CONTRACTILITY AND ULTRASTRUCTURE OF GLYCEROL-EXTRACTED FIBROBLASTS IN TISSUE CULTURE

Chick heart fibroblasts outgrown from heart explants of nine-day embryos were glycerol-extracted for 1/2 hour, 1 and 12 days. (d-)filaments with a diameter of 60-80 å existing everywhere in the cytoplasma and in addition finer (f-)filaments with a diameter of 20-30 å in the cortical layer of the cells withstand the extraction. Occasionally some d-filaments have divided into subfilaments with a diameter of 20-30 å. Contraction induced by ATP results in a rounding up of the fibroblast. An electron dense material is found in a shell-like arrangement around the condensed cell. This material consists of d- and f-filaments just like the cortical layer of unextracted cells. The ATP-induced electron dense material and the cortical layer are supposed to be the contracted and the d-filaments dispersed in the cytoplasma the relaxed state of an intracellular contractile system. © 1969 Springer-Verlag.