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PubMed2002

Early development of the retina and pineal complex in the sea lamprey: comparative immunocytochemical study.

Lampreys have a complex life cycle, with largely differentiated larval and adult periods. Despite the considerable interest of lampreys for understanding vertebrate evolution, knowledge of the early development of their eye and pineal complex is very scarce. Here, the early immunocytochemical organization of the pineal complex and retina of the sea lamprey was studied by use of antibodies against proliferating cell nuclear antigen (PCNA), opsin, serotonin, and gamma-aminobutyric acid (GABA). Cell differentiation in the retina, pineal organ, and habenula begins in prolarvae, as shown by the appearance of PCNA-negative cells, whereas differentiation of the parapineal vesicle was delayed until the larval period. In medium-sized to large larvae, PCNA-immunoreactive (-ir) cells were numerous in regions of the lateral retina near the differentiated part of the larval retina (central retina). A late-proliferating region was observed in the right habenula. Opsin immunoreactivity appears in the pineal vesicle of early prolarvae and 3 or 4 days later in the retina. In the parapineal organ, opsin immunoreactivity was observed only in large larvae. In the pineal organ, serotonin immunoreactivity was first observed in late prolarvae in photoreceptive (photoneuroendocrine) cells, whereas only a few of these cells appeared in the parapineal organ of large larvae. No serotonin immunoreactivity was observed in the larval retina. GABA immunoreactivity appeared earlier in the retina than in the pineal complex. No GABA-ir perikaryon was observed in the retina of larval lampreys, although a few GABA-ir centrifugal fibers innervate the inner retina in late prolarvae. First GABA-ir ganglion cells occur in the pineal organ of 15-17 mm larvae, and their number increases during the larval period. The only GABA-ir structures observed in the parapineal ganglion of larvae were afferent fibers, which appeared rather late in development. The time sequence of development in these photoreceptive structures is rather different from that observed in teleosts and other vertebrates. This suggests that the unusual development of the three photoreceptive organs in lampreys reflects specialization for their different functions during the larval and adult periods.

Aging↗

PubMed1979

Postnatal neurogenesis in the kitten retina.

Postnatal neurogenesis in the kitten retina was studied using 3H-thymidine radioautography. Kittens were injected with 3H-thymidine at 1 day, 10 days, 3 weeks or 4 weeks after birth and allowed to survive until 14 weeks of age. Labeled neuronal nuclei were not found in the ganglion cell layer in any of the retinas, but they were seen in the other nuclear layers of the same retinas. In retinas from kittens injected at one day after birth, the peripheral 80% of the length of the retina (in sections cut parallel to the dorsoventral meridian) contained labeled nuclei; the central 20%, around the optic disc, contained no labeled nuclei. Near the ora serrata most nuclei in both inner and outer nuclear layers were labeled. Away from the ora serrata the proportion of labeled to unlabeled nuclei gradually decreased. Labeled nuclei extended farther centrally in the the inner than the outer nuclear layer. The same pattern of labeling was repeated in retinas from kittens injected at ten days after birth, but fewer nuclei were labeled, and the central, unlabeled region around the optic disc was longer--55% of the length of the retina. Only a few nuclei near the ora serrata were labeled in retinas from kittens injected at three weeks after birth, and no labeled neurons were found in kittens injected at four weeks. From these results we conclude that all of the ganglion cells in the kitten retina are present by one day after birth, as are all of the other neurons in the central retina. In peripheral regions of the inner and outer nuclear layers, proliferation of cells destined to become neurons continues up to three weeks after birth.

Animals↗

PubMed1992

Local regeneration in the retina of the goldfish.

