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Biomedical subjects

T Chinzei

Publications and source records attributed to T Chinzei.

At least 19 recordsLinked to original sources
PubMed1998

Physiological control of a total artificial heart: conductance- and arterial pressure-based control.

To obtain a physiological response by a total artificial heart (TAH), while eliminating the hemodynamic abnormalities commonly observed with its use, we proposed the use of a conductance- and arterial pressure-based method (1/R control) to determine TAH cardiac output. In this study, we endeavored to make use of a variable more closely tied to central nervous system (CNS) efferents, systemic conductance, to provide the CNS with more direct control over the output of the TAH. The control equation that calculates the target cardiac output of the TAH was constructed on the basis of measurement of blood pressures and TAH flow. The 1/R control method was tested in TAH-recipient goats with an automatic method by using a microcomputer. In 1/R control animals, the typical TAH pathologies, such as mild arterial hypertension and substantial systemic venous hypertension, did not occur. Cardiac output varied according to daily activity level and exercise in a manner similar to that observed in natural heart goats. These results indicate that we have determined a control method for the TAH that avoids hemodynamic abnormalities exhibited by other TAH control systems and that exhibits physiological responses to exercise and daily activities under the conditions tested. The stability of the control and the complete lack of inappropriate excursions in cardiac output is suggestive of CNS involvement in stabilizing the system.

Animals↗
PubMed1997

Development of the undulation pump total artificial heart.

The undulation pump is a small size continuous flow displacement type blood pump that has been developed for an artificial heart. Using undulation pumps, 2 types of implantable total artificial hearts (TAHs), the undulation pump TAH (UPTAH) type 1 (UPTAH 1) and UPTAH type 2 (UPTAH 2) were developed. Both UPTAHs were designed to be small enough to implant into the chest of a goat, the experimental animal. UPTAH 1 could be reduced in size to 75 mm in diameter and 78 mm in length. The weight was 520 g. UPTAH 2 could be reduced in size to 75 mm in diameter and 80 mm in length. The weight was 650 g. UPTAH 2 could be tested in an animal experiment using an adult female goat weighing 52.3 kg. The UPTAH 2 could be implanted successfully into the goat's chest with a good fit. The goat stood after the surgery and extubation and survived for 3 h and 40 min; thus, the potential of the UPTAH for a practical implantable TAH was demonstrated.

Animals↗
PubMed1997

Use of a catecholamine sensor in the control of an artificial heart system.

An electrochemical sensor system to allow real-time measurement and feedback of catecholamine concentrations was developed for use in the control of artificial hearts. Electrochemical analyses were carried out using a carbon fiber working electrode, an Ag-AgCl reference electrode, and a potentiostat. The operating parameters of the pneumatically-driven artificial heart system were altered in accordance with the algorithm for changes in the catecholamine concentration. The minimum detectable concentrations of both adrenaline and noradrenaline in a mock circulatory system using a phosphate-buffered solution were approximately 1-2 ng/ml (10(-8) mol/L). An artificial heart control system utilizing this set-up performed satisfactorily without delay, although sensor sensitivity decreased when placed in goat plasma instead of a phosphate-buffered solution, due to the adsorption of various substances such as plasma proteins onto the electrodes. This study demonstrated the future feasibility of a feedback control system for artificial hearts using catecholamine concentrations.

Adsorption↗
PubMed1996

A percutaneously accessible pulsatile left ventricular assist device: modified assist device type 5.

To provide percutaneous access, a new circulatory assist system was developed. We call this newly developed system the modified assist device (MAD). The system is composed of a sac-type blood pump and cannula. Inflow and outflow valves are mounted in the apex and at the side wall 10 cm from the apex of the cannula, respectively. During systole, the blood is sucked from the left ventricle through the inflow valve of the cannula connected to the blood pump, and during diastole, the blood is ejected to the root of the aorta through the outflow valve. In vitro and in vivo evaluations of the pump performance were performed. The maximum flow rate of 1.9 L/min was obtained in the mock circulatory system. In our animal experiment, effective systolic unloading and diastolic augmentation were observed by activation of this system during regular sinus rhythm. In conclusion, the MAD-5 is thought to be percutaneously accessible and increases systemic and coronary flow.

