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Biomedical subjects

M Yamamuro

Publications and source records attributed to M Yamamuro.

At least 37 records · Page 2Linked to original sources
PubMed1998

Three-dimensional anisotropy contrast (3DAC) magnetic resonance imaging of the human brain: application to assess Wallerian degeneration.

Three-dimensional anisotropy contrast (3DAC) magnetic resonance imaging is a new algorithm for the treatment of apparent diffusion tensor using the three primary colors. To determine if 3DAC has a clinical application for human brain, six normal volunteers and twenty patients with supratentorial cerebrovascular accidents were examined using clinical magnetic resonance imaging (MRI), and the changes in the 3DAC images associated with Wallerian degeneration of the pyramidal tract were evaluated. The 3DAC images exhibited impressive anatomical resolution. In all chronic stage patients with hemiparesis, the colors in the pyramidal tract were faded. Patients examined during the acute stage who later recovered from hemiparesis had no visible changes of the 3DAC image, whereas patients who recovered poorly showed distinct color fading in the pyramidal tract within 14 days following stroke. In conclusion, very fine anatomical structures are visible on 3DAC images, and it can be used as a diagnostic tool for the human brain.

Aged↗
PubMed1997

Incidence and clinical significance of linear defects ascribed to interrenuncular septa on 99Tcm-DMSA SPET.

99Tcm-dimercaptosuccinic acid (99Tcm-DMSA) planar and single photon emission tomographic images from 100 children were reviewed to analyse whether linear defects corresponding to anatomical characteristics of interrenuncular septum (IRS) could be seen. Thirty sites in 30 kidneys (20 right, 10 left) from 27 patients were determined as showing IRS. They were seen less frequently in patients less than 7 years of age. The prevalence of IRS in the patients with vesico-ureteric reflux (VUR) was not significantly different from that in the patients without VUR. The interrenuncular septum was never seen on planar images and was most clearly demonstrated on conventional coronal tomographic images. The linear defects ascribed to IRS on 99Tcm-DMSA scintigrams were of a similar incidence to that reported previously. However, IRS is still an unestablished structure, and there is no evidence that these linear defects actually correspond to the structure described as the interrenuncular septum.

Child↗
PubMed1997

[1H and 31P-magnetic resonance spectroscopy of cerebral infarction in rats].

Magnetic resonance spectroscopy (MRS) allows the noninvasive study of metabolism in vivo. In order to further understand the time course of biochemical changes during cerebral infarction, we performed the MRS study with pathological analysis. The left middle cerebral artery (MCA) was occluded in spontaneously hypertensive male rats (SHR) by the method of Tamura et al. The spectra were obtained from the infarcted hemisphere by placing the surface coils over the left side of the calvarium. 31P and 1H-MRS were performed at 3 hours, 24 hours and 7 days after MCA occlusion. Ischemic lesions caused by the left MCA occlusion extended into the parietal lobe and caudate putamen. After 3 hours of ischemia, vacuolated neurophils and shrunken neurons were observed. At 24 hours, these changes were severe. After 7 days, infiltration of monocytes and capillary hyperplasia were seen, and neurons had disappeared. At the acute stage of ischemia the phosphocreatine/inorganic phosphate (PCr/Pi) peak ratio decreased. After 7 days of ischemia, these changes became obscure. The intracellular pH (pHi) decreased after 3 hours of ischemia and recovered almost to the control level at 24 hours post ischemia. Alkalosis was apparent 7 days after ischemia. This alkalosis might be due to increased permeability of the deteriorated blood brain barrier. Although the lactate level was high 24 hours post ischemia, the pHi was almost normal. The N-acetylaspartate/creatine ratio decreased significantly from the acute stage of stroke. This decrease correlated with pathological changes. The correlation of the magnetic resonance spectra with the histological results may opens aspects for monitoring stroke therapy and a new approach to tissue characterization.

Animals↗
PubMed1995

Changes in serum myosin light chain I following aortocoronary bypass operations.

