Interference Effect between ϕ and Λ(1520) Production Channels in the γp→K

The ϕ-Λ(1520) interference effect in the γp→K^{+}K^{-}p reaction has been measured for the first time in the energy range from 1.673 to 2.173 GeV. The relative phases between ϕ and Λ(1520) production amplitudes were obtained in the kinematic region where the two resonances overlap. The measurement results support strong constructive interference when K^{+}K^{-} pairs are observed at forward angles but destructive interference for proton emission at forward angles. Furthermore, the observed interference effect does not account for the sqrt[s]=2.1 GeV bump structure in forward differential cross sections for ϕ photoproduction. This fact suggests possible exotic structures such as a hidden-strangeness pentaquark state, a new Pomeron exchange, or rescattering processes via other hyperon states.

Near-threshold Lambda(1520) production by the gamma(p)-->K{+}Lambda(1520) reaction at forward K+ angles.

Differential cross sections and photon-beam asymmetries for the gamma(p)-->K{+}Lambda(1520) reaction have been measured with linearly polarized photon beams at energies from the threshold to 2.4 GeV at 0.6or=5/2 or by a new reaction process, for example, an interference effect with the phi photoproduction having a similar bump structure in the cross sections.

Near-threshold photoproduction of Lambda(1520) from protons and deuterons.

Photoproduction of Lambda(1520) with liquid hydrogen and deuterium targets was examined at photon energies below 2.4 GeV in the SPring-8 LEPS experiment. For the first time, the differential cross sections were measured at low energies and with a deuterium target. A large asymmetry of the production cross sections from protons and neutrons was observed at backward K+/0 angles. This suggests the importance of the contact term, which coexists with t-channel K exchange under gauge invariance. This interpretation was compatible with the differential cross sections, decay asymmetry, and photon beam asymmetry measured in the production from protons at forward K+ angles.

Cross sections and beam asymmetry for K;{+}Sigma;{*-} photoproduction from the deuteron at E_{gamma}=1.5-2.4 GeV.

The Sigma(1385) resonance, or Sigma;{*}, is well known as part of the standard baryon decuplet with spin J=3/2. Measurements of the reaction gammap-->K;{+}Sigma;{*0} are difficult to extract due to overlap with the nearby Lambda(1405) resonance. However, the reaction gamman-->K;{+}Sigma;{*-} has no overlap with the Lambda(1405) due to its charge. Here we report the first measurement of cross sections and beam asymmetries for photoproduction of the Sigma;{*-} from a deuteron target. The cross sections at forward angles range from 0.4 to 1.2 mub, with a broad maximum near E_{gamma} approximately 1.8 GeV. The beam asymmetries are negative, in contrast with positive values for the gamman-->K;{+}Sigma;{-} reaction.

Differential cross section and photon-beam asymmetry for the gamma n --> K+ Sigma- reaction at E gamma = 1.5-2.4 GeV.

Differential cross sections and photon-beam asymmetries have been measured for the gamma n --> K+ Sigma- and gamma p --> K+Sigma0 reactions separately using liquid deuterium and hydrogen targets with incident linearly polarized photon beams of E gamma = 1.5-2.4 GeV at 0.6 < cos ThetacmK< 1. The cross section ratio of sigma K+ Sigma-/sigma K+ Sigma0, expected to be 2 on the basis of the isospin 1/2 exchange, is found to be close to 1. For the K+ Sigma- reaction, large positive asymmetries are observed, indicating the dominance of K* exchange. The large difference between the asymmetries for the K+ Sigma- and K+ Sigma0 reactions cannot be explained by simple theoretical considerations based on Regge model calculations.

Near-threshold diffractive psi-meson photoproduction from the proton.

Photoproduction of a phi meson on protons was studied by means of linearly polarized photons at forward angles in the low-energy region from threshold to Egamma = 2.37 GeV. The differential cross sections at t = -|t|min do not increase smoothly as Egamma increases but show a local maximum at around 2.0 GeV. The angular distributions demonstrate that phi mesons are photoproduced predominantly by helicity-conserving processes, and the local maximum is not likely due to unnatural-parity processes.

Beam-polarization asymmetries for the p(gamma-->, K+)Lambda and p(gamma-->, K+)Sigma(0) reactions for E(gamma)=1.5-2.4 GeV.

Beam polarization asymmetries for the p(gamma-->,K+)Lambda and p(gamma-->,K+)Sigma(0) reactions are measured for the first time for E(gamma)=1.5-2.4 GeV and 0.6

Evidence for a narrow S = +1 baryon resonance in photoproduction from the neutron.

The gamman-->K(+)K(-)n reaction on 12C has been studied by measuring both K+ and K- at forward angles. A sharp baryon resonance peak was observed at 1.54+/-0.01 GeV/c(2) with a width smaller than 25 MeV/c(2) and a Gaussian significance of 4.6sigma. The strangeness quantum number (S) of the baryon resonance is +1. It can be interpreted as a molecular meson-baryon resonance or alternatively as an exotic five-quark state (uuddsmacr;) that decays into a K+ and a neutron. The resonance is consistent with the lowest member of an antidecuplet of baryons predicted by the chiral soliton model.

