Fig. 3.

Testing hypothesis of progenitors in normal neonatal development. (A) CAII starts being expressed at embryonic day 18.5. To test whether neogenesis occurs after birth, double-Tg mice were killed at 4 weeks of age after the expected waves of neogenesis (immediately after birth and around weaning). (B and C) At 4 weeks of age, some islets have costaining of β-galactosidase (green) and insulin (B), or glucagon (C) in red. Double-positive cells are shown as yellow in merged panels. (D) At 4 weeks of age, marked (β-galactosidase-positive) acinar cells are found as single scattered cells or in clusters localized to a lobe, suggesting new lobe formation since birth. (E) Quantification of positive islets/total islets, with each circle representing a single animal. At 4 weeks β-galactosidase⁺ insulin-positive cells were 16.7% ± 3.0% of all insulin-positive cells (mean: 345/2,268 insulin-positive cells per animal; 8 animals). (Scale bar, 50 μm.)