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PubMed1977

A study of oil of bergamot and its importance as a phototoxic agent. II. Factors which affect the phototoxic reaction induced by bergamot oil and psoralen derivatives.

Using a standardized open photopatch test technique, the phototoxic reactions produced by bergamot oil bergapten (5-methoxypsoralen) the active component of the oil, and xanthotoxin (8-methoxypsoralen) were studied. The reaction was affected by a range of factors such as the vehicle (PMF or ethanol), the concentration of ethanol in the vehicle, the skin site, the interval between application of the psoralen and irradiation, the hydration of the skin, and the degree of natural or sun-induced pigmentation. Repeated photopatch testing at the same skin site produced an increase in sensitivity. Eye colour, natural susceptibility to suntanning, age, and sex, had no effect on the phototoxic response to psoralens.

Adolescent↗
PubMed1987

Observations on the pigmentation of the pigeon iris.

There are three genetically controlled iris types found in the pigeon, two of which contain stromal pigment cells, the third lacks pigment cells. The yellow (gravel) and white (pearl) iris types have pigment cells that contain birefringent pigment granules (crystals) and are ultrastructurally similar to iridophores of poikilothermic vertebrates. Both these iris types contain guanine as a major "pigment" and, in addition, the yellow iris contains at least two yellow fluorescing pigments that are tentatively identified as pteridines. The pigment cells of the yellow and white irises are structurally identical differing only in the presence or absence of these yellow pigments. The stromal pigment cells of the white iris correspond in structure and pigment chemistry to classical iridophores although they lack strong irridescence and are therefore perhaps best considered leucophores. The pigment cells of the yellow iris can be considered "reflecting xanthophores" having the combined properties of both classical xanthophores and iridophore/leucophores.

Aging↗
PubMed1990

Iris stromal pigment cells of the ringed turtle dove.

Irides from adult Ringed Turtle Doves (Streptopelia risoria) were examined using both light and electron microscopy. The anterior surface of the iris stroma contained numerous large venous sinuses overlying bright yellow pigment cells which we classified as "reflecting xanthophores." The pigment cells were filled with irregularly arranged yellow reflecting crystals and occasional pterinosome-like structures. The irides were extracted in NaOH and the extracted pigments analyzed using paper chromatography and spectrophotometry. A unique bright orange fluorescent band was found in the iris extract, but the chemical nature of the band was not determined. Although guanine was expected to be a major component of the reflecting "platelets," based on previous work with other Columbiformes, it could not be demonstrated chromatographically or spectrophotometrically.

Animals↗
PubMed1994

The mouse pink-eyed dilution gene: association with hypopigmentation in Prader-Willi and Angelman syndromes and with human OCA2.

Mutations at the mouse pink-eyed dilution locus, p, cause hypopigmentation. We have cloned the mouse p gene cDNA and the cDNA of its human counterpart, P. The region of mouse chromosome 7 containing the p locus is syntenic with human chromosome 15q11-q13, a region associated with Prader-Willi syndrome (PWS) and Angelman syndrome (AS), both of which involve profound imprinting effects. PWS patients lack sequences of paternal origin from 15q, whereas AS patients lack a maternal copy of an essential region from 15q. However, the critical regions for these syndromes are much smaller than the chromosomal region commonly deleted that often includes the P gene. Hypopigmentation in PWS and AS patients is correlated with deletions of one copy of the human P gene that is highly homologous with its mouse counterpart. A subset of PWS and AS patients also have OCA2. These patients lack one copy of the P gene in the context of a PWS or AS deletion, with a mutation in the remaining chromosomal homologue of the P gene. Mutations in both homologues of the P gene of OCA2 patients who do not have PWS or AS have also been detected.

Albinism, Oculocutaneous↗
PubMed2004

The pigmentation of human iris influences the uptake and storing of zinc.

