Biomedical subjects

Y Katahira

Publications and source records attributed to Y Katahira.

At least 37 records · Page 2Linked to original sources

PubMed1993

Real-time cardiac output estimation of the circulatory system under left ventricular assistance.

A new method for indirect and real-time estimation of the cardiac output of the circulatory system supported by the left ventricular assist device (LVAD) was proposed. This method has low invasiveness and is useful for clinical application of the LVAD since it needs only two measurements: the outflow rate of blood from the LVAD and the aortic pressure. The proposed method is based on a system identification technique for the time series model of the cardiovascular system and requires less computational time than other methods with similar estimation accuracy. Hence, the proposed method could be implemented in a personal computer system and realize the on-line and real-time estimation of the instantaneous outflow rate of the natural heart. The efficiency and limitation of the method were discussed on the basis of the results obtained from in vitro experiment using a mock circulatory system and in vivo experiment using an adult goat. It was revealed that the method could obtain a fairly high correlation coefficient between the true stroke volume of the natural heart and its estimate of more than 0.99 (in vivo) or 0.95 (in vivo). This means that there is a fair possibility of applying the proposed estimation system to the clinical use.

Animals↗

PubMed1993

Identification of human T cell leukemia virus type IIb infection in the Wayu, an aboriginal population of Colombia.

Human T cell leukemia virus type II (HTLV-II) is endemic in a number of native American populations and high rates of infection have also been demonstrated in intravenous drug abusers (IVDAs). Studies of virus isolates in the latter population have shown the existence of two closely related subtypes of the virus, HTLV-IIa and HTLV-IIb. To characterize the viruses present in native Americans, we analyzed by nucleotide sequence analysis the proviruses from the Wayu, an aboriginal population residing in Colombia, South America. The results showed HTLV-IIb infection in this population, and also demonstrated remarkable conservation of sequence when compared to the proviruses in IVDAs.

Base Sequence↗

PubMed1993

Dependence of baroreceptor-mediated sympathetic outflow on biventricular assist device driving frequency.

To investigate the drive condition of the artificial heart from a neurophysiological point of view, the dynamic transduction characteristics of the baroreflex system were analyzed by means of sympathetic neurograms. Two pneumatically actuated ventricular assist devices were implanted as biventricular bypasses (BVBs) in adult mongrel dogs to compare the natural heart circulation and prosthetic circulation. After BVB pumping was initiated, the natural heart was electrically fibrillated. Renal sympathetic nerve activity (RSNA) was recorded to analyze sympathetic outflow. Coherence function between the arterial pressure and RSNA was calculated to evaluate the linearity of the baroreflex system. The largest peak coherency was observed when BVB was driven at the frequency of natural heart beat prior to electrical fibrillation, which suggests that the baroreflex system shows the largest linearity at this frequency. These results suggest the possibility that the natural heart beat frequency is the setting frequency at which the baroreflex system transfers the hemodynamic rhythm to the sympathetic outflow.

Animals↗

PubMed1992

Differences in HTLV-I integration patterns between skin lesions and peripheral blood lymphocytes of HTLV-I seropositive patients with cutaneous lymphoproliferative disorders.

We examined HTLV-I integration patterns in nine cases of HTLV-I-seropositive patients with cutaneous lymphoproliferative disorders. The Southern blot on EcoRI digests of DNA revealed a discrete band of HTLV-I provirus (monoclonal integration) in either skin lesions or peripheral blood lymphocytes (PBL). Four cases showed the monoclonal integration of HTLV-I provirus only in skin lesions: one case showed only in PBL and two cases showed in both skin and PBL. The Southern blot on PstI digests of DNA revealed a 2.4 Kb band of the internal construct of HTLV-I provirus (polyclonal integration) in the PBL of EcoRI-negative samples. The difference in HTLV-I integration patterns between skin lesions and PBL in these cases suggests that the monoclonal outgrowth of HTLV-I-infected cells in the skin is causatively associated with the pathogenesis of cutaneous ATL.

Aged↗

PubMed1992

An automatic control algorithm for the optimal driving of the ventricular-assist device.

