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Biomedical subjects

M Takamiya

Publications and source records attributed to M Takamiya.

At least 37 records · Page 2Linked to original sources
PubMed1999

Autonomic function in hypertensive patients with neurovascular compression of the ventrolateral medulla oblongata.

OBJECTIVE: To study whether abnormalities of autonomic function exist in patients with essential hypertension and neurovascular compression (NVC) of the medulla oblongata. SUBJECTS AND METHODS: We studied 25 untreated patients with essential hypertension (13 men and 12 women, 27-74 years old). High-resolution magnetic resonance imaging and magnetic resonance angiography were used to detect NVC. Twenty-four-hour ambulatory monitoring of blood pressure and electrocardiogram were performed, and the power spectrum of heart rate variability was analyzed. On a separate day, various autonomic activity tests, including mental stress, hand grip, cold pressor, and Valsalva maneuver were performed. Baroreflex sensitivity was calculated from changes of blood pressure and R-R interval during phenylephrine infusion. A clonidine suppression test was also performed, with measurement of plasma catecholamine levels. RESULTS: Fourteen of 25 patients (56%) had NVC (C group), and 11 patients did not have NVC (NC group). There were no significant differences in age, sex, family history, or duration of hypertension between the C and NC groups. Average 24-h systolic blood pressure was similar between the two groups, although 24-h diastolic blood pressure was higher in the C group than the NC group. Daytime, night-time, and 24-h heart rate was significantly higher in the C group than in the NC group. Night-time low frequency/high frequency ratio was slightly higher in the C group. Plasma norepinephrine levels were significantly higher (467 +/- 217 versus 299 +/- 122 pg/ml), and baroflex sensitivity was slightly lower in the C group than in the NC group. Responses of blood pressure and heart rate to mental stress, cold pressor, hand grip, Valsalva maneuver, phenylephrine infusion, and clonidine tests were not significantly different between the two groups. CONCLUSIONS: NVC of the medulla oblongata was frequently found in patients with essential hypertension. Patients with NVC appeared to have enhanced sympathetic nervous activity compared with those without the compression.

Adult↗
PubMed1999

Histologic comparison of coronary and iliac atherectomy tissue from cases of in-stent restenosis.

Pathologically, restenotic lesions after stenting were investigated by use of atherectomized tissues of seven coronary and seven iliac arteries. The mean interval of the stent deployment to restenosis was 9.1 months for the coronary artery and 33.7 months for the iliac artery, indicating a 3.7-fold longer interval for the latter. This study does not include cases of acute thrombotic occlusion. The atherectomized tissue from restenotic coronary arteries showed abundant neointima with alpha-actin-positive and ultrastructually synthetic-type smooth muscle cells in a rich myxomatous extracellular matrix. In the iliac arteries, the predominant component of restenosis consisted of organized thrombi. The neointima of the iliac arteries was mature, and only a small amount of spindle cells were observed in the hyalinized matrix. The tissue that developed restenosis after stenting was different in the coronary and iliac arteries included in this series. This study on the atherectomized tissue suggests that even in the chronic stage, a major cause of in-stent restenosis among the larger caliber vessels such as the iliac artery is not neointima but stent thrombosis.

Aged↗
PubMed1999

Saline-jet aspiration thrombectomy catheter. Clinical results in patients with venous thrombosis.

PURPOSE: To evaluate hydraulic thrombectomy using a saline-jet aspiration thrombectomy catheter in the treatment of venous thrombosis. MATERIAL AND METHODS: Ten patients underwent 12 hydraulic thrombectomy procedures using 2.7 or 4.0 mm catheters. The site of the thrombus was either central, peripheral or in portal veins. The age of the thrombi was between 2 and 60 days (mean 19.7 days). The efficacy of hydraulic thrombectomy was evaluated based on the aspirated thrombus ratio (ATR), i.e. the volume of the thrombus aspirated divided by the volume of the thrombus before thrombectomy. ATR was estimated by comparing the angiograms of the lesion before and after thrombectomy. RESULTS: Soft thrombi were usually rapidly removed. ATR was >2/3 in 3, 2/3-1/3 in 2, 1/3-0 in 4, and 0 in 1 patient. The activation time of the injector was 23-224 s (mean 102 s) and the volume of aspirated blood was 30-680 ml (mean 250 ml). Compensatory infusion of saline was performed for blood loss, and 400 ml of packed red blood cells was transfused in 1 patient. No complications of the hydraulic thrombectomy were observed. Thrombolysis or additional treatment were performed in 9 patients. CONCLUSION: Hydraulic thrombectomy using this catheter can contribute to the treatment of venous thrombosis.

