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Results for “Retinal Rod Photoreceptor Cells”

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At least 19 recordsLinked to original sources
PubMed1984

A new histo- and cytochemical method for demonstration of cyclic 3',5'-nucleotide phosphodiesterase activity in retinal rod photoreceptor cells of the rat.

Cyclic 3',5'-mononucleotide phosphodiesterase (cyclic nucleotide PDEase) activity was studied histo- and cytochemically in the retinal rod photoreceptor cells of the rat by means of a newly developed technique utilizing the intrinsic 5' nucleotidase activity instead of an exogenous 5' nucleotidase source (snake venom). Cyclic GMP and was used as a substrate, the intense activity of phosphodiesterase (PDEase) was distributed over the entire rod outer segments; reaction product was observed on the plasmalemma and on the disk membranes of the outer segments. A slight reaction was also observed on the plasmalemma of the inner segments. However, no precipitate was found in the perinuclear and synaptic regions of the rod photoreceptors. In contrast, when cyclic AMP was utilized as a substrate, a moderate reaction was seen in the synaptic region of the plexiform layer. The intensity of the reaction in the outer segments was much reduced in comparison to the results with cyclic GMP. The enzyme activity was almost completely inhibited by 2 mM 3-isobutyl-1-methylxanthine (IBMX) or 2 mM theophylline, which were potent inhibitors of PDEase. To confirm the propriety of our new cytochemical method, the localization of 5' nucleotidase was also studied utilizing 5' AMP or 5' GMP as substrates. In contrast to the activity of cyclic nucleotide PDEase, the activity of 5' nucleotidase was distributed on all membranes of the photoreceptors from the synaptic outer plexiform layer to the tip of outer segments.(ABSTRACT TRUNCATED AT 250 WORDS)

5'-Nucleotidase↗
PubMed1986

Inhibition of oligosaccharide processing and membrane morphogenesis in retinal rod photoreceptor cells.

Castanospermine (Cas), an inhibitor of alpha-glucosidase I, blocks "trimming" of the N-linked oligosaccharide Glc3Man9GlcNAc2, thus preventing normal glycoprotein maturation. With use of a dual-label protocol, Xenopus retinas incubated in the presence of Cas exhibited at least a 2.3-fold increase in the incorporation of [3H]mannose into total retina Cl3CCOOH-precipitable material, whereas incorporation of [14C]leucine was not significantly affected, relative to controls. Analysis of NaDodSO4/PAGE fluorograms of solubilized retinas and rod outer segment (ROS) membranes indicated a relatively selective effect of Cas on opsin (the rod visual pigment apoglycoprotein). The apparent molecular mass of opsin was increased by approximately 2500 in the presence of Cas; the incorporation of [3H]mannose into opsin was enhanced about 2.3-fold without a significant effect on [14C]leucine incorporation, relative to controls. Electron microscopic autoradiography of retinas incubated for 4 hr with [3H]mannose showed that the number of newly formed ROS discs in Cas-treated retinas was not significantly different from controls, but the silver grain density over those discs was about 2.6-fold greater than in controls. The morphology of the newly formed discs was comparable under both conditions. Thus, opsin bearing abnormally large oligosaccharides can be accommodated in the process of disc morphogenesis. These results suggest that the structural requirements for opsin's oligosaccharides, with regard to their potential role as determinants of disc morphogenesis, are not stringent. Furthermore, post-translational processing of N-linked oligosaccharides is not essential for the normal intracellular routing and cell surface expression of membrane glycoproteins.

Alkaloids↗
PubMed1995

Abnormal activation and inactivation mechanisms of rod transduction in patients with autosomal dominant retinitis pigmentosa and the pro-23-his mutation.

