Locus of symptom limitation and exercise response to bronchodilation in chronic obstructive pulmonary disease.

Purpose: To evaluate the concordance between subjective and objective indices of muscle fatigue during exercise and to assess the significance of the perception of dyspnea and leg fatigue for the exercise response to bronchodilation in chronic obstructive pulmonary disease (COPD).

Methods: Sixty-eight patients with COPD performed either 2 constant work-rate cycling exercises or 2 endurance shuttle walking tests. These tests were preceded by nebulization of placebo or 500 mug of ipratropium bromide.

Biophysical characteristics of a new mutation on the KCNQ1 potassium channel (L251P) causing long QT syndrome.

The congenital long QT syndrome (LQTS) is a hereditary cardiac disease characterized by prolonged ventricular repolarization, syncope, and sudden death. Mutations causing LQTS have been identified in various genes that encode for ionic channels or their regulatory subunits. Several of these mutations have been reported on the KCNQ1 gene encoding for a potassium channel or its regulatory subunit (KCNE1).