Age-related changes in central and peripheral contrast sensitivity (original) (raw)
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Endothelial glycoconjugates: a comparative lectin study of the brain, retina and myocardium
Journal of Anatomy, 2000
There is evidence that the endothelial cell (EC) glycocalyx is a significant determinant of vascular permeability, acting as a charge-size filter to permeant molecules. We have therefore examined its oligosaccharide composition in 3 classes of microvessel with differing permeabilities. EC in rat brain, retina and myocardium were labelled with a panel of lectins and subjected to a semiquantitative analysis. Surprisingly, no substantial differences were evident for any lectin labelling between the 3 microvessel types despite their marked morphophysiological diversity. In particular, all showed substantial sialic acid expression, with Maackia amurensis (MAA) labelling sialic acid in an α2-3 linkage to β-galactose and Sambucus nigra (SNA) recognising sialic acid in an α2-6 linkage to β-galactose. Arachis hypogaea (PNA) binding after neuraminidase digestion indicated the presence of Gal β1-3GalNAc attached to terminal sialic acid. The results therefore show that the sequences NeuNAc α2-3Gal β1-3GalNAc and NeuNAc α2-6Gal β1-3GalNAc are strongly expressed in the 3 microvessel types irrespective of their permeability properties. This homogeneity suggests that these lectin ligands may be involved in a common set of EC functions, e.g. cell :cell and cell :matrix interactions. However, we cannot rule out the possibility that glycocalyx differences may exist between vessels in the paracellular cleft which may alter its filtration properties.
Neurochemical Research, 2006
Carbohydrate structures between retinal neurons and retinal pigment epithelium (RPE) play an important role in maintaining the integrity of retinal adhesion to underlying RPE, and in retinal detachment pathogenesis. Since relevant knowledge is still in the primary stage, glycotopes on the adult retina of mongrel canines (dog), micropigs and Sprague-Dawley rats were examined by lectino-histochemistry, using a panel of 16 different lectins. Paraffin sections of eyes were stained with biotinylated lectins, and visualized by streptavidin-peroxidase and diaminobenzidine staining. Mapping the affinity profiles, it is concluded that: (i) all sections of the retina reacted well with Morniga M, suggesting that N-linked glycans are present in all layers of the retina; (ii) no detectable human blood group ABH active glycotopes were found among retinal layers; (iii) outer and inner segments contained glycoconjugates rich in ligands reacting with T α (Galβ1–3GalNAcα1-Ser/Thr) and Tn (GalNAcα1-Ser/Thr) specific lectins; (iv) cone cells of retina specifically bound peanut agglutinin (PNA), which recognizes T α residues and could be used as a specific marker for these photoreceptors; (v) the retinas of rat, dog and pig, had a similar binding profile but with different intensity; (vi) each retinal layer had its own binding characteristic. This information may provide useful background knowledge for normal retinal physiology and miscellaneous retinal diseases, including retinal detachment (RD) and age-related macular degeneration (ARMD).
