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Biomedical subjects

T Nakazawa

Publications and source records attributed to T Nakazawa.

At least 235 records · Page 13Linked to original sources
PubMed1996

Modification of a pivot bearing system on a compact centrifugal pump.

The pivot bearing centrifugal blood pump was developed as a long-term centrifugal ventricular assist device (VAD) as well as a cardiopulmonary bypass pump. This pivot bearing supported centrifugal pump with an eccentric port (CIE) incorporates a seal-less design with a blood stagnation-free structure. This pump can provide flows of 12 L/min against 650 mm Hg total pressure head at 3,600 rpm, and in a CPB condition 5 L/min against 350 mm Hg total pressure head at 2,600 rpm. Very recently, the pivot bearing system was modified to obtain a stable and smooth spinning movement. The material of the female pivot was changed from ceramic to polyethylene. Three kinds of bearings were tested simultaneously with bovine blood in two types of in vitro circuits to determine the blood damage from the bearings. Pressure differences across the pump (total head pressure, delta P) of 140 mm Hg (n = 12) and 330 mm Hg (n = 12) were examined. The normalized index of hemolysis (NIH) was slightly higher in a ball bearing (BB) pump than in a polyethylene bearing (PB) pump and statistically higher than the BioMedicus Pump (BP-80) on delta P of 140 mm Hg. When the delta P was at 330 mm Hg, a comparison between the three types of pumps revealed no difference in NIH. In addition, the primary vane of the impeller was redesigned to obtain an atraumatic structure. In the second study (n = 14), there was no difference in the NIH between BP-80 and the current model when the delta P was 300 mm Hg (0.019 +/- 0.002 vs. 0.027 +/- 0.006, p = 0.3) and/or when the delta P was 100 mm Hg (0.0008 +/- 0.0001 vs. 0.0014 +/- 0.0002, p = 0.07). The modified pivot bearing had an improved spinning condition and no change in hemolysis. A proper selection of pivot bearing materials is important to develop an atraumatic centrifugal pump. The modification of the bearing system and redesign of the vane enabled a compact centrifugal pump to become a reality.

Animals↗
PubMed1996

Pump power loss and heat generation in a pivot bearing-supported Gyro centrifugal pump (C1E3).

Pump power loss is defined as input power that is not used for the output work of the pump. Less pump power loss means a higher pump efficiency. A common opinion is that the pump power loss is closely related to heat generation of the pump, which may affect not only the endurance of pump materials, but also blood damage in a blood pump. In this study, the relationship between pump power loss and heat generation in centrifugal blood pumps was investigated using the pivot-bearing supported Gyro C1E3 pump (C1E3) and Bio-Medicus pump (BP-80) under four different total pressure heat/flow conditions. A single special torque measuring driver motor was used for operating both the C1E3 and BP-80 in the four conditions. The pump power loss was calculated from the measured motor torque and hydraulic power. The changes in blood temperature were measured while the pump was operated at room temperature (25 degrees C) to obtain the following findings: First, the C1E3 caused less pump power loss and less temperature increase in blood than the BP-80 in all clinical simulated conditions that were tested; and second, the pump power loss and heat generation had a linear correlation with temperature rise from 22 to 25 degrees C in both the C1E3 and BP-80. During this period, approximately 30% of the pump power loss was transformed to heat, independent of the centrifugal blood pump type, provided that heat conduction through the pump housing and tubing was negligible during this particular period.

Animals↗
PubMed1996

Safety margin of magnetic coupling distance in decoupling of a pivot bearing-supported Gyro centrifugal pump (C1E3).

The pivot bearing-supported Gyro C1E3 centrifugal pump is driven by magnetic coupling. The magnetic coupling distance (MCD) between the impeller magnet and the driver magnet affects both hydraulic performance and hemolysis. Although a greater MCD causes less hemolysis, it increases the risk of decoupling of the impeller magnet. Therefore, it is important to consider the effect of the MCD on both hemolysis and decoupling when the C1E3 pump is applied in various circulatory assist conditions. This study investigates the effect of the MCD on decoupling in a C1E3 pump that is driven by the Nd-Fe-B composite ring-shaped magnets. The results will determine which MCD is the most practical in all assist device conditions. The MCD of the C1E3 pump was varied from 9.5 to 14.5 mm by inserting spacers between the bottom pump housing and the driver magnet. At a rotational speed just before the decoupling occurred, the flow rate and total pressure head were measured. The results revealed that a MCD between 9.5 and 14.5 mm was enough to produce a flow rate of more than 10 L/min without decoupling, and a MCD of less than 11.5 mm was required when the total pressure head was more than 500 mm Hg. Thus, the limiting factor for the MCD of the C1E3 pump is the total pressure head rather than the flow rate. An MCD of less than 11.5 mm is required to prevent decoupling of the impeller of the C1E3 pump with the specific Nd-Fe-B magnets in the full range of clinical circulatory assist conditions.

