Thermoelectric signature of quantum critical phase in a doped spin-liquid candidate

Quantum spin liquid is a nontrivial magnetic state of longstanding interest, in which spins are strongly correlated and entangled but do not order; further intriguing is its doped version, which possibly hosts strange metal and unconventional superconductivity. A promising candidate of the doped spin liquid is a triangular-lattice organic conductor, κ-(BEDT-TTF)₄Hg_2.89Br₈, recently found to hold metallicity, spin-liquid-like magnetism, and BEC-like superconductivity. The nature of the metallic state with the spin-liquid behaviour is awaiting to be further clarified. Here, we report the thermoelectric signature that mobile holes in the spin liquid background are in a quantum critical state and it pertains to the BEC-like superconductivity. The Seebeck coefficient divided by temperature, S/T, is enhanced on cooling with logarithmic divergence indicative of quantum criticality. Furthermore, the logarithmic enhancement is correlated with the superconducting transition temperature under pressure variation, and the temperature and magnetic field profile of S/T upon the superconducting transition change with pressure in a consistent way with the previously suggested BEC-BCS crossover. The present results reveal that the quantum criticality in a doped spin liquid emerges in a phase, not at a point, and is involved in the unconventional BEC-like nature.

Phase Diagram for Light-Induced Superconductivity in κ-(ET)_{2}-X

Resonant optical excitation of certain molecular vibrations in κ-(BEDT-TTF)_{2}Cu[N(CN)_{2}]Br has been shown to induce transient superconductinglike optical properties at temperatures far above equilibrium T_{c}. Here, we report experiments across the bandwidth-tuned phase diagram of this class of materials, and study the Mott insulator κ-(BEDT-TTF)_{2}Cu[N(CN)_{2}]Cl and the metallic compound κ-(BEDT-TTF)_{2}Cu(NCS)_{2}. We find nonequilibrium photoinduced superconductivity only in κ-(BEDT-TTF)_{2}Cu[N(CN)_{2}]Br, indicating that the proximity to the Mott insulating phase and possibly the presence of preexisting superconducting fluctuations are prerequisites for this effect.

Senescent endothelial cells exacerbate pulmonary hypertension through notch-mediated juxtacrine interaction with pulmonary artery smooth muscle cells

Background

Despite recently developed clinical therapies, vascular remodelling in pulmonary arterial hypertension (PAH) progressively worsen. Hemodynamic unloading has been proposed to normalize the remodelled pulmonary vascular structures in the lungs. Recently, it has been reported that cellular senescence was associated with the irreversibility of pulmonary vascular structures after hemodynamic unloading.

Purpose

This study aims to elucidate the role of senescent endothelial cells (ECs) in the pathogenesis of PAH.

Methods

We generated EC-specific progeroid mice in which ECs undergo premature senescence by overexpressing the dominant-negative form of telomere repeat-binding factor 2 under the control of the VE-cadherin promoter. Following three weeks of hypoxia exposure, the PH phenotypes were assessed by RVSP, lung histology, and RT-qPCR. The interaction of human pulmonary artery ECs (hPAECs) and human pulmonary artery smooth muscle cells (hPASMCs) was indirectly and directly explored through the co-culture system. Gamma-secretase inhibitor (DAPT) was administrated to inhibit Notch signalling both in the in-vitro and in-vivo study.

Results

EC-specific progeroid mice showed exacerbated pulmonary hypertension after chronic hypoxia exposure, accompanied by the enhanced medial SMCs proliferation in the distal pulmonary arteries. Contact-mediated interaction with senescent hPAECs increased proliferation and migration capacities in hPASMCs, while no such effects were detected in the absence of ECs-SMCs contact. Consistently, senescent ECs highly expressed Notch ligands, thus activated Notch signalling in hPASMCs, leading to increased Notch target genes in hPASMCs. Pharmacological inhibition of Notch signalling attenuated the enhanced SMCs proliferation and migration induced by senescent hPAECs, as well as the worsened PH phenotypes in EC-specific progeroid mice.

Conclusions

Our data established a crucial role of senescent ECs in the PAH pathogenesis through the dysregulated SMC functions via juxtacrine signaling. Senescent ECs are attracting targets for further pathological-targeted therapy to cure PAH completely.

Funding Acknowledgement

Type of funding sources: None.

Terahertz-field-induced polar charge order in electronic-type dielectrics

Ultrafast electronic-phase change in solids by light, called photoinduced phase transition, is a central issue in the field of non-equilibrium quantum physics, which has been developed very recently. In most of those phenomena, charge or spin orders in an original phase are melted by photocarrier generations, while an ordered state is usually difficult to be created from a non-ordered state by a photoexcitation. Here, we demonstrate that a strong terahertz electric-field pulse changes a Mott insulator of an organic molecular compound in κ-(ET)₂Cu[N(CN)₂]Cl (ET = bis(ethylenedithio)tetrathiafulvalene), to a macroscopically polarized charge-order state; herein, electronic ferroelectricity is induced by the collective intermolecular charge transfers in each dimer. In contrast, in an isostructural compound, κ-(ET)₂Cu₂(CN)₃, which shows the spin-liquid state at low temperatures, a similar polar charge order is not stabilized by the same terahertz pulse. From the comparative studies of terahertz-field-induced second-harmonic-generation and reflectivity changes in the two compounds, we suggest the possibility that a coupling of charge and spin degrees of freedom would play important roles in the stabilization of polar charge order.

