Biomedical subjects

T Shimono

Publications and source records attributed to T Shimono.

At least 73 records · Page 4Linked to original sources

PubMed1994

Reticuloendothelial function following cardiopulmonary bypass: laboratory and electron microscopy findings.

Several studies on the effects of cardiopulmonary bypass (CPB) on the reticuloendothelial system (RES) function have been performed previously, but different results have been reported. This study was carried out to determine the effect of CPB on RES function in a canine model simulating clinical CPB. Nine dogs undergoing surgery with CPB were compared with an identical number of dogs subjected to thoracotomy without CPB. A lipid emulsion test was performed in all dogs before and after the surgical procedure to measure RES phagocytic index, i.e., phagocytic function. Kupffer cell iron uptake under conditions of iron loading following CPB was examined histologically, and any ultrastructural changes in the Kupffer cells were observed by electron microscopy. In both groups, the RES phagocytic index showed a significant decline after surgery. However, a comparison of the two groups revealed that there was a significantly greater decrease in the CPB group (P < 0.05). Moreover, histologic evidence of iron uptake in Kupffer cells was strongly suppressed in the CPB group. Electron microscopy of the Kupffer cells showed that the number of phagosomes, especially deformed erythrocytes, increased after CPB. These findings suggest that RES function is significantly impaired following CPB, and an increase in the amount of material, especially deformed erythrocytes, to be processed by the RES is responsible, in part, for the depressed RES phagocytic function. The prevention of hemolysis during CPB may preserve the RES function following CPB.

Animals↗

PubMed1994

Is it true that cardiac operations with cardiopulmonary bypass impair the reticuloendothelial system?

Reticuloendothelial system (RES) function after cardiac operations is a controversial issue. Sequential changes in plasma fibronectin levels and RES phagocytic function were studied after a cardiac operation and a lung operation (control). In the cardiac operation group, the plasma fibronectin level decreased until the third postoperative day and increased thereafter. Reticuloendothelial system phagocytic function remained unchanged on the third postoperative day and then it increased. However, in the control group it increased significantly after operation. In the past, investigators have demonstrated a decline in plasma fibronectin levels following cardiac operation and have assumed that RES function was impaired. However, this sequential study showed that phagocytic function was not impaired, but its enhanced phase was delayed. Moreover, our previous morphologic studies demonstrated that RES function was potentially activated after cardiopulmonary bypass. It appears that the delay of the enhanced phase is caused by the overloading of substances which must be processed by the RES during cardiopulmonary bypass. Thus, we conclude that cardiac operation produces hyperactive, yet oversaturated RES function. There is no impairment of RES function after cardiac operations.

Adult↗

PubMed1994

Metabolic and energetic aspects of the growth response of Streptococcus rattus to environmental acidification in anaerobic continuous culture.

Streptococcus rattus, a serotype b strain of mutans streptococci, was grown in an anaerobic glucose-limited chemostat. The molar growth yield of glucose [Yglucose, g dry wt (mol glucose)-1] together with the maximum growth yields (Ymax) and maintenance coefficients for glucose utilization and calculated ATP generation were estimated as a function of pH. When the pH was lowered from 7.0 to 5.0, Yglucose decreased, with a concomitant gradual change in the composition of the end product from a mixture of formate, acetate and ethanol to one mostly of lactate. Whereas the Ymax for glucose decreased without any change in the Ymax for ATP on acidification, both of the maintenance coefficients markedly increased. Kinetic and immunochemical examinations indicated the presence of an F1F0-type proton-translocating ATPase in the membrane fraction prepared from bacterial cells grown under acidic conditions; no detectable level of the enzyme was found in cells grown at neutral pH. However, when incubated with glucose under non-growing conditions, these acid-adapted and unadapted cells showed an insignificant difference in the ability to maintain the intracellular pH alkaline relative to the acidic environments. These results suggest that the organism responds and adapts to environmental acidification by sacrificing some energy cost in terms of both the efficiency of glucose utilization to generate ATP and the extra maintenance required to continue biomass production as efficiently as under neutral pH.

