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  • Ok, so you're reading the newspaper, or you're watching the news

  • and they're talking about some new medical technology,

  • Some breakthrough treating congestive heart failure or regrowing muscle tissue in wounded soldiers.

  • I bet you that that story is going to mention that this new type of therapy uses stem cells.

  • And I bet you, like most people, are going to listen along and just go [nods agreeably]

  • Without actually knowing what stem cells are, because who has time to know what stem cells are?!?

  • Today, we are making time.

  • You have lots of different types of cells in your body.

  • You've got muscle cells, and skin cells, and liver cells, and brain cells,

  • Most of these cells have to be replaced every once in a while.

  • Your tastebuds, for instance, are replaced every 10 days or so,

  • Skin cells are replaced every couple of weeks, and liver cells turn over every 300-500 days.

  • The cells that are doing the replacing of the old cells, and the repairing of the damaged tissue are adult stem cells, also called somatic stem cells.

  • The different sort of cells, skin cells, liver cells, retina cells, muscle cells and intestine cells,

  • They all have very specific jobs and they're built in very specific ways to do those jobs.

  • Different shapes, sizes, contents, mean you can't just stick a muscle cell into a damaged liver an expect it to start breaking down your alcohol for you.

  • Somatic stem cells, on the other hand haven't decided what the heck they're gonna be.

  • They're undifferentiated. They haven't specialized yet.

  • Like a college freshman, or, let's face it, a recent college graduate. They have no idea what they're going to do with their lives.

  • but just like there are different types of college graduates, there are different types of adult stem cells.

  • Some can become more different kinds of things than others.

  • Pluripotent adult stem cells can become many different types of cells all over the body,

  • However, they're really hard to track down because there are so few of them in each organ or tissue.

  • There also multi potent adult stem cells which are more common in the body,

  • but restricted in the kind of cell they can become

  • it is kinda like the difference between graduating from trade school where you have been trained to do a few different possible jobs

  • and graduating with a degree in philosophy or something

  • equally unprepared for all jobs

  • so yeah , stick a Pluripotent cell in a damaged liver

  • and it just happily becomes a liver cell

  • pretty cool

  • but there are some even better types of stem cells to be had

  • embryonic stem cells

  • which are also Pluripotent

  • these are the cells inside a human embryo when it is a blastocyst

  • basically just a tiny nugget of human cells four or five days old

  • which is destroyed in the process of removing the stem cells from inside it

  • these embryonic cells are obtained from in vitro fertilization clinics

  • that fertilize eggs outside of the mother's body for couples who are having trouble conceiving

  • naturally, these clinics have some left over fertilized eggs

  • so with the donor's permission they are given to scientists doing stem cell research

  • now the main advantage of the embryonic stem cells is that

  • while adult stem cells can be grown in culture for time

  • meaning they can be made to multiply over and over in a nutrient solution

  • they can't grow as long or as fast as the embryonic stem cells

  • which can be maintained indefinitely into the right conditions

  • after just six months in culture , a single wad of 30 embryonic stem cells will have yielded millions of stem cells

  • which can go on to develop pretty much into any type of cell in the body

  • also adult stem cells if used in some sorts of transplant therapies are more likely to be rejected than embryonic stem cells

  • stem cell research is currently pretty hopin

  • embryonic stem cells are being used by researchers all over the world

  • to figure out how to repair or replace damaged cells and organs and create new drugs

  • but regulations have taken their toll

  • there are only about thirty five stem cell lines or families of identical pluripotent stem cells that are available for federally funded research in America

  • whereas Europe has a couple thousand

  • so there , now you never have to " nod along " your way through another news report about stem cells again

  • thanks for watching this episode of SciShow

  • if you have any questions , comments or suggestions

  • you can find us on Facebook and twitter or of course down in the comments below

  • and if you wanna keep getting smarter with us here in SciShow

  • you can go to and subscribe

  • transcription by Dr.A

Ok, so you're reading the newspaper, or you're watching the news


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B1 中級

幹細胞 (Stem Cells)

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    Study English に公開 2021 年 01 月 14 日