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Articles by K Ito
Total Records ( 8 ) for K Ito
  T Nakano , S Sekine , K Ito and T. Horie
 

The multidrug resistance-associated protein 2/ATP-binding cassette transporter family C2 (Mrp2/Abcc2) is an ATP-dependent export pump that mediates the transport of a variety of organic anions. Abcc2 is mainly expressed on the canalicular membrane of hepatocytes and also the brush-border membrane of intestinal epithelial cells. We have previously reported that Abcc2 is rapidly internalized from the canalicular membrane during acute oxidative stress, which induces protein kinase C (PKC) activation in rat liver. However, it has not been elucidated whether PKC is involved in the regulation of Abcc2 localization in other tissues. In this study, we investigated this issue in rat intestinal epithelia. Exposure to thymeleatoxin, a conventional PKC (cPKC) activator, for 20 min reduced the cumulative glutathione S-bimane efflux for 40 min via Abcc2 from 30.3 ± 2.1 nmol/cm to 18.1 ± 1.6 nmol/cm. Likewise, the Abcc2 expression in the brush-border membrane of the small intestine was reduced to half that of the control without changing the total amount of Abcc2 present in the homogenate. Immunoprecipitation analysis suggested an interaction between Abcc2 and ezrin, a scaffolding protein that is dominantly expressed in the intestine. Thymeleatoxin treatment decreased the amount of the active form (C-terminally phosphorylated form) of ezrin and the amount of Abcc2 that coimmunoprecipitated with ezrin. These results indicate that cPKC activation diminishes the protein-protein interaction between ezrin and Abcc2. In conclusion, the phosphorylation status of ezrin correlates with the cell surface expression of Abcc2 in the rat small intestine, which may be regulated by cPKC.

  T Nakano , S Sekine , K Ito and T. Horie
 

The multidrug resistance-associated protein 2/ATP-binding cassette transporter family C2 (Mrp2/Abcc2) is an ATP-dependent export pump that mediates the transport of a variety of organic anions. Abcc2 is mainly expressed on the canalicular membrane of hepatocytes and also the brush-border membrane of intestinal epithelial cells. We have previously reported that Abcc2 is rapidly internalized from the canalicular membrane during acute oxidative stress, which induces protein kinase C (PKC) activation in rat liver. However, it has not been elucidated whether PKC is involved in the regulation of Abcc2 localization in other tissues. In this study, we investigated this issue in rat intestinal epithelia. Exposure to thymeleatoxin, a conventional PKC (cPKC) activator, for 20 min reduced the cumulative glutathione S-bimane efflux for 40 min via Abcc2 from 30.3 ± 2.1 nmol/cm to 18.1 ± 1.6 nmol/cm. Likewise, the Abcc2 expression in the brush-border membrane of the small intestine was reduced to half that of the control without changing the total amount of Abcc2 present in the homogenate. Immunoprecipitation analysis suggested an interaction between Abcc2 and ezrin, a scaffolding protein that is dominantly expressed in the intestine. Thymeleatoxin treatment decreased the amount of the active form (C-terminally phosphorylated form) of ezrin and the amount of Abcc2 that coimmunoprecipitated with ezrin. These results indicate that cPKC activation diminishes the protein-protein interaction between ezrin and Abcc2. In conclusion, the phosphorylation status of ezrin correlates with the cell surface expression of Abcc2 in the rat small intestine, which may be regulated by cPKC.

  K Ito and S. Lechevalier
 

Although heterogeneity in the performance of firms is a well-established stylized fact, we still lack full understanding of its origins and the reasons why it persists. Instead of assuming that performance differences are exogenous, this article focuses on two endogenous strategies—innovation and global engagement—and interprets them as two ways to accumulate knowledge and improve firms’ capabilities. We are particularly interested in analyzing interactions between these strategies and their effect on firms’ performance. By using a firm-level panel dataset drawn from a Japanese large-scale administrative survey for the years 1994–2003, we first find that innovation and exporting strategies are characterized by complementarities, which define coherent productive models or patterns of learning. Second, we show that these different strategies lead to various performances in terms of productivity and survival. Third, by using a propensity score-matching approach, we show that these differences in performance are lasting. Overall, our article shows that the interaction of innovation and export investments is a source of permanent differences in performance among firms.

  K Ito , H Yoshii , J Asakuma , A Sato , A Horiguchi , M Sumitomo , M Hayakawa and T. Asano
  Objective

Renal cell carcinoma (RCC) with a high-nucleolar-grade component is considered to be an aggressive type of tumor. In the present study, we evaluated the impact of the presence of the worst-nucleolar-grade component and also tried to determine predictors for recurrence and prognosis in patients with the worst grade component.

Methods

We evaluated 314 patients with RCC. A three-graded system was used for nucleolar grading, the patients were classified into four groups according to the presence of the worst nucleolar grade (Grade 3) and the occupancy of each grade, and clinicopathological factors and clinical outcomes were compared. In patients of Grade 3 components (Groups 1 and 2), factors influencing on prognosis and recurrence were evaluated by multivariate analysis.

Results

There was no significant difference in clinicopathological factors between Group 1 (with Grade 3-dominant tumors) and Group 2 (with tumors in which Grade 1 or 2 was dominant and there were Grade 3 components). Neither did cause-specific survival or recurrence-free survival differ significantly between those two groups. In multivariate analysis, only distant metastasis was an independent predictor for prognosis in all patients with Grade 3 components. Moreover, an elevated C-reactive protein (CRP) level (≥1 mg/dl) was the only independent predictor of recurrence in N0M0 patients.

