Samples of the sorted cells are concentrated on glass slides by cytocentrifugation, fixed in 2.5% paraformaldehyde for 10 mins, and then immunofluorescence stained for human glucagon (Sigma, Cat. #G2654), insulin (Dako, Cat. #A0564), Somatostatin (SST, ZYMED, Cat. #18-0078) and ghrelin (Abcam, Cat. #ab209790) to confirm purity. Secondary antibodies conjugated with Dylight-dyes (Jackson ImmunoResearch) are used for fluorescence detection. Digital images of fluorescence-labeled cells are acquired using a Zeiss fluorescence axial microscope attached with a digital camera or with a Zeiss LSM410 confocal laser-scanning microscope.