Search PubMed⌕ Search

Biomedical subjects

R J Deckelbaum

Publications and source records attributed to R J Deckelbaum.

At least 163 records · Page 9Linked to original sources
PubMed1980

The role of different albumin preparations on production of human plasma lipoprotein-like particles in vitro.

Because we found apoprotein contamination of some high-grade commercial albumins, we studied this effect on formation of lipoprotein-like particles during lipolysis of human very low density lipoprotein (VLDL) in vitro. After a 1-hr incubation with purified bovine milk lipoprotein lipase, over 98% VLDL triglyceride was hydrolyzed in the presence of either albumin B (apoprotein-rich) or albumin C (apoprotein-poor), with a weight ratio of albumin to triglyceride of 60 to 1. Lipoproteins of density < 1.019 g/ml ("IDL"), 1.019 to 1.063 g/ml ("LDL"), and 1.063 to 1.21 g/ml ("HDL") were then isolated by ultracentrifugation. Recovery of non-triglyceride VLDL constituents in "IDL" and "LDL" was similar for albumin B or albumin C. "LDL" was the major catabolic product of in vitro VLDL lipolysis independent of the albumin used. The yield of "HDL," however, was 5- to 6-fold greater with albumin B. All lipoproteins produced with albumin B were richer in phospholipid, apoproteins C and A-I, relative to lipoproteins produced in the presence of albumin C. With albumin B, cholesterol/phospholipid molar ratios were <1 in all in vitro produced lipoproteins, but were >1 with albumin C. All these differences can be ascribed to the presence in albumin B of 0.2 mg apoprotein A-I/g albumin and 1.8 mg phospholipid/g albumin; these components were not detected in albumin C. Thus, two thirds of "HDL" recovered with VLDL lipolysis in the presence of albumin B can be accounted for by albumin itself and only one third from constituents of VLDL. Adding equivalent amounts of both apoproteins removed from albumin B and phospholipid to albumin C markedly decreased the disparities in results but addition of each alone did not. These results prove "inert" albumins serve other than as fatty acid and lysolecithin acceptors in in vitro model systems, and do influence formation of lipoproteins during in vitro VLDL catabolism.-Deckelbaum, R. J., T. Olivecrona, and M. Fainaru. The role of different albumin preparations on production of human plasma lipoprotein-like particles in vitro.

Albumins↗
PubMed1977

Thermal behavior of human plasma high density lipoprotein.

Human plasma low density lipoprotein displays a reversible thermal transition between 20 and 40 degrees C, due to a phase transition of its core cholesterol ester from a smectic to a more liquid-like state. To determine if the cholesterol of high density lipoprotein (HDL) displays similar thermal behavior, the human lipoprotein and its extracted lipid have been examined by differential scanning calorimetry, low angle X-ray scattering and polarizing microscopy. Neither HDL2**(d 1.063--1.125--1.21 g/ml) nor HDL3(d1.125--1.21g/ml) show thermal transitions between O and 60 degrees C. By contrast cholesterol ester isolated from HDL and mixtures of cholesterol oleate and linoleate show reversible liquid crystalline transitions between 20 and 40 degreesC. X-ray scattering studies of HDL2 and HDL3 performed at 10 degreesC show no scattering fringes attributable to a smectic phase of cholesterol ester. When HDL is heated to temperatures above 60 degreesC a broad, double-peaked endotherm is observed. The first component (peak temperature=71 degreesC) corresponds to a selective release of apoprotein A-1 from the lipoprotein, and the second component (peak temperature=90 degreesC) to a more generalized disruption of lipoprotein structure with release of cholesterol ester and apoprotein A-2. Following the thermal disruption of HDL, reversible liquid crystalline transitions of cholesterol ester can be seen by differential scanning calorimetry and polarizing microscopy, showing the presence of large domains of cholesterol ester. The absence of cholesterol ester transitions in intact HDL may indicate an interaction of cholesterol ester molecules with the protein-phospholipid surface of HDL that prevents the formation of an organized lipid phase. The high temperature behavior of HDL indicates that apoprotein A-1 is less important than apoprotein A-2 in maintaining the HDL apolar lipids in the form of a stable miroemulsion.

Calorimetry↗
PubMed1977

Failure of complete bile diversion and oral bile acid therapy in the treatment of homozygous familial hypercholesterolemia.

Two patients with nomozygous familial hypercholesterolemia, refractory to medical therapy, underwent complete bile diversion by common-duct ligation and cholecystostomy, in an attempt to arrest the progression of their xanthomatosis and atherosclerosis by depletion of body cholesterol. Clofibrate was given after operation to one patient, and cholic acid to both, in an effort to enhance further the negative sterol balance. Bile diversion produced an increase of six to eight times in gastrointestinal sterol output, which was not increased further by either clofibrate or cholic acid therapy. Despite a calculated sterol loss of 560 g over 14 months in one patient and 400 g over 10 months in the other, neither plasma cholesterol nor xanthoma size decreased. Continuity of the biliary tree was therefore restored. The data suggest that patients with homozygous familial hypercholesterolemia respond to even massive gastrointestinal sterol depletion with equal increases in sterol synthesis.

