Biomedical subjects

S Naganuma

Publications and source records attributed to S Naganuma.

At least 37 records · Page 2Linked to original sources

PubMed1995

Fractal dimension analysis of the oscillated blood flow with a vibrating flow pump.

To analyze the hemodynamic parameters during circulation with oscillated blood flow, nonlinear mathematical analyzing techniques, including fractal theory, were utilized. Vibrating flow pumps (VFP) were implanted as a left heart bypass, and the ascending aorta was clamped to constitute the total left heart circulation with oscillated blood flow in acute animal experiments using 7 adult goats. Using nonlinear mathematical analyzing techniques, reconstructed attractors of the arterial blood pressure waveform in the phase space during natural circulation and oscillated circulation were analyzed. Using the Grassberger-Procaccia correlation dimension analyzing technique, fractal dimension analysis of the reconstructed attractor was performed. During VFP bypass, lower fractal dimensions of the reconstructed attractor were shown compared with those during natural heart circulation. The results suggest that lower dimensional chaotic dynamics contributed to the circulation with oscillated blood flow.

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

[Differential patterns of the number and proportion of blood leukocytes following endurance exercise of moderate, strenuous and severe conditions].

A study was conducted to elucidate the acute effects of endurance exercise on white blood cells by setting three conditions of different intensity and duration; (a) an upper limit of aerobic exercise for health promotion and (b) superior limits within endurance exercise tolerance for untrained persons were prescribed separately for the same healthy untrained male student volunteers (n = 10) at intensities of 85% and 95% of the individual anaerobic threshold (AT) values for 1 h and 1.5 h, respectively, on a bicycle ergometer. In addition, (c) participants in a 100-km marathon race (n = 20) who continued running for 10-13 h were examined. Every condition caused significant leukocytosis due to predominant neutrophilia and, to a minor degree, a significant increase in monocyte number, the magnitude of which depended on the severity of endurance workload and persisted even 1 h after the termination of exercise. Simultaneously, microscopic evaluation of blood smears revealed the occurrence of an increased proportion of band neutrophils and a decreased proportion of hypersegmented neutrophils (shift to the left) following exercise in condition (b) but not in (a), suggesting that neutrophils are mobilized partly from the bone marrow reserve to the circulation. On the other hand, peripheral lymphopenia was observed after the termination of endurance exercise. These phenomena closely mimicked the known effects of exogenous glucocorticoid administration, suggesting an association with endogenous stress hormone (cortisol) secretion following strenuous exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1995

Chaotic behavior of hemodynamics with ventricular assist system.

In order to analyze hemodynamic parameters during left ventricular assistance as an entity and not as decomposed parts, non-linear mathematical techniques were utilized. Pneumatically actuated ventricular assist systems (VAS) were implanted as left heart bypasses in acute animal experiments, using healthy adult mongrel dogs. By the use of the non-linear mathematical technique, the arterial blood pressure waveform (AP) was embedded into the four-dimensional phase space and projected into the three-dimensional phase space. The Lyapunov numerical method was used as an adjunct to the graphical analysis of the state space. The phase portrait of the attractor showed a complex structure; a three dimensional solid torus with a screw type structure as a part, suggesting deterministic chaos in the AP without left ventricular assistance. Positive lyapunov exponents confirmed the existence of chaos. During counterpulsation mode left ventricular assistance, the phase portrait of the attractor showed a more complex structure, and positive Lyapunov exponents suggested a greater dimensional deterministic chaos. However, non-structured patterns were seen in the phase space during internal mode VAS driving, suggesting the possibility of dissipative dynamics in the four dimensional phase space. These results suggest that the cardiovascular system with counterpulsation mode VAS driving is in a homeochaotic state, which is thought to be a flexible and intelligent control system. And there is greater dimensional complex dynamics in the circulatory regulatory system with VAD during internal mode assistance.

Animals↗

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↗

PubMed1994

Carotid arterial impedance during oscillated blood flow.

