In some respects I am very ignorant about this subject and would like to know more about it technically. Specifically, how are the cells derived? I mean, are an egg and sperm joined and then cells taken immediatly after they fuse? Or is it a few hours, days, weeks, months…?
Also, I hear an argment for the research is that the cells would be disposed of anyway. Does this mean that they’re only taken from, oh, I can’t think of any better terms than, miscarriages or aborted fetuses?
How far along does the embryo have to be to take the cells?
That’s it for the questions, thank you for your time.
Not so sure about the other question, but the embryos to be discarded are from In-Vitro Fertilization clinics. Many embryos are created in the IVF clinics, but not all are implanted into the woman. The rest go to the incinerator.
No abortions or miscarriages involved.
OK, you have a lot of questions…
I mean, are an egg and sperm joined and then cells taken immediatly after they fuse? Or is it a few hours, days, weeks, months…? How far along does the embryo have to be to take the cells?
Generally four to eight days, depending on the kind of stem cell you want. There are three names for the developing organism: Zygote, the fertilized cell. Blastocyst, after it divides but before the cells differentiate into specific functions. And Embryo, multicellular and showing cellular differntiation. The stem cells are generally harvested during the Blastocyst stage.
This page shows pictures of the latter two stages.
This site offers a very detailed and technical description of human embyronic development. It’s fascinating.
When people talk about retrieving stem cells from “embryos,” they really mean blastocysts. But facts and accuracy seldom have much relevance to public debate on issues like this.
Also, I hear an argment for the research is that the cells would be disposed of anyway.
This refers to blastocysts or embryos that were fertilized in vitro for couples who were having trouble conceiving. Currently, it’s the only “accepted” method, and it’s the method that Bush today said he’d approve.
The latest debate was set off by the fact that someone mixed human sperm and egg for the first time with an intent to harvest the blastocyst for its stem cells.
The third way to make a blastocyst is by cloning. To do this you take a human egg, remove the nucleus, and replace the nucleus with that of a cell from the person you want to clone. Medically speaking, this is the ideal way to create stem cells, because this way you can clone just the tissue or organ you need to replace in the patient, and not worry about rejection, because it his tissue. But ethically, it’s a nightmare… you’ve got human cloning combined with harvesting a potential future human.
Researchers have also found stem cells in blood, bone marrow, and other places in fully developed humans, but they’re more limited in the kind of tissues they can become. Stem cells from Blastocysts can become any human cell, and can possibly even be coaxed into forming entire organs.
Thanks to your answers and listening to President Bush’s speach, I understand a lot more now. Thank you.