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Biomedical subjects

B J Burri

Publications and source records attributed to B J Burri.

34 records · Page 2Linked to original sources
PubMed1993

Comparison of the properties and concentrations of the isoforms of retinol-binding protein in animals and human beings.

We used size-exclusion high-performance liquid chromatography (HPLC) to investigate the properties of the 2 isoforms of Vitamin A-containing (holo) retinol-binding protein (RBP) in animals: the form that is bound to transthyretin (holo-TTR-RBP), and the form that does not bind to TTR (holo-free RBP). We also used radial immunodiffusion to measure immunologically active RBP (apo + holo RBP). We compared the isoforms of RBP in animals with those of human beings to determine which animal is the best model of human RBP. Size-exclusion HPLC detected holo-free and holo-TTR-RBP in every animal species studied. Apparent concentration of holo-TTR-RBP varied among species: that of rabbits and dogs >> that of apes, sheep, goats, monkeys, rhinoceroses, felids, rats, human beings, and deer > that of pigs, zebra, and bison > that of penguins. Dogs have unusual RBP chromatograms; they have high concentration of RBP, but also appear to transport much of their vitamin A on protein other than RBP. Human RBP antibody preparations could detect apo + holo RBP immunologic activity only in apes, monkeys, and felids. Apes and monkeys appeared to have complete cross-reactivity to human RBP antibodies. Felids may have substantial, but partial, cross-reactivity. Apes and monkeys appear to be the most relevant animal models for study of human RBP transport. However, there is a need for less-expensive models. Further research is needed, but in the interim, rats or sheep may be satisfactory for some purposes.

Animals↗
PubMed1991

Assay of human transthyretin-bound holo-retinol-binding protein with reversed-phase high-performance liquid chromatography.

We describe a reversed-phase high-performance liquid chromatographic method for the determination of vitamin A-transporting (holo) transthyretin-bound (TTR) retinol-binding protein (RBP) concentrations in serum or plasma. Holo-TTR-RBP and free retinol derived primarily from free RBP are consistently observed with this chromatographic method. Holo-TTR-RBP concentrations determined by this method are highly correlated to holo-TTR-RBP concentrations measured by chromatography. This method has the advantage of using less expensive columns and having peak areas which are more proportional to their true concentrations in plasma, as determined by comparison to purified protein spectrophotometry and radial immunodiffusion. The percentage of RBP circulating as holo-TTR-RBP decreased significantly as the total concentration of RBP or retinol increased. Because purified holo-TTR-RBP did not dissociate under these chromatographic conditions, this suggests that more vitamin A circulates as holo-free RBP or free retinol in the blood of people with high serum RBP.

Adult↗
PubMed1991

Platelet aggregation in humans is affected by replacement of dietary linoleic acid with oleic acid.

The effect of concentrations of linoleic acid (LA) on platelet aggregation was measured in seven healthy adult males. Subjects were randomly divided into two groups; these groups were fed natural food diets of identical composition except that one was high in LA (11.5% of energy) and low in oleic acid (OA) (7.4% of energy), the other was low in LA (4.5% of energy) and high in OA (15.7% of energy). The thresholds of ADP- and collagen-induced platelet aggregation were increased significantly by the high LA diet even though the intake of total fat and saturated fatty acids did not differ in these diets.

Adenosine Diphosphate↗
PubMed1990

Effect of low-calorie diets on plasma retinol-binding protein concentrations in overweight women.

The concentrations of total protein, albumin and retinol-binding protein, a major transport protein for vitamin A, are significantly decreased by protein-calorie malnutrition. Weight-loss diets, sometimes involving severe energy deficits over prolonged periods of time, are common in the United States. The effect, if any, of prolonged low calorie weight-loss diets with normal intakes of protein on albumin, total protein and retinol-binding protein concentrations (and potentially on vitamin A metabolism) had not been extensively studied. We measured total protein, albumin, apo + holo retinol-binding protein and holo-free- and holo-transthyretin-bound retinol-binding protein concentrations during the course of a nutritionally adequate weight-loss diet (50% calorie restriction). We found that this type of dieting did not affect total protein, albumin or apo + holo, holo-free or holo-transthretin-bound retinol-binding protein concentrations significantly. This suggests that protein intake is more critical than caloric intake for retinol-binding protein status.

