Endothelin elicits long-lasting vasoconstriction in the coronary bed. This remarkable spastic response raises the question whether or not the metabolic adaptive mechanisms of the coronaries are activated under endothelin effect. The role of the compensatory mediators adenosine and inosine was investigated before and after intracoronary (ic.) administration of endothelin-1 (ET-1, 1.0 nmol) using 1-min reactive hyperemia (RH) tests on in situ dog hearts (n=15) with or without blocking the ATP-sensitive potassium (K +ATP) channels by glibenclamide (GLIB, 1.0 mmol min –1, ic.). The release of adenosine and inosine via the coronary sinus was measured by HPLC during the first minute of RH. Endothelin-1 reduced baseline coronary blood flow (CBF) and RH response (hyperemic excess flow (EF) control vs. ET-1: 81.7±13.6 vs. 43.4±10.9 ml, P<0.01), while it increased the net nucleoside release (adenosine, control vs. ET-1: 58.9±20.4 vs. 113.7±39.4 nmol, P<0.05; inosine: 242.1±81.8 vs. 786.9±190.8 nmol, P<0.05). GLIB treatment alone did not change baseline CBF but also reduced RH significantly and increased nucleoside release (EF control vs. GLIB: 72.1±11.7 vs. 31.9±5.5 ml, P<0.01; adenosine: 18.8±4.6 vs. 63.0±24.8 nmol, P<0.05; inosine: 113.0±37.2 vs. 328.2±127.5 nmol, P<0.05). Endothelin-1 on GLIB-treated coronaries further diminished RH and increased nucleoside release (EF: 21.5±8.0 ml, P<0.05 vs. GLIB; adenosine: 75.3±28.1 nmol, NS; inosine: 801.9±196.6 nmol, P<0.05 vs. GLIB). The data show that ET-1 reduces metabolic adaptive capacity of the coronaries, and this phenomenon is due to decreased vascular responsiveness and not to the blockade of ischemic mediator release from the myocardium. The coronary effect of ET-1 may partially be dependent on K +ATP channels. _;
Authors:Csaba Kővágó, Ákos Hornyák, Violetta Kékesi and Miklós Rusvai
Complete genome sequences of bovine viral diarrhoea virus types 1 and 2 (BVDV-1 and 2) deposited in the GenBank were submitted to bioinformatic analysis using a recombination-detecting software. The results indicate that recombination events are not rare in the case of BVDV, which frequently causes immunotolerance and, consequently, persistent infection in calves. The lack of specific immunity provides an ideal possibility for multiple infections by antigenically related but genetically different BVDV strains, and hence recombinations may occur. Among the 62 BVDV-1 genomes five recombinants and their possible parent strains, while among the 50 BVDV-2 genomes one simple recombinant and its parent strains were identified, which were supported by extremely strong probability values (P values varying between 1.26 × 10–4 and 1.58 × 10–310). Besides the newly identified recombinants, recombination events described previously were confirmed, but in some of these cases former information was completed with new data, or different parent(s) were suggested by the programme (RDP 4.46 BETA) used in this study.
Authors:Z. Dudás Györki, A. Kollár, F. Manczur, Violetta Kékesi and K. Vörös
The aim of this study was to characterise the development of cardiac dilatation induced by chronic volume overload in 12 dogs. Bilateral arteriovenous fistulas were created between the common femoral arteries and the femoral veins, and the animals were serially studied with transthoracic echocardiography for a period of 12 weeks after the operation. Compared to the measurements obtained before the operation (week 0), the data obtained at the end of the experimental period showed significantly increased left ventricular volume measured by 2D-echocardiography (from 25.1 cm
to 43.8 cm
, p < 0.0001 in diastole and from 8.6 cm
to 16.8 cm
, p < 0.001 in systole), and left ventricular diameter measured by M-mode echocardiography (from 26.2 mm to 32.6 mm, p < 0.0001 in diastole and from 17.1 mm to 20.6 mm, p < 0.001 in systole). The size of the left atrium also increased in transversal (from 29.2 mm to 33.6 mm, p < 0.01) but not in longitudinal diameter. In spite of a significant cardiac chamber dilatation over the 12-week period, left ventricular systolic functional variables (fractional shortening, FS % and ejection fraction, EF %), and also the left ventricular systolic and diastolic free wall thickness remained unchanged. In this study we demonstrated that chronic progressive volume overload resulted in gradual dilatation of the canine heart, and that the pathological process can be monitored successfully by serial echocardiography. We found that left atrial dilatation occurred without the development of mitral regurgitation and/or detectable left ventricular dysfunction.