Electronic and spin structures of CaMn4Ox clusters in the S0 state of the oxygen evolving complex of photosystem II. Domain-based local pair natural orbital (DLPNO) coupled-cluster (CC) calculations using optimized geometries and natural orbitals (UNO) by hybrid density functional theory (HDFT) calculations

Domain-based local pair natural orbital (DLPNO) coupled cluster single and double (CCSD) with triple perturbation (T) correction methods were performed to elucidate the relative stabilities of ten different intermediate structures of the CaMn4Ox cluster in the S0 state of the oxygen evolving complex (OEC) of photosystem II (PSII). Full geometry optimizations of all the S0 intermediates were performed by the UB3LYP-D3/Def2-TZVP methods, providing the assumed geometrical structures and starting natural orbitals (UNO) for DLPNO-CCSD(T)/Def2TZVP calculations. The effective exchange integrals (J) for the spin Hamiltonian models for the ten intermediates were obtained by the UB3LYP/Def2-TZVP calculations followed by the general spin projections. DLPNO-CCSD(T) calculations followed by the CBS extrapolation procedure elucidated that the (II, III, IV, IV) and (III, III, III, IV) valence states in the CaMn4O5 cluster of the OEC of the PS II were nearly degenerated in energy in the S0 state, indicating an important role of dynamical electron correlation effects for the valence and spin fluctuations in strongly correlated electron systems (SCESs) consisting of 3d transition metals.

Endothelial cell premature senescence exacerbates pulmonary arterial hypertension through contact-mediated interaction with vascular smooth muscle cells

Introduction

Pulmonary arterial hypertension (PAH) is characterized by remodelling and stenosis of the pulmonary arteries, ultimately leading to the right heart failure and death. Endothelial cell (EC) dysfunction is thought to play a central role in the pathogenesis of PAH by mediating the structural changes in pulmonary vasculatures. Various stresses promote premature senescence in EC, which may modify vascular disorders; however, the role of EC senescence in the development of PAH remains poorly understood.

Purpose

We aimed at investigating the potential role of EC premature senescence in the development of PAH.

Methods

We recently generated EC-specific progeroid mice in which ECs specifically undergo premature senescence by overexpressing the dominant-negative form of telomere repeat-binding factor 2 (published in Nat Commun 2020). These EC-specific progeroid mice were exposed to hypoxia (10% O2 for three weeks) to induce pulmonary hypertension. Also, we prepared premature senescent ECs using human pulmonary artery ECs (hPAECs) and explored their interaction with human pulmonary artery smooth muscle cells (hPASMCs) in two different conditions; direct and indirect interactions. For indirect coculture, hPASMCs were seeded onto the culture insert, while hPAECs were plated on the culture plate, and they were cocultured in the same well and medium so that secreted factors derived from senescent ECs could access to SMCs through the insert pores. For direct coculture, hPAECs were seeded onto the bottom side of the insert, while hPASMCs were cultured on the top side of the same insert, so that cell-to-cell contact could be made through the pores.

Results

After chronic hypoxia exposure, the EC-specific progeroid mice showed higher right ventricular systolic pressure and increased right ventricular mass as compared to wild-type (WT) mice, indicating exacerbated pulmonary hypertension. Histological analysis of the lung revealed a significantly enhanced muscularization in the small pulmonary arteries in EC-specific progeroid mice compared to WT mice. Mechanistically, we identified that direct coculture with premature senescent hPAECs enhanced proliferation and migration in hPASMCs, while no such effects were detected in indirect coculture condition.

Conclusion

To our knowledge, this is the first report that reveals a crucial role of EC premature senescence in the development of PAH. Our in vitro studies suggest that contact-mediated interaction between premature senescent ECs and SMCs is critically involved in its underlying mechanism. Therefore, EC premature senescence is a novel attractive pharmacotherapeutic target for the treatment of PAH.

Funding Acknowledgement

Type of funding source: None

Topological charge transport by mobile dielectric-ferroelectric domain walls

The concept of topology has been widely applied in condensed matter physics, leading to the identification of peculiar electronic states on three-dimensional (3D) surfaces or 2D lines separating topologically distinctive regions. In the systems explored so far, the topological boundaries are built-in walls; thus, their motional degrees of freedom, which potentially bring about new paradigms, have been experimentally inaccessible. Here, working with a quasi-1D organic material with a charge-transfer instability, we show that mobile neutral-ionic (dielectric-ferroelectric) domain boundaries with topological charges carry strongly 1D-confined and anomalously large electrical conduction with an energy gap much smaller than the one-particle excitation gap. This consequence is further supported by nuclear magnetic resonance detection of spin solitons, which are required for steady current of topological charges. The present observation of topological charge transport may open a new channel for broad charge transport-related phenomena such as thermoelectric effects.

P6008Inhibin Beta-A is a novel gene involved in the development of pulmonary arterial hypertension through inhibiting BMPRII-signaling in endothelial cells

Introduction

Pulmonary Arterial Hypertension (PAH) is marked by vascular remodeling process that eventually causes pressure increase. Endothelial cells (EC) dysfunction is known to be a major cause for pulmonary vascular remodeling; however, the molecular mechanism remains to be elucidated.

