The Experts below are selected from a list of 270 Experts worldwide ranked by ideXlab platform
Jeremy Nathans - One of the best experts on this subject based on the ideXlab platform.
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Spectral sensitivities of Human cone visual pigments determined in vivo and in vitro.
Methods in enzymology, 2000Co-Authors: Andrew Stockman, Lindsay T. Sharpe, Shannath L. Merbs, Jeremy NathansAbstract:Publisher Summary This chapter summarizes the current status of the spectral sensitivity curves that underlie normal and anomalous Human Color Vision, with an emphasis on in vivo psychophysical measurements in genetically well-characterized subjects and in vitro measurements with recombinant cone pigments. The existence of polymorphisms among normal M and L pigment genes, most especially the A180/S180 polymorphism, means that a single set of cone fundamentals will accurately describe the Color Vision of only a subset of normal trichromats, and that in the construction of an average set of fundamentals it is important that the weighting of polymorphic types within the test population match that in the general population. Thus, the in vivo determination of the cone fundamentals requires an analysis of the spectral sensitivity curves for subjects whose visual pigment gene sequences reveal which of the various possible pigments they possess. By building on advances in molecular biology and exploiting high-precision in vivo and in vitro techniques, significant progress has been made toward the goal of fully cataloging the rich diversity of cone photopigments that underlie normal and anomalous Human Color Vision.
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THE EVOLUTION AND PHYSIOLOGY OF Human Color Vision : INSIGHTS FROM MOLECULAR GENETIC STUDIES OF VISUAL PIGMENTS
Neuron, 1999Co-Authors: Jeremy NathansAbstract:The author would like to thank Hui Sun, Clark Riley, and Philip Smallwood for assistance with Figure 1, Figure 2, Figure 5 and Samir Deeb, John Mollon, Ed Pugh, and Ted Sharpe for helpful comments on the manuscript.
Daniel D. Oprian - One of the best experts on this subject based on the ideXlab platform.
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Molecular determinants of spectral properties and signal transduction in the visual pigments.
Current opinion in neurobiology, 1992Co-Authors: Daniel D. OprianAbstract:Site-directed mutagenesis of the visual pigment rhodopsin has provided a wealth of information regarding amino acid residues responsible for the determination of the spectral properties of the chromophore, the amino acids involved in activation and inactivation of the protein, and the effect of amino acid substitutions found in patients with retinitis pigmentosa. In addition, cell culture systems have now been established for expression of the three Human Color Vision pigments, opening the way for a similar attack on the structure and function of these important proteins.
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Design, Chemical Synthesis, and Expression of Genes for the Three Human Color Vision Pigments
Biochemistry, 1991Co-Authors: Daniel D. Oprian, Ana B. Asenjo, Ning Lee, Sandra L. PelletierAbstract:Color Vision in Humans is mediated by three pigments from retinal cone photoreceptor cells: blue, green, and red. We have designed and chemically synthesized genes for each of these three pigments. The genes were expressed in COS cells, reconstituted with 11-cis-retinal chromophore, and purified to homogeneity using an immunoaffinity procedure. To facilitate the immunoaffinity purification, each pigment was modified at the carboxy terminus to contain an additional eight amino acid epitope for a monoclonal antibody previously used to purify bovine rhodopsin. The spectra for the isolated pigments had maxima of 424, 530, and 560 nm, respectively, for the blue, green, and red pigments. These maxima are in excellent agreement with the maxima previously observed by microspectrophotometry of individual Human cone cells. The spectra are the first to be obtained from isolated Human Color Vision pigments. They confirm the original identification of the three Color Vision genes, which was based on genetic evidence [Nathans, J., Thomas, D., & Hogness, D.S. (1986) Science 232, 193].
Samir S. Deeb - One of the best experts on this subject based on the ideXlab platform.
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Genetics of variation in Human Color Vision and the retinal cone mosaic.
