The DOPA-reaction was used to identify tyrosinase in the nucleus and cytoplasm of the neural crest melanoblast of Taricha torosa, the California newt. In this urodele there is a nuclear DOPA-positive response during the normal embryonic development from the late blastula stage to the nucleus of the early melanocyte. During the gastrula stages, all nuclei of this newt are DOPA-positive. This positive nuclear response fades away after the formation of the neural crest, save in the melanoblasts. The only cells that give a positive DOPA marking in the cytoplasm are the melanoblasts. This cytoplasmic reaction appears while the melanoblast nucleus still gives a DOPA-positive reaction. Tyrosinase activity, as marked by unlabeled DOPA, has ceased in the fully mature melanocyte. The red nuclei, seen in some of the animals in the maturing melanocyte and adjacent tissues, may be in the hallachrome stage of melanin formation. There is a diffuse distribution of DOPA reactivity in the resting nucleus, and an adherence of the DOPA-marking in the region of the dividing chromosomes in the mitosis of DOPA-positive nuclei of the melanoblast. These observations suggest that tyrosinase may be among the chromosomally bound enzymes of the chromatin space.
Article| November 01 1969
ENZYME LOCALIZATION DURING MELANOGENESIS
Harriet M. McCurdy
From the Department of Biology, University of Victoria, Victoria, B. C., Canada
Received: March 28 1969
Revision Received: June 27 1969
Online ISSN: 1540-8140
Print ISSN: 0021-9525
Copyright © 1969 by The Rockefeller University Press.
Harriet M. McCurdy; ENZYME LOCALIZATION DURING MELANOGENESIS . J Cell Biol 1 November 1969; 43 (2): 220–228. doi: https://doi.org/10.1083/jcb.43.2.220
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