Cell to cell association in Zajdela ascitic hepatoma. An ultrastructural study.

Zajdela ascitic hepatoma cells exist as small islands of two or more cells in addition to single cells. It is now shown that the number of cells per island is directly proportional to the age of the tumor. The number of single cells is maximal 24 h after transplantation of the tumor. Various types of inter-cellular connections are seen between adjacent cells in the island. These junctions are predominant in the apical regions of the cells. The electron-dense material present at junctional sites disappears from several sites after treatment of the islands with chelating agents such as EDTA, EGTA and citrate; the latter being most effective. No appreciable effect on the removal of electron-dense material from the junctional sites is observed when the islands are treated with either collagenase or trypsin.