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941.
Boura C Muller S Voegel JC Schaaf P Stoltz JF Menu P 《Cell biochemistry and biophysics》2006,44(2):223-231
Recently, the use of polyelectrolyte films has been suggested as a new versatile technique of surface modification aimed at tissue engineering. In the present study, we evaluated the expression of intercellular adhesion molecule (ICAM)-1 of endothelial cells (ECs) seeded on two types of polyelectrolyte multilayer films either terminated by poly(D-lysine) (PDL) or poly(allylamine hydrochloride) (PAH). This work showed that chemical stimulations with tumor necrosis factor (TNF)-alpha induced the ICAM-1 expression of ECs differently depending largely on the film architecture employed. Compared with PAH-ending films, the PDL-ending ones upregulated the ICAM-1 expression of the ECs after a prolonged exposition to TNF-alpha, rendering this film type less favorable in tissue engineering. Cytochalasin D (an F-actin disrupting agent) showed the involvement of the cytoskeleton in the upregulation of ICAM-1 for cells deposited on films terminated by PDL. The PAH-ending films did not perturb the ICAM-1 expression of ECs and might thus enhance the seeding of ECs in vascular engineering. 相似文献
942.
Hrabovská A Debouzy JC Froment MT Devínsky F Pauliková I Masson P 《The FEBS journal》2006,273(6):1185-1197
The purpose of this work was to study the catalytic properties of rat butyrylcholinesterase with benzoylcholine (BzCh) and N-alkyl derivatives of BzCh (BCHn) as substrates. Complex hysteretic behaviour was observed in the approach to steady-state kinetics for each ester. Hysteresis consisted of a long lag phase with damped oscillation. The presence of a long lag phase, with no oscillations, in substrate hydrolysis by rat butyrylcholinesterase was also observed with N-methylindoxyl acetate as substrate. Hysteretic behaviour was explained by the existence of two interconvertible butyrylcholinesterase forms in slow equilibrium, while just one of them is catalytically active. The damped oscillations were explained by the existence of different substrate conformational states and/or aggregates (micelles) in slow equilibrium. Different substrate conformational states were confirmed by 1H-NMR. The K(m) values for substrates decreased as the length of the alkyl chain increased. High affinity of the enzyme for the longest alkyl chain length substrates was explained by multiple hydrophobic interactions of the alkyl chain with amino acid residues lining the active site gorge. Molecular modelling studies supported this interpretation; docking energy decreased as the length of the alkyl chain increased. The long-chain substrates had reduced k(cat) values. Docking studies showed that long-chain substrates were not optimally oriented in the active site for catalysis, thus explaining the slow rate of hydrolysis. The hydrolytic rate of BCH12 and longer alkyl chain esters vs. substrate concentration showed a premature plateau far below V(max). This was due to the loss of substrate availability. The best substrates for rat butyrylcholinesterase were short alkyl homologues, BzCh - BCH4. 相似文献
943.
944.
Trias Astériou Jean-Claude Vincent Frédéric Tranchepain Brigitte Deschrevel 《Matrix biology》2006,25(3):166-174
Hyaluronidase and high levels of hyaluronan are found together in tumours. It is highly likely that hyaluronidase activity controls the balance between high molecular mass hyaluronan and oligosaccharides, and thus plays an important role in cancer development. The hyaluronan hydrolysis catalysed by bovine testicular hyaluronidase was studied as a model. The kinetics was investigated at pH 5 and 37 degrees C using the colorimetric N-acetyl-d-glucosamine reducing end assay method. While the substrate dependence obtained in the presence of 0.15 mol L(-1) ionic strength exhibited a Michaelis-Menten behaviour, an atypical behaviour was observed under low ionic strength: for increasing hyaluronan concentrations, the initial reaction rate increased, reached a maximum and then decreased to a very low level, close to zero at high substrate concentrations. One of the various hypotheses examined to explain this atypical behaviour is the formation of non-specific complexes between hyaluronan and hyaluronidase based on electrostatic interactions. This hypothesis is the only one that can explain all the experimental results including the variation of the reaction medium turbidity as a function of time and the influence on the initial reaction rate of the hyaluronan concentration over hyaluronidase concentration. However, phenomena such as the high viscosity of highly concentrated hyaluronan solutions or the steric exclusion of hyaluronidase from hyaluronan solutions may contribute to the atypical behaviour. Finally, the biological implications of the non-linear and non-monotonous shape of the hyaluronan-hyaluronidase substrate dependence in the regulation of the hyaluronan chain molecular mass are discussed, in particular in the case of cancer development. 相似文献
945.
We investigate the genetic structure and molecular selection pattern of a sympatric population of Sinorhizobium meliloti and Sinorhizobium medicae. These bacteria fix nitrogen in association with plants of the genus Medicago. A set of 116 isolates were obtained from a soil sample, from root nodules of three groups of plants representing among-species, within-species and intraline diversity in the Medicago genus. Bacteria were characterized by sequencing at seven loci evenly distributed along the genome of both Sinorhizobium species, covering the chromosome and the two megaplasmids. We first test whether the diversity of host plants influence the bacterial diversity recovered. Using the same data set, we then analyse the selective pattern at each locus. There was no relationship between the diversity of Medicago plants that were used for sampling and the diversity of their symbionts. However, we found evidence of selection within each of the two main symbiotic regions, located on the two different megaplasmids. Purifying selection or a selective sweep was found to occur in the nod genomic region, which includes genes involved in nodulation specificity, whereas balancing selection was detected in the exo region, close to genes involved in exopolysaccharide production. Such pattern likely reflects the interaction between host plants and bacterial symbionts, with a possible conflict of interest between plants and cheater bacterial genotypes. Recombination appears to occur preferentially within and among loci located on megaplasmids, rather than within the chromosome. Thus, recombination may play an important role in resolving this conflict by allowing different selection patterns at different loci. 相似文献
946.
