HISTOGENESIS OF MELANOCYTES

[摘要] Morphologic, histochemical, ultrastructural and embryologic parallels between melanocytes and mast cells have been presented which suggest that melanocytes and mast cells have a common connective tissue stem cell, and that under some circumstances mast cells represent a transitional phase in the development of melanocytes. The principal morphologic findings include: The presence of cells containing both mast granules and melanin granules, in many pathological sections. The structural relationship of mast cells to nevus cell islands. The association and similarity in appearance of mast cells and pigment-containing cells in many pathological sections. The ultrastructural similarity between mast cell granules and nevus cell granules, and the presence within mast cell granules of electron dense particles arranged along linear striations, closely resembling the pattern of early melan-ization of nevus cell granules. The principal histochemical findings include: The capability of mast cells to produce dopa melanin. The demonstration of peroxidase activity in mast cells, nevus cells and mealno-cytes. The demonstration of tyrosinase positive cells in the upper dermis in a case of urticaria pigmentosa. Embryologic studies of others are cited which indicate that the connective tissue of the dermis may be of neural crest origin. A possible biochemical basis for the transformation of mast granules into melanin granules had been proposed; that melanin precursors may polymerize by forming salt linkages with electronegative sulfate radicals on acid mucopolysaccharides present in mast cell granules.