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Biomedical subjects

S Toyama

Publications and source records attributed to S Toyama.

At least 91 records · Page 5Linked to original sources
PubMed1982

Demonstration of two distinct antigenic determinants on hepatitis B e antigen by monoclonal antibodies.

Mice were immunized against hepatitis B e antigen (HBeAg) isolated from sera of asymptomatic carriers of hepatitis B virus. Their spleen cells were fused with mouse myeloma (NS-1) cells, and 5 clones of hybridoma cells secreting antibody against HBeAg (anti-HBe) were isolated. For the production of anti-HBe in large scale, cells were cultivated both in vitro and in the peritoneal cavity of ascitic mice. Although monoclonal antibodies produced by these clones showed a strong reactivity of anti-HBe in hemagglutination tests, individual monoclonal anti-HBe did not reveal any precipitin line in immunodiffusion. When 2 of the 5 monoclonal antibodies were mixed together, however, some combinations showed a precipitin line against HBeAg, whereas others did not. Utilizing solid-phase radioimmunoassay involving a number of combinations of monoclonal antibodies used for solid-phase and radiolabeling, the 5 antibodies were classified into 2 groups. Three of the anti-HBe antibodies were found to be directed to 1 determinant of HBeAg (determinant a); the remaining 2 to the other determinant (determinant b). Determinants a and b were detected on HBeAg in the serum, as well as on the polypeptide of 19,000 daltons (P19) derived from the nucleocapsid of hepatitis B virus. Monoclonal anti-HBe antibodies with different specificities may provide useful tools in delineating the antigenic structure of HBeAg and also in evaluating immune responses of the host directed to its subdeterminants.

Animals↗
PubMed1982

Detection of human osteosarcoma-associated antigen(s) by monoclonal antibodies.

Hybrid cell lines have been derived from a fusion between mouse myeloma cells, NS1, and spleen cells from mice immunized with freshly resected osteosarcoma cells from an untreated patient. Of the 276 hybrids obtained, five secreted antibodies which bound to osteosarcoma tissues but not to autologous skin fibroblasts. The antibodies from three of these five hybrids, OST6, OST7, and OST15, reacted with all of five osteosarcoma tissues and with one chondrosarcoma tissue but not with other malignant or benign tumors. Tests of various normal tissues were negative, except for weak binding to a subpopulation of chondrocytes in articular cartilage. The reciprocal binding inhibition test showed that OST6, OST7, and OST15 antibodies were directed against different antigenic determinants.

Animals↗
PubMed1981

Properties of crystalline L-ornithine: alpha-ketoglutarate delta-aminotransferase from Bacillus sphaericus.

The distribution of bacterial L-ornithine: alpha-ketoglutarate delta-aminotransferase (L-ornithine:2-oxo-acid aminotransferase [EC 2.6.1.13]) was investigated, and Bacillus sphaericus (IFO 3525) was found to have the highest activity of the enzyme, which was inducibly formed by addition of L-ornithine or L-arginine to the medium. L-Ornithine:alpha-ketoglutarate delta-aminotransferase, purified to homogeneity and crystallized from B. sphaericus, had a molecular weight of about 80,000 and consisted of two subunits identical in molecular weight (41,000) and in amino-terminal residue (threonine). The enzyme exhibited absorption maxima at 278,343, and 425 nm and contained 1 mol of pyridoxal 5'-phosphate per mol of enzyme. The formyl group of pyridoxal 5'-phosphate was bound through an aldimine linkage to the epsilon-amino group of a lysine residue of the protein. The enzyme-bound pyridoxal 5'-phosphate, absorbing at 425 nm, was released by incubation with phenylhydrazine to yield the catalytically inactive form. The inactive enzyme, which was reactivated by addition of pyridoxal 5'-phosphate, still had a 343-nm peak and contained 1 mol of a vitamin B6 compound. The holoenzyme showed positive circular dichroic bands at 340 and 425 nm, whereas the inactive form had no band at 425 nm. The enzyme was highly specific for L-ornithine and alpha-ketoglutarate and catalyzed delta-transamination between them to produce L-glutamate and L-glutamate-gamma-semialdehyde, which as spontaneously converted to delta 1-pyrroline-5-carboxylate. The enzyme activity was significantly affected by nonsubstrate amino acids, amines, and carbonyl reagents.

Amino Acids↗
PubMed1980

Studies on the kinetics and stoichiometry of inactivation of Pseudomonas omega-amino acid:pyruvate transaminase by gabaculine.

