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Articles by K. Saito
Total Records ( 7 ) for K. Saito
  M. Toshihiro , K. Saito , S. Takikawa , N. Takebe , T. Onoda and J. Satoh
 

Aims We prospectively studied Japanese workers with impaired fasting glucose (IFG) and/or impaired glucose tolerance (IGT) and analysed possible risk factors for diabetes, including psychosocial factors such as stress.

Methods The participants were 128 male Japanese company employees (mean age, 49.3 ± 5.9 years) with IFG and/or IGT diagnosed by oral glucose tolerance test (OGTT). Participants were prospectively studied for 5 years with annual OGTTs. The Kaplan–Meier method and Cox’s proportional hazard model were used to analyse the incidence of diabetes and the factors affecting glucose tolerance, including anthropometric, biochemical and social–psychological factors.

Results Of 128 participants, 36 (28.1%) developed diabetes and 39 (30.5%) returned to normal glucose tolerance (NGT) during a mean follow-up of 3.2 years. Independent risk factors for diabetes were night duty [hazard ratio (HR) = 5.48, P = 0.002], higher fasting plasma glucose (FPG) levels within 6.1–6.9 mmol/l (HR = 1.05, P = 0.031), stress (HR = 3.81, P = 0.037) and administrative position (HR = 12.70, P = 0.045), while independent factors associated with recovery were lower FPG levels (HR = 0.94, P = 0.017), being a white-collar worker (HR = 0.34, P = 0.033), non-smoking (HR = 0.31, P = 0.040) and lower serum alanine aminotransferase (ALT) levels (HR = 0.97, P = 0.042).

Conclusions In addition to FPG levels at baseline, psychosocial factors (night duty, stress and administrative position) are risk factors for Type 2 diabetes, while being a white-collar worker, a non-smoker and lower serum ALT levels are factors associated with return to NGT in Japanese workers with IFG and/or IGT.

  Y. Heianza , Y. Arase , K. Fujihara , H. Tsuji , K. Saito , S. D. Hsieh , S. Kodama , H. Shimano , N. Yamada , S. Hara and H. Sone
  Aims  We aimed to characterize the association of insulin resistance, impaired insulin secretion and β-cell dysfunction in relation to HbA1c levels in a non-diabetic range in Japanese individuals without clinically diagnosed diabetes.

Methods  This cross-sectional study included 1444 individuals without a history of outpatient treatment of diabetes or use of insulin or oral hypoglycaemic agents. The homeostasis model assessment of insulin resistance and beta-cell function, insulinogenic index, Matsuda index and disposition index were calculated using data from 75-g oral glucose tolerance tests and compared across quintile (Q) categories of HbA1c levels.

Results  Fasting plasma glucose and 30-min and 60-min plasma glucose (PG) levels were significantly higher when HbA1c exceeded 36 mmol/mol (5.4%). A HbA1c concentration of 36-37 mmol/mol (5.4-5.5%) (Q3) was significantly associated with a 15% lower homeostasis model assessment of β-cell function value and 31% lower insulinogenic index value compared with HbA1c ≤ 32 mmol/mol (≤ 5.1%) (Q1) (<0.01). Further, a HbA1c concentration of 38-40 mmol/mol (5.6-5.8%) (Q4) was associated with 17% (<0.01) and 24% (<0.05) reductions in those indexes, respectively. However, the homeostasis model assessment of insulin resistance was not significantly elevated and the Matsuda index was not significantly lower unless HbA1c exceeded 41 mmol/mol (5.9%). Individuals with HbA1c ≥ 41 mmol/mol (≥ 5.9%) (Q5) had a 69% lower disposition index than those with a HbA1c concentration of ≤ 32 mmol/mol (≤ 5.1%) (Q1).

Conclusions  Elevated HbA1c levels ≥ 41 mmol/mol (≥ 5.9%) were associated with substantial reductions in insulin secretion, insulin sensitivity and β-cell dysfunction in Japanese individuals not treated for diabetes. High normal HbA1c levels of 36-40 mmol/mol (5.4-5.8%) were also associated with impaired insulin secretion without marked insulin resistance in Japanese individuals.

