Biomedical subjects

H Takano

Publications and source records attributed to H Takano.

At least 613 records · Page 34Linked to original sources

PubMedDate not supplied

Progress of an electrohydraulic total artificial heart system with a separate energy converter.

We have been developing an electrohydraulic total artificial heart (EHTAH) system. The system consists of diaphragm blood pumps, an abdominally placed energy converter, an internal controller, a transcutaneous energy transfer (TET) system, a transcutaneous optical information transfer system, and internal and external lithium-ion (Li-ion) batteries. The energy converter was optimized to obtain better oil transfer. Maximum cardiac output and efficiency of the EHTAH were increased from 8 L/min to 10 L/min and from 10% to 12%, respectively. The volume of the energy converter was reduced from 280 to 210 ml. The pumping unit was successfully implanted in 68-85 kg calves without anatomic problems, and the calves survived up to 10 days with good circulatory results. The maximum temperature rise of the implanted energy converter was only 1 degrees C. Stable performance of the TET system was confirmed in goats for more than 1 month. DC-DC energy transfer efficiency with 20 W of energy transmission remained within the range of 80% to 85%, and no significant temperature rise was observed in the implanted circuit. The internal Li-ion battery was also evaluated in a goat, and the maximum temperature rise during the charging period was 1.5 degrees C, while the charging and discharging times were 72 and 58 min, respectively. We conclude that our system has progressed in its development as a practical implantable system.

Animals↗

PubMedDate not supplied

Influence of pulsatile and nonpulsatile left heart bypass on the hormonal circadian rhythm.

We investigated endocrine circadian rhythm (CR) during pulsatile and nonpulsatile left heart bypass (PLHB and NLHB). A ventricular assist device (VAD) was installed in five goats. After 2 weeks of PLHB, NLHB was subsequently conducted for 4 weeks. The levels of melatonin, cortisol, and renin activity were measured every 2 hours for 24 hours on the last day of the second PLHB week and the second and fourth NLHB weeks. Acquired data were compared with those of the normal control goats (Cont) to determine the presence or absence of CR, as well as the timing, acrophase, amplitude, and mesor of CR. Variations in melatonin, CR were consistently detected at all sampling points. In contrast, CR of cortisol during PLHB and NLHB was observed in a few cases, although considerable CR was noted in most of the Cont cases. The variations in renin activity indicated CR in most of the Cont cases and in all cases at all sampling points during PLHB and NLHB, whereas their acrophases were diversified. In conclusion, the CR of melatonin, reflecting the fundamental circadian clock, was maintained during both PLHB and NLHB, while it could be modified for stress sensitive cortisol and hemodynamic responsive renin during these bypass modalities.

Animals↗

PubMedDate not supplied

Noninvasive assessment method to determine the anatomic compatibility of an implantable artificial heart system.

To assess the anatomic compatibility of an artificial heart (AH), we attempted to develop a computer environment that would facilitate a reliable simulation of an AH implanted in the human thorax. A three-dimensional thoracic computer model with a ventricle-resected heart was constructed, by using manually extracted contour points of the aorta, pulmonary artery, atria, atrioventricular valves, diaphragm, and thoracic wall from a set of consecutive CT images. Such a model enabled simulation of an AH implantation by orienting the AH model in it. Error evaluation on CT imaging and contour extraction with a Plexiglas cylindrical phantom showed that the diameter of the extracted phantom contour was approximately 2 mm smaller than its original with a standard deviation of <0.5 mm. Errors in contour and surface reconstruction could be reduced to far less than 1 mm under constrained conditions. A study on the influence of breathing revealed that variations in some thoracic dimensions between inspiration and expiration could reach 10 mm. In summary, computer simulation of AH implantation is a worthwhile approach with acceptable accuracy, although further considerations of extreme thoracic situations will be required.

Computer Simulation↗

PubMedDate not supplied

Mixed venous oxygen saturation as a promising parameter for physiologic control of total artificial heart.