We have studied regeneration of the retina in the goldfish as a model of regenerative neurogenesis in the central nervous system. Using a transscleral surgical approach, we excised small patches of retina that were replaced over several weeks by regeneration. Lesioned retinas from three groups of animals were studied to characterize, respectively, the qualitative changes of the retina and surrounding tissues during regeneration, the concomitant cellular proliferation, and the quantitative relationship between regenerated and intact retina. The qualitative and quantitative analyses were done on retinas prepared using standard methods for light microscopy. The planimetric density of regenerated and intact retinal neurons was computed in a group of animals in which the normal planimetric density ranged from high to low. Cell proliferation was investigated by making intraocular injections of 5-bromo-2'-deoxyuridine (BUdr) at various survival times to label proliferating cells and processing retinal sections for BUdr immunocytochemistry. The qualitative analysis showed that the surgery created a gap in the existing retina that was replaced with new retina over the subsequent weeks. The BUdr-labeling experiments demonstrated that the excised retina was replaced by regeneration of new neurons. Neuroepithial-like cells clustered on the wound margin and migrated centripetally, appositionally adding new retina to the old. The quantitative analysis showed that the planimetric density of the regenerated neurons approximated that of the intact ones.

Animals↗

PubMed1998

Effects of taurine and light on retinal GABA content and the efflux of 14C-GABA and 14C-aspartate from frog retina.

GABA content of isolated, dark adapted frog retina was found to be 3.15 +/- 0.28 mM. After 30 minutes of exposure to intense light (200 lx), retinal GABA levels increased about 70%. Interestingly, incubation of dark adapted retina for 30 minutes with medium containing 0.4 mM taurine also led to a 70% increase in GABA levels. Since the light-induced elevation in GABA content was reduced over 50% by a simultaneous injection of 0.02 mM strychinine, it is likely that the light-induced GABA change is partly mediated by the release of taurine from the retina seen after light exposure. However, incubation of isolated retina with medium containing increasing concentrations of taurine (1, 2 and 20 mM), caused a progressive rise in 14C-GABA efflux from retina that was preloaded with 2.2 microM GABA and exposed to dim light (0.05 lx). It was also shown that taurine (1 and 5 mM) dramatically reduced 14C-aspartate efflux from retina preloaded with radioactive aspartate and exposed to dim light conditions. By comparison, intense light stimulation (40 lx) reduced basal 14C-aspartate efflux while dark exposure increased 14C-aspartate loss from the isolated retina. We found that taurine depressed the b-wave signal of frog retina, with the maximum effect occurring at a concentration of 1 mM. Addition of strychnine (0.4 mM) reversed the taurine effect on the b-wave, indicating that taurine receptors must be present in the inner retina. By contrast, taurine (0.1-20 mM) had no effect on the P111 component of the ERG initiated by either aspartate or cobalt. However, taurine exerted a modest depressant activity on P111 initiated by glutamate. The significance of these data relative to the putative neurotransmitter function of taurine in the inner retina is discussed.

Animals↗

PubMed1991

Elevated level of protein phosphatase 2A activity in retinas of rd mice.

Phosphorylation of rhodopsin is not detectable in vitro in the retina of the rd mouse. We investigated the enzymatic system responsible for this abnormality by measuring the levels of rhodopsin kinase and protein phosphatase 2A in normal (rd/+) and diseased (rd/rd) mouse retinas of several ages. For each enzyme, we developed micro assays that were suitable for measuring enzyme activity in one-half mouse retina. Our results indicate that rhodopsin kinase activity is identical in rd/+ and rd/rd retinas until post-natal day 11, and it decreases thereafter in the rd/rd retina, correlating with the loss of rod photoreceptors that occurs in this tissue. Protein phosphatase 2A has a constant level of activity in rd/+ retinas from ages 5 to 32 days but it is higher than normal in rd/rd retinas from post-natal days 5 to 10. It then decreases to levels that are comparable to those in rd/+ retina. Although the rd/rd extract contains the elevated protein phosphatase 2A activity, when rd/rd and rd/+ retinal extracts are each subjected to gel filtration, the elution profiles of protein phosphatase 2A activity appear to be quantitatively identical. This apparent loss of rd/rd phosphatase activity suggests a difference in the regulatory behavior of the enzyme in the normal and degenerative retinas. Thus, the failure to detect in vitro phosphorylation of rhodopsin in the rd/rd retina seems to result from the elevated level of protein phosphatase 2A activity which could more rapidly remove the phosphate from phosphorylated rhodopsin. Since protein phosphatase 2A is a ubiquitous enzyme with broad specificity, an elevation in its activity also could affect other protein phosphorylations.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗

PubMed1985

Cortisol receptors and inducibility of glutamine synthetase in embryonic retina.

