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Calvin Blackman Bridges (1889-1938)
Calvin Blackman Bridges studied chromosomes and heredity in the US throughout the early twentieth century. Bridges performed research with Thomas Hunt Morgan at Columbia University in New York City, New York, and at the California Institute of Technology in Pasadena, California. Bridges and Morgan studied heredity in Drosophila, the common fruit fly. Throughout the early twentieth century, researchers were gathering evidence that genes, or what Gregor Mendel had called the factors that control heredity, are located on chromosomes.
David Wildt's Evolving Ethics Concerning the Roles of Wildlife Reproductive Sciences in Species Conservation
David Wildt is an animal reproductive biologist who directs the Conservation Biology Institute in Fort Royal, Virginia. In 1986, Wildt argued that artificial reproductive technologies should only be used for species conservation efforts if standard techniques to aid natural reproduction are not effective. Between 1986 and 2001, Wildt revised his views and values primarily in relation to two things: which methods captive breeding programs ought to use, and how reproductive scientists ought to contribute to the larger work of conservation.
"How do Embryos Assess Risk? Vibrational Cues in Predator-Induced Hatching of Red-Eyed Treefrogs" (2005), by Karen Warkentin
In 'How do Embryos Assess Risk? Vibrational Cues in Predator-Induced Hatching of Red-Eyed Treefrogs' (2005), Karen Warkentin reported on experiments she conducted to see how red-eyed treefrog embryos, Agalychnis callidryas, can distinguish between vibrations due to predator attacks and other environmental occurrences, such as storms. Though the ability of red-eyed treefrogs to alter their hatch timing had been documented, the specific cues that induce early hatching were not well understood.
Subject: Experiments, Organisms
"Sheep Cloned by Nuclear Transfer from a Cultured Cell Line" (1996), by Keith Campbell, Jim McWhir, William Ritchie, and Ian Wilmut
In 1995 and 1996, researchers at the Roslin Institute in Edinburgh, Scotland, cloned mammals for the first time. Keith Campbell, Jim McWhir, William Ritchie, and Ian Wilmut cloned two sheep, Megan and Morag, using sheep embryo cells. The experiments indicated how to reprogram nuclei from differentiated cells to produce live offspring, and that a single population of differentiated cells could produce multiple offspring. They reported their results in the article 'Sheep Cloned by Nuclear Transfer from a Cultured Cell Line' in March 1996.
Elinor Catherine Hamlin (1924- )
Elinor Catherine Hamlin founded and helped fund centers in Ethiopia to treat women affected by fistulas from obstetric complications. Obstetric fistulas develop in women who experience prolonged labor, as the pressure placed on the pelvis by the fetus during labor causes a hole, or fistula, to form between the vagina and the bladder (vesicovaginal fistula) or between the vagina and the rectum (rectovaginal fistula). Both of those conditions result in urinary or fecal incontinence, which often impacts womenÍs social status within their communities.
Subject: People, Reproduction
Nettie Maria Stevens (1861-1912)
Multiple theories about what determines sex were tested at the turn of the twentieth century. By experimenting on germ cells, cytologist Nettie Maria Stevens collected evidence to support the connection between heredity and the sex of offspring. Stevens was able to interpret her data to conclude that chromosomes have a role in sex determination during development. For her time, she was an emerging breed: a woman of science making the leap from the world of data collection to that of male-dominated interpretive work.
Subject: People, Reproduction
James Alexander Thomson (1958- )
James Alexander Thomson, affectionately known as Jamie Thomson, is an American developmental biologist whose pioneering work in isolating and culturing non-human primate and human embryonic stem cells has made him one of the most prominent scientists in stem cell research. While growing up in Oak Park, Illinois, Thomson's rocket-scientist uncle inspired him to pursue science as a career. Born on 20 December 1958, Thomson entered the nearby University of Illinois Urbana-Champaign nineteen years later as a National Merit Scholar majoring in biophysics.