Equipment Design↗
PubMed1999

[Assessment of left ventricular function by 201Tl ECG-gated myocardial SPECT].

We applied the QGS program for LV function analysis (described by Germano, 1995) to a 201Tl SPECT study at rest, and estimated its accuracy. We performed 201Tl ECG-gated myocardial SPECT in 25 patients with ischemic heart disease under an acquisition time used in the routine 99mTc ECG-gated SPECT study. The quality of the gated images was visually assessed with a 4-point grading system. LVEDV, LVESV, LVEF determined by the QGS program were compared with those by Simpson's method on biplane LVG in 25 patients. Regional wall motion scores in 7 myocardial segments were assessed on the three-dimensional display created by the QGS program and the cine display of biplane LVG with a 5-point grading system. Wall motion scores obtained by the QGS program were compared with those by LVG. Although 72.0% of 201Tl ECG-gated SPECT images were fair or poor in image quality, there were good correlations between the values obtained by the QGS program and LVG (LVEDV: r = 0.82, LVESV: r = 0.88, LVEF: r = 0.89). In addition, wall motion scores by the QGS program were correspondent to those by LVG in 77.1% of all 175 myocardial segments. We conclude that the QGS program provides high accuracy in evaluating left ventricular function even from 201Tl ECG-gated myocardial SPECT data.

Aged↗
PubMed1999

[MR angiography of steno-occlusive lesions of intracranial arteries: a comparative study between turbo MRA and conventional MRA].

PURPOSE: To compare the quality and diagnostic accuracy of images of intracranial steno-occlusive lesions obtained by conventional MRA and turbo MRA reconstructed using the zero-filled interpolation technique in the slice-select direction. MATERIALS AND METHODS: Eighteen patients with suspected steno-occlusive lesions of the intracranial arteries were studied with two types of three-dimensional time-of-flight angiography and conventional digital subtraction angiography. In total, 45 steno-occlusive lesions were quantitatively measured using calipers and correlated with DSA stenosis. A phantom that simulated vessels with stenosis was also imaged using the two types of MRA under the same conditions as those employed in the clinical study. RESULTS: Compared with conventional MRA, turbo MRA reduced the jaggedness of vessels and offered appearances more similar to those of DSA in the antero-posterior and lateral views. The severity of stenosis was classified into five grades based on the percentage of occlusion: not significant (0-24%), mild (25-49%), moderate (50-74%), severe (75-99%), and occlusive (100%). Neither turbo MRA nor conventional MRA showed any discrepancy from DSA above grade-1 stenosis. CONCLUSION: The advantage of turbo MRA is its ability to reduce the jaggedness of vessels on conventional MRA, and to simplify the recognition of vessel contours without prolonging acquisition time. Turbo MRA and conventional MRA have equally high diagnostic accuracy for steno-occlusive lesions.

Aged↗
PubMed1999

Intravascular ultrasound observations during iliac stent deployment.

BACKGROUND: To evaluate the role of intravascular ultrasound (IVUS) during iliac stent deployment, with comparison of four major types of iliac stents. METHODS: Thirty-eight iliac arteries of 37 patients were observed with intravascular ultrasound after implantation of various stents including Palmaz stents in 10, Memotherm stents in 11, Wallstent in 10, and Strecker stents in 7. Quantitative measurements on ultrasound included the ratio of the short-axial to the long-axial diameters of the stent (symmetry index), the ratio of stent cross-sectional area to that of the reference lumen (expansion index), and stent-to-wall apposition. RESULTS: Intravascular ultrasound revealed significant differences among four major types of iliac stent, in spite of satisfactory angiographic appearances in all patients. It demonstrated significant deformity of the Strecker stent (symmetry index of 0.76-0.09) compared with other stents. The Memotherm stent and the Palmaz stent were superior to other stents in terms of degree of expansion (mean expansion index of 0.87 and 0.82 respectively). Stent cross-sectional area greater than 80% of the reference lumen could be sufficient for iliac stent deployment. The Palmaz stent was superior to other stents in terms of stent-to-wall apposition. CONCLUSIONS: Intravascular ultrasound can provide precise and useful cross-sectional morphological and quantitative information in terms of stent configuration, degree of stent expansion, and stent-to-wall apposition.

