Lithium inhibition of phosphofructokinase

The mode of action of lithium in prophylaxis of recurrent affective disorder is unknown although it has been suggested that lithium might compete with magnesium in magnesium dependent processes. We have previously shown pyruvate kinase to be inhibited by lithium and the present study demonstrates a small inhibition by lithium of phosphofructokinase that is also a major regulatory step in glycolysis. Inhibition of PFK was competitive with respect to ATP and magnesium and noncompetitive with respect to potassium and fructose-6-phosphate. Inhibition was enhanced at reduced concentrations of magnesium.     

The cell cycle and its relationship to development in Dictyostelium discoideum.

When deprived of exogenous nutrients some amoebas of Dictyostelium discoideum do continue to progress through the cell cycle. There are two distinct periods when mitotic cell division occurs. Labeling studies show that during the first period, which begins at the onset of development and ceases at the first visible signs of aggregation (rippling), only those cells which are beyond a certain point in G2 at the initiation of development divide. The second period of mitotic activity begins at tip formation, reaches maximum activity at the grex stage, and ceases during early culmination. Significantly, examination of the development of amoebas harvested when in the stationary phase of growth (and thus arrested in G2) shows that these cells still undergo mitotic cell division during the second period but do not show any such division during the preaggregation phase. The extent to which increases in cell number can be taken to be indicative of mitotic cell division varies from one culture to another due to the presence of variable numbers of multinucleate cells which become mononucleate during the first 10 hr of development. However, when due allowance has been made for the existence of these cells in axenically growing amoebal populations, our data show that by completion of fruiting body construction there has been a doubling in cell number as a direct result of mitotic cell division. Nuclear DNA synthesis also occurs at two distinct periods during development, these coinciding with the periods of mitotic activity. However, since no more than 35% of the cells have undergone nuclear DNA synthesis by the end of the developmental phase, our results are inconsistent with the conclusion that all cells accumulate at a position in G2 at the time of aggregation. Our results do suggest, however, that mitotic cell division of a fraction of the cells may be an integral part of the developmental phase.     

Rat-brain pyruvate kinase: Purification and effects of lithium

Purified pyruvate kinase was prepared from pooled brains obtained from untreated rats. Its properties suggest that it is similar to type 'M' pyruvate kinase. Lithium inhibition was demonstrated at pharmacologically significant lithium concentrations (7%-12% at 2 mmol 1-1 Li) and this was similar in character to that previously seen in rabbit muscle pyruvate kinase, namely noncompetitive with respect to phosphoenol pyruvate, K+, and Mg2+ but competitive with ADP.     

Alfred Nicholson Leeds and the first fossil egg attributed to a ‘saurian’

Discovered by the nineteenth century collector Alfred Nicholson Leeds, the first object to be described (1898) as a fossil reptile egg is a unique find from the Oxford Clay near Peterborough. It also comes from one of a very small number of Jurassic localities worldwide that can claim to have yielded a fossil egg. Given its historical and contemporary significance, this object is reassessed in the light of increased understanding of such objects. Data from scanning electron microscopy, computerised tomography, synchrotron imaging, X-ray diffraction and petrographic thin sectioning prove inconclusive. However, the presence of apparent external openings resembling angusticanaliculate pores – a pore type common only to certain types of dinosaur eggshell – in both size and sparseness of distribution prevents its summary dismissal as not being a dinosaurian egg.     

Phenological records of English garden plants in Leeds (Yorkshire) and Richmond (Surrey) from 1946 to 2002. An analysis relating to global warming

Graphical analysis of first-flowering dates of selected garden plants 1946–2002 shows an earlier trend, which appears to be linked to temperature and global warming. Some species, however, seem to buck this trend, which may be linked to photoperiodic response. Combined graphs of species selected at intervals throughout the calendar year reveal a rhythm or wave of several years in Leeds 1946–1962 and a less marked rhythm in Richmond 1961–2002.     

