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Somatic Cell Nuclear Transfer in Mammals (1938-2013)
In the second half of the
twentieth century, scientists learned how to clone organisms in some
species of mammals. Scientists have applied somatic cell nuclear transfer to clone human and
mammalian embryos as a means to produce stem cells for laboratory
and medical use. Somatic cell nuclear transfer (SCNT) is a technology applied in cloning, stem cell
research and regenerative medicine. Somatic cells are cells that
have gone through the differentiation process and are not germ
cells. Somatic cells donate their nuclei, which scientists
Subject: Theories, Technologies, Processes
“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.
Subject: Publications, Processes, Reproduction
Luc Antoine Montagnier (1932-2022)
Luc Montagnier studied viruses, the immune system, and cancer in France during the second half of the twentieth century. In his early career, Montagnier studied how cancer-causing viruses replicate and infect host cells. He received the Nobel Prize in Physiology or Medicine in 2008 for his team’s discovery that a retrovirus, human immunodeficiency virus, or HIV, was the cause of acquired immunodeficiency syndrome, or AIDS. AIDS is a chronic condition that results from HIV infection and damages the immune system.
Subject: People, Processes, Experiments
Pearl Luella Kendrick (1890–1980)
Pearl Luella Kendrick researched prevention for pertussis, commonly known as whooping cough, in Grand Rapids, Michigan, during the mid-1900s. Pertussis is a respiratory disease that mainly affects infants and young children. During the 1920s, pertussis was responsible for more deaths in children in the United States than any other disease. In the 1930s, Kendrick created one of the first pertussis vaccines that underwent large-scale clinical trials.
Subject: People, Publications, Processes
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.
Subject: Technologies, Processes
Zidovudine or Azidothymidine (AZT)
In 1964, Jerome Horwitz synthesized the drug zidovudine, commonly abbreviated ZDV, otherwise known as azidothymidine, or AZT, at Wayne State University School of Medicine in Detroit, Michigan. Horwitz and his colleagues originally developed zidovudine to treat cancers caused by retroviruses. In 1983, Nobel Prize in Physiology or Medicine recipients Françoise Barré-Sinoussi and Luc Montagnier discovered a new retrovirus, the human immunodeficiency virus, or HIV, at the Pasteur Institute in Paris, France.
The Meselson-Stahl Experiment (1957–1958), by Matthew Meselson and Franklin Stahl
In an experiment later named for them, Matthew Stanley Meselson and Franklin William Stahl in the US demonstrated during the 1950s the semi-conservative replication of DNA, such that each daughter DNA molecule contains one new daughter subunit and one subunit conserved from the parental DNA molecule. The researchers conducted the experiment at California Institute of Technology (Caltech) in Pasadena, California, from October 1957 to January 1958.
Subject: Processes, Experiments
The Development of Silicone Breast Implants for Use in Breast Augmentation Surgeries in the United States
In the 1960s, two plastic surgeons from the United States, Thomas Dillon Cronin and Frank Judson Gerow, collaborated with the Dow Corning Corporation, which specialized in silicone products, to create the first silicone breast implant. Surgeons used the implant, named the Cronin-Gerow implant, to improve the look of a woman’s breasts, by correcting for asymmetry, augmenting the size, or creating a more uplifted profile.
Subject: Technologies, Processes
Sex-determining Region Y in Mammals
The Sex-determining Region Y (Sry in mammals but SRY in humans) is a gene found on Y chromosomes that leads to the development of male phenotypes, such as testes. The Sry gene, located on the short branch of the Y chromosome, initiates male embryonic development in the XY sex determination system. The Sry gene follows the central dogma of molecular biology; the DNA encoding the gene is transcribed into messenger RNA, which then produces a single Sry protein.
Multiplex Automated Genome Engineering (MAGE)
Multiplex Automated Genome Engineering, or MAGE, is a genome editing technique that enables scientists to quickly edit an organism’s DNA to produce multiple changes across the genome. In 2009, two genetic researchers at the Wyss Institute at Harvard Medical School in Boston, Massachusetts, Harris Wang and George Church, developed the technology during a time when researchers could only edit one site in an organism’s genome at a time.
Subject: Technologies, Processes
Hedgehog Signaling Pathway
The hedgehog signaling pathway is a mechanism that directs the development of embryonic cells in animals, from invertebrates to vertebrates. The hedgehog signaling pathway is a system of genes and gene products, mostly proteins, that convert one kind of signal into another, called transduction. In 1980, Christiane Nusslein-Volhard and Eric F. Wieschaus, at the European Molecular Biology Laboratory in Heidelberg, Germany, identified several fruit fly (Drosophila melanogaster) genes.
Fetal programming, or prenatal programming, is a concept that suggests certain events occurring during critical points of pregnancy may cause permanent effects on the fetus and the infant long after birth. The concept of fetal programming stemmed from the fetal origins hypothesis, also known as Barker’s hypothesis, that David Barker proposed in 1995 at the University of Southampton in Southampton, England.
Subject: Processes, Theories, Reproduction
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.
Subject: Processes, Reproduction
Tissue engineering is a field of regenerative medicine that integrates the knowledge of scientists, physicians, and engineers into the construction or reconstruction of human tissue. Practitioners of tissue engineering seek to repair, replace, maintain, and enhance the abilities of a specific tissue or organ by means of living cells. More often than not stem cells are the form of living cells used in this technology. Tissue engineering is one of the disciplines involved in translating knowledge of developmental biology into the clinical setting.
Hartsoeker's Homunculus Sketch from Essai de Dioptrique
This embryology image is a pencil sketch by Nicolaas Hartsoeker, published as part of his 1694 French-language paper entitled Essai de Dioptrique, a semi-speculative work describing the sorts of new scientific observations that could be done using magnifying lenses. Dioptrique was published in Paris by the publishing house of Jean Anisson. The image depicts a curled up infant-like human, now referred to as a homunculus, inside the head of a sperm cell.
Beadle's One Gene-One Enzyme Hypothesis
Between 1934 and 1945, George Beadle developed a hypothesis that each gene within the chromosomes of organisms each produced one enzyme. Enzymes are types of proteins that can catalyze reactions inside cells, and the figure shows that each enzyme controls a stage in a series of biochemical reactions. The top box in this figure represents a normal process of enzyme production and biochemical reactions, and the bottom box shows how Beadle's experiments affected the normal biochemical process.
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.
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.
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.
Subject: Technologies, Processes
According to the US National Institutes of Health (NIH), the standard American source on stem cell research, three characteristics of stem cells differentiate them from other cell types: (1) they are unspecialized cells that (2) divide for long periods, renewing themselves and (3) can give rise to specialized cells, such as muscle and skin cells, under particular physiological and experimental conditions. When allowed to grow in particular environments, stem cells divide many times. This ability to proliferate can yield millions of stem cells over several months.
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.
Subject: Processes, Reproduction
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.
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.
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.
The Notch Signaling Pathway in Embryogenesis
The Notch signaling pathway is a mechanism in animals by which adjacent cells communicate with each other, conveying spatial information and genetic instructions for the animal's development. All multicellular animals utilize Notch signaling, which contributes to the formation, growth, and development of embryos (embryogenesis). Notch signaling also contributes to the differentiation of embryonic cells into various types of cells into various types of cells, such as neurons.