A classification of the fibrin network structures formed from the hereditary dysfibrinogens

OBJECTIVE

The main objective was to study the relationships of the molecular defects in 38 dysfibrinogens with their fibrin networks.

METHODS AND RESULTS

Scanning electron microscopic analyses revealed that all the fibrins formed under the same conditions had networks composed of either normal thickness fibers or thin fibers, accompanied by a variety of alterations in the network structure and characteristics. We classified these fibrin networks into five classes, designated normal, less-ordered, porous A, porous B and lace-like networks. The dysfibrinogens with defects in fibrinopeptide A release or the E:D binding sites formed normal or less-ordered networks, while those with defects in the D:D association formed porous A networks composed of many tapered terminating fibers, despite having fibers of normal width, and containing many pores or spaces. The porous B and lace-like networks were composed of highly branched thin fibers because of defects in the lateral association among protofibrils, and the major difference between them was the porosity of the porous B networks. All the porous B networks were easily damaged by mechanical stress, whereas the lace-like networks retained high resistance to such stress, indicating that the network strength was not dependent on the fiber width, but on the porosity that led to fragility of the network.

CONCLUSION

Impairment of the D:D association is the major disturbing factor that leads to the formation of porous fibrin networks. The porosity may be introduced by severe impairment of the D:D association, as well as the lateral association, as has often been observed by extra glycosylation or defects in Ca2+ binding.

Induction of immune tolerance by neonatal intravenous injection of human factor VIII in murine hemophilia A

Inhibitory antibody formation is the most serious complication of factor (F)VIII replacement therapy in hemophilia A patients. FVIII-deficient mice were used to study new approaches for induction of immune tolerance. Neither antiFVIII inhibitory antibodies nor antiFVIII IgGs were observed in 13 of 14 adult mice that received 0.05 U g(-1) body weight of human FVIII intravenously within 24 h after birth and repeated injections as adults. In contrast, high FVIII antibody titers (>50 Bethesda Units mL(-1)) developed in seven of 13 mice injected on day 3 postpartum and in all adult mice not treated neonatally. One of nine mice and three of 17 mice developed high-titer antiFVIII inhibitory antibody when they were treated initially with 2-fold (0.1 U g(-1) body weight) and 10-fold higher doses (0.5 U g(-1) body weight) FVIII on day 0, respectively. A human FVIII-specific T-cell proliferative response was absent in splenocytes from neonatally treated mice. The tolerance was FVIII specific because antitoxoid antibodies developed after immunization with tetanus toxoid. Splenocytes failed to proliferate or produce interferon (IFN)-gamma in response to FVIII stimulation, yet still secreted interleukin-2. A proliferative response was restored with exogenous IFN-gamma or interleukin-12, suggesting that lack of inhibitor to FVIII was due to IFN-gamma-dependent anergy. Thus, exposure on day 0 to physiological levels of FVIII antigen might be important for induction of immune tolerance. This immune tolerance model may provide a basis for new approaches to prevention of FVIII inhibitors during replacement therapy.

Hypofibrinogenemia caused by a nonsense mutation in the fibrinogen Bbeta chain gene

Congenital hypofibrinogenemia, fibrinogen Tottori II, caused by a nonsense mutation in the fibrinogen Bbeta chain gene, was found in a 68-year-old Japanese female. The plasma fibrinogen level was 99.2 mg dL(-1) as determined by the thrombin time method. No overt molecular abnormalities were observed in purified patient fibrinogen by SDS-PAGE analysis. After sequencing all exons and exon-intron boundaries of three fibrinogen genes, we found a heterozygous single point mutation of T-->G at position 3356 of the patient fibrinogen Bbeta chain gene. This nucleotide mutation results in a nonsense mutation (TAT sequence for Bbeta 41Tyr to TAG sequence for a translation termination signal). The mutation was confirmed by polymerase chain reaction-restriction fragment length polymorphism analysis, since this nucleotide mutation results in a new NheI recognition sequence at this position. These data indicated that the nonsense mutation of the fibrinogen Bbeta chain gene caused a truncated fibrinogen Bbeta chain, which may not be assembled in the fibrinogen molecule.

Concentration of 17beta-estradiol using an immunoaffinity porous hollow-fiber membrane

We describe attempts to achieve high throughput of 17beta-estradiol (E2) analysis, including the development of an immunocleanup membrane using polyclonal antibodies and an enzyme-linked immunosorbent assay (ELISA) using monoclonal antibodies. An epoxy-group-containing monomer, glycidyl methacrylate (GMA), was graft-polymerized onto a porous hollow-fiber membrane. Subsequently, anti-estrogen (ES) antibody, as a ligand, was coupled with the epoxy group. The ligand density ranged from 3.1 to 5.8 mg/g of the GMA-grafted porous hollow-fiber membrane. A 1.0 microg/L E2 solution was forced to permeate through pores rimmed by the anti-ES-antibody-immobilized polymer chains, at a constant permeation rate. A breakthrough curve, that is, the change in the E2 concentration of the effluent penetrating the outside of the hollow fiber with a change of the effluent volume, was determined. Bound E2 in amounts ranging from 0.42 to 0.80 microg was quantitatively eluted with 3-5 mL of methanol in the permeation mode. The higher permeation rate of the E2 solution resulted in the higher overall binding rate of E2 to the anti-ES-antibody-immobilized porous hollow-fiber membrane because of the negligible diffusional mass-transfer resistance of E2 to the antibody.

S-Adenosyl-L-homocysteine hydrolase is sequestered into actin rods in Dictyostelium discoideum spores

Here we show evidence that S-adenosyl-L-homocysteine hydrolase (SAHH) is linked to the actin cytoskeleton. Actin rods formed in Dictyostelium discoideum spores during the final stage of development are structurally composed of novel bundles of actin filaments. SAHH only accumulates with actin at this stage of development in the life cycle of D. discoideum. Recently SAHH is believed to be a target for antiviral chemotherapy and the suppression of T cells. Our finding may contribute to designing novel antiviral and immunosuppressive drugs.

