Advances in Photoreception Proceedings of a Symposium on Frontiers of Visual Science (1990) / Chapter Skim
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Cone Visual Pigments in Monkeys and Humans
Cone Visual Pigments in Monkeys and Humans
Pages 19-30
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From page 19... ...
Microspectrophotometric recording from primate photoreceptors is difficult: the cone outer segments are small, with diameters of only 1 to 2 ~m, and they break down structurally within a relatively short time. Thus, the transverse absorbance spectra recorded from them have maximum densities of only about 0.015 to 0.020 with low signal-to-noise ratios.
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From page 20... ...
, but it increases to about 2 nm at 565 nm, with the F/Fmax value being the shorter, since at longer wavelengths the transformation, when expressed on a wavelength basis, yields a slightly broader curve than the >~/4 transformation. LONG- TO MIDDLE-WAVE PIGMENTS Old World Monkeys and Humans The cone pigments in macaques are well established.
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From page 21... ...
; MG, Cercopithecus cephus (moustached guenon) ; and RH, Macaca mulatta (rhesus)
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From page 22... ...
We have recently made measurements from another five human eyes enucleated because of melanoma; the distributions of the long- and middle-wave cones are shown in Figure 2. These distributions are remarkably similar to those of the Old World primates, with mean Oman of 563.7 and 531.4 nm Table 1~: a similarity reflected in the spectral sensitivity measurements obtained from suction electrode techniques both in macaques (Baylor et al., 1987)
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From page 23... ...
The bottom panel is a summary histogram of the five individuals.
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From page 24... ...
that is distinctly different from that proposed for the inheritance of color vision in humans and, by inference, in all Old World primates. The model postulates that there is only one genetic locus for a pigment in the red-green spectral range; · there are three alleles that can occur at the locus, the three alleles corresponding to the three slightly different opsins of the photopigments; · the locus is on the X-chromosome; and · in those females that are heterozygous at the locus, only one of the two alleles is expressed, owing to Lyonization or X-chromosome inactivation, so that only one pigment is manufactured in any one ce11.
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From page 25... ...
In the common marmoset, Callithr~c jacchus jacchus, three pigments are available in the red-green spectral region, but these are different from those in Saimiri, with Oman at about 543, 557, and 564 nm Travis et al., 1988~. The P564 is again similar to the long-wave pigment in Old World monkeys, but the two pigments at shorter wavelengths are not common to Old World species, although there are reports of cones from macaques containing a pigment with Oman; at about 543 nm (Bowmaker et al., 1978; MacNichol et al., 1983~.
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From page 26... ...
. SHORT-WAVE CONES Old World Monkeys and Humans Attempts to establish by microspectrophotometry the spectral location and shape of the absorbance spectra of short-wave cone pigments have been made more difficult by the relative rarity of short-wave cones, normally less than 10 percent of the cone population, and by the problems of shortwave scatter and the probable contamination of spectra by photoproducts (for a discussion, see Mansfield et al., 1984~.
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From page 27... ...
Spectral Location of Pigments As with the photopigments maximally sensitive in the red-green spectral region, the short-wave pigments of primates also appear to cluster at distinct spectral locations those of Old World monkeys and squirrel monkeys cluster at about 431 nm, that of the marmoset at about 424 nm, and that of humans at about 420 nm (Figure 3~. The mean spectra for the three pigments are shown together in Figure 4d, where the spectral displacements
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From page 28... ...
The top panel of each pair plots the mean absorbance spectra before and after bleaching, and the bottom panel plots the difference spectrum derived from the bleaching. The prebleach spectra and difference spectra have been normalized to 100 percent.
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From page 29... ...
and may imply that there are constraints on the structure of visual pigments that determine their spectral sensitivities. Clearly, to elucidate such problems, more information is needed on the amino acid sequences of a number of primate opsins as well as a further understanding of the tertiary arrangement of opsin and retinal within the disc membranes of the cone outer segments.
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From page 30... ...
Thomas, and D.S. Hogness 1986 Molecular genetics of human color vision: the genes encoding blue, green and red pigments.
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