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At least 109 records · Page 6Linked to original sources
PubMed2005

Persistence time of loss-of-function mutations at nonessential loci affecting eye color in Drosophila melanogaster.

Persistence time of a mutant allele, the expected number of generations before its elimination from the population, can be estimated as the ratio of the number of segregating mutations per individual over the mutation rate per generation. We screened two natural populations of Drosophila melanogaster for mutations causing clear-cut eye phenotypes and detected 25 mutant alleles, falling into 19 complementation groups, in 1164 haploid genomes, which implies 0.021 eye mutations/genome. The de novo haploid mutation rate for the same set of loci was estimated as 2 x 10(-4) in a 10-generation mutation-accumulation experiment. Thus, the average persistence time of all mutations causing clear-cut eye phenotypes is approximately 100 generations (95% confidence interval: 61-219). This estimate shows that the strength of selection against phenotypically drastic alleles of nonessential loci is close to that against recessive lethals. In both cases, deleterious alleles are apparently eliminated by selection against heterozygous individuals, which show no visible phenotypic differences from wild type.

Animals↗
PubMed2004

Validation of the FAMACHA eye color chart for detecting clinical anemia in sheep and goats on farms in the southern United States.

Recent studies on sheep and goat farms in the southern United States indicate that multiple-anthelmintic resistance in Haemonchus contortus is becoming a severe problem. Though many factors are involved in the evolution of resistance, the proportion of the parasite population under drug selection is believed to be the single most important factor influencing how rapidly resistance develops. Therefore, where prevention of resistance is an important parallel goal of worm control, it is recommended to leave a portion of the animals untreated. Recently, a novel system called FAMACHA was developed in South Africa, which enables clinical identification of anemic sheep and goats. When H. contortus is the primary parasitic pathogen, this system can be applied on the farm level to reduce the number of treatments administered, thereby increasing the proportion of the worm population in refugia. Since most studies validating the FAMACHA method have been performed in South Africa, it is important that the method be tested in other regions before its use is broadly recommended. We performed a validation study of FAMACHA by testing the system in sheep (n = 847) and goats (n = 537) of various breeds and ages from 39 farms located in Arkansas, Georgia, Louisiana, Florida, and the US Virgin Islands. The color of the ocular conjunctiva of all animals were scored on a 1-5 scale using the FAMACHA card, and blood samples were collected from each animal for determination of packed cell volume (PCV). Fecal samples were also collected from a majority of the animals tested for performance of fecal egg counts (FEC). Correlations between PCV and eye scores, PCV and FEC, and FEC and eye scores were all highly significant for both sheep and goats (P < 0.001). Data for both FAMACHA scores and PCV were evaluated using two separate criteria for anemia: eye score values of 3, 4 and 5 or 4 and 5, and PCV values of < or =19 or < or =15 were considered anemic. Specificity was maximized when eye score values of 4 and 5 were considered anemic and PCV cut off for anemia was < or =19, but sensitivity was low. In contrast, sensitivity was 100% for both sheep and goats when eye score values of 3, 4 and 5 were considered anemic and PCV cut off was < or =15, but specificity was low. In both sheep and goats, predictive value of a negative was greater than 92% for all anemia and eye score categories, and was greater than 99% for both eye score categories when an anemia cutoff of < or =15 was used. Predictive value of a positive test was low under all criteria indicating that many non-anemic animals would be treated using this system. However, compared to conventional dosing practices where all animals are treated, a large proportion of animals would still be left untreated. These data indicate that the FAMACHA method is an extremely useful tool for identifying anemic sheep and goats in the southern US and US Virgin Islands. However, further studies are required to determine optimal strategies for incorporating FAMACHA-based selective treatment protocols into integrated nematode control programs.

Anemia↗
PubMed1978

[Estimation of the heritability of hair and eye color].

In the present study the colours of hair are regarded as quantitative genetic characters. The genetic and environmental components of the total variance of the characters are determined by analysis of correlation between parents and children as well as full sibs. An analysis of correlation coefficients makes it possible to further examine whether autosomal dominance or X-linked factors play a role in the inheritance. The correlations between the parents make the genetical analysis more complicated as they raise the correlation coefficients between relatives. The estimates of heritability are 0.61 (hair-colour) and 0.80 (eye-colour). These estimates may serve as preliminary values of orientation. Only further studies will show whether the relative large part of the variance caused by the environment can be confirmed. Dominance may play a small role in the case of hair colour, while it seems to be absent in eye-colour. There are no sufficient indications of X-linked factors for both characters.

Adult↗
PubMed1979

Isolation and biochemical analysis of a temperature-sensitive scarlet eye color mutant of Drosophila melanogaster.

