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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Sexual plant reproduction 12 (2000), S. 310-313 
    ISSN: 1432-2145
    Keywords: Key words Meiosis ; Arabidopsis ; Pelota
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  We have identified a plant homologue of the Drosophila meiotic gene Pelota in Arabidopsis thaliana (AtPelota1). This gene maps to chromosome 4 of Ara- bidopsis and is one of two Pelota homologues present in this plant. When the expression pattern of AtPelota1 was examined it was found to be expressed at similar levels in all plant tissues tested (whole plant, bud, stem, leaf and root). This expression pattern corresponds to that seen for some other Arabidopsis meiotic genes and their homologues. A search of the databases reveal that the AtPelota gene family is widespread with homologues present in higher and lower eukaryotes and archaebacteria, but not eubacteria.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-6849
    Keywords: Arabidopsis ; fertility ; meiosis ; mutants ; T-DNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A secondary screen of the Feldmann collection of T-DNA transformed Arabidopsis lines identified several meiotic mutants. We used a spreading technique combined with DAPI staining in a detailed cytogenetic analysis of meiotic chromosome behaviour in four of these mutants, all of which are putatively T-DNA tagged and therefore candidates for molecular and functional analysis of the mutated genes. Two of them are defined as ‘synaptic’ mutants, showing greatly reduced association of homologous chromosomes at metaphase I: one is asynaptic, showing failure of synapsis during prophase I, whereas the other is desynaptic and is characterized by normal but non-maintained synapsis. Another mutant is defective in meiotic cell cycle control and undergoes a third meiotic division, resembling a second division but without an additional round of chromosome duplication. A further mutant shows meiosis-limited chromosome disruption, resulting in extensive chromosome fragmentation combined with other defects. All four mutants experience very irregular chromosome distribution during the meiotic divisions, resulting in abnormal numbers and/or sizes of microspores, with resulting reduced fertility.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 104 (1980), S. 425-431 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Viable cell samples containing 93% pure granulocytes were obtained from human blood using the techniques of dextran sedimentation followed by centrifugal elutriation. The resting transmembrane potential (Em) of human granulocytes was estimated using the fluorescent lipophilic cation, Di-S-C3(5), from the null point for potassium - i.e., the external K concentration at which there is no change in Em in response to valinomycin (a K ionophore). The Em of human granulocytes, as calculated from the Nernst potential for K at the null point, is approximately - 100 mV. Data indicate that this large transmembrane potential is due in part to the presence of an electrogenic Na-K pump in human granulocytes which is stimulated by external potassium and inhibited by ouabain.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 106 (1981), S. 75-83 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Treatment of human granulocytes with concanavalin A, phorbol myristate acetate (PMA), N-formyl-methionyl-leucyl-phenylalanine (FMLP), and A23187 (a calcium ionophore) stimulates the release of superoxide anion and the generation of chemiluminescence. The fluorescent probe, Di-S-C3(5), has been used to monitor shifts in membrane potential in response to these stimulants which precede the secretion of superoxide. Concanavalin A, PMA, and FMLP induce a biphasic shift in transmembrane potential (Em), i.e., a rapid depolarization followed by a prolonged hyperpolarization. This depolarization is dependent on both external sodium and calcium while the hyperpolarization is inhibited by ouabain which blocks the electrogenic Na-K pump. In contrast, A23187 induces a rapid and prolonged depolarization. This monophasic shift in Em is dependent on external calcium. These results suggest that depolarization acts as a signal to initiate events associated with the “respiratory burst” of these phagocytes.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0749-503X
    Keywords: Hansenula ; haemoglobin ; integration ; continuous culture ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Recombinant human haemoglobin A (rHbA) was produced by a leucine-requiring strain of Hansenula polymorpha which had been transformed with an integration vector containing the Saccharomyces cerevisiae LEU2 gene and cDNAs for the expression of α and β globin each driven by the H. polymorpha MOX promoter. After 40 generations in a chemostat it was found that the integrated vector had become amplified in the host strain. In some cases this led to an increase in LEU2 gene dosage, but a loss of globin expression cassettes. In other cases the globin gene dosage also increased. These changes coincided with an increase in rHbA production in the culture, which was reversed when the dilution rate was increased. Isolates from a chemostat culture producing elevated levels of rHbA were grown in fed-batch fermentations, resulting in higher productivities than when inoculated with the parent strain. The rHbA produced was purified and characterized. Oxygen binding studies and electrospray mass spectrometry showed that the rHbA had been processed and assembled correctly, and behaved as a fully functional co-operative tetramer.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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