K Okamoto

Kumamoto University, Kumamoto, Kumamoto Prefecture, Japan

Are you K Okamoto?

Claim your profile

Publications (56)75.82 Total impact

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Nitric oxide (NO) is increasingly being used in medical applications. Currently, a gas cylinder of N2 mixed with a high concentration of NO is used in the NO inhalation system. However, this arrangement is potentially risky due to the possibility of accidental leak of NO from the cylinder. The presence of NO in air leads to the formation of nitric dioxide (NO2), which is toxic to the lungs. Therefore, an on-site generation of NO would be very desirable for patients with acute respiratory distress syndrome and other related illnesses. Previously, our group reported the production of NO using a pulsed arc discharge. In this work, the prototype of the on-site NO generator was developed and the performances of the NO generator were demonstrated for medical applications.
    10/2009; 115.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Nitric oxide (NO) is increasingly being used in medical treatments of high blood pressure, acute respiratory distress syndrome and other illnesses related to the lungs. Currently a NO inhalation system consists of a gas cylinder of N2 mixed with a high concentration of NO. This arrangement is potentially risky due to the possibility of an accidental leak of NO from the cylinder. The presence of NO in the air leads to the formation of nitric dioxide (NO2), which is toxic to the lungs. Therefore, an on-site generator of NO would be highly desirable for medical doctors to use with patients with lung disease. To develop the NO inhalation system without a gas cylinder, which would include a high concentration of NO, NAMIHIRA et al have recently reported on the production of NO from room air using a pulsed arc discharge. In the present work, the temperature of the pulsed arc discharge plasma used to generate NO was measured to optimize the discharge condition. The results of the temperature measurements showed the temperature of the pulsed arc discharge plasma reached about 10,000 K immediately after discharge initiation and gradually decreased over tens of microseconds. In addition, it was found that NO was formed in a discharge plasma having temperatures higher than 9,000 K and a smaller input energy into the discharge plasma generates NO more efficiently than a larger one.
    Plasma Science and Technology 01/2008; 9(6):747. · 0.60 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In 1987, Nitric oxide (NO) was identified as an effective treatment involving endothelium-derived relaxing factor (EDRF)<sup>1</sup>. NO has attracted lots of attention from the discovery. And now, NO is increasingly being used in medical treatments for some illness related lung. Currently a system of NO inhalation has a gas cylinder of N 2 mixed with a high concentration of NO. However, this method is potentially risky due to the possibility of accidental leak of NO from the cylinder. In addition, gas cylinder is too heavy to carry around and too expensive to be used for all patients. Therefore, an on-site generation of NO would be highly desirable for patient, who is suffering lung disease, and medical doctors. Previous researches reported that NO is produced by pulsed arc discharge in the mixture of N 2 and O 2 , and NO concentration increases with the increasing of pulse repetition rate and energy storage capacitance<sup>2–4</sup>. In this paper, the detail about a prototype of NO generator by pulsed arc discharge based on the optimal discharge condition has been reported. As the results, it is observed that NO concentration in the outlet gas is about almost 1000ppm and rise time is about 20 to 30 sec. These conditions are enough for NO inhalation therapy. Additionally, NO concentration is adjustable by changing pulse repetition rate.
    Pulsed Power Conference, 2007 16th IEEE International; 07/2007
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In 1987, Nitric oxide (NO) was identified as an effective treatment involving endothelium-derived relaxing factor (EDRF)1. NO has attracted lots of attention from the discovery. And now, NO is increasingly being used in medical treatments for some illness related lung. Currently a system of NO inhalation has a gas cylinder of N2 mixed with a high concentration of NO. However, this method is potentially risky due to the possibility of accidental leak of NO from the cylinder. In addition, gas cylinder is too heavy to carry around and too expensive to be used for all patients. Therefore, an on-site generation of NO would be highly desirable for patient, who is suffering lung disease, and medical doctors. Previous researches reported that NO is produced by pulsed arc discharge in the mixture of N2 and O2, and NO concentration increases with the increasing of pulse repetition rate and energy storage capacitance2-4. In this paper, the detail about a prototype of NO generator by pulsed arc discharge based on the optimal discharge condition has been reported. As the results, it is observed that NO concentration in the outlet gas is about almost 1000ppm and rise time is about 20 to 30 sec. These conditions are enough for NO inhalation therapy. Additionally, NO concentration is adjustable by changing pulse repetition rate.
