Substance P Induces Rapid and Transient Membrane Blebbing in U373MG Cells in a p21-Activated Kinase-Dependent Manner

U373MG astrocytoma cells endogenously express the full-length neurokinin 1 receptor (NK1R). Substance P (SP), the natural ligand for NK1R, triggers rapid and transient membrane blebbing and we report that these morphological changes have different dynamics and intracellular signaling as compared to the changes that we have previously described in HEK293-NK1R cells. In both cell lines, the SP-induced morphological changes are Gq-independent, and they require the Rho, Rho-associated coiled-coil kinase (ROCK) signaling pathway. Using confocal microscopy we have demonstrated that tubulin is phosphorylated subsequent to cell stimulation with SP and that tubulin accumulates inside the blebs. Colchicine, a tubulin polymerization inhibitor, blocked SP-induced blebbing in U373MG but not in HEK293-NK1R cells. Although p21-activated kinase (PAK) is expressed in both cell lines, SP induced rapid phosphorylation of PAK in U373MG, but failed to phosphorylate PAK in HEK293-NK1R cells. The cell-permeable Rho inhibitor C3 transferase inhibited SP-induced PAK phosphorylation, but the ROCK inhibitor Y27632 had no effect on PAK phosphorylation, suggesting that Rho activates PAK in a ROCK-independent manner. Our study demonstrates that SP triggers rapid changes in cell morphology mediated by distinct intracellular signaling mechanisms in U373MG versus HEK293-NK1R cells

Concentration and Distribution of E_R, A_L and P in Silica-Based Optical Fiber Preforms by Sims

AbstractSecondary ion mass spectrometry (SIMS) was used to measure the Er, Al and P distributions across (perpendicular to) and along (parallel to) the axis of Er3+-doped silica based preforms and fibers prepared by a solution doping technique. Specially prepared low-melting silicate glass standards containing known concentrations of Er were used to calibrate the spectrometer to obtain a semi-quantitative measurement of the Er concentration. It was found that the Er concentration can vary along a 4-cm section of the preform by as much as a factor of two. The Al concentration also changed along the length of the preform, but to a smaller degree. Finally, instrumental limitations for measuring the Er, Al and P distributions in the optical fiber samples were determined.</jats:p