Archive for: January, 2013

Corrida de Guadalupe-Reyes

Jan 03 2013 Published by under Uncategorized

A few years ago, I received an email from a teacher in my kids' school:

Hello Dr. Namnezia, I teach French and Spanish at Yourkids' School.  A colleague mentioned you to me as someone who had lived in Mexico. I will be doing a cultural unit next week on the Mexican symbol, La Virgen de Guadalupe, with our 6th grade Spanish class.  We were hoping you could visit the class and talk in English or in simple Spanish to them about La Virgen and what she means to most Mexicans, and also what she meant to you and your family.

My reply was:

Thanks for asking me to talk in your class, and yes, I was born and raised in Mexico City. However, I am probably not the person you want to to talk to your class about La Virgen de Guadalupe, since I am Jewish! (yes, there are Jews in Mexico, and no, they are not all sepharadic from Spain). So "La Virgen" didn't really mean much at all to me and to my family. Perhaps when you do a unit about how Mexican society can be just as culturally and ethnically diverse as that of the United States, I'll be happy to visit.

I have to admit my reply was a little snippy, but I was annoyed at the assumptions this dude was making. However, I have to admit he really did have a point, albeit a small one. See, in Mexico (and in a bunch of other places) the holiday season isn't quite over yet, there's still one more hurrah: Día de los Reyes, or Day of the Kings, also known as Epiphany. This marks the end of what is referred to as "Corrida de Guadalupe-Reyes", which means a bunch of parties that occur between Dec. 12, Day of the Virgin of Guadalupe and Jan. 6, Kings Day. Some take this time as a personal challenge to go to a party and get drunk every day of the corrida. That's 26 days of drinking. Growing up in a heavily catholic country one cannot but help celebrating some of these holidays. Not really as a family, but at friends' houses, and at school, and at friends of friends' houses, and the neighbors, you get the idea. We didn't really do Christmas, or celebrate the day of the Virgin of Guadalupe, but we definitely did Kings Day. Not much in the way of exchanging presents, but in eating delicious Rosca de Reyes. Rosca is a delicious round, fluffy sweet bread, covered in crusty sugary bits alternating with dried fruit. Inside somewhere is one (or many) little plastic doll representing baby jesus. Or Jesús as they say in those parts. Everybody cuts a piece, and whoever gets the doll has to throw a party with tamales sometime in February. Since we didn't do the tamale thing, my goal was to get as many dolls as possible. I think I had collected dozens as a kid. In contrast, my grandfather told me that once he actually made himself swallow jesus to avoid throwing a tamale party. He also told me, since he was fond of talking about such things, that it took three days for him to "pass" jesus.

So, if you are depressed that the holidays are  over, you've opened your presents, ate your fruitcake, lit your Hanukkah candles, stayed up until midnight to greet 2013, given the Christmas tree the ol' heave-ho down the front steps, now's your chance to keep 'em going for a few more days. Get yourself to your local Mexican bakery and order a big Rosca de Reyes. On January 6, eat it up and as a bonus you or one of your friends has to throw a tamale party in February.

RoscaDeReyes003

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Rita Levi Montalcini and Nerve Growth Factor: Repost

Jan 03 2013 Published by under Uncategorized

This last week one of my neuroscience heroes, Rita Levi Montalcini, passed away at the age of 103. In her honor, I decided to repost a post I wrote a few months ago about one of her greatest contributions to science: nerve growth factor. In addition there's a nice profile of her and her work in Nature. Here's the repost:

A Neuroscience Field Guide: Nerve Growth Factor

Nerve growth factor, NGF for short, is a soluble protein that is secreted by various tissues in the body, and it promotes the growth of nerve cell processes and survival of neurons. It is the first of a class of molecules known as neurotrophins which are very important for the development and function of the nervous system.

What is remarkable about NGF is how it was discovered and by whom. NGF was discovered by Rita Levi-Montalcini an Italian, Jewish young doctor. She originally became interested in a set of experiments by renowned embryologist Viktor Hamburger which had observed that removing a limb bud from a chicken embryo caused the sensory neurons that innervated the undeveloped limb to die off. This suggested that there was something about the target tissue that promoted neurons' survival in the embryo.

Levi-Montalcini had just graduated from medical school when Mussolini issued the "Manifesto per la Difesa della Razza", which ultimately led to a ban of all non-Aryans from having professional and academic careers. Undaunted, Levi-Montalcini set up a laboratory in her bedroom in her parents house and then after the bombing of Turin in her family's country cottage. After the War she was invited to St. Louis, MO to join Viktor Hamburger where she remained for many years and where she performed her Nobel Prize-winning research.

One of her initial observations was that if you implant specific mouse tumor cells on a chick embryo, sensory neurons will grow rapidly and sprout new axons which will innervate the tumor cells, again confirming that certain target tissues can promote nerve growth in embryonic tissues. The question was how did the target tissues do this? The key experiment came when she and her colleagues grew on one end of a cell culture dish some of these mouse tumor cells, and on the other a bit of neural tissue known as a sensory ganglion. After a few days, she observed that the neurons in the sensory ganglia grew a bunch new axons, and these axons seemed to be oriented toward the tumor cells. As if they were being attracted. This told her that the tumor cells were actually releasing some soluble factor into the growth media. The factor promoted growth of nerve cells and helped them live longer in a culture dish. This factor was later isolated by biochemist Stanley Cohen and shown to be a protein which they dubbed, imaginatively, nerve growth factor. Both Cohen and Levi-Montalcini received Nobel Prize in 1986.

 

From Levi-Montalcini's Nobel Lecture: Drawing of the cell culture experiment. The tissue on the left is the mouse tumor cells, the tissue on the left is the sensory ganglion. Note the axons growing out towards the mouse tissue.

 

How does NGF work? Now we know that NGF, as well as several other similar proteins known as neurotrophins, activate receptors in target cells which are called tyrosine receptor kinases, or Trk. Trks are proteins which are on the surface of neurons that when activated by NGF cause a series of cellular processes which cause embryonic neurons to grow new axons and to survive. Any cells which do not find their target will undergo a self-destructive process called apoptosis, thus help in the developing nervous system keep appropriate connections and eliminate inappropriate ones. Furthermore, NGF could form the basis of new therapies for treating various degenerative brain disorders and maybe promote neural regeneration after injury.

Rita Levi-Montalcini is now 103 years old, the oldest living Nobel laureate. Apparently she uses NGF eye-drops daily (it's true!).

Rita Levi-Montalcini in 2009, at her 100th birthday party.

 

Further Reading

Rita Levi-Montalcini Nobel Lecture and her Autobiography

Stanley Cohen Nobel Lecture

 

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