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Biomedical subjects

A Tonomura

Publications and source records attributed to A Tonomura.

At least 19 recordsLinked to original sources
PubMed2006

Shear stress facilitates tissue-engineered odontogenesis.

Numerous studies have demonstrated the effect of shear stress on osteoblasts, but its effect on odontogenic cells has never been reported. In this study, we focused on the effect of shear stress on facilitating tissue-engineered odontogenesis by dissociated single cells. Cells were harvested from the porcine third molar tooth at the early stage of crown formation, and the isolated heterogeneous cells were seeded on a biodegradable polyglycolic acid fiber mesh. Then, cell-polymer constructs with and without exposure to shear stress were evaluated by in vitro and in vivo studies. In in vitro studies, the expression of both epithelial and mesenchymal odontogenic-related mRNAs was significantly enhanced by shear stress for 2 h. At 12 h after exposure to shear stress, the expression of amelogenin, bone sialoprotein and vimentin protein was significantly enhanced compared with that of control. Moreover, after 7 days, alkaline phosphatase activity exhibited a significant increase without any significant effect on cell proliferation in vitro. In vivo, enamel and dentin tissues formed after 15 weeks of in vivo implantation in constructs exposure to in vitro shear stress for 12 h. Such was not the case in controls. We concluded that shear stress facilitates odontogenic cell differentiation in vitro as well as the process of tooth tissue engineering in vivo.

Alkaline Phosphatase↗
PubMed2002

Observation of structures of chain vortices inside anisotropic high- Tc superconductors.

In order to elucidate the formation mechanism of unconventional arrangements of vortices in high- Tc superconducting thin films at an inclined magnetic field to the layer plane, we investigated the structures of vortex lines inside the films by Lorentz microscopy using our 1-MV field-emission electron microscope. Our observation results concluded that vortex lines are tilted to form linear chains in YBaCu3O(7,8). Vortex lines in the chain-lattice state in Bi2Sr2CaCu2O(8+delta), on the other hand, are all perpendicular to the layer plane, and therefore only vortices lined up along Josephson vortices form chains.

Journal Article↗
PubMed2001

Oscillating rows of vortices in superconductors.

Superconductors can be used as dissipation-free electrical conductors as long as vortices are pinned. Vortices in high-temperature superconductors, however, behave anomalously, reflecting the anisotropic layered structure, and can move readily, thus preventing their practical use. Specifically, in a magnetic field tilted toward the layer plane, a special vortex arrangement (chain-lattice state) is formed. Real-time observation of vortices using high-resolution Lorentz microscopy revealed that the images of chain vortices begin to disappear at a much lower temperature, Td, than the superconducting transition temperature, Tc. We attribute this image disappearance to the longitudinal oscillation of vortices along the chains.

Journal Article↗
PubMed2001

Observation of individual vortices trapped along columnar defects in high-temperature superconductors.

Many superconductors do not entirely expel magnetic flux-rather, magnetic flux can penetrate the superconducting state in the form of vortices. Moving vortices create resistance, so they must be 'pinned' to permit dissipationless current flow. This is a particularly important issue for the high-transition-temperature superconductors, in which the vortices move very easily. Irradiation of superconducting samples by heavy ions produces columnar defects, which are considered to be the optimal pinning traps when the orientation of the column coincides with that of the vortex line. Although columnar defect pinning has been investigated using macroscopic techniques, it has hitherto been impossible to resolve individual vortices intersecting with individual defects. Here we achieve the resolution required to image vortex lines and columnar defects in Bi2Sr2CaCu2O8+delta (Bi-2212) thin films, using a 1-MV field-emission electron microscope. For our thin films, we find that the vortex lines at higher temperatures are trapped and oriented along tilted columnar defects, irrespective of the orientation of the applied magnetic field. At lower temperatures, however, vortex penetration always takes place perpendicular to the film plane, suggesting that intrinsic 'background' pinning in the material now dominates.

Journal Article↗
PubMed2000

Development of a 1 MV field-emission transmission electron microscope.

We developed a 1 MV field-emission transmission electron microscope. This paper reports details and specifications of the instrument. The microscope was designed to obtain a bright and coherent electron beam by using the field emission gun equipped with a pre-accelerating magnetic lens and the high-voltage power supply with high stability (0.5 ppm min(-1)). Using this microscope, the brightness of 1.8 x 10(10) A cm(-2) sr(-1) and the lattice resolution of 49.8 pm were attained.

