Cournand, Andre-Frederic (1895-1988) French Physiologist Andre-Frederic Cournand was born in Paris on September 24, 1895, to Jules Cournand, a stomatologist, and his wife Marguerite Weber. He received his early education at the Lycee Condorcet, received a bachelor’s degree at the Faculte des Lettres of the Sorbonne in 1913, and received a diploma of physics, chemistry, and biology of the Faculte des Sciences the following year.
He began medical studies in 1914, but served in the French Army from 1915 to 1918, returning to medical studies at the Interne des Hopitaux de Paris in 1925. He received an M.D. from the Faculte de Medecine de Paris in May 1930 and secured a residency in the Tuberculosis (later Chest) Service of the Columbia University Division at Bellevue Hospital, New York. He became chief resident of this service and conducted research on the physiology and phys-iopathology of respiration under the guidance of Dickinson W. richards. He became an American citizen in 1941 and retired from Columbia in 1964.
Together, Cournand and Richards collaborated in clinical lung and heart research. They perfected a procedure introduced by Werner Forssmann and called Forssmann’s procedure, now called cardiac catheteriza-tion (a tube is passed into the heart from a vein at the elbow). This made it possible to study the functioning of the diseased human heart and to make more accurate diagnoses of the underlying anatomic defects. They also used the catheter to examine the pulmonary artery, improving the diagnosis of lung diseases as well. He shared the Nobel Prize in physiology or medicine with Dickinson W. Richards and Werner forssmann for their discoveries concerning heart catheterization and circulatory changes in 1956.
Cournand served on the editorial boards of many medical and physiological publications, including Circulation, Physiological Reviews, The American Journal of Physiology, and also Journal de Physiologie and Revue Frangaise d’Etudes Cliniques et Biologiques. He was a member of numerous scientific organizations and received awards for his work. He died on February 19, 1988, at Great Barrington, Massachusetts.
Court (lek) The area defended by individual males within an area where birds gather for display and courtship.
Covalent bond A region of relatively high electron density between nuclei that arises at least partly from sharing of electrons and gives rise to an attractive force and characteristic internuclear distance.
Crista The inner membrane of mitochondrion, where respiration takes place; location of the electron transport chain and enzymes that catalyze ATP synthesis. Also the term applied to sensory cells within an ear’s semicircular canal that detect fluid movement. Also means crest, such as the crista galli, the comb on a rooster.
Croll, James (1821-1890) British Carpenter, Physicist James Croll was born in Cargill, Perthshire, Scotland, on January 2, 1821. He was the son of David Croll, a stonemason from Little Whitefield, Perthshire, and Janet Ellis of Elgrin. He received an elementary school education until he was 13 years old. His knowledge of science was the result of vigilance, since he was self-taught. On September 11, 1848, he married Isabella MacDonald, daughter of John MacDonald.
Croll started his career as a carpenter apprenticed to a wheelwright when he was young; then he became a joiner at Banchory and opened a shop in Elgin. In 1852, he opened a temperance hotel in Blairgowrie, and later, in 1853, became an insurance agent for the Safety Light Assurance Company ending up in Leicester.
His first book, The Philosophy of Theism, was published in 1857 and based on the influence of the metaphysics of Jonathan Edward. However due to an injury, he ended up obtaining a job as a janitor at Anderson’s College and Museum in Glasgow in 1859. Being a janitor gave him enough free time after his daily chores to utilize the museum’s extensive library. There, he would spend the night reading books on physics, including the works of Joseph A. Adhemar, the French mathematician, who noted in 1842 that the Earth’s orbit is elliptical rather than spherical. Adhe-mar proposed in his book Revolutions de la Mer, Deluges Periodics (Revolutions of the sea, periodic floods) that the precession of the equinoxes produced variations in the amount of solar radiation striking the planet’s two hemispheres during the winter time (insolation), and this, along with gravity effects from the sun and moon on the ice caps, is what produced ice ages alternately in each hemisphere during a 26,000-year cycle. Precession is the slow gyration of Earth’s axis around the pole of the ecliptic, caused mainly by the gravitational pull of the sun, moon, and other planets on Earth’s equatorial bulge. Croll also read about the new calculations of the Earth’s orbit by French astronomer Urbain Jean Joseph Leverrier (a discoverer of the planet Neptune).
