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 A in diameter) and 100-A filaments (90–110 A). 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 processes1,3. In contrast, the 100- A filaments have been observed only in a limited number of cell types, such as tissue culture cells2,4, smooth5 and skeletal6 muscle cells, nerve cells7,8 and tumour cells9,10, and are thought not to be actin-like2,3,10,11. The function of 100- A filaments is not clear although they have been suggested to act in the intracellular transport of organelles in fibroblasts4, the axoplasmatic transport in nerve cells12,13 and the spreading of cells3, or to serve as a cytoskeleton14. Induction of 100-A filaments by colcemide6 and cytochalasin B and colcemide15,16 has also been demonstrated. A clue to their function may lie in the demonstration, reported here, that the distribution of the 100-A filaments differs in resting and locomotive cells.