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At least 1,477 records · Page 82Linked to original sources
PubMed1996

Cytomegalovirus antigenemia in acquired immunodeficiency syndrome patients with untreated cytomegalovirus retinitis.

PURPOSE: To determine the frequency of cytomegalovirus (CMV) viremia in patients with acquired immunodeficiency syndrome (AIDS) and untreated CMV retinitis using conventional cell culture isolation and the sensitive CMV antigenemia assay. METHODS: We examined 24 AIDS patients with ophthalmologic diagnosis of untreated CMV retinitis and 24 AIDS patients without present or past retinitis (control patients) from three medical centers between September 1992 and March 1994. Cytomegalovirus antigenemia was detected by an indirect peroxidase staining in 300,000 cytocentrifuged neutrophils, using a mixture of murine monoclonal antibodies directed against the pp65 lower matrix protein of CMV. RESULTS: Positive antigenemia was demonstrated in eight (33.3%) of the 24 retinitis patients and in none of the 24 control patients (P < .001). Only two of the eight antigenemia-positive patients had a concurrent positive CMV isolation from blood leukocytes by conventional cell culture assay. CONCLUSIONS: These results emphasize the risk of extraocular disease in AIDS patients with CMV retinitis because the virus is often present in peripheral blood leukocytes. The CMV antigenemia assay may be a simple and rapid means of identifying those patients with unilateral retinitis at highest risk of developing CMV retinitis of the fellow eye or of visceral CMV disease if intravitreal injections or implants are used as sole treatment for CMV retinitis.

AIDS-Related Opportunistic Infections↗
PubMed1978

Human retinal dysplasia.

We studied the ultrastructure of the four types of dysplastic rosettes and compared them with retinoblastoma rosettes. Dysplastic rosettes have morphologic characteristics intermediate between the normal photoreceptor layer and retino-blastoma rosettes; Müller cells contribute to the formation of dysplastic but not neoplastic rosettes. Abnormality in the relationship between the retina and the retinal pigment epithelium is frequent in cases with spontaneously occurring retinal dsyplasia and is consistent with previous observations that the retinal pigment epithelium influences the development of retinal morphology and function. We believe the normal developmental sequence of cell death and disappearance of necrotic cells may have gone awry in retinal dysplasia.

Abnormalities, Multiple↗
PubMedDate not supplied

Light deprivation suppresses the light response of inner retina in both young and adult mouse.

The retinal synaptic network continues its development after birth in mammals. Recent studies show that postnatal development of retinal circuitry depends on visual stimulation. We sought to determine whether there is a time period during which the retina shows evidence of increased plasticity. We examined the effects of light deprivation on the retinal light response of mouse retina using electroretinogram (ERG) measurements. Our results showed that dark rearing mice from birth to postnatal day (P) 30, 60, and 90 suppressed the amplitudes of oscillatory potentials (OPs) and the magnitudes of suppression were age independent. In addition, dark-rearing-produced suppression of OP amplitudes can be completely reversed in both young and adult mice by returning them to cyclic light/dark conditions for 1 to 2 weeks. However, the recovery time course was age dependent with younger animals needing a longer time to achieve a full recovery. Furthermore, dark rearing of P60 mice raised under cyclic light/dark conditions for 30 days resulted in a similar magnitude of suppression of OP amplitudes as in age-matched mice dark reared from birth. These findings demonstrate that both the normal developmental changes and the maintenance of mature inner retinal light response in adult animals require visual stimulation. These results indicate a degree of activity-dependent plasticity in mouse retina that has not been previously described.

Aging↗
PubMed1999

Cytomegalovirus retinitis in advanced HIV-infected patients treated with protease inhibitors: incidence and outcome over 2 years.

