The role of B cells for in vivo T cell responses to a Friend virus-induced leukemia

B cells can function as antigen-presenting cells and accessory cells for T cell responses. This study evaluated the role of B cells in the induction of protective T cell immunity to a Friend murine leukemia virus (F-MuLV)-induced leukemia (FBL). B cell-deficient mice exhibited significantly reduced tumor-specific CD4+ helper and CD8+ cytotoxic T cell responses after priming with FBL or a recombinant vaccinia virus containing F-MuLV antigens. Moreover, these mice had diminished T cell responses to the vaccinia viral antigens. Tumor-primed T cells transferred into B cell-deficient mice effectively eradicated disseminated FBL. Thus, B cells appear necessary for efficient priming but not expression of tumor and viral T cell immunity.     

共刺激分子配体B7-H1基因真核表达载体和转基因细胞的构建

以PHA刺激的小鼠外周血单核细胞中抽提的总RNA为模板,通过RT-PCR技术,扩增出B7-H1基因。按常规方法克隆进pEF6V5His A载体,重组质粒经鉴定后采用脂质体法转染CHO细胞,48h后进行间接免疫荧光试验,72h后用Blasticidin进行筛选,挑选出能稳定表达B7-H1的细胞株。结果表明：成功地克隆小鼠B7-H1基因并构建了用于表达B7-H1基因的真核表达载体,经间接免疫荧光试验证明,该基因在CHO细胞中得到表达。经Western-blot检测表明筛选出的转基因细胞稳定表达了B7-H1基因。     

Intranuclear localization of mercury in vivo

Purified nuclei isolated from mice challenged with nonlethal levels of mercury chloride (10-(3)M) in drinking water for 4 to 7 weeks (experimental) and from animals given deionized water (control) were fractionated and the subsequent fractions were analyzed for mercury by flameless atomic absorption. Control (active) euchromatin contained 1.75 +/- 0.53 micrograms of mercury per milligram of DNA. There was a 12- to 15-fold enrichment of mercury in the euchromatin fraction of challenged animals. Mercury was not detected in control (inactive) heterochromatin, and only trace levels (parts per billion) appeared in experimental heterochromatin. It seems likely that mercury can be incorporated into chromatin as a metal-protein complex, but the possibility of protein-mercury-DNA or mercury-DNA complexes within euchromatin cannot be excluded.     

Critical roles for Rac1 and Rac2 GTPases in B cell development and signaling

The Rac1 guanosine triphosphatase (GTPase) has been implicated in multiple cellular functions, including actin dynamics, proliferation, apoptosis, adhesion, and migration resulting from signaling by multiple receptors, including the B cell antigen receptor (BCR). We used conditional gene targeting to generate mice with specific Rac1 deficiency in the B cell lineage. In the absence of both Rac1 and the highly related Rac2, B cell development was almost completely blocked. Both GTPases were required to transduce BCR signals leading to proliferation, survival and up-regulation of BAFF-R, a receptor for BAFF, a key survival molecule required for B cell development and maintenance.     

An essential role for BLNK in human B cell development

The signal transduction events that control the progenitor B cell (pro-B cell) to precursor B cell (pre-B cell) transition have not been well delineated. In evaluating patients with absent B cells, a male with a homozygous splice defect in the cytoplasmic adapter protein BLNK (B cell linker protein) was identified. Although this patient had normal numbers of pro-B cells, he had no pre-B cells or mature B cells, indicating that BLNK plays a critical role in orchestrating the pro-B cell to pre-B cell transition. The immune system and overall growth and development were otherwise normal in this patient, suggesting that BLNK function is highly specific.     

The role of ocular muscle proprioception in visual localization of targets

The role of ocular muscle proprioception in the localization of visual targets has been investigated in normal humans by deviating one eye to create an experimental strabismus. The passively deviated eye was covered and the other eye viewed the target. With a hand-pointing task, targets were systematically mislocalized in the direction of the deviated nonviewing eye. A 4- to 6-degree error resulted when the nonviewing eye was offset 30 degrees from straight ahead. When the eye was deviated, the perceived "straight-ahead" was also displaced, by a similar amount, in the same direction. Since the efferent motor commands to the displaced and to the nondisplaced eyes are presumably identical by the law of equal innervation, the mislocalization of visual objects must be attributed to the change in proprioceptive information issued from the nonviewing, deviated eye. Thus proprioception contributes to the localization of objects in space.     

