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J K Bowmaker

Publications and source records attributed to J K Bowmaker.

At least 55 records · Page 3Linked to original sources
PubMed1991

Photosensitive and photostable pigments in the retinae of Old World monkeys.

Microspectrophotometric measurements of retinal receptors are reported for eight species of Old World monkey. Although the animals vary greatly in size, colourings and habitat, they all appear to be trichromats and the peak sensitivities of their cones invariably lie near 430, 535 and 565 nm. This consistent pattern contrasts with the results reported earlier for New World monkeys and with the results reported here for Tupaia glis. The trichromacy of frugivorous catarrhine monkeys may have co-evolved with a particular class of coloured fruit. Short-wave cones were rare in all species. The ratio of the numbers of middle-wave and long-wave cones varied between individual animals, but had an overall value close to unity. In the case of all the species examined here, we have recorded a photostable pigment in the inner segments of rods and cones. The latter pigment has a peak sensitivity close to 420 nm and an absorbance spectrum that is narrower than that of a photosensitive visual pigment.

Animals↗
PubMed1988

Polymorphism of visual pigments in a callitrichid monkey.

Microspectrophotometric measurements of visual pigments have been obtained for a large sample of New World monkeys of the species Callithrix jacchus jacchus. These animals exhibit a polymorphism of visual pigments. The rods (Lmax 499 nm) and the short-wave receptors (Lmax 423 nm) appear to be common to all animals but individuals differ in the number and spectral position of pigments in the green-yellow spectral region. The latter pigments cluster near 545, 559 and 567 nm. Male monkeys draw one pigment from this set and female monkeys may draw one or two. The results are generally consistent with a genetic theory that postulates in Callithrix three possible alleles for a single locus in the X-chromosome. It appears that polymorphisms of cone pigments may be widespread among neotropical primates.

Animals↗
PubMed1987

Polymorphism of photopigments in the squirrel monkey: a sixth phenotype.

We describe here a trichromatic type of squirrel monkey that resembles Old World monkeys in having two well-separated photopigments in the red-green part of the spectrum; the cones of this phenotype have peak sensitivities close to 430, 536 and 564 nm. The existence of such animals is predicted by a genetic model that postulates three alleles for a single locus on the X-chromosome of the squirrel monkey. The three alleles correspond to three different photopigments in the red-green spectral range. A male monkey, or a homozygous female, will be dichromatic, combining short-wave cones with just one of the cone types in the red-green range. But a female monkey, if heterozygous at the locus, draws any two of the three alleles from the set. X-chromosome inactivation ensures that the two alleles are expressed in different subpopulations of retinal cone, giving the monkey the basis for trichromatic colour vision. This model requires three trichromatic types of female squirrel monkey. The photopigment complements of two types have previously been reported and microspectrophotometric data are now given for the third type. Behaviourally, this third type of trichromat gives precise Rayleigh matches that are intermediate between those of the other two types of trichromat. The polymorphism of photopigments in the squirrel monkey may be maintained by the heterozygous advantage enjoyed by the trichromatic females. This would be an instructive instance of heterozygous advantage because it is a case where X-chromosome inactivation plays a crucial role in segregating the two different gene-products into different cells.

Animals↗
PubMed1987

Ultraviolet receptors, tetrachromatic colour vision and retinal mosaics in the brown trout (Salmo trutta): age-dependent changes.

Microspectrophotometric analysis of the visual receptors of "yearling" brown trout, Salmo trutta, revealed three cone types, double cones with visual pigments absorbing maximally at about 600 and 535 nm, and two types of single cone with lambda max at about 440 and 355 nm. Two-year-old fish did not possess the u.v. cone cells. Microscopical analysis of the cone mosaic in "yearling" trout showed a square pattern of double cones with a central single cone and corner single cones, but in two-year-old trout the corner cones were absent. It is concluded that u.v. sensitivity is derived from the corner cones of the mosaic, and that it is only present in young trout.

Aging↗
PubMed1985

Two types of trichromatic squirrel monkey share a pigment in the red-green spectral region.

Microspectrophotometric measurements have been obtained for individual photoreceptors from four female squirrel monkeys (Saimiri sciureus) that had been shown behaviourally to be trichromatic. Relative to a normal human observer, two of the monkeys required more red light for a Rayleigh match; the other two required more green light than a normal human observer. In the red-green spectral region, the first type of monkey was found to have two cone pigments with peak sensitivities at approximately 536 and 549 nm, whereas the second type was found to have pigments with peak sensitivities at approximately 549 and 564 nm. By maximum likelihood estimation it was shown that the microspectrophotometric data could be described by a model that assumed only three underlying distributions, two of which were present in each type of monkey. The fit of this model was as good as one in which a "double normal" distribution was fitted individually to the data for each animal. This result is consistent with a genetic theory that postulates in Saimiri three possible alleles for a single locus on the X-chromosome; the heterozygous female enjoys trichromacy because Lyonisation ensures that only one photopigment is manufactured in any given cone.

