PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Eye Color”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 937 records · Page 52Linked to original sources
PubMed1988

Magnetic field effects on pineal N-acetyltransferase activity and melatonin content in the gerbil--role of pigmentation and sex.

The ambient geomagnetic field influences a variety of biological phenomena. Electrical and biochemical parameters of the rodent pineal gland are influenced by the alteration of weak magnetic fields (MF), the magnetic receptor probably residing in the retina. However, open questions concern the role of retinal pigmentation as well as species- and sex-specific differences in MF perception. We therefore exposed male and female naturally pigmented and albino Mongolian gerbils, as well as Sprague-Dawley (SD) rats to a 60 degrees rotation of the horizontal component of the ambient MF. Alteration of nocturnal pineal melatonin content and N-acetyltransferase (NAT) activity were utilized as a parameter for assessing magneto-sensitivity. In pigmented gerbils, MF exposure resulted in no significant changes in pineal melatonin synthesis. In contrast, albino gerbils and SD rats exhibited--regardless of sex--significant decreases in pineal NAT activity and melatonin content following MF exposure. These results suggest that in rodents hypopigmentation appears to favor magnetoperception. The available evidence indicates that the pigmentation of the retina could play a crucial role.

Acetyltransferases↗
PubMed1996

Illumination has no effect on rats' behavior in the elevated plus-maze.

Male Wistar rats Shoe:Wist(Shoe) were tested in the elevated plus-maze under three different illumination levels (30, 300, and 900 lx). It was found that illumination did not change percentage of time spent in closed arms, number of closed arm entries, or time spent on open arms, or total arm entry. This confirms earlier findings that rat's behavior in the elevated plus-maze is independent of light levels.

Albinism↗
PubMed1980

A genetic study of the susceptibility of Anopheles gambiae to Plasmodium berghei.

In a study of the genetics of susceptibility and refractoriness of Anopheles gambiae to Plasmodium species, nine generations of selection resulted in a completely susceptible line and an entirely refractory line to Plasmodium berghei (a rodent malaria). The F1 progeny from reciprocal crosses between the lines differed in their susceptibility to the parasite. Backcrosses to the parent did not produce proportions of susceptible and refractory individuals consistent with single gene inheritance or with cytoplasmic inheritance but the influence of a sex linked factor was demonstrated.

Animals↗
PubMedDate not supplied

Effects of iris pigmentation on response of ocular pressure to timolol.

Timolol ophthalmic solution effectively reduced mean intraocular pressure (IOP) in Negro and Caucasian patients with chronic open angle glaucoma and untreated IOP of 22 mm Hg or higher. No differences in pressure lowering response were observed among the races although the Negroes required somewhat higher timolol concentrations to produce similar reductions from baseline IOP. Negro patients also appeared to have a more severe disease as indicated by the number of prior antiglaucoma drugs required and the untreated (baseline) pressures. An unexpected finding was the significantly greater number of Caucasians with dark irides who were discontinued from therapy because of inadequate pressure reduction.

Adult↗
PubMed1989

The spectral transmission of the lens and cornea of the brown trout (Salmo trutta) and goldfish (Carassius auratus)--effect of age and implications for ultraviolet vision.

This study reports spectral transmission curves (250-700 nm) for the lenses and corneas of two teleost species known to be u.v. sensitive; brown trout (Salmo trutta) aged 0-3 yr, and goldfish (Carassius auratus) aged 0-4 yr. In both cases there is a decrease in lenticular short-wave transmission with increased age which cannot be explained by an increase in lens size alone. Corneas of goldfish go through a similar ageing process while those of the trout do not. An orange pigmentation located in the dorsal cornea of goldfish is also described.

Aging↗
PubMed1989

The spectral transmission of freshwater teleost ocular media--an interspecific comparison and a guide to potential ultraviolet sensitivity.

Based on their spectral transmission, the lenses of 50 teleost species can be classified into three categories: "type 1" colourless lenses with 50% transmission points between 315 and 354 nm, "type 2" lenses which also appear colourless but have 50% cut-off points around 362-405 nm, and "type 3" lenses which are visibly yellow (50% transmission 425-450 nm). Most corneas transmit all wavelengths down to around 300 nm, with only 3 species showing a distinct yellow colouration. This distribution of ocular media transmission is related both to the phylogenetic group of the fish and to their photic environment.

Animals↗
PubMed1990

The intraocular straylight function in 129 healthy volunteers; dependence on angle, age and pigmentation.

