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  • Articles  (8)
  • Springer  (8)
  • American Association of Petroleum Geologists
  • 1995-1999  (8)
  • 1990-1994
  • 1905-1909
  • 1999  (8)
  • Biology  (8)
  • 1
    Electronic Resource
    Electronic Resource
    Enhanced Evolvability in Immunoglobulin V Genes Under Somatic Hypermutation (1999)
    Springer
    Journal of molecular evolution 49 (1999), S. 23-26 
    Details
    ISSN: 1432-1432
    Keywords: Key words: Genome evolution — Adaptability — Somatic hypermutation — Affinity maturation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Darwinian theory requires that mutations be produced in a nonanticipatory manner; it is nonetheless consistent to suggest that mutations that have repeatedly led to nonviable phenotypes would be introduced less frequently than others—if under appropriate genetic control. Immunoglobulins produced during infection acquire point mutations that are subsequently selected for improved binding to the eliciting antigen. We and others have speculated that an enhancement of mutability in the complementarity-determining regions (CDR; where mutations have a greater chance of being advantageous) and/or decrement of mutability in the framework regions (FR; where mutations are more likely to be lethal) may be accomplished by differential codon usage in concert with the known sequence specificity of the hypermutation mechanism. We have examined 115 nonproductively rearranged human Ig sequences. The mutation patterns in these unexpressed genes are unselected and therefore directly reflect inherent mutation biases. Using a χ2 test, we have shown that the number of mutations in the CDRs is significantly higher than the number of mutations found in the FRs, providing direct evidence for the hypothesis that mutations are preferentially targeted into the CDRs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00006530
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of reforestation methods on genetic diversity of lodgepole pine: an assessment using microsatellite and randomly amplified polymorphic DNA markers (1999)
    Springer
    Theoretical and applied genetics 98 (1999), S. 793-801 
    Details
    ISSN: 1432-2242
    Keywords: Key words Pinus contorta ; Silviculture ; Reforestation ; Gene conservation ; RAPD ; SSR ; DNA analyses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  We examined the effects of different methods of forest regeneration on the genetic diversity of lodgepole pine (Pinus contorta var ‘latifolia’) using two different DNA-based molecular markers [randomly amplified polymorphic DNA (RAPDs) and microsatellites or simple sequence repeats (SSRs)]. Genetic diversity was estimated for 30 individuals in each of four populations for the following three stand types: (1) mature lodgepole pine (〉100 years); (2) 20- to 30-year-old harvested stands left for natural regeneration; (3) 20- to 30-year-old planted stands (4 stands of each type); and one group of 30 operationally produced seedlings. There was no significant effect of stand type on expected heterozygosity, although allelic richness and diversity were much higher for SSRs than for RAPDs. Expected heterozygosity ranged from 0.39 to 0.47 based on RAPDs and from 0.67 to 0.77 based on SSRs. The number of alleles per locus for SSRs ranged from 3 to 34 (mean 21.0), and there was a significant relationship between sequence repeat length and the number of alleles at a locus. Both marker types showed that over 94% of the variation was contained within the populations and that the naturally regenerated stands sampled had lower (not significant) expected heterozygosity than the planted or unharvested stands. The group of seedlings (assessed by RAPDs only) had expected heterozygosity and allele frequencies similar to those of the unharvested stands. Genetic distance measures were higher than obtained previously in the species using isozyme markers. There was no correlation between the two marker types for pair-wise genetic distances based on populations analyzed by both methods. Pair-wise genetic distance measures and an ordination of allele frequencies for both marker types showed little effect of geographic location or stand type on genetic similarity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001220051136
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  • 3
    Electronic Resource
    Electronic Resource
    The third leg: Molecular dynamics simulations of lipid binding proteins (1999)
    Springer
    Molecular and cellular biochemistry 192 (1999), S. 143-156 
    Details
    ISSN: 1573-4919
    Keywords: molecular dynamics ; LBP ; FABP ; structure-function ; protein-lipid interactions ; rational drug design
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Molecular dynamics computer simulations can provide a third leg which balances the contributions of both structural biology and binding studies performed on the lipid binding protein family. In this context, these calculations help to establish a dialogue between all three communities, by relating experimental observables with details of structure. Working towards this connection is important, since experience has shown the difficulty of inferring thermodynamic properties from a single static conformation. The challenge is exemplified by ongoing attempts to interpret the impact of mutagenesis on structure and function (i.e. binding). A detailed atomic-level understanding of this system could be achieved with the support of all three legs, paving the way towards rational design of proteins with novel specificities. This paper provides an outline of the connections possible between experiment and theory concerning lipid binding proteins.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006818203334
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  • 4
    Electronic Resource
    Electronic Resource
    Genetic relationships among Stylosanthes species revealed by RFLP and STS analyses (1999)
    Springer
    Theoretical and applied genetics 99 (1999), S. 1179-1186 
    Details
    ISSN: 1432-2242
    Keywords: Key words Stylosanthes ; DNA markers ; Genetic relationships
