Biomedical subjects

Hisashi Tanaka

Publications and source records attributed to Hisashi Tanaka.

At least 19 recordsLinked to original sources

PubMed2006

Sonophotocatalysis of oxalic acid solution.

Sonophotocatalysis of oxalic acid was performed in various atmospheric conditions. Sonophotocatalysis means a coupled reaction of sonolysis and photocatalysis. CO(2), CO and H(2) were obtained. The yield of CO(2) was twice larger than the sum of yields of photocatalysis and sonolysis in an Ar atmosphere. Namely, synergistic effect was observed. Further improvement was observed after pre-sonication. Hydrogen peroxide produced during sonication is a key material for the synergistic effect. In surroundings including O(2), however, synergistic effect could not be observed. The role of ultrasonic waves on the sonophotocatalysis of organic compounds was investigated.

Journal Article↗

PubMed2006

MRI and CT findings of the giant cell tumors of the skull; five cases and a review of the literature.

PURPOSE: To investigate CT and MR findings of giant cell tumors (GCTs) of the skull, an unusual site for such tumors. MATERIALS AND METHODS: CT and MR features of five histologically proven giant cell tumors of the skull were retrospectively reviewed. We also reviewed 22 cases in the literature that included MR or CT findings. RESULTS: Three of the tumors originated from the temporal bone with predominantly medial extension, and the other two were centered in the body of the sphenoid bone and featured symmetrical soft tissue extension. CT images with bone window settings showed reactive bone changes for all three tumors of the temporal bone, suggesting slow growth for example, an expanded intradiploic space, expansive remodelling and development of foci of pressure erosion. GCTs of the sphenoid bone showed purely osteolytic changes without remodelling. Although the MR signals and enhancement patterns varied, all the tumors of the temporal bone had a markedly low intensity area on T2-weighted images, which was not seen in the tumors of the sphenoid bone. The findings for our cases generally corresponded to those reported in the literature. CONCLUSION: Giant cell tumors of the skull have two preferential sites and may have characteristic tendencies as to their extent. Bone changes and MR signals appear to show differences between the two sites.

Adolescent↗

PubMed2006

Quantitative study of changes in oxidative metabolism during visual stimulation using absolute relaxation rates.

In the context of quantitative functional MRI (fMRI), deoxyhemoglobin (dHb) content is the essential physiological parameter for calibrating the blood oxygenation level-dependent (BOLD) signal. In studies on humans, the baseline dHb content or its equivalent has been evaluated indirectly by means of carbon dioxide breathing as a physiological reference condition. In this study with normal volunteers, quantitative mapping of baseline dHb content was performed in a direct manner by measuring the reversible contribution of the effective transverse relaxation rate. The BOLD signal change in the visual cortex during 8 Hz flicker visual stimulation was calibrated based on the quantitative map of baseline dHb content. The calibrated relaxation rate change that represents the stimulation-induced fractional change of dHb content decreased by 14% within the activated visual cortex. Simultaneous measurement of cerebral blood flow (CBF) with BOLD showed an increase of 59%. From the calibrated relaxation rate and CBF changes, the cerebral metabolic rate of oxygen (CMRO2) was calculated to increase by 19-28% within the activated visual cortex. The ratio of the CBF increase to the CMRO2 increase was 2-3:1, which agreed well with results of similar quantitative fMRI studies for humans. The method proposed here for quantitative evaluation of the BOLD signal may be applicable not only to fMRI for normal human subjects, but also to physiologically altered or diseased states, because it requires no physiological perturbation.

Adult↗

PubMed2006

Anthocyanin-rich purple potato flake extract has antioxidant capacity and improves antioxidant potential in rats.

