Embryo Project Encyclopedia

Endoderm is one of the germ layers-- aggregates of cells that organize early during embryonic life and from which all organs and tissues develop. All animals, with the exception of sponges, form either two or three germ layers through a process known as gastrulation. During gastrulation, a ball of cells transforms into a two-layered embryo made of an inner layer of endoderm and an outer layer of ectoderm. In more complex organisms, like vertebrates, these two primary germ layers interact to give rise to a third germ layer, called mesoderm. Regardless of the presence of two or three layers, endoderm is always the inner-most layer. Endoderm forms the epithelium-- a type of tissue in which the cells are tightly linked together to form sheets-- that lines the primitive gut. From this epithelial lining of the primitive gut, organs like the digestive tract, liver, pancreas, and lungs develop.

The sex of a reptile embryo partly results from the production of sex hormones during development, and one process to produce those hormones depends on the temperature of the embryo's environment. The production of sex hormones can result solely from genetics or from genetics in combination with the influence of environmental factors. In genotypic sex determination, also called genetic or chromosomal sex determination, an organism's genes determine which hormones are produced. Non-genetic sex determination occurs when the sex of an organism can be altered during a sensitive period of development due to external factors such as temperature, humidity, or social interactions. Temperature-dependent sex determination (TSD), where the temperature of the embryo's environment influences its sex development, is a widespread non-genetic process of sex determination among vertebrates, including reptiles. All crocodilians, most turtles, many fish, and some lizards exhibit TSD.

The Human Papillomavirus (HPV) strains 16 and 18 are the two most common HPV strains that lead to cases of genital cancer. HPV is the most commonly sexually transmitted disease, resulting in more than fourteen million cases per year in the United States alone. When left untreated, HPV leads to high risks of cervical, vaginal, vulvar, anal, and penile cancers. In 1983 and 1984 in Germany, physician Harald zur Hausen found that two HPV strains, HPV-16 and HPV-18, caused cervical cancer in women. In the early twenty first century, pharmaceutical companies Merck & Co. and GlaxoSmithKline created HPV vaccines protecting against HPV-16 and HPV-18, which have reduced the number of HPV infections by fifty-six percent in the US. Discovering HPV strains 16 and 18 allowed physicians to test for those cancer-causing cell populations using Pap smears, a diagnostic tool that collects cells from the woman's cervix to identify cancerous cases of HPV infection. By identifying the cancerous strains of HPV-16 and HPV-18 and utilizing preventative measures such as the Pap smear and HPV vaccines, the rates of cervical cancer and other HPV-related cancers have reduced.

Where Are My Children? is an anti-abortion silent film released in the United States on 16 April 1916. The film was directed by Lois Weber and Phillips Smalley and produced by Universal Film Manufacturing Company/Lois Weber Productions in Universal City, California. In the film, Weber tells a story of an attorney who wants to have children and raise a family, but his wife chooses to abort her pregnancies, fearing that having children will ruin her social activities. In the early 1900s, information about contraception was not freely available or legal to obtain. Physicians were allowed to distribute contraceptives only if the woman would be put in a life-threatening circumstance were she to get pregnant. In the film, Weber encourages contraceptives as a means of family planning, but advocates against abortions. Where Are My Children? is one of the first films to discuss birth control and family planning, and it is among the first to push against motion picture censorship of contraception and family planning in cinema.

From 1977 to 1987, Harald zur Hausen led a team of researchers across several institutions in Germany to investigate whether the human papillomavirus (HPV) caused cervical cancer. Zur Hausen's first experiment tested the hypothesis that HPV caused cervical cancer rather than herpes simplex virus type 2 (HSV-2), the then accepted cause. His second and third experiments detailed methods to identify two previously unidentified HPV strains, HPV 16 and HPV 18, in cervical cancer tumor samples. The experiments showed that HPV 16 and 18 DNA were present in cervical tumor samples. Zur Hausen concluded that HPV, not HSV-2, caused cervical cancer, which enabled researchers to develop preventions, such as the HPV vaccine.

Gattaca is a 1997 science fiction film produced in the US that depicts a future society that uses reproductive technology and genetic engineering in order to produce genetically enhanced human beings. By selectively choosing certain genes, scientists and physicians ensure that individuals born using reproductive technologies have desirable physical and psychological traits and prevent undesirable traits. The film tells a story of Vincent Freeman, a man conceived without the aid of reproductive technology, who works to overcome his genetic disadvantages compared to his enhanced counterparts in order to achieve his dream of a career in space travel. The film was directed and written by Andrew Niccol and released by Columbia Pictures in Culver City, California, on 24 October 1997. Gattaca addresses the ethical uses of biotechnology, gene manipulation, and genetic engineering, and the film helps illustrate the debate over human genetic engineering research and implications.

Собачье сердце (Heart of a Dog) is a novella written in 1925 by author and playwright Mikhail Bulgakov in Moscow, USSR, later Russia. An early English translation was published in 1968. Heart of a Dog tells the story of a stray dog named Sharik, who is found by a surgeon, and undergoes extensive surgery for experimental purposes to create a New Soviet man, someone committed to the ideals of communism in the Soviet Union. In Heart of a Dog, Bulgakov satirizes the communist revolution in the Soviet Union and the concept of a New Soviet man, and criticizes the science and practice of eugenics.

Tomorrow's Children is a film that tells the story of Alice Mason, a young woman whom the US government forcibly sterilizes because she comes from a family with a history of alcoholism, mental illnesses, and physical disabilities, traits that they considered biologically determined and inferior. The film, released in 1934, was directed by Crane Wilbur, produced by Bryan Foy, written by Wilbur and Wallace Thurman, and released by Foy Productions Ltd. Tomorrow's Children criticized forced sterilization and the eugenics movement in the United States in addition to protesting film censorship regulations in the early 1900s.

In Australia in the 1940s, Norman McAlister Gregg observed a connection between pregnant women who contracted the rubella virus, or German measles, and cataract formation in their children's eyes. Gregg published his findings in the 1941 article Congenital Cataract following German Measles in the Mother in Transactions of the Ophthalmological Society of Australia. In the article, Gregg analyzed seventy-eight cases of congenital cataracts and suggested that the mothers' environmental factors could cause birth defects, otherwise known as teratogenic effects. Gregg's paper on the teratogenic effects of an environmental agent, the rubella virus, changed the study of birth defects to include viruses as potential causes or teratogens.

Solomon A. Berson helped develop the radioimmunoassay (RIA) technique in the US during the twentieth century. Berson made many scientific contributions while working with research partner Rosalyn Yalow at the Bronx Veterans Administration (VA) hospital, in New York City, New York. In the more than twenty years that Berson and Yalow collaborated, they refined the procedures for tracing diagnostic biological compounds using isotope labels. In the late 1950s they developed the RIA based on the ability to trace the competition between and ligands, or small molecules that bind to specific sites of other biomolecules, and proteins for the same molecular binding site, a process called competitive binding. Scientists widely used Berson and Yalow's RIA, as these methods permit the use of a minimal sample of blood for accurate measurements of biological molecules such as hormones that cause the production of antibodies. Berson and Yalow's research has advanced the study of physiology, including that of the reproductive system, with particular applications to the diagnosis and treatment of infertility.