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Articles by Y. Okada
Total Records ( 6 ) for Y. Okada
  A Nakamizo , T Inoue , Y Kikkawa , K Uda , Y Hirata , K Okamura , M Yasaka and Y. Okada

BACKGROUND AND PURPOSE: Extracranial-intracranial (ECIC) bypass grafts have been assessed postoperatively by various neuroradiologic techniques. The aim of this prospective study was to evaluate postoperative changes in ECIC bypass graft by using superficial temporal artery duplex ultrasonography (STDU). Furthermore, this study assessed the ability of STDU to predict cerebrovascular reserve capacity (CVR).

MATERIALS AND METHODS: Forty-five consecutive patients who underwent ECIC bypass procedure for atherosclerotic internal carotid artery occlusion were enrolled in this prospective study. All patients underwent single-photon emission CT and STDU preoperatively, 14 days after, 3 months after, 1 year after, and 2 years after ECIC bypass.

RESULTS: The diameter and flow velocities of the ipsilateral superficial temporal artery (STA), and regional cerebral blood flow (rCBF) showed increase during the first 2 weeks and then remained stable, whereas CVR showed a constant improvement up to 2 years after surgery. The STA diameter and mean STA flow velocity correlated significantly with CVR at 1 year after surgery (r 2 = 0.1232 and r 2 = 0.08716, respectively; P < .05). A cutoff value of 1.8 mm STA diameter was determined as the most reliable value to predict CVR greater than 10% at 1 year after surgery. The positive predictive value was calculated as 96.6%, the negative predictive value as 43.8%, the sensitivity as 75.7%, the specificity as 87.5%, and the likelihood ratio as 6.056.

CONCLUSIONS: ECIC bypass grafts can be assessed postoperatively in a noninvasive fashion with STDU. This technique provides information regarding patency as well as quantitative assessment of bypass function. Moreover, STDU is useful to predict CVR improvement.

  T Shichita , T Ogata , M Yasaka , K Yasumori , T Inoue , S Ibayashi , M Iida and Y. Okada

Purpose: This study aimed to clarify the angiographic characteristics of radiation-induced carotid stenosis. Methods: We evaluated 11 carotid arteries of patients after radiotherapy (radiotherapy group) and 26 carotid arteries of age- and gender-matched patients without a history of radiotherapy (control group). All patients had carotid stenosis detected by digital subtraction angiography (DSA). We developed an original coordinate system on the DSA to determine the accurate length and location of the carotid lesion. Results: Radiation-induced carotid lesions were significantly longer than carotid lesions caused by atherosclerosis. The maximal stenosis of radiation-induced carotid lesions tended to be at the end of the stenotic area and within a wider range than the nonradiation-induced lesions, including in the proximal common carotid artery (CCA). Conclusions: Radiation-induced stenotic lesions seem to exist in a wide range of carotid artery, including the CCA, along the vessel, and show maximal stenosis near the end of the stenotic area.

  Y. Okada , K. Kawasumi , N. Mori , I. Yamamoto and T. Arai
  Obesity is associated with the metabolic syndrome, diabetes, hypertension and chronic inflammation and early detection of weight gain and prompt intervention are the keys to promoting increased quality of life and longevity in veterinary animals. We evaluated the changes in Malate Dehydrogenase (MDH), Lactate Dehydrogenase (LDH) and MDH/LDH ratio as energy metabolism markers in dogs before and after the 4-week overfeeding trial. The acute weight gain was attained by overfeeding of 2x Daily Energy Requirement (DER) separated into 3 meals/day (overfed group). The experimentally overfed dogs showed about 28.2% increase in the Body Weight (BW), the increase of Body Condition Score (BCS) from 1.9-3.4 and significant elevations were noted in Triglyceride (TG), total cholesterol (TC), glucose (GLU) alkaline phosphatase (ALP), Blood Urea Nitrogen (BUN), leukocyte MDH and LDH. Although not significant, both the plasma MDH and LDH activities decreased, whereas leukocytic MDH and LDH activities increased in the overfed group after the feeding trial. Both the resultant plasma and leucocytic M/L ratios showed mild increase in the over-fed group after the feeding trial. In conclusion, assays of MDH, LDH and M/L ratio on plasma and leukocytes are not sensitive as diagnostic tools for detecting acute weight gain. The diagnostic significance of the above mentioned parameters should be further examined on various types of weight gain and target tissues.
  Y. Okada , K. Kawasumi , M. Koide , Y. Hirakawa , N. Mori , I. Yamamoto and T. Arai
  Background: Aging is generally associated with alterations in physical activity, weight status and energy metabolism, which predisposes aged individuals to metabolic syndrome. In this manuscript, age effects on energy metabolic indicators of similar physical activity and weight status but of varying ages were investigated. Materials and Methods: Energy metabolic indicators, such as plasma adiponectin, leukocytic AMP-activated protein kinase, plasma malate dehydrogenase and lactate dehydrogenase along with common plasma metabolites, were measured in healthy young (AV = 7.1 years) and aged (AV = 14.1 years) riding horses of similar physical activity, diet and weight status. Malate dehydrogenase and lactate dehydrogenase ratio was also calculated as the indicator of energy metabolism. Results: Plasma adiponectin concentration and leukocytic AMP-activated protein kinase activity in aged horses were significantly lower than those in young horses (p<0.05, Mann-Whitney U test). Although not significant, energy metabolism indicators, malate dehydrogenase, lactate dehydrogenase and their ratio were lower in aged group when compared to those of young group. Conclusion: The present results indicate the decline in energy metabolism with aging in healthy horses even without any visible changes in adiposity. Such changes reflect dysfunction of energy metabolism and predispose the aged individuals to the development of metabolic syndrome.
  S Yamashita , O Katsumata and Y. Okada

