Long-term rod dark adaptation in man. Threshold measurements, rhodopsin regeneration and allosteric sensitivity regulation. An evaluation |
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Authors: | ULF STABELL,BJØ RN STABELL |
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Affiliation: | Ulf Stabell, Department of Psychology, University of Oslo, Pb. 1094 Blindern, N-0317 Oslo 3, Norway |
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Abstract: | Recent evidence strongly suggests that the relationship between threshold elevation ( T ) and fraction of bleached rhodopsin ( B ), obtained during a major, middle period of long-term rod dark adaptation in man, is well described by a power function, i. e., T = k · Bn , where k is a multiplicative constant and n is the exponent. Due primarily to the low reliability of measurements of rhodopsin regeneration, however, the exponent n of the power function cannot, at present, be given an exact value. Available information indicates that the value of the exponent ranges between 2.4 and 4. Implications of this uncertainty are discussed within the framework of the allosteric, tetrameric model of rod dark adaptation. It is concluded that this model in its simplest form may only offer a first approximation of the real system implicated in the process. |
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Keywords: | dark adaptation rods rhodopsin regeneration allosteric protein cooperativity human |
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