Influence of Sex Hormones and Desoxycorticosterone on Melanophore Differentiation in Birds

Recently, it was found that explants of skin ectoderm from embryos of New Hampshire Red fowl occasionally yielded black melanophores, but red ones differentiated rarely, and a majority of the cultures were entirely negative. Since an examination of regenerating feathers from the adult (in which the plumage is predominantly red) showed that there was an abundance of red melanophores, it seemed desirable to find out what factors influence the differentiation of these pigment cells. The purpose of this report is to summarize some of the results which have been obtained by using sex hormones and a hormone of the adrenal cortex.∗

In these experiments, a piece of skin was removed from the dorsal midline of a 6-day chick embryo (New Hampshire Red or Rhode Island Red) and divided into bilateral halves. One of these was explanted into a clot made up of embryonic extract mixed with plasma containing the sex hormone, and a control culture was made of the other half. Crystalline hormones were shaken up in blood plasma. Sesame oil, olive oil, and hormones dissolved in them were emulsified with plasma. Concentrations of hormones ranged from 20 to 300 γ per cc.

Red melanophores differentiated in cultures treated with sex hormones within 24 to 48 hours, and were similar to those in the regenerating feathers of adult birds. They were slightly smaller than black melanophores, and contained sub-spherical, orange-red granules which partially dissolved in alcohol or xylol after the cells were fixed. The rapid, almost vibratory, movement of these granules within the living cell indicated that the cytoplasm must be extremely fluid. Black melanophores contained dark-brown or black, rod-shaped granules which moved very slowly in living cells and were insoluble in alcohol and xylol.