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Displaying 101 - 125 of 2023 items.

Gastrulation in Gallus gallus (Domestic Chicken)

Gastrulation is an early stage in embryo development in which the blastula reorganizes into three germ layers: the ectoderm, the mesoderm, and the endoderm. Gastrulation occurs after cleavage but before neurulation and organogenesis. Ernst Haeckel coined the term; gaster, meaning stomach in Latin, is the root for gastrulation, as the gut is one of the most unique creations of the gastrula.

Format: Articles

Subject: Processes

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

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

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

Franklin William Stahl (1929– )

Franklin William Stahl studied DNA replication, bacteriophages, and genetic recombination in the US during the mid-twentieth and early twenty-first centuries. With his colleague Matthew Meselson, Stahl performed an experiment called the Meselson-Stahl experiment, which provided evidence for a process called semi-conservative DNA replication. Semi-conservative replication is a process in which each strand of a parental DNA double helix serves as a template for newly replicated daughter strands, so that one parental strand is conserved in every daughter double helix.

Format: Articles

Subject: People

Butt Out for Baby (2003), by Child and Youth Health, South Australia

Butt Out for Baby was a smoking cessation intervention guide, aimed at community health workers, that the Child and Youth Health group published in 2003. The literature was released as the chief publication of the Butt Out for Baby Project, a multiple-resource smoking cessation program directed toward young parents and pregnant smokers, following the revelation of a relatively high rate of smoking among that group. The authors published the pamphlet in Adelaide, South Australia, and did not credit themselves individually.

Format: Articles

Subject: Publications

Photograph 51, by Rosalind Franklin (1952)

On 6 May 1952, at King’s College London in London, England, Rosalind Franklin photographed her fifty-first X-ray diffraction pattern of deoxyribosenucleic acid, or DNA. Photograph 51, or Photo 51, revealed information about DNA’s three-dimensional structure by displaying the way a beam of X-rays scattered off a pure fiber of DNA. Franklin took Photo 51 after scientists confirmed that DNA contained genes. Maurice Wilkins, Franklin’s colleague showed James and Francis Crick Photo 51 without Franklin’s knowledge. Watson and Crick used that image to develop their structural model of DNA.

Format: Articles

Subject: Publications

Francois Jacob (1920-2013)

Francois Jacob studied in
bacteria and bacteriophages at the Institut Pasteur in Paris, France,
in the second half of the twentieth century. In 1965, Jacob won the
Nobel Prize in Physiology or Medicine with Andre M. Lwoff and
Jacques L. Monod for their work on the genetic control of enzyme
synthesis. Jacob studied how genes control and regulate metabolic
enzymes in the bacterium Escherichia
coli (E. coli) and in lysogenic
bacterial systems. He contributed to theories of transcriptional gene

Format: Articles

Subject: People

Fortunio Liceti (1577–1657)

Fortunio Liceti studied natural philosophy and medicine in Italy during the first half of the seventeenth century. Liceti wrote greater than seventy works on a wide range of topics, including the human soul, reproduction, and birth defects observed in animals and human infants. In the seventeenth century, people commonly addressed birth defects using superstition and considered them as signs of evil, possibly caused by spiritual or supernatural entities. Liceti described infants with birth defects as prodigies and monsters to be admired and studied rather than feared.

Format: Articles

Subject: People

De Monstruorum Causis, Natura et Differentiis (On the Reasons, Nature and Differences of Monsters) (1616), by Fortunio Liceti

In 1616 in Padua, Italy, Fortunio Liceti, a professor of natural philosophy and medicine, wrote and published the first edition of De Monstruorum Causis, Natura et Differentiis (On the Reasons, Nature, and Differences of Monsters), hereafter De monstruorum. In De monstruorum, Liceti chronologically documented cases of human and animal monsters from antiquity to the seventeenth century. During the seventeenth century, many people considered such monsters as frightening signs of evil cursed by spiritual or supernatural entities.

Format: Articles

Subject: Theories

Sir Graham Collingwood Liggins (1926-2010)

Sir Graham Collingwood Liggins devoted much of his professional life to obstetric research. Liggins demonstrated that hormones created by the fetus helped initiate labor, rather than hormones originating solely from the mother. Liggins also discovered that cortisol given to pregnant mothers helped delay premature labor, and that it increased the likelihood that premature infants would breathe normally after birth. Prior to cortisol treatment, premature infants often died of respiratory distress syndrome characterized by the inability to inflate immature lungs.

Format: Articles

Subject: People, Reproduction

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.

Format: Articles

Subject: Processes

Victor Ambros (1953-)

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.

Format: Articles

Subject: People

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

Neural Crest

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.

