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Mesenchyme

Mesenchyme is a type of animal tissue comprised of loose cells embedded in a mesh of proteins and fluid, called the extracellular matrix. The loose, fluid nature of mesenchyme allows its cells to migrate easily and play a crucial role in the origin and development of morphological structures during the embryonic and fetal stages of animal life. Mesenchyme directly gives rise to most of the body's connective tissues, from bones and cartilage to the lymphatic and circulatory systems.

Format: Articles

Subject: Processes

Golgi Staining Technique

The Golgi staining technique, also called the black reaction after the stain's color, was developed in the 1870s and 1880s in Italy to make brain cells (neurons) visible under the microscope. Camillo Golgi developed the technique while working with nervous tissue, which required Golgi to examine cell structure under the microscope. Golgi improved upon existing methods of staining, enabling scientists to view entire neurons for the first time and changing the way people discussed the development and composition of the brain's cells.

Format: Articles

Subject: Technologies, 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

Johannes Holtfreter (1901-1992)

Johannes Holtfreter made important discoveries about the properties of the organizer discovered by Hans Spemann. Although he spent much time away from the lab over many years, he was a productive researcher. His colleagues noted that the time he spent away helped revitalize his ideas. He is credited with the development of a balanced salt medium to allow embryos to develop; the discovery that dead organizer tissue retains inductive abilities; and the development of specification, competence, and distribution of fate maps in the developing frog embryo.

Format: Articles

Subject: People

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

"Versuche zur Analyse der Induktionsmittel in der Embryonalentwicklung" (1932), by Hermann Bautzmann, Johannes Holtfreter, Otto Mangold, and Hans Spemann

In "Versuche zur Analyse der Induktionsmittel in der Embryonalentwicklung," published in Naturwissenschaften in 1932, Hermann Bautzmann, Johannes Holtfreter, Otto Mangold, and Hans Spemann jointly reported on experiments each had conducted testing the activity of organizers killed by boiling, freezing, alcohol, and drying. Each of the authors had been independently conducting similar experiments, when Holtfreter made a breakthrough allowing him to produce many more successful transplantations.

Format: Articles

Subject: Experiments

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

"Visualizing Human Embryos" (1999), by Bradley Richard Smith

In March 1999 Bradley Richard Smith, a professor at the University of Michigan, unveiled the first digital magnetic resonance images of human embryos. In his article "Visualizing Human Embryos for Scientific American," Smith displayed three-dimensional images of embryos using combinations of Magnetic Resonance Microscopy (MRM), light microscopy, and various computer editing. He created virtual embryo models that it is possible to view as dissections, animations, or in their whole 3D form. Smith's images constitute a new way of visualizing embryos.

Format: Articles

Subject: Outreach, Publications

Eduard Friedrich Wilhelm Pflüger (1829-1910)

Eduard Friedrich Wilhelm Pflüger was a physiologist known for his research on respiration, the respiratory quotient, experimenting on the effects of electricity on muscles and nerves, and his study of the ovaries and egg development. His experiments on how the gravitational orientation of frog eggs affects their cleavage plane inspired embryologists such as Wilhelm Roux and Gustav Born to conduct their own experiments using frog eggs.

Format: Articles

Subject: People

Methylmercury and Human Embryonic Development

Methylmercury (MeHg) is an organic form of mercury that can damage the developing brains of human fetuses. Women who consume methylmercury during pregnancy can bear children who have neurological issues because methylmercury has toxic effects on the nervous system during embryonic development. During the third week of gestation, the human nervous system begins to form in the embryo. During this gestational period, the embryo's nervous system is particularly susceptible to the influence of neurotoxins like methylmercury that can result in abnormalities.

Format: Articles

Subject: Reproduction, Disorders

"The Results of Operations for the Cure of Cancer of the Breast Performed at the Johns Hopkins Hospital from June, 1889, to January, 1894" (1894), by William Stewart Halsted

In 1894, William Stewart Halsted published The Results of Operations for the Cure of Cancer of the Breast Performed at the Johns Hopkins Hospital from June, 1889, to January, 1894, in the medical journal Annals of Surgery. In the article, Halsted describes the results from fifty of his operations on women with breast cancer, performed at Johns Hopkins Hospital in Baltimore, Maryland. Those operations involved a surgical procedure Halsted called radical mastectomy, which consists in removing all of the patient’s breast tissue, chest muscle, and underarm lymph nodes.

Format: Articles

Subject: Publications

Truman William Brophy (1848–1928)

Truman William Brophy developed a cleft palate surgical repair, later called the Brophy Operation, in the late nineteenth century US. The procedure improved facial aesthetics and speech in cleft palate patients. A cleft palate occurs during development when the palatal bones in the roof of the mouth don't completely fuse, leaving an opening, or cleft, in the upper lip and mouth. Brophy's cleft repair used compression inside and outside of the mouth to push the palatal bones into normal alignment shortly after birth.

