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RISS 인기검색어
- 검색키워드
- 저자 : Kazuhiko Yamamoto (검색결과 16 건)
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Yamamoto, Kazuhiko,Song, Yeong-Wook,Li, Zhan-guo BioMed Central 2018 Arthritis research & therapy Vol.20 No.-
<P>Europe and North America have been leaders in rheumatology for many years. However, for more than a decade now the East Asian region has been catching up dramatically. Some aspects of rheumatology in East Asia are now almost comparable to those in the European League Against Rheumatism (EULAR) and the American College of Rheumatology (ACR). In this article, we describe recent progress in rheumatology in East Asia, focusing specifically on Japan, Korea, and China.</P>
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Epidemiologic study on gestational trophoblastic diseases in Japan
Eiko Yamamoto,Kimihiro Nishino,Kaoru Niimi,Kazuhiko Ino 대한부인종양학회 2022 Journal of Gynecologic Oncology Vol.33 No.6
Objective: This study aims to estimate the population-based incidence of gestational trophoblastic diseases (GTDs) and to identify the characteristics of gestational trophoblastic neoplasia (GTN) in Japan. Methods: The annual number of GTD and live births from 1974 to 2018 were used to estimate the incidence of GTD. The data of 1,574 GTN cases from 1999 to 2018 were analyzed to identify the characteristics of low-risk GTN, high-risk GTN, placental site trophoblastic tumor (PSTT), and epithelioid trophoblastic tumor (ETT). Results: The incidence of hydatidiform mole was 2.02 per 1,000 live births on average which decreased from 1974 to 2008 and increased from 2009 to 2018. The incidence of low-risk GTN, high-risk GTN, PSTT, and ETT was 15.3, 3.5, 0.3, and 0.07 per 100,000 live births, respectively. The estimated incidence of post-molar GTN was 9.8% of molar patients. High-risk GTN was diagnosed more pathologically, had more various kinds of antecedent pregnancies, and had longer intervals after the antecedent pregnancy compared to low- risk GTN. Furthermore, 8.2% of high-risk GTN occurred after the subsequent non-molar pregnancy of hydatidiform mole. The cumulative percentage of developing high-risk GTN after hydatidiform mole reached 89.3% at the 60th month. Conclusion: The incidence of hydatidiform mole, low-risk GTN, high-risk GTN was 2.02 per 1,000 live births, 15.3 per 100,000 live births, and 3.5 per 100,000 live births, respectively. High-risk GTN was diagnosed more pathologically and later after the antecedent pregnancy than low-risk GTN. Following molar patients for five years is needed to improve the mortality of malignant GTN.
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Atmospheric Corrosion Behavior on Low Alloy Steels under Seashore Environment
Noda, Kazuhiko,Yamamoto, Masahiro,Masuda, Hiroyuki,Kodama, Toshiaki 한국부식방식학회 2002 Corrosion Science and Technology Vol.31 No.3
Atomic force microscope (AFM) measurements and scanning chemical microscopy (SCHEM) were performed for the investigation of atmospheric corrosion behavior of low alloy steels. The high sensitivity profile was determined by AFM for iron surface with droplets of synthetic seawater following the exposure to corrosive atmosphere. Simultaneously with AFM surface potential on iron was detected using a Kelvin force microscope (KFM) system during rusting process. Microvisualization of rusting iron surface is to be demonstrated in this paper in the form of parallel mapping of profile and surface potential distribution using the in-situ measuring technique. At relative humidity (RH) of 40%, growth rate of rusting on iron greatly increased in comparison with the case of RH of 30%. The water condensation in the presence of MgCl₂ is the main reason of the enhanced corrosion rate with increasing of relative humidity. In advance to the rust formation, a zone of less noble potential was detected by KFM around the droplet of synthetic seawater although AFM showed no irregularity in the profile image. It can be explained by this less noble potential that the rusting reaction initiated in the vicinity of the seawater droplet. The efficiency of alloy elements (Ni, Cr) on the atmospheric corrosion morphology was explained by SCHEM system. It has been proven that AFM system combined with KFM and SCHEM sjstem was effective in the investigation of atmospheric corrosion of iron and steel which otherwise was dificult to evaluate by conventional method.