Format: Articles

Subject: Theories

Fetal Alcohol Syndrome (FAS)

The concept Fetal Alcohol Syndrome (FAS) refers to a set of birth defects that occur in children born to mothers who abused alcohol during pregnancy. The alcohol-induced defects include pre- and post-natal growth deficiencies, minor facial abnormalities, and damage to the developing central nervous system (CNS).

Format: Articles

Subject: Disorders

Countdown to Life: The Extraordinary Making of You (2015), by the British Broadcasting Corporation and The Open University

In 2015, the British Broadcasting Corporation (BBC) partnered with The Open University to produce the three-part documentary series, Countdown to Life: The Extraordinary Making of You. Michael Mosley, a British television producer and journalist, hosts the documentary. Along with narrating animated scenes of a growing fetus in the womb, Mosley meets with individuals around the world who experienced mutations that can arise in the womb. Introduced over the course of the three episodes, several people share their personal stories of how their bodies did not develop correctly prior to birth.

Format: Articles

Subject: Publications

Study of Fossilized Massospondylus Dinosaur Embryos from South Africa (1978-2012)

In 1978, James Kitching discovered two dinosaur embryos in a road-cut talus at Roodraai (Red Bend) in Golden Gate Highlands National Park, South Africa. Kitching assigned the fossilized embryos to the species of long necked herbivores Massospondylus carinatus (longer vertebra) from the Early Jurassic period, between 200 and 183 million years ago. The embryos were partially visible but surrounded by eggshell and rock, called matrix. Kitching said that the eggs were too delicate to remove from the matrix without damage.

Format: Articles

Subject: Theories, Organisms

Chemical Induction

Research in chemical induction seeks to identify the compound or compounds responsible for differentiation in a developing embryo. Soren Lovtrup compared the search for these compounds to the search for the philosopher's stone. It was based on the assumption that the differentiating agents have to be chemical substances either within cells or in the extracellular matrix.

Format: Articles

Subject: Processes

Human Betterment Foundation (1928-1942)

In 1928 Ezra Seymour Gosney founded the non-profit Human Betterment Foundation (HBF) in Pasadena, California to support the research and publication of the personal and social effects of eugenic sterilizations carried out in California. Led by director Gosney and secretary Paul Popenoe, the HBF collected data on thousands of individuals in California who had been involuntarily sterilized under a California state law enacted in 1909. The Foundation's assets were liquidated following Gosney's death in 1942.

Format: Articles

Subject: Organizations, Reproduction

Congenital Rubella Syndrome (CRS)

Congenital rubella syndrome (CRS) can occur in children whose mothers contracted the rubella virus, sometimes called German measles, during pregnancy. Depending on the gestational period when the mother contracts rubella, an infant born with CRS may be unaffected by the virus or it may have severe developmental defects. The most severe effects of the virus on fetal development occur when the mother contracts rubella between conception and the first trimester.

Format: Articles

Subject: Disorders

David H. Hubel and Torsten N. Wiesel’s Research on Optical Development in Kittens

During 1964, David Hubel and Torsten Wiesel studied the short and long term effects of depriving kittens of vision in one eye. In their experiments, Wiesel and Hubel used kittens as models for human children. Hubel and Wiesel researched whether the impairment of vision in one eye could be repaired or not and whether such impairments would impact vision later on in life. The researchers sewed one eye of a kitten shut for varying periods of time.

Format: Articles

Subject: Experiments

"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

Infant Mortality: Results of a Field Study in Johnstown, PA., Based on Births in One Calendar Year (1915), by Emma Duke

The book Infant Mortality: Results of a Field Study in Johnstown, PA., Based on Births in One Calendar Year (1915), written by Emma Duke, detailed one of the first infant mortality field studies conducted by the US Children's Bureau. In the study, Duke and her colleagues collected information about over one thousand infants in the city of Johnstown, Pennsylvania. They used that information, along with interviews conducted with the families of the infants, to identify factors that affected infant mortality rates in the community.

Format: Articles

Subject: Experiments, Publications

The Development of the Neural Crest and the Migration of Neural Crest Cells (NCCs) in the Embryos of Various Vertebrates

This diagram shows how NCCs migrate differently in rats, birds and amphibians. The arrows represent both chronology of NCCs migration and the differential paths that NCCs follow in different classes of animals. The solid black portion of each illustration represents the neural crest, and the large black dots in (c) and in (f) represent the neural crest cells. The speckled sections that at first form a basin in (a) and then close to form a tube in (f) represent the neural ectoderm. The solid white portions represent the epidermal ectoderm.

Format: Graphics

Subject: Theories, Processes