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The Stem Cell Revolution

by David Stevens, MD, MA (Ethics)

Today's Christian Doctor - Winter 2001

"Stem cells have the ability to differentiate into a variety of tissues. This means, through careful engineering, stem cells could be used to repair a damaged brain or heart, rebuild a knee, restore injured nervous system connections, treat diabetes and much more. That's the potential power of stem cells, and the reason the University of Minnesota is investing greatly in its Stem Cell Institute - the first of its kind. The Institute today will change medicine as we know it tomorrow."
Medical Bulletin - University of Minnesota, 2001

There is a revolution going on in medicine that will likely have as great, if not greater, an impact than the dawn of the antibiotic era 60 years ago. As one writer commented, it is "as though they had stumbled upon a packet of magic seeds that, depending on where they were planted, could grow carrots, broccoli, corn or cabbage."1 These magic seeds are stem cells that theoretically can give rise to any of the 210 different types of tissues in the human body and can divide and multiply for an indefinite period of time. This opens a new frontier of possibilities. Could stem cells be guided to produce islet cells for transplant into diabetics, programmed to replace heart muscle damaged by an infarction or even be used to reconnect a damaged spinal cord in a paraplegic? Maybe, but not tomorrow or next year as many would think after listening to the media.

As a Christian dentist or physician, your patients, friends and church look to you for guidance on complex issues that involve science and morality. My goal is to give you the scientific, biblical and ethical information you need to speak authoritatively in this case. I also want to help you think through the complex ethical questions surrounding this issue. Though the Christian Medical & Dental Associations (CMDA) does not yet have an official statement on stem cells, many of our ethical statements address the issues raised.


To begin with, some definitions will be helpful. Stem cells are thought to be totipotent, pluripotent or multipotent.

  • "totipotent" stem cells, such as a fertilized human egg, can become an entire human being; 
  • "pluripotent" stem cells, such as those found in a seven-day embryo (a blastocyst) can develop into any body cell type but can't become an entire human being;
  • "multipotent" stem cells can only differentiate into the same tissue type. For example, a bone marrow stem cell can differentiate into a monocyte, WBC or lymphocyte but not into kidney, heart muscle or brain.

Have you got that? If you do, you are only three years out of date because it is not nearly that simple. Recent studies have demonstrated that bone marrow stem cells can differentiate into other tissue types and there is evidence that pluripotent stem cells from a seven-day multipotent could develop into an embryo.2,3,4

Sources of Stem Cells

There are five, or, maybe soon, six sources of stem cells.

  • Embryonic Stem Cells - are harvested from the inner cell mass of the blastocyst seven to ten days after fertilization and early cell differentiation. The embryo at this stage may be up to 200 cells in size.5
  • Fetal Stem Cells - are often taken from the germline tissues that will make up the ovaries or testes of aborted fetuses.6
  • Umbilical Cord Stem Cells - are taken from umbilical cord blood, which contains stem cells similar to those found in the bone marrow of newborns.7
  • Placenta Derived Stem Cells: Anthrogensis Corporation recently announced the development of a commercial process that can extract ten times as many stem cells from a placenta as from cord blood.8
  • Adult Stem Cells: Tissues, like bone marrow, lung, pancreas, brain, breast, fat, skin and even tooth pulp (We can thus draw you dentists into this ethical issue!) contain stem cells that have been isolated.9 In the public debate, umbilical cord and placenta stem cells are included in the term "adult stem cells," though they are not adult at all.
  • De-differentiation of Somatic Cells: PPL Limited, the Scottish biotech company that developed "Dolly," is trying to create stem cells by the "de-differentiation" of somatic cells. Using skin or other cells, they hope to cause a cell to revert back to its stem cell ancestor.

How Stem Cells are Used

Presently, there are five proposed stem cell applications.

  • Functional Genomics - Scientists will use them to try to understand the complex events of cell development.
  • Drug Testing: Stem cells could allow scientists to test new drugs using human cell lines, which could hasten new drug development.
  • Cell Therapy: If cells could be guided to differentiate into specific cell populations, they could be used to treat diseases characterized by cell death such as diabetes, multiple sclerosis, myocardial infarctions or strokes. 
  • Gene Therapy: These cells? ability to integrate and generate new cells within an organ makes stem cells prime candidates to deliver gene therapy to replace genetically defective cells.
  • Organ Generation: Stem cells could become the seeds of an unlimited source of lab grown organs for transplantation.10

There are already 15,000 adult stem cell therapies carried out in this country each year. Bone marrow derived stem cells are used in cancer and autoimmune treatment protocols to replace/repair patients? hemopoietic systems after high dose chemotherapy or radiation. These treatment protocols are used to treat brain tumors, retinoblastoma, ovarian cancer, sarcomas, multiple myeloma, leukemia, breast cancer, neuroblastoma, renal cell carcinoma and juvenile rheumatoid arthritis as well as other diseases.11 Scientists thus have broad experience in many aspects of adult stem cell therapy. 

