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The properties of Escherichia coli proteins from Arabidopsis thaliana (At), humans (Hs) and the yeast Saccharomyces cerevisiae (Sc) are analyzed and compared in order to assess the biochemical evolution of DNA polymerase [eta] (Pol[eta]) in plants. The studies have shown that the DNA sequences surrounding cyclobutane thymine dimers (T[CPD]T) has strongly affected Pol[eta] activity.

The effects of sustained mutational loading during multigenerational propagations, appearance of apparent single- and perhaps multiple-locus phenotypes and an overall trend toward decreased fitness are demonstrated. Analyses of insertion /deletion mutation at six repeat-sequence loci showed each Atmsh2-1 line to have evolved its own fingerprint the results of as many as 10 microsatellite mutations in a single line.

Chromosomal rearrangements may complicate construction of Arabidopsis with multiple TDNA-insertion mutations. Here, crossing two lines homozygous for insertions in AtREV3 and AtPOLH (chromosomes I and V, respectively) and selfing F1 plants yielded non-Mendelian F2 genotype distributions: frequencies of + /++ /+ and 1/1 2/2 progeny were only 0.42 and 0.25%. However, the normal development and fertility of double mutants showed AtPOLH-1 and AtREV3-2 gametes and 1/1 2/2 embryos to be fully viable. F2 distributions could be quantitatively predicted by assuming that F1 selfing produced inviable ( 1,2) and (+ ,+) gametophytes 86% of the time. Some defect intrinsic to the F1 selfing process itself thus appeared responsible. In selfing AtREV3+ /2 single mutants, imaging of ovules and pollen showed arrest or abortion, respectively, of half of gametophytes; however, gametogenesis was normal in AtREV3 2/2 homozygotes. These findings, taken together, suggested that T-DNA insertion at AtREV3 on chromosome I had caused a reciprocal I–V translocation. Spreads of meiosis I chromosomes in selfing AtREV3+ /2 heterozygotes revealed the predicted cruciform four-chromosome structures, which fluorescence in situ hybridization showed to invariably include both translocated and normal chromosomes I and V. Sequencing of the two junctions of T-DNA with AtREV3 DNA and the two with gene At5g59920 suggested translocation via homologous recombination between independent inverted-repeat T-DNA insertions. Thus, when crosses between TDNA-insertion mutants yield anomalous progeny distributions, TDNA-linked translocations should be considered. [ABSTRACT FROM AUTHOR]

To assess how evolution might have biochemically shaped DNA polymerase 1/ (Polt/) in plants. we expressed in E.scherichia co/i proteins from .4rabidopsis thu/lana (At), humans (Hs). and the yeast Saecharomycea cereuisiae (Sc), purified them to near homogeneity, and compared their properties. Consistent with the multiple divergent amino acids within mostly conserved polymerase domains, the polymerases showed modest, appreciable, and marked differences. respectively, in salt and temperature optima for activity and thermostability. We compared abilities to extend synthetic primers past template cyclobutane thymine dimers (T[CPD]T) or undamaged T-T under physiological conditions (80-I It) mM salt). Specific activities for "standing-start" extension of synthetic primers ending opposite the second template nucleotide 3' to T-T were roughly similar. DUriTig subsequent "running-start" insertions past T-T and the next 5' (N + I) nucleotide, AtPolt7 and HsPolij appeared more processive. but DNA sequence contexts strongly affected termination probabilities. Lesion-bypass studies employed four different templates containing TICPD]Ts, and two containing pyrimidine (6--t')-pyrimidinone photoproducts (16-415). AtPol~ made the three successive insertions [opposite the TICPD]T and (N + I) nucleotidesi that define bypass nearly as well as HsPoltj and somewhat better than ScPol~. Again, sequence context elfects were profound. Interestingly, the level of insertion opposite the (N - I) nucleotide 3' to TICPD1T by HsPolt/ and especially AtPolsi, but not ScPolli. was reduced (up to 4-fold) relative to the level of insertion opposite the (N - I) nucleotide 3' to T-T. Evolutionary conservation of efficient T[CPD]T bypass by HsPolq and AtPols~ may reflect a high degree of exposure of human skin and plants to solar UV-B radiation. The depressed (N - I) insertion upstream of T[CPDIT (but not T-T) may reduce the extent of gratuitous error-prone insertion. [ABSTRACT FROM AUTHOR]

