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Mechanistic Realization of the Turtle Shell

Turtle morphology is unlike that of any other vertebrate. The uniqueness of the turtle's bodyplan is attributed to the manner in which the turtle's ribs are ensnared within its hard upper shell. The exact embryological and genetic mechanisms underpinning this peculiar anatomical structure are still a matter of debate, but biologists agree that the evolution of the turtle shell lies in the embryonic development of the turtle.

Format: Articles

Subject: Processes

Hanging Drop Tissue Culture

The hanging drop tissue culture is a technique utilized in embryology and other fields to allow growth that would otherwise be restricted by the flat plane of culture dishes and also to minimize the surface area to volume ratio, slowing evaporation. The classic hanging drop culture is a small drop of liquid, such as plasma or some other media allowing tissue growth, suspended from an inverted watch glass. The hanging drop is then suspended by gravity and surface tension, rather than spreading across a plate.

Format: Articles

Subject: Technologies

Brian K. Hall (1941- )

Brian Hall is the son of Doris Garrad and Harry Hall, and was born in Port Kembla, NSW Australia, on 28 October 1941. He attended the University of New England in Armidale NSW, graduating in 1963 with a BSc in zoology, in 1965 with a BSc (Honors) in zoology, and in 1968 with a PhD in zoology. His PhD thesis, undertaken under the supervision of Patrick D. F. Murray, FAA was on the differentiation of bone and secondary cartilage in chicken embryos.

Format: Articles

Subject: People

"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

Studies of Thalidomide's Effects on Rodent Embryos from 1962-2008

Thalidomide is a sedative drug introduced to European markets on 1 October 1957 after extensive testing on rodent embryos to ensure its safety. Early laboratory tests in rodent populations showed that pregnant rodents could safely use it, so doctors prescribed Thalidomide to treat morning sickness in pregnant women. However, in humans Thalidomide interfered with embryonic and fetal development in ways not observed in rodent tests.

Format: Articles

Subject: Organisms, Reproduction, Disorders

The Diversity of Animals: An Evolutionary Study (1962), by Edward Stuart Russell

In 1962 the journal Acta Biotheoretica published the final work of the biologist Edward Stuart Russell, a full eight years after his death. Entitled The Diversity of Animals: an Evolutionary Study, this short, unfinished manuscript on evolution received little recognition in the scientific presses despite both its technical discussion of adaptations in decapods (crabs, shrimp, etc.) and its different approach to evolutionary theory. The precise reason for this neglect is unclear.

Format: Articles

Subject: Publications

Maurice Ralph Hilleman (1919–2005)

Maurice Ralph Hilleman developed vaccines at the Merck Institute of Therapeutic Research in West Point, Pennsylvania, during the twentieth century. Over the course of his career at Merck, Hilleman created over forty vaccines, making him one of the most prolific developers of vaccine in the twentieth century. Of the fourteen vaccines commonly given to children in the US by 2015, Hilleman was responsible for eight of them. Hilleman's most widely used vaccine was his measles, mumps, and rubella (MMR) vaccine.

Format: Articles

Subject: People

John Philip Trinkaus (1918-2003)

John Philip Trinkaus studied the processes of cell migration and gastrulation, especially in teleost fish, in the US during the twentieth century. Called Trink by his friends, his social confidence and work ethic combined to make him a prolific and decorated developmental biologist. His scientific contributions included investigations of several different aspects of embryology.

Format: Articles

Subject: People

"Adenocarcinoma of the Vagina: Association of Maternal Stilbestrol Therapy with Tumor Appearance in Young Women" (1971), by Arthur L. Herbst, et al.

Published in 1971, Adenocarcinoma of the Vagina: Association of Maternal Stilbestrol Therapy with Tumor Appearance in Young Women, by Arthurs L. Herbst and colleagues, was the first piece of literature connecting maternal use of the drug diethylstilbestrol (DES), also called stilbestrol, with the development of a rare and severe form of vaginal cancer in young women. Diethylstilbestrol was later classified as an endocrine disruptor, a substance that disrupts the hormonal function of the body in those exposed to it during development or later in life.

Format: Articles

Subject: Publications

Charles Bonnet (1720-1793)

Charles Bonnet was a naturalist and philosopher in the mid eighteenth century. His most important contribution to embryology was the discovery of parthenogenesis in aphids, proving that asexual reproduction of offspring was possible. In his later life, he was an outspoken defender of the theory of generation now known as preformationism, which stated that offspring exist prior to conception preformed in the germ cell of one of their parents.

Format: Articles

Subject: People

"Induction and Patterning of the Primitive Streak, an Organizing Center of Gastrulation in the Amniote" (2004), by Takashi Mikawa, Alisa M. Poh, Kristine A. Kelly, Yasuo Ishii, and David E. Reese

"Induction and Patterning of the Primitive Streak, an Organizing Center of Gastrulation in the Amniote," (hereafter referred to as "Induction") examines the mechanisms underlying early amniote gastrulation and the formation of the primitive streak and midline axis. The review, authored by Takashi Mikawa and colleagues at Cornell University Medical College, was published in Developmental Dynamics in 2004.

Format: Articles

Subject: Publications

Hans Spemann (1869-1941)

Hans Spemann was an experimental embryologist best known for his transplantation studies and as the originator of the "organizer" concept. One of his earliest experiments involved constricting the blastomeres of a fertilized salamander egg with a noose of fine baby hair, resulting in a partially double embryo with two heads and one tail.