Croll decided to work on the origins of the ice ages, since he did not agree with the prevailing attitude that they were leftover relics from the biblical Great Flood, and additionally he found errors in Adhemar’s work. Croll came to the conclusion that the overriding force changing climate and creating the ice ages on Earth was due to variations in insolation, which is the rate of delivery of solar radiation per unit of horizontal surface, i.e., the sunlight hitting the Earth.
Croll first realized that Adhemar did not take into account the shape of the Earth’s orbit that varied over time and its effect on precession, so he calculated the eccentricity over several million years. This eccentricity (the distance between the center of an eccentric and its axis), in this case the degree of Earth’s elliptic orbit, he proposed, varied on a time scale of about 100,000 years. Since variations in eccentricity only produced small changes in the annual radiation budget of Earth, and not enough to force an ice age, Croll developed the idea of climatic feedbacks, such as changes in surface albedo (reflection). He predicted that the last ice age was over about 80,000 years ago.
During the 1860s, he published his theories in a number of papers: "On the Physical Cause of Changes of Climate during Geological Epochs" (1864); "The Eccentricity of the Earth’s Orbit" (1866, 1867); "Geological Time and Date of Glacial and Miocene Periods" (1868); "The Physical Cause of the Motion of Glaciers" (1869, 1870); "The Supposed Greater Loss of Heat by the Southern Hemisphere" (1869); "Evolution by Force Impossible: A New Argument against Materialism" (1877). During this time he was the keeper of maps and correspondence at the Scottish Geological Survey starting in 1867, where he mingled with some of the best geologists of the time until he retired in 1880.
In 1875 he published Climate & Time in Their Geological Relations, where he summed up his research on the ancient condition of the Earth. on January 6, 1876, he was elected a fellow of the Royal Society of London. Charles Darwin was among the many supporters of his nomination. He received an LL.D. (law degree) that year from St. Andrews College. While his main interests were in the field of paleoclimate change, he also put forth theories about ocean currents and their effects on climate during modern times.
However, some of his thoughts and ideas were wrong. For example, Croll believed that ice ages varied in the hemispheres, and his estimated age for the last ice advance ending 80,000 to 100,000 years ago was wrong. It ended between 14,000 and 10,000 years ago, as research currently shows. Because of these errors, Croll fell out of vogue until 1912, when Yugoslav geologist Milutin Milankovitch revised Croll’s theories in his book, Canon of Insolation.
Croll published close to 90 papers on a variety of subjects, such as "Ocean Currents" (1870, 1871, 1874); "Change of Obliquity of Ecliptic: Its Effect on Climate" (1867); "Physical Cause of Submergence during Glacial Epoch" (1866, 1874); "Boulder Clay of Caithness & Glaciation of North Sea" (1870); "Method of Determining Mean Thickness of Sedimentary Rocks" (1871);and "What Determines Molecular Motion? The Fundamental Problem of Nature" (1872).
A famous debate on the nature of deep-sea circulation between Croll and Irish scientist William Carpenter during the 1860s to 1880s was well discussed in the literature and around scientific circles via correspondence. In 1885, he published Climate and Cosmology to answer critics of his earlier work Climate & Time in Their Geological Relation. Five years later, plagued by ill health his whole life, he died in Perth on December 15, at age 69, shortly after publishing a small book called The Philosophical Basis of Evolution.
Cro-Magnon An early group of Homo sapiens (humans) that lived in Europe around 40,000 years ago.
