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Biomedical subjects

S Nitta

Publications and source records attributed to S Nitta.

At least 91 records · Page 5Linked to original sources
PubMed1996

Extracting 1/f fluctuation from the arterial blood pressure of an artificial heart.

We have studied the fluctuations of an artificial circulation for the analysis of the physiological aspects; however, the conventionally used fast Fourier transform (FFT) method cannot separate harmonic oscillations, such as respiratory and Mayer waves, from the 1/f fluctuation, which has been though to represent underlying fractal dynamics. Fractal structure was shown in the strange attractor with chaotic dynamics, which is thought to be a flexible and intelligent system. In this study, the coarse-graining spectral analyzing (CGSA) method was utilized to quantitatively evaluate the proportion of the 1/f fluctuation in the total power in the frequency domain and to analyze artificial circulation in the whole system. We implanted two pneumatically actuated ventricular assist devices as biventricular bypasses (BVBs) in chronic animal experiments using 4 healthy adult goats. To compare the natural and prosthetic circulation of each experimental animal, the BVB-type complete prosthetic circulation model with electrically induced ventricular fibrillation was adopted. All hemodynamic parameters of natural and prosthetic circulation were recorded under awake conditions and calculated with the use of a personal computer. With the use of the CGSA method, time-series data of the hemodynamics were analyzed and fractal percentages, extracting the 1/f fluctuation from a given time series, were calculated. Fractal percentages of the arterial blood pressure were 85.8 +/- 10.7% and 82.0 +/- 7.3% with natural and artificial circulation, respectively (not significant [NS]). 1/f fluctuation showed the characteristics of being fractal in a time series. The fractal structure showed robustness and error resistance in nonlinear dynamics. Therefore, our results suggest that the circulatory regulatory system of the artificial heart may have desirable characteristics such as error resistance.

Animals↗
PubMed1996

Ultrasonic tissue characterization of renal cell carcinoma tissue.

The purpose of this study was to characterize renal cell carcinoma tissue by the measurement of microacoustic properties. A scanning acoustic microscope system operating in the frequency range of 100-200 MHz was employed and the attenuation constant and sound speed were measured on the two-dimensional distribution. The values of attenuation constant and sound speed were lower in both kinds of cancer cells than those in normal kidney, although a significant difference was not found between the clear cell and granular cell. Also, both acoustic parameters of cancer cells were significantly lower than those in hemorrhage and fibrosis. These data suggest that the elasticity of renal cell carcinoma tissue may be lower than that of normal kidney. Moreover, the high intensity echo in clinical echography may be related to the heterogeneity of the microacoustic field in the carcinoma tissue.

Acoustics↗
PubMed1996

[Pleural fibroma with a cavity-like air space].

A 45-year-old man was admitted to the hospital because of an increase in the size of an abnormal shadow on chest X-ray films over the preceding 5 years. A chest X-ray film on admission revealed a round air space in a mass-like shadow in the right upper lung field. Results of physical examination, sputum cytologic examination, and Ziehl-Neelsen staining were negative. Histopathological examination of a percutaneous lung biopsy specimen revealed a benign fibrous tumor of the pleura. Thoracotomy revealed a pedunculated tumor arising from the visceral pleura at the apical segment of the right upper lobe. A wedge resection was done. Histological examination revealed that the tumor consisted of regularly-shaped spindle cells with densely collagenous tissue. Normal lung tissue was found to be invaginated into the tumor tissue. These findings are consistent with the radiologic findings.

Fibroma↗
PubMed1996

[Peri- and postoperative courses in patients undergoing concomitant cardiac and pulmonary operations].

We studied peri- and postoperative courses in patients undergoing concomitant cardiac and pulmonary operations (CCPO), which included pulmonary resection and coronary artery bypass grafting (CABG). Of eight patients who had lung cancer and ischemic heart disease (IHD), six underwent CCPO and two patients first had percutaneous transluminal coronary angioplasty (PTCA) followed by lung surgery at an interval after the first procedure. Twelve patients with lung cancer who underwent only pulmonary surgery and 13 patients with IHD who were treated with CABG were studied as controls. We compared peri- and postoperative characteristics among these groups of patient. Operating time, bleeding volume during surgery, amount of drainage discharge within 24 hours after the operation, and ICU days were significantly increased in the CCPO group in comparison with the two control groups. In the CCPO group, mechanical ventilatory support time and administration days after the operation were significantly increased in comparison with the lung operation group, but not in comparison with CABG group. The two patients who sequentially underwent PTCA and lung surgery had postoperative courses similar to the CCPO patients. All CCPO patients were ambulatory upon discharge. None of the CCPO patients died from postoperative complications involving the respiratory tract or the circulatory system. Our data suggest that CCPO is available for patients with both heart and lung diseases when complications can be avoided by appropriate management, although these procedures are extremely invasive. We believe that CCPO should be attempted in patients with definite indications for such a procedure.

