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Nymark S, Frederiksen R, Woodruff ML, Cornwall MC, Fain GL. Bleaching of mouse rods: microspectrophotometry and suction-electrode recording. J Physiol 2012; 590:2353-64. [PMID: 22451436 DOI: 10.1113/jphysiol.2012.228627] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
When a substantial fraction of rhodopsin in a rod photoreceptor is exposed to bright light, the rod is desensitized by a process known as bleaching adaptation. Experiments on isolated photoreceptors in amphibians have revealed many of the features of bleaching adaptation, but such experiments have not so far been possible in mammals. We now describe a method for making microspectrophotometric measurements of pigment concentration and suction-electrode recording of electrical responses over a wide range of bleaching exposures from isolated mouse rods or pieces of mouse retina. We show that if pigment is bleached at a low rate in the presence of bovine serum albumin (BSA), and intermediate photoproducts are allowed to decay, mouse rods are stably desensitized; subsequent treatment with exogenous 11-cis retinal results in pigment regeneration and substantial recovery of sensitivity to the dark-adapted value. Stably bleached wild-type (WT) rods show a decrease in circulating current and acceleration of the time course of decay, much as in steady background light; similar effects are seen in guanylyl cyclase-activating protein knockout (GCAPs(-/-)) rods, indicating that regulation of guanylyl cyclase is not necessary for at least a part of the adaptation produced by bleaching. Our experiments demonstrate that in mammalian rods, as in amphibian rods, steady-state desensitization after bleaching is produced by two components: (1) a reduction in the probability of photon absorption produced by a decrease in rhodopsin concentration; and (2) an equivalent background light whose intensity is proportional to the fraction of bleached pigment, and which adapts the rod like real background light. These two mechanisms together fully account for the ‘log-linear' relationship in mammalian retina between sensitivity and per cent bleach, which can be measured in the steady state following exposure to bright light. Our methods will now make possible an examination of bleaching adaptation and pigment regeneration in mouse animal lines with mutations or other alterations in the proteins of transduction.
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Affiliation(s)
- S Nymark
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA 02118-2526, USA
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Reuter T. Fifty years of dark adaptation 1961–2011. Vision Res 2011; 51:2243-62. [DOI: 10.1016/j.visres.2011.08.021] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2010] [Revised: 08/24/2011] [Accepted: 08/24/2011] [Indexed: 02/07/2023]
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The Bleaching and Regeneration of Rhodopsin in the Living Eye of the Albino Rabbit and of Man. ACTA ACUST UNITED AC 2010. [DOI: 10.1080/713818686] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Abstract
PRIMARY OBJECTIVE To expand upon earlier findings of elevated dark adaptation (scotopic) thresholds in photosensitive individuals with traumatic brain injury (TBI). METHODS AND PROCEDURES To assess scotopic thresholds in individuals with TBI (n = 17) manifesting varying degrees of photosensitivity (mild, moderate or marked), but without retinal dysfunction, to those of non-photosensitive, visually-normal individuals (n = 21) using a hand-held dark adaptometer. MAIN OUTCOMES AND RESULTS The group mean scotopic threshold for the TBI group was significantly higher than that of the visually-normal group. Over 50% (nine out of 17) of the TBI group exhibited elevated thresholds. There was no correlation between the threshold value and degree of photosensitivity. CONCLUSION The elevated scotopic thresholds suggest an abnormality in cortical gain control. An anomalous adaptive response may develop due to cortical damage, thereby attenuating subjective light sensation.
