
The Excitable Mitochondria - mrkgnao
http://inference-review.com/article/the-excitable-mitochondria
======
undersuit
When Hewitt started wrapping up his musings near the end I got one of those
moments of clarity.

I love the fairy wasps, just an ingenious technique they employ to be so
small. I wrote a paper about them and xenophyophores in my 200-level Biology
class. Fairy wasps discard many of their cellular machinery to maintain their
small size, xenophyophores have massive redundancy of organelles and nuclei to
service their absolutely massive size for a single celled organism. I am
fascinated by these techniques and I made comparisons to techniques we perform
in Computer Science like compiling, parallel processing, and forking.

Now I discover from this article's sources that we mammals possess organelle
movement that brings us closer to Multinucleate fungi. The description of the
use of mitochondria by white blood cells was also fascinating.

Still only understand like 20% of this article, but I'm damn interested.

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Symmetry
I suppose sharing of mitochondria would explain why the number of glial cells
corresponds linearly to brain volume rather than scaling with the number of
neurons. When you think about it extremely long cells like neurons do have a
problem with control and intra-cellular tranfer of organelles would solve a
lot of problems. I'm not at all sure about other aspects of that article but
it's in the nature of man to be mistaken about some things while they are
correct about others.

I've also been surprised to read about genetic differences between brain cells
recently that are as large as the genetic differences between immune cells and
far larger than the normal sort of somatic mosaicism you get by typical errors
copying that you see in other organs.

~~~
spqr0a1
It's essential to the growth pattern of dendrites that neurons are able to
recognize and avoid themselves. There's evidence that alternative splicing
(the genetic differences you mentioned) arose in cadherins before even the
immune system. Basically alternative splicing provides each neuron with a
random key that has a ~1/30,000 chance of collision.

~~~
Symmetry
This gets encoded into some sort of external marker I assume?

~~~
spqr0a1
Yup, cadherins are transmembrane proteins and the variable domains are exposed
on the external surface.

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tudorw
Mitochondria are fascinating, and it seems probably very very old too! Nick
Lane ([http://www.nick-lane.net/](http://www.nick-lane.net/)) writes a lot
about the subject in;

[https://www.amazon.co.uk/Power-Sex-Suicide-Mitochondria-
mean...](https://www.amazon.co.uk/Power-Sex-Suicide-Mitochondria-
meaning/dp/0199205647)

[https://www.amazon.co.uk/Vital-Question-Why-life-
way/dp/1781...](https://www.amazon.co.uk/Vital-Question-Why-life-
way/dp/1781250367)

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jayajay
The introduction is rather lengthy, if you're looking to skip to the part
regarding mitochondria:

"The Brain is What, Exactly?" section starts a bit before halfway scroll.

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artifaxx
Wow, if mitochondria need to be modeled in that level of detail for accurate
simulations of neurons that could be problematic. Exaflops of computational
power were already the estimate just for simulating the neurons/synapses of a
human brain[0], and this would increase that computational requirement orders
of magnitude I imagine. Still quite fascinating.
[0][http://www.riken.jp/en/pr/press/2013/20130802_1/](http://www.riken.jp/en/pr/press/2013/20130802_1/)

~~~
omgtehlion
Relax. No one simulates hardware down to separate electrons, the same thing
applies here, I suppose.

We just need to find and agree on enough high-level representation and proceed
with it.

P.S. that electronics CAD analogy the author used is really confusing and
incorrect.

~~~
ChuckMcM
Its more the difference between a cycle accurate system simulator and a
functionally accurate system simulator.

Understanding the additional input from the mitochondria however might help
with building more accurate FMRI type systems.

~~~
artifaxx
That is a good distinction to make, but if we don't know exactly what the
cycle is things get harder to figure out. Neurons hold state and we aren't
sure how much yet, let alone a deterministic method of computing it.
[https://www.scientificamerican.com/article/new-estimate-
boos...](https://www.scientificamerican.com/article/new-estimate-boosts-the-
human-brain-s-memory-capacity-10-fold/)

------
rudolf0
I don't know enough about neuroscience to determine if this is a possible
genius revelation or quackery or somewhere in between. Any scientists willing
to comment?

~~~
abecedarius
I'm in the same position as you, but I checked one especially interesting
claim near the beginning: "We know that organelles, such as mitochondria, are
transferred from neuron to neuron. This presents a challenge to any doctrine
based on discrete parts." This is supported by a ref to a paper on
mitochondria being transferred from neurons to glia for autophagy, i.e.
disposal. This makes the original sentence seem misleading to me, or at least
lazy about finding a reference to similar transfers that are more functionally
central. This makes me less interested in understanding the rest of the
article.

~~~
Noseshine
I did a quick search and found this:
[http://physiologyonline.physiology.org/content/28/6/414](http://physiologyonline.physiology.org/content/28/6/414)

    
    
      > First, in vitro intercellular organelle transfer has been described in a highly diverse 
      > assortment of cell types, including human and rodent, differentiated and multipotent, 
      > malignant and benign, epithelial and mesenchymal, and neuronal. Thus it is safe to 
      > conclude that the capability of one cell to donate or receive an organelle from another 
      > cell is clearly widespread throughout mammalian cell types in culture.
    

Stressed cells being rescued from apoptosis by organelle transfer through
tunneling nanotubes (TNTs):

[http://www.nature.com/cdd/journal/v22/n7/full/cdd2014211a.ht...](http://www.nature.com/cdd/journal/v22/n7/full/cdd2014211a.html)

    
    
      > Further studies demonstrated that microtubule-containing TNTs were formed by stressed cells, 
      > which had lost cytochrome c but did not enter into the execution phase of apoptosis 
      > characterized by caspase-3 activation. Moreover, mitochondria colocalized with microtubules in 
      > TNTs and transited along these structures from healthy to stressed cells.
    

[http://www.the-
scientist.com/?articles.view/articleNo/43835/...](http://www.the-
scientist.com/?articles.view/articleNo/43835/title/Mitochondria-Exchange/)

~~~
johnhewitt123
Thanks Noseshine for your supporting links. No need for imagination, it's all
very well documented. Some of the recent studies of transfer to and from
healthy neurons have been weakly critiqued earlier this year, while others,
for example showing that mitochondrial transfer through the formation of
syncytial networks is ESSENTIAL for the survival of glioblastoma in the brain
seem fairly indisputable.

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UhUhUhUh
Thanks so much for posting this. I've always been partial to mitochondria but
that takes the cake. It's going to take me a while to digest.

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peter303
Related to mitchlorians which power The Force?