Adenosine Triphosphate↗

PubMed1994

An ultimate, compact, seal-less centrifugal ventricular assist device: Baylor C-Gyro pump.

We have developed a compact, seal-less, all-purpose centrifugal pump, the Baylor C-Gyro pump, which is intended as a long-term ventricular assist device (VAD) as well as a cardiopulmonary bypass pump. In attaining this goal, we began with eliminating the shaft seals by adopting a pivot bearing system at the impeller shaft. In addition, a ring magnet encased in the bottom of the impeller was coupled magnetically to a driver magnet placed outside the pump housing (C1 Prototype). This first model yielded satisfactory performance in vitro with a flow rate of 8 L/min against 250 mm Hg at 2,400 rpm, and an index of hemolysis (IH) of 0.0083 g/100 L using bovine blood. In the second model, the C1 Eccentric Inlet Port Model, the inlet bearing support bar in the prototype were eliminated without reducing the prototype's performance. These designs for antithrombogenicity are being tested by the first in vivo experiment, which has lasted for more than 2 weeks.

Animals↗

PubMed1994

Successful thermal management of a totally implantable ventricular assist system.

Thermal management of the implantable ventricular assist system (VAS) is important not only from the pathophysiological point of view but also from the standpoint of system endurance. The heat distribution within the Baylor VAS was measured using different motor housing materials and environmental conditions. The temperature of the circulating water in the mock loop was set at 37 degrees and 42 degrees C. A polycarbonate motor housing was not a suitable material because of the high temperature development in the actuation system. An anodized aluminum housing demonstrated excellent heat conductivity. The surface temperature of this motor housing was 41.6 degrees C when immersed in circulating water at 42 degrees C. Heat conduction from the motor to the circulating blood revealed an effective thermal path. In the worst case, the heat flux of the motor to the circulating blood revealed an effective thermal path. In the worst case, the heat flux of the motor housing was calculated to be less than 0.062 W/cm2--an acceptable level for the surrounding tissues.

Equipment Design↗

PubMed1994

In vitro and in vivo validation tests for total artificial heart.

Properly planned in vitro and in vivo studies are mandatory to validate blood pump performance. However, standard procedures for in vitro and in vivo tests of total artificial heart (TAH) performance still do not exist. At Baylor College of Medicine, standard tests procedures for performance validation of the totally implantable TAH have been established. In this paper, these in vitro tests protocols (performance mapping tests, accelerated endurance test, hemolysis test, flow visualization tests, etc.) are described as well as in vivo test procedures (TAH implantation procedure, including surgical technique, postoperative management and tests, etc.). In addition, pathological protocols are presented. In our experience, these procedures are very simple, easy to perform, and inexpensive. These protocols are proposed as standard in vitro and in vivo tests for a TAH.

Animals↗

PubMed1994

Oversaturation status of reticuloendothelial system following cardiopulmonary bypass.

In the past, it was generally believed that the phagocytic function of the reticuloendothelial system (RES) was depressed after cardiopulmonary bypass (CPB), but several investigators reported differing results. Therefore, this study was performed to determine the effect of CPB on RES function, experimentally and clinically. Six dogs undergoing CPB (CPB group) were compared with an identical number of dogs subjected to thoracotomy without CPB (control group). A lipid emulsion test was performed in all dogs before and after the surgical procedure to measure RES phagocytic function. Any ultrastructural changes in Kupffer cells were observed by electron microscopy. In both groups, the RES phagocytic index showed a significant decline after surgery. However, comparison of the 2 groups revealed that there was a significantly greater decrease in the CPB group (p < 0.05). Electron microscopy of the Kupffer cells showed that the number of phagosomes, especially those containing deformed erythrocytes, increased after CPB. Twenty patients undergoing cardiac surgery requiring CPB (Group A) and 8 patients undergoing pulmonary resection (Group B) were studied. RES phagocytic function was determined 3 days prior to surgery and 3 days postoperatively using the lipid emulsion test. No significant difference was observed in the preoperative phagocytic indices between the 2 groups. The phagocytic function remained almost unchanged in Group A on the third postoperative day, compared with the preoperative value, but it increased significantly in Group B on the third postoperative day, compared with the preoperative value. The intergroup difference was significant on the third postoperative day (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1994

Development and evaluation of antithrombogenic centrifugal pump: the Baylor C-Gyro Pump Eccentric Inlet Port Model.

