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  • 1
    Publication Date: 2013-08-15
    Description: The response of eukaryotic cells to ionising radiation (IR)-induced double-strand DNA breaks is highly conserved and involves a DNA repair mechanism characterised by the early phosphorylation of histone protein H2AX (producing the active form H2AX). Although the expression of an induced H2AX variant has been detected in Drosophila melanogaster , the expression and radiation response of a H2AX homologue has not been reported in economically important fruit flies. We use Bactrocera tryoni (Diptera: Tephritidae, Queensland fruit fly or ‘Q-fly’) to investigate this response with a view to developing molecular assays to detect/quantify exposure of fruit flies to IR and consequent DNA damage. Deep sequencing confirmed the presence of a H2AX homologue that we have termed H2AvB (i.e. variant Bactrocera ) and has an identical sequence to a histone reported from the human disease vector Glossina morsitans . A linear dose–response of H2AvB (0–400 Gy IR) was observed in whole Q-fly pupal lysates 24h post-IR and was detected at doses as low as 20 Gy. H2AvB signal peaked at ~20min after IR exposure and at 24h post-IR the signal remained elevated but declined significantly by 5 days. Persistent and dose-dependent H2AvB signal could be detected and quantified either by western blot or by laser scanning cytometry up to 17 days post-IR exposure in histone extracts or isolated nuclei from adult Q-flies (irradiated as pupae). We conclude that IR exposure in Q-fly leads to persistent H2AvB signals (over a period of days) that can easily be detected by western blot or quantitative immunofluorescence techniques. These approaches have potential as the basis for assays for detection and quantification of prior IR exposure in pest fruit flies.
    Print ISSN: 0267-8357
    Electronic ISSN: 1464-3804
    Topics: Biology , Medicine
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  • 2
    Publication Date: 2016-06-23
    Description: G-quadruplexes (G4) are highly stable tetra-stranded DNA secondary structures known to mediate gene regulation and to trigger genomic instability events during replication. G4 structural stability can be affected by DNA methylation and oxidation modifications; thus nutrients such as folate that have the ability to alter these processes could potentially modify the genomic occurrence of G4 elements. Hela cells were cultured in a range of folate concentrations or in the presence or absence of 5-aza-2'-deoxycytidine, a DNA-methyltransferase inhibitor. G4 structures were then quantified by immunofluorescence using an automated quantitative imaging system. G4 frequency in Hela cells and nuclei area mean were increased in 20nM folate medium compared with 2000nM folate, as well as in the presence of 5-aza-2'-deoxycytidine when compared to cells non-exposed to 5-aza-2'-deoxycytidine. These changes were exacerbated when pyridostatin, a G4 stabilising ligand, was added to the culture medium. G4 intensity in Hela cells cultured in deficient folate condition with pyridostatin was highly correlated with DNA damage as measured by H2AX immunofluorescence ( r = 0.71). This study showed for the first time that cellular G4 balance is modifiable by low folate concentrations and that these changes may occur as a consequence of DNA hypomethylation. Although the exact mechanism by which these changes occur is unclear, these findings establish the possibility that nutrients could be utilised as a tool for sustaining genome integrity by modifying G4 frequency at a cellular level.
    Print ISSN: 0267-8357
    Electronic ISSN: 1464-3804
    Topics: Biology , Medicine
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  • 3
    Publication Date: 2015-11-06
    Description: According to the World Health Organization, the obesity epidemic is a threat. Brazil is not an exception, and the objective of this article is to analyze the effects of a "fat tax" there. For this purpose, the estimation of a demand system was carried out and policy simulations were performed using the estimated parameters. The simulation results indicate that to be successful, this "fat tax" must be combined with a subsidy on healthy food. Another contribution was the analysis of a linear symmetric revenue-neutral tax schedule with more pronounced changes to micronutrient intake at no net cost to the government.
    Keywords: D12 - Consumer Economics: Empirical Analysis, D13 - Household Production and Intrahousehold Allocation, I18 - Government Policy ; Regulation ; Public Health
    Print ISSN: 2040-5790
    Electronic ISSN: 2040-5804
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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