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At least 1,099 records · Page 61Linked to original sources
PubMed1992

Genetic and molecular analysis of recessive alleles at the pink-eyed dilution (p) locus of the mouse.

Recessive mutant alleles at the pink-eyed dilution (p) locus on mouse chromosome 7 reduce pigmentation of both the coat and eyes. Here we describe the properties and complementation interactions of 10 p alleles, including 6 not previously reported. Several alleles that cause additional phenotypes affecting development, reproduction, and behavior were shown to be deletions by using DNA probes derived from the p region. An alignment of functional and marker-defined units is proposed, giving a linear complementation map that orders at least four functional loci. The characterization of a nested set of deletions around p will facilitate detailed molecular analyses of the genes and developmental functions associated with this part of the mouse genome.

Alleles↗
PubMed1994

Molecular basis of dark-eyed albinism in the mouse.

Dark-eyed albino (C44H) is a recessive allele at the mouse albino (c) locus, which encodes tyrosinase (monophenol,L-dopa:oxygen oxidoreductase, EC 1.14.18.1), the key enzyme in melanin synthesis. Similar to type IB oculocutaneous albinism in humans, overall production of pigment is greatly reduced in dark-eyed albino mice and obvious only in the eyes. We have studied the molecular basis of the c44H mutation and show that expression of the tyrosinase gene is not affected. After sequencing tyrosinase cDNA isolated from c44H/c44H homozygotes, we uncovered a single base alteration from wild type leading to a serine-to-isoleucine exchange. The importance of this mutation was demonstrated by generating transgenic mice containing a mutated tyrosinase minigene. This showed that the single base change was sufficient to severely depress pigment production in transgenic mice. We therefore conclude that the point mutation is responsible and sufficient to generate the dark-eyed albino phenotype.

Albinism↗
PubMed1996

Overexpression of a Rrp1 transgene reduces the somatic mutation and recombination frequency induced by oxidative DNA damage in Drosophila melanogaster.

Recombination repair protein 1 (Rrp1) includes a C-terminal region homologous to several DNA repair proteins, including Escherichia coli exonuclease III and human APE, that repair oxidative and alkylation damage to DNA. The nuclease activities of Rrp1 include apurinic/apyrimidinic endonuclease, 3'-phosphodiesterase, 3'-phosphatase, and 3'-exonuclease. As shown previously, the C-terminal nuclease region of Rrp1 is sufficient to repair oxidative- and alkylation-induced DNA damage in repair-deficient E. coli mutants. DNA strand-transfer and single-stranded DNA renaturation activities are associated with the unique N-terminal region of Rrp1, which suggests possible additional functions that include recombinational repair or homologous recombination. By using the Drosophila w/w+ mosaic eye system, which detects loss of heterozygosity as changes in eye pigmentation, somatic mutation and recombination frequencies were determined in transgenic flies overexpressing wild-type Rrp1 protein from a heat-shock-inducible transgene. A large decrease in mosaic clone frequency is observed when Rrp1 overexpression precedes treatment with gamma-rays, bleomycin, or paraquat. In contrast, Rrp1 overexpression does not alter the spot frequency after treatment with the alkylating agents methyl methanesulfonate or methyl nitrosourea. A reduction in mosaic clone frequency depends on the expression of the Rrp1 transgene and on the nature of the induced DNA damage. These data suggest a lesion-specific involvement of Rrp1 in the repair of oxidative DNA damage.

Alkylating Agents↗
PubMed1998

Identification of morc (microrchidia), a mutation that results in arrest of spermatogenesis at an early meiotic stage in the mouse.

The microrchidia, or morc, autosomal recessive mutation results in the arrest of spermatogenesis early in prophase I of meiosis. The morc mutation arose spontaneously during the development of a mouse strain transgenic for a tyrosinase cDNA construct. Morc -/- males are infertile and have grossly reduced testicular mass, whereas -/- females are normal, indicating that the Morc gene acts specifically during male gametogenesis. Immunofluorescence to synaptonemal complex antigens demonstrated that -/- male germ cells enter meiosis but fail to progress beyond zygotene or leptotene stage. An apoptosis assay revealed massive numbers of cells undergoing apoptosis in testes of -/- mice. No other abnormal phenotype was observed in mutant animals, with the exception of eye pigmentation caused by transgene expression in the retina. Spermatogenesis is normal in +/- males, despite significant transgene expression in germ cells. Genomic analysis of -/- animals indicates the presence of a deletion adjacent to the transgene. Identification of the gene inactivated by the transgene insertion may define a novel biochemical pathway involved in mammalian germ cell development and meiosis.

