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Biomedical subjects

B Lewis

Publications and source records attributed to B Lewis.

At least 37 records · Page 2Linked to original sources
PubMed1990

Effect on plasma lipids and lipoproteins of postmenopausal oestrogen therapy with added dydrogesterone.

In a prospective, randomized, cross-over study, 14 postmenopausal women completed 9 months of treatment with conjugated equine oestrogens, 1.25 mg daily. Seven women added dydrogesterone 20 mg daily for 12 days during months 2, 3 and 4, and then 10 mg daily for an identical time in months 5, 6 and 7. The other seven women added the two dydrogesterone doses in reverse sequence. No dydrogesterone was taken during months 8 and 9. Lipids and lipoproteins were measured before treatment and at the end of months 4, 7 and 9. Lipids were also estimated in an untreated (reference) group of eight postmenopausal women on two occasions 6 months apart; these showed significant changes in HDL2- and HDL3-cholesterol. In the treatment group, HDL-cholesterol and apolipoprotein (apo) A1 were significantly higher and LDL-cholesterol and apo B were significantly lower at months 4, 7 and 9 compared with baseline values. Triglyceride levels were increased significantly over baseline values, but remained within the normal range. No significant differences between the two dydrogesterone doses were observed on any lipid and lipoprotein fraction, nor were there any differences between the oestrogen-only and oestrogen/dydrogesterone treatment phases. Dydrogesterone appears to cause little, if any, lipid and lipoprotein changes and assessment in a larger population of postmenopausal women is warranted.

Dydrogesterone↗
PubMed1990

Diet and exercise as regulators of lipid risk factors.

Comparisons of different countries have shown that populations with a low dietary intake of saturated fat also have a low mortality from coronary heart disease. Controlled-feeding experiments have shown that the potential for altering plasma cholesterol levels and, consequently, altering the risk of coronary heart disease by dietary modification is great. However, in practice the influence of dietary advice to the general population on plasma cholesterol levels has been less pronounced. Several investigators have shown that by decreasing the intake of saturated fats and dietary cholesterol and increasing the intake of polyunsaturated fats and foods providing soluble fibre, plasma cholesterol levels can be reduced by up to 29% and low density lipoprotein (LDL)-cholesterol by over 33%. In most studies, levels of high density lipoprotein (HDL)-cholesterol are not materially altered by modern lipid-lowering diets; generally, plasma levels are maintained, or increased after correction of overweight is is achieved. It has been calculated that the risk of fatal coronary heart disease is 32% lower in subjects consuming such a diet than in those following a typical American diet, and life expectancy is 5 years greater in the former group. Life expectancy is also 2 to 3 years longer in populations habitually following low fat diets than in Western populations. Frequent exercise has been inversely related to risk of coronary heart disease. Physically active individuals have a more favourable lipoprotein profile than sedentary individuals but the extent of a direct effect of exercise on lipoprotein levels is not known.

Cholesterol↗
PubMed1979

Splanchnic production of discoidal plasma high-density lipoprotein in man.

The morphology of human plasma high-density lipoprotein (H.D.L.) subfractions in arterial and hepatic venous blood from seven human subjects was investigated by electron microscopy. The H.D.L.3 subclass from both sources and the H.D.L.2 subclass from arterial blood were composed of spherical particles, identical with normal human peripheral venous H.D.L. In contrast, H.D.L.2 isolated from hepatic venous blood was composed of a mixture of spherical and discoidal particles. The latter tended to form rouleaux, and had a diameter similar to that of nascent H.D.L. particles obtained from the peripheral venous blood of a patient with lecithin: cholesterol acyltransferase deficiency. This supports the view that nascent H.D.L. is secreted into the splanchnic bed in man.

Adult↗
PubMed1979

Lipodystrophy with hyperlipidaemia: the role of insulin in very low density lipoprotein over-synthesis.

A patient with partial lipodystrophy is described in whom hypertriglyceridaemia was accompanied by marked hyperinsulinaemia. The hyperlipidaemia was due to increased plasma levels of very low density lipoprotein (VLDL). Kinetic studies, performed after injection of autologous radioiodinated VLDL, indicated that the raised VLDL levels were associated with over-production of this lipoprotein. Administration of diazoxide led to a substantial fall in serum insulin levels, accompanied by reduction in VLDL production and in serum triglyceride concentration. The possible role of insulin in inducing hyperlipidaemia by causing over-production of VLDL is discussed.

