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Biomedical subjects

R I Levy

Publications and source records attributed to R I Levy.

At least 91 records · Page 5Linked to original sources
PubMed1977

High density lipoprotein metabolism in man.

The turnover of (125)I-high density lipoprotein (HDL) was examined in a total of 14 studies in eight normal volunteers in an attempt to determine the metabolic relationship between apolipoproteins A-I (apoA-I) and A-II (apoA-II) of HDL and to define further some of the determinants of HDL metabolism. All subjects were first studied under conditions of an isocaloric balanced diet (40% fat, 40% carbohydrate). Four were then studied with an 80% carbohydrate diet, and two were studied while receiving nicotinic acid (1 g three times daily) and ingesting the same isocaloric balanced diet. The decay of autologous (125)I-HDL and the appearance of urinary radioactivity were followed for at least 2 wk in each study. ApoA-I and apoA-II were isolated by Sephadex G-200 chromatography from serial plasma samples in each study. The specific activities of these peptides were then measured directly. It was found that the decay of specific activity of apoA-I and apoA-II were parallel to one another in all studies. The mean half-life of the terminal portion of decay was 5.8 days during the studies with a balanced diet.Mathematical modeling of the decay of plasma radioactivity and appearance of urinary radioactivity was most consistent with a two-compartment model. One compartment is within the plasma and exchanges with a nonplasma component. Catabolism occurs from both of these compartments. With a balanced isocaloric diet, the mean synthetic rate for HDL protein was 8.51 mg/kg per day. HDL synthesis was not altered by the high carbohydrate diet and was only slightly decreased by nicotinic acid treatment. These perturbations had effects on HDL catabolic pathways that were reciprocal in many respects. With an 80% carbohydrate diet, the rate of catabolism from the plasma compartment rose by a mean of 39.1%; with nicotinic acid treatment, it fell by 42.2%. Changes in the rate of catabolism from the second compartment were generally opposite those in the rate of catabolism from the plasma compartment, suggesting that these two catabolic pathways may be reciprocally regulated.

Adolescent↗
PubMed1977

Primary type V hyperlipoproteinemia. A descriptive study in 32 families.

We have studied 32 kindreds identified by propositi with primary type V hyperlipoproteinemia. The clinical presentation, metabolic associations, and natural history confirm the distinctiveness of primary type V hyperlipoproteinemia from other lipoprotein abnormalities. Although the underlying defect(s) remains unknown, several factors such as obesity, alcohol, drugs, and diet are able to modify the glyceridemia, the major manifestation of this disorder. Abnormalities of postheparin lipolytic activity or its subfractions do not appear to be involved in the pathogenesis of primary type V. The prevalence of hyperuricemia, diabetes, pancreatitis, and xanthomatosis appears high among the 32 propositi; the last two entities are much less prevalent in the relatives, even among those relatives classified as hyperglyceridemic. There is no evidence in these families of excessive coronary artery disease prevalence. Triglyceride levels are positively associated with age in this population, especially among women. Average triglyceride levels were lower for women than for men before age 50.

Adult↗
PubMed1976

Therapeutic failure in familial type II hyperlipoproteinemia.

The extended use of diet and cholestyramine therapy in familial type II hyperlipoproteinemia was examined in patients who previously participated in a short-term, double-blind trial. A striking secondary failure in therapeutic response during 4 yr of use of this therapy was noted with plasma cholesterol rising an average of 15%. A 3 mo, out-patient, follow-up study designed to reinforce patient motivation and dietary and drug adherence resulted in a prompt but partial reversal of this therapeutic deterioration in 16 patients. Additional inpatient studies confirmed that patient noncompliance with the dietary regimen was the major factor responsible for the secondary failure. Cholestyramine together with a low cholesterol diet can be an effective agent in familial type II hyperlipoproteinemia, given a comprehensive program of out-patient follow-up with continued emphasis on dietary principles and drug adherence.

Adult↗
PubMed1976

Serum chloride analysis, bromide detection, and the diagnosis of bromism.

Current methods for determining serum chloride concentration vary in specificity. Laboratory detection of bromide in serum is usually dependent on spuriously high chloride values. In the absence of historical information, the chemical identification of bromide in serum may be the only diagnostic sign of bromism. Bromide may be found in as many as 1% of sera obtained from inpatients of a general hospital. Ion-selective electrodes and some thiocyanate methods for chloride analysis can be highly sensitive to bromide (interference). Chloride electrodes are also sensitive to iodide.

Aged↗
PubMed1976

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Cardiology↗
PubMed1976

Lipid, glucose, and insulin interrelationships in normal, prediabetic, and chemical diabetic subjects.

