Shortly after the discovery of the CFTR gene in 1989 [14], several research groups developed modified Ussing chambers for transepithelial measurements across native tissues from the rectum and other regions of the intestinal mucosa to study the CF ion transport defect in the intestine [15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31]. The gene discussed is CFTR; the disease is cystic fibrosis.