Aflatoxin B1: binding to DNA in vitro and alteration of RNA metabolism in vivo

Aflatoxin B(1) binds to both native and denatured DNA, as shown by spectroscopy and equilibrium dialysis. It also strongly inhibits incorporation of cytidine into rat liver nuclear RNA and lowers the RNA content of the nucleus. The extremle toxicity and carcinogenicity of aflatoxin B(1) may be direct results of the affinity of this agent for DNA.     

Neurofibromas in NF1: Schwann cell origin and role of tumor environment

Neurofibromatosis type 1 (NF1) is one of the most prevalent dominantly inherited genetic diseases of the nervous system. NF1 encodes a tumor suppressor whose functional loss results in the development of benign neurofibromas that can progress to malignancy. Neurofibromas are complex tumors composed of axonal processes, Schwann cells, fibroblasts, perineurial cells, and mast cells. Through use of a conditional (cre/lox) allele, we show that loss of NF1 in the Schwann cell lineage is sufficient to generate tumors. In addition, complete NF1-mediated tumorigenicity requires both a loss of NF1 in cells destined to become neoplastic as well as heterozygosity in non-neoplastic cells. The requirement for a permissive haploinsufficient environment to allow tumorigenesis may have therapeutic implications for NF1 and other familial cancers.     

拟南芥ATMYB2转录因子的cDNA序列分析及其细胞定位

根据GenBank中收录的拟南芥At Myb2基因(GenBank登录号:AK229140)的cDNA序列设计1对引物,对拟南芥中叶片提取的总RNA进行扩增和克隆,并将拟南芥ATMYB2蛋白氨基酸序列进行同源性比较和蛋白定位分析.结果表明:At Myb2基因cDNA全长为816 bp,编码272个氨基酸和1个终止密码子,具有2个典型的MYB类转录因子基因的DNA结合区,分别为23-70、79-118位氨基酸,属于典型的R2,R3-MYB转录因子;经过氨基酸比对发现,拟南芥ATMYB2蛋白与水稻的ATMB18蛋白同源性最高,为44.60%.对拟南芥At Myb2基因进行RT-PCR扩增,结果表明基因片段未发生任何突变;通过拟南芥ATMYB2与EGFP形成融合蛋白对AT-MYB2进行了定位,发现ATMYB2蛋白在细胞核内能够表达,符合作为转录因子的表达特征.     

番茄 SlMAPK7基因的亚细胞定位与组织表达特性

分离番茄 SlMA PK7基因,利用实时荧光定量反转录聚合酶链反应技术分析在番茄不同组织和花发育不同时期 SlMA PK7的表达特性,发现该基因在雄蕊的表达量明显高于其他组织,在长度4.6～6.5 mm 的花蕾中表达量最高;通过构建黄色荧光蛋白融合表达载体,利用基因枪介导洋葱内表皮细胞的瞬时表达,发现SlMA PK7基因表达蛋白定位在细胞核和细胞膜中;为进一步研究 SlMA PK7的表达特性,分离克隆了SlMA PK7基因的启动子序列,利用 PLACE 和 PlantCARE 软件预测出其含有多种典型的 SlMA PK 启动子顺式作用元件;通过瞬时表达分析该启动子活性,经农杆菌介导转化拟南芥,GUS(β‐glucuronidase ,β‐葡萄糖苷酶)组织化学染色发现,在幼苗期 SlMA PK7主要集中在顶端分生组织和根尖分生组织中表达,在成年植株中则集中在花器官中表达.以上结果表明,SlMA PK7可能在细胞核和细胞膜中参与番茄多种信号的传导,并可能在花器官的发育过程中行使功能.     

HCV persistence and immune evasion in the absence of memory T cell help

Spontaneous resolution of hepatitis C virus (HCV) infection in humans usually affords long-term immunity to persistent viremia and associated liver diseases. Here, we report that memory CD4+ Tcells are essential for this protection. Antibody-mediated depletion of CD4+ Tcells before reinfection of two immune chimpanzees resulted in persistent, low-level viremia despite functional intra-hepatic memory CD8+ Tcell responses. Incomplete control of HCV replication by memory CD8+ Tcells in the absence of adequate CD4+ Tcell help was associated with emergence of viral escape mutations in class I major histocompatibility complex-restricted epitopes and failure to resolve HCV infection.     

