93 results on '"Naoki Okuda"'
Search Results
2. Death, reoperation, and late cardiopulmonary function after truncus repairCentral MessagePerspective
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Takaya Hoashi, MD, PhD, Kenta Imai, MD, PhD, Naoki Okuda, MD, Motoki Komori, MD, Yoshikazu Ono, MD, Kenichi Kurosaki, MD, and Hajime Ichikawa, MD, PhD
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truncus arteriosus ,truncal valve regurgitation ,truncal root dilatation ,Diseases of the circulatory (Cardiovascular) system ,RC666-701 ,Surgery ,RD1-811 - Abstract
Objective: To identify the late surgical outcomes of truncus arteriosus. Methods: Fifty consecutive patients with truncus arteriosus who underwent surgery between 1978 and 2020 at our institute were enrolled in this retrospective, single institutional cohort study. The primary outcome was death and reoperation. The secondary outcome was late clinical status, including exercise capacity. The peak oxygen uptake was measured by a ramp-like progressive exercise test on a treadmill. Results: Nine patients underwent palliative surgery, which resulted in 2 deaths. Forty-eight patients went on to truncus arteriosus repair, including 17 neonates (35.4%). The median age and body weight at repair were 92.5 days (interquartile range, 10-272 days) and 3.85 kg (interquartile range, 2.9-6.5 kg), respectively. The survival rate at 30 years was 68.5%. Significant truncal valve regurgitation (P = .030) was a risk factor for survival. Survival rates were similar between in the early 25 and late 25 patients (P = .452). The freedom from death or reoperation rate at 15 years was 35.8%. Significant truncal valve regurgitation was a risk factor (P = .001). The mean follow-up period in hospital survivors was 15.4 ± 12 years (maximum, 43 years). The peak oxygen uptake, which was performed in 12 long-term survivors at a median duration from repair of 19.7 years (interquartile range, 16.8-30.9 years), was 70.2% of predicted normal (interquartile range, 64.5%-80.4%). Conclusions: Truncal valve regurgitation was a risk factor for both survival and reoperation, thus improvement of truncal valve surgery is essential for better life prognosis and quality of life. Slightly reduced exercise tolerance was common in long-term survivors.
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- 2023
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3. Impact of right ventriculotomy for tetralogy of Fallot repair with a pulmonary valve–sparing procedureCentral MessagePerspective
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Yoshikazu Ono, MD, Takaya Hoashi, MD, PhD, Kenta Imai, MD, Naoki Okuda, MD, Motoki Komori, MD, Kenichi Kurosaki, MD, and Hajime Ichikawa, MD, PhD
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inverse probability weighting ,pulmonary valve-sparing procedure ,right ventriculotomy ,tetralogy of Fallot ,Diseases of the circulatory (Cardiovascular) system ,RC666-701 ,Surgery ,RD1-811 - Abstract
Objectives: The study objectives were to reconfirm the superiority of the pulmonary valve-sparing procedure versus the transannular patch procedure for repair of tetralogy of Fallot and to evaluate the influence of a right ventriculotomy in the pulmonary valve-sparing procedure. Methods: Between 1978 and 2003, 440 patients (aged
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- 2022
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4. Long-Term Influence of Atrial Switch Operation on Hemodynamics After the Rastelli Procedure
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Takaya Hoashi, Kenta Imai, Naoki Okuda, Motoki Komori, Kenichi Kurosaki, and Hajime Ichikawa
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Pediatrics, Perinatology and Child Health ,Cardiology and Cardiovascular Medicine - Abstract
The study aimed to investigate the long-term influence of atrial switch on post-Rastelli hemodynamic condition. Of 112 patients with transposition of the great arteries (TGA) or TGA-type double outlet right ventricle, ventricular septal defect (VSD), and pulmonary stenosis (PS) who underwent intra-cardiac repair between 1979 and 2018, 50 patients with levo-TGA underwent atrial switch and Rastelli as an anatomic repair and 62 patients with dextro-TGA underwent Rastelli. Postoperative outcomes were retrospectively compared. The median follow-up durations were 20.1 years (interquartile range: 4.3, 32.4) in the Rastelli group and 15.3 years (7.1, 23.0) in the atrial switch plus Rastelli group (p = 0.19). Sex, age, and weight at operation were similar in both groups. Overall survival rates at 30 years were 69.8% in the Rastelli group and 80.1% in the atrial switch plus Rastelli group (p = 0.18). The atrial switch plus Rastelli group required more frequent catheter interventions (p 0.001), mainly for caval obstruction (n = 8) and atrial arrhythmia (n = 6). Medication was more frequent in the atrial switch plus Rastelli group (p = 0.009). Exercise capacity was similarly reduced in two groups. Protein-losing enteropathy (PLE) occurred in three long-term survivors in the atrial switch plus Rastelli group (p = 0.07). Concomitantly performed atrial switch operation did not affect long-term survival and exercise capacity after Rastelli procedure. However, the occurrence of PLE, a frequent need for medication, and catheter interventions after atrial switch plus Rastelli may result from atrial switch under the post-Rastelli condition.
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- 2022
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5. A propensity score-matched comparison between Mako robotic arm-assisted system and conventional technique in total hip arthroplasty for patients with osteoarthritis secondary to developmental dysplasia of the hip
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Kei Sato, Atsuko Sato, Naoki Okuda, Matsubara Masaaki, and Hideyuki Koga
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Orthopedics and Sports Medicine ,Surgery ,General Medicine - Abstract
The clinical effectiveness of robotic arm-assisted systems remains unclear for total hip arthroplasty (THA) in patients suffering from osteoarthritis secondary to developmental dysplasia of the hip (DDH).Patients with DDH who underwent primary THA were included in this study. We conducted a propensity score-matched comparison between THAs using a robotic arm-assisted system (Mako group) versus those using the manual procedure (manual group) to compare the absolute differences in cup placement angles measured using postoperative computed tomography and those planned preoperatively.A total of 217 patients with osteoarthritis due to DDH met the inclusion criteria. Eighty-four patients were matched as the Mako group and 84 as the manual group. The differences were smaller in the Mako group than the manual group in terms of both inclination and anteversion angles (1.1 ± 1.0 versus 4.2 ± 3.1, respectively; 95% CI, 2.4 to 3.8; p 0.0001, and 1.2 ± 1.1 versus 5.8 ± 4.0, respectively; 95% CI, 3.7 to 5.5; p 0.0001).The robotic arm-assisted system may provide more accurate cup placement in THA for DDH.
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- 2022
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6. Availability Analysis of a Multibase System with Lateral Resupply between Bases.
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Naoki Okuda, Nobuyuki Tamura, Tetsushi Yuge, and Shigeru Yanagi
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- 2015
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7. The reduced left ventricular stroke volume does not fully recover after pulmonary valve replacement in patients with repaired tetralogy of Fallot
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Kenta Imai, Kenichi Kurosaki, Naoki Okuda, Hajime Ichikawa, Hideo Ohuchi, Tetsuya Fukuda, Takashi Yasukawa, and Takaya Hoashi
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Adult ,Pulmonary and Respiratory Medicine ,medicine.medical_specialty ,030204 cardiovascular system & hematology ,030218 nuclear medicine & medical imaging ,Right ventricular ejection fraction ,03 medical and health sciences ,0302 clinical medicine ,Internal medicine ,Pulmonary Valve Replacement ,Left ventricular Stroke volume ,Humans ,Medicine ,In patient ,Tetralogy of Fallot ,Heart Valve Prosthesis Implantation ,Pulmonary Valve ,business.industry ,Clinical events ,Stroke Volume ,General Medicine ,Stroke volume ,medicine.disease ,Pulmonary Valve Insufficiency ,Treatment Outcome ,Right heart ,Ventricular Function, Right ,Cardiology ,Surgery ,Cardiology and Cardiovascular Medicine ,business - Abstract
OBJECTIVES The present study was conducted to investigate the decrease in left ventricular stroke volume index (LVSVI) that is caused by pulmonary regurgitation-induced right heart dysfunction and its clinical implications before and after pulmonary valve replacement (PVR). METHODS Between January 2010 and December 2019, 30 adults who underwent surgical PVR for chronic pulmonary regurgitation with right ventricular dilation late after tetralogy of Fallot (TOF) repair were included. All patients were evaluated using cardiac magnetic resonance before PVR. The median interval from TOF repair to PVR was 29 [25th, 75th percentile: 25, 37] years. The median pulmonary regurgitation fraction and right ventricular end-diastolic volume index were 56 [48, 66] % and 203 [187, 239] ml/m2. Twenty-three patients (76.7%) were re-evaluated 1 year after PVR. RESULTS Before PVR, the median LVSVI was 40 [35, 46] ml/beat/m2. A lower LVSVI was associated with a longer interval from TOF repair to PVR (r = −0.40, P = 0.029) and a lower right ventricular ejection fraction (r = 0.52, P = 0.004). A lower LVSVI was not associated with a higher right ventricular end-diastolic volume index. LVSVI remained unchanged after PVR. The patients were subdivided into Normal-stroke volume index (SVI) and Subnormal-SVI groups using the preoperative LVSVI cut-off value of 35 mL/beat/m2. Compared with the Normal-SVI group, the Subnormal-SVI group had a higher incidence of ablation therapy before PVR (4.7 vs 2.3 patient-years, P = 0.044). After PVR, LVSVI in the Subnormal-SVI group was still lower (40 [34, 42] vs 44 [42, 47] ml/beat/m2, P = 0.038) despite the right ventricular end-diastolic volume index normalization. There was no difference in the clinical event incidence between the 2 groups during the follow-up period. Brain natriuretic peptide level in the Subnormal-SVI group was higher within 3 years after PVR (P = 0.046). CONCLUSIONS Reduced left ventricular stroke volume did not fully recover after PVR. PVR for patients with repaired TOF should be performed before the left ventricular stroke volume begins to decrease.
