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Biomedical subjects

F Yamamoto

Publications and source records attributed to F Yamamoto.

At least 163 records · Page 9Linked to original sources

Isoproterenol and the genesis of reperfusion-induced arrhythmias in isolated rat heart: adrenoceptor or free radical-mediated mechanisms?

In the isolated rat heart, reperfusion-induced arrhythmias were exacerbated by isoproterenol (0.01-1.0 microM). The proarrhythmic action of isoproterenol was primarily the result of a beta 1-receptor-mediated tachycardia rather than via a free radical-mediated process, since it was prevented competitively by the beta 1-receptor antagonist metoprolol, but not by the free radical scavengers mannitol, superoxide dismutase, and catalase. If heart rate was maintained by electrical pacing, the protective action of metoprolol against the isoproterenol-induced arrhythmias was lost. At high concentrations (5 and 50 microM), metoprolol alone produced a bradycardia that was probably not related to beta 1 blockade, and this resulted in some nonspecific antiarrhythmic activity. The data provide evidence that, in this model, heart rate during ischaemia is an important determinant of reperfusion-induced arrhythmias, and that free radical formation from the oxidation of high levels of exogenous isoproterenol present at the time of reperfusion does not contribute in a major way to the detrimental action of isoproterenol.

Animals↗

[The optimal oxygenation of cardioplegic solution--the buffer effect of carbon dioxide and pH control].

A series of studies was undertaken to establish the optimal oxygenation of St. Thomas' Hospital cardioplegic solution (ST). Using an isolated working rat heart model of cardiopulmonary bypass and the cardioplegic arrest the effect of oxygenation of ST were investigated in this study. The effects of oxygenated ST with various O2/CO2 mixture (100% O2, 99% O2 + 1% CO2, 98% O2 + 2% CO2, 95% O2 + 5% CO2) upon post ischemic functional recovery were compared with those of non-oxygenated ST. Under both normothermic and hypothermic conditions, the pH of the St. Thomas' gassed with 99% O2 + 1% CO2 mixture was maintained at 7.8, and this cardioplegic solution showed highest percent recovery of aortic flow. On the contrary, the pH of St. Thomas' cardioplegic solution oxygenated with 100% O2 exceed 9.0 and it showed lethal effect upon postischemic cardiac function. Thus oxygenation of NaHCO3 containing crystalloid cardioplegic solution oxygenated with 100% O2 is rather harmful and the 99% O2 + 1% CO2 gas is the crucial gas mixture for clinical and experimental use with oxygenated ST.

Animals↗

[Massive traumatic hematoma localized in the basal ganglia: treatment by CT-guided stereotactic aspiration surgery].

A case of massive traumatic hematoma of the basal ganglia which was treated successfully by CT-guided stereotactic aspiration surgery, was reported. A 6-year-old boy was admitted 2 hours after a traffic accident. He had no neurological focal signs except for disturbance of consciousness on admission. CT scan revealed a massive hematoma in the right basal ganglia. His neurological status gradually deteriorated 6 hours after the trauma and the size of the hematoma increased on serial CT scan. Then, CT-guided stereotactic aspiration surgery was performed and about 15.5 ml of hematoma clot was successfully evacuated. He made an uneventful recovery from the operation and gradually improved. The final outcome was that he showed moderate disability at 3 months after the trauma. The possible mechanism of development of hematoma in this lesion, and indication of CT-guided stereotactic aspiration surgery were also discussed.

Basal Ganglia Diseases↗

[Surgical therapy of congenital aortic valvular stenosis in neonates and infants].

