Biomedical subjects

Katsuyuki Nakanishi

Publications and source records attributed to Katsuyuki Nakanishi.

8 recordsLinked to original sources

PubMed2006

Molecular characterization of a transport vesicle protein Neurensin-2, a homologue of Neurensin-1, expressed in neural cells.

We have isolated and characterized a novel cDNA encoding a small neuronal membrane protein showing high sequence homology to Neuro-p24/Neurensin-1, a protein containing a microtubule-associated domain at the carboxyl-terminus and exclusively localized to small vesicles of neurons. The newly identified Neurensin-2 constitutes two-membrane spanning domains but not the microtubule-binding domain, with a molecular mass of 28 kDa. Neurensin-2 mRNA is expressed only in brain, whereas the protein expressed in various neurons including those of the thalamus/hypothalamus and hippocampus, of postnatally developing mice. While the levels of Neurensin-1 mRNA and protein in retinoic acid-exposed mouse neuroblastoma Neuro2a cells increased, those of Neurensin-2 mRNA and protein remained unchanged. When the Neurensin-2 cDNA was transfected into Neuro2a cells, Neurensin-2 was expressed in small vesicles including lysosomes in the perinuclear region. On the cotransfection of Neurensin-1 and -2 cDNA into Neuro2a cells, Neurensin-2 was mainly found in small vesicles of the cell body and Neurensin-1 in those of growth cones. In nerve growth factor-stimulated PC12 cells, the intracellular localization of these proteins also differed. Furthermore, immunochemical staining of mouse brain revealed that Neurensin-1 and -2 had a similar distribution in many regions such as the Diagonal band, hippocampus, amygdaloid nucleus, and habenula nucleus, but differed in the intracellular localization as follows: Neurensin-1 was found mainly in neuritic processes, while Neurensin-2 was found in cell bodies. Thus, both Neurensin-1, and -2 are localized in small vesicles in neural cells, but their localizations of the vesicles are not always the same by each other, suggesting that they are under separate regulation.

Animals↗

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

Whole body MRI for detecting metastatic bone tumor: comparison with bone scintigrams.

PURPOSE: To compare the effectiveness of whole body MRI (WB-MRI [magnetic resonance imaging]) and bone scintigram (BS) at detecting bone metastasis. MATERIALS AND METHODS: WB-MRI was performed on 16 patients for detecting bone metastasis (6 breast carcinoma, 7 prostatic carcinoma, 1 renal cell carcinoma [RCC], 1 hepatocellular carcinoma [HCC], and 1 primary unknown). BS was also performed in all cases. Patients were placed on a table top extender (Philips Medical Systems). The maximal longitudinal field of view (FOV) was 200 cm. At first, the total spine was imaged in the sagittal plane with a three-station approach for two image sets (fast spin-echo [SE] T1-weighted images [T1WI] and short tau inversion recovery [STIR] images). The whole body was then imaged in the coronal plane with a seven-station approach for two image sets (fast field echo [FFE] T1WI and STIR). Total examination time, including patient positioning, was within 40 min. Three independent radiologists interpreted the imaging data. RESULTS: WB-MRI identified 5 cases of 24 lesions as bone metastasis, while BS identified 3 cases of 25 lesions. Concordance between WB-MRI and BS was seen in 3 cases of 22 lesions (81%). For two cases of 2 lesions, which were identified only with WB-MRI, the lesions were located in the sacrum and thoracic spine. For one case of 3 lesions, which was identified only with BS, the lesions were located in the skull and rib. CONCLUSION: WB-MRI was an excellent method for screening bone metastasis, especially the vertebral body.

Aged↗

PubMed2003

Heme positively regulates the expression of beta-globin at the locus control region via the transcriptional factor Bach1 in erythroid cells.

The transcription factor Bach1 heterodimerizes with small Maf proteins to repress Maf recognition element (MARE)-dependent gene expression. The repressor activity of Bach1 is inhibited by the direct binding of heme. To investigate the involvement of Bach1 in the heme-dependent regulation of the expression of the beta-globin gene, mouse erythroleukemia (MEL) cells were cultured with succinylacetone (SA), a specific inhibitor of heme biosynthesis, and the level of beta-globin mRNA was examined. A marked decrease of beta-globin mRNA in SA-treated cells was observed, and this decrease was reversed by the addition of hemin. An iron chelator, desferrioxamine, also lowered the level of beta-globin mRNA. The heme-dependent expression of beta-globin is a transcriptional event since the expression of the human beta-globin gene promoter-reporter gene containing the microlocus control region (microLCR) was inhibited when human erythroleukemia K562 cells and MEL cells were cultured with SA. Hemin treatment restored the decrease in promoter activity caused by SA. The control of the microLCR-beta-globin promoter reporter gene by heme was dependent on DNase I-hypersensitive site 2 (HS2), which contains MARE. The MARE binding activity of Bach1 in K562 and MEL cells increased upon SA treatment, and the increase was diminished by the treatment with hemin. Transient expression of Bach1 suppressed the microLCR activity, and this repressor activity was cancelled by treatment with hemin. The expression of a mutated Bach1 lacking heme-binding sites led to a loss in the heme responsiveness of the microLCR. Furthermore, chromatin immunoprecipitation experiments revealed that Bach1 bound to the MARE of HS2 increased by the treatment of MEL cells with SA, and this was cancelled by hemin. We propose that heme positively regulates the beta-globin gene expression by blocking the interaction of Bach1 with the MARE in the LCR.

Animals↗

PubMed2003

Measurement of lesion area and volume by three-dimensional spoiled gradient-echo MR imaging in osteonecrosis of the femoral head.