Biochemical and Biophysical Research Communications, 1997
modify protein configuration and properties leading to In order to investigate the mechanisms involved in structural and functional alterations (2). They could diabetic retinopathy, we studied the effects of adalso bind to specific cell surface receptors and alter vanced glycosylation end products (AGE) on retinal the normal cell function by modification of the gene microvascular cell glycoproteins. Bovine retinal periexpression or induction of oxidative stress (3, 4). Our cytes (BRP) and endothelial cells (BREC) were incuhypothesis is that AGE could be involved in the alterbated in the presence of AGE-modified albumin and ation of cell-cell interactions observed in diabetic reticell glycoproteins analyzed by lectin affinoblotting nopathy by modifying some carbohydrate moieties in and metabolic radiolabeling with sugar precursors. the cell glycocalix. Indeed, these cell-coating glycocon-Selective modifications in the glycoprotein sugar jugates play a major role in cell adhesion and recognichains were observed mainly in BREC and for a 210 tion processes (5). The aim of the present study was to kDa membrane glycoprotein. Indeed, a 40% decrease investigate whether the sugar composition of the retiof a(2,3) sialic acid, b(1,3) galactose or a(1,6) fucose nal microvascular cell glycoproteins could be modified content was observed without significant protein in the presence of AGE. For this purpose, bovine retinal amount changes. These glycoprotein alterations were pericytes and endothelial cells were cultured in the related to the concentration of AGE. Neither BRP nor BREC glycoproteins were modified when cells were presence of AGE and cell glycoproteins were analyzed incubated with high glucose or fructose concentra-by affinoblotting using lectins recognizing specific sugtions. These results suggest a new diabetic pathogenic ars of glycoproteins, as well as by metabolic labeling mechanism in which a protein post-translational modwith radioactive sugars precursors. ification, in this case glycation, could modify another post-translational process such as the enzymatic gly-MATERIALS AND METHODS cosylation. ᭧ 1997 Academic Press Materials. Chemicals were of analytical grade and purchased from Sigma unless otherwise specified. Electrophoresis reagents were from BDH and labeled sugars from DuPont NEN. AGE of bovine serum albumin (AGE-BSA) and its control (Control BSA
Glycobiology, 1998
Rod and cone photoreceptors project from the outer retinal surface into a carbohydrate-rich interphotoreceptor matrix (IPM). Unique IPM glycoconjugates are distributed around rods and cones. Wheat germ agglutinin (WGA) strongly decorates the rod matrix domains and weakly decorates the cone matrix domains. This study characterizes the major WGAbinding glycoprotein in the human IPM, which we refer to as SPACR (sialoprotein associated with cones and rods). SPACR, which has a molecular weight of 147 kDa, was isolated and purified from the IPM by lectin affinity chromatography. A polyclonal antibody to SPACR was prepared that colocalizes in tissue preparations with WGA-binding domains in the IPM. Sequential digestion of SPACR with N-and O-glycosidases results in a systematic increase in electrophorectic mobility, indicating the presence of both N-and Olinked glycoconjugates. Complete deglycosylation results in a reduction in the relative molecular mass of SPACR by about 30%. Analysis of lectin binding allowed us to identify some of the structural characteristics of SPACR glycoconjugates. Treatment with neuraminidase exposes Galβ1-3GalNAc disaccharide as indicated by positive peanut agglutinin (PNA) staining, accompanied by the loss of WGA staining. Maackia amurensis agglutinins (MAA-1 and MAA-2), specific for sialic acid in α2-3 linkage to Gal, bind SPACR, while Sambucus nigra agglutinin (SNA), specific for α2-6 linked sialic acid, does not, indicating that the dominant glycoconjugate determinant on SPACR is the O-linked carbohydrate, NeuAcα2-3Galβ1-3GalNAc. The abundance of sialic acid in SPACR suggests that this glycoprotein may contribute substantially to the polyanionic nature of the IPM. The carbohydrate chains present on SPACR could also provide sites for extensive crosslinking and participate in the formation of the ordered IPM lattice that surrounds the elongate photoreceptors projecting from the outer retinal surface.
Glycogen metabolism in the rat retina: Glycogen content in retina
Journal of Neurochemistry - J NEUROCHEM, 2003
It has been reported that glycogen levels in retina vary with retinal vascularization. However, the electrical activity of isolated retina depends on glucose supply, suggesting that it does not contain energetic reserves. We determined glycogen levels and pyruvate and lactate production under various conditions in isolated retina. Ex vivo retinas from light-and dark-adapted rats showed values of 44 ± 0.3 and 19.5 ± 0.4 nmol glucosyl residues/mg protein, respectively. The glycogen content of retinas from light-adapted animals was reduced by 50% when they were transferred to darkness. Glycogen levels were low in retinas incubated in glucose-free media and increased in the presence of glucose. The highest glycogen values were found in media containing 20 mM of glucose. A rapid increase in lactate production was observed in the presence of glucose. Surprisingly, glycogen levels were the lowest and lactate production was also very low in the presence of 30 mM glucose. Our results suggest that glycogen can be used as an immediate accessible energy reserve in retina. We speculate on the possibility that gluconeogenesis may play a protective role by removal of lactic acid.