Centrifugation↗
PubMed1996

Hemolytic characteristics of a pivot bearing supported Gyro centrifugal pump (C1E3) simulating various clinical applications.

Centrifugal blood pumps are playing a key role in circulatory mechanical assist systems including cardiopulmonary bypass (CPB), right and left ventricular assist devices (RVAD and LVAD), percutaneous cardiopulmonary support (PCPS), and extracorporeal membrane oxygenation (ECMO). Each of these circulatory assist systems requires specific flow and pressure conditions. In vitro hemolysis tests were performed using five compact mock loops with flow and pressure set equivalent to clinical conditions. These studies determined the hemolytic characteristics and clinical applicability of the pivot bearing-supported Gyro centrifugal pump with an eccentric port (C1E3) compared with the Bio-Medicus pump (BP-80). Normalized index of hemolysis (NIH) values of the C1E3 were less than those of the BP-80 under all conditions; in particular, they were significantly less in the CPB, LVAD, and RVAD conditions. In addition, linear correlation was observed between NIH values, rotational pump speed (RPM), total pressure head (delta P), and flow rate (Q) with both the C1E3 and BP-80: NIH = a(RPM/Q) + b, NIH = c(delta P/Q) + d. However, the slopes (a and c) of these equations were smaller with the C1E3 than those with the BP-80, which suggests that the C1E3 has decreased hemolytic characteristics when increasing the RPM and delta P. In other words, the increase of RPM and delta P results in less shear stress with the C1E3 than with the BP-80. One cause of these decreased hemolytic characteristics of the C1E3 is thought to be less pump power loss against an increase of RPM and delta P than with the BP-80. Furthermore, the average exposure time is shorter with the C1E3 than with the BP-80 because the priming volume of the C1E3 (30 ml) is smaller than that of the BP-80 (80 ml). From the point of both shear stress and exposure time, the C1E3 has less hemolytic features than the BP-80.

Animals↗
PubMed1996

The dsbB gene product is required for protease production by Burkholderia cepacia.

Burkholderia cepacia KF1, isolated from a pneumonia patient, produces a 37-kDa extracellular metalloprotease. A protease-deficient and lipase-proficient mutant, KFT1007, was complemented by a clone having an open reading frame coding for a 170-amino-acid polypeptide which showed significant homology to Escherichia coli DsbB. KFT1007, a presumed dsbB mutant, also failed to show motility, and both protease secretion and motility were restored by the introduction of the cloned dsbB gene of B. cepacia. The mutant KFT1007 excreted a 43-kDa polypeptide that is immunologically related to the 37-kDa mature protease. These results suggested that the dsbB mutant secretes a premature and catalytically inactive form of protease and that disulfide formation is required for the production of extracellular protease by B. cepacia.

Amino Acid Sequence↗
PubMed1996

Bile secretion in rats with indomethacin-induced intestinal inflammation.

The objective of this study was to characterize the bile secretion, including the composition of biliary bile acids, bile salt pool size, and transcytotic vesicle transport, in a rat model of subacute intestinal inflammation induced by indomethacin. Indomethacin treatment significantly decreased bile acid-independent bile flow and biliary secretion of bile acid and cholesterol, while increasing biliary phospholipid output in vivo. Although indomethacin treatment did not change the bile salt pool size in vivo, alpha- and beta-muricholic acids were significantly deceased and hyodeoxycholic and deoxycholic acids were increased in bile. Bile flow and the transport maximum of taurocholate did not decrease, and biliary horseradish peroxidase output was significantly enhanced in isolated perfused livers from indomethacin-treated rats. Endotoxin in the portal blood was significantly increased in rats treated with indomethacin. Clindamycin slightly reduced intestinal inflammation but significantly prevented decreases in bile flow, bile acid output, and transport maximum of taurocholate. We conclude that, although biliary secretory function was apparently decreased in vivo, that of hepatocyte function was maintained in this model.

