Suppressor cell activity in tumor-bearing mice. III. Co-purification of a factor inhibiting cellular DNA synthesis and DNA polymerase activity

The factor(s) derived from fibrosarcoma-induced suppressor T cells was sensitive to pronase and neuraminidase, but not to trypsin, beta-galactosidase, DNase, or RNase. Protein and RNA, but not DNA, synthesis were required to mediate suppression. Suppressor T cell-derived factor(s) could be precipitated by a 50% saturated ammonium sulfate (SAS) solution. The 50% SAS fraction inhibited both in vitro and in vivo spleen cell blastogenesis, whereas the 80% and unprecipitated fractions had no inhibitory activity. Using Sephadex G-200 chromatography, the 2nd protein fraction (fraction II) contained an inhibitor of both DNA polymerases (IDP) and DNA synthesis (IDS) activity, which possessed no cytotoxic activity. In vitro DNA polymerase alpha activity was suppressed by fraction II, whereas DNA polymerase beta and gamma activities remained unchanged. Molecular weight of IDP/IDS, as determined by Sephadex G-200 gel filtration chromatography, was approximately 14,500. Attempts to separate IDP/IDS activities found in fraction II by anion-exchange chromatography and slab gel electrophoresis were not successful, which suggested that the 2 activities were the same or very similar molecules.     

甘肃不同矿区样品中的细菌多样性

甘肃矿产资源丰富,矿区酸性矿坑水(acid mine drainage,AMD)及周边土壤中嗜酸微生物种类丰富,具有相当大的研究价值.本研究通过Illumina高通量测序方法,对甘肃省4个矿区AMD及周边土壤中的细菌群落组成、相似性及功能组成进行分析.结果 表明,煤矿样品GNM细菌物种组成最为丰富,金矿样品LNJ1与紫金矿样品LNZJK细菌组成最相似,与属于铜矿的BYT物种较相近,与LNJ1同地区的LNJ2样品细菌组成相比较远.所有样品细菌主要分为放线菌门(Actinobacteria)、拟杆菌门(Bacteriodetes)、厚壁菌门(Firmicutes)和变形菌门(Proteobacteria)四大门,其中变形菌门(Proteobacteria)丰度最高.放线菌门(Actinobacteria)中不动杆菌属(Acinetobacter)、类诺卡氏属(Nocardioides)和芽球菌属(Blastococcus)表现出较高丰度;厚壁菌门(Firmicutes)中微小杆菌属(Exiguobacterium)和芽孢杆菌属(Bacillus)表现出较高丰度,且微小杆菌属(Exiguobacterium)丰度极高.通过功能预测发现,与煤矿样品GNM相比,LNJ1、LNJ2、BYT和LNZJK4个金属矿区样品中的微生物具有较强的氨基酸与碳源的转运与代谢、转录等功能以及较低的能量生产与转运、无机离子转运与代谢能力.通过探究AMD中的细菌多样性及其与重金属之间的相互关系,了解AMD采样区微生物群落结构,以期挖掘出更为丰富的具有重金属抗性的菌株资源,以应用于生物浸矿和环境修复等领域.     

IL-12, but not IL-18, is critical to neutrophil activation and resistance to polymicrobial sepsis induced by cecal ligation and puncture

