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Results for “Retinal Cone Photoreceptor Cells”

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At least 19 recordsLinked to original sources
PubMed1995

Circadian rhythms in mice can be regulated by photoreceptors with cone-like characteristics.

In this report we have characterized the photopigments mediating circadian phase shifts in retinal degenerate (rd) mice. In aged rd/rd mice, which lack detectable opsin, high performance liquid chromatography (HPLC) was used to quantify the photopigment chromophore 11-cis-retinaldehyde. This chromophore was photoisomerized in whole eyes, suggesting the presence of a functional opsin-based photopigment system. We also analyzed the spectral sensitivity of phase shifting circadian locomotor rhythms. Our data implicate a photopigment that is consistent with the involvement of the middle wavelength-sensitive cone photoreceptors (M-cones; lambda(max) = 511 nm) found in the mouse retina. In addition, discrete near-ultraviolet (UV-A) pulses were capable of eliciting large phase shifts in circadian locomotor activity rhythms. This result is consistent with the involvement of the short wavelength-sensitive cone photoreceptors (UV-cones; lambda(max) = 359 nm) in photoentrainment. Collectively, these data suggest that both cone classes of the mouse may mediate the photic regulation of circadian rhythms. If this is the case, circadian sensitivity can be maintained by very few degenerate cones. Alternatively, an unknown class of ocular photoreceptor may fulfill this function.

Animals↗
PubMed1995

Permeability and interaction of Ca2+ with cGMP-gated ion channels differ in retinal rod and cone photoreceptors.

We studied the ionic permeability of cGMP-dependent currents in membrane patches detached from the outer segment of retinal cone and rod photoreceptors. Reversal potentials measured in membranes exposed to symmetric Na+ but with varying cytoplasmic Ca2+ concentrations reveal that the permeability ratio, PCa/PNa, is higher in the cGMP-gated channels of cones (7.6 +/- 0.8) than in those of rods (3.1 +/- 1.0). Ca2+ blocks both channels in a voltage-dependent manner. At any Ca2+ concentration, the channel block is maximal near the ionic reversal potential. The maximal block is essentially identical in channels of cones and rods with respect to its extent and voltage and Ca2+ dependence. The Ca2+ block is relieved by voltage, but the features of this relief differ markedly between rods and cones. Whereas the Boltzmann distribution function describes the relief of block by hyperpolarizing voltages, any given voltage is more effective in relieving the Ca2+ block in cones than in rods. Similarly, depolarizing voltages more effectively relieve Ca2+ block in cones than in rods. Our results suggest that channels contain two binding sites for Ca2+, one of which is similar in the two receptor types. The second site either interacts more strongly with Ca2+ than the first one or it is located differently in the membrane, so as to be less sensitive to membrane voltage. The channels in rods and cones differ in the features of this second site. The difference in Ca2+ permeability between the channels is likely to result in light-dependent changes in cytoplasmic Ca2+ concentration that are larger and faster in cones than in rods. The functional differences between channels, therefore, may be critically important in explaining the differences in the phototransduction signal of the two photoreceptor types.

Ambystoma↗
PubMed1995

Rod transduction parameters from the a wave of local receptor populations.

The analysis of electroretinogram a waves from locally stimulated populations of rods is complicated by the presence of scattered light within the eye. Scattered-light and cone contributions can be assessed after brief flashes of light designed to saturate only rods in the locally stimulated area. Subtracting the scattered-light and the cone responses from the local electroretinogram gives a pure rod a wave that can be fitted with models of photoreceptor activity. We demonstrate the feasibility of this technique by recording local rod a waves from a group of five normal subjects and by fitting the a waves with the rod model to derive transduction parameters. The local rod a waves are compared with expected responses derived from simulations in which the response of the entire retina to heterogeneous illumination is mimicked.

Adult↗
PubMed1994

Postreceptoral contribution to macular dysfunction in retinitis pigmentosa.

