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Biomedical subjects

H Hamanaka

Publications and source records attributed to H Hamanaka.

At least 19 recordsLinked to original sources
PubMed2003

Wear properties of Ti and Ti-6Al-7Nb castings for dental prostheses.

Titanium has been increasingly applied to dental prostheses because of its biocompatibility. However, application remains limited, due to the low strength and poor wear resistance of unalloyed titanium. The purpose of this study is to evaluate the wear resistance of high-strength Ti-6Al-7Nb alloy castings for dental application. Test specimens were cast from commercially pure titanium (CP-Ti grades 2 and 3) and Ti-6Al-7Nb alloy ingots, and subjected to a wear test simulating the occlusal loading pattern. Wear resistance was evaluated by the weight loss during the test. Ti-6Al-7Nb alloy was found to exhibit lower weight loss than CP-Ti. Moreover, scanning electron microscopic (SEM) observation after the test revealed that the worn surface of Ti-6Al-7Nb alloy is much smoother than that of CP-Ti. These results indicate that Ti-6Al-7Nb alloy castings can be used to produce dental prostheses of improved wear resistance and mechanical strength.

Biomechanical Phenomena↗
PubMed2002

Effect of heat treatment with the mould on the super-elastic property of Ti-Ni alloy castings for dental application.

Tensile property of Ti-50.85Ni (mol %) alloy castings was investigated quantitatively in relation to the thermal behavior accompanied with phase transformation to evaluate the effect of heat treatment after casting with the mould in air. The heat treatment temperature was 713 or 773 K, and the period was 0.9, 1.8, or 3.6 ks. Apparent proof stress of the castings decreased with increasing period of heat treatment, and the decrease was larger with the treatment at 773 K. Residual strain also decreased by the heat treatment, however, it was low with the treatment for relatively short period, i.e. 713 K-0.9 and 1.8 ks, and 773 K-0.9 ks treatments. From the thermal behavior measured by differential scanning calorimetry (DSC), the ascent in the transformation temperatures and the increase in the thermal peak height appeared to influence the changes in the tensile property. These changes by heat treatment were believed to be effective to utilize more flexibility, less stress and less permanent deformation in dental castings.

Journal Article↗
PubMed2002

Case report. Phaeohyphomycosis caused by Phialophora verrucosa developed in a patient with non-HIV acquired immunodeficiency syndrome.

A 53-year-old woman had asymptomatic multiple nodules on her gluteal region for 6 months. She had a history of systemic corticosteroid treatment for Evans' syndrome. Recently she had developed an immunodeficiency condition with CD4+ cell depletion without an HIV infection and a normal serum gamma globulin level. A smear from the purulent exudate of the nodules revealed many brown-coloured hyphae, spores and few large dark-brown cells. A short, hairy, dark-brown coloured colony was cultivated on Sabouraud glucose agar. Slide culturing revealed only a Phialophora-type conidia formation, and the fungus was diagnosed as Phialophora verrucosa. Severe immunosuppressive condition (non-HIV acquired immunodeficiency syndrome) of this patients after systemic corticosteroid treatment for Evans' syndrome predisposed an opportunistic cutaneous fungal infection due to P. verrucosa. Cases with cutaneous infection due to P. verrucosa reported in Japan are summarized and discussed.

Acquired Immunodeficiency Syndrome↗
PubMed2000

Altered cholesterol metabolism in human apolipoprotein E4 knock-in mice.

Thevarepsilon4 allele of apolipoprotein E (apoE) is associated with an increased risk of developing Alzheimer's disease (AD). To accurately determine the isoform-specific effects of human apoE on brain functions under physiological and pathological situations, we created mice expressing human apoE4 isoform in place of mouse apoE by utilizing the gene-targeting technique on the embryonic stem cells (knock-in). The homozygousvarepsilon4 (4/4) mice correctly expressed human apoE4 in the serum and the brain. The human apoE in the brain was found primarily in the astrocytes as was the mouse apoE in the wild-type (+/+) mice. In the 4/4 mice, the serum cholesterol level was 2.5-fold that of the +/+ littermate controls on a regular diet. This marked elevation was accounted for by an accumulation of very low and low density lipo-proteins. In the brains of the 4/4 mice, however, the amounts of total cholesterol and phospholipids were significantly decreased compared with the +/+ littermates. These findings indicate that cholesterol and lipid metabolism is markedly altered in the 4/4 mice. Our human apoE4 knock-in mice will be useful in clarifying the role of apoE in the etiologies of AD and cardiovascular diseases in relation to cholesterol and lipid metabolism.