We prospectively studied the incidence of cytomegalovirus (CMV) retinitis in 93 patients treated with highly active antiretroviral therapy (HAART) containing a protease inhibitor (PI), during a median follow-up period of 24 months. The median initial CD4+ count was 22 cells/microl (range, 1-311 cells/microl), and the median plasma HIV viral load was 5.1 log10 copies/ml (range, 2.4-6.4 log10 copies/ml). The fundus was examined monthly in patients with a history of CMV retinitis or an initial CD4+ count <50 cells/microl and every 3 months in the other patients. Of patients with previously controlled CMV retinitis, 1 of 7 relapsed. In addition, 6 of 59 patients with a CD4+ count <50 cells/microl and no history of CMV retinitis before starting PI therapy developed CMV retinitis. Of them, 3 had at least one relapse during follow-up. CD4+ counts were <40 cells/microl at the time of primary or recurrent CMV retinitis, except in two cases (147 cells/microl and 203 cells/microl). In conclusion, the incidence of CMV retinitis was 0.091 per patient-year among study subjects with advanced HIV infection who were receiving HAART (95% confidence interval [CI], 0.037-0.145). The time to progression of CMV retinitis (mean, 215 days; 95% CI, 113-317 days) was longer than reported before widespread use of PIs.

AIDS-Related Opportunistic Infections↗
PubMed1989

Axial myopia increases the risk of retinal complications after neodymium-YAG laser posterior capsulotomy.

We conducted a retrospective analysis of Q-switched neodymium-YAG laser capsulotomies performed in 122 eyes between April 1984 and June 1987. Retinal complications occurred in 3 (2.5%) of 121 eyes followed up for 1 year and in 2 (3.6%) of 55 eyes followed up for 2 years. Four eyes developed rhegmatogenous retinal detachments and 1 developed an acute symptomatic retinal tear. No patients developed clinical cystoid macular edema (visual acuity 20/30 or worse). These retinal complications were significantly correlated with axial myopia, preexisting vitreoretinal disease, male gender, younger age, vitreous prolapse into the anterior chamber, and spontaneous extension of the capsulotomy.

Adolescent↗
PubMed1997

Migration and synaptogenesis of cone photoreceptors in the developing mouse retina.

Mouse retinal photoreceptor cell generation and morphogenesis take place in a well-characterized temporal sequence. Both rod and cone photoreceptor differentiation and synaptogenesis occur postnatally, but the relative timing of these events has been difficult to document due to the paucity of cell-specific markers. We have found that antibodies to neuron-specific enolase (NSE) preferentially label a subpopulation of photoreceptors in the outer nuclear layer (ONL) of the mouse retina in addition to labeling ganglion, amacrine, bipolar, and horizontal cells within the inner layers of the retina. The appearance of NSE immunoreactivity in the different classes of retinal neurons during development showed a close temporal relationship to the onset of expression of the synaptic vesicle-associated protein SV2 and clearly preceded the sequential development of synaptic connections in both inner and outer synaptic layers. The NSE-immunoreactive photoreceptors were identified as cones by dual labeling of their inner segments with the lectin peanut agglutinin or by colabeling with antisera to cone photopigments. Axonal extensions of NSE-labeled cone cells were shown to interact with those of differentiating horizontal cells as early as postnatal day 3 (P3). Colocalization of NSE with SV2 indicated that cone cells began to make synaptic contacts with horizontal cell processes several days prior to the development of rod synaptic terminals. Between P4 and P11, cone photoreceptor cell nuclei were observed to be scattered at various levels throughout the ONL and thus appeared to have become displaced from their previous position directly beneath the outer limiting membrane (OLM). By P12, the cone nuclei had migrated sclerad once again and were now observed to be neatly aligned adjacent to the OLM. In the rd mouse mutant, this migratory process was delayed, so that, at P12, positioning of the cone cell nuclei within the ONL was still quite irregular. Thus, we have identified a late migratory phase for cone photoreceptors during the second week after birth that correlates with the timing of maturation of the rod synaptic terminals just prior to eye opening. The types of cues used by maturing cone cells for their eventual sclerad location remain to be elucidated.

Animals↗
PubMed1994

[Development of epimacular membrane following rhegmatogenous retinal detachment surgery].

To understand the development of epimacular membrane following rhegmatogenous retinal detachment surgery, we studied 105 eyes which had undergone scleral buckling procedure. The membrane was observed in 25 eyes (24%) one month after surgery, and showed gradual increase in its occurrence up to some 50% at nine months postoperatively. Eyes without preoperative posterior vitreous detachment showed no membrane during the postoperative course. A comparison between preoperative detached macula cases with intact macula cases revealed that the occurrence of the membrane was higher in the intact macula cases, being 68% at 12 months after surgery.

