Enders, John Franklin (1897-1985) American Virologist John Franklin Enders was born on February 10, 1897, at West Hartford, Connecticut, to John Ostrom Enders, a banker in Hartford, and Harriet Goulden Enders (nee Whitmore). He was educated at the Noah Webster School at Hartford and St. Paul’s School in Concord, New Hampshire. In 1915 he went to Yale university, left to become an air force pilot in 1918, and returned to get his B.A. in 1920. He received a Ph.D. at Harvard in 1930 for a thesis that presented evidence that bacterial anaphylaxis and hypersensitivity of the tuberculin type are distinct phenomena, and he stayed at Harvard until 1946 as a teacher.
In 1938 Enders began the study of some of the mammalian viruses and undertook, in 1941, in collaboration with others, a study of the virus of mumps. This work provided serological tests for the diagnosis of this disease and a skin test for susceptibility to it. It also demonstrated the immunizing effect of inactivated mumps virus and the possibility of attenuating the virulence of this virus by passing it through chick embryos. It showed that mumps often occurs in a form that is not apparent but that nevertheless confers a resistance that is as effective as that conferred by the visible disease.
In 1946 Enders established a laboratory for research in infectious diseases at the Children’s Medical Center at Boston. The understanding of viruses at the time was scant, and development of an antipolio vaccine depended on gaining the ability to grow sufficient quantities of the polio virus under laboratory control. The stumbling block was that poliovirus cultures could be kept alive for a useful length of time only in nerve tissue, and that was hard to obtain and maintain.
Enders, along with T. H. weller and F. C. rob-bins, found that viruses could be grown on tissues treated with penicillin to retard bacterial growth, and they were also successful in growing mumps and polio viruses as well. The ability to grow and study polio led to the development of a vaccine later by Salk and Sabin. The research opened the way to other vaccines against highly contagious childhood diseases such as measles, German measles (rubella), and mumps. Enders, Robbins, and Weller shared the 1954 Nobel Prize in medicine for this pioneering work.
Enders was a member of many organizations. Considered one of the most important contributors of the 20th century, Enders also provided insight to links between viruses and cancer, and the pattern and process of tumor growth. He died on September 8, 1985.
Endocrine gland A ductless organ that produces and secretes hormones into the bloodstream.
Endocrine system A collection of glands that work interdependently and produce hormones that regulate the body’s growth, metabolism, and sexual development and function. The endocrine system consists of: two adrenal glands, located on the top of each kidney; the pancreas, found in the abdominal cavity behind the stomach; the parathyroid and thyroid, located at the base of the neck; the pituitary, located at the base of the brain; and the ovaries and testes, the female and male sex glands.
Each of the endocrine glands produces hormones that are targeted to a particular area of the body and are released into the bloodstream and serve to regulate the activity of various organs, tissues, and body functions.
Endocytosis A process by which liquids or solid particles are taken up by a cell through invagination of the plasma membrane. The plasma membrane creates a "well" in which the substances settle, become surrounded, and are then pinched off into a vesicle that can be transported through the cell.
Endoderm one of three primary germ layers in embryonic development (along with mesoderm and ectoderm). The endoderm is the inner layer of cells and gives rise to organs and tissues associated with digestion and respiration.
Endodermis A parenchyma tissue that regulates the transport of materials into the vascular bundles of most roots, stems, and leaves. It surrounds the vascular cylinder; is especially prominent in roots; and has suberized Casparian strips, a band of suberin (waxy substance) within the anticlinal walls. It is the innermost layer of the cortex in plant roots.
Endogenous Originating internally. In the description of metal ion coordination in metalloproteins, endogenous refers to internal, or protein-derived, llgands.
Endomembrane system The collection or network of membranous organelles, such as the endoplasmic reticulum and the Golgi apparatus, that are inside a eukaryotic cell; divides the cytoplasm into compartments with various functions, with the compartments related via direct physical contact or by the use of membranous vesicles.
