Search PubMed⌕ Search

Biomedical subjects

Y Shigematsu

Publications and source records attributed to Y Shigematsu.

At least 55 records · Page 3Linked to original sources
PubMed2000

Posttherapeutic intraaxial brain tumor: the value of perfusion-sensitive contrast-enhanced MR imaging for differentiating tumor recurrence from nonneoplastic contrast-enhancing tissue.

BACKGROUND AND PURPOSE: Differentiation of tumor recurrence from treatment-related changes may be difficult with conventional MR imaging when newly enhancing lesions appear. Our aim was to determine the value of perfusion-sensitive contrast-enhanced MR imaging for differentiating recurrent neoplasm from nonneoplastic contrast-enhancing tissue. METHODS: Twenty patients in whom new enhancing lesions developed within irradiated regions were examined prospectively with perfusion-sensitive contrast-enhanced MR imaging. Twelve of them also underwent thallous chloride Tl 201 single-photon emission tomography (201Tl-SPECT). Normalized relative cerebral blood volume (rCBV) ratios and thallium indexes were evaluated to determine whether the new enhancing lesions were recurrent or not. Five instances of tumor recurrence and one of radiation necrosis were verified histologically; in the others, tumor recurrence was distinguished by lesions that progressively increased in size on serial MR examinations over at least 5 months, and nonneoplastic contrast-enhancing tissue was distinguished by lesions that disappeared or decreased in size on serial MR studies over at least 9 months. RESULTS: When normalized rCBV ratios were higher than 2.6 or lower than 0.6, enhancing lesions were either recurrent (n = 5) or nonneoplastic contrast-enhancing tissue (n = 3), respectively. All nonneoplastic contrast-enhancing tissue had a low thallium index, whereas three of four recurrent lesions had a high index. CONCLUSION: An enhancing lesion with a normalized rCBV ratio higher than 2.6 or lower than 0.6 may suggest tumor recurrence or nonneoplastic contrast-enhancing tissue, respectively. In these cases, further examination with 201Tl-SPECT may not be necessary. However, when the normalized rCBV ratio is between 0.6 and 2.6, 201Tl-SPECT may be useful in making the differentiation.

Adolescent↗
PubMed1999

Regulated expression of human angiotensinogen gene by hepatocyte nuclear factor 4 and chicken ovalbumin upstream promoter-transcription factor.

We previously identified various upstream and downstream regulatory elements and factors important for hepatic expression of the human angiotensinogen (ANG) gene, the precursor of vasoactive octapeptide angiotensin II. In the present study, to further investigate the molecular mechanism of human ANG transcriptional regulation, we generated transgenic mice carrying the fusion gene composed of the 1. 3-kilobase promoter of the human ANG gene, its downstream enhancer, and the chloramphenicol acetyltransferase reporter gene. Because expression of the chloramphenicol acetyltransferase gene was observed strongly in the liver and weakly in the kidney, we suspected that hepatocyte nuclear factor (HNF) 4 with a tissue expression pattern similar to that of the reporter gene would regulate ANG transcription. In vitro assays indicated that HNF4 bound to the promoter elements and strongly activated the ANG transcription, but that chicken ovalbumin upstream promoter transcription factor (COUP-TF), a transcriptional repressor, dramatically repressed human ANG transcription through the promoter elements and the downstream enhancer core elements. Furthermore, COUP-TF dramatically decreased the human ANG transcription in the mouse liver by the Helios Gene Gun system in vivo. These results suggest that an interplay between HNF4 and COUP-TF could be important in hepatic human ANG transcription.

Angiotensins↗
PubMed1999

Modifications in electrospray tandem mass spectrometry for a neonatal-screening pilot study in Japan.

In a neonatal-screening pilot study for inherited disorders in organic acid and amino acid metabolism, we analyzed butyrated acylcarnitines and amino acids in blood spots of more than 20,000 newborns by electrospray tandem mass spectrometry. In order to screen urea cycle disorders, we performed multiple scanning functions with additional stable isotope-labelled internal standards, since such reported functions as neutral loss of m/z 102 or 109 for butyrated amino acids were not sufficient. Arginine levels were measured with arginine-13C6. Hypocitrullinemia for the screening of some urea cycle disorders was detectable by measurement with synthesized citrulline-d6, although we did not find any such disorders. In the acylcarnitine analysis, we found a patient with propionic acidemia, who has been treated effectively. The increasing false positive rate due to the use of pivalic acid-containing antibiotics in the diagnosis of isovaleric acidemia was a problem in Japan.

