Quantum-spin-liquid states in the two-dimensional kagome antiferromagnets ZnxCu4-x(OD)6Cl2

A three-dimensional system of interacting spins typically develops static long-range order when it is cooled. If the spins are quantum (S=1/2), however, novel quantum paramagnetic states may appear. The most highly sought state among them is the resonating-valence-bond state, in which every pair of neighbouring quantum spins forms an entangled spin singlet (valence bonds) and these singlets are quantum mechanically resonating among themselves. Here we provide an experimental indication for such quantum paramagnetic states existing in frustrated antiferromagnets, Zn(x)Cu(4-x)(OD)(6)Cl(2), where the S=1/2 magnetic Cu2+ moments form layers of a two-dimensional kagome lattice. We find that in Cu(4)(OD)(6)Cl(2), where distorted kagome planes are weakly coupled, a dispersionless excitation mode appears in the magnetic excitation spectrum below approximately 20 K, whose characteristics resemble those of quantum spin singlets in a solid state, known as a valence-bond solid, that breaks translational symmetry. Doping with non-magnetic Zn2+ ions reduces the distortion of the kagome lattice, and weakens the interplane coupling but also dilutes the magnetic occupancy of the kagome lattice. The valence-bond-solid state is suppressed, and for ZnCu(3)(OD)(6)Cl(2), where the kagome planes are undistorted and 90% occupied by the Cu2+ ions, the low-energy spin fluctuations become featureless.

Ultrahigh resolution optical coherence tomography of Barrett's esophagus: preliminary descriptive clinical study correlating images with histology

BACKGROUND AND STUDY AIMS

Endoscopic ultrahigh resolution optical coherence tomography (UHR OCT) achieves an axial image resolution of approximately 5 microm, which is 2 - 3 times finer than standard endoscopic OCT imaging. This study investigated the capability of endoscopic UHR OCT for imaging patients with Barrett's esophagus.

PATIENTS AND METHODS

Fivty volunteers previously diagnosed with Barrett's esophagus underwent UHR OCT. Imaging was performed at 1.3 microm wavelengths with approximately 5 microm axial and approximately 15 microm transverse resolutions using a 1.8 mm/diameter linear-scanning catheter introduced through the accessory channel of a standard endoscope. OCT images were compared with endoscopic diagnosis and pinch biopsy histological appearances.

RESULTS

UHR OCT images of normal esophagus, Barrett's esophagus, high grade dysplasia and esophageal adenocarcinoma were evaluated. UHR OCT images of the normal esophagus exhibited characteristic layered architecture with uniform epithelium, while images of Barrett's esophagus corresponded to crypt-like glandular structures. High grade dysplasia and esophageal adenocarcinoma images exhibited more heterogeneous structures corresponding to irregular, heterogeneous tissue morphology from distorted and cribriform or villiform glandular architecture. Fine features can be discerned more clearly with endoscopic UHR OCT.

CONCLUSIONS

This study evaluated new endoscopic OCT technology and demonstrated the feasibility of carrying out UHR OCT imaging in conjunction with standard endoscopy for in vivo real-time imaging of Barrett's esophagus, dysplasia, and esophageal adenocarcinoma. A survey of normal and abnormal upper gastrointestinal tissues was performed using a research prototype OCT system with the highest axial resolution to date, and can serve as a baseline for future investigation.

Direct transition from a disordered to a multiferroic phase on a triangular lattice

We report the first direct transition from a paramagnetic and paraelectric phase to an incommensurate multiferroic in the triangular lattice antiferromagnet RbFe(MoO4)(2). Ferroelectricity is observed only when the magnetic structure has chirality and breaks inversion symmetry. A Landau expansion of symmetry-allowed terms in the free energy demonstrates that chiral magnetic order can give rise to a pseudoelectric field, whose temperature dependence agrees with experiment.