Glutamine synthetase (GS) is a marker enzyme for Müller glia cells in neural retina. In chick embryo retina GS begins to increase sharply on the 16th day of development, but can be precociously induced by premature supply of the inducer, cortisol, already on the 8th day. At this stage GS inducibility is low, but it increases progressively with embryonic age. We investigated whether there was a corresponding age-dependent increase of cortisol-binding molecules (cortisol receptors) and found that their level is highest in the early retina and decreases with development. In light of this inverse relationship, we examined whether functional characteristics of these receptors change with age, but detected no differences. In in vitro tests, receptors from older retina translocated cortisol into nuclei from young retina, and vice versa, with similar effectiveness. Also, cortisol receptors from liver cells (which differ from retina receptors) can translocate the hormone into retina nuclei, and vice versa. These findings indicate that translocation of cortisol receptors is neither tissue-specific or age-dependent, nor is it conditional on the total amount of receptors normally present in cells. Therefore, the age-dependent increase of GS inducibility in embryonic retina cannot be directly related to quantitative or functional differences of cortisol receptors and is evidently controlled primarily at the gene level. The very large amount of cortisol-binding molecules in early embryonic retina raises the possibility that they play some role in early differentiation of retina cells unrelated to hormone binding.

Animals↗

PubMed1984

Differential ontogenesis of D1 and D2 dopaminergic receptors in the chick embryo retina.

The differentiation of D1 and D2 dopamine receptors was investigated during the ontogenesis of the chick embryo retina. Our results reveal an interesting complexity in dopaminergic differentiation, with one major receptor system developing before synapses and another one developing after. The dopamine-dependent increase of chick retina cAMP level differentiates early during retina ontogeny. By the embryonic day 10-11 10(-4) M dopamine and ADTN elicit a 13-fold increase in cAMP content of the retina. However, [3H]spiperone (D2 ligand) binds very little to crude membrane preparation of retinas from embryos in the same developmental stage (12-13 fmol/mg protein). High specific binding of [3H]spiperone is only detected after the embryonic day 17-18, attaining 80 to 100 fmol of specific spiperone binding sites in the retinas from post-hatched animals. Apomorphine also promotes the accumulation of cAMP of retinas from early embryonic stages. However, it is only 20-30% as effective as ADTN or dopamine. In addition, while the dopamine responsiveness of the tissue decreases sharply during its ontogeny, the apomorphine effect remains practically constant throughout this period. Both dopamine and apomorphine are equally effective in eliciting cAMP accumulation of retinas from post-hatched animals. Moreover, apomorphine is a potent inhibitor of dopamine-induced cAMP level of the embryonic tissue. The results presented here indicate that D1 and D2 receptors differentiate independently from each other, and that apomorphine elevates retina cAMP levels via a subclass of D1 receptors that does not desensitize significantly during retina development.

Animals↗

PubMed1996

Distribution of CD44 in the retina during development and the rds degeneration.

