Robert O. Becker Quote

However, the morphogenetic field no longer has to account for every-thing. Acceptance of dedifferentiation lets us divide regrowth into two phases and better understand each. The first phase begins with the cleanup of wound debris by phagocytes (the scavenger race of white blood cells) and culminates in dedifferentiation of tissue to form a blastema. Redifferentiation and orderly growth of the needed part constitute the second phase. Simplifying the problem in this way should give biologists an immediate sense of accomplishment, for the first stage is now well under-stood. After phagocytosis, while the other tissues are dying back a short distance behind the amputation line, the epidermal cells divide and mi-grate over the end of the stump. Then, as this epidermis thickens into an apical cap, nerve fibers grow outward and subdivide to form individual synapselike connections the neuroepidermal junction (NEJ) - with the cap cells. This connection transmits or generates a simple but highly specific electrical signal in regenerating animals: a few hundred nanoamperes of direct current, initially positive, then changing in the course of a few days to negative.