SEARCH · Search PubMed

Results for “RETINA”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 523 records · Page 29Linked to original sources

PubMed1985

The topography of ganglion cell production in the cat's retina.

The ganglion cells of the cat's retina form several classes distinguishable in terms of soma size, axon diameter, dendritic morphology, physiological properties, and central connections. Labeling with [3H]thymidine shows that the ganglion cells which survive in the adult are produced as several temporally shifted, overlapping waves: medium-sized cells are produced before large cells, whereas the smallest ganglion cells are produced throughout the period of ganglion cell generation (Walsh, C., E. H. Polley, T. L. Hickey, and R. W. Guillery (1983) Nature 302: 611-614). Large cells and medium-sized cells show the same distinctive pattern of production, forming rough spirals around the area centralis. The oldest cells tend to lie superior and nasal to the area centralis, whereas cells in the inferior nasal retina and inferior temporal retina are, in general, progressively younger. Within each retinal quadrant, cells nearer the area centralis tend to be older than cells in the periphery, but there is substantial overlap. The retinal raphe divides the superior temporal quadrant into two zones with different patterns of cell addition. Superior temporal retina near the vertical meridian adds cells only slightly later than superior nasal retina, whereas superior temporal retina near the horizontal meridian adds cells very late, contemporaneously with inferior temporal retina. The broader wave of production of smaller ganglion cells seems to follow this same spiral pattern at its beginning and end. The presence of the area centralis as a nodal point about which ganglion cell production in the retinal quadrants pivots suggests that the area centralis is already an important retinal landmark even at the earliest stages of retinal development. This sequence of ganglion cell production differs markedly from that seen in the retinae of nonmammalian vertebrates, where new ganglion cells are added as concentric rings to the retinal periphery, and also bears no simple relationship to the cat's retinal decussation line. However, it can be related in a straightforward manner to the organization of axons in the cat's optic tract, suggesting that the fiber order in the tract represents a grouping of fibers by age.

Animals↗

PubMed1983

Cyclic GMP systems in the retina.

Evidence for the presence of multiple cyclic GMP (cGMP) systems in the vertebrate retina is examined. Levels of this cyclic nucleotide are characteristically high in the photoreceptor cell, whereas in the inner retina they are similar to those found in other areas of the central nervous system. Guanylate cyclase and cGMP phosphodiesterase show a similar uneven distribution, with very high levels of activity in outer segments. At least three forms of guanylate cyclase, one of which may be unique to the photoreceptor cell, have been described. Similarly, differences in the regulation of cGMP phosphodiesterase within localized areas of retina indicate the existence of multiple forms of this enzyme. Factors that influence cGMP levels also have regionally variable effects. Light adaptation leads to reduced cGMP levels in the distal retina, whereas inner retina layers do not show parallel changes. Calcium suppresses the formation of cGMP in photoreceptors, but has no effect or stimulates cGMP formation in the inner retina. Cellular depolarization appears to reduce levels of cGMP in photoreceptors and increases it in the inner retina. Furthermore, endogenous proteins whose phosphorylation is apparently controlled by cGMP seem to be localized to specific retinal cells or subcellular organelles. These data lead to the conclusion that multiple cGMP systems exist in the retina, each with a distinct location and function.

3',5'-Cyclic-GMP Phosphodiesterases↗

PubMed1984

Effect of embryonic age on aggregability, histogenesis and biochemical differentiation in the embryonic chick and quail neural retina.

In this paper, the different ages of the chicken and quail embryonic retina cell aggregates are used to examine the aggregation, histogenesis, and the induction of glutamine synthetase (GS) elicited by hydrocortisone. The results show that the GS inducibility in the retina cells increases at a slow rate, then rises sharply on the 9th day, and after 9 days, the GS inducibility of aggregates decreases with the increase of embryonic age. The observed value of induced GS activity in the chick retina cells coaggregate with quail embryonic retina cells is less than the expected value. Bispecific cell coaggregates were observed when the 9-day chicken embryonic retina cells and the 71/2-day quail embryonic retina cells were combined and coaggregated, the chicken and quail cells formed three retinal rosettes. When the 9-day chicken embryonic retina cells were commingled with the 13-day quail embryonic retina cells, in the coaggregates, only one retinal rosette was formed.

