Search PubMed⌕ Search

Biomedical subjects

J Watkins

Publications and source records attributed to J Watkins.

At least 145 records · Page 8Linked to original sources
PubMed1982

Effects of histamine type 2 receptor stimulation on myocardial function in normal subjects.

Myocardial histamine(H)2 receptor stimulation has been studied in six normal men. Since histamine is a potent vasodilator, the haemodynamic effects of histamine infusion were compared with those of nitroprusside at equihypotensive doses, to identify changes in myocardial contractility attributable to vasodilatation. After H1 receptor blockade with mepyramine, subjects received, in single blind crossover fashion, either histamine alone and with the H2 receptor antagonist cimetidine, or nitroprusside alone and with cimetidine. Echocardiographic left ventricular dimensions, plasma catecholamines, blood pressure, and heart rate were measured. The rise in catecholamines suggested similar baroreflex activation by both histamine and nitroprusside. Echo ejection phase indices did not alter significantly after nitroprusside, but histamine caused an increase in percentage fractional shortening from 38.2 +/- 4.1 to 53.5 +/- 3-6% and in mean fibre shortening velocity from 1.31 +/- 0.19 to 1.99 +/- 0.22 cm/s. These changes were both greatly reduced by cimetidine and suggest that H2 receptor stimulation in man causes a direct positive inotropic response.

Adult↗
PubMed1981

Effects of exercise training on left ventricular mass in patients with ischemic heart disease.

To determine whether exercise training results in increased left ventricular mass in patients with ischemic heart disease, we obtained echocardiograms in 14 coronary patients before and after an average of seven months (range 3 to 14 months) of supervised arm and leg exercise. Each echocardiogram was interpreted jointly by two blinded observers, using three different measurement conventions and a semiautomated method of analysis to minimize errors of interpretation. Exercise training led to subjective improvement in all 14 patients, and to an objective increase in functional capacity in 13 of 14 patients, as evidenced by an increase in maximal oxygen consumption estimated from symptom-limited treadmill exercise testing (8.8 +/- 2.7 (SD) and 10.7 +/- 2.5 METS before and after training, respectively, p less than 0.01). However, this functional improvement was not accompanied by any significant change in left ventricular end-diastolic diameter, or posterior wall or interventricular septal thickness. Likewise, left ventricular cross-sectional area (CSA), an index of left ventricular mass which corrects for altered ventricular volume and theoretically reflects directional changes in mass despite nonuniform wall thickness, did not change significantly after training by any measurement convention (CSA = 18.0 +/- 6.5 and 17.6 +/- 6.5 cm2 before and after training, respectively, by American Society of Echocardiography measurements). These data strongly suggest that improved functional capacity after exercise training in patients with ischemic heart disease is not due to exercise-induced left ventricular hypertrophy.

Adult↗
PubMed1981

Clinical correlates in hypertensive patients with left ventricular hypertrophy diagnosed with echocardiography.

Seventy-three hypertensive patients were evaluated with M mode and two dimensional echocardiography. Left ventricular hypertrophy was found in 37 patients (51 percent); 29 had concentric hypertrophy and the remaining 8 had disproportionate septal thickening. Factors that did not influence the distribution of patients in the group with left ventricular hypertrophy and normal subjects included (1) duration of hypertension, (2) level of blood pressure, (3) age, (4) body surface area, and (5) race. More of the patients who had a normal left ventricular mass (32 or 89 percent) than of those who had hypertrophy (22 or 59 percent) were receiving two or more antihypertensive drugs. Electrocardiography was very insensitive in identifying left ventricular hypertrophy in these patients. The presence of increased left ventricular mass was associated with a greater incidence of other target organ disease.

Adrenergic beta-Antagonists↗
PubMed1981

Regulation of norepinephrine release by peripheral alpha 2-receptor stimulation.

Although extensive evidence obtained in animals and in vitro supports the existence of an alpha-receptor-mediated inhibitory regulation of norepinephrine release, the importance of such a system in man is not established. Norepinephrine release was physiologically stimulated by change of posture and dynamic exercise in subjects while they were infused with phenylephrine, a predominant alpha 1-receptor agonist, alpha-methylnorepinephrine, a predominant alpha 2-agonist, and saline. Agonist infusions were administered both at rates that induced a slight elevation in supine systolic pressure and at nonpressor rates. Agonist concentrations that induced much the same pressor responses (alpha 1) were assumed on the basis of in vitro experiments to differ substantially in their affinity for alpha 2-receptors. The hemodynamic response and the increase of plasma norepinephrine induced by changes in posture and exercise were of the same order during infusions of alpha-methylnorepinephrine, phenylephrine, and saline. Similar results from the "nonpressor" as from "pressor" agonist infusions suggested that baroreflex-induced reduction in sympathetic neuronal activity had not confounded the results. Correction of plasma concentrations for individual values of norepinephrine clearance provided an index of norepinephrine release into the circulation that was not changed by phenylephrine or alpha-methylnorepinephrine. These results raise the question of the importance of peripheral alpha 2-receptors in the regulation of norepinephrine release in man.