Calibration↗
PubMed1999

3D TOF turbo MR angiography for intracranial arteries: phantom and clinical studies.

This work investigated whether turbo magnetic resonance angiography (MRA) can replace conventional MRA in screening examination of intracranial arteries. A phantom was used to evaluate the effect of the zero-filling interpolation (ZFI) technique on spatial resolution and partial volume effect. Thirty-one consecutive patients underwent both turbo MRA with a slice thickness of 0.7 mm (data were measured as 1.33 mm sections) and conventional MRA with 1.0 mm sections. In the phantom studies, ZFI did not improve the spatial resolution, but the partial volume effect was somewhat reduced. In the clinical evaluation, turbo MRA showed better signal-to-noise and contrast-to-noise ratios of the intracranial major vessels than conventional MRA. The lesions included cerebral aneurysms less than 3 mm in diameter, occlusive vascular disease, arteriovenous malformations, and arteriovenous fistulas. These were all depicted on both turbo MRA and conventional MRA. Turbo MRA is a useful screening procedure because of its capability of delineating lesions in approximately half the usual imaging time. J. Magn. Reson. Imaging 1999;10:939-944.

Adult↗
PubMed1999

Rest-redistribution thallium-201 myocardial scintigraphic study in cardiac amyloidosis.

BACKGROUND: Histopathological study in amyloid heart demonstrates that myocyte destructed by the extracellular deposition of amyloid protein together with viable myocyte is present. We hypothesized that rapid thallium washout may be found in amyloid heart as in regions which have a mixture of viable myocyte and scar tissue in patients with myocardial infarction. Thus, the purpose of this study was to evaluate the extent and severity of myocardial damage due to amyloid deposits using the washout rate of the tracer on rest-redistribution thallium-201 (201Tl) myocardial scans in cardiac amyloidosis patients. METHODS: Rest-redistribution 201Tl myocardial scintigraphy was performed in 5 patients with biopsy-proved systemic amyloidosis with cardiac involvement (amyloidosis group). The initial and delayed images were obtained 15 min and 4 h, respectively, after intravenous injection of the tracer of 111 MBq. Washout rate of the tracer was calculated. Twelve patients with no apparent heart disease served as controls (control group). RESULTS: Mean washout rate of the whole heart was higher in the amyloidosis group than in the control group (56 +/- 9% vs 36 +/- 6%, p < 0.001). Particularly, 4 of the 5 patients in the amyloidosis group presented a very high rate of thallium clearance which ranged from 57 to 61%, and died in less than a year. In the remaining 1 patient who had a normal washout rate of the tracer in the first study, it changed from 40 to 53% during the 5-year follow-up period. CONCLUSIONS: Washout rate in the setting of rest and delayed 201Tl images may represent the severity of amyloid depositions in the myocardium and may provide prognostic information.

Aged↗
PubMed1999

Effect of antihypertensive therapy on aortic distensibility in patients with essential hypertension: comparison with trichlormethiazide, nicardipine and alacepril.

To assess the effect of antihypertensive drugs on aortic distensibility, we evaluated the aortic distensibility of 33 hypertensive patients before and after antihypertensive treatment by using cine magnetic resonance imaging. Thirty three hypertensive patients were divided into three groups and treated for 12 weeks with 2-4 mg trichlormethiazide per day (n = 10), 80 mg nicardipine per day (n = 13) and 50 mg alacepril per day (n = 10). There were no significant differences in mean age and mean blood pressure among the three groups. Cine magnetic resonance was performed at ascending and descending aortic levels. Aortic area was measured at the maximum and minimum frames. The effect of antihypertensive therapy on aortic distensibility was evaluated as the percent change from before treatment to after treatment. There were no significant differences in pulse pressure before and after treatment with trichlormethiazide, nicardipine and alacepril. After treatment with these drugs, mean blood pressure in all groups decreased (trichlormethiazide and nicardipine, P < .01; alacepril, P < .05), (the maximum area--the minimum area) and aortic distensibility in all groups increased significantly (each P < .01). Percent changes in aortic distensibility after treatment were significantly higher with nicardipine (ascending, 346.6 +/- 255.9%; descending, 338.8 +/- 246.5%, each P < .05) and alacepril (ascending, 369.7 +/- 238.8%, P < .05; descending, 306.9 +/- 123.3%, P < .01) than with trichlormethiazide (ascending, 146.0 +/- 139.6%; descending, 129.3 +/- 97.5%). In conclusion, nicardipine and alacepril have a beneficial effect on aortic distensibility.

