Biomedical subjects

R M Graham

Publications and source records attributed to R M Graham.

At least 199 records · Page 11Linked to original sources

PubMed1976

A prescreening device for cancer of the uterus.

A prescreening device for cancer of the uterus was based on the slower sedimentation rate of cells from a vaginal aspirate in the presence of cancer than in its absence. The apparatus recorded the increase in light transmission through the test tube as the cells fell. This mechanical examination of the rate of fall of vaginal and cervical cells did not diagnose cancer, but it identified the normal specimens free of cancer or infections. The negative specimens comprised the bulk of diagnostic material. There was a small increase in false-negative rate compared with the false-negative rate in standard cytologic tests, but this was counterbalanced by the increase in the number of specimens examined.

Adult↗

PubMed1976

The role of renin in the antihypertensive action of beta-adrenoreceptor blocking agents.

Since the original reports suggesting that the antihypertensive action of beta-adrenoreceptor blocking drugs is related to their inhibitory action on renin release, much evidence has been put forward both to refute and support this hypothesis. Our studies of the acute and chronic effects of treatment with propranolol in hypertensive patients showed that the antihypertensive action of the drug was of later onset than the initial cardio-depressant and renin-suppressive effects and had little relationship to the pre-treatment levels of treatment-induced changes in plasma renin activity (PRA). When pindolol was substituted for propranolol in these studies PRA rose, but blood pressure control was undisturbed. Again, in animal experiments, although a range of different beta-adrenoreceptor blocking agents induced decreases in both blood pressure and PRA, the hypotensive effects of pindolol was associated with a rise in PRA. Further, PRA proved to be a poor guide to therapeutic effectiveness in the treatment of an unselected population of hypertensive patients with propranolol. It is concluded that the antihypertensive action of beta-adrenoreceptor blocking agents, as a class, is not dependent upon suppression of PRA.

Adrenergic beta-Antagonists↗

PubMed1976

Haemodynamic effects of prazosin.

Parzosin, 0.001 to 10 mg/kg, was administered intravenously to anesthetized normal rats. In the dose range 0.001 to 0.01 mg/kg, the drug induced highly significant, dose-related falls in blood pressure, pulse pressure and heart rate. With doses above 0.01 mg/kg, there was a plateau in hypotensive efficacy and a diminution in negative chronotropic activity. Both actions of prazosin (0.01 mg/kg) were unaffected by vagal blockade with atropine, while hypotensive potency was unimpaired after beta-adrenoreceptor blockade. The vasodilator, diazoxide, lowered blood pressure, widened pulse pressure and caused tachycardia in rats pre-treated with pentolinium. In contrast, all effects of prazosin were abolished by ganglion blockade. These findings, together with the absence of compensatory tachycardia or gross renin hypersecretion during prazosin-induced hypotension, are compatible with an antisympathotonic mode of action for the drug. However, consistent with its effects on cyclic nucleotide distribution, prazosin appears to enhance isoprenaline-induced beta-receptor stimulation.

Animals↗

PubMed1976

Suppression of renin release by timolol.

The beta-adrenergic blocking agent, timolol, administered to resting rabbits as an i.v. bolus (0.125 mg/kg) sustained by a 2-hr infusion at 0.0625 mg/kg/hr, caused significant depression of plasma renin activity (PRA) to 49% of the control level. Significant correlations emerged between the fall in mean blood pressure and changes in both heart rate and PRA. Timolol also antagonized isoprenaline-induced renin release. In anaesthetized normal rats, timolol (0.2 mg/kg i.p.) suppressed mean plasma renin concentration (PRC) to 16% of the pre-treatment value. Furthermore, the mean PRC of normal rats, bled immediately after decapitation, to avoid stimulating renin secretion, was reduced by 55% one hr after i.p. injection of timolol. The potency of timolol in this respect was 8 times that of dl-propranolol. Thus, in rabbits and rats, timolol effectively depresses both basal and stimulated plasma renin levels.

Adrenergic beta-Antagonists↗

PubMed1975