Ecological theory predicts that a complex community formed by a number of species is inherently unstable, guiding ecologists to identify what maintains species diversity in nature. Earlier studies ...often assumed a community with only one interaction type, either an antagonistic, competitive, or mutualistic interaction, leaving open the question of what the diversity of interaction types contributes to the community maintenance. We show theoretically that the multiple interaction types might hold the key to understanding community dynamics. A moderate mixture of antagonistic and mutualistic interactions can stabilize population dynamics. Furthermore, increasing complexity leads to increased stability in a "hybrid" community. We hypothesize that the diversity of species and interaction types may be the essential element of biodiversity that maintains ecological communities.
What allows interacting, diverse species to coexist in nature has been a central question in ecology, ever since the theoretical prediction that a complex community should be inherently unstable. ...Although the role of spatiality in species coexistence has been recognized, its application to more complex systems has been less explored. Here, using a meta-community model of food web, we show that meta-community complexity, measured by the number of local food webs and their connectedness, elicits a self-regulating, negative-feedback mechanism and thus stabilizes food-web dynamics. Moreover, the presence of meta-community complexity can give rise to a positive food-web complexity-stability effect. Spatiality may play a more important role in stabilizing dynamics of complex, real food webs than expected from ecological theory based on the models of simpler food webs.
We developed a set of universal PCR primers (MiFish-U/E) for metabarcoding environmental DNA (eDNA) from fishes. Primers were designed using aligned whole mitochondrial genome (mitogenome) sequences ...from 880 species, supplemented by partial mitogenome sequences from 160 elasmobranchs (sharks and rays). The primers target a hypervariable region of the 12S rRNA gene (163–185 bp), which contains sufficient information to identify fishes to taxonomic family, genus and species except for some closely related congeners. To test versatility of the primers across a diverse range of fishes, we sampled eDNA from four tanks in the Okinawa Churaumi Aquarium with known species compositions, prepared dual-indexed libraries and performed paired-end sequencing of the region using high-throughput next-generation sequencing technologies. Out of the 180 marine fish species contained in the four tanks with reference sequences in a custom database, we detected 168 species (93.3%) distributed across 59 families and 123 genera. These fishes are not only taxonomically diverse, ranging from sharks and rays to higher teleosts, but are also greatly varied in their ecology, including both pelagic and benthic species living in shallow coastal to deep waters. We also sampled natural seawaters around coral reefs near the aquarium and detected 93 fish species using this approach. Of the 93 species, 64 were not detected in the four aquarium tanks, rendering the total number of species detected to 232 (from 70 families and 152 genera). The metabarcoding approach presented here is non-invasive, more efficient, more cost-effective and more sensitive than the traditional survey methods. It has the potential to serve as an alternative (or complementary) tool for biodiversity monitoring that revolutionizes natural resource management and ecological studies of fish communities on larger spatial and temporal scales.
Although species richness has been hypothesized to be highest at 'intermediate' levels of disturbance, empirical studies have demonstrated that the disturbance-diversity relationship can be either ...negative or positive depending on productivity. On the other hand, hypothesized productivity-diversity relationships can be positive, negative or unimodal, as confirmed by empirical studies. However, it has remained unclear under what conditions each pattern is realized, and there is little agreement about the mechanisms that generate these diverse patterns. In this study, I present a model that synthesizes these separately developed hypotheses and shows that the interactive effects of disturbance and productivity on the competitive outcome of multispecies dynamics can result in these diverse relationships of species richness to disturbance and productivity. The predicted productivity-diversity relationship is unimodal but the productivity level that maximizes species richness increases with increasing disturbance. Similarly, the predicted disturbance-diversity relationship is unimodal but the peak moves to higher disturbance levels with increasing productivity. Further, these patterns are well explained by the opposite effects of productivity and disturbance on competitive outcome that are suggested by the change in community composition along these two environmental gradients: higher productivity favours superior competitors while higher disturbance levels favour inferior competitors.
The thermal behavior along with certain characteristics of geopolymers produced from local Cameroonian metakaolin and heated up to 1000°C were examined. Geopolymers fired up to 900°C had the same ...physical aspect as initial ones and those fired at 1000°C warped, were glazed and blistered. The TG showed elimination of water according to two stages. The dilatometric curves of preheated samples showed shrinkage between 90 and 250°C followed by expansion and sintering. The samples heated up to 700°C were amorphous and new crystalline phases appeared around 900°C. The microstructure of geopolymers heated between 300 and 900°C showed progressive disruption and the linear shrinkage increased. The water absorption of the samples fired up to 700°C increased slightly and tremendously around 900°C. A drastic decrease of compressive strength was observed with the samples fired between 300 and 900°C. Hence, the characteristics of geopolymers lessened with elimination of the water which forms hydration spheres around the compensating cations (Na+) opposed to tetrahedral groups AlO4− along with transformation of amorphous phase.
