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Biomedical subjects

H Koga

Publications and source records attributed to H Koga.

At least 433 records · Page 24Linked to original sources
PubMed1982

Regional cerebral blood flow in patients with vertebrobasilar disease.

We have investigated the changes in regional cerebral blood flow (rCBF) in patients with occlusive vertebrobasilar disease. Fifty patients who showed severe stenosis or occlusion of the vertebrobasilar artery territory were studied by angiography. Lesions in 13 of these patients were limited to the vertebrobasilar artery (limited VB group), and 37 patients showed combined vertebrobasilar/carotid artery lesions (combined VB-C group). Measurements of rCBF in the group of 50 patients using the intravenous xenon 133 technique showed that there was a significant decrease in the mean rCBF (47.5 +/- 1.4 ml/100 gm/min) as compared with 19 age-matched normal subjects (54.9 +/- 1.8 ml/100 gm/min. There was also a significant difference in mean rCBF between the combined VB-C group (45.6 +/- 1.5 ml/100 gm/min) and a group of 153 patients with limited carotid artery lesions (C group, 49.8 +/- 1.0 ml/100 gm/min). However, no significant difference in mean rCBF was found between the limited VB group and normal subjects. There were no differences in rCBF when evaluated according to the presence or absence of angiographic collateral circulation via the posterior communicating artery (Pcom). Good correlation was found between mean rCBF and direction of collateral flow via the Pcom (p less than 0.05). The value of hemispheric rCBF of patients with carotid system transient ischemic attacks (TIAs) was significantly lower than that of patients with vertebrobasilar system TIAs (p less than 0.02). In cerebral autoregulation tests of 24 patients with occlusive vertebrobasilar disease (7 patients from the limited VB group and 17 patients from the combined VB-C group), 13 of these 24 patients (54%) showed an impairment of autoregulation.

Aged↗
PubMed1982

Structure of the lambda tof repressor protein in solution. Heat stability and its relation to binding ability to DNA.

The lambda tof repressor protein was purified from E. coli cells retaining lambda dv plasmids by applying DNA-cellulose chromatography. 3H-labeled lambda dv and lambda imm21dv DNA, carrying and lacking lambda operators, respectively, were prepared and the binding activity of the lambda tof protein to the DNA was examined. Non-specific binding to lambda imm21dv DNA is completely lost at 30 degrees C, whereas specific binding to the DNA carrying the operators is retained even above 40 degrees C. The conformation of the lambda tof protein was analysed by means of circular dichroism and 1H-NMR spectra. The change in the molar ellipticity at 222 nm vs. temperature in CD spectra indicated a transition between two states with Tm at 42 degrees C. The 360 MHz 1H-NMR spectra revealed the presence at 20 degrees C of another change in local conformation of interaction which was not detected by the CD spectra. 1H-NMR also indicated the coexistence of thermal transitions with exchange rates faster and slower than the NMR time scale at about 50 degrees C, which is explained by the presence of domain structures. The NMR titration curve of the His residue gave a normal pK value showing its location on the surface of the protein. These conformational behaviors are well correlated to the specific and non-specific DNA binding activity of the lambda tof protein. The assignments of 1H resonance signals to some specific residues, including His 35 and Tyr 26, were established. It will be useful to determine the tof-DNA interaction.

Bacterial Proteins↗
PubMed1982

Oxygen--insensitive nitrofuran reductases in Salmonella typhimurium TA100.

The present study demonstrated by DEAE-cellulose column chromatography that oxygen-insensitive nitrofuran reductases in Salmonella typhimurium TA100 consisted of at least two reductases, NADPH- and NAD(P)H-linked enzymes. The NADPH- and NADH-linked activities of the latter enzyme seemed to originate from a single enzyme, because both activities were similarly inactivated by heat and urea treatments, and also inhibited by dicumarol. On the other hand, the NADPH-linked enzyme was less sensitive to heat, urea and dicumarol. Furthermore, the study showed that the NAD(P)H-linked enzyme was a flavoenzyme which could be inactivated by dialysis against 1 M potassium bromide and reactivated by FMN.

Apoenzymes↗
PubMed1982

Superior and inferior vena cava flow velocity in patients with anomalous pulmonary vein connection.

The superior and inferior vena cava flow velocities (SVC and IVC flow velocities) of 3 patients with anomalous pulmonary vein connection were recorded with the Doppler flowmeter catheter. The cases consisted of a patient with partial anomalous pulmonary vein connection to the SVC (Case 1), one with total anomalous pulmonary venous connection to the SVC (Case 2), and one with partial anomalous pulmonary vein connection to the IVC (Case 3). The SVC and IVC recordings of these patients were compared with those of 10 normal subjects, 20 patients with atrial septal defect and 150 patients with other heart diseases. The SVC and IVC flow velocities in the latter group of 180 patients showed a biphasic pattern, having systolic (S) and diastolic (D) waves, the peak S wave occurring around midsystole. In Cases 1 and 2, the SVC flow velocity showed a markedly delayed peak S wave, similar to the pattern of the pulmonary vein flow velocity; this pattern was also seen in the IVC flow velocity in Case 3. This abnormal pattern could be useful in diagnosing anomalous pulmonary vein connection.

