ULTIMATE COMPUTING - Quantum Consciousness Studies

122 Cytoskeleton/Cytocomputer
Aristotle, Wolff noted that the chick started as “globules” or cells that seemed to
have no functional (relation to one another. With time, distinct groups of cells
emerged to form the structures that become the hen’s principle organs. Further
evidence against the preformation theory came in 1900, when Hans Adolf Driesch
demonstrated that a sea urchin embryo, when cut in half, develops into two
complete embryos (Burnside, 1974).
Aristotle’s epigenesis theory of differentiation states that homogeneous
spheres begin to divide, yielding more spheres which themselves divide. The
“cells” begin to exhibit differences in structure and function and a “collective
coherence.” Each cell knows where to go, when to go there, which cells to
congregate with, and how to work cooperatively. Excluding the possibility that a
transcendental intelligence personally oversees the development of each
organism, the conclusion is that the original cell contains enough information to
orchestrate the entire process. Aristotle would probably be even more amazed to
discover that during early embryological development each cell is totipotential: it
can take on the role of any tissue in the body. We now know that the
chromosomal DNA in each cell contains all genetic information. We are
beginning to understand how specific genes are turned on and off. Cells appear to
take on the role of their environment due to morphological “trophic” influence
conveyed by cytoskeletal axoplasmic transport within their “innervating” nerve
cells.
Much of the mystery of biological form and differentation thus focuses on the
growth, pathfinding and trophic capabilities of embryological neurons. The form,
architecture, and connections which nerve processes make not only establish
tissue and body shape, but synaptic connections and brain “hardware.”
How do neuronal processes know where and when to send their processes and
establish connections The mystery has been likened to the “Indian rope trick”
fable in which a “fakir” tosses a rope into the air where it mysteriously stays rigid.
He then climbs up the rope, pulls the lower portion up, and disappears! The
embryological Indian rope trick depends on neuronal shape and orientation: the
number of young axons and dendrites (“neurites”) which arise from the cell body,
their direction, degree of branching, how far they grow, and where and how they
form synapses. All these factors are manifested by the cytoskeleton. The
centriole/MTOC establishes cell polarity and orientation and presumably
“launches” the extending processes. The tips of lengthening neurites are
specialized areas of cytoplasm called “growth cones” which not only grow
outward, but participate in decisions about direction, branching, and termination
of extension. Growth cones can sense changes in local environment and, acting in
concert with other cytoskeletal elements within the neurite, shift direction, branch,
or form synapses. Growth cone activities are remarkably similar to movement in
amoeba and other simple organisms. They continually probe their surroundings
by sending out and then retracting delicate ruffles known as lamellipodia, and
finger-like projections called filopodia or microspikes. These dynamic microappendages
are comprised of meshworks and parallel arrays of actin filaments.
MT and neurofilaments from the neurites splay into the growth cones, but
generally stop short of the actin-rich areas (Bunge, 1986).
The roles of MT and actin in axonal extension have been studied by Yamada,
Spooner and Wessells (1970). Addition of cytochalasin B, which is known to alter
actin filaments, blocks neurite outgrowth if added before extension has begun.
Treatment of extending axons with cytochalasin B results in cessation of the
“ruffling” activity of the growth cone with little immediate effect on the neurite
shaft. In contrast, antimicrotubule agents such as colchicine leave growth cone
activity unaffected but block neurite extension. Continued exposure results in