Search

Displaying 201 - 225 of 660 items.

Fate Map

Early development occurs in a highly organized and orchestrated manner and has long attracted the interest of developmental biologists and embryologists. Cell lineage, or the study of the developmental differentiation of a blastomere, involves tracing a particular cell (blastomere) forward from its position in one of the three germ layers. Labeling individual cells within their germ layers allows for a pictorial interpretation of gastrulation. This chart or graphical representation detailing the fate of each part of an early embryo is referred to as a fate map.

Format: Articles

Subject: Processes

The Neuron Doctrine (1860-1895)

The neuron doctrine is a concept formed during the turn of the twentieth century that describes the properties of neurons, the specialized cells that compose the nervous system. The neuron doctrine was one of two major theories on the composition of the nervous system at the time. Advocates of the neuron doctrine claimed that the nervous system was composed of discrete cellular units. Proponents of the alternative reticular theory, on the other hand, argued that the entire nervous system was a continuous network of cells, without gaps or synapses between the cells.

Format: Articles

Subject: Theories

Nicole Le Douarin and Charles Ordahl's Experiments on the Developmental Lineages of Somites

Through various studies developmental biologists have been able to determine that the muscles of the back, ribs, and limbs derive from somites. Somites are blocks of cells that contain distinct sections that diverge into specific types (axial or limb) of musculature and are an essential part of early vertebrate development. For many years the musculature of vertebrates was known to derive from the somites, but the exact developmental lineage of axial and limb muscle progenitor cells remained a mystery until Nicole Le Douarin and Charles P.

Format: Articles

Subject: Experiments

Wilhelm Friedrich Phillip Pfeffer (1845-1920)

Wilhelm Friedrich Phillip Pfeffer studied plants in Germany during the late nineteenth and early twentieth centuries. He started his career as an apothecary, but Pfeffer also studied plant physiology, including how plants move and react to changes in light, temperature, and osmotic pressure. He created the Pfeffer Zelle apparatus, also known as the Pfeffer Cell, to study osmosis in plants. PfefferÕs experiments led to new theories about the structure and development of plants.

Format: Articles

Subject: People

"β-Catenin Defines Head Versus Tail Identity During Planarian Regeneration and Homeostasis" (2007), by Kyle A. Gurley, Jochen C. Rink, and Alejandro Sánchez Alvarado

Alejandro Sánchez Alvarado's laboratory group has employed molecular tools to investigate old questions about regeneration and as a result have identified some of the molecular mechanisms determining polarity. Recent work by his group has shown Wnt-β-catenin signaling determines whether a tail or a head will form during regeneration in planarians. This study was motivated by work Thomas Hunt Morgan conducted in the late nineteenth century.

Format: Articles

Subject: Experiments

Nerve Growth Factor

Nerve growth factor (NGF) is a signaling protein and growth factor implicated in a wide range of development and maintenance functions. NGF was discovered through a series of experiments in the 1950s on the development of the chick nervous system. Since its discovery, NGF has been found to act in a variety of tissues throughout development and adulthood. It has been implicated in immune function, stress response, nerve maintenance, and in neurodegenerative diseases.

Format: Articles

Subject: Processes

Effects of Prenatal Alcohol Exposure on Ocular Development

Maternal consumption of alcohol (ethanol) can result in a range of alcohol-induced developmental defects. In humans, those collective birth defects are called Fetal Alcohol Spectrum Disorders, with the most severe manifestation being Fetal Alcohol Syndrome (FAS). FAS is defined by pre- and post-natal growth retardation, minor facial abnormalities, and deficiencies in the central nervous system (CNS). The eye and ocular system development is particularly susceptible to the effects of prenatal alcohol exposure and can result in visual impairment or blindness.

Format: Articles

Subject: Disorders, Reproduction

Craig C. Mello (1960- )

Craig C. Mello is an American developmental biologist and Nobel Laureate, who helped discover RNA interference (RNAi). Along with his colleague Andrew Fire, he developed gene knockouts using RNAi. In 006 Mello won the Nobel Prize in Physiology or Medicine for his contribution. Mello also contributed to developmental biology, focusing on gene regulation, cell signaling, cleavage formation, germline determination, cell migration, cell fate differentiation, and morphogenesis.