Purpose

This study aims to identify novel genes and mechanisms involved in PAH development.

Methods

We performed DNA microarray analysis using RNA samples isolated from human ECs of various vascular beds (including lung microvessels) and organs (including lung). We subsequently searched for genes highly and specifically expressed in lung microvessels since these genes are likely involved in pulmonary circulation homeostasis maintenance. Once found, we confirmed its expressional changes during hypoxia in ECs and lung tissues. We next analyzed its role in EC functions using human pulmonary artery ECs (hPAECs) by in vitro angiogenesis assay, using both candidate gene overexpression via retrovirus transfection and treatment with its active form using appropriate recombinant protein. To explore the role of candidate gene in PAH development in vivo, we generated EC-specific knockout mice and transgenic mice in which the candidate gene is genetically deleted and activated in ECs, respectively. PAH was induced by chronic hypoxia exposure (10% O2- for 3 weeks). Lastly, to explore the underlying mechanisms, we analyzed expressional alterations in possible signaling pathways in ECs that could relate with the effect of the candidate gene.

Results

From microarray analysis, we identified inhibin Beta-A (INHBA) as a candidate gene that was highly and specifically expressed in human lung microvascular ECs. INHBA homo-dimerization is known to produce activin A (ActA), a TGF-beta superfamily member. Hypoxia exposure caused significant decrease of INHBA mRNA expression in ECs and mouse lung tissues. Both INHBA overexpression and ActA-treatment in hPAECs caused dramatic reduction of their angiogenic capacities (reduced migration and tube formation capability with increased apoptosis). In vivo, EC-specific INHBA overexpressing mice (VEcad-INHBA-TG) showed exacerbated hypoxia-induced PAH, assessed by higher right ventricular systolic pressure (RVSP) and more severely remodeled pulmonary arteries. By contrast, EC-specific INHBA knockout mice (INHBA-floxed/VEcad-Cre-TG) showed significant amelioration of PAH, shown by reduced RVSP and vascular remodeling. Furthermore, we found that INHBA overexpression and ActA-treatment induced a marked reduction of BMPRII, known to play pivotal roles in PAH, in hPAECs by accelerating its lysosomal degradation.

Conclusion

We identified a novel gene that is crucially involved in PAH development. INHBA and/or ActA negatively regulates EC functions potentially through its BMPRII-altering capability. Gain- and loss-of-function studies in mice revealed that INHBA pathways are promising therapeutic targets for the treatment of PAH.

Strange metal from a frustration-driven charge order instability

Interparticle interactions are self-conflicting rather than cooperative on particular lattices. When such geometrical frustration occurs, charge ordering (CO) can be destabilized into non-trivial charge states such as the recently observed charge glass (CG). A more extreme case is the frustration-induced quantum melting of the CO that has been theoretically proposed. Here, we report d.c. charge transport and noise spectroscopy measurements for a triangular-lattice organic conductor situated close to the CO or CG. Our experiments demonstrate that these materials can host a strange metal with unusual charge dynamics, which we attribute to frustration-induced fluctuations of the CO or CG. Our results also show that the anomalous charge fluctuations can freeze into an insulating state when uniaxial stress is applied, which reduces the geometrical frustration. The present observations suggest the existence of the frustration-induced quantum melting of charges analogous to spin liquids.

Evidence for solitonic spin excitations from a charge-lattice-coupled ferroelectric order

Topological defects have been explored in different fields ranging from condensed matter physics and particle physics to cosmology. In condensed matter, strong coupling between charge, spin, and lattice degrees of freedom brings about emergent excitations with topological characteristics at low energies. One-dimensional (1D) systems with degenerate dimerization patterns are typical stages for the generation of topological defects, dubbed "solitons"; for instance, charged solitons are responsible for high electrical conductivity in doped trans-polyacetylene. Here, we provide evidence based on a nuclear magnetic resonance (NMR) study for mobile spin solitons deconfined from a strongly charge-lattice-coupled spin-singlet ferroelectric order in a quasi-1D organic charge-transfer complex. The NMR spectral shift and relaxation rate associated with static and dynamic spin susceptibilities indicate that the ferroelectric order is violated by dilute solitonic spin excitations, which were further demonstrated to move diffusively by the frequency dependence of the relaxation rate. The traveling solitons revealed here may promise the emergence of anomalous electrical and thermal transport.

In Situ Tissue Engineering of the Bile Duct Using Polypropylene Mesh-Collagen Tubes

Multiple attempts have been made to replace biliary defects with a variety of materials. Recently, successful biliary reconstruction using the Gore-Tex vascular graft has been reported experimentally and clinically We designed a new artificial bile duct consisting of collagen sponge and polypropylene mesh. We presently evaluated the feasibility of using this prosthesis as a scaffold for bile duct tissue regeneration in a canine model. Our prosthesis, a sponge made from porcine dermal collagen, is reinforced with a polypropylene mesh cylinder. We used the prosthesis to reconstruct the middle portion of the common bile duct in seven beagle dogs to evaluate its efficacy. While one dog died of biliary stricture 8 months after operation, six survived without problems to scheduled time points for tissue evaluation at 1 to 12 months. All prostheses had become completely incorporated into the host. A confluent epithelial lining was observed within 3 months. In cholangiograms the prosthesis displayed long-term patency in the six dogs and provided satisfactory bile drainage for up to 12 months. Our graft thus shows promise for repair of biliary defects and should lead to development of a new treatment for biliary reconstruction.

