Biomedical subjects

Atsuo Tanaka

Publications and source records attributed to Atsuo Tanaka.

18 recordsLinked to original sources

PubMed2005

Novel method to estimate and display cerebral cortical degeneration using diffusion-weighted magnetic resonance imaging.

Previous studies have shown that diffusion-weighted imaging (DWI) is useful for detecting microstructural degradation of neuronal tissue in neurodegenerative diseases. Mapping of cortical degeneration by DWI is potentially useful, but is extremely difficult, mainly because of the partial volume effect resulting from the surrounding cerebrospinal fluid (CSF). In this study a novel method to map and display the cortical damage in neurodegenerative diseases using DWI is proposed. Instead of measuring the cortical diffusivity, the diffusivity of white matter directly beneath the cortex, where neuronal fibers enter or exit the overlying cortex, was measured and mapped onto the cortical surface. The map was viewed in a form of three-dimensional (3D) rendering. Patients with Alzheimer's disease (AD) showed cortical damage in the temporal and parietal cortices, and a patient with frontotemporal dementia showed damage in the frontal lobe, consistent with the typical topographical distribution of histopathological cortical damage in each of these diseases. The results suggest that subcortical diffusivity closely reflects cortical damage, and that the current mapping technique is a promising tool for evaluating neurodegenerative diseases.

Adult↗

PubMed2005

Age-related structural changes in the young adult brain shown by magnetic resonance diffusion tensor imaging.

RATIONALE AND OBJECTIVE: Structure of the brain is generally thought to remain stationary over the course of young adulthood. However, there is some evidence that microstructural changes of the brain do occur during this period. Magnetic resonance diffusion tensor imaging (DTI) provides quantitative measures of structural changes in the brain. We used DTI to detect possible age-related structural changes in the brains of young adults. MATERIALS AND METHODS: Twenty-five healthy adults in their 20s and 30s were studied using DTI. Maps of mean diffusivity and fractional anisotropy (FA) were created for subsequent histogram and region-of-interest analyses, and the results were correlated with the respective ages of the subjects. RESULTS: The histogram analysis revealed a significant increase in the mean FA value (r = 0.407, P < .05) and a significant decrease in FA peak height (r = -0.578, P < .002) with increasing age. No age-related changes were observed in indices derived from mean diffusivity maps. Region-of-interest analysis showed no focal white matter regions with significant FA change. CONCLUSION: Quantitative DTI revealed age-related structural changes in the brains of young adults. Changes on FA histograms observed in this study were considered to be related to changes in the relative volumes of gray and white matter and may represent maturational changes.

Adult↗

PubMed2005

[Case of traditional herbal medicine-induced aristolochic acid nephropathy developing to end-stage renal failure].

A 48-year-old male was referred to our university hospital for severe azotemia with muscle cramp. He had been taking Chinese herbs as a traditional medicine to reduce hyperuricemia for about 9 months. Urinalysis showed trace proteinuria and hematuria without any casts. Renal glucosuria was also observed. In addition to azotemia, hyperchloremic metabolic acidosis and severe anemia were revealed. Hemodialysis was conducted and his general condition improved. A renal biopsy specimen revealed severe interstitial fibrosis and tubular atrophy with cellular degeneration. No remarkable glomerular changes were observed except for wrinkling of the basement membrane in a few glomeruli. Aristolochic acid was detected in the Chinese herbs, leading to the diagnosis of aristolochic acid nephropathy (AAN). His renal dysfunction was considered to be irreversible and he underwent maintenance hemodialysis. In Japan, AAN or Chinese herbs nephropathy decreased after an outbreak from 1995 to 2000. The public should be warned again that Chinese herbs, which are not permitted by the Japanese government, may contain aristolochic acid.

Aristolochic Acids↗

PubMed2004

Validation of the CBF, CBV, and MTT values by perfusion MRI in chronic occlusive cerebrovascular disease: a comparison with 15O-PET.