It was previously demonstrated that the 90 kDa cell adhesion molecule CD44 is localized to Müller cell apical microvilli which project into the interphotoreceptor matrix in the adult retina. For the current report, the distribution of CD44 was studied in developing normal BALB/c mouse retinas and in rds mutant mouse retinas of various ages. Using immunoperoxidase techniques, positive label for CD44 was first detected on Müller cell microvilli after 7 days postnatal in BALB/c retinas and the band of label widened as the microvilli elongated and the retina reached maturity. Labeling of the radiating Müller cell bodies within the retina was also observed during development, and this distribution of CD44 is most likely related to retinal cell differentiation and maturation which are taking place at this time. This label was not observed in mature retinas. In the rds mouse retina, a normal labeling pattern for CD44 was observed on Müller cell microvilli at early ages, prior to photoreceptor degeneration. During the time course of the degeneration, microvillar labeling was still seen, however labeling of the radiating Müller cell bodies within the retina increased dramatically. Following degeneration, the Müller cell microvilli appeared to have retracted or collapsed and the inner retinal labeling was not observed. Only a residual label remained at the level of the outer limiting membrane. The increased presence of CD44 within the rds retina during photoreceptor degeneration is likely due to an upregulation of CD44 synthesis by the Müller cells and/or to the transfer of CD44 from retracting microvilli into lower portions of the Müller cells.

Age Factors↗

PubMed1996

The overrepresentation of the fovea and adjacent retina in the striate cortex and dorsal lateral geniculate nucleus of the macaque monkey.

The central part of the retina, which includes the fovea, is substantially overrepresented in the topographic map of the retina in the striate cortex. We tested whether this simply reflects the uneven distribution of ganglion cells in the retina in accordance with the "principle" of peripheral scaling, or whether there is additional expansion of the fovea and adjacent retina in the retinocortical projection. Wheatgerm agglutinated horseradish peroxidase was injected into the striate cortex of three rhesus macaque monkeys so as to surround the representation of the fovea at a mean eccentricity of 8.6 degrees, and the retinae were processed histochemically to stain the retrogradely and transneuronally labelled ganglion cells which projected topographically to the injection sites. This enabled regions of the striate cortex to be related precisely to corresponding regions of the dorsal lateral geniculate nucleus and retina. Mathematical models of the distribution of ganglion cells in the retina, clipped, three-dimensional computer reconstructions of the striate cortex and lateral geniculate nucleus, and counts of neurons in the latter, were used to calculate the proportion of neurons allocated to the marked perifoveal region at each stage of projection. This was used to calculate the relative allocation of neurons to the representation of the fovea and surrounding retina among the different stages of the visual pathway. The values obtained showed that the cortical representation of the perifovea was expanded two to three times more than could be accounted for on the basis of ganglion cell topography in the retina, and that the expansion occurred both between the retina and the thalamus, and between the thalamus and the cortex. These results are inconsistent with the idea that peripheral scaling is a general principle of sensory representation in the cortex. They could also explain why many visual thresholds, including hyperacuities, cannot be accounted for by peripheral factors such as ganglion cell density.

Animals↗

PubMed1989

Spatial distribution of glutamate, taurine and GABA in teleosts and mammals retina: in vivo and in vitro study.

Teleost and amphibian retina grows throughout life at the circumferential margin distal to the center. Retinas of two teleosts, goldfish and Eugerres plumieri; and two mammals, rat and rabbit were dissected into concentric regions; center and periphery; or center, intermediate and periphery. The concentration of glutamic acid, taurine, and gamma-aminobutyric acid was determined in these areas. A non-significant difference was found between the center and periphery of retinas dissected into two regions. By dissecting the teleost retina in three concentric regions a progressive increase of gamma-aminobutyric acid and taurine for center to periphery was observed, which was statistically significant for taurine. Rat and rabbit retina did not present this difference. The concentration of these amino acids was also determined in two concentric regions of goldfish retina 24 hr after crush of the optic nerve. Taurine content significantly increased in the center of the regenerating retina, but not in the periphery. Outgrowth was measured in explants prepared from central and peripheral retina in the presence of exogenous taurine. The amino acid produced an increase of the nerve growth index of central explants, but inhibited the growth from peripheral explants. This report presents a correlation between taurine concentration in a region of the retina that could be considered as embryonic tissue, suggesting that this amino acid plays a role in the formation of new cells. Moreover, the results from post-crush and cultured retina, with respect to taurine concentration or regenerating effect, suggest a saturation of the taurine-enriched zone.

