Role of the zinc fingers of HIV-1 nucleocapsid protein in maturation of genomic RNA

The nucleocapsid protein of HIV-1 consists of two basic amino acid regions and two zinc fingers. We investigated the requirement of these domains for the structural conversion of a 39mer RNA covering the dimerization initiation site by using three peptides; wild-type NCp7, a mutant in which the two zinc fingers are mutated, and another mutant in which the two zinc fingers are deleted. The two mutants exhibited similar conversion activities to each other, which were lower than that of the wild-type, indicating that the two basic regions exhibit some activity for RNA chaperone, as we suggested before, and the zinc fingers enhance the efficiency of this activity.     

Determination of the primary structure of homologous proteins by sequence analysis of peptide mixtures

We propose a rapid method to determine the primary structure of a protein knowing the sequence of a homologous protein. The method consists in submitting both the reduced and alkylated proteins to an enzymatic or chemical hydrolysis and performing the sequence analysis of the peptide mixtures. The assessment of the unknown sequence and the degree of identity of the two proteins are reached by comparing the two sequence analyses. The sequences of all the possible peptides present in the two mixtures are reconstructed and the differences in the two sequences are determined. If necessary, the differences can be confirmed by performing a mass spectrometric analysis of the two mixtures. We used this procedure on two homologous proteins of known sequence to furnish an application example of the method.     

A possible role of myosin conformers in provision of dual-stage superprecipitation kinetics of natural actomyosin

It has been shown that synchronous starting and successive accomplishment of superprecipitation on the two types of actomyosin complexes lead to the two-stage kinetics of this reaction. By means of a temperature change different balance of two types of actomyosin macromolecules can be achieved. We conclude that two different structural forms (conformers) of myosin cause two non-equivalent functional states of the whole actomyosin complex.     

Action of natural selection in lines of Drosophila selected for a new level of canalization

Summary Four lines of Drosophila melanogaster previously selected for a stabilized phenotype of two extra dorsocentral bristles were examined for 20 generations of canalizing selection and relaxation of selection. A substantial frequency of flies with either two anterior or two posterior extra bristles was maintained in the relaxed lines. These patterns were the only ones tolerated by natural selection, i.e., the only symmetric ones. It was concluded that anterior and posterior dorsocentral bristles are two independent development structures, and the results are discussed in relation to two proposed genetic systems for bristle determination.     

Presence and stoichiometry of two forms of subunit 6 of the mitochondrial ATPase complex of yeast

One of the mitochondrically coded components of the yeast mitochondrial ATPase complex (subunit 6) can be resolved into two components on certain polyacrylamide gels in the presence of sodium dodecyl sulfate. Purification of the ATPase complex from commercially processed yeast as well as immunoprecipitation of the holo-enzyme from cells labeled in vivo with 14C-labeled amino acids demonstrate that both forms of subunit 6 are physically associated with the assembled enzyme and present in two copies each per complex. One-dimensional papain-generated peptide maps of the two components are identical except for the mobility of a single fragment. It is concluded that the two components of subunit 6 are different forms of a single protein and are present on an average of two copies each per complex.     

ATP binding to two sites is necessary for dimerization of nucleotide-binding domains of ABC proteins

ATP binding cassette (ABC) transporters have a functional unit formed by two transmembrane domains and two nucleotide binding domains (NBDs). ATP-bound NBDs dimerize in a head-to-tail arrangement, with two nucleotides sandwiched at the dimer interface. Both NBDs contribute residues to each of the two nucleotide-binding sites (NBSs) in the dimer. In previous studies, we showed that the prototypical NBD MJ0796 from Methanocaldococcus jannaschii forms ATP-bound dimers that dissociate completely following hydrolysis of one of the two bound ATP molecules. Since hydrolysis of ATP at one NBS is sufficient to drive dimer dissociation, it is unclear why all ABC proteins contain two NBSs. Here, we used luminescence resonance energy transfer (LRET) to study ATP-induced formation of NBD homodimers containing two NBSs competent for ATP binding, and NBD heterodimers with one active NBS and one binding-defective NBS. The results showed that binding of two ATP molecules is necessary for NBD dimerization. We conclude that ATP hydrolysis at one nucleotide-binding site drives NBD dissociation, but two binding sites are required to form the ATP-sandwich NBD dimer necessary for hydrolysis.     