Animals↗
PubMed2000

Stress transmission through Ti-Ni alloy, titanium and stainless steel in impact compression test.

Impact stress transmission of Ti-Ni alloy was evaluated for biomedical stress shielding. Transformation temperatures of the alloy were investigated by means of DSC. An impact compression test was carried out with use of split-Hopkinson pressure-bar technique with cylindrical specimens of Ti-Ni alloy, titanium and stainless steel. As a result, the transmitted pulse through Ti-Ni alloy was considerably depressed as compared with those through titanium and stainless steel. The initial stress reduction was large through Ti-Ni alloy and titanium, but the stress reduction through Ti-Ni alloy was more continuous than titanium. The maximum value in the stress difference between incident and transmitted pulses through Ti-Ni alloy or titanium was higher than that through stainless steel, while the stress reduction in the maximum stress through Ti-Ni alloy was statistically larger than that through titanium or stainless steel. Ti-Ni alloy transmitted less impact stress than titanium or stainless steel, which suggested that the loading stress to adjacent tissues could be decreased with use of Ti-Ni alloy as a component material in an implant system.

Journal Article↗
PubMed2000

Super-elastic property of Ti-Ni alloy for use in dentistry.

The super-elasticity of Ti-Ni alloy was investigated in tensile and bending tests to evaluate the mechanical properties of the castings and heat treatment effect on the bending properties of the wires for new clinical applications of the alloy in prosthodontics and orthodontics. In terms of the tensile properties of the castings, apparent proof stress increased and elongation decreased with the small increase in nickel content or with the decrease in titanium purity. This result suggests that precise control of the materials is indispensable to utilize the super-elasticity in dental cast appliances. In terms of the bending properties of Ti-Ni alloy wires, low residual deflection and small load/deflection ratio were obtained by the second heat treatment between 733 and 813 K, which was found to be suitable for the shape memory treatment of orthodontic appliances. Moreover, the functional force was changeable within this treatment temperature range.

Biocompatible Materials↗
PubMed1999

Apolipoprotein E is found in astrocytes but not in microglia in the normal mouse brain.

Apolipoprotein E (apoE) is a known risk factor for Alzheimer's disease, but neither its roles in the pathogenesis nor its exact physiological functions in the brain is known. In order to study the apoE protein in the brains of normal mouse and transgenic mouse models of neurodegeneration, hamster monoclonal antibodies (MAbs) specific to mouse apoE were generated. N- and C-terminal fragments of mouse apoE protein were produced in E. coli as fusion proteins and used to immunize Armenian hamsters. Specificity of the antibodies was established by immunoblotting against sera and brain homogenates of wild type and apoE-deficient mice. MAb 884F11 was found most suitable for immunohistochemistry on 4% PFA-fixed brain tissues. The strongly positive structure in the normal brain was the astrocytes as identified by simultaneous staining for GFAP with lesser and regionally variable diffuse staining of the neuropil. GFAP-positive cells were variable in their content of apoE. ApoE immunoreactivity in the hippocampus and neocortex did not coincide with the tomato lectin binding, indicating that this apolipoprotein is not detectable in the microglial cells of the normal adult mouse brain.

Animals↗
PubMed1999

Melanocyte melanin augments sparfloxacin-induced phototoxicity.

Quinolone has become one of the common causative agents of drug-induced photosensitive dermatitis, and its phototoxicity has now become a clinical issue. The mechanisms of long-lasting phototoxicity induced by sparfloxacin (SPFX) were investigated using melanotic and amelanotic melanoma cell lines. The sensitivities to SPFX and UVA irradiation up to 6 J/cm2 of both cells were not significantly different. However, the melanotic melanoma cell cultured with 1-150 microg/ml of SPFX showed significantly higher sensitivity to UVA irradiation compared with that of the amelanotic melanoma cell. By pulse culture with SPFX, the bound SPFX level of melanotic cell line was 10-20 times higher than that of the amelanotic cell line. These data strongly suggest that the melanin in melanocytes and keratinocytes accumulates the antibacterial quinolone and increases its tissue concentration in the basal epidermis and contributes to the long-lasting photo-injury and liquefaction degeneration of the basal cells in antibiotic quinolone phototoxic dermatitis.

Anti-Infective Agents↗
PubMed1999

Topical tocoretinate improved hypertrophic scar, skin sclerosis in systemic sclerosis and morphea.

