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PubMed1980

Vector magnitude operation in color vision models: derivation from signal detection theory.

Using the theory of signal detection, we have derived an expression for the detectability of a visual stimulus in terms of the general zone theory of color and brightness vision. This derived relationship elicidates the theoretical foundation of the Guth vector model for color vision by showing that the nonlinear vector magnitude operation used by Guth may arise from the observer decision-making process. Testable predictions of stimulus detectability are generated by the derived expression.

Color Perception↗
PubMed1987

Amacrine cells with neurotensin- and somatostatin-like immunoreactivities in three species of teleosts with different color vision.

Neurotensin- and somatostatin-like immunoreactivities were localized by pre-embedding techniques in retinal whole-mounts and radial sections of a monochromatic glass catfish (Kryptopterus bicirrhis), a dichromatic cichlid species (Aequidens pulcher), and the tetrachromatic roach (Rutilus rutilus). Both neuropeptides were observed in perikarya and processes of amacrine cells. For a precise identification of cell types, tangential and radial views were correlated with Golgi-impregnated material. The dendritic pattern defining the morphological subtype of amacrine cells was determined by the given neuropeptide or by the species-specific degrees of complexity of retinal structure and function. Neurotensin-like immunoreactivity was localized in amacrine cells of intermediate size, radial symmetry and dendrites with numerous varicosities; they were monostratified in sublayer 3 of the inner plexiform layer. This cell type was common to all three species. In the mono- and dichromatic retinas, a single type of amacrine cell with somatostatin-like immunoreactivity was found with radially oriented, varicose dendrites in sublayer 5. In the tetrachromatic roach retina, two somatostatin-positive amacrine cell types were found with very different patterns of ramification; furthermore, both of these types occurred in more than one sublayer. Possible functional implications for color vision of neuropeptide-specific amacrine cells with uniform morphology in all three species and those with a more varied morphology in the tetrachromatic roach are discussed.

Animals↗
PubMed1998

The "five-sites" rule and the evolution of red and green color vision in mammals.

Amino acid changes S180A (S-->A at site 180), H197Y, Y277F, T285A, and A308S are known to shift the maximum wavelength of absorption (lambda max) of red and green visual pigments toward blue, essentially in an additive fashion. To test the generality of this "five-sites" rule, we have determined the partial amino acid sequences of red and green pigments from five mammalian orders (Artiodactyla, Carnivora, Lagomorpha, Perissodactyla, and Rodentia). The result suggests that cat (Felis catus), dog (Canis familiaris), and goat (Capra hircus) pigments all with AHYTA at the five critical sites have lambda max values of approximately 530 nm, whereas rat (Rattus norvegicus) pigment with AYYTS has a lambda max value of approximately 510 nm, which is accurately predicted by the five-sites rule. However, the observed lambda max values of the orthologous pigments of European rabbit (Oryctolagus cuniculus), white-tailed deer (Odocoileus virginianus), gray squirrel (Sciurus carolinensis), and guinea pig (Cavia procellus) are consistently more than 10 nm higher than the predicted values, suggesting the existence of additional molecular mechanisms for red and green color vision. The inferred amino acid sequences of ancestral organisms suggest that the extant mammalian red and green pigments appear to have evolved from a single ancestral green-red hybrid pigment by directed amino acid substitutions.

Amino Acid Sequence↗
PubMedDate not supplied

Number and variations of the red and green visual pigment genes in Japanese men with normal color vision.

PURPOSE: We analyzed the red/green visual pigment genes in color-normal Japanese men to understand the relationship between color anomalies and genetic defects. METHODS: DNA from 120 color-normal Japanese men was subjected to polymerase chain reaction (PCR)-amplification for exons 2-5 of the red/green visual pigment genes and the PCR products were sequenced. The red:green gene ratios were estimated from the sequencing electropherograms of exon 5 and also from MvaI-restriction fragment analysis of the same exon. The first gene and the downstream genes in the pigment gene array were separately analyzed by PCR, direct sequencing, and/or single-strand conformation polymorphisms. RESULTS: The red:green gene ratios estimated from the ratios of peak heights of nucleotides on the sequencing electropherograms coincided with those estimated from the MvaI-restriction fragment analysis. Among the subjects analyzed, they were 1:1 in 43% (n = 52), 1:2 in 41% (n = 49), 1:3 in 6% (n = 7), and 1:>3 in 9% (n = 11). The first gene in the pigment gene arrays was red in all subjects. Only 1 subject (N22) had a green-red hybrid gene. Exons 2 and 4 had 2 haplotypes each, but exon 3 was highly polymorphic. Exon 5 of the green genes had one polymorphism at codon 283 with a frequency of 32%. CONCLUSIONS: The features of visual pigment genes in color-normal Japanese men were revealed. The data and establishing techniques may be useful for analyzing these genes in color-deficient subjects in the Japanese population.

Color Perception↗