Animals↗

PubMed1982

Identification of the endogenous retinoids associated with three cellular retinoid-binding proteins from bovine retina and retinal pigment epithelium.

The endogenous retinoids associated with three cellular retinoid-binding proteins from bovine retina and retinal pigment epithelium have been identified by their spectral characteristics and their co-migration with authentic retinoids on high performance liquid chromatography. All-trans-retinol is the only retinoid associated with the cellular retinol-binding protein from retina and retinal pigment epithelium. The saturation of the binding site with native ligand is 0.95 +/- 0.05 mol of retinoid/mol of protein for cellular retinol-binding protein purified from frozen and fresh retina and retinal pigment epithelium. All-trans-retinoic acid has been identified as the endogenous ligand associated with the cellular retinoic acid-binding protein of cattle retina. The saturation of the binding site of cellular retinoic acid-binding protein from frozen and fresh retina (the protein is absent in extracts of retinal pigment epithelium) is about 0.2 mol of retinoid/mol of protein, probably a minimum value due to losses of the ligand. Retinoic acid has not been detected previously in retina. Cellular retinaldehyde-binding protein from retina purifies with two endogenous ligands which cochromatograph on high performance liquid chromatography with 11-cis-retinaldehyde and 11-cis-retinol and occur in a ratio of approximately 3:1, respectively. The binding site of cellular retinaldehyde-binding protein from frozen retina is nearly fully occupied with these two ligands (saturation greater than 0.9 mol of retinoids/mol of protein). In contrast, purified cellular retinaldehyde-binding protein from retinal pigment epithelium carries only 11-cis-retinaldehyde as an endogenous ligand. The saturation of the binding site with this ligand is greater than 0.95.

Animals↗

PubMed1994

Sparing of the ipsilateral retina after anterior chamber inoculation of HSV-1: requirement for either CD4+ or CD8+ T cells.

PURPOSE: To determine whether CD4+ T cells, CD8+ T cells, or both CD4+ and CD8+ T cells are required for preservation of the ipsilateral retina after uniocular anterior chamber inoculation of herpes simplex virus type 1 (HSV-1). METHODS: Adult-thymectomized BALB/c mice were T cell depleted by administration of anti-CD4 monoclonal antibody (mAb), anti-CD8 mAb, or anti-CD4 mAb and anti-CD8 mAb together. Control mice were thymectomized but were not T cell depleted. HSV-1 (KOS) was inoculated in one anterior chamber. At intervals after inoculation, the injected eyes were examined histopathologically or homogenized to determine the kinetics of infectious virus recovery. Additional groups of in vivo depleted mice were injected with wild type KOS and RH116 (a mutant of KOS containing the Escherichia coli beta-galactosidase gene) to determine whether viral genes were expressed in the retina in any of the mice. RESULTS: In the inoculated eyes of mice depleted of both CD4+ and CD8+ T cells, there was a significantly higher incidence of acute destructive retinitis at days 9 and 14 postinoculation (PI), and the titer of virus recovered at day 14 PI was significantly higher. Viral gene expression in the retina and the optic nerve was observed after day 7 PI only in the group of mice depleted of both CD4+ and CD8+ cells. In contrast, acute destructive retinitis was not observed in nondepleted mice or in mice depleted of either CD4+ or CD8+ T cells alone, and virus recovery was not significantly different among these three groups of mice. No virus-infected cells were observed in the optic nerve or the sensory retina of nondepleted mice, of mice depleted of only CD4+ cells, or of mice depleted of only CD8+ cells. CONCLUSION: The results of these studies suggest that either CD4+ or CD8+ T cells can spare the retina of the injected eye after uniocular anterior chamber inoculation of HSV-1. Because virus appeared after day 7 PI in the ipsilateral optic nerve and retina only in mice depleted of both CD4+ and CD8+ T cells, these results suggest that spread of virus to the ipsilateral retina occurs via the optic nerve and that either CD4+ or CD8+ T cells can prevent spread of virus to the inoculated eye resulting in sparing of the ipsilateral retina.

Animals↗

PubMed1994

Immunolocalization of integrins in the human retina.

