Micromanipulation of mitotic chromosomes in PTK2 cells using laser-induced optical forces ("optical tweezers")

To study the potential use of optical forces to manipulate chromosome movement, we have used a Nd:YAG laser at a wavelength of 1.06 microns focused into a phase contrast microscope. Metaphase and anaphase chromosomes were exposed while being monitored by video microscopy. The results indicated that when optical forces were applied to late-moving metaphase chromosomes on the side closest to the nearest spindle pole, the trapped chromosomes initiated movement to the metaphase plate. The chromosome velocities were two to eight times the normal rate depending on the chromosome size, geometry, and trapping site. At the initiation of anaphase, a pair of chromatids could be held by the optical trap and kept motionless throughout anaphase while the other pairs of chromatids separated and moved to opposite spindle poles. As a result, the trapped chromosome either was incorporated into one of the daughter cells or was lost in the cleavage furrow, or the two chromatids eventually separated and moved to their respective daughter cells. If the trap was removed at the beginning of anaphase B, the chromosome moved back to the poles. Our experiments demonstrate that the laser-induced optical force trap is a potential new technique to study noninvasively the mitotic spindle of living cells.     

禿杉组织培养研究

本文详细报道了从秃杉(Taiwania flousiana Gaussen)离体胚诱导不定芽、不定根及从无菌苗茎端培养再生植株的过程。诱导不定芽要求较低的蔗糖浓度(以3％最好);同时BA是必须的,在附加0.1—3 mg/1 BA的White培养基上,从离体胚的子叶或胚轴上诱导了不定芽的发生(以1 mg/1最好);NAA与BA结合使用,对不定芽诱导无促进作用;适当提高光照有利于不定芽的诱导。在诱导不定芽的同时,在子叶表面还观察到有许多无结构的“不定突起”。不定芽起源于子叶表皮下1—2层细胞。IBA对诱导离体胚上产生不定根效果较好。在有或无生长素的培养基上,从生长1月龄的无菌苗茎端培养获得了不定根的产生,在加有细胞分裂索的培养基上,从无菌苗上产生了腋芽。     

3-磷酸甘油醛脱氢酶胍变性时的活力及构象变化

酵母3-磷酸甘油醛脱氢酶在盐酸胍溶液中的内源荧光及剩余活力的变化结果提示:apo酶及holo酶的活力在胍浓度为0.5M左右可完全丧失.同时伴有内源荧光强度的下降,光谱宽度的增加和335nm最大发射峰的红移(提示了色氨酸残基的暴露).与已经报导的肌肉酶(内源荧光强度在胍浓度为0.4—1.2M范围相对稳定)不同,酵母酶内源荧光在此浓度范围内表现为逐渐降低.在0.7M胍溶液中,内源荧光变化动力学过程只能测出一相,而酶失活动力学过程为快慢两相,快相动力学速度常数至少大于内源荧光降低速度常数三个数量级以上.以上结果提示:低浓度胍可引起该酶的完全失活,活性部位的空间构象比酶分子的构象更易受到变性剂的扰乱;有一个色氨酸残基位于或靠近酶的活性部位.     

转移及非转移肿瘤移植后615小鼠血液流变学变化的研究

血道高转移瘤株FC、淋巴合并血道高转移瘤株U14、淋巴道高转移瘤株H22、非转移瘤株P615分别接种于336只纯系近交615小鼠.不同时间取血并处死动物,进行组织学及血液流变学检查.将转移瘤发展过程分为潜伏期、侵袭期、转移早、中、晚期,非转移瘤发展过程分为潜优期、增殖期、囊腔形成期及中心坏死期.本实验结果显示,不同转移能力及途径肿瘤发展的不同时期血液流变学变化规律不同,因而表明肿瘤侵袭、转移与血液流变学变化之间存在互为因果的紧密关系.其临床诊断及治疗意义被讨论.     

应用地理信息系统模拟森林景观动态的研究

根据地理信息系统的结构,通过数据文件的转换,把它与森林动态模型有机地结合起来,可实现对森林景观动态的模拟和预测。这种模拟方法的数据输入灵活,运行速度快,尤其是它可以获得一些以各种图表的形式输出的模拟结果。本文用文字和框图详细描述了地理信息系统的组成与结构,及森林动态模型的选择与运行方式,并以长白山森林景观为例,叙述了这种模拟方法的整个过程。     

与胎儿珠蛋白基因持续表达有关的(A_γδβ)°—地贫纯合子及杂合子的分子鉴别

我们分子鉴别了一个缺失型中国(A_γδβ)°-地贫家系。先证者为这一缺失的纯合子,具有中度贫血症状。家系的另五个成员均为这一缺失的杂合子,其胎儿血红蛋白(HbF)为16—21％,接近或达到HPFH杂合子的HbF水平,并且几乎不表现贫血症状。限制性内切酶图谱分析证明了β-珠蛋白基因簇内的DNA顺序缺失,缺失的5′端点位于Aγ基因IVSⅡ内,3′端点在β-珠蛋白基因下游区远端,距HPFH-2的3′缺失端点上游区约11kb。缺失的总长度约为80kb。本文讨论了这一缺失导致胎儿血红蛋白在成人中持续活跃表达的可能机制。     

cDNAs encoding members of a family of proteins related to human sterol carrier protein 2 and assignment of the gene to human chromosome 1 p21----pter.

Sterol carrier protein 2 (SCP2) is believed to play a key role in intracellular lipid movement. Here we report the cloning and nucleotide sequences of cDNAs encoding SCP2-related proteins of 58.85 kD and 30.8 kD and the assignment of the SCP2 gene to human chromosome 1 p21-pter. The SCP2-related proteins share common deduced carboxyl amino acid sequences with SCP2 and the cDNAs have a common 3' untranslated nucleotide sequence. The mRNAs encoding these proteins increased in a coordinate fashion as human placental cytotrophoblasts differentiated into syncytiotrophoblasts in culture. Our observations document the existence of a family of related proteins encoded by the human SCP2 gene.