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PubMed1991

Differential expression and localization of brain-type and mitochondrial creatine kinase isoenzymes during development of the chicken retina: Mi-CK as a marker for differentiation of photoreceptor cells.

The expression and the cellular- as well as subcellular-distribution of brain-type B-CK and mitochondrial Mi-CK during development of the chicken retina was studied by immunoblotting, immunofluorescence and immunogold methods. B-CK expression and accumulation in retina was high from early stages of embryonic development on, decreased slightly around hatching and remained high again during adulthood. At early stages of development (days 2-5), B-CK was more or less evenly distributed over the entire retina with the exception of ganglion cells, which were stained more strongly for B-CK than other retinal precursor cells. Then, at around day 10, the beginning of stratified immunostaining by anti-B-CK antibody was noted concomitant with progressing differentiation. Finally, a dramatic increase in staining of the differentiating photoreceptor cells was seen before hatching (day 18) with weaker staining of other cell types. At hatching, as in the adult state, most of the B-CK was localized within rods and cones. Thus, during retinal development marked changes in the immunostaining pattern for B-CK were evident. By contrast, Mi-CK expression was low during development in ovo and rose just before hatching with a predominant accumulation of this isoenzyme within the ellipsoid portion of the inner photoreceptor cell segments. Mi-CK accumulation in the retina coincided with functional maturation of photoreceptors and therefore represents a good marker for terminal differentiation of these cells. B-CK, present from early stages of retina development, seems to be relevant for the energetics of retinal cell proliferation, migration and differentiation, whereas the simultaneous expression of both B- and Mi-CK around the time of hatching indicates a coordinated function of the two CK isoforms as constituents of a PCr-circuit involved in the energetics of vision, which, in autophagous birds, has to be operational at this point in time.

Animals↗

PubMed2005

Expression and function of the neuronal gap junction protein connexin 36 in developing mammalian retina.

With the advent of transgenic mice, much has been learned about the expression and function of gap junctions. Previously, we reported that retinal ganglion cells in mice lacking the neuronal gap junction protein connexin 36 (Cx36) have nearly normal firing patterns at postnatal day 4 (P4) but many more asynchronous action potentials than wild-type mice at P10 (Torborg et al. [2005] Nat. Neurosci. 8:72-78). With the goal of understanding the origin of this increased activity in Cx36-/- mice, we used a transgenic mouse (Deans et al. [2001] Neuron 31:477-485) to characterize the developmental expression of a Cx36 reporter in the retina. We found that Cx36 was first detected weakly at P2 and gradually increased in expression until it reached an adult pattern at P14. Although the onset of expression varied by cell type, we identified Cx36 in the glycinergic AII amacrine cell, glutamatergic cone bipolar cell, and retinal ganglion cells (RGCs). In addition, we used calcium imaging and multielectrode array recording to characterize further the firing patterns in Cx36-/- mice. Both correlated and asynchronous action potentials in P10 Cx36-/- RGCs were significantly inhibited by bath application of an ionotropic glutamate receptor antagonist, indicating that the increase in activity was synaptically mediated. Hence, both the expression patterns and the physiology suggest an increasing role for Cx36-containing gap junctions in suppressing RGC firing between waves during postnatal retinal development.

Animals↗

PubMed1977

Pseudophakic retinal detachment.

Our experiences with a small group of patients who had intraocular lens implants performed at the time of cataract extraction, and who subsequently developed retinal detachment are reviewed. The technical problems related to retinal detachment surgery in the presence of intraocular lenses and the results of this surgery are summarized.

Adult↗

PubMed1999

Activin family members in the developing chick retina: expression patterns, protein distribution, and in vitro effects.

