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H Akiho

Publications and source records attributed to H Akiho.

At least 37 records · Page 2Linked to original sources
PubMed1995

Can the artificial heart make the circulation become fractal?

In order to analyze the hemodynamic parameters in prosthetic circulation as an entity and not as decomposed parts, non linear mathematical analyzing techniques, including the fractal dimension analyzing theory, were utilized. Two pneumatically actuated ventricular assist devices were implanted, as biventricular bypasses (BVB), in chronic animal experiments, using four healthy adult goats. For the comparison between the natural and prosthetic circulation in the same animals, the BVB type complete prosthetic circulation model with ventricular fibrillation, was adopted. All hemodynamic parameters with natural and prosthetic circulation were recorded under awake conditions, and calculated with a personal computer system. Using the non-linear mathematical technique, the arterial blood pressure waveform was embedded into the return map as the beat-to-beat time series data and fractal dimension analysis were performed to analyze the reconstructed attractor. By the use of the Box counting method, fractal dimension analysis of the hemodynamics was performed. Return map of the hemodynamics during natural and artificial circulation showed fractal characteristics, and fractal dimension analysis of the arterial blood pressure revealed the fact that lower dimensional fractal dynamics were evident during prosthetic circulation. Fractal time series data is suggested to have robustness and error resistance, thus our results suggest that the circulatory regulatory system with an artificial heart may have these desired characteristics.

Animals↗
PubMed1994

Direct inhibitory effect of atrial natriuretic peptide on isolated caecal circular smooth muscle cells via soluble guanylate cyclase.

Atrial natriuretic peptide (ANP) relaxes the vascular smooth muscle via particulate guanylate cyclase. Smooth muscle cells isolated from the caecal circular muscle layer of the guinea pig were used to examine the direct inhibitory effect of ANP on those cells. The role of adenylate cyclase, particulate guanylate cyclase, and soluble guanylate cyclase in the direct inhibitory effect of ANP on contraction of this muscle cell induced by carbachol was investigated. ANP inhibited the contractile response produced by 10(6)M carbachol in a concentration-dependent manner, with an IC50 value of 8nM. An inhibitor of adenylate cyclase (2',5'-dideoxyadenosine) and two inhibitors of particulate guanylate cyclase (HS-142-1, and PMA) had no significant effect on the relaxation produced by ANP. In contrast, an inhibitor of soluble guanylate cyclase (LY83583) significantly and completely inhibited the relaxation produced by ANP. This is the first report demonstrating the direct inhibitory action of ANP on the isolated caecal smooth muscle cells via soluble guanylate cyclase, which differs from the intracellular mechanism responsible for the relaxation of vascular smooth muscle produced by ANP.

Aminoquinolines↗
PubMed1994

Fluctuations of the sympathetic nerve discharges in animals without natural heartbeat.

To assess the effect of artificial circulation on the circulatory regulatory system, rhythmical fluctuations in the cardiovascular system and autonomic nerve discharges were analyzed in animal experiments using adult mongrel dogs. Two pneumatically actuated ventricular assist devices were implanted as total biventricular bypass (BVB) under general anesthesia; then, the natural heart was electrically fibrillated to constitute the BVB part of the complete prosthetic circulation model. All hemodynamic data and sympathetic nerve discharges were recorded and calculated in the computer system by the use of spectral analyzing methods. In the power spectrum of the arterial blood pressure waveform during prosthetic circulation, the Mayer wave peak was significantly decreased though the respiratory wave peak was not significantly changed. However, the Mayer wave peak in sympathetic nerve discharges was significantly increased though the respiratory wave peak was not significantly changed. These results suggest that rhythmical fluctuations are a necessary response of the circulatory regulatory system including the autonomic nervous system. However, sympathetic nerve discharges respond to the artificial heart without rhythmical fluctuations.

Animals↗
PubMed1993

Decrease in coupling of Gs in v-src-transformed NIH-3T3 fibroblasts: possible involvement of tyrosine phosphorylation of Gs by pp60v-src.