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- 2021
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8. Midterm Outcomes and Frequency of Osteolysis of Total Hip Arthroplasty Using Cementless Modular Stem for Asian Patients
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Masaaki Matsubara, Naoki Okuda, Sachiyuki Tsukada, Akimasa Kimura, Masanori Kase, and Atsuko Sato
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Reoperation ,musculoskeletal diseases ,medicine.medical_specialty ,Osteolysis ,Arthroplasty, Replacement, Hip ,Radiography ,Prosthesis Design ,03 medical and health sciences ,0302 clinical medicine ,Asian People ,medicine ,Deformity ,Humans ,Orthopedics and Sports Medicine ,Retrospective Studies ,Fixation (histology) ,030222 orthopedics ,business.industry ,Modular system ,Metal debris ,Middle Aged ,musculoskeletal system ,medicine.disease ,Prosthesis Failure ,Surgery ,Treatment Outcome ,Dysplasia ,Hip Joint ,Hip Prosthesis ,medicine.symptom ,business ,Follow-Up Studies ,Total hip arthroplasty - Abstract
Modular stems are useful for total hip arthroplasty (THA) in anatomically difficult dysplasia. Here, we present mean 6.8-year outcomes of cementless primary THA using S-ROM-A (modified modular stem for Asian patients) femoral prosthesis in anatomically difficult cases.Charts of 373 patients (461 hips) undergoing THA (mean age, 58 years) were reviewed for clinical evaluation of modified Merle d'Aubigné-Postel score and Kaplan-Meier survivorship with revision for any reason as the end point. For radiographic analysis, 331 patients (412 hips) followed up for ≥5 years were included. Bearing couples were metal-on-metal (n = 145), metal-on-polyethylene (n = 120), and ceramic-on-polyethylene (n = 147). Radiography and multiplanar computed tomography were performed.No postoperative dislocation or deep infection occurred. Mean modified Merle d'Aubigné-Postel score improved significantly (10.9 points preoperatively, 16.7 points at last follow-up; P.001). Cumulative 5- and 10-year stem survival rates were 100% and 84%, respectively (95% confidence interval, 75%-93%). All stems were classified as bone ingrown fixation. Osteolysis occurred in metal-on-metal (42.8%) and metal-on-polyethylene (15.8%) groups. Mean time to osteolysis was ~3 years, with no significant difference between 3 groups (P = .264). In logistic regression, lower cup inclination angle was significantly associated with osteolysis (odds ratio, 0.914; 95% confidence interval, 0.84-0.99; P = .029).S-ROM-A femoral prosthesis achieved excellent midterm fixation, and the modular system was useful in primary THA with severe deformity. Bearing couples are potentially associated with adverse reactions to metal debris. S-ROM-A with ceramic-on-polyethylene bearing couples may be an option for anatomically difficult THA.
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- 2020
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9. Comparison of long-term outcomes of atrial switch with Rastelli and physiological repair using left ventricle-to-pulmonary artery conduit for levo-transposition of the great arteries
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Yoshikazu, Ono, Takaya, Hoashi, Kenta, Imai, Naoki, Okuda, Motoki, Komori, Kazuki, Tanimoto, Kenichi, Kurosaki, and Hajime, Ichikawa
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Pulmonary and Respiratory Medicine ,Surgery ,Cardiology and Cardiovascular Medicine - Abstract
The objectives of this study was to compare the long-term outcomes of anatomic repair using atrial switch with the Rastelli procedure versus physiological repair with left ventricle-to-pulmonary artery conduit for patients with levo-transposition of the great arteries, ventricular septal defect, and left ventricular outflow tract obstruction.Of patients with levo-transposition of the great arteries who underwent biventricular repair between 1978 and 2001, 31 hospital survivors after anatomic repair of atrial switch and the Rastelli (anatomic group) and 14 hospital survivors after physiological repair with left ventricle-to-pulmonary artery conduit (physiological group) were enrolled. Survival rates, reoperation rates, and most recent conditions were compared.The overall survival rate at 20 years was 79.7% (95% CI, 66.4%-95.6%) in the anatomic group and 85.1% (95% CI, 68.0%-100%) in the physiological group (P = .87). The reoperation rate at 10 years was 19.8% (95% CI, 5.6%-34.0%) in the anatomic group and 52.0% (95% CI, 25.0%-79.1%) in the physiological group (P = .067). Only patients in the physiological group underwent systemic tricuspid valve replacement. The anatomic group showed a better cardiac index at catheterization (2.79 ± 0.75 L/min/mPreservation of the left ventricle as the systemic ventricle using anatomic repair contributes to better cardiopulmonary condition compared with physiological repair.
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- 2023
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10. Patient-Prosthesis Mismatch Associated With Somatic Growth After Mechanical Mitral Valve Replacement in Small Children: Metrics for Reoperation and Outcomes
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Yuji Nakamura, Takaya Hoashi, Kenta Imai, Naoki Okuda, Motoki Komori, Kenichi Kurosaki, and Hajime Ichikawa
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Pulmonary and Respiratory Medicine ,Surgery ,General Medicine ,Cardiology and Cardiovascular Medicine - Abstract
Reoperation after pediatric mitral valve replacement (MVR) is inevitable due to patient-prosthesis mismatch (PPM) associated with somatic growth. We analyzed potential metrics for PPM and outcomes of redo MVR for valve upsizing. Between 1999 and 2018, 15 children without obstructive left heart lesions other than mitral stenosis underwent initial MVR with a 16-mm ATS-Advanced Performance valve. We analyzed hemodynamic data from 28 postoperative catheterizations and concomitant echocardiograms. The median age and body weight at initial MVR were 4.9 months (25th, 75th percentile: 3.6, 6.6) and 5.9 kg (5.0, 7.3). Redo MVR was planned when patients had congestive heart failure and postcapillary pulmonary hypertension (PH) due to PPM: systolic pulmonary arterial pressure (SPAP)35 mm Hg and pulmonary capillary wedge pressure (PCWP)15 mm Hg on catheterization. Indexed effective orifice area (iEOA) and mean transmitral pressure gradient (TMPG) were strongly correlated with SPAP (r = -0.72, P0.001 and r = 0.75, P0.001) and PCWP (r = -082, P0.001 and r = 0.84, P0.001). Cut-off values for detecting postcapillary PH due to PPM were 1.0 cm
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- 2021
11. Short-term outcomes of EXCOR Paediatric implantation
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Motoki Komori, Takaya Hoashi, Heima Sakaguchi, Kenta Imai, Naoki Okuda, Norihide Fukushima, Kenichi Kurosaki, and Hajime Ichikawa
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Pulmonary and Respiratory Medicine ,Cardiomyopathy, Dilated ,Heart Failure ,Treatment Outcome ,Adolescent ,Heart Transplantation ,Humans ,Surgery ,Heart-Assist Devices ,Cardiology and Cardiovascular Medicine ,Child - Abstract
OBJECTIVES The aim of this study was to review a single institution’s experience with EXCOR Paediatric implantation. METHODS Patients RESULTS Overall median age and weight for all 20 children at implantation were 10.8 (interquartile range, 7.9–33.2) months and 6.3 (4.6–10.2) kg. Ten patients (50%) weighed 20 months. One patient died. Seven patients underwent heart transplant. Heart transplant has not been performed in the last 1.5 years. Five patients were weaned from EXCOR support after native myocardial recovery, including a patient with dilated cardiomyopathy who recovered after 24 months of EXCOR support. Major complication-free survival at 6, 12 and 18 months were 79.3%, 49.6% and 38.6%, respectively. Body weight CONCLUSIONS Survival during EXCOR Paediatric support was good, but it prolonged the wait time for a heart transplant. The number of major complications increased over time and was not negligible, especially in small children.
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- 2021
12. Intermediate-term outcomes of deferred Norwood strategy
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Takaya Hoashi, Kenta Imai, Naoki Okuda, Motoki Komori, Kenichi Kurosaki, and Hajime Ichikawa
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Pulmonary and Respiratory Medicine ,Treatment Outcome ,Hypoplastic Left Heart Syndrome ,Palliative Care ,Humans ,Surgery ,General Medicine ,Alprostadil ,Pulmonary Artery ,Cardiology and Cardiovascular Medicine ,Norwood Procedures ,Retrospective Studies - Abstract
OBJECTIVE The aim of this study was to assess outcomes of the deferred Norwood strategy, i.e. planned Norwood following routine bilateral pulmonary artery banding and ductal stenting or continuous prostaglandin E1 administration. METHODS Forty-five patients with hypoplastic left heart syndrome and its variants treated with the deferred Norwood strategy between 2012 and 2021 were enrolled. Mid-term outcomes were retrospectively reviewed. The median follow-up period after Norwood in hospital survivors was 4.6 years (interquartile range: 1.9, 6.8). RESULTS Fourteen patients (31.1%) had no risk factors. The median age and weight at Norwood were 1.8 months (0.9, 3.5) and 3.1 kg (2.7, 3.6). Transplant-free survival at 6 years was 84.5%. Birth weight ≤2.5 kg and systemic atrioventricular valve (SAVV) regurgitation ≥ moderate after birth were not risk factors for mortality; body weight at Norwood ≤2.5 kg, however, was a risk factor [hazard ratio (HR), 11.3; 95% confidence interval (CI), 1.2–11; P = 0.036]. Twenty-two (48.9%) underwent Fontan with no mortalities, and 7 (15.5%) are awaiting Fontan. Freedom from SAVV surgery at 5 years was 53.1%. SAVV regurgitation ≥ moderate after birth was a risk factor for SAVV surgery (HR, 16; 95% CI, 3.6–71; P < 0.001); however, ductal stenting had a protective effect against SAVV surgery (HR, 0.09; 95% CI, 0.01–0.68; P = 0.019). Freedom from both surgical and catheter-based pulmonary artery intervention at 3 years was 27.1% CONCLUSIONS Although deferred Norwood provided acceptable intermediate-term survival, the Fontan completion rate was unsatisfactory. SAVV surgery and pulmonary artery intervention were frequently required.
