Abnormal methylation of spermatozoa induced by benzo(a)pyrene in rats.

Epigenetic mutations caused by pollutants are possibly linked to many diseases. Benzo(a)pyrene (BaP) is one of the most representative air pollutants and has aroused wide concern because of its strong carcinogenicity. The reproductive toxicity induced by BaP has been identified, but little is known about the characteristics of the methylation changes induced by BaP. In this study, a methylated DNA immunoprecipitation sequencing method was used to detect the methylation of sperm DNA of rats exposed to BaP. Compared with the respective genes in normal rats, there were 3227 hypomethylated genes and 828 hypermethylated genes after BaP exposure. Gene ontology enrichment analysis reported that differentially methylated genes (DMGs) were enriched in the localization, single-multicellular organism process and plasma membrane. Kyoto Encyclopedia of Genes and Genomes pathway analysis showed that the DMGs were significantly enriched in the Ras signalling pathway, Rap1 signalling pathway, pancreatic secretion and neuroactive ligand-receptor interaction. DisGeNET disease spectrum analysis showed that DMGs were associated with infertility and certain genetic diseases. Further research needs to be done to explore whether these abnormal methylation are transgenerational.

[Regulation of cell deformation induced by RhoA/ROCK signaling pathway in osteogenic differentiation of human mesenchymal stem cells].

Objective: To investigate whether the cell deformation induced by RhoA/ROCK signaling pathway plays a regulatory role in the osteogenic differentiation in human mesenchymal stem cells (hMSCs). Methods: The primary hMSCs were cultured until the P3 generation was added to the osteogenic induction solution for 14 days, and the expression levels of RhoA and ROCK-1 proteins were detected by immunofluorescence. Another P3 generation hMSCs cells were divided into induction group, blank plus drug group and medicated group, and the induction group was induced by simple osteogenic induction; the blank drug-added group was added to the osteogenic induction solution and the solvent dimethyl sulfoxide (DMSO) for induction culture; the medicinal group was added with osteogenic induction solution and Y-27632 (RhoA/ROCK signaling pathway inhibitor) dissolved in DMSO for induction culture. The proliferation of the cells was detected by CCK-8 methods. The changes of cytoskeleton in each group were observed by fluorescence microscope. The expression changes of osteogenic genes alkaline phosphatase (ALP), osteocalcin (OCN) and runt-relatedtranscriptionfactor-2 (RUNX-2) in each group were detected by real time polymerase chain reaction (RT-PCR) and ALP staining. The t test was used for data comparison between the two groups. Results: There were significant differences in the expression of RhoA and ROCK-1 protein before and after osteogenic induction of hMSCs (22.7±2.1 vs 14.7±0.6 and 24.3±1.5 vs 20.3±0.6, t=-6.414, -4.243, both P<0.05). Mesenchymal stem cell proliferation on day 1, 5, 9 and day 14 in the medicated group were comparable with those in the induction group (F=0.427, 1.000, 0.298, 1.314, all P>0.05). The cytoskeleton of the medicated group showed obvious spindle-shaped changes, and the cell spreading area became smaller. From the three groups of ALP staining on the 14th day, it can be seen that the color of the medicated group was significantly lighter than that of the induction group. The results of RT-PCR showed that the expression of osteogenic phenotypic genes increased with the induction time in the induction group and the blank drug-treated group, the expression levels of osteogenic phenotype genes ALP, OCN and RUNX-2 in the drug-treated group were gradually decreased with the induction time. The expression of ALP in the drug-treated group was significantly lower than those in the other two groups at 14th day (F=25.891, P=0.001); the expression of OCN in the drug-treated group was significantly lower than those in the other two groups at 11th and 14th days (F=5.773, 25.382, both P<0.05); the expression of RUNX-2 in the drug group was significantly lower than those in the other two groups at 11th and 14th days (F=34.972,10.808, both P<0.05). Conclusion: The RhoA/ROCK signaling pathway may play a role in promoting osteogenic differentiation of hMSCs through mediating cytoskeletal deformation.

Peroxisome proliferator-activated receptor delta regulates lipid droplet formation and transport in goat mammary epithelial cells.

