To elucidate the biochemical mechanism of osteogenesis, the effect of matrix geometry upon the osteogenesis induced by bone morphogenetic protein (BMP) was studied. A series of five porous hydroxyapatites with different pore sizes, 106-212, 212-300, 300-400, 400-500, and 500-600 microns, was prepared. A block (approximately 5 x 5 x 1 mm, 40.0 mg) of each hydroxyapatite ceramics was combined with 4 micrograms of recombinant human BMP-2 and implanted subcutaneously into the back skin of rat. Osteoinductive ability of each implant was estimated by quantifying osteocalcin content and alkaline phosphatase activity in the implant up to 4 wk after implantation. In the ceramics of 106-212 microns, the highest alkaline phosphatase activity was found 2 wk after implantation, and the highest osteocalcin content 4 wk after implantation, consistent with the results observed with particulate porous hydroxyapatite [Kuboki, Y. et al. (1995) Connect. Tissue Res. 32: 219-226]. Comparison of the alkaline phosphatase activities at 2 wk and the osteocalcin contents at 4 wk after implantation revealed that the highest amount of bone was produced in the ceramics implants with pore size of 300-400 microns. In the ceramics with smaller or larger pore sizes, the amount of bone formation decreased as the pore size deviated from 300-400 microns. The results indicated that the optimal pore size for attachment, differentiation and growth of osteoblasts and vascularization is approximately 300-400 microns. This study using chemically identical but geometrically different cell substrata is the first demonstration that a matrix with a certain geometrical size is most favorable for cell differentiation.

Telomerase activation is thought to be a critical step in cellular immortalization and carcinogenesis. The human telomerase catalytic subunit (hTERT) is a rate limiting determinant of the enzymatic activity of human telomerase. In the previous study, we identified the proximal 181 bp core promoter responsible for transcriptional activity of the hTERT gene. To identify the regulatory factors of transcription, transient expression assays were performed using hTERT promoter reporter plasmids. Serial deletion assays of the core promoter revealed that the 5'-region containing the E-box, which binds Myc/Max, as well as the 3'-region containing the GC-box, which binds Sp1, are essential for transactivation. The mutations introduced in the E-box or GC-box significantly decreased transcriptional activity of the promoter. Overexpression of Myc/Max or Sp1 led to significant activation of transcription in a cell type-specific manner, while Mad/Max introduction repressed it. However, the effects of Myc/Max on transactivation were marginal when Sp1 sites were mutated. Western blot analysis using various cell lines revealed a positive correlation between c-Myc and Sp1 expression and transcriptional activity of hTERT. Using fibroblast lineages in different stages of transformation, we found that c-Myc and Sp1 were induced to a dramatic extent when cells overcame replicative senescence and obtained immortal characteristics, in association with telomerase activation. These findings suggest that c-Myc and Sp1 cooperatively function as the major determinants of hTERT expression, and that the switching functions of Myc/Max and Mad/Max might also play roles in telomerase regulation.

The synthesis and processing of nanoparticles consisting of metallic nanocrystal cores and organic monolayer shells promise interesting technological applications. Here, we report the synthesis of gold nanoparticles modified with ionic liquids based on the imidazolium cation. Aggregation-induced color changes of the gold nanoparticles in an aqueous solution were used as an optical sensor for anions via anion exchange of ionic liquid moiety. We also demonstrated the phase transfer of the gold nanoparticles from aqueous media to ionic liquid.

Background:The expression of Ltype amino-acid transporter 1 (LAT1) is tumour-specific and has been shown to have essential roles in cell growth and survival. However, little is known regarding the clinical significance of LAT1 expression in pancreatic cancer. This study was conducted to determine the prognostic significance of LAT1 expression.Methods:A total of 97 consecutive patients with surgically resected pathological stage I–IV pancreatic ductal adenocarcinoma were retrospectively reviewed. Tumour sections were stained by immunohistochemistry for LAT1, CD98, Ki-67 and vascular endothelial growth factor (VEGF), and microvessel density was determined by CD34 and p53.Results:L-type amino-acid transporter 1 and CD98 were highly expressed in 52.6% (51/97) and 56.7% (55/97) of cases, respectively (P=0.568). The expression of LAT1 within pancreatic cancer cells was significantly associated with disease stage, tumour size, Ki-67, VEGF, CD34, p53 and CD98. Ltype amino-acid transporter 1 expression was confirmed to be a significant prognostic factor for predicting poor outcome by multivariate analysis.Conclusion:Ltype amino-acid transporter 1 expression is a promising pathological marker for the prediction of outcome in patients with pancreatic cancer.

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