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The effect of compounding procedure on morphology and crystallization behavior of isotactic polypropylene/high-density polyethylene/carbon black (iPP/HDPE/CB) composite was investigated. iPP/HDPE/CB composites were prepared by four compounding procedures (A: iPP + HDPE + CB; B: iPP/HDPE + CB; C: HDPE/CB + iPP; D: iPP/CB + HDPE). Scanning electron microscopy observation showed that CB particles are mainly distributed in HDPE in all composites, and the phase morphology of composites was obviously affected by a compounding procedure. The size of the HDPE/CB domains in the composites prepared by procedures A and D decreased with the increase in CB content, whereas that of HDPE/CB in the composites prepared by procedures B and C rarely changed with the increase in CB content. The crystallization behaviors of the composites were significantly affected by their phase morphology, which resulted from the variation of compounding procedure. The isothermal crystallization rate of iPP in the composites prepared by procedures A and D was obviously increased, which may originate from the small HDPE/CB droplets dispersed in the iPP phase. The non-isothermal crystallization curves of composites prepared by procedure D represented two peaks because the iPP component in these composites had the fastest crystallization rate, whereas the curves of composites prepared by other compounding sequences only exhibited one peak. Moreover, the crystallinity of HDPE almost increased by one time with the incorporation of only 1 phr CB because the CB particles selectively located in the HDPE phase, and the crystallinity of HDPE decreased with the further increase of CB content because of the strong restriction of CB on the HDPE chains. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this work, gradient materials with low electrical resistivity were prepared by compounding isotactic polypropylene (iPP)/high density polyethylene (HDPE) blends with carbon black (CB) through extruding and injection molding. Contact angle measurements and morphology measurements showed that the CB particles were selectively located in HDPE phase and the final composites had a gradient structure that the HDPE/CB phase exhibited different morphologies in the skin layer and core layer of the composites under different processing procedures. The main factors influencing the formation of the functional gradient materials (FGM), including screw speed during extruding, iPP types and CB contents were discussed. They affect the phase morphology by shear stress, the restoration of HDPE phase, and the viscosity ratio of polymer blends, respectively. In conclusion, iPP/HDPE/CB FGM could be formed easily in the composites blending with the iPP type with narrow molecular weight distribution (MWD) and higher CB content extruded at higher screw speed. The electrical properties of iPP/HDPE/CB composites were studied and the results showed that screw speed in extrusion significantly influenced the percolation curve and electrical property of the final composites. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Objective: To investigate the feasibility of human bone marrow mesenchymal stem cells (hBMSCs) in vitro differentiation into vascular smooth muscle cells with induction of platelet-derived growth Factor BB (PDGF-BB)., Methods: Bone marrow mesenchymal stem cells of adult healthy donors were separated from iliac crest aspiration and expanded in DMEM-LG medium. Cells at passage 1 were transferred to EGM-2 medium containing PDGF-BB (20 ng/ml) and cultured for 14 days. The expression of SM alpha-actin, SM calponin, SMMHC and SM 22alpha were detected by immunofluorescence and observed with fluorescence microscope. mRNA expression of SMalpha-actin, SM calponin, SMMHC as well as SM 22alpha was analyzed by RT-PCR. The method of Western-Blot was applied to determine protein expression of SM 22alpha. Cells with induction were observed for the expression of SM alpha-actin,SM calponin,SMMHC by FACs analysis., Results: With the induction of PDGF-BB, the morphology of cells changed to a spindle fibroblastic appearance. By fluorescence microscope observation, expression of SM alpha-actin, SM calponin and SMMHC was found intracellularly in PDGF-BB treated hBMSCs at 14 days. Western-Blot detection confirmed SM 22alpha expression by 14 days induction. RT-PCR of characteristic vascular smooth muscle cells related genes, such as SM alpha-actin, SM calponin, SMMHC and SM 22alpha revealed differentiation of vascular smooth muscle cells phenotype in monolayer culture upon stimulation with PDGF-BB for 14 days. The positive expression of SM alpha-actin, SM calponin and SMMHC in induced cells was significantly higher than that in non-induced cells (P < 0.05, n=3)., Conclusion: These results suggested hBMSCs could be differentiated into vascular smooth muscle cell phenotype with PDGF-BB induction in vitro.

cAMP response element-binding (CREB) proteins are a family of mammalian transcription activators that mediate cAMP and calcium-dependent gene expression through the cAMP response element (CRE). CREB4 is a novel member of the human CREB family. RT-PCR showed CREB4 transcripts were found in lung carcinoma LX-1, colon adenocarcinoma CX-1, prastatic adenocarcinoma PC-3, colon carcinoma G1-112, and pancreatic adenocarcinoma G1-103. Constructing CREB4 and CREB(215-395aa) fusion protein with the entire prokaryotic LexA protein respectively disclosed that CREB4 protein functioned as a transcription activator and its N-terminal accounted for the activation ability. Furthermore,a fusion protein of GFP and full-length CREB4 was localized in cytoplasm,whereas the fusion protein of GFP and a deletion mutant lacking the C-terminal putative transmembrane domain was translocated in nucleus. Our results suggested that putative transmembrane domain of CREB4 protein was associated with modulation of its function for the transcriptional activation.