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Brain Soup

By Shlomo Maital

Suzana Herculano-Houzel

How do you count the number of neurons (brain cells) in a brain (whether human or animal)?   Dr. Suzana Herculano-Houzel, Vanderbilt University, has found a creative way.

   Previously, the method was to take samples of brain tissue, freeze it, put it under a microscope and count neurons. But this was inaccurate, because neuron density in brains varies widely, depending on the place within the brain.   Using this method we thought the brain had 100 billion neurons. That’s not a lot – elephants have three times more!

   Herculano-Houzel read an old 1970’s study, suggesting, why not measure the amount of DNA in a brain, then divide by the amount of DNA per neuron?   Hmmm… problem is, DNA per neuron varies widely.

   So she developed a new, creative method.   Take a brain.   Puree it using a blender. (Honest!).   Brain soup, she calls it.   Mark the neurons with a chemical dye, then mark again with a red dye to mark the nucleus of the neurons. Neurons have only one nucleus, like all cells. So if you count the neuron nucleuses, you can compute how many neurons there are in the brain.

   Answer?   86 billion.   Or, 14% fewer than we thought (100 b.).

   So why are humans so smart? The key part of the brain, that makes us smart, is the cerebral cortex, that wrinkled outer part of the brain. Because it is wrinkled, it has a lot of surface area, enabling more neurons to pack it.   Turns out we have 16 b. neurons in the cerebral cortex, while orangutans and gorillas have 9 billion, and chimps have 6 billion. (Those are respectable numbers – those primates are clever!).

     And those 16 b. neurons in the cerebral cortex are waht makes us smart, and it is probably where Dr. Suzana got the idea…   Hey, why did no-one else think of it before?

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Can Down’s Syndrome Help Cure Alzheimer’s?

By Shlomo  Maital   

Down's

About eight years ago, the BBC reported this: 

   Scientists believe they have found a possible cause for mental impairment in Down’s syndrome.   They have identified a gene that, if over-produced, can cause some brain cells to stop working properly. The next step, say the US researchers in journal Neuron, is to find the mechanism for the process.  This, they say, could ultimately lead to finding a way to “turn down” the gene expression so mental decline might be stopped or even reversed.   People with Down’s syndrome have three copies of chromosome 21, instead of the normal two – this is called trisomy 21.  ….Many people with Down’s syndrome go on to develop dementia, similar to early-onset Alzheimer’s disease, by the age of 40.   In both Down’s syndrome and this form of Alzheimer’s, brain cells, or neurons, responsible for learning, memory and attention, wither and die.    Lead researcher Professor William Mobley, director of the Neuroscience Institute at Stanford University, said: “We’ve been interested in those neurons and why they get sick for some time.”

   Now, reports the BBC, in its excellent Science program,  Down’s syndrome persons are making major contributions to Alzheimer’s research.  Because Down’s syndrome individuals almost all develop the same type of ‘plaque’ dementia that afflicts Alzheimer’s sufferers, potential preventive drugs can be tested on Down’s syndrome persons well before they are 40, to see which drug actually works as a preventative, and whether such drugs really do prevent  the brain’s neurons from being gummed up by protein.

    It would be truly wonderful, if the Down’s syndrome persons willing to help scientists research Alzheimer’s  really do help find a drug that acts as a preventative.  Perhaps one day,  just as many of us take 75 mg. of aspirin daily as a stroke preventive,  we will take 75 mg. of a preventive drug daily– and the scourge of Alzheimer’s dementia will be defeated.     Once the protein plaque has taken hold, little can be done.  But clearly the direction for battling Alzheimer’s lies in preventing or forestalling it.   Let’s hope. 

     Thanks, Down’s people.  We love you.

Blog entries written by Prof. Shlomo Maital

Shlomo Maital
September 2019
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