HODGKIN (Hodgkin), Alan

genus. February 5, 1914
English biophysicist Alan Lloyd Hodgkin was born in Benberi (Oxfordshire). After the death of his father, George L. Hodgkin in Baghdad during the First World War X. and his younger twin brothers were brought up his mother, Marie (Wilson), Hodgkin. Alan attended school in Malvern and Holte to income in 1932. at Trinity College, Cambridge University. From an early age he was interested in the history of science, particularly in ornithology, but at Cambridge he became interested in physiology, particularly the activities of nerve cells.
. Electrical origin of nerve impulses found in the experiments of Luigi Galvani in the late XVIII century
. At the beginning of XX century. Germany physiologist Julius Bernstein suggested, . that unstimulated nerve cells are galvanic cells with the potential of rest (the difference in electrical potential between the outer and inner surfaces of cells in the rest), . that is determined by unequal distribution of ions (charged particles) in the membrane,
. Bernstein hypothesized, . that the nerve impulse is an action potential - the permeability of the membrane with a time change - and ions from both sides come in contact with each other and neutralize the resting potential, when the membrane comes in its original state, . restore the original resting potential,
. 'The central point in the theory - as he said later, H. - is that the spread of momentum from one point to another by means of electric currents, which move between resting and active regions. The action potential is not just an electrical trace of the pulse, and the reason for its spread. "
During his studies at Trinity X. performed preliminary studies on the electrical properties of nerves. One of his teachers, a physiologist Edgar D. Adrian suggested that he use a relatively large and strong axons (nerve fibers) of marine crab Carcinus maenas. H. followed this advice and found that individual fibers can easily be isolated for experiments. In 1936, Mr.. He became a Fellow of Trinity College, working under the leadership of Archibald in. Hill, who sent a copy of the dissertation X. Herbert C. Gasser. Gasser invited X. in 1937/38 r. at the Rockefeller Institute (now - Rockefeller University) in New York. At the same time, X. visited the Oceanographic Institute in Massachusetts, where he met with Kenneth. Kolya N.D. Curtis, who used in the experiments of individual nerve fibers, isolated from the squid. Squid axon belonging to the largest of the now well-known and reach 1 mm in diameter, whereas the axons of marine crabs - no more than 0.3 mm, and the axons of mammals are even smaller diameter. 'Cole and Curtis developed a method, . allows to measure changes in electrical conductivity of the membrane during the pulse, . - Wrote later H., . - The analysis of their experiments showed, . that the membrane is a significant increase in the conductivity, . which coincides with the electrical changes',
. These results aroused particular interest among H., as they indicate the presence of membrane permeability to ions. If this is confirmed, it would have found the cause of building peace.
X. returned to Cambridge in 1938. and began to work with Andrew Huxley, a talented graduate student in. They used the methods developed by X. in the United States in experiments on axons of Carcinus. 'To our surprise, it was found that the action potential was often much greater than the resting potential', - the later X. Scientists have found that in contrast to the predictions of Bernstein's action potential not only to neutralize (or depolarized), the resting potential, but it greatly exceeded.
X. Huxley and later began to be used for experiments axons of squid, which are large enough and can be used for total immersion in their membrane microelectrodes. These studies confirmed the results of experiments on the crab axons, showing that the inner surface of the nerve cell membrane is charged negatively in relation to the outer. In cases of the action potential instead of the expected potential difference of 60 millivolts X. and Huxley recorded a potential difference of 90 millivolts or more, suggesting the temporary emergence of a large positive charge on the inner surface of the axonal membrane to the outside.
Complete research X. prevented the second world war. Most of the war years he worked on radar systems, the Air Force.
Returning to Cambridge after the war, X. worked in the physiological laboratory, and in 1945. he and Andrew Huxley published the results of its pre-war work. Their development of ionic mechanisms in living organisms have attracted the attention of other Cambridge scientists, and soon formed a small team to continue research in this direction. Adrian supported them, reducing the teaching load and securing grants Rockefeller Foundation.
. The resting potential arises due to the permeability of the membrane only for certain ions, which leads to varying concentrations of different ions on both sides of the membrane
. The concentration of positively charged sodium ions below the inner surface of the membrane compared to the outside, for positively charged potassium ions the opposite situation. Many large organic molecules inside the cell are negatively charged, and although the pores in the membrane allow potassium ions to move back and forth, sodium ions and organic ions, which are significantly larger, can not pass through the membrane. The resulting resting potential, T. to. positively charged potassium ions move out of the cell (where they are in high concentration) to the outside (where their concentration is below). Pre-war research X. and Huxley demonstrated, . that the cause of the action potential can not be moving only potassium ions; to exceed caused by potassium ions and the resting potential to cause an action potential, . requires the participation of other ion, . and the most suitable ion, . they believe, . be the sodium ion.,
. According to the sodium hypothesis, first the cell membrane becomes more permeable to sodium ions than potassium ions, which is achieved through the opening of sodium channels, or gates
. Sodium ions rush into the cell, making the inner surface of the axonal membrane temporarily positively charged, as was shown X. and Huxley. 'A simple consequence of the sodium hypothesis is that the magnitude of the action potential is determined by the concentration of sodium ions in the extracellular fluid', - said X. He, together with Bernard Katz conducted the first experiments to test this hypothesis in 1947. and proved that the action potential - but not resting potential - varies depending on the concentration of sodium ions into the extracellular space.
. H., Huxley, and Katz began a series of experiments to test the permeability of the axonal membrane to various ions at different levels of voltage
. In 1952, Mr.. They presented a mathematical theory, . details of which were developed by Huxley, in accordance with this theory, the action potential is explained as the movement of sodium ions into the cell with subsequent movement of potassium ions from the cell to restore the resting potential,
. In the same year X. became a professor of the Royal Society. The theory proposed by X. and Huxley, offers exhaustively complete biophysical description of the action potential, although the methods of investigating the molecular mechanisms of nerve impulse (membrane structures that control the movement of ions) have been available only in the 80's.
X. and Huxley won the Nobel Prize in Physiology or Medicine 1963. 'for their discoveries concerning the ionic mechanisms involved in excitation and inhibition in the peripheral and central parts of the nerve cell membrane'. They shared the prize with John C. Eccles. In a speech when giving the award Ragnar Granit of the Karolinska Institute said that the 'ionic theory of nerve impulse X. and Huxley contains principles that are applicable also to the impulses in the muscles, including electrocardiography, which is of clinical importance '. Their discovery, said Granite, 'is a milestone on the path to understanding the nature of excitability'.
Since 1970, Mr.. by 1981. H. was a professor of biophysics. Since 1978, Mr.. by 1984. he led Trinity College. From 1966 to 1976. H. is president of the Marine Biological Association, and from 1959 to 1963. - A member of the Medical Research Society.
During his first visit to the U.S. X. at Rockefeller Institute met Kay Rous, daughter of Peyton Rous. They married in 1944. while in X. in the U.S. for military service. They had a son and three daughters.
In addition to the Nobel Prize, X. received the Royal Medal (1958) and the Copley Medal of Royal Society of London (1965). Winner of numerous honorary degrees, . He is a member of the Royal Society and Royal Academy of Sciences of Denmark, . foreign member of the American Academy of Arts and Sciences, . National Academy of Sciences of India, . Academy of Sciences and the Royal Irish Academy,