Animals↗
PubMed2001

Lipid peroxidation in porcine irises: dependence on pigmentation.

PURPOSE: Pigmentation of the iris is caused by varying amounts of melanin pigment granula in a constant number of melanocytes in the superficial stroma. Melanin has been shown to act as antioxidant. We have now investigated lipid peroxidation in dependence on stromal pigmentation in isolated porcine irises. METHODS: The same number of lightly and heavily pigmented porcine irises (visual selection) were homogenized (1 : 20 w/v) in buffer (50 mmol/l phosphate buffer and 4 mmol/l sodium azide). 500 microl homogenate were incubated at 37 degrees C in duplicate for 5, 10, 20 and 40 min in absence and presence of Fe2+ as inducer of lipid peroxidation. The amount of lipid peroxidation was assayed by the thiobarbituric acid (TBA) test. The results are expressed as nmol of TBA reactive material (TBAR) produced/mg protein. Fe2+ concentration of the supernatant was determined spectrophotometrically with 1,10 orthophenanthroline. Concentrations of D-glucose and D -fructose in iris tissue homogenates were determined spectrophotometrically by enzymatic bioanalysis. RESULTS: 70, 180 and 360 micromol/l Fe2+ induced lipid peroxidation. A plateau region was reached after 20 min. The amount of lipid peroxidation differed in dependence on stromal pigmentation in porcine irises. The effect was most significant at 180 micromol/l Fe2+, which induced 1.373 +/- 0.138 nmol TBAR/mg protein in lightly compared to 0.491 +/- 0.125 nmol TBAR/mg protein in heavily pigmented irises after 10 min incubation (p < 0.0001, n = 4). Similar effects (factor 2-3) were also measured after 20 and 40 min incubation. On the other hand, the content of Fe2+ in the supernatant was the same within error. Sugar concentrations (D-glucose and D-fructose) did not differ significantly for the two differently pigmented iris tissues. CONCLUSIONS: There is a stronger induction of lipid peroxidation in lightly compared to heavily pigmented porcine irises. This effect may be related to the difference in stromal melanin content and its antioxidant activity.

Animals↗
PubMed2002

Fuchs' heterochromic iridocyclitis: clinical manifestations in dark-eyed Mexican patients.

PURPOSE: To describe the clinical features of Fuch's heterochromic iridocyclitis (FHI) in dark-eyed Mexican patients. MATERIAL AND METHODS: A longitudinal, retrospective, and analytical study of the clinical features of FHI patients was performed. It reviewed the clinical charts of all patients with a diagnosis of FHI seen at the Inflammatory Eye Diseases Clinic of 'Dr. Luis Sánchez Bulnes' Hospital between April 1988 and September 1999. RESULTS: Data of 68 patients (136 eyes) were reviewed. One eye was affected in 89.71% of the cases (61 patients). Fifty patients had brown eyes and iris heterochromia was clinically evident in 25%. Mild stellate keratic precipitates were seen in 80% of the affected eyes. Blurring of the iris surface was found in 40 eyes; iris nodules (Koeppe and/or Busacca) were present in half the cases. A cataract was observed in 69% of the affected eyes, 57.7% of which underwent surgery. Ocular hypertension was present in 30.66% of the affected eyes, glaucoma in 4%. CONCLUSIONS: The more common clinical features in this group of patients were fine and stellate keratic precipitates, atrophy of the iris crypts, and iris nodules. Clinically evident iris heterochromia was present in only 25% of the affected eyes. FHI diagnosis in brown-eyed patients cannot rely on iris heterochromy only.

Adolescent↗
PubMed1998

Interdependence of eye and hair colour, skin type and skin pigmentation in a Caucasian population.

