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Articles by Y Hayashi
Total Records ( 12 ) for Y Hayashi
  K Iskandar , Y Cao , Y Hayashi , M Nakata , E Takano , T Yada , C Zhang , W Ogawa , M Oki , S Chua , H Itoh , T Noda , M Kasuga and J. Nakae
 

Both insulin and leptin signaling converge on phosphatidylinositol 3-OH kinase [PI(3)K]/3-phosphoinositide-dependent protein kinase-1 (PDK-1)/protein kinase B (PKB, also known as Akt) in proopiomelanocortin (POMC) neurons. Forkhead box-containing protein-O1 (FoxO1) is inactivated in a PI(3)K-dependent manner. However, the interrelationship between PI(3)K/PDK-1/Akt and FoxO1, and the chronic effects of the overexpression of FoxO1 in POMC neurons on energy homeostasis has not been elucidated. To determine the extent to which PDK-1 and FoxO1 signaling in POMC neurons was responsible for energy homeostasis, we generated POMC neuron-specific Pdk1 knockout mice (POMCPdk1–/–) and mice selectively expressing a constitutively nuclear (CN)FoxO1 or transactivation-defective (256)FoxO1 in POMC neurons (CNFoxO1POMC or 256FoxO1POMC). POMCPdk1–/– mice showed increased food intake and body weight accompanied by decreased expression of Pomc gene. The CNFoxO1POMC mice exhibited mild obesity and hyperphagia compared with POMCPdk1–/– mice. Although expression of the CNFoxO1 made POMCPdk1–/– mice more obese due to excessive suppression of Pomc gene, overexpression of 256FoxO1 in POMC neurons had no effects on metabolic phenotypes and Pomc expression levels of POMCPdk1–/– mice. These data suggest a requirement for PDK-1 and FoxO1 in transcriptional regulation of Pomc and food intake.

  H Yamanaka , Y Hayashi , Y Watanabe , H Uematu and T. Mashimo
  Background

Hoarseness is a common complication after tracheal intubation and prolonged hoarseness may be very limiting for a patient. This study was designed to examine the duration of hoarseness after tracheal intubation and to identify risk factors that may increase the duration of hoarseness.

Methods

We prospectively studied 3093 adult patients (aged 18–77 yr), over a 3 yr period who required tracheal intubation. Postoperative hoarseness was assessed on the day of operation and on postoperative days 1, 3, and 7 by standardized interview by the resident anaesthetist managing the patient. If postoperative hoarseness was still present on postoperative day 7, the patient was followed up until complete resolution. We evaluated age, gender, weight, Cormack grades, duration of intubation, and the anaesthetic agents used as factors affecting the duration of hoarseness after tracheal intubation.

Results

Hoarseness was observed in 49% of patients on the day of surgery and in 29%, 11%, and 0.8% on 1, 3, and 7 postoperative days, respectively. Multiple regression analysis showed that patient age and duration of intubation, but not gender, weight, Cormack grades, or the agents used, were significant predictors of increased duration of hoarseness after tracheal intubation. We found three patients with arytenoid cartilage dislocation (0.097%) in our study population.

Conclusions

The age of the patient and duration of intubation were significant factors in the duration of hoarseness after tracheal intubation. In addition, the incidence of arytenoid cartilage dislocation was 0.097%.

  M Toyofuku , T Kimura , T Morimoto , Y Hayashi , H Ueda , K Kawai , Y Nozaki , S Hiramatsu , A Miura , Y Yokoi , S Toyoshima , H Nakashima , K Haze , M Tanaka , S Take , S Saito , T Isshiki , K Mitsudo and on Behalf of the j Cypher Registry Investigators
 

Background— Long-term outcomes after stenting of an unprotected left main coronary artery (ULMCA) with drug-eluting stents have not been addressed adequately despite the growing popularity of this procedure.