Animals↗
PubMed1996

Allergic responses reduce the relaxant effect of beta-agonists but not potassium channel openers in guinea-pig isolated trachea.

This study was conducted to determine whether the relaxant effect of adenosine triphosphate (ATP)-sensitive potassium channel (KATP) openers on airway smooth muscle are reduced during the hyporesponsiveness of beta-adrenergic receptors. Isometric tension was measured and dose-response curves were constructed for levcromakalim (a KATP opener), Y-26763 (another KATP opener), isoprenaline and theophylline in guinea-pig isolated trachea that was challenged with ovalbumin or pretreated in vitro with either isoprenaline or the KATP openers. Antigen challenge in vitro significantly reduced the potency but not the efficacy of isoprenaline in tracheal strips from actively sensitized guinea-pigs. The concentration of drug that produced a half-maximum inhibition (IC50) was 0.014 +/- 0.004 microM in the challenge group versus 0.006 +/- 0.001 microM in the control group (p < 0.05; n = 9). The IC50 of levcromakalim (1.73 +/- 0.17 microM; n = 6) and of theophylline (110 +/- 3.1 microM; n = 6) were unaffected. Exposure to 4 microM isoprenaline for 30 min evoked beta-adrenergic hyporesponsiveness: the IC50 of isoprenaline rose significantly from 0.010 +/- 0.001 to 0.017 +/- 0.002 microM (p < 0.01; n = 6). No effect was observed on the relaxant actions of levcromakalim and theophylline. In contrast, prior incubation with either levcromakalim or Y-26763 (300 microM for 30 min) significantly reduced the subsequent potency and efficacy of levcromakalim, but did not alter the effects of isoprenaline and theophylline. We conclude that the relaxant effect of the adenosine triphosphate-sensitive potassium channel openers was independent of beta-adrenergic hyporesponsiveness in airway smooth muscle of guinea-pigs.

Adrenergic beta-Agonists↗
PubMed1996

Nucleotide sequence of a cDNA coding for cyclophilin of the sea urchin Hemicentrotus pulcherrimus.

We present the nucleotide sequence of a cDNA coding for cyclophilin homologue of the sea urchin Hemicentrotus pulcherrimus. The 1,755-nucleotide sequence contains a 492-bp open reading frame corresponding to a translation product of 164 amino acids. Comparison of the deduced amino acid sequence with the previous data shows a high degree of conservation (approximately 80% homology). Southern blot analysis of genomic DNA suggests the presence of a multigene for sea urchin cyclophilin. Northern blot analysis indicates a mRNA size of approximately 3 kb and that message is accumulated at blastula stage.

Amino Acid Isomerases↗
PubMed1996

Solitary plasmacytoma of the skull vault--case report.

A 55-year-old female presented with a rare solitary plasmacytoma restricted to the skull vault without systemic myelomatosis. She had a 9-month history of a slowly growing soft mass in the right temporal region. Neuroradiological examination revealed a skull defect and an extradural tumor. The whole layer of the skull was destroyed by the tumor, but the dura was not involved. The tumor was totally removed, and postoperative radiotherapy was given. Follow-up examination after 2 years showed she was free from local recurrence or evidence of systemic involvement. Complete surgical resection with adjuvant radiation therapy is the treatment of choice. Although the prognosis is good, regular lifelong examinations for myelomatosis are required.

Carotid Artery, External↗
PubMed1996

Identification of major biliary and urinary metabolites of ecabapide in rats.

1. The structures of major biliary and urinary metabolites of ecabapide in rat were identified by comparison with authentic standards using lc-ms and 1H-nmr spectrometry. 2. A major metabolite was found in the bile obtained from rat after an oral dose of 14C-ecabapide and identified as the amidaldehyde derivative. In the urine, two polar metabolites were characterized as the phenolic sulphates. Further, two lipophilic metabolites were identified as alcohol derivatives, and two others as oxamic acids. 3. From these results, it was estimated that the first step in the metabolism of ecabapide in rat was oxidative N-dealkylation to produce the amidaldehyde. This amidaldehyde was further metabolized by two routes, one by reduction of the amidaldehyde into the corresponding alcohol followed by mono-demethylation and subsequent aromatic O-sulphation, the second by oxidation of the amidaldehyde into the oxamic acid followed by mono-demethylation and subsequent aromatic O-sulphation.