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Affiliation(s)
- T Du
- Department of Vision Sciences, State University of New York/State College of Optometry, New York 10036, USA
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Morton RA, Pitt GA. Aspects of visual pigment research. ADVANCES IN ENZYMOLOGY AND RELATED AREAS OF MOLECULAR BIOLOGY 2006; 32:97-171. [PMID: 4892505 DOI: 10.1002/9780470122778.ch4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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Affiliation(s)
- J E Dowling
- BIOLOGICAL LABORATORIES OF HARVARD UNIVERSITY, CAMBRIDGE
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WEALE RA. Bleaching experiments on eyes of living grey squirrels (Sciurus carolinensis leucotis). J Physiol 2003; 127:587-91. [PMID: 14368551 PMCID: PMC1365743 DOI: 10.1113/jphysiol.1955.sp005279] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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Abstract
In the isolated retina of the bullfrog (Rana catesbiana) illumination of one part of a ganglion cell's receptive field increased the light threshold (for response by that cell) not only in the illuminated part but also in the unilluminated parts of the field. Scattered light is insufficient to account for the effect. Apparently it depends on changes in the efficiency of excitation transmission along the neural pathways from photoreceptors to ganglion cell.
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Abstract
The effects of light adaptation on the increment threshold, rhodopsin content, and dark adaptation have been studied in the rat eye over a wide range of intensities. The electroretinogram threshold was used as a measure of eye sensitivity. With adapting intensities greater than 1.5 log units above the absolute ERG threshold, the increment threshold rises linearly with increasing adapting intensity. With 5 minutes of light adaptation, the rhodopsin content of the eye is not measurably reduced until the adapting intensity is greater than 5 log units above the ERG threshold. Dark adaptation is rapid (i.e., completed in 5 to 10 minutes) until the eye is adapted to lights strong enough to bleach a measurable fraction of the rhodopsin. After brighter light adaptations, dark adaptation consists of two parts, an initial rapid phase followed by a slow component. The extent of slow adaptation depends on the fraction of rhodopsin bleached. If all the rhodopsin in the eye is bleached, the slow fall of threshold extends over 5 log units and takes 2 to 3 hours to complete. The fall of ERG threshold during the slow phase of adaptation occurs in parallel with the regeneration of rhodopsin. The slow component of dark adaptation is related to the bleaching and resynthesis of rhodopsin; the fast component of adaptation is considered to be neural adaptation.
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Stabell U, Stabell B. Long-term rod dark adaptation in man. Threshold measurements, rhodopsin regeneration and allosteric sensitivity regulation. An evaluation. Scand J Psychol 1996; 37:259-68. [PMID: 8856998 DOI: 10.1111/j.1467-9450.1996.tb00658.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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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Affiliation(s)
- U Stabell
- Department of Psychology, University of Oslo, Norway
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Abstract
Using a Wright colorimeter the ordinary long-term, long-wave cone dark-adaptation curve was measured at 0, 2, 4, 7, 17, 25, 40 and 49 degrees nasally in the visual field. In opposition to previous findings, the results show that the dark-adaptation function of the long-wave cones changes markedly when the test field is moved outward from the rod-free fovea. It is suggested that the kinetics of the long-wave cone photopigment change with eccentricity. Also, at variance with previous findings, the present curves at all eccentricities may reasonably well be interpreted as consisting of three different sections; a first section where the threshold decreases rapidly, followed by a major, approximately linear section and a terminating section that converges asymptotically towards the final level of sensitivity. This finding suggests that the dark-adaptation process of the cone system, under the given experimental conditions, is based on three somewhat different processes.
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Affiliation(s)
- B Stabell
- Department of Psychology, University of Oslo, Norway
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Abstract
The ordinary long-term rod and cone dark-adaptation curves have generally been assumed to follow a single exponential rate of recovery. However, in two previous papers on rod dark-adaptation (Stabell et al., 1986a, b), the recovery curve was found to consist of three different sections. The results of the present paper show the same type of recovery function with three different sections for the long-term dark-adaptation curve of the long-wave cone system. During the major, middle section log cone threshold, like log rod threshold, is linearly related to the logarithm of the concentration of bleached photopigment. Presupposing that the bleached cone photopigment acts as a ligand, the change in threshold level obtained during the middle section of the dark-adaptation curve is well described by the change in activity rate of an allosteric, postively cooperative enzyme built as a dimer.
