Different distribution of pattern of 100-Å filaments in resting and locomotive leukaemia cells

Abstract

Two types of filaments have been described in the cytoplasm of non-muscular cells—microfilaments (40–70 Å in diameter) and 100-Å filaments (90–110 Å). Microfilaments have been found in almost every type of animal cell¹, and they are known to be actin-like² and believed to have a role in many contractile processes^1,3. In contrast, the 100- Å filaments have been observed only in a limited number of cell types, such as tissue culture cells^2,4, smooth⁵ and skeletal⁶ muscle cells, nerve cells^7,8 and tumour cells^9,10, and are thought not to be actin-like^2,3,10,11. The function of 100- Å filaments is not clear although they have been suggested to act in the intracellular transport of organelles in fibroblasts⁴, the axoplasmatic transport in nerve cells^12,13 and the spreading of cells³, or to serve as a cytoskeleton¹⁴. Induction of 100-Å filaments by colcemide⁶ and cytochalasin B and colcemide^15,16 has also been demonstrated. A clue to their function may lie in the demonstration, reported here, that the distribution of the 100-Å filaments differs in resting and locomotive cells.