Age Factors↗
PubMed1999

Mass screening for Wilson's disease: results and recommendations.

Wilson's disease is a treatable inherited disorder of copper metabolism. Established treatments include the use of oral chelating agents and the establishment of a minimum copper diet, although prognosis mainly depends on the extent of liver or nervous system damage present before treatment. Once irreversible damage has occurred, the effect of these treatments is diminished and the patient's quality of life compromised. Therefore, the establishment of a mass screening system able to detect Wilson's disease patients presymptomatically has been discussed. Recently, a monoclonal antibody specific to holoceruloplasmin has been developed. This antibody was used in a nationwide screening trial of 126,810 newborn infants, but no Wilson's disease patients were identified. However, three patients out of 24,165 were diagnosed with Wilson's disease using this specific antibody in a screening performed during the period from late infancy to elementary school. The age of 3 years is thought to be the best point for Wilson's disease mass screening. In this paper, a review of mass screening for Wilson's disease in Japan using a specific monoclonal antibody to holoceruloplasmin is presented.

Antibodies, Monoclonal↗
PubMed1999

Value of dynamic susceptibility contrast magnetic resonance imaging in the evaluation of intracranial tumors.

The degree of tumor malignancy generally correlates to tumor grade, and the direct measurement of tumor vasculature is desired. Dynamic susceptibility contrast magnetic resonance imaging can provide relative cerebral blood volume and, therefore, is one of the most reliable methods to evaluate tumor vasculature in vivo. Tumor vessel size is extremely variable due to complex tumor angiogenesis, and the gradient-echo echo-planar imaging (GE-EPI) technique, which is sensitive to the total vascular bed, is well suited for this purpose. As many studies have shown, dynamic susceptibility contrast magnetic resonance imaging is more useful for grading glioma than conventional magnetic resonance imaging. We found that this technique can also provide supplementary information to differentiate between malignant lymphoma and glioma because the absence of tumor neovascularization of malignant lymphoma leads to low rCBV, which is in contrast to those of malignant gliomas. Indeed, this technique can be used for the differentiation of extra-axial tumors such as between meningioma and neurinoma. Recently, this technique has been focused toward determining the stereotactic biopsy site, monitoring the embolization of effect in meningioma, or evaluation of treatment effects after radiation therapy. However, the value of tumor rCBV is affected by many conditions such as the T1 relaxivity effects of gadolinium in the extravascular space. To establish the usefulness of this technique, further examination will be needed.

Adult↗
PubMed1999

Clinical implications of circulating soluble Fas and Fas ligand in patients with acute myocardial infarction.

BACKGROUND: Apoptotic cell death is the major form of myocardial damage produced by coronary ischemic events. OBJECTIVE: To assess whether circulating levels of soluble Fas (sFas), an inhibitor of apoptosis, and sFas ligand, an inducer of apoptosis, in patients with coronary artery disease are greater than normal. METHODS: Forty-seven patients [acute myocardial infarction (AMI) in 17, old myocardial infarction (OMI) in 15, stable angina in 15] and 10 normal control subjects participated in this study. Serum levels of sFas and sFas ligand in all patients were measured, and cardiac catheterizations were performed. RESULTS: Serum levels of sFas were greater than normal only in patients with AMI (4.6 +/- 1.6 ng/ml); the levels were significantly higher than those in patients with OMI (2.1 +/- 0.6 ng/ml) and stable angina (2.2 +/- 0.5 ng/ml), and in normal subjects (2.0 +/- 0.6 ng/ml; P < 0.0001). However, there was no difference among serum levels of sFas ligand for all groups. For patients with AMI, there was no significant correlation between serum levels of sFas and peak levels both of plasma creatine phosphokinase and of plasma myosin light chain type I as clinical indexes of infarct size. However, there were significant correlations between serum levels of sFas and both pulmonary artery wedge pressure (r = 0.767, P = 0.0003) and left ventricular end-diastolic pressure (r = 0.629, P = 0.03). CONCLUSIONS: Circulating sFas increases in concentration in relation to the severity of hemodynamic conditions in patients with AMI, but it is independent from size of infarct. Therefore, circulating sFas could play an important role as the marker of pathophysiologic conditions associated with cardiomyocyte apoptosis in AMI.

Aged↗
PubMed1999

Brain lesions: when should fluid-attenuated inversion-recovery sequences be used in MR evaluation?

