| From: hamish | 29/11/2001
12:19:11 |
| Subject: Stem Cells |
post id:
516718 |
| I am *completely* confused now!.
I heard Dr Karl say this morning that that US company didnt clone
anything, all they did was create a hollow ball with no stem cells
inside. If they didnt clone anything, as they were supposed to have done, what did they do? I have heard that stem cells are the holy grail of genetic research, because they can become anything. 1/what exactly is a stem cell/ 2/Why can they become any type of cell, whereas other cells cant be turned into different types of cells? 3/how do they know which sort of cell to become? how would you tell them which sort of cell to be? Meg, this is where I need your illumination because I have heard a million different stories and am totally baffled. Can someone put me straight on all this? | |
| From: reprise ® | 29/11/2001
12:27:01 |
| Subject: re: Stem Cells |
post id:
516732 |
| I didn't understand this one
either until I was reading New Scientist yesterday. Under British law at
least, the product of this process can't be regarded as a human embryo
because it doesn't involve the combining of a human ovum and a human sperm
as those terms are generally applied in science. The "egg" is effectively
a hollowed out shell (in Britain, apparently they used a cow ovum and a
cell from the leg of a human male). The "egg" is the medium which allows
the cell to reproduce - kind of like when we grow bacteria in a
laboratory. It's miles away from any technique which would allow us to
grow an embryo much less a full human being, as I understand
it. | |
| From: ZedP ® | 29/11/2001
12:28:49 |
| Subject: re: Stem Cells |
post id:
516736 |
| Basically, what it appears the
researchers did was add a somatic nucleus to an egg and allowed it to
develop to the blastocyst stage (a ball of cells with a large space in the
middle called a blastocoel). If it had nothing in it, I'm assuming that
the there were no embryo cells, just trophoblastic cells (cells that will
go on and form part of the placenta). Just something that sprang to mind
and that I'm not totally sure on, is it possible that there was no
maternal imprinting, only paternal imprinting (AFAIK paternal imprinting
is needed for the development of the placenta etc...) Stem cells are the embryo cells (the earliest stem cells anyway) that can go on and form any tissues. They are known as totipotent. As development proceeds, these cells begin to differentiate further and further so that the type of tissues that they can form become less and less. They reach a certain critical differentiation when they can only form one cell type. This is all under the control of genes. Exactly how, I don't know - my limit is basic reproductive biology. I'll leave the control to the geneticists. | |
| From: Thermus aquaticus ® | 29/11/2001
12:33:44 |
| Subject: re: Stem Cells |
post id:
516750 |
| hamish, It's no wonder you are confused. Dr Karl doesn't know what he is talking about with respect to this topic (and many others), so I wouldn't listen to him. His analysis this morning was painful to listen to. What the ACT company did was clone a human cell using nuclear transfer (a la Dolly), then develop the cloned embryo to the blastocyst stage (or close to it). A blastocyst is the hollow ball of cells which was referred to. Inside can be found embryonic stem cells (ES cells). Whether or not they managed to extract any ES cells from the blastocyst does not change the fact that the embryo was cloned. | |
| From: Thermus aquaticus ® | 29/11/2001
12:36:48 |
| Subject: re: Stem Cells |
post id:
516763 |
From the ACT
website........ | |