scholarly journals Rod sensitivity and visual pigment concentration in Xenopus.

1978 ◽  
Vol 72 (6) ◽  
pp. 801-819 ◽  
Author(s):  
G A Engbretson ◽  
P Witkovsky
Keyword(s):  
Vitamin A ◽  
Visual Pigment ◽  
Intramuscular Injection ◽  
Maximum Level ◽  
Ocular Tissue ◽  
Rapid Rate ◽  
Constant Illumination ◽  
Light Responses ◽  
Criterion Response ◽  
Piii Component

Xenopus larvae were raised on a vitamin A-free diet under constant illumination until their visual pigment content had decreased to between 8% of normal and an undetectably low level. After the intramuscular injection of 2.1 X 10(13-2.1 X 10(16) molecules of [3H]vitamin A, ocular tissue showed a rapid rate of uptake of label which reached a maximum level of incorporation by 48 h. Light-microscopic autoradiography revealed that the retinal uptake of label was concentrated within the receptor outer segments. Spectral transmissivity measurements at various times after injection were made upon intact retinas and upon digitonin extracts. They showed that visual pigment with a lambdamax of 504 nm was formed in the retina and that the amount formed was a function of incubation time and the magnitude of the dose administered. Electrophysiological measures of photoreceptor light responses were obtained from the PIII component of the electroretinogram, isolated with aspartate. The quantal flux required to elicit a criterion response was determined and related to the fraction of visual pigment present. The results showed that rod sensitivity varied linearly with the probability of quantal absorption.

Photoreceptor thresholds and visual pigment levels in normal and vitamin A-deprived Xenopus tadpoles

1976 ◽  
Vol 39 (6) ◽  
pp. 1272-1287 ◽  
Author(s):  
P. Witkovsky ◽  
E. Gallin ◽  
J. G. Hollyfield ◽  
H. Ripps ◽  
C. D. Bridges
Keyword(s):  
Vitamin A ◽  
Visual Pigment ◽  
Structural Integrity ◽  
Absolute Threshold ◽  
Normal Diet ◽  
Rod Outer Segments ◽  
Sensitivity Functions ◽  
Outer Segments ◽  
Piii Component ◽  
Dietary Deficiency

1. Measurements of the aspartate-isolated PIII component of the electroretinogram (ERG) were used to estimate photoreceptor threshold in dark-adapted tadpoles of the clawed toad, Xenopus laevis raised on a normal diet. Spectral sensitivity functions established that the rod mechanism governed absolute dark thresholds from stage 40 to the end of premetamorphic development. 2. Parallel measures of rod outer-segment dimensions and visual pigment levels demonstrated a) that visual pigment concentration remained constant at all tadpole stages, and b) that the fall in threshold over the course of premetamorphic development depended exclusively on the increased probability of quantal absorption that accompanied the growth of the rod outer segments. 3. When tadpoles were obtained from vitamin A-deficient females and raised subsequently on a vitamin A-free diet, the first appearance of the ERG was delayed and its absolute threshold raised, with respect to controls. 4. Histological examination of vitamin A-deprived retinas indicated that rod outer segments retained their structural integrity in spite of up to a 75% loss of visual pigment. 5. The threshold rise which accompanied a fall in visual pigment levels, whether effected by dietary deficiency or by bleaching, was greater than could be attributed solely to a reduction in the probability of quantal absorption.

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.

Comparative Value of Three Sources of Vitamins A and D for Fattening Pigs

1954 ◽  
Vol 1954 ◽  
pp. 45-47
Author(s):  
R. S. Barber ◽  
R. Braude ◽  
M. E. Coates ◽  
G. F. Harrison ◽  
K. G. Mitchell ◽  
...  
Keyword(s):  
Vitamin D ◽  
Vitamin A ◽  
Intramuscular Injection ◽  
Fish Meal ◽  
List Type ◽  
Cod Liver Oil ◽  
Commercial Preparation ◽  
Single Intramuscular Injection ◽  
Fattening Pigs

The efficacy of three sources of vitamins A and D supplements was tested in an experiment with fattening pigs involving the following four treatments :(1) Control—basal meal.(2) As control, but at one week of age the pigs had been given a single intramuscular injection of a commercial preparation, supplying 500,000 i.u. of vitamin A and 100,000 i.u. of vitamin D3.(3) Basal meal + 1 % cod-liver oil (containing 500 i.u./g. of vitamin A and 68 i.u./g. of vitamin 3), supplying 2,270 i.u. of vitamin A and 309 i.u. of vitamin D3 per lb. of diet.(4) Basal meal + synthetic vitamins A and D concentrate (containing 50,000 i.u./g. of vitamin A and 5,000 i.u./g. of vitamin D3), added to supply 2,250 i.u. of vitamin A and 300 i.u. of vitamin D3 per lb. of diet.The basal meal which was the standard fattening diet used at Shinfield consisted of: fine miller’s offal 50, barley meal 30, flaked maize 10, white fish meal 10, all parts by weight. It should be noted that the diet contained a precursor of vitamin A, and it was calculated that this would provide about one-third of the recommended allowance of vitamin A for fattening pigs.

