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Biomedical subjects

Y Takami

Publications and source records attributed to Y Takami.

At least 55 records · Page 3Linked to original sources
PubMed1998

[Current treatment burn wounds: alternative wound coverage methods].

In patients with massive burn injuries and very limited skin donor sites, both acute-phase and long-term problems of skin loss must be solved by the use of alternative wound closure materials. Alternative materials can be used for either temporary wound coverage or for permanent wound closure. Recently, allogenic skin grafts have most commonly been used as alternative wound closure material. However, research is ongoing on many new materials to provide a readily available substitute for skin allografts for permanent wound closure. The best approach to the development of alternative permanent wound closure materials is to incorporate the host's own cellular and structural components. Four general strategies have been devised so far based on the type of matrix structure and cellular content: allografts; cultured epidermal grafts; dermal matrix grafts; and cultured-dermal matrix composite grafts. Several approaches using combined alternative wound closure materials have been used, including transplantation of artificial dermal matrix with thin epidermal autografts, and transplantation of artificial dermal matrix containing human fibroblasts. Ultimately, the best candidate materials for permanent wound closure after extensive burn injury must be determined in prospective, randomized, controlled clinical trials.

Burns↗
PubMed1997

One allele of the major histone gene cluster is enough for cell proliferation of the DT40 chicken B cell line.

Thirty-nine of the 44 chicken histone genes are located in a major histone gene cluster of 110 kb, the others residing in four separate regions. We generated a heterozygous chicken DT40 mutant, 1/2 delta110 kb, devoid of one allele of the cluster, using gene targeting techniques. Analyses of the mutant revealed that the growth rate of DT40 cells was unchanged even in the absence of one allele of the cluster. Moreover, analyses involving a RNase protection assay, SDS-PAGE or Triton-acid-urea-PAGE revealed not only that in the 1/2 delta110 kb mutant the steady-state levels of total mRNAs of gene families H1, H2A, H2B, H3 and H4 remained constant, but also that the amounts of histones H1, H2A, H2B, H3 and H4 were not changed. A comparison by 2D-PAGE revealed no changes in total cellular protein patterns of the mutant. These observations demonstrate that all the histone gene families have the inherent ability to compensate for the disruption of one allele of the gene cluster, with no influence on cell functions.

Alleles↗
PubMed1997

Biocompatibility of alumina ceramic and polyethylene as materials for pivot bearings of a centrifugal blood pump.

The double pivot bearings in the Gyro C1E3 centrifugal blood pump incorporate a high-purity alumina (Al2O3) ceramic and an ultra-high-molecular-weight polyethylene (UHMWPE). This centrifugal pump has been developed as a completely sealless pump for long-term usage. The combination of Al2O3 and UHMWPE are the materials of choice for the acetabular bearing in artificial joints, which have proven to be clinically reliable for over 10 years. Previous studies have examined the biocompatibility of Al2O3 and UHMWPE as bulky implant materials. The present study investigated this material as a blood-contacting material using a standard assessment in vitro and in vivo analysis. The examined items were systemic toxicity, sensitization (guinea pig maximization test), cytotoxicity (elution test), mutagenicity (Ames test), direct contact hemolysis, and thrombogenicity. The studies were performed according to the United States Pharmacopoeia and published previous studies. The samples of both Al2O3 and UHMWPE demonstrated no differences from the negative controls in all tests. These findings indicate that both Al2O3 and UHMWPE are biocompatible materials for double-pivot bearings in the centrifugal blood pump.

Aluminum Oxide↗
PubMed1997

Manganese-dependent Dopa/tyrosine sulfation in HepG2 human hepatoma cells: novel Dopa/tyrosine sulfotransferase activities associated with the human monoamine-form phenol sulfotransferase.

Human monoamine (M)-form phenol sulfotransferase (PST) was PCR-cloned and transiently expressed in COS-7 cells. The recombinant enzyme was demonstrated to display not only the previously reported sulfotransferase activity toward dopamine, but also novel manganese-dependent Dopa/tyrosine sulfotransferase activities. These results imply a new functional role of the human M-form PST in the homeostatic regulation of Dopa and tyrosine.