Aged↗
PubMed1996

Strange hemodynamic attractor parameter with 1/R total artificial heart automatic control algorithm.

To evaluate the automatic control algorithm of the total artificial heart (TAH) as an entity, and not just as parts, a non-linear mathematical analyzing technique including chaos theory was utilized. Chronic experiments on the biventricular bypass type artificial heart implantation were performed in healthy adult goats after the natural ventricles were removed. Hemodynamic time series data were recorded under the awake standing condition with TAH 1/R and fixed driving. Time series data were recorded on a magnetic tape and analyzed on a personal computer system with an A-D converter. Using the nonlinear mathematical technique, the time series data were embedded into the phase space and the Lyapunov numerical method was carried out for the quantitative evaluation of the sensitive dependence on the initial condition of the reconstructed attractor. Calculation of the largest Lyapunov exponents suggested that the reconstructed attractor of the left pump output during TAH 1/R control was a larger dimensional strange attractor, a characteristic pattern of deterministic chaos. A total system indicating chaotic dynamics was thought to be a flexible and intelligent control system. Thus, our results suggest that 1/R TAH control may be suitable for the biventricular assist type total artificial heart.

Algorithms↗
PubMed1996

Spectral analysis of hemodynamics during left ventricular assistance.

In order to analyze the autonomic nervous system during left ventricular (LV) assistance, fluctuations in hemodynamic derivatives were evaluated by a spectral analyzing method using a fast fourier transform (FFT) methodology. After the left pleural cavity was opened through the fourth intercostal space under general anesthesia, a pneumatically driven ventricular assist system was implanted as in left heart bypasses in chronic animal experiments, using three healthy adult goats. Hemodynamic parameters with and without LV assistance were recorded on a magnetic tape in the awake condition then analyzed in a computer system through an A-D convertor. Power spectral analysis was performed on a beat-to-beat basis for the evaluation of the fluctuations. During copulsation mode LV assistance, Mayer wave fluctuations (0.1 Hz) were significantly increased compared with counterpulsation mode LV assist, suggesting an increase in sympathetic tone. Co-pulsation mode LV assist is reported to increase the afterload of the natural left ventricle, thus, the sympathetic tone may be increased to maintain a natural heart output.

Analysis of Variance↗
PubMed1996

Fluctuations of the hemodynamic derivatives during left ventricular assistance using oscillated blood flow.

To analyze the autonomic nervous system during left heart bypass with a vibrating flow pump (VFP), fluctuations in hemodynamic derivatives were evaluated by the spectral analysis method using fast fourier transform methodology. After the left pleural cavity was opened through the fourth intercostal space under general anesthesia, a VFP was implanted as the left heart bypass device in chronic animal experiments using 3 healthy adult goats. Hemodynamic parameters with and without VFP assistance were recorded on magnetic tape in awake animals and were analyzed by computer through an analog to digital convertor. Power spectral analysis was performed on a beat-to-beat basis for the evaluation of the fluctuations. During left heart bypass with the VFP, Mayer wave fluctuations were decreased significantly although respiratory waves were not changed significantly. These results suggest that sympathetic nervous system modulation was changed under the influences of the left heart bypass with VFP. By using this analysis methodology, truly physiologic ventricular assistance may be achieved.

Animals↗
PubMed1996

[The effect of basic fibroblast growth factor (bFGF) on early bronchial revascularization].