Animals↗

PubMed2005

Characterization of a transgenic mouse line lacking photoreceptor development within the ventral retina.

A unique transgenic mouse line was generated by incorporating a minigene that contained a cone-specific human cone transducin alpha-subunit (GNAT2) promoter, an attenuated diphtheria toxin A (DTA) gene, and an enhancer element from human interphotoreceptor retinoid-binding protein (IRBP) gene. This transgenic mouse line is designated h-GNAT2pro-DTA. During postnatal retinal development, both transgenic and non-transgenic retinas showed similar morphology and thickness at P1. Between ages P8 and P30, all retinal layers became recognizable in non-transgenic and also in transgenic dorsal retinas. However, in the ventral retina of the transgenic mice the photoreceptor layers did not develop. This aberration occurred as a result of abnormal cellular development, rather than as a consequence of retinal degeneration. In adult transgenic animals, approximately 44% of the retina located dorsally appeared morphologically normal, whereas 32% of the retina located ventrally was completely lacking photoreceptor development. The 24% mid-retinal region exhibited transitional morphology containing malformed photoreceptors. At P360 or older, the thickness of retina layers was reduced in both dorsal and ventral regions. The abnormality observed in transgenic retinas involved mainly the photoreceptors; the other retinal cell types were all present in both dorsal and ventral retinas. Since the DTA gene was only expressed in cone cells, the absence of cone photoreceptors in the transgenic retina was to be expected. However, what was unexpected was the concomitant absence of rod photoreceptors in the ventral retina, suggesting that the presence of cones may be important for the development of rods. This new transgenic line can lead to better understanding of photoreceptor development, and may serve as a new animal model for studying photoreceptor-related retinal diseases.

Animals↗

PubMed2003

The cholecystokinin system in the rat retina: receptor expression and in vivo activation of tyrosine phosphorylation pathways.

High levels of endogenous cholecystokinin (CCK) are present in the rat retina and restricted to amacrine cells. Two types of CCK receptors exist but their expression and intracellular transduction pathways coupled in the rat retina are unknown. The aims of this study were to investigate CCK receptors expression in rat retina and to study downstream tyrosine phosphorylation pathways. For this purpose, total mRNA isolated from rat retina was subjected to RT-PCR analysis. Isolated rat retinas were incubated in presence of CCK. Soluble proteins in retinal homogenates were immunoprecipitated with anti-phoshpotyrosine or anti-p130(Cas) specific monoclonal antibodies and subjected to SDS-PAGE, followed by Western blotting analysis. Both types of CCK receptor mRNAs, A and B, are present in the rat retina. Incubation of retina with CCK induced a rapid increase in several phosphotyrosine-containing bands with molecular masses greater than 30 kDa. Western Blotting and immunoprecipitation with a specific monoclonal antibody identified one of the phosphotyrosine bands as the adapter protein p130(Cas). Tyrosine phosphorylation of p130(Cas) induced by CCK in rat retina was time and concentration dependent: CCK induced tyrosine phosphorylation of p130(Cas) occurred rapidly with the maximum effect observed at 2.5 min incubation with 1 microM CCK. Our data clearly identified CCK-A and CCK-B receptor mRNAs in the rat retina and demonstrated that they are functional, stimulating tyrosine phosphorylation pathways. Our results provide novel biochemical information to further understand the physiological role of CCK A and B receptors in rat retina.

Adaptor Proteins, Vesicular Transport↗

PubMed2000

Optical coherence tomography of the neurosensory retina in rhegmatogenous retinal detachment.