This paper presents a new method of keeping one of the most suitable driving conditions for regulating the outflow volume from the ventricular-assist device (VAD). The experimental results from a mock circulatory system have shown that the relationship between the stroke volume and the systolic duration of the VAD can be specified by the combination of characteristic curves of the positive and negative drive pressures. The optimal operating point on the characteristic curve have been defined as the point at which thrombosis on the blood-contacting surface and hemolysis due to mechanical damage can be avoided and at which the driving energy can be minimized. The present analysis has been revealed that the optimal operating point is the vertex of the triangular figure obtained from the characteristic curve. The algorithms for keeping the optimal operating point and for regulating the stroke volume have been also proposed.

Algorithms↗

PubMed1992

Expression of human T-cell lymphotropic virus type-1 gene products in the short-term cultured skin tissues of an adult T-cell leukemia/lymphoma patient with cutaneous manifestations.

Adult T-cell leukemia/lymphoma (ATLL) is recognized as a disease etiologically associated with human T lymphotropic virus type-1 (HTLV-1) infection, but, neither viral replication nor specific virus antigen expression have been detected on ATLL cells distributed in organs, including skin. To examine the latent expression of HTLV-1 in the cutaneous lesions of ATLL patients, we cultured the lesional skin tissues in vitro and applied immunofluorescence staining with mouse monoclonal antibodies Lt-4, GIN-14, and F10, which react with p40tax, p19 and gp21, respectively. We recognized HTLV-1 specific antigens on clustered ATLL cells only in the deeper dermis of the skin after 24 hrs cultivation of the lesional skin tissue from an ATLL patient in RPMI-1640 medium supplemented with 20% fetal calf serum. In the electron microscope, we observed HTLV-1 like particles, 80-140 nm in diameter with envelope and core structures, in the same tissue specimen. These findings suggest that HTLV-1 gene products may be expressed in the skin lesions of ATLL patients and involved in the pathogenesis of skin eruptions in cutaneous type ATLLs. To our knowledge, this is the first report that envisages the potency of intracutaneous HTLV-1 expression in vivo.

Aged↗

PubMed1992

Mayer waves in dogs with total artificial heart.

To assess the effect of a total artificial heart (TAH) on the autonomic nervous system a power spectral analysis of the hemodynamics in a TAH animal was done by the maximum entropy method. Two pneumatically driven sac-type ventricular assist devices were implanted as total biventricular bypass (BVB) in adult mongrel dogs to compare the differences between natural heart and TAH. Once the BVB was pumping, the natural heart was electrically fibrillated to constitute the BVB-type TAH model. In the arterial pressure waveform in animals with TAH, respiratory waves were not changed (97.7 +/- 24.6%) though Mayer waves were significantly decreased (47.5 +/- 22.6%) compared with the animal with a natural heart. These results suggest that prosthetic hemodynamics in the TAH animal affect fluctuations in the cardiovascular system.

Animals↗

PubMed1992

Estimation of the following cardiac output using sympathetic tone and hemodynamics for the control of a total artificial heart.

A sympathetic neurogram is potentially useful for the development of a real time total artificial heart (TAH) control system. We used sympathetic tone and hemodynamic derivatives to estimate the following cardiac output in acute animal experiments using adult mongrel dogs. Moving averages of the mean left atrial pressure and mean aortic pressure were used as parameters of the preload and afterload, respectively. Renal sympathetic nerve activity (RSNA) was employed as a parameter of sympathetic tone. Equations for the following cardiac output were calculated using multiple linear regression analysis of the time series data. A significant correlation was observed between the estimated and following measured cardiac output. These results suggest the potential usefulness of the sympathetic neurogram for the real time TAH automatic control system.

Animals↗

PubMed1992

Cardiac-related sympathetic nerve activity during circulation with only the left ventricular assist device.