We have investigated whether the activin family of growth factors is involved in the regulation of retinal cell differentiation. Immunocytochemistry and in situ hybridization have shown that activin/inhibin subunits alpha, betaA, and betaB; receptors II and IIB; follistatin; and a follistatin-like gene are expressed in different regions of the chick embryo retina in developmentally regulated patterns. When tested in dissociated retinal cultures, activin did not appear to affect cell survival or proliferation, but it exerted marked inhibitory effects on the differentiation of photoreceptors, while stimulating the differentiation of nonphotoreceptor neurons; both effects were concentration-dependent and follistatin-sensitive. The results are consistent with the possibility that activin family members play significant roles in the regulation of retinal development.

Activin Receptors↗

PubMed1989

Development of neuropeptide Y-immunoreactive neurons in the rat retina.

Neuropeptide Y-like immunoreactivity (NPY-LI) was examined in the rat retina by radioimmunoassay and immunocytochemistry during prenatal and postnatal development. NPY-LI appears late in gestation (embryonic day [E18]), at which time it is present in small quantities (0.038 +/- 0.005 pm/mg protein) and the NPY-LI is confined to cells in the ganglion cell layer. The concentration of NPY-LI rises steadily over pre- and postnatal development; and on postnatal day 6 (P6), immunoreactive cells first appear in the inner nuclear layer. At eye opening (P13), there is a large increase in NPY-LI (0.207 +/- 0.035 pm/mg protein), and immunoreactive cells can be seen in the innermost row of the inner nuclear layer (INL) as well as in the ganglion cell layer (GCL). As the retina matures, the levels of NPY-LI fall to adult levels (0.080 +/- 0.019 pm/mg protein) and the peptide is confined to two subpopulations of cells, one in the INL and one in the GCL. The transient increase in NPY-LI at eye opening suggests that it may have a role at this time in modulating developing retinal circuitry. This pattern is very different from that of somatostatin-like immunoreactivity which appears earlier in development in high quantities and decreases prior to synaptogenesis and eye opening.

Aging↗

PubMed2000

Progressive outer retinal necrosis caused by herpes simplex virus type 1 in a patient with acquired immunodeficiency syndrome.

OBJECTIVE/BACKGROUND: To identify the etiologic agent of rapidly progressive outer retinal necrosis (PORN) in a 32-year-old man with acquired immunodeficiency syndrome (AIDS), who had retinitis developed from cytomegalovirus (CMV). Multiple yellowish spots appeared in the deep retina without evidence of intraocular inflammation or retinal vasculitis, diagnosed clinically as PORN. Death occurred after failure of multiple organs. DESIGN: Case report. METHODS: Both globes were taken at autopsy, fixed in formalin, and examined histopathologically and immunohistochemically to identify causative agents in the retinal lesions. MAIN OUTCOME MEASURE: Immunohistochemistry. RESULTS: All layers of the retina were severely damaged and contained focal calcification. Cytomegalic inclusion bodies were found in cells in the damaged retina of the right eye. Immunohistochemical studies for herpesviruses revealed the presence of CMV antigens in the right retina at the posterior pole and herpes simplex virus type 1 (HSV-1)-specific antigen in the periphery of both retinas. No varicella-zoster virus (VZV) antigen was detected in either retina. CONCLUSIONS: PORN has been described as a variant of necrotizing herpetic retinopathy, occurring particularly in patients with AIDS. Although the etiologic agent has been reported to be VZV, HSV-1 can be an etiologic agent.

AIDS-Related Opportunistic Infections↗

PubMed2000

Quantitation of peripheral blood cytomegalovirus DNA for monitoring recurrent cytomegalovirus retinitis in pediatric solid organ transplant recipients.

Cytomegalovirus (CMV) infection is a major concern following solid organ transplantation, especially in the pediatric population who remain at high risk of primary infection. CMV disease leads not only to increased patient and graft morbidity, but also to increased health care costs. This study describes the usefulness of a quantitative CMV polymerase chain reaction (PCR) technique for monitoring peripheral blood CMV DNA in pediatric recipients of kidney and liver allografts who had recurrent CMV retinitis. The incidence of CMV disease in 28 pediatric transplant recipients was 28.6%, one-half of whom developed retinitis. Two of these patients had recurrent retinitis on cessation of anti-viral treatment. A peripheral blood CMV DNA copy number of > or =500/microg of DNA was associated with recrudescence of the retinitis in these patients. We conclude that the measurement of peripheral blood CMV DNA by PCR is a useful tool for the surveillance of disease resolution and recurrence. This is particularly important in patients with CMV retinitis, who may remain asymptomatic for a period of time, despite recurrences.

