Investigative ophthalmology & visual science
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Invest. Ophthalmol. Vis. Sci. · Aug 2004
Controlled drug release from an ocular implant: an evaluation using dynamic three-dimensional magnetic resonance imaging.
The ability of an episcleral implant at the equator of the eye to deliver drugs to the posterior segment was evaluated, using a sustained-release implant containing gadolinium-DTPA (Gd-DTPA). The movement of this drug surrogate was assessed with magnetic resonance imaging (MRI) in the rabbit eye. The results were compared with a similar implant placed in the vitreous cavity through a scleral incision at the equator. ⋯ In vivo, episcleral implants at the equator of the eye did not deliver a significant amount of Gd-DTPA into the vitreous, and no compound was identified in the posterior segment. A 30-fold increase in vitreous Gd-DTPA concentration occurred in the enucleated eyes, suggesting that there are significant barriers to the movement of drugs from the episcleral space into the vitreous in vivo. Dynamic three-dimensional MRI using Gd-DTPA, and possibly other contrast agents, may be useful in understanding the spatial relationships of ocular drug distribution and clearance mechanisms in the eye.
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Invest. Ophthalmol. Vis. Sci. · Jul 2004
Comparative StudyTear secretion induced by selective stimulation of corneal and conjunctival sensory nerve fibers.
To measure the increase in tear secretion evoked by selective stimulation of the different populations of sensory receptors of the cornea and conjunctiva by using moderate and intense mechanical, chemical, and cold stimuli. ⋯ Reflex tear secretion caused by corneal stimulation seems to be chiefly due to activation of corneal polymodal nociceptors, whereas selective excitation of corneal mechanonociceptors or cold receptors appears to be less effective in evoking an augmented lacrimal secretion. Conjunctival receptors stimulated at equivalent levels do not evoke an increased tear secretion.
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Invest. Ophthalmol. Vis. Sci. · Jul 2004
Ex vivo adenovirus-mediated gene transfer to corneal graft endothelial cells in mice.
Genetic modulation of donor tissue before corneal transplantation may have the potential to modulate alloimmunity and/or to prevent corneal endothelial cell death. This study was conducted to optimize adenovirus-mediated gene transfer to donor corneal endothelium and to delineate the kinetics of marker gene expression in syngeneic and allogeneic corneal grafts. ⋯ Adenoviral vector can selectively and efficiently deliver exogenous gene(s) to the endothelium of corneal grafts during hypothermic organ preservation. Gene expression is retained in vivo in corneal syngeneic grafts for longer periods than are allogeneic grafts.
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Invest. Ophthalmol. Vis. Sci. · Jun 2004
Pseudomonas aeruginosa with lasI quorum-sensing deficiency during corneal infection.
To understand the importance of Pseudomonas aeruginosa quorum-sensing systems in the development of corneal infection, the genotypic characteristics and pathogenesis of seven ocular isolates with low-protease and acyl homoserine lactone (AHL) activity and quorum-sensing mutants of PAO1 deficient in lasI, lasR, or rhlR were investigated in the study. ⋯ These results indicate that quorum-sensing deficiency may occur naturally in clinical isolates, and the possession of lasI and hence a functional Las quorum-sensing system may be important in development of corneal infection.
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Invest. Ophthalmol. Vis. Sci. · May 2004
Acetylcholine protection of adult pig retinal ganglion cells from glutamate-induced excitotoxicity.
To determine which glutamate receptor (GluR) subtypes are responsible for glutamate-induced excitotoxicity in cultured adult pig retinal ganglion cells (RGCs) and to characterize the neuroprotective effect of acetylcholine (ACh) on pig RGCs. ⋯ This was the first report of a modified panning technique to isolate adult pig RGCs. Cell viability was relatively high using this method, and both large and small RGCs grew extensive neurites in culture. The finding that both NMDA and non-NMDA GluRs were involved in glutamate-induced excitotoxicity suggests that isolated pig RGCs provide a good model for glaucoma. In addition, activation of AChRs may be useful in protecting RGC from excitotoxic insults occurring in neurodegenerative diseases such as glaucoma.