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Volume 39 (1998)
- Issue 4 Pages 239-
- Issue 3 Pages 165-
- Issue 2 Pages 93-
- Issue 1 Pages 1-
Volume 39, Issue 4
Displaying 1-6 of 6 articles from this issue
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MIKIO SAITO, TAKANORI YANAI, HIDENAO HASEGAWA, NAOFUMI AKATA, SYOUKO K ...1998 Volume 39 Issue 4 Pages 239-242
Published: 1998
Released on J-STAGE: March 27, 2006
JOURNAL FREE ACCESSDownload PDF (192K) -
TAKASHI NAKANISHI, KENTAROH MIWA, RIKA OHKI1998 Volume 39 Issue 4 Pages 243-250
Published: 1998
Released on J-STAGE: March 27, 2006
JOURNAL FREE ACCESSSpecific radioactivities of residual europium (Eu)-152 were measured in six roof tile samples exposed to the Nagasaki atomic bomb at two locations. The ground distances of the two locations from the hypocenter are 1020 m and 1060 m. In order to obtain reliable data, Eu-enriched samples (from 207 to 855 mg) were prepared by separating Eu from each roof tile sample (from 1 to 2 kg). For the major aliquot of the Eu-enriched sample, residual radioactivity of 152Eu was measured using a low-energy photon spectrometer. For the minor aliquot of the Eu-enriched sample, Eu content was determined by neutron activation analysis. Results of the specific radioactivity (152Eu/Eu, Bq mg-1) corrected to the time of bombing were in a range from 0.080 to 0.446. Although the measured values showed some scattering, they are moderately consistent with the calculated values by the DS86 methodology, i.e. the average ratio of the calculated to measured values is 1.3 ± 0.8.View full abstractDownload PDF (319K) -
HAMID REZA SHAHMOHAMMADI, EZAT ASGARANI, HIROAKI TERATO, TAKESHI SAITO ...1998 Volume 39 Issue 4 Pages 251-262
Published: 1998
Released on J-STAGE: March 27, 2006
JOURNAL FREE ACCESSHalobacteriumm salinarium, a member of the extremely halophilic archaebacteria, contains a C50-carotenoid namely bacterioruberin. We have previously reported the high resistance of this organism against thelethal actions of DNA-damaging agents including ionizing radiation and ultraviolet light (UV). In this study, we have examined whether bacterioruberin and the highly concentrated salts in this bacterium play protective roles against the lethal actions of ionizing radiation, UV, hydrogen peroxide, and mitomycin-C (MMC).
The colourless mutant of H. salinarium deficient in bacterioruberin was more sensitive than the red-pigmented wild-type to all tested DNA-damaging agents except MMC. Circular dichroism (CD) spectra of H. salinarium chromosomal DNA at various concentrations of KCl (0-3.5 M) were similar to that of B-DNA, indicating that no conformational changes occurred as a result of high salt concentrations. However, DNA strand-breaks induced by ionizing radiation were significantly reduced by the presence of either bacterioruberin or concentrated KCl, presumably due to scavenging of free radicals.
These results suggest that bacterioruberin and intracellular KCl of H. salinarium protect this organism against the lethal effects of oxidative DNA-damaging agents.View full abstractDownload PDF (524K) -
FUMIKO OBATA, TATSUO NUNOSHIBA, TAMOTSU HASHIMOTO-GOTOH, KAZUO YAMAMOT ...1998 Volume 39 Issue 4 Pages 263-270
Published: 1998
Released on J-STAGE: March 27, 2006
JOURNAL FREE ACCESSAn improved system to examine forward mutations that occurred in the supF gene of Escherichai coli carried on a multicopy plasmid is described. The system was validated by measuring spontaneous mutations of supF plasmids propagated in wild-type, recA- and mutM- mutY- E. coli strains, the mutation frequencies of which were 1.3 × 10-7, 6.3 × 10-7 and 1.5 × 10-6, respectively. Sequence analysis of the supF mutant plasmids revealed that G:C→T:A and G:C→C:G transversions dominated. This improved system allows rapid scoring and sequencing forward mutations in the supF gene, thus permitting its use as a genetic target for repair and mutagenesis studies in bacteria and mammalian cells.View full abstractDownload PDF (344K) -
RIICHI TAWA, YUTAKA KIMURA, JUN-ICHIRO KOMURA, YOSHINORI MIYAMURA, AKI ...1998 Volume 39 Issue 4 Pages 271-278
Published: 1998
Released on J-STAGE: March 27, 2006
JOURNAL FREE ACCESSEffects of ionizing radiation on the level of genomic DNA methylation in liver, brain and spleen of mouse as well as in two kinds of cultured cells were examined by high-performance liquid chromatography. Ten Gy of whole body X-radiation reduced the 5-methyldeoxycytidine contents by about 40% within 8 hours after irradiation in liver. Similar effects were observed at 4 or 7 Gy of X-ray irradiation. However, no such change was detected in brain, spleen and cultured cells. The data indicate that radiation-induced alteration in genomic DNA methylation is not ubiquitous among different tissues and cells.View full abstractDownload PDF (322K) -
TAKAHITO OKUDA, KIMIKO NISHIZAWA, YOSUKE EJIMA, SHIGEKAZU NAKATSUGAWA, ...1998 Volume 39 Issue 4 Pages 279-287
Published: 1998
Released on J-STAGE: March 27, 2006
JOURNAL FREE ACCESSTo determine the genetic effect of static magnetic fields (SMF), which are not supposed to produce any significant DNA damage, we took advantage of DNA mismatch repair (MMR) deficient cells, in which all the errors produced during DNA replication are left uncorrected. We first established a simple and less labor-intensive method to analyze genetic changes in microsatellite repetitive sequences in the MMR-deficient cells. After exposure to a strong SMF (6.34T) for 24h, both MMR deficient HCT 116 cells and proficient HeLa S3 cells did not exhibit any significant effect on microsatellite changes. Moreover, when HCT116 cells were synchronized at the G1/S boundary by aphidicolin and exposed to SMF during the whole S-phase, no increase in microsatellite changes was either observed. In contrast, irradiation by a low dose X-ray (2Gy) significantly increased microsatellite changes in HCT116 cells. This suggested that exposure to strong SMF may not induce any significant level of genetic changes in microsatellite sequences.View full abstractDownload PDF (366K)
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