Because embryonic stem cells have a different potential that adult stem cells (e.g. not every organ has adult stem cells). Also embryonic stem cells are capable of prolonged, undifferentiated proliferation in culture meaning an unlimited supply.
I, personally, don't consider an egg stuck with a needle and injected with a sperm and allowed to grow in a petri dish for a couple of days a human being.
Well, let's see, the conceived is growing, duplicating its own unique orders for construction, and within two days has already differentiated cells to build his or her own placenta (yes, the sex can be determined at this age) for life support if he or she can locate 'mommy'. The stem cells now circulating in your blood stream are the duplicate program you've been expressing ever since you began cell division growth. When you were two cells, you were already a distinct human ORGANISM, and each and every cell you made from then to now has had the exact same rpogram within it, and the 'now stem cells' merely have to reach a site in your body and receive chemical signals in order to leap into differentiation to replace a damaged or dying cell. The recent discovery of multipotent adult progenitor cells (MAPCs- pronounced map seas) and subsequent very wide range of tissues they can and do differentiate into means your body has a virtual endless supply of stem cells already matched to your unique histamine patterns of your immune system, so tissue rejection isn't a factor. And, oh yes, they can be extracted from your blood and cultured, to increase the numbers for re-injecting into your prime delivery system. All this complexity started with one mega-cell, the zygote of you, and has continued as you ever since. You proved you were an individual human organism when your first cell divided to form two cells and you've been the same individual organism ever since. It would matter not a whit if your conception and first cell divisions occurred in a petri dish or your mother's fallopian tube, the idiocy of Orrin Hatch not withstanding.
You're right that this is your personal opinion. The scientific fact is that the embryos are human beings.
Adult stem cells have shown the ability to double and live in culture to the same extent as the embryonic, with fewer genetic and chromosomal abnormalities.
http://www.csu.edu.au/learning/ncgr/gpi/odyssey/dolly-cloning/nuclear_transfer_technology.html
http://www.csu.edu.au/learning/ncgr/gpi/odyssey/dolly-cloning/nuclear_transfer_technology.html
A couple of points: Sperm injection is a rare form of IVF, requiring more technology and is more premeditated than the usual process of just bringing the gametes together in the dish. Also, in order for use, the embryos are at least 5 days old. In animal models, the only way embryonic cells have proven useful is in cloned cells (SCNT) which are implanted and harvested before birth. The results aren't any more promising than adult stem cells in analogous tests.
Adult Stem Cell Research More Effective Than Embryonic Cells
Stem Cells Not the Priority for Alzheimer's
Lies About Fetal Stem Cell Research [Free Republic]
Stem cells without benefit of embryos
Michael Fumento Interview [DDT, Global Warming, Fuel Cells, Stem Cells, AIDS, Biotech, AD/HD, Etc.]
SELLING LIES (Stem Cell Myths exposed by Michael Fumento)
FREE Book on Stem Cells and Cloning in understandable language
*In 2000, Israeli scientists implanted Melissa Holley's white blood cells into her spinal cord to treat the paraplegia caused when her spinal cord was severed in an auto accident. Melissa, who is 18, has since regained control over her bladder and recovered significant motor function in her limbs - she can now move her legs and toes, although she cannot yet walk.
This is exactly the kind of therapy that embryonic-stem-cell proponents promise - years down the road. Yet Melissa's breakthrough was met with collective yawns in the press with the exception of Canada's The Globe and Mail. Non-embryonic stem cells may be as common as beach sand.
They have been successfully extracted from umbilical cord blood, placentas, fat, cadaver brains, bone marrow, and tissues of the spleen, pancreas, and other organs. Even more astounding, the scientists who cloned Dolly the sheep successfully created cow heart tissue using stem cells from cow skin. And just this week, Singapore scientists announced that they have transformed bone-marrow cells into heart muscle.
Research with these cells also has a distinct moral advantage: It doesn't require the destruction of a human embryo. You don't have to be pro-life to be more comfortable with that.
*In another Parkinson's case, a patient treated with his own brain stem cells appears to have experienced a substantial remission with no adverse side effects. Dennis Turner was expected by this time to require a wheelchair and extensive medication. Instead, he has substantially reduced his medication and rarely reports any noticeable symptoms of his Parkinson's. Human trials in this technique are due to begin soon.
*Bone marrow stem cells, blood stem cells, and immature thigh muscle cells have been used to grow new heart tissue in both animal subjects and human patients. Indeed, while it was once scientific dogma that damaged heart muscle could not regenerate, it now appears that cells taken from a patient's own body may be able to restore cardiac function. Human trials using adult stem cells have commenced in Europe and other nations. (The FDA is requiring American researchers to stick with animal studies for now to test the safety of the adult stem cell approach.)
*Harvard Medical School researchers reversed juvenile onset diabetes (type-1) in mice using "precursor cells" taken from spleens of healthy mice and injecting them into diabetic animals. The cells transformed into pancreatic islet cells. The technique will begin human trials as soon as sufficient funding is made available.
*In the United States and Canada, more than 250 human patients with type-1 diabetes were treated with pancreatic tissue (islet) transplantations taken from human cadavers. Eighty percent of those who completed the treatment protocol have achieved insulin independence for over a year. (Good results have been previously achieved with pancreas transplantation, but the new approach may be much safer than a whole organ transplant.)
*Blindness is one symptom of diabetes. Now, human umbilical cord blood stem cells have been injected into the eyes of mice and led to the growth of new human blood vessels. Researchers hope that the technique will eventually provide an efficacious treatment for diabetes-related blindness. Scientists also are experimenting with using cord blood stem cells to inhibit the growth of blood vessels in cancer, which could potentially lead to a viable treatment.
*Bone marrow stem cells have partially helped regenerate muscle tissue in mice with muscular dystrophy. Much more research is needed before final conclusions can be drawn and human studies commenced. But it now appears that adult stem cells may well provide future treatments for neuromuscular diseases.
*Severed spinal cords in rats were regenerated using gene therapy to prevent the growth of scar tissue that inhibits nerve regeneration. The rats recovered the ability to walk within weeks of receiving the treatments. The next step will be to try the technique with monkeys. If that succeeds, human trials would follow.
*In one case reported from Japan, an advanced pancreatic cancer patient injected with bone marrow stem cells experienced an 80 percent reduction in tumor size.
* In separate experiments, scientists researched the ability of embryonic and adult mouse pancreatic stem cells to regenerate the body's ability to make insulin. Both types of cells boosted insulin production in diabetic mice. The embryonic success made a big splash with prominent coverage in all major media outlets. Yet the same media organs were strangely silent about the research involving adult cells.
Stranger still, the adult-cell experiment was far more successful - it raised insulin levels much more. Indeed, those diabetic mice lived, while the mice treated with embryonic cells all died. Why did the media celebrate the less successful experiment and ignore the more successful one?
* Another barely reported story is that alternative-source stem cells are already healing human illnesses.
*In Los Angeles, the transplantation of stem cells harvested from umbilical-cord blood has saved the lives of three young boys born with defective immune systems.