CD70 expression in thymic carcinoma.

CD70, a type II transmembrane glycoprotein, is a member of the tumor necrosis factor (TNF) family that mediates the interaction between B- and T-lymphocytes. CD70 has been shown to be expressed by malignant lymphoma, especially Hodgkin's disease, and by nasopharyngeal carcinoma, both of which are frequently associated with Epstein-Barr virus (EBV). In this study, we investigated the expression of CD70 in epithelial cells of various types of thymic epithelial tumors and its association with EBV. Immunohistochemical expression of CD70 was studied on frozen tissue. In a series of 27 thymic epithelial tumors, including thymic carcinomas (n = 8), atypical thymomas (n = 5), thymomas (n = 13), and thymic carcinoid (n = 1), 7 (88%) thymic carcinomas and 1 (20%) atypical thymoma showed positive immunoreactivity for CD70, whereas CD70 was not detected in other tumors. Twenty-four intrathoracic malignant epithelial tumors of nonthymic origin, including lung (n = 17), esophagus (n = 5), and mesothelium (n = 2), showed no immunoreactivity for CD70. Northern blot analysis also revealed that CD70 messenger RNA was expressed in 2 of 2 thymic carcinomas, 0 of 2 atypical thymomas. and 0 of 2 thymomas. All of the 27 thymic epithelial tumors were EBV-negative as assessed by EBV-encoded small RNA in situ hybridization. The expression of CD70 is closely related to the pathogenesis of thymic carcinoma but unrelated to EBV infection in the thymus.

Molecular genetic analysis and mutation screening of the VHL gene in a Japanese family with von Hippel-Lindau disease.

Von Hippel-Lindau (VHL) disease is an autosomal dominantly inherited familial cancer syndrome which predisposes individuals to a variety of malignant and benign tumors. Its penetrance is almost 100% by 61-70 years of age. We have identified a germline mutation in the VHL gene of a Japanese male patient with a retinal hemangioma in the left eye, an intracranial hemangioblastoma, a left renal tumor and bilateral pheochromocytomas. Screening for the mutation was performed in all members of the patient's family at risk for VHL disease. The mutation identified in the patient was a missense mutation at codon 238 (CGG to CAG). The elder daughter, who did not show any clinical symptoms, was found to carry the same mutation. In order to detect and treat tumors in VHL patients at an earlier stage, it is necessary to identify and screen for the VHL gene mutation in all family members known at risk.

Pyothorax-associated lymphoma: development of Epstein-Barr virus-associated lymphoma within the inflammatory cavity.

Pyothorax-associated lymphoma (PAL) is a B cell lymphoma that develops in Japanese patients with tuberculosis-associated chronic pyothorax (TaCP). Epstein-Barr virus (EBV) has been shown to be causally related to PAL. To clarify the developmental process of PAL, the systemic and local presence of EBV, and serum profile of anti-EBV antibodies was investigated in TaCP. EBV genome was found in peripheral blood mononuclear cells by PCR in a 10(-4)-10(-5) amount of Raji cell-DNA in three of four patients with TaCP, but was also identified in patients with pyothorax caused by other diseases (2/2) or without pulmonary diseases (2/6). EBER1 in situ hybridization and EBNA2 immunocytochemistry revealed clusters of EBV-carrying cells in the cavity content (3/18) but not at the pyothorax wall; EBV(+) histological lymphoma cells were found in two cases and EBV(+) mononuclear cells were found in one case. A simultaneous increase in serum titers of anti-EBV viral capsid antigen IgG and IgA antibodies was observed in TaCP (4/16). These results suggest that a local factor, an inflammatory cavity, has a pivotal role in the development of PAL, which might be reflected in the serum titers of anti-EBV antibodies in patients with TaCP.

Epstein-Barr virus-associated gastric carcinoma and Epstein-Barr virus infection of the stomach.

