Ultrastructural and biological observations on neoplastic growth control obtained by contact inhibition.

Friend erythroleukaemia and HeLa cells grown in suspension were artificially kept in close contact by centrifugation in capillary tubes for short periods. This treatment induced evident inhibition of the growth rate in both cell lines and a parallel decrease of labeled nucleotide incorporation. Electron microscopy showed extensive close contact of the plasma membranes in Friend erythroleukaemia cells, and the appearance of junctional complexes between HeLa cells.