Biomedical subjects

T Kokubo

Publications and source records attributed to T Kokubo.

At least 127 records · Page 7Linked to original sources

PubMed1998

Tyrosinase epitope recognized by an HLA-DR-restricted T-cell line from a Vogt-Koyanagi-Harada disease patient.

Human T-cell-mediated autoimmune diseases are often genetically linked to particular alleles of HLA class II genes. Vogt-Koyanagi-Harada's (VKH) disease, which is regarded as an autoimmune disorder in multiple organs containing melanocytes, has been found to be associated with HLA-DR4 (DRB1(*)0405) and HLA-DR53 (DRB4(*)0101). Tyrosinase is a melanoma antigen (Ag) expressed by normal melanocytes as well as melanoma cells against which responses by autologous T cells have been detected. We established a T-cell line from the peripheral blood of a patient with VKH disease which responded to synthetic peptides corresponding to tyrosinase. The T-cell line was generated which recognized the tyrosinase p188 - 208 peptide when presented by the HLA-DR4 (DRB1(*)0405) molecule on the surface of HLA class II-expressing L-cell transfectants. The minimal antigenic peptide which induced T-cell responses was an 11-amino-acid sequence and located at tyrosinase p193 - 203 (E-I-W-R-D-I-D-F-A-H-E). This peptide contained the DRB1(*)0405-binding peptide motif (hydrophobic residues (Y, F, W) at position 1 as an anchor residue, and negatively charged residues (D, E) at position 9), which corresponded to the W at p195 and the D at p203. These observations demonstrate that tyrosinase peptides are immunogenic, and may be a candidate for an autoantigen in VKH disease, suggesting that probing the T-cell responses against synthetic peptides is a productive approach for identifying the autoantigenic peptides associated with autoimmune diseases including VKH disease.

Amino Acid Sequence↗

PubMed1998

Development of Epstein-Barr virus-associated B cell lymphoma after intensive treatment of patients with angioimmunoblastic lymphadenopathy with dysproteinemia.

Evolution of angioimmunoblastic lymphadenopathy with dysproteinemia (AILD) into aggressive B cell lymphoma is thought to be a rare event and the cause of this transformation has not been fully elucidated. We describe two patients with AILD that progressed to aggressive large-cell lymphoma with a B cell phenotype. At presentation, the lymph nodes of both patients showed the typical features of AILD by hematoxylin-eosin staining. Immunohistochemical staining with monoclonal antibodies revealed positive staining of atypical cells with UCHL-1 and negative staining with L-26. In situ hybridization of EBV RNA showed rare positive cells in one patient and was negative in the other patient. At relapse, both patients showed systemic lymph nodes swelling, which is characteristic of diffuse large immunoblastic lymphoma. Single-cell analysis with monoclonal antibodies and immunohistochemical staining showed the monoclonal proliferation of B cells. Southern blot analysis of the lymph nodes showed a rearrangement in both patients of the Ig heavy chain gene and germ line configuration of the T cell receptor beta chain gene. Southern blot analysis using the EBV terminal repeat region probe detected clonal proliferation of EBV in the lymph nodes of both patients. In situ hybridization studies identified considerable EBV mRNA in both patients. These observations suggest that EBV proliferation plays an important role in the development of B cell lymphoma that arises from AILD. We suggest that infection or reactivation of EBV may occur in some patients with AILD, probably due to their immunodeficient state, and that this infection or reactivation is directly involved in the development of B cell lymphoma.

Herpesviridae Infections↗

PubMed1998

Evidence for a site-specific fucosylation of N-linked oligosaccharide of immunoglobulin A1 from normal human serum.