Purification of docosahexaenoic acid ethyl ester using a silver-ion-immobilized porous hollow-fiber membrane module

Docosahexaenoic acid ethyl ester (DHA-Et) was purified by adsorption on Ag-ion-immobilized membranes via selective interaction between silver ion and carbon-carbon double bonds of DHA-Et. Silver ions were immobilized onto sulfonic-acid-group-containing porous hollow-fiber membranes at an Ag ion density of 1.4 mol/kg of membrane, and 30 membranes were housed in one module (inner diameter = 18 mm and effective length = 80 mm). The adsorption isotherms of DHA-Et in various organic solvents revealed that DHA-Et was adsorbed on the immobilized Ag ions with a DHA-Et/Ag ion molar binding ratio of 1/5 in methanol, and that acetonitrile was the solvent of choice for the elution of the adsorbed DHA-Et. Permeation of bonito oil ethyl ester solution in methanol through the Ag-ion-immobilized hollow-fiber membrane module demonstrated that the displacement adsorption of other lower unsaturated fatty-acid ethyl esters by DHA-Et proceeded along the membrane thickness. The purity of DHA-Et was improved to 99 wt % by permeating first bonito oil ethyl ester containing 95 wt % DHA-Et and then acetonitrile through the module.

High conversion in asymmetric hydrolysis during permeation through enzyme-multilayered porous hollow-fiber membranes

We describe a novel porous hollow-fiber support for immobilizing aminoacylase in multilayers. Epoxy-group-containing polymer chains were grafted onto a porous hollow-fiber membrane by radiation-induced graft polymerization of glycidyl methacrylate, and subsequently a diethylamino group as an anion-exchange group was introduced into the graft chain. Aminoacylase was adsorbed in multilayers by allowing the amioacylase buffer solution to permeate through the pores across the hollow fiber; the graft chains provided three-dimensional space for the enzymes because of their electrostatic repulsion. The adsorbed enzyme at a degree of multilayer binding of 15 was cross-linked with glutaraldehyde to prevent leakage. An acetyl-DL-methionine solution was allowed to permeate through the pores surrounded by the aminoacylase-immobilized graft chain. Production of L-methionine was observed at a 4.1 mol/h per L of the fiber for a space velocity of 200 h(-1), defined as the flow rate of the effluent penetrating the outside surface of the hollow fiber divided by the membrane volume including the lumen.

Comparison of L-tryptophan binding capacity of BSA captured by a polymer brush with that of BSA adsorbed onto a gel network

A polymer brush containing a diethylamino group as an anion-exchange group was appended onto a polymer substrate by radiation-induced graft polymerization and subsequent chemical modifications. Bovine serum albumin as a chiral ligand for L-tryptophan was bound to the polymer brush at a density ranging from 17 to 150 g BSA/l. For comparison, BSA was adsorbed onto the gel network containing a diethylaminoethyl group. The molar binding ratio of L-tryptophan to BSA on the polymer brush was 1.7-fold higher than that to BSA on the gel network.

Mode of perturbation of Asahi fibrin assembly by the extra oligosaccharides

Steric hindrance by the backbone of extra oligosaccharides at gamma-Asn 308 may cause the repulsive force to widen the junction at the D:D interface, and thus, interfere with the longitudinal elongation and lateral association of protofibrils.

Hereditary disorders of fibrinogen

Fibrinogen, a 340-kDa plasma protein, is composed of two identical molecular halves each consisting of three non-identical A alpha-, B beta- and gamma-chain subunits held together by multiple disulfide bonds. Fibrinogen is shown to have a trinodular structure; that is, one central nodule, the E domain, and two identical outer nodules, the D-domains, linked by two coiled-coil regions. After activation with thrombin, a pair of binding sites comprising Gly-Pro-Arg is exposed in the central nodule and combines with its complementary binding site a in the outer nodule of another molecules. By using crystallographic analysis, the alpha-amino group of alpha Gly-1 is shown to be juxtaposed between gamma Asp-364 and gamma Asp-330, and guanidino group of alpha Arg-3 between the carboxyl group of gamma Asp-364 and gamma Gln-329 in the a site. Half molecule-staggered, double-stranded protofibrils are thus formed. Upon abutment of two adjacent D domains on the same strand, D-D self association takes place involving Arg-275, Tyr-280, and Ser-300 of the gamma-chain on the surface of the abutting two D domains. Thereafter, carboxyl-terminal regions of the alpha-chains are untethered and interact with those of other protofibrils leading to the formation of thick fibrin bundles and networks. Although many enigmas still remain concerning the exact mechanisms of these molecular interactions, fibrin assembly proceeds in a highly ordered fashion. In this review, these molecular interactions of fibrinogen and fibrin are discussed on the basis of the data provided by hereditary dysfibrinogens on introducing representative molecules at each step of fibrin clot formation.

Cloning of a novel G protein-coupled receptor, SLT, a subtype of the melanin-concentrating hormone receptor

A DNA fragment encoding an amino acid sequence possessing common features to the G protein-coupled receptor (GPCR) superfamily was found in the human genomic sequence, and from this information, the full-length cDNA of a novel GPCR, designated SLT, was cloned from the human hippocampus cDNA library. SLT showed the highest homology to the melanin-concentrating hormone (MCH) receptor, SLC-1 (31.5% identity), and to a lesser extent, to the somatostatin (SST) receptor subtypes. MCH exhibited agonistic behavior when applied to the SLT-expressing CHO cells at subnanomolar doses whereas more than 200 known peptides, including SST and cortistatin, did not. These results indicated that MCH is the cognate ligand of the SLT receptor and that this newly cloned GPCR is the second subtype of the MCH receptor. Quantitative polymerase chain reaction analysis of the SLT gene expression in human tissues showed that the SLT receptor is expressed mainly in brain areas including the cerebral cortex, amygdala, hippocampus, and corpus callosum, as well as in a limited number of peripheral tissues. The distribution of the SLT nearly overlapped that of SLC-1, suggesting that some of the neural functions of MCH may be mediated by both of these receptor subtypes.