Blood perfusion of systemic circulation is influenced by the physical characteristics of artery. Several investigations proposed that the physical parameters of vessels are determined by neurological factors, hormonal factors, and physical properties of arteries among others. In this study, arterial impedance was estimated because it may express the condition of vessels. To examine the change of arterial impedance according to the blood flow pattern, the typical sine wave blood flow (oscillated flow) was used during total cardiopulmonary bypass (CPB) because it is considered the most simple pulsatile flow. CPB using oscillated blood flow was performed in acute experiments on adult goats. Total systemic flow was controlled to remain at approximately 80 ml/min. Carotid arterial flow, aortic pressure, central venous pressure, and systemic flow were measured. Total peripheral resistance, carotid arterial resistance, systemic impedance, and carotid arterial impedance were calculated to evaluate blood flow distribution during CPB. This study suggested that the parameters of carotid arterial blood flow changed according to the change of flow frequency during oscillated blood flow. This change may occur because arterial impedance was influenced by flow frequency; therefore, the blood flow of the carotid artery was significantly changed according to the change of the frequency component of blood flow.

Animals↗

PubMed1994

Chaotic hemodynamic during oscillated blood flow.

A vibrating flow pump (VFP), which can generate oscillated blood flow (10-50 Hz/min), has been developed by our team for the artificial heart system. However, the flow pattern of this pump was different from that of the natural heart; therefore, it is important to analyze the effect of this oscillated blood flow on the circulatory regulatory system. To analyze the hemodynamics of high frequency oscillated blood flow as an entity, (not decomposed), nonlinear mathematical techniques were utilized. VFPs were implanted between the left atrium in animal experiments using adult goats. After the implantation procedure, the ascending aorta was clamped to constitute the complete left heart circulation with VFP. Using a nonlinear mathematical technique, an arterial blood pressure waveform was embedded into four-dimensional phase space and projected into three-dimensional phase space. The Lyapunov numerical method was used as an adjunct to graphic analysis of the state space. Phase portrait of the attractor showed a high dimension complex structure, suggesting deterministic chaos during natural circulation. However, phase portrait of the hemodynamics during oscillated blood flow showed a single circle with banding and a forbidden zone, similar to a limit-cycle attractor, suggesting a lower dimensional dynamic system. Positive Lyapunov exponent during oscillated blood flow suggests the existence of lower dimensional chaotic dynamics. These results suggest that the circulatory regulatory system during oscillated blood flow may be a lower dimensional homeochaotic state; thus, hemodynamic parameters must be carefully regulated when unexpected external stimuli are present.

Animals↗

PubMed1993

Stimulation of acyl-CoA:cholesterol acyltransferase activity by brefeldin A in macrophage J774 cells.

Brefeldin A (BFA), an inhibitor of secretory pathway, enhances incorporation of radiolabeled cholesterol and oleate into cholesteryl esters in cultured cells [12]. We studied the mechanism for this effect of BFA in the macrophage J774. When incubated with 2.7 microM BFA in the absence of lipoproteins, J774 cells synthesized and accumulated 1.5- to 4-fold more cholesteryl esters than did cells which received no BFA. BFA caused neither an elevation of cholesterol synthesis, inhibition of its secretion nor changes in cholesterol transport to plasma membrane, esterification of plasma membrane cholesterol and cholesteryl ester hydrolysis. Acyl-CoA:cholesterol acyltransferase (ACAT) activity in microsomes from BFA-treated cells was 1.5- to 1.8-fold higher than that from control cells. The effect of BFA was diminished by treatment with low temperature, which is known to abolish BFA effect on Golgi formation.

Acetates↗

PubMed1993

Differentiation of transiently ischemic from infarcted myocardium by thallium-201 exercises scintigram after active ergometer rehabilitation.

