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Search Results: 1 - 10 of 1971 matches for " Naoki Kojima "
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Implementability by a Canonical Indirect Mechanism of an Optimal Two-Dimensional Direct Mechanism  [PDF]
Naoki Kojima
Theoretical Economics Letters (TEL) , 2017, DOI: 10.4236/tel.2017.72016
Abstract: The present paper investigates the multi-dimensional mechanism design in which buyers have taste and budget as their private information. The paper shows an easy proof of a two-dimensional optimal direct mechanism by a one-dimensional indirect mechanism: A canonical mechanism in the traditional one-dimensional setting, i.e., function of one variable, the buyers taste. It also sheds light on where the difficulty lies implementability of a general direct mechanism—not optimal—by a canonical mechanism.
Two-Dimensional Mechanism Design and Implementability by an Indirect Mechanism  [PDF]
Naoki Kojima
Theoretical Economics Letters (TEL) , 2017, DOI: 10.4236/tel.2017.76107
Abstract: This paper studies the problem on two-dimensional mechanism design where the buyer’s taste and budget are his private information. The paper investigates the problem by the method of dimension-reduction, i.e., by focusing only on the buyer’s budget and constructing an indirect mechanism: function of one variable, the buyer’s budget. It is an approach quite antipodal to that by Kojima [1] where he focused on the buyer’s taste instead of his budget. It is shown that the seller does not lose any money by adopting the indirect mechanism of this paper. In other words, the seller’s revenue-maximizing direct mechanism is implemented by such an indirect mechanism
Comparison of the Motion Accuracy of a Six Degrees of Freedom Radiotherapy Couch with and without Weights  [PDF]
Akihiro Takemura, Shinichi Ueda, Kimiya Noto, Hironori Kojima, Naoki Isomura
International Journal of Medical Physics,Clinical Engineering and Radiation Oncology (IJMPCERO) , 2013, DOI: 10.4236/ijmpcero.2013.23010
Abstract: In this study, we compared the motion accuracy of six degrees of freedom (6D) couch for precision radiotherapy with or without weights attached to the couch. Two digital cameras were focused on the iso-center of a linear accelerator. Images of a needle which had been fixed to the 6D couch were obtained using the cameras when the couch moved in translation and rotation around each axis. The three-dimensional (3D) coordinates of the needle were calculated from coordinate values in the images. A coordinate error of the needle position relative to the theoretical position was calculated. The errors were obtained with or without a 60 kg weight attached to the 6D couch, and these errors were compared with each other. The mean distance of the 3D error vectors for the weighted test was 0.21 ± 0.11 mm, and >0.16 ± 0.09 mm for the non-weighted test (p < 0.05). However, the difference of two values was 0.06 mm which is smaller than the minimum distance the 6D couch system can correctly move. The variance of 0.16 mm for the Y coordinate errors for the weighted test only was larger than that for the non-weighted test, which was 0.06 mm (p < 0.05). We found that a total weight of 60 kg did not affect the accuracy of the 6D couch clinically. However, the variance of the Y coordinate errors was increased. This might suggest that the addition of this weight increased the uncertainty of the motion of the 6D couch.

Mab21l2 Is Essential for Embryonic Heart and Liver Development
Yohei Saito, Takuya Kojima, Naoki Takahashi
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0032991
Abstract: During mouse embryogenesis, proper formation of the heart and liver is especially important and is crucial for embryonic viability. In this study, we showed that Mab21l2 was expressed in the trabecular and compact myocardium, and that deletion of Mab21l2 resulted in a reduction of the trabecular myocardium and thinning of the compact myocardium. Mab21l2-deficient embryonic hearts had decreased expression of genes that regulate cell proliferation and apoptosis of cardiomyocytes. These results show that Mab21l2 functions during heart development by regulating the expression of such genes. Mab21l2 was also expressed in the septum transversum mesenchyme (STM). Epicardial progenitor cells are localized to the anterior surface of the STM (proepicardium), and proepicardial cells migrate onto the surface of the heart and form the epicardium, which plays an important role in heart development. The rest of the STM is essential for the growth and survival of hepatoblasts, which are bipotential progenitors for hepatocytes and cholangiocytes. Proepicardial cells in Mab21l2-deficient embryos had defects in cell proliferation, which led to a small proepicardium, in which α4 integrin expression, which is essential for the migration of proepicardial cells, was down-regulated, suggesting that defects occurred in its migration. In Mab21l2-deficient embryos, epicardial formation was defective, suggesting that Mab21l2 plays important roles in epicardial formation through the regulation of the cell proliferation of proepicardial cells and the migratory process of proepicardial cells. Mab21l2-deficient embryos also exhibited hypoplasia of the STM surrounding hepatoblasts and decreased hepatoblast proliferation with a resultant loss of defective morphogenesis of the liver. These findings demonstrate that Mab21l2 plays a crucial role in both heart and liver development through STM formation.
