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991.
Blends of poly-(epsilon-caprolactone) and polysaccharides in tissue engineering applications 总被引:1,自引:0,他引:1
Ciardelli G Chiono V Vozzi G Pracella M Ahluwalia A Barbani N Cristallini C Giusti P 《Biomacromolecules》2005,6(4):1961-1976
Bioartificial blends of poly-(epsilon-caprolactone) (PCL) with a polysaccharide (starch, S; dextran, D; or gellan, G) (PCL/S, PCL/D, PCL/G 90.9/9.1 wt ratio) were prepared by a solution-precipitation technique and widely characterized by differential scanning calorimetry analysis (DSC), Fourier transform infrared-attenuated total reflectance spectroscopy (FTIR-ATR), optical microscopy (OM), wide-angle X-ray diffraction analysis (WAXD), and thermogravimetry (TGA). DSC showed that the polysaccharide reduced the crystallinity of PCL and had a nucleation effect, which was also confirmed by OM analysis. Hoffman-Weeks analysis was performed on PCL and blend samples allowing calculation of their equilibrium melting temperatures (). WAXD showed that the crystalline unit cell type was the same for PCL and blends. FTIR-ATR did not evidence interactions between blend components. Thermal stability was affected by the type of polysaccharide. Microparticles (<125 microm) were produced from blends by cryogenical milling and characterized by scanning electron microscopy analysis (SEM). Selective laser sintering (SLS), a new rapid prototyping technology for scaffold fabrication, was applied to sinter blend microparticles according to a PC-designed two-dimensional geometry (strips and 2 x 2 mm(2) square-meshed grids). The optimal experimental conditions for sintering were established and laser beam parameters (beam speed, BS, and power, P) were found for each blend composition. Morphology of sintered objects was analyzed by SEM and found to be dependent on the morphology of the sintered powders. Sintered samples were analyzed by chemical imaging (CI), FTIR-ATR, DSC, and contact angle analysis. No evidence of the occurrence of degradation phenomena was found by FTIR-ATR for sintered samples, whereas DSC parameters of PCL and blends showed changes which could be attributed to some molecular weight decrease of PCL during sintering. CI of sintered samples showed that the polysaccharide phase was homogeneously dispersed within the PCL matrix, with the only exception being the PCL/D blend. The contact angle analysis showed that all samples were hydrophilic. Fibroblasts were then seeded on scaffolds to evaluate the rate and the extent of cell adhesion and the effect of the polysaccharides (S, D, G) on the bioactivity of the PCL-based blends. 相似文献
992.
Strambio-de-Castillia C Tetenbaum-Novatt J Imai BS Chait BT Rout MP 《Journal of proteome research》2005,4(6):2250-2256
A problem faced in proteomics studies is the recovery of tagged protein complexes in their native and active form. Here we describe a peptide, Bio-Ox, that mimics the immunoglobulin G (IgG) binding interface of Staphylococcus aureus Protein A, and competitively displaces affinity-purified Protein A fusion proteins and protein complexes from IgG-Sepharose. We show that Bio-Ox elution is a robust method for the efficient and rapid recovery of native tagged proteins, and can be applied to a variety of structural genomics and proteomics studies. 相似文献
993.
Turnbull AP Kümmel D Prinz B Holz C Schultchen J Lang C Niesen FH Hofmann KP Delbrück H Behlke J Müller EC Jarosch E Sommer T Heinemann U 《The EMBO journal》2005,24(5):875-884
BET3 is a component of TRAPP, a complex involved in the tethering of transport vesicles to the cis-Golgi membrane. The crystal structure of human BET3 has been determined to 1.55-A resolution. BET3 adopts an alpha/beta-plait fold and forms dimers in the crystal and in solution, which predetermines the architecture of TRAPP where subunits are present in equimolar stoichiometry. A hydrophobic pocket within BET3 buries a palmitate bound through a thioester linkage to cysteine 68. BET3 and yeast Bet3p are palmitoylated in recombinant yeast cells, the mutant proteins BET3 C68S and Bet3p C80S remain unmodified. Both BET3 and BET3 C68S are found in membrane and cytosolic fractions of these cells; in membrane extractions, they behave like tightly membrane-associated proteins. In a deletion strain, both Bet3p and Bet3p C80S rescue cell viability. Thus, palmitoylation is neither required for viability nor sufficient for membrane association of BET3, which may depend on protein-protein contacts within TRAPP or additional, yet unidentified modifications of BET3. A conformational change may facilitate palmitoyl extrusion from BET3 and allow the fatty acid chain to engage in intermolecular hydrophobic interactions. 相似文献
994.
Region-specific effects of hypothyroidism on the relative expression of thyroid hormone receptors in adult rat brain 总被引:6,自引:0,他引:6
The aim of this study was to determine whether changes in the circulating thyroid hormone (TH) and brain synaptosomal TH content
affected the relative levels of mRNA encoding different thyroid hormone receptor (TR) isoforms in adult rat brain. Northern
analysis of polyA+RNA from cerebral cortex, hippocampus and cerebellum of control and hypothyroid adult rats was performed in order to determine
the relative expression of all TR isoforms. Circulating and synaptosomal TH concentrations were determined by radioimmunoassay.