Autoantibody against prothrombin aberrantly alters the proenzyme to facilitate formation of a complex with its physiological inhibitor antithrombin III without thrombin conversion

Acquired coagulation factor inhibitors include pathologic immunoglobulins that specifically bind to coagulation factors and either neutralize their procoagulant activity, accelerate their clearance from the circulation, or have proteolytic activity to degrade them into inactive polypeptides. Here, an autoantibody against prothrombin is described in a patient with serious hemorrhagic diatheses. The autoantibody exerts its influence by a previously unknown mechanism in which it inhibits coagulation through aberrant activation of the proenzyme in a catalytic manner. The antibody-bound prothrombin formed a stable stoichiometric complex with antithrombin III, consisting of intact prothrombin and an antithrombin III molecule cleaved at the (393)Arg-(394)Ser bond. The antibody dissociated from prothrombin after the complex formation with antithrombin III. Although the bound antibody elicited protease activity from prothrombin, the complex was not able to convert fibrinogen to fibrin or to activate protein C. Thus, this is the first description of an autoantibody that induces protease-like activity from a human proenzyme, permitting subsequent neutralization by its physiological inhibitor. (Blood. 2001;97:3783-3789)

End-linked homodimers in fibrinogen Osaka VI with a B beta-chain extension lead to fragile clot structure

The authors have identified a 12-residue carboxyl-terminal extension of Lys-Ser-Pro-Met-Arg-Arg-Phe-Leu-Leu-Phe-Cys-Met in a dysfibrinogen derived from a woman heterozygotic for this abnormality and associated with severe bleeding. This extension is due to a T-to-A mutation that creates AAG encoding Lys at the stop (TAG) codon, thus translating 36 base pairs in the noncoding region of the Bbeta gene. The extra Cys residues appear to be involved in 1 or 2 disulfide bonds between 2 adjacent abnormal fibrinogen molecules, forming a fibrinogen homodimer as indicated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Indeed, about half of the fibrinogen molecules exist as end-linked dimers oriented in parallel or with an angle, as observed by transmission electron microscopy. These end-linked dimers may well alter the conformations of D and DD regions on fibrin assembly, leading to increased fiber branching at their sites in the growing protofibrils. By scanning electron microscopy, the Osaka VI fibrin network appears to have a lacelike structure composed of highly branched, thinner fibers than the normal fibrin architecture. Such fibrin networks may be easily damaged to form large pores when fluids are allowed to pass through the gels. The fragility of Osaka VI fibrin clots, further confirmed by permeation and compaction studies, may account for the massive bleeding observed in this patient. (Blood. 2000;96:3779-3785)

High-speed recovery of germanium in a convection-aided mode using functional porous hollow-fiber membranes

A porous hollow-fiber membrane capable of recovery of germanium from a liquid stream was prepared by radiation-induced graft polymerization of an epoxy-group-containing vinyl monomer, glycidyl methacrylate, and subsequent functionalization with 2,2'-iminodiethanol, di-2-propanolamine, N-methylglucamine, and 3-amino-1,2-propanediol. The functional group density was as high as 1.4 mol per kg of the resultant hollow fiber. The polymer chains containing functional groups surrounding the pores enabled a high-speed recovery of germanium during permeation of a germanium oxide (GeO2) solution through the pores of the hollow fiber. Because of a negligible diffusional mass-transfer resistance, germanium concentration changes with the effluent volume, i.e., breakthrough curves, overlapped irrespective of the residence time of the solution, which ranged from 0.37 to 3.7 s across the hollow fiber. After repeated use of adsorption and elution, the adsorption capacity did not deteriorate.

Multilayer binding of proteins to polymer chains grafted onto porous hollow-fiber membranes containing different anion-exchange groups

Various anion-exchange groups were introduced into the polymer chains grafted onto a porous hollow-fiber membrane for protein recovery by radiation-induced graft polymerization and subsequent functionalization of a monomer containing an epoxy group. The graft chains extended from the pore surface toward the pore interior, resulting in the multilayer binding of proteins to the graft chains. Combinations of three anion-exchange groups, namely, amino (AM), ethylamino (EA), and diethylamino (DEA) groups, and three proteins, namely, beta-lactoglobulin, bovine serum albumin, and urease, were examined to evaluate the degree of multilayer binding of protein to the graft chains in the permeation mode. Multilayer binding was observed for hollow-fiber membranes containing EA and DEA groups, with conversions of epoxy groups to EA or DEA groups of higher than 80%. The amount of adsorbed protein remained constant irrespective of the conversion for the hollow-fiber membrane containing an AM group. The dependence of the flux on the conversion was consistent with that of the degree of multilayer binding to the graft chains.

A monoclonal antibody specific to the granulocyte-derived elastase-fragment D species of human fibrinogen and fibrin: its application to the measurement of granulocyte-derived elastase digests in plasma

When granulocytes are stimulated under certain clinical conditions, elastase is released therefrom and digests fibrin(ogen) independently of the plasmin system, which may also be mobilized simultaneously. Thus, discrimination of these 2 systems becomes urgent for the diagnosis and treatment of the underlying diseases. Using as immunogen a 97-kd granulocyte-elastase digest of human fibrinogen, we raised an antibody IF-123 that specifically recognizes elastase digests of human fibrin(ogen). The 97-kd elastase fragment resembles plasmic fragment D(1), and the epitope of this antibody is located on the Aalpha (196-204) residue segment. This segment appears to be masked in fibrin(ogen) but exposed when the Aalpha Leu 204-Ile 205 peptide bond is cleaved by elastase. Cathepsin G concomitantly released from granulocytes failed to expose the epitope. By an enzyme immunoassay using IF-123 as the capture antibody, the elastase digests of fibrin(ogen) can be measured in plasma samples without interference by abundantly coexisting fibrinogen. Indeed, we found that the elastase digests were mostly elevated in patients with inflammation or malignant tumors, but remained in a normal range in patients with a benign gastrointestinal tract disease such as duodenal ulcer and polyps in the gallbladder or the colon. Like the plasmic D-dimer, the elastase digests predominantly consisted of the DD/E complex and DD/E-containing high-molecular weight derivatives apparently corresponding to the phase-3 plasmic digests of cross-linked fibrin. (Blood. 2000;95:1721-1728)

