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Biomedical subjects

S Mitsuhashi

Publications and source records attributed to S Mitsuhashi.

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

International experiences with ofloxacin, a new quinolone.

In vitro and in vivo antibacterial activities of ofloxacin, a new quinolone, are presented. Ofloxacin was found to be characterized by potent bactericidal activity due to its strong inhibition of bacterial DNA gyrase. The high antibacterial activity of ofloxacin in vivo was discussed with respect to its physiochemical properties, i.e., hydrophobicity and bioavailability including high serum concentrations and easy entry into bacterial cells.

Anti-Bacterial Agents↗
PubMed1986

Antibacterial activity of ofloxacin and its mode of action.

The antibacterial activity of ofloxacin against Enterobacteriaceae, Pseudomonas aeruginosa, Haemophilus influenzae, Branhamella catarrhalis, and Neisseria gonorrhoeae was comparable to norfloxacin and enoxacin, and far exceeded the activity of pipemidic acid and nalidixic acid. The activity of ofloxacin was two to eight times less than that of ciprofloxacin. Ofloxacin was more active against Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pneumoniae, Acinetobacter spp., Legionella spp., and Bacteroides fragilis, than norfloxacin, enoxacin, pipemidic acid and nalidixic acid, and the activity of ofloxacin was comparable to that of ciprofloxacin. Ofloxacin was two to seven times more effective than norfloxacin in systemic infections in mice with S. aureus, Escherichia coli, Serratia marcescens and P. aeruginosa. Ofloxacin strongly inhibited DNA supercoiling activity of DNA gyrase purified from E. coli KL-16. There is a parallel relationship between antibacterial activity of ofloxacin and its inhibitory action against DNA gyrases from ofloxacin-susceptible and ofloxacin-resistant clinical isolates of E. coli. These results indicate that the high bactericidal action of ofloxacin and the related new quinolone agents can be explained by their potent inhibitory activities against DNA gyrase in bacterial cells.

Animals↗
PubMed1986

In-vitro antibacterial activity of BO-1165, a new monobactam antibiotic.

BO-1165 has excellent antibacterial activity against Gram-negative bacteria but it is almost inactive against Gram-positive and anaerobic bacteria. BO-1165 was more active than the four reference drugs against Escherichia coli, Salmonella spp., Shigella spp., Klebsiella pneumoniae, Serratia marcescens, indole-positive and indole-negative Proteus. Also, BO-1165 exhibited high antibacterial activity against strains of Pseudomonas aeruginosa (MIC50, 3.12 mg/l) and P. cepacia (MIC50, 1.56 mg/l), but did not against Ps. maltophilia strains. BO-1165 had good stability to plasmid-mediated and chromosome-mediated beta-lactamases. However, the compound was slightly hydrolyzed by the beta-lactamases isolated from Proteus vulgaris, Ps. cepacia, Klebsiella oxytoca and Ps. maltophilia, which were capable of hydrolyzing aztreonam.

Aztreonam↗
PubMed1986

In-vitro antibacterial activity of L-105, a new cephalosporin.

L-105 (sodium(-)-(6R, 7R)-7-[(Z)-2-(2-amino-4-thiazolyl)-2-methoxyimino- acetamido]-3-[1,2,3-thiadiazol-5-yl)thiomethyl]-8-oxo-5-thia-1-aza bicyclo [4.2.0]oct-2-ene-2-carboxylate) is a new semisynthetic cephalosporin derivative. The in-vitro antibacterial activity of L-105 against clinical isolates of 18 bacterial species was compared with those of cefmenoxime, cefoperazone and cefazolin. Its spectrum against Gram-negative bacteria was similar to that of cefmenoxime. Moreover, against Gram-positive bacteria, including Staphylococcus aureus, coagulase negative staphylococci, Streptococcus faecalis, Str. pneumoniae and Str. pyogenes, L-105 was more potent than cefmenoxime and cefoperazone. Against Gram-positive bacteria, including Staph. aureus which is comparatively resistant to most third-generation cephalosporins, it was nearly equal in potency to cefazolin. L-105 was stable to various penicillinases and cephalosporinases. However, this compound was slightly hydrolyzed by oxyiminocephalosporinases, i.e., the enzymes produced by Pseudomonas cepacia and Ps. maltophilia.

Cefazolin↗
PubMed1986

Differences in susceptibility to quinolones of outer membrane mutants of Salmonella typhimurium and Escherichia coli.

The mechanism of penetration of quinolones through the bacterial outer membrane was studied with lipopolysaccharide-deficient and porin-deficient mutants. The data indicated that the lipopolysaccharide layer might form a permeability barrier for hydrophobic quinolones such as nalidixic acid but not for hydrophilic quinolones such as norfloxacin and ciprofloxacin. The results also showed that quinolones with a low relative hydrophobicity appeared to permeate through OmpF porin, whereas quinolones with a low relative hydrophobicity appeared to permeate through OmpF porin, whereas quinolones with a high relative hydrophobicity appeared to permeate through both OmpF porin and phospholipid bilayers.

