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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

Edward Donnall Thomas (1920-2012)

Edward Donnall Thomas, an American physician and scientist, gained recognition in the scientific community for conducting the first bone marrow transplant, a pioneering form of hematopoietic stem cell transplantation (HSCT). Bone marrow transplants are considered to be the first successful example of tissue engineering, a field within regenerative medicine that uses hematopoietic stem cells (HSCs) as a vehicle for treatment. Prior to Thomas's groundbreaking work, most blood-borne diseases, including certain inherited and autoimmune diseases, were considered lethal.

Format: Articles

Subject: People

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

"Development, Plasticity and Evolution of Butterfly Eyespot Patterns" (1996), by Paul M. Brakefield et al.

Paul M. Brakefield and his research team in Leiden, the Netherlands, examined the development, plasticity, and evolution of butterfly eyespot patterns, and published their findings in Nature in 1996. Eyespots are eye-shaped color patterns that appear on the wings of some butterflies and birds as well as on the skin of some fish and reptiles. In butterflies, such as the peacock butterfly Aglais, the eyespots resemble the eyes of birds and help butterflies deter potential predators.

Format: Articles

Subject: Experiments

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

Osmotic Investigations: Studies on Cell Mechanics (1877), by Wilhelm Pfeffer

Wilhelm Pfeffer published his book Osmotische Untersuchungen: Studien Zur Zellmechanik (Osmotic Investigations: Studies on Cell Mechanics) in 1877 during his time as a professor of botany at the University of Basel in Basel, Switzerland. Gordon R. Kepner and Eduard J. Stadelmann translated the book into English in 1985. Verlag von Wilhelm Engelmann in Leipzig, Germany, published the original book in German in 1877 and Van Nostrand Reinhold Company in New York, New York, published the English version in 1985.

Format: Articles

Subject: Publications

Cord Blood Banking

Cord blood banks are institutions designed to store umbilical cord blood (UCB) stem cells. UCB, a source of hematopoietic stem cells (HSCs), has garnered attention from scientific and medical communities since its first successful use in a hematopoietic stem cell transplant (HSCT) in 1988. The umbilical cord is the lifeline by which the growing fetus is nourished by the mother. Once regarded as medical waste, the umbilical cord has become a source of lifesaving treatment.

Format: Articles

Subject: Technologies, Reproduction

Hematopoietic Stem Cells

The discovery of hematopoietic stem cells (HSCs) provided a pioneering step in stem cell research. HSCs are a type of multipotent adult stem cell, characterized by their ability to self-renew and differentiate into erythrocyte (red blood cell) and leukocyte (white blood cell) cell lineages. In terms of function, these cells are responsible for the continual renewal of the erythrocytes, leukocytes, and platelets in the body through a process called hematopoiesis. They also play an important role in the formation of vital organs such as the liver and spleen during fetal development.

Format: Articles

Subject: Processes

Some of the Cells that Arise from Animal Gastrulas with Three Germ Layers

From a developing embryos three primary germ layers, ectoderm (green), mesoderm (pink) and endoderm (yellow), a variety of differentiated cell types and organ systems arise, far more than are shown here. The three primary germ layers are shown during the gastrula stage because they become distinct at the gastrula stage. The germ cells (blue) are pre- cursors to sperm and egg cells, and they are set aside early in development, and are thought to arise from the ectoderm.

Format: Graphics

Subject: Theories, Processes

Alexis Carrel's Immortal Chick Heart Tissue Cultures (1912-1946)

In an effort to develop tissue culture techniques for long-term tissue cultivation, French surgeon and biologist Alexis Carrel, and his associates, produced and maintained a series of chick heart tissue cultures at the Rockefeller Institute in New York City. From 1912 to 1946, this series of chick heart tissue cultures remained alive and dividing. Since the duration of this culture greatly exceeded the normal chick life span, the cells were deemed immortal.

Format: Articles

Subject: Experiments

The inductive capacity of oral mesenchyme and its role in tooth development (1969-1970), by Edward J. Kollar and Grace R. Baird

Between February 1969 and August 1970 Edward Kollar and Grace Baird, from the University of Chicago in Chicago, Illinois, published three papers that established the role of the mesenchyme in tooth induction. Drawing upon a history of using tissue interactions to understand differentiation, Kollar and Baird designed their experiments to understand how differentiated structures become specified. Their work overturned a widely accepted model that epithelium controls the identity of the structure, a phenomenon called structural specificity.

Format: Articles

Subject: Experiments

"Ethical Issues in Human Stem Cell Research: Executive Summary" (1999), by the US National Bioethics Advisory Commission

Ethical Issues in Human Stem Cell Research: Executive Summary was published in September 1999 by The US National Bioethics Advisory Commission in response to a national debate about whether or not the US federal government should fund embryonic stem cell research. Ethical Issues in Human Stem Cell Research recommended policy to US President William Clinton's administration, which advocated for federal spending on the use of stem research on stem cells that came from embryos left over from in vitro fertilization (IVF) fertility treatments.

