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PubMed2003

Light-evoked excitatory and inhibitory synaptic inputs to ON and OFF alpha ganglion cells in the mouse retina.

Bipolar cell and amacrine cell synaptic inputs to alpha ganglion cells (alphaGCs) in dark-adapted mouse retinas were studied by recording the light-evoked excitatory cation current (DeltaIC) and inhibitory chloride current (DeltaICl) under voltage-clamp conditions, and the cell morphology was revealed by Lucifer yellow fluorescence with a confocal microscope. Three types of alphaGCs were identified. (1) ONalphaGCs exhibits no spike activity in darkness, increased spikes in light, sustained inward DeltaIC, sustained outward DeltaICl of varying amplitude, and large soma (20-25 microm in diameter) with alpha-cell-like dendritic field approximately 180-350 microm stratifying near 70% of the inner plexiform layer (IPL) depth. (2) Transient OFFalphaGCs (tOFFalphaGCs) exhibit no spike activity in darkness, transient increased spikes at light offset, small sustained outward DeltaIC in light, a large transient inward DeltaIC at light offset, a sustained outward DeltaICl, and a morphology similar to the ONalphaGCs except for that their dendrites stratified near 30% of the IPL depth. (3) Sustained OFFalphaGCs exhibit maintained spike activity of 5-10 Hz in darkness, sustained decrease of spikes in light, sustained outward DeltaIC, sustained outward DeltaICl, and a morphology similar to the tOFFalphaGCs. By comparing the response thresholds and dynamic ranges of alphaGCs with those of the preganglion cells, our data suggest that the light responses of each type of alphaGCs are mediated by different sets of bipolar cells and amacrine cells. This detailed physiological analysis complements the existing anatomical results and provides new insights on the functional roles of individual synapses in the inner mammalian retina.

Action Potentials↗
PubMed1999

Long-term full-thickness embryonic rabbit retinal transplants.

PURPOSE: To establish the light and electron microscopic morphology of long-term full-thickness embryonic rabbit retinal transplants, with special attention paid to graft- host integration. METHODS: Eighteen rabbits received a complete embryonic neuroretina 19 days after conception. The transplants were positioned under the host retina, flat against the host retinal pigment epithelium with proper polarity, using a vitrectomy technique. After surviving 3 to 10 months, the transplants were examined by light and electron microscopy. RESULTS: The outer retina of the host had degenerated in all specimens. In 16 of the 18 eyes, well-laminated transplants with correct polarity, measuring up to 3.2 mm in length, were found. The transplants displayed long outer segments facing the host retinal pigment epithelium, and they were laminated to the level of the inner plexiform layer in which fusion with the host was often evident. Fusion was more prominent in the oldest transplants. Electron microscopy revealed bundles of neurites at different levels of maturation in close contact with Müller cell fimbriae at regular intervals along the graft-host border. CONCLUSIONS: Full-thickness embryonic rabbit retinal transplants positioned with correct polarity develop into large laminated retinas and survive without immunosuppression for at least 10 months. Host and graft adapt and almost reconstruct the normal retinal appearance. Ultrastructurally, well-developed photoreceptors and many normal synapse types are seen, and neuron sprouting is evident at the graft-host border.

Animals↗
PubMed1999

Early retinal development in the zebrafish, Danio rerio: light and electron microscopic analyses.

The morphological differentiation of the zebrafish retina was analyzed by using light (LM) and transmission electron (TEM) microscopy between the time of initial ganglion cell differentiation (approximately 32 hours postfertilization; hpf) and shortly after the point when the retina appears functional (approximately 74 hpf), i.e., when all major cell types and basic synaptic connections are in place. The results show that the inner retinal neurons, like the photoreceptor and ganglion cells, differentiate first within the ventronasal region, and differentiation subsequently spreads asymmetrically into the nasal and dorsal regions before reaching the ventrotemporal retina. In addition, we show that the attenuation of the optic stalk occurs in parallel with ganglion cell differentiation between 32 and 40 hpf. The first conventional synapses appear within the inner plexiform layer simultaneously with the first photoreceptor outer segment discs at 60 hpf; functional ribbon triads arise within photoreceptor synaptic terminals at 65 hpf; and synaptic ribbons occur within bipolar cell axon terminals at the time larvae exhibit their first visual responses (approximately 70 hpf). Although development is initially more advanced within the ventronasal region between 50 and 60 hpf, development across the retina rapidly equilibrates such that it is relatively comparable within all quadrants of the central retina by 70 hpf. An area within the temporal retina characterized by tightly packed and highly tiered cones emerges with subsequent development. Retinal differentiation in the zebrafish corresponds with that generally described in other vertebrates and can be correlated with the development of visual and electroretinographic responses in the animal.