The direct compensation method allows for an accurate (standard deviation below 0.05 log unit) determination of intraocular light scattering between 3.5 and 25 deg of scattering angle and is suitable for untrained subjects. The method was used to study population behaviour and individual variation in 129 volunteers between 20 and 82 yr of age, visual acuity equal to or better than one and no apparent eye pathology. The results indicate straylight to increase with the 4th power of age, doubling at 70. In addition to the age dependence, there was great variation between individuals. Part of this is due to negative correlation with pigmentation.

Adult↗
PubMed1993

Light scattering in the eye of the blowfly chalky mutant: the effect on spectral sensitivity of photoreceptors R1-6.

In non-pigmented insect eyes, stray light causes the narrowing of the spectral sensitivity functions of the visual cells, and this effect is shown to be a sensitive tool for estimation of the stray light absorption by a photoreceptor. Spectral sensitivity functions of single cells of Calliphora chalky mutants were obtained in three sets of experiments with different contribution of stray light in total light absorption by a visual cell, and the relative parasitic absorption due to stray light appeared to be as high as 70% of total absorption even with a point light source. The effect of light scattering may be of some functional significance in non-pigmented parts of the wild type eyes as, for instance, in the dorsal rim area of the crickets.

Animals↗
PubMed1984

Photophysiological functions of visual pigments.

In order to gain a fundamental understanding of functions of a visual pigment, i.e., photoreception and phototransduction, it is essential to elucidate the molecular structure of visual pigment, its photochemical behavior and connection of the pigment to the molecular physiological amplification mechanism for excitation of a visual cell. A rhodopsin, a rod visual pigment, is composed of an 11-cis-retinal bound with an apo-protein, opsin, through a protonated Schiff-base. Competitive inhibition of beta-ionone on regeneration of rhodopsin from an 11-cis-retinal and cattle opsin demonstrated the existence of a hydrophobic linkage between the beta-ionone ring of the retinal and the hydrophobic region of opsin. Owing to these two linkages, the 11-cis-retinal is fixed in an opsin cleft. As a result, it is endowed with new physiological functions as a chromophore of rhodopsin; the change of 11-cis-retinal (lambda max = 369 nm, epsilon = 26,400) to rhodopsin (lambda max = about 500 nm, epsilon = 40,600) brings not only a spectral shift from near ultraviolet to visible regions and an intensification of the molecular extinction coefficient, but also an increase of a quantum yield of 11-cis-retinal to all-trans form. High quantum yield of rhodopsin suggests rapid formation of the first photoproduct. Study of the first photoproduct was accelerated by the finding of bathorhodopsin, which was formed by irradiation at liquid nitrogen temperatures. The change of rhodopsin to bathorhodopsin has been inferred to be due to a photoisomerization of the chromophore from 11-cis to a twisted all-trans form. This isomerization hypothesis has been verified by the following experimental results. Irradiation of 7-cis- and 9-cis-rhodopsins at liquid nitrogen temperature produced the same bathorhodopsin as that from 11-cis-rhodopsin, indicating that the chromophore of bathorhodopsin should be in all-trans or transoid form. 7-Membered-rhodopsin, in which the rotation of 11-12 double bond of the retinylidene chromophore is locked, did not form bathorhodopsin by excitation of picosecond laser photolysis. This fact indicates that bathorhodopsin is a product formed by photoisomerization of the chromophore. Rhodopsin showed a positive circular dichroism (CD) in the visible while bathorhodopsin showed a remarkable negative CD. The reversal of the sign of CD indicates that not only large conformational change of the retinylidene chromophore occurs during the conversion of rhodopsin to bathorhodopsin, but also the direction of twist of the chromophore reverses. It is inferred that the chromophore of bathorhodopsin is a twisted trans form.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1982

Regulation of white locus expression: the structure of mutant alleles at the white locus of Drosophila melanogaster.

We have analyzed the structures of 19 mutant alleles at the white locus of Drosophila melanogaster. Thirteen of the mutant alleles in our selected sample arose spontaneously, and of these, seven are associated with insertions of non-white-region DNA sequence elements. Several lines of evidence strongly suggest that these insertions are responsible for their associated mutant alleles, and further suggest that most or all of these insertions are transposons. Moreover, the white locus DNA sequences can be divided into two nonoverlapping domains on the basis of the properties of the two domains as mutational targets. One of these domains behaves, in this regard, in the manner expected of functional coding sequences, whereas the other does not. We propose a model for the nature and function of the presumptive noncoding white locus genetic elements. The two domains of the white locus defined by our studies are approximately coextensive with the functionally distinct subintervals of the locus defined by previous genetic analysis. Lastly, our results strongly suggest that the dominant, mutable wDZL allele results from the insertion of a transposon outside of, but near, the white locus. This putative transposon apparently carries genetic elements that act at a distance to repress expression of the white locus.

Alleles↗