PURPOSE: Integrins are cell surface proteins that participate in interactions between cells and with extracellular matrix. Binding of integrins to their ligands influences cell activities including proliferation, migration, and differentiation. Expression of integrin subunits from three different subfamilies were examined in human retina. METHODS: Integrins were detected in frozen sections of two human retinas with an avidin-biotin-complex immunohistochemical technique, using nine different monoclonal antibodies specific for alpha 2, alpha 3, alpha 4, alpha 5, alpha 6, alpha v, beta 1, beta 2, and beta 3. One retina was from a patient who had conjunctival squamous cell carcinoma, and the other was from uninvolved regions of an eye with a choroidal melanoma. RESULTS: All integrins tested were detectable in consistent patterns in two retinas. All except alpha 2 and alpha 4 were stained vibrantly in retinal and choroidal vessels. All alpha subunit staining of vessels showed overlap or close proximity to beta 1 staining. In addition to vessels, beta 1 was also present in the internal limiting membrane; alpha 2, alpha 3, alpha 4, alpha 5, and beta 2 were all found throughout much of the neural retina, albeit with distinctive staining patterns. Other than in association with vessels, alpha 6 and alpha v were not detected in neural retina, and beta 3 was only weakly detected in the nerve fiber layer; alpha 4 and beta 2 were expressed in the retinal pigment epithelium; beta 1 and beta 2 were strongly expressed in drusen present in one of the eyes. CONCLUSION: Nine integrin subunits have been found to have unique distributions in adult human retina. An understanding of the distribution in normal retina can serve as a useful contrast to patterns of staining associated with retinal diseases.

Antibodies, Monoclonal↗

PubMed1994

The neural retina maintains integrins in the apical membrane of the RPE early in development.

PURPOSE: The retinal pigment epithelium (RPE) lines the interface between the neural retina and the choroid. Early in chicken development, the beta 1 family of integrins resides in the apical (facing the neural retina) and basolateral (facing the choroid) membranes of RPE. Later in development, integrins reside only in the basolateral membranes, which is more typical of simple transporting epithelia. The authors examined whether the distribution of integrins is regulated by the neural retina. METHODS: Individual integrins were examined by studying the individual alpha-subunits that form heterodimers with the beta 1 subunit. The expression and distribution of these subunits were determined by immunoblotting and immunocytochemistry. RESULTS: Subunits alpha 3 and alpha 6 exemplified contrasting behaviors. Early and late in development, alpha 3 was found only in the basal membranes. As was beta 1, the distribution of alpha 6 was nonpolarized early in development but was basal later in development. The effect of the immature neural retina was determined by reconstituting the RPE:neural retinal interface in explant culture. Absent the neural retina, alpha 6 and beta 1 were removed from the apical membrane. When present, the immature neural retina maintained both subunits in the apical membrane. The neural retina was effective only if the outer (primordial photoreceptor) surface of the retina apposed the RPE. CONCLUSIONS: These data suggest that matrix or intercellular interactions determine the distribution of individual integrins. Further, the changes in integrin distribution during development reflect the maturation of the primordial interphotoreceptor matrix or photoreceptor cell layer.

Animals↗

PubMed1993

Agonist-induced desensitization of dopamine D-1 receptors in bovine retina and rat striatum.

We have investigated agonist-induced desensitization of dopamine (DA) D-1 receptor mediated accumulation of adenosine 3':5'-cyclic monophosphate (cAMP) in bovine retinas and rat striata in vitro. Tissues were exposed to various pharmacological agents for 60 min, washed and homogenized. D-1 agonist-promoted accumulation of cAMP in the presence of adenosine 5'-triphosphate (ATP) and 5'-guanylylimidodiphosphate (GppNHp) was then measured. Retinas and striata incubated with DA or (+) SKF 38393 (100 microM each) displayed diminished capacities to accumulate cAMP when they were re-exposed to the same drugs. As expected, retinas and striata treated wtih (+) SKF 38393 also showed an attenuated formation of cAMP when restimulated with DA. In addition, D-1 receptors in retinas that had been treated with quinpirole, a D-2 agonist, did not become desensitized. Furthermore, 0.2 microM SCH 23390 prevented D-1 receptor subsensitivity caused by 100 microM DA. Interestingly, retinas and striata incubated with forskolin, a direct stimulator of adenylyl cyclase, also displayed a diminished enzymatic response to restimulation by the same agent, as well as by DA. Additionally, retinas incubated with 100 microM DA were refractory to forskolin-induced cAMP formation. Finally, results of 3H-SCH 23390 binding to control and DA-treated retinas indicated that agonist treatment did not induce significant changes in either receptor density or binding affinity. The data indicate that bovine retinas and striatal slices in vitro are suitable to investigate various aspects of the desensitization of neuronal responses to DA D-1 agonists or forskolin.