PURPOSE: To clarify the pathologic changes of the detached neurosensory retina in rhegmatogenous retinal detachment. METHODS: Retinal images were prospectively examined by optical coherence tomography in 25 eyes of 25 consecutive patients with rhegmatogenous retinal detachment. We excluded the patients whose retinal detachment did not involve the central fovea or patients with poor fixation during optical coherence tomography (OCT) examination. Optical coherence tomography was scanned through the center of the fovea. The patients ranged in age from 15 to 77 years (mean, 45 years; SD, 20 years). The period from onset of subjective symptoms of retinal detachment to OCT ranged from 2 to 60 days (mean, 16 days; SD, 18 days). Optical coherence tomography findings, best-corrected visual acuity, and the height of the retinal detachment at the central fovea were statistically analyzed using ANCOVA (analysis of covariance) and the Mann-Whitney U test. RESULTS: In 25 eyes of 25 patients, OCT of the detached neurosensory retina at and adjacent to the center of the fovea demonstrated normal retinal structure (10 eyes, 40%), intraretinal separation (7 eyes, 28%), and an undulated separated outer retina (8 eyes, 32%). Three statistically significant factors affected best-corrected visual acuity: intraretinal separation (P = .001), intraretinal separation with undulated outer retina (P = .001), and height of retinal detachment at the central fovea (P<.001). Best-corrected visual acuity was significantly worse in the 15 eyes with intraretinal separation with or without an undulated outer retina than in the 10 eyes with retinal thickening but no intraretinal separation (P = .036). The eight eyes with undulated separated outer retina showed significantly higher retinal detachment at the central fovea than the seven eyes with intraretinal separation but no undulated outer retina (P = .009) and the 10 eyes without intraretinal separation (P = .016). The duration from onset of subjective symptoms to OCT was not related to the occurrence of intraretinal separation of the detached retina. CONCLUSIONS: Intraretinal separation of the detached retina occurred frequently and shortly after retinal detachment in rhegmatogenous retinal detachment and was one of the factors associated with poor vision in rhegmatogenous retinal detachment. Best-corrected visual acuity significantly decreased in the highly detached retina.

Adolescent↗

PubMed2003

Metabolic mapping in mammalian retina: a biochemical and 3H-2-deoxyglucose autoradiographic study.

It has long been known that mammalian retinas metabolize glucose aerobically to lactic acid and carbon dioxide. The classical view holds that glucose is the primary substrate for energy metabolism in all retinal cells, and that photoreceptor cells have the highest rates of glycolysis and respiration. A different and more recent view is that the Müller cells are the principal, if not sole aerobic producers of lactate, which then serves as the primary fuel for the mitochondria in photoreceptor cells and other retinal neurons. In this paper, we have examined these two competing hypotheses in rat and guinea pig retinas by identifying the cellular sites of glucose uptake and phosphorylation via hexokinase by means of autoradiographic studies with 3H-2-deoxyglucose (3H-2DG). The rat retina serves as a vascular model and the guinea pig retina serves as an avascular model. Rat and guinea pig eyecups were incubated in oxygenated, bicarbonate-buffered media containing glucose in the presence of labeled and unlabeled 2DG. Biochemical measurements of lactate production and ATP content were made on rat retinas incubated with different concentrations of glucose and 2DG in order to establish the optimal condition for conducting the autoradiographic studies with 3H-2DG. The optimal substrate concentrations were 1mM glucose and 0.25 mM 2DG. Results showed that following incubation of dark-adapted rat eyecups for 1 hr in media containing 1mM glucose/0.25 mM 2DG and supplemented with 3H-2DG, the label was distributed throughout all the layers of the retina, from the ganglion cell layer to the retinal pigment epithelium, with denser label associated with the outer retina (photoreceptors) relative to the density of label in the inner retina, as evaluated by counts of silver grains in individual retinal layers. Exposure of rat eyecups to light did not alter the relative distribution of label, but did increase total grain counts by 70%. However, uptake of labeled 2DG, as measured by scintillation counting of radioactivity in trichloroacetic acid extracts, was not significantly different between light- and dark-adapted rat retinas. In guinea pig eyecups, labeled 2DG was distributed throughout all the retinal layers. Addition of 10mM lactate or pyruvate to the glucose/2DG media produced no measurable change in the density or distribution of label in the eyecups. Measurements of the activity of hexokinase in rat retinas revealed that this enzyme was present in both the mitochondrial and cytosolic fractions. The present results suggest that as long as the availability of ambient glucose is adequate, retinal neurons use glucose, rather than glial-derived lactate, as the major substrate for the production of high energy phosphates.