PURPOSE: The leading edge of the rod a-wave in normal human subjects can be fit with a computational model of the activation phase of transduction to provide parameters analogous to those obtained from individual photoreceptors. The authors extend this work to the kinetics of recovery after saturating flashes. METHODS: Electroretinograms were recorded from three patients with autosomal dominant retinitis pigmentosa and the pro-23-his rhodopsin mutation, two patients with rod monochromatism, and five normal subjects. Rod-only a-waves were obtained for a series of flashes ranging from 4.4 to 10.1 ln (1.9 to 4.4 log) scot td-sec. One set of parameters describing the activation process was derived from fits to the a-wave model. A double-flash paradigm was used to study inactivation mechanisms. The first flash was achromatic and varied in intensity (I(f)) from 6.1 to 13.9 ln (2.6 to 6.0 log) scot td-sec. The second flash was a short-wavelength probe held constant at 9.3 ln (4.0 log) scot td-sec. Cone components were elicited with a photopically matched long-wavelength stimulus and were computer subtracted. Recovery at each I(f) was followed by measuring the amplitude to the probe flash at various interstimulus intervals (ISI). The critical time (Tc) before the initiation of rod recovery was determined from the function relating relative rod amplitude to ISI. RESULTS: Recovery from activation was similar in normal subjects and in patients with rod monochromatism. Over a large range of I(f) above rod saturation, Tc increased in proportion to ln I(f). The mean slope of the function relating Tc to I(f) was 2.3 s/ln I(f) when I(f) varied between 11 and 13.9 ln scot td-sec. Patients with retinitis pigmentosa and the pro-23-his rhodopsin mutation had a decrease in the gain of activation. They also had significantly slower than normal recovery after high test flash intensities, such that the slope of the function relating Tc to ln I(f) was 12.1 seconds. CONCLUSION: Available data from other species imply that complete, transient activation of transducin (T saturation) occurs within or below the investigated range of flash intensities. Based on the slope of the delay function (delta Tc/ delta ln I(f)) above 11 ln scot td-sec, the authors hypothesize that the lifetime of activated rhodopsin (R) in normal human rods is approximately 2.3 seconds. In patients with the pro-23-his mutation, the gain of the activation mechanism is reduced and the reaction determining the delta Tc/ delta ln I(f) slope is markedly slowed. The activated species that exhibits this prolonged lifetime could be the mutant rhodopsin itself.

Adolescent↗
PubMedDate not supplied

Movement of retinal along cone and rod photoreceptors.

Single isolated photoreceptors can be taken through a visual cycle of light adaptation by bleaching visual pigment, followed by dark adaptation when supplied with 11-cis retinal. Light adaptation after bleaching is manifested by faster response kinetics and a permanent reduction in sensitivity to light flashes, presumed to be due to the presence of bleached visual pigment. The recovery of flash sensitivity during dark adaptation is assumed to be due to regeneration of visual pigment to pre-bleach levels. In previous work, the outer segments of bleached, light-adapted cells were exposed to 11-cis retinal. In the present work, the cell bodies of bleached photoreceptors were exposed. We report a marked difference between rods and cones. Bleached cones recover sensitivity when their cell bodies are exposed to 11-cis retinal. Bleached rods do not. These results imply that retinal can move freely along the cone photoreceptor, but retinal either is not taken up by the rod cell body or retinal cannot move from the rod cell body to the rod outer segment. The free transfer of retinal along cone but not along rod photoreceptors could explain why, during dark adaptation in the retina, cones have access to a store of 11-cis retinal which is not available to rods. Additional experiments investigated the movement of retinal along bleached rod outer segments. The results indicate that retinal can move along the rod outer segment, but that this movement is slow, occurring at about the same rate as the regeneration of visual pigment.

Ambystoma↗
PubMed1996

Retinal photoreceptor fine structure in the Australian galah (Eolophus roseicapillus) (Aves).

