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Ionic Conductance

alex taylor ataylor at superior.carleton.ca
Tue Nov 15 16:47:31 EST 1994

In article <3a3gq4$nk at portal.gmu.edu>,
Harry Erwin <herwin at science.gmu.edu> wrote:
>I believe it was Peter Mitchell who worked out the mechanism of
>oxidative phosphorylation. It involves a proton conductance through a
>membrane, which overcomes the problems with the charge on the proton.
>The reason I bring this up is that there is a problem with neural
>spines--the spine neck is quite narrow, and does not allow ionic flow
>between the spine and the dendrite. 
>However, my taking a course from Harold Morowitz on metabolism begins to
>provide some insight here. He keeps emphasizing the importance of static
>cell structure to how the cell operates. (He's taken metazoans down
>nearly to absolute zero and then revived them--which you could not do if
>persistent dynamics were necessary to life.) The problem with the spine
>neck would go away if there were some sort of biological structure that
>supported the necessary ion flow. I.e., ion wires through the neck...

Actually, it would be very difficult to demonstrate that any sort of
conductance was occurring through the neck of the spine. However, ions
can flow through some rather small spaces, and certainly it has been
shown that certain dendrites have ion channels on them or associated
with them. It would be my bet that in fact the spines would be either
conductive or associated with cconducting structures.

>Has anyone looked to see if microtubules supported ionic conductance?
>That would also start to provide some insight into their role in the
>protistan neuroskeleton. Based on structure, they might even function as
>some sort of coaxial cable.

No. And it is highly unlikely from a physical standpoint alone. The
capacitance and resistive problems would be enormous. 

Alex Taylor

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