The Current Debate

The debate that has raged in our country focuses around whether federal funding should be used to fund research that requires the destruction of human embryos. CMDA has maintained that federal funds should not be allocated in this manner because such funding is illegal, immoral and unnecessary.

It is illegal because the "Dickey Amendment," which has been attached yearly to National Institutes of Health budgets states, "None of the funds made available in this Act may be used for research in which a human embryo or embryos are destroyed, discarded or knowingly subjected to risk of injury...."12 Unfortunately, under the Clinton administration, an end run was done around this prohibition through guidelines that stated that the NIH could fund embryonic stem cell research as long as federal funds weren't used to actually destroy the embryos. These guidelines circumvented the intent of the Act and created a powerful incentive for destroying human embryos.

Destructive embryonic research is immoral as well. At its core, this debate is not about science but about human rights. Proponents of stem cell research know it is impossible to take away the inalienable right to life from human beings, so they are taking away the embryos? humanity by referring to them as "clumps of cells" or "primordial masses of tissue." In interview after interview, prominent scientists have testified that embryos are not human beings at all. Yet a cursory consultation of the dictionary reveals that a human being is: "A member of the genus Homo and especially of the species H. sapiens."13 If human embryos are not human beings, then what are they? Are they monkeys, pigs or cows? Of course not, they are human beings.

Though there are few atrocities whose scope compares to slavery, there are some disturbing parallels between the justifications made for slavery 150 years ago and what is being said today to justify the destruction of embryos in the process of stem cell research. Slavery was justified in two ways. It was alleged that African-Americans were subhuman because they didn't look, think or speak like Caucasian Americans. Once humanity is taken away from individuals, they then can be treated like property. They can be enslaved and abused on a plantation or confined to a lab till they die of old age or are dissected under a microscope.

Slavery was also justified by predictions of economic ruin and damage to the well-being of the general population if the slaves were freed. It was claimed that the United States would never take its rightful place among the world's great powers without a cheap source of manual labor. President Lincoln didn't buy this utilitarian argument. Despite enormous political pressures and a civil war, he issued the Emancipation Proclamation. Though it ultimately cost him his life, he showed moral statesmanship. He is now seen as the greatest U.S. President of all time. Of course, American ingenuity triumphed and today we have the greatest economy in world history.

In the stem cell debate, it is also argued that without federal funding, the United States will lose its lead in science. We're told that research will move offshore and the best scientists will move to other countries. These are gross overstatements, since only around half a dozen biotech companies out of close to a thousand are involved in embryonic stem cell research and twice as much investment money is pouring into companies doing adult stem cell research.

Biblical, Ethical and Moral Considerations

What does the Bible say about this issue? Most importantly, the Bible says that man is made in God's image (Genesis 1:26-27, 9:5-7). God's image is not based on human capacity such as the ability to reason or have relationships. The image of God is something humans possess as part of their nature or essence. The Scriptures describe a continuity of human personhood from before birth (Psalm 51:5, 39:13-16). Man is not seen as just another animal. God gave humankind dominion over animals (Genesis 1:26). The Bible also teaches that we are not to unjustly take human life (Deuteronomy 5:17). What drives these points home is the fact that Christ?s incarnation began with a miraculous fertilization (Luke 1:43; 26-38). Our Savior was once a one-cell embryo. 

There are many ethical principles that argue against destroying embryos. The ethical principle of autonomy states that no one may act in a way that will affect another person without his or her informed consent. There is no greater violation of autonomy than to take a person's life. Our Declaration of Independence states that "All men are created equal and endowed by their Creator with certain inalienable rights, among which are the right to life, liberty and the pursuit of happiness." The right to life is "inherent" in the sense that it is bound to the human essence of a person. It cannot be bestowed or taken away by another person, legislative body or court unless a person has forfeited his or her right to life by killing someone with intent and forethought.