Mott transition by an impulsive dielectric breakdown

The transition of a Mott insulator to metal, the Mott transition, can occur via carrier doping by elemental substitution, and by photoirradiation, as observed in transition-metal compounds and in organic materials. Here, we show that the application of a strong electric field can induce a Mott transition by a new pathway, namely through impulsive dielectric breakdown. Irradiation of a terahertz electric-field pulse on an ET-based compound, κ-(ET) ₂Cu[N(CN) ₂]Br (ET:bis(ethylenedithio)tetrathiafulvalene), collapses the original Mott gap of ∼30 meV with a ∼0.1 ps time constant after doublon-holon pair productions by quantum tunnelling processes, as indicated by the nonlinear increase of Drude-like low-energy spectral weights. Additionally, we demonstrate metallization using this method is faster than that by a femtosecond laser-pulse irradiation and that the transition dynamics are more electronic and coherent. Thus, strong terahertz-pulse irradiation is an effective approach to achieve a purely electronic Mott transition, enhancing the understanding of its quantum nature.

Electronic crystal growth

Interacting atoms or molecules condense into liquid, and, when cooled further, they form a crystal. The time evolution of the atomic or molecular ordering has been widely studied as a nonequilibrium emergence of order from a supercooled liquid or a glass. Interacting electrons in a variety of correlated electron systems also form crystals, but observing the time evolution of electronic crystallization has been experimentally challenging. Here, working with an organic conductor exhibiting a supercooled charge liquid or charge glass as a metastable state, we observed electronic crystal growth through resistivity and nuclear magnetic resonance measurements. The temperature profile of the crystal growth is similar to those observed in classical systems and reveals two distinct regimes for the mechanism of electronic crystallization.

Alendronate does not prevent long bone fragility in an inactive rat model

The lack of estrogen and inactivity are both important in the pathogenesis of osteoporosis in elderly women, and there have been no appropriate rodent studies to examine the effects of common bisphosphonates on these two components separately. We compared the efficacy of alendronate (ALN) on the long bones of aged female rats, which were sedentary, estrogen deficient, or both. The rats were either forced to remain in a sitting position or allowed to walk in standard cages with or without ALN administration. The 8-week experimental period began 5 weeks after ovariectomy or sham surgery. Parameters of the hindlimb bones were determined by a three-point bending test, peripheral quantitative computed tomography, microfocus computed tomography, confocal laser Raman microspectroscopy, and dynamic histomorphometry. Regardless of ovariectomy, ALN was ineffective against the deterioration of breaking stress caused by sitting even though the trabecular bone mineral density was significantly higher in the sitting-ALN groups. Toughness was significantly deficient in the ovariectomy sitting-ALN group. This was in agreement with the bone geometry with a greater marrow space. Sitting also increased the mineral-to-matrix ratio and the carbonate-to-phosphate ratio, both indicative of aged bone. A greater loss of proteinaceous amide intensity compared with mineral intensity resulted in an increased mineral-to-matrix ratio in the presence of ALN. Sitting resulted in deficits in the quality and the geometry of cortical bone, resulting in fragility. The use of bisphosphonates, such as ALN, may provide a therapy best suited for osteoporotic individuals whose daily activity is not limited.

Quantum Spin Liquid Emerging from Antiferromagnetic Order by Introducing Disorder

Quantum spin liquids, which are spin versions of quantum matter, have been sought after in systems with geometrical frustration. We show that disorder drives a classical magnet into a quantum spin liquid through conducting NMR experiments on an organic Mott insulator, κ-(ET)_{2}Cu[N(CN)_{2}]Cl. Antiferromagnetic ordering in the pristine crystal, when irradiated by x rays, disappears. Spin freezing, spin gap, and critical slowing down are not observed, but gapless spin excitations emerge, suggesting a novel role of disorder that brings forth a quantum spin liquid from a classical ordered state.

Pressure-induced Mott transition in an organic superconductor with a finite doping level

We report the pressure study of a doped organic superconductor with a Hall coefficient and conductivity measurements. We find that maximally enhanced superconductivity and a marginal-Fermi liquid appear around a certain pressure where mobile carriers increase critically, suggesting a possible quantum phase transition between strongly and weakly correlated regimes. This observation points to the presence of a criticality in Mottness for a doped Mott insulator with tunable correlation.

High-frequency nuclear quadrupole resonance apparatus for use in pressure cell

A high-frequency NMR apparatus for use in pressure cell is described. All components of the resonance circuit are set in the pressure cell. This method makes the resonance frequency much less influenced by large stray capacitance residing at the electrical feedthrough of the pressure cell. With the use of this apparatus, a pressure-induced neutral-ionic phase transition in DMTTF-QBr(4) was successfully observed by (79)Br nuclear quadrupole resonance, whose resonance frequency is ∼300 MHz.