Endometrium The lining (mucous membrane) of the uterus and cervix. The endometrium becomes thicker as the menstrual cycle advances in preparation for a fertilized egg. If fertilization does not occur, the endometrium is shed with the menstrual flow. It consists of the stratum functionale, a thick part of endometrium that is lost during menstruation, and the stratum basal, a layer retained during menstruation that serves as a stem source for regeneration of the upper stratum functionale.
A cancerous growth in the endometrium is called endometrial cancer, and an overgrowth in the endometrium, called endometrial hyperplasia, can cause abnormal menstrual bleeding and become pre-cancerous.
Endoparasite Any parasitic organism that lives and feeds from inside its host. See also ectoparasite.
Endoplasmic reticulum (ER) An extensive convoluted membranous network in the cytoplasm of eukaryotic cells containing two types. The first is a rough endoplasmic reticulum, so called because it appears to be rough due to its surface being covered with ribosomes, that functions to help cells process proteins in sacs called cisternae. The second type of ER is smooth ER and helps cells to process fats. ER generally contains enzymes to break down both proteins and fats. See also cell.
Endorphin (endogenous morphine or opiod) A class of endogenous (made in the body) hormones produced in the brain and anterior pituitary that are chemically similar to opiate drugs (such as morphine) and are released to cope with acute stress and to deal with pain.
Endoskeleton An internal skeleton.
Endosperm A nutrient, food-storage tissue, formed from double fertilization (sperm cell fuses to two polar nuclei) in the seeds of angiosperms, which nourishes the developing embryo.
Endospore A thick-coated, environmentally resistant protective seedlike cell produced within a bacterial cell that is exposed to harsh conditions. In mycology, it is the term for spores formed on the inside of a sporangium; a spore produced within a spherule.
Endosymbiotic theory A theory on the evolution of eukaryotic cells. Originally mitochondria and chloro-plasts were free-living self-replicating cells that developed a symbiotic relationship with prokaryote cells and eventually lost their independence.
Endothelium The simple thin layer of endothelial cells that lines blood and lymph vessels. It plays a number of roles, including acting as a selective barrier for molecules and cells between the blood and surrounding tissues, and secreting and modifying several veinous signaling molecules. The endothelium also helps to make up the blood-brain barrier between the central nervous system and the rest of the body; summons and captures white blood cells (leukocytes) to the site of infections; regulates coagulation of the blood at trauma sites; controls contraction and relaxation of veins; and regulates the growth of the veinous muscular cells, among others.
It is also the term used for the innermost layer of the eye’s cornea, one cell layer thick (5-10 microns or 0.005-0.01 millimeters), that provides hydration balance to maintain the cornea’s transparency.
Endothelium-derived relaxing factor (EDRF) The factor originally described as EDRF is NO., produced by a specific P-450-type of enzyme from arginine upon response of a cell to a biological signal (molecule). Different types of cells respond differently to the presence of NO…
Endotherm A warm-blooded animal, one is which the internal temperature does not fluctuate with temperature of environment, but is maintained by a constant internal temperature regulated by metabolic processes. Examples include birds and mammals.
Endothermic The state of being warm-blooded or producing heat internally. In chemistry, it is a reaction where heat enters into a system, with the energy absorbed by a reactant.
Endotoxin A large toxic molecule consisting of polysaccharide, lipid A, and other components found in the outer cell wall of specific gram-negative bacteria. Also called pyrogen or lipopolysaccharide.
Energy Classically defined as the capacity for doing work, energy can occur in many forms such as heat (thermal), light, movement (mechanical), electrical, chemical, sound, or radiation. The first law of thermodynamics is often called the Law of Conservation of Energy and states that energy cannot be created or destroyed but only transformed from one form into another.
Enhancer A regulatory element of a gene. A site on DNA that increases transcription of a region even if it is distant from the transcribed region. One gene can have many enhancers.