Adenylyl Cyclases↗

PubMed1996

Temporal and spatial regulation of integrin vitronectin receptor mRNAs in the embryonic chick retina.

PURPOSE: To identify integrin vitronectin receptor subunit mRNAs in the developing avian retina and to track their expression. METHODS: Reverse transcription-polymerase chain reaction was used to identify integrin vitronectin receptor subunit mRNAs expressed in embryonic chick retina. cDNA clones encoding the beta 5 subunit were isolated and sequenced. Expression patterns of mRNAs encoding alpha v, beta 3, and beta 5 subunits were analyzed using northern analysis and in situ hybridization. RESULTS: Integrin beta 1, beta 3, and beta 5 subunit mRNA were identified in embryonic day 6 chick retina. The sequence of chicken beta 5 was 77% identical to that of human beta 5, and sequences with known signaling functions were highly conserved. Integrin alpha v, beta 3, and beta 5 mRNAs were expressed throughout the development of the embryonic retina, with the highest levels per retina observed around the embryonic day 9. In situ hybridization showed that both beta 3 and beta 5 were expressed throughout the developing retina, particularly in undifferentiated neuroepithelial precursor cells. At later times, beta 3 was expressed uniformly throughout the retina, whereas beta 5 expression was highest in a band throughout the central retina. CONCLUSIONS: The strong conservation of sequences with known signaling functions in chicken beta 5 suggests that it functions in a manner similar to human beta 5. Spatial expression patterns of vitronectin receptor subunits at early times of development point to a range of possible functions beyond axon outgrowth, including retinoblast proliferation, adhesion, and migration.

Amino Acid Sequence↗

PubMedDate not supplied

A gliacentric view of the human retina.

The structure of retina was historically described using light microscopy histological sections. This description placed prime importance on neural elements and their interconnections is establishing retinal structure. Of the 10 retinal layers, 7 are neural elements. This neurocentric description is, however, not the only way to view the retina. After considering various pathological conditions, we believe that an alternative description of the retina exists, based on glial cells. The gliacentric view may better enhance our understanding of vascular pathologies of the retina. In contrast to the classical view of a 10 sheet neurocentric structure, we propose a gliacentric structure composed of two sheet. This model is supported by the embriological development of the retina, originating from two neuroepithelial sheets (the two layers of the optic vesicle). These neuropithelial layers later develop into two monostratified stheets composed of epithelial cells with the following characteristics: a basement membrane at the basal side, villi at the apical side and intercellular junction complexes at the lateral aspects of the cells. The neural network of the retina lies embedded within these sheets. This gliacentric model has not only theoretical implications but bay also explain why various pathologies of the retina are limited to one compartment rather than extending the entire thickness of the retina.

Epithelial Cells↗

PubMed1996

A SNARE complex containing syntaxin 3 is present in ribbon synapses of the retina.

In contrast to conventional synapses, which release neurotransmitter transiently, ribbon synapses formed by photoreceptors and bipolar cells of the retina release neurotransmitter continuously and modulate the rate in response to light. Both modes of release are mediated by synaptic vesicles but probably differ in the regulation of docking and fusion of synaptic vesicles with the plasma membrane. We have found that syntaxin 1, an essential component of the core fusion complex in conventional synapses, is absent from ribbon synapses of the retina, raising the possibility that these synapses contain a different type of syntaxin or syntaxin-like protein. By immunoprecipitating syntaxin 1-depleted retina and brain extracts with a SNAP-25 antibody and microsequencing the precipitated proteins, syntaxin 3 was detected in retina complexed with SNAP-25, synaptobrevin, and complexin. Using an anti-syntaxin 3 antiserum, syntaxin 3 was demonstrated to be present at high levels in retina compared to brain. Immunofluorescent staining of rat retina sections confirmed that syntaxin 3 is expressed by photoreceptor and bipolar cells in the retina. Thus, in the retina, expression of syntaxin 3 is correlated with ribbon synapses and may play a role in the tonic release of neurotransmitter.

