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Biomedical subjects

R Sutton

Publications and source records attributed to R Sutton.

At least 73 records · Page 4Linked to original sources
PubMed1988

Role of atrial pressure and rate in release of atrial natriuretic peptide.

To investigate whether atrial natriuretic peptide (ANP) release during paroxysmal tachycardia is due to increased atrial rate or increased atrial pressure, plasma ANP concentrations were measured during atrial pacing at increasing rates in six alpha-chloralose-anesthetized dogs whose atrial pressures were maintained artificially low by balloon occlusion of the inferior vena cava (IVC). These ANP concentrations were compared with those seen during identical increasing atrial rates in the same dogs without IVC occlusion. During incremental pacing without IVC occlusion, pulmonary wedge pressure (PWP; mean +/- SE) rose progressively from 5.3 +/- 1.6 at 200 to 20.2 +/- 2.3 mmHg at 350 beats/min (P less than 0.01), and right atrial pressure (RAP) rose progressively from 2.5 +/- 0.9 at 200 to 6.7 +/- 2.1 mmHg at 350 beats/min (P less than 0.05). At the same time, arterial and coronary sinus ANP concentrations rose from 116 +/- 55 and 339 +/- 91 to 1,126 +/- 226 and 1,960 +/- 456 pmol/l, respectively (P less than 0.01). In contrast, incremental pacing with IVC occlusion produced no significant increase in PWP and RAP. Arterial and coronary sinus ANP concentrations during IVC occlusion were, respectively, 208 +/- 126 and 388 +/- 159 at 200 and 261 +/- 83 and 345 +/- 80 pmol/l at 350 beats/min (NS). This study demonstrates that the release of ANP during tachycardia is primarily dependent on increased atrial pressure and not atrial rate.

Animals↗
PubMed1988

Atrial natriuretic peptide inhibits postural release of renin and vasopressin in humans.

The effects of infusions of atrial natriuretic peptide (ANP) on the hormonal and hemodynamic responses to head-up tilt were investigated in six healthy adults. Head-up tilt at 45 degrees for 2 h during placebo saline infusion caused a 7% fall in blood volume accompanied by increases in plasma renin activity (PRA) and plasma arginine vasopressin (AVP) of 112 and 175%, respectively. Head-up tilt was repeated during an infusion of ANP producing a four- to sixfold increase in plasma ANP concentrations. This resulted in an 18% fall in plasma volume, yet despite this greater fall in plasma volume, PRA did not change. Two subjects experienced vasovagal symptoms toward the end of the ANP infusions accompanied by large increases in plasma AVP. In the other four subjects, plasma AVP remained unchanged during ANP infusions. Both procedures resulted in similar increases in plasma norepinephrine levels and in heart rate. Infusion of ANP prevents the posturally stimulated release of renin and AVP.

Adult↗
PubMed1988

Anaphylaxis following "Hexabrix" during routine coronary angiography.

A case is described of an anaphylactic reaction to "Hexabrix 320" radiographic contrast medium in a patient undergoing routine coronary angiography. The case is reported because such reactions to "Hexabrix" are considered rare, because the patient was pretreated with hydrocortisone and chlorpheniramine, and because of the continuous monitoring that occurred during the procedure.

Aged↗
PubMed1987

Regulation and specificity of glucose-stimulated insulin gene expression in human islets of Langerhans.

The insulin response of cultured human islets of Langerhans was measured at both mRNA and polypeptide levels in response to natural and pharmacological stimuli. We report a dosage dependent stimulation of both mRNA levels and insulin secretion by extracellular glucose, and present evidence that islet responsiveness can be divided into two temporal phases: an early response, apparently under post-transcriptional control, and a late phase in which insulin messenger accumulates. Although glucose effects in man are similar to rodents, there are important differences, especially with respect to modulation of glucose stimulation by activators of beta-cell protein kinases.

Cells, Cultured↗
PubMed1987

Ovarian response to PMSG and GnRH in ewes immunised against oestradiol-17 beta.

Forty-six adult merino ewes were immunised against oestradiol-17 beta-6 carbomethyloxime:human serum albumin and 48 comparable ewes were used as controls in an experiment to study the effects of gonadotrophin releasing hormone (GnRH) on ovulatory responses after treatment with pregnant mare's serum gonadotrophin (PMSG). All the ewes were treated with progestogen sponges for 14 days and received 1500 iu PMSG on the 12th day. Twenty-four control and 24 immunised ewes received 25 micrograms GnRH 21.5 hours and 23 hours after the sponges were withdrawn. Plasma samples were collected between 17 and 50 hours after the sponges were withdrawn and assayed for luteinising hormone (LH). Immunisation reduced the proportion of ewes which ovulated and their rate of ovulation. Injection of GnRH increased the proportion of immunised ewes ovulating (P less than 0.0005) and their rate of ovulation (P less than 0.0001). More unovulated follicles were observed in immunised ewes regardless of GnRH treatment (P less than 0.0001). The rate of recovery of eggs was reduced after immunisation. Treatment with GnRH produced a surge of LH of equal magnitude in the control and immunised ewes although not as many immunised ewes ovulated.

Animals↗
PubMed1987

ATP-sensitive K+ channels in human isolated pancreatic B-cells.

Glucose-stimulated insulin release from rodent pancreatic B-cells is thought to be initiated by the closing of ATP-sensitive K+ channels in the plasma membrane as a consequence of glucose metabolism. We have identified an ATP-sensitive K+ channel in membrane patches excised from human B-cells which is similar to that found in rodent B-cells in conductance, kinetics, ATP sensitivity and its inhibition by sulphonylureas. In man, the ATP-sensitive K+ channel may also have a central role in glucose-stimulated insulin secretion and may be (linked to) the receptor for the hypoglycemic sulphonylureas.

Adenosine Triphosphate↗
PubMed1987

Predictive power of progesterone receptor status in early breast carcinoma.

Progesterone receptor status (PgR) and oestrogen receptor status (ER) were examined in 332 women with stage I-II breast carcinoma treated at a single centre either by simple mastectomy with (n = 283) or without (n = 6) axillary clearance, or by segmental mastectomy with (n = 18) or without (n = 25) axillary clearance and radiotherapy; median follow-up time was 40 (range 10-60) months. Neither the concentration nor the presence of PgR related to either disease-free interval or survival. However both the presence and the concentration of ER were found to be associated with a longer disease-free interval amongst patients with stage II tumours (P less than 0.01). From this study it appears that progesterone receptor status does not predict outcome in early breast carcinoma.

Adult↗
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↗