level. We found that Nun severely reduced the accumulation of mature, biologically active tRNA and promoted the accumulation of short, promoter-proximal transcripts whose 3' ends were dispersed over a 100-nucleotide region downstream of nutL. These results are consistent with the hypothesis that Nun terminates transcription within the region immediately downstream of nutL and are inconsistent with the hypothesis that the only action of Nun is to prevent translation of genes located downstream of the nut site. The stability, small size, and easily assayable biological function of suppressor tRNA recommend it as a reporter of transcription in other systems.
Assuntos
Colífagos/genética , Escherichia coli/genética , Expressão Gênica , Genes Supressores , Genes Virais , RNA de Transferência de Glicina/genética , Fatores de Transcrição/metabolismo , Proteínas Virais/metabolismo , Bacteriófago lambda/genética , Bacteriófago lambda/metabolismo , Sequência de Bases , Northern Blotting , Clonagem Molecular , Colífagos/metabolismo , Escherichia coli/metabolismo , Genótipo , Dados de Sequência Molecular , Conformação de Ácido Nucleico , Plasmídeos , RNA de Transferência de Glicina/biossíntese , Mapeamento por Restrição , Supressão Genética , Transcrição GênicaRESUMO
We report the sequence of a region of the PR operon of lambdoid phage HK022 and an analysis of the proteins it encodes. This region has DNA sequence elements and open reading frames that resemble those found in phages lambda, P22, and phi 80. The open reading frames encode homologs of the lambda CII transcription activator, the P22 DNA replication proteins, and a fourth protein of unknown function.
Assuntos
Bacteriófago lambda/genética , Colífagos/genética , DNA Helicases , Genes Virais , Proteínas Virais/genética , Proteínas Estruturais Virais/genética , Sequência de Aminoácidos , Proteínas de Bactérias/genética , DnaB Helicases , Dados de Sequência Molecular , Óperon , Alinhamento de Sequência , Homologia de Sequência de Aminoácidos , Fatores de Transcrição/genéticaRESUMO
E. coli lysogenic for the temperate, lambda-related phage HK022 do not support lambda growth. The exclusion of lambda is caused by the HK022 nun gene product, which blocks the expression of genes located downstream of and in the same transcription unit as the lambda nutL and nutR sequences. Transcripts terminating prematurely at or near nutR have been detected after inactivation of lambda repressor in lambda, HK022 dilysogens. Nun therefore appears to be a transcription termination factor with a remarkable specificity; it converts the lambda nut sequences, which normally interact with lambda N protein to suppress transcription termination, into terminators. These and other similarities between Nun-promoted termination and N-promoted antitermination argue strongly that the mechanisms of the two reactions have steps in common.