Biomedical subjects

A Nagpurkar

Publications and source records attributed to A Nagpurkar.

26 records · Page 2Linked to original sources

PubMed1987

The role of the female Syrian hamster protein on the interaction between serum lipoproteins and heparin.

We have previously shown the effect of phosphorylcholine-binding proteins from rat (PCBP) and rabbit (CRP) on the precipitation of serum lipoproteins by heparin in presence of Ca2+. The present paper describes the effect of a phosphorylcholine-binding protein from the female Syrian hamster (FP) on the lipoprotein precipitation reaction. The precipitation of lipoproteins by heparin was lower in assays using female hamster serum in which FP is a prominent protein, compared with assays with male serum in which FP is present in very low concentration. Depletion of FP from female serum resulted in increased lipoprotein precipitation. The addition of purified FP to assays using human very low density lipoprotein (VLDL) inhibited the precipitation reaction. The precipitation of lipoproteins was also examined using serum from male hamsters treated with diethylstilbestrol and female hamsters treated with testosterone, treatments known to modulate the levels of FP. Results indicate an inverse relationship between serum FP levels from normal and hormone-treated hamsters and the precipitation of lipoproteins from their serum. The partially desialylated FP when added to precipitation assays using human VLDL resulted in reduced inhibition of VLDL precipitation.

Animals↗

PubMed1986

Inhibition of the binding of low density lipoproteins to liver membrane receptors by rat serum phosphorylcholine binding protein.

Rat serum phosphorylcholine binding protein (PCBP) is characterized by its Ca2+ dependent property to bind phosphorylcholine ligand. PCBP immobilized on sepharose has been shown to selectively bind human plasma apo B and E containing lipoproteins. The present report describes an inhibitory effect of PCBP on the binding of human 125I-LDL to LDL receptors on estradiol treated rat liver membranes. Pre-incubation of liver membranes with PCBP did not affect the binding of 125I-LDL to the membranes. Gel filtration analysis of the incubation products from the LDL-receptor assay showed a concentration dependent binding of 125I-PCBP to LDL. The inhibitory effect of PCBP is likely due to the formation of LDL-PCBP complex and not due to the binding of PCBP to the LDL receptor site.

Animals↗

PubMed1985

Contrasting effect of phosphorylcholine-binding protein from rat and rabbit on heparin-lipoprotein interaction: a role of sialic acid.

The effect of rat phosphorylcholine-binding protein (PCBP) and rabbit C-reactive protein (CRP) on the serum lipoprotein-heparin-Ca2+ precipitation reaction has been examined. Rabbit CRP, a nonglycosylated acute-phase protein, has been isolated from the serum after turpentine-induced inflammation following an isolation procedure similar to that used for rat PCBP. The mobilities of rabbit CRP and rat PCBP on polyacrylamide gel electrophoresis and immunoelectrophoresis have been found to be different. Rabbit CRP, even though a P-choline binding protein, was found to have no inhibitory effect on the serum lipoprotein-heparin-Ca2+ precipitation reaction. Desialylated rat PCBP obtained by enzymatic desialylation of rat PCBP no longer inhibited the precipitation reaction, even though it retained its P-choline binding property and immunochemical identity with rat PCBP. The results suggest that the binding of rat PCBP and rabbit CRP to the P-choline moiety is not a sufficient requirement, and it now appears that the sialic acid moiety must also be present on these proteins to observe the inhibition of lipoprotein precipitation. This requirement is fulfilled by rat PCBP, but not by rabbit CRP which is nonglycosylated.

Animals↗

PubMed1984

Synthesis and secretion of serum phosphorylcholine-binding protein by rat hepatocytes.

The incorporation of [1-14C]glucosamine into rat serum phosphorylcholine-binding protein in an isolated rat hepatocyte system was used to demonstrate the synthesis and secretion of this protein by the liver. The hepatocytes after incubating with colchicine resulted in an increased intracellular accumulation of phosphorylcholine-binding protein and less of the synthesized phosphorylcholine-binding protein was secreted into the medium. The synthesis of phosphorylcholine-binding protein was found to be significantly impaired when the hepatocytes were incubated with tunicamycin. The radiolabelled phosphorylcholine-binding protein co-eluted with exogenous phosphorylcholine-binding protein as a homogeneous peak by affinity chromatography. The identity of the radiolabelled phosphorylcholine-binding protein was further established by quantitative immunoprecipitation, polyacrylamide gel electrophoresis and isoelectric focusing.

Animals↗

PubMed1983

Interaction of rat serum phosphorylcholine-binding protein with phospholipid-containing liposomes.