Prior treatment with vitamin K(2) significantly improves the efficacy of risedronate

Prior 8-week treatment with menatetrenone, MK-4, followed by 8-week risedronate prevented the shortcomings of individual drugs and significantly increased the strength of ovariectomized ICR mouse femur compared to the ovariectomized (OVX) controls. Neither MK-4 following risedronate nor the concomitant administration may be recommended because they brought the least beneficial effect.

INTRODUCTION

The objective of this study was to determine the best combinatory administration of risedronate at 0.25 mg/kg/day (R) with vitamin K(2) at approximately 100 microg MK-4/kg/day (K) to improve strength of osteoporotic mouse bone.

METHODS

Thirteen-week-old ICR mice, ovariectomized at 9-week, were treated for 8 weeks with R, K, or R plus K (R/K), and then, either the treatment was withdrawn (WO) or switched to K or R in the case of R and K. After another 8 weeks, the mice were killed, and mechanical tests and analyses of femur properties by peripheral quantitative computed tomography, microfocus X-ray tube computed tomography, and confocal laser Raman microspectroscopy were carried out.

RESULTS

The K to R femur turned out superior in parameters tested such as material properties, bone mineral density, BMC, trabecular structure, and geometry of the cortex. The increased cross-sectional moment of inertia, which occurred after K withdrawal, was prevented by risedronate in K to R. In addition to K to R, some properties of R to WO diaphysis and K to WO epiphysis were significantly better than OVX controls.

CONCLUSION

Prior treatment with MK-4 followed by risedronate significantly increased femur strength in comparison to the OVX controls.

Predictability of investment behavior from brain information measured by functional near-infrared spectroscopy: a bayesian neural network model

In line with previous studies using fMRI and as is apparent from experimental results, cerebral blood flow (oxygenated hemoglobin (oxyHb) concentration) in the medial prefrontal cortex (MPFC) and orbital cortex (OFC) as is observed with fNIRS (functional near-infrared spectroscopy) is presumed to be closely related to reward prediction and risk prediction as part of decision-making under risk. Results of analysis using a predictive model with a three-layer perceptron revealed that changes in the oxyHb concentration in cerebral blood as indicated by fNIRS observation include information to effectively predict investment behavior. This paper indicates that adding oxyHb concentration at the aforementioned sites in the brain as a predictive factor allows prediction of subjects' investment behavior with a considerable degree of precision. This fact indicates that information provided by fNIRS allows valid analysis of investment behavior and it also suggests a wide-ranging practical applicability for this information like investment assistance using fNIRS.

Spin ordering and enhancement of electronic heat capacity in an organic system of (DI-DCNQI)(2)(Ag(1-x)Cu(x))

Thermodynamic measurements on the organic system of (DI-DCNQI)(2)(Ag(1-x)Cu(x)) (x = 0,0.05, 0.71, 0.90) were performed to study the change from the charge-ordered (CO) insulating state to the π-d hybridized metallic state. A thermal anomaly associated with the antiferromagnetic transition that occurred in the charge-ordered lattice was observed at 6.2 K from the temperature dependence of the heat capacity of (DI-DCNQI)(2)Ag. We have found that the magnetic entropy around the peak is only 1.5% of Rln2, corresponding to the full entropy expected for the formula unit of (DI-DCNQI)(2)Ag. This anomaly is suppressed down to about 3 K in the x = 0.05 sample owing to the disorders induced in the CO lattice. In the metallic concentration of x = 0.90, the low-temperature electronic heat capacity coefficient, γ was found to be enhanced by up to about 63.6 mJ K(-2) mol(-1) probably owing to the cooperative effect of π-d hybridization and intersite Coulomb interaction (V).

Overexpression of RegIV in peritoneal dissemination of gastric cancer and its potential as A novel marker for the detection of peritoneal micrometastasis

BACKGROUND

Regenerating gene type IV (RegIV) is a candidate marker for cancer and inflammatory bowel disease. In this study, its potential as a novel marker for the detection of gastric cancer peritoneal micrometastases was examined.

PATIENTS AND METHODS

RegIV mRNA levels in the peritoneal washes of 95 gastric cancer patients and 22 with benign disease were quantified by real-time RT-PCR. To examine whether expression of RegIV enhance tumorigenicity or not, thirty two mice were injected intraperitoneally or subcutaneously with RegIV transfectants of TMK-1 cells, parental TMK-1 cells, or neomycin control transfectants.

RESULTS

RegIV expression was markedly higher in patients with peritoneal metastases compared to those without. The level of RegIV mRNA in gastric cancer patients was related to the extent of wall penetration. A cut-off value for RegIV-positive expression was based on an analysis of negative control patients with benign disease, and gastric cancer patients above the cut-off value constituted the micrometastasis (MM+) group. Based on this criteria, 3 out of 43 T1 or T2 cases were MM+ (93% specificity). Among 15 patients with peritoneal dissemination (7 out of 15 cases were positive by cytology), 14 cases were positive for RegIV expression (93% sensitivity), while analysis of carcinoembryonic antigen (CEA) mRNA failed to detect micrometastases in 4 cases (73% sensitivity). Combined analysis of CEA and RegIV improved the accuracy of diagnosis to 100%. The prognosis of RegIV-positive cases was significantly worse than that of RegIV-negative cases. Multivariate analysis using the Cox proportional hazards model suggested that RegIV may be an independent prognostic factor. Stable expression of RegIV significantly enhanced peritoneal metastasis in an animal model of gastric cancer.