Animals↗
PubMed1997

Arrestin and phosducin are expressed in a small number of brain cells.

Retinal photoreceptor rods and pinealocytes contain well-characterized proteins such as arrestin and phosducin whose expression is highly restricted to these cell types. Transgenic mice having a LacZ gene under the control of an arrestin promoter expressed beta-galactosidase (beta-Gal) in the photoreceptor rods and pinealocytes. In addition, it was expressed in very small numbers of discrete cells in the habenular commissura, amygdala, ventral tegmental area and superior colliculus of the brain. Immunocytochemical studies with antibody probes revealed that high level of arrestin and phosducin were also found in the same cell types. Furthermore melatonin was found in those cells of the habenula commissura. The results indicate that novel cell types are present in the brain tissues. Since high levels of arrestin and phosducin expression are generally restricted to photoreceptor rod cells and pinealocytes, these data suggest that certain brain cells may have functions similar to pinealocytes.

Animals↗
PubMedDate not supplied

Cell viability of retinal photoreceptor evaluated by polar distribution of Ca(2+) and electrical charge.

The polar organisation is characteristic to the living cell and disappears with the cell functional decay. Here we report experimental evidence that frog retinal photoreceptor rod cell shows a polar distribution of the electrical charge and of free cytosolic Ca(2+) along its length. Retinal rod cells were loaded with Calcium sensitive dye (Green1) and examined under fluorescence microscopy coupled with an image analysis system. In addition, suspension of rod cells was placed in direct current electric field for electrical polarity assessment. Both polar Ca(2+) and electrical charge distribution can be objectively measured and quantified providing thus a fine test for cell viability. Such a test is required in checking the functional integrity of photoreceptors used in retinal transplant.

Animals↗
PubMed2004

Constitutive opsin signaling: night blindness or retinal degeneration?

A subset of genetic mutations in photoreceptor-specific genes results in abnormally prolonged activation of transducin-mediated photosignaling in rod cells. In humans and animal models, these mutations cause visual dysfunctions ranging from a mild stationary night blindness to severe, early-onset retinal degeneration. There are mechanistic differences between mutations causing night blindness and those causing retinal degeneration. Here, we hypothesize that mutations causing continuous activation of the visual cascade as the result, for example, of the inability of the photoreceptor to regenerate rhodopsin, lead to retinal degeneration; those mutations that can terminate signaling, even if only partially and intermittently, slow the rate of degeneration sufficiently to give rise to stationary night blindness. Furthermore, we hypothesize that a prolonged decrease in intracellular calcium concentration resulting from persistent activation is responsible for triggering apoptotic rod-cell death.

Animals↗
PubMed1981

Distribution of anionic sites on the surface of retinal pigment epithelial and rod photoreceptor cells.

The distribution of anionic (negatively charged) groups on the surface of retinal pigment epithelial cells (RPE), rod photoreceptor cells (RP) and discarded rod outer segments (R0S) was studied by labeling these groups with cationic ferritin (CF) at different pH values. In normal neonatal rats, characteristic CF binding patterns were observed on the RPE cell surface at pH values ranging from 1.8-7.2. Similar distributions were seen on the surface of RPE cells from RCS-p+ rats with inherited retinal degeneration. Treatment of RPE cells from normal neonates with several different degradative enzyme preparations prior to CF labeling, did not alter the density or distribution of CF molecules at any of the pH values tested. In normal adult rats, CF binding to RPE cells was essentially similar to that observed in neonates. In RP cells, heavy CF labeling at pH 1.8 was seen on the surface of the inner and outer segments and connecting cilium. CF labeling patterns on discarded R0S undergoing phagocytosis were similar to those on RPE cells at all pH values except pH 5.5. The findings indicate that anionic sites are present on the surface of RPE and RP cells and on discarded R0S undergoing phagocytosis. There is no evidence that such sites are involved in the phagocytic defect characteristic of RCS-p+ rats. Adult-like patterns of anionic sites on RPE cells appear early in postnatal development; their resistance to a wide range of degradative enzymes suggests that the carbohydrates or proteins containing these anionic moieties are organized in a complex fashion in the RPE cell surface.