出血性大肠杆菌O157：H7的Tir与stx1／2B融合基因的构建和表达

为了更好防治由出血性大肠杆菌O157：H7引起的疾病,尝试研制基因工程疫苗．其中亚单位疫苗具有很大优势。方法：构建表达tir和stxb的融合基因。将tir基因中间295个氨基酸残基（Tir295）与stxB亚基基因72个氨基酸串联。构建pET28a—stx2b—Tir295-stx1b重组质粒,将其转化于BL21（DE3）,用IPTG进行诱导表达,经SDS--PAGE电沫检测,该融合蛋白获得了高效表达。结果：薄层扫描分析表明,目的蛋白表达量占菌体总蛋白含量的30％左右。结论：由于该融合蛋白由Tir、stx1b和stx2b三部分抗原组成．可刺激机体产生针时转位紧密素受体（Tir）和志贺毒素（stx）的抗体,在EHEC0157亚单位疫苗设计或单克隆抗体抗制备中具有重要价值。     

红花檵木LcDRF1和LcDRF2基因克隆及亚细胞定位分析

[目的]克隆红花檵木二氢黄酮醇-4-还原酶(DFR)基因(LcDFR1和LcDFR2),并对其进行亚细胞定位,为揭示红花檵木花青苷的分子合成机理提供理论依据.[方法]基于红花檵木转录组数据,以红花檵木叶片cDNA为模板,RT-PCR克隆LcDFR1和LcDFR2基因开放阅读框(ORF)序列,利用生物信息学软件对其进行分析,并通过烟草叶片瞬时表达方法观察蛋白的亚细胞定位情况.[结果]克隆获得的红花檵木LcDFR1和LcDFR2基因ORF序列分别为1014和993 bp,分别编码337和330个氨基酸残基.LcDFR1与LcDFR2的氨基酸序列相似性为77%,二者与其他物种DFRs氨基酸序列的相似性均较高,其中与葡萄、山核桃、拟南芥等双子叶植物的DFRs氨基酸序列相似性为64%~84%,而与单子叶植物玉米和水稻的DFRs氨基酸序列相似性为58%~61%,表明不同物种DFRs氨基酸序列具有较高的保守性.在基于DFRs氨基酸序列相似性构建的系统发育进化树上,LcDFR1与牡丹和芍药的DFRs聚为一类,而LcDFR2与烟草和番茄的DFRs聚为一类.结合前人研究结果推测LcDFR1和LcDFR2的氨基酸序列中均包含保守的NADP结合域和底物结合域.但三级结构预测结果均未预测到二者的底物结合位点,也未预测到LcDFR2的NADP结合位点.LcDFR1和LcDFR2亚细胞定位于细胞质,在细胞质中行使催化功能.[结论]LcDFR1和LcDFR2在红花檵木细胞质中催化花青苷物质的生物合成,但二者在进化过程中产生底物偏好性、催化能力等功能差异.     

新型吸附剂AAN对黄曲霉毒素B1、B2、G1、G2的体外吸附研究

 对蒙脱石进行复合改性，构建了新型纳米吸附材料AAN，分别从振荡时间、吸附剂用量、溶液pH、平衡温度几个方面研究了AAN对黄曲霉毒素B1、B2、G1、G2的吸附情况，确定了最佳吸附条件。结果表明AAN对黄曲霉毒素的吸附作用强，二者之间的吸附属于强化学吸附；吸附速度快，60min可以达到吸附平衡；解吸率低，小于10％。这些结果提示AAN作为一种新型纳米吸附剂，应用前景十分广阔。     

稻谷陈化过程中维生素B1、B2变化的动力学研究

为进一步了解稻米在陈化过程中维生素营养品质的变化趋势，尽量减少其损失和改善粮食维生素营养品质，采用人工陈化法，对稻米陈化过程中维生素B1、B2含量变化的动力学特征进行了研究。结果表明，陈化过程中稻米维生素B1和维生素B2含量损失严重，以45℃储藏约150d，维生素B1含量损失为74％，维生素B2含量损失67％；在45℃时，维生素B1的酶催化反应速率方程为1／V=41．807／C 65．211；维生素B2的酶催化反应速率方程为1／V=58．523／C 33．751。维生素B2的解离速率是维生素B1的两倍。储藏温度是严重影响稻米维生素含量的因素之一。     

