Fig. 1. Characteristics of wild-type and uw-mutant primary murine melanocytes in culture. (A,B) Phase contrast photomicrographs of wild-type and uw-mutant melanocytes. (C,D) Bright-field microphotographs emphasizing the pigmentation of wild-type and uw-mutant melanocytes. (E,F) Bright-field microphotographs showing the pigmented vesicles secreted by uw-mutant melanocytes into the medium (arrows) and their absence in the medium of wild-type melanocytes. All photomicrographs are shown at the same magnification. (G) Media were collected from wild-type and from uw-mutant melanocytes, and were centrifuged to show the similar appearance of those samples (i.e. no soluble melanin was present). (H) Pigmented vesicles released into the medium by uw-mutant melanocytes can be readily sedimented by centrifugation, a process not seen in wild-type melanocytes. (I) Melanin content of extracts of wild-type and uw-mutant melanocytes.