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C D Bridges

Publications and source records attributed to C D Bridges.

At least 73 records · Page 4Linked to original sources
PubMed1983

Selective utilization of vitamins A1 and A2 by goldfish photoreceptors.

The rhodopsin/porphyropsin (visual pigment) ratios in the goldfish retina were induced to change over a 300-day treatment period of specified light and temperature conditions. A concomitant but much slower change in the ratios of retinyl/3-dehydroretinyl ester in the pigment epithelium (RPE) was observed. If the changes in the visual pigment ratios were dependent on the nonselective sequestering of chromophores from the RPE ester pool, then the visual pigment changes might mirror those of the esters in the RPE. However, the relatively greater rate of visual pigment changes compared to that of the RPE esters suggests that goldfish photoreceptors synthesize their visual pigment from a relatively small pool of chromophore precursor rather than from the overall pool of retinyl and 3-dehydroretinyl esters stored in the RPE.

Animals↗
PubMed1982

Vitamin A transport between retina and pigment epithelium--an interstitial protein carrying endogenous retinol (interstitial retinol-binding protein).

We have demonstrated and partially characterized an interstitial retinol-binding protein (IRBP) confined to bovine interphotoreceptor matrix (IPM). The native protein is a concanavalin A-binding glycoprotein with a mol. wt of 260 k as measured by gel-filtration and size-exclusion high-performance liquid chromatography. On SDS-gels, its mol. wt is 140-145 k. Since the protein is glycosylated, this value is probably too high. Hence, the native protein may be a dimer consisting of two identical subunits. The endogenous ligand has been analyzed by high-performance liquid chromatography--it consists mainly of all-trans retinol. Occasionally, retinal and 11-cis retinol are also associated with it. The amount of retinol bound to IRBP increases when the eyes are illuminated. The total binding capacity was estimated to represent 4-5% of the retinol released from a total rhodopsin bleach. We have established that, like serum retinol-binding protein, IRBP can be also bind retinoic acid, although it has not been established that retinoic acid is an endogenous ligand. The fluorescence emission lambda max for IRBP with its native ligand is at 470 nm and the excitation lambda max for this fluorescence is at 333 nm. Other retinoid carriers in the interphotoreceptor matrix have molecular weights of about 15 and 33 k. These probably correspond to cellular retinol- and retinal-binding proteins, respectively. Since both proteins have been identified in the pigment epithelium and retina cytosols, their presence in the IPM could be a result of cell damage. We conclude that interstitial retinol-binding protein is the best candidate for a transport protein carrying retinol between the rod outer segments and the pigment epithelium.

Animals↗
PubMed1982

Vitamin A in human eyes: amount, distribution, and composition.

The amount, distribution, and composition of vitamin A stored in the eyes of 29 postmortem donors was determined by a combination of techniques, including high-pressure liquid chromatography. The vitamin A concentration in the pigment epithelium-choroid (RPE-Ch) was the highest observed for human non-liver tissue and amounted to 7.9 +/- 4.3 nmol/eye (n = 28), or 10.4 +/- 7.1 microgram/gm (n = 27). There was no evidence for significant losses during the interval between death and enucleation or during subsequent storage at 4 degrees C. The vitamin A extracted from the retina was 15.3% of that in the corresponding RPE-Ch. By measuring rhodopsin regeneration in retinal homogenates incubated with 11-cis retinal, we estimated that the amount of vitamin A in the RPE-Ch of fully dark-adapted eyes would represent 2.5 mole equivalents of the retinal rhodopsin, a value similar to that found in the frog. A preponderance of the vitamin A in the eye was esterified (98.3% in the RPE-Ch, 79.3% in the retina) and consisted principally of stearate and palmitate in the ratio of 1:4.8. A small amount of oleate was also detected. The ratio of 11-cis isomer over the all-trans averaged 1.52 +/- 0.48 (n - 11). Variable, usually small proportions of 13-cis retinyl esters were also present. Intact RPE-Ch or isolated RPE cells esterified exogenous all-trans-3H2-retinol to the same fatty acids in roughly the same proportions as in the endogenous stores. The all-trans configuration was mainly retained during uptake and esterification, although some isomerization to 13-cis also occurred. No 11-cis isomer was formed under these conditions.

Choroid↗
PubMed1981

Lectin receptors on cells isolated from the turtle retina.

The presence of specific oligosaccharides on the surface of retinal cells was examined by incubating FITC-labeled lectins with cells dissociated from papain-treated turtle retinas. The pattern and intensity of binding was found to vary among the cells examined. With Con A, there was strong surface staining of both rods and cones, with an intense ring of fluorescence above the nucleus. The bipolar and ganglion cells also showed strong surface labeling. In Müller (glial) cells there was intense fluorescence in the apical, microvillous region. In contrast, the horizontal cells and their axons showed weak staining. When RCA-60, RCA-120, and WGA were incubated with photoreceptors, bipolar cells, or horizontal cells, little fluorescence was visible. However, all three lectins bound strongly to the Müller cells. In contrast, the Lotus lectin did not bind to any of the cells examined. In all the cases, lectin binding was inhibited by the appropriate haptene sugar. Further, prior treatment cells with neuraminidase did not alter lectin binding to any cell type. These results suggest differences in the distribution of lectin receptors among specific cell types, and particularly between neurons and glial cells in the vertebrate retina.