Strong frequency dependence of particle aggregation in applied ac-electric fields is reported for colloidal assembly under positive dielectrophoresis. A curious low-frequency threshold ωth on the order of 104–105 Hz is observed for the onset of collecting submicron latex particles at the high-field regions near coplanar electrodes. Similar to the dielectrophoretic crossover frequency, ωth is independent of medium conductivity, σm at low-salt concentration, yet scales with σm0.5 at high-salt concentrations. This intriguing salt effect suggests the distinct contribution from Stern and diffuse layer conductance to the interfacial polarization mechanism of latex particles in nonuniform ac fields. [ABSTRACT FROM AUTHOR]

[Display omitted] Studies suggest that exposure to potential endocrine disrupting chemicals (pEDCs) may contribute to adverse health outcomes, but pEDC exposures among firefighters have not been fully characterized. Previously, we demonstrated the military-style silicone dog tag as a personal passive sampling device for assessing polycyclic aromatic hydrocarbon exposures among structural firefighters. This follow-up analysis examined the pEDC exposures based on department call volume, duty shift, and questionnaire variables. Structural firefighters (n = 56) were from one high and one low fire call volume department (Kansas City, MO metropolitan area) and wore separate dog tags while on- and off-duty (n dogtags = 110). The targeted 1530 analyte semi-quantitative screening method was conducted using gas chromatography mass spectrometry (n pEDCs = 433). A total of 47 pEDCs were detected, and several less-frequently-detected pEDCs (<75%) were more commonly detected in off- compared to on-duty dog tags (conditional logistic regression). Of the 11 phthalates and fragrances detected most frequently (>75%), off-duty pEDC concentrations were strongly correlated (r = 0.31–0.82, p < 0.05), suggesting co-applications of phthalates and fragrances in consumer products. Questionnaire variables of "regular use of conventional cleaning products" and "fireplace in the home" were associated with select elevated pEDC concentrations by duty shift (paired t -test). This suggested researchers should include detailed questions about consumer product use and home environment when examining personal pEDC exposures. [ABSTRACT FROM AUTHOR]

• Silicone dog tags are a new configuration of personalized passive sampling device. • Silicone dog tags detected 18 PAHs not previously reported as firefighter exposures. • Firefighters have higher chemical exposures on– compared to off-duty. • Concentrations were more correlated to fire attack numbers than firefighter rank. • Silicone dog tags can provide quantitative exposure data on chemical mixtures. Occupational chemical hazards in the fire service are hypothesized to play a role in increased cancer risk, and reliable sampling technologies are necessary for conducting firefighter chemical exposure assessments. This study presents the military-style dog tag as a new configuration of silicone passive sampling device to sample individual firefighters' exposures at one high and one low fire call volume department in the Kansas City, Missouri metropolitan area. The recruited firefighters (n = 56) wore separate dog tags to assess on– and off-duty exposures (n dogtags = 110), for a total of 30 24 h shifts. Using a 63 PAH method (GC–MS/MS), the tags detected 45 unique PAHs, of which 18 have not been previously reported as firefighting exposures. PAH concentrations were higher for on– compared to off-duty tags (0.25 < Cohen's d ≤ 0.80) and for the high compared to the low fire call volume department (0.25 ≤ d < 0.70). Using a 1530 analyte screening method (GC–MS), di-n-butyl phthalate, diisobutyl phthalate, guaiacol, and DEET were commonly detected analytes. The number of fire attacks a firefighter participated in was more strongly correlated with PAH concentrations than firefighter rank or years in the fire service. This suggested that quantitative data should be employed for firefighter exposure assessments, rather than surrogate measures. Because several detected analytes are listed as possible carcinogens, future firefighter exposure studies should consider evaluating complex mixtures to assess individual health risks. [ABSTRACT FROM AUTHOR]