Network


Latest external collaboration on country level. Dive into details by clicking on the dots.

Hotspot


Dive into the research topics where Gen Yamamoto is active.

Publication


Featured researches published by Gen Yamamoto.


Hepatology Research | 2014

Effects of oral intake of hydrogen water on liver fibrogenesis in mice

Yukinori Koyama; Kojiro Taura; Etsuro Hatano; Kazutaka Tanabe; Gen Yamamoto; Kojiro Nakamura; Kenya Yamanaka; Koji Kitamura; Masato Narita; Hiromitsu Nagata; Atsuko Yanagida; Taku Iida; Keiko Iwaisako; Hikohito Fujinawa; Shinji Uemoto

Liver fibrosis is the universal consequence of chronic liver diseases. Sustained hepatocyte injury initiates an inflammatory response, thereby activating hepatic stellate cells, the principal fibrogenic cells in the liver. Reactive oxygen species are involved in liver injury and are a promising target for treating liver fibrosis. Hydrogen water is reported to have potential as a therapeutic tool for reactive oxygen species‐associated disorders. This study aimed to investigate the effects of hydrogen water on liver fibrogenesis and the mechanisms underlying these effects.


Journal of Surgical Research | 2013

Effect of olprinone on liver microstructure in rat partial liver transplantation

Kenya Yamanaka; Etsuro Hatano; Khota Iguchi; Gen Yamamoto; Motohiko Sato; Kan Toriguchi; Kazutaka Tanabe; Kenji Takemoto; Kojiro Nakamura; Noriyuki Koyama; Masato Narita; Hiromitsu Nagata; Kojiro Taura; Shinji Uemoto

BACKGROUND Donor safety is a major concern in living-donor liver transplantation. However, partial grafts do not meet the functional demands of recipients and lead to small-for-size syndrome (SFSS). In a previous study, we showed that olprinone (OLP), a selective phosphodiesterase ІІІ inhibitor, up-regulates endothelial nitric oxide synthase level in the liver and attenuates shear stress, sinusoidal endothelial cell injury, and hepatocyte apoptosis after excessive liver resection in a rat model. We aimed to examine whether OLP treatment has beneficial effects on SFSS in a rat model of partial liver transplantation (PLT). METHODS We performed experiments in a rat model of 30% PLT. In the OLP group, we inserted an osmotic pump with OLP into the peritoneal cavity 48 h before liver graft sampling. Recipient rats were not treated with OLP. We examined the liver microstructure by electron microscopy and biochemical examination, and determined the 7-d survival of recipients. RESULTS In the OLP group 1 h after PLT, the sinusoidal endothelial cells of the liver were well preserved and we observed few vacuolar structures in hepatocytes. The total serum bilirubin level 1 wk after PLT tended to be lower in the OLP group than in the controls, and the liver microstructures were also well preserved in the OLP group. The probability of survival in the OLP group (100%; 14 of 14 rats) was significantly higher than that in the control group (75%; 15 of 20 rats). CONCLUSIONS Olprinone treatment was demonstrated to have therapeutic potential to overcome SFSS.


Annals of Surgery | 2017

Usefulness of Mac-2 Binding Protein Glycosylation Isomer for Prediction of Posthepatectomy Liver Failure in Patients With Hepatocellular Carcinoma.

Yukihiro Okuda; Kojiro Taura; Kenji Yoshino; Yoshinobu Ikeno; Takahiro Nishio; Gen Yamamoto; Kazutaka Tanabe; Yukinori Koyama; Etsuro Hatano; Shiro Tanaka; Shinji Uemoto