Mixed venous oxygen saturation (SvO2) has been proposed as one of the suitable parameters for physiologic control of a total artificial heart (TAH). To establish the practical application of SvO2, we investigated the response of cardiac output (CO) and SvO2 to step-loaded exercise. A normal calf was surgically equipped with an ultrasonic flowmeter probe and an oximetry catheter in the pulmonary artery to measure CO and SvO2, respectively. Three stage step treadmill exercise tests (1, 2, and 4 km/h) were performed three times. While CO increased from 8.9 L/min at preexercise level to 9.7, 10.2 and 11.4 L/min at 1, 2, and 4 km/h, respectively, SvO2 decreased from 59.6% to 56.8, 55.3, and 52.2%, respectively. There existed a linear correlation between the magnitude of changes in CO and SvO2. CO and SvO2 exhibited a similar course of change, expressing an inverted exponential curve. The time constant of SvO2 was from 19 to 35 seconds, whereas that of CO was from 21 to 39 seconds. We conclude that SvO2 changes in close association with CO during exercise and has good potential to be a parameter for physiologic control of a TAH, by reflecting the recipient's CO demand without conspicuous time delay.

Animals↗

PubMedDate not supplied

Performance of a newly developed implantable centrifugal blood pump.

The performance of the newly developed implantable centrifugal blood pump was investigated in vitro. The pump was developed with the end goal of building a versatile system that includes a left ventricular assist system with an internal secondary battery or an implantable biventricular assist system with two implantable blood pumps. The hydrodynamic characteristics and efficiency of the blood pump were evaluated, and the mechanical damage to the blood caused by the blood pump was assessed through a hemolysis test using fresh goat blood. The pump could generate 120 mm Hg at a flow rate of 5 L/min and a motor speed of 2,500 rpm. The electric input power to the pump was approximately 5 watts under these working conditions. The hemolysis caused by the pump was a bit higher than that by the former model, but stayed within an acceptable range. Performance of the pump in vitro was considered sufficient for a left ventricular assist device, although further design improvement is necessary in terms of hemolysis and system efficiency to improve biocompatibility of the pump.

Animals↗

PubMedDate not supplied

Prostaglandin synthesis inhibitor improves hypotension during normothermic cardiopulmonary bypass.

Hypotension is a major systemic side effect during cardiopu monary bypass (CPB), especially at normothermia. We previously reported that prostaglandin (PG) might play a substantial role in hypotension. The purpose of this study was to clarify whether a PG synthesis inhibitor (PGSI) could improve hypotension during CPB. Thirty-six patients undergoing cardiac surgery with normothermic CPB (35-37 degrees C) were divided into two groups: a PGSI group (n = 18), whose members wer given a PGSI before and during CPB, and a control group (n = 18). In both groups, perfusion flow was sufficient and pressure was maintained at above 45 mm Hg by infusion of metaraminol, a vasoconstrictor. The mean arterial pressure throughout CPB was significantly higher in the PGSI group than in the control group (57 +/- 4 vs. 48 +/- 3 mm Hg, p < 0.01), whereas the dose of infused metaraminol was significantly lower in the PGSI group (13 +/- 7 vs. 21 +/- 6 mg, p < 0.01). The blood base excess was not significantly different (1.0 +/- 1.6 vs. 1.7 +/- 1.9 mmol/L, p = 0.28), and urine output was significantly higher in the PGSI group (503 +/- 179 vs. 354 +/- 112 ml/hr, p < 0.01). In conclusion, PGSI can improve hypotension during CPB and increase urine output without impairing peripheral circulation.

Aged↗

PubMedDate not supplied

Vascular suppression technique in MRI using Gd-DTPA: improving image quality of MR myelography.

PURPOSE: To delete signals of juxta-thecal venous structures on MR myelograms, we evaluated the potential of Gd-DTPA as a negative contrast material in experiments and actual MR myelograms. METHOD: We measured the signals of Gd-DTPA solutions of various concentrations on T2-weighted turbo-SE and turbo-STIR images. The experiments revealed that 0.83 mmol/L Gd-DTPA worked as a negative contrast material in turbo-STIR. Subsequently, we obtained turbo-STIR myelograms of 31 patients who complained of lumbago or sciatica before and after intravenous administration of 0.15 mmol/kg Gd-DTPA, which was presumed to provide the optimal plasma density in vivo. RESULTS: On postcontrast MR myelograms, the venous signals around the thecal sac decreased remarkably in almost all the cases as compared with precontrast images. In these cases, the nerve roots could be observed clearly. CONCLUSION: Gd-DTPA can work as a negative contrast material in turbo-STIR sequences. This characteristic should be used to improve the image quality of MR myelography using turbo-STIR.