RATIONALE AND OBJECTIVES: To evaluate the reliability of cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) values obtained by deconvolution algorithm perfusion-weighted MR imaging (D-PWI), we compared these values with those obtained by first-moment algorithm perfusion-weighted MR imaging (F-PWI) and 15O-PET. SUBJECTS AND METHODS: Six healthy volunteers and eleven patients with chronic occlusive cerebrovascular disease were studied with both perfusion-weighted MR imaging and 15O-PET, and region-of-interest analyses were performed. Normalization factors for CBF and CBV values obtained by D-PWI were determined as the mean values of 15O-PET divided by those of D-PWI in healthy volunteers. Then these values were used in analyzing the data of the patients. RESULTS: The MTT value obtained by D-PWI was 6.1 +/- 0.5 seconds on the non-occluded side, 6.4 +/- 0.7 seconds on the minimally to moderately stenosed side, and 6.7 +/- 1.2 seconds on the severely stenosed to occluded side. These values were significantly correlated with those obtained by F-PWI (r = 0.83; P < .001), and with those obtained by 15O-PET (r = 0.78; P < .05). However, the CBF and CBV values obtained by D-PWI did not correlate with those obtained by 15O-PET. CONCLUSION: MTT values obtained by D-PWI were reliable parameters of cerebral hemodynamics, but the CBF and CBV values obtained by D-PWI were not always reliable.

Adult↗

PubMed2004

Prevalence of stenoocclusive lesions in the renal and abdominal arteries in moyamoya disease.

OBJECTIVE: The extracranial involvement of moyamoya disease has been reported in several studies. The main purpose of this study was to determine the prevalence of stenoocclusive lesions in the renal and major abdominal arteries in moyamoya disease. MATERIALS AND METHODS: Abdominal angiography was performed in 73 patients with idiopathic moyamoya disease. The findings of abdominal angiography were retrospectively reviewed for the presence and appearance of stenosis in the renal and other major abdominal arteries. RESULTS: Four (5%) of 73 patients presented with unilateral renal artery stenosis. Three patients had moderate stenosis, and one patient had mild stenosis. In the three patients with moderate stenosis, the renal artery stenosis was located in the proximal region of the main branch. Two patients (3%) with moderate stenosis of the unilateral renal artery had renovascular hypertension. No statistically significant differences were observed in age, sex, and the cerebral angiographic stage between patients with and without renal artery stenosis. No stenosis was found in the abdominal aorta or celiac, superior mesenteric, common hepatic, splenic, and proximal common iliac arteries. No occlusions were found in any abdominal arteries. CONCLUSION: The prevalence of renal artery stenosis in patients with moyamoya disease was 5% (4/73). Involvement of the proximal region of the renal artery was dominant. No stenosis was found in other abdominal arteries.

Abdomen↗

PubMed2004

Differentiation of cavernous hemangioma from schwannoma of the orbit: a dynamic MRI study.

OBJECTIVE: The purpose of this study was to determine the capability of dynamic contrast MRI to differentiate hemangioma from schwannoma of the orbit. MATERIALS AND METHODS: Sixteen patients (three males and 13 females; mean age, 39 +/- 17.3 [SD] years; age range, 10-71 years) with unilateral orbital tumors, including eight cavernous hemangiomas and eight schwannomas, were examined. In addition to conventional MRI, we performed a dynamic contrast study (fast spin-echo sequence, 20-sec interval) after bolus administration of the contrast material (gadopentetate dimeglumine, 0.1 mmol/kg). We evaluated the features of the contrast enhancement spread pattern and the tumors' time-intensity curves. RESULTS: In the early phase, all the hemangiomas started the enhancement from one point or portion, although all the schwannomas started the enhancement from a wide area. The difference in the contrast-enhancement spread pattern features between the two types of tumors was statistically significant (p < 0.0001). The gradient of the time-intensity curve did not show a significant difference. CONCLUSION: Hemangioma and schwannoma of the orbit can be differentiated by the contrast-enhancement spread pattern on dynamic MRI.

