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Biomedical subjects

H Hamanaka

Publications and source records attributed to H Hamanaka.

At least 37 records · Page 2Linked to original sources
PubMed1996

6B4 proteoglycan/phosphacan, an extracellular variant of receptor-like protein-tyrosine phosphatase zeta/RPTPbeta, binds pleiotrophin/heparin-binding growth-associated molecule (HB-GAM).

A major chondroitin sulfate proteoglycan in the brain, 6B4 proteoglycan/phosphacan, corresponds to the extracellular region of a receptor-like protein-tyrosine phosphatase, PTPzeta/RPTPbeta. Here, we purified and characterized 6B4 proteoglycan-binding proteins from rat brain. From the CHAPS (3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonic acid) extract of brain microsomal fractions, 18-, 28-, and 40-kDa proteins were specifically isolated using 6B4 proteoglycan-Sepharose. N-terminal amino acid sequencing identified the 18-kDa protein as pleiotrophin/heparin-binding growth-associated molecule (HB-GAM). Scatchard analysis of 6B4 proteoglycan-pleiotrophin binding revealed low (Kd = 3 nM) and high (Kd = 0.25 nM) affinity binding sites. Chondroitinase ABC digestion of the proteoglycan decreased the binding affinities to a single value (Kd = 13 nM) without changing the number of binding sites. This suggested the presence of two subpopulations of the proteoglycan with different chondroitin sulfate structures. Heparin potently inhibited binding of 6B4 proteoglycan to pleiotrophin (IC50 = 3.5 ng/ml). Heparan sulfate and chondroitin sulfate C inhibited moderately (IC50 = 150 and 400 ng/ml, respectively), but, in contrast, chondroitin sulfate A and keratan sulfate were poor inhibitors (IC50 > 100 microg/ml). Immunofluorescence and immunoblotting analyses indicated that both 6B4 proteoglycan and PTPzeta are located on cortical neurons. Anti-6B4 proteoglycan antibody added to the culture medium suppressed pleiotrophin-induced neurite outgrowth of cortical neurons. These results suggested that interaction between 6B4 proteoglycan and pleiotrophin is required for the action of pleiotrophin, and chondroitin sulfate chains on 6B4 proteoglycan play regulatory roles in its binding.

Amino Acid Sequence↗
PubMed1995

Mechanical properties of the binary titanium-zirconium alloys and their potential for biomedical materials.

Mechanical properties of titanium-zirconium binary alloys were investigated in order to reveal their possible use for new biomedical materials and to collect useful data for alloy design through a hardness test, a tensile test, and optical microscopy. The hardness of the alloy containing 50% zirconium was approximately 2.5 times as large as the hardness of pure titanium and pure zirconium. Tensile tests showed a similar tendency. No changes between hardness of as cast specimens and as homogenized specimens were observed, nor were changes in microstructures noted. Comparisons between the Ti-6Al-4V alloy and the Ti-Zr-6Al-4V alloy indicated that a titanium-zirconium alloy could provide a base material for a new biomedical alloy. From these results, it was concluded that new alloys for biomedical materials should be designed as titanium-zirconium base alloys.

Alloys↗
PubMed1995

Purification, characterization and developmental expression of a brain-specific chondroitin sulfate proteoglycan, 6B4 proteoglycan/phosphacan.

