Left ventricular summit premature ventricular contractions treated by venous ethanol infusion: Scar assessment by magnetic resonance imaging

Left ventricular (LV) summit premature ventricular contractions (PVCs) are often unresponsive to radiofrequency (RF) ablation. Retrograde venous ethanol infusion (RVEI) can be a valuable alternative in this scenario. A 43-year-old woman without structural heart disease presented with LV summit PVCs unresponsive to RF ablation because of their deep-seated origin. Unipolar pace mapping performed through a wire inserted into a branch of the distal great cardiac vein (GCV) demonstrated 12/12 concordance with the clinical PVCs thus indicating close proximity to PVCs' origin. RVEI abolished the PVCs without complications. Subsequently, magnetic resonance imaging (MRI) evidenced an intramural myocardial scar produced by ethanol ablation. In conclusion, RVEI effectively and safely treated PVC arising from a deep site in the LVS. The scar provoked by chemical damage was well characterized by MRI imaging.

High magnetoresistance at low magnetic fields in self-assembled ZnO-Co nanocomposite films

The solid phase growth of self-assembled nanocrystals embedded in a crystalline host matrix opens up wide perspectives for the coupling of different physical properties, such as magnetic and semiconducting. In this work, we report the pulsed laser growth at room temperature of thin films composed of a dispersed array of ferromagnetic Co (0001) nanoclusters with an in-plane mono-size width of 1.3 nm, embedded in a ZnO (0001) crystalline matrix. The as-grown films lead to very high values of magnetoresistance, ranging at 9 T from -11% at 300 K to -19% at 50 K, with a steep decrease of the magnetoresistance at low magnetic fields. We establish the relationship between the magnetoresistance behavior and the magnetic response of the Co nanocluster assembly. A spin-dependent tunneling of the electrons between the Co nanoclusters through and by the semi-insulating ZnO host is achieved in our films, promising with regard to magnetic field sensors or Si-integrated spintronic devices. The effects of thermal annealing are also discussed.

Tailored electric and optical properties of Nd doped ZnO: from transparent conducting oxide to photon down-shifting thin films

Tunable properties from transparent conducting to photon down-shifting are obtained with slight change in O₂ pressure during Nd:ZnO film growth.

Formation of oriented nanostructures in diamond using metallic nanoparticles

A simple, fast and cost-effective etching technique to create oriented nanostructures such as pyramidal and cylindrical shaped nanopores in diamond membranes by self-assembled metallic nanoparticles is proposed. In this process, a diamond film is annealed with thin metallic layers in a hydrogen atmosphere. Carbon from the diamond surface is dissolved into nanoparticles generated from the metal film, then evacuated in the form of hydrocarbons and, consequently, the nanoparticles enter the crystal volume. In order to understand and optimize the etching process, the role of different parameters such as type of catalyst (Ni, Co, Pt, and Au), hydrogen gas, temperature and time of annealing, and microstructure of diamond (polycrystalline and nanocrystalline) were investigated. With this technique, nanopores with lateral sizes in the range of 10-100 nm, and as deep as about 600 nm, in diamond membranes were produced without any need for a lithography process, which opens the opportunities for fabricating porous diamond membranes for chemical sensing applications.

[Induction chemotherapy for head and neck epidermoid carcinomas]

The standard treatment for head and neck inoperable squamous cell carcinoma is an association of radiotherapy and platinum. However, only one patient out of three remains alive five years after diagnosis. The interest in induction chemotherapy was renewed by the introduction of taxanes combined with cisplatinum and 5-fluoro-uracile. The triple association taxane-cisplatinum-5-fluoro-uracile yielded improved survival when compared to cisplatinum-5-fluoro-uracile. Wider use of taxane-cisplatinum-5-fluoro-uracile is limited by its toxicity and the lack of randomized comparison with a concomitant chemoradiotherapy scheme including optimal doses of platinum. Until the results of new phase III trials are published, the choice between induction chemotherapy followed by concomitant chemoradiotherapy or concomitant chemoradiotherapy alone has to be made on an individualized basis, taking into account the patient's medical condition, the ability of the medical team to deal with intensive treatment regimens, and the clinical/pathological characteristics of the tumour.