Animals↗
PubMed1997

An approximately half set of histone genes is enough for cell proliferation and a lack of several histone variants causes protein pattern changes in the DT40 chicken B cell line.

Of the 44 chicken histone genes, 39 are located in a major histone gene cluster of 110 kb, the others residing in four separate regions. The 42 sequenced genes encode six H1 variants, three H2A variants, four H2B variants, two H3 variants, and one histone H4. To clarify the influence on cell functions of simultaneous deletion of an approximately half set of the genes and some of the variants, we generated homozygous chicken DT40 mutants by disruption of two allelic segments of 57 kb, containing the 21 genes, using gene targeting techniques. Analyses with antisense RNA probes common or specific for gene families H1, H2A, H2B, H3 and H4 indicated that the remaining members of each of the gene families were expressed more in the mutants than in DT40 cells, resulting in maintenance of constant steady-state levels of mRNAs. Two-dimensional polyacrylamide gel electrophoresis showed that in the mutants several cellular proteins newly appeared or increased, and some other proteins disappeared or decreased quantitatively. These results demonstrate that all the histone gene families have the inherent ability to compensate for the disruption of a fair number of their own constituents. Furthermore, some of the histone variants are involved in regulation of the expression of putative genes that encode the proteins that varied in mutant DT40 cells, this participation is not compensated for by any residual variant of the same histone subtype(s).

Animals↗
PubMed1997

Flow characteristics and required control algorithm of an implantable centrifugal left ventricular assist device.

As the clinical application of LVADs has increased, attempts have been made to develop smaller, less expensive, more durable and efficient implantable devices using rotary blood pumps. Since chronic circulatory support with implantable continuous-flow LVADs will be established in the near future, we need to determine the flow characteristics through an implantable continuous-flow LVAD. This study describes the flow characteristics through an implantable centrifugal blood pump as a left ventricular assist device (LVAD) to obtain a simple non-invasive algorithm to control its assist flow rate adequately. A prototype of the completely seal-less and pivot bearing-supported centrifugal blood pump was implanted into two calves, bypassing from the left ventricle to the descending aorta. Device motor speed, voltage, current, flow rate, and aortic blood pressure were monitored continuously. The flow patterns revealed forward flow in ventricular systole and backward flow in diastole. As the pump speed increased, an end-diastolic notch became evident in the flow profile. Although the flow rate (Q [l/min]) and rotational speed (R [rpm]) had a linear correlation (Q = 0.0042R - 5.159; r = 0.96), this linearity was altered after the end-diastolic notch was evident. The end-diastolic notch is considered to be a sign of the sucking phenomenon of the centrifugal pump. Also, although the consumed current (I [A]) and flow rate had a linear correlation (I = 0.212Q + 0.29; r = 0.97), this linearity also changed after the end-diastolic notch was evident. Based upon the above findings, we propose a simple algorithm to maintain submaximal flow without inducing sucking. To maintain the submaximal flow rate without measuring flow rate, the sucking point is determined by monitoring consumed current according to gradual increases in voltage.

Algorithms↗
PubMed1997

A method for determining the distribution of fluoride, calcium and phosphorus in human dental plaque and the effect of a single in vivo fluoride rinse.

A new sampling method, capable of sampling plaque from its surface to its interior for quantitative studies, was modified to meet some of the requirements for the determination of the fluoride and mineral (Ca and P) profiles within dental plaque formed in vivo. Plaque samples were repeatedly collected from the same individual, using special devices, before a single fluoride rinse (900 parts/10(6) fluoride) and 10 min and 24 hr after rinse. The method allowed examination of fluoride, calcium and phosphorus distribution along the entire thickness of plaque. Fluoride content significantly increased throughout the sample 10 min after rinsing, indicating the fluoride had rapidly penetrated into the plaque. Although the elevated fluoride concentrations diminished almost to baseline with 24 hr, a high correlation was found between fluoride and minerals in each plaque fraction. It is concluded that this technique will be useful for evaluating the fluoride and mineral behaviour in the saliva/plaque and plaque/enamel interfaces, and the anti caries efficacy of fluoride applications.

