Early embryology; making a formed body (Introduction)

by David Turell , Monday, December 05, 2016, 23:58 (2910 days ago) @ David Turell

Embryonic stem cells take both biochemical and mechanical clues to decide what to become:

http://phys.org/news/2016-12-powerful-technique-reveals-mechanical-environment.html

"Whether building organs or maintaining healthy adult tissues, cells use biochemical and mechanical cues from their environment to make important decisions, such as becoming a neuron, a skin cell or a heart cell.

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"The growth and development of a living organism is a choreography of cellular movements and behaviors that follow internal genetic guidelines and specific biochemical and mechanical signals. All these events conspire over time to create a variety of complex forms and textures that make our tissues and organs functional.

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"'Growing stem cells on synthetic surfaces with different levels of compliance showed that stem cells would become a different cell type depending solely on the mechanical environment they perceive. If you put embryonic stem cells on a substrate like Jell-O—mechanically similar to brain tissue—they turn into neurons. But if you put them on something harder, similar to embryonic bone, they turn into bone-like cells."

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"The scientists applied their new technique to study how the vertebrate body axis is mechanically built. Using embryos of zebrafish, which was selected for its rapid development and optical transparency, they could show that the mechanical properties of the tissue change along the body axis, facilitating the extension of the body at its posterior end. Inserting magnetic droplets at different locations in the tissue, and generating forces by applying a magnetic field to the droplets, the researchers showed that the tissue behaves like a fluid while growing, with similar mechanical characteristics as thick honey. The data showed that the tissue is more fluid at the posterior end where it was growing, and becomes less fluid far from the growing region.

"'It is similar to glass-blowing," said Campàs. "The tissue is more fluid in growing regions and 'fixes' its shape by becoming less fluid where it does not need to expand."

"The scientists' findings have wide implications in the effort to understand how organs are sculpted into their shapes and how cells respond to their native mechanical environment both in healthy tissues and during disease. The Campàs lab is studying several of these questions, including how limbs are built and how mechanical changes in tumors affect the behavior of malignant cells and the growth of the tumor."

Comment: This is not growth or development by cell committee. Each cell has to respond exactly to the stimuli it receives chemically, mechanically and genetically to form a proper organisms from early embryo to completed form with proper functions. All automatic. Logically multicellularity develops from single cells. If those single cells were originally basically automatic in their responses to stimuli, it is easy to imagine how they agglomerated into multicellular with full cooperative behavior. If they were accustomed to act independently, necessarily they had to give up that independence to join in a multiple cell, multiple organ animal. To me it seems like multicellularity occurred more easily if the original joining cells were automatic.