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At least 163 records · Page 9Linked to original sources
PubMed1999

RBE-LET relationships of high-LET radiations in Drosophila mutations.

The relative biological effectiveness (RBE) of 252Cf neutrons and synchrotron-generated high-energy charged particles for mutation induction was evaluated as a function of linear energy transfer (LET), using the loss of heterozygosity for wing-hair mutations and the reversion of the mutant white-ivory eye-color in Drosophila melanogaster. Loss of heterozygosity for wing-hair mutations results predominantly from mitotic crossing over induced in wing anlage cells of larvae, while the reverse mutation of eye-color is due to an intragenic structural change (2.96 kb-DNA excision) in the white locus on the X-chromosome. The measurements were performed in a combined mutation assay system so that induced mutant wing-hair clones as well as revertant eye-color clone can be detected simultaneously in the same individual. Larvae were irradiated at the age of 3 days post oviposition with 252Cf neutrons, carbon beam or neon beam. For the neutron irradiation, the RBE values for wing-hair mutations were larger than that for eye-color mutation by about 7 fold. The RBE of carbon ions for producing the wing-hair mutations increased with increase in LET. The estimated RBE values were found to be in the range 2 to 6.5 for the wing-hair. For neon beam irradiation, the RBE values for wing-hair mutations peak near 150 keV/micron and decrease with further increase in LET. On the other hand, the RBE values for the induction of the eye-color mutation are nearly unity in 252Cf neutrons and both ions throughout the LET range irradiated. We discuss the relationships between the initial DNA damage and LET in considering the mechanism of somatic mutation induction.

Animals↗
PubMed2001

Unique morphology of the human eye and its adaptive meaning: comparative studies on external morphology of the primate eye.

In order to clarify the morphological uniqueness of the human eye and to obtain cues to understanding its adaptive significance, we compared the external morphology of the primate eye by measuring nearly half of all extant primate species. The results clearly showed exceptional features of the human eye: (1) the exposed white sclera is void of any pigmentation, (2) humans possess the largest ratio of exposed sclera in the eye outline, and (3) the eye outline is extraordinarily elongated in the horizontal direction. The close correlation of the parameters reflecting (2) and (3) with habitat type or body size of the species examined suggested that these two features are adaptations for extending the visual field by eyeball movement, especially in the horizontal direction. Comparison of eye coloration and facial coloration around the eye suggested that the dark coloration of exposed sclera of nonhuman primates is an adaptation to camouflage the gaze direction against other individuals and/or predators, and that the white sclera of the human eye is an adaptation to enhance the gaze signal. The uniqueness of human eye morphology among primates illustrates the remarkable difference between human and other primates in the ability to communicate using gaze signals.

Adaptation, Physiological↗
PubMed1987

Pteridines and purines as major pigments of the avian iris.

Stromal pigments from the irises of 28 species of birds having brightly colored eyes were extracted and analyzed. Carotenoids were present in six species and they were the sole bright pigment in only two of these. The iris pigments of the majority of the birds examined were soluble in 0.1 M NaOH and chromatographic analysis indicated they were primarily pteridines and purines. The pteridines often occurred in a crystalline state, either alone or, more commonly, in conjunction with purines.

Animals↗
PubMed1987

The association of solar ultraviolet and skin melanoma incidence among caucasians in the United States.

Using recent data from cancer incidence surveys and measures of UVB exposure levels at seven geographic locations within the United States, we estimate the dose-response relation between UVB and skin melanoma incidence. Mathematical models used information from general population interview studies conducted in these locations to adjust for potentially confounding factors such as age, skin color, ancestry, eye color, hair color, sunburn sensitivity, prevalence of moles, freckles, and hours spent outdoors, use of sunscreen/lotion, and other variables. The effect of geographic UVB exposure on incidence was found to be statistically significant (p less than 0.01) after adjusting for each variable and certain combinations of these variables. We found that incidence rates for those skin melanomas arising in the face, head, neck, or upper extremities (i.e, the most exposed sites) were more sensitive to UVB increases than the incidence rates for those lesions occurring in the ordinarily less exposed sites of the trunk and lower extremities.