Animals↗
PubMed2004

Disturbed visual system function in methionine synthase deficiency.

BACKGROUND: Isolated functional methionine synthase deficiency occurs in the cblE and cblG defects of methylcobalamin metabolism and is one of a number of causes of severely elevated plasma homocysteine. Clinical features are predominantly of a neurological nature but also include functional restriction of the visual system manifesting as loss of visual acuity and nystagmus. As yet, the origin and pathogenesis of impaired vision have not been explained. MATERIALS AND METHODS: We investigated a patient who was proven by complementation analysis in cultured fibroblasts to belong to the cblG complementation group. Ganzfeld electroretinograms (ERG) and flash visual evoked potentials (VEP) were recorded over a period of 4 years. RESULTS: Amplitudes of all International Society for Clinical Electrophysiology of Vision (ISCEV) standard responses were below normal. The greatest reductions were of rod response to 24 microV, of standard combined response (SC) b-wave to 120 microV, of oscillatory potentials (OP) to 5 microV, of cone response b-wave to 35 microV, and of 30 Hz flicker response to 8 microV. Except for SC and cone a-waves at age 2.5 and 3.5 years, as well as cone b-wave at 3.5 years, amplitudes remained at a subnormal level at follow-up examinations. Implicit times were slightly prolonged (SC b-wave 6 ms, OPs 2 ms, cone b-wave 2 ms, 30 Hz flicker 4 ms) or fell within the normal range. Responses of the flash VEP were severely deformed but reproducible. CONCLUSIONS: This is the first report of detailed investigations of the visual system in a patient with isolated methionine synthase deficiency. Reduced oscillatory potentials suggest microvascular damage to the retina through homocysteine. Decreased photoreceptor function as well as ganglion cell loss as indicated by pathological flash VEPs may reflect a cytotoxic impact of homocysteine on neurons of the visual pathway.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗
PubMed2000

Rhodopsin transport in the membrane of the connecting cilium of mammalian photoreceptor cells.

The transport of the photopigment rhodopsin from the inner segment to the photosensitive outer segment of vertebrate photoreceptor cells has been one of the main remaining mysteries in photoreceptor cell biology. Because of the lack of any direct evidence for the pathway through the photoreceptor cilium, alternative extracellular pathways have been proposed. Our primary aim in the present study was to resolve rhodopsin trafficking from the inner to the outer segment. We demonstrate, predominantly by high-sensitive immunoelectron microscopy, that rhodopsin is also densely packed in the membrane of the photoreceptor connecting cilium. Present prominent labeling of rhodopsin in the ciliary membrane provides the first striking evidence that rhodopsin is translocated from the inner segment to the outer segment of wild type photoreceptors via the ciliary membrane. At the ciliary membrane rhodopsin co-localizes with the unconventional myosin VIIa, the product of human Usher syndrome 1B gene. Furthermore, axonemal actin was identified in the photoreceptor cilium, which is spatially co-localized with myosin VIIa and opsin. This actin cytoskeleton of the cilium may provide the structural bases for myosin VIIa-linked ciliary trafficking of membrane components, including rhodopsin.

Actins↗
PubMedDate not supplied

Human embryonic retinal cell transplants in athymic immunodeficient rat hosts.

This study investigates the possibility to use the athymic "nude" rat as a host for the transplantation of human embryonic retinal cells without immunosuppression. The long-term development of such transplants is compared with results from our earlier study that used immunosuppressed rats, and showed transplant immunoreactivity for S-antigen. Several additional cell markers have been included: rhodopsin, rod (alpha-transducin, neuron-specific enolase (NSE), synaptophysin (SYN), cone-specific opsins, vimentin, cellular retinaldehyde binding protein (CRALBP), glial fibrillary acidic protein (GFAP), rat major histocompatibility antigen class II (MHC-II) and a rat macrophage marker (Ox-42). Human retinal cells (9-13 wk postconception) were transplanted to the eyes of 28 athymic rats. Host rats were kept in microisolator cages for up to 48 wk after surgery. Host immune response and the development of the transplants were studied using histology, immunohistochemistry and electron microscopy. When using retinas of donors 9-11 wk postconception, transplants grew to 2-3 mm in diameter with many rosettes, in 31 of 35 eyes. Transplants derived from donors 12-13 wk postconception did not survive as well (8 out of 11 eyes), were smaller and less organized. All transplants fused well with the host retina, better than corresponding transplants to immunosuppressed rat hosts. Most transplants appeared to be healthy, even after long survival times, and only occasionally were MHC-II positive macrophages observed in transplants or host retinas. All retinal layers were observed, except for an inner limiting membrane on the vitreous surface. The oldest transplants (34-57 wk total age = donor age + time after surgery) exhibited well developed photoreceptors, rods and cones, with inner and outer segments. SYN-staining showed the development of inner and outer plexiform layers. Although many cones stained for SYN and NSE, few were immunoreactive for red-green or blue opsin. Most rods became immunoreactive for S-antigen and rhodopsin. Transplant Müller cells stained for vimentin and CRALBP. Immunoreactivity for GFAP developed slowly and was not completely expressed in all transplant Müller cells until 44 wk total age. Nude rats offer an excellent model for the study of human retinal xenografts without the negative effects of immunosuppression. Compared to immunosuppressed rats, transplantation to nude rats gives consistent results and superior long-term survival of hosts and transplants.