Journal Article↗
PubMed1999

Cisplatin in combination with irinotecan in the treatment of patients with malignant pleural mesothelioma: a pilot phase II clinical trial and pharmacokinetic profile.

BACKGROUND: The purpose of this study was to assess the efficacy and toxicity of a combination of cisplatin and irinotecan (CPT-11) in the treatment of patients with malignant pleural mesothelioma and to characterize the pharmacokinetic profiles of CPT-11 and its active metabolite, 7-ethyl-10-hydroxycamptothecin (SN-38). METHODS: Fifteen previously untreated patients with malignant pleural mesothelioma were treated with cisplatin (60 mg/m2 on Day 1) and CPT-11 (60 mg/m2 on Days 1, 8, and 15) administered intravenously and followed by a 1-week rest period. The course of treatment was repeated every 28 days. After intravenous administration, the levels of CPT-11 and SN-38 in the plasma and pleural fluid were determined for each histologic subtype of mesothelioma. RESULTS: All patients were evaluable for response and toxicity. Four partial responses (response rate of 26.7%) with a median response duration of 25.9 weeks and 2 regressions of evaluable disease (overall response rate of 40%) were observed. The median survival time after chemotherapy was 28.3 weeks, and the median time to treatment failure was 22.1 weeks. The 1-year survival rate for all patients was 38.5%. Toxicity was well tolerated, and there were no treatment-related deaths. World Health Organization Grade 3 leukopenia occurred in 3 patients (20%), and Grade 1 or 2 diarrhea occurred in 3 patients (20%). There was no excess toxicity in patients with large pleural effusions compared with those with no pleural effusions. CPT-11 and SN-38 were detected in the pleural fluid 1 hour after intravenous administration. The maximum concentrations of CPT-11 and SN-38 in the pleural fluid were 36.5% and 75.8%, respectively, of the corresponding plasma values. CONCLUSIONS: The combination of cisplatin and CPT-11 had definite activity against malignant pleural mesothelioma and was well tolerated. The intravenous administration of CPT-11 produced adequate distribution of CPT-11 and its active metabolite SN-38 into the pleural fluid and allowed a higher concentration of the more active SN-38 to make contact with mesothelioma cells in the thoracic cavity. These results warrant further clinical evaluation of this combination chemotherapy for the treatment of malignant pleural mesothelioma in a confirmatory Phase II trial.

Adult↗
PubMed1998

Interleukin 6 and its relationship to clinical parameters in patients with malignant pleural mesothelioma.

The relationship between interleukin 6 (IL-6) levels and clinical parameters was studied in 25 patients with malignant pleural mesothelioma. The serum levels of IL-6, C-reactive protein, alpha1-acid glycoprotein and fibrinogen were significantly higher in mesothelioma than in lung adenocarcinoma with cytology-positive pleural effusion. Serum IL-6 levels correlated with the levels of the acute-phase proteins. We demonstrated a high incidence of thrombocytosis (48%) and a significant correlation between platelet count and the serum IL-6 level. The level of IL-6 in the pleural fluid of patients with mesothelioma was significantly higher than in the pleural fluid of patients with adenocarcinoma, and was about 60-1400 times higher than in the serum. However, even higher levels of IL-6 in the pleural fluid and of thrombocytosis were found in patients with tuberculous pleurisy. These results indicate that large amounts of IL-6 from the pleural fluid of patients with mesothelioma leak into the systemic circulation and induce clinical inflammatory reactions. These profiles are not specific to mesothelioma as similar profiles are found in patients with tuberculous pleurisy. However, the detection of a markedly increased level of IL-6 in pleural fluid argues against a diagnosis of adenocarcinoma.

Adenocarcinoma↗
PubMed1996

Direct Observation of Vortex Dynamics in Superconducting Films with Regular Arrays of Defects

The microscopic mechanism of the matching effect in a superconductor, which manifested itself as the production of peaks or cusps in the critical current at specific values of the applied magnetic field, was investigated with Lorentz microscopy to allow direct observation of the behavior of vortices in a niobium thin film having a regular array of artificial defects. Vortices were observed to form regular and consequently rigid lattices at the matching magnetic field, at its multiples, and at its fractions. The dynamic observation furthermore revealed that vortices were most difficult to move at the matching field, whereas excess vortices moved easily.

Journal Article↗
PubMed1995

Recent developments in electron holography for phase microscopy.