Four patients with systemic scleroderma (SSc), 4 patients with morphea, and 4 patients with hypertrophic scar were treated with topical tocoretinate for 6 months to 3 years and studied clinically and histopathologically. Clinically, all of the lesions responded to this therapy. The stiffness of the skin lesions, glossy appearance of the lesions, and telangiectasia improved. Histopathologically, the proliferated collagen fibers decreased in thickness, and the inter-fiber spaces increased. Immunoreactive tenascin-C expressed in the proliferated deep dermal fibers of the SSc and hypertrophic scar lesions was markedly decreased compared with the level before the topical tocoretinate therapy. Topical tocoretinate has been used for the treatment of ulcers; it is also a potent treatment for sclerotic skin diseases.

Administration, Topical↗
PubMed1998

Sparfloxacin-induced photosensitivity and the occurrence of a lichenoid tissue reaction after prolonged exposure.

BACKGROUND: A new antibacterial quinolone, sparfloxacin (SPFX), frequently causes photosensitive dermatitis and sometimes induces a treatment-resistant lichenoid tissue reaction (LTR). OBJECTIVE: We attempted to determine the factors that induce LTR in SPFX-induced photodermatitis. METHODS: Thirteen patients with SPFX photosensitive dermatitis were studied clinically and histopathologically. RESULTS: Six of the 13 patients had acute dermatitis with epidermal spongiosis and focal epidermal HLA-DR and intercellular adhesion molecule-1 (ICAM-1) expression with CD4+ cell infiltration. The other seven displayed LTR with basal cell liquefaction degeneration and diffuse epidermal HLA-DR and ICAM-1 expression associated with CD8+ cells. The seven patients with LTR were exposed to UV and SPFX for more than 2 weeks after the appearance of their initial eruption, whereas the six patients with acute dermatitis were treated within 2 weeks. The acute dermatitis lesions cleared significantly within 2 weeks, but the LTR lesions persisted for more than 6 weeks. CONCLUSION: Patients with quinolone-induced photosensitivity should be treated within 2 weeks of onset to prevent LTR.

Adult↗
PubMed1998

Increased cutaneous immunoreactive stem cell factor expression and serum stem cell factor level in systemic scleroderma.

Skin hyperpigmentation and itching are characteristic findings in systemic sclerosis (SSC) patients. Stem cell factor (SCF, c-kit ligand) is a multifunctional cytokine which can promote melanocyte and mast cell development. We investigated the SCF expression histopathologically in normal and SSC skin, and compared the expression with the serum SCF levels measured with a specific enzyme-linked immunosorbent assay. The epidermal and dermal immunoreactive SCF expression was markedly higher in the forearm skin of edematous phase SSC patients than in that of normal subjects. Tissue SCF expression declined from the sclerotic phase to the atrophic phase, where it was close to the normal level. In contrast, the elevated serum SCF level seen in the edematous phase samples was further increased in the sclerotic phase samples. The serum SCF level decreased in the atrophic phase, but it still remained at a level higher than that of the normal controls. Itching and increase of dermal mast cell number are characteristic of edematous phase SSC, and are in bears a parallel to the presently observed dermal SCF expression profile. Pigmentation is significant in sclerotic phase SSC and lasts to the atrophic phase, which may correspond to the serum SCF level observed here. These results indicate a contribution of the fibroblast membrane integral SCF in dermal mast cell development, and of the soluble serum SCF to melanocyte activation in SSC.

Adult↗
PubMed1998

Amount of hydroxyl radical on calcium-ion-implanted titanium and point of zero charge of constituent oxide of the surface-modified layer.

To compare the surface properties of calcium-ion (Ca2+)-implanted titanium with those of titanium and to investigate the mechanism of bone conductivity of Ca2+-implanted titanium, amounts of hydroxyl radical of Ca2+-implanted titanium and titanium were estimated. Also, the point of zero charge (p.z.c.) of oxide constituting surface oxides of Ca2+-implanted titanium and titanium was determined. Results showed that the amount of active hydroxyl radical on Ca2+-implanted titanium was found to be significantly larger than that on titanium, indicating that the number of electric-charging sites of Ca2+-implanted titanium in electrolyte is more than that of titanium. The p.z.c. values of rutile (TiO2), anatase (TiO2), and perovskite (CaTiO3), were estimated to be 4.6, 5.9, and 8.1, respectively. Thus, Ca2+-implanted titanium surface is charged more positively in bioliquid than titanium, accelerating the adsorption of phosphate ions.

Journal Article↗
PubMed1998

Mechanical properties and corrosion resistance of Ti-6Al-7Nb alloy dental castings.

