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  • 1
    Electronic Resource
    Electronic Resource
    Inhibition of non-vesicular glutamate release by group III metabotropic glutamate receptors in the nucleus accumbens (2003)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 87 (2003), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Previous in vitro studies have shown that group III metabotropic glutamate receptors (mGluRs) regulate synaptic glutamate release. The present study used microdialysis to characterize this regulation in vivo in rat nucleus accumbens. Reverse dialysis of the group III mGluR agonist l-(+)-2-amino-4-phosphonobutyric acid (L-AP4) decreased, whereas the antagonist (R,S)-α-methylserine-O-phosphate (MSOP) increased the extracellular level of glutamate. The decrease by L-AP4 or the increase by MSOP was antagonized by co-administration of MSOP or L-AP4, respectively. Activation of mGluR4a by (1S,3R,4S)-1-aminocyclopentane-1,2,4-tricarboxylic acid or mGluR6 by 2-amino-4-(3-hydroxy-5-methylisoxazol-4-yl)butyric acid had no effect on extracellular glutamate. (R,S)-4-Phosphonophenylglycine (PPG), another group III agonist with high affinity for mGluR4/6/8, reduced extracellular glutamate only at high concentrations capable of binding to mGluR7. The increase in extracellular glutamate by MSOP was tetrodotoxin-independent, and resistant to both the L-type and N-type Ca2+ channel blockers. L-AP4 failed to block 30 mm K+-induced vesicular glutamate release. Blockade of glutamate uptake by d,l-threo-β-benzyloxyaspartate caused a Ca2+-independent elevation in extracellular glutamate that was reversed by L-AP4. Finally, (S)-4-carboxyphenylglycine, an inhibitor of cystine-glutamate antiporters, attenuated the L-AP4-induced reduction in extracellular glutamate. Together, these data indicate that group III mGluRs regulate in vivo extracellular glutamate in the nucleus accumbens by inhibiting non-vesicular glutamate release.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.2003.02093.x
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  • 2
    Electronic Resource
    Electronic Resource
    A novel cyclic GMP-dependent protein kinase is expressed in the ring stage of the Plasmodium falciparum life cycle (2002)
    Oxford, UK : Blackwell Science Ltd.
    Molecular microbiology 44 (2002), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Cyclic GMP-dependent protein kinases (PKGs) are the major mediators of the cGMP signal transduction pathway and regulate a variety of physiological effects. We report here the characterization of an unusual PKG from the human malaria parasite Plasmodium falciparum (designated PfPKG). The 97.5 kDa protein contains some of the structural features of mammalian PKGs but, uniquely, contains a third predicted cGMP binding site and a degenerate fourth. Using both protein kinase activity assays and Western blotting with native P. falciparum proteins, we demonstrate here that PfPKG is expressed predominantly in the ring stage of the life cycle, suggesting a role in the development of asexual blood stage parasites. An Escherichia coli-derived recombinant protein (PfPKG2, Met115-Phe853) was purified and shown to have phosphotransferase activity in terms of both substrate phosphorylation and auto-phosphorylation. This activity was stimulated at least fivefold by 1.0 μ M cyclic GMP, but was not stimulated by cAMP or by 8-pCPT-cGMP, which is a potent activator of mammalian PKGs. Several protein kinase inhibitors exhibited a range of inhibitory effects on PfPKG activity. Biochemical analysis therefore shows that PfPKG is distinct from mammalian PKGs with respect to both cyclic nucleotide analogue activation and inhibition profiles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2002.02948.x
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  • 3
    Electronic Resource
    Electronic Resource
    The gametocyte-activating factor xanthurenic acid stimulates an increase in membrane-associated guanylyl cyclase activity in the human malaria parasite Plasmodium falciparum (2001)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 42 (2001), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Sex is an obligate step in the life cycle of the malaria parasite and occurs in the midgut of the mosquito vector. With both Plasmodium falciparum and Plasmodium berghei, the tryptophan metabolite xanthurenic acid induces the release of motile male gametes from red blood cells (exflagellation), a prerequisite for fertilization. The addition of cGMP or phosphodiesterase inhibitors to cultures of mature gametocytes has also been shown to stimulate exflagellation. Here, we demonstrate that there is a guanylyl cyclase activity associated with mature P. falciparum gametocyte membrane preparations, which is dependent on the presence of Mg2+/Mn2+ but is inhibited by Ca2+. Significantly, this activity is increased on addition of xanthurenic acid. In contrast, a xanthurenic acid precursor (3-hydroxykynurenine), which is not an inducer of exflagellation, does not induce this guanylyl cyclase activity. These results therefore suggest that xanthurenic acid-induced exflagellation may be mediated by activation of the parasite cGMP signalling pathway.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2001.02665.x
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  • 4
    Electronic Resource
    Electronic Resource
