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The Source-Sink Model

The source-sink model, first proposed by biologist Francis Crick in 1970, is a theoretical system for how morphogens distribute themselves across small fields of early embryonic cells. A morphogen is a substance that determines the fate and phenotype of a group of cells through a concentration gradient of itself across that group. Crick’s theory has been experimentally confirmed with several morphogens, most notably with the protein bicoid , the first discovered morphogen. The model provides a theoretical structure for the understanding of some features of early embryonic development.

Format: Articles

Subject: Theories

Bicoid

Bicoid is the protein product of a maternal-effect gene unique to flies of the genus Drosophila . In 1988 Christiane Nüsslein-Volhard identified bicoid as the first known morphogen . A morphogen is a molecule that determines the fate and phenotype of a group of cells through a concentration gradient across that developing region. The bicoid gradient, which extends across the anterior-posterior axis of Drosophila embryos, organizes the head and thorax.

Format: Articles

Subject: Processes

"Genetic Programming: Artificial Nervous Systems, Artificial Embryos and Embryological Electronics" (1991), by Hugo de Garis

In 1991, Hugo de Garis' article "Genetic Programming: Artificial Nervous Systems, Artificial Embryos and Embryological Electronics" was published in the book Parallel Problem Solving from Nature. With this article de Garis hoped to create what he envisioned as a new branch of artificial embryology called embryonics (short term for "embryological electronics"). Embryonics is based on the idea of adapting the processes found in embryonic development to build artificial systems.

Format: Articles

Subject: Publications

"Screening for Congenital Hypothyroidism" (1991), by Delbert A. Fisher

In his 1991 article Screening for Congenital Hypothyroidism, Delbert A. Fisher in the US reported on the implementation and impact of mass neonatal screening programs for congenital hypothyroidism (CH) from the early 1970s through 1991. CH is a condition that causes stunted mental and physical development in newborns unless treatment begins within the first three months of the newborn's life. In the early 1970s, regions in Canada and the US had implemented screening programs to diagnose and treat CH as quickly as possible after the infant's birth.

Format: Articles

Subject: Publications, Technologies

Marcello Malpighi (1646-1694)

Marcello Malpighi studied chick embryos with microscopes in Italy during the seventeenth century. Trained as a medical doctor, he was among the first scientists to use the microscope to examine embryos at very early stages. Malpighi described early structures in chick embryos, and later scientists used his descriptions to help develop the theory of preformationism.

Format: Articles

Subject: People

"Experiments in Plant Hybridization" (1866), by Johann Gregor Mendel

During the mid-nineteenth century, Johann Gregor Mendel experimented with pea plants to develop a theory of inheritance. In 1843, while a monk in the Augustian St Thomas's Abbey in Brünn, Austria, now Brno, Czech Repubic, Mendel examined the physical appearance of the abbey's pea plants (Pisum sativum) and noted inconsistencies between what he saw and what the blending theory of inheritance, a primary model of inheritance at the time, predicted.

Format: Articles

Subject: Experiments

"Congenital Cataract following German Measles in the Mother" (1941), by Norman McAlister Gregg

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.

Format: Articles

Subject: Publications

Gunther von Hagens (1945- )

Gunther von Hagens invented a plastination technique and created Body Worlds, a traveling exhibit that has made anatomy part of the public domain. Von Hagens invented the plastination technique in 1977 while working at Heidelberg University in Heidelberg, Germany. Von Hagen's plastination technique preserves real bodies and tissues by the removal of the fluid and replacement with resin. Body Worlds features three-dimensional, plastinated human bodies.

Format: Articles

Subject: People, Outreach, Reproduction

Fetus in Fetu

Fetus in fetu is a rare variety of parasitic twins , where the developmentally abnormal parasitic twin is completely encapsulated within the torso of the otherwise normally developed host twin. In the late eighteenth century, German anatomist Johann Friedrich Meckel was the first to described fetus in fetu, which translates to “fetus within fetus.” Fetus in fetu is thought to result from the unequal division of the totipotent inner cell mass , the mass of cells that is the ancestral precursor to all cells in the body.