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Sugiura, Tsutomu,Yamamoto, Kazuhiko,Horita, Satoshi,Murakami, Kazuhiro,Tsutsumi, Sadami,Kirita, Tadaaki Korean Academy of Periodontology 2016 Journal of Periodontal & Implant Science Vol.46 No.3
Purpose: This study investigated the effects of bone density and crestal cortical bone thickness at the implant-placement site on micromotion (relative displacement between the implant and bone) and the peri-implant bone strain distribution under immediate-loading conditions. Methods: A three-dimensional finite element model of the posterior mandible with an implant was constructed. Various bone parameters were simulated, including low or high cancellous bone density, low or high crestal cortical bone density, and crestal cortical bone thicknesses ranging from 0.5 to 2.5 mm. Delayed- and immediate-loading conditions were simulated. A buccolingual oblique load of 200 N was applied to the top of the abutment. Results: The maximum extent of micromotion was approximately $100{\mu}m$ in the low-density cancellous bone models, whereas it was under $30{\mu}m$ in the high-density cancellous bone models. Crestal cortical bone thickness significantly affected the maximum micromotion in the low-density cancellous bone models. The minimum principal strain in the peri-implant cortical bone was affected by the density of the crestal cortical bone and cancellous bone to the same degree for both delayed and immediate loading. In the low-density cancellous bone models under immediate loading, the minimum principal strain in the peri-implant cortical bone decreased with an increase in crestal cortical bone thickness. Conclusions: Cancellous bone density may be a critical factor for avoiding excessive micromotion in immediately loaded implants. Crestal cortical bone thickness significantly affected the maximum extent of micromotion and peri-implant bone strain in simulations of low-density cancellous bone under immediate loading.
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Sugiura, Tsutomu,Yamamoto, Kazuhiko,Horita, Satoshi,Murakami, Kazuhiro,Tsutsumi, Sadami,Kirita, Tadaaki Korean Academy of Periodontology 2017 Journal of Periodontal & Implant Science Vol.47 No.4
Purpose: The purpose of this study was to investigate the effects of implant tilting and the loading direction on the displacement and micromotion (relative displacement between the implant and bone) of immediately loaded implants by in vitro experiments and finite element analysis (FEA). Methods: Six artificial bone blocks were prepared. Six screw-type implants with a length of 10 mm and diameter of 4.3 mm were placed, with 3 positioned axially and 3 tilted. The tilted implants were $30^{\circ}$ distally inclined to the axial implants. Vertical and mesiodistal oblique ($45^{\circ}$ angle) loads of 200 N were applied to the top of the abutment, and the abutment displacement was recorded. Nonlinear finite element models simulating the in vitro experiment were constructed, and the abutment displacement and micromotion were calculated. The data on the abutment displacement from in vitro experiments and FEA were compared, and the validity of the finite element model was evaluated. Results: The abutment displacement was greater under oblique loading than under axial loading and greater for the tilted implants than for the axial implants. The in vitro and FEA results showed satisfactory consistency. The maximum micromotion was 2.8- to 4.1-fold higher under oblique loading than under vertical loading. The maximum micromotion values in the axial and tilted implants were very close under vertical loading. However, in the tilted implant model, the maximum micromotion was 38.7% less than in the axial implant model under oblique loading. The relationship between abutment displacement and micromotion varied according to the loading direction (vertical or oblique) as well as the implant insertion angle (axial or tilted). Conclusions: Tilted implants may have a lower maximum extent of micromotion than axial implants under mesiodistal oblique loading. The maximum micromotion values were strongly influenced by the loading direction. The maximum micromotion values did not reflect the abutment displacement values.
