An electron microscopy study of the effects on dibutyryl cyclic AMP on Chinese hamster ovary cells

The effect of reverse transformation agents (dibutyryl 3′:5′ cyclic adenosine monophosphate plus synergizing compounds like testosterone) on Chinese Hamster Ovary cells has been studied by scanning and transmission electron microscopy, under conditions of low and high cell density. The disappearance of the cell surface knobs or blebs and the cell elongation previously described by light microscopy are even more striking under the higher resolving power of electron microscopy. The cell elongation is accompanied by and appears to be due to an increase in number of microtubules per unit volume of cytoplasm, and a change in their distribution from a random arrangement to an orderly alignment in parallel to each other and to the long axis of the cell. Increasing cell density, and therefore number of cell contacts in untreated cultures, causes the morphology to change in the direction to be expected if the cellular concentration of cyclic AMP is increased. Ultrastructural details of the cells in the various conditions studied are presented.