The preoperative evaluation, surgical course, and early follow-up results of 5 infants less than 4 months of age who underwent aortic valvotomy for severe valvular stenosis between 1983 and 1985 were reviewed to determine the early prognosis of these neonates. Two of the 5 patients had been used respiratory support due to severe congestive heart failure and dyspnea. Emergency aortic valvotomy was performed in all during cardio-pulmonary bypass which achieve maximal relief of the stenosis without significant causing aortic insufficiency. There was a single operative death and there was one late death at 2 months after surgery who was regarded to have a extensive endocardial fibroelastosis. The other three patients have had a favorable early prognosis during mean follow-up period of 1.78 (0.4-3.8) years. They had been followed by means of two-dimensional and doppler echocardiography, which inferred that the aortic pressure gradient had been kept under 41 mmHg and which indicated that there were no LV enlargement to prove significant aortic valve insufficiency. These results indicate that early infants with severe valvular stenosis can undergo sufficient valvotomy safely and have a favorable early prognosis.

Aortic Valve↗

[Extended direct anastomosis for coarctation of the aorta and interruption of the aortic arch].

Between March, 1986 and May, 1988, extended direct anastomosis was performed for coarctation of the aorta (CoA) (5 infants) and interruption of the aortic arch (IAA) (3 infants). The aortic arch was hypoplastic in 3 patients. The incision was made in the inferior aspect of the aortic arch proximal to the origin of the carotid or brachiocephalic artery, which was then anastomosed to the descending aorta. Pulmonary artery banding was placed in 4 patients with associated complex cardiac anomalies. Aortic cross-clamp time was 19-54 minutes (mean 41 minutes). Pressure gradient between upper and lower extremity was 0-10 mmHg (mean 4 mmHg). There were no operative deaths and no neurologic complications. The peak flow velocity at the site of aortic reconstruction measured by Doppler echocardiographic study after surgery was 1.2-2.5 m/sec (mean 1.7 m/sec). This procedure has the advantages of leaving the subclavian artery intact and no aortic shelf tissue. And it can be applied in IAA or CoA with hypoplastic aortic arch.

Aorta, Thoracic↗

[Changes in lymphocyte subsets, neutrophil function and complement levels in patients with complications following open heart surgery].

In order to evaluate the immune response during and after open heart surgery, we have studied 34 patients who received open heart surgery under extracorporeal circulation. Age range of these patients were from 41 to 76 years. These patients were divided into three groups, depending upon existence of multiple organ failure (MOF), low output syndrome (LOS) and non-LOS and non-MOF diagnosed from our criteria. The following cytological and immunological study has been performed pre-operatively, immediately after and on 1, 2, 7 and 14th postoperative day; 1) the leukocyte differential cell count, 2) function test of neutrophils, 3) lymphocyte subpopulation and subsets, 4) serum level of complement fractions (C3, C4) and CH 50. By lymphocytes analysis, postoperative early reduction of OKT 3 (CD 3) and OKT 4 (CD 4) was observed in patients with poor prognosis. Patients with the postoperative high activity of NBT reduction test was developed into MOF. Complement activity (C3, C4, CH50) decreased during surgery and recovered to preoperative level in patients without LOS and MOF. However in MOF patients, these values showed lower level than that of patients without LOS and MOF. Our data suggested that lymphocytes and leukocytes tests were useful to evaluate the prognosis in open heart surgery.

Adult↗

[Coexistence of multiple metastatic brain tumors from thyroid carcinoma and cerebral aneurysms].

A 73-year-old woman was admitted with coexistence of multiple metastatic brain tumor and cerebral aneurysm. She has been operated on for a tumor of the thyroid gland 3 years before. Computed tomography (CT) scan revealed well-defined, homogeneously enhanced masses in the left frontal and right posterior temporal region. Right carotid angiography showed a tumor stain supplied by the branch of the fronto-polar artery. Left carotid angiography showed an aneurysm at the anterior communicating artery and a tumor stain supplied by the posterior temporal artery. Total removal of the bilateral tumor and aneurysmal neck clipping were performed simultaneously with bi-frontal craniotomy and right temporal craniotomy in April of 1988. Histology of tumor was papillary carcinoma. The surgical indication and treatment for patients with coexistence of multiple brain tumor and cerebral aneurysm were discussed.

