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Biomedical subjects

O Abe

Publications and source records attributed to O Abe.

At least 19 recordsLinked to original sources
PubMed2006

Continuous shipboard sampling system for determination of triple oxygen isotopes and O2/Ar ratio by dual-inlet mass spectrometry.

A continuous shipboard sampling system was developed for the determination of the isotopic composition of the triple oxygen isotopes and oxygen to argon (O(2)/Ar) ratios in dissolved air. In this system, dissolved air is separated by a hollow fiber membrane degassing module. This system collects dissolved air quantitatively and rapidly. The sample flow rate through the membrane is critical for the fractionation of the oxygen isotopes and the O(2)/Ar ratio and should be < 2 mL/min. Fractionation of oxygen between the liquid and gas phase of the air-saturated water was found to be similar to that of earlier reports. The advantages of this method over existing techniques include rapid collection of samples (30 min/sample), high efficiency in extraction of gases from the liquid phase, and the lack of a sample preparation step (e.g. degassing).

Argon↗
PubMed2004

Diffusion property following functional hemispherectomy in hemimegalencephaly.

Diffusion-tensor imaging (DTI), a unique magnetic resonance technique for analysis of diffusion-anisotropy of the brain, can identify subtle white matter changes in vivo. To investigate changes of truncated neurofibers, DTI was conducted prior to and following functional hemispherectomy in a female infant for refractory epilepsy associated with hemimegalencephaly. Anisotropy of the amputated pyramidal tract decreased relative to the unaffected side after surgery, which reflects secondary degeneration in neurofibers. In DTI applied to infants, differentiation between developmental changes and changes associated with the current phenomenon must be evaluated cautiously. Standardization of diffusion-tensor analysis of developmental change is desirable.

Adult↗
PubMed2003

Chromatographic separation of nitrogen, argon, and oxygen in dissolved air for determination of triple oxygen isotopes by dual-inlet mass spectrometry.

A chromatographic system was developed to separate oxygen from nitrogen, argon, carbon dioxide, and water vapor mixture for the determination of precise isotopic ratio measurements of oxygen in dissolved air. This system separates oxygen not only quantitatively but also rapidly as well; typical oxygen separation takes about 30 min. Fractionation of oxygen between liquid and gas phase was found to be similar to that of earlier reports.

Journal Article↗
PubMed2003

Neuro-Behçet's disease: analysis of apparent diffusion coefficients.

Little is known about the diffusion properties of brain lesions in neuro-Behçet's disease (NBD). We looked at 19 NBD lesions (13 active, six chronic) in six patients, using diffusion-weighted MRI (DWI). We calculated the apparent diffusion coefficients (ADC) of the lesions and compared them with normal contralateral brain, expressing this ratio as relative ADC (rADC). The rADC was 1.29+/-0.33 in active and 1.44+/-0.47 in chronic lesions, i.e., significantly higher than in the control regions. Increased diffusivity in both active and chronic phases in NBD is different from the pattern in ischaemic infarcts, so that ADC analysis might be helpful for differentiating between these conditions.

Adolescent↗
PubMed2003

Three-dimensional white matter tractography by diffusion tensor imaging in ischaemic stroke involving the corticospinal tract.

Diffusion tensor MR imaging (DTI) provides information on diffusion anisotropy, which can be expressed with three-dimensional (3D) white matter tractography. We used 3D white matter tractography to show the corticospinal tract in eight patients with acute or early subacute ischaemic stroke involving the posterior limb of the internal capsule or corona radiata and to assess involvement of the tract. Infarcts and the tract were shown simultaneously, providing information on their spatial relationships. In five of the eight patients, 3D fibre tract maps showed the corticospinal tract in close proximity to the infarct but not to pass through it. All these patients recovered well, with maximum improvement from the lowest score on manual muscle testing (MMT) up to the full score through rehabilitation. In the other three patients the corticospinal tract was shown running through the infarct; reduction in MMT did not necessarily improve favourably or last longer, other than in one patient. As 3D white matter tractography can show spatial relationships between the corticospinal tract and an infarct, it might be helpful in prognosis of gross motor function.

Aged↗
PubMed2003

Voxel-based analysis of MRI reveals anterior cingulate gray-matter volume reduction in posttraumatic stress disorder due to terrorism.