Molecules that are highly expressed in tumour endothelial cells (TECs) may be candidates for specifically targeting TECs. Using DNA microarray analysis, we found that the lysyl oxidase (LOX) gene was ...upregulated in TECs compared with its expression in normal endothelial cells (NECs). LOX is an enzyme that enhances invasion and metastasis of tumour cells. However, there are no reports on the function of LOX in isolated TECs.
TECs and NECs were isolated to investigate LOX function in TECs. LOX inhibition of in vivo tumour growth was also assessed using β-aminopropionitrile (BAPN).
LOX expression was higher in TECs than in NECs. LOX knockdown inhibited cell migration and tube formation by TECs, which was associated with decreased phosphorylation of focal adhesion kinase (Tyr 397). Immunostaining showed high LOX expression in human tumour vessels in vivo. Tumour angiogenesis and micrometastasis were inhibited by BAPN in an in vivo tumour model.
LOX may be a TEC marker and a possible therapeutic target for novel antiangiogenic therapy.
Intestinal permeation enhancers are a crucial component of many oral formulations, without which many drugs would show an insufficient absorption in the gut. The present study sought to provide a ...better understanding of the molecular interaction of such absorption enhancers with the intestine, by investigating the effect of the surfactant-like permeation enhancer dodecylmaltoside (DDM) on Caco-2 cells. The extent to which the action of DDM is apportioned between the para- and transcellular routes was addressed by examining the transport of relevant marker compounds (3H-mannitol and 3H-propranolol, respectively). In the case of 3H-mannitol, a robust permeation enhancement was achieved with 0.5 mM DDM (∼6-fold), whereas little effect was seen on the permeation of 3H-propranolol. Concomitantly measured TEER values revealed a rapid onset of action of DDM with a swift recovery and complete restitution (>90%) within 4 h after washout. To localize the site(s) of action of DDM at the absorptive surface of Caco-2 cells, sulfo-NHS-SS-biotin, a membrane-impermeable compound, was applied apically. In the presence of 0.5 mM DDM, translocated biotin was found to be accumulated toward bicellular contacts, whereas no biotin permeation was observed in untreated control cells. Western blot analysis of DDM-treated and untreated Caco-2 cells revealed an interaction of DDM with specific tight junction associated proteins, resulting in a reduction of claudin-3 and -4 and also occludin, as well as a depletion of claudin-2 from lipid rafts. Collectively, the results presented provide a more in depth understanding of the molecular mechanism(s) underlying the permeation-enhancing actions of DDM.
We isolated tumour endothelial cells (TECs), demonstrated their abnormalities, compared gene expression profiles of TECs and normal endothelial cells (NECs) by microarray analysis and identified ...several genes upregulated in TECs. We focused on the gene encoding biglycan, a small leucine-rich repeat proteoglycan. No report is available on biglycan expression or function in TECs.
The NEC and TEC were isolated. We investigated the biglycan expression and function in TECs. Western blotting analysis of biglycan was performed on sera from cancer patients.
Biglycan expression levels were higher in TECs than in NECs. Biglycan knockdown inhibited cell migration and caused morphological changes in TECs. Furthermore, immunostaining revealed strong biglycan expression in vivo in human tumour vessels, as in mouse TECs. Biglycan was detected in the sera of cancer patients but was hardly detected in those of healthy volunteers.
These findings suggested that biglycan is a novel TEC marker and a target for anti-angiogenic therapy.
Tight junctions (TJs) play pivotal roles in the fence and barrier functions of epithelial and endothelial cell sheets. Since the 1980s, the modulation of the TJ barrier has been utilized as a method ...for drug absorption. Over the last decade, the structural and functional biochemical components of TJs, such as occludin and claudin, have been determined, providing new insights into TJ-based pharmaceutical therapy. For example, the modulation of the claudin barrier enhances the jejunal absorption of drugs, and claudin expression is deregulated in cancer cells. Claudin is a co-receptor for the hepatitis C virus. Moreover, claudin is modulated during inflammatory conditions. These findings indicate that claudins are promising drug targets. In this review, we discuss the seeds of claudin-based drug development, which may provide potential pharmaceutical breakthroughs in the future.
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