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Tsutomu Sugiura,Kazuhiko Yamamoto,Satoshi Horita,Kazuhiro Murakami,Sadami Tsutsumi,Tadaaki Kirita 대한치주과학회 2016 Journal of Periodontal & Implant Science Vol.46 No.3
Purpose: This study investigated the effects of bone density and crestal cortical bone thickness at the implant-placement site on micromotion (relative displacement between the implant and bone) and the peri-implant bone strain distribution under immediate-loading conditions. Methods: A three-dimensional finite element model of the posterior mandible with an implant was constructed. Various bone parameters were simulated, including low or high cancellous bone density, low or high crestal cortical bone density, and crestal cortical bone thicknesses ranging from 0.5 to 2.5 mm. Delayed- and immediate-loading conditions were simulated. A buccolingual oblique load of 200 N was applied to the top of the abutment. Results: The maximum extent of micromotion was approximately 100 μm in the low-density cancellous bone models, whereas it was under 30 μm in the high-density cancellous bone models. Crestal cortical bone thickness significantly affected the maximum micromotion in the low-density cancellous bone models. The minimum principal strain in the peri-implant cortical bone was affected by the density of the crestal cortical bone and cancellous bone to the same degree for both delayed and immediate loading. In the low-density cancellous bone models under immediate loading, the minimum principal strain in the peri-implant cortical bone decreased with an increase in crestal cortical bone thickness. Conclusions: Cancellous bone density may be a critical factor for avoiding excessive micromotion in immediately loaded implants. Crestal cortical bone thickness significantly affected the maximum extent of micromotion and peri-implant bone strain in simulations of low-density cancellous bone under immediate loading.
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Tsutomu Sugiura,Kazuhiko Yamamoto,Satoshi Horita,Kazuhiro Murakami,Sadami Tsutsumi,Tadaaki Kirita 대한치주과학회 2017 Journal of Periodontal & Implant Science Vol.47 No.4
Purpose: The purpose of this study was to investigate the effects of implant tilting and the loading direction on the displacement and micromotion (relative displacement between the implant and bone) of immediately loaded implants by in vitro experiments and finite element analysis (FEA). Methods: Six artificial bone blocks were prepared. Six screw-type implants with a length of 10 mm and diameter of 4.3 mm were placed, with 3 positioned axially and 3 tilted. The tilted implants were 30° distally inclined to the axial implants. Vertical and mesiodistal oblique (45° angle) loads of 200 N were applied to the top of the abutment, and the abutment displacement was recorded. Nonlinear finite element models simulating the in vitro experiment were constructed, and the abutment displacement and micromotion were calculated. The data on the abutment displacement from in vitro experiments and FEA were compared, and the validity of the finite element model was evaluated. Results: The abutment displacement was greater under oblique loading than under axial loading and greater for the tilted implants than for the axial implants. The in vitro and FEA results showed satisfactory consistency. The maximum micromotion was 2.8- to 4.1-fold higher under oblique loading than under vertical loading. The maximum micromotion values in the axial and tilted implants were very close under vertical loading. However, in the tilted implant model, the maximum micromotion was 38.7% less than in the axial implant model under oblique loading. The relationship between abutment displacement and micromotion varied according to the loading direction (vertical or oblique) as well as the implant insertion angle (axial or tilted). Conclusions: Tilted implants may have a lower maximum extent of micromotion than axial implants under mesiodistal oblique loading. The maximum micromotion values were strongly influenced by the loading direction. The maximum micromotion values did not reflect the abutment displacement values.
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Mechanism of Tolerance to Intranuclear Autoantigens
Kimito, Kawahata,Yoshikata, Misaki,Kazuhiko, Yamamoto 가톨릭 의과학연구원 2001 가톨릭 의과학연구원 국제학술대회 Vol.5 No.-
Immune response to systemic nuclear autoantigens is a distinctive feature of system lupus erythe matosus. Healthy individuals usually keep immunological toerance to nuclear antigens. Even though central tolerance or thymic deletion is importnat, this is usually not perfect. In some experiments, T cells specific for a nuclear autoantigen could be detectde even in peripheral blood of healthy individuals.
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