Six new ems-induced scarlet mutants were selected. Four of these were partially pigmented, with xanthommatin levels ranging from 12% to 45% of normal. In one (st754ts), pigment production was temperature sensitive; the level of xanthommatin changed from less than 10% of normal at 29 C to more than 70% at 18 C. In all of the new mutants tested, the level of early pupal 3-hydroxykynurenine was as low as that in st1. Thus reduced larval accumulation of this metabolite also appears to be a characteristic feature of scarlet mutants. Temperature-pulse and temperature-shift experiments were carried out with st754ts to determine the temperature-sensitive period for the scarlet gene during development. The major sensitive period commenced prior to the onset of pigmentation and was over before adult emergence. Thus the initiation of xanthommatin synthesis is not brought about by the activation of the scarlet gene. In similar experiments carried out with a temperature-sensitive white mutant (Wbl), a similar temperature-sensitive period was obtained.

Animals↗
PubMed2006

The frequency and distribution of minocycline induced hyperpigmentation in a rheumatoid arthritis population.

OBJECTIVE: Minocycline is particularly useful in patients with rheumatoid arthritis (RA) with previous major sepsis, where anti-tumor necrosis factor is relatively contraindicated. Pigmentation is a documented side effect, but predisposing factors in an RA population have not been established. We investigated minocycline induced pigmentation in a population with RA to determine whether skin type and eye color influence predisposition to this side effect. METHODS: Patients with RA attending a rheumatology unit who had received minocycline were contacted by telephone and some were also interviewed in the clinic. Those receiving therapy for more than 3 months were assessed. Hair color, eye color, tendency to burn in the sun, and dose and duration of therapy were documented. The frequency, type, and distribution of pigmentation were established. RESULTS: Of 37 patients identified, 10 were excluded because the duration of therapy was less than 3 months. Of the remaining 27 patients, 85% were female, with median age 64 years (range 44-88) and median disease duration 23.5 years (range 4-51). Eleven patients (41%) developed pigmentation after a median of 12 months. Four of the 11 stopped their minocycline due to pigmentation. Hair color, eye color, and tendency to burn in the sun did not predict patients who developed pigmentation. CONCLUSION: Pigmentation is a common side effect in patients receiving minocycline therapy for more than 3 months. Most patients do not stop therapy due to pigmentation. Those who stop are more likely to be female, less than 70 years of age, and have facial pigmentation.

Adult↗
PubMed1998

The sugarless mutation affects the expression of the white eye color gene in Drosophila melanogaster.

Investigation of a modifier locus displaying a darker eye phenotype in white-apricot flies led to the isolation of the gene encoding UDP-glucose dehydrogenase (UDPGDH). The P-element insertion l(3)05007 occurs upstream of the transcription start site of the sugarless (sgl) gene and greatly reduces its transcription at various developmental stages. A single abundant sgl transcript shows a ubiquitous distribution and encodes a 53-kDa protein which is 64% identical in sequence to bovine UDP-glucose dehydrogenase. Overexpression of sgl in E. coli resulted in synthesis of a protein with high levels of UDPGDH activity. Expression of three genes that participate in pigment deposition, white, scarlet and brown, was significantly affected in populations segregating for sgl, suggesting that it is the decrease in UDPGDH level that produces the modifying effect observed. In addition, genetic effects on white-apricot were observed in sgl-wingless and sgl-hedgehog double mutants. Recent data have indicated an effect of UDPGDH on cell surface glycosaminoglycans (GAGs) which modulate the activity of growth factors, and in particular wingless signaling. Our results suggest that the levels of GAGs are rate limiting for cell-cell signaling pathways which mediate changes in gene expression.

ATP-Binding Cassette Transporters↗
PubMed1987

Phenotypic characters related to skin type and minimal erythemal dose.

Minimal erythemal dose (MED) was determined in 155 healthy Caucasoid subjects. Hair color, eye color, number of freckles, and history of sun reactivity and tanning ability, according to the system proposed by Fitzpatrick, were also recorded. In the subjects with skin type I, the values of MED were relatively homogeneous, whereas in subjects with skin types II, III and IV there was a wide variation of MED values. In spite of this variation, a good correlation was found between MED and skin types. MED was found to correlate with hair color, eye color and number of freckles only for some variants of these characters. Low values of MED correlated significantly with red hair, blue eyes and highly freckled skin. Between other variants of the same characters, MED values did not differ significantly. This means that phenotypic characters suggest low MED values only in individuals with red hair, blue eyes and many freckles. In these subjects the phenotypic characters studied may be considered indicative of cancer risk. For all other Caucasoid people the phenotypic characters studied are not predictive of MED nor, probably, of cancer risk.

Adolescent↗