Adaptor Proteins, Vesicular Transport↗

PubMed1996

Postnatal development and the differential expression of presynaptic terminal-associated proteins in the developing retina of the Brazilian opossum, Monodelphis domestica.

In the present study we have characterized the postnatal (PN) development of the retina in the Brazilian opossum, Monodelphis domestica. Monodelphis, a small, pouchless marsupial, undergoes a protracted period of postnatal development. Using bromodeoxyuridine immunohistochemistry, we have investigated postnatal neurogenesis of the retina. In addition, we have examined the differentiation of the retina by using antibodies directed against the presynaptic terminal-associated proteins synaptotagmin, Rab3A, synaptophysin and synaptosomal-associated protein-25 (SNAP-25), and have characterized their spatial and temporal distribution during postnatal development. This study is the first systematic comparison of the developmental expression of multiple presynaptic terminal-associated proteins in relation to retinal neurogenesis and differentiation. At birth (1PN), the Monodelphis retina was relatively undifferentiated morphologically and birthdating analysis revealed mitotically active cells throughout the retina. The 8PN retina was organized into two cellular layers: an outer region of mitotically active neuroepithelial cells and an inner region of postmitotic cells. The inner plexiform layer formed between 5PN and 10PN, and exhibited unique patterns of immunoreactivity with the antibodies used in this analysis. By 25PN the retina was well laminated, and synaptotagmin-, Rab3A-, synaptophysin- and SNAP-25-like immunoreactivities exhibited distinct and specific patterns within the plexiform layers, although they had not yet achieved their mature, adult patterns. These results indicate that each of these proteins exhibits developmentally regulated changes in its cellular localization, and therefore may play important roles during morphogenesis and synaptogenesis of the vertebrate retina.

Animals↗

PubMed1997

Visual pigment assignments in regenerated retina.

Retinas of adult teleost fish can regenerate after injury. Two important issues regarding this phenomenon are the assembly of the regenerated retina and the neuronal images of the visual scene that the regenerated retina produces. Here we report experiments in which the visual pigment content of photoreceptors derived from native and regenerated sunfish retinas was determined by microspectrophotometry. In native retina, there is an apparently perfect correspondence between cone morphology and visual pigment content; all rods contain a middle-wavelength pigment, all single cones contain a different middle-wavelength pigment, and all double cone members contain a long-wavelength pigment. The visual pigments in regenerated rods and double cones were the same as in native retina; however, triple cones, a morphology never observed in native retina, contained the long-wavelength pigment. Moreover, although approximately 60% of regenerated single cones contained the expected middle-wavelength pigment, all other single cones contained the long-wavelength pigment. This mismatch between morphology of regenerated single cones and their visual pigment assignment indicated the following: (1) There is a degree of independence between the mechanisms that establish cone morphology and pigment content during regeneration, which suggests that cone photoreceptor regeneration is not a straightforward recapitulation of the normal cone photoreceptor developmental plan. (2) Although anomalous, the long-wavelength single cones may enable regenerated retina to restore the native spectral sampling of the visual scene.

Animals↗

PubMed1997

Identification of lutein and zeaxanthin oxidation products in human and monkey retinas.