[Total pharyngolaryngectomy in the 21st century: indications, oncologic and functional outcomes]

INTRODUCTION

The development of laryngeal preservation protocols has considerably modified the indications for total (pharyngo-)laryngectomy (TPL). The objectives of our study are to analyze the current indications for TPL and to evaluate the oncologic and functional outcomes after TPL and their predictive factors.

METHODS

All patients who underwent TPL for squamous cell carcinoma of the larynx or hypopharynx, at our institution, between 2000 and 2009, were included in this retrospective study. Predictive factors of oncologic and functional outcomes were assessed in univariate and multivariate analyzes.

RESULTS

A total of 130 patients were enrolled in our study including 119 men and 11 women, with a mean age of 65.9 years. TPL was realized for salvage in 65 patients. Extra-laryngeal tumor extension (n = 42) was the main indication for TPL in the 65 remaining patients. Overall survival was 49 and 41% at 3 and 5 years respectively. In multivariate analysis, primary tumor site (hypopharynx in comparison to larynx; p = 0.04) has a significant pejorative impact on overall survival. Oral alimentation (no enteral nutrition) was recovered successfully by 94% of the patients. In multivariate analysis, primary tumor site (hypopharynx) has a significant pejorative impact on functional results (deglutition: p < 0.0001; phonation: p = 0.03).

CONCLUSION

Primary tumor site is one of the main predictive factor of oncologic and functional outcomes after TPL.

Fatigue of zirconia and dental bridge geometry: Design implications

Zirconia is currently used as a framework material for posterior all-ceramic bridges. While the majority of research efforts have focused on the microstructure and corresponding mechanical properties of this material, clinical fractures appear to be largely associated with the appliance geometry.

OBJECTIVE

The objective of this study was to estimate the maximum stress concentration posed by the connector geometry and to provide adjusted estimates of the minimum connector diameter that is required for achieving 20 years of function.

METHODS

A simple quantitative description of the connector geometry in an all-ceramic 4-unit bridge design is used with published stress concentration factor charts to estimate the degree of stress concentration and the maximum stress.

RESULTS

The magnitude of stress concentration estimated for clinically relevant connector geometries ranges from 2 to 3. Using previously published recommendations for connector designs, adjusted estimates for the minimum connector diameter required to achieve 20 years of clinical function are presented.

SIGNIFICANCE

To prevent clinical fractures the minimum connector diameter in multi-unit bridges designs must account for the loads incurred during function and the extent of stress concentration posed by the connector geometry.

Nanocomposite indium tin oxide thin films: formation induced by a large oxygen deficiency and properties

We report on the formation and properties of nanocomposite indium tin oxide thin films which are grown by pulsed-electron beam deposition under a low oxygen pressure leading to the formation of highly non-stoichiometric indium tin oxide films. For growth at room temperature these films are amorphous and insulating, while at higher temperatures, the oxygen deficiency leads to a disproportionation reaction with the formation of metallic clusters (indium or indium tin clusters) embedded in a stoichiometric crystalline indium tin oxide. This matrix is well crystallized and even epitaxial for growth on c-cut sapphire single crystal substrates. The presence of the metallic clusters induces specific transport properties, i.e. a metallic conductivity at room temperature followed by a superconducting transition at low temperature (about 6 K). Moreover, the solid-liquid and liquid-solid phase transitions in the metallic clusters can be clearly seen from the resistivity curves as a function of temperature (in the room temperature to 450 K range), through specific changes in resistivity and the appearance of a hysteresis cycle.

Benzodiazepines and elderly drivers: a comparison of pharmacoepidemiological study designs

PURPOSE

Contradictory results were published from two studies in the late 1990s about the effects of long half-life benzodiazepine use on the risk of motor vehicle crashes (MVCs) in the elderly. The use of different study designs could explain the differences observed in these studies.

METHODS

The results of an unmatched case-control study were compared to those of a case-crossover study using the same prescription claims database to determine whether the current use of benzodiazepines increased the risk of MVCs.