CONCLUSION

These findings suggest that RegIV mRNA expression has the potential to serve as a novel marker for detecting peritoneal dissemination in gastric cancer.

Negative regulation of MEKK1/2 signaling by serine-threonine kinase 38 (STK38)

Mitogen-activated protein kinases (MAPKs) are activated through the kinase cascades of MAPK, MAPK kinase (MAPKK) and MAPKK kinase (MAPKKK). MAPKKKs phosphorylate and activate their downstream MAPKKs, which in turn phosphorylate and activate their downstream MAPKs. MAPKKK proteins relay upstream signals through the MAPK cascades to induce cellular responses. However, the molecular mechanisms by which given MAPKKKs are regulated remain largely unknown. Here, we found that serine-threonine protein kinase 38, STK38, physically interacts with the MAPKKKs MEKK1 and MEKK2 (MEKK1/2). The carboxy terminus, including the catalytic domain, but not the amino terminus of MEKK1/2 was necessary for the interaction with STK38. STK38 inhibited MEKK1/2 activation without preventing MEKK1/2 binding to its substrate, SEK1. Importantly, STK38 suppressed the autophosphorylation of MEKK2 without interfering with MEKK2 dimer formation, and converted MEKK2 from its phosphorylated to its nonphosphorylated form. The negative regulation of MEKK1/2 was not due to its phosphorylation by STK38. On the other hand, stk38 short hairpin RNA enhanced sorbitol-induced activation of MEKK2 and phosphorylation of the downstream MAPKKs, MKK3/6. Taken together, our results indicate that STK38 negatively regulates the activation of MEKK1/2 by direct interaction with the catalytic domain of MEKK1/2, suggesting a novel mechanism of MEKK1/2 regulation.

Frequent silencing of RUNX3 in esophageal squamous cell carcinomas is associated with radioresistance and poor prognosis

Radiotherapy is an effective treatment for some esophageal cancers, but the molecular mechanisms of radiosensitivity remain unknown. RUNX3, a novel tumor suppressor of gastric cancer, functions in transforming growth factor (TGF)-beta-dependent apoptosis. We obtained paired samples from 62 patients with advanced esophageal cancers diagnosed initially as T3 or T4 with image diagnosis; one sample was obtained from a biopsy before presurgical radiotherapy, and the other was resected in surgical specimens after radiotherapy. RUNX3 was repressed in 67.7% cases of the pretreatment biopsy samples and 96.7% cases of the irradiated, resected samples. The nuclear expression of RUNX3 was associated with radiosensitivity and a better prognosis than cytoplasmic or no RUNX3 expression (P<0.003); cytoplasmic RUNX3 expression was strictly associated with radioresistance. RUNX3 was downregulated and its promoter was hypermethylated in all radioresistant esophageal cancer cell lines examined. Stable transfection of esophageal cancer cells with RUNX3 slightly inhibited cell proliferation in vitro, enhanced the antiproliferative and apoptotic effects of TGF-beta and increased radiosensitivity in conjunction with Bim induction. In contrast, transfection of RUNX3-expressing cells with a RUNX3 antisense construct or a Bim-specific small interfering RNA induced radioresistance. Treatment with 5-aza-2'-deoxycytidine restored RUNX3 expression, increased radiosensitivity and induced Bim in both control and radioresistant cells. These results suggest that RUNX3 silencing promotes radioresistance in esophageal cancers. Examination of RUNX3 expression in pretreatment specimens may predict radiosensitivity, and induction of RUNX3 expression may increase tumor radiosensitivity.

HIV-1 Vpr induces ATM-dependent cellular signal with enhanced homologous recombination

An ATM-dependent cellular signal, a DNA-damage response, has been shown to be involved during infection of human immunodeficiency virus type-1 (HIV-1), and a high incidence of malignant tumor development has been observed in HIV-1-positive patients. Vpr, an accessory gene product of HIV-1, delays the progression of the cell cycle at the G2/M phase, and ATR-Chk1-Wee-1, another DNA-damage signal, is a proposed cellular pathway responsible for the Vpr-induced cell cycle arrest. In this study, we present evidence that Vpr also activates ATM, and induces expression of gamma-H2AX and phosphorylation of Chk2. Strikingly, Vpr was found to stimulate the focus formation of Rad51 and BRCA1, which are involved in repair of DNA double-strand breaks (DSBs) by homologous recombination (HR), and biochemical analysis revealed that Vpr dissociates the interaction of p53 and Rad51 in the chromatin fraction, as observed under irradiation-induced DSBs. Vpr was consistently found to increase the rate of HR in the locus of I-SceI, a rare cutting-enzyme site that had been introduced into the genome. An increase of the HR rate enhanced by Vpr was attenuated by an ATM inhibitor, KU55933, suggesting that Vpr-induced DSBs activate ATM-dependent cellular signal that enhances the intracellular recombination potential. In context with a recent report that KU55933 attenuated the integration of HIV-1 into host genomes, we discuss the possible role of Vpr-induced DSBs in viral integration and also in HIV-1 associated malignancy.

