Harvard neuroscientists have made a discovery that turns 160 years of neuroanatomy on its head.
Myelin, the electrical insulating material in the body long known to be essential for the fast transmission of impulses along the axons of nerve cells, is not as ubiquitous as thought, according to new work led by Professor Paola Arlotta of the Harvard Stem Cell Institute (HSCI) and the University’s Department of Stem Cell and Regenerative Biology, in collaboration with Professor Jeff Lichtman of Harvard’s Department of Molecular and Cellular Biology.
“Myelin is a relatively recent invention during evolution,” says Arlotta. “It’s thought that myelin allowed the brain to communicate really fast to the far reaches of the body, and that it has endowed the brain with the capacity to compute higher-level functions.”
In fact, loss of myelin is a feature in a number of devastating diseases, including multiple sclerosis and schizophrenia.
But the new research shows that despite myelin’s essential roles in the brain, “some of the most evolved, most complex neurons of the nervous system have less myelin than older, more ancestral ones,” said Arlotta, co-director of the HSCI neuroscience program.
What this means, she said, is that the higher one looks in the cerebral cortex — closer to the top of the brain, which is its most evolved part — the less myelin one finds. Not only that, but “neurons in this part of the brain display a brand-new way of positioning myelin along their axons that has not been previously seen. They have ‘intermittent myelin’ with long axon tracts that lack myelin interspersed among myelin-rich segments.”
“Contrary to the common assumptions that neurons use a universal profile of myelin distribution on their axons, the work indicates that different neurons choose to myelinate their axons differently,” Arlotta said. “In classic neurobiology textbooks, myelin is represented on axons as a sequence of myelinated segments separated by very short nodes that lack myelin. This distribution of myelin was tacitly assumed to be always the same, on every neuron, from the beginning to the end of the axon. This new work finds this not to be the case.”
The results of the research by Arlotta and postdoctoral fellow Giulio Srubek Tomassy, the first author on the report, are published in the latest edition of the journal Science.
The paper is accompanied by a “perspective” by R. Douglas Fields of the Eunice Kennedy Shriver National Institute of Child Health and Human Development at the National Institutes of Health, who said that Arlotta and Tomassy’s findings raise important questions about the purpose of myelin, and “are likely to spark new concepts about how information is transmitted and integrated in the brain.”
Arlotta and Tomassy collaborated closely on the new work with postdoctoral fellow Daniel Berger of the Lichtman lab, which generated one of the two massive electron microscopy databases that made the work possible.
“The fact that it is the most evolved neurons, the ones that have expanded dramatically in humans, suggest that what we’re seeing might be the ‘future.’ As neuronal diversity increases and the brain needs to process more and more complex information, neurons change the way they use myelin to achieve more,” said Arlotta.
Tomassy said it is possible that these profiles of myelination “may be giving neurons an opportunity to branch out and ‘talk’ to neighboring neurons.” For example, because axons cannot make synaptic contacts when they are myelinated, one possibility is that these long myelin gaps may be needed to increase neuronal communication and synchronize responses across different neurons. He and Arlotta postulate that the intermittent myelin may be intended to fine-tune the electrical impulses traveling along the axons, in order to allow the emergence of highly complex neuronal behaviors.
“My little boy David loves watching the Fantastic Four films, he especially loves Chris Evans and spends a lot of time playing at being Johnny Storm. (…) He’s got his walls covered with Johnny Storm pictures too and he knows all the lines. We were recently staying with my best friend Tom who lives in Manchester, England and found out that Chris Evans was coming to town. David was disappointed to find that we’d have already left before the film crew arrived so he sat down and made a card with some pictures for Chris Evans and wrote him a little note. (…) I wish I’d scanned it but I never thought. On the front he did a little picture of Johnny Storm flying across the sky and inside another picture of a scene from the first movie with some speech bubbles and he wrote a little note to Chris saying he was his favourite actor. His ‘uncle’ Tom promised he’d try to get it to Chris Evans for him.
Tom took the card to the film site but security was so tight that he couldn’t get near anyone so he left the card with a note saying who it was from and that he was sorry not to get to take a photo for David’s birthday which was soon. The security guy told him to write down his address and he’d try to find someone to pass it to but made no promises as everything was crazy. That was on Friday 24th Sept. The following morning Tom received a special ‘next day delivery’ from Chris Evans! In it was a brilliant photo of Chris holding up David’s little card, a birthday card with a message from Chris Evans, he’d also signed two BluRay DVD covers with a little message on each for David. On one it said ‘FLAME ON!’ and was signed and on the other it said ‘DREAM BIG, BUDDY’ and was also signed.” (x)
"MODERN DAY LYNCHINGS"
Kody (Pretty Boy) Ingham (pictured above) was found hanging from a tree in front of his white girlfriends house on July 15, 2013 (the same night as the George Zimmerman verdict) in Athens, Texas. it was chalked up as a suicide and no investigation ensued, even though two hours prior he called his mother to pick him up from the site he died at. no newspaper article, just a four sentence obituary in the local papers and his family has been trying hard to make any mainstream news channel blow up the story to find the killers.
Roy Veal was found hanging in Woodville, Mississippi in 2004. he originally lived in Seattle and went to his mother’s home in Woodville to help her fight for the rights to their family land against a white man. Oil had been found underneath the land.
Roy’s head was covered with a pillow case and burned papers of the documented proof he had to prove his mothers’ ownership were found burned at his feet. He was later found hanging from a tree. His death was ruled a suicide.
His family is still trying to get attention for the case
Reynard Johnson, 17, was found hanging from a tree on his front lawn on June 16, 2000 in Kokomo, Mississippi. His death was ruled a suicide even though the belt around his neck was not his. Authorities said since no hate group left a message by the body, there was nothing to investigate. Family members said the motive was his relationship with a white girl, he was constantly being harassed because of this.
This stuff still happens guys. Boosting
Lynchings with actual ropes are still happening.