The retinal photoreceptors of the galah (Eolophus roseicapillus), an Australian cockatoo, consist of rods, single cones and double (unequal) cones present in a ratio of about 1:3:3 respectively. The rods are long slim cells which are believed to undergo retinomotor movements. The rod inner segment displays an ellipsoid of mitochondria, much rough endoplasmic reticulum (RER), numerous polysomes and some autophagic vacuoles. No hyperboloid of glycogen was noted. Single cones show a slightly tapered outer segment, no oil droplet but a prominent ellipsoid at the apex and glycogen scattered throughout the inner segment. Double cones consist of a chief member which displays a heterogeneous oil droplet but no paraboloid of glycogen and an accessory cone with no oil droplet but a prominent paraboloid. All cones show below the ellipsoid plentiful polysomes, RER, Golgi zones and autophagic vacuoles. Cones are not felt to undergo retinomotor movements. In the light-adapted state the pigment-laden apical processes of the retinal epithelium (RPE) cells surround all photoreceptor types down to the inner segments. Along the length of the contiguous membranes between the two members of the double cones are membrane densifications that are presumed to be junctions. All cone photoreceptors are relatively small in diameter and hence closely packed. Rods and cones (both types) display both invaginated (ribbon) and superficial (conventional) synaptic sites.

Adaptation, Ocular↗
PubMed1993

Retinal photoreceptor fine structure in the red-tailed hawk (Buteo jamaicensis).

The retinal photoreceptors of the red-tailed hawk (Buteo jamaicensis) consist of rods, single cones and double (unequal) cones present in a ratio of about 2:1:5. In the light-adapted state, the rods are slender elongated cells with outer segments that reach to the retinal epithelial (RPE) cells. The inner segment displays an ellipsoid of mitochondria, plentiful polysomes, some rough ER and Golgi zones. The rod nucleus is located deep within the outer nuclear layer and the synaptic spherule displays both invaginated (ribbon) and superficial (conventional) synaptic sites. Single cones show a thin tapering outer segment, a large electron lucent oil droplet at the apex of the inner segment and an ellipsoid of mitochondria. Double cones consist of a larger chief member which displays a thin tapering outer segment and an electron dense oil droplet as well as a smaller accessory cone which shows no oil droplet, an ellipsoid and a paraboloid of glycogen. As in the single cone, polysomes, RER and Golgi zones are also noted in the inner segments of both members of the double cone. Near the external limiting membrane the chief and accessory cones show membrane specializations indicative of junctions on their contiguous surfaces. All cone photoreceptors are of a smaller diameter than is normally reported for avian species. Both single and double cones display several invaginated synapses as well as numerous superficial synaptic sites.

Animals↗
PubMed1996

Regulation of sensitivity in vertebrate rod photoreceptors by calcium.

Over the past decade and a half, there have been great advances in our understanding of how light is transduced into electrical signals by the retinal rod and cone photoreceptors in vertebrates. One essential feature of these sensory neurons is their ability to adapt to background illumination, which allows them to function over a broad range of light intensities. This adaptation appears to arise mostly from negative feedback on phototransduction that is mediated by calcium ions. Recent work has suggested that this feedback is fairly complex, and involves several pathways directed at different components of phototransduction. From direct measurements of these feedback pathways in rods, it is possible to evaluate their relative contributions to the overall sensitivity of the cell. At the same time, these feedback mechanisms, as currently known, appear to be sufficient for explaining the change in sensitivity of rods during adaptation to light.

Animals↗
PubMed1994

Visual function testing: clinical correlations.

Visual function tests provide criteria to determine the extent and type of retinal malfunction in patients with retinal disease. This chapter provides an overview of some selected measures of retinal function that are useful as aids in diagnosis of retinal diseases, particularly those that involve the cone and rod photoreceptors.

Adolescent↗
PubMedDate not supplied

[The cytostructure and morphogenesis of the rod outer segments].

This paper is a review discussing the cytomolecular structure of the rods, retinal photoreceptor cells, whose structural uniformity contributed to the progress in studies of their structure and morphogenesis in the vertebrate eye. Recent studies of protein and phospholipid metabolism in the rod inner segment have been reviewed. The structure of the outer segment connecting cilium is discussed with reference to the TEM and SEM, freeze-fracture, biochemical and immunological studies. The membranes of the rod outer segment undergo continuous renewal. The use of fine biochemical methods permitted to find differences in the structure of the plasma membrane surrounding the rod outer segment and the membrane discs, that fill this segment. Recent hypotheses dealing with morphogenesis of the rod outer segment membrane discs are also discussed. Special attention is paid to actin and myosin, as well as a small transient fraction of galactose-containing rhodopsin.