Dynamic changes in dopaminergic neurotransmission induced by a low concentration of bisphenol-A in neurones and astrocytes

One of the most common chemicals that behaves as an endocrine disruptor is the compound 4,4'-isopronylidenediphenol, called bisphenol-A (BPA). We previously reported that prenatal and postnatal exposure to BPA potentiated central dopaminergic neurotransmission, resulting in supersensitivity to psychostimulant-induced pharmacological actions. Many recent findings have supported the idea that astrocytes, which are a subpopulation of glial cells, play a critical role in neuronal transmission in the central nervous system. The present study aimed to investigate the role of neurone-astrocyte communication in the enhancement of dopaminergic neurotransmission induced by BPA. We found that treatment of mouse purified astrocytes and neurone/glia cocultures with BPA in vitro caused the activation of astrocytes, as detected by a stellate morphology and an increase in levels of glial fibrillary acidic protein. A low concentration of BPA significantly enhanced the Ca2+ responses to dopamine in both neurones and astrocytes. Furthermore, a high concentration of BPA markedly induced the activation of caspase-3, which is a marker of neuronal apoptotic cell death in mouse midbrain neurone/glia cocultures. By contrast, treatment with 17beta-oestradiol (E2) had no such effects. Prenatal and neonatal exposure to BPA led to an enhancement of the dopamine-dependent rewarding effect induced by morphine. These findings provide evidence that BPA alters dopamine responsiveness in neurones and astrocytes and that, at least in part, it may contribute to potentiate the development of psychological dependence on drugs of abuse.

Mott transition from a spin liquid to a Fermi liquid in the spin-frustrated organic conductor kappa-(ET)2Cu2(CN)3

The pressure-temperature phase diagram of the organic Mott insulator kappa-(ET)2Cu2(CN)3, a model system of the spin liquid on triangular lattice, has been investigated by 1H NMR and resistivity measurements. The spin-liquid phase is persistent before the Mott transition to the metal or superconducting phase under pressure. At the Mott transition, the spin fluctuations are rapidly suppressed and the Fermi-liquid features are observed in the temperature dependence of the spin-lattice relaxation rate and resistivity. The characteristic curvature of the Mott boundary in the phase diagram highlights a crucial effect of the spin frustration on the Mott transition.

Unconventional critical behaviour in a quasi-two-dimensional organic conductor

Changing the interactions between particles in an ensemble--by varying the temperature or pressure, for example--can lead to phase transitions whose critical behaviour depends on the collective nature of the many-body system. Despite the diversity of ingredients, which include atoms, molecules, electrons and their spins, the collective behaviour can be grouped into several families (called 'universality classes') represented by canonical spin models. One kind of transition, the Mott transition, occurs when the repulsive Coulomb interaction between electrons is increased, causing wave-like electrons to behave as particles. In two dimensions, the attractive behaviour responsible for the superconductivity in high-transition temperature copper oxide and organic compounds appears near the Mott transition, but the universality class to which two-dimensional, repulsive electronic systems belongs remains unknown. Here we present an observation of the critical phenomena at the pressure-induced Mott transition in a quasi-two-dimensional organic conductor using conductance measurements as a probe. We find that the Mott transition in two dimensions is not consistent with known universality classes, as the observed collective behaviour has previously not been seen. This peculiarity must be involved in any emergent behaviour near the Mott transition in two dimensions.

Frequent loss of RUNX3 gene expression in remnant stomach cancer and adjacent mucosa with special reference to topography

Our previous studies suggest that a lack of RUNX3 function is causally related to the genesis and progression of human gastric cancer. This study was conducted to determine whether alteration of RUNX3 gene expression could be detected in the normal-looking gastric remnant mucosa, and to ascertain any difference in the potential of gastric carcinogenesis between the anastomotic site and other areas in the remnant stomach after distal gastrectomy for peptic ulcer (RB group) or gastric cancer (RM group), by analysing RUNX3 expression with special reference to topography. A total of 89 patients underwent distal gastrectomy for gastric cancer from the intact stomach (GCI group) and 58 patients underwent resection of the remnant stomach for gastric cancer (RB group: 34 cases, RM group: 24 cases). We detected RUNX3 and gene promoter methylation by in situ hybridisation, quantitative reverse transcriptase-polymerase chain reaction (RT-PCR), and methylation-specific PCR. The interval between the initial surgery and surgery for remnant gastric cancer (interval time) was 10.4 years in the RM group, and 27.5 years in the RB group. Cancers in the RB group were significantly more predominant in the anastomosis area (P<0.05). Within the tumour, downregulation of RUNX3 expression ranged from 74.7 to 85.7% in the three groups. The rate of downregulation of RUNX3 of adjacent mucosa was 39.2% (11 in 28 cases) in RB and 47.6% (10 in 21 cases) in RM, which are significantly higher than that of the GCI group (19.5%, 17 in 87 cases). In noncancerous mucosa of the remnant stomach in the RB group, RUNX3 expression decreased more near the anastomosis area. In the RM group, however, there were no significant differences in RUNX3 expression by sampling location. Based on RUNX3 downregulation and clinical features, residual stomach mucosa of the RM group would have a higher potential of gastric carcinogenesis compared to the RB or GCI group. Gastric stump mucosa of the RB group has higher potential especially than other areas of residual stomach mucosa. Measurement of RUNX3 expression and detection of RUNX3 methylation in remnant gastric mucosa may estimate the forward risk of carcinogenesis in the remnant stomach.