Glycopeptides containing the N-linked oligosaccharide from human serum IgA1 were analyzed by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOFMS). Two glycopeptides, GP1 and GP2, prepared from the endoproteinase Asp-N digest of the IgA1 heavy chain, were derived from the CH2 domain (N-glycan site at Asn263) and the tailpiece portion (N-glycan site at Asn459), respectively. The structure of the attached sugar chain was deduced from the mass number of the glycopeptide and confirmed by a two-dimensional mapping technique for a pyridylaminated oligosaccharide. GP1 was composed of two major components having a fully galactosylated bianntena sugar chain with or without a bisecting N-acetylglucosamine (GlcNAc) residue. On the other hand, the GP2 fraction corresponded to the glycopeptides having a fully galactosylated and fucosylated bianntena sugar chain partly bearing a bisecting GlcNAc residue. Thus, the site-specific fucosylation of the N-linked oligosaccharide on the tailpiece of the alpha1 chain became evident for normal human serum IgA1.

Amino Acid Sequence↗

PubMed1998

Apatite formation on silica gel in simulated body fluid: effects of structural modification with solvent-exchange.

The prerequisite for glasses and glass-ceramics to bond to living bone is the formation of biologically active bone-like apatite on their surfaces. It has been shown that even a pure silica gel forms the bone-like apatite on its surface in a simulated body fluid. In the present study, pore structure of silica gels prepared by hydrolysis and polycondensation of tetraethoxysilane in an aqueous solution containing polyethylene glycol was modified by 1M HNO3, and 0.1M and 1M NH4OH solution treatments. The three kinds of resultant gels all contained large amounts of silanol groups and trisiloxane rings, but differ greatly in pore structure of nanometre pore size. Irrespective of these differences, all the gels formed the bone-like apatite on their surface in the simulated body fluid. It was speculated that a certain type of structural unit of silanol groups, which is easily formed in the presence of the polyethylene glycol, is effective for the apatite formation.

Journal Article↗

PubMed1998

Apatite-organic polymer composites prepared by a biomimetic process: improvement in adhesion of the apatite layer to the substrate by ultraviolet irradiation.

A dense and uniform layer of highly bioactive apatite can be formed in arbitrary thickness on any kind and shape of organic polymer substrates by the following biomimetic process. The substrate is first placed in contact with granular particles of CaO, SiO2-based glass soaked in a simulated body fluid with ion concentrations nearly equal to those of human blood plasma for forming apatite nuclei, and then soaked in another fluid highly supersaturated with respect to the apatite for making the apatite nuclei grow. In the present study, the polymer substrates were pretreated with ultraviolet (UV) light, and then subjected to the biomimetic process described above. By UV irradiation, the induction period for the apatite nucleation of poly(ethylene terephthalate) (PET), poly-ether sulphone (PESF), polyethylene (PE), poly(methyl methacrylate) (PMMA) and polyamide 6 (N6) substrates were reduced form 24 h to 10 h. The adhesive strengths of the apatite layer to the substrates increased from 2.5-3.2 MPa to 4.5-6.0 MPa for PET, PESF and PMMA, and from about 1.0 MPa to 4.0-6.5 MPa for PE and N6 substrates. These results have been explained by assuming that silicate ions, which induce apatite nucleation, are easily adsorbed on the substrates due to the formation of polar groups, with an improved hydrophilic nature, on the polymer surfaces by UV irradiation.

Journal Article↗

PubMed1998

Chemical surface treatment of silicone for inducing its bioactivity.

It has been confirmed that the apatite nucleation is induced by silanol (Si-OH) groups formed on the surfaces of materials and/or silicate ions adsorbed on them. It was previously shown that apatite nuclei are formed on organic polymers when the polymers are placed on CaO, SiO2-based glass particles soaked in a simulated body fluid (SBF) with ion concentrations nearly equal to those of human blood plasma, and that they grow spontaneously to form a dense and uniform apatite layer together with high adhesive strength to the substrates when the polymers are soaked in another solution with ion concentrations 1.5 times the SBF. In the present study, silanol groups bonded covalently to the surface of the silicone substrate were formed and its apatite-forming ability was examined. When silicone substrates were treated with 5 or 10 M NaOH with pH 7.25 at 36.5 degrees C for more than 3 h, silanol groups were formed on the surfaces of the substrates. When thus NaOH-treated substrates were soaked in 1.5SBF at 36.5 degrees C, a bone-like apatite was formed on the substrates in a short period.

