Percutaneous cervical oesophageal cannulation in the dog for the performance of prolonged oesophageal pH and manometric studies

Traditional methods for obtaining oesophageal access in experimental animals are unsuitable for prolonged (24 h) oesophageal pH evaluation, a procedure that is commonly employed in the assessment of human patients suspected of having gastroesophageal reflux disease. In the present study, we describe a six-year experience with a technique of percutaneous oesophagostomy for the performance of serial 24 h oesophageal pH and manometric studies involving 62 dogs and a total of 208 oesophageal cannula placement procedures. The results indicate a considerable improvement over previously described techniques with respect to simplicity of surgical technique, associated morbidity, oesophagostomy management, animal conditioning, and avoidance of chemical and excessive physical restraints in animals undergoing oesophageal pH and manometric evaluation.     

The effect of time left alone at home on dog welfare

The aim of this study was to investigate the effect of time left alone on dog behaviour and cardiac activity. Twelve privately owned dogs, with no history of separation related behaviour problems, were video-recorded on three different occasions when left alone in their home environment. The treatments lasted for 0.5 h (T_0.5); 2 h (T₂) and 4 h (T₄). Video-recording started 10 min before the owner left the house and continued until 10 min after the owner returned, so that interactions between dog and owner as well as behaviour during separation could be studied. Data on heart rate (HR) and heart rate variability (HRV) were collected within the same time period in each treatment. In addition to analysing behaviours separately, behaviours were also grouped together and defined as new variables; physically active, attentive behaviour, vocal, interaction initiated by owner and interaction initiated by dog. There were no differences in behaviour between treatments at equivalent time intervals until the owner returned, although a number of differences were observed at reunion with the owner. Dogs showed a higher frequency of physical activity (P < 0.05) and attentive behaviour (P < 0.01) in T₂ (0.37 ± 0.07; 0.52 ± 0.08, mean frequency of occurrence/15 s ± SE) and T₄ (0.48 ± 0.08; 0.48 ± 0.07) compared to T_0.5 (0.20 ± 0.07; 0.21 ± 0.05). They also showed more tail wagging (P < 0.01) and interacted more with their owners (P < 0.01) in T₂ (0.27 ± 0.08; 0.47 ± 0.09) and T₄ (0.26 ± 0.04; 0.42 ± 0.09) compared to T_0.5 (0.09 ± 0.04; 0.14 ± 0.03). After a longer time of separation, the dogs also showed higher frequencies of lip licking (P < 0.05) and body shaking (P < 0.05) at the owner's return (T_0.5 = 0.09 ± 0.05; T₂ = 0.24 ± 0.08; T₄ = 0.27 ± 0.06 and T_0.5 = 0.03 ± 0.01; T₂ = 0.08 ± 0.03; T₄ = 0.07 ± 0.01, respectively). There was a tendency for higher HR (P < 0.1) during the first and second minute after reunion in T₂ (127.6 ± 1.25, mean bpm ± SE; 111.3 ± 1.24) compared to T_0.5 (106.2 ± 1.06; 87.5 ± 1.02). According to the results of this study, the effect of time left alone was shown by a more intense greeting behaviour by the dog towards their owner as well as by a higher frequency of physical activity and attentive behaviour when the owner returned, already after 2 h of separation. Although this study cannot distinguish between whether dogs were aware of the length of time they were alone (but did not signal it) or whether they were unaware until reminded of it by the return of their owner, it does confirm that dogs are affected by the duration of time at home alone.     

Assessment of fatty acids in dog left ventricular myocardium

The concentration and composition of fatty acids in four lipid classes in biopsies of dog left ventricular myocardium were determined, using gas-liquid chromatography. When precautions were taken to minimize lipolysis during storage of the tissue and the homogenization process, the following results were obtained: 29 ± 10 nmol non-esterified fatty acids, 2.98 ± 2.41 μmol triacylglycerol, 149 ± 51 nmol cholesteryl esters and 23.76 ± 3.38 μmol phospholipid (expressed as fatty acid moiety per gram of wet tissue). The concentration of non-esterified fatty acids was 15 to 300 times lower than reported in literature.The main constituents of the non-esterified fatty acids were palmitic, stearic and oleic acid. Triacylglycerol consisted of approximately 40% esterified oleic acid. Linoleic acid accounted for 40% of the fatty acids in the cholesteryl-esters class. More than half of the fatty acid moiety of total phospholipids was linoleic acid and arachidonic acid.     