The Relationship between Assessment Skills and Nursing Knowledge  [PDF]
Keiko Aizu, Kasumi Mikami, Ryoko Tsuchiya, Mayumi Shimizu, Nanae Kojima, Naoki Oka, Yoshiko Nishizawa
Open Journal of Nursing (OJN) , 2015, DOI: 10.4236/ojn.2015.512114
Abstract: This research aimed to clarify the relationship between nursing students’ levels of structural knowledge and assessment skills. Participants were 17 third-year university students majoring in nursing who participated individually in the experiments. The experiments included a nursing-scene task, free-recall task, and sorting task. Experiments were conducted before and after their clinical practice. Each student’s level of structural knowledge was calculated from the free-recall and sorting task responses, and each student’s assessment skill was calculated from the nursing-scene task responses. Levels of structural knowledge were significantly higher in post-examination compared with pre-examination (p < 0.01). Assessment skills scores were also significantly higher in post-examination compared with pre-examination (p < 0.001). When comparing assessment skills in relation to levels of structural knowledge, the high-structured group (n = 5) had significantly higher scores for their conclusions and reasons than the low-structured group (n = 5) (p < 0.001). Information-collecting scores in the task case did not differ between the low- and high-structured groups, although the high-structured group tended to mention information that was not included in the task case (p < 0.10). Well-structured knowledge of students in the high-structured group seemed to enable them to acquire and activate highly related information during assessment. Students in the high-structured group apparently made assessments not only by using information given but also by over viewing information comprehensively.
Roles of metalloproteinase-3 and aggrecanase 1 and 2 in aggrecan cleavage during human meniscus degeneration
Gintaro Ishihara,Toshihisa Kojima,Yoshimichi Saito,Naoki Ishiguro
Orthopedic Reviews , 2009, DOI: 10.4081/or.2009.e14
Abstract: The meniscus plays important roles in proper knee function. It was recently reported that meniscus degeneration was associated with progression of osteoarthritis (OA). However, little is known about the effects of degradative enzymes on the meniscus matrix, primarily collagen type I and aggrecan, during OA. This study examined the effects of metalloproteinase (MMP) and aggrecanase on the destruction of aggrecan in the human meniscus. Eighteen trimmed meniscus portions were collected during partial menisectomy. Specimens were categorized into 3 groups according to the modified Copenhaver classification based on the degrees of damage to collagen bundles. Histological and immunohistochemical studies were conducted. Sections were stained with antibodies against MMP-3, aggrecanase 1 and 2, and their specific cleavage sites of aggrecan. Their localizations and staining ratios in the inner superficial and outer deep zones of the meniscus were determined separately. The population of chondrocyte-like cells increased with degeneration of the meniscus. MMP-3 and aggrecanase 1 and 2 are primarily expressed and activated in chondrocyte-like cells. MMP-3 expression and activation increased with degeneration and the population of chondrocyte-like cells. Changes in aggrecanase 1 expression with the degeneration were not clearly detected, whereas the expression of aggrecanase 2 was associated with progression of degeneration. MMP-3 and aggrecanases, particularly aggrecanase 2, expressed in chondrocyte-like cells could play important roles in aggrecan degradation in the human meniscus.