The Baylor C-Gyro Pump Eccentric Inlet Port Models (C1E) have been developed aiming for a long-term centrifugal ventricular assist device (VAD) as well as a cardiopulmonary bypass pump. The eccentric inlet port models are characterized by their unique inlet port and secondary impeller vanes. An inlet female pivot bearing, which was fixed to a supporting bar in the prototype model, is directly embedded into the ceiling of the pump casing. An inlet port is then placed off-center to avoid the bearing area, and it is angled between 0 to 90 degrees from the upright position. In addition, small secondary vanes were incorporated into the impeller bottom to accelerate the washout flow behind the impeller. These features attained design objectives proposed for higher antithrombogenicity: a seal-less pump chamber, no stationary parts in the blood path, and acceleration of the secondary flow behind the impeller. The first in vivo experiment using C1E pumps showed excellent antithrombogenicity for up to 18 days when the experiment ceased due to severe infection in the calf.

Animals↗

PubMed1994

Surgical treatment of primary lung cancer in patients less than 40 years of age.

PURPOSE AND METHODS: The major purpose of this study was to determine whether the survival rate in young lung cancer patients after surgical treatment differs from that in older patients. An analysis was performed for all patients with bronchogenic carcinoma who underwent surgery at Mie University Hospital from 1965 to 1990. RESULTS: Of 803 patients, 24 (2.99%) were 33 to 39 years old. At the time of surgery, the disease was diagnosed as stage I in seven patients (29%), stage II in four (17%), stage IIIa in seven (29%), stage IIIb in two (8%), and stage IV in four (17%), while 46.3% of the patients older than 40 years of age had either stage IIIa, IIIb, or IV disease. All of the 24 patients less than 40 years of age underwent thoracotomy: curative resection in 14 cases, palliative resection in sex, and probe-thoracotomy in four. The 5-year survival rate for all stages of disease was 31.4% in these 24 patients, and 41.9% in 603 patients greater than 40 years of age. The 5-year survival rate for stage I disease was 35.7% in the seven younger patients and 78.0% in the 207 older patients; for stage II, it was 25.5% in the four younger patients and 40.6% in the 98 older patients; for stage III, it was 33.3% in the nine younger patients and 15.6% in the 250 older patients; and for stage IV, it was 25% in the four younger patients and 6.6% in the 48 older patients. There were no significant differences in survival rate between the two age groups for all patients or for those with each stage of disease. CONCLUSION: Although younger patients tended to have more advanced disease, long-term survival in these patients did not differ from that of older patients.

Adult↗

PubMed1994

New surgical method of chordal replacement for mitral valve incompetence with echocardiographic guidance. An experimental study.

Chordal replacement with expanded polytetrafluorethylene suture has become a procedure of choice for repairing anterior leaflet prolapse among certain surgeons. However, most surgeons believe that the chordal replacement is too complicated and not reproducible. This report introduces a new method of chordal replacement using intraoperative epicardial and transesophageal echocardiography. Three dogs underwent the following procedures. One major marginal chorda of an anterior mitral leaflet was resected during cardiopulmonary bypass. A specially designed 3-0 polytetrafluoroethylene suture, having straight needles, was attached to the anterior leaflet by a mattress suture. Then the needles were brought from the root of the anterior papillary muscle to the outside of the left ventricle. After the bypass flow was reduced, both ends of the polytetrafluoroethylene suture were pulled under echocardiographic guidance until valve competence was achieved. At that point, the suture was temporarily tied. When cardiopulmonary bypass was discontinued, competence was again confirmed and the suture was tied permanently. When the procedures were completed, echocardiography showed trivial regurgitation and good pliability of the anterior leaflets in all animals. Left atrial pressures were sufficiently decreased. It appears that this new technique is reproducible for all surgeons because the optimal length of polytetrafluoroethylene chordae is determined with the valve functioning.

