PubMed Health⌕ Search

Biomedical subjects

J E Mackenzie

Publications and source records attributed to J E Mackenzie.

8 recordsLinked to original sources
PubMed1988

Influence of pretreatment with a monoamine oxidase inhibitor (phenelzine) on the effects of buprenorphine and pethidine in the conscious rabbit.

The existence of a severe toxic interaction (occasionally fatal) from the clinical use of pethidine and monoamine oxidase (MAO) inhibitors is well established. The present study evaluates the possibility of such an interaction existing for the opioid partial agonist buprenorphine. Conscious rabbits (n = 6 in each group) pretreated 18-24 h previously with physiological saline or the MAO inhibitor phenelzine 20 mg kg-1 s.c. were subsequently given physiological saline, pethidine 5 mg kg-1 i.v. or buprenorphine 0.1 or 1.0 mg kg-1 i.v. Whilst saline was without effect and phenelzine produced only a small increase in the rabbit temperature, the combination of phenelzine and pethidine produced a marked, prolonged hyperpyrexia (+4.4 +/- 0.19 degrees C; P less than 0.001), hypertension (+33.9 +/- 3.1 mm Hg; P less than 0.01) and agitation. Three rabbits died, at 35, 45 and 55 min after the pethidine-phenelzine combination. Buprenorphine was without significant effect on any parameter when given after phenelzine. In the model used buprenorphine, in contrast to pethidine, showed no interaction with the MAO inhibitor phenelzine.

Animals↗
PubMed1986

The haemodynamic and metabolic effects of tolmesoxide with special reference to impaired myocardial function.

The haemodynamic, metabolic and regional blood flow effects of the vasodilator, tolmesoxide (1 mg kg-1 min-1 for 20 min by intravenous infusion) were examined in two groups of greyhound dogs anaesthetized with alpha-chloralose and mechanically ventilated. One group of dogs was thoracotomized and subjected to acute coronary artery occlusion. In these dogs tolmesoxide was infused 2.5 h after occlusion when there was evidence of impaired myocardial function. Tolmesoxide administration resulted in marked systemic hypotension which was associated with myocardial stimulation (increase in heart rate and LVdP/dtmax). These effects were less marked in thoracotomized dogs subjected to coronary artery occlusion. Cardiac stimulation was attenuated by pretreatment with the beta-adrenoceptor antagonist, atenolol. Peripheral resistance and left ventricular end-diastolic pressure (LVEDP) were reduced by tolmesoxide. In spite of the systemic hypotension, the marked reduction in LVEDP resulted in an enhanced subendocardial driving pressure and an increased blood flow to ischaemic regions of the left ventricular wall as measured with Xe133 clearance. Blood flow to normal regions of the left ventricular wall was also increased by tolmesoxide. A metabolic and respiratory acidosis may have contributed to the haemodynamic effects of tolmesoxide. Plasma renin levels were significantly elevated by the drug. Tolmesoxide administration thus resulted in cardiac stimulation, reduced both pre-load and after-load, yet maintained coronary and pulmonary perfusion. This haemodynamic profile of tolmesoxide would explain the beneficial effects obtained with this drug in the treatment of cardiac failure.

Animals↗
PubMed1977

Comparative effects of glyceryl trinitrate on venous and arterial smooth muscle in vitro; relevance to antianginal activity.

1. A quantitative in vitro study has been made of the actions of glyceryl trinitrate and sodium nitrite on vascular smooth muscle (dog femoral artery and saphenous vein; rat portal vein); these have been compared with the actions of papaverine, isoprenaline, salbutamol, pentaerythritol tetranitrate and trimetazidine. 2. Glyceryl trinitrate was more active on the saphenous vein than on the femoral artery in inhibiting noradrenaline and potassium-induced tone. 3. Unlike glyceryl trinitrate, sodium nitrite and isoprenaline, papaverine and diazoxide inhibited noradrenaline-induced contractions of venous and arterial smooth muscle to the same extent. 4. The selective dilator effects of glyceryl trinitrate on venous smooth muscle may explain its action in alleviating the pain of angina pectoris. It is suggested that the use of these three vascular smooth muscle preparations (arterial, and veins with and without spontaneous myogenic activity) is a useful initial screening procedure for prospective antianginal drugs acting by venodilatation.

Angina Pectoris↗
PubMed1976

Halothane 0.2-4% analysis by gas chromatography.

The katharometer detector is better suited to the analysis of gaseous halothane (0.2-4%) than is the flame ionization detector, since the peak heights are directly proportional to concentration, and are more reproducible.

Chromatography, Gas↗
PubMed1973

Effects of oxyfedrine on isolated portal vein and other smooth muscles.

1. Oxyfedrine (0.01-1.0 mug/ml), inhibited spontaneous myogenic activity in rat isolated portal vein and carbachol-induced contractions of rat isolated uterus, and relaxed the rabbit duodenum and the guinea-pig tracheal chain preparation. These actions were prevented by the beta-adrenoceptor blocking drug alprenolol. Oxyfedrine was a relatively weak beta-adrenoceptor stimulant (10-100 times less active than isoprenaline) but its actions were more prolonged.2. In the same concentrations, oxyfedrine reduced or prevented the inhibition of myogenic activity of the rat portal vein induced by isoprenaline and by repeated doses of oxyfedrine itself, acting as a partial agonist at beta-adrenoceptor sites.3. Oxyfedrine, 1-12 mug/ml increased myogenic activity in the rat portal vein. This effect was not due to direct or indirect stimulation of alpha-adrenoceptors (because it was unaffected by phentolamine) or to potentiation of acetylcholine or 5-hydroxytryptamine.4. Oxyfedrine (>20 mug/ml) inhibited spontaneous myogenic activity in the portal vein and relaxed the saphenous vein contracted with noradrenaline. This spasmolytic effect of the drug was not due to beta-adrenoceptor stimulation or to inhibition of phosphodiesterase since it was unaffected by alprenolol and by concentrations of imidazole which antagonized the effects of the active phosphodiesterase inhibitor, papaverine. In the portal vein this effect of oxyfedrine was similar to that of the calcium inhibitor iproveratril; some of the effects of oxyfedrine on venous smooth muscle may be mediated through effects on calcium transport.

Adrenergic beta-Agonists↗