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H Nagano

Publications and source records attributed to H Nagano.

At least 19 recordsLinked to original sources
PubMed1992

Photostability and biological activity of fluoroquinolones substituted at the 8 position after UV irradiation.

Q-35 [1-cyclopropyl-6-fluoro-1,4-dihydro-8-methoxy-7-(3-methylaminopiperid ine-1-yl)-4-oxoquinoline-3-carboxylic acid], a fluoroquinolone, has absorbance peaks at 333 and 286 nm. No spectral change was observed even when this aqueous solution was irradiated with 3 J of long-wavelength UV light (UVA) per cm2. On the other hand, its derivatives, which are unsubstituted (8-H analog) or which are substituted with fluorine at the 8 position (8-F analog), were found to have decreased antibacterial activities with a simultaneous increase in their cytotoxicities when they were degraded in a dose-dependent manner with respect to UVA irradiation. Similar results were observed with the other available fluoroquinolones. Enoxacin and lomefloxacin exposed to 0.3 J of irradiation per cm2 and norfloxacin, ofloxacin, and ciprofloxacin exposed to 1 J of irradiation per cm2 underwent absorption spectrum changes, an accompanying decrease in antibacterial activity, and an increase in cytotoxic activity. These results suggest that the introduction of a methoxy group into the 8 position of quinolones plays an important role in the stability of fluoroquinolones against irradiation by UV light.

Animals↗
PubMed1979

The mode of inhibitory action by pyridoxal 5-phosphate on DNA polymerase-alpha and -beta.

The kinetics of the inhibition of DNA polymerases-alpha and -beta from sea urchin embryos by pyridoxal 5-phosphate were studied. The inhibition of DNA polymerase-alpha activity by pyridoxal 5-phosphate was competitive with activated DNA but noncompetitive with each deoxynucleoside triphosphate. With poly(dC)-oligo(dG)12-18 as a template-primer, however, the inhibition of DNA polymerase-alpha was competitive with dGTP but noncompetitive with the template-primer. These results suggest that DNA polymerase-alpha interacts with activated DNA and poly(dC)-oligo(dG)12-18 in different ways. The inhibition of DNA polymerase-beta by pyridoxal 5-phosphate was competitive with deoxynucleoside triphosphate using activated DNA as a template-primer and noncompetitive with activated DNA. Using poly(rA)-oligo(dT)12-18 as a template-primer, DNA polymerase-beta activity yielded sigmoid curves against both dTTP and the template-primer concentrations and was inhibited by pyridoxal 5-phosphate noncompetitively with respect to both dTTP and the template-primer. These results indicate that the inhibitory mode of DNA polymerase-alpha by pyridoxal 5-phosphate is different from that of DNA polymerase-beta.

Animals↗
PubMed1979

Different effects of D-glucose anomers for respiration of bacterial germinated spores.

Effects of alpha- or beta-D-glucose on the respiration of germinated spores (only germinated spores not including swollen spores and elongated spores) of Bacillus subtilis and B. megaterium were studied. In our conditions, net amount of oxygen consumed by 10(10) germinated spores of B. subtilis per min after addition of alpha- or beta-D-glucose was 1.6 microgram or 6.6 microgram (beta/alpha = 4.13), while that by B.megaterium was 4.5 microgram of 6.8 microgram (beta/alpha = 1.51), respectively. However, the net amounts of oxygen consumed by 10(10) vegetative cells per min after addition of alpha- or beta-D-glucose were identical, for B.subtillis in both cases 443.0 microgram and for B.megaterium in both cases 604.4 microgram.

Bacillus megaterium↗
PubMed1979

Identification of gamma-like DNA polymerase from sea urchin embryos.

A gamma-like DNA polymerase devoid of DNA polymerase-alpha and -beta activities was prepared from the nuclear fraction of blastulae of the sea urchin, Hemicentrotus pulcherrimus. The enzyme sedimented at the position of an approximate sedimentation coefficient of 3.3 S under high salt conditions by sucrose gradient centrifugation. An isoelectric point was determined to be pH 5.8. The enzyme activity was sensitive to sulfhydryl blocking reagents. Poly(rA) . oligo(dT)12--18 followed by poly(dA) . oligo(dT)12--18 was effectively utilized as a template-primer. From the above results, this polymerase seems to resemble the vertebrate DNA polymerase-gamma.

Animals↗
PubMed1979

Inhibition by aphidicolin of cell cycle progression and DNA replication in sea urchin embryos.

