ULTIMATE COMPUTING - Quantum Consciousness Studies

94 Cytoskeleton/Cytocomputer
Figure 5.9: Microtubules in mitotic PtK2 cell labeled with tyrosine tubulin
immunogold. The spindle pole region (MTOC) at left is a focus for spindle MT
which radiate toward chromosomes (dark material). Insert upper right:
kinetochore MT attaching chromosome. With permission from Geuens,
Gundersen, Nuydens, Cornellisen, Bulinski, DeBrabander (1986).
Between cell division cycles (“interphase”), the MT system is relatively
quiescent and “radial.” Most cell MT are anchored at one end to the MTOC,
although they don’t appear to contact any structures. Rather, MT minus ends are
somehow stabilized by the “pericentriolar material.” This favors MT assembly
and protects against disassembly by binding and capping the minus end of MT.
Most tubulin is polymerized during interphase, however free MT not radiating
from the MTOC occur near the periphery of the cell. Except for free MT, the
network is rather stable with low turnover rates and minimal treadmilling and
dynamic instability.
During “prophase”, the cytoskeleton prepares for the separation of duplicated
chromosomes so the cell can make a copy of itself. DeBrabander (1985):
It appears that nature selected a near fail safe microtubule based mechanism
to allow the eukaryotic cell to handle more and more complex genetic libraries.