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Biomedical subjects

R Sutton

Publications and source records attributed to R Sutton.

At least 235 records · Page 13Linked to original sources
PubMed1987

Reduced plasma renin activity in elderly subjects in response to vasovagal hypotension and head-up tilt.

The sympathoadrenal and renin-angiotensin systems play an important role in the cardiovascular responses induced by head-up tilt. In young people, hypotension and postural changes induced by tilt produce significant increases in plasma renin activity. The response of plasma renin activity to prolonged tilt and subsequent vasovagal hypotension has not been assessed in the elderly. Seventeen elderly subjects (10 with carotid sinus syndrome and seven age-matched controls) were studied during 45 minutes of recumbency and 120 minutes of head-up tilt to 40 degrees. Intra-arterial systolic blood pressure and heart rate were monitored continuously and plasma renin activity was measured at frequent intervals. Ten subjects developed vasovagal syncope during tilt (at 32 +/- 18 min). Systolic blood pressure and heart rate fell by 70 +/- 20 mmHg and 20 +/- 7 beats . min-1 (P less than 0.001 and P less than 0.01, respectively). Plasma renin activity did not change in syncopal subjects and remained unchanged up to 60 min after syncope. In seven subjects who completed 120 min of tilt without symptoms, heart rate rose during tilt but plasma renin activity remained unchanged. Plasma renin activity is not influenced by marked hypotension or prolonged head-up tilt in the elderly.

Aged↗
PubMed1987

Enhanced vagal activity and normal arginine vasopressin response in carotid sinus syndrome: implications for a central abnormality in carotid sinus hypersensitivity.

The relation between arginine vasopressin and vagal activity in carotid sinus syndrome was studied in 10 patients and 17 age matched controls using head up tilt as a stimulus. Of the controls, seven had unexplained syncope and 10 were healthy elderly subjects with no previous history of syncope. Subjects were studied supine for 45 min and thereafter during 120 min head up tilt to 40 degrees. Phasic arterial pressure and heart rate were monitored throughout. Serum was sampled at frequent intervals to measure arginine vasopressin, noradrenaline, and adrenaline concentrations. Seventy per cent of carotid sinus patients had vasovagal syncope at (mean(SD)) 25(4) min after tilt compared with 43% of subjects with unexplained syncope and one healthy elderly control. The maximum (mean(SD)) fall in systolic blood pressure and heart rate was 70(20) mmHg and 20(7) beats.min-1 (p less than 0.001 and p less than 0.01 respectively). Arginine vasopressin, noradrenaline, and adrenaline concentrations rose significantly in syncopal subjects (p less than 0.001, p less than 0.01, and p less than 0.05 respectively). Changes in systolic blood pressure, heart rate, and hormone concentrations were similar for patients with carotid sinus syndrome and control subjects. For those who completed the tilt period without the development of symptoms, systolic blood pressure and arginine vasopressin and adrenaline concentrations were unchanged, whereas noradrenaline concentrations and heart rate rose significantly. Vasovagal activity is thus appreciably increased in carotid sinus syndrome. Furthermore, the afferent limb of the carotid sinus reflex appears to be intact in patients with carotid sinus syndrome since the pattern of arginine vasopressin release was not different from controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1987

Urinary tract infection with anaerobic bacteria following endoscopic urethral instrumentation.

A prospective study of the pathogenic role of anaerobic bacteria was undertaken by suprapubic bladder aspiration in 100 patients prior to routine endoscopic urethral instrumentation. Anaerobic and/or micro-aerophilic bacteria were isolated from the suprapubic specimens of 11 patients (greater than 10(5) organisms/ml from 8), with identical species growing heavily from corresponding cystoscopic specimens and/or urethral swabs. Previous cystoscopies in all 11 patients and the presence of bladder tumour at the time of sampling in six were significantly and independently associated with the isolation of anaerobic bacteria from suprapubic specimens. It was concluded that transurethral instrumentation entails a definite risk of anaerobic urinary infection in addition to the recognised risk of aerobic urinary infection. The findings suggest that the antibiotics used as prophylaxis for or treatment of patients undergoing transurethral procedures should be effective against anaerobic bacteria.

Adult↗
PubMed1987

The NASPE/BPEG generic pacemaker code for antibradyarrhythmia and adaptive-rate pacing and antitachyarrhythmia devices.

A new generic pacemaker code, derived from and compatible with the Revised ICHD Code, was proposed jointly by the North American Society of Pacing and Electrophysiology (NASPE) Mode Code Committee and the British Pacing and Electrophysiology Group (BPEG), and has been adopted by the NASPE Board of Trustees. It is abbreviated as the NBG (for "NASPE/BPEG Generic") Code, and was developed to permit extension of the generic-code concept to pacemakers whose escape rate is continuously controlled by monitoring some physiologic variable, rather than determined by fixed escape intervals measured from stimuli or sensed depolarizations, and to antitachyarrhythmia devices including cardioverters and defibrillators. The NASPE/BPEG Code incorporates an "R" in the fourth position to signify rate modulation (adaptive-rate pacing), and one of four letters in the fifth position to indicate the presence of antitachyarrhythmia-pacing capability or of cardioversion or defibrillation functions.

Bradycardia↗
PubMed1987

Effects of endogenous atrial natriuretic peptide released by rapid atrial pacing in dogs.