RESULTS

There were 5579 cases and 12 911 controls identified between the years 1990 and 1993 in the province of Quebec, Canada. The case-control approach demonstrated an increased rate of injurious MVC associated with the current use of long-acting benzodiazepines [odds ratio (OR) 1.45; 95% confidence interval (CI): 1.12-1.88]. The case-crossover approach applied to all cases did not show any association [OR 0.99; 95%CI: 0.83-1.19]. However, among the cases restricted to subjects with four or less prescriptions filled in the previous year, corresponding more to transient exposures, the OR was elevated [OR 1.53; 95%CI: 1.08-2.16].

CONCLUSIONS

Differences in study design and analysis may explain some of the discrepancies in previous results. Both study designs provide evidence that long-acting benzodiazepines appear to be associated with an increased risk of MVC.

Temporal changes in whole-blood and plasma glutathione in ICU patients with multiple organ failure

OBJECTIVE

This study investigated the temporal changes in whole-blood and plasma glutathione in ICU patients with multiple organ failure.

DESIGN AND SETTING

Prospective and descriptive pilot study performed in an ICU with eight beds at a university hospital.

PATIENTS

Critically ill patients (n=11) with multiple organ failure and ICU stay of at least 6 days were consecutively included. Patients with chronic obstructive pulmonary disease (n=21) and healthy volunteers (n=10) were used as reference groups.

MEASUREMENTS AND RESULTS

Whole-blood and plasma glutathione were measured every 72 h. Total glutathione and the reduced fraction were determined in whole blood. The oxidized fraction and the redox status were calculated from these values. In plasma only the total concentration was determined. Patients were studied for 6-15 days. Nutrition was supplied according to routines supplying basal needs including glutamine. Both total and reduced glutathione was found to be depleted in whole blood compared to the reference groups. Redox status indicated continuing oxidative stress. Plasma glutathione showed higher values in total concentrations than the reference groups.

CONCLUSIONS

This study demonstrates that glutathione remains depleted in whole blood. This contrasts to what has previously been shown in skeletal muscle where a restitution of glutathione concentration is seen.

Measurement of dijet azimuthal decorrelations at central rapidities in pp collisions at sqrt s =1.96 TeV

Correlations in the azimuthal angle between the two largest transverse momentum jets have been measured using the D0 detector in p (-)p collisions at a center-of-mass energy sqrt[s]=1.96 TeV. The analysis is based on an inclusive dijet event sample in the central rapidity region corresponding to an integrated luminosity of 150 pb(-1). Azimuthal correlations are stronger at larger transverse momenta. These are well described in perturbative QCD at next-to-leading order in the strong coupling constant, except at large azimuthal differences where contributions with low transverse momentum are significant.

Search for supersymmetry with gauge-mediated breaking in diphoton events at D0

We report the results of a search for supersymmetry (SUSY) with gauge-mediated breaking in the missing transverse energy distribution of inclusive diphoton events using 263 pb(-1) of data collected by the D0 experiment at the Fermilab Tevatron Collider in 2002-2004. No excess is observed above the background expected from standard model processes, and lower limits on the masses of the lightest neutralino and chargino of about 108 and 195 GeV, respectively, are set at the 95% confidence level. These are the most stringent limits to date for models with gauge-mediated SUSY breaking with a short-lived neutralino as the next-to-lightest SUSY particle.

Measurement of the B0s lifetime in the exclusive decay channel B0s-->J/psiphi

Using the exclusive decay B0s-->J/psi(mu+mu-)phi(K+K-), we report the most precise single measurement of the B0s lifetime. The data sample corresponds to an integrated luminosity of approximately 220 pb(-1) collected with the D0 detector at the Fermilab Tevatron Collider in 2002-2004. We reconstruct 337 signal candidates, from which we extract the B0s lifetime, tau(B0s)=1.444(+0.098)(-0.090)(stat)+/-0.020(sys) ps. We also report a measurement for the lifetime of the B0 meson using the exclusive decay B0-->J/psi(mu+mu-)K*0(892)(K+pi-). We reconstruct 1370 signal candidates, obtaining tau(B0)=1.473(+0.052)(-0.050)(stat)+/-0.023(sys) ps, and the ratio of lifetimes, tau(B0s)/tau(B0)=0.980(+0.076)(-0.071)(stat)+/-0.003(sys).

