Amino acid signatures in the detached cat retina.

PURPOSE: Expressions of certain macromolecules are altered by experimental retinal detachment in the cat. Related alterations in micromolecular signatures of neurons, Müller cells, and the retinal pigment epithelium (RPE) were investigated. METHODS: High-performance immunochemical mapping, image registration, and quantitative pattern recognition were combined to analyze the amino acid contents of virtually all retinal cell types after 3 to 84 days of detachment. RESULTS: Retinal micromolecular signatures showed a spectrum of alterations. The glutamate contents of Müller cells increased and remained elevated for weeks after detachment. Multispectral signatures of Müller cells showed massive metabolic instability in early detachment stages that ultimately resolved as a homogeneous profile significantly depleted in glutamine. Retinal pigment epithelial cell signals also changed dramatically, displaying an initial glutamate spike and then a prolonged decline, even as taurine levels followed an opposite pattern of initial loss and slow restoration. Neurotransmitter signatures of surviving neurons showed extensive precursor-level variation, and, in one case, GABAergic horizontal cells displayed anomalous sprouting. CONCLUSIONS: Dramatic changes in Müller cell amino acid signatures triggered by retinal detachment are partially consistent with losses in glutamine synthetase activity. Taurine signal variations suggest that orthotopic RPE cells attempt to regulate abnormal taurine concentrations in the enlarged subretinal space. Surviving neurons possess characteristic neurotransmitter signals, but their metabolite regulation seems abnormal. On balance, microchemical and structural anomalies develop in the detached cat retina that represent serious barriers to recovery of normal visual function.

Amino acid signatures in the normal cat retina.

PURPOSE: To establish a nomogram of amino acid signatures in normal neurons, glia, and retinal pigment epithelium (RPE) of the cat retina, guided by the premise that micromolecular signatures reflect cellular identity and metabolic integrity. The long-range objective was to provide techniques to detect subtle aberrations in cellular metabolism engendered by model interventions such as focal retinal detachment. METHODS: High-performance immunochemical mapping, image registration, and quantitative pattern recognition were combined to analyze the amino acid contents of virtually all cell types in serial 200-nm sections of normal cat retina. RESULTS: The cellular cohorts of the cat retina formed 14 separable biochemical theme classes. The photoreceptor --> bipolar cell --> ganglion cell pathway was composed of six classes, each possessing a characteristic glutamate signature. Amacrine cells could be grouped into two glycine- and three gamma-aminobutyric acid (GABA)-dominated populations. Horizontal cells possessed a distinctive GABA-rich signature completely separate from that of amacrine cells. A stable taurine-glutamine signature defined Müller cells, and a broad-spectrum aspartate-glutamate-taurine-glutamine signature was present in the normal RPE. CONCLUSIONS: In this study, basic micromolecular signatures were established for cat retina, and multiple metabolic subtypes were identified for each neurochemical class. It was shown that virtually all neuronal space can be accounted for by cells bearing characteristic glutamate, GABA, or glycine signatures. The resultant signature matrix constitutes a nomogram for assessing cellular responses to experimental challenges in disease models.

Pattern recognition of amino acid signatures in retinal neurons.

Pattern recognition of amino acid signals partitions the cells of the goldfish retina into nine statistically unique biochemical theme classes and permits a first-order chemical mapping of virtually all cellular space. Photoreceptors, bipolar cells, and ganglion cells display a set of unique, nominally glutamatergic type E1, E1+E2, and E4 signatures, respectively. All horizontal cells are assignable to a GABAergic gamma 2 class or a non-GABAergic class with a glutamate-rich E3 signature. The amacrine cell layer is largely a mixture of (1) a taurine-dominated T1 Müller's cell signature and (2) GABAergic gamma 1, glycinergic G1, and dual glycinergic/GABAergic G gamma 1 amacrine cell signatures. Several major conclusions emerge from this work. (1) Glutamatergic, GABAergic, and glycinergic neural signatures and glial signatures account for over 99% of the cellular space in the retina. (2) All known neurons in the goldfish retina are associated with a set of conventional nonpeptide neurotransmitters. (3) Multiple forms of metabolic profiles are associated with a single nominal neurotransmitter category. (4) Glutamate and aspartate contents exhibit overlapping distributions and are not adequate univariate probes for identifying cell classes. (5) Signatures can serve as quantitative measures of cell state.

Amino acid signatures in the primate retina.

Pattern recognition of amino acid signals partitions virtually all of the macaque retina into 16 separable biochemical theme classes, some further divisible by additional criteria. The photoreceptor-->bipolar cell-->ganglion cell pathway is composed of six separable theme classes, each possessing a characteristic glutamate signature. Neuronal aspartate and glutamine levels are always positively correlated with glutamate signals, implying that they largely represent glutamate precursor pools. Amacrine cells may be parsed into four glycine-dominated (including one glycine/GABA immunoreactive population) and four GABA-dominated populations. Horizontal cells in central retina possess a distinctive GABA signature, although their GABA content is constitutively lower than that of amacrine cells and shows both regional and sample variability. Finally, a taurine-glutamine signature defines Müller's cells. We thus have established the fundamental biochemical signatures of the primate retina along with multiple metabolic subtypes for each neurochemical class and demonstrated that virtually all neuronal space can be accounted for by cells bearing characteristic glutamate, GABA, or glycine signatures.