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  • 1995-1999  (191)
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  • 1
    ISSN: 1432-072X
    Keywords: Key words K+-ATPase ; Lactobacilli ; Potassium pump ; 2 ; 3-Butanedione ; Enzyme-phosphate complex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Lactobacillus helveticus ATCC 15009 (wild-type) membrane preparations hydrolyzed Mg2+-ATP as a function of K+ concentration (2–200 mM). Mg2+-ATP hydrolysis by L. helveticus membranes was strongly inhibited in the absence of exogenous K+, while it amounted to 6 nmol ATP hydrolyzed min–1 (mg membrane protein)–1 at 50 mM KCl (saturating conditions) and pH 7.2. The K+-dependent ATPase of L. helveticus displayed a relatively high affinity for potassium ions (K m = 800 μM) and was not affected by pretreatment of membranes with N,N’-dicyclohexylcarbodiimide. Membrane preparations were subjected to hypotonic shock to obtain a maximum yield of open profiles. The formation of a maximum level of enzyme-phosphate complex with a molecular mass of approximately 82 kDa was induced upon treatment of L. helveticus membrane preparations with low concentrations of [γ-32P]ATP in the presence of K+ and La3+ ions and was visualized by acidic SDS-PAGE. It was concluded that L. helveticus membranes contain an inwardly directed K+ pump whose presence is discussed in terms of its putative role in cytoplasmic pH regulation.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 1997-09-08
    Print ISSN: 0302-8933
    Electronic ISSN: 1432-072X
    Topics: Biology
    Published by Springer
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Microbial ecology 35 (1998), S. 205-212 
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Intestinal microbiota comprise a complex ecosystem whose equilibrium is crucial for the health of animal species. For humans, data exist on the microbiota composition in adult subjects, but few studies have addressed the microbiota composition in infants. In particular, data on the presence and species distribution of members of the genus Lactobacillus in newborns (less than one week old) are lacking. In the present work, the feces of healthy newborns were sampled to determine the taxonomic composition of Lactobacillus in the intestinal microbiota in a group of 16 neonates. In total, 1640 colony-forming units (CFU) were isolated, of which 420 grouped in the Lactobacillus genus by means of primary phenotypic characterization. The 420 isolates were further grouped into 125 strains on the basis of identical plasmid profiles. Of these 125 strains, 21 turned out to be permanent, i.e., they were identified in the feces of the same subject on several consecutive days. Sugar fermentation, DNA/DNA hybridization, and S-layer protein determination enabled us to classify 52 of the 125 strains as follows: L. paracasei (40 strains), L. delbrueckii sp. (1 strain), and L. acidophilus (sensu stricto) (11 strains). Based on the same criteria, the remaining 73 strains were tentatively allotted to the Johnson subgroup B, although hybridization experiments with probes specific for L. gasseri and L. johnsonii species were not performed. The presence of new species among these 73 strains cannot be excluded. Surprisingly, the obligately heterofermentative lactobacilli, L. reuteri in particular, were entirely absent from the feces of healthy newborns.
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  • 4
    ISSN: 1432-0983
    Keywords: Key words Farnesylpyrophosphate synthase (FPPS)-gene ; Isoprenoids ; Gibberellins ; Fungi
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Farnesylpyrophosphate synthase (FPPS) is a key enzyme in isoprenoid biosynthesis. Several classes of essential metabolites, including sterols, quinones, carotenoids and gibberellins, are terpenoids with high biological activity. The structural gene for FPP synthase was isolated from two ascomycete fungi, Neurospora crassa and Gibberella fujikuroi. A comparative analysis of the nucleotide sequences of both FPPS genes revealed the presence of introns at the same positions at the 5′ end of the coding regions. Furthermore, the most conserved region of the gene was isolated from two other plant pathogenic fungi, Sphaceloma manihoticola and Claviceps purpurea, by PCR. Sequence analysis showed a high degree of similarity between the deduced proteins of all known FPP synthase genes. In contrast to animals, all analyzed fungi contain a single copy of the gene, although FPP is the precursor for essential sterol and quinone biosynthesis and secondary metabolites, such as gibberellins, as well. Transcription analysis in different light regimes has shown that the FPPS genes in G. fujikuroi and N. crassa are not regulated by light induction.