Crossing over A process during meiosis when alleles on homologous chromosomes (chromosomes that pair with each other at meiosis) switch places, increasing the possible combinations of alleles and thus increasing the variability of the whole genome. Also called recombination.
Cross-pollination When pollen from the anther of a flower of one plant is transferred to the flowers (stigma) of a different plant.
Cross-reactivity The ability of an immunoglobulin, specific for one antigen, to react with a second antigen. A measure of relatedness between two different anti-genic substances.
Crustacea All crustaceans have two pairs of antennae, a pair of mandibles, a pair of compound eyes (usually on stalks), two pair of maxillae on their heads, and a pair of appendages on each body segment (head, thorax, and abdomen). There are about 30,000 species of this subphylum within five classes (Remi-pedia, Cephalocarida, Branchiopoda, Maxillopoda, and Malacostraca). Includes lobsters, crabs, crayfish, shrimp, copepods, isopods, barnacles, and others.
Many of them are important economic species for human consumption.
Cryptic Describes the ability to conceal or camouflage.
Cryptic coloration A camouflage technique whereby an organism matches its background, concealing itself from predators or prey, e.g., the peppered moth. See also mimicry.
Crystal field Crystal field theory is the theory that interprets the properties of coordination entities on the basis that the interaction of the ligands and the central atom is a strictly ionic or ion-dipole interaction resulting from electrostatic attractions between the central atom and the ligands. The ligands are regarded as point negative (or partially negative) charges surrounding a central atom; covalent bonding is completely neglected. The splitting or separation of energy levels of the five degenerate d-orbitals in a transition metal, when the metal is surrounded by ligands arranged in a particular geometry with respect to the metal center, is called the crystal field splitting.
Cuticle A protective impermeable waxy substance formed from the polymer cutan that covers the outside of leaves, stems, and fruits and forms the protective layer of arthropods.
Cyanobacteria Bacteria, formerly known as blue-green algae; aquatic and photosynthetic organisms that live in water and manufacture their own food. Their fossils go back more than 3.5 billion years, making them the oldest known species, and they are the contributors to the origin of plants.
Cybernetics The science that studies the methods to control behavior and communication in animals (and machines).
Cyclic AMP (cAMP; 3′,5′-AMP) Cyclic adenosine monophosphate. A compound synthesized from ATP (by the enzyme adenylyl cyclase) in living cells that acts as an intercellular and extracellular second messenger mediating peptide and amine hormones.
Cyclic electron flow Two photosystems are present in the thylakoid membrane of chloroplasts: photosys-tem I and photosystem II. The two photosystems work together during the light reactions of photosynthesis. The light-induced flow of electrons beginning with and returning to photosystem I to produce ATP without production of NADPH (nicotine adenine dinucleotide phosphate with hydrogen ) is cyclic electron flow. The generation of ATP by this process is called noncyclic photophosphorylation.
Cyclin A protein found in dividing cells that activates protein kinases (cyclin-dependent protein kinases), a type of enzyme that adds or removes a phosphate group from a target protein and controls the progression of one phase of the cell cycle to the next. The concentration of the cyclin increases and decreases during the cell cycle.
Cyclin-dependent kinase A protein kinase, an enzyme involved in regulating cell growth and division, that must be attached to cyclin to become activated.
Cytochrome A heme protein that transfers electrons and exhibits intense absorption bands (the a and P bands, the a band having the longer wavelength) between 510 and 615 nm in the reduced form. Cytochromes are designated types a, b, c, or d, depending on the position of the a band, which depends on the type of heme. The iron undergoes oxidation-reduction between oxidation states Fe(II) and Fe(III). Most cytochromes are hemochromes, in which the fifth and sixth coordination sites in the iron are occupied by strong field ligands, regardless of the oxidation state of iron. Cytochromes can be distinguished by the wavelength of the a band, such as cytochrome c-550. Certain specific cytochromes with particular functions are designated with suffixes, such as cytochrome a1, b2, etc.