Anthocyanins from various vegetables and fruits have antioxidant activities, however, the bioactivities of coloured potato anthocyanins are not well studied. We examined the antioxidant capacities of pigmented fractions from purple potato flakes in vitro, and the antioxidant potentials of purple potato flakes in vivo. 1,1-Diphenyl-2-picrylhydrazyl radical scavenging activity of the pigmented fraction from Hokkai no. 92 (H92) potato flakes was higher than that from Kitamurasaki (KM) potato flakes. Extracts equivalent to 600 microg pigmented fractions from KM and H92 potato flakes inhibited linoleic acid oxidation in the order trolox>H92> or =KM>control. Rats were fed 25% KM or H92 potato flake diets for 4 weeks. The major anthocyanin was identified as petanin. Control rats were fed a diet with cornstarch instead of potato flakes for 4 weeks. The serum antioxidant potential level in the H92 group was significantly higher than that in the control group. The degree of hepatic lipid peroxidation in the H92 group was significantly lower than that in the control group. Hepatic Cu/Zn-superoxide dismutase (SOD), Mn-SOD and glutathione peroxidase (GSH-Px) mRNA levels in the H92 group were significantly higher than those in the control group. Similar significant differences in Cu/Zn-SOD and Mn-SOD mRNA levels between the KM and control groups were found. The present results suggest that purple potato flakes have antioxidant functions with regard to radical scavenging activity and inhibition of linoleic acid oxidation, and that they improve the antioxidant potentials in rats by enhancing hepatic Mn-SOD, Cu/Zn-SOD and GSH-Px mRNA expression.

Animals↗

PubMed2006

Large DNA palindromes as a common form of structural chromosome aberrations in human cancers.

Breakage-fusion-bridge cycles contribute to chromosome aberrations and generate large DNA palindromes that facilitate oncogene amplification in cancer cells. At the molecular level, large DNA palindrome formation is initiated by chromosome breaks, and genomic architecture such as short inverted repeat sequences facilitates this process in mammalian cells. However, the prevalence of DNA palindromes in cancer cells is currently unknown. To determine the prevalence of DNA palindromes in human cancer cells, we have developed a new microarray-based approach called Genome-wide Analysis of Palindrome Formation (GAPF, Tanaka et al., Nat Genet 2005; 37: 320-7). This approach is based on a relatively simple and efficient method to purify "snap-back DNA" from large DNA palindromes by intramolecular base-pairing, followed by elimination of single-stranded DNA by nuclease S1. Comparison of Genome-wide Analysis of Palindrome Formation profiles between cancer and normal cells using microarray can identify genome-wide distributions of somatic palindromes. Using a human cDNA microarray, we have shown that DNA palindromes occur frequently in human cancer cell lines and primary medulloblastomas. Significant overlap of the loci containing DNA palindromes between Colo320DM and MCF7 cancer cell lines suggests regions in the genome susceptible to chromosome breaks and palindrome formation. A subset of loci containing palindromes is associated with gene amplification in Colo320DM, indicating that the location of palindromes in the cancer genome serves as a structural platform that supports subsequent gene amplification.

Base Pairing↗

PubMed2005

Assessment of the three-dimensional relationship of the ossific nuclei and cartilaginous anlagen in congenital clubfoot by 3-D MRI.

PURPOSE: Radiographic measurement is the usual method used to objectively determine the extent of a congenital clubfoot deformity. Although radiographs have been used clinically to estimate the size and location of tarsal bones through measurements of the ossific nuclei, it is not clear to what extent these relationships are actually reflected in these measurements. So, we used a 3-D MRI system that could more objectively estimate sizes and positional relationships. MATERIAL AND METHOD: We evaluated 5 patients with unilateral congenital clubfoot deformity. Magnetic resonance imaging was performed of both feet using 1.5-T magnet. Based on the resulting magnetic resonance imaging volume data, a three-dimensional surface bone model was reconstructed by the Marching Cubes method. We used this model to perform a comparative analysis of the volume and volume ratio of each cartilaginous anlage and ossific nucleus, the length of the talus and the calcaneus, and the position of the center of gravity of ossific nuclei within the cartilaginous anlagen. We measured the relationship between the ossific nuclei and cartilaginous anlagen in the talus and calcaneus of patients with unilateral clubfoot deformity. RESULT: In clubfeet talus volume was reduced by 20.1% and calcaneal volume was reduced by 15.7%. Furthermore, the volume of the talar ossific nucleus was reduced by 42.6% and that of the calcaneal ossific nucleus was reduced by 12.1%. The length of the clubfoot talus was 8.2% shorter than normal, and that of the calcaneus was 4.8% shorter. CONCLUSION: The assessment technique presented herein was shown to be useful in ascertaining the various pathological characteristics associated with clubfoot.

Calcaneus↗

PubMed2005

Widespread and nonrandom distribution of DNA palindromes in cancer cells provides a structural platform for subsequent gene amplification.