Animals↗
PubMed1985

The visual pigments of the weever fish, Trachinus vipera: a microspectrophotometric study.

Microspectrophotometric analyses of the visual pigments of the weever fish, Trachinus vipera, demonstrate the presence of a rhodopsin with peak sensitivity at 502 nm, and two cone visual pigments. Identical twin cones are green-sensitive containing a P5281, and single cones are blue-sensitive containing a P4401. The dichromacy of the weever is discussed in relation to its photic environment and feeding behaviour.

Animals↗
PubMed1984

Variations of colour vision in a New World primate can be explained by polymorphism of retinal photopigments.

The squirrel monkey (Saimiri sciureus) exhibits a polymorphism of colour vision: some animals are dichromatic, some trichromatic, and within each of these classes there are subtypes that resemble the protan and deutan variants of human colour vision. For each of ten individual monkeys we have obtained (i) behavioural measurements of colour vision and (ii) microspectrophotometric measurements of retinal photopigments. The behavioural tests, carried out in Santa Barbara, included wavelength discrimination, Rayleigh matches, and increment sensitivity at 540 and 640 nm. The microspectrophotometric measurements were made in London, using samples of fresh retinal tissue and a modified Liebman microspectrophotometer: the absorbance spectra for single retinal cells were obtained by passing a monochromatic measuring beam through the outer segments of individual rods and cones. The two types of data, behavioural and microspectrophotometric, were obtained independently and were handed to a third party before being interchanged between experimenters. From all ten animals, a rod pigment was recorded with lambda max (wavelength of peak absorbance) close to 500 nm. In several animals, receptors were found that contained a short-wave pigment (mean lambda max = 433.5 nm): these violet-sensitive receptors were rare, as in man and other primate species. In the middle- to long-wave part of the spectrum, there appear to be at least three possible Saimiri photopigments (with lambda max values at about 537,550 and 565 nm) and individual animals draw either one or two pigments from this set, giving dichromatic or trichromatic colour vision. Thus, those animals that behaviourally resembled human protanopes exhibited only one pigment in the red-green range, with lambda max = 537 nm; other behaviourally dichromatic animals had single pigments lying at longer wavelengths and these were the animals that behaviourally had higher sensitivity to long wavelengths. Four of the monkeys were behaviourally judged to be trichromatic. None of the latter animals exhibited the two widely separated pigments (close to 535 and 567 nm) that are found in the middle- and long-wave cones of macaque monkeys.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1984

Microspectrophotometry of vertebrate photoreceptors. A brief review.

Since the early 1960s, measurements of the absorbance spectra of both photosensitive and inert pigments within intact isolated visual receptor cells have been achieved in a great number of species, including representatives of all the vertebrate groups as well as some invertebrates, principally the insects. The technique has meant a rapid advance in our understanding of the basis of colour vision throughout the animal kingdom as well as increasing our knowledge of the behaviour of visual pigments in situ. A review of these advances, especially within the fish, birds and primates is presented with emphasis on the limitations of the technique, and the intriguing questions that microspectrophotometric analysis of the pigments of visual receptor cells has raised.

Amphibians↗
PubMed1983

Human visual pigments: microspectrophotometric results from the eyes of seven persons.

The material for this work was obtained from seven eyes removed because of malignant growths. Foveal and parafoveal samples of the retinas were taken and transverse measurements were made of the absorbance spectra of the outer segments of the rods and cones, using a Liebman microspectrophotometer. Four kinds of spectra were obtained with absorbance peaks at the following wavelengths: rods, 496.3 +/- 2.3 nm (n = 39); red cones, 558.4 +/- 5.2 nm (n = 58); green cones, 530.8 +/- 3.5 nm (n = 45); blue cones, 419.0 +/- 3.6 nm (n = 5). The distribution of the peaks was unimodal for the rods. For the red and green cones, however, there was evidence for bimodal distributions, with sub-population maxima at 563.2 +/- 3.1 nm (n = 27) and 554.2 +/- 2.3 nm (n = 31) for the reds and at 533.7 +/- 2.1 nm (n = 23) and 527.8 +/- 1.8 nm (n = 22) for the greens. A substantial difference in mean spectral location of the red cones was observed between patient 1 (561 nm) and patient 4 (553 nm). Both patients were classified as normal trichromats by all clinical tests of colour vision but there was a clear difference in their relative sensitivities to long-wave fields. In both direction and magnitude, this difference proved to be that required by the microspectrophotometric results.

