Integrin signaling downregulates filopodia during muscle-tendon attachment
JOURNAL OF CELL SCIENCE
Authors: Richier, Benjamin; Inoue, Yoshiko; Dobramysl, Ulrich; Friedlander, Jonathan; Brown, Nicholas H.; Gallop, Jennifer L.
Abstract
Cells need to sense their environment to ensure accurate targeting to specific destinations. This occurs in developing muscles, which need to attach to tendon cells before muscle contractions can begin. Elongating myotube tips form filopodia, which are presumed to have sensory roles, and are later suppressed upon building the attachment site. Here, we use live imaging and quantitative image analysis of lateral transverse (LT) myotubes in Drosophila to show that filopodia suppression occurs as a result of integrin signaling. Loss of the integrin subunits alpha PS2 and beta PS (also known as If and Mys, respectively, in flies) increased filopodia number and length at stages when they are normally suppressed. Conversely, inducing integrin signaling, achieved by the expression of constitutively dimerised beta PS cytoplasmic domain (di beta), prematurely suppressed filopodia. We discovered that the integrin signal is transmitted through the protein G protein-coupled receptor kinase interacting ArfGAP (Git) and its downstream kinase p21-activated kinase (Pak). Absence of these proteins causes profuse filopodia and prevents the filopodial inhibition mediated by di beta. Thus, integrin signaling terminates the exploratory behavior of myotubes seeking tendons, enabling the actin machinery to focus on forming a strong attachment and assembling the contractile apparatus.
Thermophysical Properties of the Medium-Chain 1-Alkyl Halides in a Wide Range of Conditions: New Experimental Data and Predictions of CP-PC-SAFT and FT-EOS
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
Authors: Melent'ev, Vyacheslav V.; Postnikov, Eugene B.; Nedyalkov, Yuriy, V; Polishuk, Ilya
Abstract
This study reports experimental density and sound velocity data of 1-chloroheptane and 1-iodoheptane at 291.45 <= T <= 413.15 K and 1 <= P <= 1961 bar along with the atmospheric pressure liquid densities at 223.15 <= T <= 423.10 K, sound velocities at 216.08 <= T <= 413.15 K, and isobaric heat capacities at 223.15 <= T <= 423.15 K. The evaluated values of the auxiliary thermodynamic properties are provided as well. An analysis performed in this study is based on the entire available high-pressure database of the medium chain 1-alkyl halides. It is demonstrated that, within its applicability range, the fluctuation theory based Tait-like equation of state (FT-EOS) predicts the high-pressure experimental data in a particularly accurate manner. The performance of the critical point based perturbed chain statistical association fluid theory (CP-PC-SAFT) is dependent on the robustness of the T-c and P-c data, whose appropriate values allow reliable predictions of densities until extremely high pressures, sound velocities, heat capacities, and the available binary high-pressure phase equilibria data. The entirely predictive CP-PC-SAFT + MYS (modified Yarranton-Satyro correlation) modeling framework yields reliable viscosity estimations of 1-alkyl chlorides and their mixtures. At the same time, it accurately predicts the pressure dependence established by the viscosity of 1-bromobutane only up to similar to 2000 bar and it tends to underestimate this property for 1-iodoalkanes. Investigation of trends established by CP-PC-SAFT allows making some essential assumptions about the regularities characteristic for thermophysical properties of 1-alkyl halides at elevated pressures.