Differential gene expression profiles of radioresistant oesophageal cancer cell lines established by continuous fractionated irradiation

Radiation therapy is a powerful tool for the treatment of oesophageal cancer. We established radioresistant cell lines by applying fractionated irradiation in order to identify differentially expressed genes between parent and radioresistant cells. Six oesophageal cancer cell lines (TE-2, TE-5, TE-9, TE-13, KYSE170, and KYSE180) were treated with continuous 2 Gy fractionated irradiation (total dose 60 Gy). We compared expression profiles of each parent and radioresistant lines on a cDNA microarray consisting of 21168 genes. In the fractionated irradiation trial, four radioresistant sublines (TE-2R, TE-9R, TE-13R, KYSE170R) were established successfully, and we identified 19 upregulated and 28 downregulated genes common to radioresistant sublines. Upregulated genes were associated with apotosis and inflammatory response (BIRC2 and COX-2), DNA metabolism (CD73), and cell growth (PLAU). Downregulated genes were associated with apoptosis (CASP6), cell adhesion (CDH1 and CDH3), transcription (MLL3), and cell cycle (CDK6). Some of these genes were known to be associated with radiation response, such as COX-2, but others were novel. Reverse transcription–polymerase chain reaction confirmed that genes selected by cDNA microarray were overexpressed in clinical specimens of radioresistant cases. Global gene analysis of radioresistant sublines may provide new insight into mechanisms of radioresistance and effective radiation therapy.

Magnetic-field-induced Mott transition in a quasi-two-dimensional organic conductor

We investigated the effect of magnetic field on the highly correlated metal near the Mott transition in the quasi-two-dimensional layered organic conductor, kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]Cl, by the resistance measurements under control of temperature, pressure, and magnetic field. It was demonstrated that the marginal metallic phase near the Mott transition is susceptible to the field-induced localization transition of the first order, as was predicted theoretically. The thermodynamic consideration of the present results gives a conceptual pressure-field phase diagram of the Mott transition at low temperatures.

Overexpression of dopa decarboxylase in peritoneal dissemination of gastric cancer and its potential as a novel marker for the detection of peritoneal micrometastases with real-time RT-PCR

We previously performed a global analysis of the gene expression of gastric cancer cell lines established from metastases to the peritoneal cavity with the cDNA microarray method, which made it possible to analyse the expression of approximately 21 168 genes for the identification of novel markers for the detection of micrometastases in the peritoneal cavity. One of the upregulated genes is dopa decarboxylase (DDC), which is responsible for the synthesis of the key neurotransmitters dopamine and serotonine. We have examined its potential as a novel marker for the detection of peritoneal micrometastases of gastric cancer.

DDC mRNA in the peritoneal wash from 112 gastric cancer patients was quantified for comparison of carcinoembryonic antigen (CEA) mRNA by means of real-time reverse transcriptase–polymerase chain reaction (RT–PCR) with a fluorescently labelled probe to predict peritoneal recurrence. The quantity of DDC and CEA correlated with wall penetration. Real-time RT–PCR could quantitate 10–10⁶ DDC-expressing gastric cancer cells per 10⁷ mesothelial cells. The cutoff value was set at the upper limit of the quantitative value for noncancer patients, and those above this cutoff value constituted the micrometastasis (MM+) group. Of 15 cases with peritoneal dissemination, 13 were MM+DDC (87% sensitivity), and one of 48 t1 cases was MM+ (98% specificity). DDC levels in peritoneal washes from patients with synchronous peritoneal metastases were more than 50 times higher than in those from patients without metastasis (P<0.01). For 15 cases of peritoneal dissemination (seven cases were cytologically positive), DDC was positive in 13 cases (87% sensitivity), but CEA failed to detect micrometastases in four cases (73% sensitivity), indicating that DDC is in some cases superior to CEA for the detection of peritoneal micrometastases of gastric cancer in terms of sensitivity as well as specificity, especially for poorly differentiated adenocarcinomas. A combination of CEA and DDC improved the accuracy of diagnosis up to 94%.

These results suggest that DDC is potentially a novel marker for peritoneal dissemination of gastric cancer and that quantitative RT–PCR of DDC is reliable and efficient for the selection of patients for adjuvant intraperitoneal chemotherapy to prevent peritoneal recurrence.

Spin liquid state in an organic Mott insulator with a triangular lattice

1H NMR and static susceptibility measurements have been performed in an organic Mott insulator with a nearly isotropic triangular lattice, kappa-(BEDT-TTF)2Cu2(CN)(3), which is a model system of frustrated quantum spins. The static susceptibility is described by the spin S=1/2 antiferromagnetic triangular-lattice Heisenberg model with the exchange constant J approximately 250 K. Regardless of the large magnetic interactions, the 1H NMR spectra show no indication of long-range magnetic ordering down to 32 mK, which is 4 orders of magnitude smaller than J. These results suggest that a quantum spin liquid state is realized in the close proximity of the superconducting state appearing under pressure.