Animals↗
PubMed1994

Rod phototransduction in retinitis pigmentosa: estimation and interpretation of parameters derived from the rod a-wave.

PURPOSE: Relationships between the Lamb and Pugh model of transduction in single rod photoreceptors and the parameters derived from human rod a-waves are examined to evaluate transduction abnormalities in retinitis pigmentosa (RP) and cone-rod dystrophy (CRD). METHODS: ERGs were obtained from 15 patients, 11 with RP and 4 with CRD, and from 15 normal subjects. Rod-only responses were derived from responses to blue (W47B) flashes over a wide range of flash energies by computer-subtracting estimates of the cone contribution. A model of the rod's response was fitted to the a-waves of the rod-only responses as well as to the responses to the blue flashes by estimating three parameters-sensitivity (S), delay (td), and maximum response (RmP3). To assess the limits of the cone contributions to the parameters of the model, ERGs were obtained from two of the patients, two normal subjects, and three additional patients with nondetectable rod responses using white flashes. RESULTS: All patients had significantly decreased values of RmP3, and eight had significantly decreased values of S compared to the control subjects. The values of the parameters estimated from the responses to the blue flashes were reasonably similar to those for the rod-only responses except in patients with nondetectable rod signals. For the white flashes, the estimate of S was considerably larger and the fit of the model noticeably poorer. CONCLUSIONS: The authors reached two conclusions. First, some forms of RP and CRD alter the activation stages of transduction. Transduction appears normal in other patients, despite extensive receptor damage as indicated by markedly reduced RmP3 values. Second, the cone contribution to a blue flash only affects the estimate of the key parameters in patients in whom the rod component is minimal. The cone contribution to a white flash contaminates the fit and the estimate of the parameters in all patients and normal subjects.

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↗
PubMed1996

Histochemical demonstration of glycogen in neurons of the cat retina.

PURPOSE: To demonstrate histochemically the cellular distribution of particulate glycogen in the cat retina and to correlate it with glucose sensitivity of neuronal electrical activities. METHODS: Free-floating, ultrathin sections of cat eyes (without glucose challenges) were stained by the periodic acid-thiocarbohydrazide-silver proteinate procedure and examined by electron microscopy. RESULTS: Muller cells were filled uniformly with fine-grain glycogen throughout all retinal layers. Particle density was higher in Muller cells of the peripheral retina than in those of central retina. Astrocytes contained little, if any, particulate glycogen. Alpha and beta ganglion cells had a heavy content of clumped glycogen granules. Rod bipolar and A17 amacrine cells of the rod pathway were stained intensely with particulate glycogen. No glycogen was seen in photoreceptor cells, cone bipolar cells, and the majority of amacrine cells, including AII cells of the rod pathway. However, one type of cone bipolar-driven amacrine cell was intensely glycogen positive. Its ultrastructural morphology, stratification pattern, and synaptology suggest that is a wide-field, axon-bearing type called A22. CONCLUSIONS: Except for the cone bipolar-driven ON-OFF A22 amacrine cell, it appears that glycogen staining preferentially labels neurons of the rod pathway. These observations are compatible with the reported sensitivity of the rod-driven electroretinogram and optic nerve response to glucose in the cat retina.

Animals↗
PubMed1996

Ultrastructure and organisation of the retina and pigment epithelium in the cutlips minnow, Exoglossum maxillingua (Cyprinidae, Teleostei).