多聚赖氨酸引起林蛙卵表面的聚集以及对分裂沟的影响

1.多聚赖氨酸能使经异硫氰基荧光素染色的卵表面均匀分布的荧光聚集成点状或块状的斑块,荧光聚集时膜下的色素颗粒随之同步聚集。早期的聚集有三种方式。2.聚集的迟早和出现斑块的大小在卵表面不同区域是不同的。腹方新月区最早;灰色新月区次之;动物性半球稍迟,荧光和色素颗粒最后都集中到动物性极形成顶帽,其余区域成为失去色素颗粒的区域;聚集引起收缩,最后植物性半球常常破裂。3.未受精卵亦出现与上述相同的反应,这提示腹方新月区可能是精子进入卵子的区域。4.细胞松弛素不能抑制多聚赖氨酸引起的聚集。5.多聚赖氨酸能抑制分裂沟的出现,能使已出现的分裂沟消失。6.失去色素颗粒区域的细胞膜在形态、功能等方面与分裂沟中的新膜相同。对新膜出现的位置和形成因素进行了讨论。     

蛙精子中心体的分离

中心体是动物和低等植物中构成有丝分裂器的重要结构和功能元件,是间期细胞质微管和分裂期纺锤体微管的组织中心。本文报道一种从蛙精子中分离中心体的简便方法:通过匀浆将精子尾部与头部脱离,用蔗糖离心去除脱落的尾部和杂质颗粒,从而得到纯化的精子头部。用含EGTA的低渗液使精核膨大,再以超声破碎,离心得到中心体的粗制品,以重复超声和离心去除染色质和中心体外围的线粒体,得到纯度较高的精子中心体。电镜观察和免疫荧光染色显示分离所得的中心体由一对中心粒和其外周物质组成。     

Study of copper(II) and nickel(II) ternary complexes involving tertiary amines and phenyl or hydroxylphenyl substituted amino acids

Formation constants of ternary complexes MAL, where M = Cu(II) or Ni(II). A = 2.2′bipyridyl. 1, 10-phenanthroline, and L = 3.4-dihydroxyphenylalanine (dopa), tyrosine, or phenylalanine have been determined by using the computer program SCOGS. It is observed that dopa coordinates with Cu(II)-A and Ni(II)-A through the aminocarboxylate and only over the pH range 3–8, though the ligand coordinates with free Cu(II) ion from the amino carboxylate end in the lower pH range (pH 2–4) and from the catechol end at the higher pH range (pH > 5). The visible spectrum of Cu-A-dopa is similar to that of Cu-A-phenylalanine or Cu-A-tyrosine over the entire pH range, confirming amino carboxylate coordination. Δ log K (K_MAL - log_KML) is found to be positive in all the six Cu(II) complexes. whereas it is negative in Ni(II) complexes. Release in the ternary complexes of the repulsion between the Cu(II) dπ electron and electrons delocalized over the phenyl ring has been proposed as a probable reason for the positive Δ log K.     

猪传染性水疱病病毒(SVDV)在微细胞和微胞质体内的复制

本实验研究了SVDV在微细胞和微胞质体两种非完整细胞体系内的复制。用秋水仙素处理IB-RS-2细胞,在含有松胞素B的Ficoll 400不连续梯度中进行高速离心,制备了大量的微细胞。微细胞在正常的培养条件下60小时后仍有70%以上存活,用SVDV感染只需4—5小时就几乎全部脱落。并证明微细胞能繁殖出有感染力的子代病毒。用松胞素B去核技术制备的微胞质体,运用扫描电镜和显微放射自显影的方法证实了SVDV可以在微胞质体内复制病毒RNA,并引起微胞质体病变。同时纯化了用松胞素B处理悬浮的IB-RS-2细胞而制备的大量的微胞质体,SVDV感染后,可以产生一定数量的有感染力的子代病毒。虽然滴度低于完整细胞繁殖的病毒,但证明了SVDV可以利用微胞质体中少量的细胞成分和酶类完成其感染、复制和装配一系列繁殖过程,产生有感染力的子代病毒。     