A homogeneous pyruvate-requiring omega-amino acid transaminase from Pseudomonas species F-126 has been examined for its behavior with gamma-aminobutyrate (GABA) as omega-amino acid substrate and for its susceptibility to the cyclic dihydroaromatic GABA analogue, gabaculine, a known suicide substrate for alpha-ketoglutarate-requiring GABA transaminases (Biochemistry 16, 4604-4610, 1977). One isomer of DL-gabaculine serves as a completely efficient titrant (no product molecules released) for this omega-amino acid transaminase by the anticipated mechanism of bound pyridoxal 5'-phosphate (PLP) derivitization. Stoichiometric titration with [2-3H]gabaculine reveals full inactivation at 0.45 labels/enzyme tetramer (see below), consistent with the subsequent demonstration that there is only 0.45 PLP molecule, bound as phenylhydrazine-titratable aldehyde form, per tetramer. Spectroscopic monitoring of inactivation also agrees with formation, on full inactivation, of 0.45 mol of m-anthranilyl-PNP adduct as the species quantitatively responsible for enzyme inactivation. Incubation of enzyme with excess PLP at 60 degrees C allows loading of enzyme with coenzyme to an average level of approximately 1 PLP/subunit, but even in this case activity is only increased up to 1.5-fold, and 1 to 1.5 molecules of gabaculine/tetramer cause complete inactivation. These data may indicate negative cooperativity between subunits.

Cyclohexanecarboxylic Acids↗
PubMed1980

Revaluation of the vectorcardiographic criteria in cases of myocardial infarction: a comparative study of the vectorcardiogram, the left ventriculogram and the scintigram.

The results of vectorcardiograms were compared with those of the left ventriculograms and scintigrams with thallium-201 in cases of myocardial infarction to confirm the vectorcardiographic criteria of the present authors. The percentage of agreement between the VCG and scintigram was 82.5% and higher than the percentage of agreement between the VCG and the left ventriculogram. The percentage of disagreement between the negative finding in the VCG and the positive finding in the scintigram was 5.1% and consequently, a close relation was found between the VCG and scintigram. However, as the possibility of infarction was high in cases in which the scintigram finding was positive, the vectorcardiographic criteria in cases in which the VCG findings were negative were rechecked and partially corrected. Consequently the percentage of negative findings were decreased to 3.2%. Our next step was to perform the following prospective study which confirmed that the disagreement found in the corrected criteria (1.0%) was in fact less than what had been observed in the initial criteria (5.0%). Accordingly, it can be concluded that the corrected vectorcardiographic criteria in myocardial infarction may be the more reliable and useful in determining the location of the infarcted area.

Heart↗
PubMed1980

The isopotential mapping of the T wave in myocardial infarction.

The isopotential mapping of the T wave in myocardial infarction was studied to find the characteristic abnormality. The negative area on the mapping at the deepest point of the negative T wave was located on the left precordial region or on the left precordial and lateral regions in cases with anterior or anterolateral infarction. In some cases with anterolateral or inferior infarction and in cases with high posterior infarction, an extensive negative area was found on the left back region. In cases with inferior infarction, the negative area was situated on the lower area of the precordial region and/or back region. The ischemic area (the area of the abnormal repolarization) was determined by studying the relation of the zero line of the maps in normal subjects and cases with myocardial infarction. Finally, a comparison between the direction of the maximum T vector and the location of the ischemic area was made.

Electrocardiography↗
PubMed1980

Coliphage HK243: biological and physicochemical characteristics.

Coliphage HK243 can form plaques on Escherichia coli C and K-12, but not B. The plaques are 1-2 mm in diameter and are opaque areas which clear upon exposure to chloroform vapor. During one-step growth, the eclipse and the latent periods are 20 and 30 min, respectively. Phage-infected cells continue to produce cell-free plaque-forming units for as long as 80 min after the end of the latent period, although at high multiplicities of infection (MOI) most cells lyse. No lysogenic bacteria have been found among survivors, so HK243 is considered a virulent phage. Some of the cells surviving a high MOI challenge are maltose negative and resistant to both HK243 and coliphage lambda. This fact has made possible the isolation of lambda-resistant mutants of lambda-lysogens. However, no serological cross-reaction between the phages lambda and HK243 has been detected. Genetic data involving three essential loci and a locus controlling plaque morphology suggest a circular linkage map. The virions are tadpole-shaped with an icosahedral head 68 nm long which is attached to a flexible tail 131 nm long. The phage has a linear, duplex DNA genome of molecular weight approximately 44 x 10(6) and a base composition of 33% adenine, 31% thymine, 16% guanine, and 20% cytosine.

Coliphages↗