PURPOSE: To compare qualitatively and quantitatively the contrast of brain lesions detected with fluid-attenuated inversion-recovery (FLAIR) and intermediate-weighted sequences at magnetic resonance (MR) imaging. MATERIALS AND METHODS: In this prospective study, 47 patients suspected of having a brain lesion underwent MR imaging with FLAIR, intermediate-weighted, and T2-weighted sequences. Qualitative assessment was performed of lesion conspicuity, detection, overall image artifact, and additional clinical information. Contrast and contrast-to-noise ratio (CNR) were calculated between lesions and the normal brain or cerebrospinal fluid (CSF). RESULTS: FLAIR images were equal to intermediate-weighted images for overall lesion conspicuity and detection but were associated more often with image artifacts. Lesion-to-background contrast was significantly higher on FLAIR than on intermediate-weighted images. FLAIR images failed to demonstrate multiple sclerosis (MS) plaques located in the basal ganglia and brain stem. CONCLUSION: Although FLAIR images provided additional information in some cases, they did not have distinct advantages over intermediate-weighted images. When cases of MS are evaluated, intermediate-weighted images are preferable to FLAIR images. Except in cases of MS, either FLAIR or intermediate-weighted sequences should be added to T2-weighted sequences at MR imaging.

Adolescent↗
PubMed1999

Serum creatinine level underestimates hypertensive renal involvement in elderly patients with essential hypertension.

It is well recognized that serum creatinine level provides a quick general assessment of renal function. However, we frequently encounter elderly hypertensive patients with renal involvement whose serum creatinine levels are within normal limits. The aim of this study was thus to determine whether serum creatinine level is a sensitive indicator of renal function in elderly hypertensive patients. Study groups were classified according to age: 82 elderly patients (aged 65 yr or older) and 98 middle-aged patients (aged 40-65 yr) with essential hypertension. To assess hypertensive renal involvement, serum creatinine and serum uric acid levels were measured. We also measured the left ventricular mass (LVM) index by using echocardiography as a marker of hypertensive target organ damage. There was no age-related difference in the LVM index, but the serum creatinine level in elderly hypertensive patients was significantly lower than that in middle-aged hypertensive patients. There was no significant difference in serum uric acid level between the two groups. In addition, the LVM index was correlated with the serum uric acid level (r = 0.46, p = 0.0001) but not with the serum creatinine level in elderly hypertensive patients. In middle-aged hypertensive patients, the LVM index was related to both serum uric acid level (r = 0.41, p = 0.007) and serum creatinine level (r = 0.43, p = 0.003). In conclusion, serum creatinine level may underestimate hypertensive renal involvement in elderly hypertensive patients. In contrast, serum uric acid level may be a sensitive indicator of hypertensive target organ damage irrespective of age.

Adult↗
PubMed1999

Detection of intracranial hemorrhage with susceptibility-weighted MR sequences.

BACKGROUND AND PURPOSE: Detection of hemorrhage is important in the diagnosis and management of a variety of intracranial diseases. We evaluated the sensitivity of the following sequences for depicting chronic hemorrhagic foci associated with susceptibility dephasing: gradient-recalled echo (GRE) imaging, GRE-type single-shot echo-planar imaging (GRE-EPI), spin-echo-type single-shot echo-planar imaging (SE-EPI), turbo spin-echo (TSE) imaging, half-Fourier single-shot turbo spin-echo (HASTE) imaging, and segmented HASTE (s-HASTE) imaging. To our knowledge, no previous comparison has been made with these techniques in the same patient. METHODS: Fifty patients with suspected chronic hemorrhage were examined prospectively with the above six sequences. Contrast-to-noise ratio (CNR), sensitivity to detection of lesions, conspicuity of internal architecture, and sensitivity to small hemorrhagic foci were evaluated. RESULTS: Hemorrhagic foci were found in 35 patients. The CNR of the GRE, GRE-EPI, SE-EPI, TSE, s-HASTE, and HASTE sequences was 30.9, 23.7, 3.6, 6.1, -29.3, and -13.1, respectively; the number of small hemorrhagic foci detected was 85, 96, 44, 22, two, and one, respectively, for the supratentorial white matter; 70, 40, 19, four, zero, and zero, respectively, for the supratentorial cortical/subcortical region; and 73, 50, 26, 37, zero, and zero, respectively, for the infratentorial/skull-base region. CONCLUSION: The GRE sequence was best for detecting susceptibility dephasing associated with chronic intracranial hemorrhage. GRE-EPI, while comparable to GRE in the supratentorial compartment, was reduced in its sensitivity near the skull base, and may be used as an alternative to GRE in uncooperative, unsedated, pediatric, or claustrophobic patients. SE-EPI should not be used in screening for intracranial hemorrhage.