Current opinion in genetics & development, 2006Co-Authors: Samir S. DeebAbstract:Variation in Human Color Vision is mainly caused by one common polymorphism (Ser180Ala) in the L pigment, and to the frequent presence of hybrid genes that encode pigments with various spectral properties. Both recombination and gene conversion between the highly homologous L and M pigment genes have generated wide variation in genotype and Color Vision phenotype. The S, M and L cones are distributed randomly in the central retina. Unlike S cones, M and L cones vary widely in number within the central retina. Determining the number of the three classes of cone and their special distribution in the living retina has significantly advanced the ability to correlate the cone mosaic in normal and Color-defective subjects with the Color Vision phenotype. The transcription factors NR2E3, TRbeta2 and RXRgamma play crucial roles in establishment of the retinal cone mosaic during eye development.
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The molecular basis of variation in Human Color Vision.
Clinical genetics, 2005Co-Authors: Samir S. DeebAbstract:Common variation in red-green Color Vision exists among both normal and Color-deficient subjects. Differences at amino acids involved in tuning the spectra of the red and green cone pigments account for the majority of this variation. One source of variation is the very common Ser180Ala polymorphism that accounts for two spectrally different red pigments and that plays an important role in variation in normal Color Vision as well as in determining the severity of defective Color Vision. This polymorphism most likely resulted from gene conversion by the green-pigment gene. Another common source of variation is the existence of several types of red/green pigment chimeras with different spectral properties. The red and green-pigment genes are arranged in a head-to-tail tandem array on the X-chromosome with one red-pigment gene followed by one or more green-pigment genes. The high homology between these genes has predisposed the locus to relatively common unequal recombination events that give rise to red/green hybrid genes and to deletion of the green-pigment genes. Such events constitute the most common cause of red-green Color Vision defects. Only the first two pigment genes of the red/green array are expressed in the retina and therefore contribute to the Color Vision phenotype. The severity of red-green Color Vision defects is inversely proportional to the difference between the wavelengths of maximal absorption of the photopigments encoded by the first two genes of the array. Women who are heterozygous for red and green pigment genes that encode three spectrally distinct photopigments have the potential for enhanced Color Vision.
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Molecular genetics of Human Color Vision.
Behavior genetics, 1996Co-Authors: Samir S. Deeb, Arno G. MotulskyAbstract:The significant advances in our understanding of Color Vision has been due to the convergence of information from behavioral and molecular genetic analyses. The molecular biology of the visual pigments; molecular genetic basis of variation in normal and abnormal Color Vision, and regulation of the genes at the LWS-MWS pigment gene locus are discussed.
Lindsay T. Sharpe - One of the best experts on this subject based on the ideXlab platform.
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Spectral sensitivities of Human cone visual pigments determined in vivo and in vitro.
Methods in enzymology, 2000Co-Authors: Andrew Stockman, Lindsay T. Sharpe, Shannath L. Merbs, Jeremy NathansAbstract:Publisher Summary This chapter summarizes the current status of the spectral sensitivity curves that underlie normal and anomalous Human Color Vision, with an emphasis on in vivo psychophysical measurements in genetically well-characterized subjects and in vitro measurements with recombinant cone pigments. The existence of polymorphisms among normal M and L pigment genes, most especially the A180/S180 polymorphism, means that a single set of cone fundamentals will accurately describe the Color Vision of only a subset of normal trichromats, and that in the construction of an average set of fundamentals it is important that the weighting of polymorphic types within the test population match that in the general population. Thus, the in vivo determination of the cone fundamentals requires an analysis of the spectral sensitivity curves for subjects whose visual pigment gene sequences reveal which of the various possible pigments they possess. By building on advances in molecular biology and exploiting high-precision in vivo and in vitro techniques, significant progress has been made toward the goal of fully cataloging the rich diversity of cone photopigments that underlie normal and anomalous Human Color Vision.
