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Biomedical subjects

R Brodersen

Publications and source records attributed to R Brodersen.

At least 19 recordsLinked to original sources
PubMed1998

Analysis of the immunological cross reactivities of 213 well characterized monoclonal antibodies with specificities against various leucocyte surface antigens of human and 11 animal species.

213 Monoclonal antibodies (mAbs) raised against leucocyte surface antigens from human and 11 animal species were analyzed for reactivities against leucocytes from human and 15 different animal species. We found 77 mAbs (36%) to cross-react. Altogether, 217 cross reactions were registered out of 3195 possible combinations (7%). Most of the cross reacting mAbs had integrin or MHC class II specificities. This study defined cross reactions on the following markers: CD1a, 1c, 2, 4, 5, 8, 9, 11a, 11b, 14, 18, 20, 21, 23, 29, 31, 41, 43, 44, 45, 45R, 46, 49, 61, 62L, TCR gamma/delta, BCR, Thy-1, MHC class I and MHC class II, Swine-WC7 and Cattle-WC1. In order to characterize the molecular weight (MW) of the corresponding cross reacting antigens, selected mAbs were used to immunoprecipitate the antigens. The MW's of the analyzed precipitated antigens were in good agreement with the MWs of the homologous antigens. The followed strategy was found to be efficient and economical in defining new leucocyte antigen reactive mAbs.

Animals↗
PubMed1996

Does ibuprofen affect bilirubin-albumin binding in newborn infant serum?

Intravenous ibuprofen is being studied in sick, premature infants for the prevention of intraventricular haemorrhage and closure of the ductus arteriosus. We tested the effect of ibuprofen on bilirubin-albumin binding in adult and newborn infant serum by measuring the free ibuprofen concentration in the presence of bilirubin (reverse displacement method). At clinically appropriate ibuprofen concentrations the free fraction of bilirubin is increased by a factor of 4. Ibuprofen may increase the risk of bilirubin encephalopathy when used in sick, premature infants.

Adult↗
PubMed1995

Displacement of one ligand by another calculated from the reverse displacement of the second ligand by the first.

This paper relates a generally applicable method for calculating mean displacement of a ligand, B, by another ligand, D, when the reverse displacement of D by B is known. The method is applied to calculating displacement of bilirubin from binding to albumin by a drug, warfarin or ceftriaxone. A binding isotherm for the drug to albumin is drawn, as the logarithm of free drug vs total drug concentration. A second binding isotherm is drawn for the drug in the presence of a certain concentration of bilirubin. The area between the two curves, up to a given total drug concentration, is measured and is divided by the concentration of bilirubin. The antilogarithm of the ratio is equal to the geometric mean of the ratio of free concentrations of bilirubin in the presence and absence of the drug when the bilirubin concentration varies from zero to the given value. The calculations are verified by comparing the direct determinations of the bilirubin displacing effect of the drugs by peroxidase kinetics.

Albumins↗
PubMed1994

Measurement of palmitate availability in serum samples: method and utility.

Palmitic acid shows a very low and unknown solubility at neutral pH. Binding equilibria of palmitate to human serum albumin accordingly cannot be investigated by measuring free and bound ligand concentrations as in conventional binding studies. It is feasible, on the other hand, to describe the binding equilibria in relative terms, by measuring the concentration, p, of reserve albumin, previously defined as the concentration of a purified standard albumin preparation which in buffered solution binds a trace amount of palmitate as tight as it is bound in the sample. Palmitate availability is calculated as C/p, when C is the concentration of bound palmitate. The general binding equation is modified to contain the availability beside relative binding constants, Li = Ki/K1,St, where K1,St is the first stoichiometric binding constant for palmitate to the standard albumin preparation. Availabilities and relative binding constants can replace free concentrations and usual binding constants in considerations of biochemical transport and enzymatic mechanisms. A method is described for measuring the concentration of reserve albumin for binding of palmitate, based upon determination of dialytic exchange rates for palmitate among identical equilibrium samples. A technique for reproducibly adding radiolabelled palmitate to the samples is given.

Adult↗
PubMed1994

High-affinity binding of two molecules of warfarin and phenprocoumon to human serum albumin.

