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PubMed1996

Naevi and pigmentary characteristics as risk factors for melanoma in a high-risk population: a case-control study in New South Wales, Australia.

The relationship between risk of cutaneous malignant melanoma and total body and site-specific naevus counts and other host factors was investigated in a Caucasian population aged 15-84 years in New South Wales, Australia. The study sample comprised 244 cases with melanoma diagnosed in 1989-1993, and 276 controls. The strongest relationship was with total body naevus count. Risk of melanoma was raised 12 times in those with more than 100 naevi compared with those with less than 10. There were also strong risks, with odds ratios of 5 or more, associated with having multiple atypical naevi, multiple large naevi, high naevus counts in sun-exposed or sun-protected areas and being unable to tan on repeated sun exposure. The effect of inability to tan was stronger at younger than older ages. Lesser risks, with odds ratios of 2-3, were associated with being prone to burn on sun exposure, having many freckles as a child and having red hair. The site distribution of naevi in males compared with females resembled the distribution of melanoma by sex. Risk of melanoma of the back was significantly more closely related to back naevus count than naevus count for the remainder of the body. For other anatomical sites, naevus count was non-significantly more closely related to naevus counts at that site than counts over the remainder of the body. Naevus count declined with age in both cases and controls. In those aged under 40, having 100 or more naevi was associated with an aetiological fraction (AF) of 41%. In those aged 60 and over, however, the AF associated with this number of naevi was only 5%.

Adolescent↗
PubMedDate not supplied

Marginal modelling of multivariate categorical data.

This paper describes likelihood methods of analysis for multivariate categorical data. The joint distribution is specified in terms of marginal mean functions, and pairwise and higher order association measures. For the association, the emphasis is on global odds ratios. The method allows flexible formulation of a broad class of designs, such as repeated measurements, longitudinal studies, interrater agreement and cross-over trials. The proposed model can be used for parameter estimation and hypothesis testing. Simple fitting algorithms are proposed. The method is illustrated using a data example.

Adolescent↗
PubMed2001

Mouse cloning with nucleus donor cells of different age and type.

We have tested different cell types as sources for nucleus donors to determine differences in cloning efficiency. When donor nuclei were isolated from cumulus cells and injected into recipient oocytes from adult hybrid mice (B6D2F1 and B6C3F1), the success rate of cloning was 1.5-1.9%. When cumulus cell donor nuclei were isolated from adult inbred mice (C57BL/6, C3H/He, DBA/2, 129/SvJ, and 129/SvEvTac), reconstructed oocytes did not develop to full term or resulted in a very low success rate (0-0.3%) with the exception of 129 strains which yielded 0.7-1.4% live young. When fetal (13.5-15.5 dpc), ovarian, and testicular cells were used as nucleus donors, 2.2 and 1.0% of reconstructed oocytes developed into live offspring, respectively. When various types of adult somatic cells (fibroblasts, thymocytes, spleen cells, and macrophages) were used, oocytes receiving thymocyte nuclei never developed beyond implantation, whereas those receiving the nuclei of other cell types did. These results indicate that adult somatic cells are not necessarily inferior to younger cells (fetal and ES cells) in the context of mouse cloning. Although fetal cells are believed to have less genetic damage than adult somatic cells, the success rate of cloning using any cell types were very low. This may largely be due to technical problems and/or problems of genomic reprogramming by oocytes rather than the accumulation of mutational damage in adult somatic cells.

Aging↗
PubMed1988

Piebaldism-Waardenburg syndrome: histopathologic evidence for a neural crest syndrome.

Piebaldism, an autosomal dominant trait, is characterized by patchy hypopigmentation of the face, anterior chest, abdomen, and limbs, heterochromia/bicolored irises, congenital megacolon, and deafness. A 4-month-old Inuit (Eskimo) boy with these manifestations also had left pulmonic artery stenosis, ocular ptosis, and unilateral duplication of the renal collecting system. Evidence is presented for both qualitative and quantitative derangement of neural crest derivatives in this syndrome. Histologically, hypoganglionosis, hyperganglionosis, and ectopic ganglia in lamina propria (neuronal colonic dysplasia [NCD]) were documented in the rectum. The appendix, proximal to the clinical transition zone, showed similar dysplasia. In the hypopigmented skin, multiple microscopic sections were devoid of melanocytes, with no melanin in adjacent basal cells. The hyperpigmented skin contained melanin throughout the basal layer, but the melanocytes were unevenly distributed. Most tissues affected in this boy are of neural crest origin; pathogenesis could be due to faulty migration along the established pathways involving either the borders (basal laminae) or the components of the extracellular matrix (fibronectin, cytotactin, laminin, glycosaminoglycans, and collagen). The similarities between piebaldism and the Waardenburg syndromes are discussed.

Abnormalities, Multiple↗
PubMed1991

Variable expression of vision in sibs with albinism.

Oculocutaneous albinism is defined by the presence of cutaneous and ocular hypopigmentation, the latter associated with nystagmus, iris transillumination, reduced retinal pigment, foveal hypoplasia, and misrouting of the optic fibers at the chiasm. The visual acuity is variable but almost always reduced. We report on two brothers with oculocutaneous albinism and markedly different visual acuity. One brother has a visual acuity of 20/100, while the second has similar cutaneous pigmentation and visual acuity of 20/20 and had not previously been recognized as having oculocutaneous albinism. Both brothers have foveal hypoplasia and misrouting of the optic fibers at the chiasm. Biochemical analysis suggests that this is a tyrosinase-related type of oculocutaneous albinism. This study demonstrates that careful observation of foveal development in relatives with normal vision is necessary to detect all individuals with albinism in a family. A suspected diagnosis of albinism may be confirmed when the visual-evoked potentials show excessive decussation of the optic fibers at the chiasm.

