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Articles by T. Hayashi
Total Records ( 8 ) for T. Hayashi
  K Yoshida , K Nakachi , K Imai , J. B Cologne , Y Niwa , Y Kusunoki and T. Hayashi

Lung cancer is a leading cause of cancer death worldwide. Prevention could be improved by identifying susceptible individuals as well as improving understanding of interactions between genes and etiological environmental agents, including radiation exposure. The epidermal growth factor receptor (EGFR)-signaling pathway, regulating cellular radiation sensitivity, is an oncogenic cascade involved in lung cancer, especially adenocarcinoma. The cytosine adenine (CA) repeat number polymorphism in the first intron of EGFR has been shown to be inversely correlated with EGFR production. It is hypothesized that CA repeat number may modulate individual susceptibility to lung cancer. Thus, we carried out a case–cohort study within the Japanese atomic bomb (A-bomb) survivor cohort to evaluate a possible association of CA repeat polymorphism with lung cancer risk in radiation-exposed or negligibly exposed (<5 mGy) A-bomb survivors. First, by dividing study subjects into Short and Long genotypes, defined as the summed CA repeat number of two alleles ≤37 and ≥38, respectively, we found that the Short genotype was significantly associated with an increased risk of lung cancer, specifically adenocarcinoma, among negligibly exposed subjects. Next, we found that prior radiation exposure significantly enhanced lung cancer risk of survivors with the Long genotype, whereas the risk for the Short genotype did not show any significant increase with radiation dose, resulting in indistinguishable risks between these genotypes at a high radiation dose. Our findings imply that the EGFR pathway plays a crucial role in assessing individual susceptibility to lung adenocarcinoma in relation to radiation exposure.

  T. Ishii , T. Hayashi and K. Yonezawa
  Constructing high-degree gene-pyramided lines has important practical implications; such lines could be used for multiple purposes, for example, as a high-powered breeding stock line, a material line for characterizing multigene interactions, or a market variety as it stands. Effectiveness of two typical marker-based schemes for constructing such lines, named AF (gene assemblage first) and BF (backcross first), is discussed. In AF, target genes of all donor parents are assembled onto the genome of a plant first, followed by backcross generations for the recovery of recipient parent genome. In BF, backcross is performed first separately for each donor, followed by generations of crossing for the assemblage of target genes. Our stochastic calculations show that BF is superior to AF when molecular selection is used for both target genes and background markers; with the same number of generations (time) and cost of genotyping, BF produces a much higher recovery of recurrent parent genome than AF. The superiority of BF weakens somewhat when target genes are selected by phenotype; AF is superior when assembling three or more unlinked target genes, or could be a choice of the breeder when assembling three or more linked genes. Otherwise, BF is superior. To minimize cost, genotyping and selection for background markers should be performed stepwise in each generation, that is, in three or four stages starting from markers closely linked with target genes to unlinked ones.
  R. Bouchi , T. Babazono , N. Yoshida , I. Nyumura , K. Toya , T. Hayashi , K. Hanai , N. Tanaka , A. Ishii and Y. Iwamoto
  Aims  Silent cerebral infarction (SCI) is an independent risk factor for future symptomatic stroke. Although the prevalence of SCI is closely related to kidney function in non-diabetic individuals, evidence is lacking whether albuminuria and/or reduced estimated glomerular filtration rate (eGFR) independently increase the risk of SCI in diabetic patients. We therefore examined the relationships between albuminuria, eGFR and SCI in patients with Type 2 diabetes mellitus (T2DM).

Methods  We studied 786 T2DM patients with an eGFR ≥ 15 ml/min 1.73/m2, including 337 women and 449 men [mean (± sd), age 65 ± 11 years]. All patients underwent cranial magnetic resonance imaging (MRI) to detect SCI. GFR was estimated using the modified three-variable equation for Japanese subjects. Albuminuria was defined as a first morning urinary albumin-to-creatinine ratio (ACR) ≥ 30 mg/g.

Results  SCI was detected in 415 (52.8%) of the subjects. The prevalence of SCI was significantly associated with both elevated ACR and decreased eGFR in univariate analysis. In multivariate logistic regression analysis, urinary ACR remained independently associated with SCI after adjusting for conventional cardiovascular risk factors [odds ratio (OR) of urinary ACR per logarithmical value: 1.89, 95% confidence interval (CI) = 1.41-2.51, P < 0.001]; however, eGFR was no longer significantly associated with SCI (OR per ml/min 1.73/m2 = 0.99, 95% CI = 0.98-1.00, P = 0.095).

Conclusion  In conclusion, albuminuria but not decreased eGFR may be an independent predictor of prevalent SCI in patients with T2DM.