Cytogenetic arguments in favour of a taxonomic revision of Lepilemur septentrionalis

Cytogenetic investigations performed on 30 specimens of Lepilemur septentrionalis confirmed the existence of 4 karyotypes differing from each other by 1-2 chromosomal rearrangements. These data, pooled with those obtained in earlier studies, showed that out of 60 animals karyotyped only two kinds of hybrids were detected, allowing us to characterise two chromosomally polymorphic populations. No natural hybrids could be found between these two populations, which could thus be considered as two separate species. The possible role of the chromosomal rearrangements in the process of reproductive isolation between these two populations is discussed.     

蛇毒清合剂治疗海蛇咬伤临床观察

目的观察蛇毒清合剂对海蛇咬伤的疗效。方法将44例海蛇咬伤患者分为治疗组22例,对照组22例,两组患者均给予常规治疗,治疗组加服蛇毒清合剂,并比较两组患者咬伤48h后的血清酶学三项（CK、LDH、AST）,比较两组患者治疗7天后的疗效、治疗结束时疗程及呼吸衰竭发生率、急性肾损伤发生率。结果两组患者临床疗效比较,治疗组优于对照组（P〈0．05）,酶学三项和疗程的差异均有统计学意义（P〈O．05）}其呼吸衰竭发生率、急性肾损伤发生率虽有差异,但无统计学意义（P〉0．05）。结论蛇毒清合剂对海蛇咬伤有显著疗效。     

台闽苣苔（苦苣苔科）花部器官的形态发生

在扫描电镜下对台闽苣苔 (T .oldhamii (Hemsl.)Solereder)进行了花部器官形态发生的观察 ,为探索该类群的个体发育、类群间的系统发育关系和进化趋势提供依据。研究发现该属植物萼片、花冠和雄蕊发生式样均为五数花类型 ,它们各自来源于花原基上分化出来的萼片原基、花冠原基和雄蕊原基 ;花冠与雄蕊的两侧对称性与花冠上唇生长稍快和退化雄蕊原基发育迟滞相关 ;萼片原基的发生和发育的顺序是不一致的 :萼片原基发生的式样为近轴中原基—远轴 2原基— 2侧原基 ,发育式样则为近轴中萼片— 2侧萼片—远轴 2萼片 ,花蕾时为镊合状排列。花冠裂片原基的发生和发育式样是一致的 ,即远轴中裂原基 (下唇中裂片 )—远轴 2侧裂原基 (下唇 2侧裂片 )—近轴 2裂原基 (上唇 2裂片 )。花蕾期卷迭式为覆瓦状排列 ,从外向内 :下唇中裂片—下唇 2侧裂片—上唇 2裂片或下唇 2侧裂片—上唇 2裂片—下唇中裂片。雄蕊原基与花冠裂片原基互生 ,前方雄蕊原基在发生上稍迟于后方雄蕊原基 ,后者与退化雄蕊原基几乎同时发生 ,但较小 ,并与近轴心皮 (或柱头上唇 )对生。将该属与玄参科 (Scrophulari aceae)的地黄属 (Rehmannia)、苦苣苔科 (Gesneriaceae)的异叶苣苔属 (Whytockia)和尖舌苣苔属 (Rhynchoglossum)的花部器官比较发现     

Additional possibilities of the formation of incorrect nucleotide pairs

Calculations of intermolecular interaction energies for the systems consisting of two nitrogen bases and one or two molecules of water have been performed by the atom--atom potential function method. In some energy minima corresponding to the arrangement of the bases with one of the bases being in the syn-orientation with respect to the sugar two bases are linked through one H-bond and one or two water bridges. Such pairs provide an additional possible pathway for the appearance of errors during template biosynthesis.     

The 11S rat seminal vesicle mRNA directs the in vitro synthesis of two precursors of the major secretory protein IV

The 11s mRNA extracted from the rat seminal vesicles directs the synthesis of two different precursors of the major secretory protein RSV-IV. These two precursors are not interconvertible and seemingly originate from different translational events. Sucrose gradients, polyacrylamide gel electrophoresis and positive hybridization translation experiments do not allow the separation of the two putatively different mRNAs. It is concluded that the two RSV-IV precursors either derive from two extremely similar, but physically not separable mRNA species, or from two different modes of translation of the same mRNA molecule.     