Journal Article↗

PubMed1998

The yeast TAF145 inhibitory domain and TFIIA competitively bind to TATA-binding protein.

The Drosophila 230-kDa TFIID subunit (dTAF230) interacts with the DNA binding domain of TATA box-binding protein (TBP) which exists in the same complex. Here, we characterize the inhibitory domain in the yeast TAF145 (yTAF145), which is homologous to dTAF230. Mutation studies show that the N-terminal inhibitory region (residues 10 to 71) can be divided into two subdomains, I (residues 10 to 37) and II (residues 46 to 71). Mutations in either subdomain significantly impair function. Acidic residues in subdomain II are important for the interaction with TBP. In addition, yTAF145 interaction is impaired by mutating the basic residues on the convex surface of TBP, which are crucial for interaction with TFIIA. Consistently, TFIIA and yTAF145 bind competitively to TBP. A deletion of the inhibitory domain of yTAF145 leads to a temperature-sensitive growth phenotype. Importantly, this phenotype is suppressed by overexpression of the TFIIA subunits, indicating that the yTAF145 inhibitory domain is involved in TFIIA function.

Amino Acid Sequence↗

PubMed1998

The Gcn4p activation domain interacts specifically in vitro with RNA polymerase II holoenzyme, TFIID, and the Adap-Gcn5p coactivator complex.

The Gcn4p activation domain contains seven clusters of hydrophobic residues that make additive contributions to transcriptional activation in vivo. We observed efficient binding of a glutathione S-transferase (GST)-Gcn4p fusion protein to components of three different coactivator complexes in Saccharomyces cerevisiae cell extracts, including subunits of transcription factor IID (TFIID) (yeast TAFII20 [yTAFII20], yTAFII60, and yTAFII90), the holoenzyme mediator (Srb2p, Srb4p, and Srb7p), and the Adap-Gcn5p complex (Ada2p and Ada3p). The binding to these coactivator subunits was completely dependent on the hydrophobic clusters in the Gcn4p activation domain. Alanine substitutions in single clusters led to moderate reductions in binding, double-cluster substitutions generally led to greater reductions in binding than the corresponding single-cluster mutations, and mutations in four or more clusters reduced binding to all of the coactivator proteins to background levels. The additive effects of these mutations on binding of coactivator proteins correlated with their cumulative effects on transcriptional activation by Gcn4p in vivo, particularly with Ada3p, suggesting that recruitment of these coactivator complexes to the promoter is a cardinal function of the Gcn4p activation domain. As judged by immunoprecipitation analysis, components of the mediator were not associated with constituents of TFIID and Adap-Gcn5p in the extracts, implying that GST-Gcn4p interacted with the mediator independently of these other coactivators. Unexpectedly, a proportion of Ada2p coimmunoprecipitated with yTAFII90, and the yTAFII20, -60, and -90 proteins were coimmunoprecipitated with Ada3p, revealing a stable interaction between components of TFIID and the Adap-Gcn5p complex. Because GST-Gcn4p did not bind specifically to highly purified TFIID, Gcn4p may interact with TFIID via the Adap-Gcn5p complex or some other adapter proteins. The ability of Gcn4p to interact with several distinct coactivator complexes that are physically and genetically linked to TATA box-binding protein can provide an explanation for the observation that yTAFII proteins are dispensable for activation by Gcn4p in vivo.

Animals↗

PubMed1998

Protective role of IgA1 glycans against IgA1 self-aggregation and adhesion to extracellular matrix proteins.

