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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Journal of fish biology 62 (2003), S. 0 
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Molecular analyses of the mitochondrial genome using restriction fragment length polymorphism (RFLP) were utilized to determine the existence of discrete populations of the tidepool sculpin Oligocottus maculosus from the Barkley Sound region of south-western Vancouver Island, British Columbia. Fifty-five haplotypes were found with three haplotypes making up 38, 16 and 8% of the total sample, respectively. Within individual tidepools, haplotype diversity ranged from 0·30 to 0·92, but haplotypes were typically closely related to one another (nucleotide diversity ranged from 0·0004 to 0·005). The majority of haplotype variation (96–97%) was located within tidepools, but a significant amount of variation (c. 3–4%) was detected among tidepools within single islands. By contrast, there was no significant differentiation among islands or between samples from the Barkley Sound area and a single sample from north-eastern Vancouver Island. The results suggest a low level of population structure within the sample area and that the distribution of haplotypes and haplotype divergences represents a demographic expansion from a single ancestral lineage beginning between 300 000 and 1 000 000 years ago. The low level of population subdivision resolved suggests that despite their ecological specialization in tidepool habitats, tidepool sculpins are influenced by demographic and genetic processes that operate on spatial scales much larger than single tidepools or islands.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK; Malden, USA : Blackwell Science Ltd
    Scandinavian journal of immunology 59 (2004), S. 0 
    ISSN: 1365-3083
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Vav1, the 95-kDa protein encoded by the vav1 proto-oncogene, is expressed exclusively in haematopoietic cells, where it becomes phosphorylated on tyrosine residues in response to antigen receptor ligation. Vav1 was found to act as a Rac1-specific guanine nucleotide exchange factor and to activate c-Jun N-terminal kinase (JNK1) in vitro and in ectopic expression systems using non-haematopoietic cells. Here, we studied the role of Vav1 in JNK1 activation in T cells versus non-haematopoietic cells. Vav1 overexpression activated JNK1 in COS7 and 293T cells but not in Jurkat T lymphocytes. In contrast, constitutively activated Rac1 efficiently stimulated JNK1 in both cell types under the same conditions. Vav1 did function in T cells because it clearly stimulated the activity of a nuclear factor of activated T-cell reporter plasmid in the same cells. Moreover, Vav1 induction of JNK1 in T cells required coexpression with calcineurin. This cooperation was cell type specific because it was not observed in COS7 or 293T cells. In contrast, Vav1 did not cooperate with calcineurin to activate either extracellular signal-regulated kinase 2 or p38. These findings demonstrate that Vav1 alone is a poor activator of the JNK1 pathway in T cells and emphasize the importance of studying the physiological functions of Vav1 in haematopoietic cells.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Plant cell reports 19 (2000), S. 1146-1154 
    ISSN: 1432-203X
    Keywords: Keywords Populus tremula ; Liquid culture ; Root explants ; Thidiazuron ; AbbreviationsANC: Ancymidol ; BA: 6-Benzyladenine ; DPB: Disposable plastic bioreactor ; GA: Gibberellic acid ; GV: Growth value ; IAA: Indole-3-acetic acid ; MSAL: Liquid medium for aspen culture ; MSAS: Semi-solid medium ; NAA : α-Naphtalene acetic acid ; TDZ: Thidiazuron
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The regeneration potential of excised aspen (Populus tremula L.) roots cultivated in liquid medium, as affected by plant growth regulators and by the position of the isolated root explant on the main root, was investigated. The effect of various levels of benzyladenine (BA) and thidiazuron (TDZ) on bud regeneration in root explants was studied. TDZ in the medium had a marked effect on bud development as compared with BA, inducing a tenfold increase in the number of buds regenerated from various root explants. TDZ enhanced both root and root-borne shoot biomass production but reduced further shoot development and elongation. The position of the isolated root sections on the main root affected regeneration, the proximal sections further away from the root tip producing the highest number of buds per explant in both BA and TDZ treatments. Buds regenerated in close proximity to the site of lateral roots in BA-treated roots, while in TDZ-treated root sections, the buds formed all over the root regardless of the presence of lateral roots. The buds developed from inner cortical and sub-epidermal cell layers, disrupting the epidermis and the inner layers. Root biomass production and growth was greatly enhanced in well-aerated bioreactor culture in the presence of 4.5×10–2 μM TDZ. A high number of the root-borne shoots could be rooted and converted to plantlets. However, while shoots regenerated in a medium with BA rooted well in a growth regulator-free medium, shoots formed in a medium with TDZ required auxin for rooting. Roots cultured in the presence of ancymidol, a gibberellin biosynthesis inhibitor, regenerated non-hyperhydric bud clusters and hyperhydric shoots. These were separated mechanically, subcultured to growth and rooting medium and transplanted ex vitro resulting in phenotypically true-to-type plantlets. The potential of liquid cultures for aspen shoot biomass production from roots is discussed.
    Type of Medium: Electronic Resource
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