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Biomedical subjects

Y Fujimura

Publications and source records attributed to Y Fujimura.

At least 289 records · Page 16Linked to original sources
PubMed1989

Blood clotting factor IX Kashihara: amino acid substitution of valine-182 by phenylalanine.

Hemophilia B Kashihara is a severe hemorrhagic disorder in which the factor IX antigen is present in normal amounts but factor IX biological activity is markedly reduced. In addition, purified factor IX Kashihara is not activated by purified factor XIa in the presence of calcium ions. Amino acid sequence analysis of one of the tryptic peptides isolated from factor IX Kashihara indicated that Val-182 (equivalent to Val-17 in the chymotrypsin numbering system) had been replaced by Phe. No substitution was found in the members of the catalytic triad His-221, Asp-269, and Ser-365 of factor IX Kashihara. The Val-to-Phe replacement found in factor IX Kashihara appears to sterically hinder the cleavage of Arg 180-Val 181 by factor XIa required for the activation of this zymogen.

Amino Acids↗
PubMed1989

[Congenital coronary artery fistula draining into the superior vena cava with giant saccular aneurysm--report of a case].

A 42-year-old woman who had a coronary artery fistula, associated with a giant coronary saccular aneurysm was reported. The coronary artery fistula originated from the proximal portion of the right coronary artery drained into the superior vena cava. The chief complaint was heart murmur which was detected at the 2nd intercostal space of the right sternal border. No other symptoms were present. The aneurysm was approximately 5 X 7 cm in size. In the operation using cardiopulmonary bypass, the proximal and distal portions of the coronary artery fistula were ligated successfully without aneurysmorrhaphy. The postoperative conditions was even without any complications. Congenital coronary artery fistulas with a giant saccular aneurysm should be surgically treated as soon as possible because of potential risk of aneurysmal rupture.

Adult↗
PubMed1989

[Raghib's syndrome associated with cor triatriatum--a rare surgical case report].

A 27-year-old male with a history of congenital heart disease was admitted for pre-operative evaluation of a cardiac malformation. Echocardiography and cardiac catheterization revealed an incomplete endocardial cushion defect with a persistent left superior vena cava which drained into the left atrium but echo-cardiographic evidence of an abnormal intra-atrial septum was not found. The patient was placed on cardiopulmonary bypass and prepared for the surgical correction of his primary cardiac lesion. Intra-cardiac examination during reconstruction of Raghib's syndrome also revealed the presence of cor triatriatum. Reghib's syndrome is characterized by the combination of abnormal drainage from the left superior vena cava into the left atrium, the presence of an atrial septal defect and the absence of a coronary sinus. To prevent secondary complications such as a brain abscess, we redirected blood flow from the left superior vena cava to the right atrium utilizing a trimmed woven dacron vascular graft that was placed in the intra-atrial position. Mitral valvoplasty, excision of the obstructing diaphragm and atrial septation were also performed successfully. Although the literature has described the surgical repair of Raghib's syndrome, its correction in combination with cor triatriatum is considered to be extremely rare.

Adult↗
PubMed1989

[Early operation for postinfarction ventricular septal perforation; report of three cases].

Three patients underwent surgery for postmyocardial infarction ventricular septal perforation (VSP) within 3 to 21 days after onset of infarction. The hemodynamic stabilization was not obtained despite aggressive medical treatment including Intra-aortic Balloon Pumping (IABP) in one patient. The others had sudden hemodynamic deterioration during IABP support. In two of the three cases, the VSP were closed via transinfarct ventriculotomy with double Dacron patch, and ventricular wall reconstruction was performed to sandwich the double septal patch between ventricular free walls with Dacron felt strips. Two of the three patients survived. Our experience suggests that early surgical intervention is essential unless medical therapy results in clinical improvement and the double patch method may provide a successful operative repair and comeout.

Adult↗
PubMed1989

Heparin-associated thrombocytopenia: observations on the mechanism of platelet aggregation.

