Embryo Project Encyclopedia

Mechanism of Notch Signaling: The image depicts a type of cell signaling, in which two animal cells interact and transmit a molecular signal from one to the other. The process results in the production of proteins, which influence the cells as they differentiate, move, and contribute to embryological development. In the membrane of the signaling cell, there is a ligand (represented by a green oval). The ligand functions to activate a change in a receptor molecule. In the receiving cell, there are receptors; in this case, Notch proteins (represented by orange forks). The Notch proteins are embedded in the receiving cell membrane, and they have at least two parts: an intracellular domain (inside the cell) and the receptor (outside the cell). Once the ligand and receptor bind to each other, a protease (represented by the dark red triangle) can sever the intracellular domain from the rest of the Notch receptor. Inside the nucleus of the receiving cell (represented by the gray area) are the cellês DNA (represented by the multi-colored helices) and its transcription factors (blue rectangles). Transcription factors are proteins that bind to DNA to regulate transcription, the first step in gene expression, which eventually yields proteins or other products. Initially, repressor proteins (represented by a red irregular hexagon) prevent transcription factors from allowing transcription. When the severed Notch receptor intracellular domain reaches the nucleus, it displaces the repressor. The transcription factor can then signal for transcription to occur. 1) There is a Notch receptor protein in the membrane of a receiving cell, and a ligand for this receptor (for example, Delta) in the membrane of the signaling cell. When the ligand binds to the receptor, the intracellular domain of the receptor changes shape. 2) Inside the receiving cell, there are proteases. Once the intracellular domain of the receptor changes shape, the protease can bind to it and shear the intracellular domain away from the rest of the receptor molecule. 3) The severed intracellular domain is shuttled to the receiving cell nucleus. Here, the intracellular domain displaces a repressor protein. This allows a transcription factor to initiate DNA transcription. During transcription, DNA is used as a template to create RNA. Following transcription, the process of translation occurs, which uses RNA as a template to create proteins. These proteins influence the behavior, fate, and differentiation of cells, which contribute to normal embryonic development

Henrietta Lacks, born Loretta Pleasant, had terminal cervical cancer in 1951, and was diagnosed at The Johns Hopkins University in Baltimore, Maryland, where researchers collected and stored her cancer cells. Those cells went on to become the first immortal human cell line, which the researchers named HeLa. An immortal cell line is an atypical cluster of cells that continuously multiply on their own outside of the organism from which they came, often due to a mutation. Lacks’s cancer cells enabled scientists to study human cells outside of the human body, though that was controversial since she did not voluntarily donate her cells for such research. Science writer Rebecca Skloot chronicled Lacks’s life in her book, The Immortal Life of Henrietta Lacks, which became a movie in 2017. Lacks’s HeLa cell line has contributed to numerous biomedical research advancements and discoveries and her story has prompted legal and ethical debates over the rights that an individual has to their genetic material and tissue.

On 23 April 2008, the US Government Accountability Office, or GAO, released a report titled, “Abstinence Education: Assessing the Accuracy and Effectiveness of Federally Funded Programs,” hereafter “Abstinence Education,” in which it investigated the scientific accuracy and effectiveness of abstinence-only education programs sanctioned by individual states and the US Department of Health and Human Services, or HHS. GAO is a government agency whose role is to examine the use of public funds, evaluate federal programs and activities, and provide nonpartisan support to the US Congress. In “Abstinence Education,” GAO found that as of August 2006, a variety of factors in such programs, such as inaccurate medical information, contributed to overall conclusions that abstinence-until-marriage programs were unsuccessful at reducing the rates of adolescent pregnancy. In “Abstinence Education,” GAO recommends that HHS implement procedures to better assure the accuracy of educational materials used in abstinence programs and to set standards that measure the effectiveness of those programs.