Humans↗
PubMed1983

How is colour perceived: the visual pigments of human cones.

Microspectrophotometric measurements obtained from individual receptor cells from the enucleated eyes of 8 normal observers and a known deuteranope are presented. In a sample of 147 receptors from seven normal eyes, 39 were rods with peak absorbance (lambda max) at 496 nm, 58 were long-wave with lambda max 558 nm, 45 were middle-wave cones with lambda max 531 nm and 5 were short-wave cones with lambda max 419 nm. There was evidence of bimodality in the distribution of both the long and middle-wave cones, but not in the rods, and a substantial difference in the mean spectral location of the long-wave cones was observed between two patients classified as normal trichromats. Psychophysical determinations of their relative sensitivity to long-wave fields showed a clear difference that proved, both in magnitude and direction, to be that required by the microspectrophotometric results. In a sample of 17 records from the eye of the deuteranope we recorded 5 rods, 2 short-wave cones and 10 long-wave cones, but no middle-wave cones. These results are concordant with psychological results obtained for the patient's remaining eye.

Color Perception↗
PubMed1980

Microspectrophotometric demonstration of four classes of photoreceptor in an old world primate, Macaca fascicularis.

1. Microspectrophotometric measurements reveal four classes of photoreceptor in the retina of the cynomolgus monkey, Macaca fascicularis, which is known to possess colour vision similar to that of a normal human trichromat. 2. Although the eyes were removed in bright illumination, the densities of pigment were comparable to those we have measured in dark-adapted rhesus retinae. 3. The mean wave-lengths of peak sensitivity (lambda max) for the four classes of photoreceptor were 415, 500, 535 and 567 nm. 4. The band widths of the absorbance spectra decreased linearly as the wave-number of peak sensitivity decreased. 5. If, by assuming a reasonable value for the axial density of the rod outer segment and correcting for lens absorption, a spectral sensitivity for human vision is reconstructed from the P500 pigment, it is found to be systematically broader than the CIE scotopic sensitivity function. 6. Given explicit assumptions, it is possible from the P535 and P567 pigments to reconstruct human psychophysical sensitivities that resemble the pi 4 and pi 5 mechanisms of W. S. Stiles. 7. Although the P415 pigment has a lambda max much shorter than that of the psychophysically measured blue mechanisms, the two spectral-sensitivity functions are brought into proximity when the microspectrophotometric data are corrected for absorption by the optic media.

Animals↗
PubMed1980

Visual pigments of rods and cones in a human retina.

1. Microspectrophotometric measurements have been made of the photopigments of individual rods and cones from the retina of a man. The measuring beam was passed transversely through the isolated outer segments. 2. The mean absorbance spectrum for rods (n = 11) had a peak at 497.6 +/- 3.3 nm and the mean transverse absorbance was 0.035 +/- 0.007. 3. Three classes of cones were identified. The long-wave cones ('red' cones) had a lambda max of 562.8 +/- 4.7 nm (n = 19) with a mean transverse absorbance of 0.027 +/- 0.005. The middle-wave cones ('green' cones) had a lambda max of 533.8 +/- 3.7 nm (n = 11) with a mean transverse absorbance of 0.032 +/- 0.007. The short-wave cones ('blue' cones) had a lambda max of 420.3 +/- 4.7 nm (n = 3) with a mean transverse absorbance of 0.037 +/- 0.011. 4. If assumptions are made about the length of cones and about pre-receptoral absorption, it is possible to derive psychophysical sensitivities for the cones that closely resemble the appropriate pi mechanisms of W. S. Stiles. 5. If assumptions are made about the length of rods and about pre-receptoral absorption, however, the psychophysical sensitivity derived for the rods is considerably broader than the C.I.E. scotopic sensitivity function.

Humans↗
PubMed1979

Visual pigment absorbance and scotopic spectral sensitivity in the goldfish, Carassius auratus.

Factors relating to the comparison of the absorbance spectra of visual pigments to experimentally determined relative spectral sensitivities of the eye are discussed with specific reference to the goldfish. It is concluded that the experimentally determined scotopic sensitivity of the goldfish can be directly related to the absorbance of goldfish porphyropsin without the need to infer input from long wavelength-sensitive cones.

Animals↗