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  • 1
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 356 (1992), S. 667-667 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] SIR - Large vestimentiferan tube worms (Pogonophora, Obturata) are typical members of both hydrothermal and cold seep communities in the Pacific Ocean (see, for example, refs 1, 2). In the Atlantic Ocean, Vestimentifera are known only from the western side, at sulphidic hydrocarbon seeps in the ...
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Previous studies of the Robertsonian polymorphism in the Atlantic dog-whelk, Nucella lapillus (2n=26–36), have been limited by the inability to identify unequivocally individual chromosomes in the karyotype. This species, as with many other marine invertebrates, has proven largely refractory to the standard (mammalian) chromosome-banding techniques. In this study, fluorescence in situ hybridization (FISH) using a rDNA probe was applied to the metaphase chromosomes of the 2n=26 and 2n=36 forms of N. lapillus. The results were compared with silver-staining of the nucleolar organizer regions (NORs). The FISH technique was shown to be more sensitive and less intrinsically prone to variation than the silver-staining method. An additional NOR/rDNA locus was observed in the 2n=36 form which, to date, has not been seen in any 2n=26 population. The 2n=36 karyotype is described for a southwest UK population that differs from that reported previously in the literature. After fission, Robertsonian metacentrics are shown to correspond to at least one subtelocentric product.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Previous studies of the Robertsonian polymorphism in the Atlantic dog-whelk, Nucella lapillus (2n = 26–36), have been limited by the inability to identify unequivocally individual chromosomes in the karyotype. This species, as with many other marine invertebrates, has proven largely refractory to the standard (mammalian) chromosome-banding techniques. In this study, fluorescence in situ hybridization (FISH) using a rDNA probe was applied to the metaphase chromosomes of the 2n = 26 and 2n = 36 forms of N. lapillus. The results were compared with silver-staining of the nucleolar organizer regions (NORs). The FISH technique was shown to be more sensitive and less intrinsically prone to variation than the silver-staining method. An additional NOR/rDNA locus was observed in the 2n = 36 form which, to date, has not been seen in any 2n = 26 population. The 2n = 36 karyotype is described for a south-west UK population that differs from that reported previously in the literature. After fission, Robertsonian metacentrics are shown to correspond to at least one subtelocentric product.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Marine biology 120 (1994), S. 415-420 
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We examined the inheritance of theMytilus edulis CaM-1 Intron 3 locus, a non-coding DNA locus with two potentially neutral length-variants. The polymerase chain reaction (PCR) was used to determine theCaM-1 genotype for 799 larvae obtained from 11 laboratory crosses. Larvae were typed singly only 8 to 24 h after fertilization. We find evidence that each allele can be inherited from either sex, that there are no barriers to fertilization between gametes of different genotypes, and that most larvae have genotypes compatible with Mendelian inheritance of the locus. Deviations from expected genotype frequencies were found in some crosses; we suggest that a contributing factor is aneuploidy in early larvae, but a major cause is more likely to be selection at a locus linked toCaM-1, occurring under the artificial laboratory culture conditions. This study demonstrates the feasibility of applying molecular genetic techniques to early larval stages of marine bivalves, and presents a new non-destructive biopsy method for DNA analysis from living adult mussels.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract PCR (polymerase chain reaction) amplification of non-coding introns in phylogenetically widespread genes, using DNA primers based on the conserved exon sequences, provides a widely applicable strategy for finding DNA polymorphisms in eukaryotic genomes. Polymorphisms in introns provide a new source of potentially neurtral genetic markers for use in population biology. Here we use this approach to design PCR primers for an intron of calmodulin genes. We show that there are at least two calmodulin genes in mussels of theMytilus edulis species complex, and using gene- and species-specific primers we resolve two alleles at a calmodulin intron locus. Population surveys using PcR of adult mussel DNA reveal that genotype frequencies at most sites surveyed in England, Scotland and Italy, conform to Hardy-Weinberg equilibrium, suggesting that this is a novel neutral genetic marker. The data also provide preliminary evidence for restricted gene flow between mussel populations on the west and northeast coasts of Britain, and for local effects around the Thames estuary.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Marine biology 118 (1994), S. 247-253 