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- 2021
13. Autologous skeletal myoblast sheet implantation for pediatric dilated cardiomyopathy: A case report
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Shigeru Miyagawa, Takayoshi Ueno, Yoshiki Sawa, Koichi Toda, Kanta Araki, Masaki Taira, Tomomitsu Kanaya, Toru Kuratani, and Naoki Okuda
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Cardiomyopathy, Dilated ,Pulmonary and Respiratory Medicine ,Cardiac function curve ,medicine.medical_specialty ,Myoblasts, Skeletal ,medicine.medical_treatment ,Transplantation, Autologous ,Cell therapy ,Surgical oncology ,Internal medicine ,medicine ,Humans ,Child ,Heart transplantation ,Skeletal Myoblasts ,business.industry ,Dilated cardiomyopathy ,General Medicine ,medicine.disease ,Cardiac surgery ,Cardiothoracic surgery ,Cardiology ,Heart Transplantation ,Surgery ,Cardiology and Cardiovascular Medicine ,business - Abstract
In children with dilated cardiomyopathy, heart transplantation is the last treatment option. However, new regenerative treatments, such as cell therapy, have attracted scientific attention. We have previously demonstrated the efficacy of autologous skeletal myoblast sheet implantation for treatment of ischemic and dilated cardiomyopathy in adults. Because of the mechanism underlying this cell therapy, a similar effectiveness is expected for patients with pediatric dilated cardiomyopathy. Herein, we describe the case of a child with dilated cardiomyopathy who underwent an autologous skeletal myoblast sheet implantation, which proved to be safe, and led to sustained maintenance and improvements in cardiac function and clinical status.
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- 2020
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14. Impact of Long-Term Support with Berlin Heart EXCOR® in Pediatric Patients with Severe Heart Failure
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Naoki Okuda, Tomomitsu Kanaya, Takuji Watanabe, Toru Kuratani, Koichi Toda, Takashi Kido, Takayoshi Ueno, Masaki Taira, Kanta Araki, and Yoshiki Sawa
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Heart Defects, Congenital ,Male ,medicine.medical_specialty ,Time Factors ,medicine.medical_treatment ,Infarction ,030204 cardiovascular system & hematology ,03 medical and health sciences ,Long-term support ,0302 clinical medicine ,Internal medicine ,medicine ,Humans ,Heart Failure ,Heart transplantation ,business.industry ,Infant ,Vascular surgery ,medicine.disease ,humanities ,Cardiac surgery ,Treatment Outcome ,030228 respiratory system ,Child, Preschool ,Ventricular assist device ,Heart failure ,Pediatrics, Perinatology and Child Health ,Cardiology ,Heart Transplantation ,Female ,Heart-Assist Devices ,Cardiology and Cardiovascular Medicine ,business ,Cerebral Bleeding ,human activities - Abstract
Berlin Heart EXCOR® (BHE) ventricular assist device (VAD) (Berlin Heart, Berlin Heart AG, Berlin, Germany) implantation is prevalent in patients with severe heart failure. However, clinical outcomes of pediatric patients on long-term BHE support remain mainly unknown. This study aimed to report our clinical experience with long-term support of pediatric patients with severe heart failure supported by BHE VAD. Clinical outcomes of 11 patients (median age 8.4 months; two male), who underwent LVAD implantation of the Berlin Heart EXCO® (BHE) VAD (Berlin Heart, Berlin Heart AG, Berlin, Germany) between 2013 and 2017 at our institution were reviewed. The median support period was 312 (range 45-661) days and five patients were supported for more than 1 year. The longest support duration was 661 days. No mortality occurred, and six patients were successfully bridged to heart transplantation, while three patients were successfully weaned off the device. Two patients are currently on BHE support while they await heart transplantation. Four patients had cerebral bleeding or infarction, but only one case of persistent neurological deficit occurred. No fatal device-related infection occurred during LVAD support. BHE VAD can provide long-term support for pediatric patients with severe heart failure with acceptable mortality and morbidity rates with long-term support.
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- 2019
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15. Impact of bilateral bidirectional Glenn anastomosis on staged Fontan strategy and Fontan circulation
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Kenichi Kurosaki, Naoki Okuda, Kenta Imai, Hideo Ohuchi, Takaya Hoashi, and Hajime Ichikawa
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Heart Defects, Congenital ,Pulmonary and Respiratory Medicine ,Pulmonary Circulation ,medicine.medical_specialty ,Vena Cava, Superior ,medicine.medical_treatment ,Heterotaxy Syndrome ,Pulmonary Artery ,030204 cardiovascular system & hematology ,Anastomosis ,Fontan Procedure ,Fontan procedure ,03 medical and health sciences ,0302 clinical medicine ,Superior vena cava ,medicine.artery ,medicine ,Humans ,cardiovascular diseases ,Thrombus ,Lung ,Superior vena cava syndrome ,business.industry ,General Medicine ,Blood flow ,medicine.disease ,Surgery ,Treatment Outcome ,medicine.anatomical_structure ,030228 respiratory system ,Pulmonary artery ,cardiovascular system ,medicine.symptom ,Cardiology and Cardiovascular Medicine ,business - Abstract
OBJECTIVES The aim of this study was to identify the impact of bilateral bidirectional Glenn (BBDG) anastomosis on staged Fontan strategy and late Fontan circulation. METHODS Of 267 patients who underwent bidirectional Glenn prior to Fontan completion between 1989 and 2013, 62 patients (23%) who underwent BBDG were enrolled in this study. Age at operation was 0.84 years (25th–75th percentile: 0.58–1.39). Thirty-three patients had heterotaxy syndrome (53%). The mean follow-up period was 12.7 ± 8.1 (max. 30.6) years. RESULTS The overall survival rate at 15 years was 73%. Although 49 patients (79.0%) went on to Fontan completion, 12 patients (19.4%) died without achieving it. Thrombus formation and poor development in a central pulmonary artery were not observed, but obstruction of the superior vena cava (SVC) occurred in 8 patients (13%), mainly those with right atrial isomerism (P = 0.037). SVC obstruction was not, however, a risk factor for mortality (P = 0.097) or Fontan completion (P = 0.41). The shape of BBDG anastomosis, symmetricity of pulmonary blood flow, impingement of caval blood flow returning from the superior and inferior vena cavae or coexisting interrupted inferior vena cava with azygos or hemi-azygos continuation did not affect late Fontan outcomes, such as overall survival, freedom from protein-losing enteropathy or pulmonary arterio-venous malformation rates. CONCLUSIONS SVC obstruction after BBDG frequently occurred, mainly in patients with right atrial isomerism; however, its direct impact on prognosis or achieving Fontan completion was not identified. Once Fontan circulation was established, the arrangement of the Fontan pathway did not affect late Fontan outcomes.
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- 2021
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16. Impact of right ventriculotomy for tetralogy of Fallot repair with a pulmonary valve-sparing procedure
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Yoshikazu Ono, Takaya Hoashi, Kenta Imai, Naoki Okuda, Motoki Komori, Kenichi Kurosaki, and Hajime Ichikawa
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Pulmonary and Respiratory Medicine ,Surgery ,Cardiology and Cardiovascular Medicine - Abstract
The study objectives were to reconfirm the superiority of the pulmonary valve-sparing procedure versus the transannular patch procedure for repair of tetralogy of Fallot and to evaluate the influence of a right ventriculotomy in the pulmonary valve-sparing procedure.Between 1978 and 2003, 440 patients (aged10 years) underwent tetralogy of Fallot repair. Of these patients, 242 (55.0%) underwent the transannular patch procedure, 106 (24.1%) underwent the pulmonary valve-sparing procedure without right ventriculotomy, and 92 (20.9%) underwent the pulmonary valve-sparing procedure with right ventriculotomy. End points focused on adverse events and included all-cause mortality, reoperation, catheter intervention, and symptomatic arrhythmias. To compare the outcomes of pulmonary valve sparing with and without right ventriculotomy, inverse probability weighting was applied to adjust for potential confounding factors.The median follow-up period was 20.3 years (interquartile range, 10.7-27.6). In all cohorts, the pulmonary valve-sparing procedure was the independent factor that reduced adverse events after tetralogy of Fallot repair (hazard ratio, 0.47; 95% confidence interval, 0.23-0.94;Right ventriculotomy for tetralogy of Fallot repair with pulmonary valve-sparing did not increase major adverse events. However, negative impacts on current status cannot be ignored.
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- 2021
17. Clinical significance of right atrial volume in patients with repaired tetralogy of Fallot
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Masaki Taira, Takayoshi Ueno, Toru Kuratani, Naoki Okuda, Takashi Kido, Koichi Toda, Yoshiki Sawa, and Tomomitsu Kanaya
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Pulmonary and Respiratory Medicine ,Adult ,Male ,medicine.medical_specialty ,Adolescent ,Cardiac Volume ,Diastole ,030204 cardiovascular system & hematology ,Right atrial ,Preoperative care ,03 medical and health sciences ,Young Adult ,0302 clinical medicine ,Pulmonary Valve Replacement ,Internal medicine ,medicine ,Humans ,Clinical significance ,In patient ,cardiovascular diseases ,Heart Atria ,Atrium (heart) ,Cardiac Surgical Procedures ,Tetralogy of Fallot ,business.industry ,Middle Aged ,medicine.disease ,medicine.anatomical_structure ,Treatment Outcome ,030228 respiratory system ,cardiovascular system ,Cardiology ,Surgery ,Female ,Cardiology and Cardiovascular Medicine ,business ,Tomography, X-Ray Computed - Abstract
OBJECTIVES Atrial arrhythmia and right ventricular (RV) diastolic dysfunction are associated with increased morbidity and mortality in patients with repaired tetralogy of Fallot (TOF). This study was performed to determine whether the preoperative right atrial (RA) volume can predict the development of atrial arrhythmia after pulmonary valve replacement (PVR) in patients with TOF. METHODS Forty-seven consecutive adult patients with repaired TOF underwent PVR from 2003 to 2018. Seventeen patients showed preoperative atrial arrhythmia and underwent the Maze procedure concomitantly. The preoperative RA volume was evaluated with computed tomography and image analysis software. RESULTS The median follow-up period after PVR was 6.8 years. Among 17 patients who underwent the Maze procedure, recurrent atrial arrhythmia developed in 8 patients. Among 30 patients without preoperative atrial arrhythmia, novel atrial arrhythmia developed in 2 patients. The RA volume index was a significant predictor according to the multivariate analysis (P = 0.003). The RA volume index showed a significant positive correlation with the RV end-diastolic pressure (P CONCLUSIONS The RA volume predicts the development of atrial arrhythmia after PVR in patients with repaired TOF. RA volume measurement is strongly recommended in the management of this patient population. Clinical trial registration number Institutional review board of Osaka University Hospital, number 16105.