Abortion, Induced↗
PubMed1998

Retinal projections in mice with inherited retinal degeneration: implications for circadian photoentrainment.

The availability of naturally occurring and transgenic retinal mutants has made the mouse an attractive experimental model to address questions regarding photoentrainment of circadian rhythms. However, very little is known about the retinal cells and the retinal projections to the nuclei of the murine circadian timing system. Furthermore, the effect of inherited retinal degeneration on these projections is not understood. In this report, we have used pseudorabies virus as a neuroanatomical tract tracer in mice to address a series of questions: Which retinal cells mediate circadian responses to light? What is the nature of the retinohypothalamic projection? What is the impact of the inherited retinal disorder, retinal degenerate (rd/rd), on the structures of the photoentrainment pathway? Our results show that a class ofretinal ganglion cell, morphologically similar to the type III ganglion cells of the rat, appears to project to central circadian structures of the mouse. They are few in number and sparsely distributed throughout the retina. The low number and broad distribution of these specialized retinal ganglion cells may be an adaptive mechanism to integrate environmental irradiance without compromising the spatial resolution required for vision. In addition, viral infection of conelike and rodlike photoreceptors and amacrinelike cells suggest that these cells may mediate or contribute to circadian responses to light. Inherited retinal degeneration has no obvious effect on the anatomy of the retinal cells or their projections to the circadian axis. These anatomical findings are consistent with our previous findings showing that aged rd/rd mice are capable of regulating their circadian rhythms by light with unattenuated sensitivity.

Animals↗
PubMed1997

Sonic hedgehog promotes rod photoreceptor differentiation in mammalian retinal cells in vitro.

The hedgehog gene family encodes secreted proteins important in many developmental patterning events in both vertebrates and invertebrates. In the Drosophila eye disk, hedgehog controls the progression of photoreceptor differentiation in the morphogenetic furrow. To investigate whether hedgehog proteins are also involved in the development of the vertebrate retina at stages of photoreceptor differentiation, we analyzed expression of the three known vertebrate hedgehog genes. We found that Sonic hedgehog and Desert hedgehog are expressed in the developing retina, albeit at very low levels, whereas Indian hedgehog (Ihh) is expressed in the developing and mature retinal pigmented epithelium, beginning at embryonic day 13. To determine whether hedgehog proteins have activities on developing retinal cells, we used an in vitro system in which much of retinal histogenesis is recapitulated. N-terminal recombinant Sonic Hedgehog protein (SHH-N) was added to rat retinal cultures for 3-12 d, and the numbers of retinal cells of various phenotypes were analyzed by immunohistochemistry. We found that SHH-N caused a transient increase in the number of retinal progenitor cells, and a 2- to 10-fold increase in the number of photoreceptors differentiating in the cultures when analyzed with three different photoreceptor-specific antigens. In contrast, the numbers of retinal ganglion cells and amacrine cells were similar to those in control cultures. These results show that Hedgehog proteins can regulate mitogenesis and photoreceptor differentiation in the vertebrate retina, and Ihh is a candidate factor from the pigmented epithelium to promote retinal progenitor proliferation and photoreceptor differentiation.

Animals↗
PubMed1996

Photoreceptor loss in age-related macular degeneration.

