Microsatellite evolution in the mitochondrial genome of Bechstein's bat (Myotis bechsteinii).

Being highly polymorphic, microsatellites are widely used genetic markers. They are abundant throughout the nuclear genomes of eukaryotes but rare in the mitochondrial genomes (mtDNA) of animals. We describe a short but highly polymorphic AT microsatellite in the mtDNA control region of Bechstein's bat and discuss the role of mutation, genetic drift, and selection in maintaining its variability. As heteroplasmy and hence mutation rate were positively correlated with repeat number, a simple mutation model cannot explain the observed frequency distribution of AT copy numbers. Because of the unimodal distribution of repeat numbers found in heteroplasmic individuals, single step mutations are likely to be the predominant mechanism of copy number alternations. Above a certain copy number (seven repeats), deletions of single dinucleotide repeats seem to be more common than additions, which results in a decrease in frequency of long alleles. Heteroplasmy was inherited from mothers to their offspring and no evidence of paternal inheritance of mitochondria was found. Genetic differences accumulated with more distant ancestry, which suggests that microsatellites can be useful genetic markers in population genetics

Clinical outcome of patients with malignant ventricular tachyarrhythmias and a multiprogrammable implantable cardioverter-defibrillator implanted with or without thoracotomy: an international multicenter study

Objectives. The long term efficacy and safety of a third-generation implantable cardioverter-defibrillator implanted with thoracotomy and nonthoracotomy lead systems was evaluated in a multicenter international study. Background. The clinical impact of transvenous leads for nonthoracotomy implantation and pacing for bradyarrhythmias and tachyarrhythmias in implantable cardioverter defibrillator systems is not well defined. Methods. The safety of the implantation procedure and clinical outcome of 1,221 patients with symptomatic and life-threatening ventricular tachyarrhythmias who underwent implantation of a third generation cardioverter defibrillator using either a thoracotomy approach with epicardial leads (616 patients) or a nonthoracotomy approach with endocardial leads (605 patients) in a nonrandomized manner was analyzed. The implantable cardioverter defibrillator system permitted pacing, cardioversion, defibrillation, arrhythmia event memory and noninvasive tachycardia induction. Results. Successful implantation of an endocardial lead system was achieved in 605 (88.2%) of 686 patients and an epicardial system in 614 (99.7%) of 616 (p 0.2). Conclusions. Third-generation cardioverter defibrillators with monophasic waveforms can be successfully implanted with epicardial (99.7%) and endocardial (88.2%) lead systems. We conclude that endocardial leads should be the implant technique of first choice. Improved patient management and tolerance for device therapy is achieved with the addition of antitachycardia pacemaker capability in these systems