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Träfflista för sökning "WFRF:(Riddell Robert) "

Sökning: WFRF:(Riddell Robert)

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  • Tidskriftsartikel (refereegranskat)
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  • Tidskriftsartikel (refereegranskat)
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  • Tidskriftsartikel (refereegranskat)
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  • Tidskriftsartikel (refereegranskat)
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5.
  • Bonn, Stefan, et al. (författare)
  • Tissue-specific analysis of chromatin state identifies temporal signatures of enhancer activity during embryonic development.
  • 2012
  • Ingår i: Nature Genetics. - 1061-4036 .- 1546-1718. ; 44:2
  • Tidskriftsartikel (refereegranskat)abstract
    • Chromatin modifications are associated with many aspects of gene expression, yet their role in cellular transitions during development remains elusive. Here, we use a new approach to obtain cell type-specific information on chromatin state and RNA polymerase II (Pol II) occupancy within the multicellular Drosophila melanogaster embryo. We directly assessed the relationship between chromatin modifications and the spatio-temporal activity of enhancers. Rather than having a unique chromatin state, active developmental enhancers show heterogeneous histone modifications and Pol II occupancy. Despite this complexity, combined chromatin signatures and Pol II presence are sufficient to predict enhancer activity de novo. Pol II recruitment is highly predictive of the timing of enhancer activity and seems dependent on the timing and location of transcription factor binding. Chromatin modifications typically demarcate large regulatory regions encompassing multiple enhancers, whereas local changes in nucleosome positioning and Pol II occupancy delineate single active enhancers. This cell type-specific view identifies dynamic enhancer usage, an essential step in deciphering developmental networks.
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6.
  • Creighton, S, et al. (författare)
  • Predictive, pre-natal and diagnostic genetic testing for Huntington's disease : the experience in Canada from 1987 to 2000.
  • 2003
  • Ingår i: Clinical Genetics. - 0009-9163 .- 1399-0004. ; 63:6, s. 462-75
  • Tidskriftsartikel (refereegranskat)abstract
    • Predictive and pre-natal testing for Huntington's Disease (HD) has been available since 1987. Initially this was offered by linkage analysis, which was surpassed by the advent of the direct mutation test for HD in 1993. Direct mutation analysis provided an accurate test that not only enhanced predictive and pre-natal testing, but also permitted the diagnostic testing of symptomatic individuals. The objective of this study was to investigate the uptake, utilization, and outcome of predictive, pre-natal and diagnostic testing in Canada from 1987 to April 1, 2000. A retrospective design was used; all Canadian medical genetics centres and their affiliated laboratories offering genetic testing for HD were invited to participate. A total of 15 of 22 centres (68.2%), currently offering or ever having offered genetic testing for HD, responded, providing data on test results, demographics, and clinical history. A total of 1061 predictive tests, 15 pre-natal tests, and 626 diagnostic tests were performed. The uptake for predictive testing was approximately 18% of the estimated at-risk Canadian population, ranging from 12.5% in the Maritimes to 20.7% in British Columbia. There appears to have been a decline in the rate of testing in recent years. Of the predictive tests, 45.0% of individuals were found to have an increased risk, and a preponderance of females (60.2%) sought testing. A greater proportion of those at < or = 25% risk sought predictive testing once direct CAG mutation analysis had become available (10.9% after mutation analysis vs 4.7% before mutation analysis, p = 0.0077). Very few pre-natal tests were requested. Of the 15 pre-natal tests, 12 had an increased risk, resulting in termination of pregnancy in all but one. Diagnostic testing identified 68.5% of individuals to be positive by mutation analysis, while 31.5% of those with HD-like symptoms were not found to have the HD mutation. The positive diagnostic tests included 24.5% of individuals with no known prior family history of HD.
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7.
