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Parallel Plate Flow Chamber (parallel + plate_flow_chamber)
Selected AbstractsAdhesion of Enterococcus faecalis 1131 grown under subinhibitory concentrations of ampicillin and vancomycin to a hydrophilic and a hydrophobic substratumFEMS MICROBIOLOGY LETTERS, Issue 1 2001Amparo M Gallardo-Moreno Abstract The effect of two subinhibitory antibiotic concentrations of ampicillin and vancomycin during growth on the adhesion of Enterococcus faecalis 1131 to glass and silicone rubber was studied in a parallel plate flow chamber. Initial deposition rates and numbers of adhering bacteria after 4 h were higher on hydrophilic glass than on hydrophobic silicone rubber, regardless of growth conditions. The presence of 1/4 minimal inhibitory concentration (MIC) of ampicillin during growth reduced enterococcal adhesion to both substrata, but growth in the presence of 1/4 MIC vancomycin did not affect the adhesion of E. faecalis. Moreover, enterococcal adhesion increased after growth in the presence of 1/8 MIC vancomycin. The increased adhesion after growth in the presence of subinhibitory concentrations of vancomycin may have strong implications for patients living with implanted biomaterials, as they may suffer adverse effects from use of this antibiotic, especially since bacteria once adhered are less sensitive to antibiotics. [source] Fluid Flow Induction of Cyclo-Oxygenase 2 Gene Expression in Osteoblasts Is Dependent on an Extracellular Signal-Regulated Kinase Signaling Pathway,,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 2 2002Sunil Wadhwa Abstract Mechanical loading of bone may be transmitted to osteocytes and osteoblasts via shear stresses at cell surfaces generated by the flow of interstitial fluid. The stimulated production of prostaglandins, which mediates some effects of mechanical loading on bone, is dependent on inducible cyclo-oxygenase 2 (COX-2) in bone cells. We examined the fluid shear stress (FSS) induction of COX-2 gene expression in immortalized MC3T3-E1 osteoblastic cells stably transfected with ,371/+70 base pairs (bp) of the COX-2 5,-flanking DNA (Pluc371) and in primary osteoblasts (POBs) from calvaria of mice transgenic for Pluc371. Cells were plated on collagen-coated glass slides and subjected to steady laminar FSS in a parallel plate flow chamber. FSS, from 0.14 to10 dynes/cm2, induced COX-2 messenger RNA (mRNA) and protein. FSS (10 dynes/cm2) induced COX-2 mRNA within 30 minutes, with peak effects at 4 h in MC3T3-E1 cells and at ,8 h in POBs. An inhibitor of new protein synthesis puromycin blocked the peak induction of COX-2 mRNA by FSS. COX-2 promoter activity, measured as luciferase activity, correlated with COX-2 mRNA expression in both MC3T3-E1 and POB cells. FSS induced phosphorylation of extracellular signal-regulated kinase (ERK) in MC3T3-E1 cells, with peak effects at 5 minutes. Inhibiting ERK phosphorylation with the specific inhibitor PD98059 inhibited FSS induction of COX-2 mRNA by 55-70% and FSS stimulation of luciferase activity by ,80% in both MC3T3-E1 and POB cells. We conclude that FSS transcriptionally induces COX-2 gene expression in osteoblasts, that the maximum induction requires new protein synthesis, and that induction occurs largely via an ERK signaling pathway. [source] Leukocyte Adhesion in Capillary-Sized, P-Selectin-Coated MicropipettesMICROCIRCULATION, Issue 2 2008Prithu Sundd ABSTRACT Objective: Leukocyte retention in lung capillaries is observed in normal physiology and following a bacterial infection. It has been hypothesized that cells either become mechanically trapped or adhere to capillary endothelial cells via adhesion molecules. We propose that retention involves both mechanical and adhesive forces and that the biochemical adhesive force is modulated by mechanical forces that alter the area of contact between leukocytes and endothelium. Methods: To probe this hypothesis, an adhesion assay has been developed in which individual HL-60 cells were aspirated into micropipettes pre-coated with P-selectin. Following aspiration, cells were exposed to physiological pressure differences. Results: Little adhesion was seen in micropipettes coated with BSA, whereas significant adhesion was observed in micropipettes coated with P-selectin. The frequency of cell arrest on P-selectin in the micropipette was much greater than on P-selectin in a parallel plate flow chamber even though the disruptive force in the micropipette assay exceeds that in the parallel plate flow chamber. These results demonstrate that receptor,ligand interactions can enhance adhesion in a capillary geometry and that differences in capillary geometry vs. venule geometry can significantly influence the adhesive phenotype. Conclusions: Taken together, these observations support the hypothesis that an interplay between mechanical and biochemical adhesive forces can play a major role in retention. [source] Electric field induced desorption of bacteria from a conditioning film covered substratumBIOTECHNOLOGY & BIOENGINEERING, Issue 4 2001Albert T. Poortinga Abstract Desorption of three oral bacterial strains from a salivary conditioning film on an indium tin oxide electrode during application of a positive (bacterial adhesion to the anode) or a negative electric current was studied in a parallel plate flow chamber. Bacterial adhesion was from a flowing suspension of high ionic strength, after which the bacterial suspension was replaced by a low ionic strength solution without bacteria and currents ranging from ,800 to +800 ,A were applied. Streptococcus oralis J22 desorbed during application of a positive and negative electric current with a desorption probability that increased with increasing electric current. Two actinomyces strains, however, could not be stimulated to desorb by the electric currents applied. The desorption forces acting on adhering bacteria are electroosmotic in origin and working parallel to the electrode surface in case of a positive current, whereas they are electrophoretic and electrostatic in origin and working perpendicular to the surface in case of a negative current. By comparison of the effect of positive and negative electric currents, it can be concluded that parallel forces are more effective in stimulating bacterial desorption than perpendicular forces. The results of this study point to a new pathway of cleaning industrial and biomedical surfaces without the use of detergents or biocides. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 76: 395,399, 2001. [source] | |||||||||||||