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PurposeTo compare the concentration of amino acids in subretinal and vitreous fluid of patients with primary rhegmatogenous retinal detachment to that of control vitreous.MethodsThis prospective, observational study measured amino-acid levels in subretinal fluid of patients undergoing scleral buckle placement (n=20) and vitreous fluid in patients undergoing pars plana vitrectomy (n=5) for primary retinal detachment. Vitreous fluid from patients undergoing vitrectomy for macular hole (n=7) or epiretinal membrane (n=3) served as a control. Subretinal fluid and control vitreous were analysed using high-pressure liquid chromatography. Retinal detachment vitreous was analysed using capillary electrophoresis-laser-induced fluorescence.ResultsMean levels of glutamate (27.0±1.7 μM), aspartate (4.1±4.0 μM), and glycine (44.1±31.0 μM) in subretinal fluid and glutamate (13.4±11.9 μM) in the vitreous were significantly elevated in retinal detachment compared to control vitreous. A significant, positive association was observed between levels of aspartate and glutamate in subretinal fluid (Spearman's correlation coefficient: 0.74, P<0.01). Mean arginine levels did not differ significantly between subretinal fluid and control vitreous. Levels of alanine, tyrosine, valine, isoleucine, leucine, and phenylalanine were significantly lower in subretinal fluid compared to control vitreous (all P<0.01).ConclusionsGlutamate levels in subretinal fluid and vitreous of patients with primary retinal detachment is significantly elevated in comparison to control vitreous. This finding lends further support to the hypothesis that elevated glutamate levels may result from ischaemia of the outer retina secondary to retinal detachment.Eye (2008) 22, 582–589; doi:10.1038/sj.eye.6702993; published online 19 October 2007 [ABSTRACT FROM AUTHOR]

By using matrix-assisted laser desorption/ionization time-of-flight MS, individual peptidergic neurons from Aplysia are assayed. A semiquantitative method is developed for comparing single-cell profiles by using spectral normalization, and peptides are localized to specific cells by mass spectrometric cell mapping. In addition to all previously identified products of the egg-laying hormone (ELH) gene, other peptides are formed from proteolytic hydrolysis of Leu-Leu residues within ELH and acidic peptide (AP). AP exhibits further processing to yield AP1-20 and AP9-27. These peptides appear to be colocalized in vesicles with ELH, transported to specific neuronal targets, and released in a Ca2+-dependent manner. A differential peptide distribution is observed at a specific target cell, and a low-frequency variation of AP, [Thr21]AP, is detected in a single animal.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI/TOF-MS) is a viable technique for the examination of biological environments. Clearly, sample preparation plays a pivotal role in the ability to obtain mass spectra from samples as complex as biological cells. The physiological salt concentrations associated with neurons from marine specimens interfere with MALDI analysis. A unique and simple rinsing procedure allows cellular clusters, individual neurons and connective tissues to be directly assayed for peptides with minimal sample handling. Isolated cells and tissues, including egg-laying hormone-releasing cells, from the central nervous systems of the model marine molluscs Aplysia californica and Pleurobranchaea californica are used to demonstrate the salt removal method. In addition to facilitating sample ionization, the MALDI matrix 2,5-dihydroxybenzoic acid serves to (i) aid in microdissections by stabilizing cell membranes, (ii) deactivate endogenous proteolytic enzymes and (iii) reduce high salt concentrations in order to improve spectral quality. Representative MALDI mass spectra are presented which indicate the presence of several neuroactive peptides previously characterized by conventional biochemical methods. More than ten individual peptides can be detected in a single cell. In spite of the chemically complex sample, the mass spectra are surprisingly free of extraneous peaks. Furthermore, both mass resolution and mass accuracy are similar to those encountered with more common MALDI samples and protocols.