鹿科动物的染色体组型及其进化

染色体是遗传物质的主要携带者。在动植物进化过程中,染色体在数量和结构上的变化,无疑对物种形成起重要的作用。染色体的变化往往引起基因的重新排列和遗传物质的增加或丢失。染色体在结构和数量上的差异还往往造成两个本来很相近的群体间的生殖隔离而形成新种。染色体组型和染色体的带型都代表着种的特性,它为不同动物在分类研究和确定其在进化过程中的位置提供了一个新的和重要的标准。可是,染色体的结构既是稳定的,同时又是可变的。染色体组型的改变是以染色体组的结构特点为基础     

凹叶厚朴大、小孢子发生和雌、雄配子体发育的研究

凹叶厚朴花药四囊型,腺质绒毡层有1-2层细胞,小孢子形成时胞质分裂方式为修饰性同时型,小孢子四分体排列方式为左右对称型．成熟花粉粒为二细胞型。四分体和小孢子在发生时有不规则变形。子房单心皮,心皮腹面壁上着生2个胚珠,胚珠倒生型,厚珠心,双珠被;孢原细胞一个,并且自表皮下第2层细胞处分化。胚囊发育为单孢蓼型。凹叶厚朴的胚胎学特征与木兰科其它植物的胚胎学特征基本相同,属于较原始的被子植物胚胎类型。在凹叶厚朴大、小孢子发生和雌、雄配子体发育过程中存在部分败育现象。本文初步探讨了凹叶厚朴濒危的生殖生物学原因。     

凹叶厚朴大、小孢子发生和雌、雄配子体发育的研究

凹叶厚朴花药四囊型,腺质绒毡层有1-2层细胞,小孢子形成时胞质分裂方式为修饰性同时型．小孢子四分体排列方式为左右对称型,成熟花粉粒为二细胞型。四分体和小孢子在发生时有不规则变形。子房单心皮。心皮腹面壁上着生2个胚珠,胚珠倒生型,厚珠心,双珠被;抱原细胞一个,并且自表皮下第2层细胞处分化。胚囊发育为单孢蓼型。凹叶厚朴的胚胎学特征与木兰科其它植物的胚胎学特征基本相同,属于较原始的被子植物胚胎类型。在凹叶厚朴大、小孢子发生和雌、雄配子体发育过程中存在部分败育现象。本文初步探讨了凹叶厚朴濒危的生殖生物学原因。     

B淋巴细胞的造血调控作用

我们以往的工作证实T细胞对造血干细胞增殖分化的调控作用,经特异或非特异性抗原激活的淋巴细胞具有更强的调控活性。为了进一步弄清细胞间相互作用在造血调控中的地位,近年来我们又探讨了B淋巴细胞对造血干、祖细胞增殖调控作用。     

高等植物叶绿体和线粒体免疫亲近性的研究

以火箭免疫电泳分析表明:大豆叶绿体抗体与大豆线粒体有免疫交叉反应,同时大豆线粒体抗体与大豆叶绿体也有免疫交叉反应,但是大豆线粒体的抗体与鼠肝线粒体之间无免疫交叉反应。这说明高等植物线粒体对叶绿体比之对动物线粒体在免疫特性上有更大的亲近性,亦即高等植物线粒体和高等植物的叶绿体有更大的同源性。经火箭免疫电泳、交叉免疫电泳和线状免疫电泳进一步分析表明:菠菜偶联因子抗体(AbCF_1)和大豆线粒体、大豆叶绿体间,大豆线粒体抗体与CF_1和大豆叶绿体之间,以及大豆叶绿体的抗体(AbC)与CF_1和大豆线粒体间有免疫交叉反应,说明两种换能器之间有免疫亲近性,并分别与CF_1存在免疫亲近性。这揭示两种换能器免疫亲近性的表现是由于存在共同物质基础所致,这内在共同物质基础是偶联因子。这个结果有力地支持高等植物叶绿体和线粒体在结构和功能上以及发生上存在同源性的观点,在理论上也为两种换能器的起源和演化上存在同源性提供了一些依据。     