Rat serum phosphorylcholine-binding protein (PCBP) has been shown to inhibit the Ca2+-modulated heparin-lipoprotein precipitation reaction. This effect of PCBP on the reaction is prevented by phosphorylcholine (P-choline). A stoichiometric relationship between the serum very low density lipoproteins and PCBP was also evident in the heparin-very low density lipoprotein precipitation reaction (Nagpurkar, A., and Mookerjea, S. (1981) J. Biol. Chem. 256, 7440-7448). A study on the binding of PCBP to artificial liposomes was initiated to understand the mechanism of interaction between PCBP and phospholipids in soluble lipoproteins. Radioiodinated PCBP was incubated with multilamellar liposomes prepared with egg phosphatidylcholine (PC) and lysophosphatidylcholine, and it was found that the binding of PCBP to multilamellar liposomes was Ca2+-dependent and required the incorporation of about 25% lysophosphatidylcholine into the liposomes. Furthermore, the binding could be inhibited by addition of P-choline. The optimum concentrations of Ca2+ and liposomes as well as time and temperature required for binding were established. Analysis of Scatchard binding data yielded an association constant K alpha of 1.8 X 10(6) M-1 and a total binding capacity of 0.96 nmol/mumol of phospholipid. Substitution of P-choline head groups by phosphorylethanolamine and phosphorylserine on the PC of liposomes reduced the binding considerably, whereas the substitution of fatty acyl moieties on the PC of liposomes was without any effect. Bovine serum albumin was required in the assay to prevent artifactual binding of 125I-PCBP to the assay tubes. The results suggest that the P-choline groups on the surface of liposomes play an important role in the binding to PCBP and this may provide a possible explanation of the effect of PCBP on the Ca2+-dependent heparin-lipoprotein precipitation reaction.

Animals↗

PubMed1983

Adsorption of rat plasma phosphorylcholine-binding protein to synthetic lipid emulsions in the presence of divalent cations.

Lipoproteinlike lipid emulsions were incubated with rat serum, plasma, or plasma-derived serum. Two previous unidentified components which bound to these emulsions only in the presence of divalent cations were identified as the rat plasma phosphorylcholine-binding proteins.

Adsorption↗

PubMed1981

A novel phosphorylcholine-binding protein from rat serum and its effect on heparin-lipoprotein complex formation in the presence of calcium.

An adsorbent was synthesized by attaching 4-aminophenylphosphorylcholine to cyanogen bromide-activated Sepharose. A phosphorylcholine (P-choline)-binding protein from rat serum was adsorbed on this affinity column which was eluted by 4 mM P-choline. The protein separated into two bands of Mr = 47,000 and 24,000 on sodium dodecyl sulfate-polyacrylamide gradient gels and contained 18% carbohydrate. A serum protein factor, precipitable by 30-50% (NH4)2SO4, was previously shown to inhibit Ca2+-heparin-rat serum very low density lipoprotein (VLDL) precipitation reaction, whereas P-choline counteracted the action of this protein (Mookerjea, S. (1978) Can. J. Biochem. 56, 746-752). It is now demonstrated that purified P-choline-binding protein prevents Ca2+-heparin-chylomicron or VLDL complex formation and P-choline reverses the effect of this protein. Antibody to P-choline-binding protein raised in rabbits produced a single precipitin line against the pure antigen. The antiserum, however, did not react against rat serum chylomicron, VLDL, low density lipoproteins, or high density lipoprotein. Human serum appears to lack P-choline-binding protein, since (a) the affinity column did not adsorb any such protein, (b) P-choline had no effect on the Ca2+-heparin-serum lipoprotein precipitation reaction, and (c) an immunodiffusion test against the antiserum was negative. However, when P-choline-binding protein was added to human serum, the lipoprotein precipitation was inhibited, and P-choline counteracted the effect of this protein. Preliminary experiments suggested a stoichiometric interaction between P-choline-binding protein and VLDL. Hydrophilic P-choline groups exposed on the surface of VLDL may possibly interact with the P-choline-binding protein and thereby affect the precipitation of lipoproteins by heparin and Ca2+.

Amino Acids↗

PubMed1978

Application of 125I radioimmunoassay to measure inhibition of precipitin reactions using carbohydrate-specific antibodies.

Antibodies raised to an artificial antigen with beta-D-galactopyranosyl groups as antigenic determinants were purified using an immunoadsorbent prepared from the hapten involved in the synthesis of the antigen. In order to study the specificity of these antibodies, 125I radiolabelling of either the artificial antigen or the antibody was used in the study of inhibitions of the precipitin reaction. The method, involving labelling of the artificial antigen and counting radioactivity in the supernatant, was found to be more accurate and faster than the usual methods based on measuring the amount of protein precipitated by chemical or spectroscopic methods.

Antibodies↗