It has been frequently reported that while myocardial viability is neglected in conventional methods of diagnosis such as left ventriculography, ECG, and exercise thallium-201 myocardial scintigraphy (Ex-Tl), revascularization often results in improving left ventricular wall motility. In the present study, the authors contrived a method to accurately evaluate the viability of the myocardium by means of exercise rehabilitation, and tested the method in clinical cases. Among patients with myocardial infarction, we selected a patient with negative viability in the diseased area as determined by chronic ECG, left ventriculography (LVG), coronary angiography and Ex-Tl. This patient went through two weeks of active exercise rehabilitation gauged with an ergometer, and was then re-examined by Ex-Tl. After the evaluation, revascularization was performed for the patient who demonstrated viability of the infarcted myocardium in EX-Tl after rehabilitation, and significant improvement in contractility was shown in the chronic LVG. These findings indicate that our method of detecting potential viability of the infarcted myocardium is of clinical significance.

Ergometry↗

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

Treatment of arteriosclerotic obstruction by LDL adsorption.

According to the authors' clinical analysis, about half of the patients who suffer from arteriosclerotic obstruction (ASO) in the lower extremity(-ies) with clinical manifestation are dyslipidemic (total cholesterol > or = 220 mg/dL or LDL cholesterol > or = 140 mg/dL). As suggested by clinical success in regression of ASO in the coronary arteries as a result of aggressive removal of LDL, LDL adsorption utilizing an extracorporeal circulation technique with a dextran sulfate/cellulose adsorbent column was applied in 33 patients (22 men and 11 women) with ASO. Clinical results obtained after a series of 10 LDL adsorption procedures as a standard showed encouraging success. Improvement in subjective symptoms was achieved as follows: 88.5% for cold lower extremity, 87.1% for intermittent claudication, 53.8% for leg/toe pain at rest, and 60% for disappearance/size diminution of ulcer/necrosis. Improvements in objective examination findings supported subjective ones: 85.7% by plethysmography, 81% by thermography and 70% by ankle pressure index. No serious complications or untoward effects were observed during or after the adsorption procedures. In conclusion, LDL adsorption appears to be a useful and safe tool in treatment of ASO patients with dyslipidemia.

Adsorption↗

PubMed1993

Identification of the deterministic chaos in cardiovascular dynamics by the use of the non-linear mathematics.

Chaotic behavior in cardiovascular dynamics was thought to be one of the important information to analyze the circulatory regulatory system. Several investigators studied the attractor in the signals of the electrocardiogram, and found the strange attractor, suggesting dynamics compatible with deterministic chaos, by the use of the non-linear mathematics. It is interesting problem to analyze the hemodynamic parameters by the use of non-linear mathematics for the determination of the physiologically optimal circulatory condition. In this study, Chaos analyzing system was developed to identify the deterministic chaos in cardiovascular regulatory system by the use of the non-linear mathematics including phase plane plots, embedding, and lyapunov exponents. Time series data of the hemodynamic parameters in the chronic animal experiments was analyzed by this system, and satisfactory attractor was obtained by the use of the phase plane plots and embedding techniques. Furthermore, calculation of the lyapunov exponents showed the existence of the deterministic chaos in arterial blood pressure in the chronic animal experiments using adult goats, suggesting this tool is useful for analyzing cardiovascular dynamic behavior.

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

Inhibition of the accumulation of lipid droplets in macrophage J774 by bafilomycin B1 and destruxin E.

Two microbial metabolites, bafilomycin B1 and destruxin E, have been found to inhibit significantly the oxidized low density lipoprotein (LDL)-induced accumulation of lipid droplets at 3 nM and 0.5 microM, respectively, in macrophage J774. The incorporation of [14C]oleate into cholesteryl esters in the cells incubated with oxidized LDL was inhibited to the same extent by the two compounds. Both compounds had no effect on the cell surface binding at 4 degrees C and the internalization of oxidized 125I-LDL as well as on the activity of acyl-CoA:cholesterol acyltransferase. However, when incubated with these compounds at 37 degrees C, receptors for oxidized LDL were partially trapped within the cell. In accordance with receptor accumulation, ATP-dependent acidification of endosomes and lysosomes was significantly inhibited by 50 nM bafilomycin B1 and 1 microM destruxin E, respectively. From these results it was concluded that the inhibition of ATP-dependent acidification of endosomes and lysosomes by bafilomycin B1 and destruxin E resulted in the reduction of oxidized LDL-induced synthesis of cholesteryl ester and thereby caused a reduced accumulation of lipid droplets in macrophage J774.