The aim of this study was to investigate the role of carbohydrate moieties attached to IgA1 hinge region in IgA1 self-aggregation and adhesion to extracellular matrix (ECM) proteins previously reported in IgA nephropathy. Serum IgA1 samples isolated from healthy individuals were digested with neuraminidase (NA), NA + beta-galactosidase, and NA + beta-galactosidase + alpha-N-acetylgalactosaminidase to remove the carbohydrates from the hinge region and were named asialo, agalacto, and naked IgA1, respectively. First, polyacrylamide gel electrophoresis was performed under the native condition, and consequently, a broad band indicating IgA1 self-aggregation was clearly observed in asialo, agalacto, and naked IgA1, but not in native IgA1. However, the broad band disappeared in sodium dodecyl sulfate-polyacrylamide gel electrophoresis under the nonreducing condition. Second, it was shown that IgA1 adhesion activities to type IV collagen, fibronectin, and laminin were significantly higher in asialo, agalacto, and naked IgA1 than in native IgA1, using enzyme-linked immunosorbent assay (asialo, agalacto, and naked versus native: P < 0.01). In addition, agalacto IgA1 had the highest affinity for all of the ECM proteins among the deglycosylated IgA1 (agalacto versus asialo and naked, P < 0.05). These results indicated that the removal of carbohydrates from the IgA1 molecule resulted in noncovalent self-aggregation and a significant increase in adhesion to the ECM proteins. It was therefore suggested that the IgA1 glycans played a protective role against aggregation and adhesion and that the underglycosylation of the IgA1 molecule found in IgA nephropathy could be involved in the nonimmunologic glomerular accumulation of IgA1.

Electrophoresis, Polyacrylamide Gel↗

PubMed1998

Analyses of IgA1 hinge glycopeptides in IgA nephropathy by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

This study was performed to analyze the structural variety of O-glycans on the IgA1 hinge in IgA nephropathy (IgAN). The IgA1 fragments containing the hinge glycopeptide (33-mer hinge peptide core (HP) + O-glycans) were separated from 13 IgAN patients, eight healthy control subjects, and 11 patients with other primary glomerulonephritides by pyridylethylation, trypsin treatment, and Jacalin affinity chromatography. Because of the use of Jacalin, only the Gal beta 1-3GalNAc residue containing IgA was analyzed. The molecular weights (MW) of the IgA1 fragments treated by the following sequential treatment by exoglycosidases were estimated using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry: (1) Sialidase treatment: the MW of the two observed peaks A and B were compatible with (A) HP + 4GalNAc + 4Gal and (B) HP + 5GalNAc + 4Gal. (2) Sialidase and galactosidase: the MW of the two identified peaks a and b were consistent with (a) HP + 4GalNAc and (b) HP + 5GalNAc. (3) Sialidase, galactosidase, and alpha-N-acetylgalactosaminidase. All subjects revealed one peak, indicating the 33-mer IgA1 hinge peptide core. The intensity rate of peak B/A was significantly decreased in the IgAN group (mean +/- SD, 1.01 +/- 0.08) compared with the negative control subjects (healthy group, 1.15 +/- 0.06, P = 0.0048; other glomerulonephritis group, 1.13 +/- 0.10, P = 0.0049; Scheffe's F test). These results suggested the presence of a defect in the Gal and/or GalNAc residues in the IgA1 hinge glycopeptides in IgAN.

Amino Acid Sequence↗

PubMed1998

The cDNA cloning and molecular characterization of a snake venom platelet glycoprotein Ib-binding protein, mamushigin, from Agkistrodon halys blomhoffii venom.