Entatic state A state of an atom or group that, due to its binding in a protein, has its geometric or electronic condition adapted for function. Derived from the Greek entasis, meaning tension.
Enterobactin A siderophore found in enteric bacteria such as Escherichia coli; sometimes called ente-rochelin.
Entomology The scientific study of the world of insects; a branch of zoology.
Entomophilous Refers to a flower pollinated by insects.
Entropy The amount of energy in a closed system that is not available for doing work; disorder and randomness in a system. The higher the entropy, the less energy available for work. The Second Law of Thermodynamics states that the entropy of the universe will always increase.
Environment The total living and nonliving conditions of an organism’s internal and external surroundings that affect an organism’s complete life span.
Environmental grain Describes an organism’s own perception of its environment and how it will react to it; a scale based on the use of space in relation to the size of an organism. Grains can be coarse (large patches) or fine (small patches).
Enzootic Affecting animals living in a specific area or limited region. Slime-blotch disease caused by Brook-lynella hostilis and its associates caused a Caribbean-wide mass fish mortality in 1980 and similar ones in south Florida and Bermuda. In 1990, enzootic pneumonia, caused by Mycoplasma hyopneumoniae was evident in 80 percent of Iowa farms, and on these farms, 32 percent of the pigs were actively infected.
Enzyme A macromolecule that functions as a bio-catalyst by increasing the reaction rate, frequently containing or requiring one or more metal ions. In general, an enzyme catalyzes only one reaction type (reaction specificity) and operates on only a narrow range of substrates (substrate specificity). Substrate molecules are attacked at the same site (regiospecificity), and only one, or preferentially one of the enantiomers of chiral substrate or of racemic mixtures, is attacked (enan-tiospecificity).
Enzyme induction The process whereby an (inducible) enzyme is synthesized in response to a specific inducer molecule. The inducer molecule (often a substrate that needs the catalytic activity of the inducible enzyme for its metabolism) combines with a repressor and thereby prevents the blocking of an operator by the repressor leading to the translation of the gene for the enzyme. An inducible enzyme is one whose synthesis does not occur unless a specific chemical (inducer) is present, which is often the substrate of that enzyme.
Enzyme repression The mode by which the synthesis of an enzyme is prevented by repressor molecules.
In many cases, the end product of a synthesis chain (e.g., an amino acid) acts as a feedback corepressor by combining with an intracellular aporepressor protein, so that this complex is able to block the function of an operator. As a result, the whole operation is prevented from being transcribed into mRNA, and the expression of all enzymes necessary for the synthesis of the end-product enzyme is abolished.
Eocene Part of the Tertiary period during the Ceno-zoic era, lasting from about 54.8 to 33.7 million years ago. Most of the orders of truly warm-blooded mammals were present by the early Eocene.
Eosinophil one of the five different types of white blood cell (WBC) belonging to the subgroup of WBCs called polymorphonuclear leukocytes. Characterized by large red (i.e., eosinophilic) cytoplasmic granules.
Eosinophil function is incompletely understood. They are prominent at sites of allergic reactions and with parasitic larvae infections (helminths). Eosinophil secretory products inactivate many of the chemical mediators of inflammation and destroy cancer cells. This phenomenon is most obvious with mast-cell-derived mediators. Mast cells produce a chemotactic factor for eosinophils.
Eosinophils are produced in the bone marrow, then migrate to tissues throughout the body. When a foreign substance enters the body, lymphocytes and neutrophils release certain substances to attract eosinophils, which release toxic substances to kill the invader. See also eosinophilia.
Eosinophil chemotactic factor of anaphylaxis (ECF-A) A substrate released from mast cells and basophils during anaphylaxis, which attracts eosinophils. A tetrapeptide mediator of immediate hypersensitivity.
Eosinophilia (blood eosinophilia) An abnormally high number of eosinophils in the blood. Not a disease in itself but usually a response to a disease. An elevated number of eosinophils usually indicates a response to abnormal cells, parasites, or allergens. See also eosinophil.
