Biomedical subjects

T Okada

Publications and source records attributed to T Okada.

At least 19 recordsLinked to original sources

PubMed2007

Diffusion tensor fiber tractography of the optic radiation: analysis with 6-, 12-, 40-, and 81-directional motion-probing gradients, a preliminary study.

BACKGROUND AND PURPOSE: Knowing the exact location of the optic radiation preoperatively is important for surgery of the temporal lobe. We hypothesized that a greater number of motion-probing gradients (MPGs) would provide better results of diffusion tensor (DT) fiber tractography of the optic radiation. To test this hypothesis, this study evaluated differences in DT fiber tractography of the optic radiation under different MPG settings. METHODS: DT images were obtained in 12 healthy volunteers (7 men, 5 women) with a mean age of 32 years (range, 22-45 years) by using a 3T MR imaging scanner with single-shot echo-planar imaging with parallel acquisition (reduction factor = 2). MPG was applied in 6, 12, 40, and 81 independent directions. The first region of interest (ROI) was placed in the occipital lobe, and the second ROI was placed in the lateral geniculate body. Fibers penetrating both ROIs were considered as the optic radiation. Anteroposterior distance between the tip of the Meyer loop and the lateral geniculate body on an axial section was defined as a loop index. Numbers of fibers and loop indices in both cerebral hemispheres were evaluated statistically. RESULTS: The optic radiation was well visualized in full length by DT fiber tractography in 20 of 24 hemispheres (83%). No significant differences were noted in number of fibers and loop indices among different MPG settings. CONCLUSION: DT fiber tractography can frequently depict almost the entire optic radiation. MPG number does not exert any significant effect on visualization of the optic radiation, and 6-directional MPG is thus sufficient for this purpose.

Adult↗

PubMed2006

Comparative immunobiology of thymic DC mRNA in autoimmune-prone mice.

New Zealand Black (NZB) mice have multiple defects in both innate and acquired immunity. A fundamental defect, described more than 25 years ago, is premature thymic involution. Subsequent studies have disclosed multiple defects in thymic epithelial cells, and it has been proposed that thymic dendritic cells (DCs) play an important role not only in thymic involution but also in the appearance of immunopathology. However, the number of available thymic DCs makes this population extremely difficult to study. We have taken advantage of our ability to isolate pure populations of thymic DCs and have examined several key mRNA levels of enzymes involved in signal transduction. Our data on NZB mice was compared to that of NZB x NZW F1 (B/WF1), BXSB-Yaa, MRL/lpr, NOD and control mice. Importantly, we demonstrate herein that a common feature in autoimmune-prone mice is an increase of thymic DC c-met mRNA. Indeed, the increase in c-met mRNA levels appeared specific to the thymus and was not noted in the spleen. Additionally, we demonstrate that E-cadherin, a downstream molecule of c-met, is also reduced. Finally, we note that the levels of HGF mRNA are normal in the autoimmune strains examined herein, confirming that the abnormality of c-met mRNA is not due to primary defects in thymic stromal cells. We submit that these results highlight the possibility of a selective defect in thymic DCs which will be a pivotal step in loss of tolerance, and suggest that future studies focus on adoptive cell transfer involving this population.

Animals↗

PubMed2006

Blockade of Angiotensin II type-1 receptor reduces oxidative stress in adipose tissue and ameliorates adipocytokine dysregulation.

Dysregulated production of adipocytokines may be involved in the development of atherosclerotic cardiovascular disease in metabolic syndrome and chronic kidney disease (CKD) associated with metabolic syndrome. The aim of this study was to determine the effects of treatment with angiotensin II (Ang II) type-1 receptor blocker (ARB) on the regulation of adipocytokines. Olmesartan, an ARB, significantly blunted the age- and body weight-associated falls in plasma adiponectin both in genetically and diet-induced obese mice, without affecting body weight, but had no effect on plasma adiponectin levels in lean mice. Olmesartan also ameliorated dysregulation of adipocytokines in obesity, such as tumor necrosis factor-alpha, plasminogen activator inhibitor-1, monocyte chemotactic protein-1, and serum amyloid A3. Olmesartan significantly reduced reactive oxygen species originating from accumulated fat and attenuated the expression of nicotinamide adenine dinucleotide phospho hydrogenase oxidase subunits in adipose tissue. In cultured adipocytes, olmesartan acted as an antioxidant and improved adipocytokine dysregulation. Our results indicate that blockade of Ang II receptor ameliorates adipocytokine dysregulation and that such action is mediated, at least in part, by targeting oxidative stress in obese adipose tissue. Ang II signaling and subsequent oxidative stress in adipose tissue may be potential targets for the prevention of atherosclerotic cardiovascular disease in metabolic syndrome and also in metabolic syndrome-based CKD.

