Biomedical subjects

J Neitz

Publications and source records attributed to J Neitz.

At least 55 records · Page 3Linked to original sources

PubMed1990

Polymorphism in normal human color vision and its mechanism.

Earlier we reported that Rayleigh matches made by males with normal color vision fall into distinct groups, and proposed that this behavior reflects an X-chromosome linked polymorphism in the spectral positioning of cone pigments (Neitz & Jacobs, 1986). In the present experiments two different color matches were obtained from each of 60 color normal males. Comparisons of the data from these two matches allowed variations in color matching that are produced by individual differences in the spectral positioning of middle and long wavelength cone pigments to be distinguished from color vision variations caused by other factors. Considered together with findings from molecular biology and spectral measurements of individual cone pigments, these results suggest that among color normal humans: (1) there are discrete variations in both middle and long wavelength cone pigments, and (2) most individuals have more than three different cone pigment types.

Color Perception↗

PubMed1989

Analysis of fusion gene and encoded photopigment of colour-blind humans.

In humans, long-wavelength-sensitive and middle-wavelength-sensitive cone pigments are encoded by genes lying in a head-to-tail tandem array on the X chromosome. Deficiencies in red-green colour vision seem to arise from unequal recombination of these normal X-linked genes. In some dichromats this recombination is believed to yield a fusion gene encoding a product with an absorption spectrum similar to that of one or the other of the normal photopigments. Until now, however, such a relationship between the structure of a pigment gene and the spectral properties of its encoded pigment has not been directly shown. We have now sequenced a fusion gene isolated from a red-green colour-blind human and determined the spectral properties of the pigment that it encodes. The absorption spectrum of the photopigment was very similar to that of normal middle-wavelength-sensitive photopigment, even though about half of its DNA coding sequence seems to be derived from a gene encoding normal long-wavelength-sensitive pigment. These results indicate the regions of the X-encoded photopigment apoproteins that are responsible for differences in their spectral tuning, and imply that the striking variations in colour vision among anomalous trichromats of a particular type are not attributable to anomalous pigments with differing spectral peaks.

Adult↗

PubMed1989

Cone monochromacy and a reversed Purkinje shift in the gerbil.

Retinal spectral sensitivity of the gerbil (Meriones unguiculatus) shows that this animal has a unique photoreceptor complement: there is only a single class of cone and the spectrum for these receptors is peak shifted toward the short wavelengths relative to the spectra obtained from rods.

Animals↗

PubMed1989

Color vision in the dog.

The color vision of three domestic dogs was examined in a series of behavioral discrimination experiments. Measurements of increment-threshold spectral sensitivity functions and direct tests of color matching indicate that the dog retina contains two classes of cone photopigment. These two pigments are computed to have spectral peaks of about 429 nm and 555 nm. The results of the color vision tests are all consistent with the conclusion that dogs have dichromatic color vision.

Animals↗

PubMed1989

Spectral sensitivity of cones in an ungulate.

Ungulates have been classified as having arrhythmic eyes in the sense that they contain features appropriate both to diurnal and nocturnal life. The former is typically associated with multiple classes of cones and a color-vision capacity. To see if an arrhythmic animal has these features, the number of cone classes was determined and the spectra of these cones were measured in a common ungulate, the domestic pig (Sus scrofa). Examination with electroretinogram (ERG) flicker photometry revealed the presence of two classes of cones in the pig's eye having average maximum sensitivity (lambda max) at 439 nm and 556 nm, respectively. This ungulate thus has the requisite retinal basis for dichromatic color vision.

Animals↗

PubMed1988

Spectral mechanisms in the tree squirrel retina.

The retina of the gray squirrel (Sciurus carolinensis) contains rods and cones in a ratio of about 2:3. The spectral mechanisms in this retina were examined in behavioral and electrophysiological experiments. Tests of color vision revealed that this animal has a spectral neutral point at about 500 nm and, thus, dichromatic color vision. Recordings made from single optic nerve fibers and results obtained from an analysis of the flicker photometric electroretinogram (ERG) indicated that vision in the gray squirrel is based on three spectral mechanisms. One of these, presumably rod-based, has peak sensitivity at about 502 nm. The other two mechanisms reflect the presence of two classes of cone having average peak sensitivity of about 444 nm and 543 nm.

Animals↗

PubMed1988

Tunicamycin-induced degeneration in cone photoreceptors.

