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Biomedical subjects

L A Simons

Publications and source records attributed to L A Simons.

At least 109 records · Page 6Linked to original sources
PubMed1980

Impaired plasma triglyceride clearance as a feature of both uremic and posttransplant triglyceridemia.

After accurate plasma volume calculation, endogenous plasma very-low-density-lipoprotein (VLDL)-triglyceride turnover rates were measured in 20 undialyzed patients with chronic renal failure (CRF) and in 16 renal transplant recipients with stable graft function. When kinetic criteria were based on a group of healthy subjects (Vmax = 36.7 mumoles/hr/kg), it was clear that, on the whole, CRF patients had a reduced capacity for VLDL-triglyceride removal (Vmax = 14.0 mumoles/hr/kg), as did graft recipients (Vmax = 19.5 mumoles/hr/kg). In transplant recipients with impaired graft function, however, extremes of both under removal and over production of VLDL-triglycerides were observed. In CRF, defective clearance was accompanied by a reduction in postheparin lipoprotein and hepatic lipase activities, although there was no statistical relationship. Enzyme activities were not reduced, however, after transplantation, and the metabolic factors responsible for defective clearance were not clearly identified.

Adolescent↗
PubMed1980

Vascular disease risk factors in women with premature menopause.

The vascular disease risk factor profile was studied in 21 women who had experienced a premature menopause due to bilateral oophorectomy. Compared with age-matched menstruating control subjects, oophorectomized women did not differ appreciably with respect to the prevalence of major vascular risk factors other than hyperlipidaemia, nor did they exhibit an excessive prevalence of vascular disease. In oophorectomized women not receiving hormone replacement therapy, the total serum cholesterol and low density lipoprotein (LDL) cholesterol levels were increased, while high density lipoprotein (HDL) cholesterol was not significantly altered. In women receiving replacement with ethinyl oestradiol, the total and LDL cholesterol were significantly decreased while HDL cholesterol was significantly increased, relative to oophorectomized women not receiving hormone replacement. The increased proportion of LDL to HDL in those not receiving hormone replacement suggests that they may be exposed to an increased theoretical long-term vascular risk, and this might justify appropriate hormone replacement in all such women, subject to certain safeguards.

Adult↗
PubMed1980

Type I hyperlipoproteinaemia and recurrent scrotal pain.

A three-year-old boy is described with type I hyperlipoproteinaemia in association with recurrent scrotal pain and hepatosplenomegaly. His parents are consanguinous and it is likely that he is homozygous for an autosomal recessive trait, characterized by the absence of plasma lipoprotein lipase following intravenous injection of heparin. Studies have been performed in a number of first degree relatives, but the findings are inconclusive. He has responded well to a low fat diet with dramatic reductions in elevated plasma triglyceride concentrations.

Adult↗
PubMed1979

High-density lipoprotein in chronic renal failure and after renal transplantation.

Serum high-density-lipoprotein (HDL) cholesterol and apoprotein (apo) A concentrations were significantly reduced at the time of renal transplantation in 26 patients with chronic renal failure. In a prospective evaluation the behaviour of HDL concentrations after grafting was found to depend on renal function. Graft function was sustained in 19 patients, in whom HDL-cholesterol and apo A concentrations increased to lie within normal limits by six months after the operation. Successful transplantation also restored to normal the lipid and protein content of HDL as expressed by the ratio of HDL cholesterol to apo A. When transplant function was not sustained (seven patients), however, no changes in HDL were observed up to the time of the graft loss. Such changes in HDL with successful kidney grafting augur well in a population with many risk factors for coronary heart disease.

Adult↗
PubMed1979

High density and low density lipoproteins in chronic renal failure before and after renal transplantation.

The hyperlipoproteinaemia accompanying chronic renal failure and renal transplantation has been re-examined in terms of the apoprotein (apo A and apo B) moieties of the high density (HDL) and low density (LDL) lipoproteins. Hypertriglyceridaemia is prevalent in chronic uraemia and is not corrected by haemodialysis or renal transplantation. Hypercholesterolaemia is characteristic only of renal allograft recipients. Apo A levels are reduced in undialyzed uraemic and remain low during haemodialysis, as well as in patients with renal allografts of less than six months duration. In renal transplant recipients of greater than one year duration, apo A levels are normalized. The normalization of apo A level is related to the stability of graft function, as determined by sequential analysis of 15 renal transplant recipients. Apo B levels are normal transplant recipients. Apo B levels are normal in uraemic and dialyzed patients, but are elevated in long term transplant recipients. Unlike apo A levels, this alteration does not appear to reflect the restoration of kidney function.

Apolipoproteins↗
PubMed1978

Coronary risk factor screening and long-term follow up: year 1 of the Sydney Coronary Heart Disease Prevention Programme.

