Search

Displaying 26 - 50 of 92 items.

Ectoderm

Ectoderm is one of three germ layers--groups of cells that coalesce early during the embryonic life of all animals except maybe sponges, and from which organs and tissues form. As an embryo develops, a single fertilized cell progresses through multiple rounds of cell division. Eventually, the clump of cells goes through a stage called gastrulation, during which the embryo reorganizes itself into the three germ layers: endoderm, ectoderm, and mesoderm. After gastrulation, the embryo goes through a process called neurulation, which starts the development of nervous system.

Format: Articles

Subject: Processes

Sperm Capacitation

Sperm capacitation refers to the physiological changes spermatozoa must undergo in order to have the ability to penetrate and fertilize an egg. This term was first coined in 1952 by Colin Russell Austin based on independent studies conducted by both Austin himself as well as Min Chueh Chang in 1951. Since the initial reports and emergence of the term, the details of the process have been more clearly elucidated due to technological advancements.

Format: Articles

Subject: Processes

Teratomas

Teratomas are embryonal tumors that normally arise from germ cells and are typically benign. They are defined as being composed either of tissues that are foreign to the area in which they form, or of tissues that derive from all three of the germ layers. Malignant teratomas are known as teratocarcinomas; these cancerous growths have played a pivotal role in the discovery of stem cells. "Teratoma" is Greek for "monstrous tumor"; these tumors were so named because they sometimes contain hair, teeth, bone, neurons, and even eyes.

Format: Articles

Subject: Processes, Disorders

The Yale Embryo

In 1934 a fourteen-day-old embryo was discovered during a postmortem examination and became famous for being the youngest known human embryo specimen at the time. The embryo was coined "the Yale Embryo," named after the location where it was discovered, Yale University in New Haven, Connecticut. During the early twentieth century, the rush to collect embryos as well as to find younger and younger embryos was at an all time high, and the Yale Embryo is representative of the this enthusiasm.

Format: Articles

Subject: Processes, Reproduction

The Apgar Score (1953-1958)

In 1952 Virginia Apgar, a physician at the Sloane Women’s Hospital in New York City, New York, created the Apgar score as a method of evaluating newborn infants’ health to determine if they required medical intervention. The score included five separate categories, including heart rate, breathing rate, reaction to stimuli, muscle activity, and color. An infant received a score from zero to two in each category, and those scores added up to the infant’s total score out of ten. An infant with a score of ten was healthy, and those with low scores required medical attention at birth.

Format: Articles

Subject: Technologies, Processes

Dissertation: Degeneration in Miniature: History of Cell Death and Aging Research in the Twentieth Century

Once perceived as an unimportant occurrence in living organisms, cell degeneration was reconfigured as an important biological phenomenon in development, aging, health, and diseases in the twentieth century. This dissertation tells a twentieth-century history of scientific investigations on cell degeneration, including cell death and aging.

Format: Essays and Theses

Subject: Processes, 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

The Process of Implantation of Embryos in Primates

Implantation is a process in which a developing embryo, moving as a blastocyst through a uterus, makes contact with the uterine wall and remains attached to it until birth. The lining of the uterus (endometrium) prepares for the developing blastocyst to attach to it via many internal changes. Without these changes implantation will not occur, and the embryo sloughs off during menstruation. Such implantation is unique to mammals, but not all mammals exhibit it.

Format: Articles

Subject: Processes

Epidermal Growth Factor

Epidermal growth factor is a signaling molecule that stimulates the growth of epidermal tissues during development and throughout life. Stanley Cohen discovered epidermal growth factor (EGF) during studies of nerve growth factor as a side effect of other experiments. EGF stimulates tissue growth by initiating a variety of cellular mechanisms. This work led to the 1986 Nobel Prize in Physiology or Medicine awarded to Cohen and Rita Levi-Montalcini.

Format: Articles

Subject: Processes

Gastrulation in Mus musculus (common house mouse)

As mice embryos develop, they undergo a stage of development called gastrulation. The hallmark of vertebrate gastrulation is the reorganization of the inner cell mass (ICM) into the three germ layers: ectoderm, mesoderm, and endoderm. Mammalian embryogenesis occurs within organisms; therefore, gastrulation was originally described in species with easily observable embryos. For example, the African clawed frog (Xenopus laevis) is the most widely used organism to study gastrulation because the large embryos develop inside a translucent membrane.

Format: Articles

Subject: Processes, Experiments

Spemann-Mangold Organizer

The Spemann-Mangold organizer, also known as the Spemann organizer, is a cluster of cells in the developing embryo of an amphibian that induces development of the central nervous system. Hilde Mangold was a PhD candidate who conducted the organizer experiment in 1921 under the direction of her graduate advisor, Hans Spemann, at the University of Freiburg in Freiburg, German. The discovery of the Spemann-Mangold organizer introduced the concept of induction in embryonic development.

Format: Articles

Subject: Processes

The Carapacial Ridge of Turtles

Two main elements characterize the skeletal morphology of turtles: the carapace and the plastron. For a turtle, the carapacial ridge begins in the embryo as a bulge posterior to the limbs but on both sides of the body. Such outgrowths are the first indication of shell development in turtle embryos. While the exact mechanisms underpinning the formation of the carapacial ridge are still not entirely known, some biologists argue that understanding these embryonic mechanisms is pivotal to explaining both the development of turtles and their evolutionary history.

