Biomedical subjects

T Masuzawa

Publications and source records attributed to T Masuzawa.

At least 37 records · Page 2Linked to original sources

PubMed2000

Characterization and identification of Borrelia isolates as Borrelia valaisiana in Taiwan and Kinmen Islands.

Eleven pure cultures of Borrelia from 3 species of wild rodents (Apodemus agrarius, Mus formosanus, Rattus losea) captured in Taichung, located in the center of Taiwan island, and on Kinmen Island were characterized. Five isolates showed restriction fragment length polymorphism (RFLP) patterns of 5S-23S rRNA gene intergenic spacer sequences identical to those of strains 5MT and 10MT, identified as Borrelia valaisiana, which were isolated in the southern tip of South Korea. Although the remaining six isolates showed novel RFLP patterns, these isolates showed more similarity to members of B. valaisiana from Korea, Japan and Europe based on 16S rRNA gene and flagellin gene sequences. This led us to speculate that transmission and proliferation of this type of borrelia occurred between Taiwan and the southern part of South Korea.

Animals↗

PubMed2000

Prevalence of Lyme disease Borrelia spp. in ticks from migratory birds on the Japanese mainland.

Borrelia sp. prevalence in ticks on migratory birds was surveyed in central Japan. In autumn, a total of 1,733 birds representing 40 species were examined for ticks. A total of 361 ticks were obtained from 173 birds of 15 species, and these ticks were immature Haemaphysalis flava (94.4%), Haemaphysalis longicornis, Ixodes columnae, Ixodes persulcatus, Ixodes turdus, and an unidentified Ixodes species. Of these, 27 juveniles of H. flava on Turdus pallidus, Turdus cardis, or Emberiza spodocephala, 2 juveniles of I. persulcatus on T. pallidus, and 1 female H. flava molted from a T. pallidus-derived nymph were positive for the presence of Borrelia by Barbour-Stoenner-Kelly culture passages. In spring, a total of 16 ticks obtained from 102 birds of 21 species were negative for the spirochete. Isolates from 15 ticks were characterized by 5S-23S rRNA intergenic spacer restriction fragment length polymorphism analysis; all isolates were identified as Borrelia garinii with pattern B/B' based on the previous patterning. According to the intergenic spacer sequences, 2 of 15 isolates, strains Fi14f and Fi24f, were highly similar to B. garinii strains 935T of Korea and ChY13p of Inner Mongolia, China, respectively. These findings indicate that Lyme disease-causing B. garinii may have been introduced to Japan by migratory birds from northeastern China via Korea. Additionally, a case of transstadial transmission of B. garinii from nymph to adult H. flava suggests that the infected H. flava may transmit Borrelia to large animals.

Animals↗

PubMed1999

Multielement compositions of marine phytoplankton samples from coastal areas of Japan by instrumental neutron activation analysis.

Phytoplankton samples were collected during spring bloom of diatoms from three coastal areas of Japan using a NORPAC P-25 net (25-micron opening) with a NGG52 prenet (335-micron opening), and 25 major and trace elements have been analyzed by INAA. Concentration ranges of analyzed phytoplankton samples are much wider than the concentration ranges compiled by Bowen (1979) except for As, and data of marine phytoplankton samples for Br, Sb, Hf, Sc, La, Ce, Sm, and Eu were not included in the compilation. The 25 analyzed elements have been categorized into three groups: elements showing positive correlation with Br, positive correlation with Al, and no positive correlation with Br or Al. The marine phytoplankton samples have been plotted on a Masuzawa-Koyama-Terazaki (MKT) plot and it proved that the MKT plot is applicable to marine phytoplankton samples.

Japan↗

PubMed1999

Three-dimensional thoracic modeling for an anatomical compatibility study of the implantable total artificial heart.

Anatomical compatibility with the thoracic cavity is important in developing a completely implantable total artificial heart (TAH). The purpose of this study was to examine the optimal morphology of our TAH and to develop a computer implantation simulation environment for preoperational discussion. As the first stage, we constructed a prototype simulation system by creating a 3-D surface model of a thoracic cavity and one of a TAH. In this system, the thoracic surface model, composed of the aorta, pulmonary artery, ventricle resected heart, diaphragm, and thoracic wall, was created based on the organ contours extracted from electrocardiogram (ECG)-synchronized ultrafast computer tomographic images. The accuracy of the thoracic model was discussed using a phantom. The fitting study can be performed on the computer with the model of the thorax and that of the TAH. In the future, construction of a database for the thoracic cavities of heart failure patients is planned to improve the morphology of the TAH.