Mcl-1 is essential for germinal center formation and B cell memory

Lymphocyte survival during immune responses is controlled by the relative expression of pro- and anti-apoptotic molecules, regulating the magnitude, quality, and duration of the response. We investigated the consequences of deleting genes encoding the anti-apoptotic molecules Mcl1 and Bcl2l1 (Bcl-x(L)) from B cells using an inducible system synchronized with expression of activation-induced cytidine deaminase (Aicda) after immunization. This revealed Mcl1 and not Bcl2l1 to be indispensable for the formation and persistence of germinal centers (GCs). Limiting Mcl1 expression reduced the magnitude of the GC response with an equivalent, but not greater, effect on memory B cell formation and no effect on persistence. Our results identify Mcl1 as the main anti-apoptotic regulator of activated B cell survival and suggest distinct mechanisms controlling survival of GC and memory B cells.     

Interferon-gamma and B cell stimulatory factor-1 reciprocally regulate Ig isotype production

Gamma interferon (IFN-gamma) and B cell stimulatory factor-1 (BSF-1), also known as interleukin-4, are T cell-derived lymphokines that have potent effects on B cell proliferation and differentiation. They are often secreted by distinct T cell clones. It is now shown that IFN-gamma stimulates the expression of immunoglobulin (Ig) of the IgG2a isotype and inhibits the production of IgG3, IgG1, IgG2b, and IgE. By contrast, BSF-1 has powerful effects in promoting switching to the expression of IgG1 and IgE but markedly inhibits IgM, IgG3, IgG2a, and IgG2b. These results indicate that BSF-1 and IFN-gamma as well as the T cells that produce them may act as reciprocal regulatory agents in the determination of Ig isotype responses. The effects of IFN-gamma and BSF-1 on isotype expression are independent.     

乐果急性、亚急性暴露对大鼠胆碱酯酶及细胞色素氧化酶影响的研究

对6周龄雄性SD大鼠分别单次灌胃给予50%(LD50)的乐果、连续5 d灌胃给予20%(LD50)的乐果,观察给药后至屠宰前大鼠的急性、亚急性毒性反应。采用丁酰硫代胆碱法测定红细胞、血清和脑组织中的胆碱酯酶;采用定量RT-PCR法测定试验大鼠肝脏中细胞色素氧化酶8个亚型的表达量。结果表明:供试大鼠用药后不同时间出现了呕吐、流泪、流涎、震颤等典型的有机磷药物中毒症状。红细胞、血清和脑组织中的胆碱酯酶均明显降低,以试验组和对照组脑组织中胆碱酯酶差异最为显著,急性暴露组大鼠脑组织中的胆碱酯酶降低80.12%,亚急性暴露组大鼠脑组织中的胆碱酯酶降低93.13%,试验组大鼠细胞色素氧化酶中CYP2B1/2亚型的表达量明显增加,为对照组大鼠表达量的4~8倍。     

应用生物信息学分析大米过敏原RAG1的B细胞表位(英文)

[目的]预测大米主要过敏原RAG1的二级结构及B细胞表位。[方法]从Expasy蛋白质数据库中获得编码大米过敏原RAG1的氨基酸序列并以此氨基酸序列为基础,通过DNAStarProtean软件,采用Gamier-Robson方案、Chou-Fasman方案和Karplus-Schulz方案预测RAG1的二级结构,用Kyte-Doolittle亲水性方案、Emini表面可及性方案、Jameson-Wolf抗原性指数方案综合预测RAG1的B细胞表位。[结果]对大米过敏原RAG1的二级结构和B细胞表位预测的结果表明,第33～44、119～129、155～163区段可能是B细胞的优势表位。[结论]本研究综合应用多方法多参数预测大米过敏原RAG1潜在的B细胞优势表位,为RAG1B细胞表位的进一步鉴定及其抗原性改造、表位疫苗设计等研究提供了理论依据。     

Alcohol metabolism: role of microsomal oxidation in vivo

A role for microsomal alcohol oxidation cannot be demonstrated in vivo. Factors affecting microsomal drug hydroxylations had no effect on alcohol metabolism in the rat in vivo. The compound SKF 525-A which inhibits, and chronic phenobarbital treatment which enhances microsomal drug hydroxylations did not alter alcohol oxidation.