Animals↗
PubMed1996

[Trends in asthma-related death among adults in Japan, 1986-1991--analysis of responses to questionnaires sent to hospitals with at least 200 beds].

The death rate among patients with asthma in Japan has been reported by Japan's Ministry of Health and Welfare to approximately 5/100,000 population. Over the past 15 years, this rate has remained relatively constant, but it is higher than that in western countries. To clarify recent trends in adult asthma mortality, the Japan Asthma Death Investigation Committee studied the clinical characteristics of 649 patients who died of asthma between 1986 and 1991. The annual number of deaths decreased slightly: from 145 in 1986 to 89 in 1991. There was a large difference between sexes: the male:female ratio was 3:2. Most patients ranged in age from 50 to 70 years old. It is noteworthy that in one third of the patients death was caused by asphyxic-type asthma, while status asthmaticus was the cause in only 23.7%. The number of patients with mild or moderate asthma was slightly increased, although patients with severe asthma accounted for at least 70% of all deaths. The main causes of fatal asthma attacks were airway infections, fatigue, and stress. Other responses on the questionnaires indicated the following areas of concern: deficiencies in patient education, delays in treatment with corticosteroids and other antiasthma drugs, and delays in provision of emergency treatment.

Adolescent↗
PubMed1996

Efficacy of disinfectants against biofilm cells of methicillin-resistant Staphylococcus aureus.

The effect of disinfectants on biofilm cells of methicillin-resistant Staphylococcus aureus (MRSA) was evaluated. Eradication of biofilm cells of MRSA by chlorhexidine gluconate, benzalkonium chloride, alkyldiaminoethyl glycine and sodium hypochlorite required a much longer time than that of planktonic cells in suspensions. Benzalkonium chloride (0.1%) and alkyldiaminoethyl glycine (0.1%) were ineffective for eradication of biofilm cells even after 1 h, but were effective for eradication of planktonic cells within 20 s. Sodium hypochlorite (0.01%) was also ineffective for eradication of biofilm cells even after 30 min, but was lethal to planktonic cells within 20 s.

Biofilms↗
PubMed1996

[Central retinal vein occlusion after embolization for spontaneous carotid cavernous sinus fistula].

A patient with spontaneous carotid-cavernous sinus fistula, who developed central retinal vein occlusion (CRVO) after interventional surgery, was reported. A 78-year-old woman was admitted with symptoms of right abducens palsy and conjunctival injection. Digital subtraction angiography (DSA) revealed bilateral carotid cavernous sinus fistulas supplied by dural branches of the carotid arteries. After embolization of the feeding arteries and the right cavernous sinus using PVA and platinum coils respectively, her symptom improved gradually. Six months after the embolization, she was readmitted because of blurred vision and abducens palsy on the left side. Engorgements of the cavernous sinuses and draining veins, and the shunt flow of the fistula were much less on DSA than those seen previously, but ophthalmologic studies showed an impending central retinal vein occlusion (CRVO) in her left eye. Prognosis of CRVO is generally poor. We discussed the mechanism of CRVO occurring after interventional surgery for CCF and the tactics for preventing it, and early detection of its development.

Aged↗
PubMed1996

[Cerebrospinal fluid neopterin levels in children with neurologic diseases].

Neopterin has been determined in blood as a marker of cellular immune system activation. We studied cerebrospinal fluid (CSF) neopterin levels in children with neurologic diseases, and the following results were obtained: (1) CSF neopterin levels markedly increased at the acute phase of bacterial meningitis, aseptic meningitis, and encephalitis as compared with those in patients without neurologic diseased. (2) In the CSF of patients with bacterial meningitis and aseptic meningitis, neopterin levels decreased more rapidly than the total cell count and 2'5' oligoadenylate synthetase (2-5 AS) did. (3) CSF neopterin in patients with non-infectious neurologic diseases was almost equal to that in patients without neurologic diseases. (4) There was no correlation between CSF neopterin and other CSF values, such as total cell count, mononuclear cell count, protein, and 2-5 AS. These results suggest that CSF neopterin is a useful marker of inflammatory central nervous diseases.

Adolescent↗
PubMed1996

Can we develop a nonpulsatile permanent rotary blood pump? Yes, we can.