Calcium↗
PubMed1997

A single copy of linker H1 genes is enough for proliferation of the DT40 chicken B cell line, and linker H1 variants participate in regulation of gene expression.

BACKGROUND: There is general agreement that large numbers of histone H1 are necessary for maintenance of the higher order structure of chromatin in higher eukaryotes. The chicken H1 gene family comprises six members per haploid genome, the total copy number being 12, and they encode six H1 variants which are considerably different from each other in amino acid sequence. We recently established that in two chicken DT40 mutants (1/2delta110kb and delta57kb), which lack, respectively, one allele of the gene cluster of 110 kb carrying six H1 genes, plus 33 core histone genes, and two copies each of four of the six H1 genes included in an approximately 57 kb segment of the cluster, expression of the remaining H1 genes is increased, resulting in constant steady-state levels of total H1 mRNAs. These results gave rise to the simple questions of how many H1 genes and how many H1 variants, at minimum, are necessary for the viability of DT40 cells. RESULTS: We generated two DT40 mutants, delta10/12H1 and delta11/12H1, which are devoid, respectively, of two copies each of five H1 genes, and those plus a single copy of the last H1 gene, in addition to 17 core histone genes. Analyses involving a RNase protection assay, SDS-PAGE and acid-urea-PAGE revealed, not only that in the delta10/12H1 mutant the steady-state levels of total H1 mRNAs and the amounts of histone H1 were not changed, but also that in the delta11/12H1 mutant both were approximately one-half the normal levels, and the amounts of HMG proteins were increased about twofold. No alteration in the growth rate or global chromatin structure was observed in either mutant. On the other hand, the protein patterns on 2D-PAGE of the delta11/12H1 mutant were definitely distinct from those of the wild-type cell line. CONCLUSION: These results indicate not only that a lack of five of the six H1 variants causes changes in the protein patterns, but also that only a single copy of the H1 genes is enough for cell proliferation.

Acids↗
PubMed1997

Mapping of pump efficiency on the pressure-flow curve of a centrifugal blood pump.

Because pump efficiency is closely related to heat generation and blood trauma in a centrifugal blood pump, it is quite important to study pump efficiencies in a variety of conditions. In the present study, pump efficiencies were mapped on the pressure head-flow rate curves of 4 different pumps; BioMedicus BioPump (BP-80), Nikkiso (NK), Gyro C1E3, and Gyro PI601 (diameter of the impeller, NK: 50 mm, C1Ee3: 65 mm, and PI601: 50 mm). The mapping of pump efficiency revealed the following findings. First, the cone type (BP-80) has less pump efficiency than the impeller type (NK and C1E3); second, the miniaturization of the C1E3 to the PI601 has resulted in an increase in pump efficiency; and third, the diameter of the impeller may contribute to the pump efficiency of an im peller type pump. The mapping of the pump efficiency, as demonstrated in this study, is useful for the analysis of hydraulic pump performance in a wide range of clinically applied conditions.

Blood Flow Velocity↗
PubMed1997

Mechanical white blood cell damage in rotary blood pumps.