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Djamgoz MB. Differential recovery rates of horizontal and amacrine cell responses from intense irradiation in the isolated retina of cyprinid fish. Neurosci Lett 1988; 88:263-70. [PMID: 3386871 DOI: 10.1016/0304-3940(88)90221-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Recovery of light sensitivity in horizontal and amacrine cells, following desensitization of photoreceptors by localized brief laser flashes (647.1 or 488 nm) in isolated retinae of roach has been studied in a comparative approach. Spectrally matching laser irradiation suppressed light-evoked horizontal cell responses for minutes, cells only recovering on average less than 10% of their pre-irradiation response levels. In contrast, transient depolarizing responses in on-off amacrine cells recovered 80% or more of their light sensitivity within 10-20 s following laser irradiation of either wavelength. Possible neural basis of the sensitization phenomenon in amacrine cells is discussed in relation to known mechanisms of synaptic transmission in the retina.
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Affiliation(s)
- M B Djamgoz
- Department of Pure and Applied Biology, Imperial College, London, U.K
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Yellott JI, Wandell BA, Cornsweet TN. The Beginnings of Visual Perception: The Retinal Image and its Initial Encoding.
Appendix:
Fourier Transforms and Shift‐Invariant Linear Operators. Compr Physiol 1984. [DOI: 10.1002/cphy.cp010307] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Gupta BD. Absorption of light in photoreceptors: transverse incidence. BIOPHYSICS OF STRUCTURE AND MECHANISM 1981; 8:35-43. [PMID: 7326354 DOI: 10.1007/bf01047104] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
The time variation of the absorption rate (i.e., the number of photons absorbed per see) in a photoreceptor when light is incident perpendicular to its axis has been studied for various species and different conditions. Due to the cylindrical geometry of the photoreceptor the expressions for the absorption rates become very complicated. Hence, simple approximate expressions for the absorption rates in the case of some of the species have been suggested. The present analysis will be useful in analysing the mechanism of the photoreceptor when light is incident perpendicular to the axis.
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Zuidema P, Gresnigt AM, Bouman MA, Koenderink JJ. A quanta coincidence model for absolute threshold vision incorporating deviations from Ricco's law. Vision Res 1978; 18:1685-9. [PMID: 726322 DOI: 10.1016/0042-6989(78)90262-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Ditchburn RW, Drysdale AE. The effect of retinal-image movements on vision. II. Oscillatory movements. PROCEEDINGS OF THE ROYAL SOCIETY OF LONDON. SERIES B, BIOLOGICAL SCIENCES 1977; 197:385-406. [PMID: 18737 DOI: 10.1098/rspb.1977.0076] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The effect of oscillatory movements imposed on an otherwise stationary image has been studied. Sinusoidal, triangular and square-wave waveforms were used. Frequencies (
f
) ranged from 0.01 to 30 Hz and peak to peak displacement (
M
) from 0.1 to 13´. The target was usually a dark line, 6´ in diameter, seen in a field of 1000td retinal illuminance. The fraction of time (
V
) for which the target was seen was measured. The results show that movement has two effects: (i) to increase
V
by causing fluctuations of illuminance in receptors near the boundary and (ii) to decrease
V
, presumably by blurring the boundary. Effect (ii) can be detected only when effect (i) is small, i. e. for very small values of
M
or for high values of
f
. The effect of square-wave movements do not agree with calculations based on the results obtained for sinusoidal waves. Thus the effects of different frequencies do not superpose in a linear way. This is possibly due to the fact that sinusoidal movements produce sinusoidal fluctuations of light only for small movements. The results obtained are compared with the results of an experiment by Yarbus (1960) and also with flicker-fusion experiments. Agreement is as good as may be expected having having regard to differences of experimental conditions. The changes in the fraction of pigment bleached in receptors near the boundary due to the movements is calculated and the ratio of the signal to photon-noise is deduced. It is found that for frequencies above 5 Hz, the response to movement is limited by photon-noise. For lower frequencies the response is limited by other processes.