Administration, Oral↗
PubMed1977

Structure and interactions of lipids in human plasma low density lipoproteins.

Temperature-dependent techniques (differential scanning calorimetry, polarizing microscopy, and x-ray scattering and diffraction techniques) were used to compare the properties of human plasma low density lipoproteins (LDL) with its extracted lipid classes. Three types of thermal transitions were characterized: (a) a reversible transition in intact LDL near body temperature associated with a liquid crystalline order-disorder phase change of cholesterol esters within the particles; (b) an irreversible high temperature transition (approximately 70-90 degrees) associated with LDL denaturation and release of cholesterol esters from the disrupted particles; and (c) low temperature transitions related to liquid crystalline and crystalline phase changes in these released esters. The temperature of the reversible transition in intact LDL varies among individual donors. Correlation analysis shows that the temperature of this transition negatively correlates with the amount of triglyceride relative to cholesterol ester in LDL. Studies on mixtures of cholesterol esters and triglycerides isolated from LDL show a similar effect, increasing amounts of triglycerides decreasing the temperature of the liquid leads to smectic liquid crystalline transition of the isolated esters. Thus, the amount of triglyceride in LDL influences the fluidity of the cholesterol esters in LDL. The enthalpy of the reversible transition in intact LDL is 0.69 cal/g of LDL cholesterol ester. This compares with 0.89 cal/g for the liquid leads to liquid crystalline transition of the cholesterol esters released from denatured LDL and 1.01 cal/g for the same transition in the extracted esters. Unlike the cholesterol esters released from denatured LDL, or isolated LDL esters, cholesterol ester in the intact LDL particle does not crystallize. These findings suggest that the behavior of cholesterol esters in intact LDL is constrained relative to their behavior when freed from the restrictions of the particle. These results together with experiments on partitioning of the individual lipid classes of LDL allow us to define the distribution and interaction of lipids in the intact LDL particle.

Calorimetry↗
PubMed1977

Structure of human plasma low-density lipoproteins: molecular organization of the central core.

Human plasma low density lipoprotein (LDL) exhibits a thermal transition over the temperature range 20-40 degrees. This transition is associated with a structural change within the lipoprotein particle and is reflected in the small-angle x-ray scattering profiles from LDL. The scattering profile of the quasispherical LDL particle at 10 degrees shows a relatively intense maximum at 1/36 A-1 which is absent from the scattering of LDL at 45 degrees. Theoretical calculations, using model electron density distributions, have been carried out to describe the packing of arrangement of the cholesterol esters, based on perturbations of the molecular packing of crystalline cholesteryl myristate, adequately reproduces the high relative intensity of the x-ray scattering maximum at 1/36 A-1. The perturbations of the packing in the crystal structure of cholesteryl myristate involve "melting" of the hydrocarbon chains of the esters together with translations of pairs of molecules parallel to the molecular long axis. The interaction of opposing steroid moieties, with C18 and C19 angular methyl groups interlocked, exhibited in the crystal structure is retained in the perturbed arrangement. At 45 degrees, thermally induced disorder of this arrangement averages the electron density of the central core. The x-ray scattering profiles of particles with a homogeneous electron density in the core region do not show a high relative intensity of the subsidiary maxima in the 1/36 A-1 region, in agreement with experimental observation. The results of these calculations support the concept that the thermal transition observed for LDL is due to a smectic leads to disordered transition of the cholesterol esters in the core of the LDL particle.

Cholesterol↗
PubMed1977

Interaction of cholesterol ester and triglyceride in human plasma very low density lipoprotein.

The properties of human plasma very low density lipoproteins (VLDL), low density lipoproteins (LDL), and their extracted lipids were compared using calorimetric, X-ray scattering, and polarizing microscopy techniques. Intact LDL, and cholesterol esters isolated from LDL and VLDL each undergo reversible changes in their physical state around body temperature. These transitions are associated with ordered liquid crystalline to liquid phase changes of the cholesterol esters. In contrast to LDL, VLDL has no reversible transitions and shows no evidence of ordered liquid crystalline structures between 10 and 45 degrees C. Therefore, unlike LDL, VLDL does not contain a separate cholesterol ester region capable of undergoing cooperative melting. Solubility studies at 37 degrees C of cholesterol esters and triglyceride isolated from VLDL show that even at a weight ratio of 1:1, which greatly exceeds the relative amount of cholesterol esters in VLDL, cholesterol ester is completely soluble in triglyceride. Thus, the cholesterol ester in VLDL is not sequestered in a separate domain within VLDL, but is dissolved in the liquid core of the particle.

Binding Sites↗
PubMed1976

Temperature-dependent 13C nuclear magnetic resonance studies of human serum low density lipoproteins.

