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Biomedical subjects

Kenji Yamazaki

Publications and source records attributed to Kenji Yamazaki.

15 recordsLinked to original sources
PubMed2005

Mechanical circulatory support devices (MCSD) in Japan: current status and future directions.

The current status and future directions of mechanical circulatory support devices (MCSDs) in Japan are reviewed. Currently used clinical MCSDs, both domestic and imported systems and continuous flow devices that are coming into the clinical arena are emphasized. Clinical MCSDs include the extracorporeal pulsatile Toyobo and Zeon systems and the implantable Novacor and HeartMate I VE. A thorough review is presented of single-ventricle continuous flow MCSDs such as the Terumo DuraHeart and the SunMedical EVAHEART and the biventricular Miwatec/Baylor systems that are on the horizon. The future directions in management of end-stage cardiac patients with MCSDs are discussed, focusing on (1) device selection - pulsatile versus continuous flow devices; (2) single-ventricle support, biventricular support, or replacement; (3) bridge to transplantation, destination therapy, or bridge to recovery; and (4) government regulatory processes and the medical industry. We hope to promote the quality of life (QOL) of end-stage cardiac patients as well as the medical industry in Japan.

Animals↗
PubMed2005

Successful application of pulmonary arterial patch for coronary angioplasty late after arterial switch operation.

Pulmonary artery is infrequently utilized as a material for coronary patch angioplasty in children. We applied a pulmonary arterial patch for coronary angioplasty on an 8-year-old boy with total occlusion of the left main coronary artery late after an arterial switch operation. The pulmonary arterial patch was easy to handle and the immediate result after the operation was satisfactory.

Angioplasty↗
PubMed2005

Plasma folate and homocysteine levels may be related to interictal "schizophrenia-like" psychosis in patients with epilepsy.

Genetic and clinical data suggest that folate and homocysteine may play a role in the pathogenesis of psychiatric disorders. The total plasma homocysteine level is a sensitive measure of a functional folate deficiency. We thus investigated whether a functional folate deficiency and/or elevated levels of plasma homocysteine may be related to interictal "schizophrenia-like" psychosis (interictal psychosis ) of epilepsy. We studied the plasma folate, vitamin B12, and homocysteine levels of 32 age- and sex-matched epileptic patients with or without interictal psychosis. Each group included 25 localization-related epilepsies and 7 generalized epilepsies. The epileptic patients with interictal psychosis had significantly lower folate levels and higher homocysteine levels than those without interictal psychosis. There were no significant differences in the vitamin B12 levels between the two groups. The present study suggests that low plasma folate and high plasma homocysteine levels may be related to the pathophysiology of interictal psychosis of epilepsy. In future studies, we should investigate whether folate supplementation, in addition to antipsychotics, might play a beneficial role in the treatment of interictal psychosis in epileptic patients. Furthermore, the present findings should be confirmed by prospective longitudinal studies in a larger group of patients with epilepsy.

Adult↗
PubMed2005

[A study on enterovirus infection in Osaka prefecture --comparison with virus isolation and RT-PCR amplifying viral protein 1 region].

Detection of viral genomes with RT-PCR, which amplifies viral protein 1 region, as well as virus isolation was performed on 860 patients (996 specimens) who had been suspected for enterovirus (EV) infection in Osaka Prefecture from April 2003 to Jury 2004. The viral positive rates of the clinical materials, combining above two procedures, were as follows: 48.2% from the feces, 38.3% from the throat swabs, and 18.0% from the cerebrospinal fluids. The positive rate by the clinical diagnosis indicated that herpangina was the highest at 44.7%, while encephalitis was the lowest at 13.4%. Out of the all specimens, the viral positive rate of RT-PCR varied from 22.3 to 24.7%, while that of virus isolation was 15.6%. The total viral positive rate of both procedures combined was 29.8%. Since the detection of EV by RT-PCR amplifing viral protein 1 region was more rapid than virus isolation and superior in detection of coxsackie group A virus, RT-PCR is an effective procedure for diagnosis of herpangina.

Adult↗
PubMed2004

A comparative study between flow visualization and computational fluid dynamic analysis for the sun medical centrifugal blood pump.

Flow visualization experiments and computational fluid dynamic (CFD) analyses were performed and the results were compared to clarify the detailed fluid dynamic characteristics for the prototype design of a centrifugal pump, namely, an implantable ventricular assist system from Sun Medical, whose hemocompatibility was previously demonstrated in a series of animal experiments. The flow visualization was conducted with particle tracking velocimetry, and the CFD analysis was performed with STAR-CD software. The findings were as follows: (1). There were no flow separations around the curved open impeller. (2). Antithrombogenic design concepts for the inducer and the vane-shaft clearance were effective in producing axial velocity along the shaft surface and generat-ing suitable shear rates against the stationary fluid. (3). Unsteady vortex shedding in the outlet, which adversely affected the fluid dynamic efficiency, was observed clearly by flow visualization. Comparison of velocity distribution measured by flow visualization and CFD analysis showed reasonably good correlation. Our findings indicate that the impeller is suitable for an implantable artificial heart. The techniques of flow visualization and CFD analysis are complementary evaluation tools in research and development efforts.

