Lipid and Protein Density in the Rat Retina: A Microradiographical Study1 (original) (raw)
Related papers
Microradiographical Determination of the Dry Mass Density in the Rat Retina1
Acta Ophthalmologica, 2009
A method for the quantitative measurement of the dry mass density in retinal tissue is presented. Cryosections of rat retinas were freeze-dried and exposed to soft X-rays together with a reference system. The section thickness was measured optically. The X-ray energy absorbed by the retinal tissue was recorded photographically and the microradiographs were evaluated photometrically. These measurements were used to estimate the dry mass density for each retinal layer. Sources of variation were evaluated. The precision was found adequate. The present method allows a localized determination of the dry mass density and of the hydration in the retina at a microscopic resolution.
Biochimica et Biophysica Acta (BBA) - Lipids and Lipid Metabolism, 1987
l-l4 C)-labeled (n -6) eicosatetraenoate, (n -3) docosapentaenoate and (n -3) docosahexaenoate (20 : 4, 22: 5 and 22: 6, respectively) are efficiently taken up and actively esterified into the lipids of bovine retina after 2 h incubation. Photoreceptor membranes, mitochondria, microsomes and postmicrosomal supernatants, which display significant differences in phospholipid and fatty acid compositions, are isolated after such incubations to study the labeling of lipids. The lipid classes preferentially labeled with the acids (1) largely differ among and within subcellular fractions, while (2) some common features in the treatment of the three polyenes are observed in each fraction. In all of them, the three acids are actively incorporated in phosphatidylcholine; ethanolamine glycerophospholipid, phosphatidylserine (PS) and phosphatidylinositol (PI) are highly labeled with 22 : 6, 22 : 5 and 20 : 4 respectively; within ethanolamine glycerophospholipid, the three label phosphatidylethanolamine in preference to plasmenylethanolamine. Most of the 14C esterified in mitochondria is in phospholipids. The endoplasmic reticulum produces in addition highly labeled triacylglycerols, also found in cytosol. High levels of l4 C-labeled diacylglycerols are observed exclusively in photoreceptor membranes, where the specific radioactivity of PI is very high. The total amounts of 14C incorporated (1) are in general similar within a given fraction for the three polyenes, but (2) largely differ among fractions. The labeling of the highly unsaturated phospholipids of photoreceptor membranes is the lowest, while the postmicrosomal supematant (whose lipids are relatively the poorest in polycnoic fatty acids) contains most of the labeled lipids isolated from retinas under these conditions. The results indicate that polyunsaturated species of retina phospholipids undergo an active synthesis and turnover, as well as an intense intracellular traffic among membranes.
Chemistry and metabolism of lipids in the vertebrate retina
Progress in Lipid Research, 1983
I. INTRODUCTION II. CELLULAR ORGANIZATION OF THE VERTEBRATE RETINA II1. STRUCTURAL ORGANIZATION OF VERTEBRATE PHOTORECEPTOR CELLS IV. LIPID COMPOSITION OF THE VERTEBRATE RETINA A. Historical considerations and general composition B. Phospholipid class composition C. Fatty acid composition D. Neutral lipids E. Glycolipids and other polar lipids V. LIPID COMPOSITION OF VERTEBRATE PHOTORECEPTOR OUTER SEGMENT MEMBRANES A. Preparation B. General composition C. Lipid class composition I. Phospholipids 2. Neutral lipids D. Fatty acid composition and phospholipid molecular species E. Molecular organization of lipids in rod outer segment disc membranes VI. LIPID METABOLISM IN THE VERTEBRATE RETINA A. Glyceride biosynthesis B. Fatty acids biosynthesis C. Ganglioside biosynthesis D. Sterol biosynthesis E. Phospholipid transfer proteins F. Base exchange reactions VII. LIPID METABOLISM 1N THE VERTEBRATE PHOTORECEPTOR CELLS A. Renewal and turnover of photoreceptor outer segment membranes 1. Renewal mechanisms 2. Proteins 3. Lipids B. Decarboxylation of phosphatidylserine to phosphatidylethanolamine C. Transmethylation of phosphatidylethanolamine to phosphatidylcholine VIII. EFFECT OF LIGHT ON THE METABOLISM OF RETINAL LIPIDS A. Gangliosides B. Phospholipids (other than inositides) C. Inositol phosphatides IX. THE IMPORTANCE OF LIP1DS IN NORMAL RETINA FUNCTION A. Lateral and rotational mobility of rhodopsin B. Rhodopsin orientation C. Rhodopsin regeneration and spectroscopic properties D. Thermal stability of rhodopsin E. Photobleaching of rhodopsin F. Effects of dietary manipulations on lipids of the retina X. ROLE OF LIPID PEROXIDATION IN RETINAL DEGENERATION A. Morphological changes in retinas exposed to pro-oxidant conditions B. Evidence for lipid peroxide accumulation in retinal degeneration C. Functional changes related to retinal lipid peroxides XI. CONCLUSIONS AND PERSPECTIVES
The Journal of Lipid Research, 2014
This article is available online at http://www.jlr.org signals to the visual centers of the brain ( 1 ). The central region is made up of several layers that include the horizontal, bipolar, and amacrine cells, which collectively process visual information from the photoreceptors, transmitting these signals to the ganglion cells. The outermost retinal neurons, the photoreceptors, are responsible for phototransduction ( 2 ). There are two types of photoreceptors, which include rods that are present in the peripheral retina and cones that are present in the central (macular) region of the retina. Rods function in dim light and manage peripheral and night vision, whereas cones are responsible for central high acuity bright light vision. The outermost layer of the retina, the retinal pigment epithelium (RPE), serves many functions, including the isomerization of all-trans retin ol into 11-cis retin al in the visual cycle, phagocytosis and degradation of shed photoreceptor tips, and the phagocytic clearance of cellular debris resulting from apoptotic and necrotic processes ( 3 ).