Subject: Theories, Disorders, Reproduction

Bowen v. American Hospital Association (1986)

The 1986 US Supreme Court decision Bowen v. American Hospital Association rejected the federal government's use of Section 504 of the Rehabilitation Act of 1973 to intervene in a hospital's treatment for neonates born with severe congenital defects. This case set a precedent for the role of government involvement in cases where parents refused consent for care of disabled newborns.

Format: Articles

Subject: Legal, Reproduction

St. Augustine (354-430)

St. Augustine of Hippo, born Aurelius Augustinus to a respectable family in the year 354 CE, is now considered one of the foremost theologians in the history of the Catholic Church. His writings, including his philosophy regarding life in the womb and the moral worth of embryos, influenced many other great thinkers of his time and throughout history.

Format: Articles

Subject: People, Religion

Clomiphene Citrate

Clomiphene citrate, more commonly known by its brand names Clomid and Serophene, is a medication prescribed to women to stimulate ovulation in order to treat infertility. It stimulates ovulation in women who do not ovulate or ovulate irregularly. This drug was created by Dr. Frank Palopoli in 1956 while he worked for Merrell Company. It first successfully induced ovulation in women in 1961 and was approved by the Federal and Drug Administration (FDA) in 1967.

Format: Articles

Subject: Technologies

Homunculus

The term homunculus is Latin for "little man." It is used in neurology today to describe the map in the brain of sensory neurons in each part of the body (the somatosensory homunculus). An early use of the word was in the 1572 work by Paracelsus regarding forays into alchemy, De Natura Rerum, in which he gave instructions in how to create an infant human without fertilization or gestation in the womb. In the history of embryology, the homunculus was part of the Enlightenment-era theory of generation called preformationism.

Format: Articles

Subject: Processes

Spermism

Spermism was one of two models of preformationism, a theory of embryo generation prevalent in the late seventeenth through the end of the eighteenth century. Spermist preformationism was the belief that offspring develop from a tiny fully-formed fetus contained within the head of a sperm cell. This model developed slightly later than the opposing ovist model because sperm cells were not seen under the microscope until about 1677.

Format: Articles

Subject: Theories

William Harvey (1578-1657)

Renowned physician and scientist William Harvey is best known for his accurate description of how blood circulates through the body. While his published work on the circulation of blood is considered the most important of his academic life, Harvey also made significant contributions to embryology with the publication of his book Exercitationes de Generatione Animalium in 1651. In this book he established several theories that would set the stage for modern embryology and addressed many embryological issues including conception, embryogenesis, and spontaneous generation.

Format: Articles

Subject: People

"Experimental Chimeras' Removal of Reproductive Barrier Between Sheep and Goat" (1984), by Sabine Meinecke-Tillmann and Burkhard Meinecke

In 1984 Sabine Meinecke-Tillmann and Burkhard Meinecke published their article "Experimental Chimeras - Removal of Reproductive Barrier Between Sheep and Goat" in Nature. Their study conquered the reproductive barrier between sheep and goats through embryo manipulation. Their article appeared in Nature on the same day that a similar experiment, conducted by Carole Fehilly, Steen Willadsen, and Elizabeth Tucker was published regarding reproductive barriers between sheep and goats.

Format: Articles

Subject: Experiments

Laparoscopy

Laparoscopy, a subfield of endoscopy, is a minimally invasive surgical procedure used to examine and operate on the internal organs of the abdomen through a small incision in the abdominal wall. The term "laparoscopy" is derived from two Greek words: laparo, meaning the soft space between hips and ribs, and skopie, meaning to examine. Today laparoscopy has broad clinical applications including for diagnosis, fertility procedures, visual representation, and surgery.

