Weak cubic CaSiO3 perovskite in the Earth's mantle.

Cubic CaSiO3 perovskite is a major phase in subducted oceanic crust, where it forms at a depth of about 550 kilometres from majoritic garnet1,2,28. However, its rheological properties at temperatures and pressures typical of the lower mantle are poorly known. Here we measured the plastic strength of cubic CaSiO3 perovskite at pressure and temperature conditions typical for a subducting slab up to a depth of about 1,200 kilometres. In contrast to tetragonal CaSiO3, previously investigated at room temperature3,4, we find that cubic CaSiO3 perovskite is a comparably weak phase at the temperatures of the lower mantle. We find that its strength and viscosity are substantially lower than that of bridgmanite and ferropericlase, possibly making cubic CaSiO3 perovskite the weakest lower-mantle phase. Our findings suggest that cubic CaSiO3 perovskite governs the dynamics of subducting slabs. Weak CaSiO3 perovskite further provides a mechanism to separate subducted oceanic crust from the underlying mantle. Depending on the depth of the separation, basaltic crust could accumulate at the boundary between the upper and lower mantle, where cubic CaSiO3 perovskite may contribute to the seismically observed regions of low shear-wave velocities in the uppermost lower mantle5,6, or sink to the core-mantle boundary and explain the seismic anomalies associated with large low-shear-velocity provinces beneath Africa and the Pacific7-9.

Novel experimental setup for megahertz X-ray diffraction in a diamond anvil cell at the High Energy Density (HED) instrument of the European X-ray Free-Electron Laser (EuXFEL).

The high-precision X-ray diffraction setup for work with diamond anvil cells (DACs) in interaction chamber 2 (IC2) of the High Energy Density instrument of the European X-ray Free-Electron Laser is described. This includes beamline optics, sample positioning and detector systems located in the multipurpose vacuum chamber. Concepts for pump-probe X-ray diffraction experiments in the DAC are described and their implementation demonstrated during the First User Community Assisted Commissioning experiment. X-ray heating and diffraction of Bi under pressure, obtained using 20 fs X-ray pulses at 17.8 keV and 2.2 MHz repetition, is illustrated through splitting of diffraction peaks, and interpreted employing finite element modeling of the sample chamber in the DAC.

A resistively-heated dynamic diamond anvil cell (RHdDAC) for fast compression x-ray diffraction experiments at high temperatures.

A resistively-heated dynamic diamond anvil cell (RHdDAC) setup is presented. The setup enables the dynamic compression of samples at high temperatures by employing a piezoelectric actuator for pressure control and internal heaters for high temperature. The RHdDAC facilitates the precise control of compression rates and was tested in compression experiments at temperatures up to 1400 K and pressures of ∼130 GPa. The mechanical stability of metallic glass gaskets composed of a FeSiB alloy was examined under simultaneous high-pressure/high-temperature conditions. High-temperature dynamic compression experiments on H2O ice and (Mg, Fe)O ferropericlase were performed in combination with time-resolved x-ray diffraction measurements to characterize crystal structures and compression behaviors. The employment of high brilliance synchrotron radiation combined with two fast GaAs LAMBDA detectors available at the Extreme Conditions Beamline (P02.2) at PETRA III (DESY) facilitates the collection of data with excellent pressure resolution. The pressure-temperature conditions achievable with the RHdDAC combined with its ability to cover a wide range of compression rates and perform tailored compression paths offers perspectives for a variety of future experiments under extreme conditions.

An improved setup for radial diffraction experiments at high pressures and high temperatures in a resistive graphite-heated diamond anvil cell.

We present an improved setup for the experimental study of deformation of solids at simultaneous high pressures and temperatures by radial x-ray diffraction. This technique employs a graphite resistive heated Mao-Bell type diamond anvil cell for radial x-ray diffraction in combination with a water-cooled vacuum chamber. The new chamber has been developed by the sample environment group at PETRA III and implemented at the Extreme Conditions Beamline P02.2 at PETRA III, DESY (Hamburg, Germany). We discuss applications of the new setup to study deformation of a variety of materials, including ferropericlase, calcium perovskite, bridgmanite, and tantalum carbide, at high-pressure/temperature.

New dynamic diamond anvil cells for tera-pascal per second fast compression x-ray diffraction experiments.