Binding equilibria of warfarin, 3-(alpha-acetonylbenzyl)-4-hydroxycoumarin, and phenprocoumon, 3-(alpha-ethylbenzyl)-4-hydroxycoumarin, to defatted human serum albumin (Kabi Vitrum) were studied by equilibrium dialysis in a 33 mM sodium phosphate buffer (pH 7.4) at 37 degrees C. The binding data were analysed in terms of several acceptable sets of binding constants using a computerized curve fitting procedure. The findings were consistent with binding of two warfarin or two phenprocoumon molecules with high affinity and additional molecules bound with lower affinity. The binding of warfarin or phenprocoumon was explained by a model with two independent and equal high-affinity binding sites besides several independent weak sites in the albumin molecule (p < 0.01, by F-test). The findings were not consistent with binding of warfarin or phenprocoumon to a single high-affinity site besides several weak sites. A model of sequential binding of several ligand molecules to one locus is proposed.

Binding Sites↗
PubMed1993

Variation in the binding affinity of warfarin and phenprocoumon to human serum albumin in relation to surgery.

The binding equilibria of warfarin and phenprocoumon with defatted human serum albumin were studied by equilibrium dialysis in 33 mM sodium phosphate buffer, pH 7.4, 37 degrees C. The binding isotherms for both ligands were consistent with binding to two similar and independent sites in the albumin molecule. The binding affinity of warfarin was markedly increased on adding palmitic acid up to palmitate 4 mol per mol albumin and then it decreased. The binding affinity of phenprocoumon varied similarly but to a lesser degree. Serum samples were obtained from 14 patients undergoing knee joint surgery, six consecutive samples from each patient. The binding affinity of warfarin and phenprocoumon added in low concentrations to the serum samples was consistently less than to purified albumin. The binding affinity for warfarin increased slightly with increasing fatty acid concentrations during surgery, but the increase was much less than expected from the in vitro studies. The binding of phenprocoumon in the serum samples was not influenced by changing fatty acid concentration. The binding affinity for both drugs decreased markedly during the three days following surgery.

Aged↗
PubMed1993

Ceftriaxone--bilirubin-albumin interactions in the neonate: an in vivo study.

The in vivo bilirubin-albumin binding interaction of ceftriaxone (CRO) was investigated in 14 non-jaundiced newborns, aged 33-42 weeks of gestation, during the first few days of life after they had reached stable clinical condition. CRO (50 mg/kg) was infused intravenously over 30 min. The competitive binding effect of CRO on the bilirubin-albumin complex was estimated by determining the reserve albumin concentration (RAC) at baseline, at the end of CRO infusion, and at 15 and 60 min thereafter. Immediately after the end of drug administration, RAC decreased from 91.9 (+/- 25.1) mumol/l to 38.6 (+/- 10.1) mumol/l (P = 0.0001). At the same time the plasma bilirubin toxicity index (PBTI) increased from 0.64 (+/- 0.40) before drug infusion to 0.96 (+/- 0.44) thereafter (P = 0.0001). The highest displacement factor (DF) was calculated to be 2.8 (+/- 0.6) at the end of drug infusion. Average total serum bilirubin concentrations decreased from a baseline value of 59.6 (+/- 27.0) mumol/l to 55.2 (+/- 27.1) mumol/l (P = 0.026). Sixty minutes after the end of CRO infusion, RAC was 58.3 (+/- 21.7) mumol/l, PBTI regained baseline, but DF was still 1.9 (+/- 0.2). No adverse events were recorded. Our results demonstrate significant competitive interaction of CRO with bilirubin-albumin binding in vivo. Thus, ceftriaxone should not be given to the neonate at risk of developing bilirubin encephalopathy.

Bilirubin↗
PubMed1993

The increase of yellow skin colour beyond that of serum bilirubin: a proposed indicator of risk for bilirubin encephalopathy in the newborn.

Forty-seven newborn infants with 1 min Apgar score < 7 were studied. On the third postnatal day the following measurements were made: yellow skin colour, serum bilirubin concentration, reserve albumin concentration and plasma pH. Given the bilirubin concentration and the regression curve between the yellow skin colour and the bilirubin concentration, delta-TcB was calculated as the difference between measured yellow skin colour and the expected yellow skin colour. There was a negative correlation between delta-TcB and Apgar score (P = 0.003), pH (P = 0.026) and reserve albumin concentration (P = 0.045). Fourteen of the included newborns had central nervous system symptoms in the days just following birth. A tendency towards higher delta-TcB was noted in this group (P = 0.08). The results suggest that further study of delta-TcB determination as a tool in the assessment of the icteric newborn infant is justified.