Age-related macular degeneration (AMD) is more prevalent among the elderly Caucasians than in Africans. A significant association between light iris colour, fundus pigmentation and incidence of AMD is reported, suggesting a possible correlation with melanin pigment. Zinc is known to bind to melanin in pigmented tissues and to enhance antioxidant capacity by function as a cofactor or gene expression factor of antioxidant enzymes in the eye. In this in vitro study, we investigated the uptake and storage of zinc in human irides. Irides of blue and brown human eyes were used. The number of melanocytes was measured. Tissues without any treatment served as controls. The irides were incubated with 100 microM zinc chloride in culture medium for 24 h. Specimens of the tissues were stored for the uptake examination. The remained pieces were further incubated for 3 and 7 d to investigate the storage of zinc. The concentration of zinc was measured by inductively coupled plasma mass spectrometry (ICP-MS). Melanocytes count was significantly higher in the brown tissues (P < 0.0001). Zinc concentration of blue coloured irides after 24 h zinc treatment was close to the controls. We did not observe any significant storing. In contrast, the concentration of zinc in brown irides was significantly increased after 24 h (P < or = 0.01) and remained at a high level for 7 d. The uptake of zinc is likely dependent on the amount of pigmentation in human iris. Therefore, we assume that in patients suffering from AMD the degree of pigmentation of the irides and eventually fundi should be under consideration when the patients are treated with zinc supplementation.

Antioxidants↗
PubMed2004

Inter-relation between variables determining constitutional UV sensitivity in Caucasian children.

BACKGROUND/PURPOSE: Sensitivity to ultraviolet (UV) light is associated with phenotypic variables like iris or hair colour or freckling, which are all strongly inter-related. We assessed the pattern of association among these factors to construct a summary measure reflecting constitutional UV sensitivity in a simple one-dimensional score with sufficient discriminating power. METHODS: Information on iris and hair colour (3 and 4 categories, respectively), freckling (none vs. any) and the reaction to mid-day summer sunlight as an outcome (dichotomized into 'burn' and 'tan') was collected in a cross-sectional study among children at school enrollment in 1999 and 2000 in Göttingen, Germany (n=3765 with complete data). Chi-squared automatic interaction detector (CHAID) analysis and log-linear modelling was used to assess the pattern of mutual inter-relations. RESULTS: Hair colour turned out to be the factor most strongly associated with UV sensitivity. In case of blonde or brown hair (the most common phenotypes in our sample), the consideration of freckling further refined the classification system, whereas iris colour did not contribute additional information. The results of the CHAID and log-linear analyses suggest a simple five-point score capturing constitutional UV sensitivity. The discriminating power of this score was high in our sample, with the proportion of persons who burned ranging from 7.7 (lowest category) to 73% (highest category). CONCLUSION: The new scoring system summarized efficiently relevant information on individual constitutional UV sensitivity in our sample. Its further validation in independent studies comprising Caucasian children or adults is necessary to assess objectively its properties for future applications.

Child↗
PubMed2006

Interaction of Hermansky-Pudlak Syndrome genes in the regulation of lysosome-related organelles.

Hermansky-Pudlak Syndrome (HPS) is a genetically heterogeneous disease caused by abnormalities in the synthesis and/or trafficking of lysosome-related organelles (LROs) including melanosomes, lamellar bodies of lung type II cells and platelet dense granules. At least 15 genes cause HPS in mice, with a significant number specifying novel subunits of protein complexes termed BLOCs (Biogenesis of Lysosome-related Organelles Complexes). To ascertain whether BLOC complexes functionally interact in vivo, mutant mice doubly or triply deficient in protein subunits of the various BLOC complexes and/or the AP-3 adaptor complex were constructed and tested for viability and for abnormalities of melanosomes, lung lamellar bodies and lysosomes. All mutants, including those deficient in all three BLOC complexes, were viable though the breeding efficiencies of multiple mutants involving AP-3 were severely compromised. Interactions of BLOC protein complexes with each other and with AP-3 to affect most LROs were apparent. However, these interactions were tissue and organelle dependent. These studies document novel biological interactions of BLOC and AP-3 complexes in the biosynthesis of LROs and assess the role(s) of HPS protein complexes in general health and physiology in mammals. Double and triple mutant HPS mice provide unique and practical experimental advantages in the study of LROs.

Animals↗
PubMed1993

Position-effect variegation and z1 mediated white repression in the In(1)wis system in Drosophila melanogaster.

