Studies on emerging radiation leukemia virus variants in C57BL/Ka mice.

To analyze the emergence of radiation leukemia virus (RadLV) variants in primary X-ray-induced C57BL/Ka thymoma and to identify the virus responsible for the very high leukemogenic potential of passaged Kaplan strain BL/VL3 preparation, we cloned several primary and passaged ecotropic RadLV infectious genomes. By restriction analysis, we found that BL/VL3 cells harbor three related but different ecotropic RadLVs. Their restriction map differs significantly from those of primary RadLVs. Hybridization analysis also indicated that BL/VL3 and primary RadLVs differ in their p15E and long terminal repeat (LTR) regions. As compared with the LTR sequence of the putative parental endogenous ecotropic provirus, the LTR sequence of primary weakly leukemogenic RadLV has only one change, a C-rich sequence, generating a 6-base-pair direct repeat just in front of the promotor. The LTR of the primary nonleukemogenic RadLV only showed few base changes, mainly clustered in R and U5. The LTR from a moderately leukemogenic passaged BL/VL3 RadLV had conserved the C-rich sequence and acquired a 43-base-pair direct repeat in U3 and several other point mutations, small insertions, and deletions scattered in U3, R, and U5. All cloned primary RadLVs were fibrotropic, and some were weakly leukemogenic. All cloned BL/VL3 RadLVs were thymotropic and nonfibrotropic. The block of their replication was found to be after the synthesis of unintegrated linear and supercoiled viral DNA. Most of the BL/VL3 RadLVs were moderately leukemogenic, and one (V-13) was highly leukemogenic, being as virulent as the Moloney strain. We propose a model for the emergence of the RadLV variants and show that the virus responsible for the high leukemogenic potential of BL/VL3 preparation is a nondefective, ecotropic, lymphotropic, nonfibrotropic, unique retrovirus which most likely arose from a parental primary RadLV similar to those studied here.     

2,4-D和6-BA对向日葵下胚轴愈伤组织生长及钙调蛋白的影响

自 Anderson和 Cormier(1979)从植物中分离提取钙调蛋白(简称 CaM)后,对它的结构功能进行了广泛的研究,发现 CaM在光合作用(Barr等 1980)、酶的激活(Matsumoto等 1983)、蛋白磷酸化(Gideon等1982)等方面均起着重要作用。还证明CaM与生长素、细胞分裂素以及α-淀粉酶的分泌等有密切关系(Elliott 1983,Raghothama等1983;Saunders等1982)Elliott认为植物激素的促     

大鼠非致瘤四倍体细胞系的建立及细胞遗传学和酶学特征

从大鼠自然诱发的肉瘤细胞中,我们建立了一个四倍体细胞系(4n=84),命名为RC(ratcell)。它具有典型的成纤维细胞外形,能在玻璃表面贴壁生长,但不能生长在琼脂半固体培养基中。该细胞在含15％小牛血清的RPMI 1640培养基中生长良好,至今已连续繁殖112世代,细胞群体倍增时间约为15小时。染色体G-带分析表明,RC为整四倍体细胞,它的1条X染色体在第32至34区为均染区。RC细胞核仁组织者(NORs)活性显然比大鼠二倍体细胞NORs活性的加倍还高(P<0.001)。这个具有非常高NORs活性的RC细胞系对于研究细胞18S+28S rRNA基因转录活性的调控、基因表达与基因剂量关系有一定的意义。RC细胞还有异常高的磷酸酯酶活性,而且它的同工酶谱也与大鼠肌肉细胞明显不同。体内接种实验和扫描电镜的观察表明,RC是非致瘤细胞。RC细胞各号染色体的C-带图样与大鼠二倍体细胞无明显的差异。     

A simple purification of calmodulin by reversed phase chromatography with hydrophobic polymer 3520

A new adsorption chromatography procedure for the purification of calmodulin from bovine brain was developed using polymeric adsorbent 3520. Calmodulin was first isolated by DEAE-Cellulose column chromatography and further purified to apparent homogeneity following elution with 50% ethanol from the adsorbent column. Polyacrylamide gel electrophoresis showed one band either in the presence of Ca2+ or EGTA. The polymeric adsorbent 3520 is a non-polar polymer lacking exchangeable groups. The selective adsorption of calmodulin is based on hydrophobic interaction within the matrix, and is Ca2+ independent. Neither high salt (0.5 M NaC1) nor EGTA (5 mM) was able to elute the CaM from the adsorption column whereas ethanol (50%) eluted it completely. This method is simple to use and it provides highly purified calmodulin with high yield.     

HBsAg重组DNA转化中国地鼠卵巢细胞二氢叶酸还原酶阴性突变株的细胞染色体变化及致瘤性

整合了含乙型肝炎病毒表面抗原(HBsAg)基因和dhfr基因的CHO-dhfr~-细胞,其染色体的畸变率和畸变类型都比亲代CHO-dhfr~-细胞高。但转化前后两系细胞的重要特性都未发生变异,即两者的染色体总数无差别,都是20条。两系细胞株接种裸鼠,均未发现有致瘤性。     

Recombinant Treponema pallidum rare outer membrane protein 1 (Tromp1) expressed in Escherichia coli has porin activity and surface antigenic exposure.