Format: Articles

Subject: Processes

Abortion

Abortion is the removal of the embryo or fetus from the womb, before birth can occur-either naturally or by induced labor. Prenatal development occurs in three stages: the zygote, or fertilized egg; the embryo, from post-conception to eight weeks; and the fetus, from eight weeks after conception until the baby is born. After abortion, the infant does not and cannot live. Spontaneous abortion is the loss of the infant naturally or accidentally, without the will of the mother. It is more commonly referred to as miscarriage.

Format: Articles

Subject: Processes, Ethics, Reproduction

Amniocentesis Prior to 1980

The extraembryonic membranes that surround and originate from the embryos of vertebrates such as birds, reptiles, and mammals are crucial to their development. They are integral to increasing the surface area of the uterus, forming the chorion (which in turn produces the placenta) and the amnion, respectively. The amnion will ultimately surround the embryo in a fluid-filled amniotic cavity. This amniotic fluid, which cushions and protects the fetus and helps prevent the onset of labor, is sampled in amniocentesis to screen for genetic diseases.

Format: Articles

Subject: Processes, Reproduction

Slime Mold Video

This video is composed of a sequence of films created by John Tyler Bonner in the 1940s to show the life cycle of the cellular slime mold Dictyostelium discoideum. As only the second person to study slime molds, Bonner frequently encountered audiences who had never heard of, let alone seen, the unusual organism.

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

The Role of the Notch signaling pathway in Somitogenesis

Among other functions, the Notch signaling pathway contributes to the development of somites in animals. It involves a cell signaling mechanism with a wide range of functions, including cellular differentiation, and the formation of the embryonic structures (embryogenesis). All multicellular animals use Notch signaling, which is involved in the development, maintenance, and regeneration of a range of tissues. The Notch signaling pathways spans two cells, and consists of receptor proteins, which cross one cell's membrane and interacts with proteins on adjacent cells, called ligands.

Format: Articles

Subject: Theories, Processes

Umbilical Cord Blood Stem Cells (UCBSC)

Umbilical cord blood (UCB) stem cells are hematopoietic stem cells (HSC) that are recovered from the blood of the umbilical cord and placenta after birth. Umbilical cord blood is rich in cells that express the CD34 molecule, a surface protein that identifies cells as stem cells. Prior to the discovery of UCB stem cells, it was standard procedure to discard the umbilical cord and placenta; now much effort is devoted to raising public awareness and to encouraging people to store or donate cord blood.

Format: Articles

Subject: Processes, Reproduction

Intraspecies Chimeras Produced in Laboratory Settings (1960-1975)

When cells-but not DNA-from two or more genetically distinct individuals combine to form a new individual, the result is called a chimera. Though chimeras occasionally occur in nature, scientists have produced chimeras in a laboratory setting since the 1960s. During the creation of a chimera, the DNA molecules do not exchange genetic material (recombine), unlike in sexual reproduction or in hybrid organisms, which result from genetic material exchanged between two different species. A chimera instead contains discrete cell populations with two unique sets of parental genes.

Format: Articles

Subject: Organisms, Processes

Reassessment of Carrel's Immortal Tissue Culture Experiments

In the 1910s, Alexis Carrel, a French surgeon and biologist, concluded that cells are intrinsically immortal. His claim was based on chick-heart tissue cultures in his laboratory that seemed to be able to proliferate forever. Carrel's ideas about cellular immortality convinced his many contemporaries that cells could be maintained indefinitely. In the 1960s, however, Carrel's thesis about cell immortality was put into question by the discovery that human diploid cells can only proliferate for a finite period.

Format: Articles

Subject: Processes, Theories

Epithelium

Frederik Ruysch, working in the Netherlands, introduced the term epithelia in the third volume of his Thesaurus Anatomicus in 1703. Ruysch created the term from the Greek epi, which means on top of, and thele, which means nipple, to describe the type of tissue he found when dissecting the lip of a cadaver. In the mid nineteenth century, anatomist Albrecht von Haller adopted the word epithelium, designating Ruysch's original terminology as the plural version. In modern science, epithelium is a type of animal tissue in which cells are packed into neatly arranged sheets.

Format: Articles

Subject: Theories, Processes

Endothelium

The endothelium is the layer of cells lining the blood vessels in animals. It weighs more than one kilogram in adult humans, and it covers a surface area of 4000 to 7000 square meters. The endothelium is the cellular interface between the circulating blood and underlying tissue. As the medium between these two sets of tissues, endothelium is part of many normal and disease processes throughout the body.

Format: Articles

Subject: Processes, Theories

“Pelvic Organ Prolapse Quantification System (POP-Q) - A New Era in Pelvic Prolapse Staging” (2011), by Cristian Persu, Christopher Chapple, Victor Cauni, Stefan Gutue, and Petrisor Geavlete

In 2011, Cristian Persu, Christopher Chapple, Victor Cauni, Stefan Gutue, and Petrisor Geavlete published “Pelvic Organ Prolapse Quantification System (POP-Q) – A New Era in Pelvic Prolapse Staging,” in the Journal of Medicine and Life. In their article, the authors explain the need for a reliable diagnostic method for describing the state of a pelvic organ prolapse, or a condition that can result from weakness or damage to the muscles that support the pelvic organs, sometimes leading to bladder, bowel, and sexual dysfunction.

Format: Articles

Subject: Publications, Processes, Reproduction

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

Homeobox Genes and the Homeobox

Homeobox genes are a cluster of regulatory genes that are spatially and temporally expressed during early embryological development. They are interesting from both a developmental and evolutionary perspective since their sequences are highly conserved and shared across an enormously wide array of living taxa.

Format: Articles

Subject: Processes