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Biomedical subjects

L A Simons

Publications and source records attributed to L A Simons.

At least 91 records · Page 5Linked to original sources
PubMed1985

On the effects of dietary n-3 fatty acids (Maxepa) on plasma lipids and lipoproteins in patients with hyperlipidaemia.

An encapsulated preparation of fish oil (Maxepa) was administered to hyperlipidaemic patients in order to establish the responsiveness of the common lipid phenotypes to dietary supplementation with n-3 fatty acids. 13 patients took 6 g/day of fish oil and 12 patients took 16 g/day in a randomized, double-blind crossover study, whereby each subject took fish oil for 3 months and matching placebo for 3 months. The study was conducted against a background diet restricted in saturated fat and cholesterol. In Types IIa and IIb hyperlipoproteinaemia there was no substantial fall in plasma cholesterol concentration. Plasma triglyceride concentrations were reduced significantly in Types IIb and IV (28% and 41% respective reductions). In a separate study using 16 g/day of fish oil in patients with Type V hyperlipoproteinaemia, plasma triglycerides were reduced by 58% and plasma cholesterol concentration by 34%. The change in plasma triglyceride concentration was significantly correlated with the basal triglyceride level (r = -0.94), and was dose-related (33% fall on 6 g/day and 58% fall on 16 g/day). The fall in plasma triglyceride concentration was accompanied by a significant reduction in the concentration of very low-density lipoprotein cholesterol (-42%), a significant rise in low density lipoprotein cholesterol (+7%), and a significant rise in high-density lipoprotein cholesterol concentration (+6%), there being no significant change in the ratio of low density to high density lipoprotein cholesterol. There were changes in the fatty acid composition of plasma and platelet lipids which reflected dietary supplementation with n-3 fatty acids, notably an increase in the proportion of eicosapentaenoic and docosahexaenoic acids which occurred in a dose-dependent fashion. Despite these changes there was no significant variation in the bleeding time, platelet count or blood viscosity during the treatment.

Adult↗
PubMed1985

Reduction in plasma cholesterol and increase in biliary cholesterol by a diet rich in n-3 fatty acids in the rat.

Cholesterol and lipoprotein metabolism were investigated in a group of rats fed a fish oil-supplemented diet, a rich source of n-3 fatty acids. For comparison purposes, other groups of rats were fed either safflower oil (n-6 fatty acids) or coconut oil (saturated fatty acids). Diets were isocaloric and contained identical amounts of cholesterol. Rats fed fish oils for 2 weeks showed a 35% lower plasma cholesterol level than rats fed safflower oil, who in turn showed a 14% lower plasma cholesterol level than those fed coconut oil. The fall in plasma cholesterol level with fish oils was associated with significant falls in low density and high density lipoprotein cholesterol levels, but with no significant change in the ratio of low density to high density lipoprotein cholesterol. The fatty acid compositions of plasma, hepatic, and biliary lipids showed relative enrichment with n-3 fatty acids, reflecting the composition of the diet. The fish oil diet increased the basal secretion rate of cholesterol into bile, but the bile acid secretion rate remained unchanged. It is suggested that n-3 fatty acids reduce the plasma cholesterol level in rats by increasing the transfer of cholesterol into bile.

Animals↗
PubMed1984

Health lifestyle education in high schools. A three-year follow-up study.

An experimental "healthy lifestyle programme" was initiated in Year 7 (first year of high school) in selected high schools in 1980 and was conducted over a three-year period. The programme had two main objectives: to influence attitudes and increase knowledge about health matters, in order to improve lifestyle; and to strengthen the general case for the more organized instruction of schoolchildren in this field. As part of the programme, children were given lessons on nutrition, physical activity and fitness, and on alcohol, tobacco and drugs. The programme was reasonably implemented in three of the four schools which took part in the experiment. Significant improvements, over three years, in attitudes and knowledge about health and nutrition and a reduction in cigarette smoking, were noted among children in schools where the programme had been implemented reasonably. The reasons for the partial success of the programme are discussed.

Attitude to Health↗
PubMed1984

Role of the liver in low-density-lipoprotein catabolism in the rat.

Plasma low-density-lipoprotein (LDL) kinetics and hepatic LDL uptake were studied in the rat after an intravenous pulse injection of [14C]sucrose-labelled LDL. Some 96% of injected radioactivity was associated with apoprotein B of LDL (d 1.020-1.050). The disappearance of labelled LDL from plasma was accompanied by a linear increase in the hepatic uptake of LDL, up to 12 h after injection. Oestradiol treatment lowered plasma cholesterol concentration by 58% and the intravascular pool of LDL by 78%. This was associated with a 4-fold increase in the fractional catabolic rate of LDL and a 2-fold increase in the hepatic uptake of LDL. Oestradiol treatment did not significantly change the synthesis rate of LDL; it decreased the skin and lung uptake of LDL, but increased adrenal uptake. These results suggest that the liver plays an important role in the regulation of plasma LDL concentration.

