107 research outputs found
In vivo mutations in human blood cells: Biomarkers for molecular epidemiology
Mutations arising in vivo in recorder genes of human blood cells provide biomarkers for molecular epidemiology by serving
as surrogates for cancer-causing genetic changes. Current markers include mutations of the glycophorin-A (GPA) or
hemoglobin (Hb) genes, measured in red blood cells, or mutations of the hypoxanthine-guanine phosphoribosyltransferase
(hprt) or HLA genes, measured in T-lymphocytes. Mean mutant frequencies (variant frequencies) for normal young adults
are approximately: Hb (4 x10-8) < hprt (5 x 10-6) = GPA (10 x 10-6) <HLA (30 x 10-6). Mutagen-exposed individuals
show decided elevations. Molecular mutational spectra are also being defined. For the hprt marker system, about 15%
of background mutations are gross structural alterations of the hprt gene (e.g., deletions); the remainder are point mutations
(e.g., base substitutions or frameshifts). Ionizing radiations result in dose-related increases in total gene deletions. Large
deletions may encompass several megabases as shown by co-deletions of linked markers. Possible hprt spectra for defining
radiation and chemical exposures are being sought. In addition to their responsiveness to environmental mutagens/carcinogens,
three additional findings suggest that the in vivo recorder mutations are relevant in vivo surrogates for cancer
mutations. First, a large fraction of GPA and HLA mutations show exchanges due to homologous recombination, an important
mutational event in cancer. Second, hprt mutations arise preferentially in dividing T-cells, which can accumulate
additional mutations in the same clone, reminiscent of the multiple hits required in the evolution of malignancy. Finally,
fetal hprt mutations frequently have characteristic deletions of hprt exons 2 and 3, which appear to be mediated by the VDJ
recombinase that rearranges the T-cell receptor genes during thymic ontogeny. Illegitimate events such as these also appear
to occur in human leukemias
Characterisation of Mutaā¢Mouse Ī»gt10-lacZ transgene: evidence for in vivo rearrangements
The multicopy Ī»gt10-lacZ transgene shuttle vector of Mutaā¢Mouse serves as an important tool for genotoxicity studies. Here, we describe a model for Ī»gt10-lacZ transgene molecular structure, based on characterisation of transgenes recovered from animals of our intramural breeding colony. Unique nucleotide sequences of the 47ā513 bp monomer are reported with GenBankĀ® assigned accession numbers. Besides defining ancestral mutations of the Ī»gt10 used to construct the transgene and the Mutaā¢Mouse precursor (strain 40.6), we validated the sequence integrity of key Ī» genes needed for the Escherichia coli host-based mutation reporting assay. Using three polymerase chain reaction (PCR)-based chromosome scanning and cloning strategies, we found five distinct in vivo transgene rearrangements, which were common to both sexes, and involved copy fusions generating ā¼10 defective copies per haplotype. The transgene haplotype was estimated by Southern hybridisation and real-timeāpolymerase chain reaction, which yielded 29.0 Ā± 4.0 copies based on spleen DNA of Mutaā¢Mouse, and a reconstructed CD2F1 genome with variable Ī»gt10-lacZ copies. Similar analysis of commercially prepared spleen DNA from Big BlueĀ® mouse yielded a haplotype of 23.5 Ā± 3.1 copies. The latter DNA is used in calibrating a commercial in vitro packaging kit for E.coli host-based mutation assays of both transgenic systems. The model for Ī»gt10-lacZ transgene organisation, and the PCR-based methods for assessing copy number, integrity and rearrangements, potentially extends the use of Mutaā¢Mouse construct for direct, genomic-type assays that detect the effects of clastogens and aneugens, without depending on an E.coli host, for reporting effects
Initial results from a field campaign of wake steering applied at a commercial wind farm ā Part 1
Wake steering is a form of wind farm control in which turbines use
yaw offsets to affect wakes in order to yield an increase in total energy
production. In this first phase of a study of wake steering at a commercial
wind farm, two turbines implement a schedule of offsets. Results exploring
the observed performance of wake steering are presented and some
first lessons learned. For two closely spaced turbines, an approximate
14 % increase in energy was measured on the downstream turbine over a
10ā sector, with a 4 % increase in energy production of the
combined upstreamādownstream turbine pair. Finally, the influence of
atmospheric stability over the results is explored.</p
Deep Eutectic Solvents (DESs) and their applications [forthcoming]
Deep Eutectic Solvents (DESs) and Their Application
Nucleotide sequence of the xanthine guanine phosphoribosyl transferase gene of E. coli.
The nucleotide sequence of the gpt coding for the enzyme xanthine guanine phosphoribosyl transferase has been determined. The gene codes for a protein of molecular weight 16,950. The construction of deletions in the gpt gene which can be used for the genetic analysis of mutations in the gpt gene, is described
The role of class-level composition and schoolsĀ“ contextual characteristics for school-aged childrenĀ“s life satisfaction: a three-level multilevel analysis
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