For many years, it was thought that nonpulsatile perfusion produced physiological and circulatory abnormalities. Since 1977, Yukihiko Nosé and his colleagues have challenged this misconception. Toward that end, they did show that if a 20% higher blood flow uses more than that required for a pulsatile blood pump, then there would be no circulatory of physiological abnormalities. These experimental findings confirm that there is no difference in clinical outcome using either a pulsatile or nonpulsatile blood pump. Furthermore, the nonpulsatile rotary blood pump demonstrates efficient and reliable performance in various clinical situations. The nonpulsatile blood pump is a simple and reliable design that is manufactured easily and that has several desirable features. There is no need to incorporate heart valves, which are the most thrombogenic and blood trauma-inducing components. A continuous flow pump does not require a large orifice inflow conduit and proves to be easier to implant in patients with minimal damage to the myocardium. There is no need to incorporate a compliance volume-shifting device, which is essential for a pulsatile blood pump. The nonpulsatile device is a continuous blood pumping system; therefore, the control system is simpler and more reliable than that of a pulsatile pump. Because of the rotary blood pump's structure, only one moving part is necessary for the blood-pumping motion. By using durable components for this moving part, a durable system becomes possible. Because the electrical motor operates continuously, the on-and-off motion required for a pulsatile pump is not necessary; therefore, it is a more efficient and durable system. Thus, this group is working on the development of a nonpulsatile blood pump as a permanently implantable assist device. To achieve this goal, it is necessary to incorporate seven features into the system: small size, atraumatic features, antithrombogenic features, antiinfection features, a simple and durable design, and low energy requirement with easy controllability.

Cardiopulmonary Bypass↗
PubMed1996

Development of a pivot bearing supported sealless centrifugal pump for ventricular assist.

Since 1991, in our laboratory, a pivot bearing-supported, sealless, centrifugal pump has been developed as an implantable ventricular assist device (VAD). For this application, the configuration of the total pump system should be relatively small. The C1E3 pump developed for this purpose was anatomically compatible with the small-sized patient population. To evaluate antithrombogenicity, ex vivo 2-week screening studies were conducted instead of studies involving an intracorporeally implanted VADs using calves. Five paracorporeal LVAD studies were performed using calves for longer than 2 weeks. The activated clotting time (ACT) was maintained at approximately 250 s using heparin. All of the devices demonstrated trouble-free performances over 2 weeks. Among these 5 studies, 3 implantations were subjected to 1-month system validation studies. There were no device-induced thrombus formations inside the pump housing, and plasma-free hemoglobin levels in calves were within the normal range throughout the experiment (35, 34, and 31 days). There were no incidents of system malfunction. Subsequently, the mass production model was fabricated and yielded a normalized index of hemolysis of 0.0014, which was comparable to that of clinically available pumps. The wear life of the impeller bearings was estimated at longer than 8 years. In the next series of in vivo studies, an implantable model of the C1E3 pump will be fabricated for longer term implantation. The pump-actuator will be implanted inside the body; thus the design calls for substituting plastic for metallic parts.

Blood Cell Count↗
PubMed1996

Evaluation of the wear of the pivot bearing in the Gyro C1E3 pump.

To estimate the lifetime of the pivot bearing system of the sealless centrifugal Gyro C1E3 pump, pivot bearing wear phenomena of the C1E3 were studied. The pivot bearing system consisted of a male and female pivot made of ceramics and ultrahigh molecular weight polyethylene (UHMWPE), respectively. First, many pumping tests were performed with the C1E3 under various pumping conditions, and the effects of impeller position and fluid on wear were analyzed. Through these preliminary tests, it was found that the wear progress of the pivot bearing consisted of initial wear and stationary wear. Most of this initial wear is caused by the plastic deformation of the polyethylene female pivot. It also was observed that bovine blood was almost comparable to water in its effect on the stationary wear rate at the same rotational speed. Based on these results, a long-term pumping test was performed with the C1E3, and initial and stationary wear rates were determined. At the same time, the maximal loosening distance (LDmax) (permissible total wear) of the C1E3 was determined experimentally from hemolytic and hydraulic performance perspectives. By using experimentally determined parameters the lifetime of the pivot bearing system of the C1E3 was typically 10 years for right ventricular assist, 8 years for left ventricular assist, and 5 years for cardiopulmonary bypass.

Animals↗