Fibrinogen Niigata with impaired fibrin assembly: an inherited dysfibrinogen with a Bbeta Asn-160 to Ser substitution associated with extra glycosylation at Bbeta Asn-158

A novel BbetaAsn-160 (TAA) to Ser (TGA) substitution has been identified in fibrinogen Niigata derived from a 64-year-old asymptomatic woman, who is heterozygotic for this abnormality. The mutation creates an Asn-X-Ser-type glycosylation sequence, and a partially sialylated biantennary oligosaccharide was linked to the BbetaAsn-158 residue. The functional abnormality was attributed to delayed lateral association of normally formed double-stranded protofibrils based on normal cross-linking of fibrin gamma-chains and tissue-type plasminogen activator-catalyzed plasmin generation by polymerizing fibrin monomers. Enzymatic removal of all the N-linked oligosaccharides from fibrinogen Niigata accelerated fibrin monomer polymerization that reached the level of untreated normal fibrin monomers, but the thrombin time was prolonged from 18.2 seconds to 113 seconds (normal: 11.2 seconds to 8.9 seconds). By scanning electron micrographic analysis, Niigata fibrin fibers were found to be more curvilinear than normal fibrin fibers. After deglycosylation, Niigata fibers became straight being similar to untreated normal fibrin fibers, whereas normal deglycosylated fibrin appeared to be less-branched than untreated normal or deglycosylated Niigata fibrin. Although normal and Niigata fibrins were similar to each other in permeation and compaction studies, deglycosylated normal and Niigata fibrins had much higher permeability and compaction values, indicating that deglycosylation had brought about the formation of more porous networks. The enzymatic deglycosylation necessitates an Asn to Asp change at position Bbeta-158 that is responsible for reducing the fiber thickness because of either local repulsive forces or steric hindrance in the coiled-coil region.

Urotensin II is the endogenous ligand of a G-protein-coupled orphan receptor, SENR (GPR14)

Two molecular species of urotensin II (UII) were isolated from porcine spinal cords and identified as the endogenous ligands of a G-protein-coupled orphan receptor, SENR (sensory epithelium neuropeptide-like receptor), which is identical to GPR14. We established a CHO cell line stably expressing the rat SENR and investigated several tissue extracts to evoke the response mediated by the SENR. Extract from porcine spinal cords showed an activity of arachidonic acid metabolites release from SENR-expressing cells and was purified using HPLC. Two active substances were isolated and their sequences were determined as GPTSECFWKYCV and GPPSECFWKYCV, which were revealed to be porcine UII. Synthetic UII peptides caused arachidonic acid metabolites release activity in the rat SENR-expressing cells with an EC(50) value of 1 nM. Three cDNAs encoding the precursor proteins of porcine UII were cloned from a porcine spinal cord cDNA library; 2 consist of 121 amino acid residues and the other, which seemed to be a splicing variant, consist of 85 residues.

Isolation and identification of melanin-concentrating hormone as the endogenous ligand of the SLC-1 receptor

Melanin-concentrating hormone (MCH), which is an orexigenic peptide, was isolated and identified as the endogenous ligand of the SLC-1 receptor. We established a CHO cell line expressing the rat SLC-1 receptor to search for its endogenous ligand. The extract of rat whole brain showed inhibition of intracellular forskolin-induced cAMP accumulation in rat SLC-1-expressing CHO cells and was purified. Using HPLC purification, we isolated and identified MCH as the endogenous ligand of the SLC-1 receptor. The authentic MCH demonstrated a dose-dependent inhibitory effect on cAMP accumulation in forskolin-stimulated rat and human SLC-1-expressing CHO cells with an EC(50) value of 0.2 nM for both the rat and human SLC-1 receptors. This is the first description of the functional receptor for MCH.

Structure and function of fibrinogen: insights from dysfibrinogens

The structure-function relationships of dysfibrinogens and their clinical implications are discussed on the basis of the data provided from representative molecules.

A new type of Ser substitution for gamma Arg-275 in fibrinogen Kamogawa I characterized by impaired fibrin assembly

A new type of substitution, Arg to Ser at gamma275, has been found in a heterozygous dysfibrinogen derived from a 23-year-old woman with no major bleeding or thrombosis. By sequence analyses of the affected gamma-chain and its gene. we found a single amino acid substitution of gamma Arg-275 to Ser in an aberrant gamma (274-302) residue peptide isolated from lysyl endopeptidase-digests of the patient's fibrinogen. In agreement with this amino acid substitution, we identified a single nucleotide exchange of A for C at position 5728 in the gamma-chain gene creating a codon (AGC) encoding Ser instead of the codon (CGC) encoding Arg at position gamma 275. Like two other known types of mutants with a His or Cys substitution at this position, the functional abnormality was characterized by delayed fibrin polymerization, most likely due to impaired abutting of two D domains of adjacent fibrin monomers in the same strand of fibrin protofibrils. The structural derangement that affects the D:D association may not be so severe as compared with those of Cys and His mutants, possessing an additional disulfide-linked Cys molecule and an imidazole ring at the mutation site, respectively.

High resolution of DL-tryptophan at high flow rates using a bovine serum albumin-multilayered porous hollow-fiber membrane

We describe a bovine serum albumin (BSA)-multilayer-adsorbed porous hollow-fiber membrane as a stationary phase that enables chiral separations at a high resolution and high rate. Epoxy-group-containing graft chains were uniformly immobilized on the surface of pores throughout a porous hollow-fiber membrane by radiation-induced graft polymerization. Subsequently, a diethylamino group as an anion-exchange moiety was introduced to the graft chains, which caused the chains to expand toward the interior of the pores due to mutual electrostatic repulsion. The expanding polymer chains provided multilayer binding sites for BSA as a chiral selector. BSA with a degree of multilayer binding of 4 specifically recognized L-tryptophan with a separation factor of 6.6 during permeation by a mobile phase (Tris-HC1 buffer) injected with a racemic solution of DL-tryptophan through the BSA-multilayered porous membrane. In addition, the separation factor was constant irrespective of flow rates of the mobile phase because of negligible diffusional mass-transfer resistance of tryptophan to BSA multilayered by the graft chains.