Adenosine Triphosphate↗

PubMed1990

Development of morphological types and distribution patterns of amacrine cells immunoreactive to tyrosine hydroxylase in the cat retina.

Using an antibody against tyrosine hydroxylase on newborn to 30-day kitten retinas, we have been able to follow the development of the dopaminergic amacrine cells of the cat retina by light-microscopical investigations of retinal wholemounts. The Type 1 or large Toh+ amacrine cells described by others (Oyster et al., 1985; Törk & Stone, 1979) and named A18 from a Golgi study (Kolb et al., 1981), is at birth (P1) an immature neuron with a small cell body and two or three simple thick radiating dendrites stratifying in stratum 1 with many of the dendrites ending in enlarged growth cones. With increasing postnatal age, the cell body size increases from 12.5 microns diameter to reach 15.5 microns diameter at P30. The dendritic fields also increase in size and complexity. At P1, cells of the central area exhibit dendritic appendages which then develop progressively until at P13 (after eye opening) they are part of rudimentary rings and by P30 the dendritic plexus of Toh+ dendrites and rings in stratum 1, typical of the adult cells, are complete. Toh+ stained processes with growth cones that run deep in stratum 5 of the inner plexiform layer and processes passing to the outer plexiform layer first become apparent at P1 in cells of central inferior retina but not till after P13 are these processes clearly expressed. At P1, the total number of Toh+ Type 1 cells is approximately 4000 and this number remains unchanged to the adult retina. However, the retina increases in size over the P1-P30 stage and thus the mean density of Type 1 Toh+ cells decreases from 30/mm2 at P1 to 18/mm2 at P30. The maximum density of Type 1 Toh+ cells occurs in central retina 2-4 mm superior temporal to the area centralis, corresponding to the maximum rod photoreceptor concentration. A second type of small Toh+ amacrine cell can be visualized at P1. This Type 2 cell is characterized by a much smaller cell body than Type 1 cells (9 microns diameter), and with faintly stained dendrites located in stratum 3 of the inner plexiform layer. During later postnatal days, Type 2 cells gradually become unstainable and only few are still seen in far peripheral retina by P23. Type 2 Toh+ cells from a total population of 40,000 cells at P1 with their highest density occurring in peripheral retina. By P13, they cannot be seen in central retina and are reduced to a total population of cells staining for the antibody of 7400 cells in far peripheral retina.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMedDate not supplied

Characterization of aldehyde dehydrogenase-positive amacrine cells restricted in distribution to the dorsal retina.

A class 1 aldehyde dehydrogenase (ALDH) catalyzes oxidation of retinaldehyde to retinoic acid in bovine retina. We used immunocytochemistry and in situ hybridization to localize this enzyme in adult and fetal bovine retinas. Specific ALDH immunoreactivity was present in the cytoplasm of wide-field amacrine cells restricted in distribution to the dorsal part of the adult retina. The somata diameters ranged from approximately 8 microns to approximately 15 microns, and the cells increased in density from approximately 125 cells/mm2 near the horizontal meridian to approximately 425 cells/mm2 in the superior far periphery. The ALDH-positive cells had somata on both sides of the inner plexiform layer (IPL) and processes in two IPL strata. The majority of ALDH-positive cells were unreactive with antibodies against known amacrine cell enzymes and neurotransmitters, including GABA and glycine. The ALDH-positive amacrine cells also did not react with anti-cellular retinoic acid-binding protein, which was present in a subset of GABA-positive amacrine cells. In flat-mounted retinas processed by in situ hybridization, the larger ALDH-positive amacrine cells tended to be more heavily labeled. In addition to amacrine cells, Müller cell processes in the inner retina were weakly immunoreactive for ALDH; however, these glial cells did not contain ALDH mRNA. The pattern of ALDH expression in fetal bovine retinas was documented by immunocytochemistry. No ALDH reactivity was found before 5.5 months; for the remainder of the fetal period, ALDH immunoreactivity was present in amacrine cells similar to those in adult retina. The ALDH-positive amacrine cells in bovine retina are novel, being limited in distribution to the dorsal retina and unlabeled with other amacrine cell-specific markers. Identification of ALDH in amacrine cells provides additional evidence that cells of the inner retina are involved in retinoid metabolism.