Mechanical trauma of white blood cells (WBC) due to the operation of a rotary blood pump was examined, using a simple method of trypan blue dye exclusion test for a cell viability measurement. The degree of WBC trauma was investigated using a roller pump (RP) and 3 commercially available centrifugal pumps (Bio-Medicus [BP], Capiox [CP], Nikkiso [NK]), and compared with the red blood cell (RBC) trauma. Each pump was operated 3 times at a flow rate of 5 L/min against the total pressure head of 350 mm Hg for 6 h in a mock circuit with 400 ml of fresh bovine blood. Blood was sampled at 2 h intervals measuring plasma free hemoglobin concentration and the percentage of damaged WBC in the trypan blue dye exclusion test. Each pump demonstrated a linear increase in the degree of WBC trauma, and there were differences among the tested pumps (RP > BP > CP > NK). These findings were similar to those of the free hemoglobin measurements. To compare the degree of RBC and WBC trauma, the probability (gamma, omega) of RBC and WBC to be damaged was calculated, respectively. gamma = delta DRBC/delta N, omega = delta DWBC/delta N where DRBC and DWBC are the ratios of the damaged RBC and WBC, respectively, and N is the passing number defined as Qt/V (Q, flow rate; t, time; V, circulating volume). The data of this study demonstrated that the omega value was approximately 20 times or more greater than the gamma equally in all the tested pumps. This suggests that a WBC is more vulnerable to mechanical damage by a rotary blood pump than a RBC.

Analysis of Variance↗
PubMed1997

Material of the double pivot bearing system in the Gyro C1E3 centrifugal pump.

A double pivot bearing system is adopted for the Gyro C1E3 centrifugal blood pump to achieve a completely sealless structure that prevents blood leakage and thrombus formation around the shaft. The double pivot bearing system is also a critical factor for blood trauma and durability of the C1E3 pump. This study focuses on the double pivot bearing material. The pump with the male ceramic and female polyethylene pivots (PE) was compared with the pump with the male ceramic and female ceramic pivots (CRM), pertaining to stability of the impeller spinning motion, hemolysis, and durability. At first, the wear rate of the pivots was recorded after operating the pumps in various rotational speeds. As for hemolysis, in vitro tests were carried out using fresh bovine blood in 2 conditions (5 L/min, 350 mm Hg and 5 L/min, 100 mm Hg). Then, stability of the spinning motion was investigated by evaluating the vibration of the pump. The two pumps with different female pivots were operated identically at 2,700 rpm, and the vibration signals were measured using an accelerometer that was mounted on the top of the pump housing. The following findings were obtained in this study. The wear sites were different between the PE and CRM. Most of the wear occurred at the top female polyethylene pivot in the PE. In contrast, most of the wear occurred at the top male ceramic pivot in the CRM. In addition, the amount of the initial wear was less and the wear rate was lower in the PE than in the CRM. The hemolysis caused by the PE was less than the hemolysis caused by the CRM. The vibration signals of the PE had less amplitude and a narrower range of frequency than the vibration signals of the CRM. In conclusion, the combination of materials male ceramic-female polyethylene are superior to the male ceramic-female ceramic for the double pivot bearing system of the Gyro C1E3 centrifugal pump because of less vibration, less hemolysis, and less wear.

Animals↗
PubMed1997

Eccentric inlet port of the pivot bearing supported Gyro centrifugal pump.

An eccentric inlet port is a unique feature of the pivot bearing supported Gyro Compact-1 Eccentric Inlet Port Model 3 (C1E3) centrifugal pump, a completely sealless centrifugal pump. The latest C1E3 has an eccentric inlet port with a 30 degree vertical angle. To investigate the adequacy of this 30 degree angle, flow visualization studies and in vitro hemolysis tests were performed, comparing 4 pumps, each with a different angle of the eccentric inlet port (0, 30, 60, and 90 degrees). The flow visualization study utilizing a tracer method focused on the flow pattern just distal to the inlet port of each pump, and each pump was operated at 5 L/min against 100 mm Hg and 5 L/min against 350 mm Hg. In the pumps with angles of 90 and 60 degrees, the flow direction changed horizontally, causing a vortex formation. In the pump with the 30 degree angle, the inflow did not change its course, resulting in minimal space for vortex formation. In the pump with the 0 degree angle, the inflow collided with the pump housing, resulting in a small vortex formation along the housing surface. The in vitro hemolysis tests at 5 L/min against 350 mm Hg revealed that the pump with the 30 degree angle was the least hemolytic and the pump with the 90 degree angle was the most hemolytic among the 4 pumps. These results suggest that the angle of the eccentric inlet port of the Gyro C1E3 pump should be 30 degrees to have less vortex formation and less red blood cell trauma.

