Magic embryology: physical forces form organs (Introduction)

by David Turell , Wednesday, September 05, 2018, 21:04 (2271 days ago) @ David Turell

Out of an original jumble of cells organs take shape and form guided by physical shapes and forces:

https://phys.org/news/2018-09-uncover-tissues-sculpted-embryogenesis.html

"'In a nutshell, we discovered a fundamental physical mechanism that cells use to mold embryonic tissues into their functional 3-D shapes," said Campàs, a professor of mechanical engineering in UCSB's College of Engineering who holds the Duncan & Suzanne Mellichamp Chair in Systems Biology.

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"Cells coordinate by exchanging biochemical signals, but they also hold to and push on each other to build the body structures we need to live, such as the eyes, lungs and heart. And, as it turns out, sculpting the embryo is not far from glass molding or 3-D printing. In their new work,"A fluid-to-solid jamming transition underlies vertebrate body axis elongation," published in the journal Nature, Campàs and colleagues reveal that cell collectives switch from fluid to solid states in a controlled manner to build the vertebrate embryo, in a way similar to how we mold glass into vases or 3-D print our favorite items. Or, if you like, we 3-D print ourselves, from the inside.

"Most objects begin as fluids. From metallic structures to gelatin desserts, their shape is made by pouring the molten original materials into molds, then cooling them to get the solid objects we use. As in a Chihuly glass sculpture, made by carefully melting portions of glass to slowly reshape it into life, cells in certain regions of the embryo are more active and 'melt' the tissue into a fluid state that can be restructured. Once done, cells 'cool down' to settle the tissue shape, Campàs explained.

"'The transition from fluid to solid tissue states that we observed is known in physics as 'jamming'," Campàs said. "Jamming transitions are a very general phenomena that happens when particles in disordered systems, such as foams, emulsions or glasses, are forced together or cooled down."

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"Zebrafish, like other vertebrates, start off from a largely shapeless bunch of cells and need to transform the body into an elongated shape, with the head at one end and tail at the other," Campàs said. The physical reorganization of the cells behind this process had always been something of a mystery. Surprisingly, researchers found that the cell collectives making the tissue were physically like a foam (yes, as in beer froth) that jammed during development to 'freeze' the tissue architecture and set its shape.

"These observations confirm a remarkable intuition made by Victorian-era Scottish mathematician D'Arcy Thompson 100 years ago in his seminal work "On Growth and Form."
"He was convinced that some of the physical mechanisms that give shapes to inert materials were also at play to shape living organisms. Remarkably, he compared groups of cells to foams and even the shaping of cells and tissues to glassblowing," Campàs said. A century ago, there were no instruments that could directly test the ideas Thompson proposed, Campàs added, though Thompson's work continues to be cited to this day."

Comment: Getting to fertilized egg to whole new organism requires major planned processes which are all coordinated in achieving the new whole one. There is no way a Darwin process could have developed this process. It is totally unexplained from an evolutionary standpoint. It had to be designed from the beginning.