Aged↗

[The effect of local injection of interferon against human malignant glioma transplanted into nude mice and the mechanism of its effect].

In order to clarify the mechanism of action of recombinant human leucocyte interferon, the effect of local injection of it to the human malignant gliomas (one oligodendroglioma, the other glioblastoma) transplanted into nude mice were evaluated. The volume of the tumors were calculated as 1/2 (short diameter [cm])2 x (long diameter[cm]). And the ratio of tumor volume (T)/original size (C) were calculated in terms of experimental day. Among the groups of control (vehicle of IFN injected), 1 million units of IFN locally injected group, 3 million units injected group, and 9 million units injected group, the effects of the treatment were statistically evaluated in terms of T/C. At the end of the experiment, each animal was injected 4 mg of BrdU intraperitoneally, and the labeling indices of the tumor tissue were measured and compared among the groups above mentioned. Local injection of IFN to the tumor was effective even at the dose of 1 million units every other day for 16 days for glioblastoma and 50 days for oligodendroglioma. The labeling index of the treated groups was significantly reduced when compared to that of control group in both tumors. And the experiment was performed to evaluate the variation of NK activity and ADCC activity of mouse spleen cells among the experimental groups. For the oligodendroglioma, NK activities were significantly increased in the 9 million units of IFN injected group when compared to those of control group. For glioblastoma, there was no definite variation of NK and ADCC activities among the groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

[External conduit repair with "valved pericardial roll"].

External conduit repair was performed in 20 patients with "valved pericardial roll (VPR)" made of own pericardium (one case) or porcine pericardium (19 cases). Intraoperative measurement of peak pressure gradients across the valve ranged from 0 to 8 mmHg (mean 1), and that from the pulmonary ventricle to the pulmonary artery ranged from 0 to 38 mmHg (mean 20). Re-evaluation of 7 patients one year after surgery shows no increase in the pressure gradient except the first case, in which VPR was made of own pericardium. In pulsed Doppler echocardiographic study, no regurgitation was found in 4 patients, mild in 6, moderate in 4, severe in 1. VPR is functioning well with longest follow up at 16 months.

Adolescent↗

[Effect of immune response during cardiopulmonary bypass on post-operative infections].

To study the effects of extracorporeal circulation on the post operative infections, the relationship between the influences of the immunologic change during cardiopulmonary bypass (CPB) and post operative change of neutrophilia was evaluated in 52 patients. These patients were divided into two groups: group A (non-infected), 19 patients whose neutrophil count increased within 15,000/microliters in peripheral blood after operation. Group B (infected), 33 patients whose neutrophil count increased 15,000/microliters or more within one week after operation. Immunoglobulins (IgG, IgA, IgM) and complement fraction (C3, C4, CH50) levels decreased significantly during CPB, but there was no significant difference between the two groups. The amount of lymphocyte subsets of helper/inducer T cell and suppressor/cytotoxic T cell showed similar change in both groups. On the contrary the amount of lymphocyte subset of Natural Killer cell showed significant increase in A group during CPB when compared with B group, suggesting immunological activation, however, in the group which showed less than 40% increase of NK cell during CPB, there was significant increase of neutrophils after operation compared with the other group which showed high increase of NK cell. These findings suggested the increased activation of the Natural Killer cell during CPB is a favorable response, especially for preventing infections after operation.

Adult↗

[A case of primary lung cancer associated with diffuse panbronchiolitis].

Pulmonary resection was performed for primary lung cancer of a 72-year-old patient which was associated with diffuse panbrochiolitis that required home oxygen therapy. The preoperative total pulmonary vascular resistance at rest was 564 dyne.sec.cm-5/m2, but thoracotomy and reduction surgery were possible by strict respiratory and circulatory control. The troublesome postoperative pulmonary phthisis was dealt with through extended control by means of total parenteral nutrition and use of the Heimlich valve.

