Localization and quantitation of blood-retinal barrier breakdown in experimental proliferative vitreoretinopathy.

Objective: To determine the contribution of the breakdown of the blood-retinal barrier (BRB) as measured with magnetic resonance imaging in the development of retinal detachment in an experimental model of proliferative vitreoretinopathy.

Methods: Contrast-enhanced magnetic resonance imaging was used to evaluate BRB breakdown in an intravitreal cell-injection model of proliferative vitreoretinopathy. Intravitreal injection of 2.

Bipolar surface electrical stimulation of the vertebrate retina.

Background: Retinitis pigmentosa with attendant photoreceptor loss can cause a profound visual handicap. We have postulated that an intraocular prosthesis that could electrically stimulate the inner retina might provide vision to some of these patients. For such a prosthesis to be feasible, electrical stimulation of the inner retina must elicit a focal retinal response.

Rate-dependent, nonlinear photoablation of ocular tissue at 308 nm.

To quantify the dependence on pulse repetition rate of 308 nm laser ablation in ocular tissue and elucidate the photoablation mechanisms involved, 85 full-thickness ab interno sclerostomies were created in six human donor eyes using an 800-microns-diameter quartz optical fiber. A laser pulse duration of 135 ns, fluence of 31 mJ/mm2, and a fixed repetition rate between 5 and 40 Hz were used for 38 sclerostomies; the remaining 47 sclerostomies were completed at various laser settings during initial experimentation. Surprisingly, the numbers of pulses required for complete penetration of the optical fiber through the fixed tissue thickness were not constant as expected but decreased nonlinearly with increasing repetition rate.

Stimulation by the antioxidant thioproline of the lymphocyte functions of old mice.

Diet supplementation with thioproline (thiazolidine-4-carboxylic acid), an intracellular sulfhydryl antioxidant and free radical scavenger, may slow the aging process of metazoans and prolongs their life span. In the present experiment Swiss mice fed thioproline (0.07%, w/w) from 13 to 22 months of age were used.

Chromosomal homologies between Drosophila lebanonensis and D. melanogaster determined by in situ hybridization.

Twelve biotin-labelled recombinant DNA probes were hybridized to polytene chromosomes of Drosophila melanogaster and D. lebanonensis. Probes were chosen in order to cover the whole chromosomal complement.

Intraocular gnathostomiasis.

The clinical and histologic features of an intraocular parasite from a 29-year-old woman are reported. The live organism was located in the posterior vitreous near the optic disc and was successfully removed by vitreous aspiration. The parasite was identified as an advanced stage larvae of Gnathostoma spinigerum.

In vivo imaging of breakdown of the inner and outer blood-retinal barriers.

Real-time contrast-enhanced magnetic resonance imaging (MRI) was used to distinguish between experimentally induced breakdown of the vascular (inner) and retinal pigment epithelial (RPE; outer) blood-retinal barrier (BRB) in vivo. Pigmented rabbits were treated with intravenous sodium iodate 30 mg/kg, (a specific RPE cell poison), intravitreal N-ethylcarboxamidoadenosine (NECA) 10(-3) mol/l (which specifically disrupts the vascular BRB), or retinal diode laser photocoagulation. Coronal T1-weighted proton images were acquired in a timed sequence after intravenous injection of gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA).

Accurate and precise measurement of blood-retinal barrier breakdown using dynamic Gd-DTPA MRI.

Dynamic T1-weighted magnetic resonance imaging (MRI) after the injection of Gd-DTPA is a promising method for investigating breakdown of the blood-retinal barrier (BRB). Previously, the authors demonstrated that in a T1-weighted image, the initial rate of change in the vitreous water MRI signal as gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA) enters the vitreous space strongly correlated with the extent of BRB breakdown. Here, a practical approach to measuring a more relevant physiologic parameter is presented: the permeability surface area product (PS).

Morphometric analysis of macular photoreceptors and ganglion cells in retinas with retinitis pigmentosa.

There have been a number of histopathologic studies of retinas that were taken post mortem from patients with retinitis pigmentosa (RP), but few have addressed the question of transneuronal degeneration of ganglion cells secondary to photoreceptor death. We studied sectioned maculae that were obtained from 41 patients with different genetic forms of RP: autosomal dominant (n = 11); X-linked (n = 9); and simplex (n = 21). We also studied sectioned maculae that were taken from 20 age-matched normal subjects.

Characterization and purification of Adh distal promoter factor 2, Adf-2, a cell-specific and promoter-specific repressor in Drosophila.

Chromatin footprinting in Drosophila tissue culture cells has detected the binding of a non-histone protein at +8 of the distal Adh RNA start site, on a 10-bp direct repeat motif abutting a nucleosome positioned over the inactive Adh distal promoter. Alternatively the active promoter is bound by a transcription initiation complex. We have characterized and purified a protein Adf-2 that binds specifically to this direct repeat motif 5'TCTCAGTGCA3', present at +8 and -202 of the distal RNA start site.

Treatment with intravitreal steroid reduces blood-retinal barrier breakdown due to retinal photocoagulation.

