62 resultados para Perineural invasion
Resumo:
Global environmental change not only entails changes in mean environmental conditions but also in their variability. Changes in climate variability are often associated with altered disturbance regimes and temporal patterns of resource availability. Here we show that increased variability of soil nutrients strongly promotes another key process of global change, plant invasion. In experimental plant communities, the success of one of the world's most invasive plants, Japanese knotweed, is two- to four-fold increased if extra nutrients are not supplied uniformly, but in a single large pulse, or in multiple pulses of different magnitudes. The superior ability to take advantage of variable environments may be a key mechanism of knotweed dominance, and possibly many other plant invaders. Our study demonstrates that increased nutrient variability can promote plant invasion, and that changes in environmental variability may interact with other global change processes and thereby substantially accelerate ecological change
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Soil biota can be important drivers of plant community structure. Depending on the balance between antagonistic and mutualistic interactions, they can limit or promote the success of plant species. This is particularly important in the context of exotic plant invasions where soil biota can either increase the biotic resistance of habitats, or they can shift the balance between exotic and native plants towards the exotics and thereby greatly contribute to their dominance. Here, we explored the role of soil biota in the invasion success of exotic knotweed (Fallopia × bohemica), one of the world's most noxious invasive plants. We created artificial native plant communities that were experimentally invaded by knotweed, using a range of substrates where we manipulated different fractions of soil biota. We found that invasive knotweed benefited more from the overall presence of soil biota than any of the six native species. In particular the presence of the full natural soil biota strongly shifted the competitive balance in favor of knotweed. Soil biota promoted both regeneration and growth of the invader, which suggests that soil organisms may be important both in the early establishment of knotweed and possibly its later dominance of native communities. Addition of activated carbon to the soil made the advantage of knotweed disappear, which suggests that the mechanisms underlying the positive soil biota effects are chemically mediated. Our study demonstrates that soil organisms play a key role in the invasion success of exotic knotweed.
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Recent publications demonstrated that a fragment of a Neospora caninum ROP2 family member antigen represents a promising vaccine candidate. We here report on the cloning of the cDNA encoding this protein, N. caninum ROP2 family member 1 (NcROP2Fam-1), its molecular characterization and localization. The protein possesses the hallmarks of ROP2 family members and is apparently devoid of catalytic activity. NcROP2Fam-1 is synthesized as a pre-pro-protein that is matured to 2 proteins of 49 and 55 kDa that localize to rhoptry bulbs. Upon invasion the protein is associated with the nascent parasitophorous vacuole membrane (PVM), evacuoles surrounding the host cell nucleus and, in some instances, the surface of intracellular parasites. Staining was also observed within the cyst wall of 'cysts' produced in vitro. Interestingly, NcROP2Fam-1 was also detected on the surface of extracellular parasites entering the host cells and antibodies directed against NcROP2Fam-1-specific peptides partially neutralized invasion in vitro. We conclude that, in spite of the general belief that ROP2 family proteins are intracellular antigens, NcROP2Fam-1 can also be considered as an extracellular antigen, a property that should be taken into account in further experiments employing ROP2 family proteins as vaccines.
Resumo:
The relative importance of ecological selection and geographical isolation in promoting and constraining genetic and phenotypic differentiation among populations is not always obvious. Interacting with divergent selection, restricted opportunity for gene flow may in some cases be as much a cause as a consequence of adaptation, with the latter being a hallmark of ecologi- cal speciation. Ecological speciation is well studied in parts of the native range of the three-spined stickleback. Here, we study this process in a recently invaded part of its range. Switzerland was colonized within the past 140 years from at least three different colonization events involving differ- ent stickleback lineages. They now occupy diverse habitats, ranging from small streams to the pelagic zone of large lakes. We use replicated systems of parapatric lake and stream populations, some of which trace their origins to different invasive lineages, to ask (i) whether phenotypic divergence occurred among populations inhabiting distinct habitats, (ii) whether trajec- tories of phenotypic divergence follow predictable parallel patterns and (iii) whether gene flow constrains divergent adaptation or vice versa. We find consistent phenotypic divergence between populations occupying distinct habitats. This involves parallel evolution in several traits with known eco- logical relevance in independent evolutionary lineages. Adaptive divergence supersedes homogenizing gene flow even at a small spatial scale. We find evidence that adaptive phenotypic divergence places constraints on gene flow over and above that imposed by geographical distance, signalling the early onset of ecological speciation.
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Loss of p53 is considered to allow progression of colorectal tumors from the adenoma to the carcinoma stage. Using mice with an intestinal epithelial cell (IEC)-specific p53 deletion, we demonstrate that loss of p53 alone is insufficient to initiate intestinal tumorigenesis but markedly enhances carcinogen-induced tumor incidence and leads to invasive cancer and lymph node metastasis. Whereas p53 controls DNA damage and IEC survival during the initiation stage, loss of p53 during tumor progression is associated with increased intestinal permeability, causing formation of an NF-κB-dependent inflammatory microenvironment and the induction of epithelial-mesenchymal transition. Thus, we propose a p53-controlled tumor-suppressive function that is independent of its well-established role in cell-cycle regulation, apoptosis, and senescence.
