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Medical AI Inquiry: You was designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.  Labels: OBJECTIVE, METHODS, RESULTS. Meshes: Alkylating Agents, Animals, Biomarkers, Disease Models, Animal, Fluoresceins, Guinea Pigs, In Situ Nick-End Labeling, Injections, Macaca mulatta, Methylnitrosourea, Mice, Mice, Inbred C57BL, Microscopy, Fluorescence, Peanut Agglutinin, Photoreceptor Cells, Vertebrate, Retinal Cone Photoreceptor Cells, Retinal Degeneration, Rhodamines, Staining and Labeling, Vitreous Body.
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Does intravitreal injection of fluorochrome-conjugated peanut agglutinin result in specific and reversible labeling of mammalian cones in vivo? Context: To investigate whether intravitreally injected peanut agglutinin (PNA) conjugated with a fluorochrome can specifically label retinal cones in vivo and to evaluate its clinical potential. Fluorescein- or rhodamine-conjugated PNA (0.005%-0.5%) was intravitreally injected into anesthetized mouse, guinea pig, or monkey and retinas were removed at various intervals for fluorescence microscopy. Immunofluorescence and TUNEL assay were carried out to investigate whether PNA injection adversely affected other retinal neurons. Gross visual function was studied in a visual cliff test. The retina of an N-methyl, N-nitrosourea (MNU)-induced mouse model of retinal degeneration was stained with PNA to evaluate how spatiotemporal pattern of the staining would reflect the progression of degeneration. Intravitreally injected PNA resulted in specific labeling of cone outer and inner segments and cone pedicles within 30 minutes over the entire retina and in all tested species. The labeling was reversible; cones did not show any labeling 3 weeks after the injection but could be restained with PNA. TUNEL signal and expression pattern of several retinal proteins in PNA-injected mouse retina were indistinguishable from normal. Similarly, visual behavior of mouse 10 hours after the injection was normal. The pattern of PNA labeling in mice with MNU-induced retinal degeneration showed progressive disappearance of cones from the center to the periphery.
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Intravitreal injection of fluorochrome-conjugated PNA results in specific and reversible labeling of mammalian cones in vivo without causing any gross adverse effects. This novel method may eventually provide a clinical tool to examine diseased retina. Final Decision: yes