Observation of the doubly strange b baryon Omegab-

We report the observation of the doubly strange b baryon Omegab- in the decay channel Omegab(-)-->J/psiOmega-, with J/psi-->mu+mu(-) and Omega(-)-->LambdaK(-)-->(ppi-)K-, in pp collisions at sqrt[s]=1.96 TeV. Using approximately 1.3 fb(-1) of data collected with the D0 detector at the Fermilab Tevatron Collider, we observe 17.8+/-4.9(stat)+/-0.8(syst) Omegab- signal events at a mass of 6.165+/-0.010(stat)+/-0.013(syst) GeV. The significance of the observed signal is 5.4sigma, corresponding to a probability of 6.7 x 10(-8) of it arising from a background fluctuation.

Detailed comparison between StochSim and SSA

Morton-Firth and Bray's stochastic simulator (StochSim) and Gillespie's stochastic simulation algorithm (SSA) are two important methods for stochastic modelling and simulation of biochemical systems. They have been widely applied to different biological problems. A key question is discussed here: Are these two methods equivalent? These two methods are compared using fundamental probability analysis. The analysis clearly shows that, when the time step in the StochSim is chosen very small, the StochSim can be viewed as a first-order approximation to the SSA. The analysis also explains why the SSA is usually much more efficient than the StochSim for biochemical systems. However, when multistate species present in a system, the StochSim clearly shows its advantage. The Complexity analysis is used to explain this advantage. The hybrid SSA (HSSA) is proposed to combine the advantages of both the StochSim and SSA. When the populations of the multistate species are small, the HSSA is very efficient. Numerical experiments are presented to verify the analysis.

Relationship between TH1/TH2 cytokines and immune tolerance in liver transplantation in rats

OBJECTIVE

To explore the relationship between Th1/Th2 cytokine expressions and immune tolerance in rat liver transplantation.

METHODS

Recipients were divided into three groups (each group = 12 rats). The allograft group underwent orthotopic liver transplantation from male Wistar-to-Sprague-Dawley (SD) rats. The isograft group of SD-to-SD liver transplantation was complemented with a control group of normal male SD rats that had sham operations. We evaluated the 2-week survival rates histological changes, as well as serum and mRNA expression levels of Th1/Th2 cytokines: interferon-gamma (IFN-gamma) and interleukin-10 (IL-10).

RESULTS

The 1-week survival in the isograft and allograft groups were 100% and 41.67%, respectively. The 2-week survival rates were 75% and 8.33% (P < .05). Light microscopic inspection revealed severe acute rejection in the allograft but not the isograft group in the first week postoperation. This observation was verified by the cellular morphology under transmission electron microscopy. Serum IFN-gamma (Th1 cytokine) levels (pg/mL) determined by enzyme-linked immunosorbent assay in the allograft, isograft, and control groups were 386.67 +/- 14.36, 159.83 +/- 16.53, and 87.83 +/- 8.67, respectively; for IL-10 (Th2 cytokine), they were 126.33 +/- 13.10, 288.33 +/- 17.10, and 70.50 +/- 7.23, respectively (P < .05, allograft vs isograft). The semiquantitative reverse-transcriptase polymerase chain reaction assay showed that expression of IFN-gamma and IL-10 mRNA was similar to that of serum levels. IFN-gamma mRNA was more highly expressed in the allograft group and IL-10 mRNA, in the isograft group (P < .05).

CONCLUSIONS

The dynamic equilibrium of Th1/Th2 cytokines is critically involved in immune tolerance. The deviation of Th1 to Th2 may be one mechanism of immune tolerance.