A large brain-specific chondroitin sulfate proteoglycan, identified with monoclonal antibody 6B4 (6B4 proteoglycan/phosphacan), was isolated from rat brain. Soluble proteoglycans in the phosphate-buffered saline extract from 20-day-old rat whole brain were fractionated by anion exchange chromatography and CsCl density gradient centrifugation. 6B4 proteoglycan was further purified by gel filtration and additional ion exchange chromatography. The molecular mass of 6B4 proteoglycan shifted from 800 to 300 x 10(3) mol. wt after chondroitinase ABC digestion. The core protein was substituted with chondroitin sulfate chains with an average molecular weight of 21,000, keratan sulfate and HNK-1 carbohydrates. Glycosidase digestion of 6B4 proteoglycan with O-glycanase, N-glycanase, endo-beta-galactosidase, or keratanase did not remove the HNK-1 epitopes. The expression of 6B4 proteoglycan was developmentally regulated in the rat cerebral cortex; appearing first at embryonic day 14, peaking at postnatal day 0, and persisting throughout adulthood at a lower level. Immunohistochemical analysis indicated that 6B4 proteoglycan was distributed along the radial glial fibers and on the migrating neurons in the embryonal rar cerebrum. The radial glial fibers were stained intensely all along their length, but the neurons in the cortical plate were not stained in contrast to the moderate staining of the migrating neurons in the intermediate zone and the subplate. From postnatal day 5 to postnatal day 20, 6B4 proteoglycan was present throughout the cortex. After postnatal day 30, staining of the neuropil was weakened, and the expression of 6B4 proteoglycan was restricted around subsets of neurons. The positive neurons were mostly non-pyramidal cells (> 95%) and were relatively concentrated in layers IV and VI of the primary somatosensory cortex. Immunohistochemical analysis of the dissociated cortical neurons indicated that 6B4 proteoglycan was distributed on the cell bodies and neurites. 6B4 proteoglycan strikingly promoted neurite extension of cortical neurons from embryonic day-16 rat embryos when coated on coverslips as a substrate. 6B4 proteoglycan is a brain-specific chondroitin sulfate proteoglycan which carries keratan sulfate and HNK-1 carbohydrates. The spatiotemporal expression profile and effects on the dissociated cerebral neurons suggest that 6B4 proteoglycan plays important roles in the migration and differentiation of neurons in the immature cortex, and also in the maintenance of subsets of neurons in the mature cortex.

Animals↗
PubMed1994

Multiple receptor-like protein tyrosine phosphatases in the form of chondroitin sulfate proteoglycan.

The possibility that some of the brain proteoglycans are receptor-like protein tyrosine phosphatases (PTPases) was investigated. Membrane-bound proteoglycan fractions were prepared from the postnuclear membrane fraction of 8-day-old rat brain by DEAE ion-exchange chromatography and CsCl density gradient centrifugation. The isolated proteoglycan fractions showed high PTPase specific activities together with the typical PTPase characteristics. Renaturation experiments indicated that chondroitin sulfate proteoglycans with 380- and 170-kDa core proteins carried the PTPase activity. The proteoglycan with 380-kDa core protein was identified as RPTP beta/zeta bearing HNK-1 carbohydrate.

Animals↗
PubMed1994

Transmembrane topology and sites of N-glycosylation of inositol 1,4,5-trisphosphate receptor.

To define the transmembrane topology of the inositol 1,4,5-trisphosphate receptor (InsP3R), we determined the subcellular location of the hydrophilic segment (residues 2463-2529 of mouse type 1 InsP3R) believed to be located at the luminal side of the endoplasmic reticulum (ER) in the six-transmembrane model but at the cytoplasmic side in the eight-transmembrane model. This hydrophilic segment includes two consensus sites for N-glycosylation (Asn-2475 and Asn-2503). We prepared an anti-peptide antibody against residues 2504-2523. Electron microscope immunocytochemical studies of mouse cerebellar Purkinje cells showed that binding of this antibody frequently occurs in the intracisternal space of the ER. We constructed three mutant receptors by site-directed mutagenesis of Asn to Gln (N2475Q, N2503Q, and N2475Q/N2503Q). By concanavalin A column chromatography of these receptors, we found that both Asn-2475 and Asn-2503 are glycosylated. These results indicate that residues 2504-2523, Asn-2475, and Asn-2503 are exposed to the ER lumen. We therefore propose that InsP3R has six membrane-spanning segments. Based on the transmembrane topology and subunit organization, we suggest that InsP3R is a member of the superfamily that includes the voltage- and second messenger-gated ion channels on the plasma membrane.

Amino Acid Sequence↗
PubMed1994

Cyclic AMP-dependent phosphorylation of an immunoaffinity-purified homotetrameric inositol 1,4,5-trisphosphate receptor (type I) increases Ca2+ flux in reconstituted lipid vesicles.

