E l ec t ron microscopy f i r s t r evea led the presence of filamentous structures intermediate in diameter between microfilaments (5-6 nm) and microtubules (20-25 nm) in eukaryotic cells. These intermediate, or 10-nm, filaments have subsequently been shown to compr ise f ive s e p a r a t e classes, distinguishable on the basis of their sub-unit molecular weights) t i ssue distr ibution~ and ...