    01/2007;
  • Atherosclerosis Supplements 01/2003; 4(2):213-213. · 9.67 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Nitric monoxide (NO) is increasingly being used in medical applications. Currently, a gas cylinder of N<sub>2</sub> mixed with a high concentration of NO is used. This arrangement is potentially risky due to the possibility of accidental leak of NO from the cylinder. The presence of NO in air leads to the formation of nitric dioxide (NO<sub>2</sub>), which is toxic to the lungs. Therefore, an on-site generation of NO would be very desirable for patients with acute respiratory distress syndrome and other related illnesses. We have recently reported on the production of NO using a pulsed arc discharge. In the present work, the discharge reactor was made simpler and smaller. NO was generated using a pulsed arc discharge in dry air and in mixtures of oxygen and nitrogen. The composition of the gas mixture after treatment with an arc discharge followed by exposure to heated molybdenum was 540 ppm of NO, 48 ppm of NO<sub>2</sub>, and the balance dry air at 0.1 MPa and 300 ± 3 K. No ozone was detected at the outlet of the system by UV absorption. The density of the brass particles emitted from the electrodes, which had diameters over 0.3 μm, was less than 1.39 μg/L. A filter could readily capture and thus remove the brass particles.
    IEEE Transactions on Plasma Science 11/2002; · 0.95 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The shortage of donor hearts has made use of non-beating hearts as cardiac grafts an attractive possibility for heart transplant candidates. The purpose of this study was to evaluate the utility of leukocyte-depleted hot shot cardioplegia for resuscitation of non-beating hearts obtained from asphyxiated dogs via an autoperfusing heart-lung circuit. Mongrel dogs were divided into 3 groups according to the warm ischemia time and the method of reperfusion before starting the autoperfusing heart-lung circuit. Group A (n=4) had 60 minutes of warm ischemia and reperfusion without leukocyte-depleted hot shot, Group B (n=5) had 30 minutes of warm ischemia and reperfusion with leukocyte-depleted hot shot, and Group C (n=7) had 60 minutes of warm ischemia and reperfusion with leukocyte-depleted hot shot. We calculated stroke work via the heart-lung circuit to evaluate cardiac function of the resuscitated hearts. The criteria for "recovery" has been reported elsewhere. Myocardial water content of the resuscitated hearts was also measured and analyzed. No inotropic agents were used. The recovery rates in groups A, B and C were 0%, 80% and 57%, respectively, and the group B rate was significantly higher than the group A rate (p=0.04). Although myocardial water content did not differ between groups B and C, it was significantly lower in recovered hearts than in non-recovered hearts (p=0.04). Significant negative correlation was observed between the maximum stroke work value and myocardial water content in the resuscitated hearts (r=0.668, p=0.03). The autoperfusing heart-lung circuit is useful for evaluation and maintenance of cardiac function. Our experimental data shows that leukocyte-depleted hot shot plays a great role for resuscitation and recovery of non-beating hearts.
    Annals of thoracic and cardiovascular surgery: official journal of the Association of Thoracic and Cardiovascular Surgeons of Asia 01/2002; 7(6):341-5. · 0.69 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A rare case of cardiac malignant fibrous histiocytoma (MFH) is reported. A 55-year-old woman complained of palpitation due to atrial fibrillation. Echocardiography, magnetic resonance imaging, and angiography demonstrated a tumor arising from the posterior wall of the left atrium. At surgery, the tumor was almost entirely resected and histologically defined as MFH. Neither chemotherapy nor irradiation was administered. Echocardiography revealed a local recurrence two months after the surgery and the patient died of advanced cachexy and heart failure 2 years later. The details of this case are presented with a review of the literature.
