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  • 1
    Electronic Resource
    Electronic Resource
    Low Synonymous Site Variation at the lacY Locus in Escherichia coli Suggests the Action of Positive Selection (1996)
    Springer
    Journal of molecular evolution 42 (1996), S. 79-84 
    Details
    ISSN: 1432-1432
    Keywords: Key words:LacY— Lactose permease — Evolution — Reduced synonymous polymorphism — Positive selection —E. coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. We have determined the nucleotide sequences of seven lacY alleles isolated from natural isolates of Escherichia coli. Nucleotide heterozygosity estimates for this locus were compared to those obtained from previous studies of intraspecific variation at chromosomal loci, revealing that lacY has unusually low synonymous site variation. The average pairwise heterozygosity of synonymous sites (Ks= 0.0112 +/− 0.0100) is the second lowest reported and the lowest for loci that have an equivalent level of nonsynonymous variation. We consider several hypotheses to explain how different forces in evolution could act to create the observed pattern of polymorphism, including selection for translational efficiency and positive selection. Our analysis most strongly supports the hypothesis that positive selection has acted on the lacY locus in E. coli.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02198831
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  • 2
    Electronic Resource
    Electronic Resource
    Low synonymous site variation at thelacY locus inEscherichia coli suggests the action of positive selection (1996)
    Springer
    Journal of molecular evolution 42 (1996), S. 79-84 
    Details
    ISSN: 1432-1432
    Keywords: LacY ; Lactose permease ; Evolution ; Reduced synonymous polymorphism ; Positive selection ; E. coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have determined the nucleotide sequences of sevenlacY alleles isolated from natural isolates ofEscherichia coli. Nucleotide heterozygosity estimates for this locus were compared to those obtained from previous studies of intraspecific variation at chromosomal loci, revealing thatlacY has unusually low synonymous site variation. The average pairwise heterozygosity of synonymous sites (Ks=0.0112+/-0.0100) is the second lowest reported and the lowest for loci that have an equivalent level of nonsynonymous variation. We consider several hypotheses to explain how different forces in evolution could act to create the observed pattern of polymorphism, including selection for translational efficiency and positive selection. Our analysis most strongly supports the hypothesis that positive selection has acted on thelacY locus inE. coli.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02198831
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  • 3
    Electronic Resource
    Electronic Resource
    Mismatch recognition in chromosomal interactions and speciation (1993)
    Springer
    Chromosoma 102 (1993), S. 369-373 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Homologous chromosomes interact during meiosis by means of proteins involved in recombination and in the recognition and repair of mismatched base pairs. Recombination proteins bring homologous chromosomes or chromosomal regions together by facilitating the search for DNA homology and by catalyzing strand exchange between homologous molecules or regions. Mismatch recognition and repair proteins act as editors of recombination and appear to disrupt those DNA associations that contain mismatched base pairs. Thus, it may be that, as chromosomes diverge in their primary sequence and become increasingly polymorphic, recombinational interactions leading to chromosome pairing and recombination tend to be inhibited. Decreasing homologous interactions within and between chromosomes will clearly contribute to maintaing the integrity of individual chromosomes and may utimately lead, as a result of sterile meioses, to the reproductive isolation of closely related species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00360400
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  • 4
    Electronic Resource
    Electronic Resource
    Über beschränkte Mengen in induktiven Limiten topologischer Vektorräume (1976)
    Springer
    Manuscripta mathematica 19 (1976), S. 365-374 
    Details
    ISSN: 1432-1785
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract In topological linear spaces convex hulls of bounded sets are, in general, not bounded. The question arises whether there is at least for every bounded set B a sequence {λν|νεℕ} of strictly positive numbers such that the set ∪{Σ l n λ v B|nεℕ} is bounded. When this obtains, bounded sets share several of the properties known in locally convex spaces. The main result of this note is an example of a countable inductive limit of complete metrizable topological linear spaces which is neither regular nor sequentially complete and also fails to have the above “bounded summability property”.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01278924
