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PubMed1987

Unusual distribution of ganglion cells in the retina of the three-toed sloth (Bradypus variegatus).

1. The distribution and size of retinal ganglion cells labelled with horseradish peroxidase (HRP) were studied in flat-mounted retinas of three-toed sloths. 2. Massive injections of HRP solution were made throughout the thalamus and midbrain in anesthetized sloths in order to retrogradely label the retinal ganglion cell population. Twenty to thirty h later the eyes were excised and the retinas flat-mounted and reacted with phenylenediamine-HCl and H2O2 to label ganglion cells, thus distinguishing them from other cells in the same retinal layer. 3. Ganglion cell density gradually increased from about 500 cells/mm2 at the far periphery to a peak of about 1,500 cells/mm2 in an area, termed the area centralis, deep in the inferior temporal retina. The presence of a vertical visual streak was also noted. 4. The area centralis contained a higher frequency of small ganglion cells than the peripheral retina where large cells predominated. 5. The unusual position of the area centralis and visual streak in the retina can be explained by the sloth's unique ability to rotate its head 180 degrees while climbing upside-down along horizontal branches so that the head is right-side-up. If it is assumed that the branch directly above the sloth's head needs to be visualized for accurate claw placement then the branch would be imaged on the inferior temporal retina in an area corresponding to the maximum density region.

Animals↗
PubMed1986

Electron microscopic immunocytochemistry of interstitial retinol-binding protein in vertebrate retinas.

Interstitial retinol binding protein (IRBP) is a soluble glycoprotein found in the interphotoreceptor matrix (IPM) and implicated in shuttling retinol between retina and pigment epithelium (PE) cells. The authors have studied the distribution of IRBP by EM immunocytochemistry. Thin sections of Lowicryl K4M embedded R. pipiens, X. laevis, bovine and human retinas were labeled sequentially with affinity purified rabbit antibovine IRBP, biotinyl-sheep antirabbit F(Ab')2, and avidin-ferritin, or with avidin and biotinyl-ferritin. Antigen was in the interphotoreceptor space and intercalated into the narrow spaces between PE cell microvilli. IRBP penetration between PE cells was delimited abruptly by the PE junctional complexes. IRBP was also observed in small vacuoles in the apical cytoplasm of PE cells and in PE cell phagosomes that contained IRBP surrounding ingested rod tips. IPM was heavily but inhomogeneously labeled. Antigen was usually deposited along the ROS and COS plasma membrane in a confluent layer, but sometimes it was distributed in large (ca. 0.2-micron thick) clumps. In bovine and human retinas, the connecting cilium was ensheathed by antigen at high density but an unlabeled halo surrounded its plasma membrane. The apical plasma membrane of the inner segment aligned along the connecting cilium was also densely coated by antigen. In both frog retinas, the ridges of the periciliary ridge complex (PRC) were coated with antigen. In none of the four species examined was Golgi labeling present. In bovine retinas, labeled vacuoles (granules) in the myoid region were found in very low numbers (15 vacuoles in 358 rod cells). Amphibian retinas also contained only small numbers of myoid vacuoles labeled by anti-IRBP. Absence of antibody binding to intracellular sites of synthesis in any of the cells that abut the interphotoreceptor matrix suggests that the antigen may be masked prior to its release from the synthetic cell(s) or that its level is below limits of detection.

Animals↗
PubMed1986

Distribution of R-cognin in late embryonic and post-hatching chicken retina.

The histological distribution of R-cognin in chick retinas was determined from embryonic day 8 through 13 wk post-hatching by indirect immunofluorescence using polyclonal anticognin. On embryonic day 8, at a developmental stage without distinct retina layers, most of the cells within the tissue exhibited fluorescence. By embryonic day 12, when the strata of the retina are delineating and initial synapses are beginning to form, R-cognin fluorescence became concentrated in the nascent ganglion cell, and to a lesser extent, inner nuclear layers. By embryonic day 16 (extending through post-hatching day 26), the staining of R-cognin was specific for the ganglion cell and nerve fiber layers. Fluorescence was prominent on the cell somal membranes but also was present on the processes of these cells at the ganglion cell layer-inner plexiform layer interface. Pre-immune serum and anticognin after preabsorption with R-cognin exhibited no fluorescence. The results demonstrated that the known decrease in R-cognin found in the retina during the latter half of embryonic development in the chick is not uniform across the retina, but that R-cognin is preferentially retained on cells within the ganglion cell layer. While cells within the ganglion cell layer also exhibit alpha-bungarotoxin binding, the majority of the latter is found in the inner plexiform layer. Thus, the observations are consistent with a role for R-cognin in the formation or maintenance of functional cell-cell connections within the entire retina prior to developmental day 11, or in retinal ganglion cell layer formation or stability subsequent to embryonic day 11.

