Embryo Project Encyclopedia

Hilde Proscholdt Mangold was a doctoral student at the Zoological Institute at the University of Freiburg in Freiburg, Germany, from 1920-1923. Mangold conducted research for her dissertation 'On the Induction of Embryonic Primordia by Implantation of Organizers from Different Species' ('Ueber Induktion von Embryonanlagen durch Implantation artfremder Organisatoren'), under the guidance of Hans Spemann, a professor of zoology at the University of Freiburg. The dissertation was the culmination of five experiments on three species of newt embryos, of the genus Triton (presently, Triturus), performed during the summers of 1921 and 1922, which resulted in a confirmation of Spemann's organizer concept. Spemann and Mangold published the dissertation in a 1924 edition of Roux's Archives for Microscopic Anatomy and Developmental Mechanics (Roux's Archiv fur Mikroskopische Anatomie und Entwicklungsmechanik)."

Conrad Hal Waddington's "Experiments on Embryonic Induction III," published in 1934 in the Journal of Experimental Biology, describes the discovery that the primitive streak induces the mammalian embryo. Waddington's hypothesis was that a transplanted primitive streak could induce neural tissue in the ectoderm of the rabbit embryo. The primitive streak defines the axis of an embryo and is capable of inducing the differentiation of various tissues in a developing embryo during gastrulation. In this experiment Waddington was, in fact, able to induce neural differentiation. Waddington noted that the tissue is "competent"; for a chick organizer, and by deduction a mammalian organizer must exist. Competence refers to a cell's ability to respond to an inducing signal, which is temporally limited to certain developmental stages. Waddington's initial work laid the foundation for many decades of research to follow, including further experiments by Waddington with the mammalian organizer.

Rosalind Elsie Franklin worked with X-ray crystallography at King's College London, UK, and she helped determine the helical structure of DNA in the early 1950s. Franklin's research helped establish molecular genetics, a field that investigates how heredity works on the molecular level. The discovery of the structure of DNA also made future research possible into the molecular basis of embryonic development, genetic disorders, and gene manipulation.

Cocaine use by pregnant women has a variety of effects on the embryo and fetus, ranging from various gastro-intestinal and cardiac defects to tissue death from insufficient blood supply. Thus, cocaine has been termed a teratogen, or an agent that causes defects in fetuses during prenatal development. Cocaine is one of the most commonly used drugs in the US and it has a history of both medical and illegal recreational use. It is a drug capable of a wide array of effects on physical and mental health. Research on the teratogenic effects of cocaine began in the early 1980s, and in 1985 research on the effects of cocaine on prenatal development gained widespread attention. Since then, numerous studies have contributed to information about the detrimental impacts of maternal cocaine use on embryonic and fetal development.

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.

The epigenetic landscape is a concept representing embryonic development. It was proposed by Conrad Hal Waddington to illustrate the various developmental pathways a cell might take toward differentiation. The epigenetic landscape integrates the connected concepts of competence, induction, and regulative abilities of the genes into a single model designed to explain cellular differentiation, a long standing problem in embryology.

Developmental Effects of Endocrine-Disrupting Chemicals in Wildlife and Humans, was published in 1993 in Environmental Health Perspectives. In the article, the authors present an account of two decades' worth of scientific research that describes the effects of certain pollutants on the health of wildlife, domestic animals, and humans, particularly when exposure takes place during embryonic growth. The term endocrine disruptor was coined in the article to describe the chemical pollutants that target the development and function of the endocrine system. Since its publication, Developmental Effects has increased research interest in endocrine disruption and has raised awareness among the general public, the scientific community, and government organizations about the effects that some chemicals may have on development and reproduction.

Victor Ambros is a professor of molecular medicine at the University of Massachusetts Medical School, and he discovered the first microRNA (miRNA) in 1993. Ambros researched the genetic control of developmental timing in the nematode worm Caenorhabditis elegans and he helped describe gene function and regulation during the worm’s development and embryogenesis. His discovery of miRNA marked the beginning of research into a form of genetic regulation found throughout diverse life forms from plants to humans. Ambros is a central figure in the miRNA and C. elegans research communities, and co-directs the RNA Therapeutics Institute.

"In vitro Experiments on the Effects of Mouse Sarcomas 180 and 37 on the Spinal and Sympathetic Ganglia of the Chick Embryo" were experiments conducted by Rita Levi-Montalcini in conjunction with Viktor Hamburger and Hertha Meyer and published in Cancer Research in 1954. In this series of experiments, conducted at the University of Brazil, Levi-Montalcini demonstrated increased nerve growth by introducing specific tumors (sarcomas) to chick ganglia. Ganglia are clusters of nerve cells, from which nerve fibers emerge. This work led to the discovery of nerve growth factor (NGF) and later the Nobel Prize in Physiology or Medicine in 1986.

Epidermal growth factor is a signaling molecule that stimulates the growth of epidermal tissues during development and throughout life. Stanley Cohen discovered epidermal growth factor (EGF) during studies of nerve growth factor as a side effect of other experiments. EGF stimulates tissue growth by initiating a variety of cellular mechanisms. This work led to the 1986 Nobel Prize in Physiology or Medicine awarded to Cohen and Rita Levi-Montalcini. At the Nobel Award ceremony Levi-Montalcini focused her acceptance speech on nerve growth factor, while Cohen focused his on epidermal growth factor. Although they presented different topics, they were close collaborators and their combined effort led to the discovery of nerve growth factor. They had worked together in Viktor Hamburger's laboratory at Washington University in St. Louis.