Heme peroxidases are responsible for the dehydrogenation and oxidation metabolism of harmaline into harmine / 中国天然药物

Harmaline and harmine are β-carboline alkaloids with effective pharmacological effects. Harmaline can be transformed into harmine after oral administration. However, enzymes involved in the metabolic pathway remain unclear. In this study, harmaline was incubated with rat liver microsomes (RLM), rat brain microsomes (RBM), blood, plasma, broken blood cells, and heme peroxidases including horseradish peroxidase (HRP), lactoperoxidase (LPO), and myeloperoxidase (MPO). The production of harmine was determined by a validated UPLC-ESI-MS/MS method. Results showed that heme peroxidases catalyzed the oxidative dehydrogenation of harmaline. All the reactions were in accordance with the Hill equation. The reaction was inhibited by ascorbic acid and excess H2O2. The transformation of harmaline to harmine was confirmed after incubation with blood, plasma, and broken blood cells, rather than RLM and RBM. Harmaline was incubated with blood, plasma, and broken cells liquid for 3 h, and the formation of harmine became stable. Results indicated an integrated metabolic pathway of harmaline, which will lay foundation for the oxidation reaction of dihydro-β-carboline. Moreover, the metabolic stability of harmaline in blood should not be ignored when the pharmacokinetics study of harmaline is carried out.

Effect of investment composition ratio for pure titanium crown and bridge on some mechanical properties of mould / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To determine the optimal composition of a self-developing investment material by measuring physical and mechanical properties of mould.</p><p><b>METHODS</b>L(9) (3(4)) orthogonal design was adopted. One hundred and fifty specimens with the size of 80 mm × 20 mm × 20 mm were prepared to measure the atmospheric temperature bending strength, high temperature bending strength and residual bending strength. Nine specimens with the size of 5 mm diameter 25 mm heigh were prepared to survey the thermal expansion curve from ambient temperature to 1150°C.</p><p><b>RESULTS</b>Strengths were greatly affected by fine powder proportion in refractory and water/powder ratio. When the content of fine powder was 35% and water/powder ratio was 1:7.5, adequate atmospheric temperature strength and high temperature strength could be achieved. Moreover, the residual strength was moderate. The thermal extension curves of specimens in experiment group were almost similar. And the average linear expansion coefficient was (4 ∼ 5) × 10(-6)/°C.</p><p><b>CONCLUSIONS</b>The three kinds of bending strength of self-developing investment material are compared with commercialized investment material for titanium casting when water/powder ratio and the content of fine powder are carefully controlled.</p>

Effect of investment for titanium crown and bridge on reactive layer of castings / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the effect of self-developing investment (FUS-invest) on the reactive layer of titanium castings.</p><p><b>METHODS</b>Three 10 mm x 10 mm x 1 mm pure titanium castings were founded using FUS-invest. Metallographical structure of reactive layer was observed. X-ray diffraction (XRD) and scanning electron microscope with energy-dispersive spectrum (EDS) were used to analyze the status of composition of the casting surface. Micro-Vickers hardness was measured.</p><p><b>RESULTS</b>The metallograph indicated that the reactive layer was composed of coarse flake-shaped alpha phase of grains. The value of micro-Vickers hardness with the range 243 to 314 MPa had not significantly difference under the depth of 105 microm beneath the surface. The XRD pattern clearly showed the peaks of ZrO2, SiO2, Mg2TiO4 and TiO2. EDS analysis demonstrated that the main elements were Al, Si, Zr and Cl.</p><p><b>CONCLUSION</b>FUS-invest is suited for pure titanium casting because of the thin reactive layer and less change to metallographical structure.</p>

Effects of the improved FUS-invest investment for zirconium-oxide titanium crown and bridge on the reaction layer / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the effects of the improved FUS-invest investment for zirconium-oxide titanium crown and bridge on the reaction layer.</p><p><b>METHODS</b>10 mm x 10 mm x 1 mm titanium castings were invested. Spectrum analysis was done to its reaction layer, the metallographic examination was observed and Vickers hardness was measured.</p><p><b>RESULTS</b>The reaction layer was not obvious by the metallographic examination. The layer with plenty of Si was hardly detectable. The needle crystal layer diffused distribution on the surface of the titanium matrix. The depth was about 55 microm. Spectrum analysis showed that the contents of Si and Zr decreased as the depth increased. The microhardness, which obviously decreased from the surface to the matrix, tended to be equal with the hardness of the matrix after the depth reached 75 microm from the surface.</p><p><b>CONCLUSION</b>The thickness of the reaction layer of the improved FUS-invest investment for zirconium-oxide titanium crown and bridge was decreased to 55 microm from 85 microm, which was the thickness before improvement.</p>