Fast compression experiments performed using dynamic diamond anvil cells (dDACs) employing piezoactuators offer the opportunity to study compression-rate dependent phenomena. In this paper, we describe an experimental setup which allows us to perform time-resolved x-ray diffraction during the fast compression of materials using improved dDACs. The combination of the high flux available using a 25.6 keV x-ray beam focused with a linear array of compound refractive lenses and the two fast GaAs LAMBDA detectors available at the Extreme Conditions Beamline (P02.2) at PETRA III enables the collection of x-ray diffraction patterns at an effective repetition rate of up to 4 kHz. Compression rates of up to 160 TPa/s have been achieved during the compression of gold in a 2.5 ms fast compression using improved dDAC configurations with more powerful piezoactuators. The application of this setup to low-Z compounds at lower compression rates is described, and the high temporal resolution of the setup is demonstrated. The possibility of applying finely tuned pressure profiles opens opportunities for future research, such as using oscillations of the piezoactuator to mimic propagation of seismic waves in the Earth.

Author Correction: Evidence for a Fe3+-rich pyrolitic lower mantle from (Al,Fe)-bearing bridgmanite elasticity data.

In Extended Data Table 1 of this Letter, some of the elastic constants were reported incorrectly. This occurred as a result of an error in the script used to generate the numbers. The values of the elastic constants at room pressure cited in the manuscript on page 544 were derived using the same erroneous script, and the correct values and 1σ-uncertainties in the last given digit are C11 = 461.3(17) GPa instead of 462.7(17) GPa; C22 = 509.7(26) GPa instead of 504.9(26) GPa; C33 = 425.7(5) GPa instead of 426.6(5) GPa; C44 = 188.8(6) GPa instead of 188.4(6) GPa; C55 = 166.5(4) GPa instead of 166.6(4) GPa; C66 = 127.2(17) GPa instead of 129.7(17) GPa; C12 = 141.7(14) GPa instead of 140.2(14) GPa; C13 = 130.0(11) GPa instead of 132.2(11) GPa; and C23 = 161.0(12) GPa instead of 159.3(12) GPa. These errors do not affect any of the conclusions and we apologize for any confusion this may have caused. Extended Data Table 1 and the room-pressure values in the text have been corrected online. The Supplementary Information of this Author Correction contains the original, incorrect Extended Data Table 1, for transparency.

Evidence for a Fe3+-rich pyrolitic lower mantle from (Al,Fe)-bearing bridgmanite elasticity data.

The chemical composition of Earth's lower mantle can be constrained by combining seismological observations with mineral physics elasticity measurements. However, the lack of laboratory data for Earth's most abundant mineral, (Mg,Fe,Al)(Al,Fe,Si)O3 bridgmanite (also known as silicate perovskite), has hampered any conclusive result. Here we report single-crystal elasticity data on (Al,Fe)-bearing bridgmanite (Mg0.9Fe0.1Si0.9Al0.1)O3 measured using high-pressure Brillouin spectroscopy and X-ray diffraction. Our measurements show that the elastic behaviour of (Al,Fe)-bearing bridgmanite is markedly different from the behaviour of the MgSiO3 endmember. We use our data to model seismic wave velocities in the top portion of the lower mantle, assuming a pyrolitic mantle composition and accounting for depth-dependent changes in iron partitioning between bridgmanite and ferropericlase. We find excellent agreement between our mineral physics predictions and the seismic Preliminary Reference Earth Model down to at least 1,200 kilometres depth, indicating chemical homogeneity of the upper and shallow lower mantle. A high Fe3+/Fe2+ ratio of about two in shallow-lower-mantle bridgmanite is required to match seismic data, implying the presence of metallic iron in an isochemical mantle. Our calculated velocities are in increasingly poor agreement with those of the lower mantle at depths greater than 1,200 kilometres, indicating either a change in bridgmanite cation ordering or a decrease in the ferric iron content of the lower mantle.

Comparison of anthracycline-induced death of human leukemia cells: programmed cell death versus necrosis.

We investigated the mode of cell death induced by the anthracyclines, aclarubicin, doxorubicin and daunorubicin in the human leukemia cell lines, HL60 and Jurkat. The cells were incubated with drug concentrations up to 500 nM for periods between 3 and 24 hours, followed by morphological and biochemical analyses. All three substances induced DNA fragmentation, evident as DNA laddering and appearance of cells with hypodiploid DNA content, externalization of phosphatidyl serine, activation of caspases and degradation of the apoptosis-specific endonuclease inhibitor DFF45. However, concentrations and times necessary for these effects to occur were different, aclarubicin being the quickest acting drug with a lag phase of 3 h, followed by daunorubicin with 6 h and doxorubicin with 24 h. More importantly, aclarubicin induced these effects while the cell membrane was intact, whereas doxorubicin and daunorubicin led to immediate loss of membrane integrity. Programmed cell death is characterised by preservation of membrane integrity in order to allow removal of apoptotic bodies, whereas cell rupture is an early event in necrosis. We therefore suggest that, in our experimental settings, doxorubicin- and daunorubicin-induced cell death occurs by necrosis, while aclarubicin induces programmed cell death.