scholarly journals Turning Cones Off: the Role of the 9-Methyl Group of Retinal in Red Cones

2006 ◽  
Vol 128 (6) ◽  
pp. 671-685 ◽  
Author(s):  
Maureen E. Estevez ◽  
Petri Ala-Laurila ◽  
Rosalie K. Crouch ◽  
M. Carter Cornwall
Keyword(s):  
Visual Pigment ◽  
Bright Light ◽  
Rapid Rate ◽  
Methyl Group ◽  
Cone Opsin ◽  
Rate Of Recovery ◽  
Kinetics Of ◽  
Flash Response

Our ability to see in bright light depends critically on the rapid rate at which cone photoreceptors detect and adapt to changes in illumination. This is achieved, in part, by their rapid response termination. In this study, we investigate the hypothesis that this rapid termination of the response in red cones is dependent on interactions between the 9-methyl group of retinal and red cone opsin, which are required for timely metarhodopsin (Meta) II decay. We used single-cell electrical recordings of flash responses to assess the kinetics of response termination and to calculate guanylyl cyclase (GC) rates in salamander red cones containing native visual pigment as well as visual pigment regenerated with 11-cis 9-demethyl retinal, an analogue of retinal in which the 9-methyl group is missing. After exposure to bright light that photoactivated more than ∼0.2% of the pigment, red cones containing the analogue pigment had a slower recovery of both flash response amplitudes and GC rates (up to 10 times slower at high bleaches) than red cones containing 11-cis retinal. This finding is consistent with previously published biochemical data demonstrating that red cone opsin regenerated in vitro with 11-cis 9-demethyl retinal exhibited prolonged activation as a result of slowed Meta II decay. Our results suggest that two different mechanisms regulate the recovery of responsiveness in red cones after exposure to light. We propose a model in which the response recovery in red cones can be regulated (particularly at high light intensities) by the Meta II decay rate if that rate has been inhibited. In red cones, the interaction of the 9-methyl group of retinal with opsin promotes efficient Meta II decay and, thus, the rapid rate of recovery.

Rhodopsin maturation antagonized by dominant rhodopsin mutants

1998 ◽  
Vol 15 (4) ◽  
pp. 693-700 ◽  
Author(s):  
PHANI KURADA ◽  
TIMOTHY D. TONINI ◽  
MICHELLE A. SERIKAKU ◽  
JONATHAN P. PICCINI ◽  
JOSEPH E. O'TOUSA
Keyword(s):  
Heat Shock ◽  
Vitamin A ◽  
Visual Pigment ◽  
Gene Activation ◽  
Dominant Allele ◽  
Wild Type ◽  
Rhodopsin Gene ◽  
Heat Shock Promoter ◽  
Complex Forms

ninaED1, a dominant allele of the major Drosophila rhodopsin gene, expresses a rhodopsin that is predominantly recovered in a 80-kD complex that likely represents rhodopsin dimers. By driving either ninaED1 or ninaE+ expression from a heat-shock promoter, we show that the 80-kD rhodopsin complex forms immediately after gene activation. In wild type, but not ninaED1, rhodopsin monomeric forms are detected at later times. The generation of monomeric forms of wild-type rhodopsin is suppressed in vitamin A-deprived flies or in flies heterozygous for the dominant rhodopsin mutation. We also show that ninaED1 expression does not affect the maturation of another Drosophila visual pigment, Rh3. These results are consistent with the view that the ninaED1 rhodopsin antagonizes an early posttranslation process that is specific for maturation of the ninaE-encoded rhodopsin.

The visual pigment and vitamin A of Xenopus laevis embryos, larvae and adults

1977 ◽  
Vol 24 (1) ◽  
pp. 7-13 ◽  
Author(s):  
C.D.B. Bridges ◽  
Joe G. Hollyfield ◽  
Paul Witkovsky ◽  
Elaine Gallin
Keyword(s):  
Vitamin A ◽  
Xenopus Laevis ◽  
Visual Pigment ◽  
Xenopus Laevis Embryos

Extraction and characterization of the blue-sensitive visual pigment of the toad Bufo marinus

1987 ◽  
Vol 65 (4) ◽  
pp. 884-887 ◽  
Author(s):  
A. J. Sillman
Keyword(s):  
Vitamin A ◽  
Visual Pigment ◽  
Chemical Properties ◽  
Bufo Marinus ◽  
Physical And Chemical Properties ◽  
Electrophysiological Studies ◽  
Physical And Chemical ◽  
Toad Bufo ◽  
And Chemical Properties

The blue-sensitive visual pigment of the green rods of Bufo marinus was extracted with digitonin. The pigment is present in an amount equal to about 11% that of rhodopsin. It is based on vitamin A1 and exhibits a maximum absorbance of 433 nm. The pigment is labile and readily destroyed by hydroxylamine, regenerates to a much greater degree than does rhodopsin, and is more effectively extracted from the membrane than is rhodopsin. The green rod pigment of Bufo marinus appears to share the same physical and chemical properties as the green rod pigments of other amphibians. Therefore, the results of electrophysiological studies on the green rods of Bufo marinus can be more confidently generalized to other species. The results are discussed in terms of the blue phototaxis that is characteristic of many amphibians.

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