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     

Two different populations of primitive erythroid cells in the ehick embryo.

Antibodies prepared against the two hemoglobins of the adult chick cross react with the two minor hemoglobins and do not react with the two major hemoglobins isolated from lysates of primitive erythroid cells of the 4-day-old embryo. The different immunological reactivities of the two primitive hemoglobin pairs have permitted us to discriminate, in smears of primitive erythroid cells, two populations on the basis of their hemoglobin contents.     

Enzyme Activities and Alcohol Tolerance in Isofemale Lines of Drosophila melanogaster Originating from Different Habitats

Enzyme activity variation was studied in a Drosophila melanogaster population from two villages (Tiszafüred and Tiszaszolos) in Hungary. Two habitats (distillery and farmyard) were sampled in both villages and 8-9 isofemale lines were established from each sample with a total of 35 lines. The activities of ADH, alphaGPDH, IDH and 6PGDH were determined on starch gel after electrophoresis in 10 F1 females of each of the 35 isofemale lines. Three sublines were established from three selected isofemale lines of all four samples (altogether 36 sublines). Alcohol tolerance of the adult flies was assayed in these sublines. The activity of ADH was similar in the two habitats; so was the sensitivity to ethanol. Accordingly, no differences in adaptation to environmental ethanol were detected between the two habitats. The deviations between the two habitats in average activities and in the total variation of enzyme activities were not consistent in the two villages. These results suggest that founder effects and genetic drift are more pronounced in distilleries than selection. The association among enzyme activities varied greatly both between the two villages and between the two habitats. The two parameters of alcohol tolerance were not significantly different between the two habitats in any of the two villages.     

The Dynamics of a Fish Stock Exploited in Two Fishing Zones

This work presents a specific stock-effort dynamical model. The stocks correspond to two populations of fish moving and growing between two fishery zones. They are harvested by two different fleets. The effort represents the number of fishing boats of the two fleets that operate in the two fishing zones. The bioeconomical model is a set of four ODE's governing the fishing efforts and the stocks in the two fishing areas. Furthermore, the migration of the fish between the two patches is assumed to be faster than the growth of the harvested stock. The displacement of the fleets is also faster than the variation in the number of fishing boats resulting from the investment of the fishing income. So, there are two time scales: a fast one corresponding to the migration between the two patches, and a slow time scale corresponding to growth. We use aggregation methods that allow us to reduce the dimension of the model and to obtain an aggregated model for the total fishing effort and fish stock of the two fishing zones. The mathematical analysis of the model is shown. Under some conditions, we obtain a stable equilibrium, which is a desired situation, as it leads to a sustainable harvesting equilibrium, keeping the stock at exploitable densities.     

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.     

Thermodynamic properties of oxidoreductase, transferase, hydrolase, and ligase reactions

Transferases formally couple together two oxidoreductase reactions or two hydrolase reactions. Therefore the thermodynamic properties of transferase reactions can be calculated from differences between thermodynamic properties of two oxidoreductase or two hydrolase reactions. Ligases couple together two hydrolase reactions, and so their thermodynamic properties can be calculated from differences between two hydrolase reactions. These relationships are demonstrated by calculating standard transformed Gibbs energies of reaction and the changes in binding of hydrogen ions at pHs 5-9 of a number of oxidoreductase, transferase, hydrolase, and ligase reactions by use of the data base BasicBiochemData2 and its recent extensions. Coupling is not restricted to two reactions, and an example is given of the coupling of three reactions.     

Searching for geometric molecular shape complementarity using bidimensional surface profiles

The study presented herein is a bidimensional approach to the complementarity of two molecular surfaces. From two chosen sections we have established a methodology of generating the optimal matching of two shapes. Our approach consists in describing two molecular surface sections by a shape vector (the angular profile), in finding their matching patterns by comparison of the two profiles, and in optimizing the relative locations of the two sections in two-dimensional space, using rotations and translations defined by geometric characteristics. The set of optimal configurations are successively displayed on a screen. Satisfying results have been obtained for the matching of the complex kallikreine Atrypsin pancreatic bovin 2. This efficient method could be used as a preprocessing for a tridimensional shape complementarity approach between two molecular surfaces.     

The cleavage initiation site establishes the posterior pole of the hydrozoan embryo

Summary When the first cleavage of the hydrozoan egg is reversibly suppressed, two cleavage furrows frequently form simultaneously at the time of the second cleavage. If these two cleavage initiation sites are far enough apart, each one specifies a site of gastrulation, and the embryo that forms develops into a two tailed planula larva. When two tailed planulae are induced to metamorphose, they form a polyp with two stalks and hydranths.     

Two chicken erythrocyte band 3 mRNAs are generated by alternative transcriptional initiation and differential RNA splicing.

The erythrocyte anion transport protein (band 3) mediates two distinct cellular functions: it provides plasma membrane attachment sites for the erythroid cytoskeletal network, and it also functions as the anion transporter between the erythrocyte cytoplasm and extracellular milieu. We previously showed that two chicken band 3 polypeptides are encoded by two different mRNAs with different translation initiation sites. Here we show that these two band 3 mRNAs are transcribed from two separate promoters within a single gene. In addition, the two pre-mRNAs are differentially spliced, leading to fusion with coding exons used in common in the two mRNAs. The chicken erythrocyte band 3 gene is therefore the first example of a gene that has two promoters within a single locus which function equally efficiently in one cell type at the same developmental stage.     