Region-specific quantitative differences in the expression pattern of all TR isoforms in euthyroid animals and hypothyroid
animals were recorded. In hypothyroidism, the levels of TRα2 mRNA (non-T3-binding isoform) were decreased in all brain regions examined. In contrast the relative expression of TRα1 was increased
in cerebral cortex and hippocampus, whereas in cerebellum remained unaffected. The TRβ1 relative expression in cerebral cortex
and hippocampus of hypothyroid animals was not affected, whereas this TR isoform was not detectable in cerebellum. The TR
isoform mRNA levels returned to control values following T4 intraperitoneal administration to the hypothyroid rats. The obtained results show that in vivo depletion of TH regulates TR gene expression in adult rat brain in a region-specific manner. (Mol Cell Biochem 278: 93–100, 2005) 相似文献
995.
996.
Paesano N Marzocco S Vicidomini C Saturnino C Autore G De Martino G Sbardella G 《Bioorganic & medicinal chemistry letters》2005,15(3):539-543
Novel benzyl- and phenyl-isothioureidic derivatives have been synthesised and evaluated as inhibitors of nitric oxide synthesis, induced in lipopolysaccharide (LPS)-activated J774.A1 macrophage cell line. The most potent iNOS inhibitor resulting was 1-methyl-3-phenyl-S-methyl isothiourea 5l. 相似文献
997.
Signoretto C Burlacchini G Pruzzo C Canepari P 《Applied and environmental microbiology》2005,71(5):2756-2761
Several human pathogens and fecal-pollution indicators may persist as viable organisms in natural environments, owing to their ability to activate different types of survival strategies. These strategies include adhesion on both abiotic and biotic surfaces and the entrance to the so-called viable but nonculturable (VBNC) state. In an 18-month survey for the detection of enterococci in both lake water and seawater, C. Signoretto et al. (Appl. Environ. Microbiol. 70:6892-6896, 2004) have shown that Enterococcus faecalis was detected mostly bound to plankton and in the VBNC state. In the present study, we show that in vitro adhesion of E. faecalis to copepods accelerated the entry of cells into the VBNC state relative to that of planktonic bacteria. VBNC E. faecalis cells maintained their adhesive properties to copepods and chitin (the main component of the copepod carapace), though to a reduced extent in comparison with growing cells. Sugar competition experiments showed interference with adhesion to both copepods and chitin by GlcNAc and only to copepods by D-mannose. Four enterococcal cell wall proteins present in both growing and VBNC cells and lipoteichoic acid were shown to be capable of binding chitin. The results indicate that copepods may represent an additional environmental reservoir of enterococci, thus suggesting the advisability of redesigning the protocols currently used for microbial detection during the evaluation of the microbiological quality of environmental samples. 相似文献
998.
High sequence conservation of human immunodeficiency virus type 1 reverse transcriptase under drug pressure despite the continuous appearance of mutations 下载免费PDF全文
999.
Pruzzo C Tarsi R Lleò MM Signoretto C Zampini M Colwell RR Canepari P 《Current microbiology》2002,45(2):105-110
The ability of viable but nonculturable (VBNC) Enterococcus faecalis to adhere to Caco-2 and Girardi heart cultured cells and to urinary tract epithelial cells (ECs) was studied. Enterococci
were harvested during the vegetative growth phase (early exponential and stationary), in the VBNC state, and after recovery
of the ability to divide. VBNC bacteria maintained their adherence capability but the efficiency of attachment was reduced
by about 50 to 70%, depending on the target cell employed. The decrease was transient, since enterococci that regained their
culturability showed adherence values similar to those observed for actively growing cells. Analysis of the invasive properties
of E. faecalis revealed that the VBNC state caused a decrease in the number of bacteria that entered the cultured HEK cells as a result
of the reduction in the number of adhering bacteria. These results highlight the importance of studies of the VBNC phenomenon,
with respect to both microbial survival in the environment and the impact on human health.
Received: 26 September 2001 / Accepted: 4 December 2001 相似文献
1000.
Osmotic stress-induced remodeling of the cortical cytoskeleton 总被引:7,自引:0,他引:7
Di Ciano C Nie Z Szászi K Lewis A Uruno T Zhan X Rotstein OD Mak A Kapus A 《American journal of physiology. Cell physiology》2002,283(3):C850-C865
Osmoticstress is known to affect the cytoskeleton; however, this adaptiveresponse has remained poorly characterized, and the underlyingsignaling pathways are unexplored. Here we show that hypertonicityinduces submembranous de novo F-actin assembly concomitant with theperipheral translocation and colocalization of cortactin and theactin-related protein 2/3 (Arp2/3) complex, which are key components ofthe actin nucleation machinery. Additionally, hyperosmolarity promotesthe association of cortactin with Arp2/3 as revealed bycoimmunoprecipitation. Using various truncation orphosphorylation-incompetent mutants, we show that cortactin translocation requires the Arp2/3- or the F-actin binding domain, butthe process is independent of the shrinkage-induced tyrosine phosphorylation of cortactin. Looking for an alternative signaling mechanism, we found that hypertonicity stimulates Rac and Cdc42. Thisappears to be a key event in the osmotically triggered cytoskeletal reorganization, because 1) constitutively active smallGTPases translocate cortactin, 2) Rac and cortactincolocalize at the periphery of hypertonically challenged cells, and3) dominant-negative Rac and Cdc42 inhibit thehypertonicity-provoked cortactin and Arp3 translocation. The Rhofamily-dependent cytoskeleton remodeling may be an importantosmoprotective response that reinforces the cell cortex. 相似文献