Thieno[2,3-d]pyrimidine-3-acetic acids. A new class of nonpeptide endothelin receptor antagonists

On the basis of structural information for the cyclic hexapeptide endothelin (ET) receptor antagonist, TAK-044, a series of thieno[2,3-d]pyrimidine-2,4-dione derivatives bearing a carboxyl group and aromatic rings that were important for receptor binding were designed, synthesized, and evaluated for ET receptor binding affinities and inhibitory activities against ET-induced vasoconstriction. Optimization of each substituent in the thieno[2,3-d]pyrimidine ring led to the discovery of a novel and potent nonpeptide ET receptor antagonist, 6-(4-methoxymethoxyphenyl)-5-methylsulfonylaminomethyl-1-(2- methylthiobenzyl)-2,4-dioxo-1,2,3,4-tetrahydrothieno[2,3-d]p yrimidine-3- acetic acid (32 g), which binded to human ETA and ETB receptor subtypes with affinities (IC50) of 7.6 and 100 nM, respectively. Compound 32 g effectively antagonized ET-induced vasoconstriction and the inhibitory effect mediated by the ETB receptor was more potent than that of bosentan, while the inhibitory effect mediated by the ETA receptor was slightly less potent than that of bosentan.

Chiral separation of DL-tryptophan using porous membranes containing multilayered bovine serum albumin crosslinked with glutaraldehyde

Bovine serum albumin (BSA) as a chiral ligand was captured uniformly throughout a porous hollow-fiber membrane at a level of 160 mg/g by the polymer chains grafted onto the membrane. BSA was bound in three layers with an end-on orientation to diethylamino groups on the graft chains which expanded from the pore surface towards the pore interior due to mutual electrostatic repulsion. Subsequently, crosslinking of BSA with a 0.025% (w/w) of glutaraldehyde in a Tris-HCl buffer (pH 8) for 4 h was effective in stabilizing the amount of BSA immobilized at a level of 150 mg/g. A solution of DL-tryptophan in a Tris-HCl buffer as a mobile phase permeated the crosslinked-BSA multilayered membrane and produced a chromatogram with a separation factor of 12. BSA leakage was not detected in the mobile phases at various pH values and organic modifiers.

Factor XIIIa cross-linking of the Marburg fibrin: formation of alpham.gamman-heteromultimers and the alpha-chain-linked albumin. gamma complex, and disturbed protofibril assembly resulting in acquisition of plasmin resistance relevant to thrombophila

The truncated Aalpha-chain of fibrinogen Marburg is partly linked with albumin by a disulfide bond. Based on the recovery of the first six amino acid residues assigned to the subunit polypeptides of fibrinogen (the Aalpha-and gamma-chains) and albumin, 0.33 mol of albumin was estimated to be linked to 1 mol of the Marburg fibrinogen. When the Marburg fibrinogen was clotted with thrombin-factor XIIIa-Ca2+, various alpham gamman heteromultimers were produced, and part of the albumin was cross-linked to the gamma-chain. Acid-solubilized Marburg fibrin monomer failed to form large aggregates that could be detected by monitoring turbidity at A350, but it was able to enhance tissue-type plasminogen-activator-catalyzed plasmin generation, though not as avidly as the normal control, indicating that the double-stranded protofibrils had, to some extent, been constructed. This idea seems to be supported by normal factor XIIIa-catalyzed cross-linking of the fibrin gamma-chains. However, the cross-linked Marburg fibrin, being apparently fragile and translucent, was highly resistant against plasmin, and its subunit components were considerably retained for 48 hours as noted by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Although the exact mechanisms are still unclear, the albumin-incorporated factor XIIIa-cross-linked Marburg fibrin seems to have undergone a critical structural alteration(s) to acquire resistance against plasmin. This aquisition of plasmin resistance may be contributed to the postoperative pelvic vein thrombosis and recurrent pulmonary embolisms in the patient after caesarian section for her first delivery at the age of 20 years.

Antagonist activity of [Thr18,gamma-methylleucine19]endothelin-1 in human endothelin receptors

Receptor binding and antagonist properties of endothelin-1 analogues, [Thr18,gamma-methylleucine19]endothelin-1, [Thr18,Leu19]endothelin-1 and [Thr18,cyclohexylalanine19]endothelin-1, were investigated using cloned human endothelin ET(A) and ET(B) receptors expressed in Chinese hamster ovary cells. Among them, [Thr18,gamma-methylleucine19]endothelin-1 had a high affinity for endothelin ET(A) and ET(B) receptors with respective Kd values of 300 and 110 pM and had no agonist activity on the stimulation of arachidonic acid release in endothelin ET(A) and ET(B) receptor-expressing cells. [Thr18,gamma-methylleucine19]Endothelin-1 had potent antagonist activity in endothelin-1-induced arachidonic acid release in endothelin ET(A) and ET(B) receptor-expressing cells with respective pA2 values of 8.2 and 8.5. In an inositol phosphates accumulation assay, [Thr18,gamma-methylleucine19]endothelin-1 also exhibited potent antagonist activity for endothelin ET(A) and ET(B) receptors with respective pA2 values of 8.0 and 8.4. In conclusion, [Thr18,gamma-methylleucine19]endothelin-1 acts as a potent and nonselective antagonist with no agonist activity for cloned human endothelin ET(A) and ET(B) receptors.

