Control Systems in the Living World - Building the Most Complex Structure on Earth - page 40

microtubule network and distribution of MAPs in the structure. The system displays
some elementary learning and implies a sort of memory. The adaptive information
processing needs to be experimentally verified, but the authors conclude that “[t]he
fine structure of the cell is a natural medium for adaptive information processing”
( Pfaffmann and Conrad, 2000 ).
In addition to its role in determining the shape and movements of the cell and the
positioning of organelles within that cell, trafficking of vesicles and stimuli through-
out the cell and evidence of processes of cell division show that, in mammal cells, the
cytoskeleton is involved in processes of gene expression ( Berfield et al., 1997; Puck
et al., 1990 ). It is hypothesized that in neurons, at least, it is the cytoskeleton that
signals the requirements for protein production to genes (Georgiev, Quantum Mind
Theories; http://www.quantum-mind.co.uk/danko-georgiev-c169.html ). In mammal
cells, the cytoskeleton is in contact with both the extracellular matrix (ECM) and the
nuclear matrix, which acts as a transducer of extracellular signals to the cell nucleus.
Intermediary filaments (IFs) are intimately connected with structural elements of
the nuclear matrix and are an integral part of the nuclear skeleton ( Tolstonog et al.,
2002 ).
In a model of regulation of microtubule networks in the cell, MAPs convey cyto-
plasmic signals to microtubules, which receive signals from the whole network of
fibrous elements of cytoskeleton. MAPs, in turn, receive the output of the processing
of cytoplasmic information from microtubules.
Some ECM molecules are connected to cell microfilaments via actin-associated
proteins, thus forming an integrated system with the intracellular elements of the
cytoskeleton ( Ingber and Folkman, 1989 ).
In response to photostimulation with near-infrared light, some unicellulars extend
pseudopodia to the side of the source of the light. It is argued that the extension can-
not be performed by the cell's production of diffusible chemical signals which would
indiscriminately affect pseudopodia throughout the cell. Hence, microtubules may
relay the signal to the specific pseudopodia. Indeed, it is observed that after adminis-
tration of antimicrotubular substances, the cell loses this ability to adapt by extending
the right pseudopodia, although it can still move ( http://www.basic.northwestern.edu/g-
buehler/nerves.htm ) . Here is the interpretation of the phenomenon by the investigator:
After receiving the light pulses the centrosome destabilizes the radial array of
microtubules which run towards the cell cortex which, in turn, will subsequently
extend special pseudopodia to the light sources. Therefore, it seems that the
observed destabilization is the signal that is propagated along the microtubles like
along “nerves”.
http://www.basic.northwestern.edu/g-buehler/nerves.htm
Based on experimental evidence, Gunter Albrecht-Buehler concluded that the
centrosome is the organelle where the integration of light signals takes place and
where microtubule signals to form pseudopodia originate ( Albrecht-Buehler, 1998 ).
A controversial explanation, and far from experimentally verified, of a control
system has been developed by physicist Roger Penrose and anesthesiologist Stuart