Animals↗

PubMed1993

Clinical experience using the Bio-pump for extracorporeal circulation during open-heart surgery.

The Bio-pump is still being used in a wide range of clinical applications such as open-heart surgery, left-heart bypass, extracorporeal membrane oxygenation, and supplementary circulation. Clinical application of the Bio-pump for extracorporeal circulation in 21 patients undergoing open-heart surgery was compared with application of the roller pump in terms of their effects on hemolysis, platelet function, and renal function. Although the amount of hemolysis was not significantly different between the Bio-pump group and the roller-pump group, platelet function was slightly better maintained in the Bio-pump group as judged by the levels of platelet factor 4, beta-thromboglobulin, and 6-keto-prostaglandin F1 alpha/thromboxane B2. There was no difference between the two pumps in terms of their effects on renal function. The above findings lead us to conclude that there is a slight advantage to use of the Bio-pump in clinical settings.

Blood Platelets↗

PubMed1993

[Selective cerebral perfusion and pharmacological cerebral protection in the patients with aortic arch aneurysm].

We have developed the protocol for selective cerebral perfusion (SCP) and pharmacological cerebral protection, and used it successfully in cases of aortic arch aneurysm. The subjects of the present study were 34 patients (28 males, 6 females) whose aortic arch aneurysm were surgically treated. Preoperative brain CT and brain scintigram showed high incidence of brain ischemia. However only 4 patients experienced a neurological episode. We conclude that our SCP technique and pharmacological cerebral protection are useful component to surgery of the aortic arch.

Adult↗

PubMed1992

[Left atrial myxomas: clinical characteristics, evaluation and considerations in classifying tumors].

Eleven patients underwent surgical excision for left atrial myxomas. Clinical symptoms, coronary angiographic findings and operative procedures were evaluated. Myxomas were classified into two types based on macroscopical findings, and clinical characteristics of these two types were analyzed. Seven cases (64%) classified as "lobular-type myxomas" were seen as lobulated, gelatinous and fragile. Four cases (36%) were classified as "round-type myxomas" were round and elastic soft. Primary symptoms included dyspnea on exertion in five cases (45%) and neurological disturbances in six cases (55%). Brain emboli were found in four patients by CT scan, and were classified as lobular-type myxomas. These eleven myxomas successfully removed in all cases. Four of these myxomas, which were pedunculated with fine fibrous stalks, were shaved along the base at the atrial septum or free wall. Others were excised completely along with a portion of the adjacent septum. Microscopic examination of the operative specimens revealed that two lobular-type myxomas with broad-based attachment to left atrial septum had invaded the atrial septum. All patients are doing well and have had no signs of myxoma recurrence at postoperative periods ranging from 10 months to 12 years (mean follow-up 5.3 years). Seven patients underwent selective coronary angiography due to a diagnosis of a coronary artery disease. All coronary angiograms were normal in all cases. In five (71%) of these seven, abnormally dilated atrial branches were seen as supplying the tumor. In two cases with round-type myxomas, neovascularity was evident and was made up of clusters of tortuous vessels with tumor blush.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1992

[Reconstructive surgery for mitral regurgitation caused by degenerative disease--indications for expansion and early clinical outcomes].

Between January 1983 and June 1990, there were 48 patients who underwent surgery for mitral regurgitation due to degenerative diseases. Among these, 20 patients received mitral valve repair. Overall operative mortality was 5% for patients who underwent valve repair, and 7.1% for those who underwent valve replacement. We standardized a maneuver for valve repair in August 1988 in an attempt to expand its indications. There were 35 patients who underwent surgery prior to that date (group 1), and 13 patients after that date (group 2). There were nine patients (25.7%) in group 1 and 2 patients (84.6%) in group 2 who underwent valve repair. Among these, one patient (11%) in group 1 died within 30 days after the operation, but there were no surgical deaths for any patients in group 2. In addition, one patient (11%) in group 1 and one (9%) in group 2 required another operation for valve replacement. Doppler echocardiographic studies performed postoperatively in 18 patients who had undergone valve repair showed that 13 (72.2%) had no regurgitation, 4 (22.2%) had trivial regurgitation, and 1 (5.6%) had mild regurgitation. Postoperative valve area as determined by continuous-wave Doppler echocardiography was 3.7 +/- 1.1 cm2 (mean +/- SD) for patients who had undergone reconstruction and 3.1 +/- 0.7 cm2 for those who had undergone replacement.