Animals↗
PubMed1981

Comparison of cytosol retinol binding proteins from bovine retina, dog liver, and rat liver.

Cytosol retinol binding proteins (CRBP's) have been purified from rat liver, dog liver, and bovine retina. All had identical molecular weights on sodium dodecyl sulfate electrophoresis. They had different RF values on non-sodium dodecyl sulfate gels at pH 8.9. The three CRBP exhibited similar absorption and fluorescence spectra. The absorbance of the ligand was perturbed after binding, the main band shifting bathochromically and exhibiting a lambda(max) at 350 nm compared with 328 nm for free retinol in hexane. Additionally, subsidiary peaks appeared at 335 and 367 nm. Rabbit antiserum against rat liver CRBP cross-reacted with CRBP's from dog liver and bovine retina. The Ouchterlony immunodiffusion technique indicated that these proteins have molecular structures with identical antigenic determinants. All three CRBP's had amino acid composition that were virtually identical, as judged by our own observations and those of other laboratories. The molecular structure of cytosol retinol binding proteins appears to be highly conserved, irrespective of species or tissue of origin.

Amino Acids↗
PubMed1981

Agglutination of isolated rod outer segments by lectins.

The interactions of ten lectins with rod outer segment (ROS) plasma membranes and the effects of various haptene sugars were examined by studying agglutination in suspensions of washed ROSs. It is concluded that agglutination sites on the ROS membrane involve receptors that are recognized by eight lectins with haptene sugar preferences that include D-Gal, D-GalNAc, D-Man, and D-GlcNAc. Lectins binding alpha-L-fucose do not induce agglutination. The identification of some receptors and the significance of these results in terms of the known complexities of lectin specificities is discussed.

Agglutination↗
PubMed1981

Lectin receptors of rods and cones. Visualization by fluorescent label.

The binding of eight fluorescence-labeled lectins to visual cells was investigated. Concanavalin A (Con A) (specific for oligosaccharides containing mannose) bound evenly to the surfaces of rod outer segments (ROSs) from frog, cattle, goldfish, and turtle (Pseudemys). In frog, binding was observed on the inner segment, with intensifications at the inner/outer segment junction and in the region of the nucleus. No binding occurred on the surfaces of ROS discs. In 0.1% Triton X-100, rods formed convoluted tubular structures that bound Con A to their surfaces. Isolated cone outer segments (COSs) showed uniform fluorescence as compared with the inner segments, which displayed only surface labeling. Only lectins with an affinity for fucose (UeA, LTA) failed to bind to the ROSs and COS. Lectins with an affinity for oligosaccharides containing galactose (RCA-120, RCA-60, and PNA) bound hardly at all to the rod inner segments. Both WGA (N-acetyl glucosamine) and SBA (N-acetyl galactosamine and galactose) bound indiscriminately to all ROSs, whereas PNA bound preferentially to the accessory cones.

Animals↗
PubMed1981

High-pressure liquid chromatography of fatty acid esters of retinol isomers. Analysis of retinyl esters stored in the eye.

We have synthesized the all-trans, 13-cis, 11-cis, and 9-cis retinyl esters of some or all of the following fatty acids: caprylic (8:0), capric (10:0), lauric (12:0), myristic (14:0), palmitic (16:0), stearic (18:0), arachidic (20:0), palmitoleic (16:1), oleic (18:1), linoleic (18:2), linolenic (18:3), arachidonic (20:4), and docosahexaenoic (22:6). Mixtures of these compounds were analyzed by high-pressure liquid chromatography on an Altex 100 chromatograph. This approach has enabled us to investigate and identify both the isomeric form and fatty acid basis of the retinyl esters present in rabbit and rat ocular tissues. Dark-adapted rabbits had 11-cis and all-trans retinyl esters, whereas light-adapted albino rats had only the all-trans isomer. The fatty acids utilized for esterification were almost wholly palmitic for the rabbit, whereas both stearic and palmitic were present in the rat esters. Rabbits are similar to frogs in that a large proportion (80%) of their ocular retinyl esters occurred in large, fluorescent oil droplets in the pigment epithelium. These are absent in rats.

Adaptation, Physiological↗
PubMed1979

Different receptors for distribution of peanut and ricin agglutinins between inner and outer segments of rod cells.

Lectins can be used as probes for cell-surface oligosaccharides1-4. These proteins display high specificities for certain haptene sugars, although the details of the sugar linkages and the three-dimensional array of the oligosaccharide may all be involved in determining the affinity of a lectin for its receptor. We have now shown that peanut and ricin agglutinins bind differentially to the surfaces of rod inner and outer segments.

Animals↗