Cytoskeleton
The term cytoskeleton directs the attention to the presence of some
locomotory system in the protoplasm, which has to determine the shape
and motion of cells. The high resolution of electron microscopy made it
possible to get some idea about it (Fig. 2–74 A, B).
image
image
Figure 2–74. Electron micrographs of cytoskeleton. A — cytoskeleton in fibroplasts, obtained after preliminary extracting the non-ionic detergents. The greater part of straight threads forming loose fascicles orientated from left to right are active filaments. The dense net in the middle of preparation is formed chiefly by intermediate filaments (Courtesy of Heuser and Kirschner, 1980) B — cytoskeleton in axon of rat, without preliminary extracting the detergents (Courtesy of S. Tsukita and H. Ishikawa; From Alberts et al., 1986)
It is still unclear whether this fine net of filaments (threads), forming the
cytoskeleton, really exists in the cytoplasm of living cells or it is a result of
aggregation of soluble macromolecules during the process of fixation and
dehydration of preparations. That directs to the idea about the failure of using
such methods of investigation and the possibly great differences between
fixed and in vivo studies of the cells. There is a deep sense in the jocular
answer to the question: what is a biologist? According to the authors of the
joke — biologist is a person, who kills the living thing to study it!