Protective effect of geranylgeranylacetone, an inducer of heat shock protein 70, against drug-induced lung injury/fibrosis in an animal model
Takayoshi Fujibayashi, Naozumi Hashimoto, Mayumi Jijiwa, Yoshinori Hasegawa, Toshihisa Kojima, Naoki Ishiguro
BMC Pulmonary Medicine , 2009, DOI: 10.1186/1471-2466-9-45
Abstract: We used a bleomycin (BLM)-induced lung fibrosis model in which mice were treated with oral 600 mg/kg of GGA before and after BLM administration. Inflammation and fibrosis were evaluated by histological scoring, hydroxyproline content in the lung and inflammatory cell count, and quantification by ELISA of macrophage inflammatory protein-2 (MIP-2) in bronchoalveolar lavage fluid. Apoptosis was evaluated by the TUNEL method. The induction of HSP70 in the lung was examined with western blot analysis and its localization was determined by immunohistochemistry.We confirmed the presence of inflammation and fibrosis in the BLM-induced lung injury model and induction of HSP70 by oral administration of GGA. GGA prevented apoptosis of cellular constituents of lung tissue, such as epithelial cells, most likely related to the de novo induction of HSP70 in the lungs. GGA-treated mice also showed less fibrosis of the lungs, associated with the findings of suppression of both production of MIP-2 and inflammatory cell accumulation in the injured lung, compared with vehicle-treated mice.GGA had a protective effect on drug-induced lung injury/fibrosis. Disease-modifying antirheumatic drugs such as methotrexate, which are indispensable for the treatment of rheumatoid arthritis, often cause interstitial lung diseases, an adverse event that currently cannot be prevented. Clinical use of GGA for drug-induced pulmonary fibrosis might be considered in the future.Rheumatoid arthritis (RA), a chronic, systemic, inflammatory autoimmune disease, causes irreversible joint deformities and functional impairment. Evidence accumulating over the past 10 years has suggested that combined treatment with disease-modifying antirheumatic drugs (DMARDs), especially methotrexate, and anti-TNFα biological agents, as early as possible after the diagnosis of RA is effective and critical for preventing substantial disability caused by bony erosions [1-4]. On the other hand, it is also well known that DMARDs and
High-resolution analysis of aberrant regions in autosomal chromosomes in human leukemia THP-1 cell line
Naoki Adati, Ming-Chih Huang, Takahiro Suzuki, Harukazu Suzuki, Toshio Kojima
BMC Research Notes , 2009, DOI: 10.1186/1756-0500-2-153
Abstract: We report large aberrations, including deletions 6p, 12p, 17p, and trisomy 8, and revealed breakpoints in the MLL and MLLT3 genes. Moreover, we found novel genomic aberrations such as a hemizygous narrow deletion partially containing the TP73 gene and homozygous deletions, including the CDKN2A, CDKN2B and PTEN genes.In this study, we identified 119 aberrant regions in autosomal chromosomes, and at least 16 of these aberrations were less than 100 kb, most of which were undetectable in the previous works. We also revealed a total of 4.6 Mb of homozygous deleted regions. Our results will provide a base to precisely understand studies involving the THP-1 cell line, especially the huge amount of data generated from the FANTOM4/Genome Network Project.As models for the study of myeloid differentiation and hematopoietic cell differentiation, several human leukemia cell lines are available [1]. Although these myeloid leukemia cell lines are blocked at certain steps in the maturation and differentiation process, they can be induced to differentiate into macrophage-like cells by several stimuli [1,2].THP-1 is a human monocytic leukemia cell line that was cultured from the blood of a 1-year-old male with acute monocytic leukemia [3]. On stimulation with phorbol 12-myristate 13-acetate (PMA), THP-1 cells cease proliferation, become adherent, and differentiate into macrophage-like cells. They resemble native monocyte-derived macrophages with respect to numerous criteria [4,5]. In comparison with other human myeloid cell lines such as HL-60, U937, KG-1 or HEL cells, differentiated THP-1 cells behave more like native monocyte-derived macrophages [5]. Because of these characteristics, the THP-1 cell line is a valuable model for studying the mechanisms involved in macrophage differentiation. Therefore, THP-1 has been used not only as a clinical model of a leukemic cell, but also as a scientific model of differentiation in response to various stimuli.Chromosome rearrangements are comm
Accuracy of Dose Delivery in Multiple Breath-Hold Segmented Volumetric Modulated Arc Therapy: A Static Phantom Study
Kimiya Noto,Shinichi Ueda,Hironori Kojima,Naoki Isomura,Akihiro Takemura,Shigeyuki Takamatsu,Tomoyasu Kumano,Tsuyoshi Takanaka
Journal of Radiotherapy , 2014, DOI: 10.1155/2014/743150