PURPOSE: To characterize fully all the major and minor carotenoids and their metabolites in human retina and probe for the presence of the oxidative metabolites of lutein and zeaxanthin. METHODS: Carotenoids of a composite of 58 pairs of human retinas and a monkey retina were elucidated by comparing their high-performance liquid chromatography (HPLC)-ultraviolet/visible absorption spectrophotometry (UV/Vis)-mass spectrometry (MS) profile with those of authentic standards prepared by organic synthesis. RESULTS: In addition to lutein and zeaxanthin, several oxidation products of these compounds were present in the extracts from human retina. A major carotenoid resulting from direct oxidation of lutein was identified as 3-hydroxy-beta, epsilon-caroten-3'-one. Minor carotenoids were identified as: 3'-epilutein, epsilon,epsilon-carotene-3,3'-diol, epsilon,epsilon-carotene-3,3'-dione, 3'-hydroxy-epsilon,epsilon-caroten-3-one, and 2,6-cyclolycopene-1,5-diol. Several of the geometric isomers of lutein and zeaxanthin were also detected at low concentrations. These were as follows: 9-cis-lutein, 9'-cislutein, 13-cis-lutein, 13'-cis-lutein, 9-cis-zeaxanthin, and 13-cis-zeaxanthin. Similar results were also obtained from HPLC analysis of a freshly dissected monkey retina. CONCLUSIONS: Lutein, zeaxanthin, 3'-epilutein, and 3-hydroxy-beta,epsilon-caroten-3'-one in human retina may be interconverted through a series of oxidation-reduction reactions similar to our earlier proposed metabolic transformation of these compounds in humans. The presence of the direct oxidation product of lutein and 3'-epilutein (metabolite of lutein and zeaxanthin) in human retina suggests that lutein and zeaxanthin may act as antioxidants to protect the macula against short-wavelength visible light. The proposed oxidative-reductive pathways for lutein and zeaxanthin in human retina, may therefore play an important role in prevention of age-related macular degeneration and cataracts.

Animals↗

PubMed1997

An expression profile of genes in human retina and isolation of a complementary DNA for a novel rod photoreceptor protein.

PURPOSE: To characterize expression patterns of active genes in human retina, and to isolate novel genes that are uniquely expressed in this tissue. METHODS: A 3'-directed complementary DNA (cDNA) library that faithfully represents the composition of messenger RNA (mRNA) was constructed with an mRNA preparation from a cadaveric human retina. A total of 925 3' terminal sequences were collected by sequencing randomly selected clones, of which 789 were regarded as representing chromosomally coded genes (gene signatures [GS]). GS were compared with each other and searched against GenBank. The resulting expression profile, listing gene species and their frequency, represents the composition of mRNA in the retina. By comparing this expression profile with those obtained from 10 other source cells or tissues, genes uniquely active in the retina were discovered, including some not previously described. A full-sized cDNA corresponding to one of these was isolated and sequenced. Its expression was analyzed by multitissue Northern hybridization and in situ hybridization to the retina specimen. It was then mapped on human chromosomes. RESULTS: In the expression profile, 108 genes were detected recurrently, suggesting that they are very active. Fifty-five of them were identified in GenBank, including the most abundant opsin gene and several other genes for phototransduction. Among the remaining novel and active genes, 19 were considered unique to retina on the basis of their representation status in other expression profiles and in dbEST. One of these was identified as a gene that encodes a novel secretory protein expressed in a rod photoreceptor that maps to chromosome 18p11.3. CONCLUSIONS: The expression profile of active genes in the retina represents the composition of mRNA, which reflects the relative activities of genes in this tissue. A comparison of this expression profile with those obtained with other tissues resulted in isolation of a novel cDNA specifically expressed in the rod photoreceptor. It is anticipated that additional novel genes that are uniquely active in the neural retina may be obtained with the same strategy, leading to further clarification of the biologic or physiological characteristics of this tissue.

Amino Acid Sequence↗

PubMed1998

Expression of ceruloplasmin in the retina: induction after optic nerve crush.

PURPOSE: To better understand the molecular program of neuronal cell death induced by axotomy, the authors attempted to identify retinal genes differentially expressed by optic nerve crush. METHODS: Total RNA isolated from rat retinas at 1 and 4 days after intraorbital optic nerve crush was used in a modification of the differential display technique. After several rounds of screening, a single reproducibly upregulated band was reamplified and cloned, and differential expression was confirmed by Northern analysis. RESULTS: Sequencing of the differentially expressed band revealed identity to the ferroxidase ceruloplasmin. Reverse transcription-polymerase chain reaction demonstrated high levels of ceruloplasmin expression in retina and liver, but minimal or no expression in brain, lung, spleen, kidney, or thymus of adult rats. The retina mRNA transcript was the same size as that of the liver, as measured by Northern blotting. In situ hybridization identified ceruloplasmin expression in the inner nuclear and ganglion cell layers of the retina, which increased after optic nerve crush. Immunoblotting confirmed expression of the same size protein product in the retina and the liver, and ceruloplasmin could be identified in the retina by immunofluorescence, which increased after optic nerve crush. CONCLUSIONS: Ceruloplasmin was expressed in the retina, and was induced by optic nerve crush. The possible role of ceruloplasmin in inhibiting reaction oxygen species in the retina after injury is discussed.