Rabbit anti-human leukocyte polyclonal antibody inhibits xenogeneic cell-mediated immune responses

We studied the interactions between human monocytes and porcine endothelial cells (PEC) as well as the effects of a new generation of rabbit anti-human leukocyte polyclonal antibody (newRALG) to inhibit xenogeneic cell-mediated immune responses. Human peripheral blood mononuclear cells (PBMC) were cocultured with the florescent dye PKH-26 labeled-PEC, which showed membrane uptake by monocytes detected by florescence activated cell scanning (FACS). Scavenger receptor (SR) ligand poly-(G) or the newRALG or Thymoglobulin was added into the cocultures followed by FACS. Lymphocyte proliferation upon exposure to PEC with or without newRALG or thymoglobulin was evaluated by a xenogeneic mixed-lymphocyte-endothelial cell reaction (xMLER). FACS analysis demonstrated that CD14+ monocytes became positive for PKH-26 following their interaction with PKH-26-labeled PEC. These PKH-26+ monocytes displayed up-regulated CD40 and CD80 expression during the PBMC-PEC interaction. Furthermore, SR blockade with poly-(G) prevented PEC membrane uptake by CD14+ monocytes. The newRALG from rabbits immunized with activated human monocytes and lymphocytes greatly reduced SR-mediated PEC membrane uptake. xMLER demonstrated strong lymphocyte proliferation in response to PEC. Lymphocyte proliferation was dramatically inhibited in dose-dependent manner by the newRALG. In summary, monocytes up-regulate costimulatory molecules during xenogeneic interactions, indicating that they may serve as a source of T-cell costimulation during xenogeneic reactions, enguling PEC membranes. This phenomenon was inhibited by poly (G), suggesting that PEC membrane uptake was via SR. The newRALG inhibited monocyte SR-mediated PEC membrane uptake and lymphocyte proliferation in response to PEC suggesting that this new polyclonal preparation may impair the initiation of xeno-specific immune responses.

Evaluation of CD86/CD28 and CD40/CD154 pathways in regulating monocyte-derived CD80 expression during their interaction with allogeneic endothelium

This study was designed to examine the role of monocyte-derived CD80 in providing costimulation to CD4+ cells, and to determine whether monocyte-derived CD80 expression is regulated by CD86/CD28 and CD40/CD154 pathways during allogeneic immunoresponses. Human endothelial cells (EC) and purified monocytes cocultured with or without CD4+ cells were analyzed by real-time quantitative polymerase chain reaction (RT-PCR) and florescence-activated cell scanning (FACS). Peripheral blood mononuclear cells (PBMC)-EC cocultures with or without costimulation blockade were analyzed by FACS. The effects of CD154 and CD28 blockade to inhibit lymphocyte proliferation were evaluated by mixed lymphocyte-EC reaction (MLER). RT-PCR demonstrated upregulation of CD80 transcripts in EC-stimulated monocytes in the absence of CD4+ cells. However, the surface expression of CD80 was undetectable. The expression of CD80 was restored in the presence of CD4+ cells. Additionally, CD80 blockade partially inhibited CD4+ cell proliferation induced by EC-conditioned monocytes. Monocytes demonstrated upregulation of CD80 on the surface during PBMC-EC interaction. CD86, CD28, and CD154 blockade did not prevent upregulation of monocyte-derived CD80 expression. CD28 and CD154 blockade partially inhibited lymphocyte proliferation of MLER. In summary, EC-stimulated monocytes upregulated CD80 expression at the transcript level but not on their surface in the absence of T cells. The surface expression of monocyte-derived CD80 is upregulated on EC-stimulated monocytes in the presence of T cells. CD154/CD40 and CD28/CD86 blockade cannot prevent monocyte-derived CD80 expression, suggesting that CD80 upregulation is through a CD154- or CD86-independent pathway. Specific therapy to prevent monocyte activation may be required for successful allograft transplantation.