MRI studies using the manual tracing method have shown a smaller-than-normal hippocampal volume in patients with posttraumatic stress disorder (PTSD). However, these studies have yielded inconsistent results, and brain structures other than the hippocampus have not been well investigated. A recently developed, fully automated method called voxel-based morphometry enables an exploration of structural changes throughout the brain by applying statistical parametric mapping to high-resolution MRI. Here we first used this technology in patients with PTSD. Participants were 9 victims of the Tokyo subway sarin attack with PTSD and 16 matched victims of the same traumatic event without PTSD. The voxel-based morphometry showed a significant gray-matter volume reduction in the left anterior cingulate cortex (ACC) in trauma survivors with PTSD compared with those without PTSD. The severity of the disorder was negatively correlated with the gray-matter volume of the left ACC in PTSD subjects. There were no significant differences in other gray-matter regions or any of the white-matter regions between two groups. The present study demonstrates evidence for structural abnormalities of ACC in patients with PTSD. Together with previous functional neuroimaging studies showing a dysfunction of this region, the present findings provide further support for the important role of ACC, which is pivotally involved in attention, emotional regulation, and conditioned fear, in the pathology of PTSD.

Adult↗
PubMed2003

MR imaging of postischemic neuronal death in the substantia nigra and thalamus following middle cerebral artery occlusion in rats.

The goal of this study was to investigate apparent diffusion coefficient (ADC) and T(2) relaxation time (T(2)) in the substantia nigra and thalamus after middle cerebral artery occlusion in rats. In the substantia nigra ipsilateral to infarct, ADC was significantly lower and T(2) was significantly higher on the third and fourth days, but they did not change significantly on the first, second, eighth and 15th days. In the ipsilateral thalamus, ADC and T(2) did not change significantly between the first and fourth days, but were significantly lower on the eighth and 15th days. This combination of MR findings suggested that secondary degeneration in the thalamus was different from that in the substantia nigra.

Animals↗
PubMed2002

Two-dimensional thick-slice MR digital subtraction angiography in the assessment of small to medium-size intracranial arteriovenous malformations.

Assessment of intracranial arteriovenous malformations (AVMs) by conventional catheter angiography carries risks; moreover, this invasive procedure is often repeated for follow-up. We investigated the clinical applicability of two-dimensional thick-slice, contrast-enhanced magnetic resonance digital subtraction angiography (2D MRDSA) with high temporal resolution in the assessment of AVMs. We performed 78 2D MRDSA studies of treated or untreated small to medium-size AVMs on a 1.5 tesla imager. Two observers independently evaluated demonstration of nidus flow void on T2-weighted images and each component of the AVM on 2D MRDSA employing a three-point grading scale. In 55 patients with AVMs, the mean ratings of nidus flow voids, feeding vessels, nidi, draining vessels and early venous filling on MRI were 2.8, 2.4, 2.6, 2.8 and 2.8, respectively. sensitivity, specificity, positive and negative predictive values for an AVM using 2D MRDSA were 87, 100, 100 and 78%, respectively and for nidus flow voids on T2-weighted images 80, 91, 96 and 66%, respectively. 2D MRDSA can thus demonstrate haemodynamic features of AVMs. It can be employed as a less invasive, dynamic angiographic tool for follow-up of AVMs previously delineated by catheter angiography.

Adult↗
PubMed2002

1H-MR spectroscopy and gray matter volume of the anterior cingulate cortex in schizophrenia.

Schizophrenic and normal control subjects were examined using both H-magnetic resonance spectroscopy (MRS) and structural MR imaging, in order to accurately assess the partial volume within the spectroscopic volume of interest (VOI) in the anterior cingulate cortex. The gray matter volume within VOI correlated positively with the N-acetyl-aspartate (NAA) to choline (Cho) ratio in schizophrenics only, not in controls. Schizophrenic patients had a reduced NAA/Cho ratio and an elevated Cho/creatine ratio compared to controls after the partial volume effect was eliminated. There was a significant negative correlation between the NAA/Cho ratio and the severity of blunted affect symptom in schizophrenics. These results provide further support to the idea that the measures of H-MRS indicate not only neuronal loss but also neuronal dysfunction in schizophrenia.

Adult↗
PubMed2002

Diffusion-weighted magnetic resonance imaging of dural sinus thrombosis.

