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  • There’s no surer sign that youre getting old than finding new gray hairs. But scientists

  • have finally identified a gene involved in the hair-graying process. What does this mean

  • and how does your hair actually go from colored to gray? Watch and weep.

  • Geneticists recently examined the DNA of more than 6,000 people and found specific genes

  • that influence things like baldness, beard thickness, hair curliness, and even unibrow...ness.

  • But the find that got the most attention was a particular variation in the IRF4 gene that

  • affects when your hair goes gray. Finding this specific graying variation in the gene

  • could help scientists develop products to slow the graying process. Or, speed it up,

  • I suppose, if you want to be a silver fox or avant garde hipster.

  • But we all actually start out gray, in a way. Before your hair pops out of your scalp, it’s

  • completely white. It gets its color from chemistryspecifically a group of pigment molecules called melanin,

  • which also determine your skintone and eye color. For hair, there’s eumelanin that

  • creates dark shades and pheomelanin that produces lighter hair colors. The proportion of these

  • two types determines yourand everyone else’s—hair color.

  • How that color gets into your initially colorless hair is up to your follicles. Every hair follicle

  • in your scalp contains cells called melanocytes, which produce melanin. As hair grows in the

  • follicle, melanocytes inject melanin pigments into your hair cells that contain keratin,

  • a protein that’s also in your skin and fingernails. So as your hair grows out of your head, it

  • gets dyed with its natural hue. Over time, our melanocytes produce less pigment, so our

  • hair starts to lighten as we age.

  • Scientists have recently found that as we get older, our hair follicles start accumulating

  • hydrogen peroxidethe same stuff people use to bleach their hair. Some hydrogen peroxide

  • is normal. We actually make our own H2O2 as melanocytes color our hair. Enzymes, especially

  • catalase, break down hydrogen peroxide and keep its concentration in check. But things

  • get out of whack when older follicles can’t generate enough catalase. Higher concentrations

  • of hydrogen peroxide attack tyrosinase , an important enzyme in melanin production.

  • No melanin, no color in your hair.

  • If you haven’t gone gray yet you probably will around the same age as your parents did.

  • But what about factors outside of age and genetics? A recent study suggests that smoking

  • can result in early onset graying. And people are always saying stress brings on the gray,

  • right? Just look at how gray presidents get while theyre in office. Some researchers

  • say emotional stress could accelerate what’s called oxidative stress, the damage caused

  • by reactive oxygen species like hydrogen peroxide. But others contend there isn’t solid scientific

  • evidence backing this up yet. I guess you could call all of these hypotheses a gray area.

  • At any rate, it’s probably not worth stressing about going gray, anyway. It’s completely

  • natural and you can totally rock the look. Share a pic of your favorite gray-haired celebrity

  • or your own cool silverdo in the comments. The Speaking of Chemistry gang needs ideas.

  • Special thanks to Jerry Weissmann, an emeritus professor at the New York University School

  • of Medicine for his help with this video. Now hit that share button and don’t forget

  • to subscribe on your way out.

There’s no surer sign that youre getting old than finding new gray hairs. But scientists


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B2 中高級 美國腔

頭髮為什麼會變白?- 說到化學 (Why Does Your Hair Turn Gray? – Speaking of Chemistry)

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    chung 發佈於 2021 年 01 月 14 日