scholarly journals Formation, conversion, and utilization of isorhodopsin, rhodopsin, and porphyropsin by rod photoreceptors in the Xenopus retina.

1978 ◽  
Vol 72 (6) ◽  
pp. 821-836 ◽  
Author(s):  
P Witkovsky ◽  
G A Engbretson ◽  
H Ripps
Keyword(s):  
Vitamin A ◽  
Spectral Sensitivity ◽  
Visual Pigment ◽  
Pigment Content ◽  
Complete Darkness ◽  
Visual Transduction ◽  
Deficient Diet ◽  
Rod Photoreceptors ◽  
Electrophysiological Measurements ◽  
Lighting Regimen

The visual pigment content of rod photoreceptors in Xenopus larvae was reduced greater than 90% through a combination of vitamin A-deficient diet and constant light. Thereafter, a dose of either all-trans-retinol or 9-cis-retinal was injected intramuscularly, leading to the formation of a rhodopsin (lambdamax 504 nm) or isorhodopsin (lambdamax 487-493 nm) pigment, respectively. Electrophysiological measurements were made of the threshold and spectral sensitivity of the aspartate-isolated PIII (photoreceptoral) component of the electroretinogram. These measures established that either rhodopsin or isorhodopsin subserved visual transduction with the same efficiency as the 519 nm porphyropsin pigment encountered normally. When animals with rhodopsin or isorhodopsin were kept in darkness or placed on a cyclical lighting regimen for 8 days, retinal densitometry showed that either pigment was being converted to porphyropsin; significantly more porphyropsin was formed as a result of cyclical lighting than after complete darkness.

Is the Fly Visual Pigment a Rhodopsin?

1983 ◽  
Vol 38 (3-4) ◽  
pp. 329-333 ◽  
Author(s):  
Klaus Vogt
Keyword(s):  
Thin Layer ◽  
Thin Layer Chromatography ◽  
Visual Pigment ◽  
Pigment Content ◽  
Deficient Diet ◽  
Absorbance Maximum ◽  
Spectral Evidence ◽  
Pigment Complex ◽  
Chromophoric Group ◽  
Layer Chromatography

Thin layer chromatography of retina extracts from Calliphora yielded, instead of retinal (or retinaloximes after NH2OH treatm ent) a considerably more polar aldehyde or its corresponding oximes. That these compounds originate from the chrom ophoric group of the visual pigment was shown by the occurrence of different stereoisomers in the extracts depending on the colour with which the intact visual pigment complex was previously illuminated. The absorbance maximum of the oxime found after blue illumination is the same as that of all-trans-retinal-oxime (356 nm). This spectral accordance means that previous spectral evidence for retinal as the chromophoric group of fly visual pigment is not conclusive. Flies raised on a carotenoid deficient diet enriched with the hydroxy-xanthophyll lutein possess a high visual pigment content. This points to a hydroxy- xanthophyll as a possible precursor of the chromophoric group

The Effect of Vitamin A on the Intermittent Nitrogen Dioxide Gas Exposure in Hamsters

1976 ◽  
Vol 34 ◽  
pp. 176-177
Author(s):  
J.C.S. Kim ◽  
M.G. Jourden ◽  
E.S. Carlisle
Keyword(s):  
Electron Microscopy ◽  
Vitamin A ◽  
Nitrogen Dioxide ◽  
Chronic Exposure ◽  
Light And Electron Microscopy ◽  
Specific Effect ◽  
Deficient Diet ◽  
Intermittent Exposure ◽  
Hypovitaminosis A ◽  
Gas Exposure

Chronic exposure to nitrogen dioxide in rodents has shown that injury reaches a maximum after 24 hours, and a reparative adaptive phase follows (1). Damage occurring in the terminal bronchioles and proximal portions of the alveolar ducts in rats has been extensively studied by both light and electron microscopy (1).The present study was undertaken to compare the response of lung tissue to intermittent exposure to 10 ppm of nitrogen dioxide gas for 4 hours per week, while the hamsters were on a vitamin A deficient diet. Ultrastructural observations made from lung tissues obtained from non-gas exposed, hypovitaminosis A animals and gas exposed animals fed a regular commercially prepared diet have been compared to elucidate the specific effect of vitamin A on nitrogen dioxide gas exposure. The interaction occurring between vitamin A and nitrogen dioxide gas has not previously been investigated.

Vitamin A Status and Hepatic Drug Metabolism in the Rat

1973 ◽  
Vol 51 (1) ◽  
pp. 6-11 ◽  
Author(s):  
G. C. Becking
Keyword(s):  
Vitamin A ◽  
Drug Metabolism ◽  
Vitamin A Deficiency ◽  
Hepatic Drug Metabolism ◽  
Deficient Diet ◽  
Hepatic Drug ◽  
Vitamin A Status ◽  
Cytochrome P 450 ◽  
Liver Vitamin

The effect of vitamin A status on hepatic drug metabolism was studied in rats. Animals were fed diets with and without vitamin A for 20 and 25 days. Weight gains of control and deficient animals were not significantly different, whereas liver vitamin A levels had decreased to less than 10% of control animals after 20 days and were essentially zero after eating the deficient diet for 25 days. Aniline metabolism in vitro and aminopyrine metabolism in vitro and in vivo were significantly lower in male weanling rats fed a vitamin A deficient diet for 20 days. No alteration in in vitro p-nitrobenzoic acid metabolism was noted after 25 days on the test. Vitamin A deficiency did not alter microsomal protein levels or cytochrome c reductase activity but deficient animals did have a lower microsomal cytochrome P-450 content. Hepatic enzyme activities and cytochrome P-450 levels were restored to values approaching those found in control animals by feeding vitamin A deficient rats the vitamin A containing diet for 21 days. Liver vitamin A levels were markedly increased after re-feeding studies but were still significantly lower than control animals.