Adolescent↗
PubMed2001

Retinal pigment epithelial tear after transpupillary thermotherapy for choroidal neovascularization.

PURPOSE: To describe two patients who developed a retinal pigment epithelial tear after transpupillary thermotherapy for choroidal neovascularization. METHOD: Case reports. RESULTS: Retinal pigment epithelial (retinal pigment epithelium) tear developed in 2 (8%) of 25 eyes after transpupillary thermotherapy for occult choroidal neovascularization associated with age-related macular degeneration. In both eyes, the retinal pigment epithelium tear developed between the treatment session and first post-treatment examination. In both eyes, the visual acuity was unchanged, but the complication of retinal pigment epithelium tear may result in decreased visual acuity when transpupillary thermotherapy is performed in an eye with good initial visual acuity. CONCLUSION: Retinal pigment epithelium tear appears to occur more frequently after transpupillary thermotherapy for poorly defined choroidal neovascularization than after conventional laser photocoagulation for poorly defined choroidal neovascularization.

Aged↗
PubMed1994

The eye in bone marrow transplantation. VI. Retinal complications.

OBJECTIVE: To evaluate the posterior segment ocular complications of patients undergoing bone marrow transplantation (BMT). DESIGN: Retrospective analysis. SETTING: Academic ophthalmology department at a tertiary care hospital with a BMT unit. PATIENTS: Patients undergoing BMT were seen by an ophthalmologist for clinical care and enrolled in a long-term follow-up study, during which they were seen 6 and 12 months after the transplantation and annually thereafter. RESULTS: Of 397 patients undergoing BMT, 51 (12.8%) developed posterior segment complications. Fourteen patients (3.5%) developed hemorrhagic complications with either intraretinal and/or vitreous hemorrhages and 17 patients (4.3%) developed cotton-wool spots in the fundus of both eyes. Eleven patients (2.8%) had bilateral optic disc edema, with eight cases attributed to the toxic effects of cyclosporine and three to other causes. Two patients (0.5%) developed serious retinal detachments. Eight patients (2.0%) developed infectious retinitis and/or endophthalmitis. Fungal infections with Candida or Aspergillus usually occurred within 120 days after BMT, while viral infections with herpes zoster or cytomegalovirus and parasitic infections with Toxoplasma occurred later. Intraocular lymphoma occurred in one patient (0.2%). CONCLUSION: Severe, potentially vision-threatening, posterior segment complications following BMT occur due to a variety of causes.

Adult↗
PubMed2001

Cell-type specific dendritic contacts between retinal ganglion cells during development.

The extent of a neuron's dendritic field defines the region within which information is processed. The dendritic fields of functionally distinct ON and OFF center retinal ganglion cells (RGCs) form separate mosaics across the retina. Within each mosaic, neighboring dendritic fields overlap by a constant amount, sampling the visual field with the appropriate coverage. Contact-mediated lateral inhibition between neighboring RGCs has long been thought to regulate both the extent and overlap of dendritic fields during development. Here we show that dendro-dendritic contact exists between developing RGCs and occurs in a manner that would regulate the formation of ON and OFF mosaics separately. Dye-filled neighboring ON and OFF ferret alpha RGCs were reconstructed using multiphoton microscopy. At all neonatal ages examined, we observed dendro-dendritic contacts between RGCs of the same sign (ON/ON; OFF/OFF), but never between cells of opposite signs (ON/OFF). Terminal dendrites of one cell often touched a dendrite of its neighbor as they intersected. In some instances, the distal dendrite of one cell formed a fascicle with the proximal process of its neighbor. Alpha cells did not form contacts with neighboring beta cells of the same sign. Together, these observations suggest that dendro-dendritic contact between RGCs is cell-type specific. Dendritic contacts were observed even before the alpha cell arbors were completely stratified, suggesting that cell-cell recognition may take place early in their development. For each cell type, the relative overlap of dendritic fields was constant with age, despite a two-fold increase in field area. We suggest that dendro-dendritic contacts may be sites of intercellular signaling that could regulate local extension of dendrites to maintain the relative overlap of RGCs within a mosaic during development.

Animals↗
PubMed1996

Experimental posttraumatic Bacillus cereus endophthalmitis in a swine model. Efficacy of intravitreal ciprofloxacin, vancomycin, and imipenem.