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- 2019
18. Cognitive function at rest and during exercise following breakfast omission
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Yasuki Higaki, Soichi Ando, Mizuki Sudo, Akira Kiyonaga, Tetsuhiko Yasuno, Takaaki Komiyama, Naoki Okuda, and Hiroaki Tanaka
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Adult ,Blood Glucose ,Male ,Elementary cognitive task ,medicine.medical_specialty ,Rest ,Experimental and Cognitive Psychology ,Neuropsychological Tests ,Affect (psychology) ,Developmental psychology ,Task (project management) ,Young Adult ,03 medical and health sciences ,Behavioral Neuroscience ,Cognition ,0302 clinical medicine ,Rest (finance) ,Heart rate ,medicine ,Cognitive development ,Humans ,0501 psychology and cognitive sciences ,050102 behavioral science & comparative psychology ,Exercise ,Breakfast ,Analysis of Variance ,Working memory ,digestive, oral, and skin physiology ,05 social sciences ,food and beverages ,030229 sport sciences ,Physical therapy ,Food Deprivation ,Psychology - Abstract
It has been suggested that breakfast omission, as opposed to breakfast consumption, has the detrimental effects on cognitive function. However, the effects of acute exercise following breakfast omission on cognitive function are poorly understood, particularly during exercise. The purpose of this study was to examine the interactive effects of breakfast and exercise on cognitive function. Ten participants completed cognitive tasks at rest and during exercise in the breakfast consumption or omission conditions. Blood glucose concentration was measured immediately after each cognitive task. We used cognitive tasks to assess working memory [Spatial Delayed Response (DR) task] and executive function [Go/No-Go (GNG) task]. The participants cycled ergometer for 30 min while keeping their heart rate at 140 beats·min(-1). Accuracy of the GNG task was lower at rest in the breakfast omission condition than that in the breakfast consumption condition (Go trial: P=0.012; No-Go trial: P=0.028). However, exercise improved accuracy of the Go trial in the breakfast omission condition (P=0.013). Reaction time in the Go trial decreased during exercise relative to rest in both conditions (P=0.002), and the degree of decreases in reaction time was not different between conditions (P=0.448). Exercise and breakfast did not affect the accuracy of the Spatial DR task. The present results indicate that breakfast omission impairs executive function, but acute exercise improved executive function even after breakfast omission. It appears that beneficial effects of acute exercise on cognitive function are intact following breakfast omission.
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- 2016
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19. Effect of endmilling conditions on surface damage of CFRP
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Yuma Moriuchi, Honoka Miyauchi, Naoki Okuda, Yoshihiro Hara, and Yuki Nishimura
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Surface (mathematics) ,Materials science ,Composite material - Published
- 2020
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20. Single-story steel structure with LVEM-isolated floor: Elastic seismic performance and design response spectrum
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Naoki Okuda, Yuji Koetaka, and Yang Xiang
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Earthquake engineering ,Materials science ,business.industry ,Isolator ,Structural system ,0211 other engineering and technologies ,Stiffness ,020101 civil engineering ,02 engineering and technology ,Structural engineering ,0201 civil engineering ,Damper ,021105 building & construction ,medicine ,Substructure ,Earthquake shaking table ,medicine.symptom ,business ,Response spectrum ,Civil and Structural Engineering - Abstract
The seismic demand of a structure could be reduced by isolating the floors using laminated visco-elastic materials (LVEM). Such a LVEM-isolated floor system exhibits many advantages, such as the embedded large mass-isolation ratio, the mitigation of floor acceleration, the easy-to-demolish characteristic, etc. This paper focuses on the elastic seismic performance of single-story steel structures equipped with the LVEM-isolated floor system, wherein the LVEM-isolators are made of acrylic visco-elastic materials. The numerical simulating approach and the dynamic analysis procedure are developed for the structural system. In the procedure, the LVEM isolators are simulated by the Kelvin-Voigt model. The numerical simulating approach is validated by shaking table tests. Based on the results of an extensive response history analysis, the effects of several key parameters on the elastic structural seismic demand are quantified. The considered parameters include the structural natural period (T), the mass-isolation ratio, and the stiffness of the LVEM isolators. The displacement response spectra for both the substructure and the LVEM isolators, namely, the λS−T spectra and the λVEM−T spectra, are developed corresponding to the ambient temperature θ = 20 °C. In the structural design, λS is used for checking the seismic capacity of the substructure, while λVEM is used for determining an appropriate deforming space for the LVEM isolators. The seismic demand of the substructure generally decreases as the LVEM isolators become more flexible and the mass-isolation ratio becomes larger. The effect of ambient temperature-changing on the proposed elastic design spectra is analyzed. Generally, such effect is more pronounced when the mass-isolation ratio increases and the stiffness of the LVEM isolator decreases. Analysis data is provided for quantifying the effect of ambient-temperature-changing on the λS−T spectra and the λVEM−T spectra. Based on the data, the structural design and evaluation could be carried out efficiently.
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- 2019
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21. Indication of Takeuchi Technique for Patients With Anomalous Origin of the Left Coronary Artery From the Pulmonary Artery
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Takaya Hoashi, Koji Kagisaki, Isao Shiraishi, Naoki Okuda, Toshikatsu Yagihara, and Hajime Ichikawa
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Adult ,Male ,Reoperation ,medicine.medical_specialty ,Time Factors ,Adolescent ,Coronary Vessel Anomalies ,Kaplan-Meier Estimate ,Pulmonary Artery ,Disease-Free Survival ,Ventricular Function, Left ,Actuarial survival ,Young Adult ,Postoperative Complications ,Left coronary artery ,Risk Factors ,medicine.artery ,Internal medicine ,medicine ,Humans ,Cardiac Surgical Procedures ,Child ,Sinus (anatomy) ,Retrospective Studies ,Aorta ,Ejection fraction ,business.industry ,Infant ,Stroke Volume ,Retrospective cohort study ,General Medicine ,Stroke volume ,Middle Aged ,Surgery ,Treatment Outcome ,medicine.anatomical_structure ,Child, Preschool ,Pulmonary artery ,Cardiology ,Female ,Cardiology and Cardiovascular Medicine ,business - Abstract
Background: Intrapulmonary tunnel repair, called the Takeuchi technique, is a unique procedure for repairing anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA). Since 1986, we have clearly defined the indication for the Takeuchi technique based on the location of the left coronary artery (LCA) orifice. Methods and Results: From 1986 to 2011, 19 consecutive patients with ALCAPA underwent surgical repair; the dual-coronary system was reconstructed in 16 of these patients with either Takeuchi (n=9: 1 male; median age 14.7 years; median weight 42.7kg) or a translocation procedure (n=7, 3 males; 0.4 years old, 5.6kg). Takeuchi was performed in patients whose LCA arose far from the aorta (middle of posterior facing sinus in 3 patients, left side of posterior facing sinus in 2, non-facing sinus in 4). The mean postoperative follow-up period was 7.4±6.1 years in the Takeuchi group and 9.3±8.5 years in the Translocation group. Actuarial survival rate at 10 years was 87.5% and 71.4%, respectively, and the freedom from either reoperation or re-intervention rate at 10 years was 67.7% and 85.7%, respectively. All the patients who died had a preoperative left ventricular ejection fraction ≤30%. Conclusions: The long-term outcome of the Takeuchi technique was acceptable. Although late reoperation and/or re-intervention cannot be disregarded, Takeuchi can be recommended when the LCA arises far from the aorta. (Circ J 2013; 77: 1202–1207)
- Published
- 2013
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22. Stroke Volume Ratio Predicts Redilatation of the Right Ventricle After Pulmonary Valve Replacement
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Tomomitsu Kanaya, Takashi Kido, Takayoshi Ueno, Naoki Okuda, Hideto Ozawa, Toru Kuratani, Yoshiki Sawa, Masaki Taira, and Koichi Toda
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Pulmonary and Respiratory Medicine ,Adult ,Male ,medicine.medical_specialty ,Heart Ventricles ,Ventricular Dysfunction, Right ,Regurgitation (circulation) ,030204 cardiovascular system & hematology ,030218 nuclear medicine & medical imaging ,03 medical and health sciences ,Young Adult ,0302 clinical medicine ,Postoperative Complications ,Internal medicine ,Pulmonary Valve Replacement ,medicine ,Humans ,cardiovascular diseases ,Tetralogy of Fallot ,Retrospective Studies ,Heart Valve Prosthesis Implantation ,Pulmonary Valve ,business.industry ,Stroke Volume ,Stroke volume ,Middle Aged ,medicine.disease ,Prognosis ,Pulmonary Valve Insufficiency ,medicine.anatomical_structure ,Ventricle ,Echocardiography ,Pulmonary valve ,Preoperative Period ,cardiovascular system ,Cardiology ,Ventricular Function, Right ,End-diastolic volume ,Surgery ,Female ,Radiology ,Cardiology and Cardiovascular Medicine ,Cardiac magnetic resonance ,business ,Tomography, X-Ray Computed - Abstract
Background This study aimed to identify the prognostic value of the preoperative stroke volume ratio (right ventricular stroke volume/left ventricular stroke volume) for redilatation of the right ventricle after pulmonary valve replacement in patients with repaired tetralogy of Fallot. Methods From April 2004 to November 2013, 20 patients with repaired tetralogy of Fallot underwent pulmonary valve replacement for pulmonary valve regurgitation and right ventricular dilatation. Serial changes in ventricular volume were examined by cardiac magnetic resonance or computed tomography imaging. The redilatation ratio was calculated for right ventricular end-diastolic and end-systolic volume indices by dividing the increment in right ventricular volume from the first (median, 1.1 years) to the second (median, 3.2 years) evaluations after pulmonary valve replacement by the first evaluation. The relationships between the stroke volume ratio and redilatation ratio were assessed. The degree of right ventricular myocardial fibrosis was examined in 13 patients and compared with the stroke volume ratio. Results Right ventricular volume (redilatation) significantly increased from a median of 1.1 to 3.2 years after pulmonary valve replacement. Significant positive correlations were detected between the stroke volume ratio and redilatation ratio of the right ventricular end-diastolic ( r = 0.50. p = 0.02) and end-systolic volume indices ( r = 0.49, p = 0.03). The stroke volume ratio also showed a significant positive correlation with the degree of right ventricular myocardial fibrosis ( r = 0.73, p = 0.005). Conclusions The preoperative stroke volume ratio can predict redilatation of the right ventricle after pulmonary valve replacement and the degree of right ventricular myocardial fibrosis.
