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Biomedical subjects

K Asada

Publications and source records attributed to K Asada.

At least 199 records · Page 11Linked to original sources
PubMed1981

[Two-dimensional echocardiography in preoperative evaluation of mitral stenosis (author's transl)].

Two-dimensional echocardiograms were correlated with the operative findings and surgical procedures in 46 patients with mitral stenosis. In addition, a new projection evaluating subvalvular lesion more precisely was reported. Two-dimensional echocardiographic findings studied were 1) pathology of the two leaflets of the mitral valve, 2) valve area, and 3) subvalvular lesion. The findings of leaflets and valve area were well correlated with the operative findings. But there were six cases with discrepancies in the initial 22 cases about the findings of subvalvular lesion; there were 5 false negative and one false positive case. It was considered that insufficient information about the appositional zone of the mitral valve and chordae tendineae made it difficult to evaluate them correctly. We have designed a new projection for delineating the subvalvular apparatus and employed in the next 24 cases, and the transducer was placed near the apical heart to visualize 4 chambers. This eliminated greatly the false positive cases (only 2 out of 24 cases). There were three cases of mitral valve replacement (MVR) in the initial 22 cases, but we could expect the necessity of MVR in only one case, and we had to perform chordotomy, papillotomy, or debridement as well as commissurotomy in two false positive cases. In the next 24 cases, however, we could predict it in all three cases of MVR before the operation. It was valuable for surgery of mitral stenosis to get enough information about the subvalvular lesion as well as mitral leaflets by two-dimensional echocardiography.

Adult↗
PubMed1978

Isolation of monomeric cytochrome f from Japanese radish and a mechanism of autoreduction.

Monomeric cytochrome f from Japanese radish (Raphanus sativus L. var acanthiformis Makino) leaves was isolated in a homogeneous state with an A420.5/A277 of 7.6. Radish cytochrome f is a single polypeptide chain with a molecular weight of about 33,000. The midpoint potential is 350 mV. The amino acid analysis indicates the existence of 3 residues of half-cystine. Radish cytochrome f contains one thiol group which reacts with 5,5'-dithiobis(2-nitrobenzoic acid) only after denaturation by sodium dodecyl sulfate. Ferricytochrome f is reduced by the superoxide radical at the rate of 6 X 10(6) M-1 s-1 at pH 7.8. Radish ferricytochrome f is also reduced slowly without an exogenous electron donor. A kinetic study and the effect of the thiol reagent indicate that the autoreduction is an intramolecular reaction and that the thiol group is an electron donor.

Amino Acids↗
PubMed1976

A new oxygenase, 2-nitropropane dioxygenase of Hansenula mrakii. Enzymologic and spectrophotometric properties.

2-Nitropropane dioxygenase, purified to homogeneity from Hansenula mrakii (IFO 0895), has a molecular weight of approximately 62,000 and consists of two subunits nonidentical in molecular weight (39,000 and 25,000). Stoichiometrical studies and the results obtained with 18O2 showed that 2 atoms of molecular oxygen are incorporated into 2 molecules of acetone formed from 2-nitropropane. In addition to 2-nitropropane, nitroethane, 3-nitro-2-pentanol, and 1-nitropropane are oxidatively dentrified. The enzyme, which exhibits absorption maxima at 274, 370, 415, and 440 nm and a shoulder at 470 nm, contains 1 mol of FAD and 1 g atom of non-heme iron per mol of enzyme. The enzyme-bound FAD is reduced by 2-nitropropane under anaerogic conditions, but the enzyme-bound Fe3+ is not affected. The introduction of oxygen to the reduced form of enzyme causes reoxidation of the enzyme. The bound FAD and Fe3+ are reduced by the addition of nitromethane, which is not a substrate, under anaerobic conditions. The aerobic dialysis of the enzyme treated with nitromethane causes reoxidation of only the Fe2+. Sodium dithionite also reduces both the enzyme-bound FAD and Fe3+ under anaerobic conditions. When the enzyme is dialyzed against 10 mM potassium phosphate buffer (pH 7.0) immediately after reduction by dithionite, the absorption spectrum similar to that of the native enzyme appeared with concomitant restoration of approximately 80% of the activity. The enzyme activity is significantly inhibited by pyrocatechol-3,5-disulfonate disodium salt, 8-hydroxyquinoline, reducing agents such as 2-mercaptoethanol, and HgCl2. The Michaelis constants are as follows: 2-nitropropane (2.13 X 10(-2) M), nitroethane (2.43 X 10(-2) M), 3-nitro-2-pentanol (6.8 X 10(-3) M), 1-nitropropane (2.56 X 10(-2) M), and oxygen (3.03 X 10(-4) M, with 2-nitropropane).

Amino Acids↗
PubMed1976

Removal of Mn from spinach chloroplasts by sodium cyanide and the binding of Mn2+ to Mn-depleted chloroplasts.

Manganese and copper were released from spinach chloroplasts by NaCN-treatment, though iron was not affected. The Hill reaction activity was also inhibited by this treatment, but was partially recovered by the addition of either Mn2+ or Cu2+, but not of Fe3+. The interaction of Mn2+ with manganese-depleted chloroplasts by NaCN-treatment was studied using 54Mn2+. A Scatchard plot shows the high and low affinity binding sites of Mn2+ on NaCN-treated chloroplast membrane; high affinity binding being specific for NaCN-treated chloroplast with a binding constant, KH, of 1.9 X 10(5) M-1, and a maximum binding number, NH, of 0.0016 g-atom per mole of chlorophyll. The low binding site was also found on untreated chloroplasts; its binding constant, KL, being 1.2 X 10(4) M-1, and its maximum binding number, NL, of 0.0112 g-atom per mole oc chlorophyll at pH 8.2 NH was proportional to the degree of the removal of Mn by NaCN-treatment and was constant at pH 4--9. NL markedly increased at a high pH with a midpoint of pH 7.9 indicating the exposure of a new, similar binding site. Light illumination partially inhibited the binding of Mn2+. Within 1 min in the dark the binding reaction reached equilibrium in the absence of pyrophosphate, however, 20 min were required to transform into pyrophosphate-resistant form. The pH dependence of the binding of Mn2+ with pKa 7.2 and the ineffectiveness of p-chloromercuribenzoate suggest the possible ligand of Mn2+ is the imidazole nitrogen of the histidine residue.

2,6-Dichloroindophenol↗