Format: Articles

Subject: People

Roy John Britten (1919-2012)

Roy John Britten studied DNA sequences in the US in the second
half of the twentieth century, and he helped discover repetitive
elements in DNA sequences. Additionally, Britten helped propose
models and concepts of gene regulatory networks. Britten studied the
organization of repetitive elements and, analyzing data from the
Human Genome Project, he found that the repetitive elements in DNA
segments do not code for proteins, enzymes, or cellular parts.
Britten hypothesized that repetitive elements helped cause cells to

Format: Articles

Subject: People

Hensen's Node

A node, or primitive knot, is an enlarged group of cells located in the anterior portion of the primitive streak in a developing gastrula. The node is the site where gastrulation, the formation of the three germ layers, first begins. The node determines and patterns the anterior-posterior axis of the embryo by directing the development of the chordamesoderm. The chordamesoderm is a specific type of mesoderm that will differentiate into the notochord, somites, and neural tube. Those structures will later form the vertebral column.

Format: Articles

Subject: Processes

Alfred Henry Sturtevant (1891–1970)

Alfred Henry Sturtevant studied heredity in fruit flies in the US throughout the twentieth century. From 1910 to 1928, Sturtevant worked in Thomas Hunt Morgan’s research lab in New York City, New York. Sturtevant, Morgan, and other researchers established that chromosomes play a role in the inheritance of traits. In 1913, as an undergraduate, Sturtevant created one of the earliest genetic maps of a fruit fly chromosome, which showed the relative positions of genes along the chromosome.

Format: Articles

Subject: People

Anne Laura Dorinthea McLaren (1927-2007)

Anne Laura Dorinthea McLaren was a developmental biologist known for her work with embryology in the twentieth century. McLaren was the first researcher to grow mouse embryos outside of the womb. She experimented by culturing mouse eggs and successfully developing them into embryos, leading to advancements with in vitro fertilization.

Format: Articles

Subject: People

Ilya Ilyich Mechnikov (Elie Metchnikoff) (1845-1916)

Ilya Ilyich Mechnikov studied phagocytes, immune function, and starfish embryos in Europe during the late nineteenth and early twentieth centuries. Mechnikov adopted the French form of his name, Élie Metchnikoff, in the last twenty-five years of his life. In 1908, he won the Nobel Prize in Physiology or Medicine with Paul Ehrlich for their contributions to immunology. Mechnikov discovered phagocytes, immune cells that protect organisms by ingesting foreign particles or microorganisms, by conducting experiments on starfish larvae.

Format: Articles

Subject: People

The Cell in Development and Inheritance (1900), by Edmund Beecher Wilson

The Cell in Development and Inheritance, by Edmund Beecher Wilson, provided a textbook introduction to cell biology for generations of biologists in the twentieth century. In his book, Wilson integrated information about development, inheritance, chromosomes, organelles, and the structure and functions of cells. First published in 1896, the book started with 371 pages, grew to 483 pages in the second edition that appeared in 1900, and expanded to 1,231 pages by the third and final edition in 1925.

Format: Articles

Subject: Publications

Ovum Humanum: Growth, Maturation, Nourishment, Fertilization and Early Development (1960), by Landrum Brewer Shettles

Ovum Humanum was written and compiled by Dr. Landrum Brewer Shettles while he worked as a doctor in New York. The publication contains an atlas of photographs of the human egg cell that Shettles took while working at Columbia Presbyterian Hospital in New York City. Stechert-Hafner, Inc, a publishing company based in New York City, published the book in 1960. The book presents a collection of color photographs that shows detail of the human egg that had never been seen before, providing a reference for scientists and doctors that documented the anatomy of these cells.

Format: Articles

Subject: Publications, Reproduction

Christiane Nusslein-Volhard (1942- )

Christiane Nusslein-Volhard studied how genes control embryonic development in flies and in fish in Europe during the twentieth and twenty-first centuries. In the 1970s, Nusslein-Volhard focused her career on studying the genetic control of development in the fruit fly Drosophila melanogaster. In 1988, Nusslein-Volhard identified the first described morphogen, a protein coded by the gene bicoid in flies. In 1995, along with Eric F. Wieschaus and Edward B.