Journal Article↗
PubMed1990

Use of free and transthyretin-bound retinol-binding protein in serum as tests of vitamin A status in humans: effect of high creatinine concentrations in serum.

We measured immunologically active (apo + holo) retinol-binding protein (RBP), vitamin A-carrying (holo) free RBP, and transthyretin-bound (TTR) holo-RBP in serum from 34 retrospective cases of fluctuating acute renal failure. All subjects had high serum creatinine concentrations caused by renal failure. Apo + holo, holo-TTR-RBP, and (especially) holo-free RBP all correlated poorly but significantly with serum creatinine concentration. Therefore, the use of any form of RBP to measure vitamin A status may be of limited value in subjects with high creatinine concentrations in serum. However, molecular-exclusion HPLC may be able to distinguish increases in RBP concentration associated with renal failure from those caused by altered vitamin A status, because renal failure causes abnormalities in the number and retention times of chromatographic peaks as well as their areas.

Acute Kidney Injury↗
PubMed1989

Liquid-chromatographic assay for free and transthyretin-bound retinol-binding protein in serum from normal humans.

We quantified vitamin A-transporting retinol-binding protein (RBP) in serum or plasma by size-exclusion "high-performance" liquid chromatography, using a TSK 2000 column and fluorescent detection of the bound retinol. Serum or plasma samples filtered through a 0.20-microns (pore size) Millex filter were applied directly to the column. The pH 7.0 mobile phase contained sodium phosphate, disodium EDTA, and mercaptoethanol. Two peaks with RBP immunological activity were eluted: the smaller peak containing at least 86% of the vitamin A, which was identified as transthyretin-bound RBP; the larger peak containing a small amount (less than 14%) of a highly fluorescent vitamin A-containing protein, identified as free RBP. Both free and transthyretin-bound RBP can be quantified by this method.

Adult↗
PubMed1988

Vitamin A analogs as tests for liver vitamin A status in the rat.

Two chlorinated retinol analogs (Ro 11-0503 and Ro 11-8284) were assayed in rat serum and correlated to retinol in liver. Rats were fed a retinol-free diet to deplete their liver stores, then repleted with 0.5, 1.0, 3.0, and 10.0 mg retinyl palmitate/kg diet. Rats were given intraperitoneal injections of the analog then killed after an additional week on the diets. Analogs were measured by HPLC. The relative abundance of both analogs in serum was inversely correlated with the amount of retinyl palmitate in the liver. Serum analog concentrations may be useful as indications of liver retinol stores.

Animals↗
PubMed1987

Molecular interactions of the intrinsic activation complex of coagulation: binding of native and activated human factors IX and X to defined phospholipid vesicles.

The assembly of proteins of the intrinsic activation complex has been partially elucidated. In the present study we examine the association of gamma-carboxylated serine proteinase zymogens factors IX and X, and their proteolytically activated counterparts factors IXa and Xa to unilamellar lipid vesicles of defined composition using three types of physical measurement. Utilizing relative light scatter to estimate the dissociation constants for binding in the presence of calcium ions, it appears that factor IXa (0.93 +/- 0.37 microM) may preferentially associate with phospholipids relative to factor IX (0.35 +/- 0.08 microM). In contrast, factor X (0.34 +/- 0.14 microM), the substrate for factor IXa, appears to bind to phospholipid with a higher affinity than factor Xa (0.58 +/- 0.13 microM). These observations are compatible with the hypothesized dynamics where the forward 'traffic' is facilitated by favoring the association of factor IXa with factor X. The dissociation constants were estimated by molecular exclusion chromatography (1.1 - 2.5 microM) and do not reflect these relative and ordered differences in association with lipid vesicles. Quasi-elastic light scatter analyses indicate that each protein appears to saturate the same vesicle surface, consistent with competition for similar surface lipids, although the molecular shell formed by factor Xa (36 A) is smaller, suggesting that it has a different packing on the phospholipid surface than the other proteins (64-79 A). The pattern of preferential affinities for phospholipid is consistent with a kinetically functional forward traffic through the reaction precursors to products, and suggests that these preferential affinities may assist in the ordering of the four proteins in the intrinsic activation complex.

