Osteoclast differentiation at growth plate cartilage-trabecular bone junction in newborn rat femur

Using 3-day-old newborn rats, we examined the differentiation processes of osteoclasts associated with the destruction of the femoral growth plate cartilage and primary trabecular bone. In the growth plate cartilage, thin mineralized areas were detected solely in the longitudinal septal cartilage matrix in the hypertrophic zone, but the transverse septal cartilage matrix between adjacent chondrocytic lacunae within a row of chondrocytes remained unmineralized. The longitudinal septal cartilage between adjacent rows of chondrocytes appeared to persist, forming the walls of opened lacunar canals. Consistent with the removal of the transverse septal cartilage matrix, the longitudinal canals of opened chondrocytic lacunae were deeply invaded by capillary vessels, mononuclear cells and multinucleated pre-osteoclasts lacking a ruffled border. CD34-positive endothelial cells of capillary vessels deeply penetrated into the transverse septal cartilage matrix facing the medullary cavity and the opened chondrocytic lacunae. ED1-positive monocytes/macrophages were distributed at the chondro-osseous junction, but they were distant from the erosive front of the transverse septa. Tartrate-resistant acid phosphatase-positive multinucleated pre-osteoclasts lacking a ruffled border and differentiated osteoclasts with a ruffled border were localized mainly at two locations: the chondro-osseous junction and the growth front of primary bone trabeculae. Osteoclasts were located on the type-I collagen-positive bone trabeculae close to the growth plate, but they appeared to be distant from the type-II collagen-positive cartilage matrix. Even within opened chondrocytic lacunae, when osteoclasts were distant from the cartilage and bone matrix, they lacked polarized cytoplasmic organization and a ruffled border. The osteoclasts located in the remaining septal cartilage also exhibited neither a ruffled border nor a clear zone. Osteoclasts with a prominent ruffled border and clear zone were located in bone matrix covering the remaining septal cartilage. These results suggest that osteoclasts require hydroxyapatite crystals and bone matrix constituents for ruffled border formation and are not involved in resorption of the unmineralized transverse and mineralized longitudinal septal cartilage without covering bone matrix at the chondro-osseous junction.     

Porcine enamel matrix derivative enhances the formation of reparative dentine and dentine bridges during wound healing of amputated rat molars

We examined the biological effects of porcine enamel matrix derivative (EMD; Emdogain) on the formation of reparative dentine and dentine bridges in rat molars after pulp amputation. The pulp chambers of upper molars of Wistar rats were perforated and the amputated pulp surfaces were directly capped with either EMD or its carrier propylene glycol alginate (PGA) as control. The cavities were then restored with glass-ionomer cement. On post-amputation days 4-30, the dissected maxillae were examined by light and electron microscopy. In PGA-capped pulp, reparative dentine had been formed over the dentine walls under the prepared cavity on day 7 post-amputation and its thickness extended until day 30. On day 30, as well as reparative dentine formation, diffuse calcification had occurred beneath the amputated wound surfaces. Dentine bridge formation under the amputated coronal pulp surface was observed in 18.2% of amputated pulp on day 30. In EMD-capped pulp, reparative dentine had already been formed by odontoblast-like cells over the dentine walls, already on day 4 post-amputation, and its thickness extended until day 30. The Ca and P weight % and Ca/P ratio of reparative dentine matrix were similar to those of pre-existing dentine matrix, and these values were not different between PGA and EMD-capped pulp. Dentine bridge formation was observed in 27.3% of EMD-capped pulp on day 30. Our results suggest that EMD enhances the formation of both reparative dentine and dentine bridges during wound healing of amputated rat molar pulp.     

An analytical study of the effect of a support geometry on frequency shift and support loss of piezoelectric ring-shaped resonators for healthcare and environmental applications

Ring-shaped resonators with one support have been designed in this work. The ring-shaped resonator reacts with a mass perturbation to provide eigenstate or frequency shifts which could transfer to electrical signals by piezoelectric effect. The aforementioned ring-shaped resonator is mainly comprised with a multilayer of Pt/Ti/PZT/Pt/Ti/SiO₂ deposited on the silicon-on-insulator wafer and expected to be a contour mode. In order to estimate the sensitivity of the ring-shaped resonator against the mass perturbation, the theoretical analysis was conducted by ANSYS from two aspects including: (a) the effect of support geometry on frequency shift and support loss (from view point of vibration mode shape); and (b) the mass application methodology. It is found that low-amplitude vibration area is smaller at narrow support, and frequency shift of trapezoid support is higher than that of rectangle support.     