Conclusions

Regardless of dominancy, the presence of the worst grade component has a significant clinical impact in RCC patients. N0M0 patients whose RCC has worst-grade components but whose CRP levels are <1 are expected to have longer recurrence-free intervals and to survive longer than those whose CRP levels are higher.

  Y Kono , K Kubota , T Aruga , A Ishibashi , M Morooka , K Ito , J Itami , M Kanemura , S Minowada and T. Tanaka
  Objective

The purpose was to monitor implanted seeds and to determine factors contributing to seed migration after permanent prostate brachytherapy.

Methods

Sixty-two consecutive patients with Stage 1 prostate cancer who underwent brachytherapy with 125I seeds between February 2008 and May 2009 were studied prospectively. On post-operative days 1, 7 and 30, scintigraphy was added to conventional radiography to monitor the migration of the implanted seeds. The prostate volume was measured during the pre-planning stage using ultrasound and during the post-planning stage using computed tomography on post-operative days 0 and 30. Magnetic resonance imaging was performed on day 30.

Results

Of the 4843 seeds implanted in the prostates of 62 patients, 108 seeds (2.2%) in 43 patients (69.4%) exhibited seed migration. Thirty-five seeds could not be identified using any of the imaging modalities and were likely passed during urination (0.7% of the total number of seeds). The maximum number of migrated seeds in one patient was 10 of the 85 implanted seeds. The fraction of patients with seed migration or loss increased from 27.4% on day 1 to 69.4% on day 30. The number of seeds that had migrated from the prostate increased from 48 (0.1% of the total number of seeds) on 1 day to 78 (1.0%) on day 7 and 108 (2.2%) on day 30. Of the seeds lost from the prostate, 38.9% embolized to the lungs. The seed loss during the first post-operative month was closely correlated with the swelling of the prostate gland between the pre-planning measurement and the post-planning measurement performed on day 0 (P < 0.0001).

Conclusions

Prostate swelling between the pre-planning and post-planning (day 0) measurements was significantly associated with seed migration, and adequate attention should be given to this issue.

  T Tanigaki , K Ito , Y Nagakubo , T Asakawa and T. Kanemura
 

In order to analyze the thermal property of nano-sized materials, an in situ observation technique that allows highly sensitive energy dispersive x-ray spectroscopic (EDX) analyses and high-resolution in situ heating observation of precision specimens is required. A method for the in situ observation of the interface reaction using an analytical transmission electron microscopy (TEM) and a specimen-heating holder was developed. The specimen holder used in this study was a direct-heating type having a fine tungsten wire heater. For sensitive analyses including an EDX map of composition changes during the interface reaction, a space toward the EDX detector with a take-off angle of 20° was made in the specimen holder. Samples were prepared by attaching a micro-sample directly to the heater using the focused ion beam (FIB) micro-sampling technique. It was confirmed that the sensitive EDX map and electron diffraction analyses were possible during the reaction, and that the resolution of this technique was of the order of 0.223 nm at 550°C.

  Y Kawakami , H Numata , K Ito and S. G. Goto
 

In this study, we investigated the diapause incidence in 3 geographic strains of the two-spotted spider mite Tetranychus urticae (Acari: Tetranychidae). Under diapause-inducing conditions of 12:12 light:dark at 15 °C, the diapause incidence was nearly 100% in a strain from northern Japan (Sapporo), whereas it was nearly 0% in 2 strains from southern Japan (Itoman and Takanabe). Reciprocal crosses clearly showed that the nondiapause phenotype is inherited in a completely dominant manner, and no maternal effect was detected. Backcrosses to the Itoman and Takanabe strains suggested that dominant nondiapause alleles control the nondiapause phenotype. To clarify the genetic basis of nondiapause in the northern population, we also established a nondiapausing variant ("selected nondiapause" abbreviated as snd) from the Sapporo strain. Crossing experiments revealed that a single recessive allele is responsible for the nondiapause phenotype. Thus, both dominant and recessive inheritance patterns of diapause were detected in the T. urticae populations studied here.

  A Larkin , S Karak , R Priya , A Das , C Ayyub , K Ito , V Rodrigues and M. Ramaswami
 

Naive Drosophila larvae show vigorous chemotaxis toward many odorants including ethyl acetate (EA). Chemotaxis toward EA is substantially reduced after a 5-min pre-exposure to the odorant and recovers with a half-time of ~20 min. An analogous behavioral decrement can be induced without odorant-receptor activation through channelrhodopsin-based, direct photoexcitation of odorant sensory neurons (OSNs). The neural mechanism of short-term habituation (STH) requires the (1) rutabaga adenylate cyclase; (2) transmitter release from predominantly GABAergic local interneurons (LNs); (3) GABA-A receptor function in projection neurons (PNs) that receive excitatory inputs from OSNs; and (4) NMDA-receptor function in PNs. These features of STH cannot be explained by simple sensory adaptation and, instead, point to plasticity of olfactory synapses in the antennal lobe as the underlying mechanism. Our observations suggest a model in which NMDAR-dependent depression of the OSN-PN synapse and/or NMDAR-dependent facilitation of inhibitory transmission from LNs to PNs contributes substantially to short-term habituation.

 
 
 
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