The Nardi-Stocum Phenomenon of Limb Regeneration.Nardi, James B., and David L. Stocum (1984). Surface properties of regenerating limb cells: Evidence for gradation along the proximodistal axis. Differentiation 25: 27-31. doi.org/10.1111/j.1432-0436.1984.tb01334.x
Displacement of grafted limb tissue along its proximo-distal axis
When elbow cells get grafted to the hand (or to the shoulder) the grafted cells somehow move back to the elbow position.
Also: Hand cells get engulfed by elbow cells,
elbow cells get engulfed by shoulder cells. etc.
Retinoic acid causes big changes in behaviors of embryonic tissues:
"Retinoic acid coordinately proximalizes regenerate patterns and blastema
differential affinity in axolotl limbs":
"Use of retinoids to analyze the cellular basis of positionl memory in regenerating amphibian limbs"
What is wrong with the following argument?
When Nardi writes "differential affinity", he means cell rearrangement behavior, partly because he regards Steinberg's thermodynamic theory as being proven fact, but also to avoid alternatives like: "That business with the bunches of cells engulfing each other."
The less people understand about thermodynamics, the less they doubt such theories.
All cases where cells gravitate back toward their original spatial arrangement, especially when the same end results can be reached by 2 or 3 or more pathways, get interpreted by many as thermodynamic minimization of free energy.
An alternative explanation is homeostasis by negative feedback cycles.