Fig. 3. Electron micrographs of melanocyte-keratinocyte co-cultures and human skin in vivo demonstrate melanosomes within filopodia. Electron micrographs of co-cultures of melanocyte and keratinocytes revealed numerous long thin projections arising from melanocyte (MC) dendrites (a,b), most of which were cut in cross section (arrowhead; c,d). A longitudinal section of a filopodia is shown in (b). Occasionally we detected osmophilic structures consistent with melanosomes within cross sections of filopodia (c,d). Melanosomes were aligned along the base of filopodia (e) and were present along the length of areas of contact between melanocytes and keratinocyte (KC; f). In human skin in vivo thin structures arising from melanocyte dendrites (MD), consistent with filopodia (fp), were easily identified (g,h) (arrows), many of which contained melanosomes (^*). Figures (i,j) show enlarged images from the boxed area of parts (g,h), respectively. The arrows show the presence of melanosomes within filopodia. Magnification x5000 (a); x40,000 (b-d); x17,000 (e); x15,000 (f), x4000 (g,h).