Cell Membrane↗
PubMed1986

Purification and properties of a beta-lactamase produced by Branhamella catarrhalis.

A beta-lactamase from Branhamella catarrhalis was purified by column chromatography. The purified enzyme hydrolyzed penicillins, such as ampicillin, carbenicillin, and piperacillin, more rapidly than cephalosporins. Furthermore, the enzyme hydrolyzed cefotaxime and cefmenoxime. The molecular weight of the enzyme was 33,000. The pI was 5.4.

Anti-Bacterial Agents↗
PubMed1986

Biochemical properties of beta-lactamase produced by Legionella gormanii.

beta-Lactamase was purified from a strain of Legionella gormanii. The molecular weight of the purified enzyme was 25,000, and its isoelectric point was 10.5. The enzyme hydrolyzed oxyiminocephalosporins, cephamycins, penicillins, and imipenem. The enzyme activity was inhibited by EDTA, Hg2+, and Cu2+, but not by clavulanic acid, sulbactam, or imipenem.

Anti-Bacterial Agents↗
PubMed1986

Isolation and characterization of norfloxacin-resistant mutants of Escherichia coli K-12.

We isolated spontaneous mutants from Escherichia coli K-12 with low-level resistance to norfloxacin. These mutants were classified into the following three types on the basis of their properties: (i) NorA appeared to result for mutation in the gyrA locus for the A subunit of DNA gyrase; (ii) NorB showed low-level resistance to quinolones and other antimicrobial agents (e.g., cefoxitin, chloramphenicol, and tetracycline), and the norB gene was considered to map at about 34 min on the E. coli K-12 chromosome; (iii) NorC was less susceptible to norfloxacin and ciprofloxacin but was hypersusceptible to hydrophobic quinolones such as nalidixic acid and rosoxacin, hydrophobic antibiotics, dyes, and detergents. Susceptibility to bacteriophages and the hydrophobicity of the NorC cell surface also differed from that of the parent strain. The norC gene was located near the lac locus at 8 min on the E. coli K-12 chromosome. Both NorB and NorC mutants had a lower rate of norfloxacin uptake, and it was found that the NorB mutant was altered in OmpF porin and that the NorC mutant was altered in both OmpF porin and apparently in the lipopolysaccharide structure of the outer membrane.

Bacterial Outer Membrane Proteins↗
PubMed1986

Familial pheochromocytoma in a child with multiple recurrence including a lesion in the intrathoracic region.

Familial pheochromocytomas were removed from the bilateral adrenal glands and the abdominal cavity of a 10-year-old female. Due to the existence of an accessory adrenal gland, it was possible to discontinue steroid supplement. The disease relapsed, however, when she was 15 years old. After removing the ectopic pheochromocytomas from the abdominal cavity and thorax, she was free from symptoms for 2 years and 6 months.

Adrenal Gland Neoplasms↗
PubMed1986

Effects of an LHRH agonist on endocrine function, LHRH receptor and LH/hCG receptor in the pituitary-gonadal axis of male rats.

The effects of an LHRH agonist (LHRHa), [D-Ser (tBu)]6 des-Gly-NH210) ethylamide, on endocrine function and the LHRH and LH/hCG receptors in the pituitary-gonadal axis were examined. The LHRHa was injected at 100 ng/100 g body weight into male rats once a day for 4 weeks and its effects were observed until 2 weeks after the end of treatment. Due to LHRHa treatment, the plasma LH concentration began to increase on day 3, reached a peak on day 7, and then decreased, although it remained above the control level during the treatment. The pituitary LH content decreased on day 1, reached a minimum (about 40% of the control) between days 3 and 7, and then was maintained at 60% of the control level until week 4. In contrast, the pituitary LHRH receptor concentration increased only on day 3, and the association constant (Ka) remained unchanged during the observation period. The testis weight and plasma testosterone concentration began to decrease on day 3, reached the minimum on day 7 and remained at this level until week 4, and their levels were not completely restored to normal 2 weeks after cessation of treatment. The testicular LH/hCG receptor concentration was decreased on day 1, and markedly decreased to 10-15% of the control value between day 7 and week 4, but the Ka value was slightly increased during the treatment. However, these values had completely recovered 2 weeks after the cessation of treatment. The testicular LHRH receptor concentration increased between days 1 and 7, returned to the control level in weeks 2 and 4, and then decreased 2 weeks after cessation of treatment. Its Ka value was reduced in weeks 2 and 4. These data suggest that the inhibitory effect of LHRHa on the gonad in male rats is not due to reduced pituitary LH release, but to changes in the number and Ka values of gonadal receptors for LH/hCG and LHRH.

Animals↗
PubMed1986

Antibacterial activity and ototoxicity in guinea pigs, and nephrotoxicity in rats of arbekacin.