Format: Articles

Subject: People

Whitner v. South Carolina (1997)

In the case Whitner v. South Carolina in 1997, the South Carolina State Supreme Court defined the concept of a child to include viable fetuses. This allowed grounds for prosecution of a pregnant womanÕs prenatal activity if those activities endangered or could potentially endanger the fetus within her. The case brought the issue of fetal rights versus pregnant womenÕs rights to light.

Format: Articles

Subject: Legal, Reproduction

Androgen Insensitivity Syndrome

Androgen Insensitivity Syndrome (AIS) is a human disorder in which an individual's genetic sex (genotype) differs from that individual's observable secondary sex characteristics (phenotypes). A fetus with AIS is genetically male with a 46,XY genotype. The term 46,XY refers to the chromosomes found in most cells of the fetus. Most cells have a total of 46 autosomes, or non-sex chromosomes, and a pair sex chromosomes, XX for genetic females, or XY for genetic males.

Format: Articles

Subject: Disorders

Ontogeny and Phylogeny (1977), by Stephen Jay Gould

Ontogeny and Phylogeny is a book published in 1977, in which the author Stephen J. Gould, who worked in the US, tells a history of the theory of recapitulation. A theory of recapitulation aims to explain the relationship between the embryonic development of an organism (ontogeny) and the evolution of that organism's species (phylogeny). Although there are several variations of recapitulationist theories, most claim that during embryonic development an organism repeats the adult stages of organisms from those species in it's evolutionary history.

Format: Articles

Subject: Publications

Sonja Vernes, et al.'s Experiments On the Gene Networks Affected by the Foxp2 Protein (2011)

In 2011, Sonja Vernes and Simon Fisher performed a series of experiments to determine which developmental processes are controlled by the mouse protein Foxp2. Previous research showed that altering the Foxp2 protein changed how neurons grew, so Vernes and Fisher hypothesized that Foxp2 would affect gene networks that involved in the development of neurons, or nerve cells. Their results confirmed that Foxp2 affected the development of gene networks involved in the growth of neurons, as well as networks that are involved in cell specialization and cell communication.

Format: Articles

Subject: Experiments

Ernst Heinrich Philipp August Haeckel (1834-1919)

Ernst Heinrich Philipp August Haeckel was a prominent comparative anatomist and active lecturer in the late nineteenth and early twentieth centuries. He is most well known for his descriptions of phylogenetic trees, studies of radiolarians, and illustrations of vertebrate embryos to support his biogenetic law and Darwin's work with evolution. Haeckel aggressively argued that the development of an embryo repeats or recapitulates the progressive stages of lower life forms and that by studying embryonic development one could thus study the evolutionary history of life on earth.

Format: Articles

Subject: People

Chorionic Villus Sampling

Chorionic villus sampling (CVS) is a test used for prenatal diagnosis. Safe to perform at an earlier stage in pregnancy than amniocentesis, CVS is another invasive prenatal diagnostic test that can be performed as early as ten weeks after the woman's last menstrual cycle. While this test does carry some risks, it is generally very effective at predicting heritable diseases during or soon after the embryonic stage of development.

Format: Articles

Subject: Technologies

Jeter v. Mayo (2005)

In Jeter v. Mayo, the Court of Appeals of Arizona in 2005 held that a cryopreserved, three-day-old pre-embryo is not a person for purposes of Arizona's wrongful death statutes, and that the Arizona Legislature was best suited to decide whether to expand the law to include cryopreserved pre-embryos. The Court of Appeals affirmed a decision by the Maricopa County Superior Court to dismiss a couple's wrongful death claim after the Mayo Clinic (Mayo) allegedly lost or destroyed several of their cryopreserved pre-embryos.

Format: Articles

Subject: Reproduction, Legal

Rock-Menkin Experiments

Dr. John Rock, a doctor of obstetrics and gynecology in Boston, and Miriam Menkin, Rock s hired lab technician, were the first researchers to fertilize a human egg outside of a human body in February of 1944. Their work was published on 4 August 1944 in an issue of Science in an article entitled "In Vitro Fertilization and Cleavage of Human Ovarian Eggs." This experiment marked the first time in history that a human embryo was produced outside of the human body, proving that in vitro fertilization was possible in humans.

Format: Articles

Subject: Experiments, 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