Tunicamycin (TM), an inhibitor of dolichylphosphate-mediated protein glycosylation, was injected intravitreally into the eyes of diurnal rodents with cone-dominated retinas. Injection of 1 microgram of the B2 isomer led to a progressive degeneration of the photoreceptor outer segments and disruption of the RPE-photoreceptor interface that took place over a 10-day period. Cone outer segments were shortened by postinjection day 6 and virtually absent by day 9. The microvilli that normally protrude from the apical surface of the retinal pigment epithelium were replaced by a fringe of shortened processes. The other retinal layers showed no morphological evidence of disruption. Retinal sensitivity, as measured by electroretinographic b-wave threshold, showed a significant and progressive decline over the 10-day course of the experiment that paralleled the disruption of retinal morphology. These results suggest that TM leads to similar morphological and electrophysiological effects on rod and cone photoreceptors.

Animals↗

PubMed1987

Action spectrum of the retinal mechanism mediating nocturnal light-induced suppression of rat pineal gland N-acetyltransferase.

The spectral properties of the retinal mechanism mediating the inhibitory effects of nocturnal light on pineal gland N-acetyltransferase (NAT) activity were determined. Pineal gland NAT activity declined linearly in albino rats exposed to different irradiances of a 460 or 580 nm monochromatic light during the middle of the dark phase of the cycle. The difference in sensitivity to the test lights is that predicted for a photopigment having peak absorbance at 495 nm, suggesting the inhibition of pineal gland N-acetyltransferase activity is mediated by the photopigment found in rat rods.

Acetyltransferases↗

PubMed1987

Early color deprivation and subsequent color vision in a dichromatic monkey.

A squirrel monkey (Saimiri sciureus) was reared for the first 4 months of life in a dim, colorless environment. Following an additional 10 months of normal visual experience, tests of color vision and spectral sensitivity were run on this animal and a control subject. The results suggest that the adult expression of dichromatic color vision does not depend on color experience during the first 4 months of life.

Animals↗

PubMed1987

Color vision polymorphism and its photopigment basis in a callitrichid monkey (Saguinus fuscicollis).

The color vision of five saddle-backed tamarins (Saguinus fuscicollis) was studied. Behavioral tests of color discrimination and spectral sensitivity indicate that this species has a color vision polymorphism. Individual monkeys have either dichromatic or trichromatic color vision. Measurements of the spectral sensitivity of cones on this species were made on nine animals with the technique of electroretinogram (ERG) flicker photometry. Both the electrophysiological and the behavioral results suggest that there are four classes of cone pigment in this species. In addition to a short wavelength sensitive cone, apparently common to all tamarins, there are three classes of middle to long wavelength cone (lambda max = 545, 557 and 562 nm). Individual animals have either one or two of the latter types. The color vision variation in this species differs for males and females.

Adaptation, Ocular↗

PubMed1987

Polymorphism of the middle wavelength cone in two species of South American monkey: Cebus apella and Callicebus moloch.

The spectral sensitivity of the middle wavelength cone was measured in two species of South American monkey, Cebus apella and Callicebus moloch, using electroretinogram (ERG) flicker photometry. Both of these species were found to have a polymorphism of the middle wavelength cone. Eight male Cebus monkeys each had only a single type of middle wavelength cone having lambda max values of either 550 or 562 nm. Eight Callicebus monkeys (7 male, 1 female) showed a similar polymorphism of the middle wavelength cone (lambda max = 549 or 561 nm). A single female of this latter species had two types of middle wavelength cone. The cone polymorphisms of these species appear very similar to that previously described for the squirrel monkey (Saimiri sciureus).

Adaptation, Ocular↗

PubMed1987

Inheritance of color vision in a New World monkey (Saimiri sciureus).

Squirrel monkeys (Saimiri sciureus) have a striking color-vision polymorphism; each animal has one of six different types of color vision. These arise from individual variation in the presence of three different middle- to long-wavelength cone pigments. The distribution of cone phenotypes was established for a large sample of squirrel monkeys, including several families, through analysis of a retinal gross potential. The results indicate that the inheritance of color vision in the squirrel monkey can be explained by assuming that the three middle- to long-wavelength cone pigments are specified by three alleles at a single locus on the X chromosome. This arrangement is discretely different from that found in Old World monkeys and humans.

Animals↗

PubMed1986

Spectral sensitivity of cat cones to rapid flicker.

Records obtained from the flicker photometric electroretinogram indicate that only a single spectral mechanism (lambda MAX = 555 nm) in the cat eye contributes to the response to 50 Hz flicker. A photopic mechanism (lambda MAX = 500-510 nm) detected in earlier studies does not respond to high frequency flicker.

Adaptation, Physiological↗

PubMed1986

Spectral mechanisms and color vision in the tree shrew (Tupaia belangeri).