Adolescent↗
PubMed2004

A patient with a de novo 15q24q26.1 interstitial deletion, developmental delay, mild dysmorphism, and very blue irises.

We report on a patient with a de novo 15q24q26.1 interstitial deletion. She presented with developmental delay, behavioral characteristics, and mild dysmorphism with very blue irises. We review the limited literature of interstitial 15q deletions. There was no distinct phenotypic overlap between these two cases in literature and the present patient. Additional reports are necessary in order to establish a possible recognizable deletion 15q24q26.1 phenotype.

Child, Preschool↗
PubMed1975

Iris pigmentation and photopic visual acuity: a preliminary study.

Visual acuity under varying conditions of light stress was tested in four human populations. It was found that the density of iris pigmentation had no significant effect on visual acuity under conditions of bright light. While some acclimatization to local light levels was observed, significant population differences in visual acuity were obtained. A hypothesis is advanced at to the adaptive value of varying densities of pigmentation of the iris based on the known heat absorption properties of melanin granules.

Anthropology, Physical↗
PubMed1981

Iris pigmentation (melanin) in idiopathic dystonic syndromes including torticollis.

Iris pigmentation was evaluated in 153 Caucasian patients with torticollis and other focal, segmental, or generalized dystonias of unknown cause. Since these disorders are rare in non-Caucasians, it was hypothesized that a relationship might exist between decreased melanin metabolism, reflected by iris pigmentation, and a genetic predisposition to these disorders of voluntary movement. Patients were separated into two groups on the basis of iris pigmentation. Compared to control groups, there was a statistically significant reversal in the ratio of patients with light eyes versus dark eyes. Further comparisons were made in two groups of patients with drug-induced nonparkinsonian dyskinesias; no significant correlation was found between their dyskinetic syndrome and iris pigmentation. Data concerning race, ethnic origin, and other disorders of the basal ganglia support the hypothesis that there may be genetic predilection in individuals whose metabolic pathways produce less systemic melanin.

Adolescent↗
PubMed1992

Position effect variegation and chromatin proteins.

Variegated phenotypes often result from chromosomal rearrangements that place euchromatic genes next to heterochromatin. In such rearrangements, the condensed structure of heterochromatin can spread into euchromatic regions, which then assume the morphology of heterochromatin and become transcriptionally inactive. In position-effect variegation (PEV) therefore, gene inactivation results from a change in chromatin structure. PEV has been intensively investigated in the fruitfly Drosophila, where the phenomenon allows a genetic dissection of chromatin components. Consequently, many genes have been identified which, when mutated, act as dominant modifiers (suppressors or enhancers) of PEV. Data available already demonstrate that genetic, molecular and developmental analysis of these genes provides an avenue to the identification of regulatory and structural chromatin components, and hence to fundamental aspects of chromosome structure and function.

Animals↗
PubMed1992

Mouse albino-deletions: from genetics to genes in development.

Six essential genes located near the mouse albino locus have been identified as required during specific periods of development. Amongst these six, each is required either during the preimplantation stages of development, at specific times during gastrulation, within 12 hrs after birth or during juvenile development. These genes were identified as a result of extensive genetic complementation analysis using embryos homozygous for the albino deletions. Although, in principal, the associated developmental abnormalities could result from loss of multiple genes, the deletion phenotype in one case is identical to that induced by chemical mutagenesis. These results indicate that the abnormalities observed in deletion homozygotes may result from single gene loss. The deletions have proven useful not only as genetic tools to localize the position of the genes, but also as molecular entry points to the regions containing these genes. The current methodology being used to isolate candidate genes from the albino region is also reviewed here.

Albinism↗
PubMed1993

Attenuation of white gene expression in transgenic Drosophila melanogaster: possible role of a catalytic antisense RNA.

We have transformed Drosophila melanogaster with a DNA construct encoding a catalytic antisense RNA directed against the primary white gene RNA transcript. Total RNA isolated from transformed flies was shown to catalyze the specific cleavage of in vitro transcribed substrate RNA, indicating the expression of a functional ribozyme. Moreover, transgenic lines carrying homozygous copies of this construct depict a further clear-cut reduction in eye pigmentation when present in a genetic background that has a priori reduced levels of white gene expression.

Alleles↗
PubMed1994

Further studies with the somatic white-ivory system of Drosophila melanogaster: genotoxicity testing of ten carcinogens.

To provide further background data for the white-ivory somatic mutation Drosophila assay, ten selected carcinogens (acetamide, acrylamide, benzo(alpha)pyrene, cyclophosphamide, diethylstilbestrol, 4-nitroquinoline N-oxide, propyleneimine, safrole, thiourea, and o-toluidine) have been tested in this system. Seventy-two hours after egg laying, larvae were fed with different concentrations of each carcinogen during the rest of their development until pupation, and the genotoxic effects were measured as significant increases in the appearance of visible mutant clones of ommatidia in the eyes of the emerging adult flies. Our results indicate that three of the ten carcinogens tested (cyclophosphamide, 4-nitroquinoline N-oxide, and propyleneimine) were strong genotoxic agents, two (diethylstilbestrol and acrylamide) induced significant positive results but without a dose-response relationship, and safrole was weakly positive. On the other hand, acetamide, benzo(alpha)pyrene, thiourea, and o-toluidine were unable to increase the frequency of mutant clones.

Animals↗