PURPOSE: The authors showed previously that parafoveal rods, but not cones, decrease during the course of adulthood in donor eyes that were screened to exclude the grossly visible macular drusen and pigmentary disturbances typical of age-related macular degeneration (AMD). Because AMD begins in the parafovea, this selective loss of rods actually may be subclinical AMD not yet visible in the fundus. If so, AMD must have a predilection for rods over cones. The authors tested this hypothesis by determining the relative numbers of cones and rods in donor eyes with mid-to late-stage AMD and in age-matched controls. METHODS: Thirteen eyes (from seven donors) with grossly visible macular drusen and pigmentary disturbances were either wholemounted for photoreceptor counts or sectioned through the fovea for histopathology and carbonic anhydrase histochemistry to label red-green cones. Eyes were assigned to AMD or control groups on the basis of histopathology and clinical history. RESULTS: Five nonexudative AMD (NE-AMD) eyes from three donors showed sparing of foveal cones and loss of rods and cones in the parafovea. In two donors, rod loss exceeded cone loss at most parafoveal locations, and in one donor, rod density was normal and cone density was reduced. In eight exudative AMD (EX-AMD) eyes from five donors, photoreceptors surviving along the margins of and overlying disciform scars were largely cones. CONCLUSIONS: Photoreceptors are lost in NE-AMD as well as in the more severe exudative form, consistent with functional and clinical studies. The authors propose that rods die in older eyes without evidence of overt retinal pigment epithelial disease. In persons susceptible to AMD, the retinal pigment epithelium becomes dysfunctional. Secondarily, rod loss continues and cones begin to degenerate. Eventually, only degenerate cones remain; ultimately, all photoreceptors may disappear.

Aged↗
PubMed2002

Animal models in research on retinal degenerations: past progress and future hope.

The retinal degenerations (RDs) are a family of inherited retinal degenerative diseases (dystrophies) that lead to vision loss. Although phenotypically very different, the RDs have several characteristics in common. They all are caused by gene mutations or at least have a genetic component in the etiology. They all lead to photoreceptor dysfunction, many leading to the death of both rod and cone photoreceptors. The mechanism of cell death in most of the RDs seems to be through the process of apoptosis. It is estimated that more than fifteen million people around the world have vision loss due to an inherited RD. Many of these are patients with the dry form of age-related macular degeneration (AMD) who retain partial functional vision. However, some have other degenerative conditions such as retinitis pigmentosa, Leber congenital amaurosis or wet AMD and can suffer from severe vision loss or total blindness.

Animals↗
PubMedDate not supplied

Processing of scotopic increments and decrements.

Rod and cone photoreceptors send their signals to ON- and OFF-retinal ganglion cells through different pathways in the primate retina. We hypothesized that increments and decrements of light may be processed differently by the rod-bipolar pathway because of the funneling of the rod signal through the rod bipolar cell. We tested this hypothesis using a psychophysical adaptation paradigm, which has provided evidence that photopic increments and decrements of light are processed by ON- and OFF-pathways in the human visual system. We had observers adapt to either a rapid-on or rapid-off sawtooth waveform, under both photopic and scotopic conditions. We then measured detection thresholds for one cycle of a rapid-on or rapid-off sawtooth stimulus. For photopic stimuli, sawtooth adaptation asymmetrically raised thresholds for test stimuli in a manner that depended on the polarity of the adaptation stimulus. For scotopic stimuli, thresholds were raised, but no significant selective adaptation effect was found. By repeating the photopic condition with sawtooth stimuli which had been filtered using an impulse response function derived for the rod system, we demonstrated that the lack of selective adaptation was not a consequence of the sluggish temporal response of the rod-bipolar pathway. We conclude instead that the reduced effectiveness of sawtooth adaptation is due to channeling of rod photoreceptor signals through the rod bipolar cell before reaching ON- and OFF-ganglion cells.

Adult↗
PubMed1999

Rescue from photoreceptor degeneration in the rd mouse by human immunodeficiency virus vector-mediated gene transfer.

Retinitis pigmentosa (RP) is the most common inherited retinal disease, in which photoreceptor cells degenerate, leading to blindness. Mutations in the rod photoreceptor cGMP phosphodiesterase beta subunit (PDEbeta) gene are found in patients with autosomal recessive RP as well as in the rd mouse. We have recently shown that lentivirus vectors based on human immunodeficiency virus (HIV) type 1 achieve stable and efficient gene transfer into retinal cells. In this study, we evaluated the potential of HIV vector-mediated gene therapy for RP in the rd mouse. HIV vectors containing a gene encoding a hemagglutinin (HA)-tagged PDEbeta were injected into the subretinal spaces of newborn rd mouse eyes. One to three rows of photoreceptor nuclei were observed in the eyes for at least 24 weeks postinjection, whereas no photoreceptor cells remained in the eyes of control animals at 6 weeks postinjection. Expression of HA-tagged PDEbeta in the rescued photoreceptor cells was confirmed by two-color confocal immunofluorescence analysis using anti-HA and anti-opsin antibodies. HIV vector-mediated gene therapy appears to be a promising means for the treatment of recessive forms of inherited retinal degeneration.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1995

Changes in retinal time scale under background light: observations on rods and ganglion cells in the frog retina.