Receptor binding and antagonist properties of a novel endothelin receptor antagonist, TAK-044 [cyclo[D-alpha-aspartyl-3-[(4-phenylpiperazin-1-yl) carbonyl]-L-alanyl-L-alpha-aspartyl-D-2-(2-thienyl) glycyl-L-leucyl-D-tryptophyl]disodium salt], in human endothelinA and endothelinB receptors

Receptor binding and antagonist properties of an endothelin (ET) receptor antagonist, TAK-044 ¿cyclo[D-alpha-aspartyl-3-[(4-phenylpiperazin-1-yl) carbonyl]-L-alanyl-L-alpha-aspartylD-2-(2-thienyl) glycyl-L-leucyl-D-tryptophyl]disodium salt¿, were investigated using recombinant human ETA and ETB receptors expressed in Chinese hamster ovary cells. The membranous ETA receptor was shown to be heterogeneous in ET-3 binding affinity (Hill coefficient = 0.54, Kd1 = 390 pM and Kd2 = 8.1 nM). This heterogeneity disappeared upon the addition of guanosine-5'-O-3-thiotriphosphate (Hill coefficient = 0.95, Kd = 7.8 nM). The Kd (from a computer program LIGAND analysis) and Ki (from Dixon plot analysis) values of TAK-044 were 95 and 120 pM for the membranous ETA receptor and 41 and 60 nM for the ETB receptor, respectively. The Kd values of TAK-044 for the ETA receptor was comparable to that of ET-1. The Ki values of TAK-044 for the cellular ETA and ETB receptors were 130 pM and 130 nM at 5,000 cells/well and 1.3 and 590 nM at 50,000 cells/well, respectively. Dixon plot analysis indicated that TAK-044 is a competitive inhibitor of ET-1 binding. TAK-044 inhibited ET-1-induced phosphatidylinositol hydrolysis and arachidonic acid release at 50,000 cells/well in a competitive manner with respective pA2 values of 8.5 and 8.7 in the ETA-expressing cells and 7.4 and 6.6 in the ETB-expressing cells. TAK-044 suppressed ET-1-induced transient increase in intracellular Ca+2 concentration in the ETA- and ETB-expressing cells with respective IC50 values of 2.8 and 230 nM. TAK-044 is a potent and competitive ETA receptor antagonist which simultaneously exhibits definite antagonist activity at the ETB receptor.

A gamma Gly-268 to Glu substitution is responsible for impaired fibrin assembly in a homozygous dysfibrinogen Kurashiki I

A new type of gamma Gly-268 (GGA) to Glu (GAA) substitution has been identified in a homozygous dysfibrinogen by analyses of the affected polypeptide and its encoding gene derived from a 58 year-old man manifesting no major bleeding or thrombosis. The functional abnormality was characterized by impaired fibrin assembly most likely due to failure to construct properly aligned double-stranded fibrin protofibrils. This presumption was deduced from the following findings: (1) Factor XIIIa-catalyzed cross-linking of the fibrin gamma-chains progressed in a normal fashion, indicating that the contact between the central E domain of one fibrin monomer and the D domain of another took place normally; (2) Nevertheless, factor XIIIa-catalyzed cross-linking of the fibrinogen gamma-chains was obviously delayed, suggesting that longitudinal association of D domains of different fibrin monomers, ie, D:D association was perturbed; (3) Plasminogen activation catalyzed by tissue-type plasminogen activator was not as efficiently facilitated by polymerizing fibrin monomer derived from the patient as by the normal counterpart. Therefore, gamma Gly-268 would not be involved in the 'a' site residing in the D domain, which functions as a complementary binding site with the thrombin-activated 'A' site in the central E domain, but would be rather involved in the D:D self association sites recently proposed for human fibrinogen. Thus, the gamma Glu-268 substitution newly identified in this homozygous dysfibrinogen seems to impair proper alignment of adjacent D domains of neighboring fibrin molecules in the double-stranded fibrin protofibril, resulting in delayed fibrin gel formation.

Localization of a calcium-dependent epitope to the amino terminal region of the Gla domain of human factor IX

We have used site-directed mutagenesis to define the epitope of calcium-dependent monoclonal antibodies to human factor IX. We demonstrate that the calcium-specific epitope includes residues 1-11 of factor IX, with apparent contributions from other regions of the protein. Antibodies JK.IX-1, -3, and -4 had critical portions of their epitopes in the first eleven amino acids of the Gla domain. These three antibodies could bind to a chimera containing the factor VII Gla domain, in which surface residues 3, 4, 5, 9, 10, and 11 were modified to those of factor IX. In contrast, the epitope of JK.IX-2 was unaffected by mutations in residues 3-11 of factor IX, but was dependent on the amino terminal tyrosine residue. Furthermore, the calcium-dependent monoclonal antibodies, JK.IX-1, -3, and -4, whose epitope include residues 3 through 11. inhibit factor IX's binding to endothelial cells, for which the binding site on factor IX has been localized to this region. Our results, together with previous studies, confirm the existence of discrete calcium and metal-dependent epitopes within the Gla domain of factor IX and show that the calcium-specific epitope lies near the amino terminus region of this domain.

Calcium ion-dependent monoclonal antibody against human fibrinogen: preparation, characterization, and application to fibrinogen purification

We have produced a high-affinity monoclonal antibody classified as IgG1 with kappa-type light chains that recognizes the calcium ion(Ca2+)-dependent conformation of the D-domain of human fibrinogen. Binding of fibrinogen in solution to the insolubilized antibody increased in the presence of increasing concentrations of up to 2 mM Ca2+, the half-maximal binding being reached at 130 microM Ca2+. The dissociation constant was estimated to be 1.6 x 10(-8) M at 2 mM Ca2+. The antibody was found also to be dependent on other divalent metal ions including Zn2+, Mn2+, Co2+ and Cu2+, but not Ba2+, Mg2+ or Sr2+. The synthetic Gly-Pro-Arg-Pro-amide peptide, which has recently been shown to bind to close proximity to the calcium binding site in the D-domain, was unable to elicit the conformation for the antigen to be recognized by this antibody. This antibody was found to be a suitable ligand for the immunoaffinity chromatography of normal and abnormal fibrinogens directly from citrated plasma depleted of the vitamin K-dependent proteins or heparinized plasma by eliminating the precipitation procedure widely adopted in conventional techniques of fibrinogen purification. Indeed, fibrinogen Marburg I with the A alpha chains depleted of the carboxy-terminal A alpha(461-610) residue segment has been purified by this technique, although this dysfibrinogen was difficult to purify by conventional precipitation techniques.