The changes in myosin light chain I (MLC I) following aortocoronary bypass were studied in 31 patients and the curves of these changes were classified into three different patterns. A peak level of 14.7 +/- 1.54 ng/ml was seen in seven patients on postoperative day (POD) 2 which decreased suddenly to less than twice the normal value by POD 7 (group 1). Another 19 patients showed a peak level of 20.7 +/- 16.5 ng/ml on POD 5, which decreased slowly and was still high even by POD 7 (group 2). The remaining five patients developed only a slight increase in the MLC I level after the operation, with a peak value of 5.5 +/- 0.8 ng/ml (group 3). Creatine kinase myocardial band and glutamic oxaloacetic transaminase also remained low in this group. No correlation existed between the peak value of MLC I and the aortic cross-clamping time, or between the peak value of MLC I and the cardiopulmonary bypass time. Furthermore, the difference in cardiac output before and after the operation did not significantly differ among the three groups. These findings indicate that the measurement of MLC I is useful for diagnosing perioperative myocardial damage and may also be useful in the study of myocardial protection.

Adult↗
PubMed1994

[Determinants of homologous blood utilization in addition to autologous blood transfusion--a multivariate study].

Since April 1989, we have been using autologous blood donation in order to avoid homologous blood transfusion as much as possible. To determine the factors which influence the necessity for homologous blood transfusion as well as autologous blood donation. Of them 77.6% (group 1) required autologous blood only, but others needed homologous blood transfusion as well as autologous blood. Using an invert analysis, preoperative factors that showed significant differences were age, body weight, number of autologous blood donations, amount of donated autologous blood, preoperative Hb and Ht. Among operative factors, aortic cross clamping time, cardiopulmonary bypass time, amount of concentrated blood from CPB circuit, amount of transfused autologous blood and amount of drainage demonstrated significant differences between groups. Univariately significant factors were studied by multivariate discriminant analysis. Total amount of drainage proved to be the best contributor of non-homologous blood transfusion surgery, followed by preoperative Hb, body weight, amount of concentrated blood from CPB circuit and amount of donated autologous blood in order of contribution Understanding these factors, homologous blood transfusion requirement may be greatly reduced. This is thought to be the largest series of autologous blood donation in Japan.

Analysis of Variance↗
PubMed1993

[Immunocytochemical and ultrastructural study of saphenous vein, internal thoracic artery, and right gastroepiploic artery in coronary artery bypass grafting].

The arterial conduits such as internal thoracic artery (ITA) and right gastroepiploic artery (GEA) are widely used in coronary artery bypass surgery because of their resistance to atherosclerosis. In this study, immunophenotypes of smooth muscle cells (SMCs) in intima and media of ITA, GEA and saphenous vein (SV) were studied using monoclonal antibodies specific to cytoskeletal proteins; actin (A), vimentin (V) and desmin (V). In addition, the ultrastructures of endothelium of these vessels were examined. The most SMCs in intima and media of ITA and GEA were found positive for (A) and (V) but negative for (D). In contrast, the majority of SMCs both in intima and media of SV were found positive for (A), (V) and (D). The ultrastructure of endothelium of ITA and GEA showed the deeper penetration of cytoplasmic process than SV, which might anchor the endothelium. We suggest the morphological difference of endothelium and phenotypic diversity of SMCs between arterial and venous grafts may account for the different susceptibility to atherosclerotic changes in coronary bypass grafting.

Arteries↗
PubMed1991

Study on the erythrocytes from myotonic dystrophy with multi-nuclear NMR.

We have studied the water permeability through membranes, the function of the Na pump, and glucose metabolism of erythrocytes of patients with myotonic muscular dystrophy (MyD) using 1H--, 23Na, and 13C-NMR techniques. A significant decrease in water permeability was recognized in the MyD erythrocyte membrane, and impaired Na pumping was suspected to be correlated with the former biochemical abnormalities in band III protein of MyD erythrocyte membrane. Significant acceleration of glycolysis in the erythrocyte for the first 160 minutes was also recognized in MyD; however, the production of lactate showed no difference between MyD and controls. The increased glucose uptake in MyD may be compensatory to the diminished pumping mechanism, but further information, such as inorganic phosphate permeability and the activity of the rate-limiting enzyme of erythrocyte glycolysis, is needed.

Adolescent↗
PubMed1990

Radionuclide assessment of left ventricular function during dobutamine infusion in patients with coronary artery disease: comparison with ergometer exercise.

