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  • 1985-1989  (5)
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Material
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Sensitive Radioimmunoassays for Histamine and tele-Methylhistamine in the Brain (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 53 (1989), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Serum albumin conjugates of histamine or tele-methylhistamine, a major catabolite, were prepared using 1,4-benzoquinone as the coupling agent and used to raise polyclonal antibodies in rabbits. The same reagent was used to prepare the [125I]iodinated tracer and treat tissue extracts submitted to the radioimmunoassays. The IC50 values of prederivatized histamine and tele-methylhistamine in the radioimmunoassays were 0.3 nM and 0.5 nM, respectively, whereas nonderivatized histamine or tele-methylhistamine, histidine, a variety of histamine derivatives, amines, etc., had at least 1,000-fold higher IC50 values. Application of the radioimmunoassays to nonpurified extracts of rat brain allowed the quantification of the two amine immunoreactivities in samples corresponding to less than 1 mg of hypothalamus. The tissue immunoreactivity corresponded to authentic histamine or tele-methylhistamine, as shown by (a) the parallel 125I-tracer displacement curves, (b) the similar elution patterns from HPLC columns, (c) the regional levels of histamine and tele-methylhistamine in brain, similar to those obtained with other methods, and (d) the clearcut effects of treatments with inhibitors of l-histidine decarboxylase or monoamine oxidase. The two radioimmunoassays appear as simple and sensitive tools to evaluate steady-state levels and turnover rates of histamine and tele-methylhistamine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1989.tb09237.x
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Carbon fixation in marine phytoplankton: carboxylase activities and stable carbon-isotope ratios; physiological and paleoclimatological aspects (1985)
    Springer
    Marine biology 87 (1985), S. 1-6 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We measured the activity of three carboxylases: RuBP carboxylase, PEP carboxylase and PEP carboxykinase of marine phytoplankton species in culture and in natural communities. Activities of the three carboxylases were measured simultaneously with stable carbon-isotope ratios. The enzymatic activities have been used to estimate the importance of β carboxylation and its impact on the 13C:12C ratio (expressed as δ13C). The marine phytoplankton species in culture were Fragilariopsis kerguelensis, Nitzschia turgiduloides, Skeletonema costatum, Phaeodactylum tricornutum, Isochrysis galbana, Dunaliella marina, and Prorocentrum micans, and the field samples were collected from different depths off the coast of Portugal (August/September, 1981). Our results indicate that, as in terrestrial plants, the δ13C value is a good indicator of the extent of β carboxylation. RuBP carboxylase activity was always predominant, whereas the δ13C value never reached values typical of the C4 pathway. The β carboxylases could be PEP carboxylase (in dinoflagellates) or PEP carboxykinase (in diatoms). β carboxylation increased at the end of the exponential growth phase in a diatom culture and with increased biomass in natural samples. We interpret these increases as an adaptative response mechanism to poor environmental conditions, especially to low light intensity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00396999
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Growth, photosynthesis and carbon metabolism in the temperate marine diatom Skeletonema costatum adapted to low temperature and low photon-flux density (1988)
    Springer
    Marine biology 100 (1988), S. 135-141 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The temperate diatom Skeletonema costatum (Grev.) Cleve was grown in low temperature and/or low light conditions. The cultures were acclimatized for at least three months before experiments were begun. Our data indicate that the initial slope of the photosynthesis vs irradiance curve (α) is controlled predominantly by light history and the light-saturated photosynthesis (P max) by temperature. The number of divisions per day decreased with decreasing light intensity, but was identical for cultures grown at 3° or 18°C. The metabolic pathways of inorganic carbon fixation were not fundamentally affected by low temperature or low light intensity, but both these factors increased labelling of C3 compounds, synthesized by the Calvin-Benson cycle, and decreased that of phosphoenolpyruvate (PEP) and other metabolites. This indicates an enhancement of ribulose-1,5-bisphosphate (RuBP) carboxylase activity, which is the first step in the C3 pathway (3-phosphoglycerate and sugar phosphate synthesis); this may optimize cell functions. At low temperatures, a seven-fold increase in RuBP carboxylase activity per cell was observed. S. costatum is able to adapt to low irradiance by increasing α and decreasing I k (the ratio of P max:α, light intensity at onset of light saturation), and to low temperature by increasing its cellular chlorophyll a and RuBP carboxylase content. However, in the latter case, adaptation is not optimal. This study revealed two main features: (1) there is evidence that RuBP carboxylase has a key function in adjustment to high rates of photosynthesis at suboptimal temperatures or irradiances; (2) adaptive mechanisms are dynamic processes and the role of the time scale in physiological adaptation should be considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392963
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Superconducting instability in the large-U limit of the two-dimensional Hubbard model (1987)
    Springer
    The European physical journal 68 (1987), S. 425-432 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have investigated numerically the pairing instabilities of Gutzwiller wavefunctions. These are equivalent to a certain form of the resonant valence bond wavefunction. The case considered is a nearly half-filled two dimensional band with interactions given by a Hubbard model with large on-site Coulomb interactions. We find that the paramagnetic normal state is unstable tod-wave pairing but stable againsts-wave pairing. The antiferromagnetic state is marginally stable against both types of pairing. These results can be explained as an interference effect resulting in enhanced antiferromagnetic spin correlation in the paired state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01471072
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Crossover from Fermi liquid to classical behavior of normal3He in the model of almost localized fermions (1986)
    Springer
    Journal of low temperature physics 64 (1986), S. 195-221 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A phenomenological extension of the model of almost localized fermions to finite temperatures is presented. It is used to calculate thermodynamic properties of the normal state of3He. No new adjustable parameters are introduced and the effective interaction strength is the same as used by Vollhardt. A good qualitative description of the crossover from Fermi liquid to classical behavior in the specific heat, spin susceptibility, and temperature-dependent pressure (or equivalently thermal expansion) is obtained. In particular, key results, such as the change in specific heat when the spin entropy saturates and the change from thermal expansion to thermal contraction at low temperatures are reproduced.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00685129
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    Paper (German National Licenses)
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