Observation and properties of the X(3872) decaying to J/psipi(+)pi(-) in pp collisions at sqrt[s]=1.96 TeV

We report the observation of the X(3872) in the J/psipi(+)pi(-) channel, with J/psi decaying to mu(+)mu(-), in pp collisions at sqrt[s]=1.96 TeV. Using approximately 230 pb(-1) of data collected with the Run II D0 detector, we observe 522+/-100 X(3872) candidates. The mass difference between the X(3872) state and the J/psi is measured to be 774.9+/-3.1(stat)+/-3.0(syst) MeV/c(2). We have investigated the production and decay characteristics of the X(3872) and find them to be similar to those of the psi(2S) state.

Search for doubly charged higgs boson pair production in the decay to mu(+)mu(+)mu(-)mu(-) in pp collisions at sqrt[s]=1.96 TeV

A search for pair production of doubly charged Higgs bosons in the process pp -->H(++)H(--) -->mu(+)mu(+)mu(-)mu(-) is performed with the D0 run II detector at the Fermilab Tevatron. The analysis is based on a sample of inclusive dimuon data collected at an energy of sqrt[s]=1.96 TeV, corresponding to an integrated luminosity of 113 pb(-1). In the absence of a signal, 95% confidence level mass limits of M(H(+/-+/-)(L))>118.4 GeV/c(2) and M(H(+/-+/-)(R))>98.2 GeV/c(2) are set for left-handed and right-handed doubly charged Higgs bosons, respectively, assuming 100% branching into muon pairs.

A precision measurement of the mass of the top quark

The standard model of particle physics contains parameters--such as particle masses--whose origins are still unknown and which cannot be predicted, but whose values are constrained through their interactions. In particular, the masses of the top quark (M(t)) and W boson (M(W)) constrain the mass of the long-hypothesized, but thus far not observed, Higgs boson. A precise measurement of M(t) can therefore indicate where to look for the Higgs, and indeed whether the hypothesis of a standard model Higgs is consistent with experimental data. As top quarks are produced in pairs and decay in only about 10(-24) s into various final states, reconstructing their masses from their decay products is very challenging. Here we report a technique that extracts more information from each top-quark event and yields a greatly improved precision (of +/- 5.3 GeV/c2) when compared to previous measurements. When our new result is combined with our published measurement in a complementary decay mode and with the only other measurements available, the new world average for M(t) becomes 178.0 +/- 4.3 GeV/c2. As a result, the most likely Higgs mass increases from the experimentally excluded value of 96 to 117 GeV/c2, which is beyond current experimental sensitivity. The upper limit on the Higgs mass at the 95% confidence level is raised from 219 to 251 GeV/c2.

Search for narrow tt resonances in pp collisions at square root of (s)=1.8 TeV

A search for narrow resonances that decay into tt pairs has been performed using 130 pb(-1) of data in the lepton + jets channel collected by the Dphi detector in pp collisions at square root of (s)=1.8 TeV. There is no significant deviation observed from the standard-model predictions at a top-quark mass of 175 GeV/c2. We therefore present upper limits at the 95% confidence level on the product of the production cross section and branching fraction to tt for narrow resonances as a function of the resonance mass MX. These limits are used to exclude the existence of a leptophobic top-color particle with mass MX<560 GeV/c2, using a theoretical cross section for a width GammaX=0.012MX.

Les agénésies isolées et familiales du corps calleux sont-elles de bon pronostic ?

Agenesia of corpus callosum belongs to a group of cerebral malformations whose prognosis is uncertain. In such cases, assessment of prognosis may benefit from eventual associated fetal, obstetrical or familial features. We report a patient with an isolated corpus callosum agenesia that led to the discovery of a similar malformation in her father. This observation demonstrates that some forms of isolated and familial corpus callosum agenesia could have a favorable outcome. However, the difficulty of the assessment of prognosis in isolated corpus callosum agenesia is emphasized and the question of parental RMI exploration in such a peculiar context is raised.