Sirt7-dependent inhibition of cell growth and proliferation might be instrumental to mediate tissue integrity during aging

Mammalian sirtuins, Sirt1-Sirt7, are recently discovered regulatory proteins, which play decisive roles in cellular metabolism, stress resistance, and proliferation. Sirtuins are homologs of the founder member of the sirtuin family, the yeast Sir2. Sir2 encodes a NAD(+)-dependent histone deacetylase and its overexpression extends the lifespan through silencing of specific chromatin regions. Lifespan extension by Sir2 homologs was also demonstrated in more complex species such as C. elegans and D. melanogaster. A longevity function has been also postulated for mammalian sirtuins, however definitive proof is still lacking. Here, we have investigated the role of the mouse Sirt7 in the control of cellular growth and proliferation. Using Sirt7 knockout and overexpressing cells we demonstrate an anti-proliferative role of Sirt7. We also show that Sirt7 expression inversely correlates with the tumorigenic potential of several murine cell lines. Considering the known role of Sirt7 as an activator of rDNA transcription we propose that Sirt7 may enable cells to sustain critical metabolic functions by inhibiting cell growth even under severe stress conditions. We conclude, that these Sirt7 functions may improve tissue integrity in aged animals.

Search for anomalous Wtb couplings in single top quark production

In 0.9 fb(-1) of pp[over] collisions, the D0 Collaboration presented evidence for single top quark production in events with an isolated lepton, missing transverse momentum, and two to four jets. We examine these data to study the Lorentz structure of the Wtb coupling. The standard model predicts a left-handed vector coupling at the Wtb vertex. The most general lowest dimension, CP-conserving Lagrangian admits right-handed vector and left- or right-handed tensor couplings as well. We find that the data prefer the left-handed vector coupling and set upper limits on the anomalous couplings. These are the first direct constraints on a general Wtb interaction and the first direct limits on left- and right-handed tensor couplings.

Search for neutral Higgs bosons in multi-b-jet events in pp[over] collisions at sqrt[s]=1.96 TeV

Data recorded by the D0 experiment at the Fermilab Tevatron Collider are analyzed to search for neutral Higgs bosons produced in association with b quarks. This production mode can be enhanced in the minimal supersymmetric standard model (MSSM). The search is performed in the three b quark channel using multijet triggered events corresponding to an integrated luminosity of 1 fb(-1). No statistically significant excess of events with respect to the predicted background is observed and limits are set in the MSSM parameter space.

Laser micro/nano fabrication in glass with tunable-focus particle lens array

Based on medium-tuned optical field enhancement effect around a self-assembled particle-lens array (PLA) irradiated with a femtosecond (fs) laser source, we demonstrated that high-precision periodical array of micro/nano-structures can be readily fabricated on glass surface or inside glass in large areas in parallel without any cracks or debris. The technique has potential for rapid fabrication of three-dimensional structures in multiple layers inside glass.

Measurement of the electron charge asymmetry in pp[over ]-->W+X-->enu+X events at sqrt[s]=1.96 TeV

We present a measurement of the electron charge asymmetry in pp[over ]-->W+X-->enu+X events at a center of mass energy of 1.96 TeV using 0.75 fb(-1) of data collected with the D0 detector at the Fermilab Tevatron Collider. The asymmetry is measured as a function of the electron transverse momentum and pseudorapidity in the interval (-3.2, 3.2) and is compared with expectations from next-to-leading order calculations in perturbative quantum chromodynamics. These measurements will allow more accurate determinations of the proton parton distribution functions.

Revealing the dynamics of gene expression during embryonic genome activation and first differentiation in the rabbit embryo with a dedicated array screening

Early mammalian development is characterized by extensive changes in nuclear functions that result from epigenetic modifications of the newly formed embryonic genome. While the first embryonic cells are totipotent, this status spans only a few cell cycles. At the blastocyst stage, the embryo already contains differentiated trophectoderm cells and pluripotent inner cell mass cells. Concomitantly, the embryonic genome becomes progressively transcriptionally active. During this unique period of development, the gene expression pattern has been mainly characterized in the mouse, in which embryonic genome activation (EGA) spans a single cell cycle after abrupt epigenetic modifications. To further characterize this period, we chose to analyze it in the rabbit, in which, as in most mammals, EGA is more progressive and occurs closer to the first cell differentiation events. In this species, for which no transcriptomic arrays were available, we focused on genes expressed at EGA and first differentiation and established a 2,000-gene dedicated cDNA array. Screening this with pre-EGA, early post-EGA, and blastocyst embryos divided genes into seven clusters of expression according to their regulation during this period and revealed their dynamics of expression during EGA and first differentiation. Our results point to transient properties of embryo transcriptome at EGA, due not only to the transition between maternal and embryonic transcripts but also to the transient expression of a subset of embryonic genes whose functions remained largely uncharacterized. They also provide a first view of the functional consequences of the changes in gene expression program.