Sacrificing embryos for their stem cells also crosses the continental divide of medical ethics. The foundational ethical principle of medicine is to "do no harm." Thus medicine has prohibited harmful research on humans. The Nuremberg Code, adopted after World War II atrocities involving the elite physicians and medical institutions of Germany states, "No experiment should be conducted where there is a prior reason to believe that death or disabling injury will occur."14  The NIH's own "Guidelines for the Conduct of Research Involving Human Subjects" states, "The voluntary consent of the human subject is absolutely essential." It then excerpts the Nuremberg Code and states, "No experiment should be conducted where there is a priori reason to believe that death or disabling injury will occur."15 Though the American Medical Association (AMA) sanctions embryonic research, its standards for investigation state, " It is fundamental social policy that the advancement of scientific knowledge must always be secondary to the primary concern for the individual."16 The Council of Europe's Convention on Human Rights of 1997, the only international code of bioethics prohibits destroying embryos for research and regulates experimentation that can take place on them.17

It is argued that: "These frozen embryos will die anyway, so what difference does it make? Shouldn't some good come out of their existence?" There is a significant moral difference between individuals dying natural deaths versus having their lives taken by another. If a patient is dying of cancer, that is a tragedy, but it doesn't give a doctor the right to harvest their heart for transplant. In the first instance the patient dies of natural causes; in the second, the doctor takes the patient's life. The doctor's action would not be justifiable, even if the patient's heart were used to help someone else. It should also be noted that it is impossible for parents to give true "informed consent" to have their child killed. They could no more do this on the basis of the "best interests" of their embryo than they could authorize it for their five-year-old.

What about the estimated 100,000 frozen embryos in U.S. IVF clinics, many of whom are not abandoned or unwanted? They wait in suspended animation for the decision of their parents. A more humane alternative to the destruction of these embryos through research is for parents to decide to put them up for adoption. This would provide a wonderful alternative for the two million infertile couples in this country. It can be argued that there will be much better maternal-child bonding if the adoptive mother carries the child through gestation and delivery. The "Snowflakes" adoption program of the Nightlight Adoption agency in California already has done this successfully, despite a paucity of laws governing embryo adoptions. John and Marlene Strege gave testimony before Congress in July 2001 while holding their child, Hannah, who had been adopted as an embryo.

What is a person?

Are these young embryonic human beings persons? Adult human beings are the result of continuous growth that begins at fertilization. There is no morally relevant break in their development. Personhood does not depend on having abilities such as the power to reason, self-awareness, a certain level of intellect or consciousness. These capacities may be latent due to the fault of certain conditions, but the internal essence of the human being is unchanged.18 Developmental markers proposed by some for personhood are arbitrary and capricious. These markers include:

  • Implantation: The essential nature of a person is not dependent on hormonal signals, the survival rate of embryos or whether twinning can occur, or has occurred.
  • Brain Development: Brain wave activity is not a marker of life/personhood like it is a marker for death. Death of the brain is irreversible. The embryo has the capacity to develop full brain activity if it is allowed to do so.
  • Pain Sensation: This "marker" confuses the sensation of harm with the reality of harm. A person is harmed, whether or not they feel their leg being needlessly cut off.
  • Quickening: Personhood is not dependent on a mother's ability to feel her baby moving.
  • Birth: Birth is just a change of location and degree of dependency. A baby is more dependent on the efforts of another after birth than it is before.19

Peter Singer, a professor at Princeton, has arbitrarily chosen one year after birth as the time to confer personhood. He states that a mature monkey has more moral value than a newborn baby does because the monkey can reason, is self-conscious and has a higher level of intellect.

Legally, what is a person? At present, 38 states recognize that life begins at conception20 and 25 states already regulate embryo/fetal research. Ten states ban harmful embryonic research all together.21 Louisiana designates IVF -derived embryos as judicial persons.22 Maine, Michigan and Massachusetts impose up to five years of imprisonment for harmful research on live embryos or fetuses.23 Five states restrict the sale of embryos; five more restrict sale for research, and eight others prohibit sale for any reason.24

Adult Stem Cell Research is More Promising

The good news is that there is an ethical alternative to embryonic stem cell research that has gotten only token recognition in the media and has been downplayed by prominent scientists. Adult stem cell research holds as much, if not more, promise as embryonic stem cell research, and we are likely get to our therapeutic goals more quickly if the federal government puts its funding into this area.25,26,27,28 

There have been no successful therapies utilizing embryonic stem cells in humans. Embryonic stem cells show signs of being genetically unstable and they are difficult to culture. It is hard to control their differentiation and it is difficult to get a pure cell culture of one cell type.29 The great advantage of embryonic stem cells is that they can differentiate into 210 different types of tissue. This is also their greatest weakness. How does a scientist direct development down just one path? Geron researchers, at the December 2000 meeting of the Society of Neuroscience, reported that they had attempted to transplant human embryonic stem cells into the brains of rats. The embryonic stem cells did not differentiate into brain cells. They stayed in disorganized clusters and brain cells near them began to die. Many reports in the lay press of embryonic stem cell success in animal models misleadingly omit the fact that these studies were done with fetal stem cells that had already differentiated into neural or other tissue stem cells.

