Search

Displaying 201 - 225 of 646 items.

Embryonic Differentiation in Animals

Embryonic differentiation is the process of development during which embryonic cells specialize and diverse tissue structures arise. Animals are made up of many different cell types, each with specific functions in the body. However, during early embryonic development, the embryo does not yet possess these varied cells; this is where embryonic differentiation comes into play. The differentiation of cells during embryogenesis is the key to cell, tissue, organ, and organism identity.

Format: Articles

Subject: Processes

"Congenital Club Foot in the Human Fetus" (1980), by Ernesto Ippolito and Ignacio Ponseti

In 1980, Ernesto Ippolito and Ignacio Ponseti published their results on a histological study they performed on congenital club foot in human fetuses. The researchers examined the feet of four aborted fetuses and compared the skeletal tissues from healthy feet to those affected by congenital club foot. Infants born with club foot are born with one or both feet rigidly twisted inwards and upwards, making typical movement painful and challenging.

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

Christopher Polge and Lionel Edward Aston Rowson’s Experiments on the Freezing of Bull Spermatozoa (1950–1952)

In 1952, researchers Christopher Polge and Lionel Edward Aston Rowson, who worked at the Animal Research Center in Cambridge, England, detailed several experiments on protocols for freezing bull semen for use in the artificial insemination of cows. Freezing sperm extends the life of a viable sperm sample and allows it to be used at later times, such as in artificial insemination. The researchers examined the effects of freezing conditions on bull sperm and how well they produce fertilized embryos once thawed.

Format: Articles

Subject: Experiments

Anatomia Uteri Humani Gravidi Tabulis Illustrata (The Anatomy of the Human Gravid Uterus Exhibited in Figures) (1774), by William Hunter

William Hunter’s Anatomia Uteri Humani Gravidi Tabulis Illustrata (The Anatomy of the Human Gravid Uterus Exhibited in Figures), hereafter called The Human Gravid Uterus, is an anatomical atlas depicting the pregnant form through both engravings and descriptions. William Hunter, an anatomist working in England during the eighteenth century, compiled the work based on observations from his dissections of pregnant women.

Format: Articles

Subject: Publications

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

Organisers and Genes (1940), by Conrad Hal Waddington

Conrad Hal Waddington's Organisers and Genes, published in 1940, is a summary of available research and theoretical framework for many concepts related to tissue differentiation in the developing embryo. The book is composed of two main conceptual sections. The first section explores the action and nature of the organizer, while the second section delves into genes and their influence on development.

Format: Articles

Subject: Publications

Julia Barlow Platt (1857-1935)

Julia Barlow Platt studied neural crests in animal embryos and became involved in politics in the US during the nineteenth and twentieth centuries. She researched how body and head segments formed in chicks (Gallus gallus) and spiny dogfish (Squalus acanthias). Platt observed that in the mudpuppy (Necturus maculosus), the coordinated migration of neural crest cells in the embryo produced parts of the nervous system, bones, and connective tissues in the head.

Format: Articles

Subject: People

"Alternative Sources of Human Pluripotent Stem Cells" (2005), by Leon Kass and the President’s Council on Bioethics

Human pluripotent stem cells are valued for their potential to form numerous specialized cells and for their longevity. In the US, where a portion of the population is opposed to destruction of human embryos to obtain stem cells, what avenues are open to scientists for obtaining pluripotent cells that do not offend the moral sensibilities of a significant number of citizens?

Format: Articles

Subject: Publications, Ethics

Matthew Howard Kaufman (1942–2013)

Matthew Kaufman was a professor of anatomy at the University of Edinburgh, in Edinburgh, UK, who specialized in mouse anatomy, development, and embryology during the late twentieth century. According to the The Herald, he was the first, alongside his colleague Martin Evans, to isolate and culture embryonic stem cells. Researchers initially called those cells Evans-Kaufman cells. In 1992, Kaufman published The Atlas of Mouse Development, a book that included photographs of mice development and mice organs over time.

Format: Articles

Subject: People

Joseph Needham (1900-1995)

Joseph Needham was an embryologist and biochemist who is most noted in science for his studies on induction in developing embryos. Needham worked with Conrad Hal Waddington to attempt to identify the compound responsible for the organizer's activity. Although he was not successful in discovering the chemical, he and Waddington learned much about the organizer. Needham was a meticulous writer, writing reviews and books about contemporary research.

Format: Articles

Subject: People

Enovid: The First Hormonal Birth Control Pill

Enovid was the first hormonal birth control pill. G. D. Searle and Company began marketing Enovid as a contraceptive in 1960. The technology was created by the joint efforts of many individuals and organizations, including Margaret Sanger, Katharine McCormick, Gregory Pincus, John Rock, Syntex, S.A. Laboratories, and G.D. Searle and Company Laboratories.

Format: Articles

Subject: Technologies, Reproduction

David Starr Jordan (1851-1931)

David Starr Jordan studied fish and promoted eugenics in the US during the late nineteenth and early twentieth centuries. In his work, he embraced Charles Darwin s theory of evolution and described the importance of embryology in tracing phylogenic relationships. In 1891, he became the president of Stanford University in Stanford, California. Jordan condemned war and promoted conservationist causes for the California wilderness, and he advocated for the eugenic sterilization of thousands of Americans.

