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Biomedical subjects

E J Hamilton

Publications and source records attributed to E J Hamilton.

10 recordsLinked to original sources
PubMed1989

Blood pressure and vasoactive hormones with improved glycaemic control in patients with diabetes mellitus.

To assess the effects of improved glycaemic control on arterial pressure and plasma levels of vasoactive hormones, we studied 5 male insulin dependent (Type 1) diabetic patients before and one month after commencement of rigorous control of blood glucose levels. On each occasion, continuous ambulatory intra arterial pressure monitoring for a 10-hour period, together with hourly venous sampling for plasma glucose and vasoactive hormone determinations, was performed under standardised conditions of diet and posture. Mean (+/- SEM) plasma glucose before and after improved glycaemic control was 9.4 +/- 0.3 and 6.6 +/- 0.4 mmol/l respectively (P less than 0.001). There was a small but significant fall in arterial pressure in each patient as well as for the group overall (mean arterial pressure fall 4.8 +/- 1.2 mmHg, p less than 0.01) after improved glycaemic control. The fall in individual (10 hr mean) diastolic arterial pressure levels correlated with concomitant falls in plasma glucose levels (r = 0.92, p less than 0.05) but not with changes in any of the other variables measured.

Adolescent↗
PubMed1988

Hormone, calcium and blood pressure relationships in primary hyperparathyroidism.

The cause of hypertension in primary hyperparathyroidism and its response to corrective surgery remains a matter of controversy. We therefore studied blood pressure, vasoactive hormones and plasma calcium responses to parathyroidectomy in six hypertensive and two normotensive patients with primary hyperparathyroidism. Twenty-four-hour intra-arterial pressure recordings, together with hourly blood sampling for plasma renin activity (PRA), aldosterone, cortisol, catecholamines and calcium levels, were undertaken in each patient before surgery and were repeated under identical conditions 3-6 months after parathyroidectomy. Mean plasma calcium was 3.03 +/- 0.1 before, and 2.35 +/- 0.02 mmol/l after, parathyroidectomy. Changes in arterial pressure were small and variable in individual patients. Group mean arterial pressures before and after surgery were identical. Plasma cortisol and PRA were significantly higher in the hypercalcaemic state (P less than 0.01 and P less than 0.05, respectively) but there was no significant difference in plasma aldosterone or catecholamine levels. No correlations between changes in plasma calcium or parathyroid hormone levels and concomitant changes in plasma concentration of other hormones were observed. Our findings show that correction of primary hyperparathyroidism has no systematic effect on arterial pressure in a heterogeneous group, including some patients with probable background essential hypertension, when evaluated 3-6 months after surgery. Compared with values after corrective surgery, mean levels of PRA and cortisol-but not aldosterone or catecholamines--are elevated in patients with primary hyperparathyroidism. These findings are consistent with an inhibitory effect of raised ionic calcium concentration on the response of the adrenal glomerulosa to angiotensin and adrenocorticotrophic hormone.

Aged↗
PubMed1986

Ambulatory pulmonary arterial pressures in humans: relationship to arterial pressure and hormones.

Six healthy volunteers were studied by use of a continuous ambulatory recording technique to document the normal range and variability of pulmonary artery pressure (PAP) and to examine its relationship to systemic arterial pressure (SAP) both at rest and during standardized interventions. Vasoactive hormone levels were measured at frequent intervals. Over 8-10 h of study the mean PAP was 15.7/6.3 mmHg. Parallel changes in PAP and SAP were observed at rest and during exercise and eating. On the contrary, PAP rose and SAP fell with hypoxia, whereas smoking was associated with a rise in SAP but no change in PAP. Sympathetic nervous system activity, as gauged by plasma norepinephrine levels, may have contributed to pressure and heart rate changes during exercise and smoking, but activity of the renin-angiotensin system was not altered by any of the maneuvers. These results provide base-line information on the level of PAP and its variability in healthy volunteers under standardized conditions. Pressures within the systemic and pulmonary circuits change in parallel under some circumstances but move in opposite directions under other conditions.