Animals↗
PubMed1986

Morphological recovery in the reattached retina.

After experimental retinal detachment in the cat, a number of morphological changes take place in retinal and RPE cells. Following reattachment, the ultrastructural relationship between the photoreceptors and the RPE is re-established, but it does not return to the predetachment state even after short detachment episodes coupled with prolonged recovery periods. All of the reattached retinae show some degree of abnormality, ranging from subtle changes in photoreceptor ultrastructure to dramatic degenerative effects in the outer retina. Abrupt transitions in morphology from one reattached area to an adjacent area are not unusual. Photoreceptor recovery varies widely between animals, and between adjacent regions within the same retina. Ensheathment of outer segments by RPE apical processes is abnormal. In some reattached areas rod outer segment dimensions and disc structure are near normal as is the displacement rate of rod outer segment discs. In others, especially in areas of RPE or Müller cell proliferation and hypertrophy, the outer segments are shortened or absent completely, and there is a reduction of cell bodies in the outer nuclear layer. In some retinae, recovery in cones is inferior to that in rods. At short detachment durations (less than 1 wk) morphological recovery in the reattached retina is optimal while at long intervals (greater than 1 month) recovery is poor. The changes at the photoreceptor-RPE interface identified in the reattached cat retina probably have adverse effects on visual recovery when they occur within the human macula.

Animals↗
PubMed1985

Amelioration of photic injury in rat retina by ascorbic acid: a histopathologic study.

It has been postulated that ascorbic acid may help to protect the retina from oxidative insult by light. To confirm this hypothesis, the authors compared light-damaged retinas of rats with or without ascorbate supplement by morphologic and morphometric studies at different time periods after light exposure. No dramatic morphologic differences were observed in the photoreceptor-retinal pigment epithelium complex between the two groups six hr after light exposure to 200 to 250-foot candles of visible light. Six to 13 days after 24 hr of exposure, the retina of rats that received ascorbate supplement showed significantly less severe damage than the retina of unsupplemented rats. The superior and temporal quadrants of the retina appeared to be most susceptible to the light damage when comparing rats with or without ascorbate supplement. These findings suggested that ascorbate ameliorates the photic injury in rat retina.

Animals↗
PubMed1984

The postnatal reduction of the uncrossed projection from the nasal retina in the cat.

We have investigated the postnatal reduction of the uncrossed projection from the nasal retina in the cat by injecting horseradish peroxidase into one optic tract of kittens and cats and retrogradely labeling the cells in the ipsilateral retina that have an uncrossed projection to the brain. The newborn kitten has over 600 uncrossed cells in the nasal retina. The number is reduced to about one-quarter of that value by postnatal day 10. The two adult cats examined had 75 and 100 of these ipsilaterally projecting nasal cells. They are distributed all across the nasal retina, and most have the morphology characteristic of gamma cells. A lesion in one optic tract in the newborn kitten results in an increase in the number of cells from the nasal retina with an ipsilateral projection at maturity. There are more of these cells in the region that has been depleted of ganglion cells by the lesion. This excess consists mostly of gamma and epsilon cells. These findings indicate that competitive factors play a role in the elimination of inappropriate ganglion cell projections in the cat, and that this process contributes to the precision of the nasotemporal division of the retina.

Amidines↗
PubMed1980

Investigations into whether 5-hydroxytryptamine is a neurotransmitter in the retina of rabbit and chicken.