    Internal Medicine 01/2002; 40(12):1222-6. · 0.97 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The purpose of this study was to investigate whether topically applied tissue factor pathway inhibitor (TFPI) reduces intimal thickness and increases long-term patency of small arterial autografts in rabbits. An entire 10-mm long section of the left femoral artery was harvested and immersed in saline solution (control group, n = 10), 100 IU/mL of heparin (heparin group, n = 15), or 40 microg/mL of TFPI (TFPI group, n = 15) for 15 minutes. Then the graft was interposed to the right femoral artery. Patency rates were determined by flow measurements throughout the time course of the study, and the grafts were analyzed for measurement of intimal thickness at 3 months after operation. Immunohistochemical analysis was performed to examine whether topically applied TFPI binds to endothelial cells of the grafts. Three-month postoperative patency rates were 10% in the control group, 47% in the heparin group, and 73% in the TFPI group. The TFPI group had a significantly higher patency rate than that of the control group (P <.005). Compared with the heparin group, the TFPI group had a significant reduction in intimal area (0.19 +/- 0.05 mm(2) vs 0.30 +/- 0.09 mm(2), P =.0051), in percentage of stenosis (35.7% +/- 7.7% vs 61.4% +/- 15.8%, P <.0001), and in intimal/media areas ratio (0.64 +/- 0.24 vs. 1.04 +/- 0.33, P =.0051). Immunohistologic analyses confirmed that topically applied TFPI bound to endothelial cells. These results indicate that topically applied TFPI reduces intimal thickness and increases long-term patency of small arterial autografts in rabbits.
    Journal of Vascular Surgery 07/2001; 34(1):151-5. · 2.98 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Inhaled nitric oxide (INO) therapy is becoming an indispensable measure in some critically ill patients with pulmonary hypertension. Most importantly, it has been shown that INO significantly reduces the necessity for extracorporeal lung assist in newborns with hypoxemic respiratory failure and pulmonary hypertension. A large number of basic and clinical studies are making great steps in delineating its physiology, techniques, side effects, and clinical efficacy. This article reviews the current knowledge of INO therapy including a novel device of nitric oxide production system.
    Nippon rinsho. Japanese journal of clinical medicine 07/2001; 59(6):1126-31.
  • [Show abstract] [Hide abstract]
    ABSTRACT: We reported a case of successful simultaneous mitral and aortic valvuloplasty using rasping procedure. A 55-year-old woman with combined valvular disease received this operation. Postoperatively, the mitral valve area increased from 1.15 cm2 to 2.03 cm2. Mitral regurgitation improved. Aortic valve pressure gradient decreased from 21 mmHg to 0 mmHg. Aortic regurgitation also improved. Cardiac Index (CI) increased from 1.94 l/min./m2 to 2.59 l/min./m2. Ejection fraction (EF) also increased from 60% to 82%. The postoperative course was uneventful. Excellent postoperative results of this procedure may be expected, not only in single valvular disease but also in combined valvular disease.
    Kyobu geka. The Japanese journal of thoracic surgery 06/2001; 54(5):419-21.
  • [Show abstract] [Hide abstract]
    ABSTRACT: We compared the operative outcomes among 14 patients who underwent the removal of left atrial myxoma with four different approaches; right lateral (n = 2), transseptal bi-atrial (Dubost, n = 4), conventional transseptal (n = 4) and superior transseptal approach (STA, n = 4). Concomitant operations were performed in 4 cases (CABG, two; aortic valvuloplasty, one; mitral valve replacement, one), and two out of 4 cases were in the STA group. The mean operation, cardiopulmonary bypass and aortic cross-clamp times were shorter in the STA group compared to the other three group. The total amount of postoperative drain discharge and the peak value of creatine kinase were also lower in the STA group compared to the other three groups. Among the patients in sinus rhythm before operation, the use of STA was associated with a greater incidence (100%) of postoperative atrial fibrillation or junctional rhythm. These rhythm disturbances were temporary, and all returned to sinus rhythms during hospital stay. We conclude that STA is an excellent approach with a nice surgical view to expose and remove the left atrial myxoma.
    Kyobu geka. The Japanese journal of thoracic surgery 04/2001; 54(3):211-4.
  • [Show abstract] [Hide abstract]