We established a novel method to isolate a single type of inositol 1,4,5-trisphosphate receptor (IP3R) among the heterogeneous population of receptors to study the regulatory mechanism of Ca2+ release. We raised in the rabbit a polyclonal antibody against synthetic peptide corresponding to amino acids 2736-2747 (pep 6) of type I IP3R (IP3-R-I) that is most abundant in cerebellum. We purified IP3R-I from a 1% 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonic acid solubilized mouse cerebellar microsomal fraction by immunoaffinity chromatography on an anti-pep 6 antibody-Sepharose 4B column with specific elution by the pep 6 peptide (GHPPHMNVNPQQ) of the IP3R-I C terminus. Immunoaffinity-purified IP3R reconstituted into lipid vesicles formed a homotetramer structure. Monoclonal antibody 18A10, which partially blocks the Ca2+ release from cerebellar microsome, almost completely inhibited IP3-induced 45Ca2+ influx into proteoliposomes, whereas monoclonal antibody that recognizes other regions did not inhibit Ca2+ influx. Both the rate and extent of 45Ca2+ influx into proteoliposomes increased 20% after incubation with the catalytic subunit of cyclic AMP-dependent protein kinase, accompanied by stoichiometric phosphorylation of IP3R protein.

Amino Acid Sequence↗
PubMed1994

Basic properties of super-elastic Ni-Ti alloy ligature wires for a new intermaxillary fixation method.

A new continuous wiring method of intermaxillary fixation with super-elastic Ni-Ti alloy ligature wires was developed to avoid the risk in postoperative emergency. Differential scanning calorimetry, three-point bending tests and fastening tests were carried out to investigate basic properties of the wires. Transformation temperatures of the Ni-Ti alloy wires were in the range suitable for exhibiting super-elasticity at body temperature. The Ni-Ti alloy wires possessed enough bending flexibility to be used in the continuous wiring method and showed great recoverable displacement in the fastening test. With use of these properties, easy removal in an emergency and uniform fixation can be attained.

Alloys↗
PubMed1993

Bending properties and transformation temperatures of heat treated Ni-Ti alloy wire for orthodontic appliances.

The effect of heat treatment temperature on bending properties and transformation temperatures of a Ni-Ti alloy wire, 1.0 mm in diameter, was investigated so that superelasticity could be used in orthodontic appliances needing shape memory processes. The heat treatment process was at 713 K for 1.8 ks and between 673 K and 813 K for 1.8 ks. A three-point bending test and differential scanning calorimetry were performed. The transformation temperatures of the wires were lowered with increasing heat treatment temperature. The reverse transformation finishing temperature was below the body temperature with the treatment above 753 K. Residual deflection of the Ni-Ti wire after bending was small with the secondary heat treatment above 733 K. The load in the unloading process was less changeable and increased with the treatment temperature between 733-813 K. Secondary heat treatment in this range was suitable for using superelasticity in expansion arch appliances.

Dental Alloys↗
PubMed1993

A case of acrogeria.

We report a 30-year-old Japanese male with acrogeria. He was in good health except for the prominent skin atrophy over the hands and feet. In the microscopic view of an atrophic skin biopsy specimen, elastic fibers were clumped and fragmented, especially in the upper dermis. Reviewing fourteen previously reported Japanese cases of acrogeria, the decrease and degeneration of elastic fibers were the prominent characteristic, as was the atrophy of subcutaneous fat.

Adolescent↗
PubMed1993

Epidermolysis bullosa acquisita (EBA) with nonclassical distribution of eruptions.

The skin lesions in epidermolysis bullosa acquisita (EBA), a mechanobullous disease, often show acral distribution. Recently, we experienced a case of EBA in which most of the skin lesions were located on the trunk. We reviewed the distribution of the skin eruptions in 58 reported cases of EBA. Although the extensor surfaces of the extremities are the most common site, there were some cases with non-acral distribution. These "nonclassical" cases should also be considered in the clinical diagnosis of EBA and other bullous diseases.

Adult↗
PubMed1993

Influence of mold materials and heat treatment on tensile properties of Ni-Ti alloy castings.