Apgar Score↗
PubMed1992

Solubility of long-chain fatty acids in phosphate buffer at pH 7.4.

The solubility of the saturated fatty acids lauric, myristic, palmitic, and stearic acid and the unsaturated oleic acid at 37 degrees C in phosphate buffer (pH 7.4) was estimated by using two independent methods. The one was a conventional solubility technique measuring the concentration of dissolved fatty acid in buffer by using radioactive compounds. The other was a dialysis exchange technique monitoring possible aggregation of solvated fatty acid anions by measuring the rate of diffusion of labelled compound across a dialysis membrane under conditions of chemical equilibrium. It was found that the results were strongly dependent on the radiochemical purity of the fatty acids. Using highly purified samples of radioactively labelled fatty acids, the solubility of monomeric laurate was shown to be greater than 500 microM, whereas the solubility of monomeric myristate was found to be 20-30 microM. Palmitate, stearate, and oleate solutions, on the other hand, showed a tendency to aggregation even at concentrations below 1 microM. Special attention was given to palmitate, as a reference compound for long-chain fatty acids, and the solubility of monomeric palmitate was estimated to be lower than 10(-10) M.

Autoradiography↗
PubMed1992

Ionization of tyrosine residues in human serum albumin and in its complexes with bilirubin and laurate.

Spectrophotometric titration of human serum albumin indicates that ionization of the 18 tyrosine residues takes place between pH 9 and 12.7. A Hill plot indicates that protons dissociate co-operatively from tyrosine residues, in pure albumin between pH 11.0 and 11.4 with a Hill coefficient 1.7, and in the bilirubin-albumin complex between pH 11.2 and 11.7 with a Hill coefficient 1.6. With a stopped-flow technique it is shown that about seven of the tyrosines ionize fast, with rate constants well above 10(2) s-1, when pH is suddenly changed from near neutral to pH 11.76. Further residues ionize slowly, with rate constants around 10(2) s-1 or less. The N-form of albumin (pH 6) contains one more fast ionizing tyrosine than the B-form of albumin (pH 10). Binding of bilirubin or laurate to the albumin molecule (molar ratio 1:1) transforms one to three of the fast ionizing tyrosines to slowly ionizing.

Bilirubin↗
PubMed1992

The effect of chloral hydrate and its metabolites, trichloroethanol and trichloroacetic acid, on bilirubin-albumin binding.

Chloral hydrate is used as a sedative in infants requiring ventilatory support. The metabolites, trichloroethanol and trichloroacetic acid, accumulate in the serum and are protein bound. The possibility that these chemicals might compete with bilirubin for albumin binding was tested using the peroxidase method and a dialysis rate method. Chloral hydrate and trichloroethanol had no effect on bilirubin-albumin binding. Trichloroacetic acid affects bilirubin-albumin binding but to a degree that would be dangerous only in infants with an unusual accumulation of this metabolite.

Bilirubin↗
PubMed1991

Binding of long-chain fatty acids to serum albumin in healthy humans. Relationship to obesity.

Equilibria of the binding of palmitate to serum albumin in adults are studied by dialysis-exchange-rate determinations. The results are used for a description of binding equilibria of fatty acids in general, as follows. 1. The reserve albumin concentration, p, for binding of palmitate is used as an approximate measure of p*, the reserve albumin concentration for binding of mixed fatty acids present in serum. 2. The total availability of fatty acids is defined as C*/p*, where C* is the total concentration of non-esterified fatty acid. 3. The fatty-acid-binding property of albumin is described by L* = p*/P = alpha C*/P, where P is the albumin concentration. The numerical value of alpha is -0.05. The above parameters are measured in sera from four healthy volunteers, in whom large variations of serum fatty acid concentration occurred. A group of 64 healthy students showed considerable variation of L* from one individual to another. It is found that L* decrease significantly with increasing body mass index (body mass divided by the square of the body length). In 42 patients with diabetes type I, L* was independent of body mass index. These findings are consistent with a previously formulated hypothesis of mechanism of obesity.