Aged↗

[Follow-up study of coronary artery bypass grafting after Kawasaki disease--early and late postoperative evaluation].

In our hospital, 22 patients with severe coronary arterial lesion after Kawasaki disease underwent coronary artery bypass grafting (CABG) since 1982. The age of the cases at surgery ranged from 1 year to 19 years. Mean age was 8.3 years. Fifteen cases were bypassed using internal mammary artery (IMA) and 5 cases using IMA and autologous saphenous vein (SVG). Two cases were bypassed using only SVG. They have been examined until now by catheterization, by Treadmill test, and by Tl-201 myocardial imaging, around 1 month (Study 1) and around 1 year (Study 2) after surgery for the evaluation of results of CABG. One patient died from acute myocardial infarction 3 months after surgery and one patient shows return of anginal attack due to graft stenosis. Other patients are almost uneventful. In the study 1,20 (100%) IMA were patent, and 7 (88%) SVG were patent. In the study 2, 11 (92%) IMA and 6 (67%) SVG remained patent. Development of left anterior descending artery distal to IMA anastomosis was shown in 8 cases in the study 2. On the follow-up study with TI-201 myocardial imaging, disappearance or decrease of perfusion defect was seen in 7 cases (59%) in the study 1 and 9 cases (75%) in the study 2. On the Treadmill test, disappearance or improvement of ischemic change was seen in 15 cases (88%) in the study 1 and 10 cases (84%) in the study 2. These results suggest that IMA is more preferable for than SVG for young children who has an indication of CABG after Kawasaki disease.

Adolescent↗

[Evaluation of the contractile state of the left ventricle before and after aortic valve replacement from end-systolic stress-volume relations in patients with chronic aortic regurgitation].

Before and one month after aortic valve replacement, the contractile state of the left ventricles in 10 patients with chronic aortic regurgitation were studied. The slope and intercept of the end-systolic stress-volume relationship (ESSVR) determined by M-mode echocardiography during intravenous infusion of Nitroprusside were used as an index of myocardial contractility. We found that the end-systolic wall stress-volume relationship from more than four points of pressure and dimension data have shown the linear relation for each subject with linear coefficients ranging from 0.848-0.997. There was no significant change in the slope of ESSVR between the pre- and early postoperative studies (1.66 +/- 0.37 to 1.92 +/- 1.02; p greater than 0.05), however, the intercept decreased significantly (44.7 +/- 32.4 to 29.4 +/- 28.0; p less than 0.01), which meant the leftward shift of the line of ESSVR and may imply the improvement of myocardial contractility. On the contrary, the fractional shortening decreased significantly (25.6 +/- 8.5 to 18.9 +/- 8.8%; p less than 0.01), reflecting marked reduction in preload or left ventricular end-diastolic volume (7.52 +/- 1.07 to 6.04 +/- 1.38; p less than 0.01). The change in the slope of the liner of ESSVR demonstrated that myocardial contractility might not be depressed at this time but rather improving.

Adult↗

[Spinal injury in children].

We reported five cases of children with spinal injuries. Spinal injuries are rare in children, and most common from the occiput to C3 in children younger than 8 years. In our cases, two younger children had upper cervical lesions and two older children had lower lesions. These differences result from anatomical characteristics, such as special histological architecture of the growth zones in younger children. One patient had a delayed onset paraplegia without radiographic abnormality. This phenomenon seems to be one of the characteristics of the spinal injuries in children. Because of this, all children with head or neck injuries should be fully investigated. A nine-month-old child who suffered from a fracture of the odontoid process with atlantoaxial dislocation was treated by immobilization only, and the result was good. Generally, fracture of the odontoid process in young children can be treated by proper immobilization. One patient with fracture dislocation of the cervical spine died as a result of cord injury. So immediate surgical decompression is mandatory for patients with evidence of cord compression.

Adolescent↗