We have characterized a new X-chromosomal inversion in Drosophila melanogaster, extending from just distal of white to just proximal of the bb locus. The inversion places the w-isoxanthopterinless (wis) allele close to heterochromatin and under the influence of position-effect variegation (PEV). The wis gene activity is also regulated by chromosome pairing-dependent z1-mediated repression. By changing the environment, using specific second site modifiers, altering the amount of heterochromatin, and disturbing the chromosome pairing, we have been able to separately affect the two regulatory phenomena and analyse their respective impact on the wis regulation. We provide evidence that under normal conditions PEV and z1 mediated white repression are additive. However, at extreme levels of wis repression by PEV, changes in the z1-mediated interactions are not observable. This indicates that PEV is epistatic to z1-mediated regulation of wis. We also show that deficiencies in the short arm of Y act as suppressors of the z1-mediated white repression. This suppression does not influence PEV and is thus not due to the lower amount of heterochromatin. We propose that nonhomologous chromosome pairing between X and Y is important for the synapsis-dependent z1-mediated repression of white transcription activity in this system.

Animals↗
PubMed1985

Pigment spots related to scleral emissaries in Eskimos, Mongols, and Caucasians.

Examinations of a series of 1241 subjects showed episcleral pigment spots bearing relation to scleral canal emissaries to be most frequent among Eskimos (prevalence 85%), somewhat less frequent among Mongols (68%), and the rarest among white Northern Europeans (16%). The prevalence is the highest among women and rises very little with increasing age. The pigmentation is most often bilateral in Eskimos (66%), more rarely so in Caucasians (18%). It is most often localized superiorly (54%). Then follows in decreasing order to frequency:inferiorly (26%), nasally (13%), and - significantly more rarely - temporally (7%). The pigmentation is most often related to an artery (90%), most often one running a radial course (39%) or in the incyclo-direction (32%). Its average length in caucasians is 1.1 mm. Pigmentations are significantly related to the colour of the iris (visible in 8% of blue irides, against in 40% of brown).

Adolescent↗
PubMed1990

Pigmentation of the eye and hair in relation to age-related macular degeneration. An epidemiological study of 1000 aged individuals.

So far, no epidemiological studies have dealt with the relationship between dark and light pigmented Caucasians and the risk of developing age-related macular degeneration (AMD). Based upon hospital referred eye patients, dark ocular pigmentation has previously been suggested as a protective factor. The present study reviews macular degeneration, defined as macular changes implicating a vision of 6/9 or less, in prevalence rates in relation to ocular pigmentation and hair colour in an ethnic homogeneous and random population of 1000 Danes, 60-80 years of age. The population was predominantly light pigmented. Brown iris colour was only present in 15.9%, dark pigmented fundi in 19.0% and a black juvenile hair colour supposed in 6.5%. The prevalence rates of AMD ranged from 16.0 to 10.5% for brown respectively blue iris colour, and from 13.3% to 9.0% for dark respectively light pigmented fundi. The presented data indicate that no significant differences in prevalence rates of AMD seem to exist between dark and light ocular pigmented Danes. An additional comparison between 100 AMD patients referred to hospital and the epidemiological sample did not reveal a difference in pigmentation. The prevalence analysis also showed that neither is juvenile hair colour of prognostic value in terms of later occurrence of AMD nor seems greyness of hair to be an independent indicator of AMD, but related to age as is AMD, when simultaneously entered into a logistic regression model.

Aged↗
PubMed1991

Iris colour and the influence of local anaesthetics on pre-corneal tear film stability.

Using non-invasive methods we report here that the stability of the pre-corneal tear film is lower in the brown eye than in the blue eye. The average stability in the blue eye is 15.8 sec (SD +/- 5.8) and in the brown eye it is 12.3 sec (SD +/- 2.9). On average, instillation of topical anaesthetics, benoxinate hydrochloride (0.4%) or amethacaine hydrochloride (0.5%), depress the stability of the pre-corneal tear film in blue eyes but not in brown eyes.

Administration, Topical↗
PubMed1994

Corneal sensation in insulin dependent and non-insulin dependent diabetics with proliferative retinopathy.

The corneal sensation of diabetic patients undergoing pan retinal photocoagulation for the treatment of proliferative retinopathy was measured using the Cochet-Bonnet aesthesiometer. Insulin dependent and non-insulin dependent diabetics both showed significantly decreased corneal sensitivity, and there was no significant change following pan-retinal photocoagulation. Insulin dependent diabetics with proliferative retinopathy had been diagnosed for a significantly longer period than non-insulin dependent diabetics, but had better corneal sensitivity than the latter group. Male patients were more likely to have brown irides, whereas there was a preponderance of blue irides amongst the females. Patients with blue irides also had significantly lower sensitivity than patients with brown irides. The results are discussed.

Adult↗