Blood Flow Velocity↗
PubMed2003

Left ventricular mass index reduction early after an isolated aortic valve replacement with St. Jude Medical 19A-HP.

OBJECTIVES: It has been reported that the left ventricular mass index (LVMI) for the hypertrophic myocardium is reduced at an early stage following surgery. In this study, those factors affecting the changes in early postoperative LVMI were investigated in cases in which a St. Jude Medical 19A-HP (19HP) mechanical heart valve was used. METHODS: We studied 16 consecutive patients with pure aortic stenosis undergoing isolated aortic valve replacement using a 19HP between January 1994 and July 2001. The patients were all female, aged 64 +/- 6 years, with a body surface area of 1.44 +/- 0.10 m2 and preoperative New York Heart Association (NYHA) classification of 2.2 +/- 0.5. All patients underwent transthoracic echocardiography at 4.2 +/- 3.3 days before and 16.3 +/- 10.2 days after operation, and cardiac catheterization within a mean period of one month before operation. The correlations between the decrease of LVMI at 16.3 +/- 10.2 days after operation and perioperative parameters were determined. RESULTS: There was significant LVMI regression postoperatively (15 +/- 12%, p = 0.01), and only a significant negative correlation between the decrease of LVMI and preoperative left ventricular pressure (LVp) [r = -0.74, p < 0.01]. There was no effective LVMI reduction in the high preoperative LVp group (> or = 210 mmHg). CONCLUSION: It is expected that in the high LVp group, huge wall stress was being applied to the left ventricular muscle immediately before surgery and in the early period after surgery. Preoperative LVp is an important index for determining the surgical timing and safe perioperative management. We recommend early surgical treatment before LVp becomes more than 210 mmHg.

Aged↗
PubMed2003

Reactive oxygen species depolymerize hyaluronan: involvement of the hydroxyl radical.

We have previously demonstrated that reactive oxygen species (ROS) are involved in cartilage degradation. A decrease in the size of hyaluronan (HA), which is the major macromolecule in synovial fluid and is responsible for imparting viscosity to it, is reported in arthritis patients. The purpose of this study is to determine the ROS that depolymerize HA. The luminol derivative, L-012, was used to determine the generation of ROS. To generate hydroxyl radicals, a mixture of hydrogen peroxide (H(2)O(2)) and ferrous ions (Fe(2+)) was added to HA. The antioxidants and the depolymerization of HA were studied in this system. The hydroxyl radical is one of the ROS, causing the depolymerization of HA, which reacts with L-01. These data suggest that hydroxyl radicals play an important role at the site of inflammation.

Journal Article↗
PubMed2003

Distal thoracic aorta hemodynamics during exercise with continuous flow left ventricular assist system.

OBJECTIVES: Continuous flow left ventricular assist systems (LVAS) are being discussed as a destination therapy. LVAS patients will have expanded activity of daily life, including exercise. In this study, we analyzed the effects of exercise on blood flow in the distal thoracic aorta of LVAD implanted animals. METHODS: Five calves with a continuous flow LVAS exercised on treadmill at two different pump flow rates (PFR), 60-80% (high PFR) and 25-30% (low PFR) of pulmonary artery flow rate. Pump, pulmonary artery and descending thoracic aorta flow waves were recorded before, during and after exercise. Systolic and diastolic flow volume in each cardiac cycle in pump and descending thoracic aorta flow was calculated. RESULTS: (1) Average flow rates - Pulmonary artery and descending thoracic aorta flow rates increased with heart rate during exercise and there was no difference between groups. (2) Pump flow wave - Pump regurgitation increased temporally during exercise at both PFRs, but sustained incidences of regurgitation after exercise were only observed at low PFR. Systolic and diastolic pump flow volume decreased during exercise at both PFRs, but systolic volume increased and diastolic volume decreased significantly after exercise at low PFR. (3) Descending thoracic aorta flow wave - At high PFR, systolic volume of descending thoracic aorta increased but diastolic flow volume decreased during exercise. At low PFR, both systolic and diastolic volume of the descending thoracic aorta decreased during exercise, but systolic volume increased and diastolic volume decreased after exercise. Systolic volume of the descending thoracic aorta in low PFR was significantly greater and diastolic volume was less than those in high PFR during and after exercise. CONCLUSION: Exercise temporarily increases pump regurgitation with continuous flow LVAS support. Average flow rate of the descending thoracic aorta was maintained by compensation from increased heart rate, although the diastolic flow of the descending thoracic aorta decreased after exercise at the lower pump flow rate. Further study will be needed to evaluate whether or not this flow decrease causes hemodynamic and/or an oxygen delivery mismatch to peripheral tissue.

