Histofluorescence of monoamines in newt forelimb regenerates

Newt forelimb regenerates were studied at various stages of development using the histofluorescent method of Falck and Hillarp. A green formaldehyde-induced fluorescence was found in nerve fibres, large dendritic cells, skin gland cells and skin gland cell secretions. To ascertain the nature of the fluorescent material, animals were submitted to treatments with L-dopa, nialamide, benserazide and reserpine, used separately or in combination and administered before cutting off the regenerates. The modifications of the fluorescence after the various treatments confirmed the monoaminic nature of the fluorophores. Catecholaminic fibres were numerous in tissues of fast-growing stages while in dedifferentiated cell areas as well as in prochondral cell condensations and in cartilage they were completely absent. Fluorescent dendritic cells that have never been described before in regenerating limbs were observed and, from their localisation and cytological appearance, classed as promelanophores (or melanoblasts).