Format: Articles

Subject: People, Reproduction

Zygote Intrafallopian Transfer

Zygote intrafallopian transfer (ZIFT) is an assisted reproductive technology (ART) first used in 1986 to help those who are infertile conceive a child. ZIFT is a hybrid technique derived from a combination of in vitro fertilization (IVF) and gamete intrafallopian transfer (GIFT) procedures. Despite a relatively high success rate close to that of IVF, it is not as common as its parent procedures due to its costs and more invasive techniques.

Format: Articles

Subject: Technologies, Reproduction

George McDonald Church (1954- )

George McDonald Church studied DNA from living and from extinct species in the US during the twentieth and twenty-first centuries. Church helped to develop and refine techniques with which to describe the complete sequence of all the DNA nucleotides in an organism's genome, techniques such as multiplex sequencing, polony sequencing, and nanopore sequencing. Church also contributed to the Human Genome Project, and in 2005 he helped start a company, the Personal Genome Project. Church proposed to use DNA from extinct species to clone and breed new organisms from those species.

Format: Articles

Subject: People

"On the Induction of Embryonic Primordia by Implantation of Organizers from Different Species" (1924), Hilde Mangold's Dissertation

Hilde Proscholdt Mangold was a doctoral student at the Zoological Institute at the University of Freiburg in Freiburg, Germany, from 1920-1923. Mangold conducted research for her dissertation 'On the Induction of Embryonic Primordia by Implantation of Organizers from Different Species' ('Ueber Induktion von Embryonanlagen durch Implantation artfremder Organisatoren'), under the guidance of Hans Spemann, a professor of zoology at the University of Freiburg.

Format: Articles

Subject: Experiments, Publications

Kass v. Kass (1998)

In Maureen Kass v. Steven Kass (1998), the Court of Appeals of New York in Albany, New York, ruled that the state should generally consider IVF consent forms signed by participants in an in vitro fertilization (IVF) program valid, binding, and enforceable in the event of a dispute. The court indicated that decisions regarding the handling of cryopreserved pre-zygotes, often called preembryos, contained within these consent forms should be upheld.

Format: Articles

Subject: Legal

A. Z. v. B. Z. (2000)

In A.Z. v. B.Z. (2000), the Supreme Judicial Court of Massachusetts in Boston, Massachusetts, affirmed a lower courtÕs decision, ruling that contracts that require a party to become a parent against his or her will are unenforceable and contrary to public policy. The case centered around A.Z. and B.Z., a divorced couple who had previously used in vitro fertilization (IVF) to start a family together during their marriage and had several preembryos cryopreserved as part of the process.

Format: Articles

Subject: Legal

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.

Format: Articles

Subject: Processes

Niemann-Pick Disease

In 1914 Albert Niemann, a German pediatrician who primarily studied infant metabolism, published a description of an Ashkenazi Jewish infant with jaundice, nervous system and brain impairments, swollen lymph nodes (lymphadenopathy), and an enlarged liver and spleen (hepatosplenomegaly). He reported that these anatomical disturbances resulted in the premature death of the child at the age of eighteen months. After extensively studying the abnormal characteristics of the infant, Niemann came to the conclusion that the disease was a variant of Gaucher's disease.

Format: Articles

Subject: Disorders

Ethics of Fetal Surgery

Surgeons sometimes operate on the developing fetuses in utero of pregnant women as a medical intervention to treat a number of congential abnormalities, operations that have ethical aspects. A. William Liley performed the first successful fetal surgery, a blood transfusion, in New Zealand in 1963 to counteract the effects of hemolytic anemia, or Rh disease.

Format: Articles

Subject: Ethics

“Revival of Spermatozoa after Dehydration and Vitrification at Low Temperatures” (1949), by Christopher Polge, Audrey Ursula Smith, and Alan Sterling Parkes

In the 1949 article “Revival of Spermatozoa after Dehydration and Vitrification at Low Temperatures,” researchers Christopher Polge, Audrey Ursula Smith, and Alan Sterling Parkes demonstrated that glycerol prevents cells from dying while being frozen. Polge and his colleagues discussed several procedures in which they had treated sperm cells from various species with glycerol, froze those cells, and then observed the physiological effects that freezing had on the treated sperm. The researchers concluded that glycerol safely preserves sperm samples from a variety of species.

Format: Articles

Subject: Publications

David Reimer and John Money Gender Reassignment Controversy: The John/Joan Case

In the mid-1960s, psychologist John Money encouraged the gender reassignment of David Reimer, who was born a biological male but suffered irreparable damage to his penis as an infant. Born in 1965 as Bruce Reimer, his penis was irreparably damaged during infancy due to a failed circumcision. After encouragement from Money, Reimer’s parents decided to raise Reimer as a girl. Reimer underwent surgery as an infant to construct rudimentary female genitals, and was given female hormones during puberty.

Format: Articles

Subject: Theories

Mesoderm

Mesoderm is one of the three germ layers, groups of cells that interact early during the embryonic life of animals and from which organs and tissues form. As organs form, a process called organogenesis, mesoderm interacts with endoderm and ectoderm to give rise to the digestive tract, the heart and skeletal muscles, red blood cells, and the tubules of the kidneys, as well as a type of connective tissue called mesenchyme. All animals that have only one plane of symmetry through the body, called bilateral symmetry, form three germ layers.

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