The effects of dobutamine on left ventricular function were assessed employing radionuclide ventriculography (RNV) in 7 normal subjects (Group 1) and 21 patients with coronary artery disease (Group 2). After routine bicycle ergometer exercise RNV, dobutamine infusion was started at 5 micrograms/kg/min and the dosage was increased by 5 micrograms/kg/min every 4 minutes to a total of 15 micrograms/kg/min. In Group 1, left ventricular ejection fraction (LVEF) increased by both ergometer exercise and dobutamine infusion. In Group 2, LVEF did not increase during exercise, but increased during dobutamine infusion without evidence of significant myocardial ischemia. Only 2 patients in Group 2 had new regional wall motion abnormality. Left ventricular end-diastolic volume (LVEDV) in Group 2 increased from 191 +/- 19 to 210 +/- 18 ml during ergometer exercise, but decreased from 193 +/- 18 to 153 +/- 19 ml during dobutamine infusion. Short-term low-dose infusion of dobutamine may be used in patients without evidence of significant myocardial ischemia, but probably cannot be substituted for exercise testing in patients with mild to moderate coronary artery disease.

Coronary Disease↗
PubMed1990

Influence of age on left ventricular performance during exercise in normal Japanese subject: assessment by radionuclide ventriculography.

To assess the effects of age on left ventricular performance, multistage supine ergometer exercise radionuclide ventriculography (RNV) was performed in 92 normal subjects. The subjects ranged in age from 24 to 86 years and were free of cardiopulmonary disease and diabetes. Age-related changes in exercise duration, left ventricular end-diastolic volume (LVEDV), left ventricular end-systolic volume (LVESV), cardiac output (CO) left ventricular ejection fraction (LVEF), left ventricular dv/dt, systolic and diastolic time indexes of dv/dt, and peak systolic pressure/left ventricular end-systolic volume (PSP/LVESV) were analyzed at rest and during the peak exercise stage. Age-related decrease in LVEDV and peak diastolic dv/dt were significant at rest. The time indexes of ECG R to peak systolic dv/dt and time of end-systole to peak diastolic dv/dt also were prolonged with age. Both maximum heart rate and exercise duration were shown to decline with age. No age-related difference was observed in LVESV, LVEF or PSP/LVESV either at rest or during exercise. However, the change of LVEF and LVESV during exercise was less in subjects aged 60 or more. These results indicate decreased left ventricular function during exercise in elderly subjects.

Adult↗
PubMed1989

Reversal of rest asynergy during exercise in patients with coronary artery disease.

The diagnosis of ischemic heart disease by radionuclide ventriculography (RNV) is performed on the basis of an abnormal response of the left ventricular ejection fraction and the occurrence, or aggravation, of regional wall motion abnormality during exercise. However, the abnormal wall motion observed by RNV at rest is improved in some patients with coronary artery disease during exercise. We examined the clinical features of such patients who showed a paradoxical response of regional wall motion. The left ventricle was divided into 4 segments: anteroseptal, apical, inferior and posterolateral. The degree of wall motion of each segment was classified into 5 grades and scored according to a 5 point system: 4 = normokinesis, 3 = hypokinesis, 2 = severe hypokinesis, 1 = akinesis and 0 = dyskinesis. The wall motion score (WMS) was calculated as the sum of each segment score. If the WMS increased by 2 points or more during exercise, the case was defined as having shown significant improvement of wall motion. Improvement in WMS was found in 26 (12%) of 209 serial patients who underwent exercise RNV, exercise thallium myocardial scintigraphy and coronary angiography. Clinically, half of these patients had a variant form of angina pectoris. With respect to coronary lesions in the segments with reversible asynergy, 12 patients had 0 vessel disease, 8 had lesions with stenosis of less than 75% and 3 showed an adequate collateral circulation. Redistribution found on the exercise thallium myocardial scintigram at the same sites of improved wall motion was identified in only 1 patient. An analysis of patients with paradoxical improvement of wall motion during exercise suggests the involvement of coronary spasm, an improvement of coronary flow reserve, such as could be produced by regression or recanalization of the main lesions, or establishment of significant collateral circulation.

Coronary Angiography↗
PubMed1987

Incidence and clinical course of right ventricular infarction: assessment with radionuclide ventriculography.

