Changes in the number and proportion of osteopontin mRNA (Opn) expressing osteocytes and osteoclasts caused by the mechanical stress applied during experimental tooth movement were examined in the present study. Opn expression was detected in the osteocytes on the pressure side at the early stage, and gradually spread to those on the tension side and also to the osteoblasts and bone-lining cells in the alveolar bone. Only 3.3% of the osteocytes located on the pressure side expressed Opn in the interradicular septum of control rats; in contrast, the value was increased to 87.5% at 48 h after the initiation of tooth movement. These results indicate that these cells responded to mechanical stress loaded on the bone with expression of the osteopontin gene.

A hydrothermal method for preparing thin films of crystalline PZT was developed by controlling the rates of nucleation and crystal growth. This method consisted of two steps of hydrothermal reaction. The first step (nucleation process) was that in which the TiO2 substrate reacted with the mixed solution of Pb and Zr to form PZT and/or PZ nuclei on the surface. Subsequently, the crystal growth of PZT was promoted as the next hydrothermal step (crystal growth process) by the reaction of the mixed solution of Pb, Zr and Ti. From the experimental results of PZT powder preparation, the conditions of the nucleation and crystal growth process were determined as at 150°C for 24 h and at 120°C for 48 h, respectively. It was verified that the thin films consisted of PZT polycrystals and showed ferroelectric properties.

BACKGROUND Osteoclastic bone resorption is an important step in bone invasion in several malignancies. Although interleukin (IL)‐6 accelerates osteoclastic bone resorption, it remains unclear whether IL‐6 may be involved in bone invasion of oral cancer. METHODS The pit formation assay with calf femur‐derived bone slices was performed to examine the bone‐resorbing activity of osteoclasts and cancer cells. The chemotaxis activity of the culture media was analyzed by the use of Boyden chamber technique. Nude mice, which were inoculated with IL‐6–producing oral cancer cells into masseter, were treated with anti–IL‐6 neutralizing antibody, and mandibular‐bone invasion of the cells was assessed. RESULTS BHY, a bone‐invasive oral cancer cell line, but not HNT, a noninvasive cell line, produced large amounts of IL‐6. In a pit formation assay, addition of conditioned medium (CM) derived from BHY but not HNT increased osteoclastic bone resorption, and the effects were inhibited by anti–IL‐6 antibody. BHY‐secreted IL‐6 showed significant chemotaxis activity for osteoclasts. Of note, CM from the cocultivation of osteoclasts and BHY markedly enhanced the cancer cell migration, and the chemotaxis activity was significantly reduced when anti–IL‐6 antibody was added into the coculture and then CM were collected, but not when the antibody was added into the CM after they were collected. Furthermore, treatment with anti–IL‐6 antibody almost completely inhibited mandibular bone invasion of BHY in nude mice. CONCLUSIONS These results strongly suggest that IL‐6 secreted by oral cancer cells plays a significant role in bone invasion. Cancer 2000;89:1966–75. © 2000 American Cancer Society.

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We demonstrate room temperature pulsed operation of nitride based multi-quantum-well (MQW) laser diodes with cleaved mirror facets grown on a conventional C-face sapphire substrate. Cleavage was performed along the <11*BAR*2*BAR*0> direction of the sapphire substrate, and the resultant facet was analyzed using an atomic force microscope (AFM) and theoretical calculation. A single peak emisson, at a wavelength of 417.5 nm, with a full width at half-maximum of 0.15 nm, was obtained. The threshold current density of the laser was 50 kA/cm2 and a voltage for the threshold current was 20 V.

The conduction-band discontinuity ΔEc and interface charge density σ have been studied for GaAs/In0.5(Ga1−xAlx)0.5P heterojunctions, prepared by metalorganic chemical vapor deposition. The dependences of ΔEc and σ on Al composition x were investigated for x from 0 to 1. The In0.5Al0.5P/ In0.5Ga0.5P heterojunction was also examined. The results suggest that the valence-band discontinuity ΔEv for GaAs/In0.5(Ga1−xAlx)0.5P is a linear function of x and is larger than ΔEc, being in reasonable agreement with results on the InAlP/InGaP heterojunction. The σ values for GaAs/InGaAlP were found to be one order of magnitude larger than those for GaAs/AlGaAs and InAlP/InGaP heterojunctions.

Lead zirconate titanate solid-solution (PZT) films with various thicknesses were synthesized on titanium substrates by repeated hydrothermal treatments. Young's modulus and the density of the PZT film were measured by the vibrating-reed technique and Archimedes' method, respectively, and they were lower than those of PZT ceramic. We fabricated bimorph-type bending actuators using those films and analyzed the displacement induced by the electric field. It was found that the piezoelectric constant and electromechanical coupling factor of the PZT film were comparable to those of the ceramic, and also that the displacement was caused by the piezoelectric effect. The actuators were bent by applied voltage without poling, because the polar axes in the as-deposited film were aligned in the direction from the film surface to the substrate.

Metalorganic chemical vapor deposition (MOCVD) growth of AlN, GaN and AlGaN on sapphire substrates was investigated, with the aim of realizing high-quality heterostructures with atomically smooth interfaces. AlN with surfaces constructed of single-atomic-layer steps was grown by the two-step growth technique, in which the thin first layer was grown at a low temperature (1250° C) and then the second layer was grown at a high temperature (1350° C). GaN with surfaces consisting of simple atomic-layer steps were successively grown on the AlN layer by optimizing the growth conditions. Marked degradation of surface flatness was not observed for Al0.2Ga0.8N grown on GaN.