The relationships between the hemodynamic, renal, and endocrine changes induced by rapid atrial pacing were studied in seven chloralose-anesthetized greyhounds paced from the right atrial appendage for 60 min at 250 beats/min. Pacing increased mean pulmonary wedge pressure, decreased cardiac output, and decreased mean arterial pressure. Systemic vascular resistance did not change significantly. Coronary sinus atrial natriuretic peptide (ANP) concentrations rose maximally within 5 min of commencing pacing. The corresponding increase in arterial ANP concentrations during this time was only 44% of its maximum value after 30 min of pacing. Plasma concentrations of arginine vasopressin were unchanged. Plasma renin activity decreased during pacing and showed a marked rebound increase at 60 min postpacing. Plasma norepinephrine levels did not change significantly during pacing. Urine flow increased during the latter 30 min of pacing. There was no significant change in sodium clearance despite high sustained concentrations of ANP. The lack of significant natriuretic and systemic vasodilator effects in association with high arterial plasma concentrations of endogenous ANP, in the absence of antagonistic mechanisms, suggests that the natriuretic and vascular effects of ANP may not be its major physiological actions.

Animals↗
PubMed1986

Head-up tilt: a useful test for investigating unexplained syncope.

Head-up tilt, a recognised stimulus to vasovagal syncope, was used to investigate syncope that remained unexplained despite full clinical and electrophysiological assessment in fifteen patients, mean age 65 +/- 10 years, who had had 15 +/- 19 episodes of unexplained syncope over periods of a week to 26 years. After overnight fast systolic blood pressure and heart rate were continuously monitored during 40 degrees head-up tilt for 60 min. Ten control subjects with no history of syncope were studied similarly. In ten patients (67%) and one control vasovagal syncope developed after 29 +/- 19 min (p less than 0.001). In symptomatic patients systolic blood pressure fell from 150 +/- 32 to 56 +/- 9 mm Hg (p less than 0.001) and heart rate from 62 +/- 9 to 38 +/- 12 beats per min (p less than 0.01). In each case symptoms during the test reproduced those previously experienced. No clinical findings predicted development of syncope during tilt. Baseline systolic blood pressure and heart rate did not differ significantly between patients and controls. Pacemakers were implanted in seven patients who have remained symptom-free since implant (follow-up 10 +/- 3 mo).

Aged↗
PubMed1986

Characterisation of phosphate binding to mitochondrial and bacterial membrane-bound ATP synthase by studies of inhibition with 4-chloro-7-nitrobenzofurazan.

The effect of phosphate on the inhibition by 4-chloro-7-nitrobenzofurazan of the ATPase activity of the proton-translocating ATP synthase in heart submitochondrial particles was investigated. Binding of phosphate protected strongly against the inhibition. A dissociation constant of 0.2 mM was determined for the enzyme X Pi complex and shown to be independent of pH in the range 7.0-8.0. The protective effect of phosphate was mimicked by arsenate but not by sulphate or malonate. Similar results were obtained for the enzyme from Paracoccus denitrificans. 2,4-Dinitrophenol enhanced phosphate binding to the mitochondrial enzyme since the protective effect of phosphate was increased. The data are compatible with protection arising from binding of phosphate to a catalytic site.

2,4-Dinitrophenol↗
PubMed1986

Stripping the long saphenous vein: peroperative retrograde saphenography in patients with and without venous ulceration.

Peroperative retrograde saphenography was used to study 80 incompetent long saphenous veins (LSV) in 60 patients with primary varicose veins. In 53 limbs presentation was uncomplicated (group A, 40 patients); in 27 limbs there was ulceration (group B, 20 patients). All limbs in group B had a normal deep system as shown pre-operatively by ascending and descending venography. Varicose changes were found in 52 (65 per cent) of 80 LSV; the overall mean length of normal vein seen was 16 cm. The incompetent LSV appears unlikely to be suitable for arterial replacement. All valves identified on operative saphenography above the knee appeared incompetent. In only 9 LSV of group B were there recognizable valves either above or below the knee, significantly fewer than 34 of group A (P less than 0.05). This finding suggests that a deficiency of saphenous valves may contribute to the development of venous ulceration. Hunterian perforators of variable size were seen on 70 saphenograms (87 per cent) passing directly from the LSV to the superficial femoral vein. Stripping of the incompetent LSV will disconnect such perforators from an incompetent system and may thus reduce the incidence of both recurrent varicose veins and persistent ulceration.

Female↗
PubMed1986

Successful autotransplantation of isolated islets of Langerhans in the cynomolgus monkey.

A recently described method for isolation of islets of Langerhans from the human pancreas has been adapted to the cynomolgus monkey pancreas. The mean yield of islets obtained from 13 monkey pancreata was 1319 islets per gram of pancreatic tissue (range 533-1800) and the usual purity of the preparation varied from 5 to 15 per cent islet tissue. Twelve cynomolgus monkeys underwent total pancreatectomy, preparation of islets from the excised pancreas and autotransplantation to either the spleen or the liver. Three animals received no transplant and became immediately diabetic, surviving 4-8 days. Four animals became normoglycaemic after intrasplenic islet transplantation, and survived 6 weeks, at which time splenectomy was performed with immediate onset of diabetes. Splenic vein insulin sampling confirmed the spleen as the source of insulin, and histological examination showed implanted islet tissue in all cases. Five animals became normoglycaemic after intrahepatic islet implantation. Three animals subsequently became diabetic at 4 and 5 months and two animals still have functioning grafts, the longest function being 9 months. These results suggest that in the cynomolgus monkey sufficient islets can be extracted from a single donor pancreas to reverse diabetes.

Animals↗