Female↗
PubMed1984

Pigmentary traits, ethnic origin, benign nevi, and family history as risk factors for cutaneous malignant melanoma.

The roles of constitutional factors and benign nevi in causation of malignant melanoma were examined in a case-control study of 511 patients and 511 matched controls in Western Australia. The strongest risk factor was the number of palpable benign nevi on a subject's arms. Compared to the risk of melanomas for persons having no palpable nevi on the arms, the relative risk of melanoma was 2.0 for persons with 1-4 nevi, 4.0 for persons with 5-9 nevi, and 11.3 for persons with 10 or more nevi (P less than .0001). Of the several pigmentary traits known to have associations with melanoma, inability to tan was the most important. Susceptibility to sunburn and hair color also had significant effects that were independent of tanning ability; however, after these traits were controlled, measured skin color and eye color had no additional effects. A reduced risk of melanoma was observed in persons having two or more Southern European grandparents [odds ratio (OR) = 0.39; P = .025]. Persons of Celtic origin did not have a significantly increased risk (OR = 1.18). Possession of one or more affected blood relatives was related to an increased risk of melanoma (OR = 2.69; P less than .0001). The effects of pigmentary traits, benign nevi, ethnic origin, and family history as risk factors were largely independent of one another.

Australia↗
PubMed1993

[Postmenopausal osteoporosis: clinical characteristics in patients first vertebral crush fracture. Results of the GRIO National Multicenter Survey. Groupe de Recherche et d'Information sur les Osteoporoses].

This national multicenter study by the French Task Force on Osteoporosis Research and Information (Groupe de Recherche et d'Information sur l'Ostéoporose GRIO) was carried out to define clinical features in women presenting with a first osteoporosis-related vertebral crush fracture. Seventy-four patients with a less than three-month history of back pain due to a first vertebral fracture documented on the basis of stringent roentgenographic criteria, were compared to 74 normal age-matched female controls. Mean age at first vertebral fracture was 67 +/- 7 years. Cases and controls filled out a 78-item questionnaire on morphology, reproductive function, environmental factors, and previous fractures. The circumstances of onset and site of the vertebral fracture were recorded. Both groups were comparable in terms of age, body weight, hair color and eye color, whereas mean height was smaller by 2 cm in cases (p < 0.02). Among data on reproductive function, the only difference was a younger age at last menses among cases (47.7 +/- 5.7 versus 49.8 +/- 4.8 years); number of pregnancies and duration of breast-feeding were comparable in cases and controls. Environmental factors (smoking, alcohol use, physical activity, dietary calcium) were similar in the two groups. Cases were more likely than controls to report a history of appendicular fractures and/or a positive family history for vertebral osteoporosis. This study in French women suggests that the first osteoporotic vertebral fracture occurs approximately 20 years after cessation of menses and that risk factors include earlier age at last menses, a history of fracture, and a family history of vertebral osteoporosis.

Age Distribution↗
PubMed1996

[Molecular nature of the unstable white-starka allele].

In 1992, Bashkirov et al. described the case of occurrence in line C(1)RM, yw/0; Dp(1; 3) wvco/+ of a unique female with light, uniformly colored eyes. This trait was not inherited together with Dp(1; 3) wvco but was linked to the X chromosome. We denoted this new allele as white-starka (wstr). It proved to be unstable, demonstrating mutational transitions to other allelic states with frequencies of 10(-3) to 10(-5). Southern blot analysis showed that the wstr mutation was induced by an insertion of an unknown sequence with a length approximately evaluated by the authors in 1992 as 7 kb. Using a wider spectrum of restriction endonucleases and a prolonged gel running, we were able to estimate the size of this insertion more precisely. According to our data, in the case of wstr we are dealing with an insertion in the locus white of a sequence 15.1 kb long. As seen from our restriction map of the allele wstr, this insertion does not resemble retroposons with long terminal repeats, but is possibly similar to LINE mobile elements of Het-A and TART types, characteristic for heterochromatin.