- Published
- 2016
23. Microscopic Structure Control of Carbon Nanofiller/Epoxy Composite by Using AC Electrical Field and the Effect on Physical Properties
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Keiichiro Tohgo, Naoki Okuda, Yoshinobu Shimamura, and Toshihiro Chiba
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Materials science ,Field (physics) ,chemistry ,visual_art ,Composite number ,visual_art.visual_art_medium ,Structure control ,chemistry.chemical_element ,Epoxy ,Composite material ,Carbon - Published
- 2010
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24. ED-71, a novel vitamin D analog, promotes bone formation and angiogenesis and inhibits bone resorption after bone marrow ablation
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Takeshi Muneta, Yoshinori Asou, Soichiro Itoh, Kenichi Shinomiya, Naoki Okuda, Shu Takeda, and Masaki Noda
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Vascular Endothelial Growth Factor A ,medicine.medical_specialty ,Histology ,Physiology ,Endocrinology, Diabetes and Metabolism ,Neovascularization, Physiologic ,Osteoclasts ,Bone and Bones ,Bone resorption ,Bone remodeling ,Mice ,chemistry.chemical_compound ,Bone Marrow Ablation ,Calcitriol ,Bone Marrow ,Osteogenesis ,Osteoclast ,Internal medicine ,medicine ,Animals ,Bone Resorption ,Vitamin D ,Mice, Inbred ICR ,Alfacalcidol ,Cell Differentiation ,Osteoblast ,Vitamins ,Surgery ,Resorption ,Disease Models, Animal ,Endocrinology ,medicine.anatomical_structure ,chemistry ,Female ,Bone marrow - Abstract
ED-71, a novel analog of 1alpha,25-(OH)2 D3, increases bone mass to a greater extent than alfacalcidol, an 1alpha,25-(OH)2 D3 prodrug. In this study, we used a murine bone marrow ablation model to compare the effect of ED-71 on bone formation and resorption in vivo with that of 1alpha,25-(OH)2 D3. We discovered that bone matrix remodeling occurring within the first week after bone marrow ablation was enhanced by a single injection of ED-71, but not by 1alpha,25-(OH)2 D3. This enhancement was associated with an increase in bone surface. Trabecular bone resorption occurring from 1 to 2 weeks after the procedure was suppressed by a single injection of ED-71, but not 1alpha,25-(OH)2 D3, with treated mice exhibiting a reduction in osteoclast numbers, despite increases in osteoblast surface. As seen with the single injection, daily administration of ED-71 also enhanced bone modeling. Bone marrow osteoblast differentiation was also augmented by ED-71 pretreatment. Furthermore, ED-71 treatment immediately after bone marrow ablation enhanced angiogenesis within the bone marrow cavity via enhancement of VEGF(120) expression. In this paper, we clearly demonstrate that ED-71 is an orally administered small molecular weight compound with an anabolic effect on bone metabolism.
- Published
- 2007
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25. Relationship between Home Blood Pressure and Longitudinal Changes in Target Organ Damage in Treated Hypertensive Patients
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Takeshi Horio, Yuhei Kawano, Sei Tsunoda, Naoki Okuda, and Shuichi Takishita
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Adult ,Male ,medicine.medical_specialty ,Office Visits ,Physiology ,Blood Pressure ,Left ventricular hypertrophy ,Electrocardiography ,chemistry.chemical_compound ,Internal medicine ,Internal Medicine ,Humans ,Medicine ,Longitudinal Studies ,Prospective Studies ,Prospective cohort study ,Antihypertensive Agents ,Aged ,Aged, 80 and over ,Creatinine ,Proteinuria ,medicine.diagnostic_test ,business.industry ,Blood Pressure Determination ,Middle Aged ,medicine.disease ,Target organ damage ,Surgery ,Self Care ,Blood pressure ,chemistry ,Echocardiography ,Cardiac hypertrophy ,Hypertension ,Cardiology ,Female ,medicine.symptom ,Cardiology and Cardiovascular Medicine ,business - Abstract
Cross-sectional studies have shown that home blood pressure (BP) correlates with hypertensive target organ damage better than clinic BP. However, there have been few longitudinal studies regarding the predictive value of home BP on the changes in organ damage in treated hypertensive patients. Clinic and home BP over a 12-month period, antihypertensive medication use, echocardiographic and electrocardiographic results, and serum creatinine and urinary protein levels were examined in 209 treated hypertensive patients in 1993. These patients were prospectively followed for 5 years. The patients were divided into 4 subgroups according to hypertension control as follows: good control (
- Published
- 2002
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26. Cause of residual hypertension after adrenalectomy in patients with primary aldosteronism
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Motomi Ando, Naoki Okuda, Shuichi Takishita, Yoshio Horita, Hatsue Ishibashi-Ueda, Hajime Nakahama, Takeshi Horio, Satoko Nakamura, Takashi Inenaga, and Yuhei Kawano
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Adenoma ,Adult ,Male ,medicine.medical_specialty ,Hypertension, Renal ,medicine.medical_treatment ,Adrenal Gland Neoplasms ,Arteriolosclerosis ,Urology ,Kidney ,Postoperative Complications ,Primary aldosteronism ,Hyperaldosteronism ,Humans ,Medicine ,Conn Syndrome ,Aged ,business.industry ,Adrenalectomy ,Glomerulosclerosis ,Middle Aged ,medicine.disease ,Surgery ,Blood pressure ,Nephrology ,Hypertension ,Female ,Kidney Diseases ,business ,Kidney disease - Abstract
The cause of residual hypertension after adrenalectomy for primary aldosteronism (PA) is unknown. The purpose of this study is to investigate the characteristic pathological kidney features associated with PA. Between 1977 and 1999 at our hospital, 26 patients with PA caused by a unilateral adrenal cortical adenoma (Conn's syndrome) underwent unilateral adrenalectomy with concurrent open-wedge renal biopsy. Patients were categorized into two groups: (1) those with normotension with diastolic blood pressure less than 90 mm Hg who were not administered antihypertensive drugs, and (2) those with residual hypertension with diastolic blood pressure of 90 mm Hg or greater who were administered medication for 6 months after surgery. Thirteen patients were cured of hypertension postoperatively, and 12 patients were administered antihypertensive medications. Glomerulosclerosis, renal arteriolosclerosis, and preoperative left ventricular mass (LVM) index were worse in the group with residual hypertension than in that with normotension (17.8% +/- 7.8% versus 9.6% +/- 3.8%; P = 0.01; 2.5 +/- 0.5 versus 1.6 +/- 0.4, Bader's grade; P = 0.005; and 165 +/- 31 versus 139 +/- 24 g/m(2); P = 0.02, respectively). Severity of tubulointerstitial injury, preoperative duration of hypertension, preoperative severity of proteinuria, plasma aldosterone level, and serum potassium concentration were not significantly different between the two groups. In conclusion, severity of glomerulosclerosis and arteriolosclerosis and LVM are related to blood pressure after adrenalectomy in patients with PA.
- Published
- 2001
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27. Effects of a low-energy diet and an insulin-sensitizing agent on ambulatory blood pressure in overweight hypertensive patients
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Yuhei Kawano, Naoki Okuda, Junichi Minami, Teruo Omae, and Shuichi Takishita
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Adult ,Male ,medicine.medical_specialty ,Ambulatory blood pressure ,Diet, Reducing ,Physiology ,medicine.medical_treatment ,Blood Pressure ,Troglitazone ,Insulin resistance ,Weight loss ,Internal medicine ,Weight Loss ,Internal Medicine ,medicine ,Hyperinsulinemia ,Humans ,Hypoglycemic Agents ,Obesity ,Chromans ,Aged ,business.industry ,Insulin ,Middle Aged ,medicine.disease ,Thiazoles ,Endocrinology ,Blood pressure ,Hypertension ,Female ,Thiazolidinediones ,Insulin Resistance ,medicine.symptom ,Cardiology and Cardiovascular Medicine ,business ,Body mass index ,medicine.drug - Abstract
OBJECTIVE To clarify the role of insulin resistance and hyperinsulinaemia in the pathogenesis of obesity-related hypertension. DESIGN An open study comparing the effects of weight reduction by low-energy diet and treatment with troglitazone, an insulin-sensitizing agent. SETTING A tertiary teaching hospital. PATIENTS Thirty overweight hypertensive patients (15 men and 15 women, mean age 61 years, mean body mass index 29.1 kg/m2). INTERVENTIONS Fifteen patients were assigned to a weight-reduction programme by low-energy diet (3360 kJ/day) for 3 weeks; the remaining 15 patients were treated with troglitazone (400 mg/day) for 8 weeks. MAIN OUTCOME MEASURES Casual and ambulatory blood pressures, glucose and lipid metabolism, and insulin sensitivity. RESULTS The baseline values of body mass index, fasting and post-glucose plasma insulin, and casual and ambulatory blood pressures were comparable between the two groups. Weight reduction (4.1 +/- 0.3 kg, mean +/- SEM) was associated with significant decreases in plasma insulin, blood glucose, homeostasis model assessment (HOMA) insulin resistance index, serum triglyceride, casual blood pressure (7.7 +/- 2.3/ 3.9 +/- 1.4 mmHg) and 24 h blood pressure (8.3 +/- 1.9/ 4.3 +/- 1.1 mmHg). Treatment with troglitazone caused comparable decreases in the metabolic parameters and HOMA index, but did not change casual or 24 h blood pressure (0.8 +/- 3.4/0.8 +/- 2.1 and 1.5 +/- 2.4/ 1.0 +/- 1.9 mmHg, respectively). CONCLUSIONS Insulin resistance/hyperinsulinaemia may not have an important role in the pathogenesis of obesity-related hypertension. The antihypertensive effect of weight reduction seems to be mediated mainly by other mechanisms.
