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PubMed1991

Contribution of glycation to human lens coloration.

To study the contribution of glycation or the Maillard reaction to the spontaneous coloration of human crystalline lens in aging, we determined 1-deoxyfructosyl adduct and the fluorescent material, which are produced in the early stage of glycation, in the proteins of normal and colored human lenses of different ages. The amount of both glycation products in the lens increased significantly in proportion to aging or the advance of lens coloration. The insolubility of lens protein also increased with the advance of glycation. In addition, the present study showed that glucose and glucose-6-phosphate have higher reactivities with human lens protein than fructose and glucose-1-phosphate. This paper demonstrates that the deeper colored or older aged lens contains larger amounts of glycation products, and that glycation between lens protein and various sugars in vivo may be a serious factor in human lens coloration or insolubilization of lens protein.

Animals↗
PubMed1994

Restriction map polymorphism in the forked and vermilion regions of Drosophila melanogaster.

Restriction map polymorphism at two X linked foci, forked and vermilion of Drosophila melanogaster was studied in three natural populations. The estimates of nucleotide variation were theta = 0.003 and pi = 0.002 for the forked region and theta = 0.004 and pi = 0.002 for the vermilion region. Three insertions (> 500 bp) were observed at each locus. Typical of other regions of this species each of these large insertions was unique in the sample. Non-random association among polymorphisms was common at the vermilion locus, while the forked locus was not polymorphic enough to test linkage disequilibrium. The amounts of restriction site and size variation in the vermilion and forked were within the range observed for other loci of D. melanogaster.

Animals↗
PubMed1989

Sun exposure and malignant melanoma among susceptible individuals.

The purpose of this case-control study was to identify susceptible subgroups, primarily based on pigmentary characteristics, at higher risk of developing melanoma when exposed to the sun. The study group, which was interviewed from 1979 to 1982, consisted of 289 consecutive patients with melanoma and 527 randomly selected controls without cancer. In general, the risk of melanoma associated with sun exposure was greater for individuals expected to be susceptible on the basis of poor ability to tan, but not other pigmentary traits. There were, in addition, some noteworthy interactions between age and sun exposure. Among subjects with poor tanning ability, the risk of melanoma associated with outdoor occupation was more than 3-fold [odds ratio (OR) = 3.3] compared to indoor occupation. In contrast, the analogous OR was much less elevated among subjects with a good ability to tan (OR = 1.5). Mixed indoor and outdoor job exposure was protective among good tanners (OR = 0.80), but not among poor tanners (OR = 1.5). A similar pattern was seen for recreational sun exposure and, when applying multiple logistic regression, for the patient's overall subjective assessment of his lifetime sun exposure. However, quantitative assessment of average hours of sun exposure did not prove to be a good indicator of melanoma risk, even among susceptible individuals. A history of severe sunburn with blistering was associated with nearly 3-fold risk among poor tanners (OR = 2.9) but was protective among good tanners (OR = 0.79). A history of nonmelanoma skin cancer or solar keratosis was a very strong risk factor (OR = 7.3), which, however, did not significantly differ in magnitude among susceptibility subgroups.

Adult↗
PubMed2002

Toxicological study of a new maintenance fluid, Veen 3G, in rats.

A study of the different volume and infusion rates of a new maintenance fluid, Veen 3G, on the general conditions of rats was investigated during the 14 days after infusion. In Experiment I, 100 ml/kg and 200 ml/kg of Veen 3G were infused at a rate of 300 ml/kg/h in male and female rats. Results were compared with those for Gurunon Ringer solution (GRS) in male and female rats. We observed only transient polyuria in animals administered by each dose of Veen 3G and GRS for 0-15 min after infusion. Necropsy was not observed in any of the animals tested 14 days after infusion. In Experiment II, 200 ml/kg of Veen 3G was infused at rates of 200, 400, 800 and 1600 ml/kg/h in male rats. At 800 and 1600 ml/kg/h, irregular respiration and decrease in movement were observed concomitantly with polyuria. Three out of 4 rats died immediately after the infusion of Veen 3G at a rate of 1600 ml/kg/h, and one rat was still alive 14 days after the infusion. In this experiment, 200 ml/kg Veen 3G was safe when we infused at a rate of less than 400 ml/kg/h in male rats. Since this rate is about 27-80 times higher than that used clinically in maintenance treatment, Veen 3G is suggested to be safe, with the exception of polyuria, in clinical situations at the standard infusion rate (5-15 ml/kg/h).

Animals↗
PubMed2000

The achromatic mechanism and mechanisms tuned to chromaticity and luminance in visual search.

