Embryo Project Encyclopedia

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.

In the 2012 case Texas Medical Providers Performing Abortion Services v. David Lakey, a US appeals court ruled as constitutional a Texas law that required abortion providers in the state to show women receiving abortions the ultrasound images of their fetuses. The law also required providers to describe the sounds of the fetuses' nascent hearts. In doing so, the court set precedent that ultrasound readings are necessary medical information for pregnant women seeking abortions, increasing the wait-period for women seeking abortions. The decision fueled debates in the early twenty-first century US abouts women's rights to abortions.

Dorothy Andersen studied cystic fibrosis in the United States during the early 1900s. In 1935, Andersen discovered lesions in the pancreas of an infant during an autopsy, which led her to classify a condition she named cystic fibrosis of the pancreas. In 1938, Andersen became the first to thoroughly describe symptoms of the medical condition cystic fibrosis. Commonly mistaken for celiac disease prior to the 1900s, Andersen defined cystic fibrosis as the build-up of pancreatic fluid in the body caused by the blockage of pancreatic ducts, and she determined that the two conditions were symptomatically different. Andersen developed an early method for
diagnosing cystic fibrosis. By conceptualizing cystic fibrosis and
defining its symptoms, Andersen laid the foundation for treatments that
enabled infants diagnosed with the disease to survive into adulthood.

Better babies contests were competitions held in state fairs throughout the US during the early twentieth century in which babies between the ages of 6 and 48 months were judged for their health. In 1908, social activist Mary de Garmo established and held the first better babies contest at the Louisiana State Fair in Shreveport, Louisiana. The contests, mirroring theories established in the US’s eugenics movement of the twentieth century, aimed to establish standards for judging infant health. Nurses and physicians judged infants participating in the contest on mental health, physical health, and physical appearance. In 1913, the Woman’s Home Companion (WHC) magazine cosponsored de Garmo’s better babies contests and introduced the competition to state fairs throughout the US. Better babies contests helped promote routine health assessments of children by medical professionals.

Meiosis, the process by which sexually-reproducing organisms generate gametes (sex cells), is an essential precondition for the normal formation of the embryo. As sexually reproducing, diploid, multicellular eukaryotes, humans rely on meiosis to serve a number of important functions, including the promotion of genetic diversity and the creation of proper conditions for reproductive success. However, the primary function of meiosis is the reduction of the ploidy (number of chromosomes) of the gametes from diploid (2n, or two sets of 23 chromosomes) to haploid (1n or one set of 23 chromosomes). While parts of meiosis are similar to mitotic processes, the two systems of cellular division produce distinctly different outcomes. Problems during meiosis can stop embryonic development and sometimes cause spontaneous miscarriages, genetic errors, and birth defects such as Down syndrome.

In 1976, the US Congress passed the Hyde Amendment, which banned the use of federal funding to pay for abortions through Medicaid. In 1976, Illinois Congressman Henry J. Hyde proposed the amendment to the Departments of Labor and Health, Education, and Welfare, Appropriation Act of 1977. In 1980, the US Supreme Court in Harris v. McRae (1980) upheld the constitutionality of the Hyde Amendment. Included annually in every Congressional appropriation act after the one passed in 1976, amended versions of the Hyde Amendment have restricted federal funding of abortion services for women participating in Medicaid.

On 30 June 1980, in a five to four decision, the US Supreme Court ruled in the Case Harris v. McRae that the Hyde Amendment of 1976 did not violate the US Constitution. The Hyde Amendment banned the use of federal funding to pay for any abortion services. The US Supreme Court's decision in Harris v. McRae overturned the decision of McRae v. Califano (1980), in which the US District Court for the Eastern District of New York had ruled that the funding restrictions established by the Hyde Amendment violated the US Constitution. After the US Supreme Court's ruling in Harris v. McRae, the Hyde Amendment continued to prohibit federal Medicaid funding for abortion services, limiting the funds available for low-income women seeking abortions.

"Induction and Patterning of the Primitive Streak, an Organizing Center of Gastrulation in the Amniote," (hereafter referred to as "Induction") examines the mechanisms underlying early amniote gastrulation and the formation of the primitive streak and midline axis. The review, authored by Takashi Mikawa and colleagues at Cornell University Medical College, was published in Developmental Dynamics in 2004. The article primarily discusses chick embryos as a model organism for nonrodent amniote gastrulation, although it intermittently touches on nonamniote gastrulation for comparative purposes. "Induction" attempts to explain the initiation of cell differentiation and embryo organization, one of the most intriguing processes of embryology.

All sexually reproducing, multicellular diploid eukaryotes begin life as embryos. Understanding the stages of embryonic development is vital to explaining how eukaryotes form and how they are related on the tree of life. This understanding can also help answer questions related to morphology, ethics, medicine, and other pertinent fields of study. In particular, the field of comparative embryology is concerned with documenting the stages of ontogeny. In the nineteenth century, embryologist Karl Ernst von Baer famously noted that embryos of different species generally start out with very similar structure and diverge as they progress through development. This similarity allows for the construction of a series of detailed stages exhibited by a range of different organisms (though in reality embryonic development is a continuous, not staggered, process) describing the progression of events that begin with conception.

The process of gastrulation allows for the formation of the germ layers in metazoan embryos, and is generally achieved through a series of complex and coordinated cellular movements. The process of gastrulation can be either diploblastic or triploblastic. In diploblastic organisms like cnidaria or ctenophora, only the endoderm and the ectoderm form; in triploblastic organisms (most other complex metazoans), triploblastic gastrulation produces all three germ layers. The gastrula, the product of gastrulation, was named by Ernst Haeckel in the mid-1870s; the name comes from Latin, where gaster means stomach, and indeed the gut (archenteron) is one of the most distinctive features of the gastrula.