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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Bulletin of mathematical biology 40 (1978), S. 865-872 
    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract This note supplies missing details and corrects some mathematical errors in the recent significant paper by Auchmuty and Nicolis (1975).
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Extremophiles 2 (1998), S. 279-287 
    ISSN: 1433-4909
    Keywords: Key words Halobacteria ; Haloarchaea ; Evaporites ; Dormancy ; 16S rRNA genes ; rRNA gene heterogeneity ; Salt mines ; Longevity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Subterranean salt deposits are the remains of ancient hypersaline waters that presumably supported dense populations of halophilic microorganisms including representatives of the haloarchaea (halobacteria). Ancient subterranean salt deposits (evaporites) are common throughout the world, and the majority sampled to date appear to support diverse populations of halobacteria. The inaccessibility of deep subsurface deposits, and the special requirements of these organisms for survival, make contamination by halobacteria from surface sites unlikely. It is conceivable that these subterranean halobacteria are autochthonous, presumably relict populations derived from ancient hypersaline seas that have been revived from a state of dormancy. One would predict that halobacteria that have been insulated and isolated inside ancient evaporites would be different from comparable bacteria from surface environments, and that it might be possible to use a molecular chronometer to establish if the evolutionary position of the subsurface isolates correlated with the geological age of the evaporite. Extensive comparisons have been made between the 16S rRNA genes of surface and subsurface halobacteria without showing any conclusive differences between the two groups. A further phylogenetic comparison exploits an unusual feature of one particular group of halobacteria that possess at least two heterogeneous copies of the 16S rRNA gene, the sequences of which may have been converging or diverging over geological time. However, results to date have yet to show any gene sequence differences between surface and evaporite-derived halobacteria that might arguably be an indication of long-term dormancy.
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  • 3
    ISSN: 1432-1211
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Previously published data suggest that both xenogeneic and allogeneic anti-Ia sera can recognize carbohydrate-defined antigenic determinants on the surface of lymphocytes. There is also evidence, based on studies with allogeneic anti-Ia sera, that protein-defined Ia antigens exist. In this paper the relationship between these two types of Ia antigen was examined. It was found that in capping studies, the allogeneic anti-Ia serum could cap off the antigens recognized by the xenogeneic antiserum, whereas the xenogeneic antibodies could, at least partially, clear the surface of lymphocytes of Ia antigens detected by the allogeneic antibodies. On the other hand, when immunoprecipitates of radioiodinated cell-surface antigens were examined by SDS-polyacrylamide-gel electrophoresis, it was found that the xenogeneic anti-Ia serum did not immunoprecipitate any labeled material. In contrast, the allogeneic antiserum immunoprecipitated a labeled molecule which corresponded to the protein-defined Ia antigen described by others. Finally, it was shown that serum Ia antigens could be bound by either mouse or rabbit anti-Ia antibody, and this binding blocked any further reactivity with either serum. These results were interpreted as suggesting that two separate classes of Ia antigen molecule appear on the lymphocyte surface-one class has carbohydrate-defined antigenic specificities and the other has protein-defined determinants. Allogeneic anti-Ia sera contain antibodies against both these antigenic systems, whereas xenogeneic sera recognize only the carbohydratedefined series. The genetic implications of this interpretation are discussed.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Bulletin of environmental contamination and toxicology 26 (1981), S. 440-445 
    ISSN: 1432-0800
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Zeitschrift für angewandte Mathematik und Physik 21 (1970), S. 825-830 
    ISSN: 1420-9039
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Notes: Zusammenfassung Es wird die Bewegung eines kleinen sphärischen Teilchens in einer Couette-Strömung untersucht. Wenn die Reynolds-Zahl grösser ist als ein kritischer Wert, so wird die Teilchen-Bewegung in laminarer Strömung instabil und verursacht Turbulenz; unterhalb des kritischen Wertes bleibt die Strömung laminar. Die kritische Reynolds-Zahl (auf Teilchen-Durchmesser und Geschwindigkeitsgradient basierend) hängt nur vom Dichteverhältnis zwischen der Flüssigkeit und der Kugelab.
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  • 6
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract English sole (Parophyrs vetulus) in Puget Sound, Washington, USA are at risk of hepatocarcinogenesis specifically in areas adjacent to polluting industrial effluents. A question concerning population and ecosystem survival is whether any of the effects of etiopathologic change are reversible. This has been approached by looking for evidence of tumor accelerating effects in an exposed population. Cellular parameters were determined by flow cytometry for hepatocytes of English sole. Cells containing hyperdiploid DNA not present in fish from reference waters, Port Madison, were found in all non-tumor-bearing and tumor bearing fish taken from a polluted site, Eagle Harbor, where incidence of hepatic neoplasia approaches 30%. Induction of altered DNA content in the exposed general hepatocyte population suggests environmental induction rather than an association with lesionsper se. In contrast, glutathione levels in hepatocytes (0.8–3.2 nmol/mg protein), were little influenced by the exposure site, consistent with the apparent lack of protection against chemically induced carcinogenesis in English sole. Association of altered DNA content with exposure site is significant for its potential contribution to biological acceleration and evidence of tumor promotion found at the tissue and organismic levels. The results support the notion that hepatocarcinogenesis in English sole in Eagle Harbor has a multi-year exposure etiology, in which potentially reversible accelerating influences have a role, and that glutathione conjugation is an inadequate mode of detoxification for these fish.