  T Ooka , Y Ogura , M Asadulghani , M Ohnishi , K Nakayama , J Terajima , H Watanabe and T. Hayashi

Mobile genetic elements play important roles in the evolution and diversification of bacterial genomes. In enterohemorrhagic Escherichia coli O157, a major factor that affects genomic diversity is prophages, which generate most of the large-size structural polymorphisms (LSSPs) observed in O157 genomes. Here, we describe the results of a systematic analysis of numerous small-size structural polymorphisms (SSSPs) that were detected by comparing the genomes of eight clinical isolates with a sequenced strain, O157 Sakai. Most of the SSSPs were generated by genetic events associated with only two insertion sequence (IS) elements, IS629 and ISEc8, and a number of genes that were inactivated or deleted by these events were identified. Simple excisions of IS629 and small deletions (footprints) formed by the excision of IS629, both of which are rarely described in bacteria, were also detected. In addition, the distribution of IS elements was highly biased toward prophages, prophage-like integrative elements, and plasmids. Based on these and our previous results, we conclude that, in addition to prophages, these two IS elements are major contributors to the genomic diversification of O157 strains and that LSSPs have been generated mainly by bacteriophages and SSSPs by IS elements. We also suggest that IS elements possibly play a role in the inactivation and immobilization of incoming phages and plasmids. Taken together, our results reveal the true impact of IS elements on the diversification of bacterial genomes and highlight their novel role in genome evolution.

  K Baba , Y. W Park , T Kaku , R Kaida , M Takeuchi , M Yoshida , Y Hosoo , Y Ojio , T Okuyama , T Taniguchi , Y Ohmiya , T Kondo , Z Shani , O Shoseyov , T Awano , S Serada , N Norioka , S Norioka and T. Hayashi

In response to environmental variation, angiosperm trees bend their stems by forming tension wood, which consists of a cellulose-rich G (gelatinous)-layer in the walls of fiber cells and generates abnormal tensile stress in the secondary xylem. We produced transgenic poplar plants overexpressing several endoglycanases to reduce each specific polysaccharide in the cell wall, as the secondary xylem consists of primary and secondary wall layers. When placed horizontally, the basal regions of stems of transgenic poplars overexpressing xyloglucanase alone could not bend upward due to low strain in the tension side of the xylem. In the wild-type plants, xyloglucan was found in the inner surface of G-layers during multiple layering. In situ xyloglucan endotransglucosylase (XET) activity showed that the incorporation of whole xyloglucan, potentially for wall tightening, began at the inner surface layers S1 and S2 and was retained throughout G-layer development, while the incorporation of xyloglucan heptasaccharide (XXXG) for wall loosening occurred in the primary wall of the expanding zone. We propose that the xyloglucan network is reinforced by XET to form a further connection between wall-bound and secreted xyloglucans in order to withstand the tensile stress created within the cellulose G-layer microfibrils.

  R Kaida , T Kaku , K Baba , M Oyadomari , T Watanabe , K Nishida , T Kanaya , Z Shani , O Shoseyov and T. Hayashi

In order to create trees in which cellulose, the most abundant component in biomass, can be enzymatically hydrolyzed highly for the production of bioethanol, we examined the saccharification of xylem from several transgenic poplars, each overexpressing either xyloglucanase, cellulase, xylanase, or galactanase. The level of cellulose degradation achieved by a cellulase preparation was markedly greater in the xylem overexpressing xyloglucanase and much greater in the xylems overexpressing xylanase and cellulase than in the xylem of the wild-type plant. Although a high degree of degradation occurred in all xylems at all loci, the crystalline region of the cellulose microfibrils was highly degraded in the xylem overexpressing xyloglucanase. Since the complex between microfibrils and xyloglucans could be one region that is particularly resistant to cellulose degradation, loosening xyloglucan could facilitate the enzymatic hydrolysis of cellulose in wood.

  A Alonso Simon , L Neumetzler , P Garcia Angulo , A. E Encina , J. L Acebes , J. M Alvarez and T. Hayashi

Bean cells that have been habituated to grow in a lethal concentration (12 µM) of 2,6-dichlorobenzonitrile (dichlobenil or DCB, a cellulose biosynthesis inhibitor) are known to have decreased cellulose content in their cell walls. Xyloglucan, which is bound to cellulose and together with it forms the main loading network of plant cell walls, has also been described to decrease in habituated cells, but whether the change on cellulose affects the xyloglucan structure besides its abundance has not been analyzed. Fragmentation analysis with xyloglucan-specific endoglucanase (XEG) and endocellulase revealed that habituation to DCB caused a change in the fine structure of xyloglucan, namely a decrease in fucosyl residues attached to the galactosyl–xylosyl residues along the glucan backbone. After the removal of herbicide from the medium (dehabituated cells), xyloglucan recovered its fucosyl residues. In addition, some cello-oligosaccharides could be detected only in habituated cells' xyloglucan digested by XEG and endocellulase, corresponding to a glucan covalently bound or co-precipitated with the hemicelluloses. These results show that structural flexibility of cell walls relies in part on the plasticity of xyloglucan composition and opens up new perspectives to further research in this field.

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