    Structure, function and evolution of microbial adenylyl and guanylyl cyclases (2004)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 52 (2004), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Cells respond to signals of both environmental and biological origin. Responses are often receptor mediated and result in the synthesis of so-called second messengers that then provide a link between extracellular signals and downstream events, including changes in gene expression. Cyclic nucleotides (cAMP and cGMP) are among the most widely studied of this class of molecule. Research on their function and mode of action has been a paradigm for signal transduction systems and has shaped our understanding of this important area of biology. Cyclic nucleotides have diverse regulatory roles in both unicellular and multicellular organisms, highlighting the utility and success of this system of molecular communication. This review will examine the structural diversity of microbial adenylyl and guanylyl cyclases, the enzymes that synthesize cAMP and cGMP respectively. We will address the relationship of structure to biological function and speculate on the complex origin of these crucial regulatory molecules. A review is timely because the explosion of data from the various genome projects is providing new and exciting insights into protein function and evolution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.2004.04067.x
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  • 5
    Electronic Resource
    Electronic Resource
    Behavior of Nonproteolytic Clostridium botulinum Type B and E Spores in Cooked Turkey and Modeling Lag Phase and Probability of Toxigenesis (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 56 (1991), S. 0 
    Details
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A spore pool inoculum (I) of 4 each type B and E nonproteolytic C. botulinum was applied at levels of log10-2 to 4 spores per 2–3g sample of cooked turkey (0, 1.47, and 2.2% brine (B), respectively), stored under vacuum at 4, 8, 12, 16, 20, and 30°C up to 180 days. Earliest toxin production at the above temperatures (T) was detected in 0% brine meat after 〉 180, 8, 4, 1.5, 1.5, and 0.5 days, in the 1.47% brine after 70, 8, 7, 2, 1.5 and 1 days, and in the 2.2% brine after 130, 10, 9, 2.5, 1.5 and 1 days, respectively. Lag phase (LP) was affected significantly by T, I, and Txl (p〈0.001) but not B (0.05〈p〈0.1). The derived model predictive of LP was: Log10 LP = 0.625 + 6.710 (1/T) + 0.0005 (I) X (T) − 0.033 (T) + 0.102 (B) − 0.102 (I) with R2= 0.970. More precise sampling plans and augmentation of our dataset will increase confidence in the model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2621.1991.tb05284.x
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  • 6
    Electronic Resource
    Electronic Resource
    Mae mediates MAP kinase phosphorylation of Ets transcription factors in Drosophila (2001)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 411 (2001), S. 330-334 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The evolutionarily conserved Ras/mitogen-activated protein kinase (MAPK) cascade is an integral part of the processes of cell division, differentiation, movement and death. Signals received at the cell surface are relayed into the nucleus, where MAPK phosphorylates and thereby modulates the ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/35077122
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  • 7
    Electronic Resource
    Electronic Resource
    Serotonin depletion attenuates cocaine-seeking behavior in rats (1999)
    Springer
    Psychopharmacology 146 (1999), S. 60-66 
    Details
    ISSN: 1432-2072
    Keywords: Key words Serotonin ; Cocaine-seeking behavior ; Food-seeking behavior ; Para-chlorophenylalanine ; Incentive motivation ; Extinction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Rationale: Alterations in serotonin (5-HT) neurotransmission during cocaine withdrawal may be involved in incentive motivation for cocaine. Objective: The present study examined the effects of 5-HT depletion on cocaine- and food-seeking behavior (i.e., non-reinforced operant responding). Methods: Separate groups of rats were trained to lever press for cocaine infusions (0.33 mg/kg/0.1 ml, i.v.) or for food pellets (45-mg Noyes food pellets) on a fixed-ratio one schedule of reinforcement during 14 daily 2-h sessions. Half of each group then received treatment with either saline or the tryptophan hydroxylase inhibitor para-chlorophenylalanine (p-CPA; 100 mg/kg, i.p.) on post-training day 5 and day 6. Twenty-four hours after their last treatment, rats were tested for cocaine- or food-seeking behavior by measuring operant responding in the absence of reinforcement until they reached an extinction criterion of no responses for 30 min. Animals were sacrificed 24 h after testing and brain 5-HT levels in various regions were quantified. Results: In cocaine-trained animals, p-CPA treatment significantly decreased cocaine-seeking behavior and produced a trend toward a decrease in extinction latency relative to saline treatment. In food-trained animals, p-CPA treatment failed to alter any of the behavioral measures during testing, suggesting that p-CPA treatment did not alter the animals’ memory or ability to perform an operant response. p-CPA significantly depleted 5-HT by 73–85% in every brain region examined. Conclusion: The results suggest that decreasing 5-HT neurotransmission may decrease incentive motivation for cocaine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002130051088
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  • 8
    Electronic Resource
    Electronic Resource