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  • 5
    ISSN: 0992-7689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract We present an analysis of ground magnetic field, ionospheric flow, geosynchronous particle, and interplanetary data during a multiple-onset substorm on 12 April 1988. Our principal results concern the modulations of the ionospheric flow which occur during the impulsive electrojet activations associated with each onset. During the first hour of the disturbance these take place every \sim12.5 min and involve the formation of a new intense westward current filament in the premidnight sector, just poleward of the preexisting extended current system driven by the large-scale flow. These filaments are \sim1 h MLT wide (\sim600 km), and initially expand poleward to a width of \sim300 km before contracting equatorward and coalescing with the preexisting current, generally leaving the latter enhanced in magnitude and/or expanded in latitude. Within the impulsive electrojets the flow is found to be suppressed to values 50–100 m s−1 or less during the first few minutes, before surging equatorward at 0.5-1.0 km s−1 during the phase of rapid coalescence. The implication is that the precipitation-induced Hall conductivity within the impulsive electrojet initially rises to exceed \sim100 mho, before decaying over a few minutes. This value compares with Hall conductivities of \sim20 mho in the quasi-steady current regions, and a few mho or less in the regions poleward of the electrojets and in the preonset ionosphere. Preliminary evidence has also been found that the flow surges propagate from midnight to the morning sector where they are associated with arrested equatorward motion or poleward contractions of the current system. These observations are discussed in terms of present theoretical paradigms of the global behaviour of fields and flows which occur during substorms.
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  • 6
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 239-241 (Nov. 1996), p. 91-98 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 140 (1996), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Three different molecular techniques were used to characterize bacterial strains isolated from dairy products and phenotypically classified as Lactobacillus casei. Some strains were taxonomically identified as Lb. casei and Lb. paracasei using 23S rRNA-targeted probes specific for Lb. casei and Lb. paracasei. Chromosomal DNA was analyzed by pulsed-field gel electrophoresis. Lb. paracasei strains had a variable number of SfiI fragments harboring rRNA genes, while Lb. casei strains showed more homogeneous patterns. The chromosome size of Lb. paracasei ATCC 334 was evaluated to be 2.17 Mb.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Materials Research 29 (1999), S. 89-116 
    ISSN: 0084-6600
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Recently there has been a resurgence of research efforts related to the investigation of new and novel materials for small-scale thermoelectric refrigeration and power generation applications. These materials need to couple and optimize a variety of properties in order to exhibit the necessary figure of merit, i.e. the numerical expression that is commonly used to compare one potential thermoelectric material with another. The figure of merit is related to the coefficient of performance or efficiency of a particular device made from a material. The best thermoelectric material should possess thermal properties similar to that of a glass and electrical properties similar to that of a perfect single-crystal material, i.e. a poor thermal conductor and a good electrical conductor. Skutterudites are materials that appear to have the potential to fulfill such criteria. These materials exhibit many types of interesting properties. For example, skutterudites are members of a family of compounds we call open structure or cage-like, materials. When atoms are placed into the interstitial voids or cages of these materials, the lattice thermal conductivity can be substantially reduced compared with that of unfilled skutterudites. These compounds exhibit electrical properties ranging from that of low-temperature superconductors to narrow gap semiconductors.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Serogroup A meningococci of subgroups III, IV-1 and IV-2 are probably descended from a common ancestor that existed in the nineteenth century. The 10.5 kb sequences spanning five distinct chromosomal loci, encoding cell-surface antigens, a secreted protease or housekeeping genes and intergenic regions, were almost identical in strains of those subgroups isolated in 1966, 1966 and 1917 respectively. During the subsequent two to three decades, all of these loci varied as a result of mutation, translocation or import of DNA from unrelated neisseriae. Thus, microevolution occurs frequently in naturally transformable bacteria. Many variants were isolated only once or within a single geographical location and disappeared thereafter. Other variants achieved genetic fixation within months or a few years. The speed with which sequence variation is either eliminated or fixed may reflect sequential bottlenecks associated with epidemic spread and contrasts with the results of phylogenetic analyses from bacteria that do not cause epidemics.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of natural products 58 (1995), S. 112-116 
    ISSN: 1520-6025
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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