  • Mullin, Lauren Gayle, 1984-, et al. (författare)
  • Analysis of hexafluoropropylene oxide-dimer acid (HFPO-DA) by liquid chromatography-mass spectrometry (LC-MS) : Review of current approaches and environmental levels
  • 2019
  • Ingår i: TrAC. Trends in analytical chemistry. - : Elsevier. - 0165-9936 .- 1879-3142. ; 118, s. 828-839
  • Forskningsöversikt (refereegranskat)abstract
    • Emerging per- and polyfluorinated compounds (PFAS) compounds are of increasing interest for environmental monitoring, one being hexafluoropropylene oxide-dimer acid (HFPO-DA), commonly referred to as GenX. The following review describes existing liquid chromatography-mass spectrometry (LC-MS) methods used to analyse HFPO-DA, including sample preparation and method sensitivity relative to other PFAS. Analytical challenges are also described, in particular the significant formation of in-source fragmentation, dimer and dimer adducts which detract from [M-H](-) signal. Lastly, detected levels of HFPO-DA in environmental and biological samples are compared across the limited number of available field exposure studies, which found several mu g/L concentrations in water samples taken near fluorochemical plant discharges.
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  • Riddell, Nicole, 1979-, et al. (författare)
  • Comparative assessment of the chromatographic separation of 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans using supercritical fluid chromatography and high resolution gas chromatography
  • 2015
  • Ingår i: Analytical Methods. - : Royal Society of Chemistry. - 1759-9660 .- 1759-9679. ; 7:21, s. 9245-9253
  • Tidskriftsartikel (refereegranskat)abstract
    • The analysis of legacy environmental contaminants, such as polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs), using high resolution gas chromatography (HRGC) is well established and universally accepted. The use of an alternative separation technique, such as packed column supercritical fluid chromatography (pSFC), may be of interest as a fast, green, and cost effective method of analyzing environmental samples. The technique is amenable to a broad range of chemical compounds and could facilitate the simultaneous analysis of multiple compound classes as well as the inclusion of thermally labile compounds in a single targeted analysis. The recent re-emergence of this technology due to the introduction of more robust and efficient instrumentation may result in an increased acceptance of pSFC analytical techniques in this area. Herein, the first reported analytical separation of PCDDs and PCDFs by pSFC is described and its separation capabilities are compared with established HRGC protocols. Elution profiles of 2,3,7,8-substituted PCDDs and PCDFs were examined and the separation of PCDD/PCDF homologue groups was found to be comparable to those accomplished using HRGC. Similarly, the resolution of tetrachlorodibenzo-p-dioxin (TCDD) congeners, as required by current regulatory methods utilizing HRGC, was demonstrated and the separation of possible co-eluting PCDD/PCDF congeners was examined and compared to that achieved using popular HRGC capillary columns. The possibility of concurrent analysis of toxic polychlorinated biphenyls (PCBs) with PCDDs and PCDFs using the developed pSFC method was also investigated. The effective separation of these environmental contaminants obtained using pSFC and subsequent detection utilizing atmospheric pressure photoionization tandem mass spectrometry at environmentally relevant levels demonstrates the promise associated with this technique for the analysis of environmental extracts.
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10.
  • Riddell, Nicole, 1979-, et al. (författare)
  • Coupling of supercritical fluid chromatography to mass spectrometry for the analysis of Dechlorane Plus : Examination of relevant negative ion atmospheric pressure chemical ionization mechanisms
  • 2017
  • Ingår i: Talanta. - : Elsevier. - 0039-9140 .- 1873-3573. ; 171, s. 68-73
  • Tidskriftsartikel (refereegranskat)abstract
    • During an investigation of the potential associated with coupling packed column supercritical fluid chromatography (pSFC) to mass spectrometry for the analysis of Dechlorane Plus and related compounds, it was found that negative ion atmospheric pressure chemical ionization (APCI) was a promising ionization technique. In the course of maximizing the responses associated with the target analytes, it proved useful to examine some aspects of the complex nature and reactivity of the corona discharge plasma generated to explain the observed ionization products. Various dopants/reagents were screened for both APCI and atmospheric pressure photoionization (APPI) in negative ion mode and mechanisms of ionization involving superoxide were elucidated based on the results obtained. Superoxide formation was found to be temperature dependent and directly related to the intensity of the ion cluster [M-Cl+O](-) obtained for the target DP analytes. Furthermore, triethylamine was identified as a reagent capable of suppressing unwanted side reactions during the ionization process and maximizing response associated with the analytes of interest. The applicability of pSFC-APCI/MS for the separation and detection of Dechlorane Plus and related compounds was demonstrated by analyzing Lake Ontario sediment and comparing the results with values reported in the scientific literature.
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