B淋巴细胞在多向造血祖细胞生长中的地位

小鼠骨髓细胞在体外培养中,加入用流式自由电泳法分离所得的高纯度正常B淋巴细胞,可使多向祖细胞(CFU-mix)集落增加至5倍;加入小鼠B淋巴瘤细胞株的条件培基(M_(12.4.1)-CM)时,CFU-mix数也可增加至4倍。单集落形态学分析结果表明M_(12.4.1)-CM可加强CFU-GEMm及p-BFU-E等早期造血祖细胞的增殖与分化。小鼠高纯度B细胞样品在体外培养中加入1000 rad照射的骨髓细胞可出现CFU-mix集落,如果再加入适量的小鼠肺条件培基,则CFU-mix数量比对照大15倍,其集落性质为CFU-GEMm,GMm及p-BFU-E。在此培养中加不同稀释度抗小鼠IgM血清,结果CFU-mix的产率与抗IgM血清的浓度成直线反比关系,当加入1:10抗小鼠IgM血清时,CFU-mix为0。作者假设在一定培养条件下,IgM阳性的部分B细胞可返祖转化为CFU-mix。     

db-cAMP对转化细胞钙调素基因表达与细胞骨架的影响

转化的C_3H_(10)T_(1/2)细胞表现增殖速度加快、表面微绒毛增加,细胞变圆,叠层生长,ConA受体呈帽状分布,微管、微丝、纤粘蛋白分布明显减少。与增殖有关的癌基因c-fos表达增强,同时发现与细胞增殖、转化和细胞骨架调节有关的钙调素(CaM)基因表达加强。用1mmo/Ldb-cAMP处理转化细胞,观察到CaM基因和原癌基因c-fos的表达分别在处理后1小时和2小时急剧下降。处理后4—5天,转化细胞表型趋正常化,大部分细胞恢复单层生长。细胞表面微绒毛和泡状物减少,ConA受体帽状分布消失,恢复分散分布在细胞膜上的特点。细胞生长明显被抑制,用优先在G_1期表达的4F_1 cDNA为探针进行分子杂交,证实了经db-cAMP处理后的细胞被阻抑在G_1期。经db-cAMP处理6天的转化细胞中微管、微丝、纤粘蛋白基本恢复正常分布。实验表明CaM的表达增强与转化细胞表型变化和细胞骨架组装减弱密切相关,db-cAMP作用后CaM表达下降是抑制转化细胞增殖并使细胞表型和细胞骨架分布趋于正常的关键事件之一。     

快中子辐射对红豆草愈伤组织细胞结构影响的电镜观察(简报)

近年来植物愈伤组织无性变异系的诱导和选择,已成为植物细胞工程中十分活跃的领域,快中子、γ射线等电离辐射也已开始被用于愈伤组织抗性变异系的诱导。观察不同剂量电离辐射在诱发植物愈伤组织变异中对细胞结构的影响,对于探讨辐射诱变的细胞学机理     

3'''',5''''-cAMP对艾氏腹水癌细胞膜功能的作用(cAMP的转运和膜蛋白分子的侧向运动)

本工作用外源性cAMP加氨茶碱处理艾氏腹水癌小鼠,于不同瘤龄期观察到癌细胞膜对cAMP的转运功能和膜内蛋白质分子侧向扩散运动的变化、以及膜内可动性蛋白质分子的百分比的改变。这些表型变化均在接种后5—7天最为显著。接种后第7天,实验组癌细胞膜对cAMP的转运加强,而膜内蛋白质分子侧向扩散运动??减慢,抑制率达72.8%,二者P值均小于0.01。而接种后第9天,实验组与对照组之间二者变化均无统计学差异。这些变化表现了癌细胞膜的功能状态的变化。进一步阐明了我们过去工作——3’,5’-cAMP对体内艾氏腹水癌细胞作用机理,接种后第9天癌细胞内cAMP水平升高不是外源性cAMP的积累,而是内源性的代谢结果;阐明了接种后第5天cAMP-PDE活性下降的动因。同时我们也进一步看到膜功能、膜结构和胞质内cAMP水平及其二酯酶活性等变化的动力学关系,以及它们和癌细胞增殖抑制之间的相互关系。从而说明这些变化在癌细胞“逆转”中的意义与其内在联系。