Adolescent↗

PubMed1984

Retinal vein occlusion: C-reactive protein and arterial hypertension.

Eighty-six patients with retinal vein occlusion (37 with central, 49 with branch vein occlusion) and 31 patients with treated essential arterial hypertension were investigated for comparison to an age-matched control group. Serum C-reactive protein (CRP) levels, erythrocyte sedimentation rate (ESR) and plasma viscosity were measured. Serum CRP levels (log10 values) were significantly elevated in patients, with hypertension (P less than 0.001) or with retinal vein occlusion (P less than 0.001) compared to control. The highest mean value of serum CRP were found in patients with both hypertension and retinal vein occlusion, and the values of ESR and serum CRP were significantly higher in this group when compared to normotensive patients with retinal vein occlusion (P less than 0.05 and P less than 0.01, respectively) or to control (P less than 0.001). Increased inflammatory activity may be present in patients with hypertension or retinal vein occlusion. In particular hypertensive patients with elevated serum CRP levels may be more at risk of developing retinal vein occlusion.

Blood Cell Count↗

PubMed1994

Tenascin-contactin/F11 interactions: a clue for a developmental role?

To understand how the extracellular matrix glycoprotein tenascin modifies cell adhesion and neurite outgrowth, we sought to isolate cellular receptors for tenascin. So far, two completely different cell surface ligands for tenascin have been detected. This we achieved by affinity chromatography of tissue extracts and of isolated proteins over tenascin-Sepharose and by solid-phase assays using the individual proteins. The first receptor, the neuronal cell adhesion molecule contactin/F11, a member of the immunoglobulin superfamily, binds to tenascin via a site in the N-terminal immunoglobulin-like domains. The binding site is within the fibronectin type III homology region at the boundary of the alternatively spliced region of tenascin, requiring that fibronectin type III homology domains 5 and 9 be adjacent, as they are in the 190 kD tenascin isoform. The close similarity in tertiary structure between type III domains and immunoglobulin-like repeats raises the possibility that we are observing a side-by-side interaction between the two molecules in a manner closely analogous to that between paired immunoglobulin domains. The second receptor is the heparan sulfate proteoglycan, glypican, which, similarly to contactin/F11, is anchored to the membrane via glycosylphosphatidylinositol. Glypican bound to a column of tenascin-Sepharose cannot be dissociated by chondroitin sulfate or dermatan sulfate, but elutes in a broad peak with a gradient of heparan sulfate and in a sharper peak with heparin. By means of fusion proteins, we have identified a potential binding site on the fifth fibronectin type III homology domain of tenascin. We are trying to define these sites more closely by means of site-directed mutagenesis. It will be interesting to see whether the interaction between tenascin and cell surface contactin/F11, and possibly cellular heparan sulfate proteoglycans, contributes to the prominent role played by tenascin in pattern formation during development of the nervous system. In a first step, we have examined the distribution of tenascin isoforms and contactin/F11 during retinal development by means of immunohistochemistry and in situ hybridization with tenascin isoform-specific probes. Tenascin isoforms 190/200 along with contactin/F11 are particularly prominent in the inner and outer plexiform layers of embryonic day 8 retina in the chick. This coordinate up-regulation was confirmed both by immunoblots and Northern blots of retinal extracts. A speculative model is presented to suggest how the unique hexabrachion may signal the cell via contactin/F11.

Amino Acid Sequence↗

PubMed2001

Effects of retinoic acid upon eye field morphogenesis and differentiation.

