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Biomedical subjects

R Fraser

Publications and source records attributed to R Fraser.

At least 343 records · Page 19Linked to original sources
PubMed1978

Filtration of chylomicrons by the liver may influence cholesterol metabolism and atherosclerosis.

A fenestrated endothelial lining of sinusoids in rat liver has been shown to separate chylomicrons of different sizes following their injection into the portal vein. This sieving may have physiological importance, since during low dietary fat intake some intestinal lipoproteins are probably small enough to contact liver cells, but during high dietary fat loads most chylomicrons are too large to pass through the filter and must first be degraded to smaller remnants. The liver plays a central role in cholesterol metabolism since it catabolises dietary cholesterol which inhibits synthesis of cholesterol to be circulated as liver-derived very low density lipoproteins (VLDL) and low density lipoproteins. The sieving of chylomicrons, remnants and other lipoproteins by the sinusoidal endothelium of the liver may thus play an important role in lipid transport, affecting the balance of various lipoprotein moieties which in turn may affect the relationship of dietary lipids to various hyperlipidaemias and atherosclerosis.

Animals↗
PubMed1978

A new large chylomicron remnant from cholesterol-fed rabbits.

The lipoproteins of density less than 1.063 g/ml of cholesterol-fed rabbits were subjected to analytical ultracentrifugation. In many rabbits two peaks were found in the very low density (Sf greater than 20) portion of the lipoprotein spectrum. They were isolated by preparative ultracentrifugation and analysed. The smaller particles (remnant chylomicrons) had a peak Sf of 37, mean diameter of 36 nm, mean density of 1.00 g/ml, and their chemical composition agreed closely with previous reports. The larger particles had a peak Sf of 270, mean diameter of 80 nm, mean density of 0.97 g/ml and a high (80%) cholesterol ester and low (4%) triglyceride content. The fatty acid composition of the cholesterol esters, phospholipids and triglycerides was similar in both fractions. It is proposed that these large lipoprotein particles are also remnant chylomicrons. Possible reasons are presented to explain the presence of this second peak in the very low density lipoprotein spectrum.

Animals↗
PubMed1978

A renal carcinoma secreting inactive renin.

1. A patient presented with mild hypertension, a raised plasma total renin concentration but a normal plasma angiotensin II concentration. The discrepancy was due to a high concentration of inactive renin in the plasma. 2. A renal carcinoma was detected and removed. The tumour contained a higher proportion of inactive renin than was found in uninvolved areas of the kidney. After unilateral nephrectomy, the plasma concentration of inactive renin fell to normal. 3. Six months later, plasma inactive renin concentration again increased and a metastasis was detected in a rib. Excision of the rib together with radiotherapy resulted in a fall in plasma inactive renin to normal. 4. The inactive renin in plasma and tumour extracts was activated to the same extent by acid treatment and by trypsin.

Aged↗
PubMed1978

An altered relation between arterial pressure and plasma angiotensin II concentration resulting from prolonged infusion of angiotensin II.

1. Infusion of angiotensin II into dogs at constant dose over 2 weeks caused a progressive rise in arterial pressure. 2. When the infusion was stopped the pressure dropped slowly from hypertensive levels over 48 h. 3. Dose-response studies at weekly intervals showed progressive elevation, without steepening, of the plasma angiotensin II-blood pressure curve. 4. Thus, during prolonged administration of angiotensin II, a given plasma concentration of the peptide can sustain a higher arterial pressure than it can during acute infusions.

Aldosterone↗
PubMed1978

Monitoring disease in England and Wales: methods applicable to routine data-collecting systems.

This paper reviews routine data-collecting systems and methods for disease surveillance in England and Wales. It discusses population-based correlation studies, which seek to explain disease trends by relating routine health statistics to possible causative agents on a secular, geographical, or occupational basis. It describes recent developments in linking information collected by routine general purpose systems as a means of identifying and following individuals exposed to potential hazards.

Death Certificates↗
PubMed1978

Angiotensin II/aldosterone dose-response curves in the dog: effect of changes in sodium balance.

The possibility that the responsiveness of plasma aldosterone concentration to angiotensin II alters with changes in sodium balance was investigated in male beagle dogs under conditions of controlled sodium and potassium intake. Angiotensin II was infused at four different rates (usually 3, 6, 12, and 24 ng/kg/min), each for 1 h, 1) after periods of normal sodium diet (32 mEq/day), 2) after moderate sodium depletion (negative cumulative sodium balance 25-58 mEq), 3) after severe sodium depletion (65-116 mEq negative cumulative sodium balance), and 4) after sodium loading (150-212 mEq positive sodium balance), daily potassium intake remaining constant (26 mEq/day) throughout. Angiotensin II/aldosterone dose-response curves after moderate sodium depletion were both elevated and steepened in comparison with those found during normal sodium intake. Severe sodium depletion was associated with even greater elevation of dose-response curves, but individual aldosterone responses to angiotensin II were irregular and unpredictable. Sodium loading significantly diminished aldosterone responsiveness to angiotensin II. Blood pressure increments during angiotensin II infusion were attenuated by sodium depletion.