Animals↗
PubMed1995

Basic study to develop the undulation pump for practical use: antithrombogenicity, hemolysis, and flow patterns inside the pump.

The undulation pump (formerly called the precessional displacement pump) is a continuous flow displacement-type blood pump that is being developed as an implantable total artificial heart. A new undulation pump was developed for chronic use and was examined with animal experiment and flow visualization studies. In the animal experiment using a left ventricular bypass in goats, severe hemolysis occurred. After driving for 12 h, thrombus formation inside the pump was found. In the flow visualization studies, the flow pattern showed that the flow inside the pump was a very complicated turbulent flow. Improvement of hemolysis and thrombus formation is important to realize implantable total artificial hearts using undulation pumps.

Animals↗
PubMed1995

New version of flow-transformed pulsatile total artificial heart with no electrical switching valve.

The flow-transformed pulsatile total artificial heart (FTPTAH) is a new pulsatile total artificial heart that consists of a single continuous flow rotary blood pump and blood flow switching valves. It can perfuse the pulmonary and the systemic circulation alternately with pulsatile flow. A new version of the FTPTAH, which consists of one undulation pump (UP), 4 jellyfish valves, and a compensatory chamber, has been proposed. The UP is a reversible continuous flow blood pump, and flow transformation is caused by switching the direction of the motor rotation so that no electrical flow switching valve is needed. A prototype model could perfuse alternately pulmonary and systemic circulation with 3.0 L/min in a mock circulation. Unoxygenated blood in the UP at the end of pulmonary circulation will be stored in the compensatory chamber by shifting a flexible membrane to the direction of the left atrium (LA); therefore, the blood is not sent to the systemic circulation.

Atrial Function↗
PubMed1995

Development of a new apparatus to observe microcirculation chronically in continuous flow blood pump research.

To observe microcirculation chronically is an important key to the successful evaluation of the continuous flow blood pump. In this study, we succeeded in developing a new apparatus by which microcirculation could be observed chronically without a microscope in a conscious animal. The apparatus utilizes a charge coupled device (CCD). A thin living tissue, such as mesentery, is put directly on a highly integrated CCD and is lit up through the tissue with a light-emitting diode (LED). The vascular nets in the tissue are projected onto the CCD like a contact photograph, which is then sent to a television screen and which can be used to analyze their motion and function. A 0.5-inch CCD having 250,000 pixels was used in this study. The cover glass of the CCD was removed, and a fiber optic plate was fixed onto the surface of the CCD for the tissue to be able to contact with the apparatus surface without clearance. The CCD as well as the LED were molded with epoxy resin for electrical insulation. The apparatus was 35 mm wide and 12 mm high with a micro stand for an LED, which can be easily implanted into an animal. The apparatus was implanted into a rabbit for 12 h. The configuration of arterioles and venules, tens of micrometers in diameter, and their motions in subcutaneous tissue could be observed.

Animals↗
PubMed1993

Possible involvement of inefficient cleavage of preprovasopressin by signal peptidase as a cause for familial central diabetes insipidus.

A transition of G to A at nucleotide position 279 in exon 1 of the vasopressin gene has been identified in patients with familial central diabetes insipidus. The mutation predicts an amino acid substitution of Thr (ACG) for Ala (GCG) at the COOH terminus of the signal peptide in preprovasopression (preproVP). Translation in vitro of wild-type and mutant mRNAs produced 19-kD preproVPs. When translated in the presence of canine pancreatic rough microsomes, wild-type preproVP was converted to a 21-kD protein, whereas the mutant mRNA produced proteins of 21 kD and 23 kD. NH2-terminal amino acid sequence analysis revealed that the 21-kD proteins from the wild-type and the mutants were proVPs generated by the proteolytic cleavage of the 19-residue signal peptide and the addition of carbohydrate. Accordingly, mutant preproVP was cleaved at the correct site after Thr-19, but the efficiency of cleavage by signal peptidase was < 25% that observed for the wild-type preproVP, resulting in the formation of a predominant glycosylated but uncleaved 23-kD product. These data suggest that inefficient processing of preproVP produced by the mutant allele is possibly involved in the pathogenesis of diabetes insipidus in the affected individuals.