Ephemeral Transitory, lasting for a brief time.
Epidermis Both plants and animals have epidermis, the "skin." Epidermis serves as a protective layer against invasion of foreign substances both chemical and animal (parasites).
In plants, it protects against desiccation; participates in gas exchange and secretion of metabolic compounds; absorbs water; and is the site of receptors for light and mechanical stimuli.
In mammals, the epidermis is a superficial layer of the skin and is subdivided into five layers or strata— the stratum corneum, the stratum basale, the stratum spinosum, the stratum granulosum, and the stratum lucidum—each with their own functions.
Epigenesis The complete and progressive development and differentiation that starts from the beginning of a fertilized egg or spore through each stage of change, guided by genetics and environment until the final adult stage is completed. A process where a genotype becomes expressed and transformed into a final phenotype.
Epiglottis A leaflike cartilaginous flap that closes and covers the glottis (middle part of the larynx) to prevent food and other objects from entering the trachea and lungs while ingesting.
Epilepsy A neurological or brain condition in which a person has a tendency to have repeated seizures. Clusters of nerve cells, or neurons, in the brain sometimes signal abnormally. It affects more than 2 million Americans, with over 180,000 new cases each year.
Endoscope view of a healthy larynx (voice box) showing resting vocal cords (v-shaped, center left and right). The vocal cords are responsible for the production of sound. Normally the epiglottis, a leaflike cartilaginous flap, closes and covers the glottis (middle part of the larynx) to prevent food and other objects from entering the trachea and lungs while ingesting.
Epinephrine Another name for adrenaline. A hormone and neurotransmitter secreted by the adrenal gland (adrenal medulla) to react to stress, exercise, low blood glucose. It is also a major component of the fight-or-flight reaction, the reaction that happens in the body when, faced with a sudden unexpected threat or stress situation, both epinephrine and norepinephrine are released.
The drug of choice for the treatment of anaphylax-is. Individuals who are allergic to insect stings and certain foods should always carry a self-injecting syringe of epinephrine.
Epinephrine increases the speed and force of heartbeats and, therefore, the work that can be done by the heart. It dilates the airways to improve breathing and narrows blood vessels in the skin and intestine so that an increased flow of blood reaches the muscles and allows them to cope with the demands of exercise. Usually treatment with this hormone stops an anaphylactic reaction. Epinephrine has been produced synthetically as a drug since 1900.
Epiparasite Any organism that extracts nutrients from its host plant by means of intermediates.
Epiphyte Any nonparasitic plant, fungus, or microorganism that grows on the surface of another plant for support but provides its own nourishment. Epiphytes can form "mats" that contain a surface of canopy plants with suspended soil and other material. A facultative epiphyte is one that commonly grows epiphytically and terrestrially, but will usually exhibit a preference for one or the other habit in a particular habitat.
Episome A plasmid (circular piece of DNA ) that can attach to and integrate its DNA in a cell and at other times exist freely and still replicate itself alone, e.g., certain bacterial viruses.
Epitasis Interaction between nonallelic genes, with one gene altering the expression of the other gene.
Epithelial tissues Closely packed layers of epithelial cells, a membranelike tissue that covers the body and lines body cavities, such as the gastrointestinal tract and the lining of the lung. Epidermal growth factor (EGF) is a hormone that causes epithelial tissues, such as skin and the cells lining the gastrointestinal tract and lungs, to grow and heal.
Epitope (antigenic determinant) These are particular chemical groups on a molecule that are antigenic, i.e., that elicit a specific immune response.
Epizootic A rapid spread of a disease throughout an area affecting an animal group, e.g., rabies (disease affecting raccoons, fox) or epizootic catarrhal enteritis (disease affecting mink). When it occurs in humans, it is called an epidemic.
Epoch A period or date of time, shorter than and part of an era, that is used in geological time tables to locate historical events. Usually refers to an event (mountain building, appearance of a species, etc.). Also called a series.
