Acidaemia produced by spinal stimulation in the pithed rat

1. Electrical stimulation of the thoraco-lumbar spinal nervous outflow in the pithed rat preparation produces a fall in arterial blood pH.2. A component of the acidaemic response results from stimulation of skeletal muscle, since the acidaemic response is reduced when contractions of muscle are blocked with gallamine.3. The residual acidaemic response in gallamine-treated rats is reduced by adrenalectomy, suggesting that catecholamines liberated from the adrenal medulla may mediate part of the effect.4. Guanethidine reduces the acidaemic response remaining in adrenalectomized, gallamine-treated rats, suggesting that the effect of noradrenaline released from sympathetic nerve endings contributes to the fall in pH.5. Neither phenoxybenzamine nor propanolol alone significantly reduces the acidaemic response in gallamine-treated rats, but a combination of the two antagonists almost abolishes the effect. Hence the acidaemia is mediated through effects of catecholamines on both alpha- and beta-adreno-receptors.6. Since acidaemia affects responses to sympathetic nerve stimulation and sympathomimetic amines, the significance of these observations is discussed with reference to the use of the pithed rat preparation for assessment of drugs affecting adrenergic mechanisms.

A quantitative study of the anticholinergic action of several tricyclic antidepressants on the rat isolated fundal strip

1. Investigations were carried out on the antagonism of the action of carbamylcholine chloride on the isolated fundus of the rat stomach by several tricyclic antidepressants.2. The anticholinergic potency of the compounds was in the order: GP 45437>amitriptyline>protriptyline>desmethylimipramine>opipramol. All of the antagonists were less effective than atropine.3. Statistical analysis was carried out to determine whether the theory of competitive antagonism would fit the data obtained.

The effect of available dietary zinc on the utilization of protein by the chick and Japanese quail

1. Chicks and quail (Coturnix japonica) were used in the measurement of net protein utilization and true digestibility of nitrogen of isolated soya-bean protein and a mixture of casein and gelatin in zinc-deficient diets.

2. The net protein utilization values for both protein sources were increased when the diets were supplemented with Zn or with the disodium salt of ethylenediaminetetra-acetic acid, as was the true digestibility of nitrogen of the isolated soya-bean protein.

The influence of infection on titres of antiglobulin antibodies

The influence of acute and chronic infection and hypergammaglobulinaemia on the titres of anti-globulin antibodies was studied in 128 patients. Very high titres of serum agglutinators were found to be associated with gram positive septicaemia. This infection had no influence on the titres of rheumatoid factors. Elevated titres of serum agglutinators may be helpful in differentiating `benign' from `malignant' gammopathy.

The effect of directly and indirectly acting sympathomimetic amines on bronchospasm in the guinea-pig during CO2 inhalation

The bronchodilator effects of nine sympathomimetic amines were tested by reduction of histamine-induced bronchospasm in guinea-pigs. Their order of potency was: isoprenaline > adrenaline > noradrenaline > orciprenaline > ethylnoradrenaline > phenylephrine > amphetamine = tyramine > ephedrine. In guinea-pigs ventilated with 10% CO2 in air, there was a marked decrease in the bronchoconstrictor activity of histamine. Under these conditions, isoprenaline, adrenaline, noradrenaline and orciprenaline were as effective as bronchodilators as they had been in guinea-pigs ventilated with air, ethylnoradrenaline was less effective, phenylephrine, amphetamine and tyramine were completely inactive, and ephedrine potentiated the bronchoconstrictor action of histamine. After returning the guinea-pigs to ventilation with air, the bronchoconstrictor activity of histamine and the bronchodilator effects of the sympathomimetic amines were restored. The cardiovascular effects of histamine and of all the sympathomimetic amines used were diminished during ventilation with 10% CO2 in air and were restored after ventilation with air was resumed.

Mutal suppression of cardiovascular effects of some beta-adrenoreceptor agonists in the cat

Observations were made of the effects of adrenaline, isoprenaline and orciprenaline on the blood pressure, heart rate and configuration of the ECG in cats. The effects of single injections of these amines in producing a rise in heart rate and a fall in blood pressure were reduced during the intravenous infusion of any one of them: the pressor response to injected adrenaline was enhanced during an infusion. Combinations of these amines did not produce changes in the configuration of the ECG. These experiments were motivated by allegations of acute toxic effects on the cardiovascular system of large doses, or of combinations, of sympathomimetic bronchodilators in asthma. No evidence of deleterious effects of interactions was obtained.

Mikulicz's Disease

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