Ten thousand self-referred Sydney inhabitants were screened for major coronary risk factors over one year. Individual "problems" were referred to general practitioners for further assessment and treatment. Seventy-four per cent of subjects have attended a general practitioner where relevant. For subjects under 65 years, 29% had unsuspected hyperlipidaemia, 11% had unsuspected hypertension, and 0.6% had unsuspected diabetes. Nineteen per cent of subjects reported a past history of hypertension, of whom 46% appeared to be well-controlled (diastolic blood pressure less than 95 mmHg). The numbers of cigarette smokers fell with increasing age. Considering hyperlipidaemia, hypertension and cigarette smoking in subjects under 40 years of age, 10.4% of males and 4.9% of females had two or more coronary risk factors. Three hundred and fifty-four subjects selected at random, who claimed to be receiving treatment as a result of initial screening were invited for retesting eight and 15 months later. Significant falls were noted in body weight, blood pressure, and plasma cholesterol readings.

Adult↗
PubMed1978

Coronary artery disease in young Australian women.

Over a 12-year period, from 1965 to 1977, 43 women under 46 years of age were documented with angiographic evidence of coronary atherosclerosis at St Vincent's Hospital, Sydney. Twenty-five of the women were able to be followed up at a mean interval of 31 months. This group of young women with coronary artery disease was compared with an age-matched control group of 660 "healthy" women drawn from the general population. Hyperlipidaemia was present in 72% of patients and in 13% of controls. Seventy-three percent of patients were regular cigarette smokers compared with 21% of controls. Only one patient out of 43 showed neither hyperlipikaemia, nor hypertension, nor smoked cigarettes, and multiple risk factors were commonly present. The level of high density or alpha-lipoprotein was significantly reduced in young women with coronary artery disease. These results highlight the presence of classical risk factors in these young women, as well as the importance of alpha-lipoproteins.

Apolipoproteins↗
PubMed1978

The effects of plasma exchange on cholesterol metabolism.

Four patients heterozygous for familial hypercholesterolaemia were treated by repeated plasma exchange with or without lipid-lowering drugs. Repeated plasma exchange without drug therapy in 3 patients was associated with a significant 18--28% decrement in plasma cholesterol level, comparing control with plateau values observed 3 weeks after exchange. Further decrements in plateau values followed the addition of lipid-lowering drugs used in combination, clofibrate--nicotinic acid or clofibrate--nicotinic acid--cholestyramine (range of total decrement 39--50%). Plasma exchange was associated with an increased excretion of endogenous faecal steroids, but this increase was completely abolished by the subsequent administration of clofibrate--nicotinic acid. This therapy prevented any increase in bile acid excretion with concomitant use of cholestyramine resin. Plasma exchange with drug therapy was associated with a sustained rise in plasma cholesterol specific radioactivity. In a fourth patient, clofibrate--nicotinic acid was administered prior to plasma exchange and led to a 24% fall in plasma cholesterol. Subsequent plasma exchange in this patient produced no sustained change in plasma cholesterol plateau level. In two patients, withdrawal of drugs allowed plasma cholesterol to return to pre-exchange control levels. These observations suggest that plasma exchange probably produced an increase in endogenous cholesterol synthesis and a mobilisation of tissue cholesterol. In relation to plateau cholesterol values 3 weeks after an exchange, the data suggested that the reduction in plasma cholesterol level with plasma exchange and drug therapy could have been achieved by intensive drug therapy alone.

Adult↗
PubMed1978

The influence of a wide range of absorbed cholesterol on plasma cholesterol levels in man.

The influence of absorbed dietary cholesterol on plasma cholesterol concentration was studied in two populations, one Seventh Day Adventist (SDA) vegetarian and one nonvegetarian, representing a broad range of plasma cholesterol values and dietary cholesterol intakes. As a group, the SDA vegetarians had significantly lower levels of plasma cholesterol and triglycerides than did the nonvegetarians. This hypolipidemic pattern in the SDA vegetarians was apparently closely related to dietary habits, sinceanother group of SDA who were nonvegetarian had significantly higher plasma cholesterol and triglyceride levels than their vegetarian counterparts. Both the dietary intake of cholesterol and the percentage absorption of cholesterol were lower in vegetarians than in nonvegetarians. The mass of cholesterol absorbed increased linearly with the mass of cholesterol ingested in all groups, but no relationship could be demonstrated between absorbed cholesterol and plasma cholesterol concentration.

Absorption↗
PubMed1978

Haematological and biochemical abnormalities associated with intralipid hyperalimentation.