The structure of the light- and dark-adapted retina, pigment epithelium and choriocapillaris of the cutlips minnow, Exoglossum maxillingua (Cyprinidae, Teleostei) is examined by light and electron microscopy. A pronounced vitreal vascularisation overlies the inner retina where the blood vessel walls, the inner limiting membrane and the Müller cell endfeet are all closely apposed. The thick Müller cell processes divide the inner plexiform layer and nerve fibre layer into discrete compartments. The ganglion cells do not form fascicles and lie within both the ganglion cell and inner plexiform layers. The inner nuclear layer consists of amacrine, bipolar, Müller cell somata and two rows of horizontal cells. The photoreceptor terminals comprise either multiple (3-5 in cone pedicles) or single (rod spherules) synaptic ribbons. These photoreceptor terminals form either a triad (rods and cones) or a quadrad (cones) arrangement of contact with the invaginating processes of the inner nuclear layer cells. The horizontal cell processes of the cone photoreceptor terminals reveal spinule formation in the light-adapted condition. Five photoreceptor types are classified using morphological criteria; triple cones, unequal double cones, large single cones, small single cones and rods. The ratio of rods to cones is approximately 7:1. All photoreceptor types show retinomotor responses. Only the cones possess accessory outer segments but both rods (8-11) and cones (15-19) possess calycal processes. The retinal pigment epithelium displays retinomotor responses where pigment granules within fine apical processes move vitread to mask the rods in the light. The cells of the retinal pigment epithelium are joined by various types of junctions and contain numerous phagosomes, mitochondria and polysomes. Bruch's membrane or the complexus basalis is trilaminate with two types of collagen fibrils comprising the central layer. The endothelia of the blood vessels of the choriocapillaris, facing Bruch's membrane, are fenestrated. Two to three layers of melanocytes interspersed between large thin-walled capillaries and several layers of collagen fibrils comprise the choriocapillaris.

Adaptation, Ocular↗
PubMed1996

Hyperpolarizing, small-field, amacrine cells in cone pathways of cat retina.

Intracellular recording and horseradish peroxidase (HRP) staining of amacrine cells in the isolated arterially perfused cat retina have revealed examples of small-field cells that hyperpolarize to light. Two were examined in detailed electron microscopic reconstructions to determine patterns of synaptic relationships within the inner plexiform layer (IPL). The cells were morphologically similar to A8 and A13 types as described in Golgi-impregnated material (Kolb et al. [1981] Vision Res. 21:1081-1114). Both types received ribbon synaptic input from rod and cone bipolar cells. The latter input was numerically predominant, occurred in both a and b sublaminae of the IPL, and arose from at least three cone bipolar types. Reciprocal synapses were evident between A13 cells and cone bipolar cells. Amacrine input occurred throughout the dendritic tree of both A8 and A13 types, and numerically exceeded bipolar cell input for A13. Gap junctions between stained, and similar-appearing unstained dendritic profiles were observed for both amacrine types. In addition, A8 engaged in gap junctions with cone bipolar profiles in sublamina b which also provided ribbon input. Synaptic output for both amacrine types occurred primarily upon amacrine and ganglion cells in sublamina a. Both cells were presynaptic upon single OFF-center beta ganglion cells running through the middle of their dendritic trees. Mixtures of rod and cone signals were found in the centrally evoked hyperpolarizations of each type. Center mechanism space constants of such types ranged from 100 to 400 microns, with antagonistic surround in 1 of 5 cases. Dopamine (250 microM) reduced receptive field space constants by one-third in one case. The synaptic organization and potential circuitry implications of these cone system-dominated amacrine types are compared and contrasted to the better-known AII and A17 types previously described for the rod system.

Animals↗
PubMed1995

Radial and tangential dispersion patterns in the mouse retina are cell-class specific.