Adiponectin↗

PubMed2006

Energetic proton acceleration and bunch generation by ultraintense laser pulses on the surface of thin plasma targets.

Energetic proton acceleration from concave targets, the front of which were irradiated with 40 fs laser pulses with an intensity of 10(20)W/cm(2), has been studied as a function of the depth of the concave shape. Three kinds of targets, a triangular concave target, a circular concave target and a parabolic concave target are considered. When the depth of the concave shape was varied, the peak proton energy showed a maximum. The underlying mechanism for the existence of a maximum peak proton energy is presented by tracing the proton trajectory. It is concluded that a parabolic concave target is the best, among the targets considered, for accelerating a proton beam, since a proton beam from a parabolic concave target goes through the strongest electric field.

Journal Article↗

PubMed2006

The rubble-pile asteroid Itokawa as observed by Hayabusa.

During the interval from September through early December 2005, the Hayabusa spacecraft was in close proximity to near-Earth asteroid 25143 Itokawa, and a variety of data were taken on its shape, mass, and surface topography as well as its mineralogic and elemental abundances. The asteroid's orthogonal axes are 535, 294, and 209 meters, the mass is 3.51 x 10(10) kilograms, and the estimated bulk density is 1.9 +/- 0.13 grams per cubic centimeter. The correspondence between the smooth areas on the surface (Muses Sea and Sagamihara) and the gravitationally low regions suggests mass movement and an effective resurfacing process by impact jolting. Itokawa is considered to be a rubble-pile body because of its low bulk density, high porosity, boulder-rich appearance, and shape. The existence of very large boulders and pillars suggests an early collisional breakup of a preexisting parent asteroid followed by a re-agglomeration into a rubble-pile object.

Journal Article↗

PubMed2006

Touchdown of the Hayabusa spacecraft at the Muses Sea on Itokawa.

After global observations of asteroid 25143 Itokawa by the Hayabusa spacecraft, we selected the smooth terrain of the Muses Sea for two touchdowns carried out on 19 and 25 November 2005 UTC for the first asteroid sample collection with an impact sampling mechanism. Here, we report initial findings about geological features, surface condition, regolith grain size, compositional variation, and constraints on the physical properties of this site by using both scientific and housekeeping data during the descent sequence of the first touchdown. Close-up images revealed the first touchdown site as a regolith field densely filled with size-sorted, millimeter- to centimeter-sized grains.

Journal Article↗

PubMed2006

Possible association between nonsynonymous polymorphisms of the anaplastic lymphoma kinase (ALK) gene and schizophrenia in a Japanese population.

We examined, for the first time, the possible association between schizophrenia and the anaplastic lymphoma kinase (ALK) gene which plays an important role in neurodevelopment. When two nonsynonymous polymorphisms (Arg1491Lys and Glu1529Asp) were examined, there were significant differences in genotype and allele distributions between patients and controls. Individuals homozygous for the minor allele (1491Lys-1529Asp) were more common in patients than in controls (p = 0.0064, odds ratio 2.4, 95% CI 1.3-4.6). These results suggest that genetic variations of the ALK gene might confer susceptibility to schizophrenia.

Alleles↗

PubMed2006

A complex polymorphic region in the brain-derived neurotrophic factor (BDNF) gene confers susceptibility to bipolar disorder and affects transcriptional activity.

Previous studies have suggested that genetic variations in the brain-derived neurotrophic factor (BDNF) gene may be associated with several neuropsychiatric diseases including bipolar disorder. The present study examined a microsatellite polymorphism located approximately 1.0 kb upstream of the translation initiation site of the BDNF gene for novel sequence variations, association with bipolar disorder, and effects on transcriptional activity. Detailed sequencing analysis revealed that this polymorphism is not a simple dinucleotide repeat, but it is highly polymorphic with a complex structure containing three types of dinucleotide repeats, insertion/deletion, and nucleotide substitutions that gives rise to a total of 23 novel allelic variants. We obtained evidence supporting the association between this polymorphic region (designated as BDNF-linked complex polymorphic region (BDNF-LCPR)) and bipolar disorder. One of the major alleles ('A1' allele) was significantly more common in patients than in controls (odds ratio 2.8, 95% confidential interval 1.5-5.3, P=0.001). Furthermore, a luciferase reporter gene assay in rat primary cultured neurons suggests that this risk allele (A1) has a lower-transcription activity, compared to the other alleles. Our results suggest that the BDNF-LCPR is a functional variation that confers susceptibility to bipolar disorder and affects transcriptional activity of the BDNF gene.