The influence of mold materials and heat treatment on the tensile properties and the transformation temperatures of Ni-Ti alloy castings was investigated by tensile test and differential scanning calorimetry (DSC) in order to apply the special properties of the alloy to dental field. The compositions of the two alloys examined were 49.0 and 49.2 at % Ti. A silica investment and a magnesia investment were used as the mold materials. Heat treatment at 440 degrees C for 1.8 ks was performed. Apparent proof strength decreased in both compositions, and residual strain increased in Ni-49.2Ti by the heat treatment. Elongation increased in Ni-49.0Ti with use of the magnesia mold or by the heat treatment. The transformation temperatures of Ni-49.2Ti increased with use of the magnesia mold. The change by the heat treatment suggested a structural change. The development of a suitable method for the casting of the alloy is expected to bring about the development of new devices and therapy in dentistry.

Calorimetry, Differential Scanning↗
PubMed1992

Super-elasticity and thermal behavior of Ni-Ti alloy orthodontic arch wires.

Bending properties and thermal behavior of twenty commercial Ni-Ti alloy orthodontic arch wires were investigated quantitatively to characterize their suitability for clinical use. There was substantial difference among the load-deflection curves obtained by a three-point bending test. Some wires exhibited super-elasticity; load decreased little with decreasing deflection. Others showed good spring-back properties only; load was nearly proportional to deflection. Thermal behavior due to phase transformation of the alloy was examined by differential scanning calorimetry (DSC). Some of the wires did not have the correct transformation temperatures to exhibit super-elasticity at body temperature. Moreover, thermal behavior was closely related to super-elasticity. There were clear thermal peaks in the DSC curves of the super-elastic wires. However, wires without super-elasticity had no peak in the DSC curves.

Dental Alloys↗
PubMed1992

The corrosion behavior of Nd2Fe14B and SmCo5 magnets.

Rare earth magnets have corrosive problems associated with their use in prostheses in various fields including orthodontics. The purpose of this study is to investigate the corrosion behavior of an Nd2Fe14B magnet and a SmCo5 magnet in an oral environment. The relations among the attractive force changes, the released elements, the weight changes and the anodic polarization measurements of the magnets were examined under immersions in 1% NaCl, 1% lactic acid, 0.05% HCl, 0.1% Na2S and Greenwood's artificial saliva at 37 degrees C for forty-two days. The results showed that the rare earth magnets underwent high corrosive assaults and large attractive force reductions by the immersions in 1% lactic acid and 0.05% HCl. The problem of corrosion of the magnets could be overcome by sealing them within laser-welded stainless steel capsules.

Corrosion↗
PubMed1992

Influence of composition and purity on tensile properties of Ni-Ti alloy castings.

The influence of composition and purity of titanium on the mechanical properties and the transformation temperatures of Ni-Ti alloy dental castings was investigated by tensile testing and differential scanning calorimetry (DSC). The compositions of the ingots were 49.0-49.2 at% of titanium content. Three grades of titanium of relatively high purity were used as starting materials. The result showed Ni-49.0Ti to be a somewhat brittle property, and Ni-49.2Ti to have low apparent proof strength and large elongation. Residual strain increased with increasing titanium content. Even small reductions of titanium purity influenced the tensile properties and the transformation temperatures, causing high apparent proof strength, low residual strain and low elongation because of the reduction in transformation temperatures.

Dental Alloys↗
PubMed1991

Salvage of distal flap necrosis by topical superoxide dismutase.

Significance of the reactive oxygen species in distal flap necrosis and the efficacy of superoxide dismutase (SOD) in salvaging necrosis have become indicated in recent studies. To enhance the therapeutic effect of SOD, topical application was designed. Water-soluble ointment containing 1% SOD was prepared, and three experiments were made to study the effect of topical SOD in improving flap survival. Simple application of SOD ointment to the upper surface of the flap had no effect, whereas its application to the under surface or occlusive dressing was effective. These effects were corroborated by assay of tissue SOD activity.

Administration, Topical↗
PubMed1991

Superoxide dismutase activity of murine ultraviolet radiation-induced fibrosarcoma cell strains.

The average superoxide dismutase (SOD) activity of seven cell strains from mouse skin fibrosarcoma induced by ultraviolet (UV) irradiation was 5.78 +/- 0.81 (mean +/- SE) unit/mg protein, while that of seven normal mouse skin fibroblasts was 5.36 +/- 1.58. Although tumor cells have been previously reported to exhibit reduced SOD activity, the present study demonstrates that there is comparable SOD activity between tumor cells and normal cells of the same tissue origin.

Animals↗