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Biomedical subjects

R Brodersen

Publications and source records attributed to R Brodersen.

At least 73 records · Page 4Linked to original sources
PubMed1983

Effect of lactate, pyruvate, acetone, acetoacetate, and beta-hydroxybutyrate on albumin binding of bilirubin.

Lactate, pyruvate, acetone, acetoacetate, and beta-hydroxybutyrate were tested for their bilirubin-displacing effect on human serum albumin. Only lactate had a significant effect at levels found in asphyxiated infants (up to 20 mM). The reserve albumin equivalent for binding bilirubin was determined, using the deputy ligand monoacetyldiaminodiphenyl sulfone (MADDS), in adult human serum albumin solution, neonatal serum, and neonatal albumin solution. Twenty mM lactate caused a 23% decrease of reserve albumin when adult albumin was used, but did not cause any change of binding when neonatal serum or neonatal albumin solution was used. It is unlikely that endogenous substances, acting as competitive ligands, cause the low binding affinity of albumin for bilirubin in sick, premature infants.

3-Hydroxybutyric Acid↗
PubMed1983

Reserve albumin and bilirubin toxicity index in infant serum.

Reserve albumin concentration (the concentration of albumin available for binding of unconjugated bilirubin) was determined in 95 sera from 76 subjects by dialysis with 14C-monoacetyl diamino diphenyl sulfone (MADDS). An index, I of bilirubin toxicity in the plasma was calculated for each subject, based on the bilirubin and reserve albumin concentrations, the affinity of bilirubin for serum albumin, and the pH-dependent solubility of bilirubin in the plasma. The values of reserve albumin and of I varied significantly with gestational age, clinical condition (whether sick or well), and serum bilirubin level. The value of reserve albumin was decreased and I was increased in association with clinical factors (e.g., hyperbilirubinemia, hypoxia, acidosis, or sepsis) recognized as increasing the risk for bilirubin encephalopathy. The lowest values of reserve albumin and the highest values of I were found in the least mature and sickest infants.

Adult↗
PubMed1983

Drug-induced displacement of bilirubin from albumin in the newborn.

Kernicterus is probably caused by precipitation of insoluble bilirubin acid in brain cells. The pigment is transferred from blood plasma to cells. The tendency for precipitation depends upon the ratio of unconjugated plasma bilirubin concentration to the concentration of reserve albumin for binding of bilirubin and is increased when part of the albumin is occupied by competitive binding of a drug. Laboratory methods are available whereby it is possible, on certain well-defined presumptions, to measure this drug effect in quantitative terms. Measurements can be made in systems with pure albumin as well as in plasma samples from treated patients. It would thus appear feasible at the present stage to establish a basis for official testing of the bilirubin-displacing effects of drugs.

Bilirubin↗
PubMed1983

Bilirubin-displacing effect of furosemide and sulfisoxazole. An in vitro and in vivo study in neonatal serum.

Sulfisoxazole and furosemide, 0.1-1.0 mM, both decreased reserve albumin concentration for bilirubin binding in pooled cord serum as estimated by rate of dialysis of 14C-monoacetyl-diamino-diphenylsulfone (MADDS) in undiluted serum at 37 degrees C. Peroxidase oxidation at a bilirubin:albumin ratio of 0.5 also showed that both drugs were capable of displacing bilirubin in vitro when added in molar excess of the albumin present. However, when aliquots of the same treated sera which had been used undiluted in the MADDS assay were diluted 40-fold and titrated with bilirubin and peroxidase, no drug-related increase in free bilirubin or decrease in reserve albumin could be shown. In vivo administration of 1 mg/kg furosemide showed no change in total bilirubin or reserve albumin by the MADDS technique in 8 infants. Estimation of the peak plasma level theoretically achievable with 1 mg/kg of furosemide suggests that peak plasma levels achieved with that dose are probably not high enough to produce significant reduction of reserve albumin, in agreement with the in vivo findings. In testing neonatal serum for bilirubin displacement by drugs, the choice of method, drug concentration, and dilution of the sample may influence the interpretation of results.