Computer Simulation↗

PubMed1999

The development of a control method for a total artificial heart using mixed venous oxygen saturation.

For physiological control of a total artificial heart (TAH), applying mixed venous oxygen saturation (SVO2) as a parameter for TAH control is a promising approach regarding sensitivity to the recipient's oxygen demand and the practical possibility of continuous monitoring using near infrared rays through transparent blood pump housings. To develop a control method for the TAH using SVO2, the relationship between SVO2 and cardiac output (CO) was investigated in a normal calf, and a control algorithm was developed based on this correlation. Then the feasibility of this method (SVO2 mode) was evaluated in a calf implanted with a pneumatic TAH and compared with the fixed drive control mode (fixed mode) in which the drive parameters were unchanged. The calf performed a graded exercise test in both modes. The CO was effectively increased from 7.3 to 13.0 L/min in the SVO2 mode, and the capacity for exercise was augmented compared to the fixed mode. We conclude that this SVO2 mode is feasible and may be effectively applied in TAH control.

Animals↗

PubMed1999

In vivo evaluation of the national cardiovascular center electrohydraulic total artificial heart.

We have been developing an electrohydraulic total artificial heart system. The system comprises an intrathoracic pumping unit composed of diaphragm type ellipsoidal blood pumps and an energy converter in addition to an electronics unit. The in vivo performance of the pumping unit was evaluated in a series of animal implantations with 3 calves weighing 62-85 kg. An interatrial shunt 4.5 mm in diameter was made in the atrial septum to compensate left-right imbalance. Two calves died early postoperatively, one of external controller power failure and the other of interatrial shunt stenosis due to thrombus formation. One calf, however, survived over 10 days under stable circulatory conditions. No abnormality was found in the oxygen metabolic condition or in major organ functions. The generation and dissipation of heat from the device was acceptable. This animal died of device malfunction caused by energy converter bearing breakdown. The device demonstrated a good anatomic fit without compromising the great vessels and adjacent tissues. It is concluded that the pumping unit has a sufficient in vivo basic performance although appropriate countermeasures are to be implemented against the detected problems concerning mechanical durability and interatrial shunt patency.

Animals↗

PubMed1999

Cardiac autonomic nervous function during long-term nonpulsatile left heart bypass.

We investigated the changes in cardiac autonomic nervous activities during long-term nonpulsatile left heart bypass (NLHB) by analyzing heart rate variability. A pulsatile ventricular assist device was installed in 3 goats, and pulsatile left heart bypass (PLHB) was conducted for 2 weeks. Then, NLHB was maintained for the following 4 weeks. The segmental data of the R-R intervals (R-Rs) was analyzed by maximum entropy spectral analysis. Changes in evaluated parameters from the last week of PLHB to the 4th week of NLHB were as follows: the mean R-Rs increased from 511 ms to 692 ms; the coefficient of variation of R-R increased from 10.2 to 14.1%; the power of the low frequency band (LF) increased from 747 ms2 to 2,855 ms2; the power of the high frequency band (HF) increased from 512 ms2 to 1,270 ms2; and the ratio of LF to HF increased from 2.6 to 6.5. These results indicated that the cardiac autonomic nervous activity, both sympathetic and parasympathetic, increased during long-term NLHB.

Analysis of Variance↗

PubMed1999

Flow visualization study to improve hemocompatibility of a centrifugal blood pump.