Even though recent evidence in goat mammary epithelial cells (GMEC) suggest a role of peroxisome proliferator-activated receptor delta (PPARD) in regulating lipid homeostasis, its role is not fully understood. Our hypothesis was that PPARD regulates lipid transport processes in GMEC and, thus, plays a crucial role in regulating fat formation. The PPARD was overexpressed using an adenovirus system (Ad-PPARD) with recombinant green fluorescent protein (Ad-GFP) as the control. Results revealed that overexpression of PPARD markedly upregulated the mRNA abundance of PPARD. Compared with the control (Ad-GFP+dimethyl sulfoxide), overexpression of PPARD alone had no effect on mRNA expression of CD36, SCD1, FABP4, ACSL1, and ADRP. The cultures overexpressing PPARD with the PPARD ligand GW0742 (GW) upregulated the expression of CD36, FABP3, FABP4, ACSL1, and ADRP. Overexpression of PPARD in GMEC plus GW increased the concentration of 16:1 and 18:1-trans and was associated with upregulation of SCD1. Compared with the control (Ad-GFP+dimethyl sulfoxide), the decrease of triacylglycerol concentration coupled with upregulation of genes related to lipid droplet secretion (e.g., ADRP and ACSL1) induced by PPARD overexpression suggests a role in lipid droplet (LD) secretion. Luciferase assay revealed that GW increased the ADRP promoter activity in a dose-dependent manner. Knockdown of PPARD impaired the increase of ADRP promoter activity induced by GW, whereas GW enhanced the activity of ADRP promoter in GMEC overexpressing PPARD. Data with the ADRP 5'-flanking truncated luciferase reporter suggest a core region (-1,444 to -990 bp) response element for the induction of GW. This core region contains a known PPARG response element (PPRE) at -1,003 to -990 bp. When the PPRE was mutated, the overexpression of PPARD had no effect on ADRP promoter activity. Collectively, these results reveal a novel role for PPARD in lipid homeostasis via promoting fatty acid transport and LD formation through a mechanism of direct binding to the promoter of key genes. Hence, PPARD activity may contribute to fatty acid transport and LD formation during lactation.

Nuclear receptor subfamily 1 group H member 2 (LXRB) is the predominant liver X receptor subtype regulating transcription of 2 major lipogenic genes in goat primary mammary epithelial cells.

In ruminants, recent research has identified a crucial role for liver X receptors (LXR) in regulating lipid metabolism in mammary cells. However, the differences between LXR subtypes in regulating ruminant lipid metabolism are unknown. We used overexpression and knockdown of LXRA and LXRB in goat primary mammary epithelial cells to distinguish subtype-specific regulation of sterol regulatory element binding protein 1c (SREBP1c) and fatty acid synthase (FASN) mRNA expression and their promoter activity. Incubation with siRNA targeting LXR decreased expression of LXRA and LXRB. Knockdown of LXRA and LXRB in cells incubated with dimethyl sulfoxide (DMSO, control) had no effect on the expression of SREBP1c or FASN. Knockdown of LXRB in cells incubated with LXR ligand T0901317 (T09) led to decreased expression of FASN, but not SREBP1c. Overexpression of LXRB plus T09 dramatically upregulated SREBP1c and FASN to levels higher than overexpression of LXRA with T09. Luciferase reporter assays in cells with site-directed mutagenesis of LXR response elements (LXRE; LXRE1 from -286 to -251 bp or LXRE2 from -235 to -219 bp) revealed that the SREBP1c promoter with the wild type or either LXRE mutation in cells supplemented with T09 decreased markedly only when LXRB was knocked down. Knockdown of LXRA and LXRB had no effect on the SREBP1c promoter when cells had a double LXRE mutation. Overexpression of LXRA only in cells incubated with T09 increased the activity of the SREBP1c promoter with the wild type and the LXRE2 mutation. In contrast, compared with each control group, overexpression of LXRB dramatically increased SREBP1c promoter activity, regardless of LXRE mutation. Furthermore, in cells stimulated with T09, knockdown of either LXRA or LXRB did not alter wild-type FASN promoter activity. Knockdown of LXRA increased wild-type and LXRE-site-mutated (LXRE from -677 to -662 bp) FASN promoter activity. Overexpression of LXRB increased wild-type and LXRE-site-mutated FASN promoter activity regardless of treatment with DMSO or T09, but overexpression of LXRA altered LXRE-site-mutated FASN promoter activity only in cells treated with DMSO. Increased activation of SREBP1c or FASN promoters containing LXRE mutations after overexpression of LXRB suggested that LXRB activates endogenous SREBP1c, which can then bind to the promoter of SREBP1c via an auto-loop circuit regulatory mechanism. Collectively, these results highlight an important role for LXRB in the transcriptional regulation of SREBP1c and FASN in goat mammary epithelial cells. Activation of this nuclear receptor controls lipogenesis via different mechanisms.