This study describes a whole embryo and embryonic field analysis of retinoic acid's (RA) effects upon Xenopus laevis forebrain development and differentiation. By using in situ and immunohistochemical analysis of pax6, Xbf1, and tyrosine hydroxylase (TH), gene expression during eye field, telencephalon field, and retinal development was followed with and without RA treatment. These studies indicated that RA has strong effects upon embryonic eye and telencephalon field development with greater effects upon the ventral development of these organ fields. The specification and determination of separate eye primordia occurred at stage-16 when the prechordal plate reaches its most anterior aspect in Xenopus laevis. Differentiation of the dopaminergic cells within the retina was also affected in a distinct dorsoventral pattern by RA treatment, and cell type differentiation in the absence of distinct retinal laminae was also observed. It was concluded that early RA treatments affected organ field patterning by suppression of the upstream elements required for organ field development, and RA's effects upon cellular differentiation occur downstream to these organ determinants' expression within a distinct dorsoventral pattern.

Animals↗

PubMedDate not supplied

Transcriptional factors involved in photoreceptor differentiation.

Regenerative medicine constitutes a potentially promising therapy for blind people suffering from retinal degenerative diseases such as retinitis pigmentosa and age-related macular degeneration. For the realization of retinal regeneration, it is necessary to establish 1) a method to produce functional photoreceptor cells in vitro and 2) successful transplantation of the donor cells to connect their axons to the recipient secondary neurons so that they can function properly. The results of experimental transplantation of human retinal photoreceptor cells from cadaveric eyes or of fetal retinal cells into the retina of RP patients have not been satisfactory, but encouraging enough to indicate that the transplantation of developing retinal cells may have beneficial results. Recently, attempts have been made to generate photoreceptor-like cells from stem cells, but it remains to be seen whether they are in fact photoreceptor cells. It is therefore important to fully understand the mechanisms involved in the development of these cells, and to characterize them not only by transcriptome but also by functional analysis.

Animals↗

PubMedDate not supplied

Morphological characterization of the retinal degeneration in three strains of mice carrying the rd-3 mutation.

Retinal development in 3 strains of rd-3/rd-3 mutant mice, previously shown to have different rates of degeneration, was studied using light, electron, and immunofluorescence microscopy. The time course and phenotype of the degeneration as well as details on the mechanism of massive photoreceptor cell loss are compared with other known retinal degenerations in mice. Up until postnatal day (P) 10, the retinas of all three strains (RBF, 4Bnr, In-30) develop similarly to those of pigmented and nonpigmented controls. TUNEL-positive cells appear in the outer nuclear layer (ONL) by P14, and reach a maximum in all three mutant strains around P21. Scattered rods and cones form a loose, monolayered ONL by 8 weeks in the albino RBF strain, by 10 weeks in the albino 4Bnr strain, and by 16 weeks in the pigmented In-30 strain. Though the initial degeneration begins in the central retina, there is no preferred gradient of cell death between central and peripheral photoreceptors. Rods and cones are present at all ages examined. During development, stacks of outer segments (OS) form in all three strains though they never achieve full adult lengths, and often have disorganized, atypical OS. Rod opsin is expressed in the developing OS but is redistributed into plasma membrane as OS degeneration proceeds. Retinal pigment epithelial (RPE) cells of all mutant strains contain packets of phagocytosed OS, and their apical processes associate with the distal ends of the OS. At their synaptic sites, photoreceptor terminals contain ribbons apposed to apparently normal postsynaptic triads. As photoreceptors are lost, Müller cells fill in space in the ONL but they do not appear to undergo significant hypertrophy or migration, though during the degeneration, glial fibrillary acidic protein (GFAP) expression is gradually upregulated. Macrophage-like cells are found frequently in the subretinal space after the onset of photoreceptor apoptosis. As OS disappear, the RPE apical processes revert to simple microvilli. Late in the degeneration, some RPE cells die and neighboring cells appear to flatten as if to maintain confluence. In regions of RPE cell loss that happen to lie above retina where the ONL is gone, cells of the inner nuclear layer (INL), wrapped by Müller cell processes, may front directly on Bruch's membrane.