Effect of antiferromagnetic spin correlations on lattice distortion and charge ordering in Pr0.5Ca1.5MnO4

We use neutron scattering to study the lattice and magnetic structure of the layered half-doped manganite Pr(0.5)Ca(1.5)MnO(4). On cooling from high temperature, the system first becomes charge-and orbital-ordered (CO/OO) near T(CO) = 300 K and then develops checkerboard-like antiferromagnetic (AF) order below T(N) = 130 K. At temperatures above T(N) but below T(CO) (T(N) Collapse

Key Words

• ce-type af order

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MESH Headings Collapse

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Hypericin photoactivation triggers down-regulation of matrix metalloproteinase-9 expression in well-differentiated human nasopharyngeal cancer cells

Recently, we have shown that hypericin-mediated photodynamic therapy (PDT) is a promising modality for the treatment of nasopharyngeal cancer (NPC). The present study evaluated the expression of matrix metalloproteinase-9 (MMP-9) following hypericin-PDT in well-differentiated HK1 NPC cells. Down-regulation of MMP-9 by hypericin-PDT was observed at the mRNA level in HK1 cells in vitro and in vivo and at the protein level in vitro. Transcriptional activities of the activator protein-1 (AP-1) and nuclear factor (NF)-kappaB regulatory elements were inhibited by PDT. We also found that PDT reduced secreted granulocyte-macrophage colony stimulating factor (GM-CSF), which is known to activate transcription of NK-kappaB and AP-1. However, incubation of untreated HK1 cells with exogenous GM-CSF abrogated the reduction of MMP-9 production in hypericin-PDT-treated cells. It would appear that PDT downregulates MMP-9 expression via inhibition of GM-CSF production, which in turn modulates AP1/NF-kappaB transcriptional activities. Suppression of MMP-9 by hypericin-PDT may have therapeutic implications.

Screening and mutagenesis of a novel Bacillus pumilus strain producing alkaline protease for dehairing

AIMS

To characterize and optimize a novel Bacillus pumilus strain isolated from biological waste which produces protease with excellent dehairing effect. This newly isolated strain could be utilized in the industrial leather dehairing process.

METHODS AND RESULTS

Bacterial strains secreting proteases were screened from biological wastes. Positive clones were further characterized by analysing their efficacy in dehairing and effects on collagen integrity. Among 171 colonies tested, a strain BA06, identified as B. pumilus, was picked owing to its efficient dehairing capabilities with minimal impact on collagen. By combined mutagenesis using UV, N-methyl-N'-nitro-N-nitrosdguanidine and Co(60)-gamma-rays, this strain was further improved with regard to its alkaline protease production. The alkaline protease activity of the mutant strain SCU11was greatly improved up to 6000 U ml(-1), in comparison with its parent strain BA06 of 1200 U ml(-1).

CONCLUSIONS

By using screening and mutagenesis methods, we have successfully created a B. pumilus strain that can produce high levels of alkaline proteases that are able to efficiently remove hair from skin with minimal damage on the collagen.

SIGNIFICANCE AND IMPACT OF THE STUDY

This strain could be used in commercial alkaline protease production for leather dehairing.

L-malate reverses oxidative stress and antioxidative defenses in liver and heart of aged rats

The intracellular levels of antioxidant and free radical scavenging enzymes are gradually altered during the aging process. An age-dependent increase of oxidative stress occurring throughout the lifetime is hypothesized to be the major cause of aging. The current study examined the effects of L-malate on oxidative stress and antioxidative defenses in the liver and heart of aged rats. Sprague-Dawley male rats were randomly divided into four groups, each group consisting of 6 animals. Group Ia and Group IIa were young and aged control rats. Group Ib and Group IIb were young and aged rats treated with L-malate (210 mg/kg body weight per day). L-malate was orally administrated via intragastric canula for 30 days, then the rats were sacrificed and the liver and heart were removed to determine the oxidant production, lipid peroxidation and antioxidative defenses of young and aged rats. Dietary L-malate reduced the accumulation of reactive oxygen species (ROS) and significantly decreased the level of lipid peroxidation in the liver and heart of the aged rats. Accordingly, L-malate was found to enhance the antioxidative defense system with an increased activity of antioxidant enzymes, such as superoxide dismutase (SOD) and glutathione peroxidase (GPx) and increased glutathione (GSH) levels in the liver of aged rats, a phenomenon not observed in the heart of aged rats. Our data indicate that oxidative stress was reversed and the antioxidative defense system was strengthened by dietary supplementation with L-malate.