Pressure-tuned quantum criticality in the antiferromagnetic Kondo semimetal CeNi2-δAs2.

The easily tuned balance among competing interactions in Kondo-lattice metals allows access to a zero-temperature, continuous transition between magnetically ordered and disordered phases, a quantum-critical point (QCP). Indeed, these highly correlated electron materials are prototypes for discovering and exploring quantum-critical states. Theoretical models proposed to account for the strange thermodynamic and electrical transport properties that emerge around the QCP of a Kondo lattice assume the presence of an indefinitely large number of itinerant charge carriers. Here, we report a systematic transport and thermodynamic investigation of the Kondo-lattice system CeNi2-δAs2 (δ ≈ 0.28) as its antiferromagnetic order is tuned by pressure and magnetic field to zero-temperature boundaries. These experiments show that the very small but finite carrier density of ~0.032 E-/formular unit in CeNi2-δAs2 leads to unexpected transport signatures of quantum criticality and the delayed development of a fully coherent Kondo-lattice state with decreasing temperature. The small carrier density and associated semimetallicity of this Kondo-lattice material favor an unconventional, local-moment type of quantum criticality and raises the specter of the Nozières exhaustion idea that an insufficient number of conduction-electron spins to separately screen local moments requires collective Kondo screening.

Coexistence of ferromagnetism and superconductivity in iron based pnictides: a time resolved magnetooptical study.

Ferromagnetism and superconductivity are antagonistic phenomena. Their coexistence implies either a modulated ferromagnetic order parameter on a lengthscale shorter than the superconducting coherence length or a weak exchange coupling between the itinerant superconducting electrons and the localized ordered spins. In some iron based pnictide superconductors the coexistence of ferromagnetism and superconductivity has been clearly demonstrated. The nature of the coexistence, however, remains elusive since no clear understanding of the spin structure in the superconducting state has been reached and the reports on the coupling strength are controversial. We show, by a direct optical pump-probe experiment, that the coupling is weak, since the transfer of the excess energy from the itinerant electrons to ordered localized spins is much slower than the electron-phonon relaxation, implying the coexistence without the short-lengthscale ferromagnetic order parameter modulation. Remarkably, the polarization analysis of the coherently excited spin wave response points towards a simple ferromagnetic ordering of spins with two distinct types of ferromagnetic domains.

Effect of Zn impurity in K0.8Fe(2-δ-x)Zn(x)Se2.

A series of K(0.8)Fe(2-δ-x)Zn(x)Se(2) single-crystal samples with nominal compositions 0 ≤ x ≤ 0.05 were grown and their physical properties were measured in order to study the effect of Zn impurity. It is found that the Zn impurity (x ≤ 0.02) does not affect the superconducting transition temperature T(c) significantly. Meanwhile the hump in resistivity which corresponds to the transition from the insulating to metallic phase quickly shifts towards low temperatures. The results imply that there should be a phase separation in this system and Zn impurity causes the enhancement of the insulating phase. The negligible effect of Zn impurity on T(c) suggests an s-wave pairing in the superconducting phase. Meanwhile there is a possibility that the Zn impurity may selectively enter into the insulting phase.

Order parameter fluctuations at a buried quantum critical point.

Quantum criticality is a central concept in condensed matter physics, but the direct observation of quantum critical fluctuations has remained elusive. Here we present an X-ray diffraction study of the charge density wave (CDW) in 2H-NbSe(2) at high pressure and low temperature, where we observe a broad regime of order parameter fluctuations that are controlled by proximity to a quantum critical point. X-rays can track the CDW despite the fact that the quantum critical regime is shrouded inside a superconducting phase; and in contrast to transport probes, allow direct measurement of the critical fluctuations of the charge order. Concurrent measurements of the crystal lattice point to a critical transition that is continuous in nature. Our results confirm the long-standing expectations of enhanced quantum fluctuations in low-dimensional systems, and may help to constrain theories of the quantum critical Fermi surface.

Coexistence of ferromagnetism and superconductivity: magnetization and Mössbauer studies of EuFe2(As1 - xPx)2.

