ULTIMATE COMPUTING - Quantum Consciousness Studies

Cytoskeleton/Cytocomputer 105
actin/neurofilament gel (microtrabecular lattice). E. Myelin layers. F. Filamin
bracketing actin. By Paul Jablonka.
5.4 The Cytoplasmic Ground Substance
MT and IF are not the finest texture of cytoplasmic organization. Smaller,
more delicate structures branch and interconnect in “gel” state networks which
comprise the substance of living material.
Three distinct cytoskeletal component systems have been well characterized:
MT, IF and actin filaments. Actin is the most versatile component. In conjunction
with other proteins it can polymerize in string-like filaments, form dynamic
branching nanoscale meshworks or geodesic polyhedrons. Even more evanescent
than labile MT, assembly of actin and associated proteins create transient
configurations of cytoplasm for specific purposes. The roots of intelligence may
well be grounded in dynamic cytoplasmic expressions such as contractile rings
which divide the cytoplasm in cell division, probing lamellipodia, and dendritic
spines and synapses in neurons.
The nature and structure of the “ground floor” of organization, the
cytoplasmic ground substance, has been explored from a number of orientations
resulting in overlapping descriptions. These include the microtrabecular lattice,
cytomatrix, and cytoplasmic solid state.
5.4.1 The Microtrabecular Lattice (MTL)
New techniques in electron microscopy developed by Keith Porter and
colleagues (1981) at the University of Colorado at Boulder have led to
observation of an irregular three dimensional lattice of slender strands throughout
the cytoplasm, interconnecting nearly everything in the cell. The interlinked
filaments appear to suspend the various cell systems, organelles, and larger
cytoskeletal elements such as microtubules and filaments with a matrix material
continuous with the individual lattice filaments. The lattice is suggestive of the
trabecular structure of spongy bone and it was named the microtrabecular lattice
(MTL, Figure 5.19).
Porter and colleagues took advantage of the properties of the high voltage
electron microscope at Boulder. This massive device is capable of accelerating
electrons across a potential drop of a million volts, ten times that of standard
electron microscopes. The extra voltage gives the electrons sufficient energy to
penetrate thick specimens or even intact cells up to several thousand nanometers
thick. Previously, cells had to be sliced into sections thinner than 200 nanometers,
and artifacts due to cell destruction were more prevalent. The high voltage
electron microscope provides more information about depth, giving a three
dimensional view of cell organization. Another innovation, the critical point
drying method (Ellisman, 1981) avoids the distorting effect of surface tension
which causes cells to collapse when they are dried in air. High voltage electron
microscopy and critical point drying have now demonstrated the MTL in all
eukaryotic cells which have been examined.
The MTL is a three dimensional lattice of slender strands called
microtrabeculi. They range in diameter from 4 to 10 nanometers with lengths of
10 to 100 nanometers. The MTL is a finely organized meshwork that divides the
ground substance into two phases, a protein rich polymerized phase comprising
the MTL, and a water rich fluid phase that fills the intratrabecular spaces. At high
magnification, microtrabeculi of the ground substance are seen to crosslink many
elements in the cytoplasm. For example, they connect microtubules with the
smooth endoplasmic reticulum. The MTL not only crosslinks, but appears to be