Calcium↗
PubMed1986

Rett syndrome revisited: a patient with biotin dependency.

A patient with Rett syndrome (cerebral atrophy associated with hyperammonemia) was studied. Primary defects of urea cycle enzymes were excluded as causes of the disorder. The analysis of urinary organic acids showed a moderate increase of lactate, methylcitrate, tiglyglycine and 3-hydroxisovalerate, indicating an abnormality of multiple carboxylases. Biotin supplementation reversed the urinary abnormalities. In fibroblasts grown with a low biotin medium propionylCoA and 3-methylcrotonylCoA carboxylase activities were reduced. Holocarboxylase synthetase activity was normal (Vmax and Km). Surprisingly the biotinidase in fibroblasts was not decreased. The data indicate that some patients with Rett syndrome might suffer from a biotin-dependent defect of unknown nature.

Amino Acids↗
PubMed1985

Heterogeneity of holocarboxylase synthetase in patients with biotin-responsive multiple carboxylase deficiency.

Holocarboxylase synthetase activity has been determined in fibroblasts of seven patients with the neonatal form of biotin-responsive multiple carboxylase deficiency. The normal Km for biotin was 15 +/- 3 nmol/l, while in the patients the values ranged from 48 to 1,062 nmol/l. The mean maximum velocity was 27% of normal. Differences among the values obtained for the Km for biotin and the heat stability of holocarboxylase synthetase suggested that the patients studied represented at least four distinct variants at the holocarboxylase synthetase locus.

Biotin↗
PubMed1981

Mutant holocarboxylase synthetase: evidence for the enzyme defect in early infantile biotin-responsive multiple carboxylase deficiency.

Biotin-responsive multiple carboxylase deficiency is an inherited disorder of organic acid metabolism in man in which there are deficiencies of propionyl-coenzyme A (CoA), 3-methylcrotonyl-CoA, and pyruvate carboxylases that can be corrected with large doses of biotin. It has been proposed that the basic defect in patients with the early infantile form of the disease is in holocarboxylase synthetase, the enzyme that covalently attaches biotin to the inactive apocarboxylases to form active holocarboxylases. We have developed an assay for holocarboxylase synthetase in extracts of human fibroblasts using as substrate apopropionyl-CoA carboxylase partially purified from livers of biotin-deficient rats. Fibroblasts from the initial patient with the infantile form of biotin-responsive multiple carboxylase deficiency were shown to have abnormal holocarboxylase synthetase activity with a maximum velocity about 30-40% of normal, a Km for ATP of 0.3 mM similar to the normal Km of 0.2 mM, and a highly elevated Km for biotin of 126 ng/ml, about 60 times the normal Km of 2 ng/ml. These results show that the primary defect in this patient is a mutation affecting holocarboxylase synthetase activity, and thus a genetic defect of the metabolism of biotin.

Amino Acid Metabolism, Inborn Errors↗
PubMed1980

Blood levels of superoxide dismutase and glutathione peroxidase in Duchenne muscular dystrophy.

Erythrocyte superoxide dismutase activities and erythrocyte and plasma glutathione peroxidase activities have been determined in Duchenne muscular dystrophy patients, genetic carriers, and normal controls. A 19% decrease in red cell superoxide dismutase activity was observed in patients with Duchenne muscular dystrophy. Genetic carriers showed a level between that of the dystrophy patients and the normal controls. No abnormality was seen in the red cell or plasma activities of glutathione peroxidase.

Adolescent↗