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Biomedical subjects

R Davies

Publications and source records attributed to R Davies.

At least 289 records · Page 16Linked to original sources
PubMed1978

Beta-blockade and blood-levels after low-dose oral propranolol: The hepatic "first-pass" threshold revisited.

Heart-rate, arterial pressure, and plasmarenin activity were determined in six normal subjects at rest and after an injection of 8 microgram isoprenaline with and without prior propranolol administered orally in a dose of 5 mg 8-hourly for a total of five doses. After propranolol, resting heart-rate, systolic pressure, and plasma-renin activity all fell significantly (P less than 0.05 to less than 0.001). When the isoprenaline-induced changes of heart-rate, diastolic pressure, and plasma renin activity without propranolol were compared to those with propranolol, these responses were greatly diminished (P less than 0.01 to less than 0.001). The percent blockade by propranolol of the isoprenaline-induced changes ranged from 65% for diastolic pressure to 77% for heart rate and 78% for plasma-renin activity. Propranolol levels determined by conventional fluorometry were below accurate detection limits, whereas those determined by gas-liquid chromatography ranged from 2.3 to 8.5 ng/ml. These findings, which demonstrate beta-blockade with low-dose propranolol, are not consistent with the existence of a postulated threshold for the hepatic "first-pass effect" in man, which is said to require saturation by single doses of 30 mg or more before propranolol enters the systemic circulation.

Administration, Oral↗
PubMed1978

The inhibiton of adrenergically provoked renin release by salbutamol in man.

1 The beta-adrenoceptor agonist salbutamol is shown to have antagonist properties by its effect on adrenergically provoked renin release in normal people. 2 It significantly reduces the rate of renin secretion provoked by either endogenous (85 dregrees head-up tilt) or exogenous (isoprenaline infusion) adrenergic stimulation. 3 Because renin is relatively simple to measure, and because in acute studies its release is relatively uninfluenced by the vagaries of direct and reflex cardiovascular effects, we suggest that, in the characterization of drugs which act on adrenergic beta-receptors, an assessment of their effects on renin release would be useful.

Adult↗
PubMed1978

Pruritus and dermographism due to intrahepatic cholestasis of infancy.

A case report of intrahepatic cholestasis of infancy presenting with chronic severe pruritus is described. This presentation is compared with similar cases attending this unit. Intrahepatic cholestasis of infancy and the pathogenesis of puritus associated with cholestasis are briefly discussed.

Cholestasis↗
PubMed1978

The uptake by the canine tibia of the bone-scanning agent 99mTc-MDP before and after an osteotomy.

The residue and extraction of technetium-labelled methylene diphosphonate (99mTc-MDP), a substance used in bone scanning, was examined in the canine tibia and found to be low. Examination of washout curves suggested that there were four compartments in cortical bone, a vascular, a perivascular, a bone fluid and a bone compartment. After an osteotomy in the canine tibia the residue of 99mTc-MDP increased. This was believed to be due to an increase in the blood supply to the bone and to an associated increase in new bone available for exchange. Bone scanning in a fracture is therefore a reflection of the vascular status of the bone being examined and of the uptake by bone. This is dependent on there being an adequate blood supply to the bone and an increased number of mineral-binding sites.

Animals↗
PubMed1978

Some effects of phenol- and thiol-nitrosation reactions on N-nitrosamine formation.

C-Nitrosophenols, produced by the nitrosation of phenols, catalyse N-nitrosamine formation. The rate of N-nitrosation of pyrrolidine, catalysed by p-nitroso-o-cresol, is fastest at about pH 5. The catalytic species is thought to be the quinone monoxime tautomer of the nitrosophenol. A possible mechanism for the catalysis is proposed. A reaction of pyrrolidine with nitrite at pH 5.0 is described, which gives enhanced N-nitrosation in the presence of p-cresol. The yield of N-nitrosopyrrolidine (NPYR) is further enhanced when this reaction is carried out under anaerobic conditions. Nitrosocysteine hydrochloride reacts with N-methylaniline at pH 2.65, 5.5 and 9.75 in the absence of nitrite to give N-nitroso N-methylaniline. The N-nitrosation of morpholine and pyrrolidine at pH 9.75 is also effected by nitrosocysteine hydrochloride. The rate of N-nitrosation at this pH decreases with increasing amine basicity. The reaction of nitrosocysteine with N-methylaniline at pH 9.75 under anaerobic conditions leads to a significant reduction in the yield of N-nitroso-N-methylaniline.

