Sister chromatid differential staining and NOR activity of BrdU-resistant sublines

Summary Two 30 g/ml BrdU-resistant sublines and two 60 g/ml BrdU-resistant sublines are induced from a Chinese hamster cell line Wg3h (HGPRT^–) by one-step and two-step selections, respectively. By inoculating the cells into BrdU-free medium or by adding more BrdU into the culture medium for 26–27 h, it was found that the two BrdU-resistant sublines analysed have very clear sister chromatid differential (SCD) staining patterns. This indicates that some of the nuclear DNA of the BrdU-resistant cells incorporate with BrdU to reach a kinetic balance. Frequencies of sister chromatid exchange (SCE) of the resistant cells are twice to four times as high as those of the Wg3h cells, depending on which BrdU-resistant subline is analysed. The SCE frequencies of the resistant cells also increase with the BrdU concentration in the medium. Analysis of silver-stained nucleolar organizer regions (NORs) indicates that the NOR activity of three out of the four BrdU-resistant sublines is significantly suppressed, i.e., averages of the Ag-NOR number and number of the chromosomes bearing Ag-NORs per cell decrease significantly. The degree of suppression for different BrdU-resistant sublines may be quite different. The suppressed NOR activity of the resistant cells can gradually be restored when the cells are inoculated into BrdU-free medium, but the recovery speed is far lower than that of the Wg3h cells. The suppression of the NOR activity of the BrdU-resistant sublines should be due to BrdU toxicity.     

pH和温度对固氮酶还原基质的影响

确定了在pH 5.2到8.7和温度22°到45℃时钼铁蛋白和铁蛋白的稳定性。按logKm和logV分别对pH作图,得到下列参数。于30℃在酸性侧,乙炔络合常数PK_b(C_2H_2)=6.43—6.50,乙炔催化常数pK_b′(C_2H_2)=4.78,在碱性侧乙炔络合常数pK_a(C_2H_2)=7.42—7.55,乙炔催化常数pK_a′(C_2H_2)=7.88—8.29,氮络合常数pK_a(N_2)=7.75—7.9及氮催化常数pK_a′(N_2)=8.08—8.68。既然pK_a与pK_b或pK_a′与pK_b′二者间隔小于3.5个单位,又按V/Km及V′对pH作图,其结果为pKb(C_2H_2)=6.28pK_a(C_2H_2)=7.68和pK_b′(C_2H_2)=5.53和pK_a′(C_2H_2)=8.93。将不同温度下的pK_b或pK_a分别对各自温度的倒数作图,其热力学数据为由pH 5.7到7.3范围内,质子移变基团的解离热⊿H(ioh)=7742卡/克分子,相应的pK_b(C_2H_2)=6.16—6.36;由pH 7.3到8.4范围内⊿H_(ion)=6983卡/克分子,相应的pK_a=8.24—8.44。这些数据指出固氮酶钼铁蛋白络合乙炔的功能基团可能具有咪唑基·巯基和氨基相类似的结构,这种推测正在用化学修饰的方法加以验证。     

亮叶杨桐(石芽茶)中黄酮类成分的研究

从广西产亮叶杨桐(Adinandra nitida Merr.ex H.L.Li)中,分得三种黄酮类成分:Ⅰ、Ⅱ和Ⅲ。经IR、UV(位移诊断)、熔点、混熔点、薄层层析鉴定:Ⅰ为芹菜素(Apigenin);Ⅱ为芹菜素-5-0-α-L-吡喃鼠李糖基(1→4-6~(?)-乙酰基-β-D-吡喃葡萄糖吡;Ⅲ为芹菜素-5-0-α-L-吡喃鼠李糖基(1→4)-β-D-吡喃葡萄糖甙。     

从乙型肝炎病毒表面抗原阳性母亲流产的胎儿查出乙型肝炎病毒标志

应用Southern blot杂交试验检测HBsAg及HBeAg均阳性母亲流产的9例胎儿肝细胞中HBV DNA的存在状态,并与其HBV血清学、免疫电镜及肝脏免疫组织化学的结果相比较。结果在3例胎肝高分子DNA中检出了整合的HBV DNA顺序,且此3例HBV DNA整合到胎肝细胞基因组并无特定部位,提示为随机整合。3例中2例的血清及肝匀浆都检出HBsAg颗粒,其胎肝细胞胞浆HBsAg也阳性;另1例受HBV感染的唯一标志是在胎肝细胞中存在着整合的HBVDNA。此外,另1例则仅胎肝细胞中HBsAg阳性而无整合的HBV DNA。在胎肝细胞中检出整合的HBV DNA进一步证实HBV子宫内传播途径的存在。     

adr亚型乙型肝炎病毒DNA的酶切图谱分析

<正> 本文报道以pAT153质粒为载体克隆的adr亚型乙型肝炎病毒(HBV)全基因的限制性内切酶图谱。重组质粒已命名为pHBV-NCl。重组质粒的提取和酶解采用常规方法。限制性内切酶为Bio-Labs公司产品。用Sepharcry S-1000纯化得到的质粒,经电泳鉴定都是完整的超螺旋DNA。经过鉴定其BamHⅠ、XhoⅠ、XbaⅠ、SstⅡ、SphⅠ、BglⅠ、BglⅡ、BstEⅡ、AceⅠ、AvaⅠ、HincⅡ、HpaⅠ等12种酶的21个切口已被定位。其中XhoⅠ、XbaⅠ、SstⅡ、     

中国人ε珠蛋白基因5′侧序列中多态性Hinc Ⅱ位点的进一步研究

本文进一步研究了我国不同民族的正常个体以及β地中海贫血患者θ珠蛋白基因5′侧序列中的多态性HincⅡ位点及其遗传性质。在广西壮族正常个体和β地中海贫血纯合子中,该多态性位点的发生频率均为75％,与正常汉族人测得值相近。家系分析资料表明,该多态性位点完全按照孟德尔规律进行遗传。     

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。     

Hypoxia-induced inhibition of converting enzyme activity: role in vascular regulation

Systemic and pulmonary vascular reactivity to graded doses of angiotensin I (ANG I), angiotensin II (ANG II), and, as a control, phenylephrine were examined in 14- or 28-day hypoxia-exposed and air control rats. Hypoxic rats exhibited pulmonary hypertension that was reversible on return to room air, but systemic arterial pressure was not altered by hypoxia. Systemic pressor responses to ANG I and ANG II were significantly less in the hypoxic rats than in the control rats at 14 and 28 days but returned to control levels in hypoxic animals that were then returned to room air, demonstrating reversibility of the hypoxia-induced changes in vascular reactivity. Pulmonary pressor responses to ANG I were significantly less at 14 days, whereas responses to ANG II were significantly greater at 28 days, in hypoxic rats than in controls. There were no significant differences in systemic and pulmonary pressor responses to phenylephrine between the hypoxic and air control animals. The altered systemic and pulmonary pressor responsiveness to ANG I and ANG II in hypoxic rats is probably related to mechanisms specific to the renin-angiotensin system, such as inhibition of intrapulmonary angiotensin-converting enzyme activity and down regulation of ANG II receptors in the systemic circulation. Further study is needed to elucidate these mechanisms.