Haematological and biochemical parameters were monitored in six patients during Intralipid hyperalimentation. A mild anaemia was consistently observed, accompanied by morphological changes in red cells, granulocytes, and platelets. All patients demonstrated an abnormally high percentage of plasma cholesterol in the unesterified form and altered plasma cholesterol esterification, but red cells were not uniformly enriched in cholesterol. These findings stress the need for careful monitoring during Intralipid therapy.

Adult↗
PubMed1978

Circulating thyroid hormone levels and adequacy of dialysis.

In vitro thyroid function tests were performed in three groups of patients with chronic renal failure who were receiving, on average, 15, 18 and 27 hours of maintenance hemodialysis per week. Total thyroxine levels were low and total triiodothyronine levels low to normal in those receiving the least dialysis (15 hours), and were significantly higher in those receiving longer dialysis. Free thyroxine levels, as measured by the effective thyroxine ratio, were normal and similar in all three groups, as were serum thyrotrophin levels. All patients were clinically euthyroid. As total hormone levels showed a significant inverse relationship to both urea and creatinine, this study suggests that there is a dialyzable metabolite retained in uremia which competes with thyroid hormones for protein-binding sites.

Adult↗
PubMed1977

Plasma cholesterol esterification in hypertriglyceridaemia.

Plasma cholesterol esterification was assessed in hypertriglyceridaemic patients and normal subjects by two in vitro methods, one using autologous substrate and one using exogenous substrate. There was a significant negative correlation between cholesterol esterification rate and the plasma triglyceride concentration when this was assessed with autologous substrate or with substrate from a hypertriglyceridaemic donor. The percentage of esterified cholesterol in plasma and the esterification rate were always reduced when the plasma triglyceride concentration exceeded 7 mmol/1 and the rate of esterification rose significantly with appropriate triglyceride-lowering therapy in such patients. Evidence is presented that the impaired cholesterol esterification observed in severe hypertriglyceridaemia is secondary to a reduced concentration of substrate high density lipoprotein cholesterol, as well as to an excess of large triglyceride-rich lipoproteins.

Adult↗
PubMed1977

The effect of cholestyramine on the faecal excretion of bile acids and neutral steroids in familial hypercholesterolaemia.

The faecal excretion of total bile acids was measured in two normal subjects and in seven patients with familial hypercholesterolaemia (four heterozygotes and three homozygotes) in the untreated state and during treatment with near-maximal doses of cholestyramine. There were no significant differences between the three groups. The increase in bile-acid excretion in response to cholestyramine was as great in the homozygotes as in the normal subjects. It is concluded that familial hypercholesterolaemia is not generally due to an inherited defect in the mechanisms for catabolizing cholesterol to bile acids.

Adolescent↗
PubMed1977

Treatment of hypercholesterolaemia with oral lecithin.

An open clinical trial was performed to evaluate the plasma cholesterol-lowering potential of oral lecithin in large doses (20--30 g/day), with or without supplementary clofibrate. Three healthy subjects and seven patients with hypercholesterolaemia were studied over periods ranging from eight weeks to 11 months. In one-third of healthy subjects and in 3/7 patients, lecithin therapy led to a significant fall in plasma cholesterol concentration (10--18% fall). Combination of lecithin and clofibrate in two of the patients led to still lower plasma cholesterol levels (21 and 22% fall). Most of the change in plasma cholesterol concentration, when it occurred, was due to a reduction in beta lipoproteins. Evidence is presented that oral lecithin may reduce plasma cholesterol levels by acting as a source of linoleic acid.

Adult↗
PubMed1976

Effects of ethanol on bile acid and cholesterol metabolism.

The effects of ethanol on plasma lipid and lipoprotein concentrations and on the fecal excretion of neutral sterols and bile acids were studied in three patients with ethanol-induced hyperlipidemia and in four normolipidemic men. In the three patients, plasma triglyceride and cholesterol concentrations were much higher with ethanol than during periods when ethanol was isocalorically substituted with either carbohydrate or both fat and carbohydrate. In the normolipidemic subjects, plasma lipids especially in very low density lipoproteins, were higher with ethanol consumption only in comparison with a balanced diet but not when compared with carbohydrate-rich diets. Triglyceride enrichment of low density lipoproteins occurred uniformly with ethanol. Total sterol excretion, measured by isotope dilution and chemical assay, was similar during ethanol and control periods in two out of the three hyperlipidemic subjects. However, the proportion of bile acids was increased in all three hyperlipidemic subjects but in only one normolipidemic subject while on ethanol. Since cholesterol turnover did not appear to be necessarily influenced by ethanol, as judged either by total endogenous sterol excretion or from the slope of the plasma cholesterol specific radioactivity-time curve, the ethanol-induced increase in bile acid excretion amy not be analogous to other clinical disorders in which increased bile acid excretion and hypertriglyceridemia are associated with raised sterol production.

Adult↗