The retina of the tree shrew (Tupaia belangeri) is heavily cone dominated, rods comprising less than 4% of the total photoreceptors. Spectral mechanisms and color vision were investigated in this species in both behavioral and electrophysiological experiments. In confirmation of an earlier investigation, the tree shrew was found to have a clear spectral neutral point (at ca 505 nm) and is thus a dichromat. Spectral sensitivity functions determined in an increment threshold discrimination task show two clear peaks (at ca 440 and 550-560 nm) with an intermediate region of lowered sensitivity centered at about 500 nm. Spectral sensitivity of the two cone types in this animal were determined using ERG flicker photometry. One of these cone classes has a peak at 556 nm; the other has a 444 nm peak.

Animals↗

PubMed1986

Reexamination of spectral mechanisms in the rat (Rattus norvegicus).

The spectral mechanisms of the rat were studied in electrophysiological and behavioral experiments. The photopic electroretinogram (ERG) was recorded (a) to rapidly flickering lights, (b) during the cone phase of dark adaptation, and (c) with a flicker photometric procedure. Each procedure indicated the presence of a single cone mechanism having a lambda max of about 510 nm. Increment-threshold spectral sensitivity functions measured in a behavioral test situation yielded the same conclusion. A behavioral experiment failed to produce any evidence for the presence of color vision in this rodent. The consistent conclusion from both behavioral and electrophysiological experiments is that the rat retina contains only a single photopic spectral mechanism.

Animals↗

PubMed1986

Retinoid-binding proteins in cone-dominant retinas.

We identified and localized interphotoreceptor (or interstitial) retinoid-binding protein (IRBP) and cellular retinaldehyde-binding protein (CRALBP) in the cone-dominant retinas of diurnal squirrels. Western blots were prepared from sodium dodecyl sulfate polyacrylamide gels (SDS-PAGE) from whole retina, and from retina proximal and distal to the photoreceptor nuclei. Blots were incubated with purified rabbit IgG's specific for the bovine retinal antigens, and the labeled components were visualized using immunoperoxidase techniques. Anti-bovine IRBP and anti-bovine CRALBP recognized single components on gels of retinal supernatants that corresponded to the electrophoretic migration of the bovine antigens. The component recognized by anti-bovine IRBP on blots of outer retinal proteins (Mr 146,000) was absent on blots of inner retinal proteins. Twelve and 24 hr after intravitreal injection of 3H-L-fucose, electropherograms showed one major peak of radioactivity that coincided with the component recognized by anti-bovine IRBP. By immunoelectron microscopy, anti-bovine CRALBP labeling was restricted to the cytoplasm of both RPE and Muller cells, with light labeling of nuclear euchromatin in both cell types. In contrast, anti-bovine IRBP recognized antigenic sites primarily in the interphotoreceptor space (IPS). Intracellular labeling was limited to occasional granules in the photoreceptor myoids and the apical RPE cytoplasm. Extracellular labeling with anti-bovine IRBP was strongly associated with patches or small clumps of amorphous, electron opaque material distributed throughout the IPS. This material was particularly prominent near the cone outer segment plasma membranes, and was tentatively identified as the residual interphotoreceptor matrix that remained after exposure to the solvents used during tissue processing. In general, the results are consistent with those obtained in rod-dominant species. In addition, they imply that cones as well as rods are responsible for IRBP synthesis in the ground squirrel.

Animals↗

PubMed1985

Color vision in squirrel monkeys: sex-related differences suggest the mode of inheritance.

Behavioral tests of vision in squirrel monkeys (Saimiri sciureus) reveal that there are widespread individual variations in color vision in this species. The variation has a sex-related component: whereas both trichromatic and dichromatic color vision occurs among female monkeys, males appear exclusively dichromatic. This finding suggests that, unlike humans, squirrel monkeys have only a single photopigment locus on the X chromosome.

Animals↗

PubMed1984

Development of spectral mechanisms in the ground squirrel retina following lid opening.

The retina of the California ground squirrel (Spermophilus beecheyi) contains three classes of photopigments (lambda max = 440, 500, 525 nm). From optic nerve recordings it was previously discovered that the effectiveness of signals from the 440 nm cone increase gradually over the weeks following lid opening. In this experiment several features of the electroretinogram (ERG) were examined to assess developmental changes in signals originating in the outer retina. As judged by threshold sensitivity, suprathreshold responsivity, or adaptability, the contribution of the 525 nm mechanism reaches its adult level two to three weeks after lid opening. The 500 nm mechanism appears to have a similar developmental time course. The development of the 440 nm mechanism was tracked using a chromatic adaptation measure. So indexed, the time required for this mechanism to reach its adult status was much greater than that for the other two mechanisms (70-80 days vs 40-45 days of age). The relatively slow development of effectiveness of the 440 spectral mechanism appears to reflect events occurring in the outer retina.

Adaptation, Physiological↗