Animals↗

PubMed1998

Theory and implementation of infomax filters for the retina.

In the first part of this paper we discuss a technical visual sensory system, which--in analogy with the retina--includes some preprocessing of visual information. In so doing, we use an information-theoretic criterion, the infomax ansatz, to optimize the response of the sensory system. In particular, it is shown that the lattice structure of the photoreceptor array has to be taken into account. By a discrete Fourier transformation on a triangular lattice we derive the frequency response of the infomax filter within the first Brillouin zone. To illustrate the response properties, infomax filters adapted to different noise levels are applied to images with different signal-to-noise ratios. This clearly demonstrates the necessity of adaptation of the filter properties to the given noise level. Furthermore, it is shown how to efficiently implement infomax-like filters by simple networks with only nearest-neighbour interactions. A two-layered network topology proves to be very advantageous in implementing the desired high-pass or low-pass properties. The network topology allows for adaption of the network to low and high noise levels by simply adjusting the nearest-neighbour couplings. In the second part of this paper, we compare the previously described information-theoretic requirements on a visual sensory system with biological facts known from the vertebrate retina. The substantial physiological response properties of the vertebrate retina are in agreement with the main features of the infomax filter. Since available experimental data lacks information which is necessary for a more quantitative comparison, we present suggestions for future experiments. Some key anatomical features of the retina of many vertebrates compare well with our two-layered implementation of the infomax filter. The analogy, in particular, concerns the adaption mechanism. To illustrate this point, we summarize some recent experiments which demonstrate that in the retina of some species adaption is based on the release of the neuromodulator dopamine by the interplexiform cells. This causes the horizontal cells to decouple. On the basis of recently gained understanding of the outer plexiform layer of the retina some further hypotheses about the functionality of the retina become obvious and possible future experiments to verify or refute them are suggested. Finally, we discuss the infomax approach from a more general point of view. In particular, we show that redundancy is essential to obtaining noise robustness of an internal representation of the environment as it is produced by a sensory system such as the retina.

Animals↗

PubMed1993

Spatial and temporal differences between the expression of short- and middle-wave sensitive cone pigments in the mouse retina: a developmental study.

In an earlier study we found a topographic separation of middlewave-sensitive (M) and shortwave-sensitive (S) cones in the adult mouse retina. In the present study we investigated the development of the two colour-specific cone types to see whether there is also a temporal difference between the expression of the specific cone visual pigments. Using two anti-cone visual pigment antibodies, COS-1 and OS-2, we compared the densities of immunopositive cone outer segments on retinal whole mounts derived from mice of various ages. The first detectable cone outer segments were the S-cones which appeared in the inferior half of the retina on postnatal day 4. At this stage, the density of the S-cones was very low (30-40 cones/retina) but increased steadily on the following days to reach a value comparable to that of adults by P30 (18,000/mm2). This cone type always remained much more abundant in the lower part of the retina throughout the whole retinal development. In the superior half of the retina, a few S-cones appeared from postnatal day 7; however, their number always remained about one order of magnitude lower than in the inferior part. In contrast, M-cone outer segments were not identifiable earlier than postnatal day 11 and were confined exclusively to the superior part of the retina during the whole developmental process. On postnatal day 12, their density was 1,900/mm2 and increased to a value of 11,000/mm2 by postnatal day 30, which represented the adult stage. As shown by comparison of isodensity lines derived from immunocytochemical reactions of whole mount retinas, the two cone types occupied complementary halves of the mouse retina with maximum density centres located in opposite retinal quadrants. We conclude that 1) in contrast to the primate retina, mouse S-cones precede the M-cones in their development, and 2) the spatial arrangements of the two cone types is maintained throughout the whole differentiation process.

Animals↗