Adolescent↗

PubMed2003

Development of combinatorial bioengineering using yeast cell surface display--order-made design of cell and protein for bio-monitoring.

A genetic system to display proteins as their active and functional forms on the cell surface of yeast, Saccharomyces cerevisiae, has been exploited. Surface-engineered (arming) cells displaying amylase or cellulase could assimilate starch or cellulose as the sole carbon source, although S. cerevisiae can not intrinsically assimilate them. Arming cells with a green fluorescent protein (GFP) from Aequorea victoria can emit green fluorescence from the cell surface in response to the environmental conditions. From these results, we attempted to construct a system to monitor the foreign protein production in yeast by simultaneous displaying the enhanced GFP (EGFP). The expression in yeast of the Escherichia coli beta-galactosidase-encoding gene was examined as an example of intracellular production and that of the human interferon-alpha (omega, IFN-omega)-encoding gene as an example of extracellular production. Their productions and the simultaneous surface-display of EGFP as a reporter were controlled by the same promoter, GAL1. The relationship among fluorescence signals and their productions was evaluated. The surface-display system, unlike one using tag-proteins, would be able to facilitate the monitoring of native protein productions in bioprocesses using living cells in real time by the combination of promoters and GFP variants.

Biomedical Engineering↗

PubMed2003

Semi-quantitative CBF and CBF ratios obtained using perfusion-weighted MR imaging.

To clarify the utility of semi-quantitative cerebral blood flow (CBF) measurements using perfusion-weighted MR imaging (PWI), a comparison of this method with quantitative CBF obtained using PET was conducted in 10 patients with chronic occlusive cerebrovascular disease and unilateral occlusion of the cerebral artery. Semi-quantitative CBF obtained using PWI and quantitative CBF obtained using PET showed no statistically significant correlation. The CBF ratios of the affected side relative to the contralateral unaffected side obtained using PWI and PET were 0.94 +/- 0.22 and 0.88 +/- 0.19, respectively. A statistically significant positive correlation was obtained between these ratios (p < 0.01). The CBF ratio, but not the semi-quantitative CBF, obtained using PWI has a potential to detect changes in the CBF.

Adolescent↗

PubMed2003

Up-regulation of the peroxisomal beta-oxidation system occurs in butyrate-grown Candida tropicalis following disruption of the gene encoding peroxisomal 3-ketoacyl-CoA thiolase.

In the yeast Candida tropicalis, two thiolase isozymes, peroxisomal acetoacetyl-CoA thiolase and peroxisomal 3-ketoacyl-CoA thiolase, participate in the peroxisomal fatty acid beta-oxidation system. Their individual contributions have been demonstrated in cells grown on butyrate, with C. tropicalis able to grow in the absence of either one. In the present study, a lack of peroxisomal 3-ketoacyl-CoA thiolase protein resulted in increased expression (up-regulation) of acetoacetyl-CoA thiolase and other peroxisomal proteins, whereas a lack of peroxisomal acetoacetyl-CoA thiolase produced no corresponding effect. Overexpression of the acetoacetyl-CoA thiolase gene did not suppress the up-regulation or the growth retardation on butyrate in cells without peroxisomal 3-ketoacyl-CoA thiolase, even though large amounts of the overexpressed acetoacetyl-CoA thiolase were detected in most of the peroxisomes of butyrate-grown cells. These results provide important evidence of the greater contribution of 3-ketoacyl-CoA thiolase to the peroxisomal beta-oxidation system than acetoacetyl-CoA thiolase in C. tropicalis and a novel insight into the regulation of the peroxisomal beta-oxidation system.

Acetyl-CoA C-Acetyltransferase↗

PubMed2003

Effect of catalase-specific inhibitor 3-amino-1,2,4-triazole on yeast peroxisomal catalase in vivo.