Nonobstructive chronic cannulation of the left circumflex coronary artery of the dog.

A cannulation technique for creating a nonobstructive port in a proximal coronary artery is described. The use of this technique in awake animals allows the blood pressure to be measured in a coronary artery distal to an experimentally produced stenosis. This port can also be used to inject drugs directly into the coronary bed.     

The role of displacement of the mitral annulus in left atrial filling and emptying in the intact dog

The variations in ventricular-atrial mitral annular position during the cardiac cycle and the simultaneous changes in left atrial silhouette area (obtained by angiography after injections of contrast material into the main pulmonary artery) were investigated in six experiments on intact dogs with chronically implanted intracardiac markers. Frame-by-frame measurements of the angiograms (120 frames/s) were used to determine, under various hemodynamic conditions, the duration, magnitude, and average rate of the mitral annular motion and of the simultaneous changes in left atrial area during atrial filling (ventricular systole) and atrial emptying (early in ventricular diastole). The mitral annulus was seen to move towards the ventricular apex during systole and towards the atrium early in diastole with the duration, average rate, and magnitude of displacement (although varying widely) showing good statistical correlations (P less than 0.0005-0.005) with the changes in projected left atrial area. These findings suggest that the duration, rate, and magnitude of atrial filling and emptying may be, in the intact heart, determined by the movements of the atrioventricular junction.     

Evaluation of extravascular resistance in the unloaded fibrillating left ventricle of the dog

In open-chest anaesthetized dogs the relative magnitude of extravascular resistance in the superficial and deep left ventricular myocardium was estimated from the flow through the isolated vascular segments inserted at different depths of the myocardium. It was confirmed that in the normally working heart extravascular resistance was significantly greater in the deep than in the superficial layer. In the unloaded fibrillating left ventricle no difference in extravascular resistance between these layers could be detected. Since it had been found previously that subendocardial preponderance of ischaemia persists in the unloaded fibrillating left ventricle (Sedek and Micha?owski, submitted for publication), the present observation is a further challenge for the current view that the subendocardium is more vulnerable to ischaemia because extravascular resistance is greater in this layer.     

Influence of the pericardium on right and left ventricular filling in the dog

We compared the influence of the pericardium on left and right ventricular (LV, RV) filling by measuring LV and RV pressures and segment lengths (SL, LV free wall, and RV inflow and outflow tracts) in six open-chest, pentobarbital sodium-anesthetized dogs before and after pericardiectomy. End-diastolic pressure (EDP) was varied by partial caval occlusion and dextran infusion. At each site the ln EDP-SL relation was fitted by linear regression and characterized by its slope and 1-Torr EDP intercept. The slope and 1-Torr intercept of the LV ln EDP-SL relation changed variably after pericardiectomy, but in each dog a change occurred that shifted this relation downward. In contrast, the RV inflow tract slope invariably decreased significantly after pericardiectomy, whereas its intercept was unchanged in all but one dog. The RV outflow tract results were similar to the inflow tract but less consistent. By the use of the raw EDP-SL data points, we calculated that the absolute contribution of the pericardium to EDP (i.e., the effective pericardial surface pressure) was similar at the three sites. However, as EDP values increased the proportional contribution of the pericardium to right ventricular end-diastolic pressure (RVEDP) increased, whereas that to left ventricular end-diastolic pressure (LVEDP) remained relatively constant. As a result, at the higher EDP values tested, the pericardium was responsible for a larger proportion of RVEDP than LVEDP.(ABSTRACT TRUNCATED AT 250 WORDS)