Aged↗
PubMed1999

Sustained elevation of plasma brain natriuretic peptide levels associated with progressive ventricular remodelling after acute myocardial infarction.

Previous studies have shown that levels of plasma brain natriuretic peptide (BNP) increase in an early phase of acute myocardial infarction. However, the relations between plasma BNP levels and left ventricular remodelling, which occurs long after acute myocardial infarction, are not fully understood. Venous plasma BNP levels were measured 2, 7, 14, 30, 90 and 180 days after the onset of acute myocardial infarction in 21 patients. Left ventricular end-diastolic volume index (EDVI, ml/m2) in acute (5 days) and chronic (6 months) phases were assessed by electron-beam computed tomography using Simpson's method. The remodelling group (n=9) was defined by an increase in EDVI >/=5 ml/m2 relative to the baseline value. Plasma BNP levels on days 2, 7, 14, 30 and 90 were significantly higher in the remodelling group than in the non-remodelling group (n=12, P<0.05). Sustained elevation of plasma BNP levels was noted from day 2 (61+/-12 pmol/l) to day 90 (55+/-12 pmol/l) and significantly decreased on day 180 (24+/-3 pmol/l) in the remodelling group. In contrast, plasma BNP levels significantly decreased from day 2 (25+/-4 pmol/l) to day 90 (9+/-1 pmol/l) and reached a steady level thereafter in the non-remodelling group. Plasma BNP levels on day 7 correlated positively with an increase in EDVI (r=0.70, P<0.001) from the acute to chronic phase. More importantly, the sustained elevation of plasma BNP (percentage decrease smaller than 25%) from day 30 to day 90 identified patients in the remodelling group with a sensitivity of 100% and a specificity of 83%. In conclusion, not only the high levels of plasma BNP in an acute phase, but also the sustained elevation of plasma BNP in a chronic phase, may be associated with progressive ventricular remodelling occurring long after acute myocardial infarction.

Adult↗
PubMed1998

Diagnostic value of plasma levels of brain natriuretic peptide in arrhythmogenic right ventricular dysplasia.

BACKGROUND: Arrhythmogenic right ventricular dysplasia (ARVD) is characterized by local or diffuse wall motion abnormalities in the right ventricle (RV), associated with recurrent ventricular tachycardia (VT) of RV origin. Brain natriuretic peptide (BNP) was first isolated from a porcine brain extract. In humans, BNP is expressed predominantly in the ventricles of failing hearts, and its expression has been observed primarily in myocytes in the interstitial fibrous area in dilated cardiomyopathy. We hypothesized that BNP is increasingly secreted from the residual myocytes within the atrophic tissue in patients with ARVD. METHODS AND RESULTS: Plasma BNP levels were measured in 17 patients with ARVD, 12 patients with idiopathic RV outflow tract tachycardia (RVOT), and 120 control subjects. We performed cardiac catheterization, RV endomyocardial biopsy, electron- beam CT, and biventricular endomyocardial mapping in the ARVD patients. There was a significant increase in plasma BNP levels in the ARVD patients compared with the RVOT patients and control subjects (61.4+/-59.6 pg/mL versus 8.3+/-5. 5 pg/mL and 9.3+/-5.8 pg/mL; P<0.0001, respectively). The plasma BNP levels had no correlation with any of the hemodynamic data, but they had a significant correlation with the RV ejection fraction (r=-0. 588, P=0.025) and with the fractionated-area scores (r=0.705, P=0. 005). Light microscopic immunohistochemistry showed strong BNP immunoreactivity in residual myocytes with fibrofatty replacement. CONCLUSIONS: These results suggest that plasma BNP levels were not increased in RVOT patients but were increased in ARVD patients, and that the increased BNP levels indicate the severity of both the RV dysfunction and the arrhythmogenic substrate.

