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Janusz Uchmaski 《Oikos》2000,90(3):539-548
To study the influence of individual variability on population dynamics an individual-based model of the dynamics of a single population consisting of different individuals is constructed. The model is based on differences in individual assimilation rates due to intraspecific competition and variability of initial weights. The model exhibits "imperfect regulation", i.e., the number of individuals in the population oscillates and sooner or later the population becomes extinct. When individual variability is included, the model produces longer population extinction times than without individual variability. The average extinction time is not however a monotonic function of the degree of individual variability. 相似文献
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The high resolution 1H and 13C nuclear magnetic resonance (NMR) spectra of galactosylceramides containing n-fatty acids and α-hydroxy fatty acids were recorded in dimethylsulfoxide solution with and without addition of D2O. From the coupling constants of the sugar ring protons, a 4C1 conformation can be deduced. In contrast to the conformation in aqueous solution, the C6 hydroxymethylene group is freely rotating around the C6C5 bond. In the ceramide residue all signals produced by protons linked to carbons bearing electronegative substituents could be attributed. The large difference in coupling constants of the methylene protons of C1′ to the C2′ methine proton of the sphingosine indicates a restricted rotation around the C1′C2′ bond. The assignments of the hydroxy and amino protons follow from the decoupling of the corresponding methine protons. 相似文献
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Mutational and epigenetic driver events profoundly alter intercellular communication pathways in cancer. This effect includes deregulated release, molecular composition, and biological activity of extracellular vesicles (EVs), membranous cellular fragments ranging from a few microns to less than 100 nm in diameter and filled with bioactive molecular cargo (proteins, lipids, and nucleic acids). While EVs are usually classified on the basis of their physical properties and biogenetic mechanisms, recent analyses of their proteome suggest a larger than expected molecular diversity, a notion that is also supported by multicolour nano‐flow cytometry and other emerging technology platforms designed to analyze single EVs. Both protein composition and EV diversity are markedly altered by oncogenic transformation, epithelial to mesenchymal transition, and differentiation of cancer stem cells. Interestingly, only a subset of EVs released from mutant cells may carry oncogenic proteins (e.g., EGFRvIII), hence, these EVs are often referred to as “oncosomes”. Indeed, oncogenic transformation alters the repertoire of EV‐associated proteins, increases the presence of pro‐invasive cargo, and alters the composition of distinct EV populations. Molecular profiling of single EVs may reveal a more intricate effect of transforming events on the architecture of EV populations in cancer and shed new light on their biological role and diagnostic utility. 相似文献
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Adrian Wiater Magorzata Pleszczyska Ewa Pietrykowska‐Tudruj Monika Janczarek Bernard Staniec Janusz Szczodrak 《Entomological Science》2019,22(1):36-41
Bacteria degrading α‐(1→3)‐glucan were sought in the gut of fungivorous insects feeding on fruiting bodies of a polypore fungus Laetiporus sulphureus, which are rich in this polymer. One isolate, from Diaperis boleti, was selected in an enrichment culture in the glucan‐containing medium. The bacterium was identified as Paenibacillus sp. based on the results of the ribosomal DNA analysis. The Paenibacillus showed enzyme activity of 4.97 mU/cm3 and effectively degraded fungal α‐(1→3)‐glucan, releasing nigerooligosaccharides and a trace amount of glucose. This strain is the first reported α‐(1→3)‐glucan‐degrading microorganism in the gut microbiome of insects inhabiting fruiting bodies of polypore fungi. 相似文献
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Nancy Witowski Elizabeth Lusczek Charles Determan Jr. Daniel Lexcen Kristine Mulier Beverly Ostrowski Greg Beilman 《PloS one》2015,10(4)
Objective
Hemorrhagic shock accompanied by injury represents a major physiologic stress. Fasted animals are often used to study hemorrhagic shock (with injury). A fasted state is not guaranteed in the general human population. The objective of this study was to determine if fed animals would exhibit a different metabolic profile in response to hemorrhagic shock with trauma when compared to fasted animals.Methods
Proton (1H) NMR spectroscopy was used to determine concentrations of metabolites from four different compartments (liver, muscle, serum, urine) taken at defined time points throughout shock/injury and resuscitation. PLS-DA was performed and VIP lists established for baseline, shock and resuscitation (10 metabolites for each compartment at each time interval) on metabolomics data from surviving animals.Results
Fed status prior to the occurrence of hemorrhagic shock with injury alters the metabolic course of this trauma and potentially affects mortality. The death rate for CPF animals is higher than FS animals (47 vs 28%). The majority of deaths occur post-resuscitation suggesting reperfusion injury. The metabolomics response to shock reflects priorities evident at baseline. FS animals raise the baseline degree of proteolysis to provide additional amino acids for energy production while CPF animals rely on both glucose and, to a lesser extent, amino acids. During early resuscitation levels of metabolites associated with energy production drop, suggesting diminished demand.Conclusions
Feeding status prior to the occurrence of hemorrhagic shock with injury alters the metabolic course of this trauma and potentially affects mortality. The response to shock reflects metabolic priorities at baseline. 相似文献9.
Laccaria bicolor aquaporin LbAQP1 is required for Hartig net development in trembling aspen (Populus tremuloides) 下载免费PDF全文
Alfonso Navarro‐RóDenas Hao Xu Minna Kemppainen Alejandro G. Pardo Janusz J. Zwiazek 《Plant, cell & environment》2015,38(11):2475-2486
The development of ectomycorrhizal associations is crucial for growth of many forest trees. However, the signals that are exchanged between the fungus and the host plant during the colonization process are still poorly understood. In this study, we have identified the relationship between expression patterns of Laccaria bicolor aquaporin LbAQP1 and the development of ectomycorrhizal structures in trembling aspen (Populus tremuloides) seedlings. The peak expression of LbAQP1 was 700‐fold higher in the hyphae within the root than in the free‐living mycelium after 24 h of direct interaction with the roots. Moreover, in LbAQP1 knock‐down strains, a non‐mycorrhizal phenotype was developed without the Hartig net and the expression of the mycorrhizal effector protein MiSSP7 quickly declined after an initial peak on day 5 of interaction of the fungal hyphae with the roots. The increase in the expression of LbAQP1 required a direct contact of the fungus with the root and it modulated the expression of MiSSP7. We have also determined that LbAQP1 facilitated NO, H2O2 and CO2 transport when heterologously expressed in yeast. The report demonstrates that the L. bicolor aquaporin LbAQP1 acts as a molecular signalling channel, which is fundamental for the development of Hartig net in root tips of P. tremuloides. 相似文献
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