Sepsis is a systemic inflammatory response resulting from local infection due, at least in part, to impaired neutrophil migration. IL-12 and IL-18 play an important role in neutrophil migration. We have investigated the mechanism and relative role of IL-12 and IL-18 in polymicrobial sepsis induced by cecal ligation and puncture (CLP) in mice. Wild-type (WT) and IL-18(-/-) mice were resistant to sublethal CLP (SL-CLP) sepsis. In contrast, IL-12(-/-) mice were susceptible to SL-CLP sepsis with high bacteria load in peritoneal cavity and systemic inflammation (serum TNF-alpha and lung neutrophil infiltration). The magnitude of these events was similar to those observed in WT mice with lethal CLP sepsis. The inability of IL-12(-/-) mice to restrict the infection was not due to impairment of neutrophil migration, but correlated with decrease of phagocytosis, NO production, and microbicidal activities of their neutrophils, and with reduction of systemic IFN-gamma synthesis. Consistent with this observation, IFN-gamma(-/-) mice were as susceptible to SL-CLP as IL-12(-/-) mice. Moreover, addition of IFN-gamma to cultures of neutrophils from IL-12(-/-) mice restored their phagocytic, microbicidal activities and NO production. Mortality of IL-12(-/-) mice to SL-CLP was prevented by treatment with IFN-gamma. Thus we show that IL-12, but not IL-18, is critical to an efficient host defense in polymicrobial sepsis. IL-12 acts through induction of IFN-gamma and stimulation of phagocytic and microbicidal activities of neutrophils, rather than neutrophil migration per se. Our data therefore provide further insight into the defense mechanism against this critical area of infectious disease.     

Evidence that Early Carboniferous ostracods colonised coastal flood plain brackish water environments

A study of the stable isotope composition (δ¹⁸O, δ¹³C) of biogenic (ostracod, mollusc) and authigenic carbonates in the Ballagan Formation, Lower Carboniferous of Scotland, coupled with evidence from sedimentology and associated fossil fauna and flora, supports the argument that this formation was deposited in a coastal flood plain setting, in brackish (0.5 < 30‰ NaCl) and hypersaline (> 40‰ NaCl) waters, but in the absence of persistent normal marine conditions. The oxygen isotope data from the Ballagan Formation divide into three clusters: a diagenetic field defined by low δ¹⁸O (< − 11‰ VPDB); an intermediary field (δ¹⁸O − 11‰ to − 9‰) composed of a mixture of known primary and secondary (diagenetic) carbonates; and samples within the range of − 9‰ to − 4‰ which, as far as we can ascertain, are largely unaltered. No samples give typical Early Carboniferous δ¹⁸O marine values. Average marine carbonates from Europe have δ¹⁸O between − 4‰ to − 3‰. The Ballagan Formation carbonates were probably deposited in evaporated freshwater and/or brackish water. This conclusion is supported by the presence of evaporites (gypsum, anhydrite, halite pseudomorphs) and common desiccation-cracked mudstone surfaces throughout the Ballagan Formation, suggesting conditions of fluctuating salinity in ephemeral bodies of water. The stable isotope data support the notion that the ostracod assemblages of the Ballagan Formation were colonising brackish water and hypersaline ecologies on a coastal flood plain during the Early Carboniferous, a stage of development that may have encouraged their colonisation of fully non-marine (limnetic) environments during the later Carboniferous. The ostracods include cytherellacean and kloedenellacean species known from marginal marine sites elsewhere, but probably tolerant of brackish water, podocopid species such as ‘Bythocypris’ aequalis that may have been adapted for brackish water settings on coastal flood plains (ephemeral lakes and lagoons), and paraparchitacean-dominated assemblages that may signal harsh (hypersaline or desiccating) environments.     

Left-handed Z-DNA

Since the Watson-Crick proposal of right-handed B-DNA, numerous studies have been devoted to the conformation of DNA. Both natural DNAs of heterogeneous sequences and synthetic DNAs are capable of adopting more than one conformation. The specific conformation a DNA adopts appears to depend mainly on its base sequence and its environmental conditions. For a given DNA, changes in environmental conditions can induce conformational transitions which occur according to cooperative or non-cooperative processes (for general reviews see Ref. 1a, b). Despite many results, molecular biologists did not put much emphasis on the polymorphism of DNA. The discovery of the intraconversion in helical sense between the right-handed B and left-handed Z conformers of DNA has brought a new interest in the polymorphism of DNA. It is now proposed that this polymorphism has important functions in biological reactions. A recent review, 'The Chemistry and Biology of Left-handed Z-DNA', by Rich et al. has just been published. We here report some of the results published in 1984 on Z-DNA.