Glycogen metabolism in the rat retina
Journal of Neurochemistry, 2003
It has been reported that glycogen levels in retina vary with retinal vascularization. However, the electrical activity of isolated retina depends on glucose supply, suggesting that it does not contain energetic reserves. We determined glycogen levels and pyruvate and lactate production under various conditions in isolated retina. Ex vivo retinas from light-and dark-adapted rats showed values of 44 ± 0.3 and 19.5 ± 0.4 nmol glucosyl residues/mg protein, respectively. The glycogen content of retinas from light-adapted animals was reduced by 50% when they were transferred to darkness. Glycogen levels were low in retinas incubated in glucose-free media and increased in the presence of glucose. The highest glycogen values were found in media containing 20 mM of glucose. A rapid increase in lactate production was observed in the presence of glucose. Surprisingly, glycogen levels were the lowest and lactate production was also very low in the presence of 30 mM glucose. Our results suggest that glycogen can be used as an immediate accessible energy reserve in retina. We speculate on the possibility that gluconeogenesis may play a protective role by removal of lactic acid.
Evaluation of ocular surface glycocalyx using lectin-conjugated fluorescein
Clinical Ophthalmology, 2010
A glycocalyx plays important roles in the ocular surface epithelium, but there is no direct simple method to evaluate ocular surface glycocalyx. We tested a wheat germ agglutinin conjugate of fluorescein (F-WGA) as a marker to demonstrate ocular surface glycocalyx in vivo. Methods: After a 5% F-WGA solution was applied to the eyes of eight healthy volunteers, fluorescent intensities of the central cornea and bulbar conjunctiva were measured by fluorophotometry. A 10% fluorescein-conjugated dextran solution served as the control. Changes in fluorescent intensities of the ocular surface following a challenge with 5% N-acetyl cysteine, a conventional mucolytic agent, were tested in the second experiment. Saline instillation served as a control. Results: The ocular surface was diffusely stained by F-WGA. Breakup of the precorneal tear film was not apparent, possibly because F-WGA was bound to the glycocalyx of the ocular surface epithelium. F-WGA fluorescent intensities were high in the superior, nasal, and inferior regions of the bulbar conjunctiva and low in the temporal conjunctiva and cornea. No such regional differences were observed with fluorescein-conjugated dextran. F-WGA fluorescent intensities decreased significantly with N-acetyl cysteine instillation, whereas they were not affected by saline instillation. Conclusion: The fluorophotometric method may be used to evaluate the glycocalyx quantitatively in the ocular surface in vivo.
Growth modulation of retinal microvascular cells by early and advanced glycation products
Diabetes Research and Clinical Practice, 1997
To investigate the possible implication of non-enzymatic glycosylation in the etiopathogenesis of the diabetic retinopathy, we studied the effect of early and advanced glycation products on the growth of retinal microvascular cells. Glucose modified products were obtained by incubating bovine serum albumin or fetal bovine serum with 0.5 M glucose for 10 (early glycation products: EG-BSA and EG-FBS, respectively) or 60 days (advanced glycation end products: AGE-BSA and AGE-FBS, respectively). Cell growth was assessed by cell counting and DNA content determination. EG-BSA or AGE-BSA significantly decreased pericyte proliferation after 8 days of culture (33 and 13% inhibition, respectively). Concerning endothelial cells, EG-BSA reduced proliferation to 40% whereas AGE-BSA increased it to 156% after 4 days of culture. The glucose-treated sera didn't exhibit the same growth effects, neither the EG-FBS nor the AGE-FBS significantly affected endothelial cell proliferation. Only the AGE-FBS showed a significant inhibitory effect on pericyte proliferation (40% inhibition). We conclude that retinal microvascular cell growth in vitro could be differently modulated by early and advanced glycation products. The inhibitory effect of AGES observed on pericyte growth, suggests that glycoxidation could be implicated in the pericyte loss observed in diabetic retinopathy.