PURPOSE: To understand the sites of macular dysfunction in retinitis pigmentosa by evaluating focal electroretinogram (FERG) fundamental and second harmonic components, which are dominated by the activity of the outer and inner retina, respectively. METHODS: FERGs were recorded in response to a uniform field (9 degrees x 9 degrees) flickered sinusoidally at either 8 Hz or 32 Hz. The fundamental components of the responses to both the 8-Hz and 32-Hz stimuli and the second harmonic of the response to the 8-Hz stimulus were measured in their amplitudes and phases. Normal subjects (n = 17), as well as patients with typical retinitis pigmentosa (n = 22), cone dystrophy (CD, n = 7) and X-linked congenital retinoschisis (XLR, n = 5) served as subjects. The fundamental (32-Hz)-second harmonic (8 Hz) amplitude ratio was taken as an index of the relative function of outer-inner layers of the macula. RESULTS: Compared to controls, patients with retinitis pigmentosa showed losses of both FERG fundamental and second harmonic and an increase of the fundamental-second harmonic ratio. Patients with CD also showed losses of both fundamental and second harmonic, but the fundamental-second harmonic ratio was normal. Patients with XLR had a selective loss of the second harmonic, resulting in an increased fundamental-second harmonic ratio. On average, the fundamental-second harmonic ratio of patients with retinitis pigmentosa tended to increase with age. CONCLUSIONS: The results suggest that in retinitis pigmentosa, both receptoral and postreceptoral sites contribute to macular dysfunction. This differs from CD and XLR, where losses appear more selective for the outer and the inner retina. Postreceptoral losses in retinitis pigmentosa may become larger with increasing age.

Adolescent↗
PubMed1994

Development of the rabbit retina. V. The question of 'columnar units'.

A qualitative and quantitative description of the columnar units in the mammalian retina, and a discussion of their ontogeny and putative functions is given. Columnar arrangements of cells exist in the developing retina which can be observed by means of scanning electron microscopy. In the adult retina, each Müller cell ensheaths a columnar group of neuronal cells. Counting the number of cells in radial H/E stained sections at various developmental stages reveals a constant ratio of neuronal cells per Müller cell, independent of the developmental stage (after postnatal day 9), and independent of the retinal topography. Such groups of cells always consist of one Müller cell, 11 rod photoreceptor cells, about 2 bipolar cells, and 1 to 2 amacrine cells. Retinal ganglion cells, cone photoreceptor cells, and horizontal cells are more sparsely distributed in the retina than these units; since they are known to arise earlier in the ontogenesis than other cell types they are considered to exist independently of the columnar units. It is suggested that the units arise by migration of groups of preneurons along a common Müller (precursor) cell; these preneurons and the corresponding Müller cell may be clonally related. In the adult retina, such columns might constitute metabolic and functional units.

Animals↗
PubMed1994

A set of early-born neurons is distinctly labeled by several defined antibodies in the adult rabbit retina.

Retinal ganglion cells, cone photoreceptor cells, and horizontal cells arise earlier in ontogenesis than the other retinal cell types. Although during the first postnatal week of life much cell proliferation occurs in the rabbit retina, 3H-thymidine labeling shows that these particular neurons are already postmitotic in neonatal animals. We show here that, in the adult retina, these early-born neurons express antigens as neuron-specific enolase, HNK-1 epitope of N-CAM, and PGP 9.5 antigen, which are not expressed by the neurons later born. It is concluded that the mammalian retina contains two genotypically different sets of neuronal cells which can be distinguished by immunocytochemistry.

Aging↗
PubMed2000

Retinal degeneration in cone photoreceptor cell-ablated transgenic mice.

PURPOSE: To examine the effect of loss of cone photoreceptor cells on retinal degeneration. METHODS: We previously identified a cone photoreceptor cell-specific promoter of human cone transducin a-subunit (GNAT2) gene. In this report, a minigene, Trc-Tox176, that contains the GNAT2 promoter, an attenuated diphtheria toxin A-chain gene, and an enhancer element from human interphotoreceptor retinoid-binding protein (IRBP) was used to generate coneless transgenic mice. Transgenic mice were identified by PCR and the copy number of the transgene was determined by Southern hybridization, and examined by histology. RESULTS: The results of immunostaining with anti-mouse GNAT2 antibodies and reverse transcription-PCR (RT-PCR) analysis with mRNA from the retinas of transgenic mice showed that cone photoreceptor cells were ablated in one of four transgenic mouse lines. The ablation of cone cells began at postnatal day 8, at the same time as the expression of endogenous GNAT2. An age-related rod degeneration was also found in this cone-ablated mouse line, beginning at postnatal day 9, proceeding from the central retina to the peripheral retina. CONCLUSIONS: Cone photoreceptor cells may play an important role in the survival of rod photoreceptor cells during mouse retina development.

Animals↗
PubMed1994

Retinal photoreceptor fine structure in the short-tailed stingray (Dasyatis brevicaudata).