Abstract: Purpose. Accuracy of dose delivery in multiple breath-hold segmented volumetric modulated arc therapy (VMAT) was evaluated in comparison to noninterrupted VMAT using a static phantom. Material and Methods. Five VMAT plans were evaluated. A Synergy linear accelerator (Elekta AB, Stockholm, Sweden) was employed. A VMAT delivery sequence was divided into multiple segments according to each of the predefined breath-hold periods (10, 15, 20, 30, and 40 seconds). The segmented VMAT delivery was compared to noninterrupted VMAT delivery in terms of the isocenter dose and pass rates of a dose difference of 1% with a dose threshold of 10% of the maximum dose on a central coronal plane using a two-dimensional dosimeter, MatriXX Evolution (IBA Dosimetry, Schwarzenbruck, Germany). Results. Means of the isocenter dose differences were 0.5%, 0.2%, 0.2%, 0.0%, and 0.0% for the beam-on-times between interrupts of 10, 15, 20, 30, and 40 seconds, respectively. Means of the pass rates were 85%, 99.9%, 100%, 100%, and 100% in the same order as the above. Conclusion. Our static phantom study indicated that the multiple breath-hold segmented VMAT maintains stable and accurate dose delivery when the beam-on-time between interrupts is 15 seconds or greater. 1. Introduction Although radiotherapy has been successfully applied to lung, liver, and pancreas tumors [1–3], breathing motion needs to be considered for the tumors located in proximity to the diaphragm [4–9]. A traditional approach is an enlarged internal margin that was added to a gross tumor volume (GTV) or a clinical target volume (CTV), resulting in possible higher complication to neighboring organs at risk (OARs) [10]. To minimize the internal margin, breath-hold with active breathing control (ABC) or patient voluntary breath-hold was used for intensity modulated radiation therapy (IMRT) [4, 10–12] among other techniques such as gating. IMRT provides more conformal dose for the target and more reduced dose for OARs compared to 3D conformal radiotherapy (3D-CRT). A disadvantage of IMRT is increased monitor units and thus beam-on-time, thereby possibly causing larger intrafractional tumor localization error [13, 14]. Volumetric modulated arc therapy (VMAT) allows a faster dose delivery while gantry and multileaf collimator (MLC) are dynamically controlled [15–19]. A combination of breath-hold and VMAT may lead to a quick and accurate treatment option for a moving tumor close to diaphragm. Nevertheless, the beam-on-time for a VMAT delivery is typically two to four minutes, thereby preventing a single breath-hold
Acinar Cell Carcinoma of the Pancreas with Colon Involvement
Naoki Asayama,Yasushi Kojima,Tomonori Aoki,Chiaki Maeyashiki,Chizu Yokoi,Mikio Yanase,Ryuichiro Suda,Hideaki Yano,Harumi Nakamura,Toru Igari
Case Reports in Medicine , 2014, DOI: 10.1155/2014/389425
Abstract: We report a case of acinar cell carcinoma of the pancreas with colon involvement that was difficult to distinguish from primary colon cancer. A 60-year-old man was admitted with a 1-month history of diarrhea. Contrast-enhanced computed tomography (CT) revealed a large tumor ( ?cm) at the splenic flexure of the colon. Colonoscopy showed completely round ulcerative lesions, and biopsy revealed poorly differentiated adenocarcinoma. Left hemicolectomy, resection of the jejunum and pancreas body and tail, and splenectomy were performed based on a diagnosis of descending colon cancer (cT4N0M0, stage IIB), and surgery was considered to be curative. Diagnosis was subsequently confirmed as moderately differentiated acinar cell carcinoma of the pancreas by immunohistochemical staining (pT3N0M0, stage IIA). Multiple liver metastases with portal thrombosis were found 8 weeks postoperatively. Despite combination chemotherapy with oral S-1 and gemcitabine, the patient died of hepatic failure with no effect of chemotherapy 14 weeks postoperatively. Correct diagnosis was difficult to determine preoperatively from the clinical, CT, and colonoscopy findings. Moreover, the disease was extremely aggressive even after curative resection. Physicians should consider pancreatic cancer in the differential diagnosis of similar cases. 1. Introduction Acinar cell carcinoma of the pancreas (ACC) is a rare malignant epithelial tumor representing 1-2% of all exocrine pancreatic neoplasms [1]. Symptoms such as weight loss, abdominal pain, nausea, and vomiting are nonspecific and are related mostly to either locally advanced tumors or metastasis [1, 2]. We present in this report a case of ACC with colon involvement that was difficult to distinguish from primary colon cancer. 2. Case Presentation A 60-year-old man with no remarkable past history was admitted to our hospital in October 2011 with a 1-month history of diarrhea and nonspecific lower abdominal pain. He also complained of losing 25?kg within the previous 2 months. He did not regularly drink alcohol and had no history of acute pancreatitis or trauma. On admission, a hard mass, approximately 15?cm in size, with an irregular surface was palpable in the left abdomen. Initial laboratory tests revealed a white blood cell count of 23,960/ L (normal: 3500–8500/ L; 91% neutrophils; normal: 46–61%), a hemoglobin level of 5.8?g/dL (normal: 13.5–17.0?g/dL), and a platelet count of 32.0?×?104/ L (normal: 15–35?×?104/ L). Serum carbohydrate antigen 19.9 (CA19–9) was 48.9?U/L (normal: 0–36.0?U/L), carcinoembryonic antigen (CEA) was
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