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Biomedical subjects

G M Bell

Publications and source records attributed to G M Bell.

At least 73 records · Page 4Linked to original sources
PubMed1989

Increased plasma atrial natriuretic factor and reduced plasma renin in patients with poorly controlled diabetes mellitus.

1. To investigate atrial natriuretic factor (ANF) and its relationship to the renin system in diabetes, we measured plasma immunoreactive ANF and plasma renin activity (PRA) in 27 non-ketotic diabetic patients without evidence of cardiac or overt renal disease, and compared them with 26 age- and sex-matched normal subjects. 2. Diabetic patients were divided prospectively into poor (PGC, n = 14) or moderate (MGC, n = 13) glycaemic control depending on their concurrent plasma glycohaemoglobin (HbA1) levels (greater than 9% or less than 9%, respectively). Plasma ANF was elevated in PGC diabetic patients (15.7 +/- 1.8 fmol/ml, mean +/- SEM) compared with MGC diabetics (9.9 +/- 0.8 fmol/ml, P less than 0.001) and normal subjects (10.1 +/- 1.3 fmol/ml, P less than 0.05). 3. In contrast, PRA was lower in the PGC diabetic patients (1.3 +/- 0.3 pmol of angiotensin 1 h-1 ml-1) compared with the other groups (2.5 +/- 0.5 and 2.1 +/- 0.2 pmol of angiotensin I h-1 ml-1, P less than 0.05). Diabetic groups had proportionally more patients with high prorenin values (over 30 ng h-1 ml-1) than the normal group, but there was no difference between the diabetic groups. 4. Among the diabetic patients, ANF was directly related to HbA1 (r = 0.49, P less than 0.005) and urinary albumin excretion (r = 0.40, P less than 0.02), and was inversely related to PRA (r = 0.36, P less than 0.04) and plasma creatinine (r = -0.42, P less than 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Atrial Natriuretic Factor↗
PubMed1988

On the renal basis for essential hypertension: nephron heterogeneity with discordant renin secretion and sodium excretion causing a hypertensive vasoconstriction-volume relationship.

We propose herein that there are two functionally abnormal nephron populations in essential hypertension: (1) a group of ischemic nephrons with impaired sodium excretion which chronically hypersecrete renin. Numerically, these ischemic nephrons comprise a minor subgroup since most patients with essential hypertension exhibit no overt evidence of renal insufficiency. (2) In reaction to this, a more numerous group of normal nephrons appears in adaptive hypernatriuresis. They have an increased distal sodium supply and consequently, a chronically suppressed renin secretion. One difference between patients with renovascular hypertension and those with essential hypertension is the intermingling of these two populations of nephrons. In our hypothesis, the adapting hyperfiltering normal nephrons accomplish the hypernatriuresis in response to saline infusion, that is characteristic of all essential hypertension. However, the unsuppressed secretion of renin, that arises from the ischemic nephron population attenuates this compensatory natriuresis in the following ways: (1) by inappropriately acting on the hyperfiltering nephrons to enhance proximal tubular sodium reabsorption; (2) by activating TGF-mediated afferent constriction in these nephrons, and (3) simultaneously, the reactive secretion of renin from ischemic nephrons is diluted by non-participation of the adapting hypernatriuretic nephrons so that plasma renin settles at a level which is insufficient to fully compensate GFR in the ischemic nephrons. These adaptive responses provide a basis for the observation that the inhibition of renin activity with converting enzyme inhibitors in essential hypertension increases renal blood flow and sodium excretion. They also explain why converting enzyme inhibitors can effectively reduce blood pressure, even when renin levels are not absolutely elevated, since any circulating renin imposed upon the adapting hypernatriuretic nephrons inappropriately impairs their sodium excretion. In addition, the theory explains why basal renin secretion is either not suppressed or inadequately suppressed in patients with essential hypertension. As a result, whole kidney homeostatic function is compromised because individual nephrons are responding to their individual stimuli to fulfil their individual need, rather than acting in concert with other nephrons. The net effect of this uncoordinated response is to shift total renal function so that systemic arterial hypertension is sustained by abnormal sodium retention for the inappropriately high plasma renin level, or vice versa.(ABSTRACT TRUNCATED AT 400 WORDS)

Homeostasis↗
PubMed1988

Acute renal failure due to interstitial nephritis induced by 'glue-sniffing' with subsequent recovery.

