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Biomedical subjects

Y Nitta

Publications and source records attributed to Y Nitta.

At least 145 records · Page 8Linked to original sources
PubMed1986

[Computerized single probe system using a cadmium telluride detector].

Using cadmium telluride (CdTe) as a detector, we assembled a computerized single probe system. The size of the CdTe used is 16 mm in diameter and 2 mm in thickness. Two types of the straight bore collimators of 16 mm in diameter were prepared. One is 16 mm in length (long type) and the other is 5 mm in length (short type). The response curves of the long and short type collimators to 57Co in water showed that the points at 10% of maximum counts were 4 cm and 3 cm in depth along the center axis. The data were accumulated by using a commercialized single cardiac probe system (OMNISCOPE) and processed by itself or transferred to the microcomputer (LSI-11/23) for further analysis. Twenty percent count loss occurred at 100 000 cps with an integral discriminator setting. This system was applied for cerebrospinal fluid (CSF) shunt flow evaluation and measurement of left ventricular ejection fraction (LVEF). Measurement of CSF shunt flow has been able to do in any patient's positioning. In 21 patients with various heart diseases, LVEFs obtained by CdTe detector were compared with those obtained by scintillation detector. There was good correlation between the LVEFs obtained by these two detectors: correlation coefficient (r)=0.939.

Cadmium↗
PubMed1983

Difference spectroscopic study of the interaction between soybean beta-amylase and substrate or substrate analogues.

1. In order to investigate the interactions between soybean beta-amylase [EC 3.2.1.2] and ligands (maltotriose as substrate, and maltose and alpha- and beta-cyclodextrins as inhibitors for the hydrolysis of maltoheptaose), the difference spectra were measured at 25 degrees C and pH 5.4, in 0.05 M acetate buffer. Each difference spectrum produced by these ligands showed a clear peak at 292-293 nm due to a tryptophan residue. In addition to this peak, the spectra of alpha- and beta-cyclodextrins showed a specific peak at 298-299 nm, and that of maltotriose showed a shoulder at 298 nm. 2. From the concentration dependency of the difference molar extinction delta epsilon, at 292-293 nm or at 298-299 nm, the dissociation constant of the enzyme-ligand complex, Kd, was evaluated for maltotriose, and alpha- and beta-cyclodextrins. For each ligand, the Kd values obtained at these two wavelengths were in good agreement with Michaelis constant, Km, or the inhibitor constant, Ki. The Kd value for maltose obtained from the titration of delta epsilon at 292 nm was also in good agreement with Ki. 3. Maltose produced a hydrophobic change in the environment of the tryptophan residue, while the interactions of maltotriose, and alpha- and beta-cyclodextrins with this enzyme caused an electrostatic change in the vicinity of the tryptophan residue in addition to the hydrophobic change. Since the signal at 298-299 nm was not found in the difference spectrum of maltose, this signal may be due to a tryptophan residue different from that which produces the signal at 292-293 nm. If both the signals are due to the same tryptophan residue, we must conclude that some conformational change is caused in the enzyme active site by the ligand binding.

Amylases↗
PubMed1983

[Double-blind comparative clinical evaluation of cefamandole and cefmetazole in the treatment of respiratory tract infections].

Cefamandole sodium (CMD), a new cephalosporin-derivative, was synthesized in the Laboratory of Eli-Lilly Co. Ltd. U.S.A. in 1972. CMD, which is several times more active than cefmetazole (CMZ, a cephamycin antibiotic) against Gram-positive cocci, is only as active as the latter antibiotic against Gram-negative bacilli. Against Haemophilus influenzae, CMD exhibits an antimicrobial activity which is as strong as that of ampicillin sodium. Our previous comparative tests on efficacy and safety of CMD versus cefazolin (CEZ) demonstrated that CMD was as effective and safe as CEZ in the treatment of respiratory tract infections. In the present clinical trial, the efficacy and safety of CMD are evaluated by a comparative double blind method using CMZ, a more recently synthesized cephamycin antibiotic, as a reference drug. For this purpose, a comparative double blind study was carried out in 50 institutions and clinics in Tohoku and Hokkaido districts in Japan. A total of 272 inpatients, who was aged over 16 years and was diagnosed as having pneumonia, lung abscess or acute infectious exacerbation of chronic obstructive pulmonary diseases, was included in this trial. They received 2 g of CMD or CMZ twice a day by intravenous drip infusions, as a rule, for 14 days. Of these patients, 264 (133 received CMD and 131 CMZ) were available for the evaluation of safety and usefulness. Two hundred and thirty-eight patients (122 received CMD and 116 CMZ) were adopted for the evaluation of efficacy. Prior to the treatment, there was no significant difference with respect to age, sex, severity of infection and underlying diseases between subjects in 2 treatment groups. An excellent or good clinical response was obtained in 82% of the patients treated with CMD, and in 81% of those treated with CMZ. Thus, there was no significant difference in cure rate between 2 treatment groups. However, an excellent clinical response was found in 12.3% of the patients treated with CMD, whereas only in 4.3% of those treated with CMZ. This difference in percentage of excellent clinical response between 2 treatment groups was statistically significant (P less than 0.05). Of the 87 patients with moderate to severe infection who were treated with CMD, 13 showed an excellent response. Only 4 of 90 patients treated with CMZ showed an excellent response. Statistically the difference in the rate of excellent response between these 2 groups was significant (P less than 0.05).(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1982

Kinetic study on chemical modification of taka-amylase A. I. Location and role of tryptophan residues.

