Nonuniform action potential durations at different sites in canine left ventricle

We studied the action potential duration (APD) of isolated ventricular muscle fibers. Action potentials were recorded from four different sites (endocardium and epicardium at the apex and the base) in the canine left ventricle by microelectrode techniques. Action potentials from endocardial and corresponding epicardial specimens, and the differential potential between them were recorded simultaneously. The APDs at 60% and 90% repolarization (APD60 and APD90) were measured during superfusion with normal (K+ = 2.7 mM) and altered (K+ = 5.4 mM) Tyrode's solutions. Results were: 1) the distributions of APDs agreed with previous descriptions from in vivo studies; 2) endo-epicardial APD gradients were different between the apex and the base, and apico-basal APD gradients were different between endocardium and epicardium; 3) the shapes of the differential potentials in normal and altered Tyrode's solution were similar to the electrocardiographic T wave form in normal and in mild hyperkalemia. It was concluded that nonhomogeneous APDs may be due to the inherent characteristics of cardiac muscle and the nonuniform endo-epicardial APD gradient helps to account for the genesis of the electrocardiographic T wave form.

Effects of hyperkalemia on local changes of repolarization duration in canine left ventricle

The effect of hyperkalemia on the distribution of ventricular repolarization properties was investigated using the interval between minimum QRS and maximum T derivatives of multiple electrograms as a measure of local repolarization duration. Local repolarization duration decreased, with more marked reduction at the epicardium than endocardium near the base, and greater decrease at the endocardium than epicardium near the apex. The nonhomogeneous reduction of repolarization duration helps account for T waveform changes due to hyperkalemia and may be a factor in the occurrence of re-entrant ventricular arrhythmias.

Fiber-optic multifunction devices using a single GRIN-rod lens for WDM transmission systems

A series of passive fiber-optic devices, which includes a new type multiplexer-demultiplexer for WDM transmission, has been developed. The multiplexer-demultiplexer is composed of a single GRIN-rod lens and interference filters. Small in size, it has low-loss and high-isolation characteristics by means of direct attachment of filters on the fiber and the lens end. Total loss and cross talk for a pair of two-channel multiplexer-demultiplexers for two LEDs are <3.0 dB and less than -30 dB, respectively. By this method, multifunction devices such as multiplexer-demultiplexers with an optical switch can be constructed using a single lens.

The short- and long-term effects of haloperidol on rat central dopamine turnover

We carried out a quantitative fluorescent histochemical analysis in rats in order to clarify the effects of chronic treatment with haloperidol on the central dopamine turnover. Long-term treatment with haloperidol showed no significant reduction of dopamine fluorescence intensities in the n. caudatus putamen, the n. accumbens, and the tuberculum olfactorium. This suggests that tolerance is established after long-term treatment with haloperidol in both mesolimbic and nigrostriatal dopamine systems, whereas tolerance is not observed in the tuberoinfundibular dopamine system.

Novel and sensitive activity stains on polyacrylamide gel of serine and threonine dehydratase and ornithine aminotransferase

A sensitive activity stain for serine and threonine dehydratase is described. After electrophoresis on thin-layer polyacrylamide gel, a reaction mixture containing L-serine or L-threonine as a substrate, NADH, lactate dehydrogenase and agar was solidified on the gel. The oxidation of NADH was recorded by contact printing on photographic paper with UV light. A novel activity stain for ornithine aminotransferase in the gel is also described. A reaction mixture containing substrates, o-aminobenzaldehyde and agar was solidified on the gel. A yellow color developed in a reaction between pyrroline-5-carboxylate and o-aminobenzaldehyde. The photograph was taken by contact printing. Both of the methods are highly sensitive and can detect less than 0.01 unit (mumol product/min at 37 degrees C) of each enzyme.

Motion of equivalent electric dipole to cardiac activity estimated from body surface potentials

By means of the least square method, the motion of an equivalent electric dipole which simulates electric activity of the heart was traced from body surface potentials. In normal case, this equivalent dipole was a good approximation.