Embryo Project Encyclopedia

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.

Between February 1969 and August 1970 Edward Kollar and Grace Baird, from the University of Chicago in Chicago, Illinois, published three papers that established the role of the mesenchyme in tooth induction. Drawing upon a history of using tissue interactions to understand differentiation, Kollar and Baird designed their experiments to understand how differentiated structures become specified. Their work overturned a widely accepted model that epithelium controls the identity of the structure, a phenomenon called structural specificity. Interactions between epithelium and mesenchyme control the development and differentiation of many parts during embryonic development, including structures like the gastrointestinal tract and hair. Thus, the realization that mesenchyme drives induction and differentiation during epithelio-mesenchymal interactions had far-reaching effects.

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.

Mesoderm is one of the three germ layers, groups of cells that interact early during the embryonic life of animals and from which organs and tissues form. As organs form, a process called organogenesis, mesoderm interacts with endoderm and ectoderm to give rise to the digestive tract, the heart and skeletal muscles, red blood cells, and the tubules of the kidneys, as well as a type of connective tissue called mesenchyme. All animals that have only one plane of symmetry through the body, called bilateral symmetry, form three germ layers. Animals that have only two germ layers develop open digestive cavities. In contrast, the evolutionary development of the mesoderm allowed in animals the formation of internal organs such as stomachs and intestines (viscera).

The Mustard Operation is a surgical technique to correct a heart condition called the transposition of the great arteries (TGA). TGA is a birth defect in which the placement of the two arteries, the pulmonary artery, which supplies deoxygenated blood to the lungs, and the aorta, which takes oxygenated blood to the body are switched. William Thornton Mustard developed the operation later named for him and in 1963 operated on an infant with TGA, and ameliorated the condition, at the Hospital for Sick Children in Toronto, Canada. Afterwards, the Mustard Operation became the primary form of corrective surgery for TGA, until the arterial switch operation largely replaced the Mustard Operation by the late 1990s. The Mustard Operation enabled surgeons to correct TGA in infants born with the life-threatening anomaly, increasing their life spans and quality of life.

Published in 1971, Adenocarcinoma of the Vagina: Association of Maternal Stilbestrol Therapy with Tumor Appearance in Young Women, by Arthurs L. Herbst and colleagues, was the first piece of literature connecting maternal use of the drug diethylstilbestrol (DES), also called stilbestrol, with the development of a rare and severe form of vaginal cancer in young women. Diethylstilbestrol was later classified as an endocrine disruptor, a substance that disrupts the hormonal function of the body in those exposed to it during development or later in life. After Herbst and his team established the connection between DES and the occurrence of breast cancer, cervical cancer, infertility, and reproductive abnormalities, the US federal government banned use the drug for pregnant women. The article was published in the New England Journal of Medicine.

Scientists use cerebral organoids, which are artificially produced miniature organs that represent embryonic or fetal brains and have many properties similar to them, to help them study developmental disorders like microcephaly. In human embryos, cerebral tissue in the form of neuroectoderm appears within the first nine weeks of human development, and it gives rise to the brain and spinal cord. In the twenty-first century, Juergen Knoblich and Madeleine Lancaster at the Institute of Molecular Biotechnology in Vienna, Austria, grew cerebral organoids from pluripotent stem cells as a model to study developmental disorders in embryonic and fetal brains. One such disorder is microcephaly, a condition in which brain size and the number of neurons in the brain are abnormally small. Scientists use cerebral organoids, which they've grown in labs, because they provide a manipulable model for studying how neural cells migrate during development, the timing of neural development, and how genetic errors can result in developmental disorders.

In 1953, Raymond Greene and Katharina Dalton, who were doctors in the UK, published The Premenstrual Syndrome in the British Medical Journal. In their article, Dalton and Greene established the term premenstrual syndrome (PMS). The authors defined PMS as a cluster of symptoms that include bloating, breast pain, migraine-headache, fatigue, anxiety, depression, and irritability. The article states that the symptoms begin one to two weeks before menstruation during the luteal phase of the menstrual cycle, and they disappear upon the onset of the menstrual period. Menstruation is the monthly series of changes a woman's body undergoes in preparation for the possibility of pregnancy. Dalton and Greene described how progesterone affected women during different phases of their menstrual cycles. The paper convinced many about the phenomenon of PMS, and docotors and scientists adopted Dalton's and Green's term. The paper furthered research about the role of hormones in physiology and of conditions linked to the reproductive system.

A germ layer is a group of cells in an embryo that interact with each other as the embryo develops and contribute to the formation of all organs and tissues. All animals, except perhaps sponges, form two or three germ layers. The germ layers develop early in embryonic life, through the process of gastrulation. During gastrulation, a hollow cluster of cells called a blastula reorganizes into two primary germ layers: an inner layer, called endoderm, and an outer layer, called ectoderm. Diploblastic organisms have only the two primary germ layers; these organisms characteristically have multiple symmetrical body axes (radial symmetry), as is true of jellyfish, sea anemones, and the rest of the phylum Cnidaria. All other animals are triploblastic, as endoderm and ectoderm interact to produce a third germ layer, called mesoderm. Together, the three germ layers will give rise to every organ in the body, from skin and hair to the digestive tract.