    Probability models to assess the safety of foods with respect toClostridium botulinum (1993)
    Springer
    Journal of industrial microbiology and biotechnology 12 (1993), S. 156-161 
    Details
    ISSN: 1476-5535
    Keywords: Predictive microbiology ; Modeling ; Clostridium botulinum ; Challenge test ; Risk analysis ; HACCP ; Food safety
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The effectiveness of a preservative system to prevent the growth ofClostridium botulinum can be expressed as the probability (P) that not even a single spore will be able to grow and produce toxin. Commerical canning processes for foods have been based upon this principle since the early 1920s. The safety of many current food marketing concepts depends on product formulation, processing, packaging and distribution variables. Direct measurement ofC. botulinum growth in a food system is difficult. Researchers have relied upon bioassay for botulinum toxin detection and Most Probable Number (MPN) techniques to quantifyC. botulinum growth in experimental food systems. The methods used to estimateP for a single spore to initiate growth will lead to a discussion on the use ofP as a dependent variable in predictive models. Modeling the effects of intrinsic and extrinsic processing variables on food safety will be presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01584184
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  • 9
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    Understanding a submarine eruption through time series hydrothermal plume sampling of dissolved and particulate constituents: West Mata, 2008–2012 (2014)
    Wiley-Blackwell
    Details
    Publication Date: 2014-10-31
    Description: Four cruises between 2008 and 2012 monitored the continuing eruption of West Mata volcano in the NE Lau Basin as it produced plumes of chemically altered water above its summit. Although large enrichments in 3 He, CO 2, Fe, and Mn were observed in the plumes, the most notable enrichment was that of H 2 , which reached concentrations as high as 14843 nM. Strongly enriched H 2 concentrations in the water column result from reactions between seawater or magmatic water and extremely hot rocks. In 2008, the observation of elevated H 2 concentrations in the water column above West Mata pointed to vigorous ongoing eruptions at the volcano's summit. The eruption was confirmed by visual observations made by the ROV Jason 2 in 2009 and demonstrated that H 2 measurements are a vital instrument to detect ongoing volcanic eruptions at the seafloor. Elevated H 2 in 2010 showed that the eruption was ongoing, although at a reduced level given a maximum H 2 concentration of 4410 nM. In 2012, H 2 levels in the water column declined significantly, to a maximum of only 7 nM, consistent with visual observations from the Quest-4000 ROV that found no evidence of an ongoing volcanic eruption. Methane behaved independently of other measured gases and its concentrations in the hydrothermal plume were very low. We attribute its minimal enrichments to a mixture of mantle carbon reduced to CH 4 and biological CH 4 from diffuse flow sites. This study demonstrates that ongoing submarine volcanic eruptions are characterized by high dissolved H 2 concentrations present in the overlying water column.
    Electronic ISSN: 1525-2027
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Published by Wiley-Blackwell on behalf of American Geophysical Union (AGU).
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  • 10
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    Geological interpretation of volcanism and segmentation of the Mariana back-arc spreading center between 12.7°N and 18.3°N (2017)
    Wiley-Blackwell
    Details
    Publication Date: 2017-05-24
    Description: The relationships between tectonic processes, magmatism, and hydrothermal venting along ∼600 km of the slow-spreading Mariana back-arc between 12.7°N and 18.3°N reveal a number of similarities and differences compared to slow-spreading mid-ocean ridges. Analysis of the volcanic geomorphology and structure highlights the complexity of the back-arc spreading center. Here, ridge segmentation is controlled by large-scale basement structures that appear to pre-date back-arc rifting. These structures also control the orientation of the chains of cross-arc volcanoes that characterize this region. Segment-scale faulting is oriented perpendicular to the spreading direction, allowing precise spreading directions to be determined. Four morphologically-distinct segment types are identified: dominantly magmatic segments (Type I); magmatic segments currently undergoing tectonic extension (Type II); dominantly tectonic segments (Type III); and tectonic segments currently undergoing magmatic extension (Type IV). Variations in axial morphology (including eruption styles, neovolcanic eruption volumes, and faulting) reflect magma supply, which is locally enhanced by cross-arc volcanism associated with N-S compression along the 16.5°N and 17.0°N segments. In contrast, cross-arc seismicity is associated with N-S extension and increased faulting along the 14.5°N segment, with structures that are interpreted to be oceanic core complexes—the first with high-resolution bathymetry described in an active back-arc basin. Hydrothermal venting associated with recent magmatism has been discovered along all segment types.
    Electronic ISSN: 1525-2027
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Published by Wiley-Blackwell on behalf of American Geophysical Union (AGU).
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