Breakage-fusion-bridge cycles contribute to chromosome instability and generate large DNA palindromes that facilitate gene amplification in human cancers. The prevalence of large DNA palindromes in cancer is not known. Here, by using a new microarray-based approach called genome-wide analysis of palindrome formation, we show that palindromes occur frequently and are widespread in human cancers. Individual tumors seem to have a nonrandom distribution of palindromes in their genomes, and a subset of palindromic loci is associated with gene amplification. This indicates that the location of palindromes in the cancer genome can serve as a structural platform that supports subsequent gene amplification. Genome-wide analysis of palindrome formation is a new approach to identify structural chromosome aberrations associated with cancer.

Cell Line, Tumor↗

PubMed2005

Determination of transverse relaxation rate for estimating iron deposits in central nervous system.

To determine the amount of iron deposits in the basal ganglia, we examined 13 healthy volunteers with a 1.5 T MRI system using three transverse relaxation rates measured with two sequences. The transverse relaxation rates comprise the reversible contribution (R2') and irreversible contribution (R2) to a phase-reversal 180 degrees -pulse sequence. The transverse relaxation rates with the estimated iron indicated that both R2 and R2' had a robust relationship with brain iron level as determined from published post mortem data. This was the case only when the analyses are limited to the subcortical gray matter regions, however. R2' was affected by macroscopic magnetic field inhomogeneity arising from the skull bases, so that it was less robust for estimating the amount of iron deposits in the basal ganglia.

Adult↗

PubMed2005

Fat-suppressed 3D spoiled gradient-echo MRI and MDCT arthrography of articular cartilage in patients with hip dysplasia.

OBJECTIVE: Our objective was to assess the diagnostic ability of MDCT arthrography for acetabular and femoral cartilage lesions in patients with hip dysplasia. MATERIALS AND METHODS: A disorder of the articular cartilage was evaluated in 20 hips of 18 patients with acetabular dysplasia who did not have osteoarthritis or who had early stage osteoarthritis before undergoing pelvic osteotomy surgery. The findings on fat-suppressed 3D fast spoiled gradient-echo MRI and MDCT arthrography of the hip were evaluated by two independent observers, and sensitivity, specificity, and accuracy were determined using arthroscopic findings as the standard of reference. Kappa values were calculated to quantify the level of interobserver agreement. RESULTS: The sensitivity and specificity for the detection of any cartilage disorder (grade 1 or higher) were (observer 1/observer 2) 49%/67% and 89%/76%, respectively, on MRI, and 67%/67% and 89%/82%, respectively, on CT arthrography. The sensitivity and specificity for the detection of cartilage lesions with substance loss (grade 2 or higher) were (observer 1/observer 2) 47%/53% and 92%/87%, respectively, on MRI, and 70%/79% and 93%/94%, respectively, on CT arthrography. CT arthrography provided significantly higher sensitivity in the detection of grade 2 or higher lesions than MRI for both observers. Interobserver agreement in the detection of grade 2 or higher cartilage lesions was moderate (kappa = 0.53) on MRI and substantial (kappa = 0.78) on CT. CONCLUSION: MDCT arthrography is a sensitive and reproducible method for assessing articular cartilage lesions with substance loss in patients with hip dysplasia.

Adolescent↗

PubMed2005

A case of systemic lupus erythematosus with complex partial status epilepticus.

We describe a woman with systemic lupus erythematosus who had complex partial status epilepticus as the sole epileptic manifestation. The patient presented with a confusional state, initially considered to be psychotic in nature, due to SLE. However, the EEG demonstrated the epileptic etiology of her symptoms. In patients with lupus presenting with prolonged episodes of confusion and behavioural disturbance, an EEG should be performed, whenever possible during the episode, even in the absence of a previous history of epilepsy.

Diagnosis, Differential↗

PubMed2004

Observation of three-dimensional fermi surfaces in a single-component molecular metal, [Ni(tmdt)2].

Rigorous evidence of metallicity of a molecular crystal consisting of single-component neutral molecules is disclosed by observing the Fermi surface through magnetic quantum oscillations. Torque magnetometry measurements of de Haas-van Alphen oscillatory signals in a single crystal of [Ni(tmdt)2] molecules (tmdt = trimethylenetetrathiafulvalenedithiolate) were performed by using a sensitive microcantilever at low temperatures in high magnetic fields to 45 T. The observed signals for all directions of magnetic field revealed unambiguously the presence of three-dimensional Fermi surfaces for both holes and electrons. The results are consistent with electronic band structure calculations for [Ni(tmdt)2].