Adolescent↗

PubMed1992

[Clinical evaluation of treatment for prosthetic valve endocarditis and analysis of factors affecting outcome of surgical therapy].

We analyzed the outcome for 18 patients with prosthetic valve endocarditis (PVE) treated between 1965 and 1990, 17 of whom had undergone valve replacement with mechanical prosthetic valves and one of whom had a bioprosthesis. Two patients developed infection within 60 days after surgery, and 16 thereafter. Fifteen patients received combined medical and surgical therapy and three medical therapy. In 14 patients, surgery had been performed during active infection. Mortality rate of those who had received combined medical and surgical therapy was 27%, and that of those who had received medical therapy was 67%. At operation, para-annular abscess was around the mitral prosthesis was found in three patients and around the aortic prosthesis in eight. Seven patients required reoperation for postoperative paravalvular leakage, in six, para-annular abscess had been found at the operation for PVE, and in one para-annular abscess had been noted. One patient who had undergone reoperation had developed reinfection after the first surgery and died due to multiple organ failure after the second operation (Danielson's translocation technique). In one patient who had complete loss of supporting tissue because of severe para-annular abscess, we had performed aortic valve replacement by implanting the aortic valve prosthesis into the left ventricle with Dacron felt-supported sutures placed in the mitral annulus and the muscles of the left ventricular outflow tract. This patient showed no postoperative infection or no paravalvular leakage.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1992

Dental fear in Japan: Okayama Prefecture school study of adolescents and adults.

A total of 3,041 students and staff in middle school in Okayama Prefecture, Japan, were surveyed regarding dental fear. Over 88% reported fear, with 42.1% classified as having high fear. Almost 70% reported acquiring dental fear prior to junior high school. A majority reported being hurt at the last appointment. Delay of dental work was also reported for over 50% of the sample. Coping, pattern of physiological upset, nondental fears, and sex and age differences were also reported. Results suggest intervention is needed to address the major dental public health problems associated with dental fear.

Adolescent↗

PubMed1991

[Mitral prosthetic valve endocarditis diagnosed by transesophageal echocardiography--a surgical case report].

The patient was a 39-year-old female who had undergone mitral valve replacement 2 years previously. Staphylococcus epidermidis was detected on blood culture. Transesophageal echocardiography revealed vegetation attached to the left atrial site of the mitral prosthesis, whereas precordial echocardiography did not reveal any abnormal echo structure. The patient was performed an emergency operation, during which the echocardiographic finding was confirmed. We conclude that performance of transesophageal echocardiography is useful when clinical features suggest prosthetic valve endocarditis.

Adolescent↗

PubMed1990

[Effects of oxygen on growth of Streptococcus mutans].

Effects of oxygen on growth of Streptococcus mutans Ingbritt (serotype c) were examined. The strain could be passaged under aerobic conditions at 37 degrees C in a peptone/yeast extract medium containing 0.2% glucose. Although the growth rate was slightly retarded under aerobic conditions (the doubling time, 60 min; 45 min under anaerobic conditions), the increment of cellular dry weight change was 35 g per mole of glucose under both conditions. To investigate such aerotolerance in growth as indicated by these results, oxygen metabolism was compared between aerobically and anaerobically grown cells. No difference was observed in the apparent rate of superoxide production or superoxide dismutation. However, aerobically grown cells showed a higher activity of hydrogen peroxide reduction with glucose as substrate and accumulated a lower level of hydrogen peroxide when incubated with glucose under aerobic conditions. In addition, hydrogen peroxide added to the medium was less inhibitory to anaerobic growth when aerobic cells were used as the inoculum. These results indicate that aerotolerance of S. mutans Ingbritt can be ascribed at least in part to its hydrogen peroxide reducing activity which is elevated under aerobic conditions.

Hydrogen Peroxide↗