The purpose of the study was to determine whether visual search can be mediated by an achromatic, or luminance, mechanism in which signals are independent of the chromaticity of the stimuli. Experiments were designed to determine whether variability in the chromaticity of distractor stimuli made it more difficult to search for a target that differed from the distractor stimuli in luminance. Variability in the chromaticity of the distractors had little or no effect on search times when the target stimulus was white. Variability in the chromaticity of the distractors increased search times when the target was a reddish or bluish chromaticity. Results obtained with white targets suggest that these searches are mediated by an achromatic mechanism in which the signals are independent of the chromaticity of the stimuli. Results obtained with reddish and bluish targets suggest that searches for those targets may be mediated by mechanisms tuned to both chromaticity and luminance. Further experiments in which observers searched for targets that differed from distractors in both chromaticity and luminance provided additional support for the second conclusion.

Attention↗
PubMed2003

Importance of genetic effects for characteristics of the human iris.

The relative importance of genetic influences (heritability) on five general textural quality characteristics of the human iris was assessed using sex and age limitation models. Colour photographs of irises were available from 100 monozygotic twin pairs, 99 dizygotic twin pairs, and 99 unrelated randomly paired age-matched German subjects. Comparative scales were constructed and two judges who were blind to zygosity independently rated five characteristic of the subjects' left iris. Inter-rater reliabilities were larger than.90 for all five scales. The heritabilities for the five iris characteristics ranged from.51-.90. No sex-specific genetic factors were found for the iris characteristics. Age-group differences in heritability were found for one of the five iris characteristics - "distinction of white dot rings". Heritability was greater for the older cohort (90%) than the younger (73%). The iris characteristics that showed the next highest additive-genetic effect were "contractional furrows" (78%) and "frequency of crypts" in the main stroma leaf (66%).

Adolescent↗
PubMed1993

Eye colour: an unconsidered variable in cognitive research?

Evidence analysed based on reaction time has contributed to the development of cognitive models of human information processing. Essential to the consideration of possible variables to be controlled when designing experimental work on cognitively related issues are variables such as the subjects' age, sex, or education. Barely a handful of studies have ever taken eye colour seriously as a variable to be controlled when exploring cognitively related issues. Very few researchers have considered the possibility that a person's eye colour might influence reaction time. The question is whether eye colour should be taken seriously when designing experimental work in cognitive psychology. In this study we found significant differences in choice reaction time using the McCarthy and Donchin (1981) paradigm, the dark-eyed subjects being faster tha the light-eyed. Implications of the findings are discussed.

Adolescent↗
PubMed2001

Eye colour and reaction time to visual stimuli in rugby league players.

Subjects with dark eye colour are thought to perform better on reactive tasks in comparison to light-eyed subjects, whereas light-eyed subjects show enhanced performance over dark-eyed subjects on self-paced activities. This study examined reaction time using unrestricted and peripheral vision and success at the self-paced activity of goal kicking in 59 elite male Rugby League players. Subjects with dark eye colour did not react significantly faster than the light-eyed subjects when tested using unrestricted vision or peripheral vision. Examination of the self-paced activity of goal kicking showed that the percentage success rate was not significantly higher in the light-eyed group than the dark-eyed group. In conclusion, there was no significant difference in reaction time to a visual stimulus or success in goal kicking between dark- and light-eyed Rugby League players.

Adolescent↗
PubMedDate not supplied

The influence of eye colour upon temporary threshold shift.

Controversy has arisen over the claim that melanin content of the iris as determined by eye colouration bears a direct relationship to susceptibility to temporary threshold shifts (TTS). A more comprehensive investigation of TTS has now been carried out which not only confirms the relationship but also indicates that earlier discordant results can be attributed to differences in methodology. The new evidence suggests that for stimulus intensities below 110 dB. (HTL re ISO, 1964) melanin content of the iris exerts its influence predominantly upon auditory adaptation while fatigue effects only become apparent at intensities above this level. The relevance of these findings to hearing conservation measures aimed at the prevention of noise-induced hearing loss is discussed.

Acoustic Stimulation↗
PubMed1980

Eye colour and susceptibility to noise-induced permanent threshold shift.

257 3rd-year apprentices were given ear, nose and throat examination, electroacoustic impedance tests and audiometry. Their eye colour was also recorded. Average hearing levels of otologically normal left ears were poorer at 4 kHz (p less than 0.05) for apprentices with eye colours indicating no melanin pigmentation of the iris than for apprentices with melanin iris pigmentation.

Acoustic Impedance Tests↗
PubMed1981

The relations of eye colour and smoking to noise-induced permanent threshold shift.

The hearing of 118 otologically normal soldiers 40 years of age or less with at least 8 years service was tested. Their eye colours were also recorded. Each soldier was questioned concerning his medical history, history of noise exposure and smoking habits. Left ear average hearing levels at 3 kHz were poorer in soldiers with eye colours indicating no melanin pigmentation of the iris than those with iris pigmentation (p < 0.05). Effects of smoking were statistically significant at one frequency but difficult to interpret in terms of current theories.