  Y. Yachi , Y. Tanaka , I. Nishibata , A. Sugawara , S. Kodama , K. Saito and H. Sone
  Aims  Maternal obesity and weight gain since early adulthood are known predictors of gestational diabetes in Western countries. However, their impact has not been evaluated well in Asia, where mean BMI levels are generally lower than in Western countries. We therefore examined the associations of BMI at age 20 years and BMI change since age 20 years with the risk of gestational diabetes in Japanese pregnant women.

Methods  Six hundred and twenty-four consecutive pregnant women without recognized diabetes before pregnancy, whose initial obstetric clinic visit was before 13 weeks' gestation, were prospectively observed. Weight at age 20 years was self-reported. Baseline height and weight measurements were obtained at the initial obstetric visit. Multivariate logistic regression analysis estimated the risk of incident gestational diabetes for BMI change since 20 years and BMI at age 20 years.

Results  Twenty-eight women developed incident gestational diabetes. By multivariate logistic regression analysis that adjusted for maternal age, parity and baseline BMI, we observed a statistically significant inverse association between BMI at age 20 years and incidence of gestational diabetes (odds ratio 0.68, 95% CI 0.51-0.92). Similarly, when we assessed the association of BMI change since age 20 years, adjusted for maternal age and parity, BMI change was associated with an increased risk of gestational diabetes (odds ratio 1.26, 95% CI 1.03-1.53). When we focused on the threshold of risk of gestational diabetes, women with BMI at 20 years of less than 18 kg/m2 had a 6.30-fold (2.26-17.59) greater risk than women with both BMI at age 20 years of 18 kg/m2 or more and BMI change since age 20 years of less than 1.85.

Conclusions  Both low BMI at age 20 years and BMI change since age 20 years were significantly associated with increased risk of incident gestational diabetes.

  Y. Heianza , Y. Arase , S. Kodama , S. D. Hsieh , H. Tsuji , K. Saito , H. Shimano , S. Hara and H. Sone
 

Aims

To investigate whether living alone was associated with the presence of undiagnosed diabetes and whether this association could be attenuated by modifiable lifestyle habits.

Methods

This cross-sectional study included 6400 Japanese men without a history of diagnosed diabetes. Individuals with currently undiagnosed diabetes were identified through fasting glucose concentration ≥7.0 mmol/l or HbA1c concentration ≥ 48 mmol⁄mol (≥ 6.5%). Effect modification was examined using body mass index, hypertension, history of dyslipidaemia, drinking habits, smoking habits, physical activity, vegetable intake, emotional stress and depressed mood.

Results

Men who lived alone (= 1098) had a significantly elevated odds ratio for having undiagnosed diabetes in an age-adjusted model (odds ratio 1.45, 95% CI 1.07, 1.96; = 0.018). After adjustment for lifestyle factors, the association was slightly attenuated (odds ratio 1.40, 95% CI 1.02, 1.91; = 0.036). After further adjustment for all factors mentioned above, living alone was still marginally significantly associated with the presence of undiagnosed diabetes (odds ratio 1.38, 95% CI 1.003, 1.90; = 0.048). A significant association of living alone with the presence of undetected diabetes was particularly observed among men who were overweight, currently smoked and were physically inactive, or had any one of those three factors.

Conclusions

The association between undiagnosed diabetes and living alone can be partially influenced by modifiable lifestyle factors. Men who lived alone, especially those who did not engage in favourable lifestyle habits, were more likely to have undiagnosed diabetes. Such individuals have a higher probability of having undetected diabetic hyperglycaemia and would need to undergo glucose tests to identify the disease.

