Role of follicular dendritic cells in the early HIV-1 infection: in vitro model without specific antibody

About 90% of HIV-1 RNA in the lymph nodes is reported to localize in follicular dendritic cellsnetwork (FDC-NW) as early as several days after infection and as much as that in the late stage. But the mechanism remains to be fully understood. To elucidate the role of follicular dendritic cells (FDC) in the early stage of HIV-1 infection, FDC-like cell strains (FDCLC) were established and they were characterized in the co-culture system with T cells for their effect on HIV-1 trapping and replication in p24 immunoassay, immunohistochemistry as well as confocal and electronmicroscopy. Established FDCLC were positive for CNA-42, S-100alpha and intercellular desmosome-like junctions. L-SIGN and DC-SIGN were also detected in FDCLC. Alu-HIV-1 PCR analysis showed no HIV-1 integration in FDCLC. FDCLC trapped HIV-1 and transferred them to uninfected MOLT-4 T cells (MOLT-4) efficiently in the absence of specific antibody. FDCLC also accelerated HIV-1 replication in HIV-1-pre-exposed MOLT-4. These unique FDCLC effects were explained, at least partly, by the fact that FDCLC up-regulated CD4 expression in MOLT-4 and helped T cells escape from apoptosis in the co-culture. These data suggest that FDC/FDCLC engage not only in trapping but also in active expansion of HIV-1 in the absence of specific antibody.     

Human follicular dendritic cells and fibroblasts share the 3C8 antigen

Although the pivotal role of follicular dendritic cells (FDCs) in humoral immune responses has been demonstrated, little is known of the molecular basis of biological functions and the cellular origin of FDC. We have recently generated a monoclonal antibody (mAb) against FDC by immunizing mice with FDC-like tonsillar stromal cells. The mAb 3C8 does not cross-react with bone marrow-derived blood cells. Partial amino acid sequencing revealed that 3C8 Ag is a novel human protein. In this study, we carried out a detailed analysis of 3C8 immunoreactivity with tonsil sections to examine cellular distribution of 3C8 Ag. 3C8 Ab recognized connective tissue fibroblasts in addition to FDC. Western blot analysis indicated that 3C8 antigen is expressed in various fibroblasts and is specific to human species. Furthermore, there was a correlation between 3C8 expression in several stromal cell lines and their co-stimulatory activity of germinal center B cell proliferation. These findings strongly support the view that FDCs originate from local fibroblasts.     

人干细胞因子受体c-Kit稳定表达细胞株的构建

 干细胞因子 (SCF)是一种重要的造血因子 ,其受体c Kit具有酪氨酸激酶活性 .SCF c Kit介导的细胞内信号转导在造血、肥大细胞的生成及其功能、以及生殖细胞和黑色素细胞的发育中起着关键的作用 .通过构建人c kitcDNA的pcDNA3.1真核表达载体 ,转染不表达人c kit的小鼠髓系祖细胞FDC P1.经Zeocin抗性筛选 ,PCR、RT PCR、Western印迹分析、流式细胞仪分析等方法检测到人c kit基因的稳定整合和表达 ,并分布于细胞表面 ,证明获得了稳定表达人c Kit受体的细胞株 .用MTT法检测重组细胞株增殖特性 ,表明重组人SCF可刺激其增殖 .为进一步研究人c Kit受体介导的细胞内信号转导及检测重组人干细胞因子生物学活性提供了有效的细胞模型     

ENVIRONMENTAL CONTROL OF STALK LENGTH IN THE BLOOM‐FORMING,FRESHWATER BENTHIC DIATOM DIDYMOSPHENIA GEMINATA (BACILLARIOPHYCEAE)1

Blooms of the freshwater stalked diatom Didymosphenia geminata (Lyngb.) M. Schmidt in A. Schmidt typically occur in oligotrophic, unshaded streams and rivers. Observations that proliferations comprise primarily stalk material composed of extracellular polymeric substances (EPS) led us to ask whether or not the production of excessive EPS is favored under nutrient‐limited, high‐light conditions. We conducted experiments in outdoor flumes colonized by D. geminata using water from the oligotrophic, D. geminata–affected Waitaki River, South Island, New Zealand, to determine the relationship between D. geminata stalk length, cell division rates, and light intensity under ambient and nutrient‐enriched conditions. Stalk lengths were measured in situ, and cell division rates were estimated as the frequency of dividing cells (FDC). FDC responded positively to increasing light intensity and to nutrient additions (N+P and P). Under ambient conditions, stalk length increased as light level increased except at low ambient light levels and temperature. Nutrient enrichment resulted in decreased stalk length and negative correlations with FDC, with this effect most evident under high light. Our results are consistent with the hypothesis that extensive stalk production in D. geminata occurs when cell division rates are nutrient limited and light levels are high. Thus, photosynthetically driven EPS production in the form of stalks, under nutrient‐limited conditions, may explain the development of very high biomass in this species in oligotrophic rivers. The responses of FDC and stalk length under nutrient‐replete conditions are also consistent with occurrences of D. geminata as a nondominant component of mixed periphyton communities in high‐nutrient streams.     

RELATIONSHIP BETWEEN THE NUMBER OF DIVIDING AND NONDIVIDING CELLS OF CYANOBACTERIA IN NORTH ATLANTIC PICOPLANKTON1

In the North Atlantic over a wide geographic region that includes various oceanic regimes and a temperature range from 10 to 22° C, an increase in the number of nondividing Synechococcus cells (X) was generally accompanied by a greater-than-proportional increase in the number of dividing cells (Y). As a result, the fraction of dividing cells (FDC = Y · (Y + X)^?1) was positively related to population size (Y + X). Recognizing that FDC is generally greater in a rapidly growing population than in a slowly growing one, our empirical finding implies a positive correlation between specific growth rate and standing stock for Synechococcus. One notable exception occurred during winter (T < 5°C) in a eutrophic coastal embayment when a decrease in cell abundance was not matched by a decrease in FDC.     