A system of indoleamine-accumulating neurons exists in the retina of several species, but the exact transmitter of these neurons is not known. 5-Hydroxytryptamine (5-HT) is a likely candidate, but there are conflicting reports on its amount in the retina. We have determined the amounts of 5-HT with two sensitive, specific, and independent methods. Because the content was found to be lower than what was expected for a neurotransmitter, the rate-limiting enzyme in the 5-HT synthesis was also estimated, as was the effect of 5-HT on cyclic AMP content of the retina. In the rabbit the 5-HT content was found to be 25 to 35 ng/gm wet weight, with not difference between light- and dark-adapted animals. There was no detectable activity of the rate-limiting enzyme tryptophan hydroxylase. It was not possible to raise the 5-HT concentration by treating the rabbits with a monoamine oxidase inhibitor and L-tryptophan. 5-HT induced no change in the cyclic AMP content of the rabbit retina. In both newly hatched and older chicken retina, the 5-HT concentration was higher than in rabbit. The 5-HT concentrations in all retinas were lower than would be expected for a monoamine neurotransmitter, and these results argue against 5-HT being the neurotransmitter of the indoleamine-accumulating neurons.

Adenosine Monophosphate↗
PubMed1980

Binding and uptake of the GABA analogue, 3H-muscimol, in the retinas of goldfish and chicken.

Gamma-aminobutyric acid (GABA) is a candidate as a neurotransmitter in the vertebrate retina. The GABA analogue muscimol has been used to probe the properties of GABA receptors in other parts of the vertebrate central nervous system (CNS). We thus used 3H-muscimol to investigate potential GABA receptors in the retinas of goldfish and chick by means of biochemical assay techniques and light microscopic autoradiography. In both animals 3H-muscimol shows specific and saturable binding with a dissociation constant (KD) of about 10 nM. GABA effectively inhibits 3H-muscimol binding at 50% inhibitory concentration (IC50) of 10(-6) M. The labeling pattern of 7 x 10(-7) M 3H-muscimol shows common features for both species in that amacrine cell bodies are intensely labeled, horizontal cells are much less so, and there is a laminar pattern throughout the inner plexiform layer (IPL). A 1 mM concentration of GABA abolishes 3H-muscimol labeling in the chick retina and throughout much of the goldfish retina except for some label over amacrine cells and the distal two thirds of the IPL. The intense somatic labeling suggests neuronal uptake of 3H-muscimol, and indeed, virtually all 3H-muscimol labeling is abolished with the addition of 0.4 mM ouabain. The uptake pattern of 3H-GABA differs from that of 3H-muscimol and is largely unaffected by the addition of 1 mM muscimol. We conclude that 3H-muscimol binding in retinas can be adequately demonstrated biochemically but that only 3H-muscimol uptake is observed with autoradiography from tissue conventionally processed through Epon. The fact that GABA can inhibit 3H-muscimol uptake whereas the reverse is not the case shows that the transport carriers for muscimol and GABA are different. Finally, the strong degree of 3H-muscimol uptake by retinal neurons raises serious questions about the use of 3H-muscimol as a probe for GABA synaptic receptors in the retina with autoradiography.

Animals↗
PubMed1984

Serotonin systems in the inner and outer plexiform layers of the vertebrate retina.

In retinas of certain nonmammalian vertebrate species such as frog, pigeon, and chick, serotonin appears to function as the neurotransmitter of a specific population of amacrine cells. Neurochemical and morphological studies have demonstrated high endogenous levels of 5-hydroxytryptamine (5-HT) as well as uptake, release, and receptor-binding activity restricted to the inner plexiform layer. In retinas from most mammalian species, uptake, release, and receptor-binding activity have also been localized to amacrine cell terminals in the inner plexiform layer. However, serotonin content in mammalian retinas is low, and attempts to localize the endogenous store of 5-HT have failed. Thus the status of serotonin as a candidate in mammalian retina is still open to question. Our more recent studies have revealed a light-sensitive serotonin system associated with photoreceptor terminals in retinas of Long-Evans rats. Uptake, synthesis, and release of [3H]serotonin have been demonstrated. Endogenous levels of 5-HT decrease in the dark and increase in the light. Electrophysiological studies are needed to illucidate the functional role(s) of serotonin within retinas of different species.

Animals↗
PubMed1978

Postembryonic development of the visual system of the locust, Schistocerca gregaria. I. Patterns of growth and developmental interactions in the retina and optic lobe.

