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  • Articles  (26)
  • Springer  (26)
  • 1995-1999  (18)
  • 1965-1969  (6)
  • 1920-1924  (1)
  • 1910-1914  (1)
  • 1905-1909
  • Biology  (26)
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  • Articles  (26)
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  • 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
    Characterization of rice α-amylase isozymes expressed by Saccharomyces cerevisiae (1995)
    Springer
    Applied microbiology and biotechnology 43 (1995), S. 1050-1055 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Two rice α-amylase isozymes, AmylA and Amy3D, were produced by secretion from genetically engineered strains of Saccharomyces cerevisiae. They have distinct differences in enzymatic characteristics that can be related to the physiology of the germinating rice seed. The rice isozymes were purified with immunoaffinity chromatography. The pH optima for amy3D (pH optimum 5.5) and Amy1A (pH optimum 4.2) correlate with the pH of the endosperm tissue at the times in rice seedling development when these isozymes are produced. Amy3D showed 10–14 times higher reactivity to oligosaccharides than Amy1A. Amy1A, on the other hand, showed higher reactivity to soluble starch and starch granules than Amy3D. These results suggest that the isozyme Amy3D, which is expressed at an early stage of germination, produces sugars from soluble starch during the early stage of seed germination and that the isozyme Amy1A works to initiate hydrolysis of the starch granules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00166924
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  • 3
    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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  • 4
    Electronic Resource
    Electronic Resource
    Human cDNA clones that modify radiomimetic sensitivity of ataxia-telangiectasia (group A) cells (1995)
    Springer
    Somatic cell and molecular genetics 21 (1995), S. 99-111 
    Details
    ISSN: 1572-9931
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Genes responsible for genetic diseases with increased sensitivity to DNA-damaging agents can be identified using complementation cloning. This strategy is based on in vitro complementation of the cellular sensitivity by gene transfer. Ataxia-telangiectasia (A-T) is a multisystem autosomal recessive disorder involving cellular sensitivity to ionizing radiation and radiomimetic drugs. A-T is genetically heterogeneous, with four complementation groups. We attempted to identify cDNA clones that modify the radiomimetic sensitivity of A-T cells assigned to complementation group [A-T(A)]. The cells were transfected with human cDNA libraries cloned in episomal vectors, and various protocols of radiomimetic selection were applied. Thirteen cDNAs rescued from survivor cells were found to confer various degrees of radiomimetic resistance to A-T(A) cells upon repeated introduction, and one of them also partially influenced another feature of the A-T phenotype, radioresistant DNA synthesis. None of the clones mapped to the A-T locus on chromosome 11q22-23. Nine of the clones were derived from known genes, some of which are involved in cellular stress responses. We concluded that a number of different genes, not necessarily associated with A-T, can influence the response of A-T cells to radiomimetic drugs, and hence the complementation cloning approach may be less applicable to A-T than to other diseases involving abnormal processing of DNA damage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02255785
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  • 5
    Electronic Resource
    Electronic Resource
    A new TNFA promoter allele identified in South American Blacks (1996)
    Springer
    Immunogenetics 44 (1996), S. 485-486 
    Details
    ISSN: 1432-1211
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002510050158
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  • 6
    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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  • 7
    Electronic Resource
    Electronic Resource
    Phosphoglucomutase electrophoretic variants in the mouse (1969)
    Springer
    Biochemical genetics 3 (1969), S. 25-35 
    Details
    ISSN: 1573-4927
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The phosphoglucomutase (PGM) electrophoretic phenotype of the mouse (Mus musculus) consists of several distinct components which can be grouped into two major zones designated PGM-1 and PGM-2. Evidence presented here indicates that each zone is controlled by a single genetic locus denoted Pgm-1 and Pgm-2, respectively. Two variant forms segregated at the Pgm-1 locus. They were codominantly expressed and inherited as alleles at an autosomal locus. The alleles were termed Pgm-1 a (fast) and Pgm-1 b (slow). These alleles were separately fixed in a number of inbred strains of mice. Preliminary evidence based on wild mouse phenotypes indicates that variant forms also exist for PGM-2 which are inherited as alleles at an autosomal locus. Genetic linkage relationships have not been determined for these loci. PGM-1 variants and PGM-2 were expressed in mouse fibroblasts in vitro.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00485972
