High resolution electrocardiography in healthy dogs: time domain parameters and comparison of the non-stationary (Wigner distribution) versus standard stationary frequency domain analysis methods.

Fractionated heart activation can be detected as late potentials from surface recordings of signal-averaged electrocardiograms (SA ECG) which are considered as a marker of sustained ventricular tachycardia. For animal studies, reference values in time and frequency domain analyses are essentially missing. In the present study, we have established reference values in SA ECG time domain analysis and time-frequency representation of heart activation in healthy dogs. A group of 25 healthy mongrel dogs (body weight 12-15 kg) was investigated. Wigner distribution and our modification of Fast Fourier transform (FFT), gliding window FFT, was applied in SA ECG frequency domain analysis. Reference values in time domain SA ECG were established. Time and voltage criteria were adapted to short duration of heart cycle and fast voltage decrement of the QRS complex in dogs. Wigner distribution and gliding window FFT were applied in order to describe mean heart activation in the frequency domain. Contribution of higher frequencies (30-80 Hz) was detected by both frequency analysis methods in the second third of ventricular activation in healthy animals. Presented results could offer a basis for further experimental arrhythmologic studies.

[The effect of streptozotocin-induced diabetes in the neonatal period on hepatic mitochondrial bioenergetics in adult rats]. / Vplyv streptozotocínového diabetu vyvolaného v neonatálnom období na bioenergetiku mitochondrií pecene dospelých potkanov.

BACKGROUND: Previous experimental studies focused on the liver mitochondrial bioenergetic changes in diabetes mellitus type I induced in adult animals. Information about the effects of persisting neonataly induced diabetes mellitus type I on the mitochondrial bioenergetics are missing. AIM: The aim of the study was to assess the degree of diabetes mellitus compensation and parameters of oxidative phosphorylation in rats aged 3 months with DM persisting from neonatal period. METHODS: DM was induced in male Wistar rats by repeated intraperitoneal administration of streptozotocine 45 mg/kg on 2nd and 9th day after birth. The concentrations of glucose, glycosylated haemoglobin, fructosamine were detected in the blood and the concentration of cholesterol and triacylglycerols in the blood and liver tissue, respectively. After mitochondria isolation from the liver we measured parameters of oxidative phosphorylation by polarography using Clark oxygen electrode. RESULTS: In the group of neonataly induced DM the concentration of glucose (23.10 +/- 1.55 vs 8.3 +/- 0.56 mmol/l), glycosylated haemoglobin (6.04 +/- 1.17 vs 3.99 +/- 0.44%) and blood cholesterol concentration (2.15 +/- 0.11 vs 1.83 +/- 0.09 mmol/l) increased significantly (p < 0.001 and p < 0.005 for cholesterol) comparing to a group of healthy rats. No statistically significant differences were found in the remaining parameters when comparing these two groups. The parameters of oxidative phosphorylation were significantly (p < 0.001) decreased in the group with DM comparing to control group of healthy animals--the index of respiratory control (4.87 +/- 0.25 vs 9.57 +/- 0.34), the rate of oxygen consumption in the stage 3 in ADP presence (88.61 +/- 4.62 vs 165.08 +/- 4.5 natO.mg/protein/min) and phosphorylation rate (203.54 +/- 7.26 vs 332.87 +/- 7.39 nmolATP.mg/protein/min) with NAD substrate glutamate. Similar trend was also seen with FAD substrate succinate. The index of oxidative phosphorylation ADP:0 was not changed in both groups. CONCLUSIONS: In 3 months old rats with neonataly induced DM the development of steatosis was not observed and uncoupling of oxidative processes from phosphorylation did not appear. Energy production was sufficient enough for normal functions of the liver and to ensure all needs of the organism. (Tab. 4, Ref. 51.)

Morphological findings after intracoronary application of endothelin-1 in dog.

BACKGROUND: Endothelin-1 is a strong vasoconstrictor, high doses of which can cause prolonged vasoconstriction. MAIN PURPOSE: The aim of our study was to investigate as to whether the endothelin-induced vasoconstriction causes irreversible morphological changes in the myocardium in experimental animals and to verify the applicability of this experimental model in the study of the impact of endothelin. METHODS: Fourteen anaesthetized dogs were administered with 400 pmol of endothelin. The substance was applied into the left anterior descending coronary artery. The serum activities of AST, CK and LD enzymes, and changes in electric activity of the myocardium were monitored. The heart of one of the dogs was analyzed morphologically. RESULTS: Following the application of endothelin, vasoconstriction supervened, lasting from 25 to 27 minutes. Five dogs developed fibrillation of ventricles and died. The dogs which survived yielded changes in the activities of the investigated enzymes and changes in electric activity which were typical of focal impairment of the myocardium in sense of necrosis. Morphologically the changes represented disseminated fibrosis or minor scars in the myocardium. CONCLUSIONS: Application of endothelin into the coronary artery can cause irreversible structural changes in the myocardium. (Fig. 1, Ref. 18.).