An autoradiographic study of the origin of intestinal blastemal cells in the newt, Notophthalmus viridescens.

Fifty adult newts were used in this investigation; in 44 animals, the intestine was transected perpendicular to its longitudinal axis approximately midway between pylorus and rectum. The free ends of the intestine were held in apposition with a single suture and replaced into the coelom. The animals were injected intraperitoneally with ³H]thymidine from 0 to 35 days after transection of the intestine and killed 6 hr later. In nontransected, control intestines, the only tissue that incorporated ³H]thymidine was the mucosal epithelium. In transected intestines, only the mucosal epithelium labeled in animals which had been injected with ³H]thymidine from 0 to 4 days after the intestine was incised. Later on, serosal cells and smooth muscle cells of the intestinal stump underwent morphological alteration, initiated the incorporation of ³H]thymidine into DNA, and began replication. At 6 days after transection, serosal cells adjacent to the plane of transection were incorporating ³H]thymidine and, at 12 days, smooth muscle cells at the transected surface were labeling. It seems probable that they both furnished cells to the intestinal blastema; the lining epithelium of the mucosa, however, did not appear to contribute to the blastema proper.