- Published
- 2000
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28. Effects of diltiazem retard on ambulatory blood pressure and heart rate variability in patients with essential hypertension
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Shuichi Takishita, Yuriko Makino, Yuhei Kawano, Teruo Omae, and Naoki Okuda
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Male ,medicine.medical_specialty ,Sympathetic Nervous System ,Ambulatory blood pressure ,Blood Pressure ,Assessment and Diagnosis ,Essential hypertension ,Drug Administration Schedule ,Prehypertension ,Diltiazem ,Electrocardiography ,Heart Rate ,Parasympathetic Nervous System ,Internal medicine ,Heart rate ,Internal Medicine ,medicine ,Humans ,Heart rate variability ,Antihypertensive Agents ,Aged ,Advanced and Specialized Nursing ,business.industry ,Vagus Nerve ,General Medicine ,Blood Pressure Monitoring, Ambulatory ,Middle Aged ,Calcium Channel Blockers ,medicine.disease ,Autonomic nervous system ,Blood pressure ,Delayed-Action Preparations ,Hypertension ,Cardiology ,Female ,Drug Monitoring ,Cardiology and Cardiovascular Medicine ,business ,medicine.drug - Abstract
Background Dihydropyridine calcium antagonists increase heart rate due to reflex activation of the sympathetic nervous system, although these effects are less obvious for long-acting agents. Objective To study the effects of diltiazem retard, a long-acting nondihydropyridine calcium antagonist, on 24h blood pressure, heart rate and autonomic nerve activity in patients with essential hypertension. Design Randomized crossover design. Methods Thirteen patients [five men and eight women, aged 64+/-2 years (mean+/-SEM)] were administered placebo or diltiazem retard (100-200mg once daily) for 4 weeks each. Ambulatory monitoring of blood pressure and heart rate, and electrocardiography were carried out at the end of each period using a multibiomedical recorder (TM-2425). Autonomic nerve activity was evaluated by power spectral analysis of variability of heart rate using the high-frequency component as an index of parasympathetic nerve activity and the ratio of the low-frequency component and the high-frequency component as an index of sympathovagal balance. Results Treatment with diltiazem retard significantly decreased 24h average blood pressure and heart rate by 11.6+/-3.6/5.7+/-1.8mmHg and 5.0+/-1.1 beats/min, respectively. The changes in daytime and night-time values were comparable. Diltiazem retard also significantly decreased daytime and 24h low:high-frequency-component ratio (2.0+/-0.2 versus 1.7+/-0.2 and 1. 8+/-0.2 versus 1.6+/-0.2, respectively). Conclusions These results indicate that diltiazem retard is effective as a once-daily antihypertensive agent and has favorable effects on heart rate and the autonomic nervous system.
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- 2000
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29. Surgical Outcome of Two Difficult Cases with Predominant Proximal Pulmonary Artery Lesions of Chronic Thromboembolic Pulmonary Hypertension
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Hiroshi Tanaka, Masatoshi Shimada, Keitaro Doumae, Takashi Murashita, Hitoshi Ogino, Yutaka Iba, Naoki Okuda, Tatsuki Fujiwara, Hitoshi Matsuda, and Hiroaki Sasaki
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medicine.medical_specialty ,Percutaneous ,Respiratory distress ,business.industry ,Case Report ,General Medicine ,Disease ,medicine.disease ,Pulmonary hypertension ,Pulmonary endarterectomy ,Surgery ,Lesion ,medicine.artery ,Pulmonary artery ,medicine ,Chronic thromboembolic pulmonary hypertension ,medicine.symptom ,business - Abstract
Pulmonary endarterectomy (PEA) for chronic thromboembolic pulmonary hypertension (CTEPH) is still challenging. The outcome of patients with proximal pulmonary artery disease is generally better than that of a distal lesion. However, we experienced poor results in two difficult cases having predominant proximal lesions even after effective PEA. Both of them had a long-time history of CTEPH and preoperative condition was critical. Although relatively large amount of thickened intima with massive thrombi were extracted from the proximal pulmonary arteries, they required postoperative percutaneous cardiopulmonary support due to residual pulmonary hypertension. Both of them finally died from pulmonary bleeding and adult respiratory distress syndrome.
- Published
- 2011
30. Peripheral vs. Central Blockade of the Renin-Angiotensin System in Spontaneously Hypertensive Rats: Comparison of Novel AT1 Receptor Antagonist TCV-116 with Angiotensin Converting Enzyme Inhibitor Delapril
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Naoki Okuda, Hiroshi Mikami, Toshio Ogihara, and Katsuhiko Kohara
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medicine.medical_specialty ,Angiotensin II receptor type 1 ,biology ,Physiology ,business.industry ,medicine.drug_class ,Delapril ,Angiotensin-converting enzyme ,Receptor antagonist ,Angiotensin II ,Natriuresis ,Endocrinology ,Blood pressure ,Internal medicine ,Renin–angiotensin system ,Internal Medicine ,biology.protein ,Medicine ,Cardiology and Cardiovascular Medicine ,business ,medicine.drug - Abstract
In the present study, we evaluated the hemodynamic and metabolic profiles derived from oral administration of the angiotensin converting enzyme inhibitor, delapril 50mg/kg/day, and the non-peptide angiotensin II type I (AT1) receptor antagonist, TCV-116 1mg/kg/day, for five days, to try to discriminate AT1 receptor-related responses from the depressor properties of chronic treatment with delapril in spontaneously hypertensive rats (SHRs). Both TCV-116 and delapril oral administrations significantly decreased blood pressure without any changes in heart rate. Delapril induced dipsogenic response and natriuresis associated with augmentation of urinary catecholamine excretion, while TCV-116 did not cause any changes in these variables. Neither delapril nor TCV-116 changed urinary excretion of prostaglandin (PG) E2 and 6-keto PG F1α. We also examined the effects of centrally administered angiotensin converting enzyme inhibitor and AT1 receptor antagonist to determine the central role of these drugs.Either the active metabolite of delapril, delapril-M1 1 mg/kg/day, or the active form of TCV-116, CV-11974 0.1mg/kg/day, were administered intracerebroventricularly for five days. Both treatments significantly decreased the blood pressure, in association with augmentation of the baroreceptor reflex control of heart rate, in response to phenylephrine injection. These findings suggest that the depressor properties of orally administered delapril are more complex than those of TCV-116, while central blockade by both angiotensin converting enzyme and AT1 receptor decreases blood pressure in part through baroreceptor sensitization. (Hypertens Res;1993 16: 239-246)
- Published
- 1993
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31. Osteopontin deficiency impairs wear debris-induced osteolysis via regulation of cytokine secretion from murine macrophages
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Norihiko Kato, Naoki Okuda, Yoshinori Asou, Kunikazu Tsuji, David T. Denhardt, Sadanori Shimizu, Masaki Noda, Kenichi Shinomiya, Takeshi Muneta, Atsushi Okawa, and Susan R. Rittling
- Subjects
Pathology ,medicine.medical_specialty ,Osteolysis ,medicine.medical_treatment ,Immunology ,Interleukin-1beta ,Bone resorption ,Proinflammatory cytokine ,Mice ,stomatognathic system ,Rheumatology ,Phagocytosis ,Osteoclast ,Interleukin-1alpha ,medicine ,Immunology and Allergy ,Animals ,Pharmacology (medical) ,Osteopontin ,Macrophage inflammatory protein ,Cells, Cultured ,Chemokine CCL3 ,Titanium ,biology ,Chemistry ,Interleukin-6 ,Tumor Necrosis Factor-alpha ,Macrophages ,Skull ,medicine.disease ,Mice, Mutant Strains ,Mice, Inbred C57BL ,Disease Models, Animal ,medicine.anatomical_structure ,Cytokine ,biology.protein ,Cancer research ,Cytokines ,Cytokine secretion ,Female ,I-kappa B Proteins - Abstract
Objective To investigate the molecular mechanisms underlying particle-induced osteolysis, we focused on osteopontin (OPN), a cytokine and cell-attachment protein that is associated with macrophage chemoattractant and osteoclast activation. Methods We compared OPN protein levels in human periprosthetic osteolysis tissues with those in osteoarthritis (OA) synovial tissues. To investigate the functions of OPN during particle-induced osteolysis in vivo, titanium particles were implanted onto the calvaria of OPN-deficient mice and their wild-type (WT) littermates. Mice were killed on day 10 and evaluated immunohistologically. The effects of OPN deficiency on the secretion of inflammatory cytokines were examined using cultured bone marrow–derived macrophages (BMMs). BMMs from OPN-deficient and WT mice were cultured with titanium particles for 12 hours, and the concentrations of inflammatory cytokines in the conditioned media were measured by enzyme-linked immunosorbent assay. Results Expression of OPN protein was enhanced in human periprosthetic osteolysis tissues as compared with OA synovial tissues. In the particle-induced model of osteolysis of the calvaria, bone resorption was significantly suppressed by OPN deficiency via inhibition of osteoclastogenesis, whereas an inflammatory reaction was observed regardless of the genotype. Results of immunostaining indicated that OPN protein was highly expressed in the membrane and bone surface at the area of bone resorption in WT mice. When BMMs were exposed to titanium particles, the concentration of proinflammatory cytokines, such as tumor necrosis factor α, interleukin-1α (IL-1α), IL-1β, and IL-6, as well as chemotactic factors, such as monocyte chemoattractant protein 1 and macrophage inflammatory protein 1α, in the conditioned medium were significantly reduced by OPN deficiency. Whereas phagocytic activity of BMMs was not attenuated by OPN deficiency, phagocytosis-mediated NF-κB activation was impaired in OPN-deficient BMMs. These data indicated that OPN was implicated in the development of particle-induced osteolysis via the orchestration of pro-/antiinflammatory cytokines secreted from macrophages. Conclusion OPN plays critical roles in wear debris–induced osteolysis, suggesting that OPN is a candidate therapeutic target for periprosthetic osteolysis.