Oxygen release behaviour of Ce(1−x)ZrxO2 powders and appearance of Ce(8−4y)Zr4yO(14−δ) solid solution in the ZrO2–CeO2–CeO1.5 system

To clarify the existence of metastable phases in the ZrO₂–CeO₂–CeO_1.5 system, evolved-oxygen gas analyses, (EGA), by heating a single phase of t′ and t″ (Ce_(1−x)Zr_xO₂) with various compositions, x, in a reducing gas and successive oxidation were carried out repeatedly. The oxygen release behaviour of the t′ and t″ phases was very complicated. The single κ phases, (Ce_(1−x)Zr_xO₂) with the composition, x=0.5 and 0.6, which were obtained by oxidizing the resulting pyrochlore as a precursor in O₂ gas at 873 K, exhibited a sharp oxygen release at the lowest temperature; the composition range of κ phase may be x=0.450.65. A new tetragonal phase t*, (Ce_(1−x)Zr_xO₂), which was attained by cyclic redox process together with annealing in O₂ gas at 1323 or 1423 K, exhibited a sharp oxygen release at the highest temperature; the composition range of t* phase may be as wide as x=0.200.65. A metastable solid solution expressed by a chemical formula of Ce_(8−4y)Zr_4yO_(14−δ) (y=01) possessing a CaF₂-related structure appeared on deoxidation of the t* phase. A ternary phase diagram containing the t* and Ce_(8−4y)Zr_4yO_(14−δ) solid solution was proposed.     

Decomposition and regeneration of methane in the absence and the presence of a hydrogen-absorbing alloy CaNi5

Suitable catalysts for the decomposition of methane into carbon and hydrogen and for the regeneration of methane by hydrogenation of the carbon have been looked for in a series of transition metals and precious metals supported on various carriers. The most active catalyst for both reactions was Ni/SiO₂. The carbon formed on this catalyst was thermodynamically less stable than graphite. The different rate equations for the decomposition of methane obtained for the fresh and carbon deposited Ni/SiO₂ suggest that the rate-determining steps are different for the two catalysts. The highest number of carbon atoms deposited per one Ni atom was 31 at 773 K. However, the number of methane molecules recovered easily at 773 K was limited to 1.5 per Ni atom.

A physical mixture of Ni/SiO₂ and CaNi₅, a hydrogen-absorbing alloy, enhanced the decomposition rate of methane, enabling the complete conversion of methane at 773 K beyond the thermodynamic limitation. The presence of CaNi₅ at 273 K separated from the catalyst in a reaction system further enhanced the decomposition of methane due to an increased hydrogen-absorbing capacity of the CaNi₅ at low temperatures. The carbon deposited on Ni/SiO₂ in this case was reactive to be hydrogenated back to methane at 773 K, giving an average 7.5 CH₄ molecules per one Ni atom.     

Biomechanical Evaluation of Ti-Nb-Sn Alloy Implants with a Low Young’s Modulus

Dental implants are widely used and are a predictable treatment in various edentulous cases. Occlusal overload may be causally related to implant bone loss and a loss of integration. Stress concentrations may be diminished using a mechanobiologically integrated implant with bone tissue. The purpose of this study was to investigate the biomechanical behavior, biocompatibility and bioactivity of a Ti-Nb-Sn alloy as a dental implant material. It was compared with cpTi. Cell proliferation and alkaline phosphatase (ALP) activity were quantified. To assess the degree of osseointegration, a push-in test was carried out. Cell proliferation and ALP activity in the cells grown on prepared surfaces were similar for the Ti-Nb-Sn alloy and for cpTi in all the experiments. A comparison between the Ti-Nb-Sn alloy implant and the cpTi implant revealed that no significant difference was apparent for the push-in test values. These results suggest that implants fabricated using Ti-Nb-Sn have a similar biological potential as cpTi and are capable of excellent osseointegration.     

Molybdenum‐Catalyzed Stereospecific Deoxygenation of Epoxides to Alkenes

Mild and simple catalytic systems consisting of molybdenum(VI) dichloride dioxide [MoO₂Cl₂] as a catalyst and a phosphine as reductant have been developed for the stereospecific deoxygenation of epoxides to alkenes. The reactions using 1,2‐bis(diphenylphosphino)ethane (dppe) and triphenylphosphine (PPh₃) proceed with retention and inversion of stereochemistry, respectively. The mild reaction tolerates the presence of various functional groups and affords stereodefined substituted olefins in good yields.

     

为进行能源管理并强化车体结构所采用的结构胶黏剂

结构胶黏剂是汽车制造过程中一种日趋重要的金属连接方式。介绍了汉高公司开发的一种汽车用结构胶黏剂的性能特点及应用工艺要求。通过实验证明结构胶黏剂对于提高车体结构性能、减轻车体质量、简化生产过程和优化生产成本来说,是一种十分有用的材料。     

Syntheses of alpha-arbutin-alpha-glycosides and their inhibitory effects on human tyrosinase

Alpha-arbutin is a tyrosinase inhibitor. We synthesized alpha-arbutin-alpha-glycosides by the transglycosylation reaction of cyclomaltodextrin glucanotransferase from Bacillus macerans using alpha-arbutin and starch as acceptor and donor molecules, respectively. We isolated and characterized two major products from the reaction mixture. The structural analyses using 13C- and 1H-NMR spectroscopy proved that they were 4-hydroxyphenyl alpha-maltoside (alpha-Ab-alpha-G1) and 4-hydroxyphenyl alpha-maltotrioside (alpha-Ab-alpha-G2). Both alpha-Ab-alpha-G1 and alpha-Ab-alpha-G2 exhibited competitive-type inhibition on human tyrosinase as alpha-arbutin does. Their K(i) values were calculated to be 0.6 mM and 2.8 mM, respectively, which is slightly and significantly higher than that of alpha-arbutin (0.2 mM).