Adult↗

PubMed2006

Recovery of zinc and lead from fly ash from ash-melting and gasification-melting processes of MSW--comparison and applicability of chemical leaching methods.

Fly ash generated from MSW ash-melting and gasification-melting plants, known as Melting Furnace Fly Ash (MFA), contains considerable amounts of heavy metals such as Pb and Zn. These metals can be recovered using a smelting furnace after "pre-treatment" for removal of unnecessary elements such as Cl, Sn and Si. Chemical methods have been studied for pretreatment in the past. However, they have been discussed only with regard to treatment cost and the concentration of Pb and Zn recovered, but neither applicability to various types of MFA nor the environmental impact have been considered. In this study, acid, alkaline and ammonia/chloride leaching methods were compared from the standpoints of: (1) applicability to MFA, (2) concentration of Pb and Zn recovered, (3) treatment cost, and (4) environmental impact. Twenty-three samples of MFAs were collected and classified into 4 types based on element contents. A Pb and Zn recovery experiment was conducted for the representative MFA of those types. The results showed: (1) MFA from gasification-melting plants cannot be treated by chemical methods; (2) the other MFA can be treated to an acceptable quality by existing smelting furnaces; (3) only MFA from electric resistance ash-melting plants can be treated easily by the water washing method; and (4) alkaline and ammonia/chloride leaching methods were more effective than acid leaching.

Carbon↗

PubMed2006

LDL particle size, fat distribution and insulin resistance in obese children.

BACKGROUND: The importance of small dense low-density lipoprotein (sdLDL) cholesterol in coronary heart disease has been demonstrated in many studies. Body fat accumulation, especially abdominal adiposity, is one of the important factors modifying the expression of sdLDL in adults. OBJECTIVE: To determine the prevalence of sdLDL in obese children, and to investigate its relationship with anthropometric and metabolic variables. SUBJECTS: A total of 30 obese children (22 males, 8 females) aged 12.6+/-0.6 years (mean+/-s.e.), who presented to our outpatient clinic with obesity. METHODS: LDL peak particle diameter was determined using gel electrophoresis. LDL subclasses were classified into sdLDL (pattern B; diameter<25.5 nm) and non-sdLDL (pattern A; diameter>or=25.5 nm). Anthropometric and metabolic variables were also determined to identify factors modifying LDL particle size. RESULTS: sdLDL was detected in 11 children (40.0%). In children with sdLDL, waist/height ratio was significantly higher (P=0.0466), and they had significantly higher triglyceride (TG) (P=0.0035) and lower high-density lipoprotein cholesterol (HDLC) levels (P=0.036). Peak LDL diameter as a continuous variable was significantly correlated with HDLC and TG levels. In multiple regression analysis, body mass index and waist/height ratio were significant determinants of the peak LDL diameter variability. CONCLUSIONS: We found a high prevalence of sdLDL in obese children, and a relationship of peak LDL diameter with abdominal fat accumulation, HDLC and TG levels. The presence of sdLDL might be an important risk factor for the metabolic syndrome.

Abdominal Fat↗

PubMed2006

Management of childhood and adolescent thyroid carcinoma: long-term follow-up and clinical characteristics.

AIM: This analysis was performed to evaluate clinical factors such as local tumor control, control of distant metastasis, survival, and complications in children and adolescents with thyroid carcinoma. MATERIALS AND METHODS: From 1960 to 2003, 21 children and adolescents (16 girls and 5 boys, aged 4 to 15 years) were treated for thyroid carcinoma in our departments. Clinical data, operative findings, pathological findings, operative procedures, intra- and postoperative complications and follow-up were evaluated. Follow-up of patients ranged from 3 to 42 years (median, 20 years). RESULTS: Papillary carcinoma was found in 20 patients (95%) and follicular carcinoma in one patient. Cervical lymph node metastases were found in 12 out of 21 patients (57.1%) when thyroid carcinoma was diagnosed, and 5 patients (23.8%) had pulmonary metastasis. In patients with pulmonary metastasis, total thyroidectomy and bilateral radical lymph node resection was performed in 3 patients, lobectomy of the thyroid and radical lymph node resection in one patient, and partial thyroidectomy in one patient. All three patients who underwent total thyroidectomy are still alive. Internal irradiation by 131I and thyroid hormone replacement therapy was administered to 2 of 3 patients with pulmonary metastasis. CONCLUSION: Despite metastasis in the lymph nodes and even the lungs, the prognosis for patients with papillary carcinoma is good. Total thyroidectomy and positive 131I therapy are recommended for childhood and adolescent thyroid carcinoma with pulmonary metastasis.

