Biomedical subjects
B Lewis
Publications and source records attributed to B Lewis.
Alcohol and abnormalities of lipid metabolism.
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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.
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.
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.
Hypothesis into theory--the development of aetiological concepts of ischaemic heart disease: a review.
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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.
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.
O-methylhydroxylamine as a reagent for NAD+ modification in urocanase.
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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.
Turnover of apolipoprotein-B in two subjects with familial hypobetalipoproteinemia.
The metabolism of the apoprotein of low-density apoliporprotein-B was studied in a father and son with familial hypobetalipoproteinemia. The synthetic rate of apolipoprotein-B was below the normal range in both subjects, while the fractional removal rate was normal. It is concluded that the subnormal concentration of low-density lipoprotein (LDL) inthese two subjects is due to a low synthetic rate. The synthetic rate of apolipoprotein-B of very low-density lipoprotein (BLDL-apoB) measured in the father was subnormal. The fraction of the VLDL-apoB pool which was oncverted into LDL-apoB was within the normal range. It is suggested that a low synthetic rate of VLDL may underlie the disorder.
Plasma-lipoprotein interrelationships.
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Accentuation of ethanol-induced fatty liver by phenobarbitone.
1. Four groups of rats received a liquid formula diet, given alone (control), or supplemented with either ethanol or phenobarbitone, or both together. 2. The ethanol-treated group showed a fall in plasma triglyceride and a rise in liver triglyceride, as compared with the control rats. 3. The phenobarbitone-treated group showed a marked rise in plasma triglyceride but not in liver triglyceride. 4. The group receiving both ethanol and phenobarbitone also showed a rise in plasma triglyceride, but this was accompanied by a striking increase in liver triglyceride. 5. These results suggest that ethanol and phenobarbitone each stimulate triglyceride synthesis but that in addition ethanol has an inhibitory effect on hepatic triglyceride secretion.
Premyxoedema: entity or nonentity?
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Osler and the Canadians in Folkestone.
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Cardiac surgery in Wessex: review of 1000 consecutive open-heart procedures.
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Lipoprotein fractionation by a precipitation method. A simple quantitative procedure.
A method is described for quantitation of the three major classes of serum lipoproteins. After precipitation of very low density lipoprotein (VLDL) using sodium dodecyl sulphate, the cholesterol and triglyceride content of this lipoprotein class is directly measured. In a second aliquot serum high density lipoprotein (HDL) lipids are measured after precipitation of VLDL and low density lipoprotein (LDL). LDL cholesterol and triglyceride contents are calculated by difference. The procedure requires 2 ml serum, and sensitivity is adequate to permit lipoprotein analyses on umbilical cord serum. Close agreement is observed between this precipitation method and preparative ultracentrifugation.
The metabolism of low density lipoprotein in endogenous hypertriglyceridaemia.
The metabolism of low density lipoprotein (LDL) was studied in eighteen hypertriglyceridaemic patients by injecting autologous radioiodinated LDL. Over 95% of the label was bound to the protein moiety of LDL and therefore the metabolic data reflect the fate and distribution of LDL apoprotein (apo B). The hypertriglyceridaemic subjects included ten with Type V, five with Type IV, two with Type III and one with Type IIb hyperlipoproteinaemia. For comparison identical studies were carried out in seven normal subjects and five patients with heterozygous familial hyperbetalipoproteinaemia (Type IIa). The groups differed considerably in mean LDL-cholesterol concentration. The patients with Type V lipoprotein pattern had significantly lower LDL-cholesterol concentration (mean 0.754 g/1) than the normal group (mean 1.237 g/1). Raised LDL-cholesterol levels were observed in all patients with heterozygous familial hyperbetalipoproteinaemia. The synthetic rate of LDL-apoprotein was found to be similar in all three groups (hypertriglyceridaemic, normal and hypercholesterolaemic). The highest synthetic rate was observed in the patient with Type IIb pattern. However, the fractional catabolic rate (FCR) of LDL-apoprotein differed significantly. The highest mean FCR was found in the Type V group (0.65 +/- 0.17 day-1) compared with 0.41 +/- 0.09 day-1 in the normal group and 0.185 +/- 0.05 day-1 in the Type IIa group. A strong inverse correlation was found between FCR and LDL apoprotein concentration in the whole series (r = -0.90, p less than 0.001) as well as within the Type V group (r = -0.87, p less than 0.01). These data indicate that the low plasma levels of LDL frequently observed in patients with very high plasma triglyceride levels are due to a high removal rate of LDL in these patients rather than to abnormal LDL synthesis.