Role of Copeptin in Predicting Postoperative Hyponatremia and Hypernatremia in Patients Undergoing Endoscopic Pituitary Adenoma Surgery.

Background And Objectives: Arginine vasopressin (AVP) is an important hormone responsible for maintaining sodium homeostasis after pituitary surgery. The measurement of AVP levels is difficult because of its short half-life (t 1/2 ). Copeptin is a preprohormone of AVP, and it is a more stable peptide, which can be used as surrogate marker for AVP.

High glucose removes natural anti-α-galactoside and anti-β-glucoside antibody immune complexes adhering to surface O-glycoproteins of normal platelets and enhances platelet aggregation.

Human natural anti-α-galactoside (anti-Gal) and anti-β-glucoside (ABG) antibodies were previously reported to recognize the serine- and threonine-rich peptide sequences (STPS) of albumin-associated O-glycoproteins (AOP1 and AOP2) as surrogate antigens, forming anti-Gal/ABG-AOP1/AOP2-albumin triplet immune complexes in plasma. Since antibodies in these triplets still possessed unoccupied binding sites, the presence of triplets on human platelets that abound in surface O-glycoproteins was examined. Upon treatment with α-galactosides and β-glucosides, normal platelets freshly isolated from young healthy individuals released triplets identical with plasma triplets according to ELISA results.

Activity of MUC1 cancer antigen-binding plasma anti-α-galactoside antibody correlates inversely with size of autologous lipoprotein(a).

Variation in ligand-binding affinity of natural plasma anti-α-galactoside antibody (anti-Gal) is a plausible reason for differing anti-cancer defense among individuals since serine- and threonine-rich peptide sequences (STPS) in the cancer-specific MUC-1 antigen are surrogate ligands for this antibody. As affinity of a natural antibody could be modulated by systemic antigens by processes including affinity maturation, we examined the contribution of the size of lipoprotein(a) [Lp(a)], an efficient autologous anti-Gal-binding macromolecule that possesses variable numbers of STPS due to genetically determined size polymorphism, towards the specific activity (activity per unit mass) of anti-Gal. Binding of purified Lp(a) to FITC-labeled anti-Gal, measured in terms of increase in fluorescence of the latter, was inhibited by LDL in proportion to Lp(a) size presumably because LDL molecules also bind noncovalently and in proportion to Lp(a) size at the O-glycosylated and STPS-rich region of Lp(a).

Amyloid β Binds to Albumin-Associated Lrp-Like Plasma O-Glycoproteins: Albumin Prevents Inhibition of Binding by LDL.

Background: Albumin was reported to engage nearly 95% of plasma Amyloid β (Aβ) and to reverse Aβ fibril formation in brain.

Objective: Since O-glycosylated LRP family of receptors capture Aβ in brain we compared Aβ binding to electrophoretically purified albumin and to O-glycoproteins AOP1 and AOP2 that adhere noncovalently to plasma albumin.

Methods: Strength of Aβ-protein interaction was measured as fluorescence increase in Fluorescentlabeled Aβ (F-Aβ) resulting from conformational changes.

Anti-α-galactoside and Anti-β-glucoside Antibodies are Partially Occupied by Either of Two Albumin-bound O-glycoproteins and Circulate as Ligand-binding Triplets.

Two heavily O-glycosylated proteins and albumin co-purified with anti-α-galactoside (anti-Gal), the chief xenograft-rejecting antibody and anti-β-glucan (ABG) antibody isolated from human plasma by affinity chromatography on respective ligand-bearing matrices. Both antibodies and O-glycoproteins co-purified with plasma albumin eluted from albumin-specific matrix. Using components of affinity-purified antibody samples separated by electrophoresis binding of either albumin or antibody to the affinity matrix of the other or binding of O-glycoprotein to either matrix was ruled out.

Plasma anti-α-galactoside antibody mediates lipoprotein(a) binding to macrophages.

Lipoprotein (a) [Lp(a)] is the dominant lipid in atherosclerotic plaques though it is much less numerous than LDL or HDL in circulation. Molecular mechanism of selective uptake of Lp(a) into macrophages is unclear. Lp(a) was reported to form circulating immune complexes with the IgG-dominated plasma anti-α-galactoside antibody (anti-Gal) using the serine- and threonine-rich peptide sequences ( STPS) on its apo(a) subunit as surrogate ligand but left the other binding site of antibody free.

Antigen-Induced Activation of Antibody Measured by Fluorescence Enhancement of FITC Label at Fc.

Three anti-carbohydrate antibodies of defined specificity isolated from plasma were used to demonstrate that macromolecular antigen binding caused considerable enhancement of fluorescence of FITC-labeled antibody. Mono and disaccharide antigens which could compete with the large antigens in antibody binding could not however produce any increase in fluorescence. Fluorescence enhancement in a given antibody sample increased with the size of the occupying macromolecular antigen.

Human plasma anti-α-galactoside antibody forms immune complex with autologous lipoprotein(a).

Anti-α-galactoside antibody (anti-Gal) from human plasma that bound to α-galactoside-bearing guar galactomannan gel and was eluted with specific sugar (affinity-purified anti-Gal ; APAG) invariably contained apo(a) and apo B subunits in a proportion close to that in plasma lipoprotein(a) [Lp(a)]. Since LDL does not contain apo(a), result suggested Lp(a) as a component of APAG. Lp(a) in APAG was complexed with anti-Gal since plate-coated anti-apo(a) captured Lp(a) along with the antibody.

apoB-independent enzyme immunoassay for lipoprotein(a) by capture on immobilized lectin (jacalin).

Enzyme immunoassay for lipoprotein(a) [Lp(a)] using antibodies to both apoB and apo(a) subunits (a-B assay) is shown to be affected by differential masking of apoB by apo(a) and the presence of LDL-Lp(a) adducts. An apoB-independent immunoassay by capturing Lp(a) through its O-glycans on microplate-coated lectin jacalin and quantitation using peroxidase-labeled anti-apo(a) (J-a assay) is described. J-a assay response is linear, more than twice as sensitive as a-B assay, and is suppressed only 18 ± 5% by non-Lp(a) O-glycan-containing proteins of serum.

Multiple specificity of human serum dextran-binding immunoglobulin: alpha (1-->6)- and beta (1-->3)-linked glucose and alpha (1-->3)-linked galactose in natural glycoconjugates are recognized.

Dextran-binding immunoglobulin (DIg) was detected in circulating immune complexes in young healthy blood donors. High molecular weight dextran or non-dialysable polysaccharides of edible sugar added to serum markedly increased DIg-containing immune complexes. DIg from plasma was purified by an improved affinity chromatography using Sephadex G-200 to increase yield.