The entire cDNA sequences of a novel snake venom platelet glycoprotein (GP) Ib-binding protein (BP) composed of an alpha/beta heterodimeric structure, termed mamushigin, from Agkistrodon halys blomhoffii were determined, that include the leader peptides (21/23 amino acid residues) and mature subunits (136/123 amino acid residues). The mature subunits of mamushigin are 37.5% identical, and showed a high degree of similarity (37.7-67.5% identity) with the respective subunits of group VII C-type lectins (19). The sequences of the leader peptides of the mamusigin subunits showed the highest similarity (alpha-73.9/beta-82.6%) with those of factor IX/X-BP from Trimeresurus flavoviridis, and the cleavage site residue in both proteins was the same Ala(-1). The GPIb-binding specificity of mamushigin is strongly supported by several lines of evidence, but mamushigin can directly aggregate normal platelets, similar to alboaggregin-B (AL-B) (1). This differs from other GPIb-BP's. In mamushigin-treated platelets, serotonin was not released, and flow cytometric analysis using a monoclonal antibody PAC-1 totally excluded platelet GPIIb/IIIa activation. Mamushigin enhanced platelet aggregation at low-shear stress, and this effect totally disappeared in the presence of GPIb-receptor blockers specific for von Willebrand factor binding, but not by GPIIb/IIIa-receptor blockers. At high-shear stress, mamushigin blocked platelet aggregation in a dose-dependent manner, as seen with other GPIb-BP's. This paper, therefore, describes the cDNA cloning and molecular characterization of mamushigin which has a different effect on platelet aggregation under different shear stress.

Agkistrodon↗

PubMed1997

Direct bone formation on alumina bead composite.

We have developed a composite (designated ABC), consisting of alumina bead powder as an inorganic filler and bisphenol-alpha-glycidyl methacrylate (Bis-GMA)-based resin as an organic matrix, which allows direct bone formation on its surface in vivo. Alumina bead powder was manufactured by fusing crushed alpha-alumina powder and quenching it. The beads took spherical form 3 microns in average size. According to powder X-ray diffraction and Fourier transform infrared spectroscopy, the alumina bead powder was composed of amorphous and delta-crystal phases of alumina in its main crystal structure. Fused-quenched silica glass-filled composite (SGC) was used as a control. The proportion of filler added to the composites was 70% w/w. Mechanical testing of the ABC indicated that it would be strong enough for use under weight-bearing conditions. No apatite formation was detected on the surfaces of either composite after soaking in simulated body fluid for 28 days in vitro. Histological examination of rat tibiae for up to 8 weeks revealed that ABC bonded to bone directly via a layer of calcium, phosphorus, and alumina with no interposed soft-tissue layer. Moreover, the amount of bone directly apposed to the ABC surface increased with time, whereas with SGC there was poor direct bone formation even at 8 weeks. The precise mechanism of direct bone formation on ABC is as yet unknown but it is possible that changes in the crystallinity of alumina, which is known to be highly biocompatible, contribute to its excellent osteoconductivity in vivo. Although bioactive materials such as Bioglass or apatite and wollastonite-containing glass-ceramic have previously been reported to form bone-like apatite on their surfaces under acellular conditions via simple chemical reactions, ABC does not have such characteristics, and presenting favorable conditions for osteoconduction and tissue calcification may lead to direct bone formation on its surface in vivo.

Aluminum Oxide↗

PubMed1997

Bioactive bone cement: comparison of AW-GC filler with hydroxyapatite and beta-TCP fillers on mechanical and biological properties.