Objective: The aim of this study was to evaluate the usefulness of the Mac-2 binding protein glycosylation isomer (M2BPGi) for the prediction of posthepatectomy liver failure (PHLF) in hepatocellular carcinoma (HCC) patients. Summary Background Data: M2BPGi is a novel serum marker of liver fibrosis. The usefulness of M2BPGi for the prediction of PHLF has not been evaluated. Methods: Clinicopathological data were analyzed in 138 HCC patients who underwent liver resection between August 2011 and November 2014. PHLF was evaluated according to the definition of the International Study Group of Liver Surgery. Performance of preoperative parameters in predicting PHLF was determined using receiver operating characteristic (ROC) analysis. Results: Serum M2BPGi level correlated with the METAVIR fibrosis score. M2BPGi levels of hepatitis C virus (HCV)-positive patients were significantly higher than those of HCV-negative patients, even in the same fibrosis stage. PHLF ≥ Grade B developed in 19 patients (13.8%). The area under the ROC curve (AUROC) of M2BPGi for the prediction of PHLF ≥ Grade B was 0.71. In multivariate analysis, M2BPGi [odds ratio (OR): 2.08, 95% confidence interval (CI) 1.28–3.55], platelet count (OR: 0.39, 95% CI 0.18–0.80), and resection rate (OR: 2.71, 95% CI 1.46–5.40) were the significant factors associated with PHLF ≥ Grade B. The AUROC of the PHLF index defined by these factors was 0.81. Notably, in patients with HCV infection, the predictive ability of M2BPGi for PHLF (AUROC 0.85) was the best among the preoperative parameters. Conclusions: M2BPGi is a useful predictor of PHLF, especially in patients with HCV infection.


Pancreas | 2017

Pancreatic Stellate Cells Have Distinct Characteristics From Hepatic Stellate Cells and Are Not the Unique Origin of Collagen-producing Cells in the Pancreas

Gen Yamamoto; Kojiro Taura; Keiko Iwaisako; Masataka Asagiri; Shinji Ito; Yukinori Koyama; Kazutaka Tanabe; Kohta Iguchi; Motohiko Satoh; Takahiro Nishio; Yukihiro Okuda; Yoshinobu Ikeno; Kenji Yoshino; Satoru Seo; Etsuro Hatano; Shinji Uemoto

Objectives The origin of collagen-producing myofibroblasts in pancreatic fibrosis is still controversial. Pancreatic stellate cells (PSCs), which have been recognized as the pancreatic counterparts of hepatic stellate cells (HSCs), are thought to play an important role in the development of pancreatic fibrosis. However, sources of myofibroblasts other than PSCs may exist because extensive studies of liver fibrosis have uncovered myofibroblasts that did not originate from HSCs. This study aimed to characterize myofibroblasts in an experimental pancreatic fibrosis model in mice. Methods We used transgenic mice expressing green fluorescent protein via the collagen type I &agr;1 promoter and induced pancreatic fibrosis with repetitive injections of cerulein. Results Collagen-producing cells that are negative for glial fibrillary acidic protein (ie, not derived from PSCs) exist in the pancreas. Pancreatic stellate cells had different characteristics from those of HSCs in a very small possession of vitamin A using mass spectrometry and a low expression of lecithin retinol acyltransferase. The microstructure of PSCs was entirely different from that of HSCs using flow cytometry and electron microscopy. Conclusions Our study showed that characteristics of PSCs are different from those of HSCs, and myofibroblasts in the pancreas might be derived not only from PSCs but also from other fibrogenic cells.


Liver Transplantation | 2018

Low Preoperative Platelet Count Predicts Risk of Subclinical Posthepatectomy Liver Failure in Right Lobe Donors for Liver Transplantation

Kenji Yoshino; Kojiro Taura; Yoshinobu Ikeno; Yukihiro Okuda; Takahiro Nishio; Gen Yamamoto; Satoru Seo; Shintaro Yagi; Koichiro Hata; Toshimi Kaido; Hideaki Okajima; Shinji Uemoto

Living donor right hepatectomy (LDRH) is a common procedure in adult‐to‐adult living donor liver transplantation, but it is associated with a higher risk of posthepatectomy liver failure (PHLF) compared with left hepatectomy because of a smaller remnant. We identified risk factors for PHLF and other complications in LDRH, verified the appropriateness of the criteria, and explored the possibility of adjusting the minimum remnant liver volume (RLV) based on individual risk. Between October 2005 and November 2017, 254 donors undergoing LDRH at Kyoto University Hospital were enrolled. Clinical data were collected retrospectively. All complications were graded according to the Clavien‐Dindo classification. No donors had grade 4 or 5 complications or clinically significant grade B or C PHLF. Grade A PHLF occurred in 30 donors (11.8%). Male sex (P = 0.01), lower preoperative platelet count (PLT; P = 0.01), higher prothrombin time–international normalized ratio (P = 0.03), higher total bilirubin (P = 0.01), smaller RLV (P = 0.03), and greater blood loss (P = 0.04) were associated with increased risk of PHLF in the univariate analysis, whereas PLT, RLV, and blood loss remained significant in the multivariate analysis. Grade 2 or 3 complications were observed in 32 (12.6%) donors. Higher body mass index (BMI; P = 0.002) and larger blood loss (P = 0.02) were identified as risk factors for complications (Clavien‐Dindo grade ≥ 2) in univariate analysis. Only BMI remained significant in the multivariate analysis. In conclusion, LDRH is performed safely with acceptable morbidity under the current criteria. Minimum RLV may be marginally adjusted by PLT and reducing intraoperative blood loss minimizes PHLF risk. Liver Transplantation 00 000–000 2018 AASLD.