We examined local effects of basic fibroblast growth factor (bFGF) on early bronchial revascularization following bronchial anastomosis. The left main bronchi of mongrel dogs (8-15 kg) were cut and sutured following peripheral radical hilar stripping. The anastomotic sites were wrapped with a pericardial fat tissue pedicle, including branches of the internal thoracic artery and vein (8 dogs group A). One ml of bFGF (Biomedical Tecnologies Inc.) dissolved in 1 ml of fibrin glue (final concentration of 20 ng/ml for a total dose of 100 ng, pH 7.15-7.5) was applied to the anastomotic sites in order to deliver the bFGF gradually and selectively (12 dogs group B). At various timepoints, changes in bronchial mucosal blood flow were measured using a laser Doppler flowmeter and left internal thoracic artery (LITA) blood flow, using an implanted electromagnetic flowmeter. On the 7th postoperative day, silicone rubber was injected into the left subclavian artery, and the revascularization pattern from branches of the LITA to the bronchus was examined histologically. Specimens were labeled as (-) when the neogenic vessels were only observed outside the bronchial wall, (1+) when observed inside the bronchial wall but not in the mucosa, and (2+) when clearly observed in the mucosa. Blood flow in the bronchial mucosa was measured as the left/right ratio. For group A, the averages immediately after operation, and on the 3rd and on the 7th postoperative days, were 0.35 +/- 0.10, 0.46 +/- 0.04, and 0.70 +/- 0.14 respectively; while, for group B, they were 0.27 +/- 0.09, 0.78 +/- 0.15, and 0.90 +/- 0.15, respectively (p < 0.01). Our results show that blood flow in the LITA increased more in group B than in group A (average 2.7 +/- 1.8 ml/min in group A, vs. 4.7 +/- 2.9 ml/min in group B). Furthermore, the pathologic findings of neovascularization were (-) in 3 cases and (1+) in 2 cases in group A, while group B showed (1+) neovascularization in 1 case and (2+) in 4 cases. These results clearly demonstrate increased revascularization in the bFGF treatment group B. We conclude that local application of bFGF is effective in stimulating early bronchial revascularization.

Anastomosis, Surgical↗
PubMed1995

Study of stimulation-secretion coupling in a flow culture system: periodic secretion of hepatocyte growth factor by interleukin-1 alpha-stimulated human embryonic lung fibroblasts.

In order to closely examine stimulation-secretion coupling, the authors developed a 'flow culture system' in which it is possible to continuously replace the culture medium. This lessens the effects of cell-derived products observed in the conventional culture system. We compared our flow culture system and the conventional culture system based on the secretion patterns and concentrations of human hepatocyte growth factor (HGF) produced by interleukin 1 alpha (IL-1 alpha)-stimulated human embryonic lung fibroblasts (MRC-5). While the cells in the conventional culture system secreted HGF at a nearly constant rate, the cells in the flow culture system secreted HGF periodically. Even short-term stimulation with IL-1 alpha for 4 h resulted in significant HGF secretion continuing for at least 46 h. Thus the inflammatory cytokine IL-1 alpha was shown to modulate fibroblast secretion of HGF. The periodic secretion of HGF may play an important role in tissue repair and regeneration. Based on the results of actually applying it, we conclude that our flow culture system is an efficient and accurate model for the detailed examination of stimulation-secretion coupling.

Cell Line↗
PubMed1995

Michaelis-Menten analysis of immobilized enzyme by affinity capillary electrophoresis.

Michaelis constant of enzymatic reaction was evaluated by affinity capillary electrophoresis using beta-galactosidase as a model enzyme and o- and p-isomers of nitrophenyl-beta-galactoside as substrates. The enzyme was immobilized on the inner surface of a fused-silica capillary by the covalent bonding through a bridging group, and the substrates were introduced into the capillary. The reaction products migrated electrophoretically toward the detection side (anodic side), while the unreacted substrates moved toward the injection side (cathodic side) on a slow electroosmotic flow generated by the weak negative charge of the immobilized enzyme. The initial velocity of the enzymatic reaction was estimated from the peak height of the product, and the Michaelis constant was calculated according to Lineweaver-Burk equation. The results (Km, 2.34 mM for o-isomer and 1.09 mM for p-isomer) were reproducible (RSD < 11.8%, n = 5). Although the estimated Michaelis constants were larger than the reported values measured in homogeneous solution, the ratio of the Michaelis constants of o-/p-isomers was in good agreement with the literature value. The present method required as low as a few microgram amount of enzyme and nanogram amount of substrate which is far smaller than those required in a conventional affinity HPLC.

Amides↗
PubMed1995

A less invasive Emax estimation method for weaning from cardiac assistance.

