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  • 1
    Electronic Resource
    Electronic Resource
    Junctions between repetitive DNAs on the PSR chromosome of Nasonia vitripennis: Association of palindromes with recombination (1994)
    Springer
    Journal of molecular evolution 38 (1994), S. 352-362 
    Details
    ISSN: 1432-1432
    Keywords: Paternal-Sex-Ratio ; Nasonia ; Repetitive DNA ; Junctions ; Recombination ; Palindromes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The Paternal-Sex-Ratio (PSR) chromosome of Nasonia vitripennis contains several families of repetitive DNAs that show significant sequence divergence but share two palindromic regions. This study reports on the analysis of junctions between two of these repetitive DNA families (psr2 and psr18). Three lambda clones that hybridized to both repeat families were isolated from PSR-genomic DNA libraries through multiple screenings and analyzed by Southern blots. Analysis of clones showed a region in which the two repeat types are interspersed, flanked by uniform blocks of each repeat type. PCR amplification of genomic DNA confirmed the contiguous arrangement of psr2 and psr18 on PSR and identified an additional junction region between these repeats that was not present in the lambda inserts. We isolated and sequenced 41 clones from the lambda inserts and genomic PCR products containing junction sequences. Sequence analysis showed that all transitions between psr2 and psr18 repeats occurred near one of the two palindromes. Based on the inheritance pattern of PSR, recombination between repeats on this chromosome must be mitotic (rather than meiotic) in origin. The occurrence of exchanges near the palindromes suggests that these sequences enhance recombination between repeat units. Rapid amplification of repetitive DNA may have been an important factor in the evolution of the PSR chromosome.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00163152
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  • 2
    Electronic Resource
    Electronic Resource
    A Study of the dielectric properties of the polymer electrolyte PEO-LiClO4 over a composition range using time domain spectroscopy (1989)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 27 (1989), S. 2011-2022 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: High frequency dielectric measurements in the range 10 MHz to 10 GHz have been performed on poly(ethylene oxide) (PEO) and its complexes with lithium perchlorate using time domain spectroscopy. Measurements were made over a wide polymer-to-salt composition range and in the temperature range 50-75°C. All samples were amorphous. A relaxation was observed for PEO and its complexes with LiClO4 in the GHz region and is attributed to the β (αa) relaxation arising from long-range segmental motion of the polymer or the ion-polymer complex. Good agreement was found between conductivity values determined by TDS and those quoted in the literature An increase in salt concentration in the polymer increases the distribution of relaxation times which may be explained in terms of increased intermolecular and intramolecular transient crosslinks. The dispersion amplitude (ε′0-ε′∫) has a maximum value between an O/Li ratio of 20:1 and 12:1 and shows a similar dependence on salt concentration as the conductivity.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1989.090271006
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  • 3
    Electronic Resource
    Electronic Resource
    Induction of paternal genome loss by the paternal-sex-ratio chromosome and cytoplasmic incompatibility bacteria (Wolbachia): A comparative study of early embryonic events (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 40 (1995), S. 408-418 
    Details
    ISSN: 1040-452X
    Keywords: Paternal genome loss ; Cytoplasmic incompatibility ; Paternal-sex-ratio chromosome ; Wolbachia ; Nasonia ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Paternal genome loss (PGL) during early embryogenesis is caused by two different genetic elements in the parasitoid wasp, Nasonia vitripennis. Paternal sex ratio (PSR) is a paternally inherited supernumerary chromosome that disrupts condensation of the paternal chromosomes by the first mitotic division of fertilized eggs. Bacteria belonging to the genus Wolbachia are present in Nasonia eggs and also disrupt paternal chromosome condensation in crosses between cytoplasmically incompatible strains. Cytoplasmic incompatibility Wolbachia are widespread in insects, whereas PSR is specific to this wasp. PGL results in production of male progeny in Nasonia due to haplodiploid sex determination. The cytological events associated with PGL induced by the PSR chromosome and by Wolbachia were compared by fluorescent light microscopy using the fluorochrome Hoescht 33258. Cytological examination of eggs fertilized with PSR-bearing sperm revealed that a dense paternal chromatin mass forms prior to the first metaphase. Quantification of chromatin by epifluorescence indicates that this mass does undergo replication along with the maternal chromatin prior to the first mitotic division but does not replicate during later mitotic cycles. Contrary to previous reports using other staining methods, the paternal chromatin mass remains condensed during interphase and persists over subsequent mitotic cycles, at least until formation of the syncytial blastoderm and cellularization, at which time it remains near the center of the egg with the yolk nuclei. Wolbachia-induced PGL shows several marked differences. Most notable is that the paternal chromatin mass is more diffuse and tends to be fragmented during the first mitotic division, with portions becoming associated with the daughter nuclei. Nuclei containing portions of the paternal chromatin mass appear to be delayed in subsequent mitotic divisions relative to nuclei free of paternal chromatin. Crosses combining incompatibility with PSR were cytologically similar to Wolbachia-induced PGL, although shearing of the paternal chromatin mass was reduced. Wolbachia may, therefore, block an earlier stage of paternal chromatin processing in the fertilized eggs than does PSR. © 1995 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1080400404
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  • 4
    Electronic Resource
    Electronic Resource
    Method development in pharmaceutical analysis employing capillary electrochromatography (1998)
    Weinheim : Wiley-Blackwell
    Electrophoresis 19 (1998), S. 2073-2082 
    Details
    ISSN: 0173-0835
    Keywords: Capillary electrochromatography ; Pharmaceuticals ; Polar neutral pharmaceuticals ; Pharmaceutical analysis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Capillary electrochromatography (CEC) has been employed to explore method development for a series of structurally related polar neutral compounds of pharmaceutical relevance. Capillaries with dimensions of 75 μm ID × 25 cm length (34.5 cm total) were packed with Spherisorb ODS-1, Hypersil phenyl, and Hypersil MOS (all 3 μm particles) and were compared in the reversed-phase mode in order to determine which phase provided the best initial performance and thus serve as the phase of choice for additional method development experiments. The various separation parameters examined for their effect on efficiency, k, resolution, and linear velocity included percent and type of organic modifier, buffer concentration, voltage, and temperature. All separations were conducted with an acidic mobile phase (aqueous mobile phase component, pH 3.0). The separation efficiencies obtained were on the order of 200000-260000 plates/m, which equates to reduced plate heights of 1.22 for columns packed with Spherisorb ODS-1. Repeatable column-to-column separation performance was demonstrated.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150191206
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