"Contributions to the Development of the Embryo. On the Artificial Production of One of the First Two Blastomeres, and the Later Development (Postgeneration) of the Missing Half of the Body" (1888), by Wilhelm Roux
Wilhelm Roux was an influential figure in the early history of experimental embryology. Although he originally studied medicine, he was invited to be a Privatdozentur, or unsalaried lecturer, at the Anatomical Institute in Breslau (Wroclaw), Poland, in 1879. He spent the next ten years at this institute, working his way from Dozent to associate professor and finally, in 1889, to director for his own institute, Institut für Entwicklungsgeschichte, or Institute for Developmental History and Mechanics.
"Further Experiments on Artificial Parthenogenesis and the Nature of the Process of Fertilization" (1900), by Jacques Loeb
Jacques Loeb broadened and corrected his earlier claims concerning artificial parthenogenesis in sea urchins in a series of experiments in 1900. He published these findings, "Further Experiments on Artificial Parthenogenesis and the Nature of The Process of Fertilization," in a 1900 issue of The American Journal of Physiology.
Ernest John Christopher Polge (1926-2006)
Twentieth-century researcher Ernest John Christopher Polge studied the reproductive processes of livestock and determined a method to successfully freeze, thaw, and utilize viable sperm cells to produce offspring in animals. In 1949, Polge identified glycerol as a cryoprotectant, or a medium that enables cells to freeze without damaging their cellular components or functions. Several years later, Polge used glycerol in a freezing process called vitrification, which enabled him to freeze poultry sperm, thaw that sperm, and use it to fertilize vertebrate embryos.
Thomas Henry Huxley (1825-1895)
In nineteenth century Great Britain, Thomas Henry Huxley proposed connections between the development of organisms and their evolutionary histories, critiqued previously held concepts of homology, and promoted Charles Darwin's theory of evolution. Many called him Darwin's Bulldog. Huxley helped professionalize and redefine British science. He wrote about philosophy, religion, and social issues, and researched and theorized in many biological fields.
Edward Stuart Russell (1887-1954)
Edward Stuart Russell was born 23 March 1887 to Helen Cockburn Young and the Reverend John N. Russell in Port Glasgow, Scotland. Friends and co-workers alike knew Russell as a quiet and focused, though always kind and helpful person. Trained in classics and biology, Russell's interests drew him to the study of historical and philosophical issues in the biological sciences, particularly morphology and animal behavior. According to Nils Roll-Hansen, Russell was one of the most influential philosophers of biology in the second third of the twentieth century.
Boris Ephrussi (1901-1979)
Boris Ephrussi studied fruit flies, yeast, and mouse genetics and development while working in France and the US during the twentieth century. In yeast, Ephrussi studied how mutations in the cytoplasm persisted across generations. In mice he studied the genetics of hybrids and the development of cancer. Working with George Wells Beadle on the causes of different eye colors in fruit flies, Ephrussi's research helped establish the one-gene-one-enzyme hypothesis. Ephrussi helped create new embryological techniques and contributed the theories of genetics and development.
The French Flag Model
The French flag model represents how embryonic cells receive and respond to genetic information and subsequently differentiate into patterns. Created by Lewis Wolpert in the late 1960s, the model uses the French tricolor flag as visual representation to explain how embryonic cells can interpret genetic code to create the same pattern even when certain pieces of the embryo are removed. Wolpert's model has provided crucial theoretical framework for investigating universal mechanisms of pattern formation during development.
Paternal Sperm Telomere Elongation and Its Impact on Offspring Fitness
Telomeres are structures at the ends of DNA strands that get longer in the DNA of sperm cells as males age. That phenomenon is different for most other types of cells, for which telomeres get shorter as organisms age. In 1992, scientists showed that telomere length (TL) in sperm increases with age in contrast to most cell of most other types. Telomeres are the protective caps at the end of DNA strands that preserve chromosomal integrity and contribute to DNA length and stability.
General Embryological Information Service, published annually by the Hubrecht Laboratory, 1949-1981
The General Embryological Information Service (GEIS) was an annual report published by the Hubrecht Laboratory in Utrecht, The Netherlands from 1949 to 1981 that disseminated contemporary research information to developmental biologists. The purpose of the annual report was to catalog the names, addresses, and associated research of every developmental biologist in the world. Pieter Nieuwkoop edited each issue from 1949 until 1964, when Job Faber began assisting Nieuwkoop. Bert Z. Salome joined the editing team in 1968 before Nieuwkoop ceased editing duties in 1971.
