Biomedical subjects

Yusuke Abe

Publications and source records attributed to Yusuke Abe.

22 records · Page 2Linked to original sources

PubMedDate not supplied

A temporal and spatial analysis of cavitation on mechanical heart valves by observing faint light emission.

Cavitation on mechanical heart valves (MHVs) could cause the mechanical failure of the occluder. A simple and reliable in vitro test method to evaluate cavitation potential must be developed. The bubble implosion damages the MHV material; thus, observing the behavior of the bubble implosion is essential. According to sonoluminescence, the collapsing cavity emits faint light. Therefore, in this study, the bubble collapse was analyzed both temporally and spatially by observing faint light emission. A photon counting system has been developed using a photomultiplier tube (H7360-01, Hamamatsu Photonics, Japan). The highest time resolution of this system is 5 microsec. A quartz optical fiber bundle of 2 mm diameter can be connected to this photomultiplier tube and traversed two-dimensionally over the MHV. The closure of the MHV triggers the photon counter, and the photons through 500 beats are recorded and integrated. A 20 mm Björk-Shiley valve was submerged in a water tank containing 10 L deionized water, and the pressure difference of 120 mm Hg was exerted on the valve at a rate of 60 bpm with a pulse duplicator. Approximately 700 microsec after the valve closure, light emission was detected along the edge of the occluder on the inflow side in the major orifice. Then, approximately 1,000 microsec after the closure, light along the occluder's edge in the minor orifice was recorded as well. Compared with the analysis, using a stroboscope and a high-speed camera, faint light was emitted from the collapsing cavities. In conclusion, sonoluminescnece was successfully observed around the MHV, and the photon counting technique and the traversing mechanism of the optical fiber bundle revealed the temporal and spatial distribution of the cavity collapse on the MHV.

Biomedical Engineering↗

PubMedDate not supplied

Microcirculation of the bulbar conjunctiva in the goat implanted with a total artificial heart: effects of pulsatile and nonpulsatile flow.

A new system to observe the microcirculation on the bulbar conjunctiva was developed using a digital high definition microscope to investigate the influence of the flow patterns on the microcirculation in a goat with a total artificial heart (TAH). The undulation pump TAH was implanted into the goat. When the whole body condition became stable, the flow pattern was modulated between the pulsatile and the nonpulsatile mode, and the changes in the microcirculation were observed. When the flow pattern was changed from pulsatile to nonpulsatile mode, the erythrocyte velocity in capillaries dropped from 526+/-83 to 132+/-41 microm/s and remained at a low level. The number of perfused capillaries decreased as well. Then the nonpulsatile flow mode was maintained for 20 minutes. After the flow pattern was returned to the pulsatile mode again, the erythrocyte velocity recovered to the initial level (433+/-71 microm/s). In many cases, the flow of the nonperfused capillaries in the nonpulsatile mode recovered to the initial level after the flow pattern was changed to the pulsatile mode again. The perfused capillary density in the nonpulsatile mode (19.7+/-4.1 number of capillaries/mm) was significantly lower than that in the pulsatile mode (34.7+/-6.3 number of capillaries/mm). It is thought that the basal and flow stimulated endothelium derived nitric oxide release in the microvessels decreased because of the disappearance of pulsatility and that the nitric oxide induced the constriction of arterioles after the flow pattern was changed to the nonpulsatile mode. At the same time, the baroceptors might sense the decrease in the arterial peak pressure or dp/dt, and the sympathetic nerve increases activities and induce the constriction of arterioles. Then, the erythrocyte velocity in capillaries would decrease. Because of the flow pattern further in the chronic phase, it is important to follow the change in the microcirculation.

Animals↗

PubMedDate not supplied

Pathophysiologic study of goats with undulation pump total artificial heart: those that survived for more than 1 month.

The undulation pump total artificial heart is an implantable total artificial heart that is being developed at the University of Tokyo. Many advances in our system have been made by the adoption of hardware and software solutions that enabled the animals with the undulation pump total artificial hearts to survive more than 1 month. Pathophysiologic observations were performed for these goats that survived. In this article, the pathophysiologic findings are described in detail for three goats that survived for 46 (goat 9916), 54 (0030), and 63 (0107) days. The microscopic findings indicated that in goat 0107 the histologic changes in key organs occurred at the termination of the experiments. Therefore, the pathophysiologic changes in goats 9916 and 0030 were mainly investigated in this study to evaluate the chronic effect caused by our total artificial heart system. The signs of chronic ischemia and cell dystrophy were observed in both the liver and kidney. Until now, 13 goats had survived more than 1 week and 6 goats survived more than 1 month, including one that survived for 63 days, which is the longest in our experimental series. The pathophysiologic results of goats 9916 and 0030 showed that the undulation pump total artificial heart might still cause some damage to the liver and the kidney. To accomplish long-term survival with the undulation pump total artificial heart, further pathophysiologic studies are required, and the necessary modifications to the total artificial heart system will need to be made.

Animals↗

PubMedDate not supplied

Functions for detecting malposition of transcutaneous energy transmission coils.

A transcutaneous energy transmission system (TETS) for artificial hearts and ventricular assist devices uses electrical coupling of power between external and implanted coils. If the position of coils changes relative to each other, the TETS cannot feed the required power of the implanted device. During activity or sleep, the coils may move accidentally. TETS users and the people around them have to pay attention to this because the range of the position where the required power can be fed efficiently is not wide. Therefore, we added functions for the position changes of the coils to the TETS. Regular, cautious, and irregular positions were introduced, and the ranges of them were decided upon in our experiments. The cautious position was determined by the area where the change of the relative position of the coils was relatively small. When the coils were in the cautious position, the circuit was tuned by way of changing the resonant point. This modulation could give good power efficiency in the cautious position. When the coils were in the irregular position, an alarm switch was turned on. These functions ease the restriction of the coil position and give better quality of life (QOL) than do the conventional TETS.

Biomedical Engineering↗