- Published
- 2010
32. [Immunologic tests: C3 receptor (CR1, 2)]
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Naoki, Okuda and Tsukasa, Seya
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Phagocytosis ,Reference Values ,Rheumatic Diseases ,Receptors, Complement 3b ,Animals ,Humans ,Lupus Erythematosus, Systemic ,Enzyme-Linked Immunosorbent Assay ,Complement Pathway, Classical ,Immunologic Tests ,Flow Cytometry ,Biomarkers ,Immune Adherence Reaction - Published
- 2005
33. Microalbuminuria and cardiovascular events in elderly hypertensive patients without previous cardiovascular complications
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Satoko Nakamura, Takeshi Horio, Hajime Nakahama, Osamu Sasaki, Takashi Inenaga, Shuichi Takishita, Naoki Okuda, and Yuhei Kawano
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Male ,medicine.medical_specialty ,Hypertension, Renal ,Physiology ,Myocardial Infarction ,Renal function ,chemistry.chemical_compound ,Risk Factors ,Internal medicine ,Internal Medicine ,Medicine ,Albuminuria ,Humans ,Cardiovascular centre ,Antihypertensive Agents ,Aged ,Creatinine ,business.industry ,Incidence (epidemiology) ,Incidence ,medicine.disease ,Pulse pressure ,Stroke ,Blood pressure ,Endocrinology ,chemistry ,Cohort ,Cardiology ,Kidney Failure, Chronic ,Microalbuminuria ,Female ,Cardiology and Cardiovascular Medicine ,business ,Follow-Up Studies - Abstract
To assist in the development of better treatments for elderly hypertensive patients, we studied the degree to which the baseline values of urinary albumin excretion (UAE) and other cardiovascular risk factors were predictive of cardiovascular complications in a cohort of elderly hypertensive patients. In 1994, we adopted 144 elderly hypertensive patients, who had been treated for more than 6 years at various clinics and more than 1 year at the National Cardiovascular Center, Osaka, Japan. They were divided into 2 groups: a NA group (n=111) with normoalbuminuria (UAE
- Published
- 2003
34. Does Breakfast Omission Impair Cognitive Function At Rest And During Exercise?
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Hiroaki Tanaka, Naoki Okuda, Takaaki Komiyama, Yasuki Higaki, Mizuki Sudo, Akira Kiyonaga, and Soichi Ando
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Rest (physics) ,medicine.medical_specialty ,Physical medicine and rehabilitation ,medicine ,Physical Therapy, Sports Therapy and Rehabilitation ,Orthopedics and Sports Medicine ,Cognition ,Psychology - Published
- 2014
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35. Effect of propranolol on central neurotransmitter release in Wistar rats analysed by brain microdialysis
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Atsushi Moriguchi, Naoki Okuda, Kazuo Yamada, Jitsuo Higaki, Katsuhiko Kohara, Hiroshi Mikami, and Toshio Ogihara
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Male ,Taurine ,Microdialysis ,Physiology ,Adrenergic beta-Antagonists ,Blood Pressure ,Propranolol ,Pharmacology ,chemistry.chemical_compound ,Heart Rate ,Physiology (medical) ,medicine ,Animals ,Amino Acids ,Rats, Wistar ,Neurotransmitter ,chemistry.chemical_classification ,Brain Chemistry ,Medulla Oblongata ,Neurotransmitter Agents ,Glutamate receptor ,Rostral ventrolateral medulla ,Amino acid ,Rats ,chemistry ,Amino acid neurotransmitter ,Injections, Intravenous ,medicine.drug - Abstract
1. The effect of propranolol on amino acid neurotransmitter release in the rostral ventrolateral medulla (RVLM) was examined in urethane-anaesthetized male Wistar rats. 2. Amino acids released in the RVLM in response to intravenous administration of propranolol (0.4 mg/kg per min; n = 6) or nitroglycerin (0.02 mg/kg per min; n = 5) were determined by the brain microdialysis method. 3. Amino acids in dialysates were analysed by high- performance liquid chromatography and were quantified by ultraviolet absorbance. 4. Administration of both intravenous propranolol and nitroglycerin significantly decreased arterial blood pressure. Heart rate was decreased only by propranolol. 5. The reduction in arterial blood pressure produced by intravenous propranolol was accompanied by a decrease in the release of the excitatory amino acid glutamate in the RVLM. 6. The reduction in arterial blood pressure following intravenous nitroglycerin was not accompanied by a release of glutamate. 7. There were no significant changes in the levels of other amino acids (glycine, taurine, GABA) following either propranolol or nitroglycerin. 8. The decrease in glutamate release in the RVLM may account, in part, for the central depressor mechanism of propranolol.
- Published
- 1999
36. 323 Nano-Structural Control of Carbon Nanotube in CNT Composite by AC Electrical Field
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Naoki Okuda, Hiroyasu Araki, Yoshinobu Shimamura, and Keiichiro Tohgo
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Materials science ,Field (physics) ,law ,Nano ,Composite number ,Carbon nanotube ,Composite material ,law.invention - Published
- 2006
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37. Predominance of nocturnal sympathetic nervous activity in salt-sensitive normotensive subjects
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Tomomi Fujisawa, Kei Kamide, Fumiaki Nakamura, Toshio Ogihara, Ryuichi Kobayashi, Atsushi Moriguchi, Hiroshi Mikami, Atsushi Kamitani, Jitsuo Higaki, Yoshikage Yo, Naoki Okuda, Masahiro Nagano, and Yoshio Nakamura
- Subjects
Adult ,Male ,medicine.medical_specialty ,Sympathetic Nervous System ,Blood Pressure ,Norepinephrine ,Electrocardiography ,Electrolytes ,Heart Rate ,Internal medicine ,Heart rate ,Internal Medicine ,medicine ,Heart rate variability ,Humans ,Circadian rhythm ,Sodium Chloride, Dietary ,Volunteer ,business.industry ,Circadian Rhythm ,Autonomic nervous system ,Endocrinology ,Blood pressure ,Mean blood pressure ,business ,Algorithms ,medicine.drug - Abstract
To assess the relation between salt sensitivity and autonomic nervous function by power spectral analysis of heart rate variability in normotensive subjects, low and high salt diets were given to 13 normotensive men (aged 25 to 39 years) for 4 days each. Autonomic function was assessed by power spectral analysis of R-R intervals based on an autoregressive algorithm from 24-h Holter electrocardiogram. Subjects whose mean blood pressure was increased more than 3 mm Hg by high salt diet were defined as salt sensitive (SS, n = 5), and the remainder as salt resistant (SR, n = 8). Using the low frequency (LF, 0.1 Hz) and high frequency (HF, 0.25 Hz) components, the LF to total power ratio (%LF) was used as a marker of sympathetic activity, and the HF to total power ratio (%HF) as a marker of parasympathetic activity. Compared to the daytime, SR revealed a decrease in %LF and an increase in %HF during the night on both diets. In SS, these circadian changes were observed only during low-salt diet. During the night, SS showed a higher %LF and a lower %HF than SR. Plasma catecholamines tended to be decreased by the high sodium diet in SR but not in SS subjects. These results suggest that the persistent nocturnal predominance of sympathetic nervous activity in a salt-sensitive men may contribute to the subsequent increase of blood pressure in these subjects.
- Published
- 1996
38. Differential control of vascular tone and heart rate by different amino acid neurotransmitters in the rostral ventrolateral medulla of the rat
- Author
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Atsushi Moriguchi, Makoto Nagano, Atsuhiro Otsuka, Ryuichi Morishita, Katsutoshi Katahira, Naoki Okuda, Koichi Higashimori, Hiroshi Mikami, Katsuhiko Kohara, and Toshio Ogihara
- Subjects
Male ,medicine.medical_specialty ,Microdialysis ,Pentobarbital ,Proline ,Physiology ,Angiotensin-Converting Enzyme Inhibitors ,Blood Pressure ,Ceronapril ,Muscle, Smooth, Vascular ,Injections ,Nitroglycerin ,Organophosphorus Compounds ,Heart Rate ,Physiology (medical) ,Internal medicine ,Heart rate ,medicine ,Animals ,Anesthesia ,Rats, Wistar ,Pharmacology ,Medulla Oblongata ,Neurotransmitter Agents ,Chemistry ,Rostral ventrolateral medulla ,Angiotensin II ,Rats ,Blood pressure ,Endocrinology ,Muscle Tonus ,Perfusion ,medicine.drug - Abstract
SUMMARY 1. To test the hypothesis that a central mechanism may play a role in the minimal reflex tachycardia noted in response to peripheral converting enzyme inhibition, we compared the effects of intravenous (i.v.) ceronapril (CER) with nitroglycerin (NTG) on neurotransmitter release in the rostral ventrolateral medulla (RVLM), using an in vivo microdialysis method in pentobarbital anaesthetized rats. 2. CER (0.1 mg/kg, i.v.) caused a progressive decrease in glutamate (GLU) release (CER 65 ± 7%vs NTG 83 ± 3% of each baseline at 140 min, P
- Published
- 1994
39. A Case Report of Efficiency of Double Filtration Plasmapheresis in Treatment of Goodpasture's Syndrome
- Author
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Hajime, Nagasu, primary, Michiko, Abe, additional, Atsunori, Kuwabara, additional, Tatsuo, Kawai, additional, Yuko, Nishi, additional, Naoki, Okuda, additional, and Katsuhiko, Sakaguchi, additional
- Published
- 2009
- Full Text
- View/download PDF
40. The effect of central amino acid neurotransmitters on the antihypertensive response to angiotensin blockade in spontaneous hypertension
- Author
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Kazuo Yamada, Naoki Okuda, Hiroshi Mikami, Toshio Ogihara, Atsushi Moriguchi, and Jitsuo Higaki
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Male ,medicine.medical_specialty ,Microdialysis ,Taurine ,Mean arterial pressure ,Physiology ,Tetrazoles ,Blood Pressure ,Rats, Inbred WKY ,Angiotensin Receptor Antagonists ,chemistry.chemical_compound ,Rats, Inbred SHR ,Internal medicine ,Internal Medicine ,medicine ,Animals ,Infusions, Intravenous ,chemistry.chemical_classification ,Medulla Oblongata ,Neurotransmitter Agents ,business.industry ,Biphenyl Compounds ,Rostral ventrolateral medulla ,Angiotensin II ,Rats ,Amino acid ,Glutamine ,Endocrinology ,chemistry ,Anesthesia ,Hypertension ,Glycine ,Benzimidazoles ,Cardiology and Cardiovascular Medicine ,business - Abstract
Objective : To investigate the effects of central amino acid neurons on the antihypertensive action of a newly developed angiotensin II type 1 receptor (AT1) antagonist, CV 11974. Materials and methods : We measured the release of various amino acids in the rostral ventrolateral medulla using the brain microdialysis technique. A microdialysis probe was inserted into the exposed rostral ventrolateral medulla in male spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats anaesthetized with urethane. Mean arterial pressure and the release of amino acids (glutamate, glycine, glutamine, taurine and y-aminobutyric acid) were monitored before and after intravenous administration of CV 11974 (5 mg/kg), nitroglycerin (5 μg/kg per min) or vehicle. Results : In SHR, CV11974 decreased mean arterial pressure (-40 ± 6 mmHg) accompanied by significant increases in the release of inhibitory amino acids, glycine (411 ± 83%) and γ-aminobutyric acid (363 ± 71%) in the rostral ventrolateral medulla, whereas intravenous nitroglycerin produced a decrease in mean arterial pressure (-35 ± 4 mmHg) without changes in amino acid release. In WKY rats, both intravenous CV 11974 and intravenous nitroglycerin produced smaller but significant decreases in mean arterial pressure (CV 11974, -18 ± 5 mm Hg ; nitroglycerin, -20 ± 7 mmHg) without change in the release of amino acids in the rostral ventrolateral medulla. Selective perfusion of glycine or γ-aminobutyric acid into the rostral ventrolateral medulla caused a larger mean arterial pressure reduction in SHR than in WKY rats. Furthermore, the use of a specific antagonist of glycine or of the γ-aminobutyric acid receptor in the rostral ventrolateral medulla attenuated the antihypertensive response induced by the intravenous AT 1 antagonist in SHR. Conclusion : The present results suggest that the release of the inhibitory amino acids glycine and γ-aminobutyric acid in the rostral ventrolateral medulla contributes to the depressor action of this AT 1 receptor antagonist in the genetic hypertensive rat model.
