Heteroepitaxial growth of ferromagnetic MnSb(0001) films on Ge/Si(111) virtual substrates

Molecular beam epitaxial growth of ferromagnetic MnSb(0001) has been achieved on high quality, fully relaxed Ge(111)/Si(111) virtual substrates grown by reduced pressure chemical vapor deposition. The epilayers were characterized using reflection high energy electron diffraction, synchrotron hard X-ray diffraction, X-ray photoemission spectroscopy, and magnetometry. The surface reconstructions, magnetic properties, crystalline quality, and strain relaxation behavior of the MnSb films are similar to those of MnSb grown on GaAs(111). In contrast to GaAs substrates, segregation of substrate atoms through the MnSb film does not occur, and alternative polymorphs of MnSb are absent

Strategies to decrease oxidative stress biomarker levels in human medical conditions: A meta-analysis on 8-iso-prostaglandin F2α

The widespread detection of elevated oxidative stress levels in many medical conditions has led to numerous efforts to design interventions to reduce its effects. Efforts have been wide-ranging, from dietary changes to administration of antioxidants, supplements, e.g., omega-3-fatty acids, and many medications. However, there is still no systemic assessment of the efficacy of treatments for oxidative stress reduction across a variety of medical conditions.The goal of this meta-analysis is, by combining multiple studies, to quantitate the change in the levels of the popular oxidative stress biomarker 8-iso-prostaglandin F2α (8-iso-PGF2α) after a variety of treatment strategies in human populations.Nearly 350 unique publications with 180 distinct strategies were included in the analysis. For each strategy, the difference between pre- or placebo and post-treatment levels calculated using Hedges’ g value of effect. In general, administration of antibiotics, antihyperlipidemic agents, or changes in lifestyle (g = − 0.63, − 0.54, and 0.56) had the largest effect. Administration of supplements, antioxidants, or changes in diet (g = − 0.09, − 0.28, − 0.12) had small quantitative effects. To fully interpret the effectiveness of these treatments, comparisons to the increase in g value for each medical condition is required. For example, antioxidants in populations with coronary artery disease (CAD) reduce the 8-iso-PGF2α levels by g = − 0.34 ± 0.1, which is quantitatively considered a small effect. However, CAD populations, in comparison to healthy populations, have an increase in 8-iso-PGF2α levels by g = 0.38 ± 0.04; therefore, the overall reduction of 8-iso-PGF2α levels is ≈ 90% by this treatment in this specific medical condition.In conclusion, 8-iso-PGF2α levels can be reduced not only by antioxidants but by many other strategies. Not all strategies are equally effective at reducing 8-iso-PGF2α levels. In addition, the effectiveness of any strategy can be assessed only in relation to the medical condition investigated

Reinterpreting the best biomarker of oxidative stress: The 8-iso-PGF2α/PGF2α ratio distinguishes chemical from enzymatic lipid peroxidation

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Moles of a Substance per Cell Is a Highly Informative Dosing Metric in Cell Culture

<div><p>Background</p><p>The biological consequences upon exposure of cells in culture to a dose of xenobiotic are not only dependent on biological variables, but also the physical aspects of experiments e.g. cell number and media volume. Dependence on physical aspects is often overlooked due to the unrecognized ambiguity in the dominant metric used to express exposure, i.e. initial concentration of xenobiotic delivered to the culture medium over the cells. We hypothesize that for many xenobiotics, specifying dose as moles per cell will reduce this ambiguity. Dose as moles per cell can also provide additional information not easily obtainable with traditional dosing metrics.</p><p>Methods</p><p>Here, 1,4-benzoquinone and oligomycin A are used as model compounds to investigate moles per cell as an informative dosing metric. Mechanistic insight into reactions with intracellular molecules, differences between sequential and bolus addition of xenobiotic and the influence of cell volume and protein content on toxicity are also investigated.</p><p>Results</p><p>When the dose of 1,4-benzoquinone or oligomycin A was specified as moles per cell, toxicity was independent of the physical conditions used (number of cells, volume of medium). When using moles per cell as a dose-metric, direct quantitative comparisons can be made between biochemical or biological endpoints and the dose of xenobiotic applied. For example, the toxicity of 1,4-benzoquinone correlated inversely with intracellular volume for all five cell lines exposed (C6, MDA-MB231, A549, MIA PaCa-2, and HepG2).</p><p>Conclusions</p><p>Moles per cell is a useful and informative dosing metric in cell culture. This dosing metric is a scalable parameter that: can reduce ambiguity between experiments having different physical conditions; provides additional mechanistic information; allows direct comparison between different cells; affords a more uniform platform for experimental design; addresses the important issue of repeatability of experimental results, and could increase the translatability of information gained from <i>in vitro</i> experiments.</p></div

A single bolus addition or sequential additions of 1,4-BQ can provide differential toxicities based on the endpoint measured.