Animals↗
PubMed1984

How "representative" are subjects attending a coronary risk factor screening programme?

Coronary risk factors were compared in two groups of subjects aged 25-64 years. One group voluntarily, and at no cost, attended a risk factor screening clinic (n = 3844), while the second group represented a population sample drawn from the metropolitan Sydney electoral roll (n = 1394). Older subjects were over-represented in the screening clinic compared with the electoral roll sample. Hypercholesterolemia was more prevalent in the screening clinic in older females, while hypertension and current cigarette smoking were less prevalent in the screening clinic in older subjects of both sexes. Obesity was less prevalent in the screening clinic in older males. A voluntary screening programme may generate a unique and possibly unreproducible population sample.

Adult↗
PubMed1984

The interactions of body weight, age, cigarette smoking and hormone usage with blood pressure and plasma lipids in an Australian community.

The predicted variation of blood pressure and plasma lipid levels, based on association with body weight, age, cigarette smoking and oral contraceptive usage, was examined in 47 000 self-referred subjects who attended a community programme for coronary risk factor screening. In both sexes, blood pressure and plasma lipid (cholesterol and triglyceride) levels were positively correlated with age and body mass index (BMI, kg/m2). Plasma triglyceride concentrations were positively correlated with cigarette smoking. Partial correlation analysis showed age and BMI to be independently correlated with blood pressure and plasma lipids. Plasma cholesterol and triglyceride levels were correlated with each other independently of the effects of age and BMI. Multiple regression analysis showed age to be a more powerful predictor of blood pressure and plasma lipid levels in females than in males, while BMI was a more powerful predictor of blood pressure and plasma lipid levels in males than in females. Current cigarette smoking did not contribute to the prediction of blood pressure or plasma cholesterol level in either sex, but did predict a 10% higher plasma triglyceride level in both sexes. Oral contraceptive usage did not contribute to the prediction of plasma cholesterol level in multiple regression analysis, but did predict higher plasma triglyceride and blood pressure levels. In view of the high prevalence of overweight people in the Australian community, weight reduction would probably be associated with a significant fall in the risk of coronary heart disease, particularly in males.

Adolescent↗
PubMed1983

Low density lipoprotein metabolism in the normal to moderately elevated range of plasma cholesterol: comparisons with familial hypercholesterolemia.

Low density lipoprotein (LDL) metabolism was investigated using a pulse injection of 125I-labeled LDL in 20 subjects who did not have familial hypercholesterolemia (FH) (plasma cholesterol 160-297 mg/dl) and in 9 subjects who did have heterozygous FH (plasma cholesterol 273-501 mg/dl). Subjects were also injected with 131I-labeled LDL chemically modified with cyclohexanedione. This technique permitted a calculation of the amount of apoLDL removed via receptor-mediated and receptor-independent pathways. In subjects without FH, 40% (range 25-49%) of LDL was cleared via receptor-mediated pathways and in subjects with FH this figure was 22% (range 3-33%). In nonfamilial hypercholesterolemia there was clear evidence of defective removal of LDL via receptor-independent pathways in association with some overproduction of apoLDL. In heterozygous FH there was evidence of defective removal of LDL via receptor-mediated pathways, while some subjects also showed evidence of overproduction of apoLDL. It is suggested that LDL catabolism via receptor-independent pathways plays a major role in regulating plasma cholesterol levels in the normal to moderately elevated range.

Adolescent↗
PubMed1982

Health attitudes and knowledge, and coronary risk factors in high-school children, Sydney and Inverell.

Attitudes to, and knowledge of, health and nutrition, together with presence of major coronary risk factors, were assessed in New south Wales high-school students at the start of an experimental healthy lifestyle programme. Data were obtained for 2596 children (mean age, 12.5 to 15.5 years), of whom 1971 lived in Sydney and 625 in rural Inverell. Girls had higher scores than boys on questions related to nutrition and fitness attitudes. Girls' scores on questions related to health attitudes and knowledge and nutrition attitudes and knowledge increased with age. The earliest precursors of coronary heart disease and chronic lung diseases were present in this group of children, of whom 20% to 30% were smoking cigarettes, 30% were overweight or obese, 8% to 15% of boys and 2% to 7% of girls had high blood pressure, and 9% had hypercholesterolaemia.