Adult↗
PubMed1985

Effects of enalapril on clinical status, biochemistry, exercise performance and haemodynamics in heart failure.

The effects of enalapril on clinical well-being, treadmill exercise performance, haemodynamic measurements, hormone levels, and plasma biochemistry in patients with moderate heart failure, were assessed in a 12-week placebo-controlled, double-blind study. Maintenance frusemide and digoxin treatment was continued throughout the study. Compared with placebo, enalapril treatment improved clinical status and increased exercise capacity. The most obvious haemodynamic change was a fall in pulmonary artery wedge pressure and pulmonary artery pressure. Enalapril-induced increases in left-ventricular ejection fraction and cardiac index, and falls in systemic arterial pressure, were small. Of the hormone indices measured, plasma renin activity rose 4-fold, angiotensin II and aldosterone fell slightly, and plasma catecholamines were unaltered by enalapril. Plasma potassium increased on average by 0.3 mmol/L during enalapril therapy. No adverse clinical or biochemical effects were observed. Enalapril has a sustained beneficial action in patients with moderate heart failure.

Adult↗
PubMed1975

Utilization of amino acids administered enterally or parenterally to young pigs.

The utilization of essential amino acids provided enterally or parenterally was compared in six growing female pigs. Crystalline amino acids in aqueous solution were administered parenterally through a central venous cannula or enterally through a stomach fistula or in the diet. Other nutrients were provided in the diet. Plasma essential amino acid concentrations were not significantly different after the enteral and intravenous treatments in either the fasting or postprandial state except for phenylalanine and histidine for which both fasting and postprandial plasma concentrations were higher after intravenous infusion than after the enteral treatment. No significant differences were observed in plasma concentrations of dispensable amino acids. Urinary amino acid concentrations showed no treatment effects. Body weight gain and nitrogen retention during intravenous treatment equaled or exceeded the respective parameters during enternal administration. Serum biochemical parameters were unaffected by route of administration except for hematocrit and serum phosphorus concentrations which were significantly lower during intravenous infusion. Serum sodium and total protein concentrations were significantly higher during the oral casein treatment than after crystalline amino acids were presented by either route of administration. The data suggest that utilization of essential amino acids is similar whether they are given enterally or intravenously.

Administration, Oral↗
PubMed1974

Screening of isoniazid inactivators by dilution test.

A modification of the screening test for the phenotyping of isoniazid inactivators is described. As this simple dilution technique does not require expensive equipment or even electricity, it can be used in poorly equipped laboratories.

Acetylation↗
PubMedDate not supplied

Endogenous angiotensin-aldosterone-pressure relationships during sodium restriction.

The effects of moderate restriction of dietary sodium and potassium supplementation on plasma levels of renin, angiotensin II, aldosterone, and cortisol and on arterial pressure were studied in 12 patients with mild essential hypertension. To define hormone-blood pressure relationships, venous hormone levels were measured hourly and intra-arterial pressure continuously for 24 hours after 4 to 6 weeks of sodium restriction, 4 to 6 weeks of potassium supplementation, and a similar period of control diet. Our results show that compared with the control diet, moderate sodium restriction was associated with increased levels of aldosterone but no overall change in renin, angiotensin II, or cortisol levels. Further, slopes of regression lines relating log renin and log angiotensin II to aldosterone were increased, as were log cortisol/aldosterone regression lines. On the contrary, regression lines of log renin and log angiotensin II versus arterial pressure were unaltered by sodium restriction. Hormone and blood pressure relationships were not changed by the potassium supplemented diet. Although confirmatory data are needed, our findings suggest that moderate sodium restriction enhances aldosterone responsiveness to endogenous angiotensin II and adrenocorticotropic hormone without diminishing the pressor activity of endogenous angiotensin II. These results may explain in part the disappointingly small hypotensive effect of modest sodium restriction in mild essential hypertension.

Adult↗