A correlation study was conducted among quantitative flow visualization analysis, computational fluid dynamic analysis, and hemolysis tests regarding the flow in a centrifugal blood pump to prevent hemolysis. Particular attention was paid to the effect of the impeller/casing gap widths on the flow in the volute and in the outlet. Flow vector maps were obtained for 250% scaled-up models with various geometries, using an argon ion laser light sheet, a high speed video camera, and particle tracking velocimetry. In terms of the results, in the small radial gap model, high shear occurred near the inside wall of the outlet and stagnation near the outside wall of the outlet whereas the standard model maintained smooth flow and low shear. The small radial gap model showed a lower head and greater hemolysis than the standard model. This head decrease could be partly restored by relocating the outlet position; however, the hemolysis level hardly decreased. From these results, it was found that the small radial gap itself is important. It was also confirmed by detailed flow visualization and simple laminar shear analysis near the wall that the small radial gap caused a wider high shear layer (110-120 microm) than the standard model (approximately 80 microm). In the small radial gap model, the high shear layer in the outlet (approximately 50 microm) is much narrower than that in the volute. Flow visualization together with the aid of computational fluid dynamic analysis would be useful to eliminate the causes of hemolysis.

Blood Flow Velocity↗

PubMed1999

Diminished vasoconstrictive function caused by long-term nonpulsatile left heart bypass.

We investigated the functional changes of the systemic vascular system due to prolonged nonpulsatile left heart bypass (NPLHB). Three adult goats underwent pulsatile left heart bypass (PLHB). Two weeks later the PLHB was changed to the NPLHB, which was conducted for 4 weeks. The aortic pulse pressure was 39 and 16 mm Hg during the PLHB and NPLHB, respectively. Systemic vascular resistance (SVR) and the plasma norepinephrine level were measured at the end of PLHB (PUL), and in the 1st, 2nd, 3rd, and 4th weeks of NPLHB (NP1w, NP2w, NP3w, and NP4w). At each point, 1 microg/kg norepinephrine was injected, and the elevation of the SVR (deltaSVR) was calculated. The SVR and the plasma norepinephrine level did not change significantly during the entire course. However, deltaSVR decreased during NPLHB and became significantly lower at NP3w and NP4w than that at PUL (NP3w: 839 +/- 164, NP4w: 746 +/- 268, and PUL: 1,239 +/- 324 dyne x s x cm(-5)). These results strongly indicated that prolonged NPLHB significantly diminished the constrictive function of the vascular system.

Animals↗

PubMed1999

Augmentative effect of pulsatility on the wall shear stress in tube flow.

Wall shear stress (WSS) has been considered to play an important role in the physiological and metabolic functions of the vascular endothelial cells. We investigated the effects of the pulse rate and the maximum flow rate on the WSS to clarify the influence of pulsatility. Water was perfused in a 1/2 inch transparent straight cylinder with a nonpulsatile centrifugal pump and a pulsatile pneumatic ventricular assist device (VAD). In nonpulsatile flow (NF), the flow rate was changed 1 to 6 L/min by 1 L/min increments to obtain standard values of WSS at each flow rate. In pulsatile flow (PF), the pulse rate was controlled at 40, 60, and 80 bpm, and the maximum flow rate was varied from 3.3 to 12.0 L/min while the mean flow rate was kept at 3 L/min. The WSS was estimated from the velocity profile at measuring points using the laser illuminated fluorescence method. In NF, the WSS was 12.0 dyne/cm2 at 3 L/min and 33.0 dyne/cm2 at 6 L/min. In PF, the pulse rate change with the same mean, and the maximum flow rate did not affect WSS. On the other hand, the increase in the maximum flow rate at the constant mean flow rate of 3 L/min augmented the mean WSS from 13.1 to 32.9 dyne/cm2. We concluded that the maximum flow rate exerted a substantial augmentative effect on WSS, and the maximum flow rate was a dominant factor of pulsatility in this effect.

Blood Flow Velocity↗

PubMed1999

Development of design methods for a centrifugal blood pump with a fluid dynamic approach: results in hemolysis tests.

The purpose of this study was to examine the relationship between local flow conditions and the hemolysis level by integrating hemolysis tests, flow visualization, and computational fluid dynamics to establish practical design criteria for centrifugal blood pumps with lower levels of hemolysis. The Nikkiso centrifugal blood pump was used as a standard model, and pumps with different values of 3 geometrical parameters were tested. The studied parameters were the radial gap between the outer edge of the impeller vane and the casing wall, the position of the outlet port, and the discharge angle of the impeller vane. The effect of a narrow radial gap on hemolysis was consistent with no evidence that the outlet port position or the vane discharge angle affected blood trauma in so far as the Nikkiso centrifugal blood pump was concerned. The radial gap should be considered as a design parameter of a centrifugal blood pump to reduce blood trauma.