Measurement of the forward-backward charge asymmetry and extraction of sin2thetaWeff in pp-->Z/gamma* + X-->e+e- +X events produced at sqrt[s] = 1.96 TeV

We present a measurement of the forward-backward charge asymmetry (A FB) in pp-->Z/gamma* + X-->e+e(-) + X events at a center-of-mass energy of 1.96 TeV using 1.1 fb(-1) of data collected with the D0 detector at the Fermilab Tevatron collider. A FB is measured as a function of the invariant mass of the electron-positron pair, and found to be consistent with the standard model prediction. We use the A FB measurement to extract the effective weak mixing angle sin2thetaWeff = 0.2326+/-0.0018(stat)+/-0.0006(syst).

Measurement of the polarization of the upsilon(1S) and upsilon(2S) states in pp collisions at square root[s]=1.96 TeV

We present a study of the polarization of the Upsilon(1S) and Upsilon(2S) states using a 1.3 fb;{-1} data sample collected by the D0 experiment in 2002-2006 during run II of the Fermilab Tevatron Collider. We measure the polarization parameter alpha=(sigma_{T}-2sigma_{L})/(sigma_{T}+2sigma_{L}), where sigma_{T} and sigma_{L} are the transversely and longitudinally polarized components of the production cross section, as a function of the transverse momentum (p_{T};{Upsilon}) for the Upsilon(1S) and Upsilon(2S). Significant p_{T};{Upsilon}-dependent longitudinal polarization is observed for the Upsilon(1S). A comparison with theoretical models is presented.

Precise measurement of the top-quark mass from lepton + jets events

We measure the mass of the top quark using top-quark pair candidate events in the lepton+jets channel from data corresponding to 1 fb;{-1} of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron collider. We use a likelihood technique that reduces the jet energy scale uncertainty by combining an in situ jet energy calibration with the independent constraint on the jet energy scale (JES) from the calibration derived using photon+jets and dijet samples. We find the mass of the top quark to be 171.5+/-1.8(stat.+JES)+/-1.1(syst.) GeV.

Observation of ZZ production in p-p collisions at sqrt s=1.96 TeV

We present an observation for ZZ-->l+l-l'+l'- (l, l'=e or mu) production in p[over]p collisions at a center-of-mass energy of sqrt[s]=1.96 TeV. Using 1.7 fb(-1) of data collected by the D0 experiment at the Fermilab Tevatron Collider, we observe three candidate events with an expected background of 0.14(+0.03)_(-0.02) events. The significance of this observation is 5.3 standard deviations. The combination of D0 results in this channel, as well as in ZZ-->l+l- nu[over]nu, yields a significance of 5.7 standard deviations and a combined cross section of sigma(ZZ)=1.60+/-0.63(stat)+0.16_-0.17(syst) pb.

Reduced antigenicity of formaldehyde-fixed arterial allografts and their potential clinical application