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  • 5
    Electronic Resource
    Electronic Resource
    Eine Bemerkung zur Division von Distributionen durch analytische Operatorfunktionen (1977)
    Springer
    Manuscripta mathematica 21 (1977), S. 25-42 
    Details
    ISSN: 1432-1785
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract The theorem of Lojasiewicz [15] on the division of distributions by analytic functions is generalized: It is the purpose of this note to treat the division by analytic Fredholm functions for operator valued distributions (Satz 1, Satz 3).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01176899
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  • 6
    Electronic Resource
    Electronic Resource
    The innervation of the pyloric region of the crab,Cancer borealis: Homologous muscles in decapod species are differently innervated (1986)
    Springer
    Journal of comparative physiology 159 (1986), S. 227-240 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The muscles of the pyloric region of the stomach of the crab,Cancer borealis, are innervated by motorneurons found in the stomatogastric ganglion (STG). Electrophysiological recording and stimulating techniques were used to study the detailed pattern of innervation of the pyloric region muscles. Although there are two Pyloric Dilator (PD) motorneurons in lobsters, previous work reported four PD motorneurons in the crab STG (Dando et al. 1974; Hermann 1979a, b). We now find that only two of the crab PD neurons innervate muscles homologous to those innervated by the PD neurons in the lobster,Panulirus interrruptus. The remaining two PD neurons innervate muscles that are innervated by pyloric (PY) neurons inP. interruptus. The innervation patterns of the Lateral Pyloric (LP), Ventricular Dilator (VD), Inferior Cardiac (IC), and PY neurons were also determined and compared with those previously reported in lobsters. Responses of the muscles of the pyloric region to the neurotransmitters, acetylcholine (ACh) and glutamate, were determined by application of exogenous cholinergic agonists and glutamate. The effect of the cholinergic antagonist, curare, on the amplitude of the excitatory junctional potentials (EJPs) evoked by stimulation of the pyloric motor nerves was measured. These experiments suggest that the differences in innervation pattern of the pyloric muscles seen in crab and lobsters are also associated with a change in the neurotransmitter active on these muscles. Possible implications of these findings for phylogenetic relations of decapod crustaceans and for the evolution of neural circuits are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00612305
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  • 7
    Electronic Resource
    Electronic Resource
    A coordinate relationship between theGALK and theTK1 genes of the Chinese hamster (1985)
    Springer
    Biochemical genetics 23 (1985), S. 677-703 
    Details
    ISSN: 1573-4927
    Keywords: Chinese hamster cells ; GALK ; TK1 ; thymidine kinase ; galactokinase ; conservation of linkage ; galactose metabolism ; thymidylate synthesis ; 5-bromodeoxyuridine ; thymidine ; trifluorothymidine ; 2-deoxy-d-galactose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Chinese hamster cells in culture were treated with various concentrations of thymidine, 5-bromodeoxyuridine, trifluorothymidine, and 2-deoxy-d-galactose. Selection was made for deficiencies in the activities of galactokinase and thymidine kinase. Selection in the presence of thymidine, 5-bromodeoxyuridine, and trifluorothymidine was expected to produce clones deficient in thymidine kinase only, whereas those deficient in galactokinase were expected to be selected in the presence of 2-deoxy-d-galactose. However, it was found that clones growing in the presence of these inhibitors were frequently deficient in both enzymes. Or if a clone was deficient in only one, the deficiency frequently was not expected according to the selection procedure. This indicates some sort of coordinate relationship between the two gene loci,GALK andTK1, which specify galactokinase and thymidine kinase, respectively.GALK andTK1 are linked in all primates and rodents in which linkage determinations have been made. It is therefore probable that this linkage has been conserved for a long period of time. It is suggested that the apparent relationship between the two genes shown by the data presented here, as well as by others, supports the conclusion that linkage has been conserved by natural selection and is therefore not fortuitous.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00554082
