| In the pursuit to further understand the process of embryo morphogenesis, a novel experimental apparatus was developed to measure the in-plane stresses present in the epithelia of early-stage Ambystoma mexicanum (axolotl) embryos. Two parallel wires are attached to an embryo normal to the direction in which the stress is to be measured at the region of interest using cyanoacrylate glue. A slit is then made between and parallel to the wires using a tungsten point. The wires displace from their original position due to stresses in the tissues. A visual tracking system and motorized micropositioner restores the original distance between the wires. Bending of the wires is measured and used to calculate the load carried across the slit portion of the tissues. Companion finite element models are used to convert the forces to an in-plane stress resultant. Forces were measured in two orthogonal directions at multiple locations in stage 13, 15, 17 and 19 axolotl embryos. In vivo stress resultants were found to range from -0.17mN/m to 1.92mN/m. The stress patterns can be attributed to components associated with internal pressure, bending of the embryo and neurulation-related morphogenetic movements. |
