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Isotretinoin (Accutane) as a Teratogen

Isotretinoin is a molecule and a byproduct (metabolite) of vitamin A, and in greater than normal amounts in pregnant women, it can cause fetal abnormalities including cleft lips, ear and eye defects, and mental retardation. Isotretinoin is commonly called by its trade name Accutane, and it's a chemical compound derived from vitamin A, or retinoic acid. Doctors prescribe isotretinoin to treat severe acne. For pregnant women, too much vitamin A or isotretinoin can also cause greater than normal rates of stillbirths and fetal disintegrations after the ninth week of gestation.

Format: Articles

Subject: Reproduction, Disorders

Ian Wilmut (1944- )

British embryologist Sir Ian Wilmut, best known for his work in the field of animal genetic engineering and the successful cloning of sheep, was born 7 July 1944 in Hampton Lucy, England. The family later moved to Scarborough, in the north of the country, to allow his father to accept a teaching position. There Wilmut met Gordon Whalley, head of the biology department at Scarborough High School for Boys, which Wilmut attended.

Format: Articles

Subject: People

"Developmental Capacity of Nuclei Transplanted from Keratinized Skin Cells of Adult Frogs" (1975), by John Gurdon, Ronald Laskey, and O. Raymond Reeves

In 1975 John Gurdon, Ronald Laskey, and O. Raymond Reeves published "Developmental Capacity of Nuclei Transplanted from Keratinized Skin Cells of Adult Frogs," in the Journal of Embryology and Experimental Morphology. Their article was the capstone of a series of experiments performed by Gurdon during his time at Oxford and Cambridge, using the frog species Xenopus laevis. Gurdon's first experiment in 1958 showed that the nuclei of Xenopus cells maintained their ability to direct normal development when transplanted.

Format: Articles

Subject: Experiments, Publications

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

Jane Maienschein (1950- )

Jane Maienschein is the daughter of Joyce Kylander and Fred Maienschein, and was born in Oak Ridge, Tennessee, on 23 September 1950. She attended MIT as a freshman and then transferred to Yale University in 1969 when Yale decided to admit women undergraduates. In 1972 she graduated with an honors degree in History, the Arts, and Letters having written a thesis on the history of science. She then attended Indiana University and studied with historian of embryology Frederick B.

Format: Articles

Subject: People

Your Baby’s Sex: Now You Can Choose (1970), by David M. Rorvik and Landrum B. Shettles

In the book Your Baby’s Sex: Now You Can Choose, David Michael Rorvik and Landrum Brewer Shettles describe methods that couples can use prior to and during conception that will increase the chances of producing a child of their desired sex. Rorvik, a science writer, and Shettles, an obstetrics and gynecology researcher and physician, co-wrote the book. Shettles developed the methods detailed in the book during the 1960s. Although the authors claim a high success rate, some researchers have contested the validity of the methods proposed in Your Baby’s Sex: Now You Can Choose.

Format: Articles

Subject: Publications

Hilde Mangold (1898-1924)

Hilde Mangold, previously Hilde Proescholdt, was a German embryologist and physiologist who became well known for research completed with Hans Spemann in the 1920s. As a graduate student, Mangold assisted Spemann and together they discovered and coined the term the "organizer." The organizer discovery was a crucial contribution to embryology that led to further understanding of the pattern of embryo differentiation of amphibians.

Format: Articles

Subject: People

Amphioxus, and the Mosaic Theory of Development (1893), by Edmund Beecher Wilson

Edmund Beecher Wilson experimented with Amphioxus (Branchiostoma) embryos in 1892 to identify what caused their cells to differentiate into new types of cells during the process of development. Wilson shook apart the cells at early stages of embryonic development, and he observed the development of the isolated cells. He observed that in the normal development of Amphioxus, all three main types of symmetry, or cleavage patterns observed in embryos, could be found. Wilson proposed a hypothesis that reformed the Mosaic Theory associated with Wilhelm Roux in Germany.

Format: Articles

Subject: Experiments

Gastrulation in Xenopus

The process of gastrulation allows for the formation of the germ layers in metazoan embryos, and is generally achieved through a series of complex and coordinated cellular movements. The process of gastrulation can be either diploblastic or triploblastic. In diploblastic organisms like cnidaria or ctenophora, only the endoderm and the ectoderm form; in triploblastic organisms (most other complex metazoans), triploblastic gastrulation produces all three germ layers.

Format: Articles

Subject: Processes

Assisted Reproductive Technologies

Assisted reproductive technologies (ART) are a collection of different techniques designed to help those who are infertile achieve a successful pregnancy. The most popular technology currently in use is in vitro fertilization (IVF), but others include gamete intrafallopian transfer (GIFT), zygote intrafallopian transfer (ZIFT), intrauterine insemination (IUI), and intracytoplasmic sperm injection (ICSI).

Format: Articles

Subject: Technologies, Reproduction

Intrauterine Pressure Catheter

An intrauterine pressure catheter (IUPC) is a device placed inside a pregnant woman’s uterus to monitor uterine contractions during labor. During labor, a woman’s uterus contracts to dilate, or open, the cervix and push the fetus into the birth canal. The catheter measures the pressure within the amniotic space during contractions and allows physicians to evaluate the strength, frequency, and duration of contractions.