Adsorption of Pseudomonas putida on clay minerals and iron oxide

Adsorption of Pseudomonas putida on minerals including montmorillonite, kaolinite and goethite was studied. The adsorption isotherms of P. putida on the examined minerals conformed to the Langmuir equation. The amount of P. putida adsorbed followed the order: goethite > kaolinite > montmorillonite. A greater extent of P. putida adsorption on minerals was observed in the range of temperature from 15 to 35 degrees C. The adsorption of P. putida on minerals decreased with the increase of pH from 3.0 to 10.0. Magnesium ion was more efficient than sodium ion in promoting P. putida adsorption on minerals. The results suggest that electrostatic interactions play a vital role in P. putida adsorption by soil colloidal factions. The information obtained in this study is of fundamental significance for the understanding of the survival and transport of bacteria in soil systems.

Incipient orbital order in half-metallic Ba2FeReO6

Largely unquenched Re 5d orbital magnetic moments in half-metallic Ba2FeReO6 drive a symmetry lowering transition from a cubic paramagnet to a compressed tetragonal (c/a < 1) ferrimagnet below Tc ~ 305 K, with a giant linear magnetoelastic constant and the spins lying spontaneously along the unique tetragonal axis. The large orbital magnetization and degree of structural deformation indicate proximity to a metal-insulator transition. These results point to an incipient orbitally ordered state in the metallic ferrimagnetic phase.

Methylation patterns ofIGFBP7 in colon cancer cell lines are associated with levels of gene expression

Altered expression of insulin-like growth factor binding protein 7 (IGFBP7) has been found in colon cancer, but the exact regulatory mechanism has not been fully investigated. In order to elucidate the mechanisms underlying aberrant IGFBP7 expression in colon cancer, we used bisulphite sequencing PCR (BSP) to detect the detailed methylation profiles of the IGFBP7 5' CpG island. Exon 1 of the IGFBP7 gene was highly methylated in IGFBP7-negative cell lines but unmethylated in IGFBP7-positive lines. The methylation status of the promoter region and the intron 1 region was not so discriminating in IGFBP7-positive and -negative cell lines. Methylation-specific PCR (MSP) confirmed the hypermethylation of IGFBP7 exon 1 in IGFBP7-negative cell lines. Treatment with 5-aza-2'-deoxycytidine (5-aza-dC) induced demethylation of the CpG island in exon 1 of IGFBP7, as examined by both MSP and bisulphate genomic sequencing. Furthermore, the expression of IGFBP7 was restored, as detected by both RT-PCR and immunocytochemistry. Our study is the first to provide detailed methylation profiles of the IGFBP7 5' CpG island and shows that hypermethylation of the CpG island in exon 1 of IGFBP7 is closely related to the absence of its expression in colon cancer cells.

p38 Mitogen-activated protein kinases is required for counteraction of 2-methoxyestradiol to estradiol-stimulated cell proliferation and induction of apoptosis in ovarian carcinoma cells via phosphorylation Bcl-2

INTRODUCTION

2-Methoxyestradiol (2ME2), a natural endogenous product of estradiol (E2) metabolism, has been shown to be a selective apoptotic agent for cancer cells but not for normal cells. In this study, we determined that 2ME2 counteracts E2-stimulated cell growth and induces apoptosis in ovarian carcinoma cells. In addition, we demonstrate that 2ME2 induces apoptosis via p38 and phospho-Bcl2 pathway.

METHODS

2ME2 and/or E2 were administered to the OVCAR-3 (human ovarian cancer) cell line. Cell growth inhibition was analyzed by [3H] Thymidine incorporation assay and DNA fluorometric assay. Cell apoptosis was tested by DNA fragmentation analysis and FACS. The signaling pathway was determined by a series of biochemical assays.

RESULTS

2ME2 inhibited estradiol-stimulated cell growth and induced apoptosis in an ovarian carcinoma cell line. MAPK and p38, but not JNK, were found to be critical mediators in this process. Expression of a dominant negative mutant of p38 kinase or p38 specific inhibitor, SB 203580, almost completely blocked the process. Furthermore, Bcl-2 phosphorylation was required for 2ME2-induced effects.

CONCLUSION

Our data suggest that 2ME2 inhibits E2-stimulated proliferation and induces apoptosis in ovarian carcinoma cells. Furthermore, activation of p38 and phosphorylation of Bcl-2 plays a critical role in the mechanism. 2ME2 therefore, may have a clinical application for the treatment of ovarian cancer.

