Fig. 1. Occurrence of prominin-1-containing particles in the ventricular fluid of the embryonic mouse brain. Double immunofluorescence of a cryosection (20 µm) of an E11.5 mouse embryo using mAb 13A4 (b,d,f, red) and antiserum E3 (a,c,f, green) directed against distinct extracellular epitopes of prominin-1. Single 5-µm optical sections of the midbrain were obtained by confocal microscopy in the middle of the cryosection (a,b) and at the level of the glass slide (c,d,f), as outlined in e. (f) Merged images of the area indicated by the white squares in c and d; note the co-localisation of the 13A4 and E3 immunoreactivities. Inset in f is a higher magnification of the particle indicated by the arrowhead in f. Bars, 10 µm.