Journal Article↗

PubMed2004

Infrared electronic absorption in a single-component molecular metal.

The infrared spectra of the crystal of transition metal complex molecules with extended-TTF ligands, Ni(tmdt)2, which is the first single-component molecular metal that has a stable metallic state even at low temperatures, exhibited an extremely low-energy electronic absorption around 2200 cm-1 (tmdt = trimethylenetetrathiafulvalenedithiolate). The systematic shift of the absorption peaks for molecules similar to Ni(tmdt)2, which range from metallic to semiconducting crystals, shows that the single-component molecular conductors are composed of molecules with unprecedentedly small HOMO-LUMO gaps.

Journal Article↗

PubMed2004

Clinical accuracy evaluation of femoral canal preparation using the ROBODOC system.

The purpose of this study was to evaluate the clinical accuracy of femoral canal preparation using postoperative reconstructed computed tomography (CT) images of 75 consecutive total hip arthroplasties performed with a two-pin-based ROBODOC system. Intraoperatively, the robot milled the femoral canal according to the preoperative planning performed with preoperative CT data and the ROBODOC workstation. Postoperative CT data was obtained 1 month postoperatively. Anteroposterior and lateral synthetic radiographs and axial images were reconstructed from CT data on the workstation. The mean difference between the preoperative planning and the postoperative CT images was less than 5% in canal fill, less than 1 mm in gap, and less than 1 degrees in the mediolateral and anteroposterior alignment. Clinical femoral canal preparation using the ROBODOC system results in a high degree of accuracy.

Adult↗

PubMed2004

Three-dimensional distribution of acetabular cartilage thickness in patients with hip dysplasia: a fully automated computational analysis of MR imaging.

OBJECTIVE: The aim of this study was to evaluate three-dimensional (3D) distribution of acetabular articular cartilage thickness in patients with hip dysplasia using in vivo magnetic resonance (MR) imaging, and to compare cartilage thickness distribution between normal and dysplastic hips. DESIGN: Forty-five dysplastic hips without joint space narrowing on radiographs and 13 normal hips underwent MR imaging with fat-suppressed 3D fast spoiled gradient echo (SPGR) sequence. Acetabular cartilage thickness was measured with a fully automated segmentation technique, and cartilage thickness distribution was compared between the dysplastic and normal hips on the celestial spherical coordinate system. RESULTS: Average cartilage thickness was significantly greater for the dysplastic hips than the normal hips (1.77 mm vs 1.34 mm). There was a general trend of gradient increase of cartilage thickness at the superolateral area in normal and dysplastic hips. The gradient increase of cartilage thickness was significantly greater in the dysplastic hips than the normal hips. CONCLUSIONS: Dysplastic hips have general thick cartilage distribution as well as more prominent gradient increase of thickness at the superolateral portion. The knowledge of fundamental morphological feature of dysplastic hips at a preradiologic stage may aid early detection of cartilage thinning in association with osteoarthritic progression, accurate computational biomechanical analysis in the hip joint, and planning periacetabular osteotomy with satisfactory cartilaginous congruency.

Acetabulum↗

PubMed2003

Comparison of the fit and fill between the Anatomic Hip femoral component and the VerSys Taper femoral component using virtual implantation on the ORTHODOC workstation.

The purpose of this study was to evaluate differences in fit and fill between an anatomic femoral component and a straight tapered femoral component, both of which were designed for proximal fit and fill using the preoperative planning workstation of the ROBODOC system (ORTHODOC). Anatomic Hip (Zimmer) and VerSys Taper (Zimmer) femoral components were each virtually implanted into 50 femora (25 dysplastic femora and 25 anatomically normal femora) using the ORTHODOC workstation. The fit and fill of the femoral components were measured on cross-sectional images. The VerSys Taper femoral components showed significantly better fit and fill than the Anatomic Hip femoral components at the lower corner of the femoral neck cut and the middle of the femoral component in both the dysplastic femora and the anatomically normal femora. The Anatomic Hip femoral components showed significantly better fit and fill than the VerSys Taper femoral components 1 cm proximal from the femoral component tip in both dysplastic femora and anatomically normal femora. There was no significant difference in fit and fill between the two types of femoral component at the center of the lesser trochanter or 1 cm distal from the center of the lesser trochanter in either dysplastic femora or anatomically normal femora. Overall, VerSys Taper femoral components appear to provide better proximal fit and fill than Anatomic Hip femoral components in both dysplastic and anatomically normal femora.