Adolescent↗
PubMed1981

Studies on oxygen-insensitive nitrofuran reductase in Escherichia coli B/r.

Oxygen-insensitive nitrofuran reductase in Escherichia coli B/r was clearly resolved by DEAE-cellulose column chromatography into two components, one NADPH-linked, and the other both NADPH- and NADH-linked. It is known that the strain requires resistance to nitrofurazone in two mutational steps. It is known that the the first step mutants had no NADPH-linked component and the second step ones had neither this component nor the NAD(P)-H-linked one. The NADPH- and NADH-linked activities of the latter component were similarly inactivated by heat or urea treatment. In addition, it was found that these activities were significantly inhibited by dicoumarol, an NAD(P)H dehydrogenase inhibitor, to similar extents. These results suggest that the activities of the NAD(P)H-linked component originate from a single enzyme. On the other hand, the NADPH-linked component was less sensitive to heat, urea and dicoumarol.

Cell-Free System↗
PubMed1980

The mutagenic activity of ethyl N-hydroxycarbamate and its related compounds in Salmonella typhimurium.

Alkyl N-hydroxycarbamates exhibited weak but significant mutagenic activity for Salmonella typhimurium TA100. The mutagenic potencies of these N-hydroxycarbamates were ranked thus: ethyl N-hydroxycarbamate greater than propyl N-hydroxycarbamate greater than methyl N-hydroxycarbamate. Acylation of ethyl N-hydroxycarbamate markedly enhanced its mutagenic activity for TA100. The highest mutagenic activity was observed with ethyl N-benzoyloxycarbamate among these acyl derivatives. Almost all the compounds were mutagenic to all the strains TA1535, TA100, TA98, especially to TA100.

Carbamates↗
PubMed1980

Structure-activity relationships of antibacterial 6,7- and 7,8-disubstituted 1-alkyl-1,4-dihydro-4-oxoquinoline-3-carboxylic acids.

Previous quantitative and qualitative structure-activity studies in antibacterial monosubstituted 1-ethyl-1,4-dihydro-4-oxoquinoline-3-carboxylic acids prompted us to synthesize the 6,7,8-polysubstituted compounds. In this paper, the preparation and antibacterial activity of the 6,7- and 7,8-disubstituted compounds and their derivatives are described. Among these compounds, 1-ethyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazinyl)quinoline-3-carboxylic acid (34) possessed many significant activities and was more active than oxolinic acid (84) against Gram-positive and Gram-negative bacteria. Structure-activity relationships are discussed.

Anti-Bacterial Agents↗
PubMed1980

Purification and characterization of hypoxanthine/guanine phosphoribosyltransferase in bovine snout epidermis.

Hypoxanthine/guanine phosphoribosyltransferase was purified from bovine snout epidermis, about 600-fold by a combination method of centrifugation, ammonium sulfate fraction, Sephadex G-200 and DEAE cellulose chromatography. Enzymatic properties of the purified enzyme were determined as follows: pH optimum 7.2, temperature optimum 56 degrees C, and 82,000 in molecular weight. In the presence of phosphoribosyl pyrophosphate, the enzyme was extremely heat-stable. The enzyme displayed Michaelis-Menten kinetics with apparent Michaelis constants for hypoxanthine, guanine and phosphoribosyl pyrophosphate of 1.59, 20.4 and 72.6 microM respectively.

Animals↗
PubMed1980

In vitro antibacterial activity of AM-715, a new nalidixic acid analog.

AM-715 [1-ethyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazinyl)-3-quinolinecarboxylic acid] is a new nalidixic acid analog. AM-715 has a broad spectrum of antibacterial activity against gram-positive and gram-negative bacteria. The antibacterial activity of AM-715 was greater than those of pipemidic acid and nalidixic acid. AM-715 had higher antibacterial activity against Pseudomonas aeruginosa than did gentamicin. Most nalidixic acid-resistant bacteria were susceptible to AM-715, and cross-resistance was not observed between AM-715 and various antibiotics. The minimal concentration of AM-715 required to inhibit the growth of 75% of the total number of clinical isolates was as follows: Escherichia coli, 0.04 mug/ml; Klebsiella pneumoniae, 0.1 mug/ml; Serratia marcescens, 0.88 mug/ml; Enterobacter spp., 0.076 mug/ml; Staphylococcus aureus, 1.10 mug/ml; P. aeruginosa, 0.38 mug/ml; and nalidixic acid-resistant strains of gram-negative bacteria, 0.62 mug/ml. AM-715 at minimal inhibitory concentrations or at slightly higher concentrations had bactericidal activity against various species of bacteria. The effect of inoculum sizes on minimal inhibitory concentrations and minimal bactericidal concentrations of AM-715 against gram-negative bacteria was smaller than on those of pipemidic acid and nalidixic acid. The dose-response curve of AM-715 indicated a steep gradient, and the 50% inhibited doses of AM-715 were 0.014 mug/ml against E. coli ML4707 and 0.21 mug/ml against P. aeruginosa NC-5.

Anti-Bacterial Agents↗