Activation of prothrombin by factor Xa bound to the membrane surface of human umbilical vein endothelial cells: its catalytic efficiency is similar to that of prothrombinase complex on platelets

Upon incubation of human prothrombin with factor Xa bound to human umbilical vein endothelial cells (HUVEC) (0.5-0.6 fmol factor Xa/10(5) cells), three bonds at Arg273-Thr274, Arg286-Thr287, and Arg322-Ile323 were cleaved, yielding and releasing fragment 1-2 and a degraded form of alpha-thrombin, but not meizothrombin, into the fluid phase. The apparent Km for prothrombin and the Vmax were 0.25 +/- 0.07 microM and 210 +/- 40 fmol thrombin/min/10(5) cells, respectively. For the maximally bound factor Xa, the calculated catalytic efficiency (kcat = 6-7 s-1) was similar to those reported for the prothrombinase complex formed on the phospholipid vesicles and natural membrane surfaces. The prothrombin derivatives lacking the 10 gamma-carboxyglutamic acid (Gla) residues-containing region were not activated by the cell-bound factor Xa. The activation rate of prothrombins with Gla residues variously modified to gamma-methyleneglutamic acids was reduced in accordance with the number of modified residues. For the inhibition of prothrombin activation, intact fragment 1 was needed; the Gla-domain alone did not affect the reaction. Binding of monoclonal antibodies to the region of 1-48 or the kringle 1 region of prothrombin also interfered with the prothrombin activation. Prothrombin activation on the surface of HUVEC appeared to proceed via formation of a cellular prothrombinase complex composed of phospholipids of HUVEC membrane, endogenous factor Va, factor Xa, and prothrombin. The Gla-domain and kringle 1 regions are indispensable for the molecule to serve as an effective substrate for the cell-bound factor Xa.

[Mass-screening for ovarian cancer by transvaginal ultrasonography--study on ultrasonographic findings]

Mass-screening for ovarian cancer by means of transvaginal ultrasonography has been performed in Aomori Prefecture since 1989. To select appropriate candidates to receive the second screening, the findings in 614 ultrasonic pictures of pelvic tumors over 30mm recorded on a VTR were studied. The results were as follows: 1) At the first screening, the rate of solid tumors was similar in each age group, but that of mixed tumors was higher in the thirties. 2) When ultrasonic findings at the first screening with that of the second screening were compared, (1) Twenty to thirty per cent of all tumors detected in the first screening had disappeared or had become under 30mm in size at the second screening. (2) About 20% of solid tumors detected in the first screening were not ovarian tumors (uterine myomas or others) in the second screening, regardless of the tumor size. (3) The rate which decided the course of therapy or follow up at the time of the second screening was not related to the ultrasonic findings for tumors smaller than 50mm. At the present time, classification of transvaginal ultrasonic findings is insufficient, and so it is difficult to use it to select appropriate candidates to receive the second screening. But the ultrasonic findings are very important in deciding on the course of therapy and follow up.

[Mass-screening for ovarian cancer by transvaginal ultrasonography--study on tumor markers at the second screening]

Examination of tumor markers (CAMPAS) at the second screening in our mass-screening for ovarian cancer was evaluated. CAMPAS has been performed in 866 women with enlarged ovaries over 30mm in size among 20,242 who received the first screening by transvaginal ultrasonography. In those with semi-malignant and malignant ovarian tumor (ovarian cancer), their serum levels of CA125, CEA, CA19-9, AFP and L-LDH were also measured (Combination Assay) and CA125, CEA, CA19-9, AFP, CA602, CA54 and CA61 antigens in removed tumor tissues were studied by immunoperoxidase staining (Tumor Assay). The results were as follows: 1) Ten of the 866 women were positive for CAMPAS, however, only one of them was found to have ovarian cancer. 2) Of the 20,242 women, six were found to have ovarian cancer: all in stage I and all detected among these 866 women. 3) Of the 6 women with ovarian cancer, three had high serum levels in the Combination Assay, and 4 had positive finding in the Tumor Assay, but of the 4 women with a positive Tumor Assay, one had different kinds of tumor markers in serum and one did not have a high serum level. Thus, CAMPAS was not useful as the second screening method in our mass-screening system for ovarian cancer.

Cyclic hexapeptide endothelin receptor antagonists highly potent for both receptor subtypes ETA and ETB

A cyclic hexapeptide, cyclo(-D-Asp-Trp-Asp-D-Leu-Leu-D-Trp-), designed from cyclo(-D-Glu-Ala-D-alloisoleucyl-Leu-D-Trp-), an ETA receptor-selective antagonist, possessed not only affinity similar to that of BQ-123 for ETA but also higher affinity for ETB than BQ-123. Further modification led to the discovery of cyclo(-D-Asp-Asp(Php)-Asp-D-Thg-Leu-D-Trp-) (Asp(Php): 1-beta-aspartyl-4-phenylpiperazine; Thg: 2-(2-thienyl)glycine) that inhibited [125I]ET-1 binding to the ETA and ETB receptors with IC50 values of 0.082 nM and 120 nM, respectively. Although this compound possesses 1470-fold less affinity for ETB than for ETA, it behaves as a non-selective antagonist that equipotently inhibits vasoconstriction mediated by both receptor subtypes ETA and ETB.