Aberrant valve formation in a centric diatom,Ditylum brightwellii

Summary Interphase cells of the centric diatom,Ditylum brightwellii (West) Grunow, were treated with a microtubule-inhibitor (amiprophosmethyl, 6×10^–7 M); the cells could proceed to divide, but the spindle apparatus in about 25% of the cells was displaced and their two sibling cells has either two nuclei or none. The cells with two nuclei formed a new valve with two labiate processes, instead of one as in normal cells. Most of the cells lacking a nucleus were unable to form a new valve, and of the 2% that did form new valves, all did so without dividing. The valves with two labiate processes were originally formed in two separate silica deposition vesicles (SDVs) and the two embryonic siliceous valves fused when these two expanding SDVs met. Accordingly, both the pattern of perforations and the shape of the marginal ridges on the new valve vary with the distance between the two initiation sites of the two SDVs. Implications of these observations in the evolution of valves in diatoms are discussed and a hypothesis on multiple origins of the valves is proposed.     

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.     

Genetic independence of the embryonic reactivity difference to cortisone- and 6-aminonicotinamide-induced cleft palate in the mouse.

The A/J strain of mice is more reactive than C57BL/6J to both cortisone- and 6-aminonicotinamide-induced cleft palate. A breeding study was set up to determine the genetic control of the differences in embryonic reactivity between the two strains to the two teratogens. In this paper the test for possible association between the two response traits is presented. In the second-backcross generation of embryos where segregation of the two traits could be studied no association was found. Therefore, any embryonic genes making major contributions to differences in reactivity between the two strains are not the same for the two teratogens.     

Autonomous DNA binding domains of lambda integrase recognize two different sequence families

The 40 kd lambda Integrase protein is shown to contain two autonomous DNA binding domains with different sequence specificities. Competition experiments in which the binding activity of Int is assayed through nuclease protection demonstrate the functional independence of the two DNA recognition specificities. Proteolytic cleavage of Int and footprinting analysis of the resulting two major peptides allow the physical separation and identification of two DNA binding domains: an amino-terminal peptide that interacts with "arm-type" sites and a carboxy-terminal peptide that binds to "core-type" sequences. In addition, the data suggest that the two domains can bind DNA simultaneously, consistent with a model in which Integrase would link two disparate DNA sequences.     

Two independent gene systems controlling recombination in Schizophyllum commune

Summary Mating competence in the fungusSchizophyllum commune is controlled by two unlinked factors, each of which consists of two closely linked loci. The recombination frequencies between the loci of each factor were determined for a dikaryon and a group of back-crosses, at two meiotic temperatures. The results establish that the frequencies of recombination in the two regions are under genetic control. Although the two regions are similar in structure and function they are under separate recombination control.     

The IH-NMR-study of the copper surrounding in plantacyanin

The 300-MHz proton NMR spectra of oxidized, reduced and apo-forms of plantacyanin were studied. The data obtained show that one of two histidines is far from copper whereas the other is a ligand of the metal. Ligands of copper are also two methionines and, possibly, tryptophan. Although the surrounding of copper in plastocyanin consists of two sulfur and two nitrogen atoms, only histidine and methionine are invariant ligand amino acids of the metal in these two copper proteins from plants.     

两类木蹄层孔菌在酶蛋白水平上的遗传分化

木蹄层孔菌（Ｆｊｏｍｅｓ　ｆｏｍｅｎｔａｒｉｕｓ）在中国东北和日本存在子实体形态不同、寄主范围明显有别的两个类型：小型和大型。用多位点分析方法研究了两者间的遗传分化状况。从两类４１个菌株的４种酶系统中检测出９个基因位点,其中８个位点上的绝大多数酶谱型都不为两者所共有,显示两个类型间的基因交流已极少发生。根据酶谱型频率得出两者间的遗传距离Ｄ＝０．９６５,属于典型的种间遗传分化。上述酶基因分化证据结合子实体形态的显著差异,提示两类木蹄层孔菌是各自独立的种。两个类型的群体在遗传多样性参数上无显著差异,可能暗示两者在起源演化上的同步性。酯酶系统有２个位点上的酶谱为不同类型所特有且稳定而清晰,可作为分子标记用于两类木蹄层孔菌的无子实体鉴定。     

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.     

Identification of the PcrA DNA helicase reaction pathway by applying advanced targeted molecular dynamic simulations

PcrA DNA helicase uses the free energy of hydrolysis and binding of ATP to unwind double-stranded DNA (ds-DNA). There are two states of PcrA, termed the substrate and product complexes and, through the conformational changes between these two states, PcrA moves along ds-DNA and separates the two strands. In this study, two different methods, namely chain minimisation (CM, less reliable method) and auto targeted molecular dynamic (TMD) simulation (more reliable), were performed to generate two different initial reaction pathways between these two states, and then fixed root mean square distance (RMSD) TMD simulation was performed to optimise these two initial pathways. In general, the two optimised pathways share very similar major conformational changes, but are different in the minor motions. The potential energy profiles of the two improved pathways are generally similar, but the one generated by the improved TMD path is slightly lower. Considering the poor reliability of the initial path generated by CM and insignificant improvements of the auto-TMD path, our study suggests that fixed RMSD TMD simulation can generate reliable reaction pathways, but the different initial paths still have some influence on the detailed conformational analysis.     

双位点核酶对乙型肝炎病毒C基因体外转录物的剪切作用

为探讨双位点核酶对乙型肝炎病毒C基因体外转录物的剪切作用,观察双位点核酶对单一核酶体外剪切的增强作用,同时比较串联核酶和混合核酶的体外切割作用,构建了核酶Rz1,Rz3, Rz1和Rz3的串联核酶(Rz13)体外转录载体, 经体外转录后切割靶RNA. 结果表明:双位点核酶,无论是串联或混合核酶均可增强单一核酶的体外切割作用, 串联和混合核酶中的单一核酶可独立发挥作用;当串联和混合数目为2个时,两者的切割效率差别不大(P＞0.05).