ULTIMATE COMPUTING - Quantum Consciousness Studies

Cytoskeleton/Cytocomputer 107
Figure 5.19: Microtrabecular lattice (MTL) in PtK2 cell cytoplasm. Microtubules
can be seen (one rising left to right on bottom) in the background of
microtrabecular lattice (MTL). Two 40 nanometer gold particles are trapped in a
vesicle within the MTL. With permission from DeBrabander (1985).
Ellisman raises the question of the importance of the cytoskeleton and MTL
in the nervous system. One consideration is modulation of membrane related
events such as receptor activity and neurotransmitter extrusion. Ellisman proposes
that the MTL is triggered by calcium ions to release neurotransmitter vesicles. In
addition, the MTL participates in other cytoskeletal functions also involving MT
and filaments. These are axoplasmic transport, turnover and maintenance of
membrane proteins and receptors, and the availability of neurotransmitters and
enzymes at synapses. Ellisman has predicted some of the functions and/or
behavior of the cytoskeleton and MTL within the nervous system. These are: 1)
the MTL is a substrate to maintain cell shape changes including synaptic
formation, and to regulate excitable properties of neurons. One example would be
changes in distribution and volume of dendritic spines and synapses with
implications for synaptic connections and perhaps learning and memory. Thus the
MTL and other cytoskeletal elements can modify synaptic function by
participating in trophic maintenance and turnover of membrane proteins to
modulate membrane excitability and neuronal signaling. 2) The MTL, according
to Ellisman, can also buffer small molecules and ions, maintaining these in
specialized locations and patterns for metabolic and electrical functions. Thus the
MTL may compartmentalize the cell, forming regions whose environments may
vary. Buffering and control of calcium ion flux may be particularly important, and
directly relate to cognitive functions. 3) The MTL can differentiate specific zones
of cytoplasm and membrane, for example controlling the types of receptors or