Adolescent↗
PubMed1998

Complete sequence and gene organization of the genome of a hyper-thermophilic archaebacterium, Pyrococcus horikoshii OT3.

The complete sequence of the genome of a hyper-thermophilic archaebacterium, Pyrococcus horikoshii OT3, has been determined by assembling the sequences of the physical map-based contigs of fosmid clones and of long polymerase chain reaction (PCR) products which were used for gap-filling. The entire length of the genome was 1,738,505 bp. The authenticity of the entire genome sequence was supported by restriction analysis of long PCR products, which were directly amplified from the genomic DNA. As the potential protein-coding regions, a total of 2061 open reading frames (ORFs) were assigned, and by similarity search against public databases, 406 (19.7%) were related to genes with putative function and 453 (22.0%) to the sequences registered but with unknown function. The remaining 1202 ORFs (58.3%) did not show any significant similarity to the sequences in the databases. Sequence comparison among the assigned ORFs in the genome provided evidence that a considerable number of ORFs were generated by sequence duplication. By similarity search, 11 ORFs were assumed to contain the intein elements. The RNA genes identified were a single 16S-23S rRNA operon, two 5S rRNA genes and 46 tRNA genes including two with the intron structure. All the assigned ORFs and RNA coding regions occupied 91.25% of the whole genome. The data presented in this paper are available on the internet at http:@www.nite.go.jp.

Chromosomes, Archaeal↗
PubMed1998

Increased bone mineral turnover without increased glucose utilization in sclerotic and hyperplastic change in fibrous dysplasia.

Fibrous dysplasia is a benign bone disorder. It is diagnosed by distinctive X-ray radiography, CT, and MRI findings. Although bone scintigraphy helps to identify the tumor origin according to accelerated bone turnover, the glucose metabolism in fibrous dysplasia has not yet been investigated. We reported a case of fibrous dysplasia in craniofacial bone which showed signs of the acceleration of bone mineral turnover without elevated glucose utilization by Technetium-99m-HMDP SPECT and Fluorine-18-FDG PET. We concluded that the growth of fibrous dysplasia needed the acceleration of bone mineral turnover without an increase in glucose metabolism.

Bone Density↗
PubMed1998

Plasma brain natriuretic peptide levels increase in proportion to the extent of right ventricular dysfunction in pulmonary hypertension.

OBJECTIVES: This study sought to investigate the influence of right ventricular (RV) hemodynamic variables and function on the secretion of brain natriuretic peptide (BNP) in patients with isolated RV overload. BACKGROUND: Plasma BNP is known to increase in proportion to the degree of left ventricular (LV) overload. However, whether BNP secretion is also regulated in the presence of RV overload remains unknown. METHODS: Plasma BNP and atrial natriuretic peptide (ANP) levels in the pulmonary artery were measured in 44 patients with RV overload: 18 with RV volume overload (RVVO) due to atrial septal defect and 26 with RV pressure overload (RVPO) due to primary or thromboembolic pulmonary hypertension. Right heart catheterization was performed in all patients. RV and LV ejection fraction, myocardial mass and volume of the four chambers were determined by using electron beam computed tomography. RESULTS: Although both plasma BNP and ANP levels were significantly elevated in patients with RV overload compared with values in control subjects, plasma BNP and the BNP/ANP ratio were significantly higher in patients with RVPO than with RVVO (BNP 294 +/- 72 vs. 48 +/- 14 pg/ml; BNP/ANP 1.6 +/- 0.2 vs. 0.8 +/- 0.2, both p < 0.05). Plasma BNP correlated positively with mean pulmonary artery pressure (r = 0.73), total pulmonary resistance (r = 0.79), mean right atrial pressure (r = 0.79), RV end-diastolic pressure (r = 0.76) and RV myocardial mass (r = 0.71); it correlated negatively with cardiac output (r = -0.33) and RV ejection fraction (r = -0.71). Plasma BNP significantly decreased from 315 +/- 120 to 144 +/- 54 pg/ml with long-term vasodilator therapy (total pulmonary resistance decreased from 23 +/- 4 to 15 +/- 3 Wood U). CONCLUSIONS: Plasma BNP increases in proportion to the extent of RV dysfunction in pulmonary hypertension.

