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Biomedical subjects

K Shimada

Publications and source records attributed to K Shimada.

At least 1,567 records · Page 87Linked to original sources
PubMed1977

Expression of a bacterial gene for guanine synthesis inserted into colicin E1 factor by an in vitro recombination.

Regulation of expression of a bacterial guaA gene inserted into colicin E1 DNA by an in vitro recombination was studied under various growth conditions. In Escherichia coli K-12 cells that carried this hybrid ColEl plasmid the level of guaA enzyme activity was not regulated by the concentration of guanine in the medium, but by the number of plasmid DNA copies. The optimal conditions for amplifying the guaA gene product by chloramphenicol treatment were determined. The level of guaA enzyme activity found under the optimal conditions was about 37 times that in extracts of wild-type E. coli cultured in guanine-free medium. The properties of the promoter for the guaA gene and applicability of this hybrid ColEl plasmid for amplification of various gene products were discussed.

Chloramphenicol↗
PubMed1977

Anaerobic bacteria in biliary disease in elderly patients.

Gallbladder bile from 52 elderly subjects who had undergone biliary tract surgery was examined for the presence of bacteria. Twelve patients had sterile bile, 18 specimens of bile yielded anaerobes as well as aerobes, and 22 yielded aerobic bacteria only. Escherichia coli was the most commonly isolated organism (30 strains). Bacteroides fragilis was the most frequently encountered anaerobic bacterium and was found in 15 patients. The Klebsiella-Enterobacter group was the second most commonly isolated group and B. fragilis was third. Clostridium perfringens was recovered in 10 specimens of bile. Anaerobic bacteria were recovered more frequently in patients with ductal obstruction. The relatively frequent isolation of anaerobes, especially of B. fragilis, in this study may be related to the anaerobic techniques used, to the age of the patients, and to the high incidence of pigment stones among the subjects.

Adult↗
PubMed1977

Studies on the surface structure of the intracytoplasmic membrane in the photosynthetic purple bacterium Chromatium vinosum by means of chemical modification.

By means of a chemical modification technique, the surface structure of the intracytoplasmic membrane (chromatophores) of the photosynthetic bacterium Chromatium vinosum was investigated. Trinitrobenzenesulfonate was employed to modify the primary amino groups of phosphatidylethanolamine and proteins. The experimental results indicate that upon the chemical modification of intact cells, the amino groups on the inner surface of the chromatophores are trinitrophenylated, while upon the modification of isolated chromatophores, the amino groups of the outer surface are trinitrophenylated. Phosphatidylethanolamine is essentially equally distributed on the inner and outer surfaces of the chromatophores, while most proteins exist at the outer surface. In particular, a protein fraction, which is soluble in a mixture of chloroform/methanol, is located at the outer surface exposing a part of the amino groups in the aqueous phase.

Bacterial Chromatophores↗
PubMed1977

Secondary promoter of the guanine operon of Escherichia coli K-12.

Evidence of a secondary promoter for the guaA gene within the guaB gene was obtained by using lambdapguaA transducing phage. The technique is generally applicable to distinguish a promoter present within a bacterial deoxyribonucleic acid segment, which has replaced the lambda b2 region of transducing phage, from the phage pI promoter.

Chromosome Mapping↗
PubMed1977

Isolation of specialized lambda transducing bacteriophages for flagellar genes (fla) of Escherichia coli K-12.

Specialized transducing lambda phages carrying the region III flagellar genes (fla) of Escherichia coli K-12 were isolated by a new method. A strain carrying both a cryptic lambda prophage near the his genes and a deletion of the attlambda gene was used as a starting strain. The lysogen of lambdacI857pga18-bio69 was isolated in which the prophage was integrated within the lambda cryptic genes by means of recombination with the residual lambda DNA. The strains with deletions starting within the prophage and ending in these fla genes were selected from among the heat-resistant survivors of the lysogen. They were then infected with heat-inducible and lysis-defective lambda phages and, thus, specialized transducing phage lines for hag and fla were obtained. High-frequency transfer lines of rare phages carrying the fla genes were isolated by inducing a strain carrying a heat-inducible lambda prophage near the his genes and selecting by transduction of a fla deletion strain. Preliminary characterization of these transducing phages is also reported.

Chromosome Mapping↗