Blood Pressure↗
PubMed1981

The relationship between reported atopy or allergy and immunoglobulins: a preliminary study.

The serum of 50 surgical patients with a history of asthma, hay fever or allergy has been analysed for IgE levels and compared with a control group without such a history. The values in the 'normal' group largely fell within the accepted range (below 200 iu./ml). Those in the 'hypersensitive' group had a wide range extending to over 1000 iu./ml but many of those with low values in this group had contact dermatitis and similar minor allergies. However, analysis of cases studied shows that any patient with a history of atopy or allergy is at risk from Cremophor-containing intravenous anaesthetics.

Adult↗
PubMed1981

left ventricular segmental wall motion-a comparison between equilibrium radionuclide angiography and contrast angiography.

The qualitative assessement of left ventricular wall motion using a four-point scale has been compared between left ventricular contrast angiography and equilibrium radionuclide angiography in the 30 degrees right anterior oblique projection. Analysis was carried out for five segments of the left ventricle. Four modes of analysis of equilibrium radionuclide angiography were compared and the reproducibility assessed. Overall accuracy of equilibrium radionuclide angiography compared to contrast angiography was greater than 82% to within one degree of motion. One method using a cine display, averaged 97%. We suggest that equilibrium radionuclide angiography using the cine display is the non-invasive investigation of choice in the screening of patients with suspected regional wall motion abnormalities.

Adult↗
PubMed1980

Attenuation of hypotensive effect of propranolol and thiazide diuretics by indomethacin.

The effects of 100 mg indomethacin daily for three weeks on blood pressure and urinary excretion of prostaglandin F2 alpha were studied in a double-blind, placebo-controlled comparison of two groups of patients with essential hypertension, eight receiving propranolol and seven thiazide diuretics. Compared with placebo, adding indomethacin to the patients' established antihypertensive treatment increased blood pressure by 14/5 Hg supine and 16/9 mm Hg erect in the patients receiving propranolol, and by 13/9 mm Hg supine and 16/9 mm Hg erect in the patients receiving thiazide diuretics (all p less than or equal to 0.05). The excretion of the major urinary metabolite of prostaglandin F2 alpha was reduced by 67% in the propranolol-treated patients and by 57% in those receiving a thiazide diuretic. Body weight increased by 0 . 8 kg (propranolol) and 1 . 1 kg (thiazide diuretic) when indomethacin was given, but there were no significant changes in creatinine clearance, urinary sodium excretion, or packed cell volume in either treatment group. These results suggest that products formed by the arachidonic acid cyclo-oxygenase contribute to the regulation of blood pressure during treatment with both propranolol and thiazide diuretics. Inhibition of the cyclo-oxygenase with indomethacin partially antagonises the hypotensive effect of these drugs.

Adult↗
PubMed1980

Plasma levodopa, dopamine and therapeutic response following levodopa therapy of Parkinsonian patients.

In a double blind placebo controlled study of 6 Parkinsonian patients given a single dose of oral levodopa, the plasma levodopa and dopamine as measured by a radioenzymatic method both correlated with clinical improvement. There was a closer correlation with plasma dopamine than with plasma levodopa and it is proposed that peripheral decarboxylation may reflect central decarboxylation.

Aged↗
PubMed1980

Absence of opiate and histamine H2 receptor-mediated effects of clonidine.

The possibility that clonidine might exert some of its effects via opiate or histamine H2 receptors has been suggested from observations in animals and man. We undertook a double-blind, randomized study in six normal subjects, comparing the effects of 0.2 mg intravenous clonidine after pretreatment with 300 mg cimetidine, 0.8 mg naloxone, and saline. There was no attenuation of the hypotension, bradycardia, sedation, inhibition of salivary flow, or reduction in plasma catecholamines after cimetidine and naloxone, but the fall in plasma catecholamines ater clonidine correlated with blood pressure, sedation, and salivary flow, suggesting a central adrenergic mechanism for these effects. It is not known whether cimetidine can cross the blood-brain barrier after short-term dosing. We conclude that in normotensive subjects the short-term effects of intravenous clonidine are probably not mediated by an action at peripheral histamine H2 or central opiate receptors.

Adult↗
PubMed1979

A simple electrophoretic technique for the estimation of complement C3 conversion: specific application to the investigation of anaphylactoid response to I.V. agents.

A simple electrophoretic technique employing commercially available agarose films is described for the routine estimation of plasma complement C3 conversion. This technique has particular value in the investigation of anaphylactoid responses in patients following the administration of intravenous hypnotic drugs, plasma substitutes or radio-contrast media.

Alfaxalone Alfadolone Mixture↗