The purpose of this investigation is to evaluate the diagnostic ability of three-dimensional spoiled gradient-echo (3D SPGR) magnetic resonance (MR) imaging in cases of osteonecrosis of the femoral head (ONFH), and to determine the accuracy of 3D SPGR imaging in area and volume measurement of ONFH. T1-weighted spin-echo (SE) and 3D SPGR imaging were performed on 20 femoral heads obtained from patients with ONFH. After MR imaging, the femoral heads were cut parallel to the imaging plane and were evaluated histologically. Areas and volumes of necrotic lesions were measured with a computer program and the deviation between MR images and anatomical measurements was evaluated. A low signal intensity band on 3D SPGR MR images was observed in all femoral heads and corresponded histologically to repaired marrow with viable fibrous mesenchymal tissue. The area proximate to the low band area coincided with the necrotic region. Both area and volume measurements by T1-weighted SE and 3D SPGR images showed a strong correlation to histological measurements. The discrepancies between histological and imaging results were minimal in 3D SPGR imaging, especially at the anterior and posterior portions of the femoral head. Three-dimensional SPGR imaging provides more accurate measurements of the area and volume of a necrotic lesion than T1-weighted SE imaging.

Bone Marrow Diseases↗

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↗

PubMed2002

The value and limitation of gadopentetate-enhanced magnetic resonance imaging in detecting the condition of anterior cruciate ligament in rheumatoid knee: comparative study with histology.

The aim of this study was to elucidate the utility and limitation of gadopentetate (Gd)-enhanced MRI as a method for evaluating the anterior cruciate ligament (ACL) in the rheumatoid arthritis (RA) knee, using both surgical macro findings and histological findings to ascertain the pathological condition of the affected knee. Thirty-six knees of 25 RA patients were studied in this study. Four imaging protocols were employed: protocol A, T1-weighted and T2-weighted sagittal images; protocol B, T1-weighted sagittal image, after infusion of Gd-DTPA (0.2 mmol/kg, i.v.); protocol C, T1-weighted angled coronal image, parallel to the ACL; and protocol D, T1-weighted angled coronal image, parallel to the ACL, after infusion of Gd-DTPA. Sagittal image was determined as previously described. Angle coronal image was newly determined as coronal image parallel to the ACL. Surgical and MRI findings of the ACL were classified into four types: Type I (normal group) indicated that the thickness of the ACL was almost normal, adequate tension was maintained (surgical findings),and the ACL had thick and a more complex appearance with a homogeneous signal intensity and well-defined borders (MRI findings). Type II (degenerated group): the ACL had degenerated and tension was reduced (surgical findings), and the ACL had thin and a more complex appearance with a less homogeneous signal intensity and less well-defined borders. This appearance was more evident on Type II than Type I (MRI findings). Type III (ruptured group): the parenchyma of the ACL remained but lacked continuity (surgical findings), and the ACL appeared as partial lack of low signal intensity (MRI findings). Type IV (absent group): the parenchyma of the ACL was practically absent (surgical findings), and the ACL appeared as complete lack of signal low signal intensity (MRI findings). The concordance rate between surgical and MRI findings was investigated. Moreover, we investigated the extent to which histological changes of the ACL could be discriminated using MRI. In RA knees, the overall concordance rate between surgical and MRI findings was 41.7% under imaging protocol A. The overall rate improved up to 69.4% under imaging protocol B. But the overall rate dropped to 36.1% under imaging protocol C. The overall rate improved up to 83.3% under imaging protocol D. Especially, significant differences between imaging protocols A and B ( p<0.05), and imaging protocols C and D ( p<0.01), with respect to ACL degenerated group, were recognized. But significant differences between imaging protocols A and C, and imaging protocols B and D, with respect to ACL degenerated group, were not recognized. The concordance rate between histological and MRI findings was 41.7% in ACL normal group, and 61.5% in ACL degenerated group. The concordance rate between surgical and MRI findings was 100% in ACL normal group, and 78.9% in ACL degenerated group. There was a significant difference in the concordance rates between histological, surgical, and MRI findings in normal group ( p<0.05). The results of this study suggested that with Gd-enhanced MRI, the degree of synovial proliferation around the ACL and the degree of degradation of the ACL in the RA knee can be evaluated more accurately than with conventional MRI; however, in RA knees with severe synovial proliferation, it may be difficult to discriminate between the invasive synovium going into the ligament from synovium surrounding the ligament. This may be a limitation of Gd-enhanced MRI at present. In the clinical setting, the present imaging technique does allow the ligament to be evaluated to a certain degree, and may prove useful in the evaluation of temporal changes in the RA knee.

Anterior Cruciate Ligament↗

PubMed1999

Bone Metastases from Soft Tissue Sarcomas.

The incidence, distribution, time of appearance, and radiologic findings of bone metastases from soft tissue sarcomas, exclusive of lymphomas, were evaluated in 320 patients with soft tissue sarcomas. Thirty patients (9.4%) had evidence of 58 bone metastases. Five of 30 patients presented with metastases, and 25 of 30 patients developed metastases up to 66 months after presentation with a mean time interval of 21.3 months. The incidence of skeletal metastases differed among histologic subtypes of sarcomas; alveolar soft part sarcoma (5 of 8), dedifferentiated liposarcoma (2 of 4), angiosarcoma (2 of 4), and rhabdomyosarcoma (5 of 16) tended to show a higher incidence of bone metastases. The sarcomas metastasized to the regional bones close to the primary tumor in 16 (53%) of 30 patients and to the axial bones in 18 (60%). On conventional radiographs, the osseous metastases demonstrated predominantly osteolytic changes, and evidence of pathological fracture was observed in 31% of 58 metastases.

Journal Article↗