Aldosterone↗
PubMed1978

[des-Asp1]angiotensin II in the dog: blood levels and effect on aldosterone.

Circulating levels of [des-Asp1]angiotensin II ([des-Asp1]-AII), angiotensin II (AII), and aldosterone were measured in five conscious beagle dogs before and during iv infusion of [des-Asp1]AII at rates of 3, 6, 12, and 24 ng/kg/min. The animals were studied after 4 days on a normal sodium and potassium diet and again after a period of sodium depletion accomplished by iv furosemide (2-5 mg/kg) and 4 days of low sodium diet (2-5 mmol/day). Compared to the normal sodium diet, sodium depletion resulted in increases in the plasma levels of aldosterone from 10 +/- 2 (SE) to 66 (16-116) ng/100 ml of AII from 16 +/- 4 to 52 +/- 13 pmol/liter and of [des-Asp1]AII from 2 +/- 0.7 to 12 +/- 4 nmol/liter. Incremental infusions of [des-Asp1]AII in the sodium replete state resulted in progressive increases in the plasma levels of aldosterone in all dogs. In comparison with a previous study in which dogs were infused with AII, it was apparent that [des-Asp1]AII was equally or slightly more potent in stimulating aldosterone and had a higher metabolic clearance rate than AII. [des-Asp1]AII stimulated aldosterone in four of the five sodium-depleted dogs but no steepening of the [des-Asp1]AII/aldosterone dose-response curves was apparent. These results do not support the hypothesis that circulating [des-Asp1]AII mediates the effect of AII on aldosterone in the dog.

Aldosterone↗
PubMed1978

Amiloride in the treatment of primary hyperaldosteronism and essential hypertension.

1. Amiloride (40 mg/day) was given to nineteen patients with primary hyperaldosteronism. There were significant falls in systolic and diastolic blood pressure, in total exchangeable sodium and in serum sodium and bicarbonate, while total exchangeable potassium, total body potassium, serum potassium, chloride and urea, plasma renin, angiotensin II and aldosterone all increased significantly. Amiloride was effective in reducing the blood pressure in patients with and without adrenocortical adenoma. No carry-over effect was seen on withdrawing amiloride. Similar changes were associated with amiloride treatment in five patients with essential hypertension; hyperkalaemia was not observed. 2. Only negligible side effects were encountered in the entire series of 24 patients.

Adult↗
PubMed1978

Hemodynamic assessment of Lillehei-Kaster tilting disc aortic and mitral prostheses.

Twenty-six patients with Lillehei-Kaster prosthetic heart valves, 15 with aortic and 11 with mitral valves, were catheterized to assess their hemodynamic performance. The calculated effective orifice areas were linearly related to but always less than their actual orifice areas. There was no significant difference in the effective orifice area of the mitral or aortic prostheses of similar size. The aortic prosthesis with an annulus diameter of 21 mm. was found to have a mean effective orifice area of 0.77 sq. cm. Our catheter studies have demonstrated no hemodynamic advantages of the Lillehei-Kaster aortic and mitral prosthetic valves over prosthetic valves.

Aortic Valve↗
PubMed1977

Amelioration of bendrofluazide-induced hypokalemia by timolol.

The beta adrenergic blocking drug, timolol, tended to correct the hypokalemia of short-term bendrofluazide treatment in 6 healthy male subjects and although the effect was small it was significant. Timolol also reduced the rise in plasma aldosterone and urine potassium excretion following bendrofluazide and increased the urine sodium/potassium ratio. There was no evidence of a shift of potassium from the intracellular to the extracellular space.

Bendroflumethiazide↗
PubMed1977

Urine electrolyte response to 18-hydroxy-11-deoxycorticosterone in normal man.

1. To assess whether the adrenal corticosteroid 18-hydroxy-11-deoxycorticosterone [18-(OH)-DOC] affects urine electrolyte excretion in normal man, seven male volunteers received 120 microgram (353 nmol) intravenously in 1 h. This was compared with glucose (50 g/l; control) and aldosterone (80 microgram, 222 nmol) infusions in the same subjects. 2. A definite though weak antinatriuretic response to 18-(OH)DOC was observed, whereas urine potassium excretion was not altered. Aldosterone increased urine potassium excretion and reduced sodium output. Urine pH was lowered by both corticosteroids, aldosterone in general having a more marked effect. Urine volume was not altered by 18-(OH)DOC. 3. Plasma concentrations of 18-(OH)DOC and aldosterone rose approximately tenfold during their respective infusions. Compared with that of aldosterone, the metabolic clearance rate of 18-(OH)DOC was slower andits plasma half-life was longer. 4. We have been able to demonstrate that 18-(OH)DOC has a definite, albeit weak antinatriuretic action in normal man, but whether or not this corticosteroid is capable of elevating the blood pressure in man remains to be shown.

18-Hydroxydesoxycorticosterone↗