Phenotypic switching of VEGF and collagen XVIII during hypoxia in head and neck squamous carcinoma cells

The present study sought to determine the potential role of stress activated MAPK and phosphatidylinositol 3-kinase (PI3K) signaling pathways in mediating phenotypic switching between angiogenic and angiostatic elements among squamous cell carcinoma (SCC) cell lines. In particular, we investigated the effects of hypoxia and those of cobalt chloride (CoCl(2)), which mimics the hypoxic response including the production of reactive oxygen species, on such phenotypic shifts. The expression and production of collagen XVIII, and CBP2/Hsp47 provided a measure of an angiostatic phenotype, while vascular endothelial growth factor (VEGF) expression was used to assess potential angiogenic states. These studies revealed that hypoxia produced a slight up-regulation of collagen XVIII and CBP2/Hsp47 that was inhibited by the stress kinase inhibitor SB203580 but was unaffected by N-acetylcysteine (NAC). In addition, VEGF expression was increased following hypoxia and this effect was reversed with inhibition of by SB203580. Conversely, CoCl(2) significantly diminished the expression of both collagen XVIII and CBP2/Hsp47 and enhanced VEGF expression. These changes were reversed by the PI3K inhibitor wortmannin and by treating cells with NAC. These studies show that phenotypic switching between collagen XVIII and VEGF is controlled by stress activated kinases under hypoxia, and PI3K signaling pathways as well as reactive oxygen species (ROS) following CoCl(2) treatment. Furthermore, modulation of the angiogenic switch is most profound during Akt activation than during activation of stress activated kinases.

Search for large extra dimensions in the monojet+E(T) channel with the DØ detector

We present a search for large extra dimensions (ED) in pp collisions at a center-of-mass energy of 1.8 TeV using data collected by the DØ detector at the Fermilab Tevatron in 1994-1996. Data corresponding to 78.8+/-3.9 pb(-1) are examined for events with large missing transverse energy, one high-p(T) jet, and no isolated muons. There is no excess observed beyond expectation from the standard model, and we place lower limits on the fundamental Planck scale of 1.0 and 0.6 TeV for 2 and 7 ED, respectively.

Targeting of human squamous carcinomas by SPA470-doxorubicin immunoconjugates

In a quest to identify a favorable target for head and neck cancers and squamous cell carcinoma, we sought to determine if Hsp47/CBP2 could be used as a target and whether the expression of this target was influenced by hypoxia. Moreover, we determined if doxorubicin (DOX) immunoconjugates directed against Hsp47/CBP2 that linked monoclonal antibodies (MAbs) to the 13-keto position of the drug possessed high cytotoxic drug activity and antibody-directed killing of antigen bearing tumor target cells. Experiments were performed using established cell lines of human oral squamous carcinoma cells (SCCs) (SCC-4, -9, -15 and -25) obtained from American Type Culture Collection (ATCC) (Manassas, VA). In addition, the UMB2 cell line is a spontaneous mutant of SCC-9 that does not express Hsp47/CBP2 was also used. Synthesis of the immunoconjugates was accomplished by thiolating the MAbs with 2 IT and reacting the MAbs with the DOX-hydrazone. The binding of MAb-DOX conjugates to SCC cells was determined by indirect immunofluorescence and analyzed using a Becton Dickinson FACS scan with Cell Quest software. Comparison of the cytotoxicity of DOX, MAb-DOX conjugates and MAb+DOX were determined using a limited dilution assay and colony survival assays during normoxia and hypoxia. These studies revealed that SCC cells treated with the SPA470-DOX conjugate for 2 h retained the original binding activity for targeted SCC cells and was significantly more potent that unconjugated DOX, DOX-hydrazone or equivalent MAb protein+DOX. Also, SPA47-DOX produced equal to and at lower concentrations greater cell killing than equivalent dose of free DOX. During hypoxia cells treated with SPA470-DOX demonstrated a small increase in colony survival and a diminishment in cytotoxicity. SPA470-DOX conjugates target SCC cells that express Hsp47/CBP2. The demonstration that SPA470-DOX is effective during hypoxia or conditions that mimic hypoxia presumes the further utility of SPA470-DOX in treating head and neck cancers.