Animals↗
PubMed2003

In vivo evaluation of a MPC polymer coated continuous flow left ventricular assist system.

The aim of this study was the evaluation of the thrombogenicity and the biocompatibility of the SunMedical EVAHEART left ventricular assist system (LVAS) coated with 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer compared to a diamond-like carbon (DLC) coating. Four calves were implanted with the MPC polymer-coated LVAS. Eight calves were implanted with DLC coated LVAS. The thrombogenicity and biocompatibility of the pumps were evaluated. At explant, 60.0 +/- 37.2% (5-85%) of the pump surface area was still coated with MPC polymer after the duration of 45.0 +/- 32.0 days. In 1 out of 4 MPC and 2 out of 8 DLC coated pumps, there was a very small amount of thrombus around the seal ring; otherwise the blood contacting surfaces were free of thrombus. Major organs were normal except for a few lesions in kidneys from both groups. The MPC polymer coated EVAHEART LVAS seems to have low thrombogenicity and high biocompatibility similar to the DLC coated system. The current study demonstrated that the MPC polymer coating shows great promise for being used as an antithrombogenic substrate for the LVAS due to its ease of application, significant cost benefit, and reduction in anticoagulation therapy in acute postoperative period.

Animals↗
PubMed2003

Precise characterization of norovirus (Norwalk-like virus)-specific monoclonal antibodies with broad reactivity.

We have been characterizing monoclonal antibodies against Norovirus (Norwalk-like virus). In the course of our study, two monoclonal antibodies generated against Norovirus genogroup II capsid protein were found to react not only to genogroup II but also to genogroup I recombinant capsid proteins. In addition, we showed that these two monoclonal antibodies reacted to a 40-amino-acid-fragment located close to the N-terminal region of genogroup II Norovirus. Similar reactivity was observed with the equivalent region of genogroup I Norovirus. In this study, we confirmed that the epitopes of the two monoclonal antibodies existed within an 11-amino-acid peptide. To obtain an idea of the reactive ranges of the two monoclonal antibodies toward different strains of Norovirus, their reactivities were investigated using 16 types of peptide constructed according to the data in GenBank and 8 recombinant capsid proteins (7 whole capsid proteins and 1 short [80-amino-acid] protein fragment). A characteristic broad reactivity of the two monoclonal antibodies is clearly shown by the results of this study. Thus, these monoclonal antibodies could be useful tools for detecting a broad range of Norovirus strains.

Amino Acid Sequence↗
PubMed2002

EVAHEART: an implantable centrifugal blood pump for long-term circulatory support.

OBJECTIVE: We developed "EVAHEART": a compact centrifugal blood pump system as an implantable left ventricular assist device for long-term circulatory support. The 55 x 64 mm pump is made from pure titanium, and weighs 370 g. The entire blood-contacting surface is covered with an anti-thrombogenic coating of diamond like carbon (DLC) or 2-methacryloyloxyethyl phosphorylcholine (MPC) to improve blood compatibility. Flows exceeding 12 L/min against 100 mmHg pressure at 2600 rpm was measured. A low-temperature mechanical seal with recirculating cooling system is used to seal the shaft. EVAHEART demonstrated an acceptably low hemolysis rate with normalized index of hemolysis of 0.005 +/- 0.002 g/100L. METHODS: We evaluated the pump in long-term in-vivo experiments with seven calves. Via left thoracotomy, we conducted left ventricular apex-descending aorta bypass, placing the pump in the left thoracic cavity. RESULTS: Pump flow rates was maintained at 5-9 L/min, pump power consumption remained stable at 9-10 W in all cases, plasma free Hb levels were less than 15 mg/dl, and the seal system showed good seal capability throughout the experiments. The calves were sacrificed on schedule on postoperative day 200, 222, 142, 90, 151, 155, and 133. No thrombi formed on the blood contacting surface with either the DLC or MPC coating, and no major organ thromboembolisms occurred except for a few small renal infarcts. CONCLUSION: EVAHEART centrifugal blood pump demonstrated excellent performance in long-term in-vivo experiments.

Animals↗
PubMedDate not supplied

Computed tomographic findings of syphilitic aortitis.

We describe the computerized tomographic (CT) findings of the aortic wall in a case of acute-phase syphilitic arteritis. The delayed phase of the contrast-enhanced CT shows a double-ring configuration of the thick thoracic aortic wall, which is similar to CT findings previously reported for Takayasu arteritis. We speculate that the resemblance of the CT findings for these two diseases accounts for their similar histopathological features.

Acute Disease↗