Amino Acid Sequence↗
PubMed1993

Pulmonary capillary pressure measured with a pulmonary arterial double port catheter in surgical patients.

We developed a pulmonary artery (PA) double port catheter technique for reliable clinical measurements of pulmonary capillary pressure (Ppc). In seven elective surgical patients, the PA double port catheter with the second PA port 1 cm proximal to the balloon was inserted. The two PA ports, connected to identical pressure measuring systems, provided the pulmonary arterial pressures (Ppa) distal and proximal to the balloon. After general anesthesia was stabilized, the two Ppas were measured simultaneously during a PA occlusion maneuver during 10 s of apnea. The instant of occlusion was determined precisely as the time when the two Ppa traces sharply diverged. A single exponential equation was fitted to the segment of distal Ppa tracing starting 0.3 s after the instant of occlusion. Ppc was determined as the value of the exponential fit extrapolated to time 0. In six of seven patients, PA occlusion occurred consistently in the early systolic phase regardless of the timing of balloon inflation. Mean Ppa, Ppc, and pulmonary arterial wedge pressure were 16.6, 11.8, and 7.6 torr. The ratio of venous to total resistance ranged from 0.37 to 0.54 (mean:0.46). We conclude that this technique is clinically feasible and valuable in precise definition of the instant of PA occlusion. By defining PA occlusion consistently, this technique can provide reliable Ppc estimation in the clinical settings.

Catheterization, Swan-Ganz↗
PubMed1991

Effects of isoflurane and fentanyl on ischemic myocardium in dogs: assessment by end-systolic measurements.

The effect of anesthetics on ischemic myocardium to which blood was supplied by a stenotic coronary artery was investigated in dogs. The ischemia was assessed by regional wall motion (ultrasonic dimension technique) using fractional shortening (FS) [(EDL - ESL)/EDL x 100] and end-systolic pressure-segment length relationships (ESPLR). The latter is considered to be a more load-independent measure of regional myocardial function. Isoflurane and fentanyl were chosen as anesthetics of current interest. On reducing the left circumflex coronary artery (LCX) flow to approximately 50% of its resting value, a decrease in FS and a rightward shift in ESPLR were observed in myocardium perfused by the LCX. Simultaneously, increases in FS were observed in the nonischemic area perfused by the left anterior descending coronary artery (LAD), which was most likely due to the intraventricular unloading effect. No significant changes of ESPLR were observed in the area supplied by LAD. Isoflurane induced a dose-dependent decrease in FS and a rightward shift in ESPLR in the ischemic myocardial segment, whereas fentanyl caused an increase in FS and tended to shift ESPLR leftward in the same area. The results suggest that isoflurane may have deleterious effects on preexisting myocardial ischemia, whereas fentanyl may not when loading conditions are taken into consideration. Fractional shortening and ESPLR seem to provide similar information about regional myocardial function.

Anesthesia, Inhalation↗
PubMed1991

[Management of cesarean section under replacement therapy with factor VIII concentrates in a pregnant case with congenital combined deficiency of factor V and factor VIII].

The congenital combined deficiency of Factor V and Factor VIII, a rare bleeding disorder, was identified in a 25-year-old woman. She was admitted to our hospital with a complaint of genital bleeding. Her prothrombin time and activated partial thromboplastin time were prolonged. She had low levels of Factor V coagulant activity (F. V:C) 14%, and Factor VIII coagulant activity (F. VIII:C), 12%, and normal levels of von Willebrand factor antigen (vWF:Ag), ristocetin cofactor (Rcof) and Protein C antigen. Her Protein C inhibitor level was slightly low. Her Rcof, vWF:Ag and F. VIII:C were elevated following administration of 1-deamino-8-D-arginine-vasopressin (DDAVP), but her F. V:C remained unchanged. Four years later, her F. VIII:C rose to 70% during the course of her pregnancy, but her F. V:C value remained low. It was expected that the vaginal delivery would be possible at the termination of pregnancy. Premature rupture of the membranes and an anomaly of rotation appeared in the course of delivery, however, and cesarean section was accomplished without excess bleeding under replacement therapy with Factor VIII concentrates. These findings suggested that DDAVP and Factor VIII concentrates were useful for management of her delivery. However the mechanisms of the rise of plasma F. VIII:C during pregnancy in a case with congenital combined deficiency of Factor V and Factor VIII are unclear.