Search for the production of single sleptons through R-parity violation in pp; collisions at square root (s) =1.8 TeV

We report the first search for supersymmetric particles via s-channel production and decay of smuons or muon sneutrinos at hadronic colliders. The data for the two-muon and two-jets final states were collected by the D0 experiment and correspond to an integrated luminosity of 94+/-5 pb(-1). Assuming that R parity is violated via the single coupling lambda'211, the number of candidate events is in agreement with expectation from the standard model. Exclusion contours are given in the (m(0),m(1/2)) and (m(x),m(v)) planes for lambda(')(211)=0.09, 0.08, and 0.07.

15-PGJ2, but not thiazolidinediones, inhibits cell growth, induces apoptosis, and causes downregulation of Stat3 in human oral SCCa cells

Activation of peroxisome proliferator-activated receptor gamma (PPARgamma) has been linked to induction of differentiation, cell growth inhibition and apoptosis in several types of human cancer. However, the possible effects of PPARgamma agonists on human oral squamous cell carcinoma have not yet been reported. In this study, treatment with 15-deoxy-Delta(12,14)-PGJ(2) (15-PGJ(2)), a natural PPARgamma ligand, induced a significant reduction of oral squamous cell carcinoma cell growth, which was mainly attributed to upregulation of apoptosis. Interestingly, rosiglitazone and ciglitazone, two members of the thiazolidinedione family of PPARgamma activators, did not exert a growth inhibitory effect. Given the critical role that the oncogene signal transducer and activator of transcription 3 (Stat3) plays in head and neck carcinogenesis, its potential regulation by PPARgamma ligands was also examined. Treatment of oral squamous cell carcinoma cells with 15-PGJ(2) induced an initial reduction and eventual elimination of both phosphorylated and unphosphorylated Stat3 protein levels. In contrast, other PPARgamma did not induce similar effects. Our results provide the first evidence of significant antineoplastic effects of 15-PGJ(2) on human oral squamous cell carcinoma cells, which may be related to downmodulation of Stat3 and are at least partly mediated through PPARgamma-independent events.

Glutathione synthetase deficiency: is gamma-glutamylcysteine accumulation a way to cope with oxidative stress in cells with insufficient levels of glutathione?

Glutathione (GSH) plays a major role in the cellular defence against oxidative stress and other vital cellular functions. It therefore seems inevitable that patients with severe depletion of GSH will not survive. However, at least some with glutathione synthetase (GS) deficiency do. This study was done to determine whether these patients have a mechanism to compensate for their GSH deficiency. Cell-free extracts of cultured fibroblasts from 9 patients with GS deficiency and 9 control subjects were analysed by HPLC for low-molecular-weight thiol compounds. The patients' cells contained 7.4 nmol of GSH per mg of protein (median; range 2.8-25.2) compared to 33.0 nmol in control fibroblasts (range 26.7-51.4) (p < 0.01). On the other hand, the patients' cells accumulated 18.1 nmol of gamma-glutamylcysteine (gamma-GC) per mg of protein (median; range 6.9-71.7), whereas the control cells contained 0.1 nmol (range 0.05-0.16) (p < 0.01). The cysteine concentrations in the patients' cells were 20.7 nmol/mg protein (median; range 9.4-52.9) compared to 8.9 nmol in control cells (range 3.0-12.4) (p < 0.01). Cultured fibroblasts from patients with GS deficiency have low levels of GSH, but instead accumulate gamma-GC. We suggest that gamma-GC, which contains both reactive groups of GSH (i.e. the sulphydryl and gamma-glutamyl groups), can compensate for GSH in the cellular defence against oxidative stress. Thus, gamma-GC may alleviate, but only partly prevent, serious consequences of insufficient GSH levels in affected patients. Since the sum of the levels of GSH and gamma-GC in GS-deficient cells (median 31.5 nmol/mg protein, range 16.2-79.0) was similar to the level of GSH alone in control cells (33.0 nmol/mg protein, range 26.7-51.4), we propose that the cultured fibroblasts may have a mechanism to regulate in a coordinated way the levels of GSH and gamma-GC; for instance, by both compounds acting as feedback inhibitors of gamma-GC synthetase.