Aging↗

PubMed2002

Normal structure and age-related changes of the equine retina.

Investigations of the pathophysiology of ocular diseases require a detailed knowledge of the microanatomy of the eye. The available information is still inadequate for the equine retina despite the importance of eye diseases in equine medicine. Here we provide a comprehensive analysis of the histologic features of the horse eye as a reference for future studies. Thirty normal eyes of 15 healthy horses were examined immediately after slaughter. The retina of the horse differs considerably in the degree and quantity of neurons and glial elements as well as in vascular patterns compared to the retina of other domestic animals. Morphometric analysis revealed that the thickness of the retina varies between 80 microm at the ora serrata and 250 microm medial to the optic disc. Approximately 90% of the equine retina is comparatively thin (< 130 microm). This is a physiologic response to the distance that oxygen can diffuse in avascular retina. Ganglion cells form a single layer in all parts of the retina. The majority of ganglion cells are very large Nissl-positive cells. Small Nissl-negative ganglion cells are less abundant. A high ganglion cell density is found only in the central area. Vascularization is virtually absent from the retina with the exception of a narrow strip around the disc of the optic nerve, as revealed by lectin histochemistry. Light microscopy of the eyes of older horses repeatedly revealed cystoid degenerations in the retina adjacent to the pars plana of the ciliary body, as well as a destruction of the regular layering of the peripheral region of the retina.

Aging↗

PubMed1996

Development of NADPH-diaphorase in the avian retina: regulation by calcium ions and relation to nitric oxide synthase.

Nitric oxide plays an important role as an intercellular messenger in the CNS. In the present work we measured NADPH-diaphorase activity, which is considered to be a marker of cells producing nitric oxide, in homogenates of the developing chick retina. The enzyme activity can be detected beginning in 8-day-old embryonic retinas with no further quantitative variations throughout development. Arginine analogues inhibit approximately 65% of the activity in embryonic retinas and 50% in posthatched retinas. The enzyme is stimulated 50% by 2 mM calcium chloride in retinas from 8 to 14 embryonic days, but this effect decreases to 20% in 17-day embryonic retinas and practically disappears in posthatched animals. The stimulation by calcium is completely blocked by arginine analogues. The decrease in enzyme activity at posthatched retinas is not due to stimulation by endogenous calcium or the presence of insufficient amounts of calmodulin, because addition of EGTA or calmodulin, respectively, did not restore the stimulation to levels observed at embryonic stages. Inhibition of NADPH-diaphorase activity by NG-nitro-L-arginine or L-NG-(iminoethyl) ornithine is concentration dependent with IC50 values of approximately 1 mM at all stages studied. However, in the presence of calcium, the inhibition by both analogues is shifted to the left and is apparently biphasic at all developmental stages, including in posthatched animals, with IC50 values in the low micromolar range. NADPH-diaphorase was also detected by histochemistry in specific groups of cells in the early embryonic retina and in subsets of amacrine and ganglion cells, as well as in photoreceptors, in more developed retinas. The results indicate that different isoforms of nitric oxide synthase are present in the chick retina and that a calcium-dependent isoform is predominant in early periods of development.

Animals↗