Effect of sodium butyric acid, sodium valerianic acid, and osmolarity on contractility of specimens of intestinal wall obtained from the cecum and spiral colon of healthy cows.

OBJECTIVE: To compare the effect of various concentrations of sodium butyric acid and sodium valerianic acid, as well as various osmolarities, on contractility of ex-vivo intestinal wall specimens obtained from the cecum and spiral colon of each of several healthy cows. SAMPLE POPULATION: Full-thickness preparations of intestinal wall, dissected parallel to the longitudinal smooth muscle layers, harvested from freshly slaughtered healthy cows. PROCEDURE: Specimens of intestinal wall were incubated for 5 minutes with various concentrations of sodium butyric acid and sodium valerianic acid as well as various osmolar concentrations of NaCl, using a crossover design. Isometric contractions were induced 7 times with carbachol (CH; 5 X 10(-6) mol/L). Contractility was defined as the maximum amplitude of contraction and the amplitude of contraction 2 minutes after addition of CH. RESULTS: Repeated addition of CH did not result in a significant effect on contractility of specimens from the cecum and spiral colon. Contractility after addition of CH was not significantly affected by prior incubation with various concentrations of sodium butyric acid or sodium valerianic acid or after an increase of osmolarity. Maximum amplitude of contraction was significantly higher in specimens from the spiral colon, compared with specimens from the cecum. CONCLUSIONS: Increases in concentrations of sodium butyric acid or sodium valerianic acid and increases in osmolarity did not inhibit contractility of intestinal wall specimens from the cecum and spiral colon of a group of healthy cows.

Generating and influencing Torsades de Pointes--like polymorphic ventricular tachycardia in isolated guinea pig hearts.

Torsades de Pointes (TdP) is a polymorphic ventricular arrhythmia which can degenerate into ventricular fibrillation. The most typical symptom of TdP is the ECG morphology where QRS complexes seem to rotate around the isoelectric baseline. Bradycardia and delayed repolarization are regarded as pathophysiologic predispositions. For better understanding of the pathophysiology and the evaluation of therapeutic or proarrhythmic potential of drugs, a functional experimental model is needed. In the present study, an experimental model of polymorphic tachyarrhythmias taken as TdP equivalents in isolated guinea pig hearts was developed. The hearts were perfused by the Langendorff technique. Bradycardia was induced by dissection of the sinus node, and prolongation of the QT interval by infusion of two inhibitors of the sodium channel inactivation, veratridine and DPI 201-106. TdP equivalents were triggered reproducibly by application of electrical single stimuli at the end of the T wave. Experiments with different concentrations of the channel active substances alone and in combination, with different perfusion times and mode of electrical stimulation (single pulse versus train stimulation), showed the highest incidence for TdP equivalents by means of an initial 30 min long infusion of 0.5 microM each veratridine and DPI 201-106 in combination with electrical single stimuli. After finishing the infusion with the channel active substances but still with lasting effects from them. TdP equivalents were triggered repeatedly in five of six experiments. The reasons for this increased TdP susceptibility after finishing the infusion are not known. In a separate series of six similarly arranged experiments, the incidence for TdP equivalents could be decreased from 83% to 12.5% (p < 0.001) by increasing the concentration of magnesium in the perfusate from 1.17 to 5.0 mM. With these experiments, the clinically known therapeutic effect of magnesium suppressing TdP could be demonstrated in an in vitro model for the first time. The results suggest that this model could be used as a base for further studies of clinical relevant drugs, especially antiarrhythmic agents, to obtain hints of possible risks of proarrhythmic effects or of suitability for therapeutic use at TdP attacks.

Incidence of thymidine-dependent enterococci detected on Mueller-Hinton agar with low thymidine content.

It was observed that 10% of urine culture isolates of enterococci tested for antimicrobial susceptibility failed to grow on commercially prepared Mueller-Hinton agar with low levels of thymidine and thymine. All strains could utilize exogenous thymidine and thymine and required only low levels (0.4-microgram disk) to support growth. All thymidine-thymine-requiring strains were resistant to trimethoprim-sulfamethoxazole.