Circulatory maintenance with a left ventricular assist device (LVAD) alone during cardiac arrest until heart transplantation has been evaluated. To assess the effect on the autonomic nervous system, the sympathetic neurogram was analyzed by power spectrum and coherence function. LVAD were inserted between the left atrium and the descending aorta in seven adult mongrel dogs and ventricular fibrillation was induced electrically. Renal sympathetic nerve activity (RSNA) was detected by bipolar electrodes attached to the left renal sympathetic nerve. Values of squared coherence between the arterial pulse wave and RSNA were calculated. Under the condition of circulatory maintenance with only LVAD, coherence at the cardiac rhythm frequency was decreased, and coherence at the LVAD pumping rhythm frequency was increased. These results indicate that the arterial pulse wave observed during maintenance of the circulation with only LVAD contributed to the sympathetic neurogram.

Animals↗

PubMed1991

Postganglionic sympathetic nerve activity with correlation to heart rhythm during left ventricular assistance.

In order to evaluate the effect of ventricular assist device (VAD) driving on the autonomic nervous system, sympathetic neurograms during left ventricular (LV) assistance were analyzed by power spectrum and coherence function. Our TH-7B pneumatically-driven sac-type VAD was used in seven adult mongrel dogs. VADs were inserted between the left atrium and the descending aorta. Renal sympathetic nerve activity (RSNA) was detected by use of bipolar electrodes attached to the left renal sympathetic nerve via a retroperitoneal approach. Values of squared coherence between the arterial pulse wave and RSNA were measured at the same frequency of cardiac and VAD pumping rhythms. During LV assistance, coherence at the cardiac rhythm frequency was decreased, and coherence at the VAD pumping rhythm frequency was increased. These results indicate that the arterial pulse wave, which was produced by the VAD assistance, contributed to postganglionic sympathetic nerve activity.

Animals↗

PubMed1991

Spectral analysis of the renal sympathetic neurogram during left ventricular assistance.

To assess the effect of left ventricular assistance on cardiac-related sympathetic nerve activity, renal sympathetic nerve activity was analysed using power spectrum and coherence function. Our TH-7B pneumatically driven sac type Ventricular Assist Device (VAD) was used in the acute experiment of 7 adult mongrel dogs. VAD were inserted between the left atrium and the descending aorta as left heart bypass. RSNA was detected by use of the bipolar electrodes attached to the left renal sympathetic nerve. Values of squared coherence between the arterial pulse wave and RSNA were measured at the cardiac rhythm and VAD pumping rhythm. Before the left ventricular assistance, coherence at the cardiac rhythm and the pumping rhythm were 0.62 +/- 0.15, 0.23 +/- 0.18 (mean +/- SD), respectively. With the VAD pumping, these values became 0.09 +/- 0.05, 0.53 +/- 0.20, respectively. These results indicate that arterial pressure wave which was created by the VAD assistance contributed to the post ganglionic sympathetic activity.

Animals↗

PubMed1991

Development and evaluation of the vibrating electromagnetically-driven artificial heart.

An vibrating electromagnetically driven univalved artificial heart was newly developed in our team. The fluid mechanical, hematological, and hemodynamical properties of this pump was evaluated in the moc circulation and animal experiments using adult goats. This vibrating electromagnetic (VEM) pump could generate more than 101/min with 10 Hz vibration, and could obtain the 2 kinds of flow and pressure patterns, such as constant peak and periodical peak patterns. The values of free Hb showed within acceptable values. We concluded that this pump is useful for totally implantable artificial heart.

Animals↗

PubMed1991

TH-7B pneumatically driven sac-type ventricular assist device and drive system.

TH-7B pneumatically driven sac-type ventricular assist device and drive system including automatic control system were developed and evaluated in the chronic animal experiments. The blood-contacting surfaces of the blood pump are coated with either Cardiothane or Cardiomat. In the chronic experiments using adult goats, only one of fifteen goats showed sudden thrombus formation after 34 pumping days. No gross findings of thrombus formation were observed in any of the cases, except for a thin circular thrombus at the junction of the connectors and the sac of the blood pump. These results suggest that antithrombogenicity of this system was satisfactory for clinical use.

Animals↗

PubMed1991

Development of the total artificial heart control system.

