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Biomedical subjects

S Nitta

Publications and source records attributed to S Nitta.

At least 109 records · Page 6Linked to original sources
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↗
PubMed1994

[Endo-tracheal intubation technique in rats using a guide wire--application for trachea transplantation].

Sometimes endo-tracheal intubation on rats is needed for experiments on the chest, but usually it is difficult. A new oral intubation technique on rats was developed. Under pentobarbital anesthesia, a tracheostomy was carried out, and a smooth coated guiding wire was inserted retrogradely up to the mouth. The tube was then inserted into the trachea from mouth along the guiding wire. This technique is applied to trachea transplantation, and subsequently reduced operative mortality markedly from 54% to 2%.

Animals↗
PubMed1994

[A case of ACTH-releasing lung carcinoid tumor presenting Cushing's syndrome].

The patient was a 47-year-old female who had undergone hypophysectomy due to Cushing's syndrome when 46 years old. In April 1992, about 1 month after the operation, chest CT-scan revealed a lesion of 8 x 8 mm in size in the right upper lobe. A high value of serum ACTH was obtained from the A3b wedge blood by cardiac catheterization. She was operated on suspicion of ACTH releasing lung tumor. During the operation, it was histologically diagnosed as lung carcinoid by a frozen section of the lesion. In addition, ACTH of the blood obtained from the right superior pulmonary vein was as high as 37,300 pg/ml, but that in the right main pulmonary artery or the radial artery was 850-970 pg/ml. Right upper lobectomy with dissection of mediastinal lymph nodes was so performed. Post-operative value of serum ACTH was significantly decreased. She was in good course, and is still asymptomatic 8 months after the operation.

Adrenocorticotropic Hormone↗
PubMed1994

[A case report of primary fibrosarcoma originated in the heart invading adjacent organs ].

A rare case of cardiogenic fibrosarcoma is reported. A 66 y.o. male with dyspnea, cough and fatigue was examined. B-mode echo, MRI, and angiography disclosed a large tumor in the left atrium. A large fibrosarcoma and 2 cm of the left atrial wall around the tumor pedicle were removed. The atrial defect and right lower pulmonary vein were repaired with a patch. Four months later, the tumor recurred in the right lung, mediastinum, and left atrium. The tumor, middle and lower lobes of the right lung, and part of the left atrial wall were excised. One year after the first operation, the patient died of air way obstruction due to another recurrence of the fibrosarcoma in the left lung, esophagus, and mediastinum. Cardiogenic fibrosarcoma invading outward for the mediastinal organs is rare.

Aged↗
PubMed1994

[Eight cases of thymic carcinoma].

Eight cases of thymic carcinoma (mean age 62 years, 5 males and 3 females) were treated in our hospital from Apr. 1988 to Mar. 1993, which were 21% of thymic epithelial tumors. The histologic subtypes of thymic carcinoma were 3 squamous, 4 undifferentiated, and 1 adenocarcinoma, respectively. Computed tomography showed extrathymic metastases to the mediastinal lymph nodes in 6 cases. All cases underwent thoracotomy, and postoperative radiotherapy or chemotherapy were performed. A case of squamous cell carcinoma in stage II who underwent total resection followed by irradiation is alive and disease free 5 years after surgery. However, the remaining 7 cases died of the disease within 29 months. 8 cases of thymic carcinoma and 7 of thymoma were studied immunohistologically on the formalin-fixed and paraffin-embedded tissues. Higher positivity of EMA in thymic carcinoma was noted comparing to ordinary thymoma, suggesting that EMA is a useful parameter of potential malignancy of the thymic epithelial neoplasms.

Adenocarcinoma↗
PubMed1994

[Conservative treatment of postoperative chylothorax in a patient with chronic traumatic aneurysm of thoracic aorta].

A 66-year-old male was admitted to our hospital because of a chronic traumatic aneurysm of the thoracic aorta caused by a traffic accident 5 years earlier. Although he had been treated successfully by patch closure under extracorporeal circulation, chylothorax gradually manifested 9 days after the operation. The fact that our conservative treatment resulted in complete recovery from chylothorax, strongly suggested that progress of nutriology was a contributing factor.

Aged↗
PubMed1994

[Loss of cardiopulmonary function in lung-resection surgery and post-operative complications].

The items, mentioned as postoperative complications in lung-resection surgery in the newest reports, are much the same to those in patients undergone general surgery. Dealing with perioperative complications in lung-resection surgery, it must be taken into account that lung resection always results in, more or less, loss of cardiopulmonary function and that most perioperative complications are caused by accidental circumstances. Perioperative risk must be assessed based upon the predicted postoperative cardio-pulmonary function, but not the frequency of perioperative complications. The role of unilateral pulmonary artery occlusion test and exercise test in lung-resection surgery, and their pathophysiological implications are discussed.

Heart↗
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

Alterations in modulation of acetylcholine release following lesion of hippocampal cholinergic neurons with the neurotoxin AF64A.

Accumulation of acetylcholine (ACh) following administration of physostigmine or tetrahydroaminoacridine (THA) normally inhibits further evoked release of ACh through presynaptic muscarinic receptors. However, in cerebral cortical slices from patients with Alzheimer's disease, ACh release is enhanced by THA, an effect mediated via nicotinic receptors. In this study, the effects of THA and physostigmine were examined in hippocampal slices from rats in which cholinergic neurons were lesioned with the neurotoxin ethylcholine mustard aziridinium (AF64A). Physostigmine and THA did not reduce the evoked release of ACh in lesioned tissues as they did in controls, and THA significantly increased release. The enhancement of release by THA was blocked by the nicotinic antagonist mecamylamine, suggesting that it was mediated through nicotinic receptors. Direct stimulation of muscarinic receptors with oxotremorine significantly reduced ACh release in control tissues, but had no effect in lesioned slices, indicating that presynaptic muscarinic receptors were no longer operative. These results suggest that adaptive changes in nicotinic and muscarinic receptors occur in AF64A-treated rats which are similar to those reported in Alzheimer's disease.

Acetylcholine↗
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

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

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↗