Polyetheretherketone--cytotoxicity and mutagenicity in vitro.

The results of the incubation of polyetheretherketone (PEEK) fibre material with seven different genotype variants of salmonella bacterium showed with and without an external metabolic activation system (S9) with no mutagenic or cytotoxic activity of the test material. In the so-called "plate incorporation test" in which the PEEK raw material is finely cut and applied direct to the agar plate without the addition of solvent there was, as expected, no evidence of cytotoxic or mutagenic effects. In the HPRT test there was a significant increase in the number of mutants per dish, both after addition of N-acetylaminofluorene and N-methyl-N'-nitro-N-nitrosoguanidine (with and without an external metabolic activation system = +S9), but not after treatment of the cells with PEEK-DMSO-eluate. This means that the PEEK material under study did not release any substances that cause V79 cells to mutate. The investigation of the toxic reaction on the material under study revealed that the number of surviving colonies per 10(5) surviving cells lay within the range of or below the solvent control even in the presence of high PEEK concentrations (5.0 microg/ml). Therefore, in summary, the study produced no evidence of cell damage caused by PEEK.

Morphological transformation of C3H/M2 mouse fibroblasts by, and genotoxicity of, extracts of human milk.

Breast cancer may be initiated by environmental/dietary agents and human milk may act as an ex vivo indicator of in vivo exposure of mammary epithelial cells to genotoxins. Extracts of human milk from UK-resident women (n=7) were tested for their abilities to morphologically transform C3H/M2 mouse fibroblasts. Genotoxicities were assessed in the Salmonella typhimurium reverse-mutation assay in the presence of S9 using strains TA1538 and YG1019, and in metabolically-competent human MCL-5 cells with the micronucleus and with the alkaline single cell gel electrophoresis (comet) assays. Two of the seven extracts were inactive in the transformation assay both in the presence or absence of S9, two appeared to be equally transforming either in the presence or absence of S9, and two other extracts induced increased transformation frequencies in the presence of S9. A seventh extract, tested only in the absence of S9, was inactive. Extracts were either active or inactive in at least three of the four tests applied. Four extracts were active or inactive in all four tests. The results suggest that human milk could be used as a resource for investigations of the as-yet-unidentified transforming agents previously detected in mammary lipid.

Cell transformation in vitro by food-derived heterocyclic amines Trp-P-1, Trp-P-2 and N(2)-OH-PhIP.

Heterocyclic aromatic amines (HCA) are formed upon frying of poultry, fish or meat and have been shown to induce tumours in rodent bioassays. We investigated the transforming activity of HCA in an in vitro assay using the M2/C3H mouse fibroblast cell line. An external metabolic activation system (rat liver homogenate) was required in order to observe any HCA-induced cytotoxic effects or cell transforming activity. Trp-P-1 and Trp-P-2 are shown to be among the most potent transforming HCA that have been detected in food. Metabolic activation of HCA has been shown to proceed via N-hydroxylation of the exocyclic amino group. Therefore, we tested 2-hydroxyamino-1-methyl-6-phenylimidazo[4,5-b]pyridine (N(2)-OH-PhIP) the activated metabolite of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine. N(2)-OH-PhIP proved to be one of the most powerful compounds with transforming activity observable at a concentration as low as 30 nM. Since 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is the most abundant HCA formed in fried and grilled food and N-hydroxylation appears to be the predominant pathway of human metabolism, these data support the hypothesis that HCA are involved in the aetiology of human cancer.

Reduction in left ventricular messenger RNA for transforming growth factor beta(1) attenuates left ventricular fibrosis and improves survival without lowering blood pressure in the hypertensive TGR(mRen2)27 Rat.