Bilirubin↗
PubMed1983

Interaction of indomethacin with adult human albumin and neonatal serum.

The binding of indomethacin to albumin was investigated at 37 degrees C, pH 7.4. The first stoichiometric binding constant is 2.5 X 10(5) M-1. Indomethacin utilizes both the bilirubin and diazepam binding functions equally. The effect on bilirubin binding to albumin is negligible at therapeutic indomethacin blood levels. Oleic acid does not affect indomethacin binding until the oleate/albumin molar ratio exceeds 2. A method for measuring the reserve albumin equivalent for binding indomethacin is described. Measurement of this reserve binding equivalent in 33 neonatal serum samples shows no significant correlation of the reserve binding to the albumin level. This methodology may be useful in studying the variable response of infants with patent ductus arteriosus to indomethacin.

Bilirubin↗
PubMed1982

Risk of bilirubin acid precipitation in preterm infants with respiratory distress syndrome: considerations of blood/brain bilirubin transfer equilibrium.

Twenty-six preterm infants with respiratory distress syndrome (RDS), were examined daily during the first 6 days of life. Twenty-six equally preterm but clinically well infants served as controls. In the RDS infants, plasma albumin concentration was low, hyperbilirubinemia was prolonged, plasma pH was decreased during the first two days, and the concentration of reserve albumin for binding of monoacetyldiaminodiphenylsulfone (MADDS), a deputy ligand for bilirubin, was decreased on the second throughout the sixth day, when compared with the controls. These factors concur in increasing the likelihood of bilirubin acid precipitation in RDS above the increased risk present in preterm infants. The plasma of the preterm controls was supersaturated with respect to crystalline bilirubin acid by an average factor 5 (index of plasma bilirubin toxicity = 0.7) on the first day of life, peaking at a factor 10 (index 1.0) on the third and fourth days while these factors were 10 and 20 (index 1.0 and 1.3), respectively, in the RDS infants. Two of the latter surpassed a level of 60 times supersaturation (index 1.8) where acute precipitation of amorphous bilirubin acid becomes possible.

Bilirubin↗
PubMed1982

Comparison between two preparations of human serum albumin in treatment of neonatal hyperbilirubinaemia.

Thirty-six newborn infants with normal birth weights and with uncomplicated hyperbilirubinaemia, treated with light, were studied. At onset of phototherapy the infants received intravenously 1 g human serum albumin (HSA) per kg body weight as a 9% solution. Two different preparations of HAS were used and compared. One of these, HSAI, contained sodium caprylate and N-acetyltryptophan, 5 mmol/l of each, as stabilizers. HSAII contained only caprylate, 5 mmol/l. Nineteen infants received HSAI and seventeen infants HSAII. The reserve albumin for binding of bilirubin, measured by the [14C] MADDS method, was low in both preparations in vitro. During the infusion, the serum concentrations of albumin and reserve albumin increased and the serum unconjugated bilirubin concentration decreased, resulting in a fall in the index of plasma bilirubin toxicity in all infants. After completion of the infusion, the serum concentrations of albumin and reserve albumin declined, and a slight rise in index occurred. The increase in the serum reserve albumin concentration was markedly higher during infusion of HSAII than of HSAI. It is concluded that infusion of both HSA preparations during phototherapy provides an immediate protection against bilirubin encephalopathy. HSAI is inferior to HSAII, probably due to its content of N-acetyltryptophan.

Bilirubin↗
PubMed1981

Bilirubin-liposome interaction. Binding of bilirubin dianion, protonization, and aggregation of bilirubin acid.