Cytochrome-c oxidase An enzyme, ferrocyto-chrome-c: dioxygen oxidoreductase, cytochrome aa3. The major respiratory protein of animal and plant mitochondria, it catalyzes the oxidation of Fe(II)-cytochrome c, and the reduction of dioxygen to water. Contains two hemes and three copper atoms, arranged in three centers. Heme a3 and copper-B form a center that reacts with dioxygen; the second heme is cytochrome a; the third site, copper-A, is a dinuclear center.
Cytochrome P-450 General term for a group of heme-containing monooxygenases. Named from the prominent absorption band of the Fe(II)-carbonyl complex. The heme comprises protoporphyrin ix, and the proximal ligand to iron is a cysteine sulfur. Cytochromes P-450 of microsomes in tissues such as liver are responsible for metabolism of many xeno-blotlcs, including drugs. Others, such as the mitochondrial enzymes from adrenal glands, are involved in biosynthetic pathways such as those of steroids. The reaction with dioxygen appears to involve higher oxidation states of iron, such as Fe(IV)=O.
Cytokines Cytokines are soluble glycoproteins released by cells of the immune system (secreted primarily from leukocytes) that act nonenzymatically through specific receptors to regulate immune responses. Cytokines resemble hormones in that they act at low concentrations bound with high affinity to a specific receptor.
Cytokinesis The final stage of mitosis, when the parent cell divides equally by cell-wall formation into two daughter cells by way of a constriction and drawing in of an actin/myosin ring around the center of the cell.
Cytoplasm The part of protoplasm in a cell outside of and surrounding the nucleus. The contents of a cell other than the nucleus. Cytoplasm consists of a fluid containing numerous structures, known as organelles, that carry out essential cell functions. See also cell.
Cytoplasmic determinants Substances distributed in an embryo, but present in an unfertilized egg, that appear in different blastomeres at the initial cleavage stage and influence their development fate.
Cytoplasmic streaming The movement and flow of cytoplasm, the living part of a cell outside the nuclear membrane. The primary method of movement of materials within cells, e.g., chloroplasts moving up to the surface of the leaf and then down, which appear to help in photosynthesis. See also cell.
Cytoskeleton The internal support system and framework of a cell, comprising numerous microfila-ments and tubules that branch throughout the cell. The cytoskeleton serves not only as mechanical support but also in transport functions.
Cytosol The semifluid portion of the cytoplasm, not including organelles.
Cytoxic T cells (T killer cells) Cells that kill target cells bearing appropriate antigen within the groove of an MHC (major histocompatibility complex) class I molecule that is identical to that of the T cell.
Dale, Henry Hallett (1875-1968) British Physiologist Sir Henry Hallett Dale was born in London on June 9, 1875, to Charles James Dale, a businessman, and Frances Ann Hallett. He attended Tollington Park College in London, Leys School, Cambridge, and in 1894 he entered Trinity College with a scholarship. He graduated through the Natural Sciences Tripos in 1898, specializing in physiology and zoology.
In 1900 he gained a scholarship and entered St. Bartholomew’s Hospital, London, for the clinical part of the medical course. He received a B.Ch. at Cambridge in 1903 and became an M.D. in 1909.
He took an appointment as pharmacologist at the Wellcome Physiological Research Laboratories in 1904 and became director of these laboratories in 1906, working for some six years. In 1914, he was appointed director of the department of biochemistry and pharmacology at the National Institute for Medical Research in London, and in 1928 he became the director of this institute, serving until his retirement in 1942, when he became professor of chemistry and a director of the Davy-Faraday Laboratory at the Royal Institution, London.
In 1911, he was the first to identify the compound histamine in animal tissues, and he studied its physiological effects, concluding that it was responsible for some allergic and anaphylactic reactions. After successfully isolating acetylcholine in 1914, he established that it was found in animal tissue, and in the 1930s he showed that it is released at nerve endings in the parasympathetic nervous system, thus establishing acetylcholine’s role as a chemical transmitter of nerve impulses.