Selective depletion of activated T cells by recombinant immunotoxin containing anti-CTLA-4 single-chain fragment of variable antibody and N-terminal fragment of perforin

We constructed a novel immunotoxin, hS83P34, by fusing the fragment containing the N-terminal 34 amino acids of human perforin to the C-terminal of humanized anti-CTLA-4 single chain fragment of variable antibody. In vitro cytotoxicity assays demonstrated that CTLA-4-positive activated human T cells and 6T-CEM were sensitive to hS83P34, while CTLA-4-negative resting T cells and endothelial cell ECV-304 were resistant to hS83P34. The IC50s of hS83P34 for activated T cells and 6T-CEM were about 0.2 micromol/L and 1.0 micromol/L, there was no obvious cytotoxicity of ECV-304 as detected at 8 micromol/L of hS83P34. In tumor graft rejection models, after treatment with 1.2 mg/kg immunotoxin every day for 12 days, the transplanted tumor cells were rescued by immunotoxin. The tumor weights of grafts of the rejection control group, nonrejection control group, and test group were 0.006 +/- 0.014 g, 0.261 +/- 0.048 g, and 0.135 +/- 0.056 g, respectively. In the early 3 days posttransplantation, there were a lot of CD4- and CD8-positive T cells infiltrating into the tumor grafts of the rejection control group, while only a few T cells were detected in the tumor grafts of the test group. According to these results, we concluded that immunotoxin hS83P34 selectively depleted activated T cells in vitro as well as in vivo in an acute rejection model.

Anisotropy and Corotation of Galactic Cosmic Rays

The intensity of Galactic cosmic rays is nearly isotropic because of the influence of magnetic fields in the Milky Way. Here, we present two-dimensional high-precision anisotropy measurement for energies from a few to several hundred teraelectronvolts (TeV), using the large data sample of the Tibet Air Shower Arrays. Besides revealing finer details of the known anisotropies, a new component of Galactic cosmic ray anisotropy in sidereal time is uncovered around the Cygnus region direction. For cosmic-ray energies up to a few hundred TeV, all components of anisotropies fade away, showing a corotation of Galactic cosmic rays with the local Galactic magnetic environment. These results have broad implications for a comprehensive understanding of cosmic rays, supernovae, magnetic fields, and heliospheric and Galactic dynamic environments.

Sulfuryl fluoride as a quarantine treatment for Anoplophora glabripennis (Coleoptera: Cerambycidae) in regulated wood packing material

The Asian longhorned beetle, Anoplophora glabripennis (Motschulsky) (Coleoptera: Cerambycidae), was probably introduced into the United States from China with solid wood packing and dunnage during the 1980s, and it has recently become established in limited infestations near several major cities in the United States. Regulated wood packing material (RWPM) arriving in the United States from China is required to undergo fumigation with methyl bromide (MeBr), to be heat treated, or kiln dried. Sulfuryl fluoride (SF) is a candidate fumigant to replace MeBr under certain conditions. SF fumigations were conducted in 432-liter Lexan chambers held in a 6.1-m (20-foot) refrigerated container for temperature control. Each fumigation consisted of 12 Populus spp. 10- by 10- by 115-cm timbers, of high moisture content, naturally infested with Asian longhorned beetle. During 2001, we fumigated wood for 24 h at a range of doses (20-112 g/m3) and temperatures (4.4, 10.0, 15.6, and 21.1 degrees C) and subjected the data to probit analysis. Confirmatory fumigations were conducted at doses of 120 and 104 g/m3 at temperatures of 10.0 and 15.6 or 21.1 degrees C, respectively, which resulted in complete kill of all larvae. Pupae that became available later in the year as temperatures warmed were fumigated at 15.6 and 21.1 degrees C with 104 g/m3, which resulted in complete pupal mortality. The next year (2002), we conducted 24-h fumigations with doses of 116 g/m3 at 4.4 and 10.0 degrees C with cold-harvested wood infested with cold-acclimated larvae. Cold-acclimated larvae required much higher concentration times time (CxT) product for control at 4.4 and 10.0 degrees C compared with nonacclimated larvae. Sulfuryl fluoride treatments at a dose of 104 g/m3 and temperature of 15.6 degrees C and above and that achieved a CxT product of 1,095 g-h/m3 or above are recommended for RWPM infested with Asian longhorned beetle larvae and pupae.