Angiotensin II recruits transforming growth factor beta(1) (TGFbeta(1)) and is related to left ventricular fibrosis. However, it is unclear whether chronic in vivo reduction in left ventricular TGFbeta(1) expression blunts fibrosis and improves outcome in angiotensin II-dependent hypertension. Four-week-old male hypertensive TGR(mRen2)27 (Ren2) rats received either normal food, low-dose losartan (0.5 mg. kg(-1). d(-1)), or tranilast (a nonspecific TGFbeta inhibitor; 400 mg. kg(-1). d(-1)) (n=10 for each group) for 12 weeks and were compared with Sprague-Dawley control rats. The effect of tranilast on survival was evaluated in 34 additional untreated homozygous Ren2 rats. Tranilast or low-dose losartan did not lower blood pressure. However, the increase in left ventricular weight (Ren2 versus SD 3.1+/-0.16 versus 2.1+/- 0.06 mg/g body wt; P<0.05) was significantly (P<0.05) blunted by both tranilast (2.7+/-0.05) and losartan (2.7+/-0.07). Both drugs prevented the increase in left ventricular TGFbeta(1) mRNA and fibronectin mRNA and blunted the increase in hydroxyproline content and the increase in perivascular fibrosis. The perivascular fibrosis score correlated significantly with the level of expression of TGFbeta(1) (r=0.62; P=0.019). In situ hybridization demonstrated increases in TGFbeta(1) mRNA, predominantly in perivascular and nonmyocyte areas. Both drugs did not prevent the decrease in systolic or diastolic dP/dt, but tranilast significantly improved the survival of untreated Ren2 rats (P=0.029). In conclusion, TGFbeta(1) mRNA expression is increased predominantly in nonmyocyte regions in the hypertrophied left ventricle in this angiotensin II-dependent model of hypertension. This increase is probably due to high angiotensin II levels rather than to hypertension. This is the first study to suggest that chronic inhibition of TGFbeta(1) expression attenuates left ventricular hypertrophy and fibrosis, even without lowering blood pressure.

Cell transformation and genotoxicity induced by bis(2, 3-dichloro-1-propyl) ether.

Bis(dichloropropyl) ether isomers have been identified in a petrochemical plant effluent through a toxicity identification evaluation study in the United States. They have also been observed in the microgram per liter range along one of the largest rivers in Europe, the Elbe River. In the present investigation, the genotoxic and transforming activity of a bis(dichloropropyl) ether isomer, bis(2,3-dichloro-1-propyl) ether, was assayed in vitro. The results demonstrate that bis(2,3-dichloro-1-propyl) ether is a potent mutagen in Salmonella typhimurium strains TA 100, TA 1535, and to a lesser extent in strain TA 98, but only when tested in the presence of a metabolic activation system (S9 mix). We have also investigated the induction of micronuclei by bis(2,3-dichloro-1-propyl) ether in the metabolically competent cell line, MCL-5. A linear, dose-dependent increase in micronuclei was observed following exposure to bis(2,3-dichloro-1-propyl) ether. The DNA strand-breaking capacity of this chemical was assessed in the alkaline single-cell gel electrophoresis ("comet") assay with MCL-5 cells. Bis(2,3-dichloro-1-propyl) ether clearly induced DNA strand breaks in the 4.5-45.5 microg/ml dose range. The ether also induced malignant transformation in C3H/M2 mouse fibroblasts after metabolic activation (S9 mix). Thus, it must be suspected that bis(2, 3-dichloro-1-propyl) ether may possess a carcinogenic potential. Since the compound along with its isomers is present in considerable concentrations in surface water, their elimination is a matter of significant public concern.

Induction of cyclooxygenase expression and enhancement of malignant cell transformation by 2,3,7,8-tetrachlorodibenzo-p-dioxin.

The potential role of arachidonic acid metabolism in the enhancement (promotion) of malignant transformation of C3H/M2 mouse fibroblasts by the tumor promoter 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was investigated using inhibitors of cyclooxygenase and lipoxygenase activities. The promoting effects of TCDD (1.5 pM) and of the reference tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA; 0.4 mM) on carcinogen (N-methyl-N'-nitro-N-nitrosoguanidine or 3-methylcholanthrene)-pre-treated fibroblasts was abolished by cotreatment with indomethacin, hydrocortisone, caffeic acid or nordihydroguaiaretic acid. A differential inhibition was found with N-(2-cyclohexyloxy-4-nitrophenyl)methanesulfonamide, a selective inhibitor of the cyclooxygenase isoenzyme COX-2: the promoting effect of TPA, but not that of TCDD, was abolished. Therefore, the role of the cyclooxygenase isoenzymes COX-1 and COX-2 during chronic exposure to TCDD was studied in more detail. Long-term treatment with TCDD (4-7 weeks) induced the expression of COX-1 and COX-2 mRNA in C3H/M2 fibroblasts (up to 2-fold). The enhanced expression of COX-2 protein in TCDD-treated fibroblasts was confirmed by western blot analysis. Concomitantly, the accumulation of the prostaglandins (PGs) PGE(2) and 6-keto-PGF(1alpha), which were identified as major metabolites of arachidonic acid in C3H/M2 cell cultures, was enhanced ( approximately 2-fold) following long-term treatment with TCDD (0.15 and 1.5 pM). The results suggest that the stimulation of arachidonic acid metabolism caused by a sustained cyclooxygenase induction is a critical event in the promoting action of TCDD in mouse fibroblasts in vitro. However, in contrast to TPA, the TCDD-mediated enhancement of malignant cell transformation may not specifically depend on the induction of COX-2 but, additionally, the induction of COX-1 activity may be necessary.