Magnetic resonance imaging (MRI) is useful to diagnose dural sinus thrombosis. However, the representative appearance of dural sinus thrombosis on diffusion-weighted MRI has not been established. This study was aimed at determining whether cytotoxic or vasogenic edema is more predominant in the affected cerebral parenchyma and assessing the time courses and prognosis of dural sinus thrombosis lesion. The studies on sixteen patients with dural sinus thrombosis who underwent diffusion-weighted MRI were retrospectively reviewed. The diagnosis was confirmed by digital subtraction angiography in 11 patients and magnetic resonance angiography in five patients. Diffusion-weighted images with echo-planar imaging were obtained using two or three b values, with the highest b value of up to 1,000 s/mm(2). A region of interest was placed on an area of abnormal signal intensity to calculate apparent diffusion coefficients (ADCs). Nine of the 16 patients had lesions with an increased ADC, whereas, three of these nine patients also had lesions with a decreased ADC. Among 11 patients who underwent initial MRI within 7 days of their last episode, eight had lesions with an increased ADC, of whom three had lesions mixed with both decreased and increased ADC areas. Follow-up studies of these three patients revealed the development of hemorrhagic infarction in two and subcortical hemorrhage in one. Vasogenic edema develops more predominantly and earlier in dural sinus thrombosis, though cytotoxic edema was also associated with the pathological changes in the early phase. Decrease of ADC value is presumed to reflect severe pathological conditions and indicate possible future development of infarction or hemorrhage.

Adult↗
PubMed2002

Hemorrhagic brain metastases with high signal intensity on diffusion-weighted MR images. A case report.

Diffusion-weighted MR imaging has been applicable to the differential diagnosis of abscesses and necrotic or cystic brain tumors. However, restricted water diffusion is not necessarily specific for brain abscess. We describe ring-enhancing metastases of lung carcinoma characterized by high signal intensity on diffusion-weighted MR images. The signal pattern probably reflected intralesional hemorrhage. The present report adds to the growing literature regarding the differential diagnosis of ring-enhancing brain lesions.

Brain Abscess↗
PubMed2001

Metabolism of 99mTc-ethylcysteinate dimer in infarcted brain tissue of rats.

UNLABELLED: Brain SPECT with 99mTc-ethylcysteinate dimer (99mTc-ECD) reveals a subacute cerebral infarct as a hypoactive area, even in the presence of postischemic hyperperfusion. The brain retention of 99mTc-ECD depends on hydrophilic conversion mediated by enzymes, and impaired enzymatic trapping is hypothesized to depress the retention efficiency in the infarcted region. The aim of this study was to determine whether the metabolic rate of 99mTc-ECD is actually reduced in infarcted brain tissue. METHODS: In 50 mmol/L phosphate buffer (pH 7.4), 99mTc-ECD was incubated for 30 min with homogenates of rat brain tissue with and without triphenyltetrazolium chloride (TTC) staining. The ratio of polar products was determined by thin-layer chromatography as a function of incubation time, and metabolic rates were obtained. Permanent focal ischemia was induced by occlusion of the right middle cerebral artery (MCA) in rats. The brain was removed 24 h after MCA occlusion, and the infarcted area was defined by TTC staining. The metabolic rate of 99mTc-ECD was determined in homogenates of infarcted tissue, contralateral noninfarcted tissue, and tissue sampled from sham-operated rats. The infarct volume was measured by direct and indirect methods to assess volume expansion caused by edema, and the metabolic rate in infarcted tissue was corrected for the effect of edema. RESULTS: TTC staining had no effect on the metabolic rate of 99mTc-ECD. The metabolic rates in the infarcted tissue were 0.222%/min +/- 0.054%/min and 0.285%/min +/- 0.064%/min before and after correction for edema, respectively. These rates were significantly lower than those in the contralateral noninfarcted tissue (0.426%/min +/- 0.028%/min) and the tissue sampled from the sham-operated rats (0.439%/min +/- 0.031%/min). No substantial difference in rates was observed between the contralateral tissue and the tissue from the sham-operated rats. CONCLUSION: The results of this study showed that infarction decreases the activity of enzymes that mediate the hydrophilic conversion of 99mTc-ECD in the brain and suggest that reduced metabolic activity is related to decreased accumulation of 99mTc-ECD in hyperperfused infarcts.

Animals↗
PubMed2000

Changes in the apparent diffusion coefficient of water and T2 relaxation time in gerbil hippocampus after mild ischemia.

Selective neuronal death of the hippocampal CA1 area after mild ischemia is known as delayed neuronal death (DND). Progression of DND was evaluated using 7T MRI in gerbils. In the CA1, the T2 relaxation time started to increase on day 3 and was significantly higher on day 4 than that of the control gerbils. However, the apparent diffusion coefficient of water (ADC) was significantly lower on day 1 than in the control and continued to decline up to day 4. Changes in T2 coincided with loss of MAP2 immunoreactivity, while the ADC decrease preceded these changes. After 1 month, the ADC had returned to within the normal range, while T2 had decreased to below the control level. These results suggest that MRI is useful for monitoring DND.