Format: Articles

Subject: Legal, Ethics

"On the Origin of Mitosing Cells" (1967), by Lynn Sagan

On the Origin of Mitosing Cells by Lynn Sagan appeared in the March 1967 edition of the Journal of Theoretical Biology. At the time the article was published, Lynn Sagan had divorced astronomer Carl Sagan, but kept his last name. Later, she remarried and changed her name to Lynn Margulis, and will be referred to as such throughout this article. In her 1967 article, Margulis develops a theory for the origin of complex cells that have enclosed nuclei, called eukaryotic cells.

Format: Articles

Subject: Publications, Theories

An Atlas of Fertilization and Karyokinesis of the Ovum (1895), by Edmund Beecher Wilson

Edmund Beecher Wilson in the US published An Atlas of Fertilization and Karyokinesis of the Ovum (hereafter called An Atlas) in 1895. The book presents photographs by photographer Edward Leaming that capture stages of fertilization, the fusion of sperm and egg and early development of sea urchin (Toxopneustes variegatus) ova, or egg cell. Prior to An Atlas, no one photographed of eggcell division in clear detail. Wilson obtained high quality images of egg cells by cutting the cells into thin sections and preserving them throughout different stages of development.

Format: Articles

Subject: Publications, Reproduction

The Singapore Bioethics Advisory Committee

Established in tandem with Singapore's national Biomedical Sciences Initiatives, the Bioethics Advisory Committee (BAC) was established by the Singapore Cabinet in December 2000 to examine the potential ethical, legal, and social issues arising from Singapore's biomedical research sector, and to recommend policy to Singapore's government.

Format: Articles

Subject: Organizations, Ethics, Legal

Edmund Beecher Wilson (1856-1939)

Edmund Beecher Wilson contributed to cell biology, the study of cells, in the US during the end of the nineteenth and the beginning of the twentieth centuries. His three editions of The Cell in Development and Inheritance (or Heredity) in 1896, 1900, and 1925 introduced generations of students to cell biology. In The Cell, Wilson described the evidence and theories of his time about cells and identified topics for future study. He helped show how each part of the cell works during cell division and in every step of early development of an organism.

Format: Articles

Subject: People

Induced Pluripotent Stem Cell Experiments by Kazutoshi Takahashi and Shinya Yamanaka in 2006 and 2007

In 2006, Kazutoshi Takahashi and Shinya Yamanaka reprogrammed mice fibroblast cells, which can produce only other fibroblast cells, to become pluripotent stem cells, which have the capacity to produce many different types of cells. Takahashi and Yamanaka also experimented with human cell cultures in 2007. Each worked at Kyoto University in Kyoto, Japan. They called the pluripotent stem cells that they produced induced pluripotent stem cells (iPSCs) because they had induced the adult cells, called differentiated cells, to become pluripotent stem cells through genetic manipulation.

Format: Articles

Subject: Experiments

"The Environment and Disease: Association or Causation?" (1965), by Austin Bradford Hill

In 1965, Austin Bradford Hill published the article “The Environment and Disease: Association or Causation?” in the Proceedings of the Royal Society of Medicine. In the article, Hill describes nine criteria to determine if an environmental factor, especially a condition or hazard in a work environment, causes an illness. The article arose from an inaugural presidential address Hill gave at the 1965 meeting of the Section of Occupational Medicine of the Royal Society of Medicine in London, England.

Format: Articles

Subject: Publications

Austin Bradford Hill (1897-1991)

During the twentieth century, Austin Bradford Hill researched diseases and their causes in England and developed the Bradford Hill criteria, which comprise the minimal requirements that must be met for a causal relationship to be established between a factor and a disease. Hill also suggested that researchers should randomize clinical trials to evaluate the effects of a drug or treatment by monitoring large groups of people.

Format: Articles

Subject: People

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

The Role of the Notch Signaling Pathway in Myogenesis

Among other functions, the Notch signaling pathway forestalls the process of myogenesis in animals. The Notch signaling pathway is a pathway in animals by which two adjacent cells within an organism use a protein named Notch to mechanically interact with each other. Myogenesis is the formation of muscle that occurs throughout an animal's development, from embryo to the end of life. The cellular precursors of skeletal muscle originate in somites that form along the dorsal side of the organism.

Format: Articles

Subject: Theories, 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

"Formation of Genetically Mosaic Mouse Embryos and Early Development of Lethal (t12/t12)-Normal Mosaics" (1964), by Beatrice Mintz

The paper "Formation of Genetically Mosaic Mouse Embryos and Early Development of Lethal (t12/t12)-Normal Mosaics," by Beatrice Mintz, describes a technique to fuse two mouse embryos into a single embryo. This work was published in the Journal of Experimental Zoology in 1964. When two embryos are correctly joined before the 32-cell stage, the embryo will develop normally and exhibit a mosaic pattern of cells as an adult.

Format: Articles

Subject: Experiments

Somites: Formation and Role in Developing the Body Plan

Somites are blocks of mesoderm that are located on either side of the neural tube in the developing vertebrate embryo. Somites are precursor populations of cells that give rise to important structures associated with the vertebrate body plan and will eventually differentiate into dermis, skeletal muscle, cartilage, tendons, and vertebrae. Somites also determine the migratory paths of neural crest cells and of the axons of spinal nerves.

Format: Articles

Subject: Processes

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