Animals↗

PubMed1999

Computational fluid dynamics analysis to establish the design process of a centrifugal blood pump: second report.

To establish an efficient design process for centrifugal blood pumps, the results of computational fluid dynamics (CFD) analysis were compared to the results of flow visualization tests and hemolysis tests, using the Nikkiso centrifugal blood pump. CFD analysis revealed that the radial gap greatly affected the shear stress in the outlet diffuser. The hemolysis study also indicated a similar tendency. To see the flow behind the impeller, we conducted a comparative study between models with and without washout holes using the CFD technique. CFD analysis indicated that flow and pressure distributions behind the impeller were different between both models, and a particle was observed to remain longer behind the impeller in the model without washout holes. In the future, CFD analysis could be a useful tool for developing blood pumps in comparison to flow visualization tests and hemolysis tests.

Computer Simulation↗

PubMed1999

Determination of members of a Borrelia afzelii-related group isolated from Ixodes nipponensis in Korea as Borrelia valaisiana.

The 16S rRNA sequences of the Korean Borrelia strains 5MT and 9MT, isolated from Ixodes nipponensis, showed identities of 99.0-99.1% to that of B. afzelii. The strains were tentatively classified as belonging to the B. afzelii-related group. In this study, Korean isolates, including these strains, were characterized further and compared with recently described new species. These strains generated a RFLP pattern that has not been found previously in RFLP analysis of the 5S-23S rRNA intergenic spacer and the flagellin gene. When phylogenetic trees were constructed, based on the 5S-23S rRNA intergenic spacer, flagellin gene and 16S rRNA sequences, these Korean isolates formed a cluster with the Borrelia strain Am501 isolated from Ixodes columnae in Japan and Borrelia valaisiana strains VS116T and UK isolated from Ixodes ricinus in Europe and were distinguishable from the other species. However, these three groups of strains were divergent from each other in the molecular masses of the putative outer surface protein A (OspA) and in the sequences of the ospA gene. These findings suggest that these Korean isolates and one Japanese isolate are members of B. valaisiana and that OspA of this species is divergent, as is that of Borrelia garinii. This led to the speculation that B. valaisiana strains are adapted to the vector ticks found in each locality.

Animals↗

PubMed1999

International multicenter evaluation of the clinical utility of a dipstick assay for detection of Leptospira-specific immunoglobulin M antibodies in human serum specimens.

We performed a multicenter evaluation of a robust and easily performed dipstick assay for the serodiagnosis of human leptospirosis. The assay is aimed at the detection of Leptospira-specific immunoglobulin M (IgM) antibodies. The study involved 2,665 serum samples collected from 2,057 patients with suspected leptospirosis in 12 countries on five continents with different levels of endemicity and different surveillance systems. The patients were grouped as laboratory-confirmed leptospirosis case patients and noncase patients based on the results of culturing and the microscopic agglutination test. Paired samples from 27.7% of the subjects were tested. Of the 485 case patients, 87.4% had a positive dipstick result for one or more samples. Of the 1,513 noncase patients, only 7.2% had a positive result. Whereas most (88.4%) of the positive samples from the case patients showed moderate to strong (2+ to 4+) staining in the dipstick assay, most (68.1%) of the positive samples from the noncase patients showed weak (1+) staining. The sensitivity of the dipstick assay increased from 60.1% for acute-phase serum samples to 87.4% for convalescent-phase samples. The specificities for these two groups of samples were 94.1 and 92.7%, respectively. The dipstick assay detected a broad variety of serogroups. The results of the dipstick assay were concordant (observed agreement, 93.2%; kappa value, 0.76) with the results of an enzyme-linked immunosorbent assay for the detection of specific IgM antibodies, a test which is often used in the laboratory diagnosis of current or recent leptospirosis. This study demonstrated that this easily performed dipstick assay is a valuable and useful test for the quick screening for leptospirosis; has a wide applicability in different countries with different degrees of endemicity; can be used at all levels of the health care system, including the field; and will be useful for detecting and monitoring outbreaks of leptospirosis.

Agglutination Tests↗

PubMed1999

Effects of 1-year ipriflavone treatment on lumbar bone mineral density and bone metabolic markers in postmenopausal women with low bone mass.