Animals↗

PubMed1992

Inhibition of the uptake of oxidized low-density lipoprotein in macrophage J774 by the antibiotic ikarugamycin.

The antiprotozoal antibiotic ikarugamycin was found to significantly inhibit oxidized low-density lipoprotein(LDL)-induced accumulation of cholesteryl ester in macrophage J774 at a concentration over 1-4 microM. Cholesteryl ester synthesis from [14C]oleate in the macrophages was similarly inhibited by the antibiotic, while the synthesis of triacylglycerol and polar lipids was not affected. The internalization of oxidized [125I]LDL in macrophages was reduced to 50% by 2 microM ikarugamycin, while cell-surface binding of oxidized [125I]LDL, lysosomal hydrolysis of the internalized oxidized [125I]LDL and microsomal acyl-coenzyme A:cholesterol acyltransferase was not detectably inhibited by 5 microM ikarugamycin. The results demonstrated that ikarugamycin inhibited cholesteryl ester accumulation in macrophage J774 by specifically inhibiting the uptake of oxidized LDL.

Adenosine Triphosphate↗

PubMed1992

[The effect of noise on sleep--changes in hypnograms of subjects exposed to repeated truck-passing sound].

The effect of traffic noise on sleep was evaluated in an experimental room using repeated recorded truck-passing sounds. The peak sound level was 55, 60 or 65 dB (A) with frequencies of three times per hour. The background noise of the exposure night was Leq 42 dB (A) and that of the control night was Leq 35 dB (A). The subjects were five students 23 to 24 years old. The sleep stage of each epoch with a 20-second duration was judged visually based on the criteria of Rechtschaffen & Kales and the data of the second night of noise-exposure and the control night were used. The sleep parameters used were total sleep time (TST), each sleep stage, % of sleep stage against TST, sleep efficiencies, sleep latency, REM latency, REM cycle, REM duration, waking from sleep, number of stage shifts, and subjective sleep judged by the OSA sleep inventory. A paired t test was used for the statistical analysis. TST, REM stage in minutes, and % of REM stage against TST of the exposure night were significantly decreased compared with those of the control night. Other objective and subjective parameters showed no changes during noise exposure. Dividing the all-night into halves, the amount and % of each sleep stage were compared between the exposure and control night. There was no change of sleep stage in the former half, but the % and amount of REM sleep in the latter half were significantly decreased as a result of the noise exposure. The decreases of REM sleep and % REM against TST, especially in the latter half of all-night sleep, were caused by the intermittent truck-passing sounds 20 to 30 times per night.

Adult↗

PubMed1992

Effect of the continuity and sampling rate of polygraphy data on sleep stage by a computerized scoring system--a reliability study.

The percentage of each sleep stage determined by visual judgment was compared with computerized judgment using continuous and three intermittent sampling data. Comparison of stage agreements of four types of computerized judgments with visual judgment were also conducted. Hypnograms of six healthy young male students were recorded on each of five nights. Data of each subject were compiled individually, and the six data were analyzed. Agreement rate of the sleep stage by computerized judgment using continuous (method A), one-third (method B), one-ninth (method C), and one-fifteenth (method D) data with that of visual judgment were compared. The agreement rate of visual and computerized judgment using method A showed no difference from that between visual and computerized judgment using method B. There was a significant loss of agreement between visual and computerized judgment using method C or D compared with that between visual and computerized judgment using method A. Paired t-tests were conducted for each stage percentage against total sleep time of visual judgment and those of computerized judgments using method A, B, C, or D. There were no significant changes in any sleep stage percentages between visual judgment and computerized judgments using method A, B, C, or D. From sleep stage agreement and the degree of difference from visual judgment, the acceptable limitation of the sampling period was concluded to be one-third of continuous data.

Adult↗