Adenocarcinoma, Follicular↗

PubMed2006

Histological differentiation between prenatally diagnosed choledochal cyst and type I cystic biliary atresia using liver biopsy specimens.

Because it is difficult to distinguish preoperatively between prenatally diagnosed choledochal cyst (CC) and type I cystic biliary atresia (BA) by ultrasound scanning or magnetic resonance imaging (MRI), some modality of discrimination for the 2 entities is required. The aim of this study was to investigate the histological differences between prenatally diagnosed CC and type I cystic BA using liver biopsy specimens. Four children with prenatally diagnosed CC and two children with prenatally diagnosed type I cystic BA were identified by fetal ultrasonography between 1985 and 2003. The control group included two children who were operated on at an earlier period due to postnatally diagnosed BA. Liver wedge biopsy in the right lobe was performed at the time of the radical operation. Histological findings of the H & E-stained liver biopsy specimens were classified into 4 grades (Grade 0, no abnormality; Grade 1, ductular proliferation without bridging fibrosis; Grade 2, ductular proliferation with bridging fibrosis; and Grade 3, liver cirrhosis). The CC group consisted of one case of Grade 0 and three cases of Grade 1. The type I cystic BA group consisted of one case each of Grade 2 and Grade 3. In the control group, both cases were Grade 2. The authors suggest that exploratory laparotomy might be avoided and, instead, histologic examination using liver biopsy specimens can be a reliable test for the differential diagnosis of CC and type I cystic BA in prenatally diagnosed neonates.

Biliary Atresia↗

PubMed2006

Effective esophageal balloon dilation for esophageal stenosis in recessive dystrophic epidermolysis bullosa.

Recessive dystrophic epidermolysis bullosa (RDEB) is an inherited disorder of squamous epithelium that results in dystrophic scarring of the skin after minor trauma. RDEB is classified into two subtypes: Hallopeau-Siemens (HS) and non-Hallopeau-Siemens (nHS). Although severe scarring of the skin is the most common and obvious complication of the disease, esophageal scarring with formation of long strictures may also develop. Treatment options for esophageal stenosis in patients with RDEB include steroids, hyperalimentation, esophageal dilation and replacement. This report describes a child who was dilated immediately after diagnosis of severe esophageal stenosis subsequent to nHS-RDEB and managed successfully. Endoscopic esophageal balloon dilation under fluoroscopic control was very useful for detecting the region of stenosis and bougienage. The literature on such injuries is reviewed here, and the problems associated with the treatment of children with esophageal stenosis associated with RDEB are discussed.

Catheterization↗

PubMed2006

Management and algorithm for focal nodular hyperplasia of the liver in children.

PURPOSE: The aim of this study was to determine an appropriate management plan for childhood and adolescent FNH, in particular to establish an algorithm for preoperative diagnosis and treatment. PATIENTS AND METHODS: Between 1985 and 2003, 4 children with FNH were diagnosed. Of these 4 patients, 3 (Group A) underwent tumor resection, and 1 (Group B) was treated by conservative management. Clinical data, pathological findings and follow-up were evaluated retrospectively. RESULTS: The 3 patients in Group A were symptomatic, while the 1 patient in Group B was asymptomatic. In 3 of 4 patients, a homogeneous tumor with a central stellate area was noted on abdominal ultrasonography, CT scan and MR imaging. In case 2, SPIO-enhanced MR imaging was useful for differentiating FNH from hepatocellular carcinoma. Though percutaneous needle biopsy was performed in case 3, a pathologically definitive diagnosis was impossible. An open biopsy was performed in case 4 and FNH was diagnosed. In case 4 treated by conservative management, the tumor size did not change during the 7 years after the diagnosis of FNH. CONCLUSION: FNH is usually treated conservatively because of the good evolutionary outcome of the lesion. Surgery is indicated in cases of complications, compressed adjacent organs, lesion progression, or for symptomatic patients. We advocate the use of less invasive SPIO-enhanced MR imaging instead of open biopsy when the diagnosis of focal liver lesions is not clear after contrast-enhanced CT scan and non-enhanced MR imaging.