We investigated the mechanism of heparin-mediated platelet aggregation in 11 patients with heparin-associated thrombocytopenia. Severe thrombocytopenia (16,000 to 66,000 platelets/microliters) developed in each patient during heparin therapy, and platelet aggregation occurred in vitro when heparin was added to mixtures of patient plasma and normal platelet-rich plasma. In 10 patients, heparin-initiated platelet aggregation was inhibited by preincubation of mixtures of normal platelet-rich plasma and heparin-associated thrombocytopenia plasma with monoclonal antiglycoprotein Ib antibodies 6D1 or LJ-Ib1. Both antibodies are directed against the von Willebrand factor binding site on glycoprotein Ib and inhibit only ristocetin-induced platelet agglutination. Purified immunoglobulin G (IgG) from patients with heparin-associated thrombocytopenia also supported heparin-induced aggregation, but equivalent amounts of antigen-binding fragments [F(ab')2] did not. We also found that F(ab')2 of LJ-Lb1 did not inhibit heparin-induced platelet aggregation but retained inhibitory activity against ristocetin-induced platelet agglutination. The monoclonal antibody 3G6, directed against the alpha-chain of glycoprotein Ib but not inhibitory of ristocetin-induced platelet agglutination, had no effect on heparin-induced platelet aggregation. Antibodies to von Willebrand factor that inhibit ristocetin-induced platelet agglutination did not inhibit heparin-mediated platelet aggregation, but antibodies to glycoprotein IIb-IIIa blocked aggregation. These data suggest that platelet aggregation in heparin-associated thrombocytopenia may be initiated by an interaction between patient IgG, heparin, and the platelet surface. Platelet activation appears to be mediated by a platelet surface crystallizable fragment (Fc) receptor.(ABSTRACT TRUNCATED AT 250 WORDS)

Heparin↗
PubMed1989

[Surgical considerations after patch closure of atrial septal defect with tricuspid annuloplasty].

Two patients with complications of embolism during the early postoperative period after patch closure of atrial septal defect with tricuspid annuloplasty were reported. Case 1: A 58-year-old woman underwent closure of an atrial septal defect and tricuspid annuloplasty by means of Kay's technique for tricuspid regurgitation. She had an episode of thromboembolism in the bilateral common femoral arteries 7 days after surgery. Thromboembolectomy was performed successfully using Fogarty's embolectomy catheter. Case 2: A 49-year-old woman underwent closure of an atrial septal defect and the tricuspid annuloplasty using Carpentier ring for tricuspid regurgitation. The patient had transient left hemiparesis on the 5th postoperative day. Both patients had atrial fibrillation and mild pulmonary hypertension before surgery. In relatively old patients (over 40 years old) with atrial septal defect, tricuspid regurgitation and atrial fibrillation, anticoagulant therapy should be started immediately after surgery to prevent thromboembolism.

Female↗
PubMed1988

Structure of the von Willebrand factor domain interacting with glycoprotein Ib.

von Willebrand factor is a multifunctional adhesive protein of plasma, platelets, and endothelial cells that mediates a crucial interaction for normal hemostasis and thrombus formation by binding to platelet membrane glycoprotein Ib. We provide here evidence that this function involves two limited noncontiguous regions of the molecule, each contained within 15 amino acid residues, separated in the linear sequence by 205 residues, and maintained in close spatial proximity in the folded molecule by disulfide bonding. Definition of this chemical structure clarifies a fundamental mechanism of platelet adhesion to thrombogenic surfaces and sets the bases for obtaining synthetic replicas that may be used to modulate platelet function.

Amino Acid Sequence↗
PubMed1988

[Levels of plasma cyclic AMP in cardiac surgery].

The actions of hormones such as catecholamines, vasopressin and growth hormones are mediated by a common intracellular second messenger, cyclic AMP (adenosine 3',5'-monophosphate). The effects of cardiac surgery on plasma cyclic AMP were studied in 32 adults patients with aorta-coronary bypass or with valvular disease. Blood specimens were obtained before operation, at the beginning and at the end of the cardiopulmonary bypass, 1, 3, 6, 9, 12, 24, 48, 72, 168 hours after surgery. The plasma cyclic AMP level during cardiac operation was elevated above the preoperative level. High levels of plasma cyclic AMP were found both in the aorta-coronary bypass and in the valvular disease immediately after the end of cardiopulmonary bypass. The plasma cyclic AMP level in patients undergoing aorta-coronary bypass with aortic clamping time more than 60 minutes was 38.6 +/- 11.7 pmol/ml, compared to 25.6 +/- 6.6 pmol/ml with aortic clamping time less than 60 minutes immediately after the end of cardiopulmonary bypass. In patients undergoing valve replacement and/or commissurotomy with aortic clamping time more than 60 minutes, the plasma cyclic AMP level immediately after the end of cardiopulmonary bypass was 113 +/- 63.3 pmol/ml, compared to 45.4 +/- 10.3 pmol/ml with aortic clamping time less than 60 minutes (p less than 0.01, Student's t test). During 24 hours after cardiac surgery, the plasma cyclic AMP concentration returned to normal range. It is considered that the plasma cyclic AMP level reflects the risk of cardiac surgery in response to homeostatic derangement.