Aging↗

PubMed1998

Randomized retinal ganglion cell axon routing at the optic chiasm of GAP-43-deficient mice: association with midline recrossing and lack of normal ipsilateral axon turning.

During mammalian development, retinal ganglion cell (RGC) axons from nasal retina cross the optic chiasm midline, whereas temporal retina axons do not and grow ipsilaterally, resulting in a projection of part of the visual world onto one side of the brain while the remaining part is represented on the opposite side. Previous studies have shown that RGC axons in GAP-43-deficient mice initially fail to grow from the optic chiasm to form optic tracts and are delayed temporarily in the midline region. Here we show that this delayed RGC axon exit from the chiasm is characterized by abnormal randomized axon routing into the ipsilateral and contralateral optic tracts, leading to duplicated representations of the visual world in both sides of the brain. Within the chiasm, individual contralaterally projecting axons grow in unusual semicircular trajectories, and the normal ipsilateral turning of ventral temporal axons is absent. These effects on both axon populations suggest that GAP-43 does not mediate pathfinding specifically for one or the other axon population but is more consistent with a model in which the initial pathfinding defect at the chiasm/tract transition zone leads to axons backing up into the chiasm, resulting in circular trajectories and eventual random axon exit into one or the other optic tract. Unusual RGC axon trajectories include chiasm midline recrossing similar to abnormal CNS midline recrossing in invertebrate "roundabout" mutants and Drosophila with altered calmodulin function. This resemblance and the fact that GAP-43 also has been proposed to regulate calmodulin availability raise the possibility that calmodulin function is involved in CNS midline axon guidance in both vertebrates and invertebrates.

Animals↗

PubMed2002

Transplanted sheets of human retina and retinal pigment epithelium develop normally in nude rats.

This study investigated whether transplanted sheets of human fetal retina together with its retinal pigment epithelium (RPE) could develop and maintain their cytoarchitecture after long survival times. Transplant recipients were nine albino athymic nu/nu rats with a normal retina. The donor tissue was dissected from fetuses of 12-17 weeks gestational age. Transplants were analyzed at 5-12 months after surgery by light and electron microscopy, and immunohistochemistry with various antibodies specific for rhodopsin, S-antigen, transducin, neurofilament and synaptophysin. In 4 of 11 transplants, the RPE stayed as a monolayer sheet and supported the development of the retinal sheet with a normal lamination, including photoreceptor inner and outer segments. Cones and rods in the organized transplants were labeled with different photoreceptor markers. Inner and outer plexiform layers, containing cone pedicles and rods spherules, were immunoreactive for synaptophysin. As the recipients had a normal retina, transplant/host integration was not expected. However, at the transplant/host interface, there were sometimes areas without glial barriers, and neurofilament-containing processes could be observed crossing between transplant and host. In other, more disorganized transplants, the RPE cells were partially dispersed or clumped together in clusters. Such transplants developed photoreceptors in rosettes, often with inner and outer segments. In conclusion, sheets of human fetal retina transplanted together with its RPE to the subretinal space of nude rats can develop and maintain perfectly laminated transplants after long survival times, indicating the potential of applying cotransplantation to human patients with retinal diseases.

Animals↗

PubMedDate not supplied

GABA-induced increases in [Ca2+]i in retinal neurons of postnatal rabbits.

Previous studies have indicated that gamma-aminobutyric acid (GABA) plays an important trophic role in the synapse formation between horizontal cells and photoreceptors in postnatal rabbit retina. However, the mechanism of the GABA effect has not been identified. Using fluo-3 Ca2+ imaging and confocal laser scanning microscopy we examined the effect of GABA on [Ca2+]i during postnatal retinal development. GABA (100 microM) evoked a fast and transient increase of [Ca2+]i in selected populations of freshly dissociated retinal cells from postnatal rabbits. This increase was apparent on postnatal day 1 and reached a maximum on day 5. Little increase in [Ca2+]i was observed in retinal cells isolated from adult rabbits. GABA receptor antagonists, picrotoxin and bicuculline, significantly reduced the response. The GABAB agonist, baclofen, did not evoke any [Ca2+]i changes. The GABA-induced increase in [Ca2+]i was observed in all retinal layers in neonatal retinal whole-mount explants. In the outer retina, the increase was seen in cone photoreceptors which were specifically labeled with peanut agglutinin (PNA). The GABA-induced increase in [Ca2+]i may provide an important mechanism for regulating cone synaptogenesis in the outer plexiform layer of the postnatal retina.