水利工程对坝下径流的影响——以葛洲坝、三峡水利枢纽为例

水利工程建设在给人类带来抗旱防洪效益、发电效益、航运效益、养殖等效益的同时,也对河流水文动态产生了一系列的影响,主要表现为对径流的调节。基于宜昌站1890—2014年径流数据,综合采用径流集中度、集中期和相位差分析等多种方法,分析了水利工程建设对径流年内分配以及枯水期的影响。结果表明:宜昌站径流集中度呈现缓慢下降趋势并在2004年发生突变,2003年以后径流集中度相对于2003年以前下降0.06(下降幅度为12.98%),说明葛洲坝水利枢纽、三峡工程建成以后宜昌站径流在年内分配变得平缓,洪峰被有效削弱,且三峡工程对宜昌站径流集中度减少的贡献率大于葛洲坝水利枢纽(贡献率分别为92.03%和7.97%);葛洲坝和三峡水利枢纽建成后,宜昌站径流重心提前8d(集中期从8月9日提前至7月31日);宜昌站进入枯水期的时间提前约20d(三峡大坝建设以前,宜昌站在12月7—11日进入枯水期,建设以后在11月底进入枯水期),水利工程对水文过程的影响可能导致下游枯水期污染加剧和湿地生境提前缩小,进而影响下游水环境和湿地生物多样性。上述结果定量揭示了水利工程对水文过程的影响及其潜在生态效应,可为认识水利工程的生态影响以及流域生态环境变化的驱动因素提供科学依据。     

Proteomic analysis of B-cell malignancies

The identification of proteins aberrantly expressed in malignant B-cells can potentially be used to develop new diagnostic, prognostic or therapeutic targets. Proteomic studies of B-cell malignancies have made significant progress, but further studies are needed to increase our coverage of the B-cell malignant proteome. To achieve this goal we stress the advantages of using sub-cellular fractionation, protein separation, quantitation and affinity purification techniques to identify hitherto unidentified signalling and regulatory proteins. For example, proteomic analysis of B-cell plasma membranes isolated from patients with mantle cell lymphoma (MCL) identified the voltage-gated proton channel (HVCN1,[1]). This protein has now been characterised as a key modulator of B-cell receptor (BCR) signalling and abrogation of HVCN1 function could have a role in the treatment of B-cell malignancies dependent on maintained BCR signalling [2]. Similarly, proteomic studies on cell lysates from prognostic subtypes of CLL, distinguished by the absence (UM-CLL) or presence (M-CLL) of somatic hypermutation of the immunoglobulin heavy chain locus identified nucleophosmin 1 (NMP1) as a potential prognostic marker [3,4]. Thus, targeted proteomic analysis on selected organelles or sub-cellular compartments can identify novel proteins with unexpected localisation or function in malignant B-cells that could be developed for clinical purposes.     

The role of cystatins in cells of the immune system

The cystatins constitute a large group of evolutionary related proteins with diverse biological activities. Initially, they were characterized as inhibitors of lysosomal cysteine proteases - cathepsins. Cathepsins are involved in processing and presentation of antigens, as well as several pathological conditions such as inflammation and cancer. Recently, alternative functions of cystatins have been proposed: they also induce tumour necrosis factor and interleukin 10 synthesis and stimulate nitric oxide production. The aim of the present review was the analysis of data on cystatins from NCBI GEO database and the literature, and obtained in microarray and serial analysis of gene expression (SAGE) experiments. The expression of cystatins A, B, C, and F in macrophages, dendritic cells and natural killer cells of the immune system, during differentiation and activation is discussed.     

Are T cells at the origin of B cell lymphomas?

Lymphoma pathogenesis is at least in some cases related to transformed B cells (BCs) arising from germinal centre reactions (GCRs). In this article possible deregulations of GCRs are investigated using in silico simulations. It is found that the final differentiation of BCs as regulated by helper T cells (TCs) is the best candidate mechanism for such a deregulation. This shifts the paradigm of BC lymphoma pathogenesis from BC transformations to an emphasized role of TC-BC interactions.     

Application of the frequency of dividing cells technique to estimate the in situ growth rate of Microcystis (Cyanobacteria)

1. Diel patterns of the frequency of dividing cells (FDC) of the bloom‐forming cyanobacteria Microcystis were investigated using both culture strains and natural populations. 2. In laboratory experiments, diel division cycles were examined twice in a 24‐h light/dark cycle during time‐course batch incubations of six culture conditions using two strains (morphospecies) of Microcystis (M. aeruginosa and M. wesenbergii). While both strains clearly showed phased cell division in the light period during the logarithmic growth phase, the peaks of FDC became unclear towards the stationary phases. Some dividing cells were always found in the dark period regardless of whether or not division had paused at the same time. 3. This result implied the inadequacy of applying the model of McDuff & Chisholm [Limnology and Oceanography (1982) vol. 27 , pp. 783–787] directly to calculate the duration of cell division. Modified equations are proposed to calculate the duration of cytokinesis as a terminal event, in which the FDC values at night are regarded as 0% and all FDC values are subtracted by the minimum FDC value. 4. The diel FDC in natural populations of M. aeruginosa and M. wesenbergii were examined at five sites from a harbour to several distances offshore in Lake Biwa. While both species showed phased cell division patterns in the daytime at the harbour, no peaks in FDC were discernible in the samples taken from the offshore sites. These results strongly suggested that Microcystis growth was higher inshore than offshore. The in situ growth rates were estimated using the new equations.