We have recently found that aphidicolin, a tetracyclic diterpene-tetraol produced by several fungi, blocks DNA synthesis of sea urchin embryos by interfering with the activity of DNA polyermase alpha. These cells fail to proliferate in the presence of aphidicolin. In continuation of these studies, we determined the drug-sensitive stage in the first cell cycle of the sea urchin Clypeaster japonicus embryo. In continuous exposure to aphidicolin (2 micrograms/ml) from five minutes after fertilization, mitotic division of the embryo was completely suppressed. Embryos were exposed to the drug at progressively later intervals and their capability for cytokinesis was examined. Evidence was thereby obtained that aphidicolin acts at the S-period to inhibit DNA synthesis resulting in developmental arrest of the embryo.

Animals↗
PubMed1979

Effects of alpha- and beta-D-glucose on germination of spores of Bacillus megaterium QM B1551.

The effects of D-glucose anomers on the germination of dormant spores of Bacillus megaterium QM B1551 were studied, alpha-D-Glucose (1 mM) slightly initiated the germination of the dormant spores during 10 min incubation at 37 degrees C, while about 60% of the dormant spores became germinated with beta-D-glucose (1 mM) in the same conditions. From the above observations and the finding that only a trace amount of alpha- or beta-D-glucose may bind with the dormant spores, it is speculated that the beta-D-glucose-stereospecific receptor site for the germination exists on the surface of the dormant spores of the bacillus.

Bacillus megaterium↗
PubMed1979

The mode of inhibitory action by aphidicolin on eukaryotic DNA polymerase alpha.

The mode of action by aphidicolin on DNA polymerase alpha from the nuclear fraction of sea-urchin blastulae was studied. The inhibition of DNA polymerase alpha by aphidicolin was uncompetive with activated DNA and competitive with the four deoxynucleoside triphosphates using activated DNA as a template-primer. For truncated (residual or limited) DNA synthesis with only three deoxynucleoside triphosphates, aphidicolin inhibited the residual synthesis more strongly in the absence of dCTP than in the absence of each of the other three deoxynucleoside triphosphates. The inhibition was reversed with excess dCTP but not with the other three deoxynucleoside triphosphates. That is, aphidicolin inhibited DNA polymerase alpha by competing with dCTP with a Ki value of 0.5 microgram/ml and by not competing with the other three deoxynucleoside triphosphates. dTMP incorporation with the activated DNA was more sensitive to aphidicolin than dGMP or dTMP incorporation with poly(dC). (dG)12-18 or poly(dA) . (dT)12-18. Similar results were obtained for DNA polymerase alpha (B form) from mouse myeloma MOPC 104E.

Animals↗
PubMed1978

Differential susceptibilities of DNA polymerases-alpha and -beta to polyanions.

The effects of various polyanions including synthetic polynucleotides on DNApolymerases-alpha and -beta from blastulae of the sea urchin Hemicentrotus pulcherrimus and HeLa cells were studied. Only DNA polymerase-alpha was inhibited by polyanions, such as polyvinyl sufate, dextran sulfate, heparin, poly(G), poly(I), poly(U) and poly(ADP-Rib). Of the various polynucleotides tested, poly(G) and poly(I) were the strongest inhibitors. Kinetic studies showed that the Ki value for poly(G) was 0.3 microgram/ml and that poly(G) had 20-fold higher affinity than activated DNA for the template-primer site of DNA polymerase-alpha. Poly(U) and poly(ADP-Rib) were also inhibitory, but they were one hundredth as inhibitory as poly(G) or poly(I). Poly(A), poly(C), poly(A).poly(U) AND POLY(I).poly(C) were not inhibitory to DNA polymerase-alpha. In contrast, DNA olymerase-beta was not affected at all by these polyanions under the same conditions.

Animals↗
PubMed1977

DNA polymerase-beta from the nuclear fraction of sea urchin embryos: characterization of the purified enzyme.

Approximately 2,500-fold purifications of DNA polymerase-beta from the nuclear fraction of blastulae of the sea urchin, Hemicentrotus pulcherrimus, was performed. The enzyme preparation, which was devoid of DNase and terminal deoxynucleotidyl transferase as contaminants, showed a sedimentation constant of 3.0 S in a sucrose density gradient, a molecular weight of 50,000 by gel filtration, and an isoelectric point of pH 8.1. The enzyme activity was resistant to sulfhydryl group inhibitors. Its optimal pH was 9.0-9.5 in Tris-maleate buffer and 10.0 in glycine buffer. The optimal NaCl concentration for the activity was 30-60 mM and about half of the activity remained at 0.4 M NaCl. As a template-primer, the enzyme preferred synthetic homopolymers to activated DNA. The order of this preference was as follows; poly (dA)-oligo (dT)12-18 greater than poly (rA)-oligo (dT)12-18 greater than activated DNA. The above results indicate that the enzyme corresponds to DNA polymerase-beta from vertebrate cells.

Animals↗