The demonstration of polypeptide hormone-secreting cells in the gastrointestinal tract.
D000447:Aldehydes; D001679:Biogenic Amines / Q000032:analysis; D004064:Digestive System / Q000166:cytology*; D005453:Fluorescence; D005612:Freeze Drying; D005768:Gastrointestinal Hormones / Q000378:metabolism*; D006651:Histocytochemistry; D008854:Microscopy, Electron
D000447:Aldehydes; D001679:Biogenic Amines; D005768:Gastrointestinal Hormones