April 05, 2018 Thursday
Bedtime Story
Suzana Herculano-Houzel counts Neurons
The paper by the Brazilian neuroscientist Suzana
Herculano-Houzel titled “The Human Brain in Numbers: A Linearly Scaled-up
Primate Brain” was published in Frontiers of Human Neuroscience on November 09,
2009.
This paper is a fascinating one and it
would require countless nights to cover merely this paper alone, leaving apart
the background knowledge over what it was constructed.
As much as I would like to quote the entire
paper, that would come at a cost of tremendous digression from the Notes of Ada
Lovelace on the Analytical Engine.
Yet I can’t help but quote the concluding
remarks of this paper as Herculano-Houzel brings into the picture a far broader
perspective of evolution in here deviating from the narrow topic of neuroscience.
Herculano-Houzel specializes in counting
neurons (and other supporting cells called glial cells) not only from different
areas of human brains but also from brains of diverse species ranging from dolphins
to the great apes and from rats to opossums.
How would you count the number of neurons
in a brain placed in your hand?
I have held the whole preserved human brain
in my hand and the feeling I got for the first time was beyond description.
I had that singular structure in my hand
that gave that person it once was his or her personality, thoughts, ideas,
dreams and aspirations and yet essentially it was just a lump of 86 billion
neurons or so with similar number of supporting glial cells.
Yet I would not have known how to count the
number of neurons that lump of tissue that I was holding in my hand contains.
Herculano-Houzel’s brain though found a
novel technique that she calls the isotropic fractionators or simple the soup
method.
This technique is easy to master even by
untrained neurobiologist and allows counting number of neuronal cells (and for
that matter even non neuronal ones) of either the whole brain or any specific dissected
brain structure.
Of course, what this method does not allow you is to count the neuronal
cells of a living brain of a living animal.
The first step of this method is to
dissolve the brain tissue of interest in a detergent by mechanical dissociation
such that an isotropic suspension of known volume is obtained.
An isotropic suspension essentially means
that a tiny fraction of the volume taken from any place of the total suspension
is an accurate representative of the whole sample.
The suspension is then stained with
anti-nuclearN antibodies (DAPI = 4’,6-diamidino-2-phenylindole) that gets
linked to the antigens of the nucleus of
only the neurons and counted under the fluorescent microscope using
hemocytometer.
DAPI is a commonly used fluorescent stain
used extensively in fluorescence microscopy in research and clinical labs all
over the world.
Hemocytometer is a thick glass microscopic
slide with rectangular indentation that creates a microscopic chamber.
Stay tuned to the voice of an average story storytelling
chimpanzee or login at http://panarrans.blogspot.com
Good night mon ami and my fellow cousin ape.
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Another great educator and a teacher that I am aware of is
Professor Subhashish Chattopadhyay in Bangalore, India.
While I narrate stories, Professor Subhashish an electronic
engineer and a former professor at BARC, does and teaches real mathematics and
physics.
He started the participation of Indian students at the
International Physics Olympiad.
Do visit him here:
All his books can be downloaded for free through this link:
For edutainment and English education of your children, I
recommend this large collection of Halloween Songs for Kids:
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