Three types of bioactive bone cement (designated AWC, HAC, and TCPC), each consisting of bisphenol-alpha-glycidyl methacrylate (Bis-GMA)-based resin and a bioactive filler of apatite and wollastonite containing glass-ceramic (AW-GC), sintered hydroxyapatite (HA), or beta-tricalcium phosphate (beta-TCP) powder were made in order to evaluate the influence of the bioactive filler on the mechanical and biological properties of bone cement. The proportion of filler added to the cements was 70% w/w. The compressive, bending, and tensile strengths and the fracture toughness of AWC were higher than HAC and TCPC under wet conditions. The cements were evaluated in vivo by packing them into the intramedullary canals of rat tibiae. An affinity index that equalled the length of bone in direct apposition to the cement was calculated for each cement and expressed as a percentage of the total length of the cement surface. Histological examination of rat tibiae up to 8 weeks after implantation revealed that AWC had higher bioactivity than HAC and TCPC. New bone had formed along the AWC surface within 2 weeks, and at 4 weeks newly formed bone surrounded the cement surface almost completely. In HAC- and TCPC-implanted tibiae, immature bone had formed directly toward but not along the cement surface at 2 weeks. Observation of cement-bone interfaces showed that AWC had bonded to the bone via a so-called "Ca-P-rich layer"; the cement-bone interface remained stable, and the width of the CA-P-rich layer became thicker with time. On the other hand, in HAC- and TCPC-implanted tibiae, the cement surface fillers were surrounded by new bone and were absorbed gradually to become bone matrix. The cement-bone interfaces went inside the cement with time. Our results indicate that stronger interstitial bonding between the inorganic filler and the organic matrix resin in AWC lead to higher mechanical properties; results also indicate that the more stable cement-bone interface and higher bioactivity of AWC are due to early and uniform apatite formation on the cement surface.

Animals↗

PubMed1997

The osteoclast-associated protease cathepsin K is expressed in human breast carcinoma.

Human cathepsin K is a novel cysteine protease previously reported to be restricted in its expression to osteoclasts. Immunolocalization of cathepsin K in breast tumor bone metastases revealed that the invading breast cancer cells expressed this protease, albeit at a lower intensity than in osteoclasts. In situ hybridization and immunolocalization studies were subsequently conducted to demonstrate cathepsin K mRNA and protein expression in samples of primary breast carcinoma. Expression of cathepsin K mRNA was confirmed by reverse transcription PCR and Southern analysis in a number of human breast cancer cell lines and in primary human breast tumors and their metastases. As this protease is known to degrade extracellular matrix, including bone matrix proteins, it is possible that cathepsin K may contribute to the invasive potential of breast cancer cells, including those that metastasize to bone. Thus, cathepsin K may be a potential target leading to the design of novel drugs for cancer therapy.

Blotting, Southern↗

PubMed1997

Cathepsin K antisense oligodeoxynucleotide inhibits osteoclastic bone resorption.

Cathepsin K is a recently identified cysteine protease which is abundantly and selectively expressed in osteoclasts. To evaluate the contribution of cathepsin K to bone resorption processes, we investigated the effect of cathepsin K antisense phosphothiorate oligodeoxynucleotide (S-ODN) on the bone-resorbing activity of osteoclasts. Rabbit osteoclasts were cultured on dentine slices for 24 h in the presence or absence of antisense S-ODN in a medium containing 100 nM TfxTM-50, polycationic liposome, as a carrier of the S-ODN. Uptake of the S-ODN by osteoclasts was confirmed microscopically using fluorescein-labeled S-ODN. The treatment with antisense significantly decreased the amount of cathepsin K protein in osteoclasts. The antisense inhibited the osteoclastic pit formation in a concentration-dependent fashion. At 10 microM the antisense reduced the total pit number and area and average pit depth by 46, 52, and 30%, respectively. The sense and mismatch S-ODNs, which were used as negative controls, had no effect on either the cathepsin K protein level or the pit formation. A nonspecific cysteine protease inhibitor, E-64, also reduced pit formation in a concentration-dependent manner with maximum reductions at 1 microM of 46, 48, and 35% in the above pit parameters. The inhibitory effect of the antisense almost equal to that of E-64 demonstrates that cathepsin K is a cysteine protease playing a crucial role in osteoclastic bone resorption.

Animals↗

PubMed1997

Drosophila TAF(II)230 and the transcriptional activator VP16 bind competitively to the TATA box-binding domain of the TATA box-binding protein.

