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81.
82.
Cohen M Joester D Geiger B Addadi L 《Chembiochem : a European journal of chemical biology》2004,5(10):1393-1399
A new concept that attributes a pivotal role to the pericellular coat in the regulation of the early stages of cell adhesion is presented. Quick, adaptable, and transient adhesion through multiple cooperative weak interactions provides the cell with an additional level of modulation in the decision-making process that precedes the commitment to adhesion at a particular site. Hyaluronan emerges as a modulator of cell adhesion in certain cells, mediating binding or repulsion through its polyelectrolyte character, in addition to its chirality and molecular-recognition properties. The biophysical properties of hyaluronan as well as its ultrastructural organization are analyzed in relation to this proposed function. 相似文献
83.
Breunig M Lungwitz U Klar J Kurtz A Blunk T Goepferich A 《Journal of nanoscience and nanotechnology》2004,4(5):512-520
For non-viral gene delivery, the carriers for DNA transfer into cells must be vastly improved. The branched cationic polymer polyethylenimine has been described as an efficient gene carrier. However, polyethylenimine was demonstrated to mediate substantial cytotoxicity. Therefore, this study is aimed at investigating per-N-methylated polyethylenimine, which is thought to have a much lower cytotoxicity due to its lower charge density. Results from a gel retardation assay and laser light scattering indicated that per-N-methylated polyethylenimine condenses DNA into small and compact nanoparticles with a mean diameter <150 nm. Furthermore, polyplexes of polyethylenimine and per-N-methylated polyethylenimine with DNA had a positive zeta potential and the polymers protected DNA from nuclease-mediated digestion. The transfection efficiency of polyethylenimine and per-N-methylated polyethylenimine was tested in CHO-K1 cells. Using green fluorescent protein as reporter gene and flow cytometry analysis, we demonstrated that per-N-methylated polyethylenimine has a lower cytotoxicity, but also a significantly lower transfection efficiency. Using propidium iodide staining, we could additionally distinguish between viable and dead cells. At NP > or = 12, per-N-methylated polyethylenimine showed a much higher cell viability and the ratio of viable and transfected cells to dead and transfected cells was about 1.5 to 1.7 fold higher than for polyethylenimine. The results of cell viability from flow cytometry analysis were confirmed by the MTS assay. Using luciferase reporter gene for transfection experiments, the gene expression of per-N-methylated polyethylenimine was lower at NP 6, 12 and 18 as compared to polyethylenimine, but at NP 24 it yielded similar levels. 相似文献
84.
85.
1. Reference values for the plasma creatinine were established using the alkaline picrate method with the Greiner Selective Analyzer GSA II in relation to the Cr 51-EDTA Clearance. Individuals with normal GFR between 93 to 159 ml/min/1.73 m2 had creatinine values in men (n = 65) from 53.7 to 119.5 mumol/l (0.61 to 1.35 mg/100 ml) and in women (n = 59) from 37.7 to 107 mumol/l (0.42 to 121 mg/100 ml). 2. The creatine determinations with the GSA II were compared to those on the Technicon Analyzer, the Beckman Creatinine Analyzer, the Gemsaec-Fast Analyzer and to the enzymatic creatinine method. A good correlation (r = 0.9780-0.984) was observed. 3. With the GSA II and the enzymatic method, bilirubin showed a minor interference which was more marked with the Beckman analyzer. 相似文献
86.
Liu QT Chen R McCarry BE Diamond ML Bahavar B 《Environmental science & technology》2003,37(11):2340-2349
Organic films on an impervious surface (window glass) were sampled at paired indoor-outdoor sites in July 2000 and characterized for their paraffinic and polar organic compositions along an urban-rural transect. Four classes of polar compounds (C11-C31 aliphatic monocarboxylic, C6-C14 dicarboxylic, nine aromatic polycarboxylic, and five terpenoid acids) constituted between 81 and 95% (w/w) of the total organic fraction analyzed comprising n-alkanes (C10-C36), 46 PAH, 97 PCBs, and 18 OC pesticides. Concentrations of the polar compounds plus their precursors, n-alkanes, ranged from 8 to 124 microg m(-20 and were dominated by monocarboxylic acids (67-89%, w/w). On outdoor windows, n-alkanes, aromatic acids, and terpenoid acids decreased in concentration along the urban-rural transect. The carbon preference index values and the interpretations of individual compounds indicate that the main sources of n-alkanes were plant waxes followed by petrogenic sources; monocarboxylic and dicarboxylic acids were from plant waxes and animal fats. Results of principal component analysis showed closer correspondence between outdoor and indoor signatures than among locations. In outdoor films, these compounds are suggested to play an important role in mediating chemical fate in urban areas by air-film exchange and facilitating "wash-off" due to their surfactant-like properties. In indoor films, these compounds provide a medium for the accumulation of more toxic compounds. 相似文献
87.