We report a case of the deliberate inhalation of a toluene-containing adhesive which caused acute renal failure and hepatic damage. Renal biopsy disclosed a severe tubulo-interstitial nephritis, renal function recovered after 14 days' haemodialysis. The literature on renal complications of toluene exposure is reviewed, this is the only case of acute renal failure due to interstitial nephritis after toluene exposure with subsequent recovery. Recovery in this case may have been related to the avoidance of further toluene exposure.

Acute Kidney Injury↗
PubMed1987

Abnormal diurnal urinary sodium and water excretion in diabetic autonomic neuropathy.

1. Diurnal patterns of urine output and sodium and potassium excretion were studied in 10 diabetic patients with and 10 without autonomic neuropathy, and in 10 normal subjects. 2. The diurnal patterns of excretion in the diabetic patients with autonomic neuropathy differed significantly from the two other groups, as a smaller proportion of the 24 h output of urine, sodium and potassium was excreted during the day and a larger proportion was excreted at night. 3. Similar changes were noted in the diurnal patterns of urinary kallikrein excretion in diabetic patients with autonomic neuropathy, and urinary kallikrein output correlated significantly with urine volume but not with urinary sodium excretion. 4. The diurnal patterns of excretion of urinary prostaglandin E2 and 6-keto-PGF1 alpha were not significantly different in diabetic patients with autonomic neuropathy. 5. Nocturia was a common complaint in this group, and the number of nocturnal voidings correlated with night urine volume. There was no evidence of premature bladder emptying. 6. The changes observed in the day/night urine output and sodium excretion could not be explained by glycosuria, insulin regimens, impaired renal function or abnormal diurnal prostaglandin excretion; their possible relevance to the diurnal changes of urinary kallikrein excretion is discussed.

6-Ketoprostaglandin F1 alpha↗
PubMed1987

Percutaneous transluminal angioplasty improves blood pressure and renal function in renovascular hypertension.

Thirty-three patients with renal angiographic evidence of significant renal artery stenosis were referred for percutaneous transluminal angioplasty. The indications were poorly controlled hypertension (n = 13) or hypertension associated with deteriorating renal function (n = 20). Their mean age was 56 (23-73) years (12 males, 21 females). Causes of the renal artery stenosis were fibromuscular dysplasia (n = 8) and atheromatous changes (n = 25). Four patients were excluded, three due to technical failure. Forty-five angioplasties were performed in 29 patients with a mean observation period after angioplasty of 18 (one to 60) months. During this period eight patients (28 per cent) had a diastolic blood pressure of less than 90 mmHg without antihypertensive drugs, a further 15 patients (52 per cent) had improved blood pressure control with a significant reduction in the number and amount of antihypertensive drugs, but six patients (20 per cent) showed no improvement in blood pressure. Hypertension associated with the stenosis of fibromuscular dysplasia responded better to angioplasty than hypertension associated with atheromatous renal artery stenosis. Improvement in renal function was noted in eight patients with no change in 16 patients. Two patients with end-stage renal failure and atheromatous intrarenal vascular disease became dialysis dependent within four weeks of the procedure. One major and four minor complications occurred but there were no deaths related to angioplasty. Together with results from other centres this study indicates that percutaneous transluminal angioplasty should be considered the initial treatment choice for all patients with renovascular hypertension due to fibromuscular dysplasia and atheromatous renal artery stenosis.

Adult↗
PubMed1985

End-organ responses to thyroxine therapy in subclinical hypothyroidism.

We studied variables known to change with thyroid hormone status in 18 patients with subclinical hypothyroidism before and during treatment with thyroxine in a dose sufficient to restore the plasma TSH response to TRH to normal. There was an associated increase in both plasma total T4 and free T4 within the normal range but plasma total T3 and free T3 were unchanged. As a result of thyroxine treatment there was a small but significant increase (P less than 0.05) in left ventricular ejection fraction (LVEF) with maximal exercise but no significant changes in LVEF at rest and moderate exercise, continuously monitored mean sleeping heart rate, day/night ratios of urinary sodium excretion, peripheral nerve conduction velocities, fasting serum triglycerides, total cholesterol (TC), high density lipoproteins (HDL) or TC/HDL ratios. On this evidence we do not consider that thyroxine replacement therapy is indicated in patients with subclinical hypothyroidism.

Adult↗
PubMed1985

Proliferative glomerulonephritis and exposure to organic solvents.