The transcription initiation factor TFIID, consisting of the TATA box-binding protein (TBP) and many TBP-associated factors (TAFs), plays a central role in both basal and activated transcription. An intriguing finding is that the 80-residue N-terminal region of Drosophila TAF(II)230 [dTAF(II)230-(2-81)] can bind directly to TBP and inhibit its function. Here, studies with mutated forms of TBP demonstrate that dTAF(II)230-(2-81) binds to the concave surface of TBP, which is important for TATA box binding. Previously, it was reported that a point mutation (L114K) on this concave surface destroys the ability of TBP to bind VP16 and to mediate VP16-dependent activation in vitro, but has no effect on basal transcription. Importantly, the same TBP mutation eliminates TBP binding to dTAF(II)230-(2-81). Consistent with these effects of the L114K mutation, dTAF(II)230-(2-81) and the VP16 activation domain compete for binding to wild-type TBP. These results indicate that transcriptional regulation may involve, in part, competitive interactions between transcriptional activators and TAFs on the TBP surface.

Amino Acid Sequence↗

PubMed1997

Behavior of fetal rat chondrocytes cultured on a bioactive glass-ceramic.

We examined the behavior of fetal rat chondrocytes cultured on a bioactive glass-ceramic containing apatite and wollastonite (A.W.G.C.). Biomaterial surface topography and profiles were evaluated by bidimensional profilometry and revealed a rough surface for the glass-ceramic compared to the plastic coverslips used as controls. Chondrocyte attachment was evaluated by measuring the number of attached cells after one day of culture and by morphological observations. Chondrocytes attached in great numbers to the material surface by means of focal contacts containing vinculin and beta1-integrin. Fluorescent labeling of actin and vimentin revealed a poor spreading of chondrocytes on the bioactive glass-ceramic compared to the plastic coverslips, where the cells appeared to adhere intimately to the surface and exhibited polygonal arrays of stress fibers. During the following days of culture, chondrocytes proliferated, colonized the surface of the material, and, finally, on day 10, formed nodular structures composed of round cells separated by a dense extracellular matrix. Furthermore, these clusters of round cells were positive for type II collagen and chondroitin sulfate, both hard markers of the chondrocyte phenotype. In addition, protein synthesis, alkaline phosphatase activity, and proteoglycan production were found to increase gradually during the culture period with a pattern similar to that observed on control cultures. These results demonstrate that the bioactive glass-ceramic tested in this study appears to be a suitable substrate for in vitro chondrocyte attachment, differentiation, and matrix production.

Actins↗

PubMed1997

Mechanical and biological properties of bioactive bone cement containing silica glass powder.

Silica glass powder (SG-P) made by a fusing-quenching method was added as a second filler to a bioactive bone cement consisting of MgO-CaO-SiO2-P2O5-CaF2 apatite and wollastonite containing glass-ceramic powder (AW-P) and bisphenol-a-glycidyl methacrylate (Bis-GMA)-based resin, to achieve a higher mechanical strength and better handling properties in use. Five types of cement were used, containing different weight ratios of AW-P/SG-P (Group 1 = 100/0; Group 2 = 75/25; Group 3 = 50/50; Group 4 = 25/75; and Group 5 = 0/100) as filler, to evaluate the effect of SG-P content on the biological, mechanical, and handling properties. The total proportion of filler added to the cements was 85% w/w. The compressive, bending, and tensile strengths and fracture toughness of the cements increased with SG-P content. The viscosity of cements also increased with SG-P content, and every cement could be handled manually. The cements were evaluated in vivo by packing the intramedullary canals of rat tibiae. An affinity index was calculated for each cement; this was the length of bone directly apposed to cement expressed as a percentage of the total length of the cement surface. Histological examination of implanted tibiae for up to 26 weeks showed that the affinity indices decreased with SG-P content and that those of all the cement groups increased with time. At 26 weeks, Groups 1 and 2 had almost identical affnity indices (79% and 75%; no significant difference) but those of the other groups remained at <50%. Group 2 had better mechanical and handling properties than Group 1, and an SG-P content in the filler of no more than 25% w/w did not interfere strongly with the bioactivity of the cement.

Animals↗