1. Five and four tryptophan residues in Taka-amylase A [EC 3.2.1.1] of A. oryzae (TAA) were modified with dimethyl(2-hydroxy-5-nitrobenzyl)-sulfonium bromide (K-IWS) in the absence and the presence of 15% maltose (substrate analog), respectively. Only one tryptophan residue was modified with dimethyl(2-methoxy-5-nitrobenzyl)-sulfonium bromide (K-IIWS) irrespective of the presence or absence of maltose. Kinetic parameters (molecular activity, k0, Michaelis constant, Km, and inhibitor constant, Ki) of the enzyme modified with K-IWS and K-IIWS were determined. The k0 value decreased with increase in the number of modified residues, but Km and Ki values and the type of inhibition were not altered by the modification. 2. The fluorescence quenching reaction of TAA with N-bromosuccinimide (NBS) proceeded in three phases. The second-order rate constants of the three phases were determined to be (4.3 +/- 0.5) x 10(5) M-1 . s-1, (2.1 +/- 0.3) x 10(3) M-1 . s-1 and (1.7 +/- 0.2) x 10(2) M-1 . s-1, respectively. In the presence of maltose, the first phase was further separated into two phases with rate constants of (4.6 +/- 0.6) x 10(6) M-1 . s-1 and (6.9 +/- 1.1) x 10(4) M-1 . s-1, respectively. On the basis of the results, it is estimated that five out of nine tryptophan residues are accessible to the solvent and among them, two tryptophan residues are substantially exposed: one is located in the maltose binding site near the catalytic site (its modification affects the catalytic function), and the other exists on the enzyme surface far from the active site.

Amylases↗
PubMed1982

Kinetic study on chemical modification of Taka-amylase A. II. Ethoxycarbonylation of histidine residues.

The modification of Taka-amylase A (TAA) [EC 3.2.1.1] of Aspergillus oryzae by diethylpyrocarbonate (DEP) was carried out at 25 degrees C and at pH 5.8 (0.1 M acetate buffer). Two out of the six histidine residues were modified with 4.6 mM DEP, and two or three histidine residues were modified with 23 mM DEP. In both cases, one of them was protected from modification by the presence of 15% maltose. The results suggest that two or three out of the six histidine residues are exposed on the surface of the TAA molecule, and one of them exists near the maltose binding site. Ethoxycarbonylation of histidine residues of TAA caused loss of the amylase activity and activation of the hydrolysis of phenyl alpha-maltoside (phi alpha M). The kinetic parameters of the modified TAA for several substrates and analogs were determined at 25 degrees C and at pH 5.3 (0.08 M acetate buffer). From the results, it was found that this alteration of the enzyme activity by the modification was not due to a change in Km value but to a change in k0 value. Thus, some of the histidine residues in TAA are suggested to play an important role in the enzyme catalytic function.

Amylases↗
PubMed1979

Kinetic study of soybean beta-amylase. The effect of pH.

1) Beta-Amylase [EC 3.2.1.2] was prepared from defatted hawk eye soybean flour. The enzyme concentration dependence of the initial velocity for the hydrolytic reaction was investigated at pH 5.4 in the range of the enzyme concentration from 6.6 x 10(-10) M to 5.0 x 10(-6) M. It was found that the initial velocity was proportional to the enzyme concentration in this range. 2) The hydrolyses of maltodextrin (DPn = 74.4) and soluble starch catalyzed by soybean beta-amylase were investigated in the pH range from 3.0 to 9.1 at 25 degrees C, and the Michaelis constant, Km, and the maximum velocity, V, for each substrate were determined at each pH. The pH-rate profile showed a bell-shaped curve, and the pH "optimum" was at 5.85. From Dixon plots of V and V/Km, the pK values were found to be 3.5 and 8.2 for the free enzyme, and 3.5 and 8.5 for the enzyme-substrate complex. The pH-rate profile in the presence of 25% methanol (v/v) was also obtained at alkaline pH. The pKe values were the same as those in the absence of methanol. Based on these results, it was estimated that the ionizable acidic group was an amino group and the basic group was a carboxyl one.

Amylases↗