Fatty acid and lipid composition of the monkey retina in diet-induced hypercholesterolemia
Atherosclerosis, 1981
We determined the fatty acid composition of the lipids of cynomolgus monkey retina in animals fed commercial chow or a saturated fat, cholesterolenriched atherogenic diet for 100 days. Doxosahexaenoic acid (22 : 6) accounted for 25.8% of the ethanolamine phosphoglyceride fatty acids, 17.6% of the serine plus inositol phosphoglyceride fatty acids, 8.4% of the choline phosphoglyceride fatty acids and 5.8% of the neutral lipid fatty acids in the retinas of the chow-fed animals. Therefore, monkey retinas, like those of other mammalian species, ordinarily contain large amounts of 22 : 6. Retinas from the monkeys fed the atherogenic diet contained less 22 : 6 as well as other polyunsaturates in each of the phospholipid classes. The decrease in polyunsaturates was compensated for by increases in palmitic, stearic, and oleic acids. There was no difference in the amount of phospholipid, the distribution of phospholipid classes, or the amount of cholesterol in the retinas of the monkeys fed the atherogenic diet. These results indicate that the single type of lipid alteration produced in the retina by a diet enriched in saturated fat and cholesterol ol is a decrease in the polyunsaturation of the retinal phospholipids. The reduction in retinal 22 : 6 content might have significance for photoreceptor function.
Biochimica et Biophysica Acta (BBA) - General Subjects, 1999
Fourier transform infrared (FT-IR) microspectroscopy is a powerful technique that can be used to collect infrared spectra from microscopic regions of tissue sections. The infrared spectra are evaluated to chemically characterize the absorbing molecules. This technique can be applied to normal or diseased tissues. In the latter case, FT-IR microspectroscopy can reveal chemical changes that are associated with discrete regions of lesion sites, which can provide insights into the chemical mechanisms of disease processes. In the present study, FT-IR microspectroscopy was used to analyze sections of retina from normal (pigmented) and albino rats. The outer segments of retinas from pigmented animals were found to have unusually strong absorption values for CNC^H unsaturation and carbonyl functional groups. Docosahexaenoic acid (DHA), a major constituent of lipids in the outer segments, also had particularly high absorption values for these functional groups, which suggests that it is responsible for those enhanced absorption values. Absorbance values for the unsaturation and carbonyl functional groups were substantially reduced in the outer segments of retinas from albino animals. This finding, together with data from other studies on light-induced oxidative events in the retina, indicates a loss of DHA by a light-induced mechanism in albino animals. The outer nuclear layer had strong absorbance values for H^C^OH and PNO functional groups, which is likely due to the sugar phosphate backbone of DNA. The outer and inner plexiform layers were found to contain greater concentrations of CH 2 and CNO functional groups than the outer and inner nuclear layers, which is due to the high concentration of synaptic connections in the former layers. In summary, FT-IR microspectroscopy revealed a unique chemical profile in the outer segments compared to other retinal layers, and this profile was altered in albino animals. ß 0304-4165 / 99 / $^see front matter ß 1999 Elsevier Science B.V. All rights reserved. PII: S 0 3 0 4 -4 1 6 5 ( 9 9 ) 0 0 1 9 5 -6 * Corresponding
Radial distribution of tocopherols in rhesus monkey retina and retinal pigment epithelium-choroid
Investigative Ophthalmology & Visual Science
To map vitamin E as a function of distance from the foveal center in the primate retina and retinal pigment epithelium (RPE)-choroid. Methods. Eyecups from rhesus monkeys were dissected with circular trephines so that the innermost disc, centered on the fovea, was in the center of a series of concentric rings. Two different types of dissection were performed. For one type, the authors used circular trephines with diameters of 1, 4, 8, and 10 mm (1,4-D), whereas for the other type the diameters were 2, 5, 8, and sometimes 10 mm (2,5-D). When possible, the neural retina was separated from the RPE-choroid. Tissues were analyzed for vitamin E, retinyl palmitate, and protein. Results. Surface area, volume, and protein were used as indexes of the amount of tissue analyzed. Distributions of vitamin E in neural retina were dependent on the tissue metric used and type of dissection performed. However, regardless of the tissue metric used, the central 1-mm disc of the 1,4-D was, on average, higher in vitamin E content than was the central 2-mm disc of the 2,5-D. This was particularly true when volume was the tissue metric. From the average values of vitamin E in a series of concentric discs, a composite plot of the vitamin E concentration in the neural retina was generated that took into consideration both types of dissection. That plot displayed a local maximum in the fovea and then precipitously declined to a minimum in the region between 0.5 and 1.0 mm eccentricity (near the foveal crest); at greater eccentricities, the vitamin E concentration rose to a value similar to that in the fovea, i.e., the composite plot indicated that vitamin E has a V-shaped distribution in the central neural retina. Vitamin E distribution in the RPE-choroid, with surface area as the tissue metric, also was measured. For this tissue, the foveal region displayed a local maximum. Conclusions. By combining the results of two different types of dissection, the authors found that in the neural retina, vitamin E displayed a minimum near die foveal crest. This minimum correlated anatomically with the site at which areolar (geographic) atrophy frequendy occurs in retinal pigment epithelial cells in die human disease, age-related macular degeneration.