Anticancer Research | 2018

Usefulness of Preoperative18F-FDG-PET in Detecting Invasive Intraductal Papillary Neoplasm of the Bile Duct

Yoshinobu Ikeno; Satoru Seo; Gen Yamamoto; Yuji Nakamoto; Yusuke Uemoto; Hiroaki Fuji; Kenji Yoshino; Tomoaki Yoh; Kojiro Taura; Shinji Uemoto

Background/Aim: Preoperative identification of the invasive component remains challenging in intraductal papillary neoplasm of the bile duct (IPNB). We evaluated the ability of preoperative 18F-fluorodeoxyglucose positron emission tomography (18F-FDG-PET) to differentiate between non-invasive IPNB, invasive IPNB, and papillary cholangiocarcinoma (CCA). Patients and Methods: The maximum standardized uptake values (SUVmax) of 11 patients with IPNB (6 non-invasive and 5 invasive) and 20 with papillary CCA who underwent pre-surgical 18F-FDG-PET were assessed. The SUVmax cut-off that predicts an invasive component was determined using receiver operating characteristic (ROC) curve analysis. Results: The SUVmax in patients with invasive IPNB and papillary CCA were significantly higher than in patients with non-invasive IPNB (p=0.035 and 0.0025, respectively). ROC curve analysis revealed an optimal SUVmax cut-off of 4.5, which had 94.5% accuracy, 76.0% sensitivity, and 100% specificity. Conclusion: Our data suggest that the preoperative 18F-FDG-PET SUVmax can differentiate non-invasive IPNB from invasive IPNB and papillary CCA.


Annals of Hepato-Biliary-Pancreatic Surgery | 2018

Sclerosing encapsulating peritonitis after living-donor liver transplantation: A case series, Kyoto experience

Vusal Aliyev; Shintaro Yagi; Ahmed Hammad; Amr Badawy; Yudai Sasaki; Yuki Masano; Gen Yamamoto; Naoko Kamo; Kojiro Taura; Hideaki Okajima; Toshimi Kaido; Shinji Uemoto

Sclerosing encapsulating peritonitis (SEP), or abdominal cocoon is a rare cause of intestinal obstruction, and still etiology remains unknown. We report a series of 4 patients with abdominal cocoon, and all the 4 patients had previously undergone living-donor liver transplantation (LDLT). There was no evidence of SEP before and during LDLT. At the time of diagnosis of SEP, 3 out of 4 patients had ascites. First and fourth patients had multiple episodes or attacks of cholangitis, which were managed by percutaneous transhepatic biliary drainage and hepaticojejunostomy, respectively. All 4 patients presented with intestinal obstruction and 3 of them underwent a successful operation. The fourth patient died due to liver failure and complications of the SEP. The first 3 patients are doing well without SEP recurrence. Our experience suggest that the prognosis of SEP is poor in patients with poor graft liver functions after LDLT.


