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PubMedDate not supplied

Gene-environment interaction in melanoma.

Gene-environment interaction can be defined as a different effect of an environmental exposure in people with different genotypes, or a different effect of a genotype in people with different histories of environmental exposure. Interaction applies when one stratum (high risk) responds differently to an exposure (sun) than another stratum (low risk). Genetic predisposition would appear to be a very important modifier of risk. This paper discusses the concept of gene-environment interaction applied to cutaneous melanoma through discussion of highly penetrant genes and their interaction with sun exposure, through discussion of low penetrant genes and their interaction with sun exposure, and by suggesting a new model for investigation of gene-environment interaction in melanoma. It is stressed that this area of investigation is extremely early in its development.

Cell Cycle↗
PubMed1975

Electrophysiologic evidence for normal optic nerve fiber projections in normally pigmented squinters.

The Siamese cat, a type of albino, has a visual pathway anomaly in which too many optic nerve fibers cross at the optic chiasm, and also frequently has strabismus. The correlation of strabismus with this defect suggests that a similar pathway defect without pigmentation anomalies, may be the cause of much human strabismus. Creel, Witkop, and King have used evoked potential methods to show that such a pathway defect likely occurs in the human albino. While unpublished control experiments verified their results on human albinos, no such defect has been found in the normally-pigmented human squinter. It is concluded that the visual pathway anomaly is limited to albinism and is not a likely cause of most human strabismus.

Adolescent↗
PubMed2001

Light-induced migration of retinal microglia into the subretinal space.

PURPOSE: To explore the effects of light exposure and deprivation on the distribution and function of microglia in the subretinal space of mice. METHODS: Using a monoclonal antibody, 5D4, that identifies resting, ramified microglia, the distribution and density of microglia in the retina, and the subretinal space were determined by confocal microscopy and by immunohistochemistry of cryopreserved sections of eyes of albino and pigmented mice exposed to diverse levels of light, ranging from complete darkness to intense brightness. Axotomized retinal ganglion cells were retrograde labeled by fluorescent tracer to determine whether the marker colocalizes to 5D4+ cells. Electron microscopy was used to evaluate microglia for evidence of phagocytosis. RESULTS: 5D4+ microglia in pigmented eyes were limited to the inner retinal layers, but in albino eyes 5D4+ cells were found in the outer retinal layers and subretinal space as well. The subretinal space of eyes of albino mice raised from birth in complete darkness contained few 5D4+ cells, but exposure to light caused the rapid accumulation of 5D4+ cells at this site. 5D4+ cell density in the subretinal space correlated directly with intensity of ambient light. Retrograde labeling of axotomized ganglion cells resulted in 5D4+ cells in the subretinal space that contained the retrograde label. Subretinal microglia contained phagocytized rod outer segment discs. On intense light exposure, 5D4+ cells adopted an active morphology, but failed to express class II major histocompatibility complex (MHC) molecules. CONCLUSIONS: Light exposure induced retinal microglia migration into the subretinal space in albino mice. Subretinal microglia appeared to augment through phagocytosis the capacity of pigment epithelium to take up the photoreceptor debris of light toxicity. The unexpected presence of these cells in the subretinal space raises questions concerning their potential contribution to immune privilege in this space and to the fate of retinal transplants.

Albinism↗
PubMed2002

Reproducibility of skin characteristic measurements and reported sun exposure history.

BACKGROUND: The aim of the present study is to investigate the reproducibility of information on sun exposure, skin characteristics and sunburn collected through a standardized questionnaire used in the multi-centre South European case-control study on skin cancer, 'Helios'. We also intended to use results from reproducibility analysis for correcting odds ratio (OR) estimates from the original study. METHODS: We re-interviewed, with the same questionnaire, a sample of 115 cases of basal cell and squamous cell carcinoma of the skin and 119 population controls, 18-26 months apart, in four centres of Italy, Spain and France. The questionnaire included questions on skin characteristics, sunburns and sun exposure histories. We investigated agreement, studying the association between the difference of the two measures and a set of explanatory variables. According to the results of the reproducibility analysis we corrected OR estimates from the original study simultaneously adjusting for random measurement error. RESULTS: Hair and eye colour showed high agreement with intra-class correlation coefficients (ICC) of 0.81 and 0.74, respectively. Lifetime sun exposure showed substantial agreement with ICC ranging from 0.68 for time spent doing outdoor work to 0.79 for time spent outdoors during holidays and holidays at the beach. The poorest agreement was found for number of lifetime sunburns (ICC = 0.25), while sunburns during childhood showed a substantial agreement (Cohen's Kappa = 0.67). Lack of reproducibility was mainly associated with subjects' education, while no significant differences were observed between cases and controls. The corrected OR showed a moderate increase with a reinforcement of the effect of sun exposure and skin reaction to sun exposure. CONCLUSION: Overall, there was good reproducibility, particularly in the case of sun exposure histories, between answers given on two different occasions to a questionnaire administered by trained interviewers. However, since measurement error can substantially bias OR toward the null value, it should be taken into account in estimates of the effect of sun exposure on risk of skin cancer.

Adult↗
PubMed2002

Eye colour as a genetic marker for fertility and fecundity of Triatoma infestans (Klug, 1834) Hemiptera, Reduviidae, Triatominae.

Eye colour of Triatoma infestans is controlled at a single autosomal locus, with black-eye as the dominant gene and red-eye as the recessive. Inheritance of these characters follows a classical Mendelian system, enabling eye colour to be used as a marker for studies of mating frequency. We found no significant differences in oviposition rates and egg hatching rates irrespective of parental phenotypes. Different mating schedules between red-eye and black-eye parents showed that eye colour did not affect mating competence. Females mated with a single male or with different males together or in succession produced similar numbers of fertile eggs, with the eye colour of the offspring reflecting exposure to the different males. We conclude that although a single mating can provide sufficient sperm for the whole reproductive life of the female, multiple matings can result in balanced assortative sperm usage from the spermatheca.

Animals↗
PubMedDate not supplied

Preoperative topical flurbiprofen-Na+ in extracapsular lens extraction role in maintaining intraoperative pupillary dilatation.

Induction of intraoperative pupillary constriction, is predominantly a prostaglandin mediated process. The most potent antiprostaglandin NSAID, Flurbiprofen was used topically to study its efficacy against the above. In a prospective double blind clinical study, 50 brown eyes undergoing planned E.C.C.E., the pupils were dilated with 10% phenylephrine and 2% homatropine 1%/tropicamide. 25 eyes received 0.03% Flurbiprofen-Na+ eye drops 1/2 hourly starting two hours before surgery. The maintained intraoperative mydriasis in the two groups before anterior chamber entry (stage I) vs at the end of complete cortex wash (stage III) was: in control group (stage I) 8.46 +/- 0.48 mm vs (stage III) 3.56 +/- 0.43 mm (highly SS); in flurbiprofen group (stage I) 8.60 +/- 0.48 mm vs (stage III) 8.01 +/- 0.63 mm (NSS). The pupillary area available for surgical manipulation in the control group was significantly decreased from 56.18 mm2 in state I to 9.94 mm2 in stage III, while in flurbiprofen group it changed insignificantly from 58.05 mm2 in stage I to 50.24 mm2 in stage III. Postoperatively after cataract was observed in 44% eyes of control group as compared to only 8% of eyes of flurbiprofen group. Thus a maintained intraoperative mydriasis in flurbiprofen group led to better E.C.L.E. which is a mandatory prerequisite to preferred and better present day posterior chamber IOL implantation.

Adult↗