The natural abundance 13C nuclear magnetic resonance (NMR) spectrum of human serum low density lipoproteins (LDL) shows significant temperature-dependent changes. These temperature-dependent spectra have been used to monitor changes in the organization of cholesterol esters within the LDL particle. Comparison with 13C NMR spectra of both cholesterol linoleate and an aqueous codispersion of cholesterol linoleate and egg phosphatidylcholine suggests that at low temperatures (10 degrees C), the cholesterol esters in LDL are organized in a smectic-like, liquid-crystalline arrangement. At temperatures above the order-disorder transition exhibited by the cholesterol esters of LDL, the cholesterol esters appear to be partially melted but still are motionally restricted compared with liquid cholesterol esters.

Carbon Isotopes↗
PubMed1975

Thermal transitions in human plasma low density lipoproteins.

Thermal analysis of human plasma low density lipoproteins reveals a broad reversible transition encompassing body temperature. The calorimetric and x-ray scattering data identify this transition as a cooperation, liquid-crystalline to liquid phase change involving the cholesterol esters in the lipoprotein. This behavior requires the presence of a region rich in cholesterol ester within the lipoprotein.

Chemical Phenomena↗
PubMed1974

Peptic ulcer disease: a clinical study in 73 children.

Seventy-three children with peptic ulcer have been admitted to The Montreal Children's Hospital and l'Hôpital Sainte-Justine over the past 11 years. The primary ulcer group comprised 39 duodenal and nine gastric ulcers; repeat contrast studies were necessary to demonstrate a crater in 25%. Vomiting was especially prominent in the younger patients (1 month to 6 years). Pain was present in the majority of older patients (6 to 18 years) but was considered "typical" in no more than one third. Bleeding occurred more commonly in the older children but five had occult bleeding only. There was a positive family history in 11 children with primary duodenal ulcers but in none of those with gastric ulcers. Follow-up in 34 cases with primary ulcers showed that close to two thirds of the older children have had recurrent problems. Bleeding and/or perforation was the most common mode of presentation in 25 cases of secondary ulcers. Corticosteroids and increased intracranial pressure were the most frequently associated factors, the younger age group being at greater risk.

Adolescent↗
PubMedDate not supplied

Normal growth in high-risk hyperlipidemic children and adolescents with dietary intervention.

OBJECTIVE: The aim of this study was to assess the safety and efficacy of lowering dietary intake of total fat, saturated fat, and cholesterol in growing children and adolescents with severe hyperlipidemia. STUDY DESIGN: This is a 3-year follow-up study conducted on a sample of convenience at three pediatric referral centers in New York City and its suburbs. Subjects were 138 children and adolescents 2 to 15 years of age (54% male), who had been referred with a diagnosis of hyperlipidemia. Those selected had total serum cholesterol values greater than the 95th percentile for age and had at least three visits over 3 years. They were placed on diets restricting total fat content to 30% of total calories and saturated fat to 10% of total calories (National Cholesterol Education Program Step I diet). Anthropometric measures, lipid profiles, and dietary assessment were obtained at each visit. Anthropometric data were analyzed by sex and age. Z scores for height and weight were calculated from NHANES II data and were compared by paired t tests (Hamill et al., 1979, Am J Clin Nutr 32:607-29). RESULTS: Total serum cholesterol dropped from 262 mg/dL at baseline to 249 mg/dL at 3-year follow-up (P = 0.003). There was no significant change in height or weight percentile, expressed as Z score, from baseline to 3-year follow up. CONCLUSIONS: In this population the supervised dietary interventions resulted in a sustained improvement of the lipid profile, with no demonstrable adverse effect on growth.

Adolescent↗
PubMedDate not supplied

Plasma triglyceride determines structure-composition in low and high density lipoproteins.

Because the association of hypertriglyceridemia and premature atherosclerosis is not due to the direct effects of the triglyceride molecule itself, we studied the effects of increased plasma triglyceride-rich lipoproteins on the composition and structure of low density lipoprotein (LDL) and high density lipoprotein (HDL). We found profound changes in the core and surface domains of both lipoproteins with increasing triglyceridemia. Core cholesterol esters were progressively depleted and replaced by triglyceride molecules. Highly significant negative correlations were found between cholesterol ester/protein ratios (r = -0.64 for LDL and -0.58 for HDL (p less than 0.001); positive correlations were found for triglyceride/protein ratios (r = 0.62 for LDL and 0.58 for HDL) and for triglyceride/cholesterol ester ratios (r = 0.70 for LDL and 0.83 for HDL) when these variables were assayed as a function of plasma triglyceride concentrations. With severe hypertriglyceridemia, triglyceride/cholesterol ester ratios of more than 1.0 were consistently observed (normal, less than 0.02). This leads to an underestimation of LDL and HDL levels when cholesterol alone is measured. At the surface, LDL and HDL were depleted of phospholipid and free cholesterol, with a relative enrichment of protein. These changes can be explained on the basis of high levels of plasma triglyceride-rich lipoproteins serving as acceptors for cholesterol esters and other constituents from LDL and HDL. Concomitantly, triglycerides are transferred to LDL and HDL. These transfer processes are likely to be mediated by the activity of lipid transfer proteins present in human plasma.

Blood Proteins↗