Background: The proform of eosinophil major basic protein (ProMBP) exists in serum from pregnant women complexed with a variable fraction of angiotensinogen (Ang). A subfraction further binds complement C3dg in a 2:2:2 complex. The function, physiology, and clinical importance of ProMBP complexes are unknown, and the specific quantification of these complexes has not been possible.
Methods: We developed an ELISA for the ProMBP/Ang complexes, using a monoclonal antibody against ProMBP for capture and a chicken anti-human Ang antiserum for detection. Calibrators were standardized with WHO IRP 78/610 for pregnancy proteins in the assay range 0.95–15.6 mIU/L.
Results: The concentrations of ProMBP/Ang complexes in serum of nonpregnant blood donors (n = 79) were log-normally distributed with a central 95th interval of 985-3655 mIU/L. In pregnancy, mean serum concentrations were increased from week 7, and the concentrations reached term concentrations in week 18. ProMBP/Ang complexes eluted in gel filtration as a broad peak with a molecular mass of ∼230 kDa. The concentration of ProMBP/Ang/C3dg increased during blood coagulation, suggesting that the ProMBP/Ang/C3dg complex may be a marker of complement activation.
Conclusions: ProMBP/Ang complexes are present in serum from nonpregnant persons as well as pregnant women, and the direct assays described here will make it possible to study the biochemistry and the clinical significance of different ProMBP complexes in pathological conditions and pregnancy.
Pregnancy-associated plasma protein A (PAPP-A) is a maternal serum marker of fetal chromosomal disease and a risk marker for adverse outcome. PAPP-A in the circulation exists both as a 2:2 complex (PAPP-A/proMBP) with the proform of eosinophil major basic protein (proMBP) and as dimeric PAPP-A. Non-PAPP-A containing proMBP complexes constitute the bulk of proMBP in maternal serum. We developed and characterized a sandwich enzyme immunoassay for PAPP-A using a polyclonal rabbit anti-PAPP-A/proMBP antibody (SSI 6823) and a monoclonal murine anti-PAPP-A/proMBP antibody (HYB 234-3), reactive with the PAPP-A part of PAPP-A/proMBP. The assay range was 2 mIU/L-500 mIU/L, intra- and inter-assay coefficients of variation <10%. The immunoreactivity eluted ahead of thyroglobulin, Mr 669 kDa, in gel filtration and bound to a heparin column. Serum concentrations of PAPP-A were determined in gestational weeks 5-13 in 167 pregnant women with normal fetuses and 39 women with Down's syndrome (DS) fetuses. The median PAPP-A MoM (multiples of the median in normal controls) in DS pregnancies was 0.30 (quartile range: 0.17-0.54). The PAPP-A logMoMs in DS pregnancies were normally distributed with a mean of -0.5927 and SD of 0.3639. When simulating the performance of PAPP-A and age as markers for DS in population screening a detection rate (DR) of 62% was found for a screen positive rate (SPR) of 5%. Together with beta-HCG and nuchal translucency, two other first trimester markers for fetal DS, a DR 90% could be obtained for an SPR of 5%.
The purpose of this study was to find out whether Ca2+ is necessary for the protective effect of phosphocreatine (PCr) on ischemic myocardium. Isolated Langendorff-perfused rat hearts were used in the study. When ischemic arrest was induced in Ca(2+)-free buffer, PCr did not exert a protective effect on ischemic myocardium. PCr improved postischemic contractile recovery of hearts subjected to ischemia in perfusion media containing 0.5 and 1.2 mmol/l Ca2+. Phosphoarginine, a structural analogue of PCr which possesses Ca(2+)-binding property similar to that of PCr did not exert any protective effect on ischemic myocardium. The effects of PCr and Ca2+ on lipid order of sarcolemmal vesicles from canine heart were studied by using ESR spectroscopy. PCr made membrane phospholipids more tightly packed at mildly acidic and neutral pH, but did not at pH 8.5. Although Ca2+ itself did not influence the membrane structure at pH 5.5, it potentiated the effect of PCr on sarcolemmal phospholipids. Thus, the protective effect of PCr on ischemic myocardium is not attributed to its Ca2+ binding properly, but Ca2+ is a necessary component of the mechanism of protective effect of PCr on ischemic myocardium.
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