We recently reported the cloning and sequencing of the gene encoding a 31-kDa Treponema pallidum subsp. pallidum rare outer membrane porin protein, designated Tromp1 (D. R. Blanco, C. I. Champion, M. M. Exner, H. Erdjument-Bromage, R. E. W. Hancock, P. Tempst, J. N. Miller, and M. A. Lovett, J. Bacteriol. 177:3556-3562, 1995). Here, we report the stable expression of recombinant Tromp1 (rTromp1) in Escherichia coli. rTromp1 expressed without its signal peptide and containing a 22-residue N-terminal fusion resulted in high-level accumulation of a nonexported soluble protein that was purified to homogeneity by fast protein liquid chromatography (FPLC). Specific antiserum generated to the FPLC-purified rTromp1 fusion identified on immunoblots of T. pallidum the native 31-kDa Tromp1 protein and two higher-molecular-mass oligomeric forms of Tromp1 at 55 and 80 kDa. rTromp1 was also expressed with its native signal peptide by using an inducible T7 promoter. Under these conditions, rTromp1 fractionated predominantly with the E. coli soluble and outer membrane fractions, but not with the inner membrane fraction. rTromp1 isolated from the E. coli outer membrane and reconstituted into planar lipid bilayers showed porin activity based on average single-channel conductances of 0.4 and 0.8 nS in 1 M KCl. Whole-mount immunoelectron microscopy using infection-derived immune serum against T. pallidum indicated that rTromp1 was surface exposed when expressed in E. coli. These findings demonstrate that rTromp1 can be targeted to the E. coli outer membrane, where it has both porin activity and surface antigenic exposure.     

Bioavailability of organic and inorganic phosphates adsorbed on short-range ordered aluminum precipitate

A nonreductive community-level study of P availability was conducted using various forms of adsorbed P. Orthophosphate (Pi), inositol hexaphosphate (IHP), and glucose 6-phosphate (G6P) were adsorbed to a short-range ordered Al precipitate. These bound phosphates provided a P source sufficient to support the growth of microbial communities from acidic Brazilian soils (oxisols). Adsorbed IHP, the most abundant form of organic phosphate in most soils, had the lowest bioavailability among the three phosphates studied. Adsorbed G6P and Pi were almost equally available. The amount of adsorbed Pi (1 cmol P kg^–1) required to support microbial growth was at least 30 times less than that of IHP (30 cmol P kg^–1). With increased surface coverage, adsorbed IHP became more bioavailable. This availability was attributed to a change in the structure of surface complexes and presumably resulted from the decreased number of high-affinity surface sites remaining at high levels of coverage. It thus appears that the bioavailability of various forms of adsorbed phosphate was determined primarily by the stability of the phosphate-surface complexes that they formed, rather than by the total amount of phosphate adsorbed. IHP, having the potential to form stable multiple-ring complexes, had the highest surface affinity and the lowest bioavailability. Bioaggregates consisting of bacteria and Al precipitate were observed and may be necessary for effective release of adsorbed P. Bacteria in the genera Enterobacter and Pseudomonas were the predominate organisms selected during these P-limited enrichments. Correspondence to: C. Shang     

小麦赤霉病的药剂防治指标模型

经过推导,得出小麦赤霉病的两类药剂防治指标模型．在保证品质、收支有余的条件下,第一类模型附加产投比较佳、净收益最佳原则,第二类模型附加产投比最佳原则．灵敏度分析和合理性分析证明了模型的正确性．模型可做为小麦赤霉病药剂防治的决策工具．同时,给出了两类模型的BASIC计算程序．     

钙／钙调素依赖性蛋白激酶对17．7kD和6kD胰腺蛋白的磷酸化

本文报导了胰腺提取物中两种可被钙／钙调素依赖性蛋白激酶磷酸化的热稳定蛋白。ＳＤＳ－ＰＡＧＥ测定其表观分子量分别为１７．７ｋＤ和６ｋＤ。经钙／钙调素依赖性蛋白激酶磷酸化后,其最大磷酸参入量为８．８μｍｏｌ／ｇ蛋白。同时磷酸化作用导致１７．７ｋＤ蛋白在ＳＤＳ－ＰＡＧＥ中迁移率发生变化。本文还进一步分析了各种阳离子对磷酸化的影响,并对此两种蛋白可能具有的生理功能进行了初步探讨。     

人体肠道细菌寡营养培养组条件的优化研究

【目的】探讨寡营养对人体肠道细菌培养组的条件。【方法】通过稀释富集培养基、固体平板和增菌肉汤培养基成分获得寡营养培养基。对健康人粪便样本分别用原液(0)、5、10、20、30和40倍稀释的富集培养基(添加羊血和瘤胃液的血培养瓶)连续增菌,在不同时间点(第0、3、6、9、15、27、30天)吸取增菌液,用YCFA (yeast casitone fatty acid)固体培养平板分离菌落;用YCFA增菌肉汤增菌后再次挑取单菌落,利用基质辅助激光解吸/电离飞行时间(matrix-assisted laser desorption/ionization time-of-flight mass spectrometry,MALDI-TOF)质谱和16S rRNA基因测序鉴定菌株。通过比较上述6种寡营养条件分离肠道菌群的效果,选取富集培养基原液、稀释10倍和30倍这3 种条件下分离效果较好的富集条件,与同样稀释倍数条件的固体平板和增菌肉汤分别组合成9种培养基条件,进一步优化肠道菌群的培养组条件。【结果】在6种寡营养富集培养基中,未稀释(原液)、10 倍和30倍稀释的富集培养基分离细菌的种类比其他...