Adolescent↗
PubMed1999

Contrast enhancement of intracranial lesions: conventional T1-weighted spin-echo versus fast spin-echo MR imaging techniques.

BACKGROUND AND PURPOSE: The T1-weighted fast spin-echo (T1-FSE) MR imaging sequence is not used routinely, since the speed advantage is not as dramatic as it is in T2-weighted imaging. We evaluated the T1-FSE sequence to determine whether this technique can replace the conventional T1-weighted spin-echo (T1-SE) sequence for routine contrast-enhanced imaging. METHODS: Sixty-nine patients with intracranial enhancing lesions underwent both T1-SE and T1-FSE sequences in a random order after administration of contrast agent. Acquisition time was 55 seconds for the T1-FSE sequence and 2 minutes 38 seconds for the SE sequence. The conspicuity of enhancing lesions, peritumoral edema, and gray-to-white matter contrast as well as motion and flow artifacts were analyzed. Signal-to-noise ratios of enhancing lesions, gray matter, and white matter as well as contrast-to-noise ratios (CNRs) of enhancing lesions, with gray matter with white matter as the standard, were calculated. RESULTS: The conspicuity of enhancing lesions was better on T1-FSE sequences than on T1-SE sequences, although the difference in the CNRs of enhancing lesions did not reach significance. Images obtained with the T1-FSE sequence showed less flow and motion artifacts than did those obtained with the T1-SE sequence. The conspicuity of peritumoral edema and gray-to-white matter contrast was lower on the T1-FSE images than on the T1-SE images. CONCLUSION: The T1-FSE sequence reduces imaging time and has the potential to replace the conventional T1-SE sequence for the evaluation of enhancing lesions in the brain when time is a consideration.

Adolescent↗
PubMed1999

Hypertrophic cardiomyopathy with mid-ventricular obstruction and splenic infarction associated with paroxysmal atrial fibrillation: a case report.

A 54-year-old woman had been treated for hypertrophic cardiomyopathy and paroxysmal atrial fibrillation since 1992. She was admitted with paroxysmal atrial fibrillation which was resolved by medical treatment. However, on the next day, left lateral chest pain appeared. Computed tomography disclosed a low density area in the spleen. She received anticoagulant therapy under a diagnosis of splenic infarction, and the pain disappeared. Echocardiography showed hypertrophic cardiomyopathy with mid-ventricular obstruction. She was treated with cibenzoline to prevent paroxysmal atrial fibrillation attack and attenuate the hemodynamic load. After treatment, the pressure gradient decreased from 41 to 7 mmHg. This patient with hypertrophic cardiomyopathy suffered a rare isolated splenic infarction associated with paroxysmal atrial fibrillation.

Anti-Arrhythmia Agents↗
PubMed1998

Virtual MRI endoscopy of the intracranial cerebrospinal fluid spaces.

We used constructive interference in steady state (CISS) 3D Fourier transform (3DFT) MRI data sets to obtain three-dimensional (3D) virtual MRI endoscopic views of the intracranial cerebrospinal fluid (CSF) spaces, processing them with a commercially available perspective endoscopic algorithm. We investigated the potential of the intracranial virtual MRI endoscopy applied to visualisation of the pathology in 13 patients with surgically confirmed trigeminal neuralgia (3), hemifacial spasm (3), acoustic neuroma (3), suprasellar germinoma (1), Langerhans cell histiocytosis (1), lateral ventricle nodules (1) and pituitary dwarfism (1). All images were acquired using a 1.5-T imager employing a circular polarised head coil. The CISS-3DFT data sets were transferred to a workstation for processing with the perspective endoscopic algorithm. Postprocessing for virtual MRI endoscopy was possible for all data sets. The lesions in 12 patients, and their complex anatomical relationships with the surrounding structures, were well seen on the 3D images. A small acoustic neuroma in the internal auditory meatus was not seen using virtual endoscopy. Although virtual MRI endoscopy has limitations, it provides 3D images which cannot be acquired using any other procedure.

Adolescent↗
PubMed1998

A case of effusive-constructive pericarditis: an efficacy of GD-DTPA enhanced magnetic resonance imaging to detect a pericardial thickening.

A 38-year-old man underwent pericardiectomy because of effusive-constrictive pericarditis. The gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA) enhanced magnetic resonance imaging showed pericardial thickening separate from the effusion, which could not be shown by unenhanced computed tomography. Gd-DTPA enhanced magnetic resonance imaging could be useful for the early detection of effusive-constrictive pericarditis.

Adult↗