Animals↗

PubMed2000

[Posterior segment involvement in HIV-related eye disease after commencement of highly-active antiretroviral therapy (HAART)].

The panel of therapeutic options available for the treatment of retroviral disorders has expanded explosively in recent years with the result that it has now become possible to reconstitute the immune function of individuals with advanced HIV-disease to a remarkable degree. The ophthalmologist is thus confronted with completely new clinical situations, courses of treatment and decisions. For example, a CMV-retinitis developing within six weeks of the onset of HAART does not necessarily require specific treatment, and reactivation of a retinitis within the same time span is often barely distinguishable from an inflammatory reaction induced by the reconstituted lymphocytes. Marked cellular infiltration of the vitreous--in the absence of an active retinal or chorioretinal lesion--is the hallmark of this immune-recovery vitreitis and responds nicely to systemic steroid treatment. In the course of retinitis, macular edema and epiretinal membrane formation are not uncommonly responsible for visual impairment. If, on the other hand, immunological parameters remain stable during the course of three months, i.e., if the CD4 cell count is more than 150-250 microliters and the plasma load of HIV-1 is less than 5-10,000 copies/microliter, then what has until now been deemed to be a lifelong therapy for CMV-retinitis may be interrupted, provided the clinical (i.e., retinal) situation can be controlled on a regular basis. In this article, an attempt is made to discuss and interpret clinical findings pertaining to posterior segment involvement in ocular HIV disease, with a view to guiding the clinical practitioner in his/her course of action.

AIDS-Related Opportunistic Infections↗

PubMed2001

neurogenin2 elicits the genesis of retinal neurons from cultures of nonneural cells.

neurogenin2 (ngn2) encodes a basic helix-loop-helix transcription factor and plays an important role in neurogenesis from migratory neural crest cells. Its role in retinal development is poorly understood. We observed that in the developing chick retina, ngn2 was expressed in a subpopulation of proliferating progenitor cells. Ectopic expression of ngn2 in nonneural, retinal pigment epithelial cell culture triggered de novo generation of cells that expressed neural-specific markers and exhibited neuronal morphologies. Further molecular and morphological analyses showed that the main products of the induced neurogenesis were cells resembling young photoreceptor cells and cells resembling retinal ganglion cells. The generation of multiple cell types suggests that ngn2 induces various retinal pathways. Thus, unlike in the peripheral nervous system where ngn2 specifies one type of sensory neuron, ngn2 in the retina is likely involved in a common step leading to different cellular pathways. Our finding that ngn2 can instruct nonneural retinal pigment epithelial cells to differentiate toward retinal neurons demonstrates one possible way to induce de novo retinal neurogenesis.

Animals↗

PubMed1979

Infrequency of retinal neovascularization following central retinal vein occlusion attributed to endothelial death.

48 patients with central retinal vein occlusion by clinical diagnosis and 10 eyes by histopathological documentation were studied and reviewed. Only 1 eye developed retinal neovascularization. Rubeosis iridis occurs in 14% of clinical cases and all of histopathologic cases. 10 long-standing neovascular glaucoma enucleated eyes following central retinal vein occlusion show absence of retinal endothelial cells. The absence of retinal capillary endothelial cells seems to be significant in explaining the rare occurrence of retinal neovascularization following central retinal vein occlusion. However, the small number sampling may reflect a biased result. Further prospective studies with more cases and time observation are required to draw the final conclusion.

Capillaries↗