3-Amino-1,2,4-triazole (3-AT) is known as an inhibitor of catalase to whose active center it specifically and covalently binds. Subcellular fractionation and immunoelectronmicroscopic observation of the yeast Candida tropicalis revealed that, in 3-AT-treated cells in which the 3-AT was added to the n-alkane medium from the beginning of cultivation, catalase transported into peroxisomes was inactivated and was present as insoluble aggregated forms in the organelle. The aggregation of catalase in peroxisomes occurred only in these 3-AT-treated cells and not in cells in which 3-AT was added at the late exponential growth phase. Furthermore, 3-AT did not affect the transportation of catalase into peroxisomes. The appearance of aggregation only in cells to which 3-AT was added from the beginning of cultivation suggests that, in the process of catalase transportation into yeast peroxisomes, some conformational change may take place and that correct folding may be inhibited by the binding of 3-AT to the active center of catalase. Accordingly, 3-AT will be an interesting compound for investigation of the transport machinery of the peroxisomal tetrameric catalase.

Amitrole↗

PubMed2003

Reliability of mean transit time obtained using perfusion-weighted MR imaging; comparison with positron emission tomography.

The purpose of this project was to assess the reliability of the cerebral mean transit time (MTT) obtained using perfusion-weighted MR imaging by comparing it with the MTT obtained when performing positron emission tomography (PET). Ten patients with chronic occlusive cerebrovascular disease were investigated. They had either unilateral internal carotid artery occlusion or middle cerebral artery occlusion. The regions-of-interest were placed in non-infarcted areas within the territory of the middle cerebral artery on the affected side. Control regions-of-interest were placed in mirrored regions of the contralateral side. Linear regression analyses were performed using the parameters of the MTT obtained with perfusion-weighted MR imaging and the MTT, cerebral blood flow, vascular reactivity, and oxygen extraction fraction obtained with PET. The respective MTTs of the affected and non-affected sides obtained with perfusion-weighted MR imaging versus those with PET were 7.3 +/- 2.2 s and 6.0 +/- 1.2 s versus 8.2 +/- 3.0 s and 6.4 +/- 1.7 s. The MTT obtained using perfusion-weighted MR imaging and PET demonstrated statistically significant correlation (r = 0.87, p < 0.0001). The MTT obtained with perfusion-weighted MR imaging correlated statistically with cerebral blood flow (r = -0.74, p < 0.001), vascular reactivity (r = -0.73, p < 0.001) and oxygen extraction fraction (r = 0.61, p < 0.01). Similarly, the MTT obtained using PET statistically correlated with cerebral blood flow (r = -0.78, p < 0.0001), vascular reactivity (r = -0.51, p < 0.05) and oxygen extraction fraction (r = 0.68, p < 0.01). The reliability of the MTT obtained using perfusion-weighted MR imaging appears to be approximately equal to that obtained with positron emission tomography.

Adolescent↗

PubMed2003

High b value diffusion-weighted imaging is more sensitive to white matter degeneration in Alzheimer's disease.

It has been reported that diffusion-weighted imaging (DWI) can detect white matter degeneration in the Alzheimer's disease (AD) brain. We hypothesized that imaging of the slow diffusion component using high b value DWI is more sensitive to AD-related white matter degeneration than is conventional DWI, and therefore we studied the effects of high b value on lesion-to-normal contrast and contrast-to-noise ratio (CNR). Seven AD patients and seven age-matched normal subjects were studied with full-tensor DWI at three different b values (1000, 2000, and 4000 s/mm(2)) without changing echo time or diffusion time, and the mean diffusivities in the parietal and occipital regions were measured. Statistical analyses revealed that use of higher b values significantly improves both lesion-to-normal contrast and CNR. We concluded that high b value DWI is more sensitive to AD-related white matter degeneration than is conventional DWI.

Aged↗

PubMed2002

Diffusion tensor in posterior cingulate gyrus: correlation with cognitive decline in Alzheimer's disease.

