Types of morphogenetic phenomena in vertebrate regenerating systems

Abstract

Within the regenerating amphibian limb the regeneration blastema represents the focus of the dominant epimorphic regenerative process. More proximally, tissue regenerative processes are prominent within certain tissues of the stump. It is not yet known whether all tissues present within the limb regenerate are laid down as part of a single allinclusive plan or whether the morphogenesis of some tissues is dependent upon secondary cues. Initial axial deviation of regenerates arising from oblique amputation surfaces (Barfurth's rule) is compared with the permanent axial deviation of regenerates from zeugopodial segments of limbs from which one skeletal element has been removed. Homeotic regenerates are commonly produced in arthropods, but they have yet to be demonstrated in regenerating vertebrate extremities. Individual tissue components of limbs regenerate well, and their morphogenesis appears to be controlled largely by the functional environment in which the regenerative process is taking place. Under appropriate conditions, terminally amputated mammalian, including human, digits produce well organized outgrowths complete with nails or claws. Whether or not this form of outgrowth is directly comparable with an epimorphically regenerating amphibian limb remains to be seen. © 1978 American Society of Zoologists.