Most people do not realize that using a few "left over" embryos from in-vitro fertilization will only allow scientists to do research. To do embryonic stem cell therapy, either tens of thousands of embryonic stem cell lines will have to be developed or the recipient patient will need to be cloned to assure histocompatibility. The clone, the twin of the patient, will be grown to the blastocyst stage in culture and then cannibalized for serviceable parts. The scientist would then have to manipulate the stem cells into the right tissue and transplant them back into the patient.30

By contrast, adult stem cells have distinct advantages. They can differentiate into many types of tissue regardless of their origin. Research with mice showed that adult stem cells can grow into heart, lung, intestine, kidney, liver, nervous tissue, muscle and other tissues.31 These cells are much more "plastic" than once thought. Bone marrow cells can become heart, brain, bone and kidney. Neural stem cells can become blood or retina. Pancreatic duct stem cells differentiated into islet cells and totally reversed diabetes in mice in a study at the University of Florida,32 while a much-vaunted study using embryonic stem cells showed that the islet-like structures produced only 1/50th of the insulin needed by a diabetic mouse; all the diabetic mice died.33 One adult marrow stem cell was able to completely repopulate the bone marrow of an immune deficient mouse.34 This points to an unlimited life span for adult stem cells. These cells are also easier to culture.35 Because the cells in question can be the patient's own cells, there is not transplant rejection or risk for genetic or viral disease transfer. Most importantly, adult stem cells seem to convert into the type of cells needed by the environment in which they are placed. If a marrow stem cell is put into a damaged kidney, it converts to a kidney type stem cell and begins to repair the damage. These cells also seem to migrate to damaged areas due to some unknown chemical signal.36 In some cases, littler or no lab manipulation seemed to be needed.

As Richard Doerflinger, spokesperson for the Conference of Bishops of the Catholic Church, testified before the Senate on July 18, 2001, adult stem cells " have repaired damaged corneas, restoring sight to people who were legally blind; they have healed broken bones and torn cartilage in clinical trials; they are being used to help regenerate heart tissue damaged by a cardiac arrest."37 Since stem cells have been found in fat, patients soon may have the side benefit of a liposuction to reduce their weight as stem cells are harvested to repair cardiac muscle destroyed by their infarction.

Conflicts of Interest and Current Events

All this data leaves one question unanswered. Why have scientists from Harvard, Stanford, the NIH and other prestigious institutions said unequivocally that embryonic stem cells are the answer to our therapeutic dilemmas? An investigative report by Neil Munro in the National Journal explains that it may be "the pecuniary interests of the physicians and scientists" that leads them to make these pronouncements. Three scientists from the above institutions were quoted 216 times in the national press. In only 17 instances was it mentioned that they were shareholders, founders or board members in private biotech companies that would benefit directly or indirectly from federal funding. With such conflicts of interest, it is impossible for them to be unbiased. Johns Hopkins? John Gearhart was co-discoverer of embryonic stem cells while working for Geron Corporation, a leading biotech firm. Geron has a profit sharing agreement with Hopkins as does the University of Wisconsin, where James Thomson, the other co-discover works. All of these scientists were special contributors to the NIH report on stem cells delivered to the President. A media that usually investigates and reports any conflict of interest has ignored this commingling of science and business. And it is not just scientists. Former Senator Connie Mack, R-Fla., who vigorously promotes federally funded embryonic stem cell research, is on the board of two biotech firms.38

Just as this article was being written, President Bush made his television address on stem cells. A number of prominent Christian leaders praised his moral statesmanship. President Bush's decision established that federal funding would only be used for experimentation with 60-plus stem cell lines already created. It wouldn't fund further destruction of embryos or incentivize scientists to destroy them. President Bush also put significant funding into adult stem cell research and appointed Leon Kass, a conservative bioethicist, to chair the President's Council on Bioethics.  CMDA was encouraged by President Bush's courage in the face of enormous political pressure, but we are also concerned. For the first time in the history of American medicine, the federal government is now funding research on human tissue obtained in an immoral manner. Though the bioethical dam didn't break, the President's decision has put a leaking crack in its face. Pressure will increase that will further erode and perhaps rupture this major ethical barrier. Sixty cell lines will not last indefinitely and though they will facilitate research, they will not allow therapy. While a definitive decision has been delayed, there will be enormous pressure to legalize the mass destruction of embryos if there is any breakthrough in research with embryonic stem cells. The President's decision says nothing about the status of embryos; therefore, the private destruction of young human beings will continue with private funds. The very scientists, universities and biotech corporations that killed embryos to start their cell lines will now be financially rewarded for doing so.

