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Biomedical subjects

J H BURN

Publications and source records attributed to J H BURN.

At least 73 records · Page 4Linked to original sources
PubMed1958

The action of sympathomimetic amines on heart rate in relation to the effect of reserpine.

When the heart-lung preparation is made from a dog treated with reserpine, catechol amines such as noradrenaline and isoprenaline have a greater effect on the rate of the heart than they have in a preparation from a normal dog. Other sympathomimetic amines such as tyramine and ephedrine, on the other hand, are found to have lost their action. Since treatment with reserpine has been shown to cause the store of noradrenaline in the heart to disappear, and the infusion of noradrenaline into the preparation made from a reserpine-treated animal restores the action of tyramine, it is concluded that substances like tyramine and ephedrine normally act by liberating noradrenaline from the store, and do not act directly. Cocaine, like reserpine, increases the effect of noradrenaline and decreases the effect of tyramine on the heart rate; it appears to block the release of noradrenaline from the store in the heart.

Amines↗
PubMed1958

The depressor action of dopamine and adrenaline.

Dopamine is a pressor agent in the spinal cat, but causes a fall of blood pressure in the guinea-pig and rabbit under urethane anaesthesia. When guinea-pigs and rabbits are injected with reserpine, which depletes the vessel walls of noradrenaline, dopamine then becomes pressor. If an intravenous infusion of noradrenaline is given the depressor action returns. An intravenous infusion of vasopressin does not have this effect.A strip of rabbit aorta is caused to contract by noradrenaline and by dopamine, but if dopamine is added at the height of a noradrenaline contraction it causes relaxation.Adrenaline causes a fall of blood pressure in the cat under ether with vagi cut. However, in a reserpine-treated cat its action is pressor. The depressor action is restored during an infusion of noradrenaline. Noradrenaline has thus been shown to cause a vasomotor reversal of dopamine and of adrenaline.

Animals↗
PubMed1957

Ventricular fibrillation in the isolated rabbit heart.

Ventricular fibrillation has been produced in the isolated and perfused rabbit heart by stimulating electrically at a rate from 500 to 700/min. When the perfusion fluid contained normal amounts of sodium, potassium and calcium, the fibrillation persisted after the stimulation was stopped in about 40% of hearts. When the sodium was reduced to half, tonicity being maintained by sucrose or by choline chloride, persistent fibrillation was observed in 100% of hearts. The addition of eserine or of atropine or of carbachol did not alter the percentage of hearts in which fibrillation persisted. The antimalarial compounds chloroquine, mepacrine, and pyrimethamine arrested persistent fibrillation, restoring a normal rhythm.

Animals↗