- Published
- 1995
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41. Central Depressor Mechanism of Angiotensin II Type 1 Receptor Antagonist in the Spontaneously Hypertensive Rat
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Atsushi Moriguchi, Kazuo Yamada, Naoki Okuda, Toshio Ogihara, Hiroshi Mikami, and Jitsuo Higaki
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medicine.medical_specialty ,Angiotensin receptor ,Spontaneously hypertensive rat ,Endocrinology ,Angiotensin II receptor type 1 ,Mechanism (biology) ,Chemistry ,medicine.drug_class ,Internal medicine ,medicine ,Cardiology and Cardiovascular Medicine ,Receptor antagonist ,Angiotensin II - Published
- 1995
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42. The Prevention of Renal Injury Progression by Angiotensin Type 1 Receptor Antagonist
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Jitsuo Higaki, Hiroshi Mikami, Naoki Okuda, Toshio Ogihara, and Katsuhiko Kohara
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Interleukin 1 receptor antagonist ,Angiotensin II receptor type 1 ,Renal injury ,medicine.drug_class ,business.industry ,Renin–angiotensin system ,medicine ,Pharmacology ,Cardiology and Cardiovascular Medicine ,Receptor antagonist ,business - Published
- 1993
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43. Welding consumables for steel plates produced by controlled rolling
- Author
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Naoki Okuda
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Consumables ,Materials science ,Mechanics of Materials ,law ,Mechanical Engineering ,Metallurgy ,Metals and Alloys ,Steel plates ,Welding ,Arc welding ,Composite material ,law.invention - Abstract
(1987). Welding consumables for steel plates produced by controlled rolling. Welding International: Vol. 1, No. 2, pp. 128-133.
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- 1987
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44. Flow rate of flux for submerged are welding from conical hoppers
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Masaharu Kumagai and Naoki Okuda
- Subjects
Engineering drawing ,Materials science ,Mechanical Engineering ,Flux ,Conical surface ,Mechanics ,Welding ,Condensed Matter Physics ,Submerged arc welding ,Grain size ,law.invention ,Volumetric flow rate ,Mechanics of Materials ,law ,Flow coefficient ,General Materials Science ,Body orifice - Abstract
The flow rate of flux for submerged arc welding has been investigated by using SiO2-CaO-MgO fused flux and 60° conical funnels. The circular orifice of the funnels was 4 to 12mm in diameter and the mean grain size of the flux grains was varied from 1.880 to 0.089mm. The test results indicate that the flow rate becomes almost maximum at the mean grain size range of 1.115 to 0.126mm independent of orifice diameter. An attempt to derive a new empirical equation which would represent the flow rate as a function of grain size DP and orifice diameter DO has been made. As a consequence of the study, it was possible to derive an improved equation which has better regression characteristic than other equations proposed previously.
- Published
- 1987
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45. Permeability of submerged arc welding flux
- Author
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Naoki Okuda and Masaharu Kumagai
- Subjects
Friction coefficient ,Materials science ,Mechanical Engineering ,Metallurgy ,chemistry.chemical_element ,Mechanics ,Condensed Matter Physics ,Nitrogen ,Grain size ,Submerged arc welding ,Flux (metallurgy) ,chemistry ,Mechanics of Materials ,Permeability (electromagnetism) ,General Materials Science ,Porosity - Abstract
Relationship between gas permeability and grain size of submerged arc welding (SAW) fluxes has been investigated to get information for the analysis of SAW process. SiO2-CaO-MgO glassy flux and SiO2-MnO porous flux were examined using a flux bed (50-mm-diameter and 50-mm-height) and nitrogen current to obtain the permeability by the D'Arcys' law.Firstly, an experimental equation which shows the relationship between the permeability and grain size was derived for the fluxes with a series of grain sizes ranging from 8×12 to 200×325 mesh. Secondly, it was shown that almost the same permeability as given by the above equation could be estimated for the glassy flux by changing the friction coefficient in the equation proposed previously by Shirai. Furthermore, the permeability of the above glassy flux with two-or four-grain size components was studied. By using the mean grain size obtained by considering the Kozeny-Carman condition, the estimation of permeability for these systems became possible with fair accuracy.
- Published
- 1985
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46. Improvement of notch toughness and soundness in longitudinal seam weld of line pipe
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Yukio Nishino, Naoki Okuda, Wada Takashi, Kazutaka Akao, Kaoru Nagatani, Toshio Ishihara, and Toyofumi Kitada
- Subjects
Toughness ,Heat-affected zone ,Materials science ,Metallurgy ,General Engineering ,Welding ,Electric resistance welding ,Submerged arc welding ,law.invention ,law ,Electrode ,Slag (welding) ,Composite material ,Base metal - Abstract
Multiple-electrode submerged arc welding process with three or four electrode is used for the production of longitudinally welded pipe. Increased welding speed is limited by the properties of flux against weld defects such as undercutting and slag inclusion and the toughness of weld metal deteriorated by impurity gas contamination.A flux with a solidification temperature of 950 to 1050°C and with a viscosity of 2.5 to 4.5 poise at 1400°C can minimize slag inclusion and undercutting. Welding of heavy wall thickness UOE pipes with a heat input above 100kJ/cm requires a flux with a high melting point and high viscosity.In order to obtain good notch toughness of weld metal at low temperature service, it is necessary to control the nitrogen content foreffective utilization of titanium and boron in weld metal. Optimum range of titanium to get high notch toughness is shifted by nitrogen content in weld metal.HAZ notch toughness of high strength line pipe is affected strongly by carbon and boron contents in base metal. Excellent notch toughness of HAZ was obtained by decreasing the carbon content in base metal below 0.05wt%.
- Published
- 1986
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47. [Untitled]
- Author
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Masaharu Kumagai and Naoki Okuda
- Subjects
Mechanics of Materials ,Mechanical Engineering ,Metals and Alloys ,Surfaces, Coatings and Films - Published
- 1984
- Full Text
- View/download PDF
48. Reductive thalliumcarbon bond cleavage in monoarylthallium(III) crown ether complexes
- Author
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Yoshikane Kawasaki, Naoki Okuda, and Hideo Kurosawa
- Subjects
chemistry.chemical_classification ,Organic Chemistry ,Iodobenzene ,chemistry.chemical_element ,Ether ,Reaction intermediate ,Ascorbic acid ,Biochemistry ,Medicinal chemistry ,Toluene ,Inorganic Chemistry ,chemistry.chemical_compound ,chemistry ,Materials Chemistry ,Thallium ,Organic chemistry ,Physical and Theoretical Chemistry ,Bond cleavage ,Crown ether - Abstract
Photolysis and thermolysis of a crown ether-stabilized phenyl(iodo)thallium(III) complex gave good yields of iodobenzene, at least partly through a phenyl radical intermediate. Reduction of a p -tolyl(hydroxo)thallium(III)-crown ether complex with P(OMe) 3 , ascorbic acid or N -benzyl-1,4-dihydronicotinamide gave toluene, but not the di- p -tolylthallium(III) species, which was formed in considerable amount in the corresponding reduction of a crown-free p -tolylthallium(III) cation.
- Published
- 1983
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49. [Untitled]
- Author
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Naoki Okuda and Kazuo Tanaka
- Subjects
Mechanics of Materials ,Mechanical Engineering ,Metals and Alloys ,Surfaces, Coatings and Films - Published
- 1982
- Full Text
- View/download PDF
50. Tetranuclear copper(II) complexes. Copper(II) complexes of schiff bases derived from histamine and salicylaldehyde or 2-pyridinecarbaldehyde
- Author
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Wasuke Mori, Naoki Okuda, Akitsugu Nakahara, and Yasuo Nakao
- Subjects
Inorganic Chemistry ,chemistry.chemical_compound ,chemistry ,Salicylaldehyde ,Inorganic chemistry ,Polymer chemistry ,Materials Chemistry ,chemistry.chemical_element ,Antiferromagnetism ,Physical and Theoretical Chemistry ,Copper ,Histamine ,Ion - Abstract
Reaction of copper(II) ions with the Schiff bases derived from histamine and salicylaldehyde or 2-pyridinecarbaldehyde were investigated in acidic and basic media. The copper(II) complexes obtained from the reactions in acidic solutions were mononuclear complexes I and II, while those from the reactions in basic solutions were tetranuclear complexes III and IV, in which the four copper(II) ions were tetrahedrally arranged. A study on magnetic property (4.2–300 K) of the tetranuclear complexes by the Faraday method suggested the presence of antiferromagnetic interactions between the four copper(II) ions.
- Published
- 1979
- Full Text
- View/download PDF
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