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  • 8
    Electronic Resource
    Electronic Resource
    A coordinate relationship between theGALK and theTK1 genes of the Chinese hamster (1985)
    Springer
    Biochemical genetics 23 (1985), S. 677-703 
    Details
    ISSN: 1573-4927
    Keywords: Chinese hamster cells ; GALK ; TK1 ; thymidine kinase ; galactokinase ; conservation of linkage ; galactose metabolism ; thymidylate synthesis ; 5-bromodeoxyuridine ; thymidine ; trifluorothymidine ; 2-deoxy-d-galactose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Chinese hamster cells in culture were treated with various concentrations of thymidine, 5-bromodeoxyuridine, trifluorothymidine, and 2-deoxy-d-galactose. Selection was made for deficiencies in the activities of galactokinase and thymidine kinase. Selection in the presence of thymidine, 5-bromodeoxyuridine, and trifluorothymidine was expected to produce clones deficient in thymidine kinase only, whereas those deficient in galactokinase were expected to be selected in the presence of 2-deoxy-d-galactose. However, it was found that clones growing in the presence of these inhibitors were frequently deficient in both enzymes. Or if a clone was deficient in only one, the deficiency frequently was not expected according to the selection procedure. This indicates some sort of coordinate relationship between the two gene loci,GALK andTK1, which specify galactokinase and thymidine kinase, respectively.GALK andTK1 are linked in all primates and rodents in which linkage determinations have been made. It is therefore probable that this linkage has been conserved for a long period of time. It is suggested that the apparent relationship between the two genes shown by the data presented here, as well as by others, supports the conclusion that linkage has been conserved by natural selection and is therefore not fortuitous.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02399403
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  • 9
    Electronic Resource
    Electronic Resource
    Structural effects of amino acid substitutions on the matrix protein of vesicular stomatitis virus (1987)
    Springer
    The protein journal 6 (1987), S. 463-472 
    Details
    ISSN: 1573-4943
    Keywords: conformational energy ; three-dimensional structure ; amino acid substitutions ; matrix protein ; vesicular stomatitis virus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The structural effects of amino acid substitutions for Gly at position 21 in the amino-terminal segment (Lys 15-Pro 26) of the matrix (M) protein of vesicular stomatitis virus (VSV) have been investigated using conformational energy analysis. Monoclonal antibody-binding experiments and protein digestion studies of the M protein indicate that this segment is important to its ribonucleoprotein recognition and its transcription-inhibitory activity. Temperaturesensitive mutants of VSV that do not bind monoclonal antibody and that are devoid of transcription-inhibitory activity are known to have the substitution of Glu for Gly at position 21. The current findings demonstrate a significant conformational change at position 21 induced by the substitution of Glu for Gly, which could explain this alteration in antibody binding and transcription-inhibitory activity. Furthermore, the results indicate that the substitution of any noncyclic L-amino acid for Gly at position 21 may be expected to produce similar changes in M protein function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00276732
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  • 10
    Electronic Resource
    Electronic Resource
    N-Methyl-N′-nitro-N-nitrosoguanidine sensitivity of E. coli mutants deficient in DNA methylation and mismatch repair (1981)
    Springer
    Molecular genetics and genomics 184 (1981), S. 562-563 
    Details
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary E. coli mutants deficient in DNA methylation (dam) and mismatch repair (mut) have been characterized with respect to their sensitivity to N-methyl-N′-nitro-N-nitrosoguanidine (MNNG). Dam bacteria are more sensitive than mutH, mutL, and mutS single mutant bacteria. Dam mutL and dam mutS double mutant bacteria are less sensitive than dam bacteria, whereas dam mutH double mutant bacteria are as sensitive as dam bacteria. This pattern of MNNG sensitivity may be a result of the specificity of the components of the E. coli mismatch repair system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00352542
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