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Biomedical subjects

H Kanazawa

Publications and source records attributed to H Kanazawa.

At least 235 records · Page 13Linked to original sources
PubMed1987

Thrombosed St. Jude Medical valve prosthesis in the right side of the heart in patients with tetralogy of Fallot.

Five patients who previously had had repair of tetralogy of Fallot underwent pulmonary valve replacement with a St. Jude Medical valve prosthesis for progressive right ventricular failure. One also underwent tricuspid valve replacement. Two of the valves subsequently became thrombotic despite anticoagulant therapy. Because of the high incidence of thrombosis, we conclude that the St. Jude Medical valve prosthesis is not a suitable prosthesis in the right side of the heart in patients with tetralogy of Fallot.

Child↗
PubMed1987

[Erectile mechanism studied using penile vascular casts in the dog].

The possible mechanism of penile erection was discussed based on the findings obtained by the scanning electron microscope observations of the penile vascular casts in the dog. Polsters protruding into the lumen of the distal helicine arteries regulate blood flow into the cavernous spaces. The drainage veins from the corpus cavernosum penis arose on the dorsal surface and crept on the corpus until changing direction perpendicularly. This suggested that these veins were efficiently compressed between the tunica albuginea and the corpus cavernosum penis during erection. For a high pressure to be maintained in the cavernous spaces during erection, a closed system separated from the systemic circulation must be required.

Animals↗
PubMed1986

Replacement of arginine 246 by histidine in the beta subunit of Escherichia coli H+-ATPase resulted in loss of multi-site ATPase activity.

A mutant strain KF43 of Escherichia coli defective in the beta subunit of H+-translocating ATPase (F0F1) was examined. In this mutant, replacement of Arg246 by His was identified by DNA sequencing of the mutant gene and confirmed by tryptic peptide mapping. The mutant F1-ATPase was defective in multi-site hydrolysis of ATP but was active in uni-site hydrolysis. Studies on the kinetics of uni-site hydrolysis indicated that the k1 (rate of ATP binding) was similar to that of the wild-type, but the k-1 (rate of release of ATP) could not be measured. The mutant enzyme had a k3 (rate of release of inorganic phosphate) about 15-fold higher than that of the wild-type and showed 3 orders of magnitude lower promotion from uni- to multi-site catalysis. These results suggest that Arg246 or the region in its vicinity is important in multi-site hydrolysis of ATP and is also related to the binding of inorganic phosphate. Reconstitution experiments using isolated subunits suggested that hybrid enzymes (alpha beta gamma complexes) carrying both the mutant and wild-type beta subunits were inactive in multi-site hydrolysis of ATP, supporting the notion that three intact beta subunits are required for activity of the F1 molecule.

Adenosine Triphosphate↗
PubMed1986

Mutational replacements of conserved amino acid residues in the beta subunit resulted in defective assembly of H+-translocating ATPase (F0F1) in Escherichia coli.

Mutant genes for the beta subunit of H+-translocating ATPase (F0F1) were cloned from Escherichia coli strains isolated in this laboratory. Determination of their nucleotide sequence revealed four missense mutations (strain KF39, Glu-41----Lys; strain KF16 and KF42, Glu-185----Lys; strain KF48, Gly-223----Asp; KF26 and 4 other strains, Ser-292----Phe). Two nonsense mutants (strain KF40, Gln-361----end; strain KF20, Gln-397----end) were also identified. Glu-41, Glu-185, and Ser-292 are conserved in the amino acid sequences of the beta subunits so far studied, and Gly-223, Gln-361, and Gln-397 are conserved in beta subunits from bacteria and mitochondria, but not in those from chloroplasts. The amounts of F1 subunits in the membranes of these strains were studied by immunochemical assay and two-dimensional gel electrophoresis. In the mutants studied, the amounts of alpha and beta subunits in the membranes were 69-21 and 46-2%, respectively, of the amounts in wild-type membranes, the amount depending on the strain. No delta and epsilon subunits were detected in membranes of a missense mutant KF16, although reduced amounts of alpha and beta subunits could be detected, suggesting that the F1 portion may not be connected to F0 through the delta and epsilon subunits. The altered residues in missense mutants or missing domains in nonsense mutants may be important for the subunit-subunit interactions or assembly of the entire complex. Genetic experiments on introduction of suppressor tRNA into strains KF40 and KF20 suggested that F1 could be active even when residue 361 or 397 was replaced by a Ser, Leu, or Tyr residue.

Base Sequence↗
PubMed1986

Escherichia coli H+-ATPase: loss of the carboxyl terminal region of the gamma subunit causes defective assembly of the F1 portion.