The visual system of the locust, Schistocerca gregaria, has a highly ordered and predictable arrangement of neurons. The retina and the outermost layer, or lamina, of the optic lobe are each composed of repeating units, ommatidia and cartridges respectively. Each ommatidium has eight photoreceptor cells, which send axons directly to a group of five neurons in the lamina to form the cartridge. The importance, for the development of this precise pattern, of the mode of growth of the two arrays and of interactions between them was investigated. The spatial and temporal sequences of cell proliferation, differentiation and death in the developing retina and optic lobe were examined quantitatively under normal and experimental conditions. The retina grows from its anterior margin by addition of new ommatidia formed from recruited epidermal cells. The lamina also grows by addition of new neurons to its anterior margin, but these neurons are derived from a stem cell population. The parallel pattern of growth of the retina and lamina may be important for the formation of neuronal connexions between them. The retina grows and differentiates even when deprived of the underlying lamina. In laminae deprived of the ingrowth of new axons from the retina, the production of new neurons is also autonomous, but these neurons do not differentiate, but degenerate. A limited amount of cell death occurs in the laminae of control insects. These two observations suggest that a plausible mechanism for coordinating the sizes of the two arrays during normal development might be production of lamina neurons in excess of requirements and death of those remaining non-innervated.

Animals↗
PubMed1995

HIV-1 and HHV-6 antigens and transcripts in retinas of patients with AIDS in the absence of human cytomegalovirus.

PURPOSE: The purpose of this study was to define the agents involved in the development of acquired immune deficiency syndrome (AIDS)-associated retinitis. To achieve this goal, the authors determined the frequency and proximity of the simultaneous presence of human immunodeficiency virus (HIV)-1, human herpesvirus (HHV)-6, and human cytomegalovirus (HCMV) in retinas of patients with AIDS with and without AIDS-associated retinitis. METHODS: Retinal sections from 50 globes from patients with AIDS were analyzed for the presence of viral antigens and transcripts. Group 1 contained 13 globes from patients with HCMV infection. Group 2 contained 20 globes from patients with retinal lesions of uncertain etiology in which HCMV antigen and transcripts were not detected. Group 3 contained 17 globes from patients with no retinal lesions. RESULTS: Retinal sections from all 13 globes (group 1) were positive for HCMV antigens and HIV-1 antigens and transcripts. Six of the 13 retinas were also positive for HHV-6 antigens and transcripts. Sections from 13 of the 20 globes (group 2) were positive for HIV-1 antigens and transcripts, and 5 of these 13 were also positive for HHV-6 antigens and transcripts. Multiple areas in sections from two of the HIV-1-positive retinas showed coinfection with HHV-6. All 17 globes (group 3) were positive for HIV-1 antigens and transcripts. Ten of these 17 retinas were also positive for HHV-6 antigens. Human cytomegalovirus antigens were not detectable in retinas from groups 2 and 3. No viral antigens or transcripts were detectable in retinal sections from 10 HIV-1 negative donors. CONCLUSION: The coexistence of HIV-1 and HHV-6 activity in more than 50% of retinas without HCMV infection suggests that HIV-1 and HHV-6 alone or in combination may predispose retinal tissue to other opportunistic agents such as HCMV during the development of AIDS-associated retinitis.

AIDS-Related Opportunistic Infections↗
PubMed1994

Surface structure of rabbit and human retina after enzymatic separation of inner limiting membrane.

In order to investigate the structure of the retina without the overlying inner limiting membrane (ILM), the ILM was separated from the retina in rabbit and human specimens by enzymatic digestion with matrisolve and trypsin. Human specimens were taken from the area between the optic disc and the fovea, while rabbit specimens were taken from 5 mm below the medullary ray. The rabbit specimens were immersed and digested in 0.05% trypsin, while the human specimens were immersed and digested in crude matrisolve. Digestion was carried out before fixation. The structure of the denuded retina without the overlying ILM was observed by scanning electron microscopy (SEM) following enzymatic digestion. In both the human and rabbit specimens, the ILM appeared to be a structure that was independent from the retina. The surface of the denuded retina appeared to be covered with Müller cell footplates, which appeared in cobblestone arrangement in rabbit specimens and in mosaic arrangement in human specimens. Adhesion between the ILM and the retina seemed to be maintained by a biochemical matrix that was digested by proteinases, in both rabbit and human specimens.

