The blocking mechanism of the Na+ channel by penticainide, a disopyramide analogue, was studied in rabbit cardiac Purkinje fibers. Na+ channel activity was measured directly by recording the slowly inactivating Na+ current or indirectly by measuring Vmax. The two-microelectrode technique was used to measure currents under voltage-clamp conditions or to impose different degrees and durations of ...

Introduction Imaging sequences reliant upon non-selective refocusing (e.g., 3D TSE, 3D GraSE, and 3D SE-EPI) widely employ either block/sinc refocusing pulses susceptible to field inhomogeneities or adiabatic pulses that demand high SAR. The aim of this work was to evaluate a sample of short, low-SAR, non-selective refocusing pulses by comparing signals acquired with a 3D SE-EPI sequence at 7 T...

We theoretically propose a procedure for designing quasi-phase-matching (QPM) gratings for compressing ultrashort optical pulses during difference-frequency generation. The grating consists of blocks of crystal with the same block length and the direction of spontaneous polarization of each block is determined by an optimal algorithm through which the sign of the nonlinear coefficient of each b...

background: central obesity and hyperinsulinaemia of polycystic ovary syndrome (pcos) are associated with chronic sympathetic over activity. objective: to evaluate the autonomic functions and to indicate the superiority, if any, for those functions in the diagnosis of sympathetic over activity in pcos women. materials and methods: sixty-four pcos patients and 40 women served as the control grou...

The opiate analgesic propoxyphene produces cardiac toxicity when taken in overdose. We recently observed a patient with propoxyphene overdose in whom marked QRS widening was reversed by lidocaine. The reversal is apparently paradoxical as both agents block the inward sodium current (INa). We examined possible mechanisms of the reversal by measuring INa in rabbit atrial myocytes during exposure ...

Aminopyridines (2-AP, 3-AP, and 4-AP) selectively block K channels of squid axon membranes in a manner dependent upon the membrane potential and the duration and frequency of voltage clamp pulses. They are effective when applied to either the internal or the external membrane surface. The steady-state block of K channels by aminopyridines is more complete for low depolarizations, and is gradual...