Adolescent↗

PubMedDate not supplied

Redundant nerve roots in patients with degenerative lumbar spinal stenosis.

Extensive fundamental and clinical investigations have been performed concerning redundant nerve roots (RNR) and the pathogenesis of cauda equina claudication (CEC) in degenerative lumbar canal stenosis (DLCS). These investigations consisted of (1) anatomic observations on RNR in 117 fixed cadaveric specimens, (2) myelographic study in 117 patients with or without DLCS, (3) operative observation on neural elements with special reference to the cauda equina in 56 DLCS patients (including a postoperative follow-up), and (4) electrophysiologic tests using spinal cord action potential recording under walking load preoperatively and intraoperative measurement of nerve conduction velocity of RNR. The RNR have neuronal losses resulting from a longer duration stenosis that suggests a sort of friction neuritis. Complicated factors contribute to the pathogenesis of CEC and the development of root gripping, such as the magnitude of RNR, the extent of the stenosis, a narrowed sac, age-dependent axial shortening of the spinal canal, and dynamic or postural factors. In cases with severe RNR, satisfactory operative results can be obtained only after thorough decompression with dural incision.

Action Potentials↗

PubMedDate not supplied

Increased serum levels of circulating intercellular adhesion molecule-1 in patients with myocarditis.

Levels of circulating intercellular adhesion molecule-1 (cICAM-1) were measured by ELISA in the sera of 21 patients with unexplained cardiac dysfunction. By evaluating the biopsy or autopsy specimens, they were classified into two groups: a myocarditis group (n = 8) and a nonmyocarditis group (n = 13). Levels of cICAM-1 were significantly higher in the myocarditis group (p < 0.01). Increased levels of cICAM-1 (> 2 SD above the control mean) were detected in 6 of 8 patients in the myocarditis group. Therefore, the detection of increased levels of cICAM-1 could be a useful marker for myocarditis.

Adult↗

PubMedDate not supplied

Bifunctional role of protein tyrosine kinases in late preconditioning against myocardial stunning in conscious rabbits.

Although protein tyrosine kinases (PTKs) have been implicated in late preconditioning (PC) against infarction, their role in late PC against stunning is unknown. Furthermore, it is unknown whether PTK signaling is necessary only to trigger late PC on day 1 or also to mediate it on day 2. Thus, conscious rabbits underwent a sequence of six 4-minute coronary occlusion/4-minute reperfusion cycles for 3 consecutive days (days 1, 2, and 3). In the control group (group I, n=7), the recovery of systolic wall thickening after the 6 occlusion/reperfusion cycles was markedly improved on days 2 and 3 compared with day 1, indicating the development of late PC against stunning. Administration of the PTK inhibitor lavendustin-A (LD-A, 1 mg/kg IV) before the first occlusion on day 1 (group II, n=7) completely prevented the late PC effect against stunning on day 2. Late PC against stunning was also abrogated when LD-A was given before the first occlusion on day 2 (group III, n=7); however, in these rabbits, the late PC effect became apparent on day 3, indicating that LD-A itself did not have any delayed deleterious actions on myocardial stunning. In group V (n=5), the sequence of 6 occlusion/reperfusion cycles resulted in a robust increase in the activity of inducible NO synthase (iNOS [assessed as Ca(2+)-independent L-citrulline formation]) and nitrite+nitrate (NO(x)) tissue levels 24 hours later (on day 2), with no concomitant change in Ca(2+)-dependent NO synthase (endothelial NO synthase and/or neuronal NO synthase) activity. Similar results were obtained on day 3 (group VIII, n=6), indicating sustained upregulation of iNOS. Administration of LD-A either on day 1 (group VI, n=5) or on day 2 (group VII, n=6) abrogated the increase in iNOS activity and NO(x) levels on day 2. LD-A had no effect on iNOS activity or NO(x) levels in the absence of PC (group X, n=5). This study demonstrates that in conscious rabbits, PTK activity is necessary not only to trigger late PC against stunning on day 1 but also to mediate the protection on day 2. This investigation also provides the first direct evidence that cardiac iNOS activity is upregulated during the late phase of ischemic PC in rabbits. Furthermore, the data indicate that PTK signaling is essential for the augmentation of iNOS activity and that PTKs modulate this enzyme at two distinct levels: at an early stage on day 1 and at a late stage on day 2. This bifunctional role of PTKs in late PC has broad implications for the signaling mechanisms that underlie the response of the heart to ischemic stress and, possibly, other stresses.