Interaction of bilirubin with phospholipid liposomes was studied at varying pH. Liposomes were prepared from egg-phosphatidylcholine, dipalmitoyl-phosphatidylcholine, phosphatidylethanolamine, egg-phosphatidylcholine, and phosphatidylethanolamine with 5% (w/w) cholesterol, phosphatidylserine, sphingomyelin, and a lipid preparation from cat brain. Experiments were also conducted with erythrocyte ghosts. Interaction with bilirubin was studied by observing quenching of fluorescence from 1,6-diphenyl-1,3,5-hexatriene, incorporated in the lipid bilayers, by gradient centrifugation of the product, by measuring light scattering during the process, and by studying the solubility and infrared spectra of the final aggregates. At pH values above 8.2, the findings are consistent with formation of a bilirubin dianion-phospholipid complex. At pH 6-8, protonization of bilirubin in the complex is indicated and is followed by self-aggregation of bilirubin acid with formation of large bilirubin particles containing a small amount of phospholipid. Results were qualitatively similar with all lipids studied; marked quantitative differences in degree of fluorescence quenching and aggregation rates were observed with liposomes from different phospholipids. Reflections on affinities and available concentrations indicate that this train of processes may be part of the toxic mechanism of bilirubin.

Animals↗
PubMed1981

Albumin administration combined with phototherapy in treatment of hyperbilirubinaemia in low-birth-weight infants.

Fifty-nine jaundiced light treated newborn infants with low birth weight were studied. At onset of phototherapy 30 infants received 1 g human serum albumin per kg body weight as a 9% solution containing sodium caprylate and N-acetyltryptophan as stabilizers. 29 infants did not receive human serum albumin and served as controls. Blood samples were taken before initiation of the therapy and again 24 and 48 h thereafter, and the following determinations were made: Serum concentrations of unconjugated bilirubin, albumin, reserve albumin for binding of bilirubin by the [14C]-MADDS method, packed cell volume and pH. Before infusion of albumin it was found that the binding fraction of serum albumin, i.e. the sum of the serum concentrations of bilirubin-albumin and reserve albumin, constituted about half of the total serum albumin concentration. The other half was non-binding, in agreement with previous findings in neonates. The effect of albumin therapy was mainly an unexpected increase of the non-binding fraction of serum albumin, while the increase of the serum reserve albumin concentration was small and the concentration of bilirubin-albumin was not changed.

Bilirubin↗
PubMed1981

Albumin reserve for binding of bilirubin in maternal and cord serum under treatment with sulphasalazine.

Twelve pregnant patients with ulcerative colitis or Crohn's disease who were being treated with sulphasalazine (SASP) were studied together with their newborn, full-term babies. An earlier study had shown almost identical concentrations of SASP and its metabolic sulphapyridine (SP) in maternal and cord serum. As controls, blood samples were collected from 25 healthy women and their newborn infants. Sera from mothers and infants were analysed for the vacant amount of high-affinity bilirubin binding site on albumin (reserve albumin) by the MADDS method. The mean reserve albumin concentration of the SASP-treated mothers was 9% lower than that of the controls, which is probably insignificant. No difference was observed in the corresponding two groups of infants. In vitro studies showed that neither SASP nor SP in therapeutic plasma concentrations had a significant bilirubin-displacing capacity. It seems that SASP preferentially is bound to other sites on albumin than to the high-affinity binding site for bilirubin. The risk of kernicterus in the full-term newborn does not seem to be increased by treatment of the mother with sulphasalazine.

Adult↗
PubMed1980

D-penicillamine, a non-bilirubin-displacing drug in neonatal jaundice.

D-penicillamine, a drug used clinically for the treatment of neonatal hyperbilirubinaemia, was tested for interference with the binding of bilirubin to human serum albumin by three methods: 1) The peroxidase technique, investigating the effect of D-penicillamine on the equilibrium concentration of unbound bilirubin in a solution containing a molar excess of albumin; 2) the MADDS method, measuring the concentration of vacant bilirubin binding site on albumin in a solution of pure albumin, or infant blood serum, with added D-penicillamine; and 3) injection of D-penicillamine into Gunn rats and determination of any decrease of plasma bilirubin which would be caused by displacement of the pigment. Results were negative in all cases. Quantitatively, the doses of D-penicillamine used clinically cannot displace bilirubin from its binding to albumin. The ameliorating effect on hyperbilirubinaemia in the newborn must be due to some other mechanism.