'On the Permanent Life of Tissues outside of the Organism' reports Alexis Carrel's 1912 experiments on the maintenance of tissue in culture media. At the time, Carrel was a French surgeon and biologist working at the Rockefeller Institute in New York City. In his paper, Carrel reported that he had successfully maintained tissue cultures, which derived from connective tissues of developing chicks and other tissue sources, by serially culturing them. Among all the tissue cultures Carrel reported, one was maintained for more than two months, whereas previous efforts had only been able to keep tissues in vitro for three to fifteen days. Carrel’s experiments contributed to the development of long-term tissue culture techniques, which were useful in the study of embryology and eventually became instrumental in stem cell research. Despite later evidence to the contrary, Carrel believed that as long as the tissue culture method was accurately applied, tissues kept outside of the organisms should be able to divide indefinitely and have permanent life.

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.

On 29 June 1988, in Bowen v. Kendrick, the US Supreme Court ruled in a five-to-four decision that the 1981 Adolescent Family Life Act, or AFLA, was constitutional. Under AFLA, the US government could distribute federal funding for abstinence-only sexual education programs, oftentimes given to groups with religious affiliations. As a federal taxpayer, Chan Kendrick challenged the constitutionality of AFLA, claiming it violated the separation of church and state. The Supreme Court found that although AFLA funded programs that aligned with certain religious ideologies, it was constitutional because it did not encourage government involvement in religion, and it held a valid secular purpose in seeking to prevent adolescent pregnancy and premarital sexual relations. By upholding AFLA, Bowen v. Kendrick enabled the US government to continue funding abstinence-only education, which researchers have found to be ineffective.

Published in 2002, prostate cancer researcher John R. Masters authored a review article HeLa Cells 50 Years On: The Good, The Bad, and The Ugly that described the historical and contemporary context of the HeLa cell line in research in Nature Reviews Cancer. The HeLa cell line was one of the first documented immortal cell lines, isolated from cervical cancer patient Henrietta Lacks in 1951 at The Johns Hopkins Hospital in Baltimore, Maryland. An immortal cell line is a cluster of cells that continuously multiply on their own outside of the original host. Though the HeLa cell line has contributed to many biomedical research advancements such as the polio vaccine, its usage in research has been controversial for many reasons, including that Lacks was a Black woman who did not knowingly donate her cells to science. In the article “HeLa Cells 50 Years On: The Good, The Bad, and The Ugly,” Masters describes that, despite the benefits of the HeLa cell line, it has caused significant negative impacts on research due to its propensity to contaminate other cell lines, which can potentially invalidate research findings.

Christiane Nusslein-Volhard studied how genes control embryonic development in flies and in fish in Europe during the twentieth and twenty-first centuries. In the 1970s, Nusslein-Volhard focused her career on studying the genetic control of development in the fruit fly Drosophila melanogaster. In 1988, Nusslein-Volhard identified the first described morphogen, a protein coded by the gene bicoid in flies. In 1995, along with Eric F. Wieschaus and Edward B. Lewis, she received the Nobel Prize in Physiology or Medicine for the discovery of genes that establish the body plan and segmentation in Drosophila. Nusslein-Volhard also investigated the genetic control of embryonic development to zebrafish, further generalizing her findings and helping establishing zebrafish as a model organism for studies of vertebrate development.

On 9 July 1990, in Moore v. Regents of the University of California, the Supreme Court of California ruled in a four-to-three decision that individuals do not have rights to a share in profits earned from research performed on their bodily materials. In its decision, the Supreme Court of California ruled that cancer patient John L. Moore did not have personal property rights to samples or fluids that his physicians took from his body for research purposes. Moore created the precedent in California that although physicians are required to disclose their research interests to their patients, patients do not have property-related claims to any samples that their physicians take from their body. The Supreme Court of California’s decision in Moore v. Regents of the University of California enabled physicians and researchers to retain legal ownership on samples taken from their patients’ bodies so that they can conduct what the court describes as socially important medical research, such as work on reproductive cancers or developmental disorders.

In 1969, Roy J. Britten and Eric H. Davidson published Gene Regulation for Higher Cells: A Theory, in Science. A Theory proposes a minimal model of gene regulation, in which various types of genes interact to control the differentiation of cells through differential gene expression. Britten worked at the Carnegie Institute of Washington in Washington, D.C., while Davidson worked at the California Institute of Technology in Pasadena, California. Their paper was an early theoretical and mechanistic description of gene regulation in higher organisms.