We have developed a new standardized method for the post-embedding immunoelectron microscopy using the same fixation, antigen retrieval and image contrasting procedures. Tissues were fixed with 4% formaldehyde containing 2.5 mM CaCl2, 1.25 mM MgCl2 in a 0.1 M 4-(2-hydroxyethyl)-piperazineethanesulfonic acid (HEPES) buffer (pH 7.4) for 2 h and then with the same fixative composition in 0.1 M HEPES buffer (pH 8.5) overnight at room temperature. Vehicle osmolarity of fixatives was adjusted to 300–330 mOsm by adding glucose. The specimens were dehydrated with dimethylformamide on ice and embedded in LR-White resin. Ultrathin sections were heated in a 20 mM Tris–HCl buffer (pH 9.0) for 1–2 h at 95°C. After immuno-gold labeling, the sections were treated with 2% glutaraldehyde containing 0.05% tannic acid in a 0.1 M phosphate buffer (pH 5.5) for 5 min and with a 1% OsO4/0.1 M phosphate buffer (pH 7.4) for 5 min, and then they were double stained with uranyl acetate and lead citrate. The standardized method yielded strong and reproducible immunoreactions for soluble, membrane-bound and filamentous proteins showing an excellent image contrast without destruction of the fine structures.

  A. H Toychiev , R. Z Sabirov , N Takahashi , Y Ando Akatsuka , H Liu , T Shintani , M Noda and Y. Okada

The maxi-anion channel with a large single-channel conductance of >300 pS, and unknown molecular identity, is functionally expressed in a large variety of cell types. The channel is activated by a number of experimental maneuvers such as exposing cells to hypotonic or ischemic stress. The most effective and consistent method of activating it is patch membrane excision. However, the activation mechanism of the maxi-anion channel remains poorly understood at present. In the present study, involvement of phosphorylation/dephosphorylation in excision-induced activation was examined. In mouse mammary fibroblastic C127 cells, activity of the channel was suppressed by intracellular application of Mg-ATP, but not Mg-5'-adenylylimidodiphosphate (AMP-PNP), in a concentration-dependent manner. When a cocktail of broad-spectrum tyrosine phosphatase inhibitors was applied, channel activation was completely abolished, whereas inhibitors of serine/threonine protein phosphatases had no effect. On the other hand, protein tyrosine kinase inhibitors brought the channel out of an inactivated state. In mouse adult skin fibroblasts (MAFs) in primary culture, similar maxi-anion channels were found to be activated on membrane excision, in a manner sensitive to tyrosine phosphatase inhibitors. In MAFs isolated from animals deficient in receptor protein tyrosine phosphatase (RPTP), activation of the maxi-anion channel was significantly slower and less prominent compared with that observed in wild-type MAFs; however, channel activation was restored by transfection of the RPTP gene. Thus it is concluded that activation of the maxi-anion channel involves protein dephosphorylation mediated by protein tyrosine phosphatases that include RPTP in mouse fibroblasts, but not in C127 cells.

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