Eye colour, hair colour and skin colour are important risk factors for malignant melanoma and non-melanoma skin cancers. There are few studies in which the distribution of these pigmentary factors in risk populations has been assessed. The purpose of this study was to investigate the prevalence of the major eye and hair colours and the distribution of skin types and skin pigmentation in a Caucasian population. In 892 Danish Caucasians, eye colour, hair colour and skin type were assessed and facultative and constitutive skin pigmentation were measured objectively using skin reflectance spectroscopy. Blue eye colour and blond hair colour and skin type II were the most frequent (60%, 67% and 33% of subjects, respectively). All four major eye colours and four major hair colours (with the exception of red hair colour) were found within skin types I-IV and we could not predict the skin type or the constitutive skin pigmentation. Skin type could not be taken to classify individuals reliably according to their facultative or constitutive skin pigmentation.

Adolescent↗
PubMed1999

Eye and hair colour, skin type and constitutive skin pigmentation as risk factors for basal cell carcinoma and cutaneous malignant melanoma. A Danish case-control study.

To assess the importance of hair and eye colour, skin type and constitutive skin pigmentation as risk factors for basal cell carcinoma and cutaneous malignant melanoma in fair-skinned Caucasians, we conducted two identical case-control studies in Denmark. We studied 145 cases with basal cell carcinoma and 174 matched controls, and 168 cases with cutaneous malignant melanoma and 176 matched controls. Controls were matched on age, gender and place of residence. Subjects indicated their hair colour before 7 years of age, and at 25 years of age and their skin phototype. Interviewers assessed the present hair colour and eye colour, and the constitutive skin pigmentation was measured objectively by skin reflectance of UV unexposed buttock skin. There were no differences between basal cell carcinoma cases and controls in hair colour or eye colour or constitutive skin pigmentation, but more cases were of skin type II than skin type IV; skin type 11 was a risk factor for basal cell carcinoma with an odds ratio (OR) of 2.3. For cutaneous malignant melanoma, more cases than controls were red-haired or blond and of skin type II, but there was no difference in constitutive skin pigmentation. Hair colour and skin type were found to be independent risk factors for cutaneous malignant melanoma; red hair vs. black/brown: OR >9.7, blond hair vs. brown/black: OR = 2.4, and skin type 11 vs. type IV: OR=2.0. There were no gender-related differences in risk factors for basal cell carcinoma and cutaneous malignant melanoma.

Adult↗
PubMed1983

Inheritance of brown-eye and colourless-eye in the mosquito Aedes aegypti.

An autosomal recessive gene bw (probably closely linked to y on chromosome 2) gives a brown eye colour. When this gene and the sex-linked gene re (red-eye) are both homozygous, a colourless-eye results. Brown-eye shows good viability and penetrance, and it has been maintained as a pure stock. Colourless-eye shows 87% penetrance in both sexes, and the females are low in viability and fertility. A colourless-eye stock has been maintained by crossing colourless-eyed males to their heterozygous red-eyed sibs. Crosses indicated no allelism between bw and ru (rust-eye), nor with w (white-eye). However some complementation between bw and w was indicated.

Aedes↗
PubMed1985

Genetic analysis of three new eye colour mutations in the mosquito, Anopheles stephensi.

Three new eye colour mutants, scarlet eye (wsca), red-spotted eye (prs) and pigmentless eye (p) were isolated in the malaria vector, Anopheles stephensi. Genetic analysis revealed that all three mutants are sex-linked and recessive to the wild type. Scarlet eye is allelic to white eye but is not to either red-spotted eye or pigmentless eye, which are allelic to each other; 5.7% recombination was observed between the white eye and pigmentless eye loci.

Animals↗
PubMed2000

Canonical correlation and chi-square: relationships and interpretation.

A 2 x 2 chi-square can be computed from a phi coefficient, which is the Pearson correlation between two binomial variables. Similarly, chi-square for larger contingency tables can be computed from canonical correlation coefficients. The authors address the following series of issues involving this relationship: (a) how to represent a contingency table in terms of a correlation matrix involving r - 1 row and c - 1 column dummy predictors; (b) how to compute chi-square from canonical correlations solved from this matrix; (c) how to compute loadings for the omitted row and column variables; and (d) the possible interpretive advantage of describing canonical relationships that comprise chi-square, together with some examples. The proposed procedures integrate chi-square analysis of contingency tables with general correlational theory and serve as an introduction to some recent methods of analysis more widely known by sociologists.