Fasting levels of plasma cholersterol and triglyceride, lipoprotein patterns, and fasting and postintravenous glucose levels of blood glucose, serum insulin, serum growth hormone, and plasma free fatty acids in a genetic potential diabetic population were compared to those in a similar normal control population. THe potential diabetic population was further divided into groups of patients with a normal (prediabetic) or abnormal (chemical diabetic) glucose tolerance test. Although no clear-cut lipid differences were noted, certain trends appeared. More type IV hyperlipoproteinemia was seen in male prediabetic (21%) and male chemical diabetic patients (19%) than in normal male subjects (5%); in female subjects only a few type IV patterns were seen. Type II hyperlipoproteinemia was not seen in any normal subject, but was noted in nearly 9% of those with chemical diabetes. Fasting cholesterol levels correlated better with age than did fasting triglyceride levels in most of the patient groups. Fasting triglyceride levels showed a significant positive correlation with the serum insulin area of the oral glucose tolerance test in the normals wna prediabetic persons, and also showed a significant positive correlation with the blood glucose area of the prediabetic and chemical diabetic patients. It is suggested that a normal relationship between triglyceride concentration and insulin response to glucose is lost in chemical diabetes. Sex differences were also noted in the inslin response and the insulin-glucose relationships during the oral glucose tolerance test, with normal menstruation women showing a significantly lower insulin-glucose relationship than the age-related men.

Adolescent↗
PubMed1975

Homozygous familial hypercholesterolemia. A possible biochemical explanation of clinical heterogeneity.

Patients with homozygous familial hypercholesterolemia fall into two groups: one responds to diet and drug therapy; the other does not. Fibroblasts from patients in each group were compared for low-density lipoprotein suppression of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity and low-density lipoprotein binding. In fibroblasts from four therapy-responsive patients, low-density lipoprotein (100 mug per milliliter) suppressed 3-hydroxy-3-methylglutaryl coenzyme A reductase activity to 41 +/- 12 per cent of control (without low-density lipoprotein) whereas fibroblast enzyme activity from two therapy-unresponsive patients was not suppressed (P less than 0.001). Low-density lipoprotein binding to fibroblasts from both groups was defective as compared to normal controls. Fibroblasts from two therapy-responsive patients had specific binding of low-density lipoprotein of 27 +/- 4 per cent of normal -- greater than the 12 +/- 2 per cent (P less than 0.005) binding to fibroblasts from one therapy-unresponsive patient. These biochemical differences may help explain the variable response to therapy in homozygous familial hypercholesterolemia.

Adolescent↗
PubMed1975

Limitations of the electrocardiographic response to exercise in predicting coronary-artery disease.

The electrocardiographic response to exercise was compared with the results of coronary angiography in 89 patients with Type II hyperlipoproteinemia who had previous myocardial infarction or typical angina or both (43 patients)(Group A), "atypical angina" (16 patients)(Group B)or positive electrocardiographic response to exercise without other evidence of cardiac disease (30 patients)(Group C). Thirty-nine of 43 in Group A had greater than or equal to 50 per cent stenosis, and 26 (67%) of these 39 had negative exercise tests. In Group B, five of the 16 had greater than or equal to 50% stenosis, and three had positive exercise tests (one patient had a false-positive test). In Group C, eleven of 30(37%) had greater than or equal to 50% stenosis; however, nine (30%) had minor stenosis (less than or equal to 50%), and 10(33%) normal coronary arteries. The diagnostic usefulness of exercise electrocardiography is limited. False-negative responses are frequent in patients with clinically suspected coronary disease, and false-positive responses frequent in asymptomatic patients.

Adult↗
PubMed1975

Structural and compositional changes attending the ultracentrifugation of very low density lipoproteins.

The effects of repetitive ultracentrifugation on the physical and chemical properties of very low density lipoproteins (VLDL) were investigated. VLDL recentrifuged one to seven times were characterized by chemical analyses, analytical ultracentrifugation and electron microscopy. The VLDL content of triglyceride was increased and the proportion of phospholipid decreased by ultracentrifugation. Recentrifugation of VLDL decreased the number of Sf-o 20-100 particles and generated particles of Sf-o greater than 400. The bulk of the material removed from VLDL by ultracentrifugation was lipoprotein having pre-beta mobility on paper electrophoresis, flotation rates of Sf-o 10-100 and a particle size of 300-400 A-O. Two ultracentrifugations separated an average of 14% of the starting VLDL protein. Characterization of the apoproteins in this material by polyacrylamide gel electrophoresis, gel chromatography, immunoprecipitation and amino acid analysis demonstrated a relatively high proportion of beta-apoprotein and relatively little C-apoproteins.

Adult↗
PubMed1975

Effect of elevated triglycerides on the diffusing capacity of man.

In view of the decreased diffusing capacity recently reported in man during lipid infusion, studies have now been made on the effects of hyperlipidemia on the diffusing capacity for carbon monoxide (DLco). In normal volunteers and patients with hyperlipidemias, DLco and plasma triglyceride concentrations were determined during fat tolerance tests and while the patients were on diets that increased or decreased triglyceride concentrations. During the fat tolerance tests, the largest triglyceride and DLco changes were from 346 mg per 100 ml with a DLco of 18.8 ml per min per mm Hg to 1,545 mg per 100 ml with a DLco of 23.4 ml per min per mm Hg. While patients were on speical diets, the largest triglyceride and DLco changes were from 5,102 mg per 100 ml and 29.0 ml per min per mm Hg to 492 mg per 100 ml and 26.4 ml per min per mm Hg, respectively. Sta tistical tests showed no significant change of DLco with change in triglyceride concentration. The data suggest that there is normally no association between change in triglyceride concentration and change in DLco, and that triglycerides normally transported in plasma, even when present in extreme amounts as chylomicrons or very-low-density lipoprotein, do not affect the DLco.

Adult↗