The fine structure of the retinal photoreceptors has been studied by light and electron microscopy in the short-tailed stingray (Dasyatis brevicaudata). The duplex retina of this elasmobranch contains rods and cones in a ratio of about 10:1. No multiple receptors were noted nor was a repeating or mosaic arrangement of the cones obvious. Only light-adapted specimens were studied but retinomotor movements of the photoreceptors were felt to be minimal or absent. The rods are large cylindrical cells with inner and outer segments of much the same diameter. Cones are short stout cells with a conical outer segment and a wider inner segment. Rod outer segment discs show peripheral incisures while cones do not. The inner segment of rods and cones are rich in organelles indicating much synthetic activity. The nuclei of rods and cones appear quite similar but cone nuclei are invariably at least partially protruded through the external limiting membrane which is formed by a series of zonulae adherentes between photoreceptor cells and Müller cells. The synaptic region of both rods and cones display both invaginated (ribbon) synapses and superficial (conventional) synapses.

Adaptation, Physiological↗
PubMed1994

Electrophysiological measurements of spectral mechanisms in the retinas of two cervids: white-tailed deer (Odocoileus virginianus) and fallow deer (Dama dama).

Electroretinogram (ERG) flicker photometry was used to study the spectral mechanisms in the retinas of white-tailed deer (Odocoileus virginianus) and fallow deer (Dama dama). In addition to having a rod pigment with maximum sensitivity (lambda max) of about 497 nm, both species appear to have two classes of photopic receptors. They share in common a short-wavelength-sensitive cone mechanism having lambda max in the region of 450-460 nm. Each also has a cone having peak sensitivity in the middle wavelengths, but these differ slightly for the two species. In white-tailed deer the lambda max of this cone is about 537 nm; for the fallow deer the average lambda max value for this mechanism was 542 nm. Deer resemble other ungulates and many other types of mammal in having two classes of cone pigment and, thus, the requisite retinal basis for dichromatic color vision.

Animals↗
PubMed1993

Presence and foveal enrichment of rod opsin in the "all cone" retina of the American chameleon.

The retinal photoreceptors of the eye of the American chameleon, Anolis carolinensis, have been considered to be exclusively cones. Its retina is unusual for possessing two foveas (areas associated with heightened visual acuity), with the major, central fovea deeply incised and very densely packed with photoreceptors. Immunoblotting and light- and electron microscopic-immunocytochemistry, using several opsin monoclonal antibodies previously found specific for rods, demonstrated the presence and localization of this protein in the Anolis retina. This visual pigment appears sparsely in a subpopulation of photoreceptors in the periphery but overwhelmingly in the central fovea. Complementary results with cone-specific antibody and lectin binding corroborated this spatial organization. These results, as well as those with geckos, suggest that photoreceptor morphology is not an accurate guide among the lacertilians to visual pigment content, and that this phylogenetic grouping may constitute a crossroads in vertebrate photoreceptor evolution.

Animals↗
PubMed2000

Acquired color vision loss and a possible mechanism of ganglion cell death in glaucoma.

PURPOSE: First, to study the cellular mechanisms of acquired color vision loss in retinal detachment and diabetic retinopathy. Second, to learn why, in glaucoma, the type of color vision deficit that is observed is more characteristic of a retinal injury than it is of an optic neuropathy. Third, to test a hypothesis of photoreceptor-induced, ganglion cell death in glaucoma. METHODS: Various histologic techniques were employed to distinguish the L/M-cones (long/medium wavelength-sensitive cones, or red/green sensitive cones) from the S-cones (short wavelength-sensitive cones, or blue sensitive cones) in humans and monkeys with retinal detachment, humans with diabetic retinopathy, and both humans and monkeys with glaucoma. To test if the photoreceptors were contributing to ganglion cell death, laser photocoagulation was used in a experimental model of glaucoma to focally eliminate the photoreceptors. As a control, optic nerve transection was done following retinal laser photocoagulation in one animal. RESULTS: Selective and widespread loss of the S-cones was found in retinal detachment as well as diabetic retinopathy. By contrast, in human as well as experimental glaucoma, marked swelling of the L/M-cones was the predominant histopathologic feature. Retinal laser photocoagulation followed by experimental glaucoma resulted in selective protection of ganglion cells overlying the laser spots. This was not seen with retinal laser photocoagulation by optic nerve transection. CONCLUSIONS: In retinal detachment and diabetic retinopathy, acquired tritan-like color vision loss could be caused, or contributed to, by selective loss of the S-cones. Both L- and M-cones are affected in glaucoma, which is also consistent with a tritan-like deficit. Although not a therapeutic option, protection of ganglion cells by retinal laser in experimental glaucoma is consistent with an hypothesis of anterograde, photoreceptor-induced, ganglion cell death.

Adult↗
PubMed1997

Localization of guanylate cyclase-activating protein 2 in mammalian retinas.