PURPOSE: The authors compare the intravitreal efficacy of ciprofloxacin, vancomycin and imipenem, in treating experimental Bacillus cereus endophthalmitis. METHODS: Thirty-three Yorkshire pigs received a surgically induced injury to the right eye, which was then repaired and injected with 8400 colony forming units of live B. cereus. Nine pigs received no therapy and served as a natural history group. Twenty-four other pigs then were randomized into a treatment group with ciprofloxacin (n = 6), vancomycin (n = 6), imipenem (n = 6), or normal saline (n = 6). Eyes were examined clinically 1, 2, 3, 4, 5, 6, 8, 12, and 24 hours after inoculation. After 24 hours, the eyes were enucleated for histologic study. RESULTS: Experimental disease was characterized by an aggressively developing endophthalmitis, with retinitis and vitritis developing at 4 hours. Histologic examination showed vitreous abscess and retinal necrosis. Both vancomycin- and imipenem-treated group had less inflammation and tissue destruction than control animals, based on the Wilcoxon rank sum test (P < 0.05). Ciprofloxacin-treated animals showed significantly more intraocular destruction and were indistinguishable from controls. CONCLUSION: Vancomycin and imipenem appear to limit inflammation and tissue destruction when given early in the course of experimental posttraumatic endophthalmitis caused by B. cereus. Results with ciprofloxacin are less conclusive and warrant further investigation.

Animals↗
PubMed1990

Target dependence of chick retinal ganglion cells during embryogenesis: cell survival and dendritic development.

The survival of retinal ganglion cells and the dendritic development were investigated a) in normal chick embryos, b) in embryos whose primordial optic lobes and adjacent areas were removed (target reduced embryos), and c) in embryos whose optic nerves were transected (target deprived embryos) in order to study the influences of central targets on developing ganglion cells. The ganglion cells were stained postmortem with the carbocyanine dye DiI. Cell body and dendritic field diameters were measured in whole-mounted retinae before and after the period of cell death at embryonic day 10 (E10) and E16. The cell densities within the ganglion cell layer were counted in cresyl violet/thionine stained retinae. The central retinal projection in target reduced embryos was studied with the anterogradely transported fluorescent marker rhodamine-B-isothiocyanate (RITC). In normal embryos, the earliest dendritic processes were observed at E6 in the central retina, whereas at E10 elaborate dendritic branching was found across the retina. Different morphological types of ganglion cells could be identified at E16. In both, target reduced embryos and target deprived embryos, the initial dendritic growth and pattern of ramification were indistinguishable from those of normal embryos up to E10. Cell body diameters, dendritic tree diameters, and cell densities were not significantly different. At the end of the naturally occurring cell death period (E16), the ganglion cell density was strongly reduced in both experimental groups compared to controls. In particular, when the optic nerve was transected, it resulted in the almost complete degeneration of ganglion cells. In target reduced embryos, a small population (about 5% of the normal number) of ganglion cells survived. The proportion of large cells was increased within the total population compared to normal retinae. Displaced ganglion cells were not affected by partial target removal but strongly affected by transection of the optic nerve. Anterograde labelling from the retina revealed that in target reduced embryos the remaining ganglion cells innervated non-tectal primary visual nuclei. The present results suggest the following: a) Before the onset of the cell death period, the growth and ramification of ganglion cell dendrites occur independently of central visual targets. b) In target reduced embryos, a small population of ganglion cells survives, namely, those cells that project to remaining central areas. Complete disconnection from central targets by transecting the optic nerve leads to the degeneration of almost all ganglion cells. c) The surviving ganglion cell population consists mainly of large ganglion cells.

Animals↗
PubMed1993

Chiasmatic course of temporal retinal axons in the developing ferret.