The maximum elastance of the ventricle (Emax) is a strong candidate for a quantitative index used for determination of the timing of weaning the patient from a left ventricular assist device (LVAD). This paper presents a new and less invasive method for deriving Emax of the left ventricle under the LVAD assistance. In this method (the CoP method), Emax can be calculated from two different end-systolic points which are produced by changing the drive phase of LVAD without any vascular clamping and any direct measurement of the left ventricular volume. Animal experiments indicated that the CoP method is useful when the measured left ventricular flow and pressure are employed. Moreover, a new technique for estimating the left ventricular flow was developed to make the CoP method less invasive without direct measurement of the flow. The technique could considerably improve the estimation accuracy of the flow in the co-pulsation mode in comparison with the previous one proposed by the authors. However, it has been revealed that the estimation accuracy of the left ventricular flow was not globally high enough to apply the CoP method to clinical cases in spite of its much less invasiveness.

Animals↗
PubMed1995

Totally implantable ventricular assist system using a vibrating flow pump.

A totally implantable ventricular assist system (VAS), including a drive system and a percutaneous electric energy transmission system, was developed and evaluated in acute animal experiments using adult goats. This newly designed VAS mainly consists of a vibrating tube, coils, magnets, and a jelly-fish valve as the outlet valve. For energy transmission, a new implantable transmitter with a plain weave structure was proposed as a noncontacting transform by using the spinal amorphous magnetic fibers. The fluid mechanical and hemodynamic properties and the efficiency of the energy transmission system were evaluated in acute animal experiments using healthy adult goats. This vibrating electromagnetic artificial heart (AH) could generate more than 10 L/min as output volume, with 10 Hz vibration using 20 volts as supplied voltage. The total efficiency of the percutaneous energy transmission system was 76%, and temperature increases were within the acceptable range, suggesting the usefulness of our newly developed implantable VAS.

Animals↗
PubMed1995

Experimental study of physiological advantages of assist circulation using oscillated blood flow.

To estimate the effect of oscillated blood flow on hemodynamics in an awake condition, left ventricular assist circulation using oscillated blood flow was performed on 3 adult goats as chronic animal examination. A vibrating flow pump (VFP) was used for generating high-frequency oscillated flow. The blood flow rate of assisted circulation was approximately 1.0 L/min, and the driving frequency of VFP was 25 Hz. Systemic vascular resistance and arterial impedance were calculated in this study. Systemic vascular resistance during assist circulation was decreased compared with that without assistance. Oscillated blood flow may be effective in decreasing vascular resistance. Moreover, it was suggested from the study of arterial impedance that motive characteristics of the vascular wall against changing blood pressure may keep their normal reaction. Therefore, oscillated blood flow may be used for left ventricular assist circulation as concluded from the study of the characteristics of blood vessels.

Animals↗
PubMed1995

Gas exchange efficiency of a membrane oxygenator with use of a vibrating flow pump.

We have developed a newly designed blood pump, named the vibrating flow pump (VFP), which can generate high frequency oscillated flow. The driving frequency is 10-50 Hz, and flow volume is linearly controlled electric power (current and voltage). The VFP was applied as the pump for extracorporeal circulation (ECC) in acute animal experiments. The gas exchange efficiency of the membrane oxygenator with the VFP and a roller pump (RP) was evaluated. Under general anesthesia with halothane, 7 adult goats underwent ECC; an inflow cannula was inserted into the right atrium, an outflow cannula was sutured to the descending thoratic aorta, and total ECC was performed with a flow of about 80 ml/min/kg. The ECC system with the VFP showed excellent gas exchange efficiency compared with that of the RP. The hemodynamics of ECC using the VFP were easily maintained within normal limits. These results suggest that the VFP is very useful as a pump for ECC; thus, a compact-sized ECC system may be achieved.

Animals↗
PubMed1995

A shorter R-R interval causes a larger endocardial R wave amplitude in cases with atrial fibrillation.

Endocardial electrograms were recorded with a Medtronic programmer model (9742A) in 15 patients with implanted pacemakers required for bradycardia and atrial fibrillation. Telemetered unipolar ventricular endocardial electrograms were recorded for 2 minutes, and the R wave amplitudes of the shortest R-R intervals were compared to that of the longest R-R intervals. Eleven of the 15 cases showed R wave amplitudes of the shortest R-R intervals an average of 2.1 mV larger than the R wave amplitudes of the longest R-R intervals. Three cases showed no difference, and one the opposite condition. In all four, the average recorded R-R interval exceeded 670 ms. The shortest R-R interval among the 11 cases with a larger R wave amplitude was 545 +/- 100 ms. The endocardial R wave amplitude of the shortest R-R intervals were larger than the R wave amplitudes of the longest R-R intervals. Shorter intervals were followed by larger endocardial R wave amplitudes (P < 0.005 with the Wilcoxon's rank sum test).

Adult↗
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

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↗