Format: Articles

Subject: People, Disorders

George Nicholas Papanicolaou (1883–1962)

George Nicholas Papanicolaou developed the Pap test in the United States during the twentieth century. The Pap test is a diagnostic procedure used to test for cervical cancer in women. Papanicolaou’s work helped improve the reproductive health of women by providing an effective means of identifying precancerous cells and improving the likelihood of early treatment and survival of cervical cancer.

Format: Articles

Subject: People, Reproduction

"A Diffusible Agent of Mouse Sarcoma, Producing Hyperplasia of Sympathetic Ganglia and Hyperneurotization of Viscera in the Chick Embryo" (1953), by Rita Levi-Montalcini and Viktor Hamburger

"A Diffusible Agent of Mouse Sarcoma, Producing Hyperplasia of Sympathetic Ganglia and Hyperneurotization of Viscera in the Chick Embryo," by Rita Levi-Montalcini and Viktor Hamburger, appeared in 1953 in the Journal of Experimental Zoology. The paper provided the first evidence that nerve growth factor is a diffusible substance. Nerve growth promoting tumors were implanted into developing embryos to determine whether the tumors stimulated growth by direct contact or by a diffusible substance.

Format: Articles

Subject: Experiments

Gavin Rylands de Beer (1899-1972)

Gavin de Beer was an English zoologist known for his contributions to evolution and embryology, in particular for showing the inadequacy of the germ layer theory as it was then proposed. He was born in London, England, on 1 November 1899, but was raised for his first thirteen years in France where his father worked for a telegraph company. He entered Magdalen College, Oxford, in 1917 but his studies were soon interrupted by World War I. After serving in the military, he returned to Oxford where he studied under Edwin Goodrich.

Format: Articles

Subject: People

Effects of Prenatal Alcohol Exposure on Basal Ganglia Development

Prenatal exposure to alcohol (ethanol) in human and animal models results 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 basal ganglia, one of the central nervous system components, are affected by exposure to ethanol during development.

Format: Articles

Subject: Disorders, Reproduction

"The Development of the Turtle Carapace" (1989), by Ann Campbell Burke

Ann Campbell Burke examines the development and evolution of vertebrates, in particular, turtles. Her Harvard University experiments, described in Development of the Turtle Carapace: Implications for the Evolution of a Novel Bauplan, were published in 1989. Burke used molecular techniques to investigate the developmental mechanisms responsible for the formation of the turtle shell.

Format: Articles

Subject: Experiments, Publications

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

Leo Kanner (1894-1981)

Leo Kanner studied and described early infantile autism in humans in the US during the twentieth century. Though Eugen Bleuler first coined the term autism in 1910 as a symptom of schizophrenia, Kanner helped define autism as a disease concept separate from schizophrenia. He helped found an early child psychiatry department in 1930 at the Johns Hopkins University Hospital in Baltimore, Maryland.

Format: Articles

Subject: People

"Autistic Disturbances of Affective Contact" (1943), by Leo Kanner

Leo Kanner published Autistic Disturbances of Affective Contact in 1943 in the journal Nervous Child. This article described the cases of eleven children with autism. Kanner described the behavior and upbringing of each child, aged two to eight, as well as the educational backgrounds of the children's.

Format: Articles

Subject: Publications

Environment and Birth Defects (1973), by James G. Wilson

Environment and Birth Defects by James Graves Wilson in the US was published in 1973. The book summarized information on the causes of malformations in newborns and aimed to acquaint policy makers with Wilson's suggestions for predicting the risks of environmental causes of birth defects, called teratogens. Wilson also provided six principles for researching teratogens, a framework revised from his 1959 article Experimental Studies on Congenital Malformations. The book has ten chapters.

Format: Articles

Subject: Publications

"Derivation of Pluripotent Stem Cells from Cultured Human Primordial Germ Cells" (1998), by John Gearhart et al.

In November 1998, two independent reports were published concerning the first isolation of pluripotent human stem cells, one of which was "Derivation of Pluripotent Stem Cells from Cultured Human Primordial Germ Cells." This paper, authored by John D. Gearhart and his research team - Michael J Shamblott, Joyce Axelman, Shunping Wang, Elizabeith M. Bugg, John W. Littlefield, Peter J. Donovan, Paul D. Blumenthal, and George R. Huggins - was published in Proceedings of the National Academy of Science soon after James A.

Format: Articles

Subject: Publications

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

John D. Gearhart

John D. Gearhart is a renowned American developmental geneticist best known for leading the Johns Hopkins University research team that first identified and isolated human pluripotent stem cells from human primordial germ cells, the precursors of fully differentiated germ cells. Born in Western Pennsylvania, Gearhart lived on the family farm located in the Allegheny Mountains for the first six years of his life.

Format: Articles

Subject: People

Spermism

Spermism was one of two models of preformationism, a theory of embryo generation prevalent in the late seventeenth through the end of the eighteenth century. Spermist preformationism was the belief that offspring develop from a tiny fully-formed fetus contained within the head of a sperm cell. This model developed slightly later than the opposing ovist model because sperm cells were not seen under the microscope until about 1677.

Format: Articles

Subject: Theories