Aged↗
PubMed1995

Use of the MIB-1 antibody for detecting proliferating cells in the retina.

PURPOSE: To study intraretinal proliferation as a response to experimental retinal detachment using an antibody that recognizes the nuclear specific antigen Ki-67 in proliferating cells. METHODS: Experimental retinal detachments were produced in cats (1, 3, 7, and 28 days) and rabbits (1, 3, and 7 days). The animals were killed and the eyes were fixed and embedded in paraffin. Histologic sections were processed for immunohistochemistry using the MIB-1 antibody to detect the Ki-67 protein. Labeled cells were identified, and the proliferative response was quantified. RESULTS: In normal cat retina, approximately 0.05 cells per millimeter of retina are labeled. In cat retina detached for 1, 3, 7, or 28 days, the number of cells labeled by MIB-1 is 0.06, 5.03, 1.38, and 0.23 cells per millimeter of retina, respectively. MIB-1 labeling yields an approximate fivefold increase over the number of proliferating cells detected in retinal sections using 3H-thymidine autoradiography. Detachment of the rabbit retina elicits a similar response as measured by MIB-1 immunohistochemistry. CONCLUSIONS: In contrast to 3H-thymidine, which labels cells in S-phase only, the MIB-1 antibody labels proliferating cells regardless of their location within the cell cycle. MIB-1 labeling, therefore, is a more accurate means of evaluating cellular proliferation in the retina and elsewhere in the central nervous system, and it is a relatively simple way of evaluating the effects of agents that may affect this response.

Animals↗
PubMed1994

Superoxide dismutase in developing mouse retina.

Superoxide dismutase (SOD) activity and the production site of H2O2 were studied in the developing mouse retina. The H2O2 production site moved from the inner to the outer region within the outer nuclear layer between the ages of 4 days through 12 days. This shift occurred in parallel with the development of the inner segments of the photoreceptor layer. SOD activity increased significantly at the age of 2-3 weeks. Both manganese-SOD (Mn-SOD) and copper-zinc SOD (Cu,Zn-SOD) activities (combined mean) in the retina of mice older than 2 weeks of age were 1.9 times greater in comparison with those of mice at the age of 2 weeks and younger. The mRNA of Cu,Zn-SOD did not change during these periods, suggesting that the translational efficiency of the mRNA and/or the stability of the SOD enzyme might increase, or the active form of the enzyme might increase during the development of the retina. The results of this study indicate that the localization and production of active oxygen change during the development of the mouse retina, and that SOD activity does exist in the retina from birth, increasing as its role in the protective system against active oxygen increases in the maturing mouse retina.

Animals↗
PubMed1994

Angiotensin II-like immunoreactivity in the retina of some mammalian species.

The decapeptide angiotensin II (AngII) is a circulating hormone and the most important endogenous vasoconstrictor. In the central nervous system (CNS), AngII has been reported to have a transmitter-like function. In the retina angiotensin I (AngI), the precursor protein of AngII, and AngI-converting enzyme (ACE), the rate-limiting enzyme for AngII synthesis, are present. Both ACE inhibition and application of an AngII antagonist affect the b-wave of the electroretinogram. In the present study we used immunocytochemical techniques to identify putative AngII-containing cells in the bovine, cat, and rabbit retina. In the rabbit retina, faintly labeled amacrine cells were visible at the inner border of the inner nuclear layer. Preincubation with protease inhibitors (PI) resulted in an enhanced immunoreaction and in the labeling of ganglion cells and fibers in the inner plexiform layer. In the bovine retina, AngII-like immunoreactivity was detectable only after preincubation with PI. Under these conditions, ganglion cells and amacrine cells as well as cells in more distal parts of the inner nuclear layer were stained. In the cat retina, AngII-like immunoreactivity was detectable only after preincubation with PI and exogenous AngII. Photoreceptor and ganglion cells showed an enhanced AngII-like immunoreaction, and amacrine cells were stained preferably in clusters that were irregularly distributed within the retina. Our results demonstrate that AngII is a putative neurotransmitter in a subpopulation of mammalian amacrine cells.