Chi-Square Distribution↗
PubMed2000

Risk factors for basal cell carcinoma.

The aim of this study was to assess the risk factors for basal cell carcinoma (BCC). A case-control study, carried out in two towns in Yugoslavia, comprised 200 BCC cases and 399 controls. For statistical analysis, univariate and multivariate logistic regressions were used. The risk factors found for BCC were: freckling before the age 15, seven or more weeks per year spent at the seaside during holidays (lifetime average), outdoor work during summer-time, occupational exposure to organic and non-organic dissolvents and organophosphatic compounds, use of tar for cosmetic purposes, and previous BCC in personal history. Subjects who tended to burn and not to tan after sun exposure also showed a significantly higher risk for BCC. Brown eyes and history of acne had a protective effect. This study confirmed the role of both constitutional and environmental factors in the development of BCC.

Acne Vulgaris↗
PubMedDate not supplied

Cohort effects in a genetically determined trait: eye colour among US whites.

BACKGROUND: While the inheritance of eye colour is likely polygenic, blue eye colour is thought to follow an inheritance pattern similar to that of a recessive trait. Consequently, age-related differences in the prevalence of blue eye colour would be unanticipated. AIM: This study explores the finding and explanation for birth cohort differences in the prevalence of blue eye colour in the US white population. SUBJECTS AND METHODS: Data from the first (1971-1975) and third (1988-1994) US National Health and Nutrition Examination Surveys (NHANES-I and NHANES-III), nationally representative surveys of the US population, were analysed. Trends in eye colour prevalence by birth cohort were analysed together with mortality rates according to eye colour. US census data (1980) were examined to explore cohort differences in ancestry and assortative mating by ancestry. RESULTS: The prevalence of blue eye colour among non-Hispanic whites in NHANES-III was 57.4% (95% CI: 50.1-64.7) for individuals born between 1899 and 1905 compared to 33.8% (95% CI: 31.3-36.5) for those born between 1936 and 1951. No association was found between survival and eye colour, nor was a cohort effect evident for primary ancestry. However, proportions reporting only one ancestry in census data declined with successive birth cohorts. CONCLUSIONS: A cohort effect in blue eye colour prevalence was found for the US white population. A secular trend of decreasing assortative mating by ancestry is the likely explanation.

Adult↗
PubMed1993

Visual pigment bleaching in isolated salamander retinal cones. Microspectrophotometry and light adaptation.

Visual pigment bleaching desensitizes rod photoreceptors greatly in excess of that due to loss of quantum catch. Whether this phenomenon also occurs in cone photoreceptors was investigated for isolated salamander red-sensitive cones. In parallel experiments, (a) visual pigment depletion by steps of bleaching light was measured by microspectrophotometry, and (b) flash sensitivity was measured by recording light-sensitive membrane current. In isolated cones, visual pigment bleaching permanently reduced flash sensitivity significantly below that due to the reduction in quantum catch, and there was little spontaneous recovery of visual pigment. The "extra" desensitization due to bleaching was most prominent up to bleaches of approximately 80% visual pigment and reached a level approximately 1 log unit beyond that due to loss of quantum catch. At higher bleaches, the effect of loss of quantum catch became more important. Bleaching did not greatly reduce the maximum light-suppressible membrane current. A 99% reduction of the visual pigment permanently reduced the circulating current by only 30%. Visual pigment bleaching speeded up the kinetics of dim flash responses. All electrical effects of bleaching were reversed on exposure to 11-cis retinal, which probably caused visual pigment regeneration. Light adaptation in photopic vision is known to involve significant visual pigment depletion. The present results indicate that cones operate with a maintained circulating current even after a large pigment depletion. It is shown how Weber/Fechner behavior may still be observed in photopic vision when the contributions of bleaching to adaptation are included.

Absorptiometry, Photon↗