Sympathetic neurogram is potentially useful for the real time total artificial heart (TAH) control system. In this study, we used sympathetic tone and hemodynamic derivatives to prospect the following cardiac output in acute animal experiments using adult mongrel dogs. Moving averages of the mean left atrial pressure and mean aortic pressure were used as the parameters of the preload and afterload, respectively. Renal sympathetic nerve activity (RSNA) was also utilized as the parameter of the sympathetic tone. Equation which prospect the following cardiac output was calculated using the multiple linear regression analysis of the time series data in adult mongrel dogs. A significant correlation was observed between the prospective and following measured cardiac output. These results suggest the potential usefulness of the sympathetic neurogram for the real time TAH automatic control system.

Animals↗

PubMed1991

Coherence function between sympathetic neurogram and arterial pulse wave in animal with total artificial heart.

To assess the influence of the total artificial heart replacement on autonomic nervous system, sympathetic neurogram was analyzed by power spectrum and coherence function. Two pneumatically driven sac-type ventricular assist devices were implanted as biventricular bypass (BVB) in adult mongrel dogs. After the BVB pumping, natural heart was electrically fibrillated to constitute the BVB type TAH model. Renal sympathetic nerve activity (RSNA) was recorded using the bipolar electrode attached to the left renal sympathetic nerve. RSNA was amplified and integrated by the use of R-C integrator. Power spectra of the RSNA and the values of squared coherence between the arterial pressure waveform and the RSNA were calculated by the computer system. In animal with TAH, coherence at the cardiac rhythm frequency was decreased, and coherence at the TAH pumping rhythm frequency was increased. These results indicate that the arterial pulse wave which was observed in TAH animal contributed to sympathetic neurogram.

Animals↗

PubMed1991

Clinical application of the ventricular assist devices in Japan.

From 1980 to March in 1989, there were 177 clinical application of ventricular assist device in Japan. Original diseases were 50% ischemic heart disease and 37% valvular disease. Duration of assistance ranged from one hour to 70 days. Thirty-one cases weaned from ventricular assistance and 11 cases became long-time survivors.

Cause of Death↗

PubMed1991

Sympathetic nerve activity during maintaining circulation with only left ventricular assist device.

Maintaining circulation with an left ventricular assist device (LVAD) alone during cardiac arrest until heart transplantation, was evaluated by the use of the sympathetic neurogram. To evaluate the influences of this method on autonomic nervous system, sympathetic neurogram was analyzed by power spectrum and coherence function. In acute animal experiments using mongrel dogs, LVAD were implanted. After the LVAD implantation, ventricular fibrillation was induced electrically. Renal sympathetic nerve activity (RSNA) was detected by the use of bipolar electrodes attached to the left renal sympathetic nerve. Values of squared coherence between the arterial pulse wave and RSNA were calculated. Under the condition of circulatory maintenance with LVAD, coherence at the cardiac rhythm frequency was decreased, and coherence at the LVAD pumping rhythm frequency was increased. These results suggest that the arterial pressure which was observed during maintaining the circulation with only LVAD contributed to sympathetic neurogram.

Animals↗

PubMed1991

Hydrodynamic endurance test of the prosthetic valve used in the various types of the ventricular assist device.

To evaluate the various basic designs of the pump chambers used in the ventricular assist devices (VADs), hydrodynamic endurance test was performed from the viewpoint of the durability of the prosthetic valves used in the VAD. For the hydrodynamic analysis, we designed three basic types of pump (sac type, diaphragm type, and pusher plate type) using the same material and having the same capacity and shape. Prosthetic valves in these VADs were tested from the standpoint of the water hammer effect, which affects the valve durability, to determine which pump design would be most durable as a prosthetic valve in the VAD. The water-hammer phenomenon was evaluated using the maximum pressure gradient (MPG) across the prosthetic valve in the moc circulatory loop. Maximum pump output was recorded when we used the diaphragm type model, and minimum MPG in the commonly used driving condition of the VAD were recorded when we used the sac type model. The results suggest that the sac type VAD model is the most durable design for the prosthetic value.

Adult↗