Animals↗
PubMed1997

Vibration assessment for thrombus formation in the centrifugal pump.

To clarify the correlation of vibration and thrombus formation inside a rotary blood pump, 40 preliminary vibration studies were performed on pivot bearing centrifugal pumps. No such studies were found in the literature. The primary data acquisition equipment included an accelerometer (Isotron PE accelerometer, ENDEVCO, San Juan Capistrano, CA, U.S.A.), digitizing oscilloscope (TDS 420, Tektronix Inc., Pittsfield, MA, U.S.A.), and pivot bearing centrifugal pumps. The pump impeller was coupled magnetically to the driver magnet. The accelerometer was mounted on the top of the pump casing to sense radial and axial accelerations. To simulate the 3 common areas of thrombus formation, a piece of silicone rubber was attached to each of the following 3 locations as described: a circular shape on the center bottom of the impeller (CI), an eccentric shape on the bottom of the impeller (EI), and a circular shape on the center bottom casing (CC). A fast Fourier transform (FFT) method at 5 L/min against 100 mm Hg, with a pump rotating speed of 1,600 rpm was used. The frequency response of the vibration sensors used spans of 40 Hz to 2 kHz. The frequency domain was already integrated into the oscilloscope, allowing for comparison of the vibration results. The area of frequency domain at a radial direction was 206 +/- 12.7 mVHz in CI, 239.5 +/- 12.1 mVHz in EI, 365 +/- 12.9 mVHz in CC, and 163 +/- 7.9 mVHz in the control (control vs. CI p = 0.07, control vs. EI p < 0.001, control vs. CC p < 0.001, EI vs. CC p < 0.001, CI vs. CC p < 0.001). Three types of imitation thrombus formations were roughly distinguishable. These results suggested the possibility of detecting thrombus formation using vibration signals, and these studies revealed the usefulness of vibration monitoring to detect thrombus formation in a centrifugal pump.

Analysis of Variance↗
PubMed1997

Effects of pulsatile flow on gas transfer of membrane oxygenator: MENOX EL-4000 and Gyro C1-E3 pulsatile mode.

It is acknowledged that pulsatile flow enhances the gas exchange performance of membrane oxygenators. However, the data for currently developed oxygenators are limited. In this study, the effect of pulsatile flow was assessed utilizing the MENOX EL-4000 oxygenator. The in vitro test was performed following the Association for the Advancement of Medical Instrumentation (AAMI) standards. Pulsatile flow was produced by the Gyro C1-E3 centrifugal pump with periodical changing of the impeller speed. In Study 1, the following 3 groups were created and examined: nonpulsatile flow, pulsatile flow of 40 bpm, and pulsatile flow of 60 bpm. The blood flow rate was maintained at 3 L/min, and the V/Q ratio was 1. In Study 2, four groups were examined, nonpulsatile flow with V/Q = 1, nonpulsatile with V/Q = 2, pulsatile with V/Q = 1, and pulsatile with V/Q = 2. The blood flow rate was maintained at 4 L/min, and the pulse frequency was set at 40 bpm. In study 1, although O2 transfer was not enhanced, CO2 transfer was significantly improved (40-50%) by pulsatile flow, regardless of pulse frequency. Study 2 demonstrated that pulsatile flow resulted in improved CO2 transfer as did higher ventilation (V/Q = 2). Furthermore, even after applying higher ventilation, the pulsatile mode enhanced CO2 transfer more than the nonpulsatile mode. It was considered that the pulsatile mode induced an active secondary flow and enhanced mixing effects, and consequently CO2 transfer was improved. In conclusion, the pulsatile flow significantly enhanced the CO2 transfer of the MENOX oxygenator. It is indicated that applying the pulsatile mode is a unique and effective method to improve the gas exchange performance for a current membrane oxygenator.