The effect of corticosteroid treatment on blood-retinal barrier breakdown caused by argon-laser panretinal photocoagulation was evaluated in the rabbit eye. One day before photocoagulation, eyes were given either a sub-Tenon (20-mg) or intravitreal (2-mg) injection of triamcinolone acetonide. The severity of blood-retinal barrier breakdown was measured after photocoagulation using rapid sequential magnetic resonance imaging following intravenous administration of gadolinium diethylenetriaminepentaacetic acid.

Transmission electron microscopic study of a subretinal choroidal neovascular membrane due to age-related macular degeneration.

From a patient with age-related macular degeneration we studied ultrastructurally a disciform scar that was removed from an eye with a vitreous hemorrhage. In cross section, the scar was divided by a retinal pigment epithelial (RPE) cell layer. The choroidal side consisted of fibrovascular tissue with active neovascular buds and inflammatory cells, including macrophages attached to the RPE basement membrane.

Blood-retinal barrier breakdown caused by diode vs argon laser endophotocoagulation.

We compared the effects of argon and diode laser endophotocoagulation on blood-retinal barrier breakdown using real-time magnetic resonance imaging following intravenous gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA) injection. Endophotocoagulation was performed on eyes of pigmented rabbits with either the argon or the diode laser to produce ophthalmoscopically similar lesions. Magnetic resonance imaging studies were performed either 2 or 7 days after laser treatment, and coronal T1-weighted proton images were obtained in the first 20 minutes following Gd-DTPA injection.

Scleral buckling surgery for stage 4B retinopathy of prematurity.

Results of scleral buckling in 15 consecutive eyes of 13 infants with stage 4B retinopathy of prematurity (ROP) were reviewed. Ten of 15 retinas achieved macular reattachment with a single scleral buckling procedure. Four of 15 retinas unable to be attached by scleral buckling were reattached after the addition of a single vitreous operation.

Retinal oxygenation and laser treatment in patients with diabetic retinopathy.

The oxygen tension in the preretinal vitreous cavity was measured in human patients undergoing vitreous operations for proliferative diabetic retinopathy. The oxygen tension was significantly higher (P = .004) over areas of retina that had been treated with panretinal photocoagulation than it was over untreated areas in the same retina.

Microgravity effects on Drosophila melanogaster development and aging: comparative analysis of the results of the Fly experiment in the Biokosmos 9 biosatellite flight.

The results are presented of the exposure of Drosophila melanogaster to microgravity conditions during a 15-day biosatellite flight, Biokosmos 9, in a joint ESA-URSS project. The experimental containers were loaded before launch with a set of Drosophila melanogaster Oregon R larvae so that imagoes were due to emerge half-way through the flight. A large number of normally developed larvae were recovered from the space-flown containers.

Oxygen-induced mitochondrial damage and aging.

Although the views of Harman and Gerschman provide a reasonable explanation for many of the effects of aging, they fail to explain why many cell types, from amoebae to mammalian spermatogonia, do not show a time-related involution, while other cells (especially the neurons) change with age. We feel that a better understanding of senescence (from the molecular to the organ and organismic levels) can be gained by integrating the free radical theory of aging with the classic concepts of Minot and Pearl on the role of cell differentiation and metabolic rate in, respectively, triggering and pacing senescence. In agreement with the above, we maintain that aging is the non-programmed but unavoidable "side effect" of oxy-radical damage to the membrane and genome of the mitochondria of irreversibly differentiated cells.

Blood-retinal barrier breakdown investigated by real-time magnetic resonance imaging after gadolinium-diethylenetriaminepentaacetic acid injection.

Recent magnetic resonance imaging (MRI) studies show that gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA) entry into the vitreous space can be used as a qualitative marker of blood-retinal barrier (BRB) disruption. To determine if a more quantitative measurement of BRB breakdown could be obtained, the utility of acquiring real-time, T1-weighted proton images was studied after Gd-DTPA injection. Two days before the MRI experiment, panretinal photocoagulation was done.

Altered distribution of basic fibroblast growth factor in diabetic retinopathy.

Basic fibroblast growth factor (FGF) is a potent endothelial cell mitogen that has been proposed to play a role in proliferative diabetic retinopathy and other neovascular processes. Our understanding of the in vivo role of basic FGF in the pathogenesis of these disorders is limited. We studied the immunolocalization of basic FGF in 16 clinical cases of diabetic retinopathy to determine whether the normal retinal distribution of basic FGF changed during the development of diabetic retinopathy and correlated with the onset of retinal neovascularization.

ADH and phylogenetic relationships of Drosophila lebanonesis (Scaptodrosophila).

Increasing data on Drosophila alcohol dehydrogenase (ADH) sequences have made it possible to calculate the rate of amino acid replacement per year, which is 1.7 x 10(-9). This value makes this protein suitable for reconstructing phylogenetic relationships within the genus for those species for which no molecular data are available such as Scaptodrosophila.

Primary culture of human retinal glia.

Glial cells of the human retina participate in various pathologic processes characterized by cell migration, proliferation, and extracellular matrix production. To study these events in vitro, a procedure was developed to obtain primary cultures of human retinal glial cells. The cultures resulting from the processing of 130 globes contained cells with variable morphology including bipolar and multipolar or stellate cells.