The incidence and prognosis of right ventricular infarction were studied by radionuclide ventriculography (RNV) in 50 consecutive cases of acute myocardial infarction. RNV was performed within thirty-six hours of symptoms and one month after onset. Right ventricular infarction was absent in all 25 patients with anterior infarction. It was found in 15 of the 25 patients with inferior infarction, accompanied by a marked reduction in right ventricular ejection fraction (28 +/- 8%), but was notably alleviated one month later with normalization of right ventricular ejection fraction (39 +/- 7%) and wall motion. These phenomena seem to be specific in right ventricular infarction.

Adult↗
PubMed1987

Cardiac tamponade in rheumatoid arthritis. Successful treatment with intrapericardial steroid administration.

Cardiac tamponade complicated by classic rheumatoid arthritis was markedly alleviated by pericardiocentesis and intrapericardial administration of steroid. For the following 2 years, no recurrence of cardiac tamponade or constrictive pericarditis was observed. According to the literature, only one other patient with cardiac tamponade complicating rheumatoid arthritis (RA) had been successfully treated patient by intrapericardial steroid administration.

Adult↗
PubMed1987

Positive intratympanic pressure in the morning and its etiology.

Intratympanic pressures were measured by tympanometer in forty ears free from disease. In the recumbent position, the first tympanogram was obtained in the morning at awakening, before swallowing. The second pressure measurement was performed in the upright position after swallowing and chewing. Twenty-two ears showed positive pressure in the middle ear before swallowing and decreased pressure after swallowing. The present results revealed no evidence of continuous gas absorption from the middle ear during sleep. The other experiment demonstrated that raising of the PCO2 level by hypoventilation increased the pressure in the middle ear. The results suggested indirectly a diffusion of carbon dioxide to the middle ear cavity from its surrounding tissue. The intratympanic pressure seems limited in part to the partial pressure gradient of gases between the middle ear cavity and its surrounding tissue when ventilation through the Eustachian tube is impaired.

Acoustic Impedance Tests↗
PubMed1987

[Acute right ventricular infarction: assessment with radionuclide ventriculography].

The clinical significance of right ventricular (RV) infarction has been neglected compared with left ventricular infarction. In recent years, however, the clinical importance of RV function in the treatment of myocardial infarction has been well recognized. We performed prospective radionuclide studies to assess the incidence and prognosis of RV infarction in 50 cases of initial acute myocardial infarction (25 cases of anterior and 25 of inferior infarction). Radionuclide ventriculography was performed within the first two days after onset of symptoms, and repeated one-two weeks and one month after the attack, respectively. RV infarction was diagnosed by the presence of severe RV regional wall motion abnormalities and positive signs of at least one of the following diagnostic signs: ST elevation at V4R in the ECG, positive 99m-technetium pyrophosphate myocardial scintigram at the RV free wall, and positive right heart catheterization findings. Results were as follows: 1. RV infarction was documented in 15 of 25 cases with inferior infarction, but there were no cases in anterior infarction. 2. There were no remarkable changes of RV ejection fraction (EF) in anterior myocardial infarction during one month (41% +/- 8% in acute phase and 43 +/- 8% in four weeks later). However, RVEF was markedly improved from 34 +/- 11% during first two days, to 38 +/- 7% during one-two weeks, and 39 +/- 8% four weeks after the attack, in cases of inferior infarction with RV infarction. Without RV infarction, RVEF in cases of inferior infarction did not show improvement. 3. In 11 of 15 cases with RV infarction, RV regional wall motion abnormalities improved to the normal range, which seemed to contribute to the improvement of RVEF. 4. Hemodynamic findings with Swan-Ganz catheters showed typical findings compatible with RV infarction only in seven of 13 cases with RV infarction. Thus this finding implies that RV failure did not always accompany RV infarction. 5. Coronary arteriography revealed that right coronary arterial lesions proximal to the RV branch were documented in all 10 cases with RV infarction who had coronary arteriography. RV infarction, caused by deranged coronary blood flow at the RV branch of the right coronary artery, showed marked improvement of RVEF during four weeks after the attack in prospective radionuclide studies. This finding was not seen in left ventricular infarction. The pathophysiological mechanism of improvement of RVEF in RV infarction would be the difference of its coronary circulation compared with that of the left ventricle.(ABSTRACT TRUNCATED AT 400 WORDS)

Cardiac Catheterization↗
PubMed1987

[Stress Tl-201 myocardial single photon emission computed tomography in diagnosing ischemic heart disease: its value and limitations].

