Huxley (Huxley), Andre( English physiologist, Nobel Prize in Physiology or Medicine, 1963)
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Biography Huxley (Huxley), Andre
genus. November 22, 1917
English physiologist Andre Filling Huxley was born in the London area Hempstid in the family of Leonard Huxley, a teacher of classical literature and the writer. His grandfather, Thomas Henry Huxley, was a scholar and writer of XIX century. Whose work has promoted the teaching of Darwin's natural selection. H., the youngest of two brothers from his father's second marriage to Rosalind Bruce, was the half brother of novelist Oldasa biologist Julian Huxley, and C. Huxley. He was educated at University College London and at Westminster School, where he showed pronounced tendency to physics and engineering, which he intended to continue to study, enrolling in 1935. at Trinity College in Cambridge. However, having passed a course in physiology, he was in 1937. transferred to the medical program and two years later became a researcher, an assistant to Alan Hodgkin at the Marine Biological Laboratory in Plymouth.
At this time, Hodgkin studying the transmission of electrical impulses along the axons (neuronal spikes). At the beginning of XX century. Julius Bernstein, . based on the work of Luigi Galvani and Walther Nernst, . suggested, . unstimulated nerve cells that carry the resting potential (electrical potential difference between the outer and inner surfaces of the cells at rest), . which is caused by uneven distribution of ions (charged particles) in the cell membrane,
. The concentration of positively charged sodium ions on the inner surface of the membrane is lower than on the outside, for positively charged potassium ions is characterized by the opposite situation. Many of the large molecules of organic substances within the cell are negatively charged. The pores in the membrane is passed through it, potassium ions, but sodium ions and ions of organic substances, which are significantly larger, can not pass through the cell membrane. The resting potential arises from the tendency of positively charged potassium ions to move from the area where their concentration is high (inside cells) in the region with their lower concentration (outside the cell).
. Bernstein suggested that the nerve impulse is an action potential
. When the permeability of the membrane is temporarily changed, ions from both sides come into contact and neutralize the resting potential, then the permeability of the membrane is restored, restoring the original resting potential. To test the theory Brenshteyna Hodgkin and X. loaded microscopic electrodes into single isolated axons of squid and measured the relative values of resting potential and action. To their surprise, they found that the change in membrane potential difference during the action potential actually turned out to be much larger than necessary for the disappearance of the resting potential. The action potential is not just brought a potential difference of the cell membrane to zero, but actually exceeded the resting potential and changed the direction of the potential difference between the inner and outer surfaces of the cell membrane.
. Since the beginning of World War II X
. Hodgkin and left their studies, and from 1940 to 1942. H. conducted experiments for the Air Defense Command, and from 1942 to 1945. - Similar work for the Department of the Navy. After the war he became an assistant professor in the department of physiology at Trinity College and with the support of the Research Society of Trinity, . grant him a scholarship in 1941, . continues to study with Hodgkin's transmission of nerve impulses.,
. The results Hodgkin and H., . published in 1954, . disproved the theory of Bernstein, . showing, . that the action potential can not be caused by the movement of only potassium ions: the process must be involved and other ion, . that exceeded the action potential due to potassium ion, the resting potential,
. Of the various ions, which are X. and Hodgkin considered for this role, most likely they seemed sodium ion. They suggested that the cell membrane contains sensitive to the difference in potential sodium channels, or passes that remain closed during the resting potential and open during depolarization of the axon. When the channels are open, . sodium ions rush from the field with their relatively high concentration (the outer surface of the membrane of the axon) for areas with relatively low concentration (the inner surface of the membrane of the axon), . leads to a temporary positive potential on the inner surface of the membrane of the axon,
. If their hypothesis about the involvement of sodium is correct, the magnitude of the action potential (but not the resting potential) should be strictly dependent on the concentration of sodium outside the cell. Test this assumption, Alan Hodgkin and Bernard Katz in 1947. have shown that they can actually change or eliminate the potential of influencing the concentration of sodium outside the cell.
H., Hodgkin and Katz began to study ion transport through the membrane of the axon at different electrical conditions. Using a voltmeter, a system for maintaining the membrane potential at selected levels in the period of observation of the flow of ions, they traced the movement of various ions with radioactive isotopes, and changes in ion concentration. Investigations were carried out on squid giant axons, . are quite large (up to a millimeter in diameter) in order, . to introduce the electrode in the membrane, . and strong enough, . to withstand, without damage to the inner membrane of substitution fluid by various combinations of ions.,
. The results of these experiments have allowed researchers to construct a mathematical model of action potential
. H. done numerous calculations on a hand calculating machine and later more complex and accurate calculations were obtained using the first digital computers (PCs). According to the model, which scientists have described in several articles in 1952, an action potential in squid axon membrane depolarization occurs in up to a certain threshold level. Depolarization opens the sodium channels, sodium ions rush into the axon, and the inner surface of the membrane for a short time becomes positively charged. Then, sensitive to changes in potential difference of potassium channels open, although more slowly than sodium, and the latter eventually closed. Potassium ions rush out of the axon, and the inner surface of the membrane of the axon gradually becomes negatively charged as compared with the outer surface of the. Within a short refractory period of membrane hyperpolarizing (becomes more negative potential than usual), t. to. output of potassium than the resting potential. Then, the resting potential is restored by the sodium-potassium pump, which uses energy cells to move potassium ions into the cell and sodium ions - from the cell and thus maintain the balance of the resting potential. Model X. and Hodgkin's been outstanding, as biochemical methods to study the components of the membrane (channels and pumps) were not developed until the 80's.
After creating a mathematical model of action potential X. became interested in the mechanism of muscle contraction, facilitated by his friendship with Archibald in. Hill. In joint work X. constructed a new type of interference light microscopy to study isolated muscle fibers.
"For their discoveries concerning the ionic mechanisms of excitation and inhibition in the peripheral and central portions of the membrane of nerve cells', X. and Hodgkin won the Nobel Prize in Physiology or Medicine in 1963, they shared it with John Eccles, who undertook a similar study on the nerve impulses. 'The nature of common electrical phenomena in the peripheral and central nervous system, . - Said Ragnar Granit of the Karolinska Institute with the presentation of awards, . - You have brought understanding of nerve impulses to the level of clarity, . that your contemporaries did not expect to see in life '.,
. From 1952 to 1960
. H. was head of research at Trinity College, from 1951 to 1959. worked as assistant director for research and lectured on experimental biophysics in the period from 1959 to 1960. In 1960, Mr.. he became professor of physiology at University College London, and in 1969. appointed research professor of the Royal Society in London University, where in 1983. is professor emeritus. From 1974 to 1980. H. headed by a Medical Research Committee for muscular dystrophy, and he - a member of the Council for Agricultural Research (1977 ... 1981), . International Council of Physiological Societies (since 1983) and the British National Committee for Physiological Sciences (1979 ... 1980),
. H. is a board member of the British and science museums.
. He was awarded the Copley Medal of Royal Society of London (1973), a member of the Royal Society and was elected an honorary or foreign member of the Royal Society of Edinburgh, the American Academy of Arts and Sciences and the Belgian Royal Academy of Medicine
. He was awarded honorary degrees from Oxford University and the University of Sheffield, Leicester, London, Andhra, Aston, Cambridge, Birmingham, Marseilles, York and East Australia.