Animals↗

PubMedDate not supplied

Effect of varying types of anti-arthritic drugs on Th1 and Th2 immune responses in mice.

The present study was undertaken to study the effect of varying types of anti-arthritic drugs on Th1 and Th2 immune responses in mice. To immunize mice, ovalbumin (OVA) emulsified with complete Freund's adjuvant was injected s.c. at the base of the tail (day 0). Indomethacin (IND) as a non-steroidal antiinflammatory drug (NSAID), dexamethasone (DEX) as a steroidal antiinflammatory drug, methotrexate (MTX), auranofin (AUR), and D-penicillamine (D-PA) as an anti-rheumatic drugs were orally administrated daily from days 0 to 20. On day 21, anti-OVA IgG2a and interferon (IFN)-gamma as indicators of Th1 responses and anti-OVA IgG1 and interleukin (IL)-10 as those of Th2 responses were measured. Treatments with IND, DEX, MTX and AUR were followed by decreases in OVA-specific IgG and proliferation of spleen cells to the antigen. Treatments with IND, DEX, MTX and AUR inhibited both Th1 and Th2 immune responses, although the inhibitory effects of these drugs on the antigen-specific IgG2a and IFN-gamma production appeared to be greater than those on IgG1 and IL-10 production. D-PA failed to influence anti-OVA IgG, IgG2a and IgG1 production as well as IFN-gamma and IL-10 secretion. Administrations of all the drugs used resulted in suppression of antigen (OVA)-induced arthritis in mice which was associated with inhibition of anti-OVA IgG2a but not IgG1 production. These results suggest that anti-arthritic drugs including IND, DEX, MTX and AUR appear to suppress Th1 and, to a lesser extent, Th2 immune responses, and their anti-inflammatory effects on human rheumatoid arthritis might be at least in part explained by downregulation by these drugs of Th1 responses involved in the disease.

Animals↗

PubMedDate not supplied

Low specificity of cytokeratin 19 mRNA expression in the peripheral blood cells from patients with ovarian tumors.

We examined CK19 mRNA expression in the peripheral blood mononuclear cells (PBMC) from patients with ovarian tumor by reverse transcriptase-polymerase chain reaction (RT-PCR) using primers which did not cross-amplify pseudogenes of CK19 gene. The incidence of positive CK19 mRNA expression in healthy individuals, benign ovarian tumor patients and ovarian cancer patients were 60% (12/20), 71% (10/14) and 84% (21/25), respectively. Although the frequency of positive CK19 mRNA expression in PBMC from ovarian tumor patients was higher than that from healthy individuals, there was no statistically significant difference between the frequencies. Moreover, one healthy control showed CK19 mRNA expression only in her menstrual period, not in her proliferative phase or secretory phase. These results suggested that CK19 is not a suitable target to detect the presence of tumor cells in the PBMC from patients with ovarian tumors.

Biomarkers, Tumor↗

PubMedDate not supplied

Partial midline fusion of the cerebellar hemispheres with vertical folia: a new cerebellar malformation?

MR imaging depicted vertically oriented folia instead of the normal horizontal folial pattern, hypoplastic cerebellar vermis, fusion of the inferior posterior cerebellum, and probable polymicrogyria in the superior cerebellar hemispheres in a child with hypotonia, nystagmus, ataxia, and psychomotor retardation. We propose that this newly discovered cerebellar malformation be added to the list of malformations associated with aplasia or hypoplasia of the cerebellar vermis, such as Dandy-Walker malformation, Joubert syndrome, tectocerebellar dysraphia, and rhombencephalosynapsis.

Ataxia↗

PubMedDate not supplied

Induction of apoptosis by dopamine in human oral tumor cell lines.