Heterocyclic aromatic amines induce DNA strand breaks and cell transformation.

Heterocyclic aromatic amines (HAAs), formed during the cooking of foods, are known to induce tumours in rodent bioassays and may thus contribute to human cancer risk. We tested six HAAs in a morphological transformation assay and in three in vitro genotoxicity assays. The morphological transforming abilities of HAAs were tested, in the presence of rat-liver S9, in the C3H/M2 fibroblast cell line. Concentration levels of 50 microM 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (8-MeIQx), 100 microM 2-amino-3,4,8-trimethylimidazo-[4,5-f]quinoxaline (4,8-DiMeIQx), 50 microM 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 100 microM 2-amino-9H-pyrido[2,3-b]indole (AalphaC), 100 microM 2-amino-3-methyl-9H-pyrido[2,3-b]indole (MeAalphaC) and 15 microM 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) induced maximum transformation potencies of 5.5, 6.6, 6.3, 5.2, 7.3 and 9.2 transformed foci per 10(4) surviving cells, respectively. Bacterial mutagenic activity was determined in the presence of rat-liver S9 using the Salmonella typhimurium reverse-mutation assay employing strain YG1019. Mutagenic potencies of 3800 revertants (revs)/ng with 8-MeIQx, 2900 revs/ng with 4,8-DiMeIQx, 3480 revs/ng with IQ, 1.6 revs/ng with AalphaC, 2.9 revs/ng with MeAalphaC and 5 revs/ng with PhIP were observed. Clastogenic activity in vitro was analysed by the micronucleus assay in metabolically competent MCL-5 cells. Dose-dependent induction of micronuclei was observed for all HAAs tested with 1-5.4% of cells containing micronuclei at 10 ng/ml. Micronucleus induction was in the order 4,8-DiMeIQx > 8-MeIQx > IQ > MeAalphaC > PhIP > AalphaC. DNA strand-breaking activity in MCL-5 cells was measured by the alkaline single cell-gel (comet) assay. The lowest effect doses for significant increases (P < or = 0.0007, Mann-Whitney test) in comet tail length (microm) were 45.5 microg/ml (200 microM) for PhIP, 90.9 microg/ml (410-510 microM) for 4,8-DiMeIQx, IQ, MeAalphaC and AalphaC, and 454.5 microg/ml (2130 microM) for 8-MeIQx. It is not yet clear which of these assays most accurately reflects the genotoxic potential to humans of compounds of this class of environmental carcinogens.

Characterization of the heparan sulfate and chondroitin sulfate assembly sites in CD44.

Isoforms of CD44 are differentially modified by the glycosaminoglycans (GAGs) chondroitin sulfate (CS), heparan sulfate (HS), and keratan sulfate. GAG assembly occurs at serines followed by glycines (SG), but not all SG are utilized. Seven SG motifs are distributed in five CD44 exons, and in this paper we identify the HS and CS assembly sites that are utilized in CD44. Not all the CD44 SG sites are modified. The SGSG motif in CD44 exon V3 is the only HS assembly site; this site is also modified with CS. HS and CS attachment at that site was eliminated by mutation of the serines in the V3 motif to alanine (AGAG). Exon E5 is the only other CD44 exon that supports GAG assembly and is modified with CS. Using a number of recombinant CD44 protein fragments we show herein that the eight amino acids located downstream of the SGSG site in V3 are responsible for the specific addition of HS to this site. If the eight amino acids located downstream from the first SG site in CD44 exon E5 are exchanged with those located downstream of the SGSG site in exon V3, the SG site in E5 becomes modified with HS and CS. Likewise if the eight amino acids found downstream from the first SG in E5 are placed downstream from the SGSG in V3, this site is modified with CS but not HS. We also show that these sequences cannot direct the modification of CD44 with HS from a distance. Constructs containing CD44 exon V3 in which the SGSG motif was mutated to AGAG were not modified with HS even though they contained other SG motifs. Thus, a number of sequence and structural requirements that dictate GAG synthesis on CD44 have been identified.