Adolescent↗
PubMed1982

Long-term treatment of hypercholesterolaemia with a new palatable formulation of guar gum.

Nineteen patients with primary hypercholesterolaemia previously stabilized on diet alone were treated with a new formulation of guar gum (6g t.d.s. with meals) in a placebo-controlled, single-blind study. Seventeen patients completed 3 months treatment without serious side effects, while 2 patients withdrew immediately because of severe diarrhoea. Thirteen patients have completed 12 months treatment with guar gum. There have been no significant changes in safety parameters. Plasma cholesterol was reduced by a significant 15% during the first 3 months of treatment (7.9 +/- 0.8 vs 6.7 +/- 1.0 mmol/l, P less than 0.001) and this effect has been sustained for 12 months. The fall in plasma cholesterol was associated with a significant 20% fall in LDL cholesterol, but with no change in HDL cholesterol. Plasma triglycerides did not change significantly. Percentage cholesterol absorption was reduced by guar gum in 4/5 normal subjects examined.

Adult↗
PubMed1982

Long-term treatment with slow release oxprenolol alone, or in combination with other drugs: effects on blood pressure, lipoproteins and exercise performance.

Twenty-eight patients with mild essential hypertension were treated with placebo for six weeks and then with active medication for a further 32 weeks. Twelve patients were well-controlled with 160-320 mg/day of slow release oxprenolol alone, 12 required oxprenolol and chlorthalidone, and four also required hydrallazine. beta-adrenergic blockade reduced the basal level of plasma free fatty acid (FFA) by 41%. A sub-maximal exercise test reduced the level of FFA by 34% during placebo treatment. The same exercise test during beta-blockade reduced the already lowered basal FFA level by a further 45%. Only female subjects experienced exercise-induced leg fatigue during beta-blockade. They always had higher FFA levels than males, but the relative changes in FFA concentration were similar in both sexes. Exercise testing induced a 52 mmHg rise in systolic blood pressure, but this was reduced to only 14 mmHg during treatment. Patients controlled on oxprenolol alone showed no significant change in plasma lipid and lipoprotein levels. Those patients ultimately requiring combination drug therapy experienced a statistically significant rise in plasma triglycerides and a significant fall in high density lipoprotein cholesterol. The biological importance of these changes is uncertain.

Blood Pressure↗
PubMed1982

Is authoritarianism the main element of the coronary-prone personality?

Clients at the Sydney Coronary Heart Disease Prevention Programme were screened for actual CHD and sufferers were compared with non-suffers on four personality scales to measure, respectively, A-B, dominance, achievement motivation and 'freneticism'. There were 112 sufferers and 201 controls. Sufferers were found to have significantly higher scores on dominance-the Ray (1976) Directiveness scale-but also to have significantly lower scores on the A-B measure. This latter reversal of the usual relationship was an artifact of the fact that older people are both more CHD prone and get lower A-B scores. When age was controlled for there was no relationship between A-B type and CHD. This left the authoritarian style of dominance measured by the Directiveness scale as the sole predictor of CHD. This was held to be a belated vindication of claims made in the pioneering work of Dunbar (1943).

Authoritarianism↗
PubMed1982

A survey of haematological values in Sydney.

A survey of haematological values in Sydney was conducted in conjunction with the Sydney Coronary Heart Disease Prevention Programme. The sample consisted of 4374 'self-referred' Sydney inhabitants between 11-90 yr of age. Comparison of the haemoglobin concentrations with those obtained in 2 previous Australian surveys suggested that the haemoglobin values in Australia have not varied in the last 25 yr.

Adolescent↗
PubMed1981

On the mechanism of plasma cholesterol reduction in the rat given probucol.

1. The effects of the cholesterol-lowering drug probucol on lipoprotein metabolism and on the key enzymes that regulate hepatic cholesterol metabolism in the rat were studied. 2. Probucol given for 2 weeks was accompanied by a significant reduction in plasma concentrations of low-density and high-density lipoproteins (LDL,HDL). The fractional catabolic rates of the apolipoproteins of HDL and LDL (apoHDL, apoLDL) were not affected by probucol, although the absolute rates of catabolism of both the apolipoproteins were significantly reduced. 3. The activities of 3-hydroxy-3-methylglutaryl-coenzyme A (CoA) reductase and cholesterol 7 alpha-mono-oxygenase, as well as the rate of hepatic sterol synthesis, were unchanged during the first 2 weeks of probucol. More prolonged probucol led to inhibition of the activity of these enzymes and reduction in sterol synthesis, although the liver cellular content of cholesterol significantly increased. 4. It is postulated that a principal mode of action of the drug is to reduce the rate of lipoprotein synthesis.

Acyl Coenzyme A↗