Private embryo commodification will continue and expand. Geron is already buying and selling embryos from IVF clinics. The Jones Institute in Virginia is paying donors for eggs and sperm, with their explicit permission to create embryos who will be destroyed. Advanced Cell Technology is trying to clone embryos using somatic cells and cow ova to create embryo farms for commercial application. England looks on with amusement. Their government has already sanctioned therapeutic cloning and destructive embryonic research. They hope to be the first to bank the proceeds of trafficking in human life.

What Can We, Then, Do?

How should Christian doctors respond? First of all we should try to correct the disinformation campaign that is going on in our own areas of influence. The debate has been framed into a false dichotomy. The public believes it has two choices. Either they must accept embryonic stem cell research or forgo lifesaving breakthroughs for themselves or their loved ones. As physicians, we are especially well equipped to educate our patients, our friends and our churches.

You can find a "Power Point" presentation to aid you in doing this at CMDA's Web site: It contains the resources used to create this article, and much more.

We also can write op-ed pieces, volunteer to be interviewed on local TV and radio stations and contact our elected representatives. CMDA has been providing media training to members and scheduling them for media opportunities. In the first seven months of 2001, CMDA had over 540 media "hits," so there is plenty to do. We are also working to place members on the President?s Council on Bioethics and other commissions and councils of the department of Health and Human Services.

Our nation is making decisions that will affect the future of science in this country and its ethical foundations for decades to come. What sort of society are we creating for our children and grandchildren? We are in a stem cell revolution. Unfortunately, a lot of human beings-people?s children-are being killed and many more are at risk. It is our job to do what we can to save them. We must honor life at every stage of development.