Adult↗
PubMed1978

Serum lipoprotiens in four European communities: a quantitative comparison.

Serum lipid and lipoprotein concentrations have been measured in 985 men and women sampled from communities in London, Naples, Uppsala and Geneva. This was done to define normal ranges, detect inter-population differences, and relate such differences to levels of lipids in the major lipoprotein classes of plasma. Cholesterol and triglyceride concentrations showed substantial differences between the four populations; levels of these lipids showed parallel trends, which were attributable to differences in low density lipoprotein and very low density lipoprotein concentrations. By contrast, high density lipoprotein cholesterol concentrations showed little or no interpopulation differences. Geographical differences in serum triglyceride and cholesterol levels were not correlated with variation in the prevalence of obesity.

Adult↗
PubMed1978

Control of biodegradative threonine dehydratase inducibility by cyclic AMP in energy-restricted Escherichia coli.

To explain the requirement for anaerobic conditions in the induction of biodegradative L-threonine dehydratase in Escherichia coli, Crookes strain, measurements of cyclic AMP (cAMP) were made during aerobic and anaerobic growth and upon an aerobic-to-anaerobic transition. Internal cAMP levels were similar (5 to 10 muM) throughout exponential growth, whether aerobic or anaerobic, but only during anaerobiosis was threonine dehydratase synthesized. When an exponentially growing aerobic culture was made anaerobic, a sharp increase in internal cAMP was noted, reaching 300 muM within 10 min and declining thereafter to normal anaerobic levels. Threonine dehydratase synthesis was detected immediately after the attainment of peak cAMP levels and continued for several generations. A similar pattern but with less accumulation of cAMP and less threonine dehydratase production was also noted upon treatment of an aerobically growing culture with KCN. Pyruvate addition at the time of anaerobic shock severely affected both cAMP accumulation and threonine dehydratase synthesis; however, externally added cAMP could partially counter the pyruvate effect on enzyme synthesis. The conclusion was reached that conditions which resulted in a temporary energy deficit brought about the major accumulation of cAMP, and this elevated level served as a signal for initiation of threonine dehydratase synthesis to supply energy by the nonoxidative degradation of threonine.

Aerobiosis↗
PubMed1978

Normal and abnormal lipid metabolism in children.

The transport of lipids in plasma, and its dietary regulation are briefly reviewed. Plasma lipid concentrations are low in the neonate, rising to near-adult levels by the age of six years. The causes of childhood hyperlipidaemia are discussed and a classification is proposed.

Biological Transport↗
PubMed1977

Influence of lipid concentrations and age on transfer of plasma lipoprotein into human arterial intima.

Transfer of low-density lipoprotein (L.D.L.2) from plasma to arterial intima was studied in 16 patients undergoing arterial surgery. Autologous labelled lipoprotein was used to demonstrate that L.D.L.2 enters the intima from plasma. Net flux of L.D.L.2 appeared to increase with age. Within each age-group the net flux of L.D.L.2 showed a pronounced positive correlation with plasma-L.D.L.-cholesterol concentrations. This may account in part for the association between hypercholesterolaemia and the development of atherosclerosis.

Adult↗
PubMed1977

Measurement of the apoproteins of human serum lipoproteins by rocket immunoelectrophoresis.

A method has been developed for assay of apolipoproteins A, B and C in human serum, using rocket immunoelectrophoresis. The technique is reasonably simple, sensitive and precise. The concentrations of apolipoproteins A, B and C in these classes of serum lipoproteins were measured in 116 healthy subjects. Concentrations of apoproteins within very low and low density lipoproteins increased with age but those of high density lipoproteins showed no consistent age trend.

Adult↗
PubMed1977

Intravenous fat tolerance. Correlation with very low density lipoprotein apoprotein B kinetics in man.

The intravenous fat tolerance test (IVFTT) has been introduced as a measure of the fractional catabolic rate of the endogenous triglyceride of plasma. To assess the validity of this test we have compared this test in 21 normal and hyperlipidaemic subjects with direct measurement of the fractional catabolic rate of autologous radio-iodinated VLDL. There was a strong positive correlation between the rate constant K2 of the IVFTT and the fractional catabolic rate of VLDL-apolipoprotein B (r=+0.87). The two rates were considerably different in magnitude. The IVFTT appears to be a valid index of the fractional catabolic rate of VLDL. Its limitations and uses are discussed.

Adult↗