Format: Articles

Subject: People

Hamburger-Hamilton Staging Series (1951)

In 1951 Viktor Hamburger and Howard Hamilton created an embryonic staging series from a combination of photographs and drawings from other researchers. The Hamburger-Hamilton stages are a sequence of images depicting 46 chronological stages in chick development. The images begin with a fertilized egg and end with a fully developed chick. The Hamburger-Hamilton staging series was produced in order to replace a previous chick staging series created in 1900. The earlier attempt lacked specific details and staged the chick embryo by using only morphological characteristics.

Format: Articles

Subject: Processes

Ovism

Ovism was one of two models of preformationism, a theory of generation prevalent in the late seventeenth through the end of the eighteenth century. Contrary to the competing theory of epigenesis (gradual emergence of form), preformationism held that the unborn offspring existed fully formed in the eggs or sperm of its parents prior to conception. The ovist model held that the maternal egg was the location of this preformed embryo, while the other preformationism model known as spermism preferred the paternal germ cell, as the name implies.

Format: Articles

Subject: Theories

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

Muriel Wheldale Onslow (1880-1932)

Muriel Wheldale Onslow studied flowers in England with genetic and biochemical techniques in the early twentieth century. Working with geneticist William Bateson, Onslow used Mendelian principles and biochemical analysis together to understand the inheritance of flower colors at the beginning of the twentieth century. Onslow's study of snapdragons, or Antirrhinum majus, resulted in her description of epistasis, a phenomenon in which the phenotypic effect of one gene is influenced by one or more other genes. She discovered several biochemicals related to color formation.

Format: Articles

Subject: People

Santiago Felipe Ramon y Cajal (1852-1934)

Santiago Felipe Ramon y Cajal investigated brains in the nineteenth and twentieth centuries in Spain. He identified and individuated many components of the brain, including the neuron and the axon. He used chick embryos instead of adult animals, then customary in brain research, to study the development and physiology of the cerebellum, spinal cord, and retina. Ramon y Cajal received the Nobel Prize in Physiology and Medicine in 1906, along with Camillo Golgi, for his work on the structure of the nervous system.

Format: Articles

Subject: People

The Game of Life, by John Horton Conway

The Game of Life, or just Life, is a one-person game that was created by the English mathematician John Horton Conway in the late 1960s. It is a simple representation of birth, death, development, and evolution in a population of living organisms, such as bacteria. Martin Gardner popularized the Game of Life by writing two articles for his column "Mathematical Games" in the journal Scientific American in 1970 and 1971. There exist several websites that provide the Game of Life as a download or as an online game.

Format: Articles

Subject: Technologies

James G. Wilson's Six Principles of Teratology

James Graves Wilson's six principles of teratology, published in 1959, guide research on teratogenic agents and their effects on developing organisms. Wilson's six principles were inspired by Gabriel Madeleine Camille Dareste's five principles of experimental teratology published in 1877. Teratology is the study of birth defects, and a teratogen is something that either induces or amplifies abnormal embryonic or fetal development and causes birth defects.

Format: Articles

Subject: Processes, Reproduction

Julia Barlow Platt (1857-1935)

Julia Barlow Platt studied neural crests in animal embryos and became involved in politics in the US during the nineteenth and twentieth centuries. She researched how body and head segments formed in chicks (Gallus gallus) and spiny dogfish (Squalus acanthias). Platt observed that in the mudpuppy (Necturus maculosus), the coordinated migration of neural crest cells in the embryo produced parts of the nervous system, bones, and connective tissues in the head.

Format: Articles

Subject: People

Ernst Haeckel's Biogenetic Law (1866)

The biogenetic law is a theory of development and evolution proposed by Ernst Haeckel in Germany in the 1860s. It is one of several recapitulation theories, which posit that the stages of development for an animal embryo are the same as other animals' adult stages or forms. Commonly stated as ontogeny recapitulates phylogeny, the biogenetic law theorizes that the stages an animal embryo undergoes during development are a chronological replay of that species' past evolutionary forms.

Format: Articles

Subject: Theories

August Antonius Rauber (1841-1917)

August Antonius Rauber was an embryologist and anatomist who examined gastrulation in avian embryos. He examined the formation of the blastopore, epiblast, and primitive streak during chick development. Subsequent researchers have further studied Rauber's findings, which has led to new discoveries in embryology and developmental biology.

Format: Articles

Subject: People

Essay: Homology

Homology is a central concept of comparative and evolutionary biology, referring to the presence of the same bodily parts (e.g., morphological structures) in different species. The existence of homologies is explained by common ancestry, and according to modern definitions of homology, two structures in different species are homologous if they are derived from the same structure in the common ancestor.

Format: Essays and Theses

Subject: Processes

Rita Levi-Montalcini (1909-2012)

Rita Levi-Montalcini is a Nobel Laureate recognized for her work in the discovery and characterization of nerve growth factor. Nerve growth factor (NGF) promotes the growth and maintenance of the nervous system in a developing system. The majority of her career has been devoted to investigating the many aspects of NGF.

Format: Articles

Subject: People

Retinoids As Teratogens

Vitamin A (retinol) is an essential vitamin in the daily functioning of human beings that helps regulate cellular differentiation of epithelial tissue. Studies have shown that an excess of vitamin A can affect embryonic development and result in teratogenesis, or the production of birth defects in a developing embryo. Excess intake of vitamin A and retinoids by pregnant women often results malformations to fetuses' skulls, faces, limbs, eyes, central nervous system.

Format: Articles

Subject: Disorders, Reproduction