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S Naganuma

Publications and source records attributed to S Naganuma.

At least 55 records · Page 3Linked to original sources
PubMed1992

[Instantaneous changes in sleep stage due to the sound of a passing truck].

The instantaneous effect of the sound of a passing truck on sleep of five male students, 23 to 25 years of age, was assessed. The peak levels of noise were adjusted to 55, 60, and 65 dB (A) with intervals of 18 and 13 minutes, and a frequency of one per hour. Background noise in the experimental room was Leq 42 dB (A). The sleep stage of each epoch was visually judged based on the criteria of Rechtschaffen & Kales. Data for pre-exposure epochs of sleep stage 2 and rapid eye movement (REM) were collected and 18 epochs, including two under noise exposure, were evaluated. Three sets of polygraphic data were sampled as controls from 10 minutes after 65 dB (A) exposure to the next exposure. Compared with the control, the percentage of stage 2 to shallower stages (stage 1, waking, or movement time (MT)) was significantly increased by exposure to 55, 60, and 65 dB (A). The change lasted for one minute with exposure to 55 dB (A), and 2 to 3 minutes with 60 and 65 dB (A). A decrease in the percentage of stage 2 to deeper stages was observed at 2 to 4 minutes after exposure to 60 and 65 dB (A). The percentage of stage 2 to MT increased at 60 and 65 dB (A). The percentage of stage REM to other stages increased with the exposure to 60 or 65 dB (A) within 4 minutes. The threshold of instantaneous change of stage 2 to shallower stages due to the sound of a passing truck was at the peak level at less than 55 dB (A), and that of stage REM to other stages at 55 to 60 dB (A).

Adult↗
PubMed1992

Acaterin, a novel inhibitor of acyl-CoA: cholesterol acyltransferase produced by Pseudomonas sp. A92.

Acaterin, a novel inhibitor of acyl-CoA: cholesterol acyltransferase (ACAT), was isolated from a culture broth of Pseudomonas sp. A92 by Diaion HP-20 column chromatography, solvent extraction and reverse phase HPLC. Spectroscopic analyses of the compound yielded 3-(1-hydroxyoctyl)-5-methyl-2(5H)-furanone as the proposed structure. In the presence of oxidized low density lipoprotein, acaterin inhibited the synthesis of cholesteryl ester in macrophage J774 by 50% at a concentration of 45 microM. Acaterin also inhibited ACAT activity in the rat liver microsomes by 50% at a concentration of 120 microM. Kinetic studies suggested that inhibition of ACAT by acaterin was noncompetitive with respect to oleoyl-CoA.

Animals↗
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

Unstable amplification of the chromosomal gene for 3-hydroxy-3-methylglutaryl coenzyme A reductase in compactin-resistant CR200 cells.

CR200 cells, a compactin-resistant clone of mouse FM3A cells, overaccumulate 3-hydroxy-3-methylglutaryl coenzyme A reductase. The elevated reductase activity is not regulated normally by low-density lipoprotein, mevalonate and 25-hydroxycholesterol. The amounts of reductase protein and mRNA were elevated in CR200 cells by 40- to 60-fold, as compared to those in parental FM3A cells and the rate of reductase transcription and the number of copies of reductase gene were increased in CR200 cells by 20- to 50-fold. In the parental cells, mevalonate and 25-hydroxycholesterol suppressed reductase transcription by greater than 90%, while that in the mutant cells was suppressed by only 20-50%, suggesting a regulatory alteration in the gene transcription in CR200 cells. When CR200 cells were grown for 10-20 weeks in the absence of compactin, levels of the gene amplification were reduced from approx. 50-fold to approx. 2-fold, along with a marked decrease in reductase activity and compactin-resistance of the cells. While the gene amplification was unstable, minute chromosomes were not seen in the cells and centrifugal fractionation and in situ analysis demonstrated that the amplified reductase gene was present on 2-3 chromosomes in the pseudotetraploidal CR200 cells having approx. 78 chromosomes. From these results it was concluded that the amplified reductase gene, which is responsible for overaccumulation of reductase, is located on chromosomes but is unstable in CR200 cells.

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↗
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↗