Search for R-parity violating supersymmetry in two-muon and four-jet topologies

We present results of a search for R-parity-violating decay of the neutralino chi;01, taken as the lightest supersymmetric particle, to a muon and two jets. The decay proceeds through a lepton-number violating coupling lambda(')(2jk) (j=1,2; k=1,2,3), with R-parity conservation in all other production and decay processes. In the absence of candidate events from 77.5+/-3.9 pb(-1) of data collected by the D0 experiment at the Fermilab Tevatron in pp collisions at sqrt[s]=1.8 TeV, and with an expected background of 0.18+/-0.03+/-0.02 events, we set limits on squark and gluino masses within the framework of the minimal low-energy supergravity-supersymmetry model.

Search for leptoquark pairs decaying into nunu+jets in pp collisions at square root[s] = 1.8 TeV

We present the results of a search for leptoquark (LQ) pairs in (85.2+/-3.7) pb(-1) of pp* collider data collected by the D0 experiment at the Fermilab Tevatron. We observe no evidence for leptoquark production and set a limit on sigma(pp*-->LQLQ-->nunu+jets) as a function of the mass of the leptoquark (m(LQ)). Assuming the decay LQ-->nuq, we exclude scalar leptoquarks for m(LQ) < 98 GeV/c(2), and vector leptoquarks for m(LQ) < 200 GeV/c(2) and coupling which produces the minimum cross section, at a 95% confidence level.

Search for the scalar top quark in pp collisions at square root[s] = 1.8 TeV

We have performed a search for scalar top quark (stop) pair production in the inclusive electron-muon-missing transverse energy final state, using a sample of pp events corresponding to 108.3 pb(-1) of data collected with the D0 detector at Fermilab. The search is done in the framework of the minimal supersymmetric standard model assuming that the sneutrino is the lightest supersymmetric particle. For the dominant decays of the lightest stop, t-->b chi+1 and t-->blnu, no evidence for signal is found. We derive cross-section limits as a function of stop ( t ), chargino ( chi+1), and sneutrino ( nu) masses.

Direct search for charged higgs bosons in decays of top quarks

We present a search for charged Higgs bosons in decays of pair-produced top quarks in pp collisions at sqrt[s] = 1.8 TeV recorded by the D0 detector at the Fermilab Tevatron collider. With no evidence for signal, we exclude most regions of the ( M(H+/-),tan(beta)) parameter space where the decay t--> H(+)b has a branching fraction >0.36 and B(H+/--->tau(nu)(tau)) is large.

Ratio of isolated photon cross sections in pp macro collisions at square root of s = 630 and 1800 GeV

The inclusive cross section for production of isolated photons has been measured in pp macro collisions at square root of s = 630 GeV with the D0 detector at the Fermilab Tevatron Collider. The photons span a transverse energy (E(T)) range from 7-49 GeV and have pseudorapidity absolute value of eta < 2.5. This measurement is combined with the previous D0 result at square root of s = 1800 GeV to form a ratio of the cross sections. Comparison of next-to-leading-order QCD with the measured cross section at 630 GeV and the ratio of cross sections show satisfactory agreement in most of the E(T) range.

Search for new physics using QUAERO: a general interface to D0 event data

We describe QUAERO, a method that (i) enables the automatic optimization of searches for physics beyond the standard model, and (ii) provides a mechanism for making high energy collider data generally available. We apply QUAERO to searches for standard model WW, ZZ, and t t macro production, to searches for these objects produced through a new heavy resonance, and to the first direct search for W'-->WZ. Through this interface, we make three data sets collected by the D0 experiment at square root of [s] = 1.8 TeV publicly available.

Chronic exposure of human mesangial cells to high glucose environments activates the p38 MAPK pathway

BACKGROUND

High glucose (HG) environments activate several protein kinase pathways in mesangial cells, including the mitogen-activated protein kinase (MAPK) pathway, ERK. The p38 MAPK pathway is activated by events that occur in the setting of diabetes, such as protein kinase C (PKC) up-regulation and cellular stresses (osmotic stress and redox changes). Substrates of activated p38 MAPK include transcription factors that are involved in the microvascular complications of diabetes. This current study investigated the mechanisms of HG-mediated activation of p38 MAPK in cultured human mesangial cells (HMCs) and the effects of p38 MAPK activation on the transcription factor activator protein-1 (AP-1).