The photoreceptors and visual pigments in the retina of the white sturgeon, Acipenser transmontanus

1990 ◽  
Vol 68 (7) ◽  
pp. 1544-1551 ◽  
Author(s):  
A. J. Sillman ◽  
M. D. Spanfelner ◽  
E. R. Loew
Keyword(s):  
Vitamin A ◽  
Visual Pigment ◽  
Visual Pigments ◽  
Spectrophotometric Analysis ◽  
White Sturgeon ◽  
Acipenser Transmontanus ◽  
Light Regimen ◽  
Cone Pigment ◽  
Spectral Absorbance

The photoreceptors in the retina of the white sturgeon, Acipenser transmontanus (Chondrostei), were studied by means of scanning electron microscopy, in situ microspectrophotometry, and spectrophotometric analysis of visual pigment extracts. The white sturgeon retina is simple in that it contains only two morphologically distinct photoreceptors. The retina is dominated by rods with large outer segments, but there is a substantial population (40%) of single cones. Evidence was found for only one rod visual pigment and one cone visual pigment. Peak spectral absorbance (λmax) of the rod pigment is near 539 nm, whereas λmax of the cone pigment is near 605 nm. Both visual pigments are porphyropsin types with chromophores based on vitamin A2. No detectable rhodopsin based on vitamin A1 is ever present, regardless of season or light regimen. The results are discussed in terms of the sturgeon's behavior, as well as the implications for the evolution of color vision.

THE TOXICITY OF BENZYLPENICILLIN IN ANIMALS ON VITAMIN A DEFICIENT TEST DIET, U.S.P. XIV

1962 ◽  
Vol 40 (1) ◽  
pp. 1685-1692
Author(s):  
Eldon M. Boyd ◽  
Dorothy A. Mulrooney ◽  
Everett J. Sargeant
Keyword(s):  
Vitamin A ◽  
Intramuscular Injection ◽  
Chronic Toxicity ◽  
Toxic Effects ◽  
Standard Laboratory ◽  
Test Diet ◽  
Deficient Diet ◽  
Effect Change ◽  
Unknown Factor ◽  
Increased Susceptibility

Young, adult albino mice and rats became more susceptible to the acute and chronic toxic effects of benzylpenicillin after they had been fed vitamin A deficient test diet, U.S.P. XIV, for about 1 month. At and after this interval, there occurred a significant increase in the percentage mortality from a single oral or subcutaneous LD50 of benzylpenicillin in mice and the chronic toxicity of a daily oral 0.1 L-LD50 of benzylpenicillin was augmented in rats. Replacement of vitamin A, in the deficient diet or by daily intramuscular injection, did not affect the increased susceptibility to benzylpenicillin toxicity. A dietary supplement containing nine other vitamins was also without effect. Change in diet alone was not a factor since rats did not become appreciably more susceptible to the toxic effects of a daily oral 0.1 L-LD50 of benzylpenicillin when their diet was changed from a standard laboratory chow to a rachitogenic test diet. Some unknown factor or factors in vitamin A deficient test diet, U.S.P. XIV, therefore, made the animals more susceptible to the toxic effects of benzylpenicillin.

Selective utilization of serum vitamin A for visual pigment synthesis

1989 ◽  
Vol 142 (1) ◽  
pp. 207-214
Author(s):  
A. T. Tsin ◽  
S. N. Gentles ◽  
E. A. Castillo
Keyword(s):  
Vitamin A ◽  
Visual Pigment ◽  
Carassius Auratus ◽  
High Performance ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Serum Vitamin ◽  
Pigment Synthesis ◽  
Goldfish Carassius Auratus ◽  
Vitamin A2

Two groups of goldfish (Carassius auratus) were subjected to light and temperature conditions known to promote a contrast in their scotopic visual pigment compositions. After 3 weeks, the porphyropsin/rhodopsin ratio in the neuroretina of these goldfish ranged from 99% porphyropsin in one group to 59% in the other. Samples of blood, liver and retinal pigment epithelium (RPE) were also removed from these animals and analysed by high-performance liquid chromatography (HPLC) for vitamin A composition. There was consistently more vitamin A2 than vitamin A1 (over 50% vitamin A2) in both vitamin A alcohol and vitamin A esters extracted from the liver and the RPE. In contrast, only 30% of all vitamin A extracted from the blood was vitamin A2. These observations suggest that it is mainly vitamin A1 that is transported in the blood, whereas vitamin A2 is selectively retained in the liver and in the RPE and used to form porphyropsin in the eye.

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