With the aim of applying a novel titanium alloy, Ti-6Al-7Nb, to a dental casting material, a comprehensive research work was carried out on its characteristics, such as castability, mechanical properties and corrosion resistance in the present study. As a result, Ti-6Al-7Nb alloy exhibited sufficient castability by a dental casting method for titanium alloys and enough mechanical properties for dental application. It is also showed excellent corrosion resistance through an immersion test in 1.0% lactic acid and an anodic polarization test in 0.9% NaCl solution. From these results, it is concluded that this Ti-6Al-7Nb alloy is applicable as a dental material in place of Ti-6Al-4V alloy, which includes cytotoxic vanadium.

Journal Article↗
PubMed1998

Influence of aging heat treatment on mechanical properties of biomedical Ti-Zr based ternary alloys containing niobium.

Titanium-zirconium based alloys containing a small amount of niobium were investigated in order to evaluate their possible use as biomedical materials. Zirconium, which belongs to the IVa group, is known to have good corrosion resistance and biocompatibility similar to titanium. As the titanium-zirconium system shows a complete solid solution, a wide variation of alloy design is available and large quantities of solid-solution hardening must be possible. Niobium, having a beta-phase stabilizing effect, was chosen as a ternary element in order to control desirably the microstructure. There have been no reports which suggest its harm to a living body. The alloys containing 2% or 3% niobium showed the highest hardness value after aging heat treatment at 773 K. In contrast to this, no alteration of hardness was seen in specimens aged at 1073 K. Through conventional X-ray diffractometry and in situ X-ray analysis using a hot stage, beta-phase precipitation in the A matrix was identified. From the above results, it is concluded that alloys containing 2%-3% niobium are hopeful candidates for new kinds of biomedical alloys, when they are heat treated under suitable conditions.

Journal Article↗
PubMed1998

Allopurinol hypersensitivity syndrome: hypersensitivity to oxypurinol but not allopurinol.

Allopurinol is a xanthine oxidase inhibitor widely used to control plasma uric acid levels. Episodes of hypersensitivity to the drug are not rare. A severe form of this with a generalized exanthem, fever and liver involvement has been termed the allopurinol hypersensitivity syndrome (AHS). Patch testing and lymphocyte stimulation testing (LST) are not helpful in confirming this sensitivity. Allopurinol works as a substrate of xanthine oxidase, and is rapidly oxidized into oxypurinol in vivo. Therefore, the biological half-life of oxypurinol is markedly longer than that of allopurinol. In addition, conspicuous pre-existing renal impairment has been noted in many AHS patients. Thus, it is possible that AHS is a manifestation of hypersensitivity to oxy-, not allopurinol. Here, we now report three cases of AHS in which there were significant lymphoproliferative reactions to oxypurinol but not allopurinol.

Adult↗
PubMed1997

Spatially and temporally regulated modification of the receptor-like protein tyrosine phosphatase zeta/beta isoforms with keratan sulphate in the developing chick brain.

Protein tyrosine phosphatase zeta (PTPzeta/RPTPbeta) is a proteoglycan-type receptor-like protein tyrosine phosphatase specifically expressed in the brain. In addition to the transmembrane form (PTPzeta-A), the extracellular splice variant (PTPzeta-S) occurs as a major soluble chondroitin sulphate proteoglycan in the brain. We prepared antibodies which specifically recognize PTPzeta-A and -S, and analysed the carbohydrate structures on the two PTPzeta isoforms in the developing chick brain. Immunoprecipitation experiments using these antibodies revealed that almost all of the keratan sulphate recognized by a monoclonal antibody (5D4) was exclusively bound to PTPzeta-A and PTPzeta-S. Addition of keratan sulphate to these proteoglycans markedly increased from embryonic day (E) 11, in contrast to the addition of Le(x) and HNK-1 carbohydrates, which gradually increased during development in accordance with expression of the core proteins, suggesting that keratan sulphate modification plays some specific roles. Moreover, at the early embryonic stage keratan sulphate was observed only in several restricted regions, especially at boundary regions such as the roof plate of the tectum, the zona limitans intrathalamica in the diencephalon, and the mesencephalon-metencephalon boundary. At the mesencephalon-metencephalon boundary, keratan sulphate modification of PTPzeta isoforms was specifically observed from E3 to E6 on a ring of cells encircling the neural tube and their radially oriented processes, which were identified as radial glial fibres. This expression pattern of keratan sulphate spatiotemporally corresponded well to the formation of the fovea isthmi, a groove separating the mesencephalon from the metencephalon. These results suggest that carbohydrates including keratan sulphate on PTPzeta isoforms play important roles in brain development by modulating the cell-cell and/or cell-substrate interactions mediated by these molecules.

Animals↗