Adult↗
PubMed1998

Aspirin renography in diagnosis of unilateral renovascular hypertension.

We previously proposed that aspirin can enhance the diagnostic sensitivity of renography with [123I] orthoiodohippurate (OIH) in patients with suspected unilateral renovascular hypertension (RVH). In this study we assessed the sensitivity and specificity of this method. Twenty-four patients, 14 with unilateral RVH and 10 with essential hypertension, were studied. For all patients with RVH, definitive diagnosis was based on the results of angiography and the response to renal arterial angioplasty after this study. For all patients with essential hypertension, we confirmed that there was little if any stenosis of the renal artery by digital subtraction angiography or Doppler sonography. Renography with [123I]OIH or 99mTc-mercaptoacetyltriglycine (MAG3) was done once before and once after the oral administration of aspirin (20 mg/kg). We considered renal blood flow to be decreased if the time to the peak in renography was 5 min or more, and defined the peak times of the kidneys as different if separated by 2 min or more. Unilateral RVH was diagnosed when both criteria were met. Renography before aspirin administration indicated RVH in 7 of the 14 patients with RVH, and renography after aspirin indicated RVH in 13 of the 14 patients. Of the 10 patients with essential hypertension, renography before and after aspirin administration showed no difference between the kidneys in 8 patients. Thus, aspirin renography increased the sensitivity from 50% to 93%, but did not change the specificity (80%) in the diagnosis of RVH. These results suggest that renography with [123I]OIH or 99mTc-MAG3 for the diagnosis of unilateral RVH is more sensitive when aspirin is used.

Adult↗
PubMed1998

Subtraction CT angiography with controlled-orbit helical scanning for detection of intracranial aneurysms.

PURPOSE: Our goal was to evaluate the utility of subtraction three-dimensional CT angiography for the detection of intracranial aneurysms. METHODS: Thirty-six patients with intracranial aneurysms were examined using newly devised controlled-orbit helical scanning and conventional angiography. Three-dimensional CT angiograms and subtraction 3-D CT angiograms were compared with conventional angiograms for their characterization of intracranial aneurysms. RESULTS: Fifty aneurysms were depicted on conventional angiograms, of which 48 (96%) were seen on the 3-D CT angiograms. Three-dimensional CT angiography was superior or equivalent to conventional angiography for depicting the shape, direction, and location of 33 (66%) of 50 aneurysms; however, it was often less useful than conventional angiography in delineating intracranial aneurysms adjacent to bone. Subtraction 3-D CT angiograms were obtained in 32 patients with a total of 46 aneurysms (in four cases, aneurysms were not depicted owing to excessive motion artifacts), and were superior or equivalent to conventional angiograms in all 46 cases. CONCLUSIONS: Subtraction 3-D CT angiography with the use of controlled-orbit helical scanning is effective in the detection of intracranial aneurysms.

Adult↗
PubMed1998

Growth curve of ruptured aortic aneurysm.

OBJECTIVE: We hypothesized that the aortic aneurysm might grow biexponentially. The object of this study was to determine the biexponential growth curve of aortic aneurysm. DESIGN: A fifteen-year retrospective review of CT images of aortic aneurysm. SETTING: Major cardiovascular referral center. PATIENTS: Patients with true aortic aneurysm who were followed up with CT and performed CT at their aneurysmal ruptures. MEASURES: The largest short-axial diameters of the outer contour of the aneurysms were measured. Aortic aneurysmal diameters were normalized by those at ruptures, and the plots were fitted to the biexponential curve. RESULTS: Eight patients out of 1481 had been followed up with CT scans. In regression analysis, the values fit well to the biexponential equation: d(t) = 0.8345 exp (0.0052 t) + 0.1653 exp (0.8275 t), r = 0.934 where d(t) is the normalized diameter, and t is months before rupture. The first part of the equation mainly expresses the slow growth, and the second expresses the rapid growth shortly before rupture. CONCLUSIONS: Aortic aneurysm began to grow faster at about three months before rupture. It is important to find out the point that the growth of aortic aneurysm changes its rate faster than before, and once the point is observed, elective repair should be considered.

Aged↗