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract On the English and French Channel coasts, the dog-whelk Nucella lapilus (L.) exhibits variation in chromosome number which appears to correlate with the degree of wave action on the shore. The more common, 2n=26 morph is typically found on exposed shores subjected to a high degree of wave action, whereas those with higher chromosome numbers, up to the recorded maximum of 2n=36, are restricted to more sheltered environments. The polymorphism is thought to be Robertsonian in nature, involving centric (centromere) fission or fusion, but detailed analysis of the polymorphism has been restricted by lack of success in labelling individual chromosomes. Using a silver-staining technique for the nucleolar organiser regions (NORs), three pairs of chromosomes, in the basic 2n=26 karyotype, have been positively identified. A series of structural chromosomal rearrangements (pericentric and paracentric inversions) affecting one pair of chromosomes involved in the numerical polymorphism is described. Significant differences exist between populations with respect to this character. These chromosomal rearrangements have the potential to reduce the level of interbreeding between the different types, and may act as isolating mechamisms between breeding groups. Structural chromosomal polymorphism is likely, therefore, to have greater significance in relation to adaptation than simple numerical variation. This finding raises important questions concerning the (cyto)taxonomic status of N. lapillus in different parts of its range.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-6849
    Keywords: karyotype evolution ; Platynereis dumerilii ; polychaete chromosomes ; Pomatoceros lamarckii ; telomeric (TTAGGG) n sequence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Using the fluorescencein situ hybridization (FISH) technique, the presence of the vertebrate telomeric sequence (TTAGGG) n was found in the chromosomes of two marine polychaetes belonging to two separate orders: one errant,Platynereis dumerilii (family Nereidae), and the other sessile,Pomatoceros lamarckii (family Serpulidae). This sequence was exclusively present at the ends of the chromosomes in both species.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 420 (2000), S. 29-43 
    ISSN: 1573-5117
    Keywords: cytogenetics ; mutations ; DNA ; chromosomes ; karyotypes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The development of cytogenetic methods applied to cells and tissues of marine invertebrates has been hampered by (1) a lack of in vitro cell lines, (2) inadequate karyotypic information (partly as a result of too few workers chasing too many organisms), and (3) the failure of their chromosomes to band satisfactorily. Compared to mammalian cytogenetics, our knowledge of marine invertebrates lags behind by several decades. With the current concern about mutagens in the marine environment, and the recognition that the cells of marine species have sensitivities to DNA-damaging agents similar to those of higher organisms, there is a need for methods which can be used (a) in environmental monitoring and (b) to screen potentially harmful substances in the laboratory. In the absence of in vitro cell lines, embryos and larvae have been used to provide a supply of dividing cells for mutation studies, although the advent of molecular methods has now brought with it the means to detect DNA damage without any need for the cells to be in a dividing state. Moreover, the use of FISH (Fluorescence In Situ Hybridisation) now makes it possible to study numerical and structural chromosomal aberrations with far greater accuracy than was previously possible. A new marine genotoxicity assay is described, based on the embryos and larvae of a tube-dwelling polychaete worm (Pomatoceros lamarkii), suitable for both laboratory studies and field monitoring. This new Pomatoceros assay provides, at the same time, a useful model for studying the consequences of adult exposure on the offspring. A novel application of marine cytogenetic research is the study of the evolutionary adaptations of invertebrates living in naturally polluted extreme environments viz. deep sea hydrothermal vents, which are typified by high levels of toxic heavy metals and radionuclides, substances known to inflict damage to DNA. Given these new methodological and conceptual advances, it is predicted that our understanding of the role played by mutation in the marine environment, both in an evolutionary and toxicological context, will increase dramatically over the next decade.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 22 (1978), S. 1977-1982 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Functional monomers were graft polymerized onto substrates consisting of magnetic iron oxides in a crosslinked PVA matrix. Initiation was carried out with H2O2 and FeSO4; other common chemical initiating systems proved unsuccessful. Peroxide treatment of the substrates must be carried out separately from the reaction with Fe2+ and monomer. The amount of grafting achieved is highly variable, depending on the nature of the monomer. Strong base and weak acid magnetic shell resins prepared by graft polymerization are useful in water treatment by flocculation and moving-bed ion exchange, respectively. A wider range of products can be obtained by chemical modification of grafted chains. The mechanism of grafting is discussed in an endeavor to explain the highly specific nature of the reaction.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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