Fibrous structures of human chromosomes observed by scanning electron microscopy.

Human chromosomes and the nucleus from cultured HeLa cells and lymphocytes were observed stereographically by scanning electron microscopy. Specimens were heated in an acetic acid solution after treatment with diluted McIlvain's buffer solution at pH 5.6. The cytoplasmic matrix adhering to the chromosomes was successfully removed, and the chromosomes were observed three-dimensionally in their original position without any significant mechanical distortion. The interphase nucleus was spherical in shape and the nuclear membrane could not be seen on its surface. The chromosome fibres were 25-35 nm in diameter and showed bumpy, looping, tortuous and knotty appearances at high magnification.