Cardiac Surgical Procedures↗
PubMed1987

A heparin-binding domain of human von Willebrand factor. Characterization and localization to a tryptic fragment extending from amino acid residue Val-449 to Lys-728.

We have recently shown that the domain of von Willebrand factor (vWF) which interacts with the platelet glycoprotein Ib (GPIb) is located in a 52/48-kDa tryptic fragment of the molecule which begins with amino acid residue Val-449. We have now established that the fragment extends to residue Lys-728 and demonstrate here that a high affinity heparin-binding domain of vWF also lies within this region and in close proximity to that for GPIb. We have used an assay employing heparin coupled to Sepharose CL-6B to show that 125I-vWF binds to heparin in a time-dependent, saturable, and reversible manner. Binding could be completely inhibited by the 52/48-kDa fragment, but was not affected by other tryptic fragments of 55, 41, 13, and 22 kDa. NH2-terminal sequencing of these fragments showed that they were derived from different parts of the molecule, as follows: 13 kDa, Gln290-Thr-Met-Val-Asp-Ser-Ser; 55 kDa, Asn730-Ser-Met-Val-Leu-Asp-Val-Ala-Phe-Val-Leu-Glu; 41 kDa, Thr1352-Val-Gln-Arg-Pro-Gly-Gln-Thr-Cys-Gln-Pro-Ile-Leu-Glu-Glu-Gl n-Cys-Leu-Val ; 22 kDa, Val1927-Thr-Gly-Cys-Pro-Pro. Direct binding of the purified 52/48-kDa fragment to heparin-Sepharose was also shown. Furthermore, crossed immunoelectrophoresis revealed complex formation between the purified 52/48-kDa fragment and free heparin. Twelve monoclonal antibodies to the 52/48-kDa fragment were evaluated for their ability to block binding of 125I-vWF to heparin. With the exception of one weak inhibitor of heparin binding, their relative efficacy in blocking heparin binding was similar to that for blocking ristocetin-induced binding to GPIb. However heparin failed to block ristocetin-independent binding of the 52/48-kDa fragment to GPIb. It is therefore likely that the two binding domains are adjacent to one another, but are not precisely congruent.

Binding Sites↗
PubMed1987

Epitope mapping of the von Willebrand factor subunit distinguishes fragments present in normal and type IIA von Willebrand disease from those generated by plasmin.

A small but consistent proportion of the von Willebrand factor (vWF) in normal plasma is composed of 189, 176, and 140 kD fragments cleaved from the 225 kD subunit. A monoclonal antibody map of vWF, based on the reactivity of individual antibodies with cyanogen bromide and tryptic fragments of known carboxy and/or amino termini, showed that in normal and IIA von Willebrand disease (vWD) plasmas the 140 kD fragment was derived from the amino-terminal region, whereas the 176 kD fragment was derived from the carboxy-terminal region of the subunit. In type IIA vWD, however, the fragments comprised a greater proportion of circulating vWF. In contrast, plasmin cleaved a 176 kD fragment from the amino terminus and a 145 kD fragment from the carboxy terminus of the subunit. Species similar to these plasmin-cleaved fragments were demonstrated in plasmas from four patients treated with fibrinolytic agents, but not in IIA vWD.

Antibodies, Monoclonal↗
PubMed1987

The von willebrand factor domain-mediating botrocetin-induced binding to glycoprotein IB lies between Val449 and Lys728.

Botrocetin, a component of Bothrops jararaca venom, induces von Willebrand factor (vWF)-dependent platelet agglutination and has been proposed as an alternative agent to ristocetin for evaluating vWF function. However, important differences between the vWF-platelet interactions induced by these two agents have suggested that different regions of vWF and the platelet may be involved in the interactions induced by the two agonists. We have recently demonstrated that binding of vWF to the platelet glycoprotein (GP) Ib receptor, either induced by ristocetin or as occurs spontaneously with asialo-vWF or vWF from IIb von Willebrand disease, is mediated by a domain residing on a 52/48-kilodalton (kD) tryptic fragment of vWF. This fragment extends from amino acid residue Val (449) to Lys (728). We have now found that this 52/48-kD fragment blocks botrocetin-induced binding of vWF to platelets and completely inhibits botrocetin-induced platelet agglutination. These results provide evidence that the vWF domain-mediating, botrocetin-induced platelet agglutination lies within the region delimited by this fragment and is therefore close to or identical with that which mediates ristocetin-induced binding and spontaneous binding of vWF to platelet GPIb. Anti-GPIb monoclonal antibodies also blocked agglutination, which showed that botrocetin, like ristocetin, induces binding of vWF to the GPIb receptor.

Amino Acid Sequence↗