Adult↗
PubMed1981

A search for the photoreceptor in the photosensitive irises of normally pigmented and albino hamsters (Mesocricetus auratus).

Hamsters are among the mammalian species whose irises are directly sensitive to light, responding with a constriction even when completely isolated from the rest of the hamster. Examination of the ultrastructure of the irises of both normally pigmented and albino hamsters disclosed a typical vertebrate iris, containing a sphincter and dilator pupillae, and anterior stromal layer, and two layers of pigment epithelial cells. No structures obviously specialized for photoreception were found. We examined the possibility that the pigment granules in the cells of the sphincter pupillae are photosensitive, and that their electron-dense melanin masks some photosensitive structure. However, this was ruled out by the observation that albino irises, which are photosensitive, are devoid of even rudimentary pigment granules. These results are consistent with the hypothesis that the sarcolemmas of the smooth muscle cells of the sphincter pupillae are photosensitive in this species.

Albinism↗
PubMed1991

The influence of eye colour on susceptibility to TTS in humans.

In order to investigate the function of the inner ear melanin, noise-induced temporary hearing loss (temporary threshold shift, TTS) was studied in humans with either blue or brown iris colour. Sixty-eight normally hearing teenage boys participated in this study. Hearing thresholds before and after exposure were established with a computerized sweep frequency audiometer in the frequency range 0.8-8 kHz. The noise exposure consisted of a 1/3 octave band-filtered noise with centre frequency 2 kHz at 105 dB SPL for 10 min. The mean TTS in the frequency range 2-8 kHz showed a significant difference with the brown-eyed subjects developing least TTS, and the blue-eyed subjects most TTS.

Adolescent↗
PubMed1996

Effects of controlled exposure of sunlight on plasma and skin levels of beta-carotene.

We conducted a randomized placebo-controlled double-blind study in 20 healthy young female students (skin type II + III, body mass index 18-22) in order to evaluate the efficacy of 10 weeks of moderate dose (30 mg/d) beta-carotene (BC) on plasma and skin beta-carotene levels during 12 days of time and intensity controlled sunlight exposure at sea level (30 degrees latitude, Red Sea, Eilath, Israel). After 12 days of controlled sun exposure (total UV dose of about 10.000J/cm2), plasma beta-carotene decreased in the placebo (p < 0.01) and beta-carotene group (not significant). In addition cutaneous beta-carotene decreased significantly in both groups. Plasma alpha-tocopherol decreased significantly (p < 0.01) during exposure time in both groups. In the supplemented group, however, the decrease of a-tocopherol was significantly greater (p < 0.01) than in the placebo group. We conclude that sunlight influences the beta-carotene and alpha-tocopherol content of blood and tissues.

Adult↗
PubMed1990

Comparative genetics of albinism.

Albinism in laboratory mammals is equivalent to human tyrosinase-negative oculocutaneous albinism, and thus the result of recessive mutation in the structural locus for tyrosinase (TYR), which prevents melanin biosynthesis. In the mouse, eight mutant alleles are now known at this locus, with differing effects on eye colour and on the degree of reduction in eumelanin and phaeomelanin pigmentation. Three of these alleles, namely chinchilla, himalayan (acromelanistic) and albino (c) itself, have also been recognized in a number of other species but only albino has been identified in man so far. The himalayan allele (equivalent to Siamese in the cat) is of particular interest because it converts tyrosinase into a thermolabile form, with greater production of melanin in colder areas of the body. The optic track misrouting found in human albinos also occurs in albino alleles in other mammals, which may also show reduced activity and stress responses. The TYR locus is on human chromosome 11, which now has at least 11 loci with homologues on mouse 7. However, their order is markedly different in the two species. For instance, c and Hbb (beta-globin), which are closely linked in mouse, rabbit, cat etc., are far apart on human 11q and 11p respectively. Moreover, some loci (e.g., Fes and Mod-2) which are close to c in the mouse appear to be on human chromosomes other than 11. This extensive chromosomal restructuring in mammalian evolution means that the effects of human albino deletions may differ greatly from those studied in the mouse, which are associated with defects of kidney, liver and thymus. Tyrosinase-positive albinos or near-albinos are known at a number of loci in mice and other mammals. They are the result of the absence or inhibition of melanocytes in the affected areas, so that no melanin is produced. In general they are associated with pathological pleiotropisms which may lead to anaemia, inner ear defects, megacolon, neurological effects, skeletal defects, microphthalmia, osteopetrosis, spina bifida, sterility and so on. Homologies between these and human loci affecting pigmentation are now being discovered.

Albinism↗