The value and limitations of stress 201T1 myocardial single photon emission computed tomography (SPECT) for diagnosing ischemic heart disease (IHD) was studied. Using a dual-head rotating gamma camera system, stress SPECT and conventional planar imaging were performed for 138 patients while they were examined by symptom-limited graded bicycle ergometer exercise. All patients underwent selective coronary arteriography and left ventriculography, and 93 had myocardial infarction (MI), 30 had effort angina (EA) and 15 were normal (control). Sensitivities for detecting IHD (SPECT: planar = 96%: 89%, p less than 0.01), individual coronary arterial lesions (left anterior descending artery = LAD, 84%: 68%, p less than 0.005; left circumflex artery = LCX, 60%: 47%, NS; right coronary artery = RCA, 88%: 69%, p less than 0.01), multivessel disease (= LAD + LCX and/or RCA, 53%: 31%, p less than 0.025), and three vessel disease (60%: 13%, p less than 0.005) were significantly higher by SPECT than by planar imaging. In addition, detection of ventricular aneurysms by SPECT was possible with a reasonably high sensitivity (94%) and specificity (84%). Signs of aneurysm included 1) an extensive anterior permanent defect, 2) a large left ventricular cavity, and 3) widening of the angle composed by the septal and lateral walls toward the apex in transaxial images. Sensitivity for detecting IHD was significantly lower in patients without MI (i.e., EA) than in patients with MI (MI: EA = 100%: 83%, p less than 0.005). Sensitivity for detecting individual coronary arterial lesions was lower in the absence than in the presence of MI (LAD; 77%: 87%, LCX; 38%: 68%, RCA; 71%: 90%, respectively), with multivessel disease than with single vessel disease, and with mild than with severe grade of stenosis. Sensitivity for detecting multivessel disease was lower in patients without MI than in those with MI (31%: 61%, respectively), and in anterior MI than in posteroinferior MI, or both MIs (36%: 69%: 100%, respectively). Stress-induced ischemia of infarcted area (anterior MI, 36%; posteroinferior MI, 24%) and ventricular aneurysm (anterior MI, 21%; posteroinferior MI, 0) masked other coronary arterial stenoses in patients with previous MI. We concluded that stress 201T1 myocardial SPECT was a useful non-invasive technique for detecting IHD and individual coronary arterial lesions, multivessel disease (especially posteroinferior MI and anterior + posteroinferior MI), three vessel disease and ventricular aneurysms. However, there were limitations in detecting multivessel disease in patients with anterior MI and EA.

Coronary Disease↗
PubMed1987

[Myocardial ischemia with negative stress electrocardiography: evaluation by stress RI studies].

Patients with negative stress electrocardiography (ECG) (no ST segment depression) were re-evaluated by means of stress RI studies including 201T1 single photon emission computed tomography (SPECT) and 99mTc-RBCs radionuclide ventriculography (RNV). Four hundred seven patients, including 303 with old myocardial infarction (OMI; SPECT: 188, RNV: 115) and 104 with effort angina (EA; SPECT: 58, RNV: 46), all of whom underwent left ventriculography and coronary arteriography, were re-evaluated by symptom-limited graded bicycle ergometer exercise RI testing. The results were as follows: 1. Among those with negative stress ECG (53% of OMI and 31% of EA), 54% and 73% of OMI and EA, respectively, had positive SPECT. 2. Among those with negative stress ECG (56% of OMI and 39% of EA), 70% and 39% of OMI and EA, respectively, had positive delta EF (poor increase in ejection fraction: delta EF less than 5%) and, 41% and 28% of OMI and EA had deteriorated regional wall motion. 3. Those with OMI and negative ECG showed no correlations with the numbers of diseased vessels, infarcted sites, or ischemic areas. In conclusion, RI testing appears to be a significantly more sensitive means of detecting stress-induced ischemia, compared to stress ECG.

Adult↗