1 Verfaille, Catherine. "Seeds of Hope." The Stem Cell Revolution. Winter 2001: 4.
2 Human embryonic stem cells differentiated into three primary germ layers and trophoblast. Thomson, J.A. et al. "Embryonic stem cell lines derived from human blastocysts." Science 282 (6 Nov. 1998):1145-47.
3 Human embryonic stem cells differentiated in culture to extraembryonic (trophoblast) and somatic stem cell lines. Reubinoff, B.E. et al. "Embryonic stem cell lines from human blastocysts: somatic differentiation in vitro." Nature Biotechnology 18 (April 2000):399-404.
4 ES cells from a monkey differentiated into three primary germ layers and trophoblast. Thomson, J.A. et al. "Isolation of a primate embryonic stem cell line." Proc. Natl. Acad. Sci.  92 (Aug. 1995): 7844-7848.
5 Thomson, James. "Embryonic stem cells derived from human blastocysts." Science 282 (6 Nov. 1998): 1145-47.
6 Shamblott, Michael, et al. "Derivation of pluripotent stem cells from cultured human primordial germ cells." PNAS 95 (Nov. 1998): 13726-31.
7 Amos, Johnathan. "Umbilical cords to repair brain damage." "BBC News" 19 Feb 2001. Http:// sci_tech/2001/san_francisco/newsid_11.../
8 "Placenta May Be Life-Affirming Alternative Source for Stem Cells." Associated Press  12 April  2001. Http://
9 For articles documenting these sources of stem cells go to <> or download my PowerPoint presentation "Stem Cells: Potential and Problems" at .
10 "Stem cells: A Primer."  National Institute of Health. May 2000. Http://
11 See .
12 Section 511, Public Health Services Act.
13 The American Heritage(r) Dictionary of the English Language, Third Edition  (c) 1996 by Houghton Mifflin Company.
14 from Trials of War Criminals before the Nuremberg Military Tribunals under Control Council Law No. 10, Vol. 2, pp. 181-182.. Washington, D.C.: U.S. Government Printing Office, 1949.
15 Consult the NIH?s Office of Human Subjects Research Web site:
16 See
17 Council of Europe, Convention on Human Rights and Biomedicine, Chapter I, Article 2: "Primacy of the human being" and Chapter V, Article 18(2): "Research on embryos in vitro" (1997).
18 For philosophical arguments for personhood see Rae, Scott B. and Paul M. Cox. Bioethics: A Christian Approach in a Pluralistic Age Grand Rapids: Eerdmans, 1999. 159-165.  A summary of their arguments is found in the Power Point presentation "Stem Cells: Potential and Problems" available for download at
19 Ibid.
20 Casey, Samuel B. "The Unchosen and Frozen: An Essay on the Need for Legislative Guidance Most Protective of Human Life in Deciding the Fate of Frozen Human Embryos in a Cold and Hard World." in Kilner, John, et al., ed. The Reproduction Revolution: A Christian Appraisal of Reproductive Technologies, Sexuality, and the Family. Grand Rapids: Eerdmans, 2000.
21 Andrews, Lori. "State Regulation of Embryo Stem Cell Research [draft]" (unpublished manuscript, commissioned by the National Bioethics Advisory Commission), p. 3.
22 Casey, op. cit., note 7.
23 Andrews, op. cit., p. 4, n. 16.
24 Andrews, op. cit., p. 12, citing Minn. Stat. Ann. § 145.422(3).
25 "The emerging truth in the lab is that pluripotent stem cells are hard to rein in. The potential that they would explode into a cancerous mass after stem cell transplant might turn out to be the Pandora?s box of stem cell research." Jonietz, Erika. "Innovation: Scouring Stem Cells" Technology Review. 2 March, 2001 http://209.58.177220/articles/jan01/innovation_jonietz
26 "Cell therapies using autologous (adult) donor cells hold tremendous promise for the treatment of both acquired and inherited diseases involving tissue degeneration and cellular dysfunction." Kaji, E.H. and Leiden, J.M. "Gene and Stem Cell Therapies." JAMA 285-5 (7 Feb. 2001): 548.
27 "The potential of tissue engineering using undifferentiated stem cells to replace organ function is even more profound. For example, it may be feasible to use pancreatic stem cells to replace islet function. Neural stem cells from adult animals have been stimulated  to form tissues from all 3 germ layers ...." Niklason, L.E. and Robert Langer. "Prospects for Organ and Tissue Replacement." JAMA 285-5 (7 Feb 2001):574 -575.
28  "Easily accessible cells from bone marrow might someday be used to treat a wide range of neurological diseases - without raising the ethical concerns that accompany the use of embryonic cells."  Stem Cells: New Excitement, Persistent Questions." Science 290 (1 Dec. 2000): 572.
29 Vogel, G. "Stem cells: New excitement, persistent questions." Science 290 (1 Dec 2000): 1672-1674.
30 "Now, a promising solution, which could potentially revolutionize transplantation medicine, would be to combine this embryonic stem cell technology with nuclear transfer technology, or cloning technology... making cells that would e fully compatible with the human patient."   Dr. Michael West, President Advanced Cell Technology, in testimony before the Senate Subcommittee on Labor, Health and Human Services and Education on Dec. 2 1998.
31 For hundreds of references confirming the adult cells potential got to http://www.stemcell
32 V. K. Ramiya, et al,  "Reversal of insulin-dependent diabetes using islets generated in vitro from pancreatic stem cells," Nature Medicine 6, 278-282, March 2000.
33 N. Lumelsky et. al., "Differentiation of embryonic stem cells to insulin-secreting structures similar to pancreatic islets," Science Express. See Published online 26 April 2001; zdoi;10.1126/science.1058866.
34 Bhatia, M. et al. "Purification of primitive human hematopoietic cells capable of repopulating immune-deficient mice." Proc. Natl. Acad. Sci. USA 94 (May 1997): 5320-25.
35 Cho, R. H. and C.E. Muller-Sieburg. "High frequency of long-term culture-initiating cells retain in vivo repopulation and self-renewal capacities." Exp. Hematol. 28 (1 Sept. 2000): 1080-86.
36 Eglitis, M.A. et al. "Targeting of marrow-derived astrocytes to the ischemic brain." Neuroreport 10 (26 April 1999): 1289.
37 Testimony of Richard M. Doerflinger on behalf of the Committee for Pro-Life Activities United States Conference of Catholic Bishops before the Subcommittee on Labor, Health and Human Services, and Education, Senate Appropriations Committee Hearing on Stem Cell Research, July 18, 2001, p. 5.
38 Munro, Neil. "Mixing Business with Stem Cells." National Journal. (17 July 2001). 2348-2349.


David Stevens, MD, MA (Ethics)