Cross Section of a Fly Intestine (IMAGE) Buck Institute for Research on Aging Caption This is a cross section through a fly intestine depicting intestinal stem cells in green and enterocytes, functional gut cells, in red with large blue nuclei. Left: Under normal conditions, stem cells are distributed throughout the basal side of the epithelium and can be activated to regenerate enterocytes. Upon constitutive elevation of cytosolic Ca2+, intestinal stem cells become rapidly activated and can regenerate enterocytes. Right: Shown here is a condition in which Ca2+ was strongly and chronically elevated, resulting in excessive stem cell proliferation and causing tumors. Credit Akos Gerencser, PhD, Buck Institute Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.