Methods and Results— j-Cypher is a multicenter prospective registry of consecutive patients undergoing sirolimus-eluting stent implantation in Japan. Among 12 824 patients enrolled in the j-Cypher registry, the unadjusted mortality rate at 3 years was significantly higher in patients with ULMCA stenting (n=582) than in patients without ULMCA stenting (n=12 242; 14.6% versus 9.2%, respectively; P<0.0001); however, there was no significant difference between the 2 groups in the adjusted risk of death (hazard ratio 1.23, 95% confidence interval 0.95 to 1.60, P=0.12). Among 476 patients whose ULMCA lesions were treated exclusively with a sirolimus-eluting stent, patients with ostial/shaft lesions (n=96) compared with those with bifurcation lesions (n=380) had a significantly lower rate of target-lesion revascularization for the ULMCA lesions (3.6% versus 17.1%, P=0.005), with similar cardiac death rates at 3 years (9.8% versus 7.6%, P=0.41). Among patients with bifurcation lesions, patients with stenting of both the main and side branches (n=119) had significantly higher rates of cardiac death (12.2% versus 5.5%; P=0.02) and target-lesion revascularization (30.9% versus 11.1%; P<0.0001) than those with main-branch stenting alone (n=261).

Conclusions— The higher unadjusted mortality rate of patients undergoing ULMCA stenting with a sirolimus-eluting stent did not appear to be related to ULMCA treatment itself but rather to the patients’ high-risk profile. Although long-term outcomes in patients with ostial/shaft ULMCA lesions were favorable, outcomes in patients with bifurcation lesions treated with stenting of both the main and side branches appeared unacceptable.

  K Zama , Y Hayashi , S Ito , Y Hirabayashi , T Inoue , K Ohno , N Okino and M. Ito
 

We report here a method of simultaneously quantifying glucosylceramide (GlcCer) and galactosylceramide (GalCer) by normal-phase HPLC using O-phtalaldehyde derivatives. Treatment with sphingolipid ceramide N-deacylase which converts the cerebrosides in the sample to their lyso-forms was followed by the quantitative labeling of free NH2 groups of the lyso-cerebrosides with O-phtalaldehyde. Using this method, 14.1 pmol of GlcCer and 10.4 pmol of GalCer, and 108.1 pmol of GlcCer and 191.1 pmol of GalCer were detected in zebrafish embryos and RPMI 1864 cells, respectively, while 22.2 pmol of GlcCer but no GalCer was detected in CHOP cells using cell lysate containing 100 µg of protein. Linearity for the determination of each cerebroside was observed from 50 to 400 µg of protein under the conditions used, which corresponds to approximately 103 to 105 RPMI cells and 5 to 80 zebrafish embryos. The present method clearly revealed that the treatment of RPMI cells with a GlcCer synthase inhibitor P4 resulted in a marked decrease in GlcCer but not GalCer, concomitantly with a significant decrease in the GlcCer synthase activity. On the other hand, GlcCer but not GalCer increased 2-fold when an acid glucocerebrosidase inhibitor CBE was injected into zebrafish embryos. Interestingly, the treatment of CHOP cells with ciclosporin A increased GlcCer possibly due to the inhibition of LacCer synthase. A significant increase in levels of GlcCer in fibroblasts from patients with Gaucher disease was clearly shown by the method. The proposed method is useful for the determination of GlcCer and GalCer levels in various biological samples.

  Y Yamauchi , M Kohno , T Hato , Y Hayashi , Y Izumi and H. Nomori
 

A 55-year-old woman with a 7 cm non-invasive thymoma and myasthenia gravis had been treated by extended thymectomy via median sternotomy 29 years ago. A microscopic 0.15 cm thymoma (microthymoma) was incidentally found in the thymus during surgery. Twenty-nine years later, a 5 cm thymoma developed in the anterior mediastinum and was surgically treated. The non-invasive first thymoma, the microthymoma and the non-invasive third thymoma were all classified as type AB thymomas according to the World Health Organization (WHO) classification and showed extremely similar histological findings. We think the mechanism underlying the local recurrence of non-invasive thymomas would be intrathymic metastasis because of their clinical and pathological features.

