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Biomedical subjects

A Yamaguchi

Publications and source records attributed to A Yamaguchi.

At least 739 records · Page 41Linked to original sources
PubMed1985

Conversion of cloxacillin into a progressive inhibitor of beta-lactamases by sulfonation and its activity against various types of these enzymes.

On the assumption of the theory that the sulfone of a penam derivative should effectively act as a suicide substrate against beta-lactamases to which the parent compound is a poor substrate, the action of cloxacillin sulfone on four different types of beta-lactamases was studied. As we expected, cloxacillin sulfone showed strong mechanism-based irreversible inactivation against type Ib penicillinase and Proteus vulgaris cephalosporinase whereas it showed no progressive inactivation against cloxacillin-hydrolyzing type II penicillinase. However, an unexpected result was that cloxacillin sulfone could not inactivate Citrobacter freundii cephalosporinase which itself could hardly hydrolyze the parent cloxacillin. The number of hydrolytic events which occurred before inactivation of type Ib penicillinase, and P. vulgaris cephalosporinase, by the inactivator was 190 and 13, respectively. These values indicate that cloxacillin sulfone is far more effective as a suicide substrate against the two types of beta-lactamases than penam sulfones so far reported. The inactivation proceeded via the formation of an irreversible enzyme-inhibitor complex which could be detected by isoelectric focusing.

Cloxacillin↗
PubMed1985

[Phase II study of 5'-DFUR (5'-deoxy-5-fluorouridine) by the Cooperative Study Group].

Phase II study of 5'-DFUR was conducted in 195 patients with malignant tumors by the Osaka Chemotherapy Cooperative Study Group. Five CR and 20 PR cases were obtained out 133 evaluable cases and the total response rate was 18.8% (15.8% in gastric, 38.1% in breast) One PR was observed for each of head & neck and esophageal cancer. It was noteworthy that four CR were observed in breast cancer. Adverse reaction was observed in 61 out of 151 cases (40.4%), and major side effects were digestive symptoms such as diarrhea (22.5%), nausea-vomiting (11.9%) and anorexia (10.6%). These results suggest that 5'-DFUR can be useful for the treatment of malignant tumors.

Administration, Oral↗
PubMed1985

[A case of leiomyosarcoma of the rectum with widespread lymph node metastases].

A case of leiomyosarcoma of is reported. A 78-year-old man was admitted with a history of constipation and deformation of the stools. Barium contrast study and sigmoidoscopy showed a submucosal tumor of the rectum. On computed tomography and angiography, the tumor was suspected of being leiomyosarcoma. Abdominoperineal resection was performed. Microscopic examination revealed a leiomyosarcoma of the rectum and widespread lymph node metastases were found. Leiomyosarcoma of the rectum is an uncommon tumor. In our country, 89 cases have been reported. Six had lymph node metastases initially and another six subsequently. We have referred to the literature on leiomyosarcoma of the rectum.

Aged↗
PubMed1984

The effect of lipopolysaccharide on lipid bilayer permeability of beta-lactam antibiotics.

The lipid-bilayer permeability of cephalosporins was extensively suppressed by addition of lipopolysaccharide to liposomal membrane in proportion to the hydrophobicity of the drugs. This suggests that the polysaccharide chain layer contributes to the barrier function. The importance of the polysaccharide chain in the barrier function was also supported by the fact that the permeability to Rd-type lipopolysaccharide-containing liposomes showed essentially the same dependency on the hydrophobicity of the cephalosporins as that of the lipopolysaccharide-free liposomes. In this case the permeability of the cephalosporins was proportional to their hydrophobicity. Similar lipopolysaccharide effect was also observed in the permeation of penicillins.

Anti-Bacterial Agents↗
PubMed1984

Novel carbapenem derivative SF2103A: studies on the mode of beta-lactamase inactivation.

A novel carbapenem, SF2103A, is a strong inhibitor of various types of beta-lactamase. Equimolar concentrations of SF2103A completely inactivated the cephalosporinases of Proteus vulgaris and Citrobacter freundii and type Ib and type II penicillinases mediated by R plasmids in a progressive manner. The inactivation of the two penicillinases and P. vulgaris cephalosporinase was apparently irreversible; however, when the inactivated enzymes were separated from excess SF2103A by gel filtration, they showed very slow reactivation. The hydrolysis of SF2103A by these three beta-lactamases was below the limit of detection. It is concluded that SF2103A acts as a tight-binding competitive inhibitor for the penicillinases and P. vulgaris cephalosporinase. In contrast, the inactivation of C. freundii cephalosporinase by SF2103A was evidently reversible. The rate constant of reactivation of the enzyme was compatible with the turnover rate of the enzyme in the steady state of SF2103A hydrolysis. Thus, SF2103A simply acts as a poor substrate for C. freundii cephalosporinase.

Anti-Bacterial Agents↗