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New Aspects of an Old Theme: The Genetic Basis of Human Color Vision
American journal of human genetics, 1998Co-Authors: Bernd Wissinger, Lindsay T. SharpeAbstract:Most of the readers of this journal can perceive the full range of Colors in the visible spectrum and, thus, are able to discriminate among the Color-coded bases of the DNA graphic on the cover and enjoy the intrinsic beauty of multiColor FISH micrographs and the brightness of dye-labeled sequencing fragments on the screen of an automatic DNA sequencer. We appreciate the palette of impressionist painters, and we deal freely with yellow submarines, green traffic lights, and red emergency buttons.
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GENETICS OF PERCEPTION '98 New Aspects of an Old Theme: The Genetic Basis of Human Color Vision
1998Co-Authors: Bernd Wissinger, Lindsay T. SharpeAbstract:Most of the readers of this journal can perceive the fullrange of Colors in the visible spectrum and, thus, areable to discriminate among the Color-coded bases of theDNA graphic on the cover and enjoy theintrinsicbeautyof multiColor FISH micrographs and the brightness ofdye-labeled sequencing fragments on the screen of anautomatic DNA sequencer. We appreciate the palette ofimpressionist painters, and we deal freely with yellowsubmarines, green traffic lights, and red emergency but-tons. Vision is the dominant sense in Humans, and formost of us life is Color coded.ColorVisionanditsdeficienciesarelong-standingcon-cerns of Human geneticists, but it was only with themolecular characterization of common forms of Color-Vision abnormalities (beginning in the late 1980s) thatmechanisms emerged to explain well-documented clin-ical findings. Now, new questions have arisen about theevolution and structural variability of the pigment genesand the regulation of their expression. In recent studies,the identification of mutations in the gene that encodesacGMP-gatedcationchannelhasresolvedthemolecularbasis of complete Color blindness, thereby extendingourknowledge of Color Vision and revealing significantanal-ogies among some very different sensory signal trans-duction systems.
Austin Roorda - One of the best experts on this subject based on the ideXlab platform.
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Spatial summation of individual cones in Human Color Vision.
PloS one, 2019Co-Authors: Brian P. Schmidt, Alexandra E. Boehm, William S. Tuten, Austin RoordaAbstract:The Human retina contains three classes of cone photoreceptors each sensitive to different portions of the visual spectrum: long (L), medium (M) and short (S) wavelengths. Color information is computed by downstream neurons that compare relative activity across the three cone types. How cone signals are combined at a cellular scale has been more difficult to resolve. This is especially true near the fovea, where spectrally-opponent neurons in the parvocellular pathway draw excitatory input from a single cone and thus even the smallest stimulus projected through natural optics will engage multiple Color-signaling neurons. We used an adaptive optics microstimulator to target individual and pairs of cones with light. Consistent with prior work, we found that Color percepts elicited from individual cones were predicted by their spectral sensitivity, although there was considerable variability even between cones within the same spectral class. The appearance of spots targeted at two cones were predicted by an average of their individual activations. However, two cones of the same subclass elicited percepts that were systematically more saturated than predicted by an average. Together, these observations suggest both spectral opponency and prior experience influence the appearance of small spots.
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Spatial summation of individual cones in Human Color Vision
2019Co-Authors: Brian P. Schmidt, Alexandra E. Boehm, William S. Tuten, Austin RoordaAbstract:The Human retina contains three classes of cone photoreceptors each sensitive to different portions of the visual spectrum: long (L), medium (M) and short (S) wavelengths. Color information is computed by downstream neurons that compare relative activity across the three cone types. How cone signals are combined at a cellular scale has been more difficult to resolve. This is especially true near the fovea, where spectrally-opponent neurons in the parvocellular pathway draw excitatory input from a single cone and thus even the smallest stimulus will engage multiple Color-signaling neurons. We used an adaptive optics microstimulator to target individual and pairs of cones with light. Consistent with prior work, we found that Color percepts elicited from individual cones were predicted by their spectral sensitivity, although there was considerable variability even between cones within the same spectral class. The appearance of spots targeted at two cones were predicted by an average of their individual activations. However, two cones of the same subclass elicited percepts that were systematically more saturated than predicted by an average. Together, these observations suggest both spectral opponency and prior experience influence the appearance of small spots.