Format: Articles

Subject: Technologies, Reproduction

Humanae Vitae (1968), by Pope Paul VI

The "Humanae Vitae," meaning "Of Human Life" and subtitled "On the Regulation of Birth," was an encyclical promulgated in Rome, Italy, on 25 July 1968 by Pope Paul VI. This encyclical defended and reiterated the Roman Catholic Church's stance on family planning and reproductive issues such as abortion, sterilization, and contraception. The document continues to have a controversial reputation today, as its statements regarding birth control strike many Catholics as unreasonable.

Format: Articles

Subject: Religion, Reproduction

Leonardo da Vinci's Embryological Drawings of the Fetus

Leonardo da Vinci's embryological drawings of the fetus in the womb and his accompanying observational annotations are found in the third volume of his private notebooks. The drawings of Leonardo's embryological studies were conducted between the years 1510-1512 and were drawn with black and red chalk with some pen and ink wash on paper. These groundbreaking illustrations of the fetus reveal his advanced understanding of human development and demonstrate his role in the vanguard of embryology during the Renaissance.

Format: Articles

Subject: Processes

Our Bodies, Ourselves (1973), by the Boston Women's Health Book Collective

Our Bodies, Ourselves, a succession to a pamphlet of resources pulled from co-ops of women in and around Boston, Massachusetts was published in New York in 1973 by Simon and Schuster. Retitled from the original Women and Their Bodies, Our Bodies, Ourselves was an effort by a group of educated, middle class women to reinforce women's ownership of their bodies. There have been eight editions of Our Bodies, Ourselves, as well as sequels such as Our Bodies, Ourselves: Pregnancy and Birth and Our Bodies, Ourselves: Menopause.

Format: Articles

Subject: Outreach, Reproduction

Fetal Surgery

Fetal surgeries are a range of medical interventions performed in utero on the developing fetus of a pregnant woman to treat a number of congenital abnormalities. The first documented fetal surgical procedure occurred in 1963 in Auckland, New Zealand when A. William Liley treated fetal hemolytic anemia, or Rh disease, with a blood transfusion.

Format: Articles

Subject: Disorders, Ethics, Reproduction

Anencephaly

Anencephaly is an open neural tube defect, meaning that part of the neural tube does not properly close or that it has reopened during early embryogenesis. An embryo with anencephaly develops without the top of the skull, but retains a partial skull, including the face. Anencephaly is one of the most common birth defects of the neural tube, occurring at a rate of approximately one in one thousand human pregnancies. The condition can be caused by environmental exposure to chemicals, dietary deficiencies, or genetic mutations.

Format: Articles

Subject: Disorders, Reproduction

George Richard Tiller (1941-2009)

George Richard Tiller, a doctor who performed abortions in Wichita, Kansas, was shot to death on 31 May 2009 by Scott Roeder. As the director of one of only a small number of clinics in the US that performed legal late-term abortions, Tiller was a target for anti-abortion activists. Though Tiller lived and worked in Kansas, his work agitated anti-abortion groups and fueled the controversy surrounding abortion at a national level. Tiller's life and death fueled the abortion debate in the US.

Format: Articles

Subject: People, Reproduction

A. Z. v. B. Z. (2000)

In A.Z. v. B.Z. (2000), the Supreme Judicial Court of Massachusetts in Boston, Massachusetts, affirmed a lower courtÕs decision, ruling that contracts that require a party to become a parent against his or her will are unenforceable and contrary to public policy. The case centered around A.Z. and B.Z., a divorced couple who had previously used in vitro fertilization (IVF) to start a family together during their marriage and had several preembryos cryopreserved as part of the process.

Format: Articles

Subject: Legal

Uniform Anatomical Gift Act (1968)

The Uniform Anatomical Gift Act (UAGA or the Act) was passed in the US in 1968 and has since been revised in 1987 and in 2006. The Act sets a regulatory framework for the donation of organs, tissues, and other human body parts in the US. The UAGA helps regulate body donations to science, medicine, and education. The Act has been consulted in discussions about abortion , fetal tissue transplants , and Body Worlds , an anatomy exhibition.

Format: Articles

Subject: Legal, Outreach, Reproduction