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Genetic relationships between 6 unclassified taxa and 24 known species of the genus Stylosanthes were investigated by RFLP and STS analyses. This allowed the diploid taxa used in this study to be classified into nine basal (genome) groups. Representative species in these groups included ’S. seabrana’/S. hamata (Group A), S. viscosa (Group B), S. humilis (Group C), S. macrocephala/S. bracteata (Group D), S. pilosa (Group E), S. leiocarpa (Group F), S. guianensis (Group G), S. tomentosa (Group H) and S. calcicola (Group I). Polyploid taxa used were grouped into five classes based on their putative genomic structures. These are AABB for S. scabra, S. aff. scabra, S. sericeiceps, S. aff. hamata and S. tuberculata; AACC for S. mexicana, S. subsericea, S. sundaica and S. sp.A; DDEE for S. capitata; AAFF for S. sympodialis; and AABBXX for S. erecta, with XX representing an unknown genome. Of the 6 unclassified taxa, three were diploids and 3 tetraploids. Of the 3 diploids, the genome of S. sp. was markedly distinct from those of all other diploids analysed in this study, with that of S. leiocarpa being the closest. The genome of S. sp.B was similar to that of S. humilis, with an average dissimilarity value of 15% between them. The genome of S. aff. viscosa was very similar to that of S. viscosa. Genetic variation between these 2 taxa was not larger than that within each of the 2 taxa. Of the 3 tetraploids, the genomic structure of S. sp.A was similar to those of S. mexicana, S. sundaica and S. subsericea, and the genomic structures of S. aff. scabra and S. aff. hamata were similar to those of S. scabra and S. sericeiceps.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001220051322
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  • 5
    Electronic Resource
    Electronic Resource
    Hyperactivation of Mitogen-Activated Protein Kinase Increases Phospho-Tau Immunoreactivity Within Human Neuroblastoma: Additive and Synergistic Influence of Alteration of Additional Kinase Activities (1999)
    Springer
    Cellular and molecular neurobiology 19 (1999), S. 249-260 
    Details
    ISSN: 1573-6830
    Keywords: MAP kinase ; tau ; protein kinase C ; wortmannin ; PD98059 ; neuroblastoma ; Alzheimer's disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mitogen-activated protein (MAP) kinase phosphorylates tau in cell-free analyses, but whether or not it does so within intact cells remains controversial. In the present study, microinjection of MAP kinase into SH-SY-5Y human neuroblastoma cells increased tau immunoreactivity toward the phosphodependent antibodies PHF-1 and AT-8. In contrast, treatment with a specific inhibitor of MAP kinase (PD98059) did not diminish “basal” levels of these immunoreactivities in otherwise untreated cells. These findings indicate that hyperactivation of MAP kinase increases phospho-tau levels within cells, despite that MAP kinase apparently does not substantially influence intracellular tau phosphorylation under normal conditions. These findings underscore that results obtained following inhibition of kinase activities do not necessarily provide an indication of the consequences accompanying hyperactivation of that same kinase. Several studies conducted in cell-free systems indicate that exposure of tau to multiple kinases can have synergistic effects on the nature and extent of tau phosphorylation. We therefore examined whether or not such effects could be demonstrated within these cells. Site-specific phospho-tau immunoreactivity was increased in additive and synergistic manners by treatment of injected cells with TPA (which activates PKC), calcium ionophore (which activates calcium-dependent kinases), and wortmannin (which inhibits PIP3 kinase). Alteration in total tau levels was insufficient to account for the full extent of the increase in phospho-tau immunoreactivity. These additional results indicate that multiple kinase activities modulate the influence of MAP kinase on tau within intact cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006981228331
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  • 6
    Electronic Resource
    Electronic Resource
    The Order of Exposure of Tau to Signal Transduction Kinases Alters the Generation of “AD-Like” Phosphoepitopes (1999)
    Springer
    Cellular and molecular neurobiology 19 (1999), S. 223-233 
    Details
    ISSN: 1573-6830
    Keywords: tau ; kinases ; signal transduction ; Alzheimer's disease ; phosphorylation ; paired helical filaments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 1. The individual and sequential influence of protein kinase C (PKC), protein kinase A (PKA) and mitogen-activated protein kinase (MAP kinase) on human brain tau was examined. 2. A range of PKC concentrations generated certain phosphoepitopes common with paired helical filaments. These epitopes were masked by higher PKC concentrations, suggesting the presence of multiple tau phosphorylation sites for which PKC exhibited differing affinities and/or conformational alterations in tau induced by sequential PKC-mediated phosphorylation. 3. Prior phosphorylation by PKC enhanced the nature and extent of AD-like tau antigenicity generated by subsequent incubation with MAP kinase yet inhibited that generated by subsequent incubation with PKA. 4. Dephosphorylation of tau prior to incubation with kinases significantly altered the influence of individual and multiple kinase incubation on tau antigenicity in a site-specific manner, indicating that prior in situ phosphorylation events markedly influenced subsequent cell-free phosphorylation. 5. In addition to considerations of the potential impact of tau phosphorylation by individual kinases, these findings extend previous studies which indicate that tau antigenicity, and, presumably, its behavior in situ, is influenced by the sequential and convergent influences of multiple kinases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006977127422
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  • 7
    Electronic Resource
    Electronic Resource
    The imprinted domain in mouse distal Chromosome 7: reagents for mutagenesis and sequencing (1999)
    Springer
    Mammalian genome 10 (1999), S. 182-185 
    Details
    ISSN: 1432-1777
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003359900965
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  • 8
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    The imprinted domain in mouse distal Chromosome 7: reagents for mutagenesis and sequencing (1999)
    Springer
    Details
    Publication Date: 1999-02-01
    Print ISSN: 0938-8990
    Electronic ISSN: 1432-1777
    Topics: Biology , Medicine
    Published by Springer
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