  Y Hayashi , M Yamamoto , H Mizoguchi , C Watanabe , R Ito , S Yamamoto , X. y Sun and Y. Murata
 

Multiple bioactive peptides, including glucagon, glucagon-like peptide-1 (GLP-1), and GLP-2, are derived from the glucagon gene (Gcg). In the present study, we disrupted Gcg by introduction of GFP cDNA and established a knock-in mouse line. Gcggfp/gfp mice that lack most, if not all, of Gcg-derived peptides were born in an expected Mendelian ratio without gross abnormalities. Gcggfp/gfp mice showed lower blood glucose levels at 2 wk of age, but those in adult Gcggfp/gfp mice were not significantly different from those in Gcg+/+ and Gcggfp/+ mice, even after starvation for 16 h. Serum insulin levels in Gcggfp/gfp mice were lower than in Gcg+/+ and Gcggfp/+ on ad libitum feeding, but no significant differences were observed on starvation. Islet -cells and intestinal L-cells were readily visualized in Gcggfp/gfp and Gcggfp/+ mice under fluorescence. The Gcggfp/gfp postnatally developed hyperplasia of islet -cells, whereas the population of intestinal L-cells was not increased. In the Gcggfp/gfp, expression of Aristaless-related homeobox (Arx) was markedly increased in pancreas but not in intestine and suggested involvement of Arx in differential regulation of proliferation of Gcg-expressing cells. These results illustrated that Gcg-derived peptides are dispensable for survival and maintaining normoglycemia in adult mice and that Gcg-derived peptides differentially regulate proliferation/differentiation of -cells and L-cells. The present model is useful for analyzing glucose/energy metabolism in the absence of Gcg-derived peptides. It is useful also for analysis of the development, differentiation, and function of Gcg-expressing cells, because such cells are readily visualized by fluorescence in this model.

  K Hirai , H Kuroyanagi , Y Tatebayashi , Y Hayashi , K Hirabayashi Takahashi , K Saito , S Haga , T Uemura and S. Izumi
 

l-kynurenine 3-monooxygenase (KMO) is an NAD(P)H-dependent flavin monooxygenase that catalyses the hydroxylation of l-kynurenine to 3-hydroxykynurenine, and is localized as an oligomer in the mitochondrial outer membrane. In the human brain, KMO may play an important role in the formation of two neurotoxins, 3-hydroxykynurenine and quinolinic acid, both of which provoke severe neurodegenerative diseases. In mosquitos, it plays a role in the formation both of eye pigment and of an exflagellation-inducing factor (xanthurenic acid). Here, we present evidence that the C-terminal region of pig liver KMO plays a dual role. First, it is required for the enzymatic activity. Second, it functions as a mitochondrial targeting signal as seen in monoamine oxidase B (MAO B) or outer membrane cytochrome b5. The first role was shown by the comparison of the enzymatic activity of two mutants (C-terminally FLAG-tagged KMO and carboxyl-terminal truncation form, KMOC50) with that of the wild-type enzyme expressed in COS-7 cells. The second role was demonstrated with fluorescence microscopy by the comparison of the intracellular localization of the wild-type, three carboxyl-terminal truncated forms (C20, C30 and C50), C-terminally FLAG-tagged wild-type and a mutant KMO, where two arginine residues, Arg461-Arg462, were replaced with Ser residues.

  K Yamakoshi , A Takahashi , F Hirota , R Nakayama , N Ishimaru , Y Kubo , D. J Mann , M Ohmura , A Hirao , H Saya , S Arase , Y Hayashi , K Nakao , M Matsumoto , N Ohtani and E. Hara
 

Expression of the p16Ink4a tumor suppressor gene, a sensor of oncogenic stress, is up-regulated by a variety of potentially oncogenic stimuli in cultured primary cells. However, because p16Ink4a expression is also induced by tissue culture stress, physiological mechanisms regulating p16Ink4a expression remain unclear. To eliminate any potential problems arising from tissue culture–imposed stress, we used bioluminescence imaging for noninvasive and real-time analysis of p16Ink4a expression under various physiological conditions in living mice. In this study, we show that oncogenic insults such as ras activation provoke epigenetic derepression of p16Ink4a expression through reduction of DNMT1 (DNA methyl transferase 1) levels as a DNA damage response in vivo. This pathway is accelerated in the absence of p53, indicating that p53 normally holds the p16Ink4a response in check. These results unveil a backup tumor suppressor role for p16Ink4a in the event of p53 inactivation, expanding our understanding of how p16Ink4a expression is regulated in vivo.

  Y Hayashi , S Kobayashi and H. Nakato
 

Heparan sulfate glycoproteins dally and dally-like define the germ cell niche in female and male Drosophila, respectively.

 
 
 
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