Animals↗
PubMed1979

Bilirubin. Solubility and interaction with albumin and phospholipid.

Bilirubin is generally considered a lipophilic substance, and its neurotoxicity is ascribed to an affinity for lipids in the central nervous system. In the present paper, it is shown that the solubility of bilirubin in apolar solvents and in triglycerides is low and increases with solvent polarity. Consequently, bilirubin should not be characterized as lipophilic. The solubility in aqueous buffers was studied under exclusion of light and was found lower than previously reported, about 7 nM at pH 7.4, temperature 37 degrees C, increasing with higher pH, approximately in inverse proportion with the squared hydrogen ion concentration. Binding of bilirubin to human serum albumin was studied by the rate of oxidation with peroxidase of the free ligand at equilibrium. The stoichiometry of proton involvement in the binding process was investigated by acidimetric titration. It is concluded that precipitation of bilirubin in vivo is thermodynamically possible. It was further demonstrated by light absorption spectroscopy that bilirubin forms a complex with phosphatidylcholine in diethyl ether and that an aqueous suspension of phosphatidylcholine enhanced aggregation of bilirubin. Transfer of bilirubin dianion from its complex with plasma albumin and precipitation of bilirubin acid with phosphatidylcholine in membranes of nerve cells is therefore possible and may account for the neurotoxicity.

Bilirubin↗
PubMed1979

Kinetics of bilirubin oxidation with peroxidase, as applied to studies of bilirubin-albumin binding.

In the determination of unbound bilirubin by rate of oxidation with peroxidase, errors may be caused by (1) phenol, propylparaben, and phenothiazines (free radical acceleration), (2) haemoglobin (peroxidase effect), and (3) ascorbate (inhibition). Such errors may be diminished by dilution 1:40, or with an anti-oxidant, tert-butyl-p-hydroxyanisole, and ascorbate oxidase.

Ascorbate Oxidase↗
PubMed1979

Bilirubin acidity. Titrimetric and 13C NMR studies.

Acidimetric titration of bilirubin IX-alpha, dissolved in excess aqueous sodium hydroxide, showed that two protons are dissociated with pK values well below 7 and that one or several additional acidic groups titrate with pK around 12.9. Precipitation of the nearly insoluble acid precluded determination of the two lower pK values by titration in aqueous solution. In dimethyl sulfoxide solution, four acidic protons were demonstrated, titrating two by two without precipitation. 13C NMR spectra of bilirubin IX-alpha were recorded and complete assignments were made by comparison with the spectra of bilirubin XIII-alpha and mesobilirubin etc. Such spectra, recorded after addition of 2 and 4 mol of base per mol of bilirubin IX-alpha, showed that both carboxyl groups are titrated by the first 2 mol of base, and both lactams by the following 2 mol of base. Cotitrations of bilirubin IX-alpha with other acids, o- and m-hydroxybenzoic acid and 2-pyridone, were used to determine relative pK values in dimethyl sulfoxide solution, and pK values for the four acidic protons of bilirubin IX-alpha in aqueous solution were calculated from the Born equation. Both carboxyl groups exhibited pK = 4.4, and both lactams pK = 13.0, in good agreement with values expected from the chemical structure of the bilirubin molecule. The implications of these findings for understanding the mechanism of bilirubin neurotoxicity are discussed.

Bilirubin↗
PubMed1978

Determination of the vacant amount of high-affinity bilirubin binding site on serum albumin.

A principle for determination of the vacant amount of the high-affinity bilirubin binding site on serum albumin in the newborn is proposed: A small amount of monoacetyl-4,4'-diaminodiphenylsulphone (MADDS) is added to the serum sample and the equilibrium of binding of this substance is assessed by measuring the rate of dialysis into another volume of the same serum. It is shown that MADDS is bound selectively to the specific bilirubin site. Results obtained after addition of varying amounts of five drugs and of oleate are compared with those found by the peroxidase method. Good agreement is found although certain deviations are encountered, as expected in the case of allosteric affects. Free bilirubin concentrations can be calculated from the results.

Bilirubin↗