In Rous sarcoma virus (RSV)-transformed NIH-3T3 fibroblasts expressing pp60v-src as tyrosine protein kinase, isoproterenol-stimulated cAMP accumulation was much lower than in normal cells. The reduction in v-src-transformed cells seemed to be mainly due to a decrease in the number of beta 2-adrenoceptors. When the membranes were phosphorylated with ATP, however, the binding affinity of isoproterenol to beta 2-adrenoceptors was reduced in transformed cell membranes by 34% compared to that in normal cell membranes. The reduction in transformed cell membranes was restored to the level of normal cell membranes by treatment of membranes with anti-pp60v-src antibody. GTP gamma S- and cholera toxin-stimulated adenylyl cyclase activities were reduced with no change in forskolin-stimulated adenylyl cyclase activity in transformed cell membranes. The reduced effect of GTP gamma S was also restored by treatment with anti-pp60v-src antibody or by adding staurosporine, which inhibits a variety of protein kinases, including tyrosine protein kinase. One of the 32P-phosphoproteins phosphorylated with [gamma-32P]ATP in v-src-transformed cell membranes was bound to GTP-agarose, and was a 46-kDa molecule on a sodium dodecyl sulfate-polyacrylamide gel. This 46-kDa 32P-labeled phosphoprotein was immunoprecipitated with anti-phosphotyrosine antibody or anti-stimulatory GTP-binding protein (anti-Gs) antibody. These results suggest that pp60v-src phosphorylates the alpha-subunit of Gs and consequently causes a decrease in the coupling of beta 2-receptors to Gs and in the coupling of Gs to adenylyl cyclase.

3T3 Cells↗
PubMed1993

Origin of the rhythmical fluctuations in the animal without a natural heartbeat.

In order to analyze the origin of the rhythmical fluctuations in the cardiovascular system, an artificial heart, which does not have rhythmical periodicities such as altering heart rate and cardiac function, was utilized in chronic animal experiments with adult goats. Two pneumatically actuated ventricular assist devices were implanted as a total biventricular bypass under general anesthesia, and then the natural heart was electrically fibrillated to constitute the biventricular bypass type of complete prosthetic circulation model. All hemodynamic data were recorded under awake conditions and were calculated in the computer system by spectral analysis methods. In the power spectrum of the arterial blood pressure of the animal with the artificial heart, the Mayer wave peak and respiratory wave peak were clearly observed, and spectral analysis including the coherence function suggests that the Mayer waves originated from the peripheral vascular resistance and the respiratory waves probably originated from the periodicities of the pulmonary circulation. These fluctuations in the circulatory system influenced the arterial baroreflex system and transfer to the sympathetic outflow through the central baroreflex system, which suggests that rhythmical fluctuations in hemodynamic parameters originate at least in part from these vascular periodicities.

Animals↗
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

[Two cases of blind pouch syndrome].

Case 1. A 39-yr-old male was presented with anemia. Initial blood examination showed remarkable iron deficiency anemia. Small bowel X-ray and abdominal CT examination revealed a dilated tract at the end of the ileum. Surgical operation was done. The surgical specimen showed side to side anastomosis which was reconstructed at the operation for rt. inguinal herniation 46 days after his birth. The oral side of the tract was remarkably dilated. Case 2. A 50-yr-old male was presented with dizziness. He had anemia and clubbed fingers. A small bowel X-ray examination was done and it showed side to side anastomosis in the middle of the small intestine. Surgical operation was performed. The surgical specimen showed side to side anastomosis about 2 m 20 cm from the Treitz' ligament, which was reconstructed during the operation for ileus when he was 10 years old. The blind portion was remarkably dilated. In both case, the anemia was improved after the operation.

Adult↗
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

Silent obstruction of the coronary stenosis between diagnostic angiography and later percutaneous transluminal coronary angioplasty without myocardial infarction.

Among 204 patients with severe coronary artery stenosis amenable to percutaneous transluminal coronary angioplasty (PTCA), 5 (2.5%) developed new silent total coronary occlusion of the vessel to be dilated without any chest symptom during the period between diagnostic coronary angiography and repeat coronary angiography at the time of the operation. We evaluated the clinical and angiographical characteristics of the patients with silent obstruction of the coronary artery in a short time, compared with the patients with unstable angina pectoris, who is considered to be suffering from acute myocardial infarction with severe chest symptom. None of the clinical variables studied showed a significant difference between the two groups. Among the angiographic variables, the degree of collateral was higher and impaired coronary perfusion distal to the lesion was more frequently found in unstable angina group. These results suggest that unstable angina is in a later stage of the ischemic heart disease compared with the time of the diagnostic angiography in patients with silent obstruction. Silent obstruction of high degree coronary stenosis is presumably due to the development of collateral circulation.

Aged↗
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↗