ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Springer  (117)
  • American Physical Society (APS)
  • American Meteorological Society (AMS)
  • 1995-1999  (52)
  • 1985-1989  (65)
Collection
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 52 (1996), S. 757-761 
    ISSN: 1420-9071
    Keywords: Vasculogenesis ; angiogenesis ; muscle ; embryonic ; metabolites ; fibroblast growth factor (FGF) ; chorioallantoic membrane (CAM)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Normal and pathological formation of blood vessels is of considerable interest both in terms of basic scientific processes and clinical applications. Angiogenic events in the adult are likely to represent persistence of developmental mechanisms, and embryos are therefore a suitable experimental model for these processes. Among embryonic tissues, muscle is particularly appropriate for investigation, since it is highly vascularised from early stages. There are a number of competing explanations of how this process is controlled. Bioassays offer advantages over conventional molecular localisation techniques, in that they reveal the presence of active processed forms of the molecules under study, rather than non-processed forms, or non-translated meassages. Using these techniques, we report here that embryonic chick muscle, taken from the stages at which blood vessels are forming, produces an angiogenic activity on the chick chorioallantoic membrane (CAM), and transforms NR6 cells in soft agar. Basic fibroblast growth factor (bFGF) is shown to be angiogenic on the CAM in the same way, and also transforms NR6 cells (NR6 cells lack functional epidermal growth factor/transforming growth factor-a receptors, and are believed to respond only to bFGF in this way). Anti-bFGF removes the transforming activity of the embryonic muscle. We conclude that this represents evidence that embryonic chick muscle is producing an FGF-like molecule which is capable of acting as an angiogenic agent at the appropriate times in development.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1432-1041
    Keywords: azathioprine ; 6-thiouric acid ; 6-mercaptopurine ; renal transplantation ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The immunosuppressive activity of azathioprine (AZA) is unpredictable and depends on the formation of intracellular thiopurine ribonucleotides. However, the quantification of these active thiopurines presents difficult analytical problems. It has recently been postulated that plasma concentrations of 6-thiouric acid (6-TU) and 6-mercaptopurine (6-MP), metabolites of AZA, may provide more readily measurable indices of the pharmacologic activity of AZA. In order to evaluate the utility of 6-TU and 6-MP plasma concentrations in monitoring AZA therapy, we studied their pharmacokinetics in 6 renal transplant patients, and their in vitro immunosuppressive potency in a mixed lymphocyte proliferation assay. A peak plasma 6-TU concentration of 710.7 ng/ml was observed at 3.8 h after oral dosing. Good correlation was observed between the elimination t1/2 of 6-TU and serum creatinine, and between AUC over 24 h and serum creatinine. However, we did not observe a second peak in plasma 6-TU concentration that could be attributed to the degradation of active AZA metabolites. 6-MP plasma concentrations in the patients were low (mean peak concentration 36.0 ng/ml) and rapidly disappeared within 8 h. In vitro immunosuppressive activity could not be demonstrated for 6-TU over a concentration range of 1.25 ng/ml to 0.25 mg/ml. We conclude that 6-TU is pharmacologically inert and is primarily eliminated by the kidneys. Our findings currently do not support the use of plasma concentrations of 6-TU or 6-MP to monitor AZA therapy. In order to optimize AZA therapy, analytical techniques that are technically feasible and that can directly quantify the active intracellular thiopurines are being explored.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Artificial intelligence review 9 (1995), S. 129-146 
    ISSN: 1573-7462
    Keywords: natural language ; multimedia ; human-computer interaction ; communication modalities ; dialogue ; generation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In the late Eighties the Natural Language Processing community began appreciating the role of multimodality in interactive systems. Intelligent multimodal systems are systems that integrate natural language (generally so far keyboard-based input, shortly also voice) with other media such as gestures in input or graphics in output. The perspective of what can be called visible interactive communication is discussed and considered as a possible new modality of natural language, after the spoken and the written ones. This should not be confused with the type of hypermedia that are now being developed. There, basically, the interface space is finite, even if one dimension may be added. Here the infinite creativity of human language is potentially preserved as the fundamental communication instrument.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Fresenius' journal of analytical chemistry 361 (1998), S. 645-646 
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A cold working steel was coated both with high temperature CVD (TiN) and moderate temperature CVD (Ti[C,N]). AES depth profiles show a significant difference at the interface, where a thin oxide layer remains detectable at deposition temperatures of 750 °C. It could be shown that an impedance signal at a frequency of 13 MHz is well suited to detect the early stages of the growth of a CVD coating.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 42 (1996), S. 352-353 