Adult↗
PubMed1990

The system and procedures of percutaneous intradiscal laser nucleotomy.

Since 1986, percutaneous intradiscal laser nucleotomy (PILN) has been studied in the authors' laser laboratory. The purpose of this report is to develop PILN as an alternative to chemonucleolysis and percutaneous discectomy, which are currently applied, and to establish a safe, easy, accurate and short-time therapy method for lumbar disc herniation. After laser irradiation, intradiscal pressures (IDP) decreased and the nucleus pulposus was gradually replaced with cartilaginous fibrous tissue. The evaluation of heat distribution with thermocouples and thermography was done to determine safe optimum irradiating conditions and to develop a new double-lumen needle and a bare quartz fiber. Neodymium-yttrium-aluminum-garnet (Nd-YAG) laser devices have been improved for easy and safe use, and a new tip type pressure transducer has been made for improved therapeutic results using this new method.

Animals↗
PubMed1990

[A neuron-specific enolase (NSE) positive leiomyosarcoma].

A 40-year-old woman with multiple skin tumors was admitted to our hospital on September 5, 1989. Extensive studies by means of light and electron-microscopic examination and immunohistochemical analysis revealed a neuron-specific enolase (NSE) positive leiomyosarcoma. The level of her elevated serum NSE decreased after receiving her initial chemotherapy, but after the fourth session of chemotherapy, the NSE began to elevate again and she died on December 25, 1989. NSE appears to be a useful marker for determining if the neuronal and neuroendocrine cells are normal. This rare case, however, seems to demonstrate that abnormal, nonneuronal cells like a sarcoma also open metabolic pathways to synthesize NSE.

Adult↗
PubMed1990

[B-chronic lymphocytic leukemia/prolymphocytic leukemia (CLL/PL)--a case report].

A 48-year-old male was admitted to our hospital on April 20, 1989 because of general fatigue and abdominal fullness. Physical examination showed hepatomegaly, massive splenomegaly, and systemic lymphadenopathy. Hematological findings revealed WBC 73,000/microliters, RBC 289 x 10(4)/microliters, Hb 8.0g/dl, and platelet 9.1 x 10(4)/microliters. WBC differential count demonstrated a mixture of 63% matured small lymphocytes and 32% prolymphocytoid cells. Bone marrow aspiration was unsuccessful with a dry tap. Surface marker analysis of peripheral blood lymphoid cells disclosed that they were positive for anti-HLA-DR, CD 5, CD 19, CD 20, CD 21, CD 25, Sm-IgM, Sm-IgD, and Sm-K. He was diagnosed as B-CLL/PL, and treated with VEPA with partial remission. CLL/PL which was advocated by Melo in 1986 is regarded as a distinct clinical entity intermediate between CLL and PLL in clinical and laboratory features. Our case is interesting with regard to good response to combination chemotherapy, though most cases of CLL/PL have a resistance to standard chemotherapy.

Antigens, CD↗
PubMed1989

Phasic capillary pressure determined by arterial occlusion in intact dog lung lobes.

In six open-chest dogs, electrocardiogram- (ECG) controlled pulmonary arterial occlusion was performed during the control period and during the infusions of serotonin and histamine. A temporal series of instantaneous pulmonary capillary pressure and the longitudinal distributions of vascular resistance and compliance were evaluated in the intact left lower lung lobe. In the control period, we found a significant phasic variation of pulmonary capillary pressure (Pc) with the cardiac cycle. The ratio of arterial to venous resistances (Ra/Rv) was 6:4, and the ratio of arterial to capillary compliances (Ca/Cc) was 1:11. During the infusions of serotonin and histamine, Pc showed similar phasic variations, despite significant hemodynamic changes induced by these agents. Serotonin predominantly increased Ra, whereas histamine predominantly increased Rv. The ratio of Rv to the total resistance decreased significantly from 0.42 to 0.32 during the infusion of serotonin and increased significantly to 0.62 during the infusion of histamine. The data suggest that phasic Pc determined by ECG-controlled arterial occlusion reflects the pulsatility in the pulmonary microvascular bed under control conditions and after alterations of the pulmonary vascular resistance by serotonin and histamine.

Animals↗