Embryo Project Encyclopedia Articles

In 2007, Françoise Baylis and Jason Scott Robert published “Part-Human Chimeras: Worrying the Facts, Probing the Ethics” in The American Journal of Bioethics. Within their article, hereafter “Part-Human Chimeras,” the authors offer corrections on “Thinking About the Human Neuron Mouse,” a report published in The American Journal of Bioethics in 2007 by Henry Greely, Mildred K. Cho, Linda F. Hogle, and Debra M. Satz, which discussed the debate on the ethics of creating part-human chimeras. Chimeras are organisms that contain two or more genetically distinct cell lines. Both publications discuss chimeras with DNA from different species, specifically in response to studies in which scientists injected human brain cells into mice. “Part-Human Chimeras,” contributes to a chain of ethical and scientific discussion that occurred in the mid-2000s on whether people should be able to conduct research on chimeras, especially in embryos.

In 2006, bioethicist Jason Scott Robert published “The Science and Ethics of Making Part-Human Animals in Stem Cell Biology” in The FASEB Journal. There, he reviews the scientific and ethical justifications and restrictions on creating part-human animals. Robert describes part-human animals, otherwise known as chimeras, as those resulting from the intentional combination of human and nonhuman cells, tissues, or organs at any stage of development. He specifically criticizes restrictions against creating part-human animals made by the National Academy of Sciences, or NAS, in 2005, arguing that while they ensure that such research is morally justifiable, they might limit scientists from conducting useful science using part-human animals or entities. Robert challenges the moral rationales behind prohibiting chimera research, arguing that they may impede scientists from conducting research that could have important benefits to biology and medicine, and suggests how to balance the conflicting moral and scientific needs of such science.

The copper intrauterine device, or IUD, is a long-term, reversible contraceptive first introduced by Howard Tatum and Jamie Zipper in 1967. Health care providers place an IUD inside a woman’s uterus to prevent pregnancy. Copper IUDs are typically made of T-shaped plastic with some portion covered with exposed copper. Prior to the invention of the first IUDs, women had few long-term options for safe and reliable birth control. Those options mostly consisted of barrier methods and the oral birth control pill, which were only effective if used correctly and consistently. For women seeking to control their fertility, a copper IUD was one of the first forms of long-term birth control that was highly effective and did not require consistent and regular action on the woman’s part to remain effective.

In the 1973 case of Roe v. Wade, the US Supreme Court ruled that laws banning abortion violated the US Constitution. The Texas abortion laws, articles 1191–1194, and 1196 of the Texas penal code, made abortion illegal and criminalized those who performed or facilitated the procedure. Prior to Roe v. Wade, most states heavily regulated or banned abortions. The US Supreme Court decision in Roe v. Wade secured women's rights to terminate pregnancies for any reasons within the first trimester of pregnancy. It also sparked legal discussions of abortion, fetus viability and personhood, and the trimester framework, setting a landmark precedent for future cases including Webster v. Reproductive Health Services (1989), Planned Parenthood v. Casey (1992), and Stenberg v. Carhart (2000).

In 2005, Ernest McCulloch and James Till published the article “Perspectives on the Properties of Stem Cells,” which discusses the various properties and future possibilities for the use of stem cells. Stem cells are unspecialized cells that can develop into several different cell types. In the article published in the journal Nature on 1 October 2005, the authors say they wrote the article to dispel misconceptions about what stem cells are, what they do, address some controversies surrounding stem cells, and discuss potential uses of stem cells. In the article, McCulloch and Till reveal how stem cell research has revolutionized cancer treatment as well as set the stage for future embryonic and adult stem cell research.

In “Explaining Recent Declines in Adolescent Pregnancy in the United States: The Contribution of Abstinence and Improved Contraceptive Use,” hereafter “Explaining Recent Declines,” researchers John S. Santelli, Laura Duberstein Lindberg, Lawrence B. Finer, and Susheela Singh discuss what led to the major decline in US adolescent pregnancy rates from 1995 to 2002. Working with the Guttmacher Institute, a reproductive health research organization, they found that the decline in US adolescent pregnancy rates between 1995 and 2002 was primarily due to improved contraceptive use. They published their article in 2007 after the US government had increased funding for abstinence-only education between 1998 and 2007. “Explaining Recent Declines” challenged US policies by asserting that there was minimal evidence to support abstinence-only sex education as the primary strategy to prevent adolescent pregnancy.

Screening for Breast Cancer with Mammography is a Cochrane systematic review originally published by Peter Gøtzsche and Karsten Jørgensen in 2001 and updated multiple times by 2013. In the 2013 article, the authors discuss the reliability of the results from different clinical trials involving mammography and provide their conclusions about whether mammography screening is useful in preventing deaths from breast cancer. Mammography is an X-ray technique used to detect abnormalities in breast tissue, such as breast cancer, which affects about twelve percent of women in the world and has a significant risk of mortality. The authors concluded that mammography screenings reduced breast cancer mortality, but resulted in problems such as overdiagnosis and overtreatment of screened women. The article Screening for Breast Cancer with Mammography contributed to the then ongoing controversy about the usefulness of mammography and provided accessible information about mammograms in seven languages.

Telomeres are sequences of DNA on the ends of chromosomes that protect chromosomes from sticking to each other or tangling, which could cause irregularities in normal DNA functions. As cells replicate, telomeres shorten at the end of chromosomes, which correlates to senescence or cellular aging. Integral to this process is telomerase, which is an enzyme that repairs telomeres and is present in various cells in the human body, especially during human growth and development. Telomeres and telomerase are required for normal human embryonic development because they protect DNA as it completes multiple rounds of replication.

Sir John Bertrand Gurdon further developed nuclear transplantation, the technique used to clone organisms and to create stem cells, while working in Britain in the second half of the twentieth century. Gurdon's research built on the work of Thomas King and Robert Briggs in the United States, who in 1952 published findings that indicated that scientists could take a nucleus from an early embryonic cell and successfully transfer it into an unfertilized and enucleated egg cell. Briggs and King also concluded that a nucleus taken from an adult cell and similarly inserted into an unfertilized enucleated egg cell could not produce normal development. In 1962, however, Gurdon published results that indicated otherwise. While Briggs and King worked with Rana pipiens frogs, Gurdon used the faster-growing species Xenopus laevis to show that nuclei from specialized cells still held the potential to be any cell despite its specialization. In 2012, the Nobel Prize Committee awarded Gurdon and Shinya Yamanaka its prize in physiology and medicine for for their work on cloning and pluripotent stem cells.

During the twentieth and twenty-first centuries, Robert Paul Lanza studied embryonic stem cells, tissues,
and endangered species as chief scientific officer of Advanced Cell
Technology, Incorporated in Worcester, Massachusetts. Lanza's team cloned
the endangered species of gaur Bos gaurus.
Although the gaur did not survive long, Lanza successfully cloned
another cow-like creature, called the banteng
(Bos
javanicus). Lanza also worked on cloning human embryos
to harvest stem cells, which could be used to treat dieases. While
previous techniques required the embryo's destruction, Lanza
developed a harvesting technique that does not destroy the embryo,
forestalling many ethical objections to human embryonic
research.