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  • 1
    Digitale Medien
    Digitale Medien
    In vivo activation of insulin receptor tyrosine kinase by melatonin in the rat hypothalamus (2004)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 90 (2004), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Melatonin is the pineal hormone that acts via a pertussis toxin-sensitive G-protein to inhibit adenylate cyclase. However, the intracellular signalling effects of melatonin are not completely understood. Melatonin receptors are mainly present in the suprachiasmatic nucleus (SCN) and pars tuberalis of both humans and rats. The SCN directly controls, amongst other mechanisms, the circadian rhythm of plasma glucose concentration. In this study, using immunoprecipitation and immunoblotting, we show that melatonin induces rapid tyrosine phosphorylation and activation of the insulin receptor β-subunit tyrosine kinase (IR) in the rat hypothalamic suprachiasmatic region. Upon IR activation, tyrosine phosphorylation of IRS-1 was detected. In addition, melatonin induced IRS-1/PI(3)-kinase and IRS-1/SHP-2 associations and downstream AKT serine phosphorylation and MAPK (mitogen-activated protein kinase) phosphorylation, respectively. These results not only indicate a new signal transduction pathway for melatonin, but also a potential cross-talk between melatonin and insulin.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1471-4159.2004.02514.x
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  • 2
    Digitale Medien
    Digitale Medien
    Colonization and extinction of ant communities in a fragmented landscape (2004)
    Oxford, UK : Blackwell Science Pty
    Austral ecology 29 (2004), S. 0 
    Details
    ISSN: 1442-9993
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Abstract  In this paper we tested the assumption that smaller and more isolated remnants receive fewer ant colonizers and lose more species. We also tested hypotheses to explain such a pattern. We sampled ants in Brazil for 3 years in 18 forest remnants and in 10 grasslands between them. We tested the influence of remnant area and isolation on colonization rate, as well as the effect of remnant area on extinction rate. We tested the correlation between remnant area and isolation to verify the landscape design. Colonization rate was not affected by remnant area or isolation. Extinction rate, however, was smaller in larger remnants. Remnant area and isolation were negatively correlated. We tested two hypotheses related to the decrease in ant species extinction rate with increased remnant area: (i) small remnants support smaller and more extinction-prone populations; and (ii) small remnants are more often invaded by generalist species, which suffer higher extinction inside remnants. The density of ant populations significantly increased with area. Generalist species presented a lower colonization rate in larger remnants, contrary to the pattern observed in forest species. Generalist species suffered more extinction than expected inside remnants. The lack of response of colonization rate to remnant area can be explained by the differential colonization by generalist and forest species. The decrease of ant population density in smaller remnants could be related to loss of habitat quality or quantity. The higher colonization by generalist ant species in the smaller remnants could be related to landscape design, because smaller remnants are more similar to the matrix than larger ones. Our results have important implications for conservation strategies because small remnants seem to be more affected by secondary effects of fragmentation, losing more forest species and being invaded more often by generalist species. Studies that compare only species richness between remnants cannot detect such patterns in species composition.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1442-9993.2004.01378.x
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  • 3
    Digitale Medien
    Digitale Medien
    Tree heterogeneity, resource availability, and larger scale processes regulating arboreal ant species richness (2003)
    Oxford, UK : Blackwell Science Pty
    Austral ecology 28 (2003), S. 0 
    Details
    ISSN: 1442-9993
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Abstract  Processes acting on different spatial and temporal scales may influence local species richness. Ant communities are usually described as interactive and therefore determined by local processes. In this paper we tested two hypotheses linked to the question of why there is local variation in arboreal ant species richness in the Brazilian savanna (‘cerrado’). The hypotheses are: (i) there is a positive relationship between ant species richness and tree species richness, used as a surrogate of heterogeneity; and (ii) there is a positive relationship between ant species richness and tree density, used as a surrogate of resource availability. Arboreal ants were sampled in two cerrado sites in Brazil using baited pitfall traps and manual sampling, in quadrats of 20 m × 50 m. Ant species richness in each quadrat was used as the response variable in regression tests, using tree species richness and tree density as explanatory variables. Ant species richness responded positively to tree species richness and density. Sampling site also influenced ant species richness, and the relationship between tree density and tree species richness was also positive and significant. Tree species richness may have influenced ant species richness through three processes: (i) increasing the variety of resources and allowing the existence of a higher number of specialist species; (ii) increasing the amount of resources to generalist species; and (iii) some other unmeasured factor may have influenced both ant and tree species richness. Tree density may also have influenced ant species richness through three processes: (i) increasing the amount of resources and allowing a higher ant species richness; (ii) changing habitat conditions and dominance hierarchies in ant communities; and (iii) increasing the area and causing a species–area pattern. Processes acting on larger scales, such as disturbance, altitude and evolutionary histories, as well as sampling effect may have caused the difference between sites.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1442-9993.2003.01290.x