Reduction of nonselective adsorption of proteins by hydrophilization of microfiltration membranes by radiation-induced grafting

Alcoholic hydroxyl groups were introduced into a polyethylene microfiltration (MF) membrane by radiation-induced graft polymerization of 2-hydroxyethyl methacrylate (HEMA), vinyl acetate (VAc), and glycidyl methacrylate (GMA). Subsequently, the VAc- and GMA-grafted membranes were quantitatively hydrolyzed into monool (single hydroxyl) and diol groups, respectively. The pure water flux of the modified membrane and the saturation capacity of bovine gamma-globulin onto the membrane were determined as a function of alcoholic hydroxyl group density. The threshold value for hydrophilization ranged between 5 and 7 mol of alcoholic hydroxyl group per kilogram of original MF membrane. Masking of the polyethylene surface with grafted polymer branches containing the diol groups was effective because approximately 70% of the pure water flux of the original MF membrane was maintained. Irrespective of the pore diameter of the original MF membrane, saturation capacities on the modified membrane correlated well with the diol group density. Saturation capacities of bovine gamma-globulin and bovine serum albumin were reduced to 1 mg/m2 of the membrane. In addition, the binding interaction changed from irreversible to reversible.

Binding of lysozyme onto a cation-exchange microporous membrane containing tentacle-type grafted polymer branches

Ion-exchange adsorption of lysozyme to the sulfonic acid (SO3H) group on polymer chains grafted onto microporous polyethylene hollow-fiber membranes was examined. The lysozyme solution was forced to permeate across the hollow fiber. Diversely anchored SO3H groups, i.e., SP and SS groups, were introduced into the membrane by reaction of the glycidyl methacrylate-grafted membrane with propanesultone and sodium sulfite, respectively. The resulting SP and SS group-containing membranes, designated as SP-T and SS-T fibers, respectively, had 95 and 77% water flux of the original membrane, respectively. The binding capacity of lysozyme as a function of the SO3H group density was compared between the SP-T and SS-T fibers from measurement of the ion-exchange breakthrough curves during the permeation of lysozyme solution across the SP-T and SS-T fibers. The binding capacity of lysozyme to the SP-T fiber remained constant, independent of the SP group density, whereas that to the SS-T fiber increased linearly with increasing SS group density. This difference was explained by means of a model whereby lysozyme adheres onto the SP group-containing grafted polymer branches, while the SS group-containing grafted polymer branches hold lysozyme in a tentacle-like manner.

Fibrinogen Mitaka II: a hereditary dysfibrinogen with defective thrombin binding caused by an A alpha Glu-11 to Gly substitution

A new type of A alpha Glu-11 to Gly substitution has been identified in a congenitally abnormal fibrinogen, fibrinogen Mitaka II, derived from a 14-year-old female suffering from easy bruising since childhood. Plasma of the patient and fibrinogen purified therefrom were found to clot slowly by thrombin but in a normal fashion by ancrod, a thrombin-like snake venom enzyme. The ancrod-clotted fibrin gels were normally solid and turbid, whereas the thrombin-clotted gels were initially fragile and transparent but became gradually normalized during further incubation. On reverse-phase high-performance liquid chromatography, there was an additional peptide group eluted distinctly later than the corresponding normal fibrinopeptide A in the clot-liquor of the patient's samples. Sequence analysis of these aberrant peptides and isolated A alpha chains of the patient's fibrinogen showed that Glu at position 11 of the abnormal A alpha chain had been replaced by Gly. Studies using 125I-labeled thrombin showed that the binding with thrombin was evidently reduced for her fibrinogen and the aberrant fibrinopeptide A as compared with that for the normal controls, indicating that A alpha Glu-11 may be critical for the fibrinogen-thrombin interaction. Indeed, A alpha Glu-11 of fibrinogen has recently been proposed to stabilize the local conformation, including the beta-turn, and to form a salt bridge between its side-chain carboxyl group and the guanidino group of Arg-173 of thrombin based on crystallographic analyses using analogs of fibrinopeptide A complexed with thrombin (Stubb et al, Eur J Biochem 206:187, 1992 and Martin et al, J Biol Chem 267:7911, 1992).

Flow cytometric analysis of surface membrane proteins on activated platelets and platelet-derived microparticles from healthy and thrombasthenic individuals

We used flow cytometry to investigate surface membrane protein expression by platelets and platelet-derived microparticles from normal individuals and a patient with Glanzmann's thrombasthenia. Microparticles were detected by both forward scatter and side scatter using FACScan. The binding of coagulation factors on microparticles was investigated by using monoclonal anti-Factor IX (IXa) and anti-Factor X (Xa) antibodies. Furthermore, the procoagulant activity of microparticles was measured with a chromogenic substrate (S-2222) using a microtiter enzyme-linked immunosorbent assay. Both types of platelets showed similar release of microparticles. Microparticles released from platelets after activation with the calcium ionophore A23187 did not bind factors IXa and Xa, but when purified factors Va and Xa were added to the incubation buffer, factor Xa binding increased markedly in both normal and thrombasthenic platelets. Both normal and thrombasthenic platelets showed a similar time-dependent release of microparticles when activated with A23187. However, the binding of an antibody to granule membrane protein-140 also increased time-dependently in normal microparticles, but was little increased in thrombasthenic microparticles. These findings suggest that glycoprotein IIb/IIIa does not participate in the expression of prothrombinase activity on the surface of activated platelets and microparticles, whereas this glycoprotein appears to have an important role in the movement of granule membrane protein-140 from platelets to microparticles.

The structure of N-linked oligosaccharides of human pancreatic bile-salt-dependent lipase

This study describes the structure of the N-linked oligosaccharide chains of bile-salt-dependent lipase isolated from the pancreatic juice of a normal donor. After hydrazinolysis, neutral sugar chains were separated from acidic chains by paper electrophoresis and were fractionated using serial column chromatography with immobilized lectins and Bio-Gel P-4 filtration. Structural analysis was performed by means of sequential glycosidase digestion and revealed that the neutral sugar chains are mainly of the biantennary complex type. Fucose residues were identified for some trimannosyl core structures and were alpha(1-6) or alpha(1-2) linked to the innermost GlcNAc residue and a terminal Gal residue, respectively. Sialyl residues were also involved in the oligosaccharide structures. Most of these structures have no linear N-acetyllactosamine repeats. Evidence from several approaches suggests that the sugar chains of the human pancreatic bile-salt-dependent lipase possess a blood-group-related antigenic determinant.