H. J. Anton, D. Weber, H. Döring
     The restitution of spinal gamglia during tail regeneration in Triturus alpestris.
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In vertebrate's tail regeneration, spinal cord regeneration is precondition for regeneration of the other tissues. In contrast to larval Lampreys, larval Anurans and Lizards, the spinal ganglia are restituted in both, larval and adult urodeles. Very little information on this subject can be found in the literature. Duesberg (2) Raposo (3) and recently Iten and Bryant (4) have published that spinal ganglia regenerate in pairs laterally to the spinal cord. Dinsmore (5) reported that in regenerated tails of Notophthalmus viridescens spinal ganglia have been developed asymmetrically. In the original tail  the last pair of spinal was found ganglia about 600 um anterior to the tail tip. Each further segment contains a pair of ganglia. In the most caudal region the distances between subsequent pairs of spinal ganglia are irregular but become increasingly regular anteriorly. The volume of the spinal ganglia increases in  caudo-cranial direction. – To investigate restitution of the spinal ganglia during tail regeneration, one third of the tail of young postmetamorphic Triturus alpestris (about 17 month after hatching in our laboratory) were amputated. About 30 days after amputation (dpa) no spinal ganglia were found within the regenerated tails. Only a few individual ganglion cells were found. At 70 dpa in all regions of the tail regenerates spinal ganglia were differentiated laterally along the spinal cord outside the neural bow region, shoving no regular segment dependent pattern. Only in the region immediately behind the  amputation level some ganglion cells were found lying between neural bow and spinal cord within the spinal meninges. In advanced stages (90-120 dpa), ganglion cells were found in large numbers and along the entire length of the regenerates. They appeared extensively both above and laterally to the spinal cord and within the roots of the spinal nerves. – Bearing in mind the common embryonic origin in the neural crest of spinal ganglia, Schwann cells and spinal meninges, we conclude from our observations that cells of the regenerating meninges may be the source of the peripheral nerve – and glial cells within the regenerating tail. In early regeneration stages initially, undifferentiated cells may migrate from the meninges to the region where the ganglia will develop in order to differentiate there. Later on, migrating cells may have already differentiated before reaching the assigned area (perhaps as a consequence of progressed differentiation in the periphery). In this way further cells may be prevented  from migrating and may differentiate in their original positions. The Schwann cells of the dorsal and ventral root and of the spinal nerve may also derive from this origin. – In fact this kind of transdifferentiation  would  be a much smaller step than if any of the other tissues, including the ependyma, were to be assumed as origin. – Lit..: 1) Goss R J (1969) Principles of Regeneration, Acad Press NY, London; 2) Duesberg (1922) C R de L’Assoc des Anat 17. 143, 3.) Raposo C R de l’Assoc des Anat 18, 441; 4.) 1t.en L E Bryant S V ( 1976)   3   exp Zool 196,283; 5)Dinsmore C E (1983) Amer soc Zool 23.I