Towards cellular receptors for prions

Transmissible spongiform encephalopathies (TSE) are attributed to the conversion of the cellular prion protein (PrP(c)) into an abnormal isoform (PrP(sc)). This can be caused by the invasion of living organisms by infectious particles, or be inherited due to mutations on the PrP(c) gene. One of the most intriguing problems of prion biology is the inability to generate the infectious agent in vitro. This argues strongly that other cellular proteins besides those added in test tubes or found in cellular preparations are necessary for infection. Despite recent progress in the understanding of prion pathology, the subcellular compartments in which the interaction and conversion of PrP(c) into PrP(sc) take place are still controversial. PrP(c) interacts with various macromolecules at the cell membrane, in endocytic compartments and in the secretory pathway, all of which may play specific roles in the internalisation of PrP(sc) and conversion of PrP(c). A specific interacting protein required for the propagation of prions was originally proposed as a prion receptor, and later referred to as a ligand, a cofactor, protein X, or a partner. However, current studies indicate that PrP(c) associates with multi-molecular complexes, which mediate a variety of functions in distinct cellular compartments. It is proposed that a deeper understanding of the mechanics of such interactions, coupled to a better knowledge of the corresponding signalling pathways and ensuing cellular responses, will have a major impact on the prevention and treatment of TSE.     

Immunohistochemical study of nasopharyngeal carcinoma using monoclonal keratin antibodies

Nasopharyngeal carcinoma (NPC) provides a unique opportunity to evaluate distinctive epidemiologic features and a possible etiologic relationship with Epstein-Barr virus (EBV) in human malignancy. The lack of a uniformly accepted pathologic classification for NPC has limited the application of this data, although the World Health Organization (WHO) developed a classification that may solve this problem. Monoclonal keratin antibodies were used for staining of NPC for evaluation of its assistance in diagnosis and classification. In the present immunohistochemical study, monoclonal keratin antibodies, designated AE1, AE2, and AE3, and a polyclonal keratin antibody (RAK) were used for study of the presence of keratin in 121 cases of NPC obtained from China and the United States. AE1 monoclonal antibody, which recognizes keratin protein classes 56.5K, 50K, and 40K, was shown to be the most sensitive and specific for NPC tumor cells among the keratin antibodies studied. In addition, some different keratin expression patterns could be identified between different kinds of epithelium and different tumor groups, with possible relevance to the histogenesis of the histologic subtypes of NPC.     

IL-12p40-overexpressing immature dendritic cells induce T cell hyporesponsiveness in vitro but accelerate allograft rejection in vivo: role of NK cell activation and interferon-gamma production

Infusion of genetically modified dendritic cells (DC) expressing immunosuppressive molecules is a potential therapy for organ rejection. IL-12p70, a cytokine produced mainly by DC and macrophages, consists of two subunits, p40 and p35. IL-12p70 is an activator of T cells, while the IL-12p40 subunit serves as a natural antagonist for IL-12p70 action. The primary aim of this study was to evaluate the effect of IL-12p40 gene-modification on both the T-cell stimulatory activity of immature DC (imDC) and their ability to prolong cardiac allograft survival. IL-12p40 gene-modified imDC (DC-p40) exhibited a phenotype characteristic of imDC and displayed impaired T-cell allostimulatory ability in vitro. However, to our surprise, for murine vascularized heterotopic heart transplantation (HHT), administration of donor-derived DC-p40 7 days prior to transplantation did not prolong allograft survival but instead significantly exacerbated cardiac allograft rejection. Further study showed that DC-p40 augmented NK cell activity both in vitro and in vivo and enhanced interferon-gamma (IFN-gamma) production in vivo, which might be due to the increased IL-23 production by DC-p40. Our data suggested that although IL-12p40 gene-modified immature DC can induce T cell hyporesponsiveness in vitro, their ability to activate NK cells and induce IFN-gamma production counterbalances this, exacerbating cardiac allograft rejection. The unexpected effects of DC-p40 limit their value in promoting allograft survival in vivo and likely reflect the complexity of IL-12p40 biology.     

大鼠肝抑素纯化及其生物活性的检测

用ＳｅｐｈａｄｅｃＧ－５凝胶过滤层析法，进一步纯化具肝抑素生物活性的大鼠肝蛋白质粗提品，以分离的大鼠再生肝的肝细胞为靶细胞，体外检测各洗脱峰浓缩物对肝细胞增殖的制率结果证明，Ｅ峰浓缩物的抑制作用最强，其活性比为粗提品的２０倍，ＳＤＳ聚丙烯酰胺电泳图及蛋白质迁移率测定表明，该浓缩物的主要成分为分子量１３．５ｋＤ的多肽。本研究对大鼠肝抑素做了初步纯化，验证了该物质在肝再生中起重要调控作用的生物效应。     

显性遗传性聋─大家系研究

本文报告江苏省淮阴县运南地区方氏家族六代６８３人的系谱、皮纹学、染色体和ＡＢＯ血型等遗传学方法的调查与检测，确定属常染色体显性遗传性聋患者１３７例。经检索这是我国首例显性遗传性聋大家系，亦是国际上的第三例聋人大家系的报告。     

Analysis of 8-hydroxydeoxyguanosine 5'-monophosphate (8-OH-dGMP) as a reliable marker of cellular oxidative DNA damage after gamma-irradiation

In order to improve 8-hydroxyguanine (8-OH-Gua) detection in DNA, we digested isolated DNA with nuclease P1 and analyzed for 8-hydroxydeoxyguanosine 5'-monophosphate (8-OH-dGMP) using a high-performance liquid chromatography system equipped with an electrochemical detector (HPLC-ECD). The amount of 8-OH-Gua in the DNA was expressed as the ratio of 8-OH-dGMP to deoxycytidine monophosphate (dCMP). Using this analysis, the background level of 8-OH-Gua in DNA from human lung carcinoma cells (A549) was several-fold lower than that obtained by a previous method. A549 cells were exposed to 20-60 Gy of gamma-radiation and an increase in 8-OH-Gua concentration was observed with increasing gamma-ray dose (0.3 residues per 10(7) dCMP per Gy). Moreover, by an immunohistochemical procedure using a commercial FITC-kit, 8-OH-Gua was clearly detected in A549 cells and the fluorescence intensity of cells with oxidative DNA damage increased with the doses of gamma-irradiation. Using an endonuclease nicking assay, we also found that gamma-rays decreased 8-OH-Gua repair activity. The results indicate that 8-OH-dGMP is a useful and sensitive marker for estimating oxidative damage in DNA.