BACKGROUND: Epstein-Barr virus (EBV) has been found to be associated with a type of gastric carcinoma (EBVaGC). However, many questions remain unanswered, such as epidemiology, and pathologic features of EBVaGC and the significance of EBV in the genesis of EBVaGC. EXPERIMENTAL DESIGN: Gastric carcinoma and non-neoplastic mucosa were evaluated to reveal the following issues: the incidence of EBVaGC in Japanese population, pathologic features and EBV genotype, clonality, and gene-expression in EBVaGC, localization of EBV in non-neoplastic stomach, and serum titer of anti-EBV antibodies in EBVaGC-carrying patients. RESULTS: Using PCR and EBER1 in situ hybridization, EBVaGC (definitely amplifiable EBV-DNA and positive EBER1-signal in the nuclei of carcinoma cells) was found in 8 of 72 gastric carcinomas (11%). The dominant genotype of EBV was type A (7/8), with type C (6/8), and F (8/8) restriction enzyme polymorphism, which are the predominant type of EBV found in throat washing of the general population in Japan. EBVaGC was found in the cardia (4/8) or body (4/8) of the stomach, and consisted of 7 advanced and 1 intramucosal carcinoma. By Southern blot analysis of EBVaGC hybridized with right- and left-side probe adjacent to the terminal repeats, EBV was present in a monoclonal episomal form in all of the EBVaGC. EBVaGC lacked expression of EBNA2 (0/8) and LMP1 (0/8) by immunocytochemistry. In non-neoplastic mucosa, EBER1 signal was identified in the infiltrating lymphocytes and shedding epithelial cells predominantly in fundic gland mucosa of patients with EBVaGC (8/8). Patients with EBVaGC showed high titers of anti-VCA IgG (8/8), anti-VCA IgA (2/8) and anti-EA IgG (7/8) antibodies just before surgery. CONCLUSIONS: EBV may infect the surface epithelium of the stomach through the reactivated EBV-carrying lymphocytes. EBV may be a factor initiating EBVaGC. Anti-EBV antibodies or EBER1 in situ hybridization may help to identify patients at high risk for EBVaGC.

Epstein-Barr virus in pyothorax-associated pleural lymphoma.

Pleural B-cell lymphoma was found in five patients with a history of pyothorax that was the sequelae of tuberculosis 35 to 47 years previously. Epstein-Barr virus (EBV) DNA was detected in all five pleural tumors by polymerase chain reaction and Southern blot hybridization. The lymphoma cells were shown to express the latent membrane protein-1 and the EBV-encoded nuclear antigen-2 by immunocytochemistry and EBV-encoded small RNA by in situ hybridization. Three cases were shown to be EBV subtype A, whereas the remaining two were subtype B, as determined by differences in the EBV-encoded nuclear antigen-2 nucleotide sequence. The patients also had high titers of antibodies against EBV. These findings suggest that EBV is causally associated with the pleural lymphomas that originate at the site of chronic inflammation and fibrosis with a latent period of more than 40 years.

The structure of HLA-B35 suggests that it is derived from HLA-Bw58 by two genetic mechanisms.

The primary structure of HLA-B51 and HLA-Bw52 suggested that HLA-B51 was derived from HLA-Bw52 by the combination of a genetic exchange with HLA-B8 and a point mutation. To investigate the evolution of the HLA-B5 cross reactive group, the HLA-B35 gene was cloned and the primary structure was determined. HLA-B35 is identical to HLA-Bw58 except in the alpha 1 domain. The alpha 1 domain of HLA-B35 except Bw4/Bw6-associated amino acids is identical to that of HLA-B51, which was suspected to be an intermediate gene between HLA-B51 and HLA-Bw52. These data suggest that HLA-B35 has evolved from HLA-Bw58 in two steps; an in vivo replacement of the alpha 1 domain with HLA-B51 and genetic exchange with one of the HLA-Bw6 genes. These three genes and HLA-Bw58 are postulated to share a common ancestor. As HLA class I molecules of a serologically cross-reactive group (CREG) have limited polymorphism, we suspected they might have evolved from a common ancestor. In fact, the structures of HLA-B51 and HLA-Bw52 in HLA-B5 CREG demonstrate that they differ by only two amino acids. Both substitutions are in the helical region of the alpha 1 domain and suggest that HLA-B51 could be derived from HLA-Bw52 by the combination of a genetic exchange with HLA-B8 and a point mutation (Hayashi et al. 1989). HLA-B35 belongs to the HLA-B5 CREG and is serologically related to Bw6, while HLA-B5 (B51 and Bw52) is related to Bw4. HLA-B35 is serologically closer to HLA-B51 than to HLA-Bw52. Therefore, we have cloned a genomic gene of HLA-B35 and determined its structure to study further the evolution of the HLA-B5 family.

Separation and determination of selenium in rocks, marine sediments and plankton by direct evolution with the bromide-condensed phosphoric acid reagent.

A new method is presented for the quantitative separation and determination of selenium by direct evolution with the bromide-condensed phosphoric acid reagent (Br(-)-CPA) from rocks, marine sediments and plankton. In the reaction with the Br(-1)-CPA, selenium(IV) and (VI) in the solid samples are evolved as selenium tetrabromide, and can be collected in an absorbing solution of 0.3M hydrochloric acid and 06M perchloric add (1:1), and then determined spectrophotometrically with 4-substituted o-phenylenediamines followed by the extraction of the resulting 5-substituted piazselenol into toluene. Elemental selenium and selenide do not react with the Br(-)-CPA, but can be determined after oxidation to selenite with potassium iodate. Therefore, successive distillations, the first with Br(-)-CPA and the second with IO(3)(-)-Br(-)-CPA, give a satisfactory means of diflerential determination of selenium(IV) and (VI), and elemental selenium and selenide. This method can be successfully applied for the separation of selenium in the neutron-activation analysis of standard rock samples, marine sediments and plankton, giving good and reliable results.