A comparative study of growth strategies in two varieties of Arrhenatherum elatius

Growth strategies of the two varieties of Arrhenatherum elatius were studied. The two varieties studied were: onion couch, which produces bulbous swollen internodes and is an arable weed of local importance, whilst tall oat-grass is more widely distributed. An experiment in which the two varieties were grown at different densities in monoculture and were harvested at intervals, highlighted various aspects of the competitive relation between the two varieties and an annual crop. Significant and consistent differences were found between the two varieties for most of the attributes measured during the two growing seasons. Tall oat-grass allocated a greater proportion of its whole shoot dry weight to producing vigorous aerial tillers, whereas onion couch allocated a greater proportion of its whole shoot dry weight to the development of basal internodes. The regulation of tiller number as a reaction to increasing density in tall oat-grass is achieved by high tiller mortality, whereas in onion couch, this stress is expressed by small tiller mortality. Growth pattern shown by the two varieties of A. elatius reflect the adaptive strategies evolved by them in two different habitats and are due to the genetic factors which determine the presence or absence of their characteristic basal internodes.     

Population size and areas of stratification in the variational model of ecosystem

The formulations of the variational task for finding the relative population size of species in community at a stationary stage of growth and of the theorem of stratification are given. Algorithms of finding the relative size of populations for communities consisting of two and three species consuming two or three resources were obtained. The borders of areas of stratification were described in which one, two, or three resources are limiting. For two species and two resources, the formulae of the dependence of relative size on the ratio of resources were derived, and the shape of this dependence for real requirements of species was demonstrated.     

Intracisternal A-particle genes: structure of adjacent genes and mapping of the boundaries of the transcriptional unit

Adjacent intracisternal A-particle (IAP) genes were identified in two different recombinant DNA clones, gamma 81 and gamma 19. In clone gamma 81, the most common form of IAP gene was separated by 5.3 kilobases from another IAP gene that had two apparent internal deletions. The two genes were in a head-to-tail configuration. In clone gamma 19, two different types of IAP genes were separated by less than 0.5 kilobase. Blot hybridization analysis of mouse DNA demonstrated that the DNA sequence found in clone gamma 81 is identical to the in vivo configuration. Using isolated DNA fragments from clone gamma 19, we mapped the boundaries of the IAP RNA by S1 digestion of RNA-DNA hybrids and by cDNA extension. With these techniques, both the 5' end and the 3' end of the IAP RNA in two different plasmacytomas (MOPC 315 and TEPC 15) were shown to fall within the long terminal direct repeat of the IAP gene. The fragment sizes generated by S1 digestion of IAP RNAs isolated from the two tumor lines were found to differ, indicating that different IAP genes may be transcribed in these two plasmacytomas.     

A comparison of the characteristics of two strains of Schistosoma intercalatum Fisher, 1934 in mice

Schistosoma intercalatum from Cameroon and Zaire each have their specific snail intermediate host. Hybridization experiments between S. intercalatum from Cameroon and Zaire have resulted in viable miracidia for only two generations. If the two strains are of the same species, cross breeding should be possible for several generations. This paper presents a comparison of the characteristics of the two strains of S. intercalatum in experimental infections in mice. Worm return, male-female worm ratio, growth rate, number of testes in male adult worms are compared. The quantitative distribution of eggs in the tissues of the mice is recorded. A comparison of the size and shape of the parasite eggs is described as are the changes in the weight of the liver and spleen of the infected mice. It is considered that the differences observed between the two strains of S. intercalatum do not necessitate a division of the two strains into two separate species.     