The kinetics of rod responses to flashes and steps of light was studied as a function of background intensity (IB) at the photoreceptor and ganglion cell levels in the frog retina. Responses of the rod photoreceptors were recorded intracellularly in the eyecup and as ERG mass potentials across the isolated, aspartate-superfused retina. The kinetics of the retinally transmitted signal was derived from the latencies of ganglion cell spike discharges recorded extracellularly in the eyecup. In all states of adaptation the linear-range rod response to dim flashes could be modelled as the impulse response of a chain of low-pass filters with the same number of stages: 4 (ERG) or 4-6 (intracellular). Dark-adapted time-to-peak (tp, mean +/- SD) at 12 degrees C was 2.4 +/- 0.6 sec (ERG) or 1.7 +/- 0.4 sec (intracellular). Under background light, the time scale shortened as a power function of background intensity, I-bB with b = 0.19 +/- 0.03 (ERG) or 0.14 +/- 0.04 (intracellular). The latency-derived time scale of the rod-driven signal at the ganglion cell agreed well with that of the photoreceptor responses. The apparent underlying impulse response had tp = 2.0 +/- 0.7 sec in darkness and accelerated as I-bB with b = 0.17 +/- 0.03. The photoreceptor-to-ganglion-cell transmission delay shortened by 30% between darkness and a background delivering ca 10(4) photoisomerizations per rod per second. Data from the literature suggest that all vertebrate photoreceptors may accelerate according to similar power functions of adapting intensity, with exponents in the range 0.1-0.2. It is noteworthy that the time scale of human (foveal) vision in experiments on flicker sensitivity and temporal summation shortens as a power function of mean luminance with b approximately 0.15.

Action Potentials↗
PubMed2001

The ability of hyperoxia to limit the effects of experimental detachment in cone-dominated retina.

PURPOSE: To determine the ability of oxygen supplementation to ameliorate the effects of retinal detachment in a cone-dominated retina. METHODS: Retinal detachments were created in the right eyes of ground squirrels and the animals immediately placed in normoxic (room air) or hyperoxic (70% oxygen) conditions for 3 days. The retinas were sampled from different regions and investigated morphologically or immunocytochemically by light or confocal microscopy. Agarose embedded sections were immunostained with antibody probes to cytochrome oxidase, synaptophysin, medium-to-long wavelength-sensitive (M/L) cone opsin, rod opsin, excitatory amino acid transporter 1 (EAAT1), glutamate synthetase (GS), cellular retinaldehyde-binding protein (CRALBP), and peanut agglutinin (PNA) lectin. Retinal wholemounts were labeled with PNA and antibodies to short (S)-wavelength-sensitive cone opsin and rod opsin. Cell death was examined using a TUNEL assay on agarose sections or using toluidine blue staining on semithin sections. RESULTS: The percentage of dying cells relative to the total nuclei in the photoreceptor layer was significantly reduced, and the total number of nuclei was greater in hyperoxic animals. Triple labeling using TUNEL, anti-M/L cone opsin and anti-rod opsin showed that hyperoxia had a remarkable effect both on the reduction of cone cell death and the maintenance of the overall structure of cone photoreceptors. Analysis of the retinal wholemounts demonstrated the preservation of PNA, S-cone, and rod opsin antibody labeling in the detachments maintained in hyperoxic conditions. Although the disruption of cytochrome oxidase and synaptophysin was seen in normoxic animals, there was minimal disruption in hyperoxic animals. Labeling with anti-EAAT1, anti-GS, and anti-CRALBP was increased in the Müller cells of normoxic animals with detachments, but was decreased in the hyperoxic animals. CONCLUSIONS: Hyperoxia prevents the degeneration of both rods and cones in retinas heavily dominated by cones and mitigates the effect of detachment on Müller cell reactivity. The current results suggest that the rescue of cones is not secondary to that of rods.

Animals↗