Recent studies on the distribution of optic axons in the mature visual pathways, as well as on the genesis of their ganglion cells of origin, suggest that the time of axonal arrival at the optic chiasm determines the side of the brain to which a temporal retinal axon will project. The present study has examined this issue directly in fetal ferrets, by determining the projection of the temporal retina at different developmental stages. Fetuses of known gestational age were fixed with paraformaldehyde and subsequently implanted with crystals of the carbocyanine dye, DiI, into either the temporal retina, or into one optic tract. The lipophilic diffusion of the dye within the plasma membrane of the axons revealed the course of temporal retinal fibers through the fetal chiasm, as well as the distribution of ganglion cells across the two retinae projecting to one optic tract. During early fetal stages, the temporal retina extends axons preferentially into the ipsilateral optic tract: the early retinal projection shows a classical partial decussation pattern. During later fetal stages, temporal retinal axons can be traced into both optic tracts, and the distribution of cells with crossed and uncrossed optic axons in the temporal retina is overlapping. These results indicate that the mature decussation patterns of retinal ganglion cell classes are not primarily the consequence of regressive phenomena such as cell death; rather, they are formed as axons navigate the chiasmatic region during development. The differences in decussation pattern between cell classes arise from the fact that the mechanisms producing the segregation of nasal and temporal retinal axons at the chiasm must change as development proceeds.

Animals↗
PubMed1993

Prenatal development of excitability in cat retinal ganglion cells: action potentials and sodium currents.

The development of precise retinofugal projections is dependent on activity-mediated events, but as yet nothing is known about the ontogeny of excitable membrane properties in retinal ganglion cells (RGCs). In order to begin to understand how functional maturity is attained in these neurons, whole-cell patch-clamp recordings were obtained from acutely dissociated RGCs of fetal and postnatal timed-pregnant cats. Current-clamp recordings revealed a pronounced developmental increase in the proportion of RGCs capable of generating action potentials. At embryonic day 30 (E30), 5 weeks before birth and during a time when RGCs are still being generated, electrical stimulation elicited spikes in only a third of the cells. None of these neurons were capable of multiple discharges in response to maintained depolarization. The proportion of spiking neurons increased during ontogeny, such that by E55 all RGCs could be induced to generate action potentials, with the majority manifesting repetitive spiking patterns. Application of tetrodotoxin abolished spike activity of all fetal RGCs, indicating that sodium-mediated action potentials are present very early in development. At the same time, voltage-clamp recordings revealed significant ontogenetic modifications in several key properties of the sodium currents (INa). These were (1) a twofold increase in Na current densities; (2) a shift in the voltage dependence of both activation and steady state inactivation: with maturity, sodium currents activate at more negative potentials, while steady state inactivation of INa occurs at less negative potentials; and (3) a decrease in decay time constants of the Na current, at membrane potentials negative to -15 mV. These developmental changes were largely restricted to the period of axon ingrowth (E30-E38), suggesting that maturation of INa is not the limiting factor for the onset of activity-dependent restructuring of retinofugal projections.

Action Potentials↗
PubMed2005

The Pax6 isoform bearing an alternative spliced exon promotes the development of the neural retinal structure.

The vertebrate retina has an area where visual cells are closely packed for proper vision that is known as a fovea, an area centralis or a visual streak. The molecular mechanism that regulates the formation of these structures and visual cell gradients is unknown. The transcription factor Pax6 is a master regulator of eye development. A Pax6 isoform that contains an exon 5a-encoded 14 amino acid insertion in its paired domain, Pax6(+5a), has different DNA-binding properties compared with the Pax6(-5a) isoform. Little is known about the functional significance of Pax6(+5a). Here, we show that Pax6(+5a) is expressed especially in the retinal portion where visual cells accumulate during eye development and, when overexpressed, induces a remarkable well-differentiated retina-like structure. Pax6(+5a) proteins that bear point mutations that are found in patients with foveal hypoplasia are unable to induce these ectopic retina-like structures. We propose that Pax6(+5a) induces a developmental cascade in the prospective fovea, area centralis or visual streak region that leads to the formation of a retinal architecture bearing densely packed visual cells.

Alternative Splicing↗
PubMed1994

Effects of lead on temporal response properties of retinal ganglion cells in developing rats.

Neonatal rats have taken in lead, during the period from their parturition to their weaning, from the milk of dams fed with water containing 0.2% lead acetate solutions. The alterations in the temporal response properties of retinal ganglion cells in adult rats (90 days) following the lead exposure at their developing stage have been studied. The results of this investigation demonstrate that the lead exposure in neonatal rats causes decreases in the optimal temporal frequency, bandwidth at half amplitude, temporal resolution and response phase of the retinal ganglion cells in adult rats. Compared with the sustained cells, the transient cells have a much greater alteration in temporal response properties.

Action Potentials↗