Genetic variability in the only two existing populations of Buller's albatross (Thalassarche bulleri bulleri) was assessed using six polymorphic microsatellite loci. Large biological samples were obtained from both the Snares (n = 99) and the Solander Islands (n = 27). Several measures of genetic differentiation including F(ST) and R(ST) and a principal coordinates analysis (PCO) suggest a complete absence of genetic structure between three breeding colonies on the Snares Islands, and between them and one breeding colony on the Solander Islands. Mark/recapture studies of recently banded albatross chicks on the Snares found high natal philopatry in T. b. bulleri, but the microsatellite DNA data suggest that sufficient gene flow still occurs between all four breeding colonies to maintain a genetically homogeneous population overall. 相似文献
947.
Vercouillie J Mavel S Galineau L Ragusa T Innis R Kassiou M Chalon S Dollé F Besnard JC Guilloteau D Emond P 《Bioorganic & medicinal chemistry letters》2006,16(5):1297-1300
As the serotonin transporter (SERT) is involved in several neurodegenerative and psychiatric disorders, radiopharmaceuticals to image the SERT by PET or SPECT would be very valuable in studying these diseases. For the development of imaging agents, we have synthesized novel derivatives of recently reported diphenylsulfide SERT ligands, in which the sulfur atom linking the two phenyl rings was replaced by an oxygen, sulfinyl, sulfonyl, amino or carbon group. Three of these exhibited good to high in vitro affinity (0.5 nM < K(i) < 11 nM) and selectivity for the SERT over the other monoamine transporters. 相似文献
948.
Bourdron J Commeiras L Barbier P Bourgarel-Rey V Pasquier E Vanthuyne N Hubaud JC Peyrot V Parrain JL 《Bioorganic & medicinal chemistry》2006,14(16):5540-5548
The synthesis of an analog of caulerpenyne having a trimethoxyaryl moiety was achieved in 11% overall yield over 11 steps. Its biological activity has been evaluated as inhibitor of in vitro tubulin polymerization or angiogenesis. 相似文献
949.
Alaoui AE Saha N Schmidt F Monneret C Florent JC 《Bioorganic & medicinal chemistry》2006,14(14):5012-5019
Two new glucuronide paclitaxel prodrugs have been synthesized. Linked to the 2'-OH of the drug by a carbonate function, they include a self-immolative spacer bearing an arylnitro or arylamino group between the drug and the glucuronic acid residue. Both prodrugs were well detoxified and easily cleaved in the presence of beta-D-glucuronidase with fast removal of the spacer, releasing paclitaxel. The arylamino spacer-containing prodrug, more stable than the corresponding nitro analogue, was selected for further studies. 相似文献
950.
Luu RA Gurnani K Dudani R Kammara R van Faassen H Sirard JC Krishnan L Sad S 《Journal of immunology (Baltimore, Md. : 1950)》2006,177(3):1516-1525
Ag presentation to CD8(+) T cells often commences immediately after infection, which facilitates their rapid expansion and control of infection. Subsequently, the primed cells undergo rapid contraction. We report that this paradigm is not followed during infection with virulent Salmonella enterica, serovar Typhimurium (ST), an intracellular bacterium that replicates within phagosomes of infected cells. Although susceptible mice die rapidly (approximately 7 days), resistant mice (129 x 1SvJ) harbor a chronic infection lasting approximately 60-90 days. Using rOVA-expressing ST (ST-OVA), we show that T cell priming is considerably delayed in the resistant mice. CD8(+) T cells that are induced during ST-OVA infection undergo delayed expansion, which peaks around day 21, and is followed by protracted contraction. Initially, ST-OVA induces a small population of cycling central phenotype (CD62L(high)IL-7Ralpha(high)CD44(high)) CD8(+) T cells. However, by day 14-21, majority of the primed CD8(+) T cells display an effector phenotype (CD62L(low)IL-7Ralpha(low)CD44(high)). Subsequently, a progressive increase in the numbers of effector memory phenotype cells (CD62L(low)IL-7Ralpha(high)CD44(high)) occurs. This differentiation program remained unchanged after accelerated removal of the pathogen with antibiotics, as majority of the primed cells displayed an effector memory phenotype even at 6 mo postinfection. Despite the chronic infection, CD8(+) T cells induced by ST-OVA were functional as they exhibited killing ability and cytokine production. Importantly, even memory CD8(+) T cells failed to undergo rapid expansion in response to ST-OVA infection, suggesting a delay in T cell priming during infection with virulent ST-OVA. Thus, phagosomal lifestyle may allow escape from host CD8(+) T cell recognition, conferring a survival advantage to the pathogen. 相似文献