Formyl peptides are potent neutrophil chemoattractants. In humans and rabbits, the formyl peptide receptor (FPR) binds N-formyl-Met-Leu-Phe (fMLF) with high affinity (Kd ≈ 1 nM). The mouse FPR (mFPR) is a low-affinity receptor for fMLF (Kd ≈ 100 nM); therefore, other agonists for this receptor may exist. Using mFPR-transfected rat basophilic leukemia cells, we found that a recently identified synthetic peptide Trp-Lys-Tyr-Met-Val-d-Met (WKYMVm) is a potent agonist for mFPR. WKYMVm induced calcium mobilization with an EC50 of 1.2–1.5 nM. Optimal chemotaxis was achieved with 1 nM of WKYMVm, but it required 100 nM of fMLF. WKYMVm stimulated rapid and potent phosphorylation of the mitogen-activated protein kinases extracellular signal-related kinases 1 and 2 when used at 50 nM. Pertussis toxin only partially blocked calcium mobilization and production of inositol 1,4,5-trisphosphate in the stimulated mFPR cells, suggesting the possibility that this receptor couples to Gα proteins other than Gi and Go. Competitive binding and desensitization data suggest that both peptides interact with the same receptor but may use nonoverlapping binding sites because WKYMVm was unable to effectively displace [3H]fMLF bound to mFPR. These results provide evidence for the presence of an alternative potent agonist for mFPR, and suggest a potential usage of WKYMVm for probing the ligand-receptor interactions with the murine formyl peptide receptor homologs.
The aim of this study was to develop and evaluate a simple and rapid cell seeding procedure for both calcium phosphate ceramic scaffolds and polymer scaffolds. Poly(d,l-lactic acid) and β-tri-calcium phosphate scaffolds were seeded with MC3T3-E1 cells in a syringe. Scaffolds were put in the syringe. After replacing the plunger, the cell suspension was drawn into the syringe. The syringe was closed and the plunger was retracted to the volume of the cell suspension to create a vacuum. This was done for 3 × 10 s. By this procedure, cells were homogenously distributed throughout the scaffold. The efficiency of cell seeding was approximately 60% for both scaffolds independent of the initial cell density. The hypotension the cells experienced for 3 × 10 s did not affect the proliferation capacity of the cells. In conclusion, this method of syringe-vacuum cell seeding is easy, quick, cheap, and easily to perform at an operating theatre.
In this study, the photonic crystal structure is employed to increase both the light extraction efficiency and the modulation bandwidth of flip-chip GaN-based light-emitting diodes (LEDs). The finite difference time domain method is utilized to investigate the influence of structure of photonic crystals on the Purcell factor and light extraction efficiency of flip-chip GaN-based LEDs. Simulation results show that the modulation bandwidth is estimated to be 202 MHz at current densities of 1000 A/cm2. The experimental result of modulation bandwidth is in accord with the simulation. The optical f-3dB of the device achieves 212 MHz at current densities of 1000 A/cm2 and up to 285 MHz at current densities of 2000 A/cm2. This design of photonic crystal flip-chip LED has the potential for applications in high-frequency visible light communication.
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