The authors previously developed a sapphire nitridation method using carbon-saturated N2–CO gas mixture to form a high-quality AlN film for III-nitride-based optoelectronic devices. In this study, the nitridation behavior of (0001) (c) plane and (112¯0) (a) plane sapphire was studied to elucidate and optimize the process at temperatures of 1823 and 1873 K. The AlN film thickness, surface morphology, crystal quality, and interfacial phenomena were investigated as functions of nitridation time and temperature. Fundamentally, the AlN film grows as a result of the diffusion process that occurs in the AlN film. The voids found at the AlN/sapphire interface indicate that the Al2O3 dissociates into Al3+ and O2− ions, and that the ions diffuse in the AlN film. However, the growth rate of AlN film does not obey the simple diffusion model. The AlN film thickness has a maximum and decreases slightly with time, which indicates that the thermal decomposition of AlN film must be considered when comprehensively describing the nitridation process.

No abstract

Prostaglandin E2 (PGE2) is generally accepted to be an immunosuppressant produced by cancer cells and their surrounding macrophages. Although several investigators have reported detecting high concentrations of PGE2 in the portal veins of patients with colorectal cancer, the relationship between these high concentrations of PGE2 in the portal vein and liver-associated immunity remains unclear. In this study, we attempted to determine if the portal administration of PGE2 suppresses the immune function of the liver in a rat model. Donryu rats were administered PGE2 via the portal vein for 7 days, following which the cytotoxic activity of hepatic sinusoidal lymphocytes (HSL) against natural killer (NK)-sensitive YAC-1 and rat syngeneic AH60C tumor cells was assessed. Purified HSL are spontaneously cytolytic; however, the continuous administration of PGE2 dramatically suppressed the cytotoxic activity of HSLs in a dose-dependent fashion. Flow cytometric analysis showed that the large granular lymphocyte (LGL) fraction, hepatic natural killer (pit) cells, and CD4-8+ killer/suppressor T cells were mainly reduced in number in the HSLs following PGE2 infusion. In this rat AH60C metastasis model, the continuous administration of PGE2 increased the number and size of metastatic tumor nodules in the liver, suggesting that high concentrations of PGE2 in the portal vein suppress liver-associated immunity and promote the formation of hepatic metastasis.

No abstract

Serine acetyltransferase (SATase, EC2.3.1.30), an enzymewhich catalyzes the biosynthesis of Oacetyl-L-serine (OAS) from L-serine and acetyl-CoA, has been purified about 33,000-fold with a yield of ll % from leaf extracts of AIlium tuberosum with a procedure involving heat treatment, ammonium sulfate fractionation, DEAE-Toyopearl chromatography, Ultrogel AcA34 gel filtration, and BlueToyopearl affinity chromatography, followed by a second filtration through Ultrogel AcA34. The isolated enzyme was apparently homogeneous as shown by PAGE with a specific activity of 231 units/mg protein. Besides this SATase activity the enzyme also had a significant level of cysteine synthase (CSase, EC 4.2.99.8) activity with a specific activity of 39.2 units/mg protein. The molecular weight of the enzyme was 650,000 by gel filtration. Subunit analysis by SDS-PAGEyielded two kinds of protein bands with a large subunit molecular weight of 35,000 and a small subunit molecular weight of 31,000. The results of Western blotting analysis using anti-rape CSase IgG suggested that the large subunk could be the CSase subunit.