    ABSTRACT: The use of cryopreserved aortic allografts in cardiovascular surgery is widespread and has resulted in excellent outcomes. However, it is controversial whether cryopreservation suppresses the antigenicity of tissue. We designed experimental models to study whether the cryopreservation process alters antigenicity in comparison with that found in fresh and glutaraldehyde treated tissues. Fresh, cryopreserved, and glutaraldehyde treated thoracic aorta from Brown Norway rats were subcutaneously implanted into Lewis rats. Inflammatory cells infiltrating around the grafts were measured on days 7, 14, 28, and 56 after implantation. The glutaraldehyde treated grafts showed significantly less infiltration than the fresh or cryopreserved grafts (p < 0.005). No significant difference was detected between the fresh and cryopreserved grafts. Another study examined the effect of modifications of the aortic allograft on subsequent allogeneic skin graft antigenicity. Subcutaneous implantation of fresh, cryopreserved, and glutaraldehyde treated aortic grafts from Brown Norway into Lewis rats resulted in subsequent skin graft rejection at 4.4+/-0.7, 5.1+/-0.8, and 6.6+/-2.1 days, respectively. There was no significant difference between the fresh and cryopreserved groups; whereas skin grafts in the glutaraldehyde group survived longer than those in the cryopreserved group. These results indicate that cryopreservation had no significant influence on antigenic suppression of arterial allografts.
    ASAIO Journal 01/2001; 47(3):202-5. · 1.39 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The purpose of this study was to evaluate the effects of locally applied TFPI on the reduction of neointimal thickness in Dacron grafts. Seven millimeter internal diameter 5 cm lengths of albumin coated knitted Dacron grafts were interposed in the infrarenal aorta in 14 mongrel dogs. Before implantation, the grafts were immersed in saline solution containing 200 microg/ml of TFPI (TFPI group, n = 7) or 100 IU/ml of heparin (control group, n = 7) for 15 minutes at room temperature. Three months after implantation, neointimal thickness and percentage of graft stenosis were measured by computerized planimetry. All grafts were patent 3 months after implantation. Thrombus was found in one graft in the TFPI group, but observed in three of seven control grafts. Neointimal thickness in the TFPI group was significantly smaller than that in the control group (mean +/- SD, 0.26 +/- 0.1 mm vs. 0.57 +/- 0.15 mm, p < 0.001). Percentage of graft stenosis was significantly lower in the TFPI group than in the control group (13.4 +/- 5.3% vs. 26.9 +/- 7.0%, p < 0.001). Scanning electron micrographs showed that the neointima of TFPI treated grafts were completely covered by endothelial cells. The present results indicate that locally applied TFPI reduces thrombogenicity and neointimal thickness in albumin coated knitted Dacron grafts.
    ASAIO Journal 01/2001; 47(4):325-8. · 1.39 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We compared the effects a novel recombinant tissue-type plasminogen activator (rt-PA) E6010 with the more conventional therapeutic agent alteplase in a new canine model of life-threatening acute pulmonary thromboembolism (APTE). Fifty milliliters of autologous blood was obtained from anesthetized, adult mongrel dogs and mixed with 10,000 units of thrombin. The left pulmonary artery, pulmonary vein, and bronchus were ligated, and previously prepared blood clots were injected via the femoral vein until the mean pulmonary artery pressure (mPA) increased to 2.5-3.0 times over baseline mPA (control). E6010 (0.4 mg/kg) or alteplase (1.33 mg/kg) was administered to other animals following inducement of APTE. In control animals, 60 min after embolization, mPA increased from 13+/-3 mm Hg to 31+/-3 mm Hg (p < 0.0001), cardiac output (CO) decreased from 1.47+/-0.35 l/min to 1.15+/-0.39 l/min (p < 0.0001), and PaO2 decreased from 101+/-31 mm Hg to 65+/-20 mm Hg (p < 0.001). E6010 significantly reduced mPA from 31+/-3 mm Hg to 25+/-4 mm Hg (p < 0.0001) 30 min after administration. In the alteplase group, however, mPA did not significantly change. At 180 min following drug administration, further reduction of mPA was significantly observed in both treatments. CO and PaO2 did not improve after either treatment. The present study indicated that E6010 more rapidly reduced pulmonary hypertension in our APTE model. Because of its rapid action, E6010 might be a promising thrombolytic agent for treatment of APTE.