含不同Anti-Waxy基因拷贝数的稻米直链淀粉含量分析

将含单拷贝Anti-Waxy基因的纯合植株分别作为父本或母本进行正反交,获得两组含双拷贝Anti-Waxy基因的杂交后代,分析了未转基因对照、转基因亲本及两组杂交后代糙米直链淀粉含量以揭示不同Anti-Waxy基因拷贝数对降低稻米直链淀粉含量程度的影响.结果显示,2个单拷贝转基因水稻糙米直链淀粉平均含量分别为10.72%和11.13%,比对照分别降低17.98%和14.84%;两组正交和反交杂交后代糙米直链淀粉平均含量分别为8.96%和8.23%,其平均值为8.60%,比2个转基因杂交亲本糙米直链淀粉含量分别降低19.78%和22.73%,比对照降低了34.20%.结果表明,增加转基因水稻基因组中Anti-Waxy基因拷贝数在一定程度上能够进一步降低稻米直链淀粉含量,通过将独立转化获得同品种转基因植株之间杂交可以成为获得高表达转基因植物的途径.     

Multilevel genetic analyses of two European supercolonies of the Argentine ant, Linepithema humile

Some ants have an extraordinary unicolonial social organization, whereby individuals mix freely among physically separated nests. Recently, it was shown that the European population of Linepithema humile consisted of two enormous unicolonial supercolonies. Workers of the same supercolony are never aggressive to each other. In contrast, aggressiveness is invariably high between workers from different supercolonies. Here we investigated whether gene flow occurs between two supercolonies. We identified a contact zone in which we sampled 46 nests. For each nest, aggression tests were conducted against workers from reference nests from both supercolonies. Workers were always very aggressive towards workers of one of the supercolonies but not to workers of the other. Thus, all nests could be clearly assigned to one of the two supercolonies. For 22 of the 46 nests, we genotyped 15-16 workers at five microsatellite loci. A four-level hierarchical analysis of variance revealed very strong genetic differentiation between the two supercolonies (F(SUPERCOLONY-TOTAL) = 0.541) and low differentiation between sectors (i.e. group of nests connected together with trails) within supercolonies (F(SECTOR-SUPERCOLONY) = 0.064). The very high differentiation between the two supercolonies indicates a lack of ongoing gene flow, a conclusion further bolstered by the finding that the two supercolonies share no common alleles at two of the five microsatellite loci. A Bayesian clustering method also revealed the occurrence of two distinct clusters. These clusters exactly match the grouping obtained by aggression tests. None of the 332 genotyped individuals were admixed despite the fact that some nests of the two supercolonies were separated by less than 30 m. These results demonstrate that the two supercolonies have completely separate gene pools.     

Fingerprinting of bacterial genomes by amplification of DNA fragments surrounding rare restriction sites.

A method for generating limited representations of total bacterial DNA, without prior knowledge of the DNA sequence, has been developed. This method consists of three steps: digestion with two restriction enzymes, ligation of two oligonucleotide adapters corresponding to the restriction sites, and selective PCR amplification of the ligation products. The method relies on the use of two restriction enzymes with considerable differences in cleavage frequency of the investigated DNA and the ligation of two different oligonucleotides, each corresponding to one of the two cohesive ends of DNA fragments. Three subsets of DNA fragments are generated during digestion and subsequent ligation: terminated with the same oligonucleotide on both 5' ends of DNA fragments (two subsets) and terminated with two different oligonucleotides. Suppression PCR allows only the third subset of DNA fragments to be amplified exponentially. The method allows bacterial species strain differentiation on the basis of the different DNA band patterns obtained after electrophoresis in polyacrylamide gels stained with ethidium bromide and visualized in UV light.     

Antiparallel alignment of the two protomers of the regulatory subunit dimer of cAMP-dependent protein kinase I

The purified type I regulatory subunit of cAMP-dependent protein kinase is a dimeric protein, and the two protomers of the dimer are linked by two interchain disulfide bonds. The disulfide linkages that join these two polypeptide chains have been identified in order to provide a structural basis for the orientation of the two chains in the asymmetric dimer. Disulfide bonds were found to exist exclusively between Cys-16 and Cys-37, and this assignment, thus, establishes a general antiparallel alignment of the two chains. Two other homologous proteins, the type II regulatory subunit and the cGMP-dependent protein kinase also are dimeric proteins. In all three proteins, a relatively small, nonhomologous, amino-terminal segment of the polypeptide chain is essential for maintaining the dimeric aggregation state.