In 1936 he shared the Nobel Prize in physiology or medicine with his friend German pharmacologist otto loewi for their discoveries in the chemical transmission of nerve impulses.
He was knighted in 1932 and appointed to the Order of Merit in 1944. In addition to numerous articles in medical and scientific journals that record his work, he was the author of Adventures in Physiology (1953), and An Autumn Gleaning (1954).
Sir Henry was president of the Royal Society (1940-45) and others, and he received many awards. He married his first cousin Ellen Harriet Hallett in 1904. He died on July 23, 1968, in Cambridge.
Dalton A unit of measurement of molecular weight based on the mass of one-twelfth the mass of 12C, i.e., 1.656 x 10-24. A dalton is also called an atomic mass unit, or amu, and is used to measure atomic mass. Protein molecules are express in kilodaltons (kDa). The dalton was named in honor of John Dalton (1766-1844), an English chemist and physicist.
Dam, Henrik (1895-1976) Danish Biochemist Carl Peter Henrik Dam was born in Copenhagen on February 21, 1895, to druggist Emil Dam and his wife Emilie (nee Peterson), a teacher. He attended the Polytechnic Institute, Copenhagen, and graduated with a degree in chemistry in 1920. The same year he was appointed assistant instructor in chemistry at the School of Agriculture and Veterinary Medicine, advancing to full instructor in biochemistry at the Physiological Laboratory of the University of Copenhagen in 1923.
In 1925 Dam became assistant professor at the Institute of Biochemistry, Copenhagen University, and three years later was promoted to associate professor until 1941. On submitting a thesis Nogle Under-s0gelser over Sterinernes Biologiske Betydning (Some investigations on the biological significance of the ster-ines) to the University of Copenhagen in 1934, he received a Ph.D. in biochemistry.
He discovered vitamin K and its anticoagulant effects while studying the sterol metabolism of chicks in Copenhagen and was awarded the Nobel Prize in physiology or medicine in 1943 for this work.
He conducted research at Woods Hole Marine Biological Laboratories in Massachusetts during the summer and autumn of 1941 and was a senior research associate at the University of Rochester, New York, between 1942 and 1945, and he was an associate member at the Rockefeller Institute for Medical Research in 1945.
Dam was appointed professor of biochemistry at the Polytechnic Institute, Copenhagen, in 1941, though the designation of his chair at the Polytechnic Institute was changed to professor of biochemistry and nutrition in 1950.
After his return to Denmark in 1946, he concentrated his research on vitamin K, vitamin E, fats, cholesterol, and nutritional studies in relation to gallstone formation.
He published over 300 articles in biochemistry and was a member of numerous scientific organizations. Dam died on April 17, 1976.
Darling effect The stimulation of reproductive activity by the activity of other members of the species in addition to the mating pair. Also called the Fraser darling effect.
Darwinian fitness The measure of an individual’s relative genetic contribution to the gene pool of the next generation; the longer an individual survives and the more it reproduces, the higher the fitness and the higher the chance that a hereditary characteristic will be reproduced.
Darwinism The evolutionary theory advanced by Charles Darwin during the mid-19th century suggesting that present-day species have evolved from simpler ancestors. A newer version of the theory is incorporated as "neo-Darwinism" or "modern synthesis."
Day-neutral plant A plant where the length of day is not an influence on development; the plant will flower regardless of day length (photoperiodism). It is now known that it is not the length of the light period, but the length of uninterrupted darkness, that is critical to floral development. Examples are tomato, corn, cucumber, and strawberries.
Decapods Crustaceans that have five pairs of walking legs and a well-developed carapace, e.g., shrimps, lobsters, hermit crabs, and crabs.
Deciduous A plant, tree, or shrub that sheds its leaves at the end of the growing season.
