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Biomedical subjects

D M Ritchie

Publications and source records attributed to D M Ritchie.

28 records · Page 2Linked to original sources
PubMed1981

SRS-A mediated bronchospasm by pharmacologic modification of lung anaphylaxis in vivo.

Antigen challenge of actively sensitized guinea pigs results in the release of histamine eicosanoids (products of the cyclooxygenase pathway of arachidonic acid metabolism) and slow reducing substance of anaphylaxis (SRS-A). By antagonizing the effects of histamine, serotonin, and acetylcholine, inhibiting the cyclooxygenase pathway and supplying arachidonic acid as substrate, the contribution of SRS-A to anaphylactic bronchospasm can be enhanced, thus allowing suitable quantitation of antagonists. This SRS-A mediated bronchospasm can be inhibited in a dose dependent fashion by FPL55712, a selective antagonist of SRS-A. This system represents an in vivo method capable of detecting compounds which inhibit SRS-A synthesis/release of SRS-A action at the effector organ.

Anaphylaxis↗
PubMed1979

Comparison of the arrhythmogenic effect of myocardial infarction in the cat and dog.

Myocardial infarction was produced in dogs and cats by occlusion of the left anterior descending coronary artery. Arrhythmia was present in dogs but not in cats 6 to 48 h after occlusion. The absence of arrhythmia in cats was not due to persistent myocardial depressant effects of anaesthesia administered during surgery. Studies in cats with surgically-induced heart block revealed multiple ventricular pacemakers but no change in average ventricular rate following coronary occlusion. These results suggest that sinus overdrive, although not elevated compared with the dog, is sufficient to suppress arrhythmia in the cat. Further, since small dogs developed significantly less arrhythmia than large dogs, heart size may be an additional factor in explaining the absence of arrhythmia in the cat.

Animals↗
PubMed1978

Helium effect on isolated nerve activity.

Various gases were administered to isolated frog sciatic nerves in which action potential amplitudes were recorded in sheathed and desheathed preparations. In the sheathed preparation, nitrogen and argon showed significant anesthetic effects while in the desheathed preparation, helium also depressed the action potential amplitude. In the desheathed frog sciatic nerve, helium demonstrates an anesthetic effect similar to 10(-6) M lidocaine suggesting that at long exposure periods helium may demonstrate anesthetic properties.

Action Potentials↗
PubMed1975

Effect of helium on membrane resistance.

Resistance measurements were made of bimolecular lipid membranes (BLM) according to Mueller and Rudin (10). With the addition of excitability inducing material (EIM), a bacterial protein, the electrical resistance of the BLM was reduced to within biological limits. Frog pericardium was used in the same system as a natural membrane comparison. Exposure of these membranes to air, oxygen and nitrogen resulted in no significant change in the resistance of the bilayers or the pericardium. Exposure to helium and helium 79%-oxygen 21% mixutre resulted in a significant increase in the membrane resistance.

Animals↗
PubMed1975

Cardiovascular and antiarrhythmic effects of carnitine.

Thresholds for electrically induced atrial fibrillation were measured in response to IV carnitine. Mean arterial pressure, heart rate, and mean aortic flow rate were also monitored. Carnitine 100 mg/kg resulted in an increase in mean aortic blood flow. The antiarrhythmic effect was much less than with 5 mg/kg quinidine, but after atropinization, 100 mg/kg carnitine was similar in antiarrhythmic effect to quinidine and did not result in the blood pressure depression seen with quinidine.

Animals↗