Distribution of sulphydryl groups and disulphide linkages in tissue proteins of quail uropygial glands.

1. The distribution of sulphydryl (-SH) groups and disulphide (S-S) linkages in the tissue proteins of quail uropygial glands was histochemically observed by a staining method using N-[7-dimethylamino-4-methyl-3-coumarinyl]maleimide. 2. In the uropygial gland, the -SH groups of the tissue proteins of glandular cells displayed a progressive change to S-S linkages concomitant with the shift from the transitional cell layer to the degenerating cell layer, suggesting that cell destruction was occurring with the products being released as secretions. This phenomenon was apparently more pronounced in the deep compared with the shallow portion of secretory tubules. 3. The above results indicated that a mechanism similar to epidermal differentiation operates in the process of holocrine secretion in the uropygial gland.