Alleles↗
PubMed1989

Genetic analysis of the claret locus of Drosophila melanogaster.

The claret (ca) locus of Drosophila melanogaster comprises two separately mutable domains, one responsible for eye color and one responsible for proper disjunction of chromosomes in meiosis and early cleavage divisions. Previously isolated alleles are of three types: (1) alleles of the claret (ca) type that affect eye color only, (2) alleles of the claret-nondisjunctional (cand) type that affect eye color and chromosome behavior, and (3) a meiotic mutation, non-claret disjunctional (ncd), that affects chromosome behavior only. In order to investigate the genetic structure of the claret locus, we have isolated 19 radiation-induced alleles of claret on the basis of the eye color phenotype. Two of these 19 new alleles are of the cand type, while 17 are of the ca type, demonstrating that the two domains do not often act as a single target for mutagenesis. This suggests that the two separately mutable functions are likely to be encoded by separate or overlapping genes rather than by a single gene. One of the new alleles of the cand type is a chromosome rearrangement with a breakpoint at the position of the claret locus. If this breakpoint is the cause of the mutant phenotype and there are no other mutations associated with the rearrangement, the two functions must be encoded by overlapping genes.

Alleles↗
PubMed1983

A genetic analysis of the pteridine biosynthetic enzyme, guanosine triphosphate cyclohydrolase, in Drosophila melanogaster.

Strains with mutant eye color were surveyed for levels of GTP cyclohydrolase (GTP CH), the first enzyme acting in the biosynthesis of pteridines, the pigments causing red eye color in Drosophila. Six strains were found to have reduced GTP CH activity. In five of the six strains, the reduction of activity is apparent only in the adult head of homozygous mutants. We show that mutations in Punch (2-97, Pu) have severe effects on GTP CH activity. In most cases, the reduction of activity is apparent in all tissues and stages that express the enzyme. The activity of GTP CH is shown to be closely correlated with the number of Pu+ genes in the genome. One ethyl methanesulfonate (EMS)-induced Pu mutant has a GTP CH enzyme that is unstable when compared with the wild-type enzyme. Mutations in Pu fall into three general classes. The largest class has a recessive lethal and eye color phenotype, 50% or higher GTP CH activity in heterozygotes, and equivalent defects in all tissues. A second class is dominant in eye color phenotype and recessive lethal, with less than 50% GTP CH activity in heterozygotes. The third class is homozygous viable and has severe reduction of activity in the adult head, but no or less severe loss in other tissues.

Alleles↗
PubMed1992

Transposable elements as a factor in the aging of Drosophila melanogaster.

We have considered the hypothesis that transposable elements may contribute to the aging process through somatic mutation. We have presented evidence to suggest that at least two elements, Copia and 412, are capable of somatic activity in adult Drosophila tissue. A strain harboring a third transposable element, P, was produced that showed eye color mosaicism and reversion to wild phenotype (red eyes) as a result of somatic and germ line transposition. A high-fat diet, known to accelerate aging, increased the frequency of eye color mosaicism and red eyes. We induced life span shortening by artificially activating somatic transposition of P elements, and the extent of reduction in life span was similar in both sexes. These data are consistent with the notion that some aspects of the age phenotype may be caused by mutational activity of transposable elements in somatic tissues. The hypothesis is readily tested in other organisms, including humans. It offers new dimensions in the understanding and management of age-associated changes.

Aging↗
PubMed1982

The unstable wDZL mutation of Drosophila is caused by a 13 kilobase insertion that is imprecisely excised in phenotypic revertants.