Exposure to organic solvents was compared by interview and questionnaire in 50 patients with biopsy-proven proliferative glomerulonephritis in whom there was no evidence of systemic disease or preceding infection with that of 100 control subjects matched for age, sex and social class. The interview was conducted by a lay person who did not know whether the interviewee was a patient with glomerulonephritis or a control subject. The exposure scores derived from the results of the questionnaires were significantly greater in the patients with glomerulonephritis than the control subjects (13,186 +/- 3,716 vs. 3,030 +/- 1,152, p less than 0.01). The degree of exposure was higher in those patients with the more severe diffuse endocapillary proliferative glomerulonephritis than in those with mesangial proliferative glomerulonephritis. In the glomerulonephritis patients solvent exposure was mainly occupational in origin and involved fuels, paints and degreasing agents in most cases. This occupational exposure was significantly greater than in the control subjects (13,061 +/- 3,858 vs. 2,878 +/- 1,146, p less than 0.01). It is suggested that exposure to organic solvents may participate in the pathogenesis of non-systemic proliferative glomerulonephritis.

Biopsy↗
PubMed1985

Red cell population distributions in healthy dogs.

Red blood cells population distributions were studied in puppies and in mature beagle dogs using the Coulter Channelyzer C-1000. Weekly measurements over a period of six months indicated that only minor fluctuations in population distribution indices occurred. Normal range studies showed that although mean cell volume was similar in young and older dogs, young dogs showed an approximately 12.5 per cent greater volume range due to an increased presence of both larger and smaller cells. The red cell population distributions conformed to a single log normal distribution. A mild anaemia was induced in mature dogs. Compensation for this led to transient changes from the usual log normal shape of the red cell population distribution.

Anemia↗
PubMed1985

Left ventricular performance in subclinical hypothyroidism.

Normal plasma thyroid hormones with elevation of thyrotrophin levels in asymptomatic patients is known as subclinical hypothyroidism. Radionuclide angiography was used to study left ventricular function in 10 such patients before and after establishment of normal thyrotrophin levels with thyroxine. Resting left ventricular ejection fraction was similar in both states but exercise left ventricular ejection fraction was less in the subclinical hypothyroid (61 +/- 3 per cent) compared with the euthyroid (68 +/- 3 per cent; p less than 0.025) state. Sodium nitroprusside caused similar increases in resting cardiac output but in subclinical hypothyroidism this resulted from a large increase in heart rate (26 +/- 4 beats/min) and reduction in stroke volume (11 +/- 4 per cent) whereas in the euthyroid state, the heart rate increment was less (14 +/- beats/min) and stroke volume was unchanged. Analysis of left ventricular pressure-volume relationships at end-systole during exercise showed a steeper pressure-volume slope in the euthyroid compared with the subclinical hypothyroid state (p less than 0.05). Subtle impairment of left ventricular function is detectable in subclinical hypothyroidism and may justify use of hormone replacement.

Adult↗
PubMed1983

The effect of minor increments in plasma thyroxine on heart rate and urinary sodium excretion.

We studied day/night (D:N) patterns of urinary sodium excretion and the 24 hour ambulatory electrocardiogram in seven normal subjects before and during the administration of T4. Thyroxine increased thyroid hormone levels within the normal range and inhibited the plasma TSH response to TRH. This was associated with a significant decrease in D:N sodium excretion (P less than 0.01) and D:N urine flow (P less than 0.01), a significant increase in mean nocturnal heart rate (P less than 0.01), and a lesser increment in mean daytime heart rate (P less than 0.05). These responses to small changes in thyroid hormone levels suggest that the anterior pituitary is not alone in recognising minor thyroid hormone excess. The clinical implication is that some patients with a normal T3 and T4 but an impaired TSH response to TRH might benefit from antithyroid treatment.

Adult↗
PubMed1982

Nocturnal natriuresis in hyperthyroidism.

We measured urine flow and the renal excretion of total solute, sodium, potassium and calcium in eleven patients with hyperthyroidism before and after treatment. Mean nocturnal sodium excretion was significantly greater (P less than 0.05) during hyperthyroidism and was unaccompanied by any significant alterations in day time or 24-h values. As a result of this nocturnal natriuresis in hyperthyroidism significant changes were noted in the ratios of day/night sodium excretion (P less than 0.005) and urinary flow (P less than 0.05). The change in ratio of day/night sodium excretion resulting from treatment of hyperthyroidism was shown to correlate significantly with the change in plasma total triiodothyronine (r=0.73, P less than 0.01). Twenty-four hour urinary calcium output was significantly greater (P less than 0.02) in hyperthyroidism but there was no significant alteration in the day/night pattern of excretion.

Adult↗