Mechanical Stability Determines Stress Fiber and Focal Adhesion Orientation.

It is well documented in a variety of adherent cell types that in response to anisotropic signals from the microenvironment cells alter their cytoskeletal organization. Previous theoretical studies of these phenomena were focused primarily on the elasticity of cytoskeletal actin stress fibers (SFs) and of the substrate while the contribution of focal adhesions (FAs) through which the cytoskeleton is linked to the external environment has not been considered. Here we propose a mathematical model comprised of a single linearly elastic SF and two identical linearly elastic FAs of a finite size at the endpoints of the SF to investigate cytoskeletal realignment in response to uniaxial stretching of the substrate.

Durotaxis as an elastic stability phenomenon.

It is well documented that directed motion of cells is influenced by substrate stiffness. When cells are cultured on a substrate of graded stiffness, they tend to move from softer to stiffer regions--a process known as durotaxis. In this study, we propose a mathematical model of durotaxis described as an elastic stability phenomenon.

A mathematical model of cell reorientation in response to substrate stretching.

It is well documented that in response to substrate stretching adhering cells alter their orientation. Generally, the cells reorient away from the direction of the maximum substrate strain, depending upon the magnitude of the substrate strain and the state of cell contractility. Theoretical models from the literature can describe only some aspects of this phenomenon.

Enzymatic conversion of dihydrotestosterone from 3-keto to 3-enol form in the rat prostate.

Dihydrotestosterone (DHT) is the active androgen, as well as a strong tumor promoter in the prostate, where several enzymes are essential for the regulation of its activity. We localized four enzymes promoting the enolization of the 3-keto group of DHT in rat prostate. The enzymes were purified by ion-exchange chromatography, acetone fractionation and gel filtration to homogeneity, and found to have molecular sizes of 19.