Morphologic Changes in Salivary-Gland Tissue of the Newborn Mouse Exposed to Parotid-Tumor Agent In Vitro2

Abstract

Salivary-gland tissue of newborn C3Hf/BiLw mice was excised and exposed to parotid-tumor agent (polyoma virus) before transferral to tissue cultures. The cultures were examined microscopically at intervals from 5 to 48 days after explantation. Control cultures were prepared and examined in the same way, without exposure to the agent. In both the test and control cultures at 5 and 12 days there was atrophy and necrosis within the explants with no significant difference between the exposed and unexposed tissues. From the 19th day onward, differences between the exposed and unexposed cultures were consistently evident. Salivary-gland epithelium in the test cultures developed characteristics very similar to those of salivary tumor cells in vivo. There was active proliferation with filling of the glandular lumens by altered cells. Solid cords of cells extended from the glands and reproduced the patterns of the analogous tumors in vivo. The mitotic index was higher in the test cultures than in the controls. Cytologic changes characteristic of salivary tumors in vivo also were noted in the exposed cultures. Nuclei were enlarged, nucleoli more prominent, and intranuclear, clear spaces were often present, sometimes surrounding a large, amphophilic body. The cytolytic effect of the agent was apparent in vitro as in vivo. It is concluded that the parotid-tumor agent acts on the salivary-gland epithelium, without intermediation of other organs, to produce morphologic changes similar to those seen in vivo.