The retina is derived from a pseudostratified germinal zone in which the relative position of a progenitor cell is believed to determine the position of the progeny aligned in the radial axis. Such a developmental mechanism would ensure that radial arrays of cells which comprise functional units in the mature central nervous system are also clonally related. The present study has tested this hypothesis by using X chromosome-inactivation transgenic mosaic mice. We report that the retina shows a conspicuous distinction for clonally related neuroblasts of different laminar and functional fates: the rod photoreceptor, Müller, and bipolar cells are aligned in the radial axis, whereas the cone photoreceptor, horizontal, amacrine, and ganglion cells are tangentially displaced with respect to them. These results indicate that the dispersion of cell classes across the retinal surface is differentially constrained. Some classes of retinal neuroblast exhibit a significant tangential, as well as radial, component in their dispersion from the germinal zone, whereas others disperse only in the radial dimension. Consequently, the majority of radial columns within the mature retina must be derived from multiple progenitors. Because the cone photoreceptor, horizontal, amacrine, and ganglion cells establish nonrandom matrices in their cellular distributions within the respective retinal layers, tangential dispersion may be the means by which these matrices are constructed.

Animals↗
PubMed1995

Light responses from one type of ON-OFF amacrine cells in the rabbit retina.

1. The light responses from one type of ON-OFF amacrine cell were recorded intracellularly in the superfused rabbit retina under various conditions of light adaptation. These recordings were obtained from cells located in a central area. 5-7 mm inferior and directly below the optic nerve head. 2. ON-OFF amacrine cells responded to the initiation and termination of light stimuli with transient depolarizations. Their receptive fields were approximately 0.8-1 mm diam and did not exhibit antagonistic center-and-surround organization. 3. The cells received rod input because they responded to very dim scotopic stimuli. With prolonged dark adaptation, the cells became more sensitive to the initiation than termination of the stimulus, because the ON component of the light response had a lower threshold than the OFF component. 4. The cells continued to respond to test flashes when the retina was adapted to a background illumination of rod-saturating intensity. Thus ON-OFF amacrine cells also receive cone input. Under these photopic conditions, a secondary afterpotential was observed following the OFF component. Its characteristics were different from those of the rod aftereffect reported in other retinal cells of the rabbit because its latency and amplitude changed with increasing stimulus intensity. 5. Intracellular injections of horseradish peroxidase showed that the recordings were obtained from a class of ON-OFF amacrine cells whose wide-field, unistratified dendrites were rigorously confined to the middle of the inner plexiform layer or stratum 3. 6. The conspicuous rod and cone inputs into a class of amacrine cells that are connected neither to rod bipolars nor to All amacrine cells strongly support the idea that in the rabbit the rod pathway uses cone bipolars as interneurons to distribute scotopic signals to ganglion and cone-driven amacrine cells.

Animals↗
PubMed1994

Immunohistochemical localization of calbindin-D28K and calretinin in the lamprey retina.

Calbindin-D28K and calretinin are homologous cytosolic calcium binding proteins localized in many retinal neurons from different species. In this report, location of cells immunoreactive to both proteins was investigated in the retina of the lamprey, Lampetra fluviatilis. This organism constitutes one of the older representative vertebrates and possesses a peculiar organization, probably unique: two-thirds of the ganglion cells are in the classical amacrine cell layer and the nerve fiber layer is located in the scleral part of the inner plexiform layer. Calbindin-like immunoreactivity was demonstrated in large bipolar cells and in cell bodies located in the inner retina. Although the distinction between labelled ganglion cells and labelled amacrine cells was rendered difficult, we hypothesized that the majority of calbindin-immunoreactive cells observed in the inner retina are ganglion cells, because of the high number of labelled fibers in the nerve fiber layer. Calretinin-like immunoreactivity was detected in both large and small bipolar cells, and also in cells located in the inner retina. Since few calretinin-immunoreactive fibers were observed in the nerve fiber layer, we assume that the latter category of cells are amacrine cells. Horizontal cells were both negative for calbindin and calretin-like immunoreactivities. Calbindin and calretinin, which are present in cones from many species, could not be detected in the photoreceptor layer favouring the rod-dominated lamprey retina. Although their distribution differs from those observed in most vertebrates, the present results indicate the good conservation of both calcium binding proteins in the retina during the vertebrate evolution.

Animals↗