Arbekacin (HBK), 1-N[(S)-4-amino-2-hydroxybutyl]-3',4'-dideoxykanamycin B, showed broad antibacterial spectra against gram-positive and gram-negative bacteria including Pseudomonas aeruginosa. It was also effective against gentamycin- or tobramycin-resistant bacteria. HBK was resistant to various aminoglycoside-inactivating enzymes except for AAC (2') and AAC (6')-IV, both of which slowly inactivated it. Even at higher dosages (150 mg/kg i.m. or greater, which resulted in some deaths), HBK never decreased the pinna reflex in guinea pigs, while 150 mg/kg or more of dibekacin (DKB) or amikacin (AMK) caused loss of this reflex. HBK has less ototoxicity than do DKB and AMK. This was confirmed by histopathological examination of the inner ear. The degree of nephrotoxicity of HBK was suggested to be similar to that of DKB as judged from serum biochemical tests, urinalysis, and histopathological findings.

Amikacin↗
PubMed1985

Synergistic anti-suppressor effect of mini cells prepared from Salmonella typhimurium and mitomycin C in EL 4-bearing mice.

The subcutaneous growth of EL4 cells was significantly accelerated when they were injected together with spleen cells collected from mice which had received EL4 cells SC 14 days previously, and all mice died within 18 days after receiving this mixture; 80% of mice which received a mixture of EL4 and spleen cells collected immediately after EL4 graft survived over 40 days. Spleen cells collected 14 days after EL4 graft suppressed the blastogenic responses of normal spleen lymphocytes to concanavalin A, pokeweed mitogen, and lipopolysaccharide of Escherichia coli in a mixed culture system. Acceleration of tumor growth was retarded when EL4 cells were injected together with spleen cells from EL4-bearing mice treated with both Salmonella typhimurium mini-cells and mitomycin C, and 60% of mice survived over 40 days. Blastogenic responses of normal spleen lymphocytes mixed with spleen cells from EL4-bearing mice treated with both mini-cells and mitomycin C were restored almost to control levels. The results suggest that combination treatment with mini-cells and mitomycin C synergistically inhibits the induction of suppressor cells in EL4-bearing mice.

Animals↗
PubMed1985

Purification and properties of a beta-lactamase from Alcaligenes dentrificans subsp. xylosoxydans.

A penicillin beta-lactamase was purified from a strain of Alcaligenes dentrificans subsp. xylosoxydans resistant to beta-lactam antibiotics. The purified enzyme preparation gave a single protein band on polyacrylamide gel electrophoresis, and its molecular weight was 18,000 from sodium dodecylsulphate-acrylamide gel electrophoresis and gel filtration. Its isoelectric point was 9.8, the optimal pH was 8.5 and the optimal temperature was 35 degrees C. The enzyme hydrolyzed penicillin G and ampicillin more rapidly than cephalosporins. Relative rates, with penicillin G as 100, were: ampicillin, 102; carbenicillin, 15; cloxacillin, less than 1; piperacillin, 9; cephaloridine, 41; cefoperazone, 36; cefpiramide, 36 and cefmenoxime, 14. Clavulanic acid, sulbactam, imipenem, and cephamycins had low affinities for the enzyme. The enzyme activity was inhibited by iodine, Hg2+, clavulanic acid and sulbactam.

Alcaligenes↗
PubMed1985

In-vitro antibacterial activity of AMA-1080.

The in-vitro antibacterial activity of AMA-1080 against both Gram-positive and Gram-negative clinical isolates was studied in comparison with that of aztreonam, cefotaxime, ceftazidime and cefoperazone. AMA-1080 showed a potent antibacterial activity against Gram-negative bacteria, particularly, the strains of Enterobacteriaceae. In addition, AMA-1080 inhibited the strains of genus Pseudomonas at the low concentrations. However, AMA-1080 showed less active against Gram-positive bacteria. It was found that AMA-1080 was highly resistant to hydrolysis by both chromosomal and plasmid-mediated beta-lactamases.

Anti-Bacterial Agents↗
PubMed1985

Purine metabolic enzymes in lymphocytes. IV. Effects of enzyme inhibitors and enzyme substrates on the blastogenic responses of human lymphocytes.

Coformycin, which is an inhibitor of adenosine deaminase, significantly inhibited in vitro blastogenic responses of human lymphocytes to both phytohaemagglutinin (PHA) and pokeweed mitogen (PWM), whereas blastogenic responses to bacterial lipopolysaccharide (LPS) were rather enhanced by the addition of coformycin. Blastogenic responses of lymphocytes to PHA and PWM were markedly suppressed by the addition of adenosine, which is a substrate of adenosine deaminase. Allopurinol, which is an inhibitor of xanthine oxidase, inhibited blastogenic responses of human lymphocytes to PHA, PWM, and bacterial LPS. Inosine (a substrate of purine nucleoside phosphorylase) and hypoxanthine (a substrate of xanthine oxidase) showed no or only a small effect on blastogenic responses of human lymphocytes. These results suggest that adenosine deaminase activity is associated with the T-cell response but not with the B-cell response and that the impaired T-cell response in adenosine deaminase deficiency is the result of intracellular retention of adenosine in T cells. The results also suggest that purine nucleoside phosphorylase or xanthine oxidase activity is associated with both T- and B-cell responses.

Adenosine↗