Analysis of Variance↗
PubMed1997

Anatomical consideration for an implantable centrifugal biventricular assist system.

A miniaturized pivot bearing-supported centrifugal blood pump (Gyro PI) has been developed as a long-term biventricular assist system (BiVAS). In this study we determined the anatomical configuration of this system using a bovine model. Under general anesthesia, a left lateral thoracotomy was performed to open the chest. Two Gyro PI-601 pumps for left and right assists were placed in the preperitoneal pocket by a subcostal abdominal incision. The left pump could be placed along the dome of the diaphragm just beneath the apex of the left ventricle. The right pump could be placed next to the left pump. The inlet and outlet ports of both pumps penetrated the diaphragm. The inlet port of the left pump, with a length of 55 mm, was inserted directly into the apex of the left ventricle. A woven Dacron graft (150 mm long, 11 mm inner diameter) was placed between the outlet port of the left pump and the descending aorta. As for the right pump, a 100 mm long and 120 degree angled inflow conduit was placed between the inlet port and the right ventricular infundibulum. The outlet port of the right pump was connected to the main trunk of the pulmonary artery using a 90 mm long, 11 mm inner diameter Dacron graft. We could perform biventricular assistance to confirm the anatomical feasibility of the Gyro implantable centrifugal BiVAS.

Animals↗
PubMed1997

Hemolysis test of a centrifugal pump in a pulsatile mode: the effect of pulse rate and RPM variance.

Centrifugal pumps are generally employed as nonpulsatile blood flow pumps; however, these pumps can produce pulsatile flow by periodically alternating the impeller rotation speed. This study investigates blood trauma due to the effect of pulse frequency and various ranges of pump speed. The hemolysis tests were conducted using the Gyro C1E3 pump. The study was divided into the following categories: Group 1 in a nonpulsatile mode; Group 2 operated at 40 bpm with 30% of speed variance; Group 3, 60 bpm with 30% of speed variance; Group 4, 40 bpm with 70% of speed variance; and Group 5, 60 bpm with 70% of speed variance. A flow rate of 3 L/min and a total pressure head of 200 mm Hg were employed in all groups to simulate a percutaneous cardiopulmonary support condition. There were no significant differences in the hemolysis levels among Groups 1, 2, and 3. However, Groups 4 and 5 exhibited a significantly higher hemolysis rate compared to the other groups. These results indicate that a high rate of speed variance increases hemolysis; however, a range of less than 30% does not affect hemolysis. The pulse rate has no significant effect on hemolysis. In conclusion, the higher speed variance increases the hemolysis level when a pulsatile mode is applied with a centrifugal pump at the given test conditions. However, a speed variance of less than 30% or a pulse rate of less than 60 bpm does not affect hemolysis.

Analysis of Variance↗
PubMed1997

Estimation of the minimum pump speed to prevent regurgitation in the continuous flow left ventricular assist device: left ventricular drainage versus left atrial drainage.

Due to the fact that centrifugal and axial pumps do not require valves, there is a possibility of back flow when the pump speed is low. To estimate the minimum required pump speed to prevent this regurgitation, an in vitro simulation test was conducted. A pulsatile pump simulated the natural heart while a centrifugal pump simulated the continuous flow left ventricular assist device (LVAD). The LVAD flow was attained from the left atrial (LA) drainage or left ventricular (LV) drainage. The minimum or regurgitate flow was observed in the systolic phase with LA drainage and in the diastolic phase with LV drainage. LV drainage always provided higher flow than LA drainage at the same pump speed. These differences are due to the various total pressure heads of the LVAD. To prevent the regurgitation, the LVAD should maintain a certain pump speed which can create positive flow against the aortic systolic pressure with LA drainage and against the aortic diastolic pressure with LV drainage. These required pump speeds can be identified by the LVAD flow-pressure curve.

Aortic Valve Insufficiency↗