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Asai H, Chiba T, Watanabe M. Cooperative conformational change in rod photoreceptor disk membrane induced by bleaching. Vision Res 1977; 17:983-4. [PMID: 595406 DOI: 10.1016/0042-6989(77)90075-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Hofmann KP, Uhl R, Hoffmann W, Kreutz W. Measurements on fast light-induced light-scattering and -absorption changes in outer segments of vertebrate light sensitive rod cells. BIOPHYSICS OF STRUCTURE AND MECHANISM 1976; 2:61-77. [PMID: 963228 DOI: 10.1007/bf00535653] [Citation(s) in RCA: 89] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Flash-induced changes of light-absorption and of light-scattering of vertebrate rod outer segments (ROS) from frog and cattle in suspension were measured at 380 and 800 nm. The photometer used allows the observation of light intensity changes under well defined angles. We studied the successive decrease of the signal amplitude in series of flashes. One flash bleaches about 1% rhodopsin. The following results are discussed: 1. The signal at 380 nm is a superposition of the absorption change caused by formation of metarhodopsin II and of a biphasic additional signal. The latter exists only for the initial range of bleaching (15 to 25% rhodopsin). 2. At 800 nm three scattering signals are observed which are characterized by their successive amplitude decrease and time course: N: A small signal with time course and successive amplitude decrease comparable to the metarhodopsin II absorption change, probably arising from a structural change within the disc membrane. Ni: A slow signal, disappearing with the first flash, which may be understood as an outer membrane effect. P: A biphasic signal with a successive decrease rate, by a factor of 10 to 20 higher than that of the metarhodopsin II signal. The two kinetically different components are separated by variation of the observation angle. Two regions of different extension appear to change structurally with different time course. "P" may reflect an influence of the light-induced transmitter release on disc shape and/or mass.
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Abstract
1. The visual pigment in a 5 degrees circular patch of the living human retina 18 degrees temporal from the fovea was studied with the Rushton retinal densitometer. The measuring light (570 nm) was selected to obviate artifacts from colour photoproducts.2. The action spectrum of a 10% bleach agrees well with the action spectrum at absolute threshold for the same patch of retina. The quantized C.I.E. scotopic spectral sensitivity curve is a good description of both spectra. Therefore, the visual pigment studied must be human rhodopsin.3. Its density has been estimated in five different ways. The results are in reasonable agreement. The optical density of human rhodopsin in vivo is about 0.35 (common logarithmic units) at its gamma(max.)4. The photosensitivity of human rhodopsin in vivo was determined by studying its rate of bleaching in response to steps of monochromatic light exposed to the dark adapted eye, by measuring the amount bleached in the steady state by monochromatic lights as well as the amount bleached by 10 sec flashes of white light.5. The results obtained by the different methods are in good agreement with each other and with previous estimates made by others using white light.6. The photosensitivity of human rhodopsin in vivo [epsilongamma(max) = 62,000 to 120,000 l./cm mole] is much higher than expected from in vitro measurements.
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Abstract
Dynamic description of most receptors, even in their near-linear ranges, has not led to understanding of the underlying physical events-in many instances because their curious transfer functions are not found in the usual repertoire of integral-order control-system analysis. We have described some methods, borrowed from other fields, which allow one to map any linear frequency response onto a putative weighting over an ensemble of simpler relaxation processes. One can then ask whether the resultant weighting of such processes suggests a corresponding plausible distribution of values for an appropriate physical variable within the sensory transducer. To illustrate this approach, we have chosen the fractional-order low-frequency response of Limulus lateral-eye photoreceptors. We show first that the current "adapting-bump" hypothesis for the generator potential can be formulated in terms of local first-order relaxation processes in which local light flux, the cross section of rhodopsin for photon capture, and restoration rate of local conductance-changing capability play specific roles. A representative spatial distribution for one of these parameters, which just accounts for the low-frequency response of the receptor, is then derived and its relation to cellular properties and recent experiments is examined. Finally, we show that for such a system, nonintegral-order dynamics are equivalent to nonhyperbolic statics, and that the efficacy distribution derived to account for the small-signal dynamics in fact predicts several decades of near-logarithmic response in the steady state. Encouraged by the result that one plausible proposal can account approximately for both the low-frequency dynamics (the transfer function s(k)) and the range-compressing statics (the Weber-Fechner relationship) measured in this photoreceptor, we have described some formally similar applications of these distributed effects to the vertebrate retina and to analogous properties of mechanoreceptors and chemoreceptors.