Format: Articles

Subject: Technologies

"The Role of Maternal Mitochondria during Oogenesis, Fertilization and Embryogenesis" (2002), by James M. Cummins

James M Cummins published 'The Role of Maternal Mitochondria during Oogenesis, Fertilization and Embryogenesis' 30 January 2002 in Reproductive BioMedicine Online. In the article, Cummins examines the role of the energy producing cytoplasmic particles, or organelles called mitochondria. Humans inherit mitochondria from their mothers, and mechanisms have evolved to eliminate sperm mitochondria in early embryonic development. Mitochondria contain their own DNA (mtDNA) separate from nuclear DNA (nDNA).

Format: Articles

Subject: Publications

Stanley Alan Plotkin's Development of a Rubella Vaccine (1969)

In the US during the late 1960s, Stanley Alan Plotkin, John D. Farquhar, Michael Katz, and Fritz Buser isolated a strain of the infectious disease rubella and developed a rubella vaccine with a weakened, or attenuated, version of the virus strain. Rubella, also called German measles, is a highly contagious disease caused by the rubella virus that generally causes mild rashes and fever. However, in pregnant women, rubella infections can lead to developmental defects in their fetuses.

Format: Articles

Subject: Experiments

Chloroplasts

Chloroplasts are the organelles in plant and algal cells that conduct photosynthesis. A single chloroplast has an outer membrane and an inner membrane, with an intermembrane space in between. Within the inner membrane, interconnected stacks of thylakoids, called granum, float in a protein rich fluid called the stroma. These thylakoid stacks contain chlorophyll, a pigment which converts sunlight into usable energy for plants and free oxygen from water. The stacks are sites of light reactions within a plant cell.

Format: Graphics

Subject: Theories, Processes

Eugen Steinach (1861–1944)

Eugen Steinach researched sex hormones and their effects on mammals in the late nineteenth and early twentieth centuries in Europe. He experimented on rats by removing their testicles and implanting them elsewhere in their bodies, and he found that the testes interstitial cells produce male sex hormones. He developed the Steinach Rejuvenation Procedure, which he claimed could rejuvenate men by increasing their production of sex hormones. Steinach’s work on female sex hormones and on ovarian extracts led to the development of the first standardized injectable estrogen.

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

Camillo Golgi's Black Reaction for Staining Neurons

In 1873 Italy, Camillo Golgi created the black reaction technique, which enabled scientists to stain and view the structure of neurons, the specialized cells that compose the nervous system. During the nineteenth century, scientists were studying cells and proposed cell theory, which describes the basic characteristics of cells as fundamental units of life. However, cell theory struggled to explain neurons as they are specialized cells and more complex in structure than cells of other tissues.

Format: Articles

Subject: Technologies

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

"Experimental Chimeras' Removal of Reproductive Barrier Between Sheep and Goat" (1984), by Sabine Meinecke-Tillmann and Burkhard Meinecke

In 1984 Sabine Meinecke-Tillmann and Burkhard Meinecke published their article "Experimental Chimeras - Removal of Reproductive Barrier Between Sheep and Goat" in Nature. Their study conquered the reproductive barrier between sheep and goats through embryo manipulation. Their article appeared in Nature on the same day that a similar experiment, conducted by Carole Fehilly, Steen Willadsen, and Elizabeth Tucker was published regarding reproductive barriers between sheep and goats.

Format: Articles

Subject: Experiments

Mechanism of Notch Signaling

Mechanism of Notch Signaling: The image depicts a type of cell signaling, in which two animal cells interact and transmit a molecular signal from one to the other. The process results in the production of proteins, which influence the cells as they differentiate, move, and contribute to embryological development. In the membrane of the signaling cell, there is a ligand (represented by a green oval). The ligand functions to activate a change in a receptor molecule. In the receiving cell, there are receptors; in this case, Notch proteins (represented by orange forks).

Format: Graphics

Subject: Theories, Processes

"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

Teratogens

Teratogens are substances that may produce physical or functional defects in the human embryo or fetus after the pregnant woman is exposed to the substance. Alcohol and cocaine are examples of such substances. Exposure to the teratogen affects the fetus or embryo in a variety of ways, such as the duration of exposure, the amount of teratogenic substance, and the stage of development the embryo or fetus is in during the exposure.

Format: Articles

Subject: Disorders

David Hunter Hubel (1926–2013)

David Hunter Hubel studied the development of the visual system and how the brain processes visual information in the US during the twentieth century. He performed multiple experiments with kittens in which he sewed kitten’s eyes shut for varying periods of time and monitored their vision after reopening them. Hubel, along with colleague Torsten Wiesel, received the 1981 Nobel Prize in Physiology or Medicine for that research.

Format: Articles

Subject: People

Roger Wolcott Sperry (1913–1994)

Roger Wolcott Sperry
studied the function of the nervous system in the US during the
twentieth century. He studied split-brain patterns in cats and
humans that result from separating the two hemispheres of the
brain by cutting the corpus callosum, the bridge between the two
hemispheres of the brain. He found that separating the corpus
callosum the two hemispheres of the brain could not communicate
and they performed functions as if the other hemisphere did not

Format: Articles

Subject: People

Mitochondria

All cells that have a nucleus, including plant, animal, fungal cells, and most single-celled protists, also have mitochondria. Mitochondria are particles called organelles found outside the nucleus in a cell's cytoplasm. The main function of mitochondria is to supply energy to the cell, and therefore to the organism. The theory for how mitochondria evolved, proposed by Lynn Margulis in the twentieth century, is that they were once free-living organisms.

Format: Articles

Subject: Organisms, Theories