Dopamine dose-dependently reduced the viable cell number of both human salivary gland tumor HSG and oral squamous cell carcinoma HSC-2, HSC-4, and NA cells. CoCl2 significantly reduced both the cytotoxic activity and radical intensity of dopamine (determined by ESR spectroscopy). Dopamine produced DNA fragments (demonstrated by TUNEL method) and induced degradation of cytokeratin by activated caspase in HSG cells (detected by an immunocytochemical method, using a specific M30 monoclonal antibody). FACS analysis demonstrated that dopamine induced DNA fragmentation, a biochemical hallmark of apoptosis, in human promyelocytic leukemia HL-60 cells. The addition of catalase did not prevent the apoptosis-inducing activity of dopamine, reducing the possibility of the involvement of H2O2 for dopamine-induced apoptosis. Dopamine transiently induced p38 mitogen-activated protein kinase (MAP kinase) phosphorylation. However, an inhibitor of p38 MAP kinase phosphorylation, SB203680, failed to inhibit the dopamine-induced apoptosis. These data suggest that p38 phosphorylation at an early stage may not be a causative event for apoptosis.

Apoptosis↗

PubMedDate not supplied

Pleomorphic adenoma of the nasal septum: MR features.

We report the MR imaging features of a pleomorphic adenoma of the nasal septum. To our knowledge, whereas the CT findings of pleomorphic adenomas of the nasal septum have been reported, the MR features of this rare entity have not been reported in the English-language literature.

Adult↗

PubMedDate not supplied

A disposable venting system.

A disposable venting system that has been utilized in over 300 cardiac operations is described. The system facilitates reduction of bubble formation in the cardiac chambers and removal of air bubbles with minimal time and effort and maximal safety.

Cardiac Surgical Procedures↗

PubMedDate not supplied

The consequence of ventricular assist on acute profound biventricular failure with induced severe myocardial injury.

The effect of ventricular assist on acute profound biventricular failure (BVF) was examined in chronic animal experiments using 10 adult goats. Induction of BVF was achieved by normothermic anoxic arrest for 30-60 min during the use of a left ventricular assist system (LVAS, eight goats), or biventricular assist system (BVAS, two goats). The LVAS could maintain near normal circulation with volume loading in six goats, and three of eight goats were weaned from LVAS after 13-18 days. In the early stages, left atrial pressure was significantly higher, and right atrial pressure was significantly lower, compared with measurements in nonweaned goats. During BVAS, circulation was well maintained without volume loading, but neither of the two goats could be weaned from VAS. Myocardial fibrosis in goats without myocardial recovery was significantly more severe. Left ventricular wall thickness was thinner in nonweaned goats and there was a significant inverse correlation between the thickness of the left ventricular free wall and the assist duration in nonweaned goats. Based on these data, it was concluded that myocardial damage was severe in nonweaned cases, and the potential for healing is affected by the severity of myocardial damage before VAS application. Prolonged unloading with VAS of these severely damaged hearts caused loss of left ventricular wall thickness.

Animals↗

PubMedDate not supplied

An integrated artificial heart-lung device.

An integrated artificial heart-lung device (IAHLD) is being developed as a novel system for simultaneous long-term support of heart and lung. The IAHLD consists of an artificial lung component (LC) and two blood pumps. The LC is made with a special composite hollow fiber membrane that prevents serum leakage. The fibers are arranged as piled-up lattices and potted in a cylindrical housing made of polyurethane. The blood pump with a single port is of a pneumatic pusher-plate type, and a Björk-Shiley valve is mounted in the port. The LC is sandwiched between the inlet and outlet pumps, and all components are integrated. This special structure provides high gas exchange efficiency, prevention of flow channeling and stagnation, and reduction of blood contacting surfaces. The prototype IAHLD had exchange rates of up to 170 ml/min of O2 and CO2 and up to 5.5 L/min of pump output. A flow visualization analysis with cineroentgenography revealed that the flow distribution within the IAHLD was uniform, without any stasis. It was concluded that the IAHLD is a promising system for long-term heart and lung support, and can be used without systemic heparinization given thromboresistant surface treatment as the next step of development.

Animals↗