Transplantation Proceedings | 2017

Case Report of Extensive Isolated Spontaneous Celiac Trunk Dissection After Liver Transplantation

K. Iwaki; Shintaro Yagi; T. Iida; E. Ogawa; Yuki Masano; T. Tajima; Shinya Okumura; Gen Yamamoto; Naoko Kamo; Kojiro Taura; Toshimi Kaido; Shinji Uemoto

Arterial dissection is a rare complication after liver transplantation (LT). We report a case of extensive isolated spontaneous celiac trunk dissection (ISCTD) up to the proper hepatic artery, left gastric artery, and splenic artery after living donor liver transplantation. A 48-year-old woman with cryptogenic liver cirrhosis underwent living donor liver transplantation. Intraoperative and postoperative Doppler ultrasound revealed sufficient flow in the hepatic artery, portal vein, and hepatic vein. On postoperative day (POD) 10, Doppler ultrasound showed reduction of hepatic arterial flow. On POD 16, a contrast-enhanced computed tomography scan showed that the ISCTD extended to the proper hepatic artery, left gastric artery, and splenic artery with an entry tear on the proximal side of the celiac trunk. Although the computed tomography scan showed ischemia of a small part of the liver, blood flow to the liver was kept to some extent. Because all false lumens were occluded by thrombi and the liver enzyme levels normalized, we chose conservative therapy with antiplatelet agents. The patient was discharged on POD 53. She remains well without any liver dysfunction after 18 months with reduction in all false lumens and a patent hepatic artery. Several cases of ISCTD have been reported apart from LT, most of which were treated with conservative therapy. We conclude that conservative therapy could be the first choice in ISCTD even after LT.


PLOS ONE | 2017

Chronological profiling of plasma native peptides after hepatectomy in pigs: Toward the discovery of human biomarkers for liver regeneration

Kohta Iguchi; Etsuro Hatano; Takashi Nirasawa; Noriyuki Iwasaki; Motohiko Sato; Gen Yamamoto; Kenya Yamanaka; Tatsuya Okamoto; Yosuke Kasai; Naohiko Nakamura; Hiroaki Fuji; Tomohito Sakai; Nobuto Kakuda; Satoru Seo; Kojiro Taura; Kei Tashiro; Shinji Uemoto; Masaya Ikegawa

Liver regeneration after partial hepatectomy (PHx) is a time-dependent process, which is tightly regulated by multiple signaling cascades. Failure of this complex process leads to posthepatectomy liver failure (PHLF), which is associated with a high rate of mortality. Thus, it is extremely important to establish a useful biomarker of liver regeneration to help prevent PHLF. Here, we hypothesized that alterations in the plasma peptide profile may predict liver regeneration following PHx and hence we set up a diagnostic platform for monitoring posthepatectomy outcome. We chronologically analyzed plasma peptidomic profiles of 5 partially hepatectomized microminipigs using the ClinProtTM system, which consists of magnetic beads and MALDI-TOF/TOF MS. We identified endogenous circulating peptides specific to each phase of the postoperative course after PHx in pigs. Notably, peptide fragments of histones were detected immediately after PHx; the presence of these fragments may trigger liver regeneration in the very acute phase after PHx. An N-terminal fragment of hemoglobin subunit α (3627 m/z) was detected as an acute-phase-specific peptide. In the recovery phase, the short N-terminal fragments of albumin (3028, 3042 m/z) were decreased, whereas the long N-terminal fragment of the protein (8926 m/z) was increased. To further validate and extract phase-specific biomarkers using plasma peptidome after PHx, plasma specimens of 4 patients who underwent PHx were analyzed using the same method as we applied to pigs. It revealed that there was also phase-specificity in peptide profiles, one of which was represented by a fragment of complement C4b (2378 m/z). The strategy described herein is highly efficient for the identification and characterization of peptide biomarkers of liver regeneration in a swine PHx model. This strategy is feasible for application to human biomarker studies and will yield clues for understanding liver regeneration in human clinical trials.


International Journal of Surgery Case Reports | 2017

Mass-forming intrahepatic cholangiocarcinoma with portal vein tumor thrombus and bile duct tumor thrombus: A case report

Kentaro Iwaki; Toshimi Kaido; Gen Yamamoto; Naoko Kamo; Shintaro Yagi; Kojiro Taura; Shinji Uemoto

Highlights • This is the first case of mass-forming intrahepatic cholangiocarcinoma with portal vein tumor thrombus and bile duct tumor thrombus, where the extrahepatic bile duct was preserved with thrombectomy.• Thrombectomy can be a valid option for intrahepatic cholangiocarcinoma with tumor thrombus, as well as for hepatocellular carcinoma.

Collaboration


Dive into the Gen Yamamoto's collaboration.

Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Researchain Logo
Decentralizing Knowledge