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  • 7
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Trisomy is the leading known cause of mental retardation and pregnancy loss in humans, yet virtually nothing is known of the underlying nondisjunctional mechanisms. Since studies of other organisms suggest an association between centromere size or sequence and meiotic nondisjunction, we recently initiated studies to examine the effect of centromere size variation on human nondisjunction. In the present report, we summarize studies correlating variation in the size of the Y-chromosome centromere with sex chromosome nondisjunction. In one set of studies, we used pulsed-field gel electrophoresis to estimate Y-chromosome alpha-satellite array lengths in normal males, and correlated these values with Y-chromosome sperm disomy levels as determined by fluorescence in situ hybridization. In a second set of studies, we determined the Y-chromosome alpha-satellite array length of 47,XYY males, since the karyotypes of these individuals are a consequence of Y chromosome nondisjunction. Neither set of studies provided evidence for an effect of Y-chromosome alpha-satellite array length on Y-chromosome nondisjunction. Thus, if there is an association between Y-chromosome centromere size and nondisjunction, the effect is subtle and below the detection levels of the present study or involves extreme size variants that were not represented in the present study population.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Immunogenetics 37 (1993), S. 415-425 
    ISSN: 1432-1211
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract We have examined the same kappa chain variable (Vϰ) region family in several mouse species in order to observe short-term, incremental change at immunoglobun (Ig) multigene loci. In the present study, the Igk-V24 family has been characterized in a Mus m. castaneus colony derived from individuals originating in Thailand and compared to the same family in Mus m. domesticus (BALB/c) and Mus pahari, representing about 1 – 2 and about 5 – 9 million years of evolution, respectively. Southern hybridization of genomic DNA with a probe encoding the prototype Igk-V24 coding region reveals restriction fragment patterns indicative of two distinct M. m. castaneus haplotypes. These haplotypes appear to result from an unequal recombination between similar gene arrays, as their restriction patterns are unique but contain many common fragments. The complexity of these patterns indicates a marked expansion in the Igk-V24 family of M. m. castaneus relative to BALB/c and M. pahari. Additional analyses using probes specific for individual subsets demonstate that the expansion is not general throughout the entire family, but is restricted to particular subsets and therefore to relatively short chromosomal segments. One subset alone accounts for most of the expansion and comprises over 40% of the entire M. m. castaneus family. The wide range of Igk-V24 family complexity seen among M. m. castaneus, M. m. domesticus, and M. pahari, as well as among the different M. m. castaneus family subsets, suggests a model of random evolution in Vϰ family copy number rather than one which is selective.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Immunogenetics 37 (1993), S. 426-436 
    ISSN: 1432-1211
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract To examine genetic variation at immunoglobulin (Ig) multigene loci over short spans of evolutionary time, we have compared members of an Ig kappa chain variable (V κ) region family from several mouse species. In this study, seven unique Igk-V24 family members have been isolated from Mus m. castaneus and characterized by nucleotide sequence determination for comparison to their counterparts in Mus m domesticus (BALB/c), and Mus pahari, representing 1–2 million years of evolution in the former case and 5–8 million years in the latter. Parsimony, together with evolutionary distances calculated for various paris of Igk-V24 family coding regions, relate all family members to a common progenitor existing roughly 24 million years ago (Mya). A significant portion of the M. m. castaneus family consists of pseudogene segments in various degrees of progressive degeneration. The substitution patterns and divergence rates for all gene segments are characteristic of their respective subsets, especially in the areas flanking the coding regions. Complex and variable patterns of diversity are seen in potentially expressed coding regions, which appear to reflect quite different selective pressures on various subregions within the V κ protein domain. These results indicate that evolutionary pressures are operating at the level of family subsets, their individual members, and subregions within similar molecules.
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  • 10
    ISSN: 1432-1211
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Ten monoclonal alloantibodies were examined by submitting each antibody to five independent tests in order to determine whether they reacted primarily with the glycoprotein or glycolipid class of Ia antigens. The tests employed were as follows: (1) the ability to precipitate an la-like protein from the cell surface as detected by SDS-PAGE; (2) inhibition by protein-la extracts free of CHO-Ia; (3) inhibition by CHO-Ia extracts free of protein-la; (4) neuraminidase sensitivity of the antigen and (5) inhibition by simple sugars. Using these tests, three of the ten monoclonal antibodies were shown to recognize a CHO-Ia antigen while seven recognized the protein class of Ia antigens. The three CHO-Ia-specific monoclonal antibodies recognized Ia specificities 2,9 and 17. Monoclonal antibodies recognizing protein-defined Ia.2 and 17 specificities were also characterized. These results imply that some Ia specificities, as defined by genetic testing, can occur both as carbohydrate-defined and protein-defined determinants.— Sugar inhibition studies showed that CHO-Ia.2 has D-glucosamine as its immunodominant sugar while CHO-Ia. 17 shows preference for aβ- linked galactose. Furthermore, studies with neuraminidase demonstrated that sialic acid plays a role in the antigenic determinants of CHO-Ia.9 and CHO-Ia.17. Finally, it is noteworthy that CHO-Ia.2, the private specificity of thek haplotype, appears to be expressed only on cells and not in serum. These studies clearly demonstrate the existence of the two Ia antigen classes and emphasize the complexity of the murineI region.
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