Adolescent↗

PubMed2006

[Unusual total anomalous pulmonary venous connection; report of a case].

We report a case of a 7-hour-old infant with total anomalous pulmonary venous connection having abberant origin of the vertical vein. His clinical condition presented hemodynamically severe pulmonary vein obstruction as common pulmonary vein atresia. Without making the definitive diagnosis, he underwent the operation at 11 hours after birth under cardiopulmonary bypass. During the operation, we could not identify the drainage vein. Although we ligated the vessel sized less than 2 mm in diameter draining into superior vena cava which was suspected to be the vertical vein. After the operation pulmonary edema was severe, but his clinical condition improved by using nitric oxide without extracorporeal membrane oxygenation (ECMO) support. Postoperative cardiac catheterization showed normal cardiac function without pulmonary venous obstruction, and moreover identified the drainage vein originated from right upper pulmonary vein. To the best of our knowledge, this is the first case where the vertical vein originated from right upper pulmonary vein. Immediate surgical treatment before the circuratory exacerbation improve the outcome for this congenital anomaly.

Humans↗

PubMed2006

[Bidirectional Glenn shunt without cardiopulmonary bypass].

From April 2002 to March 2005, 18 patients having undergone bidirectional Glenn shunt (BDG) without cardiopulmonary bypass (CPB) [off-pump BDG] were retrospectively reviewed. During BDG anastomosis, a temporary bypass was established between superior vena cava (15) or innominate vein (3) and main pulmonary artery (16) or right atrium (2). Hemodynamics and oxygenation were maintained well throughout the temporary bypass time. There was no emergent use of CPB. Mean transpulmonary pressure gradient immediately after and 24 hours after the BDG were 6.7 and 5.6 mmHg, respectively. Echocardiography showed mild flow turbulence at the anastomosis in 1 case. This simple and inexpensive technique provided good surgical view with stable hemodynamics enabling satisfactory BDG in selected cases. Furthermore, it could avoid adverse effects of CPB such as lung injury and possible blood transfusion. This experience would encourage off-pump BDG combined with more challenging procedures.

Anastomosis, Surgical↗

PubMed2005

Neural mechanisms underlying the processing of Chinese words: an fMRI study.

The present study employed functional magnetic resonance imaging (fMRI) to investigate the neural mechanisms underlying orthographic, phonological and semantic processing of single character Chinese words. Twelve right-handed native Chinese speakers participated in the study. Three fundamental linguistic tasks including orthographic judgment, phonological matching and semantic association task were used. Our results demonstrated robust activation in the left posterior inferior temporal cortex (BA 37) for all three tasks. While the phonological matching task produced left-lateralized activation in the inferior frontal and parietal regions, semantic association task showed considerable bilateral activation in the inferior frontal and occipito-parietal regions. Direct comparison between phonological matching and semantic association task yielded semantic related activation in the anterior portion of the left inferior frontal gyrus (BA 47) and the right inferior frontal region (Broca's homology; BA 45). Behaviorally, there was no difference in response time between phonological matching and semantic association task. Our findings suggested that differential neural pathways were involved in the processing of meaning and sound of single-character Chinese words. The present study provided systemic information of the neural substrates underlying the processing of different components of Chinese language.

Adult↗

PubMed2005

Synthetic biodegradable polymers as drug delivery systems for bone morphogenetic proteins.

Bone morphogenetic proteins (BMP) induce bone formation in vivo, and clinical application in repair of bone fractures and defects is expected. However, appropriate systems to deliver BMP for clinical use need to be developed. We synthesized a new synthetic biodegradable polymer, poly-D,L-lactic acid-para-dioxanone-polyethylene glycol block copolymer (PLA-DX-PEG), to serve as a biocompatible, biodegradable polymer for recombinant human (rh) BMP-2 delivery systems. In animal experiments, new bone was efficiently formed and a large bone defect was repaired using PLA-DX-PEG/rhBMP-2 composites. In addition, this new polymer could be used as an injectable delivery system for rhBMP-2. The rhBMP-2/PLA-DX-PEG composites also could be combined with other materials such as hydroxyapatite or titanium. This new synthetic polymer might be used for rhBMP-2 delivery in various clinical situations involving repair of bone, leading to great changes in orthopedic treatment.

Animals↗