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Biomedical subjects

Y Ota

Publications and source records attributed to Y Ota.

At least 199 records · Page 11Linked to original sources
PubMed1981

Constriction of the fetal ductus arteriosus by glucocorticoid hormones.

Hydrocortisone, prednisolone, and betamethasone were injected into a rat that was 21 days pregnant, and the fetal ductus arteriosus was studied using the rapid whole-body freezing technique. All these glucocorticoids constricted the fetal ductus arteriosus in a dose-dependent relationship. Fetal ductal constriction was maximum 1 to 4 hr after injection and was significantly more prominent in premature fetuses than in mature ones.

Animals↗
PubMed1980

Dilatation of the ductus arteriosus by prostaglandins and prostaglandin's precursors.

We studied the effects of prostaglandins and their precursors in animal models. Rabbit ductus arteriosus constricted rapidly after delivery. PGE1, and PGE2, and arachidonic acid injected SC dilated the ductus over 60 min. Orogastrically administered PGE2 dilated the ductus for 3 hr. PGF2a and arachidonic acid showed weak ductus-dilating effects. Response of the ductus to PGE1 was most prominent in the first hr after birth. Pretreatment with indomethacin blocked the ductus-dilating effect of arachidonic acid.

Age Factors↗
PubMed1979

Gene expression of an Escherichia coli ribosomal RNA promoter fused to structural genes of the galactose operon.

The promoter region of the rrnB ribosomal RNA gene of Escherichia coli has been ligated within the epimerase gene (galE) of the galactose operon in a lambda phage vector. The recombinant lambda phage has been characterized by restriction mapping and assays of both galK (galactokinase) gene activity and galactose messenger RNA hybridization. In such lyosgens, expression of the fused galactose operon occurs as a function of growth rate in a manner characteristic of ribosomal RNA gene expression and is subject to stringent control by amino acid availability for protein synthesis. Galactose messenger RNA arising from the ribosomal promoter is not as metabolically stable as ribosomal RNA.

Bacteriophage lambda↗
PubMed1978

Studies on polypeptide-chain-elongation factors from an extreme thermophile, Thermus thermophilus HB8. 1. Purification and some properties of the purified factors.

Polypeptide chain elongation factors have been purified from an extreme thermophile, Thermus thermophilus HB8. By chromatography on a DEAE-Sephadex column, the factors were separated into two peaks; peak I contained a complex of EF-Tu and EF-Ts, while peak II was composed of EF-Tu.gdp and EF-G. These factors were subsequently purified to homogeneous states and crystallized. The EF-Tu . EF-Ts complex could be resolved into EF-Tu and EF-Ts by chromatography on a Sephadex G-200 column in the presence of 8 M guanidine-HCl. The complex could be reconstituted from EF-Tu and the renatured EF-Ts. No immunological cross-reaction was detected between EF-Tu, EF-Ts, and EF-G from T. thermophilus and the antibodies to their corresponding Escherichia coli factors. The molecular weight of EF-Tu . GDP determined by sedimentation equilibrium and sodium dodecylsulfate/polyacrylamide gel electrophoresis was 49000 and 51000 respectively. On the other hand, the molecular weight of EF-Ts was estimated as 27000 and 64000, respectively, by sodium dodecylsulfate/polyacrylamide gel electrophoresis and Sephadex gel filtration, suggesting that the protein existed probably as a dimer. The molecular weight of the EF-Tu . EF-Ts complex determined by sedimentation equilibrium and by gel filtration, was 142000 and 220000, respectively. Since the molar ratio of EF-Tu to EF-Ts in the EF-Tu . EF-Ts complex was one to one, it was suggested that the complex was composed of 2 mol each of EF-Tu and EF-Ts. The molecular weight of EF-G was estimated as 85000, 80000 and 78000 by equilibrium centrifugation, gel filtration, and sodium dodecylsulfate/polyacrylamide gel electrophoresis respectively.

Crystallization↗
PubMed1977

Purification and properties of the polypeptide chain release factor (RF-4) from an extreme thermophile, Thermus thermophilus HB8.

The polypeptide chain release factor 1 (RF-1) has been purified from an extreme thermophile, Thermus thermophilus HB8. The purification procedure included steps of aqueous two-phase partition, ammonium sulfate fractionation, and column chromatographies on DEAE-Sephadex, Sephadex G-150, and CM-Sephadex. The preparation was more than 90% pure as judged by polyacrylamide gel electrophoresis. The specific activity was about 3.3 pmol of formyl-[3H]-methionine released in 1 min at 25 degrees C per microgram of protein under the standard assay conditions using 4 pmol of the initiation complex and 1 nmol of UpApG. The molecular weight as determined by gel filtration on Sephadex G-150 and by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, was 58,000 and 45,000, respectively. As expected, the factor was extremely heat-stable, 50% of its activity remaining after incubation for 5 min at 84 degrees C. Several properties of the reaction catalyzed by RF-1 are also described.

Bacterial Proteins↗