Elastic scattering of low energy pions by nuclei and the in-medium isovector pi N amplitude

Measurements of elastic scattering of 21.5 MeV pi+ and pi- by Si, Ca, Ni and Zr were made using a single arm magnetic spectrometer. Absolute calibration was made by parallel measurements of Coulomb scattering of muons. Parameters of a pion-nucleus optical potential were obtained from fits to all eight angular distributions put together. The `anomalous' s-wave repulsion known from pionic atoms is clearly observed and could be removed by introducing a chiral-motivated density dependence of the isovector scattering amplitude, which also greatly improved the fits to the data. The empirical energy dependence of the isoscalar amplitude also improves the fits to the data but, contrary to what is found with pionic atoms, on its own is incapable of removing the anomaly.Comment: 20 pages, 5 figures, 5 tables. V2 added details on uncertainties,extended discussion. To appear in PR

The in-medium isovector pi N amplitude from low energy pion scattering

Differential cross sections for elastic scattering of 21.5 MeV positive and negative pions by Si, Ca, Ni and Zr have been measured as part of a study of the pion-nucleus potential across threshold. The `anomalous' repulsion in the s-wave term was observed, as is the case with pionic atoms. The extra repulsion can be accounted for by a chiral-motivated model where the pion decay constant is modified in the medium. Unlike in pionic atoms, the anomaly cannot be removed by merely introducing an empirical on-shell energy dependence.Comment: 9 pages, 2 figures. Minor changes, to appear in PR

Pionic charge exchange on the proton from 40 to 250 MeV

The total cross sections for pionic charge exchange on hydrogen were measured using a transmission technique on thin CH2 and C targets. Data were taken for pi- lab energies from 39 to 247 MeV with total errors of typically 2% over the Delta-resonance and up to 10% at the lowest energies. Deviations from the predictions of the SAID phase shift analysis in the 60 to 80 MeV region are interpreted as evidence for isospin-symmetry breaking in the s-wave amplitudes. The charge dependence of the Delta-resonance properties appears to be smaller than previously reported

Low Energy Analyzing Powers in Pion-Proton Elastic Scattering

Analyzing powers of pion-proton elastic scattering have been measured at PSI with the Low Energy Pion Spectrometer LEPS as well as a novel polarized scintillator target. Angular distributions between 40 and 120 deg (c.m.) were taken at 45.2, 51.2, 57.2, 68.5, 77.2, and 87.2 MeV incoming pion kinetic energy for pi+ p scattering, and at 67.3 and 87.2 MeV for pi- p scattering. These new measurements constitute a substantial extension of the polarization data base at low energies. Predictions from phase shift analyses are compared with the experimental results, and deviations are observed at low energies.Comment: 15 pages, 4 figure

pi+- p differential cross sections at low energies

Differential cross sections for pi- p and pi+ p elastic scattering were measured at five energies between 19.9 and 43.3 MeV. The use of the CHAOS magnetic spectrometer at TRIUMF, supplemented by a range telescope for muon background suppression, provided simultaneous coverage of a large part of the full angular range, thus allowing very precise relative cross section measurements. The absolute normalisation was determined with a typical accuracy of 5 %. This was verified in a simultaneous measurement of muon proton elastic scattering. The measured cross sections show some deviations from phase shift analysis predictions, in particular at large angles and low energies. From the new data we determine the real part of the isospin forward scattering amplitude.Comment: 13 pages, 5 figures. To appear in PL

Urochordate Histoincompatible Interactions Activate Vertebrate-Like Coagulation System Components

The colonial ascidian Botryllus schlosseri expresses a unique allorecognition system. When two histoincompatible Botryllus colonies come into direct contact, they develop an inflammatory-like rejection response. A surprising high number of vertebrates' coagulation genes and coagulation-related domains were disclosed in a cDNA library of differentially expressed sequence tags (ESTs), prepared for this allorejection process. Serine proteases, especially from the trypsin family, were highly represented among Botryllus library ortholgues and its “molecular function” gene ontology analysis. These, together with the built-up clot-like lesions in the interaction area, led us to further test whether a vertebrate-like clotting system participates in Botryllus innate immunity. Three morphologically distinct clot types (points of rejection; POR) were followed. We demonstrated the specific expression of nine coagulation orthologue transcripts in Botryllus rejection processes and effects of the anti-coagulant heparin on POR formation and heartbeats. In situ hybridization of fibrinogen and von Willebrand factor orthologues elucidated enhanced expression patterns specific to histoincompatible reactions as well as common expressions not augmented by innate immunity. Immunohistochemistry for fibrinogen revealed, in naïve and immune challenged colonies alike, specific antibody binding to a small population of Botryllus compartment cells. Altogether, molecular, physiological and morphological outcomes suggest the involvement of vertebrates-like coagulation elements in urochordate immunity, not assigned with vasculature injury

Upregulation of Cellular Bcl-2 by the KSHV Encoded RTA Promotes Virion Production

Apoptosis of virus infected cells can restrict or dampen full blown virus propagation and this can serve as a protective mechanism against virus infection. Consequently, viruses can also delay programmed cell death by enhancing the expression of anti-apoptotic proteins. Human Bcl-2 is expressed on the surface of the mitochondrial membrane and functions as the regulator of the delicate balance between cell survival and apoptosis. In this report, we showed that the replication and transcription activator (RTA) encoded by KSHV ORF 50, a key regulator for KSHV reactivation from latent to lytic infection, upregulates the mRNA and protein levels of Bcl-2 in 293 cells, and TPA-induced KSHV-infected cells. Further analysis revealed that upregulation of the cellular Bcl-2 promoter by RTA is dose-dependent and acts through targeting of the CCN9GG motifs within the Bcl-2 promoter. The Bcl-2 P2 but not the P1 promoter is primarily responsive to RTA. The results of ChIP confirmed the direct interaction of RTA protein with the CCN9GG motifs. Knockdown of cellular Bcl-2 by lentivirus-delivered small hairpin RNA (shRNA) resulted in increased cell apoptosis and decreased virion production in KSHV-infected cells. These findings provide an insight into another mechanism by which KSHV utilizes the intrinsic apoptosis signaling pathways for prolonging the survival of lytically infected host cells to allow for maximum production of virus progeny

Expression of the proapoptotic protein Bid is an adverse prognostic factor for radiotherapy outcome in carcinoma of the cervix

The Bcl-2 family of apoptotic regulators is thought to play an essential role in cancer development and influence the sensitivity of tumour cells to radiotherapy. Bid is an abundantly expressed Bcl-2 family protein playing a central role in various pathways of apoptosis by integrating and converging signals at the mitochondria. The relevance of apoptotic modulation by Bcl-2 and related proteins in tumour development and radiation response for human tumours remains undefined. Therefore, a study was made regarding the expression of Bid in patients with locally advanced cervix carcinoma who received radiotherapy. Bid expression was assessed using immunohistochemistry in pretreatment archival biopsies from 98 patients. The data were correlated with clinicopathologic characteristics and treatment outcome. Pretreatment tumour radiosensitivity data were available for 60 patients. Strong Bid expression was associated with a patient age less than the median of 52 years (P=0.034) and poor metastasis-free survival. In multivariate analysis, after allowing for stage, Bid expression was a significant prognostic factor for both disease-specific and metastasis-free survival (P=0.026). It is concluded that strong tumour Bid expression is associated with poor outcome following radiotherapy regardless of intrinsic tumour cell radiosensitivity, and is adverse prognostic for disease-specific and metastasis-free survival in younger patients