This paper reports on the recent remarkable progress made in electron phase microscopy, especially due to the development of both a "coherent" field-emission electron beam and the related image processing techniques. With these techniques, the phase distribution of an electron beam transmitted through a specimen can now be measured with a precision of within 1/100 of the electron wavelength to observe the thickness distribution of a uniform specimen at the atomic level, the magnetic domain structures in a ferromagnetic thin film, and individual vortices in a superconducting thin film. Vortices in superconducting thin films have become dynamically observable by Lorentz microscopy.

Holography↗
PubMed1994

In vitro growth suppression and morphological change in a human renal cell carcinoma cell line by the introduction of normal chromosome 3 via microcell fusion.

Cytogenetic and molecular studies of human renal cell carcinoma (RCC) have suggested that the genetic and functional losses of one or more putative tumor suppressor genes on the short arm of chromosome 3 play a crucial role in the development of this disease. To examine whether the introduction of chromosome 3 has any effects on the biology of RCC cells, we introduced either chromosome 3, 7, or 11 from normal human fibroblasts into a newly established human RCC cell line with loss of heterozygosity for 3p, via microcell-mediated chromosome transfer. Microcell hybrids containing an introduced, intact chromosome 3 showed a significant reduction in in vitro growth rate and saturation density together with morphological alteration; these properties were not altered in microcell hybrids containing an introduced chromosome 7 or 11. During long-term cultivation, one of the clones that had lost the introduced chromosome 3 showed growth properties and morphology similar to those of the parental cell lines. Thus, our findings provide additional evidence for the presence of a putative tumor suppressor gene or genes on normal chromosome 3p and indicate that the gene is a dominant, negative growth regulator whose loss promotes progressive features of the neoplastic phenotype.

Carcinoma, Renal Cell↗
PubMed1994

Aspartate aminotransferase-linked immunoglobulin complexes in serum of a patient with primary biliary cirrhosis.

A 51-year-old woman who had been treated for primary biliary cirrhosis (PBC) was admitted to our hospital for evaluation of unexplained, isolated, persistently increased aspartate aminotransferase (AST) activity. Results of laboratory tests on admission showed: AST 171 KU, alanine aminotransferase 28 KU, and anti-mitochondrial titer 1/1280. Results of hepatitis B surface antigen (HBs Ag) and hepatitis C virus antibody (HCV Ab; C100-3) assays were negative. Histology of a liver biopsy specimen was compatible with a diagnosis of PBC (stage III of Scheuer's classification). The molecular size of serum AST was estimated to be more than 500,000 by high-performance size-exclusion liquid chromatography. Electrophoretic analysis showed an abnormal band of AST between supernatant AST (sAST) and mitochondrial AST (mAST), which band was characteristic of AST-immunoglobulin complexes (AST-Ig). Ouchterlony double-diffusion and immunoprecipitation tests identified the immunoglobulin component as IgM. The presence of AST-Ig appeared to be responsible for the elevated serum AST.

Aspartate Aminotransferases↗
PubMed1993

Mapping the breakpoint of a constitutional translocation on chromosome 22 in a patient with NF2.

Neurofibromatosis type 2 (NF2) is an autosomal dominant disorder characterized by development of bilateral acoustic neurinomas and increased incidence of meningiomas. Frequent losses of I allele of chromosome 22 in neurinomas and meningiomas has indicated that the gene responsible for NF2 functions as a tumor suppressor. Although the NF2 gene has been mapped within a 13 cM region between D22S1 and D22S28 by linkage analysis, its location with respect to D22S15 is uncertain. We previously reported an NF2 patient with a constitutional balanced translocation t(4;22)(q12;q12.2); the NF2 gene is probably disrupted at the breakpoint. To define the location of this breakpoint on chromosome 22, we performed fluorescence in situ hybridization (FISH) with DNA markers in the NF2 region and determined the physical order of 5 loci: D22S1-NF2-LIF-D22S15-D22S32.

Base Sequence↗
PubMed1992

Constitutional translocation t(4;22) (q12;q12.2) associated with neurofibromatosis type 2.

We report on a female patient with bilateral acoustic neurinomas and other tumors in the central nervous system (neurofibromatosis type 2: NF2) and the constitutional translocation, t(4;22) (q12;q12.2). The precise identification of the translocation breakpoint (q12.2) on chromosome 22 implies the refined localization of a gene responsible for NF2, and would provide a clue to its molecular characterization and to the isolation of the gene. Chromosomes of a paraspinal neurinoma from the patient were also analyzed, and the same karyotype as seen in cultured peripheral lymphocytes was found. The patient's father was also a carrier of the translocation, but he had no clinical symptoms of NF2, nor did other relatives. Several explanations are offered for the different expression of the translocation between the patient and her father.

Adult↗