Magnetization and (57)Fe and (151)Eu Mössbauer studies of EuFe(2)(As(1 - x)P(x))(2) (x = 0-1.0) at temperatures (5-300 K) have been performed. The magnetization studies show a decrease of the divalent Eu sublattice antiferromagnetic transition temperature from T(AFM) = 20 K for x = 0 to 16 K at x≈0.2. For x > 0.2, the Eu sublattice is ferromagnetically ordered at T(FM), which increases up to 27 K for x = 1.0. For 0.2 < x < 0.5, the system becomes superconducting. (151)Eu Mössbauer studies in the antiferromagnetic range show a constant saturation hyperfine field of 26.2 T and that the magnetization is almost perpendicular to the c-axis. On the other hand, in the ferromagnetic range, the hyperfine field increases up to 30.8 T (for x = 1) and the easy axis is almost parallel to the c-axis. In both regions the magnetic axis seems to be tilted from the basal plane or the c-axis by ∼ 20°. The (57)Fe Mössbauer studies show no magnetism in the iron site for x > 0.2, yet at 5 K exhibit transferred magnetic hyperfine fields (∼1 T) from the ferromagnetically ordered Eu sublattice, even in the superconducting region. Superconductivity in the presence of ferromagnetism is generally not observable. However, transferred magnetic hyperfine fields in the superconducting state are observed here for the first time.

Fermi surface nesting induced strong pairing in iron-based superconductors.

The discovery of high-temperature superconductivity in iron pnictides raised the possibility of an unconventional superconducting mechanism in multiband materials. The observation of Fermi-surface (FS)-dependent nodeless superconducting gaps suggested that inter-FS interactions may play a crucial role in superconducting pairing. In the optimally hole-doped Ba(0.6)K(0.4)Fe(2)As(2), the pairing strength is enhanced simultaneously (2Delta/T(c) approximately 7) on the nearly nested FS pockets, i.e., the inner hole-like (alpha) FS and the 2 hybridized electron-like FSs, whereas the pairing remains weak (2Delta/T(c) approximately 3.6) in the poorly nested outer hole-like (beta) FS. Here, we report that in the electron-doped BaFe(1.85)Co(0.15)As(2), the FS nesting condition switches from the alpha to the beta FS due to the opposite size changes for hole- and electron-like FSs upon electron doping. The strong pairing strength (2Delta/T(c) approximately 6) is also found to switch to the nested beta FS, indicating an intimate connection between FS nesting and superconducting pairing, and strongly supporting the inter-FS pairing mechanism in the iron-based superconductors.

Superconductivity induced by Ni doping in SmFe(1-x)Ni(x)AsO.

Superconductivity with a T(c) of about 10 K is observed in the Ni-doped SmFe(1-x)Ni(x)AsO system. The measurements of resistivity and magnetic susceptibility show that the spin-density wave (SDW) order is quickly suppressed with increasing Ni content, and superconductivity emerges as x≥0.04. T(c)(mid) shows a maximum of 10.8 K at x = 0.06, and it drops to lower than 2 K as x>0.12. Meanwhile, the upper critical field (H(c2)(0)) is estimated to be about 40 T for the optimally-doped sample (x = 0.06). The normal state thermopower is negative for all the Ni-doped samples, indicating that an electron-type charge carrier dominates in the transport properties. Moreover, the magnitude of the room-temperature thermopower increases with increasing Ni content, and then shows a broad peak around x = 0.06. We found that there is an obvious correlation between the anomalously enhanced thermopower and superconductivity. A phase diagram is derived based on the transport measurements and a dome-like T(c)(x) curve is established.

Band-dependent normal-state coherence in Sr2RuO4: evidence from Nernst effect and thermopower measurements.

We present the first measurement on the Nernst effect in the normal state of the odd-parity, spin-triplet superconductor Sr2RuO4. Below 100 K, the Nernst signal was found to be negative, large, and, as a function of magnetic field, nonlinear. Its magnitude increases with the decreasing temperature until reaching a maximum around T* approximately equal to 20-25 K, below which it starts to decrease linearly as a function of temperature. The large value of the Nernst signal appears to be related to the multiband nature of the normal state and the nonlinearity to band-dependent magnetic fluctuation in Sr2RuO4. We argue that the sharp decrease in the Nernst signal below T* is due to the suppression of quasiparticle scattering and the emergence of band-dependent coherence in the normal state.

Tissue and species distribution of the glutathione pathway transcriptome.