Angiotensin II↗
PubMedDate not supplied

Putrescine, polyamines, and N1-acetylpolyamine levels in retina, visual cortex and cerebellum of free-running mice kept under continuous light or darkness.

Putrescine, spermidine and spermine levels were detected in the retina, visual cortex, cerebellum and parietal cortex of CD1 mice exposed to 36h continuous light or darkness. Retinal putrescine and polyamine concentrations were found to be highest in dark-adapted mice, and the stimulation of dark-adapted retina with flicker illumination was also accompanied by a significant decrease in putrescine, spermidine and spermine levels. In visual cortex as well as in cerebellum spermidine and spermine contents were higher in dark-adapted mice in comparison to light-exposed animals, while in parietal cortex no significant change was found neither in spermidine nor spermine levels. In the brain areas studied flicker illumination produced no significant decreases in putrescine and polyamine contents. The total polyamines expressed as putrescine equivalents were noticeably decreased in retina, visual cortex and cerebellum of light-adapted mice. In the retina spermine/spermidine molar ratio was significantly higher than in dark-adapted mice. The administration of N1, N2-bis-(2,3-butadienyl)-1,4-butanediamine (MDL 72527) produced a strong decrease of retinal putrescine and spermidine concentrations in both dark-adapted and light-exposed mice, and in the retina of mice exposed to continuous light a significant decrease in the spermine level was also observed. According to the influence on polyamine reutilization, after the irreversible inhibition of polyamine oxidase by MDL 72527, in the retina N1-acetylspermidine and N1-acetylspermine accumulation was highest in light-adapted mice. On the contrary in visual cortex, cerebellum and parietal cortex the MDL 72527 administration produced a more marked decrease of putrescine and spermidine contents in mice kept in continuous darkness.

Animals↗
PubMed1993

[Expression of modified nucleoside, 1-methyladenosine in intraocular tumors and the retinas].

1-methyladenosine is one of the modified nucleosides, the levels of which are elevated in urine of patients with malignant tumors. We report herein immunohistological expression of 1-methyl-adenosine in tumor cells and retinas. Eight retinoblastomas, 4 malignant melanomas, two metastatic choroidal tumors, 3 retinal dysplasias, one intraocular hemorrhage and 5 normal eye retinas in human were examined. In addition, 8 experimental rabbit choroidal tumor XV2s, and 5 normal rabbit retinas were examined. 1-Methyladenosine was expressed in almost all malignant tumors and retinas with these tumors, while there was little expression in benign tumor cells, retinas with benign tumor and retinas in normal eyes. Results in rabbits were almost the same as in humans. Examination of expression of 1-methyladenosine is expected to be useful for the histological diagnosis of intraocular tumors.

Adenosine↗
PubMed1993

Oxygen distribution in the macaque retina.

PURPOSE: Oxygen distribution was characterized in the macaque retina, which is more like the human retina than others studied previously. METHODS: Profiles of oxygen tension (PO2) as a function of distance were recorded in a parafoveal region about halfway between the fovea and optic disk, and from the fovea in one animal. A one-dimensional diffusion model was used to determine photoreceptor oxygen consumption (QO2). RESULTS: In the parafovea, the PO2 decreased as the electrode was withdrawn from the choroid toward the inner retina, reaching a minimum value during dark adaptation of about 9 mmHg at about 70% retinal depth, and then increasing more proximally. Approximately 90% of the oxygen requirement of the photoreceptors was supplied by the choroidal circulation and 10% by the retinal circulation. In light adaptation, there was a monotonic PO2 gradient from the choroid to the inner retina, indicating that all of the oxygen used by photoreceptors was supplied by the choroid. In the fovea, the choroid supplied almost all the oxygen in both dark and light adaptation, with a minor supply from the vitreous humor. Dark-adapted foveal oxygen consumption was lower than parafoveal oxygen consumption. Light reduced the oxygen consumption of the photoreceptors, in both regions studied, by 16-36%. CONCLUSIONS: The results show that oxygenation of the parafoveal monkey retina is similar to that previously observed in the cat area centralis. In the fovea, the oxygen distribution differs as expected considering the thinner retina and the absence of inner retinal neurons and retinal circulation.

Animals↗