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  • 4
    Digitale Medien
    Digitale Medien
    Prevalence of secreted autotransporter toxin gene among diffusely adhering Escherichia coli isolated from stools of children (2003)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 227 (2003), S. 0 
    Details
    ISSN: 1574-6968
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: In this report, we analyzed the prevalence of the sat gene in 336 Escherichia coli samples collected from stools of children with and without diarrhea in Brazil and in 100 uropathogenic E. coli strains. The results show a high correlation between diffusely adhering E. coli (DAEC) and the presence of sat (44%) in intestinal isolates. DAEC strain FBC114 expresses a 107-kDa protein, which showed 98% homology with Sat.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1016/S0378-1097(03)00688-8
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  • 5
    Digitale Medien
    Digitale Medien
    Videolaparoscopic cholecystectomy induces a hemostasis activation of lower grade than does open surgery (2000)
    Springer
    Surgical endoscopy and other interventional techniques 14 (2000), S. 170-174 
    Details
    ISSN: 1432-2218
    Schlagwort(e): Key words: Blood clotting activation — Open and videolaparoscopic cholecystectomy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Background: Tissue injury after trauma and surgery may induce alterations in blood coagulation and fibrinolysis, and the hypercoagulable state observed after surgery can be associated with the risk of postoperative thromboembolic complications. Recently, videolaparoscopic (VLPS) cholecystectomy has been introduced, and its advantages over the open procedure seem related to the reduced surgical trauma. The aim of this study was to investigate hemostatic system alterations in patients who undergo open and VLPS cholecystectomy. Methods: Fibrinogen, prothrombin fragment F1+2, D-dimer, and plasminogen activator inhibitor type-1 (PAI-1) activity was determined in 10 patients who underwent open (group A) and 10 patients who underwent VLPS cholecystectomy (group B), respectively. Blood samples were obtained the day of surgery in the morning (B1), after anesthesia (A1), 1 hour after the start of surgery (S1), then 30 min (E.05) and 24 h (E.24) after the surgery. Results: No significant differences were observed in baseline values between groups A and B for the parameters investigated. At 24 h after surgery, fibrinogen increased significantly (p 〈 0.05) in group A and also was significantly higher than in group B (p 〈 0.05). In group A, a marked increase in F1+2 levels (p 〈 0.01) was observed in all the samples, with the maximum values on the first day after surgery (3.7 nmol/l; 1.2–6.0 nmol/l), whereas in group B, a slight but significant increase in F1+2 levels (2.1 nmol/l; 1.1–3.9 nmol/l; p 〈 0.01) was observed only 30 min after the end of surgery. In both groups A and B, D-dimer markedly increased after surgery, without statistical significant differences between the two groups at any time. The PAI-1 activity plasma levels remained in the normal range during and after surgery in both groups. Conclusions: These results indicate that VLPS surgery induces an activation of the clotting system that, although of low degree and short duration, can lead to a transient prothrombotic state.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004649900093
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  • 6
    Digitale Medien
    Digitale Medien
    Compounds Extracted from Phyllantus and Jatropha elliptica Inhibit the Binding of [3H]Glutamate and [3H]GMP-PNP in Rat Cerebral Cortex Membrane (2000)
    Springer
    Neurochemical research 25 (2000), S. 211-215 
    Details
    ISSN: 1573-6903
    Schlagwort(e): Glutamate ; guanine nucleotides ; antinoception ; naturally-occurring compounds
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Glutamate is to be considered a nociceptive neurotransmitter and glutamatergic antagonists present antinoceptive activity. In this study we investigated the effects of the naturally occurring antinociceptive compounds rutin, geraniin and quercetine extracted from Phyllanthus, as well as the diterpene jatrophone, extracted from Jatropha elliptica on the binding of [3H]glutamate and [3H]GMP-PNP [a GTP analogue which binds to extracellular site(s), modulating the glutamatergic transmission] in rat brain membrane. Jatrophone inhibited [3H]glutamate binding and geraniin inhibited [3H]GMP-PNP binding. Quercetine inhibited the binding of both ligands. These results may indicate a neurochemical parameter possibly related to the antinoceptive activity of these natural compounds.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007567302504
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