Flow modulation effect on N incorporation into GaAs(1-x)Nx films during chemical beam epitaxy growth
  H. Suzuki , K. Nishimura , K. Saito , Y. Ohshita , N. Kojima and M. Yamaguchi
 

The change in the surface concentration of N ([N]s) on a GaAs surface under N and As source injections is investigated using the N atomic layer doping (N-ALD) technique, and the key factor determining [N]s is discussed. The As and N precursors source gases are trisdimethylaminoarsenic (TDMAAs, [N(CH3)2]3As) and monomethylhydrazine (MMHy, N2H3CH3), respectively. N-ALD layers are prepared by using two gas injection sequences (A: MMHy injection and B: MMHy and TDMAAs injections). [N]s increases with decreasing growth temperature in both sequences. [N]s in sequence A is higher than that of sequence B. In sequence B, Δ[N]st is proportional to exp(–tN), where t and τN are the gas injection time and the residence time of N, respectively. It is observed that the number of vacant sites, [V]s,N, remaining constant during gas injections. In sequence A, Δ[N]st cannot be fitted by a single exponential function, indicating that [V]s,N is not constant. From these results, we suggest that the vacant sites at the surface are created not only by N desorption but also by As desorption. It has been found that As desorption is enhanced by MMHy injection. As desorption reaction has been confirmed by in situ auger electron spectroscopy measurements. These results indicate that [N]s is determined by the competitive absorption between N and As, [V]s,N, and τN.

  D Albinsky , M Kusano , M Higuchi , N Hayashi , M Kobayashi , A Fukushima , M Mori , T Ichikawa , K Matsui , H Kuroda , Y Horii , Y Tsumoto , H Sakakibara , H Hirochika , M Matsui and K. Saito
 

Plant metabolomics developed as a powerful tool to examine gene functions and to gain deeper insight into the physiology of the plant cell. In this study, we screened Arabidopsis lines overexpressing rice full-length (FL) cDNAs (rice FOX Arabidopsis lines) using a gas chromatography–time-of-flight mass spectrometry (GC–TOF/MS)-based technique to identify rice genes that caused metabolic changes. This screening system allows fast and reliable identification of candidate lines showing altered metabolite profiles. We performed metabolomic and transcriptomic analysis of a rice FOX Arabidopsis line that harbored the FL cDNA of the rice ortholog of the Lateral Organ Boundaries (LOB) Domain (LBD)/Asymmetric Leaves2-like (ASL) gene of Arabidopsis, At-LBD37/ASL39. The investigated rice FOX Arabidopsis line showed prominent changes in the levels of metabolites related to nitrogen metabolism. The transcriptomic data as well as the results from the metabolite analysis of the Arabidopsis At-LBD37/ASL39-overexpressor plants were consistent with these findings. Furthermore, the metabolomic and transcriptomic analysis of the Os-LBD37/ASL39-overexpressing rice plants indicated that Os-LBD37/ASL39 is associated with processes related to nitrogen metabolism in rice. Thus, the combination of a metabolomics-based screening method and a gain-of-function approach is useful for rapid characterization of novel genes in both Arabidopsis and rice.

  T.X. Li , K. Kuwana , K. Saito , H. Zhang and Z. Chen
  We have conducted experimental and numerical studies on flame synthesis of carbon nanotubes (CNTs) to investigate the effects of three key parameters – selective catalyst, temperature and available carbon sources – on CNT growth. Two different substrates were used to synthesize CNTs: Ni-alloy wire substrates to obtain curved and entangled CNTs and Si-substrates with porous anodic aluminum oxide (AAO) nanotemplates to grow well-aligned, self-assembled and size-controllable CNTs, each using two different types of laminar flames, co-flow and counter-flow methane–air diffusion flames. An appropriate temperature range in the synthesis region is essential for CNTs to grow on the substrates. Possible carbon sources for CNT growth were found to be the major species CO and those intermediate species C2H2, C2H4, C2H6, and methyl radical CH3. The major species H2, CO2 and H2O in the synthesis region are expected to activate the catalyst and help to promote catalyst reaction.
 
 
 
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