METHODS

HMCs were cultured in 5 mmol/L D-glucose [normal glucose (NG)] or 30 mmol/L D-glucose (HG) for seven days. Cells were also treated with HG for brief periods of time (0.5 to 4 hours) to assess the acute effects of HG on p38 MAPK. Using Western blotting of HMC lysates, changes in the tyrosine and threonine phosphorylation of p38 MAPK were measured. The kinase activity of immunoprecipitated p38 MAPK was determined by an in vitro assay that measured the phosphorylation and activation of MAPKAP kinase-2, an intermediary signaling protein downstream of p38 MAPK. To investigate the role of osmotic stress in HG activation of p38 MAPK, cells were acutely treated with mannitol (25 to 250 mOsm/L x 5 to 60 min) or were grown seven days in media supplemented with mannitol at concentrations iso-osmotic to HG media. To investigate the role of PKC in HG-mediated p38 MAPK activation, HMCs were treated with the PKC inhibitors GF 109203X, Ro 32-0432, or rottlerin during the last several hours of HG treatment. HG conditioned cells were also treated with the antioxidants L-N-acetylcysteine (L-NAC) or diphenyliodonium (DPI) prior to harvest. To determine a functional significance of HG-mediated p38 MAPK activation, the DNA binding of the transcription factor complex AP-1 was measured by electrophoretic mobility shift assay.

RESULTS

The p38 MAPK pathway was not activated by the acute addition of HG to the HMCs. However, activation of p38 MAPK in HMCs grown seven days in HG was demonstrated by increased tyrosine and threonine phosphorylation of p38 MAPK proteins and increased kinase activity of immunoprecipitated p38 MAPK. As assessed by a kinase assay, p38 MAPK activity in cells grown in HG for seven days exceeded that of NG cells by more than 250%. This difference was not due to differences in the amount of p38 MAPK protein between the treatment groups. Acute osmotic activation of p38 MAPK occurred at extremely high mannitol concentrations (250 mOsm/L) that exceeded the osmotic stress of acute HG. Furthermore, in cells grown for seven days in mannitol at concentrations similar to HG, p38 MAPK activity was similar to control values. Phorbol ester (PMA) treatment stimulated a twofold increase in p38 MAPK activity. The addition of GFX or Ro 32-0432 to HG cells, at concentrations that inhibited PMA activation of p38 MAPK, did not inhibit the glucose-mediated p38 MAPK activation. Rottlerin, a PKC delta inhibitor, also failed to reverse the HG-mediated p38 MAPK activation. Treatment of HG cells with L-NAC or DPI inhibited the HG-mediated p38 MAPK phosphorylation. As we have previously shown, DNA binding of the transcription factor complex AP-1 was increased in HG cells. This binding was reversed by treatment of the HG cells with the p38 MAPK inhibitor SB 203580.

CONCLUSIONS

Chronic exposure of HMC to HG concentrations activates the p38 MAPK pathway. This activation appears to be independent of changes in the amount of total p38 MAPK produced by the cells, independent of chronic osmotic stress and independent of PKC activation. The reversal of p38 MAPK by L-NAC and DPI suggests the glucose-mediated p38 MAPK activation may occur via reactive oxygen species. The activity of AP-1, a transcription factor complex that regulates several genes involved in diabetic nephropathy, is reversed when the p38 MAPK pathway is inhibited. These findings suggest the p38 MAPK pathway may be an important pathway involved in diabetic complications.

Search for heavy particles decaying into electron-positron pairs in pp collisions

We present results of searches for technirho (rho(T)), techniomega (omega(T)), and Z' particles, using the decay channels rho(T),omega(T),Z'-->e(+)e(-). The search is based on 124.8 pb(-1) of data collected by the D0 detector at the Fermilab Tevatron during 1992-1996. In the absence of a signal, we set 95% C.L. upper limits on the cross sections for the processes pp-->rho(T),omega(T),Z'-->e(+)e(-) as a function of the mass of the decaying particle. For certain model parameters, we exclude the existence of degenerate rho(T) and omega(T) states with masses below about 200 GeV. We exclude a Z' with mass below 670 GeV, assuming that it has the same couplings to fermions as the Z boson.