Animals↗
PubMed2000

Contrast-enhanced magnetic resonance imaging of the cranial nerves in patients with acoustic schwannoma: correlation with surgical findings.

Eighteen patients with acoustic schwannoma were examined on a 1.5-T magnetic resonance imaging (MRI) unit with precontrast and postcontrast T1-weighted spin-echo sequences. Each abnormality was assessed in terms of the size, location, extensions and signal intensity of the lesions. If a nerve was enhanced and was involved by the tumor around the fundus of the internal auditory canal (IAC), the nerve was interpreted to be the originating nerve. The postcontrast T1-weighted images revealed enhanced masses of the cerebellopontine angle and/or the IAC in all cases. In 11 of the 19 operated patients with shwannomas, the site of tumor origin (or origin nerve) was confirmed by surgery. In 2 of the 11 cases (18%), surgical findings coincided with the T1-weighted image findings. Facial nerve enhancement on the ipsilateral side of the tumor was noted in 10 cases (53%) and the contralateral facial nerve enhancement was demonstrated in 7 (70%). The enhancement of facial nerve associated with acoustic schwannoma was not correlated to the degree of nerve compression by the tumor. These results demonstrate that it was possible, although infrequent, to predict the site of origin of acoustic schwannoma before surgery in some patients. Improvement of the imaging matrix or multiplanar reconstruction techniques with three-dimensional data acquisition may make it possible to overcome the limitations of MRI.

Adult↗
PubMed2000

Temporal changes of the apparent diffusion coefficients of water and metabolites in rats with hemispheric infarction: experimental study of transhemispheric diaschisis in the contralateral hemisphere at 7 tesla.

The purpose of the present study was to clarify the temporal changes of the apparent diffusion coefficients (ADCs) of cerebral metabolites during early focal ischemia using stimulated echo acquisition mode with short echo time at a 7 T magnet to assess the pathophysiology of the reduction in diffusion properties observed both in the ischemic cerebral hemisphere and in the contralateral hemisphere. The ADCs of metabolites in the infarcted hemisphere 1 hour and 3 hours after the onset of ischemia decreased with 25% and 29% for choline containing compounds (Cho), 16% and 26% for creatine and phosphocreatine (Cre), and 19% and 19% for N-acetylaspartate (NAA), respectively, compared with the ADC values 2 hours later in the contralateral hemisphere. There were decreases in the ADC of Cho, Cre, and NAA with 21%, 7%, and 18% 8 hours later, respectively, in the noninfarcted hemisphere, which suggested transhemispheric diaschisis in rats with focal cerebral ischemia. The present study proposed that the diffusion characteristics of the brain metabolites might offer new insights into circulatory and metabolic alteration in the cerebral intracellular circumstance.

Animals↗
PubMed1999

Phase II study of KRN8602, 3'-deamino-3'-morpholino-13-deoxo-10-hydroxycarminomycin hydrochloride, MX2 x HCl in patients with metastatic breast cancer.

PURPOSE: KRN8602 (3'-deamino-3'-morpholino-13-deoxo-10-hydroxycarminomycin hydrochloride, MX2 x HCl) is a newly developed anthracycline that has been found to be effective against multidrug-resistant tumor cells in vitro and in vivo. In order to clinically confirm these promising preclinical observations, we performed a phase II trial of KRN8602 in patients with anthracycline-resistant metastatic breast cancer. METHODS: Of 41 patients registered with metastatic breast cancer, 37 were eligible and were given at least two cycles of KRN8602 15 mg/m2 per day at 3-4 week intervals by intravenous bolus injection on days 1, 2, and 3. RESULTS: Of the 37 patients, 6 (16.2%, with a 95% confidence interval of 4.3-28.1%) had a partial response (PR). No complete responses (CRs) were observed. The difference between response rates according to prior history of anthracycline administration was not significant. Myelosuppression was moderately severe, with grade 3 or 4 leukopenia occurring in 65%. Severe nausea/vomiting was observed in 44% of the patients. CONCLUSIONS: The results indicate that KRN8602 has modest activity in refractory metastatic breast cancer and is associated with relatively severe toxicity. Furthermore, the preclinical finding that KRN8602 overcomes anthracycline resistance was not reliably reproduced in this clinical phase II trial.

Adult↗