Organization and chromosomal localization ofβ-tubulin genes inLeishmania donovani

The genomic organization and chromosomal location of theβ-tubulin isogenes inLeishmania donovani promastigotes has been studied by nucleic acid hybridization techniques using a cloned β-tubulin gene. We have cloned aβ-tubulin gene fragment, 3.3 kbp long, from genomic DNA ofLeishmania donovani using a heterologousβ-tubulin DNA as probe. Restriction maps of this clone have been prepared. It has been estimated that there are approximately 11–15 copies of theβ-tubulin genes per haploid genome. The majority of these isogenes are arranged in a tandem repeat with a length of 3.5 kbp on a single chromosome. In addition a few dispersed gene copies at different chromosomal loci were detected by pulse field gradient gel electrophoresis. Part of the internal coding region of the gene has been sequenced to confirm the identity of theβ-tubulin clone and is found to be nearly identical to that ofLeishmania mexicana amazonensis.     

Role of Ca2+ in induction and secretion of dengue virus-induced cytokines

The present study was undertaken to investigate the role of calcium ions (Ca₂₊) in the induction and secretion of the dengue type 2 virus induced cytotoxic factor and the cytotoxin. This was done by using calcium channel blocking drugs such as verapamil, nifedipine or diltiazem hydrochloride. The production of cytotoxic factor was significantly reduced by treatment of dengue type 2 virus infected mice with verapamil. Similarly, a dosedependent inhibition of the secretion of cytotoxic factor was observed, when spleen cells of the virus-primed mice were treatedin vitro with the 3 calcium channel blockers. The production of cytotoxin by macrophages was abrogated by pretreatment with calcium channel blockers but had little effect on its secretion as shown by treatment of macrophages with verapamil at 1 h after the induction to later periods up to 18 h. The findings thus show that in the induction of both the cytokines Ca₂₊ plays a critical role; on the other hand it is required for the secretion of the cytotoxic factor but not for that of the cytotoxin.     

豆科根瘤内气体交换和气体扩散模型研究

近年来的研究表明根瘤皮层内存在着可调节的气体扩散屏障,它是由根瘤皮层内的一层细胞及填充在胞间隙的水层构成的,而根瘤是通过改变填充该层胞间隙的水层厚度来调节对气体扩散的阻力。本文概述了关于模拟豆科根瘤内气体交换和气体扩散的数学模型研究,阐明调节根瘤内含类菌体细胞维持低氧分压的有关问题。模型研究使我们获得了对共生固氮根瘤内极为复杂的微生态环境的初步认识,有待于通过改进试验和借助其他理论进一步探索根瘤气体交换和气体扩散的本质。     

植物叶绿素含量与大气中SO2浓度相关性研究

本文对厦门市5个样点、6种常见绿化树种及盆栽植物蕹菜的叶绿素含量、叶片含硫量及大气中SO_2浓度分析测定,得出了6种植物叶绿素a、b变化趋势是:鼓浪屿、厦门大学>火车站、后江埭>电化厂;叶片含硫量的变化趋势与叶绿素a、b含量变化相反。表明植物叶片叶绿素含量与大气中SO_2浓度和叶片含硫量呈负相关,并计算蕹菜叶绿素含量与大气SO_2浓度相关模式(y=-0.0138x 0.1958),为大气环境评价提供生物学依据。     

白细胞介素2受体α链基因转录起始点和5'调控区结合蛋白的初步研究

 借助于5'和3'末端删切后重建的IL-2R a链基因调控区次级克隆,在体外合成有放射性同位素参入的反意义RNA探针与总RNA进行液相杂交,结果表明TPA或PHA分别活化的T细胞在IL-2R a链表达过程中都在不同程度上有选择地利用了调控区内分别为-58(5')和+1(3')位两个转录起始点中3'转录起始点。热休克使PHA活化细胞更明显地利用+1位点。PHA诱导Jurkat细胞表达IL-2RamRNA斑点杂交证实,Jurkat细胞在活化16小时表达IL-2Ra基本达到高峰,至24小时已明显下降。根据这一规律提取PHA诱导活化15小时的Jurkat细胞S100和NE,进行有关结合蛋白的研究,初步结果显示磷酸纤维素柱的KCI洗脱组分中存在着DNA结合蛋白,有关结合蛋白性质的研究正在进行中。     

山莨菪碱对经有限蛋白水解后的脑突触膜Ca~(2+)-ATPase的影响

 从猪脑中提取钙调蛋白和突触质膜,我们研究了山莨菪碱对经有限蛋白水解和磷脂酶A_2处理后的突触膜Ca~(2+)-ATPase活性影响。发现药物对不同预处理后的Ca~(2+)-ATPase表现出不同影响并调节钙调蛋白对它的激活作用。     

人U_1和U_2snRNA基因定位缺失和取代突变

 用寡聚核苷酸诱导的定位突变法,将人U_1和U_2snRNA基因的5'-端调控区域的一段能与SV_(40)T抗原相结合的DNA删去,造成缺失突变,改变这段DNA核苷酸的排列顺序,造成取代突变。突变株用原位杂交法筛选,由限制性内切酶电泳图谱分析和DNA顺序测定得到证实。突变率约为5％。     

用人DNA介导的基因转移修复中国仓鼠细胞的HPRT缺陷

 中国仓鼠卵巢细胞(CHO-K1)经N-甲基-N'-硝基-N-亚硝基胍(MNNG)诱变和6-巯基鸟嘌呤(6-TG)选择,得到稳定的次黄嘌呤磷酸核糖转移酶(HPRT)缺陷细胞株,酶活性仅为野生型的6.5％。用磷酸钙共沉淀法和电脉冲法向HPRT-细胞转移人宫颈癌细胞(HeLaS_3)基因组DNA,纠正了CHO细胞的HPRT缺陷。酶活性提高了6.9倍,达到野生型的45％。用Alu序列探针进行分子杂交,证实经过基因转移并连续传代15次以上的受体细胞中含人DNA序列。表明人的有关基因已稳定地整合到CHO细胞的染色体中。     

Embryogenic cells in plant tissue cultures: Occurrence and behavior

Summary Plants develop from meristems where cells proliferate and are partitioned into layers that eventually differentiate to form the various tissues and organs of the plant. A phenomenon unique to certain plant tissues is the ability to inducede nova a range of developmental patterns, including embryogenesis. The temporal and spacial distribution of these developmental competencies suggests that regulatory proteins, rather than a lack of signals or signal receptors, shield specific developmental genes from signals that otherwise would confuse development. Studies involving embryogenic cells demonstrate that they are not strongly shielded from developmental signals, thus they are not determined. Furthermore, the normal development of zygotic and somatic embryos is readily perturbed by abnormal physicochemical environments. This suggests that embryogeny remains developmentally plastic until differentiation is largely completed. The ability to induce somatic embryogenesis from specific tissues by specific signals is providing opportunities to further the molecular characterization of the menagerie of genetic regulation involved in development. Much of this review was presented at a Moet-Hennessy Louis Vuitton sponsored conference, Control of Morphogenesis in Plants, Aix Les Bains, France, September, 1989. Studies in our laboratory were supported in part by grants from the National Aeronautics and Space Administration (Cooperative Agreement No. NCC2-139), the Utah State University Biotechnology Center, and by the Utah Agricultural Experiment Station, Utah State University, Logan, UT 84322-4845 (approved as journal paper no. 3928).