Adult↗
PubMed1991

Effect of drug combinations on bilirubin-albumin binding.

Drugs which compete with bilirubin for albumin binding may increase the risk of kernicterus. Fortunately, few drugs are strong competitors. However, in neonatology, many drugs are used simultaneously. We have studied the effect of drug combinations on bilirubin binding using human serum albumin and the peroxidase method. Combinations of aminophylline with phenobarbital, cefotaxime and vancomycin were studied as well as the combination of vancomycin and cefotaxime. The results show that the bilirubin-displacing effect of the drug combinations cannot be predicted from each drug's individual effect. These results are consistent with a flexible model of albumin binding. Combinations of drugs which are both albumin-bound and reach high serum concentrations should be tested for their combined effect on bilirubin binding and this information used in deciding on treatment in sick, premature infants.

Aminophylline↗
PubMed1990

Thermodynamic parameters for binding of fatty acids to human serum albumin.

Binding of laurate and myristate anions to human serum albumin has been studied over a range of temperatures, 5-37 degrees C, at pH 7.4. The binding curves indicate that the strength of binding of the first few molecules of fatty acid to albumin (r less than 5) decreases with increasing temperature, whereas binding of the following molecules seems to proceed independently of temperature. Binding data were analyzed according to the general binding equation yielding several sets of acceptable binding constants within a probability limit of 0.75. From the temperature dependence of the first step constant, it was possible to calculate values for the changes in enthalpy and entropy during the initial binding step. For the medium-chain fatty acids, laurate and myristate, binding of the first molecule to albumin appeared to be enthalpic, with a tendency to an increasing contribution of entropy to binding energy with increasing chain length of the fatty acid.

Humans↗
PubMed1990

Multiple fatty acid binding to albumin in human blood plasma.

Binding equilibria of long-chain fatty acids to human serum albumin, in serum or plasma, were studied by a dialysis exchange rate technique. Palmitate was added to citrated plasma in vitro and it was observed that between six and ten palmitate molecules were bound to albumin with nearly equal affinity. Observations in vivo gave similar results in the following series: (a) in two volunteers with increased fatty acid concentrations after fasting, exercise, and a cold shower: (b) in three male volunteers in whom high concentrations of non-esterified fatty acids, up to 4.6 mM, were induced by intravenous administration of a preparation of lecithin/glycocholate mixed micelles, and (c) in 81 patients with diabetes mellitus, type I. The binding pattern of palmitate in serum or plasma is essentially different from that observed with palmitate added to buffered solutions of pure albumin when two molecules are tightly bound and about four additional molecules with lower affinity. The differences may partly be explained by the presence of chloride ions in blood plasma, reducing the affinity for binding of the first two fatty acid molecules, and partly by facilitated binding of several molecules of mixed fatty acids, as found in plasma.

Diabetes Mellitus, Type 1↗
PubMed1990

Two-dimensional electrophoresis of the fatty acid binding protein from human heart: evidence for a thiol group which can form an intermolecular disulfide bond.

A 100,000 g supernatant from human heart muscle, containing cytosolic proteins with some contaminating plasma proteins, was analyzed for fatty acid binding protein (FABP) by two-dimensional electrophoresis (2-DE) using isoelectric focusing under nondenaturing conditions in the first dimension. FABP purified from human heart muscle was found to comigrate with a major spot in 2-DE gels of the supernatant. This spot was comparable with those of the myoglobins in staining intensity. When purified FABP was charged with [3H]palmitate and subjected to nondenaturing 2-DE, radioactivity always comigrated with this protein. Under denaturing and reducing conditions in the second dimension, FABP was found to have a pI of 5.3 and an apparent molecular weight of 15,000. Isoforms of FABP, reported here for the first time to occur in human heart muscle, were observed as minor spots focusing at pH 5.1 and 5.7. When electrophoresis in the second dimension was carried out under denaturing but nonreducing conditions, an additional protein appeared at pH 5.3 with an apparent molecular weight of about 30,000. This protein was identified as a dimer of FABP and evidence for the involvement of an intermolecular disulfide bond in this dimerization is presented.

Carrier Proteins↗