Guanylate cyclase-activating proteins (GCAP1 and GCAP2) are thought to mediate the intracellular stimulation of guanylate cyclase (GC) by Ca2+, a key event in recovery of the dark state of rod photoreceptors after exposure to light. GCAP1 has been localized to rod and cone outer segments, the sites of phototransduction, and to photoreceptor synaptic terminals and some cone somata. We used in situ hybridization and immunocytochemistry to localize GCAP2 in human, monkey, and bovine retinas. In human and monkey retinas, the most intense immunolabeling with anti-GCAP2 antibodies was in the cone inner segments, somata, and synaptic terminals and, to a lesser degree, in rod inner segments and inner retinal neurons. In bovine retina, the most intense immunolabeling was in the rod inner segments, with weaker labeling of cone myoids, somata, and synapses. By using a GCAP2-specific antibody in enzymatic assays, we confirmed that GCAP1 but not GCAP2 is the major component that stimulates GC in bovine rod outer segment homogenates. These results suggest that although GCAP1 is involved in the Ca2+-sensitive regulation of GC in rod and cone outer segments, GCAP2 may have non-phototransduction functions in photoreceptors and inner retinal neurons.

Animals↗
PubMedDate not supplied

Visual pigments, cone oil droplets and ocular media in four species of estrildid finch.

A microspectrophotometric study was conducted on the retinal photoreceptors of four species of bird: cut-throat finches (Amadina fasciata), gouldian finches (Erythrura gouldiae), white-headed munias (Lonchura maja) and plum-headed finches (Neochmia modesta). Spectral characteristics of the photoreceptors in all four species were very similar. Rods contained a medium-wavelength-sensitive visual pigment with a wavelength of maximum absorbance at 502-504 nm. Four spectrally distinct types of single cone contained a visual pigment with wavelength of maximum absorbance at either 370-373 nm (ultraviolet-sensitive), 440-447 nm (short-wavelength-sensitive); 500 nm (medium-wavelength-sensitive) or 562-565 nm (long-wavelength-sensitive). Oil droplets in the ultraviolet-sensitive single cones showed no detectable absorption between 330 nm and 800 nm. Oil droplets in the short-, medium-, and long-wavelength-sensitive single cones had cut-off wavelengths at 415-423 nm, 510-520 nm and 567-575 nm, respectively. Double cones contained the visual pigment with wavelength of maximum absorbance at 562-565 nm observed in long-wavelength-sensitive single cones. Only the principal member of the double cone pair contained an oil droplet (P-type, cut-off wavelength at 414-489 nm depending on species and retinal location). Spectral transmittance of the intact ocular media of each species was measured along the optic axis. Wavelengths of 0.5 transmittance for all species were very similar (316-318 nm).

Animals↗
PubMed1998

Regeneration of the newt retina: order of appearance of photoreceptors and ganglion cells.

The adult newt regenerates a functional retina following removal or destruction of the original retina. We studied the order of appearance of cell types in the regenerating retina by using immunohistochemical techniques. An antibody that recognizes the alpha subunit (260 kDa) of voltage-dependent Na+ channels was found to label a 255-kDa band in Western blots of crude membrane fractions from the normal retina. Cryosections of normal retina revealed intense Na+ channel immunoreactivity in somata and axons of ganglion cells, weaker immunoreactivity in somata of amacrine cells, and no immunoreactivity in the inner plexiform layer. In the same sections, immunoreactivity to a monoclonal antibody (RB-1) specific to newt cones was intense in the photoreceptor layer. In regenerating retinas, double staining with the Na+ channel antibody as a possible marker of ganglion cells and RB-1 antibody first revealed immunoreactive cells at the intermediate stage (three to five cells thick), which does not exhibit segregated synaptic layers. Na+ channel-immunoreactive ganglion cells appeared before the RB-1-immunoreactive photoreceptors. Because ganglion cells also appear before photoreceptor cells in normal development, common mechanisms may control both the generation and the regeneration of the newt retina.

Animals↗
PubMed1998

Comparative morphology of distal neurons in larval and adult zebrafish retinas.

Distal retinal cells from larval (7-10 days postfertilization) and adult zebrafish retinas were cultured in 70% L-15 medium for 4-5 d and comparable cell types identified. Four photoreceptor types were observed in adult retinal cultures, whereas only single cones were isolated from larval retinas. Horizontal cells in both larval and adult cultures were distinguished by their large size and stellate morphology and two subtypes, A and B, were recognized. Bipolar cells were readily identified in adult cultures, but rare in larval cultures. Two bipolar cell types, large and small, were distinguished. Measurements of the various cell types are provided.

Animals↗