Aniline Compounds↗
PubMed1977

Disseminated histoplasmosis in an English patient with diabetes mellitus.

Histoplasma capsulatum is not endemic in Britain. We report a case of disseminated histoplasmosis in an English man who had not ventured out of northern Europe for 30 years. The disease presented as painful mouth ulcers and hepatosplenomegaly six months after he had developed maturity-onset diabetes. The origin of the infecting fungus may have been from within the United Kingdom or alternatively it may have existed as an intraoral saprophyte for over 30 years.

Diabetes Complications↗
PubMed1977

The effect of isoprenaline on plasma renin activity in man: a dose-response curve.

Four normal subjects on a free sodium intake received intravenous isoprenaline in doses of 2, 4, 8 and 16 microgram over 2 min. Three of the subjects received a second infusion of 8 microgram. The rate of renin release indexed by changes in plasma renin activity increased in all subjects at each dose level. The mean peak levels of plasma renin were 9%, 29% and 77% above the mean control levels at doses of 2, 4 and 8 microgram respectively. The response of 16 microgram was no different from that seen with 8 microgram. The renin response obtained at 8 microgram was highly reproducible such that the coefficient of variation for duplicate estimations of plasma renin (twelve duplicates) ranged from 1.7 to 4%.

Dose-Response Relationship, Drug↗
PubMed1977

The interrelationship between the release of renin and vasopressin as defined by orthostasis and propranolol.

The concentration of both plasma renin and plasma arginine vasopressin rose in normal subjects after an 85 degrees head-up tilt. Plasma renin activity, which increased 70-80% above the supine value, was maximal at 15 or 30 min, whereas the six- to seven-fold increase of plasma arginine vasopressin concentration was observed between 30 and 45 min. Intravenous propranolol administered just before tilt was used to investigate the possibility that the delayed rise of arginine vasopressin was stimulated by renin. Although the response of plasma renin was completely abolished by propranolol, the response of vasopressin was unaffected. These findings suggest that the release of vasopressin that follows isosmolar hypovolemia achieved by orthostasis may occur independently of changes in the renin-angiotensin system in the presence of propranolol.

Adult↗
PubMed1977

Electrocardiographic response to intravenous urography: prospective evaluation of 275 patients.

A total of 275 consecutive patients referred for intravenous urography were monitored for electrocardiographic changes during administration of Conray 400 or Renovist II in the form of either intravenous bolus or infusion. Three patients who received Conray (two bolus and one infusion) developed sustained ventricular tachycardia; they reverted to sinus rhythm with intravenous lidocaine. A statistically significant (P less than .05) number of patients developed a heart rate increase of 10 beats/min or more with bolus of either drug (65 of 128) compared to infusion (21 of 147). Depression of ST segment (greater than or equal to 0.5 mm) was encountered statistically more often (P less than .05) with bolus (20 of 128) compared to infusion (six of 147). Increase of corrected QT of 0.10 sec or more was observed more often (P less than .05) with bolus (43 of 128) compared to infusion (five of 147). Abnormal resting ECG, coronary artery disease, or congestive heart failure imposed a higher (P less than .05) risk for development of ventricular tachycardia, ST depression, or ectopic ventricular beats. It is concluded that a bolus injection be very cautiously administered to patients with risk factors such as abnormal ECG, coronary artery disease, or congestive heart failure during intravenous urography and that resuscitative facilities be available.

Adolescent↗
PubMed1976

Is the adrenergic control of renin release dominant in man?

Two beta-blocking agents with different properties were used to define the adrenergic component of the renin release which follows orthostasis. Five normal young subjects were tilted to 85 degrees for 30 min on four separate occasions. In two control studies the release of renin, as indicated by changes in plasma-renin activity, was highly reproducible. The effects of intravenous oxprenolol and intravenous propranolol, were then compared under the same experimental conditions. Oxprenolol attenuated the renin response in all subjects without completely abolishing it. Propranolol completely abolished the renin response. The difference in the ability of these agents to suppress renin release may be related to the presence (oxprenolol) or absence (propranolol) of intrinsic sympathomimetic activity. The increased rate of renin release in orthostasis seems to be mediated entirely by the adrenergic nervous system.

Adult↗