    Annals of thoracic and cardiovascular surgery: official journal of the Association of Thoracic and Cardiovascular Surgeons of Asia 10/2000; 6(5):299-303. · 0.69 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We report the results of long-term follow up in 9 patients who underwent pericardiectomy for constrictive pericarditis. In order to test whether if congestive liver dysfunction due to the disease could be reversible or not after the surgical repair, the patients were evaluated by indocyanine green (ICG) clearance test. All the patients improved in NYHA classification after long-term periods following surgical repairs. The percentage of ICG retention at 15 minutes (ICG-R15) improved in most of the patients. However, two patients who had a long history from the onset before surgery became worse in ICG-R15. From the above reports, reversibility of hepatic function might be dependent on the duration of liver congestion before surgical repairs.
    Kyobu geka. The Japanese journal of thoracic surgery 08/2000; 53(7):567-70.
  • [Show abstract] [Hide abstract]
    ABSTRACT: We studied the combined effects of inhaled nitric oxide (INO) and positive end expiratory pressure (PEEP) during mechanical ventilation in patients with acute respiratory distress syndrome (ARDS). Eleven patients received 0 and 4 parts per million of INO in random order for 30 min at PEEP levels of 0, 5, and 10 cm H2O. Respiratory and cardiovascular parameters were measured. The addition of INO and PEEP significantly improved arterial oxygenation (p < 0.005 and p < 0.0001, respectively). The combined effect of INO and PEEP on arterial oxygenation was remarkable during 10 cm H2O PEEP. There was synergistic effect on arterial oxygenation by combining INO and 10 cm H2O PEEP. The present study showed that the combination of INO and 10 cm H2O PEEP enhanced arterial oxygenation in patients with ARDS.
    Artificial Organs 05/2000; 24(5):390-5. · 1.87 Impact Factor
  • Transplantation Proceedings 04/2000; 32(2):336-8. · 0.95 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Nitric monoxide (NO) is widely used in medical treatment of acute respiratory distress syndrome (ARDS). The production of NO is of interest to the medical community. In the present work, NO is generated by pulsed discharges between two rod electrodes in a mixture of nitrogen and oxygen. An arc discharge having a temperature of about 10000 K was produced, which was sufficient to generate NO. Some of the important parameters affecting the production of NO have been investigated. These include the percentage of O<sub>2</sub> (6-94%) in the mixture of Na and O<sub>2</sub>, the energy of the discharge (0.5-12 J/pulse), the pulse repetition rate (0.54.5 pps) and the flow rate (1.35-5.4 l/min) of the gas mixture. NO<sub>2</sub> produced in the discharge was successfully changed to NO using a heated molybdenum tube, NO<sub>2</sub> must be extracted from the gas before clinical inhalation. The concentration of ozone was completely eliminated by bubbling the gas mixture through water. A maximum of NO and a minimum of NO<sub>2</sub> concentrations were generated when the proportion of O<sub>2</sub> in the gas mixture was in the range of 20-27%. The concentrations of NO and NO<sub>2</sub> increased with increasing pulse repetition rate and with decreasing flow rate of the mixture. In all cases, No<sub>2</sub> was effectively removed using a heated molybdenum tube
    IEEE Transactions on Plasma Science 03/2000; · 0.95 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The expression of matrix metalloproteinases (MMPs) and their inhibitors (TIMPs) by human vascular smooth muscle cells (SMC) was monitored as a function of the phenotypic modulation in vitro. Cell phenotype was manipulated by varying serum concentration and cell density. Synthetic phenotype was characterized by a minimum expression of the contractile proteins and a maximal proliferation rate. Contractile phenotype was quiescent and expressed a maximal level of contractile proteins. Synthetic cells expressed the highest levels of both MMP-1 and TIMP-1 and displayed maximal collagenolytic activity. No significant change was detected in MMP-2 expression or catalytic activity. Enzyme immunoassays revealed that MMP-1 expression fell by 77+/-2.4-95+/-0.5%, and that of TIMP-1 by 34+/-0.5-59+/-1.9%, as the cells acquired a contractile phenotype. The level of the MMP-1/TIMP-1 complex was similarly reduced by 78+/-2.9-85+/-1.6%. These data demonstrate that the expression of MMP-1 and TIMP-1 are coordinately regulated with SMC phenotype.
    Connective Tissue Research 02/2000; 41(2):143-53. · 1.98 Impact Factor

Publication Stats

290 Citations
75.82 Total Impact Points

Institutions

  • 1990–2009
    • Kumamoto University
      • • Bioelectrics Research Center
      • • Department of Computer Science and Elecrical Engineering
      • • Department of Anesthesiology
      Kumamoto, Kumamoto Prefecture, Japan
  • 2008
    • Shinshu University
      Shonai, Nagano, Japan
  • 2000–2002
    • Kurume University
      • Department of Pathology
      Куруме, Fukuoka, Japan