Katharine McCormick (1876-1967)
Katharine Dexter McCormick, who contributed the majority of funding for the development of the oral contraceptive pill, was born to Josephine and Wirt Dexter on 27 August 1875 in Dexter, Michigan. After growing up in Chicago, Illinois, she attended the Massachusetts Institute of Technology (MIT), where she graduated in 1904 with a BS in biology. That same year, she married Stanley McCormick, the son of Cyrus McCormick, inventor and manufacturer of the mechanized reaper.
Subject: People, Ethics, Reproduction
Telomeres and Telomerase in Cellular Aging (Senescence)
Telomeres are sequences of DNA on the ends of chromosomes that protect chromosomes from sticking to each other or tangling, which could cause irregularities in normal DNA functions. As cells replicate, telomeres shorten at the end of chromosomes, which correlates to senescence or cellular aging. Integral to this process is telomerase, which is an enzyme that repairs telomeres and is present in various cells in the human body, especially during human growth and development.
Biological Clocks and the Formation of Human Tooth Enamel
Tooth enamel contains relics of its formation process, in the form of microstructures, which indicate the incremental way in which it forms. These microstructures, called cross-striations and striae of Retzius, develop as enamel-forming cells called ameloblasts, whcih cyclically deposit enamel on developing teeth in accordance with two different biological clocks. Cross-striations result from a twenty-four hour cycle, called a Circadian rhythm, in the enamel deposition process, while striae of Retzius have a longer periodicity.
Early in the process of development, vertebrate embryos develop a fold on the neural plate where the neural and epidermal ectoderms meet, called the neural crest. The neural crest produces neural crest cells (NCCs), which become multiple different cell types and contribute to tissues and organs as an embryo develops. A few of the organs and tissues include peripheral and enteric (gastrointestinal) neurons and glia, pigment cells, cartilage and bone of the cranium and face, and smooth muscle.
Cerebral Organoid as a Model System in the Study of Microcephaly
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.
The Genetic Control and Cytoplasmic Expression of 'Inducibility' in the synthesis of B-galactosidase" (1959), by Arthur B. Pardee, Francois Jacob, and Jacques Monod
Between 1957 and 1959, Arthur Pardee, Francois Jacob, and Jacques Monod conducted a set of experiments at the Pasteur Institute in Paris, France, that was later called the PaJaMa Experiments, a moniker derived from the researchers' last names. In these experiments, they described how genes of a species of single-celled bacteria, called Escherichia coli (E. coli), controlled the processes by which enzymes were produced in those bacteria.
Sex Determination in Humans
In humans, sex determination is the process that determines the biological sex of an offspring and, as a result, the sexual characteristics that they will develop. Humans typically develop as either male or female, primarily depending on the combination of sex chromosomes that they inherit from their parents. The human sex chromosomes, called X and Y, are structures in human cells made up of tightly bound deoxyribonucleic acid, or DNA, and proteins.
Elizabeth Dexter Hay (1927–2007)
Elizabeth Dexter Hay studied the cellular processes that affect development of embryos in the US during the mid-twentieth and early twenty-first centuries. In 1974, Hay showed that the extracellular matrix, a collection of structural molecules that surround cells, influences cell behavior. Cell growth, cell migration, and gene expression are influenced by the interaction between cells and their extracellular matrix.
Hamlin Fistula Ethiopia (1974- )
Hamlin Fistula Ethiopia is a nonprofit organization that began in 1974 as a joint endeavor by Reginald and Catherine Hamlin and the Addis Ababa Fistula Hospital in Addis Ababa, Ethiopia. Hamlin Fistula Ethiopia promotes reproductive health in Ethiopia by raising awareness and implementing treatment and preventive services for women affected by obstetric fistulas. It also aims to restore the lives of women afflicted with obstetric fistulas in Ethiopia and eventually to eradicate the condition.
Subject: Organizations, Reproduction, Outreach