The goal of this study was to compare and contrast the basal gene expression levels of the various enzymes involved in glutathione metabolism among tissues and genders of the rat, mouse and canine. The approach taken was to use Affymetrix GeneChip microarray data for rat, mouse and canine tissues, comparing intensity levels for individual probes between tissues and genders. As was hypothesized, the relative expression in liver, lung, heart, kidney and testis varied from gene to gene, with differences of expression between tissues sometimes greater than a 1000-fold. The pattern of differential expression was usually similar between male and female animals, but varied greatly between the three species. Gstp1 appears to be expressed at high levels in male mouse liver, reasonable levels in canine liver, but very low levels in male rat liver. In all species examined, Gstp1 expression was below detectable levels in testis. Gsta3/Yc2 expression appeared high in rodent liver and female canine liver, but not male canine liver. Finally, Mgst1 and Gpx3 expression appeared to be lower in canine heart and testis than seen in rodents. Given the critical role of the glutathione pathway in the detoxification of many drugs and xenobiotics, the observed differences in basal tissue distribution among mouse, rat and canine has far-reaching implications in comparing responses of these species in safety testing.

Reentrant behaviour in Y-doped Ho(0.75)Y(0.25)Ni(2)B(2)C single crystal.

The transport and superconducting properties of Ho(0.75)Y(0.25)Ni(2)B(2)C single crystals were investigated to study the competing effects between superconductivity and magnetism. The superconducting transition temperature T(c) is 7.6 K, determined from the resistivity transition; meanwhile, the commensurate antiferromagnetic (AFM) transition occurs at T(N) of 3.9 K, which is lower than that of pure HoNi(2)B(2)C (T(N)≈5 K). Ho(0.75)Y(0.25)Ni(2)B(2)C reentered into the normal state at T(m) (T(N)

High field phase diagram of cuprates derived from the Nernst effect.

Measurements of the Nernst signal in the vortex-liquid state of the cuprates to high fields (33 T) reveal that vorticity extends to very high fields even close to the zero-field critical temperature T(c0). In overdoped La2-xSrxCuO4, we show that the upper critical field H(c2)(T) curve does not end at T(c0), but at a much higher temperature. These results imply that T(c0) corresponds to a loss in phase rigidity rather than a vanishing of the pairing amplitude. An intermediate field H*(T)<

Determining the Wiedemann-Franz ratio from the thermal hall conductivity: application to Cu and YBa2Cu3O6.95.

The Wiedemann-Franz (WF) ratio compares the thermal and electrical conductivities in a metal. We describe a new way to determine its value, based on the thermal Hall conductivity. The technique is applied to copper and to untwinned YBaCuO. In the latter, we uncover a T-linear dependence and suppression of the Hall-channel WF ratio. We discuss the implications of this suppression. The general suppression of the WF ratio in systems with predominant electron-electron scattering is discussed.

M-wave of the toad electroretinogram.

1. In the retina, two distinct, light-evoked releases of K+ have been described. One takes place in the outer plexiform layer (OPL) and is termed the "distal K+ increase." The other takes place in the inner plexiform layer (IPL) and is termed the "proximal K+ increase." Although the distal K+ increase generates the electroretinogram (ERG) b-wave, the contribution of the much larger proximal K+ increase to the ERG is less well understood. In this paper we detail our investigation of the proximal K+ increase and its contribution to the ERG. We describe an ERG component, the M-wave, which had not heretofore been observed in the diffuse-flash, vitreal ERG. 2. We studied the proximal K+ increase and the ERG M-wave in the isolated retina preparation of the toad, Bufo marinus. We used K(+)-sensitive microelectrodes, as well as conventional intra- and extracellular microelectrodes, to record K+ changes, the local (or intraretinal) ERG, the vitreal ERG, and Müller cell responses. 3. As in earlier studies of the amphibian and cat M-wave, we readily observed an M-wave in the intraretinal, or local, ERG (LERG). The M-wave we studied had characteristics similar to those of M-waves that were previously described. Specifically, we found that the M-wave was generated by a Müller cell response to the proximal K+ increase and that both the proximal K+ increase and the LERG M-wave were spatially tuned. 4. We used the aspartate receptor agonist, N-methyl-DL-aspartate (NMA), to reveal that an M-wave is present in the vitreal ERG. Researchers who previously investigated the M-wave were unable to identify an M-wave in the vitreal ERG. We found that the toad ERG M-wave was a small, positive potential that was partially obscured by the much larger b-wave and slow PIII components. 5. We observed that picrotoxin (PTX) had an excitatory effect on inner retina, as evidenced by an enhanced proximal K+ increase and an enhanced M-wave. This result indicates that it is likely that GABAergic inhibition in inner retina plays an important role in retinal processing in the toad. 6. At threshold, we found that the ERG consisted mainly of an M-wave, indicating that the amphibian threshold ERG is driven by proximal retina. This result is analogous to previous observations of the threshold ERG in cat. However, in cat, the M-wave and threshold response have been described as distinct ERG components.(ABSTRACT TRUNCATED AT 400 WORDS)