To determine whether the diffusion abnormalities in brains with Alzheimer's disease (AD) correlate with disease severity, we studied 34 AD patients using diffusion tensor MRI. Mean diffusivity and fractional anisotropy (FA) as well as three eigenvalues (lambda1, lambda2, and lambda3) of the diffusion tensor of the posterior cingulate white matter correlated with the Mini-Mental State Examination (MMSE) score. The mean diffusivity and the three eigenvalues showed significant correlation with the MMSE score. On the other hand, no significant correlation was seen between the FA and MMSE score. Our results suggested that mean diffusivity and the eigen-values, but not FA, reflect progression of AD-related histopathlogical changes in the posterior cingulate white matter and may be useful biological indices to monitor AD.

Aged↗

PubMed2002

MR relative cerebral blood flow mapping of Alzheimer disease: correlation with Tc-99m HMPAO SPECT.

RATIONALE AND OBJECTIVES: To evaluate the value of magnetic resonance (MR) perfusion imaging for diagnosis of Alzheimer disease (AD), the authors compared relative cerebral blood flow (CBF) maps obtained with MR perfusion imaging and technetium-99m hexamethyl-propyleneamine oxime (HMPAO) single photon emission computed tomography (SPECT) in patients with AD. MATERIALS AND METHODS: Eight patients with AD were studied with MR perfusion imaging and HMPAO SPECT. The relative CBF maps from the two techniques were spatially coregistered, and relative CBF values in 13 cerebral gray matter regions (total, 26 regions of interest) were compared with regression analysis. To evaluate the degree of deviation of each brain region from the regression line, a P value for the residual was calculated for each region. RESULTS: A significant overall correlation was seen between the relative CBF values produced by the two techniques (r = .68, P < .0001). Smaller P values for the residuals were obtained in the anterior cingulate cortex (P = .05) and posterior cingulate cortex (P < .001), indicating larger deviations in these regions. When data from these two regions were eliminated, the correlation coefficient rose to 0.80 (P < .0001). CONCLUSION: Despite fairly large discrepancies in the anterior and posterior cingulate cortices, the relative CBF map obtained with MR imaging is generally in close agreement with the HMPAO SPECT map, suggesting that MR perfusion imaging can provide clinically useful information regarding CBF abnormalities in patients with AD.

Adult↗

PubMed2002

Structurally and functionally conserved domains in the diverse hydrophilic carboxy-terminal halves of various yeast and fungal Na+/H+ antiporters (Nha1p).

Genes encoding the Na(+)/H(+) antiporter (Nha1p) from Candida tropicalis (C.t.), Hansenula anomala (H.a.) (also named Pichia anomala), and Aspergillus nidulans (A.n.) were cloned, and the nucleotide sequences were determined. The deduced primary sequences revealed highly conserved hydrophobic regions and rather diverse hydrophilic regions. Among the seven known Nha1p sequences, Schizosaccharomyces pombe (S.p.) Nha1p is exceptional in lacking the hydrophilic region. Within the diverse hydrophilic regions, we found six conserved regions (C1-C6). Expression of C.t. Nha1p in Saccharomyces cerevisiae (S.c.) cells lacking NHA1 and ENA1 (Na(+)-ATPase) complemented the salinity-sensitive phenotype, suggesting that C.t. Nha1p is functionally related to S.c. Nha1p. Expression of various truncated forms of the C-terminal half of S.c. and C.t. Nha1p showed essentially the same phenotype for both species: deletion of the C4-C6 region caused cell growth to be more resistant to high salinity than the wild type, suggesting an inhibitory function of these domains on the antiporter activity. However, complete loss of C1-C6 caused a severe growth defect under conditions of high salinity, suggesting a defect in antiporter activity. The DeltaC2-C6 form of C.t. Nha1p, containing only C1, restored the retarded cell growth at high salinity more than the control vector alone, but to a value lower than the wild type. These results suggest an essential role for C1 and an activating role of the C2-C3 region in the functional expression of Nha1. High expression of the DeltaC2-C6 form of S.c. Nha1p was toxic for yeast cells, although low expression was not, suggesting that the overexpression of C1 is toxic. The results in this study suggest that the diverse hydrophilic region of yeast and fungal Nha1p has six conserved domains with conserved functions in terms of expression of Nha1p activity.