Mutant genes for the gamma subunit of H+-translocating ATPase (H+-ATPase) were cloned from eight different strains of Escherichia coli isolated in this laboratory. Determination of their nucleotide sequences revealed that they are amber nonsense mutations: a Gln codon at position 15, 158, 227, 262, and 270, respectively, was replaced by a termination codon in these strains. As terminal Met is missing in the gamma subunit, these results indicate that these strains are capable of synthesizing fragments of gamma subunits of 13, 156, 225, 260, and 268 amino acid residues, respectively. Studies on the properties of membranes of these strains suggested the importance of the region between Gln 269 and the carboxyl terminus (residue 286) for forming a stable F1 complex with ATPase activity and the region between Gln 226 and Gln 261 for normal interaction of F1 with F0. The sequence from Gln 261 to Gln 269 also seemed to be important for stability of F1 assembly on the membranes. The high frequency of the nonsense mutations suggested that the number of essential residues is limited in this subunit. Comparison of the homologies of the amino acid sequences of the gamma subunits from four different sources confirmed this notion: 19% of amino acid residues are identically conserved in these four strains, and the conserved regions are the amino terminal and carboxyl terminal regions.

Adenosine Triphosphate↗
PubMed1986

Synthesis and secretion of protein by hepatocytes entrapped within calcium alginate.

The ability of entrapped hepatocytes to secrete plasma proteins was examined for the purpose of developing a biological artificial liver. Hepatocytes were isolated from adult rat liver by perfusion with collagenase. Isolated hepatocytes were entrapped within calcium alginate. The entrapped cells induced tyrosine aminotransferase (TAT) in the presence of dexamethasone and dibutyryl-cyclic AMP and retained the ability to induce TAT for 7 days. Moreover, entrapped cells could synthesize and secrete a biologically active form of coagulation Factor II, prothrombin. Two plasma proteins, lecithin: cholesterol acyltransferase and cholinesterase, were also secreted into the medium. Thus, hepatocytes within calcium alginate showed liver-specific characteristics, and these activities were almost comparable with those of monolayer-cultured cells.

Alginates↗
PubMed1986

Serum from patients with autoimmune diseases induces in vitro production of disease-associated antibodies by peripheral blood mononuclear cells from normal subjects.

Antibodies present in serum of patients with rheumatoid arthritis (RA), autoimmune thyroid diseases, and myasthenia gravis are preferentially cytotoxic to suppressor T lymphocytes from normal subjects induced by Concanavalin A. The aim of this study was to determine whether the lymphocytotoxic antibodies found in patients with these diseases also react with regulatory T cells to facilitate production of the autoantibodies responsible for each disease. Peripheral blood mononuclear cells (PBMC) from normal subjects were treated with serum from patients and complement. After washing, residual viable cells were cultured with pokeweed mitogen for 7 days. Immunoglobulin M rheumatoid factor and antihuman thyroglobulin antibody (anti-hTgAb) in the culture supernatants were measured by RIA. Anti-hTgAb was produced in culture supernatants of PBMC treated with serum samples from patients with autoimmune thyroid diseases, whereas serum samples from patients with RA, myasthemia gravis, or normal subjects did not stimulate production of detectable anti-hTgAb. In contrast, Immunoglobulin M rheumatoid factor was produced by normal PBMC treated only with serum from patients with RA. When normal T cells treated with serum were cultured with autologous untreated non-T cells in the presence of pokeweed mitogen, autoantibodies also were produced. Furthermore, the production of anti-hTgAb was suppressed by adding untreated T cells to the mixture of treated T cells and untreated non-T cells. These results suggest that lymphocytotoxic antibodies found in patients with autoimmune disorders may cause disease-associated suppressor T cell dysfunction.

Adolescent↗
PubMed1986

Long-term postoperative status of tetralogy of Fallot.

From 1965 to 1984, 279 patients with tetralogy of Fallot underwent corrective surgery at Niigata University Hospital, and 228 patients were closely followed postoperatively. Late deaths occurred in 12 cases (5.3%), and overall event-free rate at 20 years postoperatively was 76.9%. The most common events were heart failure due to residual cardiac anomaly and symptomatic ventricular arrhythmias. Treadmill test by Ellestad protocol was performed on 74 postoperative patients, 49% of whom could not complete the protocol. These patients had higher RVEDP and lower RVEF than completing patients. Holter ECG was done on 48 long-term postoperative patients, 48% of whom showed complex ventricular arrhythmias. The age at operation was older and postoperative elapsed time was longer in patients with complex ventricular arrhythmias. Although most postoperative TF patients are able to enjoy a normal social life, the treadmill test and Holter ECG revealed that many patients had latent RV dysfunction and complex ventricular arrhythmias with or without significant symptoms. Since the number of symptomatic patients increases after 15 years postoperatively, a regular check-up with cautious observation is important for the patients' care.

Arrhythmias, Cardiac↗