Adult↗

PubMed2003

Quantitative mapping of cerebral deoxyhemoglobin content using MR imaging.

In this study, we present a magnetic resonance imaging (MRI) method for quantifying cerebral deoxyhemoglobin content that is based on a measurement of the reversible contribution (R'2) of the transverse relaxation rate under the assumption of a quantitative relationship between R'2 and deoxyhemoglobin content. A numerical simulation was performed assuming a specific pulse sequence conventionally employed for R'2 measurement. The results showed a near linear relationship between R'2 and deoxyhemoglobin content in the physiological range of oxygen extraction for almost all sized vessels, although a large diffusion effect for capillary sized vessels compromised the relationship. Concerning the methodology for R'2 measurement, a theoretical analysis showed that multiexponential transverse signal decay of brain parenchyma may result in a considerable underestimation or overestimation of R'2, if a conventional method is employed for R'2 quantification. A modified method for correcting the effect of multiexponential signal decay was employed for R'2 measurement of the brain in normal volunteers. The results showed a high level of agreement between the R'2 values measured in our study and those estimated from physiological parameters obtained using other modalities such as PET. In the context of BOLD contrast-based functional MRI, the method proposed provides a quantitative mapping of baseline cerebral deoxyhemoglobin content, which is the essential physiological parameter for calibrating the stimulation-induced BOLD signal change and mapping neuronal activity in a quantitative manner by functional MRI.

Adult↗

PubMed2003

Limits on the accuracy of 3-D thickness measurement in magnetic resonance images--effects of voxel anisotropy.

Measuring the thickness of sheet-like thin anatomical structures, such as articular cartilage and brain cortex, in three-dimensional (3-D) magnetic resonance (MR) images is an important diagnostic procedure. This paper investigates the fundamental limits on the accuracy of thickness determination in MR images. We defined thickness here as the distance between the two sides of boundaries measured at the subvoxel resolution, which are the zero-crossings of the second directional derivatives combined with Gaussian blurring along the normal directions of the sheet surface. Based on MR imaging and computer postprocessing parameters, characteristics for the accuracy of thickness determination were derived by a theoretical simulation. We especially focused on the effects of voxel anisotropy in MR imaging with variable orientation of sheet-like structure. Improved and stable accuracy features were observed when the standard deviation of Gaussian blurring combined with thickness determination processes was around square root of 2/2 times as large as the pixel size. The relation between voxel anisotropy in MR imaging and the range of sheet normal orientation within which acceptable accuracy is attainable was also clarified, based on the dependences of voxel anisotropy and the sheet normal orientation obtained by numerical simulations. Finally, in vitro experiments were conducted using an acrylic plate phantom and a resected femoral head to validate the results of theoretical simulation. The simulated thickness was demonstrated to be well-correlated with the actual in vitro thickness.

Anatomy, Cross-Sectional↗

PubMed2003

[Head retraction reflex-like movements with severe bulbar symptoms in a patient with stiff-person syndrome].

A 57-year-old woman developed muscular stiffness and painful cramps, which were relieved by administration of dantrolene sodium. Her serum level of antibodies to glutamic acid decarboxylase (GAD) was markedly elevated and continuous muscular activities were observed on resting surface EMG. These features were compatible with those in stiff-person syndrome (SPS). She was found to have thymoma on CT scan. Immediately after thymomectomy, which was histologically diagnosed as a benign hyperplasia, she developed head retraction reflex-like movements evoked by sensory stimulation to the face, which were followed by severe bulbar symptoms with dysphagia and respiratory arrest. Postoperative myasthenia gravis was excluded clinically. While somatosensory evoked EMG on splenius muscle initially showed biphasic responses with latency of 15 msec and 55 msec, respectively after oral angle non-painful electric stimulation, the late potential phase disappeared after the patient recovered from bulbar symptoms. This suggests that head retraction reflex-like movements of this patient reflected the attenuation of inhibitory potentials from the brainstem.

Autoantibodies↗