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Abstract
The shapes of the photocurrent responses of rat rods, recorded with microelectrodes from the receptor layer of small pieces of isolated retinas, have been investigated as a function of temperature and of stimulus energy. Between 27 and 37 degrees C the responses to short flashes can be described formally as the output of a chain of at least four linear low-pass filters with time constants in the range 50-100 msec. The output of the filter chain is then distorted by a nonlinear amplitude-limiting process with a hyperbolic saturation characteristic. Flashes producing approximately 30 photons absorbed per rod yield responses of half-maximal size independently of temperature. The maximum response amplitude is that just sufficient to cancel the dark current. The rate of rise of a response is proportional to flash energy up to the level of 10(5) photons absorbed per rod, where hyperbolic rate saturation ensues. The responses continue to increase in duration with even more intense flashes until, at the level of 10(7) photons absorbed per rod, they last longer than 50 min. The time-courses of the photocurrent and of the excitatory disturbance in the rod system are very similar. The stimulus intensity at which amplitude saturation of the photocurrent responses begins is near that where psychophysical "rod saturation" is seen. An analysis of these properties leads to the following conclusions about the mechanism of rod excitation. (a) The kinetics of the photocurrent bear no simple relation to the formation or decay of any of the spectroscopic intermediates so far detected during the photolysis of rhodopsin. (b) The forms of both the amplitude- and rate-limiting processes are not compatible with organization of rhodopsin into "photoreceptive units" containing more than 300 chromophores. Even at high stimulus intensities most rhodopsin chromophores remain connected to the excitatory apparatus of rods. (c) The maximum rate of rise of the photocurrent is too fast to be consistent with the infolded disks of a rod outer segment being attached to the overlying plasma membrane. Most of the disks behave electrically as if isolated within the cell. (d) Control of the photocurrent at the outer segment membrane is not achieved by segregation of the charge carriers of the current within the rod disks. Instead, it is likely to depend on control of the plasma membrane permeability by an agent released from the disks.
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Eakin RM, Brandenburger JL. Osmic staining of amphibian and gastropod photoreceptors. JOURNAL OF ULTRASTRUCTURE RESEARCH 1970; 30:619-41. [PMID: 4191168 DOI: 10.1016/s0022-5320(70)90056-0] [Citation(s) in RCA: 60] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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BONTING SJOERDL. The Mechanism of the Visual Process. ACTA ACUST UNITED AC 1969. [DOI: 10.1016/b978-1-4831-9971-9.50013-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/07/2023]
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Galindo IG. A charge transfer process in the visual pigments. THE BULLETIN OF MATHEMATICAL BIOPHYSICS 1967; 29:677-90. [PMID: 5582147 DOI: 10.1007/bf02476919] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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WALD G. The Receptors of Human Color Vision: Action spectra of three visual pigments in human cones account for normal color vision and color-blindness. Science 1964; 145:1007-16. [PMID: 14172613 DOI: 10.1126/science.145.3636.1007] [Citation(s) in RCA: 279] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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WHITE H. On visual adaptation: II. The electroretinogram and the bipolar cells. Bull Math Biol 1963; 25:125-39. [PMID: 14000316 DOI: 10.1007/bf02478271] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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WILLIAMS TP. Quantal Absorption and the Electroretinogram. Nature 1963; 198:964-6. [PMID: 14000938 DOI: 10.1038/198964a0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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