<p><b>(A)</b> Clonogenic survival of MIA PaCa-2 cells was evaluated after a bolus addition of 600 fmol cell^-1 of 1,4-BQ or incremental additions of 1,4-BQ every 20 min over the 4-h exposure period (12 separate but equal additions) to yield a total dose of 600 fmol cell^-1. Controls represent additions of DMSO only to the culture media using protocols parallel to additions of 1,4-BQ. Clonogenic survival was the same for both exposure methods (<i>n</i> = 3, error bars are standard deviation of the mean). There is no statistical difference in the clonogenic survival between the two protocols. Each is different from the controls (<i>p</i> < 0.05). <b>(B)</b> Cell viability as indicated with trypan blue staining produced quite different results using a bolus dose of 1,4-BQ <i>vs</i>. sequential addition (<i>n</i> = 3, error bars are standard deviation of the mean). A single bolus addition produces a significant difference between control and sequential addition (<i>p</i> < 0.05). Whereas the sequential addition is the same as the control (<i>p</i> > 0.05).</p

Dose of 1,4-BQ expressed as mol cell^-1 allows direct comparisons between different experimental conditions and more accurately reports toxicity than initial concentration in medium.

<p>Clonogenic survival of A549 cells was observed after a 4-h exposure to 1,4-BQ using two different experimental conditions: orange square, 13 x 10⁶ cells exposed in 15.0 mL of medium; green diamond, 1.55 x 10⁶ cells exposed in 20.0 mL medium. The doses are expressed in: <b>(A)</b> Initial concentration in medium (μM), note that EC₅₀ depends on the physical setup of the experiment; <b>(B)</b> Mol cell^-1 basis (here fmol cell^-1); note that ED₅₀ is independent of the physical setup of the experiment. The two clonogenic survival curves are representative experiments with each point being the median of six plates. Error bars represent the standard error of the median; many error bars are smaller than the symbol.</p

Clonogenic survival correlates directly with intracellular ATP concentration following exposure to 1,4-BQ.

<p>Clonogenic survival of MIA PaCa-2 cells following 4-h exposure to (0–1000 fmol cell^-1) 1,4-BQ was plotted against intracellular ATP concentration of MIA PaCa-2 cells also following 4-h exposure to (0–1000 fmol cell^-1) 1,4-BQ. Clonogenic survival directly correlates with intracellular ATP concentration following 4-h exposure to 1,4-BQ. Clonogenic survival is presented as the mean of <i>n</i> = 3 biological replicates with error bars representing the standard error of the mean. Intracellular ATP is presented as the mean of <i>n</i> = 2 biological replicates with error bars representing the standard error of the mean. Some error bars are smaller than the symbols.</p

Depiction of target theory and exposure to 1,4-BQ.

<p>The ten quinone moieties shown in each scenario represents the same mol cell^-1. Here we assume that there are a certain number of sensitive/reactive “targets” within cells and the number of targets is proportional to intracellular volume. Damage to some fraction of those targets will produce a biological effect. Because larger cells have a greater number of targets, more 1,4-BQ will be required to produce the same biological effect as observed with smaller cells.</p

ED₅₀ of 1,4-BQ correlates directly with intracellular volume and mass of protein per cell for C6, MB231, A549, MIA PaCa-2, and HepG2 cell lines.

<p><b>(A)</b> The dose of 1,4-BQ (mol cell^-1) at which 50% clonogenic survival was observed for each cell type is plotted vs. the measured intracellular volume (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0132572#pone.0132572.t001" target="_blank">Table 1</a>). The correlation coefficient R² is 0.74. Each cell line has <i>n</i> = 2 for biological replicates, <i>n</i> = 3 within each replicate. The measured intracellular volume represented is the mean of two different methods of measuring intracellular volume. Each cell line was measured (<i>n</i> = 3) using a Z2 Coulter Counter and a Moxi Z Mini Automated Cell Counter in ISOTON II Diluent (Beckman Coulter, Inc.). Error bars represent the standard error of the mean; some error bars are smaller than the symbol. <b>(B)</b> Mass of protein per cell directly correlates with intracellular volume (R² = 0.76). Protein content was measured in the five cell lines used (C6, MDA-MB231, A549, MIA PaCa-2, and HepG2) by the SDS-Lowry protein assay. Some of the uncertainties in protein mass per cell are smaller than the symbols. Error bars represent the standard error of the mean. Each protein measurement has <i>n</i> = 3 for biological replicates, <i>n</i> = 3 within each replicate. <b>(C)</b> The ED₅₀ of 1,4-BQ for C6, MB231, A549, MIA PaCa-2, and HepG2 cells (mol cell^-1) is plotted vs. measured protein mass (pg) per cell. The correlation coefficient R² is 0.96. Error bars represent the standard error of the mean. <b>(D)</b> The ED₅₀ of 1,4-benzoquinone is expressed as fmol of 1,4-benzoquinone per pg protein for a cell. Each protein measurement has <i>n</i> = 3 for biological replicates, <i>n</i> = 3 within each replicate. Error bars represent the propagation of error as determined from the standard error of the means for both protein measurements and ED₅₀ of 1,4-BQ. When dose of 1,4-BQ is expressed as fmol pg^-1, there was no statistical difference in the ED₅₀ of 1,4-BQ observed across the different cell lines. ANOVA showed <i>p</i> > 0.05 for all comparisons.</p