In vitro studies have shown that ipriflavone affects both bone formation and bone resorption, but the effect in early-stage postmenopausal women with low bone mass and a high turnover of bone metabolism is unknown. In this prospective study, we randomly assigned 60 patients with postmenopausal osteopenia or osteoporosis to receive either 600 mg/day of ipriflavone or 0.8 g/day calcium lactate, and compared the effects on bone mineral density (BMD) from the 2nd to 4th lumbar vertebrae (L2-4) and bone metabolic markers before and after one year of treatment. In the iprifravone-treated (IP) group, L2-4 BMD was similar before and after treatment (0.78 and 0.77 g/cm(2), respectively), but in the calcium lactate-treated (CL) group, L2-4 BMD decreased significantly from 0.81 to 0.79 g/cm(2) after 1 year of treatment (p < 0.0001). Furthermore, the rate of the decrease in L2-4 BMD was significantly greater in the CL group than in the IP group (p < 0.01). The median deoxypyridinoline (Dpd) level was significantly lower after 1 year of treatment (5.8 mmol/mmol creatinine [Cr]) than the baseline value (10.2 mmol/mmol Cr) in the IP, but not in the CL group, suggesting that IP treatment suppresses bone resorption.

Adult↗

PubMed1999

[Percutaneous dilational tracheostomy: report of 9 cases].

Nine patients with CNS damage who had been transferred to our critical care unit were treated with a commercially available kit for percutaneous dilational tracheostomy (PDT). The mean procedure time was about 11 minutes, and the perioperative complication rate was 22% (2/9). Only one complication, wound infection, occurred, and the patient was cured with conventional therapy. On the other hand, premature extubation of the translaryngeal tube occurred in one case. Long-term complications like tracheal stenosis and tracheal malacia were not experienced in two patients. They were discharged from the hospital after decannulation. In conclusion, the advantages of PDT include a short procedure time, the ability to perform the procedure at the bedside, and reduced stimulation of the trachea. Because of the safety and simplicity of the procedure, we recommend PDT for patients with CNS damage.

Adult↗

PubMed1998

Reduced calcium elevation in hippocampal CA1 neurons of ischemia-tolerant gerbils.

Transient forebrain ischemia causes selective neuronal death in the hippocampal CA1 neurons. A short sublethal ischemic episode preceding ischemia of longer duration is known to increase tolerance against cell death. The mechanisms of this ischemic tolerance are still poorly understood. Here we show, using Ca2+ imaging, that intracellular calcium ([Ca2+]i) elevation in CA1 neurons after an anoxic-aglycemic episode is markedly inhibited in the ischemia-tolerant gerbil. The hippocampus of gerbils which did not acquire tolerance showed a high [Ca2+]i elevation during the anoxic-aglycemic episode, similar to controls. Since hypoxia/ischemia-induced neurodegeneration can be triggered by cytoplasmic Ca2+ overload, the tolerant gerbil may regulate calcium and keep [Ca2+]i below the critical level for initiating neuronal death.

Animals↗

PubMed1998

Vi-deficient and nonfimbriated mutants of Salmonella typhi agglutinate human blood type antigens and are hyperinvasive.

We generated nonfimbriated mutants from both Vi-positive and -negative Salmonella typhi to analyze the role of type 1 fimbriae and Vi-antigen in bacterial invasion. A Vi-defective mutant of S. typhi GIFU 10007-3 was more invasive than the wild-type strain GIFU 10007. The wild-type strain expressing Vi-antigen did not agglutinate both Saccharomyces cerevisiae and human erythrocytes but Vi-defective mutants were able to agglutinate S. cerevisiae and human erythrocytes. Nonfimbriated mutants from Vi-negative GIFU 10007-3 lost the ability to adhere to S. cerevisiae but still could agglutinate human erythrocytes. The Vi-negative mutant increased secreted proteins and became 5-fold more invasive than the wild-type strain. Nonfimbriated Vi mutants became 50-120-fold more invasive than the wild-type GIFU 10007. To determine why nonfimbriated Vi mutants still agglutinate human red blood cells, we searched bacterial proteins that could bind human blood-type antigens. We finally identified a candidate 37 kDa outer membrane protein that recognized fucosyl-galactose, a structure common to blood type A, B and H antigens.

ABO Blood-Group System↗