Amino Acid Sequence↗

PubMed2002

Direct and efficient production of ethanol from cellulosic material with a yeast strain displaying cellulolytic enzymes.

For direct and efficient ethanol production from cellulosic materials, we constructed a novel cellulose-degrading yeast strain by genetically codisplaying two cellulolytic enzymes on the cell surface of Saccharomyces cerevisiae. By using a cell surface engineering system based on alpha-agglutinin, endoglucanase II (EGII) from the filamentous fungus Trichoderma reesei QM9414 was displayed on the cell surface as a fusion protein containing an RGSHis6 (Arg-Gly-Ser-His(6)) peptide tag in the N-terminal region. EGII activity was detected in the cell pellet fraction but not in the culture supernatant. Localization of the RGSHis6-EGII-alpha-agglutinin fusion protein on the cell surface was confirmed by immunofluorescence microscopy. The yeast strain displaying EGII showed significantly elevated hydrolytic activity toward barley beta-glucan, a linear polysaccharide composed of an average of 1,200 glucose residues. In a further step, EGII and beta-glucosidase 1 from Aspergillus aculeatus No. F-50 were codisplayed on the cell surface. The resulting yeast cells could grow in synthetic medium containing beta-glucan as the sole carbon source and could directly ferment 45 g of beta-glucan per liter to produce 16.5 g of ethanol per liter within about 50 h. The yield in terms of grams of ethanol produced per gram of carbohydrate utilized was 0.48 g/g, which corresponds to 93.3% of the theoretical yield. This result indicates that efficient simultaneous saccharification and fermentation of cellulose to ethanol are carried out by a recombinant yeast cells displaying cellulolytic enzymes.

Cellulase↗

PubMed2002

Construction of yeast strains with high cell surface lipase activity by using novel display systems based on the Flo1p flocculation functional domain.

We constructed a novel cell-surface display system, using as a new type of cell-wall anchor 3,297 or 4,341 bp of the 3' region of the FLO1 gene (FS or FL gene, respectively), which encodes the flocculation functional domain of Flo1p. In this system, the N terminus of the target protein was fused to the FS or FL protein and the fusion proteins were expressed under the control of the inducible promoter UPR-ICL (5' upstream region of the isocitrate lyase of Candida tropicalis). Using this new system, recombinant lipase with a pro sequence from Rhizopus oryzae (rProROL), which has its active site near the C terminus, was displayed on the cell surface. Cell-surface display of the FSProROL and FLProROL fusion proteins was confirmed by immunofluorescence microscopy and immunoblotting. Lipase activity reached 145 IU/liter (61.3 IU/g [dry cell weight]) on the surface of the yeast cells, which successfully catalyzed the methanolysis reaction. Using these whole-cell biocatalysts, methylesters synthesized from triglyceride and methanol reached 78.3% after 72 h of reaction. To our knowledge, this is the first example of cell-surface display of lipase with high activity. Interestingly, the yeast cells displaying the FLProROL protein showed strong flocculation, even though the glycosylphosphatidylinositol anchor attachment signal and cell-membrane-anchoring region of Flo1p had been deleted from this gene. The cell-surface display system based on FL thus endows the yeast strain with both novel enzyme display and strong flocculation ability.

Flocculation↗

PubMedDate not supplied

A case of lymphangioleiomyomatosis affecting the supraclavicular lymph nodes.

The case of a 46-year-old woman with lymphangioleiomyomatosis (LAM) involving the supraclavicular, mediastinal, and pelvic lymph nodes in addition to the lungs is reported. Computed tomography incidentally revealed multiple thin-walled pulmonary cysts and low-attenuating masses in the supraclavicular, mediastinal, and retroperitoneal lymph nodes. A biopsy of the supraclavicular mass was performed and diagnosed as LAM histopathologically. The common sites of extrapulmonary LAM include retroperitoneal and mediastinal lymph nodes; however, supraclavicular lymph node involvement is extremely rare.

Contrast Media↗