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  • 8
    Electronic Resource
    Electronic Resource
    Evolutionary evidence for a regulator gene controlling the lactate dehydrogenase B gene in rodent erythrocytes (1969)
    Springer
    Biochemical genetics 3 (1969), S. 525-536 
    Details
    ISSN: 1573-4927
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Erythrocyte and tissue lactate dehydrogenase (LDH) electrophoretic patterns of 26 rodent species from ten families were examined. The LDH B gene was observed to range in erythrocyte expression from species without detectable B subunits to those which predominantly expressed B subunits. However, the shift in erythrocyte B gene expression was not observed in the tissue LDH electrophoretic patterns between rodent species. Species which did not express erythrocyte B subunits, or only small quantities of B subunits, were restricted to the suborder Myomorpha. In erythrocytes of other rodent species, and most mammals, LDH B subunits are expressed equally or in excess of A subunits. The results suggest either structural differences in the LDH B gene between Myomorph and non-Myomorph rodents or a regulator gene which controls the expression of the B gene in Myomorph erythrocytes. Existing evidence favors the latter hypothesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00485474
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  • 9
    Electronic Resource
    Electronic Resource
    Identification of the molecular basis for phosphorylase hypersensitivity in cultured diabetic cardiomyocytes (1995)
    Springer
    Molecular and cellular biochemistry 145 (1995), S. 131-139 
    Details
    ISSN: 1573-4919
    Keywords: glycogen phosphorylase ; alloxan-diabetes ; cardiomyocytes ; cGMP ; phosphodiesterase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The focus of this study was to identify the molecular basis for the hypersensitive response of glycogen phosphorylase activation to epinephrine stimulation in alloxan diabetic-derived cardiomyocytes. Cyclic AMP levels were found not to be significantly different between normal and diabetic-derived cells while cGMP concentrations were found consistently to be significantly lower in diabetic-derived cells than in normal cells. Treatment with cyclic GMP analogues did not affect phosphorylase activation by epinephrine in normal cardiomyocytes whereas, IBMX, a nonselective phosphodiesterase inhibitor, had a significant effect on basal and agonist-stimulated phosphorylase activity in both normal and diabetic-derived cardiomyocytes. Differences in the time course for the rate of decay of phosphorylasea from agonist-stimulated to basal levels were observed between normal and diabetic cells. After 3 h in primary culture, phosphorylasea activity returned to basal levels more quickly in normal than in diabetic-derived cells while after 24 h in culture, the time for phosphorylasea decay was not significantly different between normal and diabetic myocytes and was longer than the 3 h response. After 3 h in primary culture, no significant difference in phosphorylase kinase activity was observed between normal and diabetic-derived cells exposed to epinephrine whereas, after 24 h in culture, phosphorylase kinase activity was significantly decreased in diabetic cells under basal and agonist-stimulated conditions. These data collectively suggest that the hypersensitive response of glycogen phosphorylase to epinephrine stimulation in diabetic-derived cardiomyocytes is not due to a defect present at the level of phosphorylase kinase but may, in part, result from an alteration in cardiac phosphodiesterase activity resulting from diminished intracellular cyclic GMP concentrations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00935485
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  • 10
    Electronic Resource
    Electronic Resource
    The amino acid substitution and some chemical properties of a variant human erythrocyte carbonic anhydrase: Carbonic anhydrase IdMichigan (1967)
    Springer
    Biochemical genetics 1 (1967), S. 171-195 
    Details
    ISSN: 1573-4927
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Carbonic anhydrase IdMichigan, an electrophoretic variant of human red cell carbonic anhydrase I, was purified from erythrocytes obtained from an individual heterozygous for the trait. Primary structural analysis indicates that a lysine residue has exchanged for a threonine residue in the variant enzyme. After isolation, there was approximately 1.8 times as much normal as variant enzyme. Thermostability studies demonstrated that carbonic anhydrase Id was more thermolabile than the normal enzyme. The normal and variant enzymes showed no differences in specific carboxylesterase activity or CO2 hydratase activity. Utilizing the carboxylesterase activity toward β-naphthyl acetate, the normal and variant enzymes had similar Michaelis constants, pH profiles, and rates of inhibition by acetazolamide. Immunochemical studies did not demonstrate an antigenic difference for the variant enzyme.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00486517
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