    ISSN: 1612-1112
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 41 (1995), S. 612-615 
    ISSN: 1612-1112
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Archiv der Mathematik 47 (1986), S. 408-409 
    ISSN: 1420-8938
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    ISSN: 1432-0983
    Keywords: Plant mitochondrial DNA ; Restriction enzyme analysis ; rRNA genes ; Tomato cell suspension cultures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Mitochondrial DNA (mtDNA) from Lycopersicon esculentum was purified from cell suspension cultures. The DNA, isolated from mitochondria purified by two successive sucrose density gradients, was uncontaminated with nuclear DNA or DNA from proplastids. The total molecular weights of BamHI, BglI, and BglII fragments indicate a mitochondrial genome size of at least 270 kb. Cross hybridization between tomato mtDNA and cloned spinach plastid genes revealed some homology. In hybridization experiments using cloned mitochondrial rRNA genes and BamHI digested total mtDNA the presence of recombination repeats is demonstrated.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    ISSN: 1432-1939
    Keywords: Nitrogen isotope discrimination ; Cape floristic region ; Fynbos ; Strandveld ; Acacia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This study examines the impacts of woody, N2-fixing invasive Acacia spp. on the patterns of nutrient cycling in two invaded ecosystems of differing nutrient status in the Cape floristic region. Patterns of soil nutrient mineralization were measured by a field incubation method while the significance of the fixation process in altering nutrient cycling was assessed by the δ15N natural abundance technique. The results confirm earlier reports that invasion by woody shrubs results in organic matter and nutrient enrichment of surface soils of both ecosystems. However, patterns of nutrient availability (phosphorus and nitrogen) were not necessarily enhanced. In the more fertile strandveld both phosphorus and nitrogen (significant at P〈0.10) showed trends towards enhanced annual mineralization rates upon invasion, while in the low nutrient fynbos system only phosphorus followed this trend. It is unclear whether this differential response is a consequence of plant- or soil-derived feedbacks on the decomposition processes in each system. The δ15N values of the soils from the invaded sites of both ecosystems indicated a strong influence of the alien species on the soil nitrogen component. However, as with other studies of natural ecosystems, the contribution of nitrogen from fixation could not be readily quantified with the δ15N natural abundance method because of problems in selecting suitable non-N2-fixing reference plants. A technique of disrupting nodule structure and function, by fumigation with O2, to obtain the δ15N value of a non-N2-fixing speciment of the study species was tried and found to overcome some of the problems associated with the lack of suitable reference plants. With this technique it was possible to detect the almost total dependence of A. saligna on N2-fixation in the fynbos soils with their low nitrogen mineralization rates. In the strandveld ecosystem with much higher soil nitrogen release rates A. cyclops was only partly dependent on fixation (about half) for its nitrogen. The nutrient enrichment of both ecosystems and trends towards enhanced rates of nutrient mineralization could have profound implications on the long-term success of alien invader clearing operations and the restoration of the indigenous flora at these sites.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 10
    ISSN: 1432-1939
    Keywords: Browsing responses ; Semi-arid shrubs ; Nonstructural carbohydrate accumulation ; Regrowth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nonstructural carbohydrate allocation patterns in response to different frequencies of simulated browsing (leaf and twig removal) were studied in the following semi-arid shrubs: Osteospermum sinuatum, a dwarf deciduous shrub, Pteronia pallens, a dwarf evergreen shrub, and Ruschia spinosa, a dwarf leaf-succulent shrub. Simulated browsing at all frequencies resulted in the elevation, or had no effect, on total nonstructural carbohydrate (TNC) concentrations of O. sinuatum plant parts, and resulted in the decrease in TNC concentrations of R. spinosa plant parts. The responses of P. pallens were intermediate with elevations as well as declines in TNC concentrations of plant parts measured in response to various clipping frequencies. At the low frequency of simulated browsing (every 26 weeks) elevations in plant TNC content were measured in the two non-succulent shrubs O. sinuatum and P. pallens. It was concluded that the overcompensation with respect to TNC accumulation observed in the two non-succulent species represents one of the ways in which excess photosynthate is utilized by browsed shrubs with a limited regiowth potential. Simulated browsing was the least detrimental with respect to biomass production to the non-succulent O. sinuatum and P. pallens, and most injurious to the leaf-succulent shrub, R. spinosa. The observed TNC allocation patterns could not adequately explain the variation among species in the production of new growth and it was concluded that some factor(s) other than the carbon resource was limiting regrowth.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...