Pharmacological modulation of fatty acid desaturation and of cholesterol biosynthesis in THP-1 cells
In THP-1 cells, simvastatin decreases, in a concentration-dependent manner, cholesterol synthesis and increases linoleic acid
(LA) conversion to its long-chain derivatives, in particular to arachidonic acid, activating Δ6 and Δ5 fatty acid (FA) desaturases.
The intermediates in cholesterol synthesis, mevalonate and geranylgeraniol, partially reverse the effects of simvastatin on
the LA conversion. The aims of this work were to evaluate: (i) the correlation between cholesterol synthesis and desaturase
activity and (ii) the possible involvement of protein isoprenylation in desaturase activity, assessed through pharmacological
treatments. THP-1 cells were incubated with [1-14C]LA or with [1-14C]di-homo-γ-linolenic acid (DHGLA) and treated with simvastatin or with curcumin and nicardipine, inhibitors of desaturases.
Curcumin was more active than nicardipine in inhibiting LA and DHGLA conversion: 20 μM curcumin, alone or with simvastatin,
totally inhibited Δ6 and Δ5 desaturation steps; 10 μM nicardipine only partially inhibited the enzymes, being more active
on Δ5 desaturase. Simvastatin treatment decreased the incorporation of acetate in cholesterol (−93.8%) and cholesterol esters
(−70.2%), as expected. Curcumin and nicardipine also decreased cholesterol synthesis and potentiated simvastatin. Finally,
the isoprenylation inhibitors (perillic acid and GGTI-286) neither affected the conversion of LA nor inhibited the Δ5 desaturase
activity. In conclusion, our results indicate that there is no direct relationship between cholesterol synthesis and desaturase
activity. In fact, simvastatin decreased cholesterol synthesis and enhanced LA conversion (mainly Δ5 desaturation), whereas
curcumin and nicardipin decreased Δ5 desaturation, with a limited effect on cholesterol synthesis. 相似文献
88.
Rogelio?RodríguezEmail author Miriam?Estevez Susana?Vargas M.?Antonieta?Mondragón 《Materials Research Innovations》2003,7(2):80-84
The synthesis and characterization of a hybrid ceramic-polymer coating with high wearing resistance and designed to cover
wood surfaces, are reported in this work. This hybrid material provides a high wearing resistance (400% higher than a conventional
commercial product typically used to protect these surfaces); additionally it has a high UV resistance and high transparency
and gloss. The wood surfaces were previously treated either with a primer coating or with a special coupling agent, before
the hybrid coating was applied; in both cases, good adhesion with the substrate was obtained.
Electronic Publication 相似文献
89.
Agustin?de?la Isla Witold?BrostowEmail author Bernard?Bujard Miriam?Estevez J.?Rogelio?Rodriguez Susana?Vargas Victor?M.?Casta?o 《Materials Research Innovations》2003,7(2):110-114
We cover teeth surfaces with nanohybrid coatings containing an inorganic ceramic and an organic copolymer constituents. We
report the first ever values of scratch penetration depth and scratch recovery for bare and coated teeth. We find that uncoated
teeth undergo viscoelastic recovery (healing) after microscratching – the first manifestation of bone viscoelasticity in tribology.
The coatings fill "valleys" in teeth surfaces. In each case a large improvement in the scratch resistance as compared to uncoated
teeth is seen. The extent of the improvement depends on the inorganic/organic component ratios in the nanohybrids.
Electronic Publication 相似文献
90.
Teodor Gabriel Crainic Guido Perboli Miriam Pezzuto Roberto Tadei 《Computers & Operations Research》2007
In this paper, we address the issue of computing fast lower bounds for the Bin Packing problem, i.e., bounds that have a computational complexity dominated by the complexity of ordering the items by non-increasing values of their volume. We introduce new classes of fast lower bounds with improved asymptotic worst-case performance compared to well-known results for similar computational effort. Experimental results on a large set of problem instances indicate that the proposed bounds reduce both the deviation from the optimum and the computational effort. 相似文献