We have analyzed the lesion in wDZL, a genetically unstable mutant allele of the eye color locus, white, of Drosophila melanogaster. We have cloned the DNA of the white locus region of flies carrying the wDZL allele and find a 13 kilobase insertion not present in the wild-type at the corresponding location. In 12 independent cases examined, reversion to a wild-type eye color phenotype correlates with the excision of a portion of this 13 kilobase insertion, indicating that the insertion is the cause of the mutation. The portion of the insertion that is excised in these eye color revertants is heterogeneous in size but appears to include the central 6 kilobases of the insertion in all cases. Many of these eye color revertants continue to undergo mutation at the white locus, indicating that the residual portion of the insertion in these revertants is sufficient to promote mutations.

Alleles↗
PubMed1989

Iris pigmentation and sociability in childhood: a re-examination.

Drawing from Rosenberg and Kagan's (1987) finding of an association between iris pigmentation and behavioral inhibition in early childhood, we sought, in the present investigation, to examine the developmental relation between eye color and social withdrawal in kindergarteners and children in grades 2 and 4. In kindergarten and grade 2, blue-eyed children were found to be overrepresented in groups of extremely withdrawn youngsters. No association was found between eye color and withdrawal in grade 4 or between eye color and extreme sociability at any grade. The results were interpreted as suggestive of the increasing role, with age, of social factors in the determination of extremely inhibited behavior.

Age Factors↗
PubMed1986

Pigment patterns in mutants affecting the biosynthesis of pteridines and xanthommatin in Drosophila melanogaster.

Eye-color mutants of Drosophila melanogaster have been analyzed for their pigment content and related metabolites. Xanthommatin and dihydroxanthommatin (pigments causing brown eye color) were measured after selective extraction in acidified butanol. Pteridines (pigments causing red eye color) were quantitated after separation of 28 spots by thin-layer chromatography, most of which are pteridines and a few of which are fluorescent metabolites from the xanthommatin pathway. Pigment patterns have been studied in 45 loci. The pteridine pathway ramifies into two double branches giving rise to isoxanthopterin, "drosopterins," and biopterin as final products. The regulatory relationship among the branches and the metabolic blockage of the mutants are discussed. The Hn locus is proposed to regulate pteridine synthesis in a step between pyruvoyltetrahydropterin and dihydropterin. The results also indicate that the synthesis and accumulation of xanthommatin in the eyes might be related to the synthesis of pteridines.

Amino Acids↗
PubMed1985

Tissue-specific and complex complementation patterns in the Punch locus of Drosophila melanogaster.

Mutations in the Punch locus result in loss of GTP cyclohydrolase activity, but all mutations do not affect the enzyme in the same way. There are at least three classes of Punch mutations. One class results in a dominant eye color, recessive lethal phenotype. A second class of mutations also causes a recessive lethal phenotype, but heterozygous mutants have normal eye color. They show loss of GTP cyclohydrolase function in all tissues where activity can be measured. Alleles comprising a third class are recessive eye color mutations that are homozygous viable. Individuals with this third type of mutation show loss of enzyme activity in the eye, but show normal or near-normal activity elsewhere. In order to examine the organization and function of this locus further, we have performed interallelic complementation tests on 25 Punch mutations, monitoring viability and enzyme activity in prepupae and adults. Most allele combinations are lethal. Those that complement do so in ways that are tissue-or stage-specific and unpredictable. Tests of mutants with tissue-specific phenotypes and of individuals mutant for complementing Punch lethal alleles lead us to conclude that Punch is a complex locus, both with respect to its organization and to its products.

Alleles↗
PubMed1991

Introduction of the transposable element mariner into the germline of Drosophila melanogaster.

