Posted on 08/23/2006 10:59:33 AM PDT by Ernest_at_the_Beach
And in 2001, President Bush declared federal funding would only be available for research using the 61 human embryonic stem cells lines already in existence, where a "life or death decision had already been made".This meant that no new lines could be created, whether from existing embryos or cloned embryos.
AND receive federal funding.
The media loves to obscure that part.
If one removes a cell from an embryo they are no longer "intact".
The consequence of such cell removal on the the further development of the organism is the question. It might have profound consequences.
Even amniocentesis which is done in utero and removes only cells from amniotic fluid has a certain rate of inducing birth defects.
At a much earlier stage of development with many less cells, taking one might make the leftover completely non-viable.
Perhaps these questions are addressed in the article, but that would mean mouse experiments.
ping for later reading
PGD on IVF-derived human embryos prior to transfer into the mother's uterus is a routine procedure. There are lots of normal healthy children running around who had one cell plucked at this stage. And some who had a cell plucked, and were then frozen for future use, because there were too many normal embryos to safely transfer into the mother at one time, and then thawed and transferred later.
That is the problem with the whole notion of regarding embryos as individual human beings. In fact, they are collections of raw materials which could still become one person, multiple persons, or a part of a person (at this stage, you can still squish two embryos together and get a single baby with mixed DNA -- happens naturally fairly often, though apparently less often than monozygotic twinning).
So far, I don't believe anyone has gotten a single cell plucked from an embryo to develop into a baby (even a baby mouse), though it may eventually be possible. I think a bare minimum of two cells is needed, because once the zygote has divided, the groundwork for inter-cell signalling about which cells will become up/down/right/left parts of the body is being laid, and the process doesn't seem to work with just one cell.
Thanks for the info. I also saw that this group earlier (in January) published an article addressing this.
This is why it seems counterintuitive that removal of a cell would not have an effect on development.
I agree with the technical comments made by Government shrinker relating to this.
Hmmm. By this reasoning, medical experimentation on convicts facing the death penalty would also be ethical, as those lives are facing destruction.
This possible development was mentioned in (IIRC) the Dec. 2005 "Smithsonian" magazine.
It was a pretty fair and balanced article; and honest about the haggling between
even scientists that have varying ethical viewpoints.
I just happened to be viewing the mag yesterday.
And couldn't help having a small smile when reading the part about how that
South Korean cloning-miracle-worker was leaving the stodgy old USA in the dust.
If there are two, they can signal each other. Keep in mind that in the case of identical twins, they have each lost a lot more than one of their original cells, and yet turn out perfectly normal. At this stage, none of the cells are committed yet to being up/down/right/left. If two cells are adjoining each other, and the contact causes them each to pump a chemical signal across the membranes into the other cell, then a chemical gradient would result (higher concentration on the side of the cell that is contact with the other cell) -- this can't happen with a single cell. I'm not saying that's exactly how it happens, but that's the basic concept of how cells communicate with adjacent cells and affect each others growth and activity.
The research on these mechanisms is progressing, but there's still a lot to learn.
http://www.sciencedaily.com/releases/2005/03/050309130549.htm
What's actually even more complicated is how the asymmetrical organs develop after a basically symmetrical body has been set up.
http://www.sciencedaily.com/releases/2006/04/060419083112.htm
There are over 1,000 children that have already been born, after the performance of this procedure. (from 6,500 IVF cycles) While long term studies haven't been done, it appears to have little affect on the embryo. Google pre-implantation genetic diagnosis. There is a lot of info out there.
Preimplantation Genetic Diagnosis and Human ImplantationA Review
************************AN EXCERPT ***********************************
Reduction of multiples and frozen embryos PGD of aneuploidy may also help reduce the number of multiple pregnancies. In the two latest studies involving a test and a control group, significantly fewer embryos were trans- ferred in the PGD groups than in control groups (Gianaroli et al., 1999; Munné et al., 1999, 2003; Werlin et al., 2003). In addition, because many embryos are abnormal, after PGD there are fewer chromosomally normal embryos remain- ing in excess of those for replacement. Therefore there are very few embryos freezable, which will alleviate the problem of accumulating, storing and eventually disposing of unwanted frozen embryos
What is the time frame of the embryo from which the cell is removed? How old is it in other words? How many cells total?
This is why PGD is becoming more and more routine (originally it was used only where one or both parents carried a serious genetic disease). Most embryos are abnormal -- not just "not perfect", but not capable of developing beyond the first days or weeks of pregnancy. In young women about half are normal; in women over 40 about 10% are normal (with wide individual variation of course). In IVF without PGD, this means that in order to have a reasonably good chance of producing one baby, 2-5 embryos are transferred (number depending mostly on the mother's age).
But the laws of chance and unpredictable individual variation result in some high order multiple pregnancies which often end disastrously. While PGD doesn't provide a 100% guarantee of a baby, it greatly reduces the problem of multiples, and of the emotional strain of miscarriages in women who have usually already been through a lot of strain over years of unsuccessful efforts to have a baby.
The procedure is typically performed on an embryo at the 4 to 10 cells stage of development. For the purposes of PGD one or two cells are removed. I would estimate that an embryo would reach the 4 to 10 cell stage at about 3 days after fertilization, but I don't know for sure.
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