This study was performed to examine the antigenicity of formaldehyde-fixed arterial allografts and their potential clinical application for hemodialysis access. Human femoral arteries were fixed with formaldehyde. New Zealand white rabbits were immunized with antigens prepared from fixed or unfixed grafts followed by anti-serum collection. The antigenicity of fixed grafts was evaluated using double-diffusion in two dimensions. Seventy-six fixed allografts were transplanted into 50 patients with end-stage renal diseases as hemodialysis access and monitored for acute rejection, blood flow, and patency rates. Anti-HLA antibody was evaluated using a panel-reactive antibody (PRA) assay in 6 patients. Formaldehyde-fixed grafts demonstrated reduced antigenicity as determined using double-diffusion in two dimensions when compared with unfixed grafts. Histological evaluation of allografts demonstrated absence of cell-mediated acute rejection after transplantation. Allografts demonstrated satisfactory blood flow with primary and secondary patency rates at 1, 2, and 3 years after allotransplantation. Serum collected from 6 patients after transplantation (mean, 3.3 +/- 3.2 years) did not demonstrate increased anti-HLA antibody levels. The allograft intimal hyperplasia was characterized by proliferation of actin-expressing smooth muscle cells. This study demonstrated that formaldehyde fixation reduced the antigenicity of arterial allografts. Acute rejection was absent after allotransplantation. The lack of increased PRA levels after allotransplantation suggested that allo-sensitization is not induced by fixed allografts. The use of formaldehyde-fixed allografts as hemodialysis access demonstrated blood flow and patency rates. Intimal hyperplasia of allografts is characterized by proliferation of actin-expressing cells. Our results supported the clinical use of formaldehyde-fixed arterial allografts for hemodialysis access.

CD4+ T-cell and monocyte interdependence during discordant xenoimmune responses

This study was designed to examine our hypothesis that human monocytes provide missing constimulatory signals to host CD4+ cells during interactions with porcine endothelial cells (PECs). PECs were isolated from the aorta. Human CD4+ T cells and monocytes were purified from peripheral blood mononuclear cells (PBMCs). A xenogeneic mixed lymphocyte-PEC reaction (xMLER) was performed to determine the proliferation of PBMCs or CD4+ cells in response to PEC. Monocyte-PEC cocultures with or without CD4+ cells were followed by analysis using fluorescence-activated cell scanning (FACS). We evaluated the CD4+ cells proliferation induced by PEC-conditioned monocytes with or without costimulation blockade. xMLER demonstrated strong lymphocyte proliferation in response to PECs. However, purified CD4+ cells showed reduced proliferative responses to PECs when compared with PBMCs. FACS analysis found that CD14+ monocytes up-regulated CD40 and CD80 expressions in the presence of CD4+ cells. PEC-activated but not resting monocytes induced CD4+-cell proliferation, which was inhibited by anti-CD154, anti-CD80, or anti-CD86 antibodies. In summary, human monocytes exposed to PECs are conditioned to up-regulate costimulatory molecules upon exposure to T cells. PEC-conditioned monocytes induced T-cell proliferation by indirect presentation. Costimulation blockade inhibited T-cell proliferation induced by PEC-conditioned monocytes. Our findings suggested that monocytes play an important role in indirect xenoantigen presentation, providing costimulation to T cells. This interaction can occur distant from the initial site of xenoantigen, but monocytes remaide void of costimulatory signals until their interaction with T cells.

Prosaposin is an AR-target gene and its neurotrophic domain upregulates AR expression and activity in prostate stromal cells

Recent studies have introduced prosaposin (PSAP) as a pleiotrophic growth factor for prostate cancer (PCa). We have previously reported that PSAP or one of its known active molecular derivatives, saposin C functions as an androgen-agonist and androgen-regulated gene (ARG) for androgen-sensitive (AS) PCa cell lines. Due to the potential significance of androgen receptor (AR)-expressing stroma in PCa, we evaluated a possible bi-directional paracrine regulatory interactions between DHT and PSAP in AR-positive prostate stromal (PrSt) cells. We report that saposin C in a ligand-independent manner increased AR expression, its nuclear content, and tyrosine phosphorylation. DHT treatment of PrSt cells increased PSAP expression. We also demonstrated both serum- and androgen-inducibility of a previously characterized hormone-responsive element (HRE) located in the proximal region of PSAP promoter. In addition, conditioned-media derived from PrSt cells and bone fibroblasts (i.e., MSF) differentially increased PSAP-promoter activity in androgen-independent (AI) PC-3 and AS LNCaP cells. Our data for the first time demonstrate that not only saposin C or PSAP regulates AR expression/activity, but also function as an ARG in PrSt. Ligand-independent activation of AR by PSAP or saposin C in PCa and stromal cells may contribute not only to prostate carcinogenesis at an early stage, but also in AI progression of the disease in an androgen-deprived tumor microenvironment.