A chimeric white gene (wpch) and other constructs containing the transposable element mariner from Drosophila mauritiana were introduced into the germline of Drosophila melanogaster using transformation mediated by the P element. In the absence of other mariner elements, the wpch allele is genetically stable in both germ cells and somatic cells, indicating that the peach element (i.e., the particular copy of mariner inserted in the wpch allele) is inactive. However, in the presence of the active element Mos1, the wpch allele reverts, owing to excision of the peach element, yielding eye-color mosaics and a high rate of germline reversion. In strains containing Mos1 virtually every fly is an eye-color mosaic, and the rate of wpch germline reversion ranges from 10 to 25%, depending on temperature. The overall rates of mariner excision and transposition are approximately sixfold greater than the rates in comparable strains of Drosophila simulans. The activity of the Mos1 element is markedly affected by position effects at the site of Mos1 insertion. In low level mosiac lines, dosage effects of Mos1 are apparent in the heavier level of eye-color mosaicism in Mos1 homozygotes than in heterozygotes. However, saturation occurs in high level mosaic lines, and then dosage effects are not observed. A pBluescribe M13+ plasmid containing Mos1 was injected into the pole plasm of D. melanogaster embryos, and the Mos1 element spontaneously integrated into the germline at high efficiency. These transformed strains of D. melanogaster presently contain numerous copies of mariner and may be useful in transposon tagging and other applications.

Alleles↗
PubMed1990

Interaction of the murine dilute suppressor gene (dsu) with fourteen coat color mutations.

The murine dilute suppressor gene, dsu, was previously shown to suppress the dilute coat color phenotypes of mice homozygous for the dilute (d), leaden (ln), and ashen (ash) mutations. Each of these mutations produce adendritic melanocytes, which results in an abnormal transportation of pigment granules into the hair shaft and a diluted coat color. The suppression of each mutation is associated with the restoration of near normal melanocyte morphology, indicating that dsu can compensate for the absence of normal d, ln and ash gene products. In experiments described here, we have determined whether dsu can suppress the coat color phenotype of 14 additional mutations, at 11 loci, that affect coat color by mechanisms other than alterations in melanocyte morphology. In no case was dsu able to suppress the coat color phenotype of these 14 mutations. This suggests that dsu acts specifically on coat color mutations that result from an abnormal melanocyte morphology. Unexpectedly, dsu suppressed the ruby eye color of ruby-eye (ru) and ruby-eye-2 (ru-2) mice, to black. The exact nature of the defect producing these two mutant phenotypes is unknown. Histological examination of the pigmented tissues of the eyes of these mice indicated that dsu suppresses the eye color by increasing the overall level of pigmentation in the choroid but not the retinal pigmented epithelium. Choroid melanocytes, like those in the skin, are derived from the neural crest while melanocytes in the retinal pigmented epithelium are derived from the optic cup. This suggests that dsu may act specifically on neural crest-derived melanocytes. These studies have thus identified a second group of genes whose phenotypes are suppressed by dsu and have provided new insights into the mechanism of action of dsu.

Animals↗
PubMed2003

Identification of trans-dominant modifiers of Prat expression in Drosophila melanogaster.

The first committed step in the purine de novo synthesis pathway is performed by amidophosphoribosyltransferase (EC 2.4.2.14) or Prat. Drosophila melanogaster Prat is an essential gene with a promoter that lacks a TATA-box and initiator element and has multiple transcription start sites with a predominant start site. To study the regulation of Prat expression in the adult eye, we used the Prat:bw reporter gene, in which the Prat coding region was replaced with the brown (bw) coding region. The pale-orange eye color of a single copy of Prat:bw prompted us to use a multicopy array of Prat:bw that was derived using P transposase mutagenesis and produces a darker-orange eye color in a bw(D); st genetic background. We used a 13-copy array of Prat:bw as a tool to recover dominant EMS-induced mutations that affect the expression of the transgene. After screening 21,000 F(1)s for deviation from the orange eye color, we isolated 23 dominant modifiers: 21 suppressors (1 Y-linked, 5 X-linked, 4 2-linked, and 11 3-linked) and 2 enhancers (1 2-linked and 1 3-linked). Quantification of their effect on endogenous Prat gene expression, using RT-PCR in young adult fly heads, identifies a subset of modifiers that are candidates for genes involved in regulating Prat expression.

Amidophosphoribosyltransferase↗