Resumo:
PURPOSE Neural invasion (NI) is a histopathologic feature of colon cancer that receives little consideration. Therefore, we conducted a morphologic and functional characterization of NI in colon cancer. EXPERIMENTAL DESIGN NI was investigated in 673 patients with colon cancer. Localization and severity of NI was determined and related to patient's prognosis and survival. The neuro-affinity of colon cancer cells (HT29, HCT-116, SW620, and DLD-1) was compared with pancreatic cancer (T3M4 and SU86.86) and rectal cancer cells (CMT-93) in the in vitro three-dimensional (3D)-neural-migration assay and analyzed via live-cell imaging. Immunoreactivity of the neuroplasticity marker GAP-43, and the neurotrophic-chemoattractant factors Artemin and nerve growth factor (NGF), was quantified in colon cancer and pancreatic cancer nerves. Dorsal root ganglia of newborn rats were exposed to supernatants of colon cancer, rectal cancer, and pancreatic cancer cells and neurite density was determined. RESULTS NI was detected in 210 of 673 patients (31.2%). Although increasing NI severity scores were associated with a significantly poorer survival, presence of NI was not an independent prognostic factor in colon cancer. In the 3D migration assay, colon cancer and rectal cancer cells showed much less neurite-targeted migration when compared with pancreatic cancer cells. Supernatants of pancreatic cancer and rectal cancer cells induced a much higher neurite density than those of colon cancer cells. Accordingly, NGF, Artemin, and GAP-43 were much more pronounced in nerves in pancreatic cancer than in colon cancer. CONCLUSION NI is not an independent prognostic factor in colon cancer. The lack of a considerable biologic affinity between colon cancer cells and neurons, the low expression profile of colonic nerves for chemoattractant molecules, and the absence of a major neuroplasticity in colon cancer may explain the low prevalence and impact of NI in colon cancer.
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A central focus of invasion biology is to identify the traits that predict which introduced species will become invasive. Behavioral traits related to locomotor activity most likely play a pivotal role in determining a species’invasion success but have rarely been studied, particularly in terrestrial invertebrates. Here, we experimentally investigated the small-scale locomotor activity of two slug species with divergent invasion success in Europe, the highly invasive slug, Arion lusitanicus, and the closely related, non-invasive and native slug, Arion rufus. To do so, we used a multi-state capture-mark-recapture approach, and hypothesized that the invasive slug has a higher moving rate (keeps on moving) and leaving rate (leaves more frequently known places). A total of 221 invasive and 241 non-invasive slugs were individually marked using magnetic transponders and released in three study sites differing in habitat type. The slugs were recaptured using shelter traps, and moving and leaving rates were estimated. Both rates were significantly higher for the invasive slug, demonstrating a higher locomotor activity which might partly explain its invasion success. Our results provide evidence for the recently suggested idea that locomotor activity might be an important trait underlying animal invasions using for the first time terrestrial invertebrates.
Resumo:
The possibility that disruptive sexual selection alone can cause sympatric speciation is currently a subject of much debate. The initial difficulty for new and rare ornament phenotypes to invade a population, and the stabilisation of the resulting polymorphism in trait and preference make this hypothesis problematic. Recent theoretical work indicates that the invasion is facilitated if males with the new phenotype have an initial advantage in male-male competition. We studied a pair of sympatric incipient species of cichlids from Lake Victoria, in which the red (Pundamilia nyererei) and blue males (P. pundamilia) vigorously defend territories. Other studies suggested that red phenotypes may have repeatedly invaded blue populations in independent episodes of speciation. We hypothesised that red coloration confers an advantage in male-male competition, assisting red phenotypes to invade. To test this hypothesis, we staged contests between red and blue males from a population where the phenotypes are interbreeding morphs or incipient species. We staged contests under both white and green light condition. Green light effectively masks the difference between red and blue coloration. Red males dominated blue males under white light, but their competitive advantage was significantly diminished under green light. Contests were shorter when colour differences were visible. Experience of blue males with red males did not affect the outcome of a contest. The advantage of red over blue in combats may assist the red phenotype to invade blue populations. The apparently stable co-existence of red and blue incipient species in many populations of Lake Victoria cichlids is discussed.
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Chelonus inanitus (Braconidae) is a solitary egg-larval parasitoid which lays its eggs into eggs of Spodoptera littoralis (Noctuidae); the parasitoid larva then develops in the haemocoel of the host larva. Host embryonic development lasts approx. 3.5 days while parasitoid embryonic development lasts approx. 16 h. All stages of host eggs can be successfully parasitized, and we show here that either the parasitoid larva or the wasp assures that the larva eventually is located in the host's haemocoel. (1) When freshly laid eggs, up to almost 1-day-old, are parasitized, the parasitoid hatches while still in the yolk and enters the host either after waiting or immediately through the dorsal opening. (2) When 1-2-day-old eggs are parasitized, the host embryo has accomplished final dorsal closure and is covered by an embryonic cuticle when the parasitoid hatches; in this case the parasitoid larva bores with its moving abdominal tip into the host. (3) When 2.5-3.5-day-old eggs are parasitized, the wasp oviposits directly into the haemocoel of the host embryo; from day 2 to 2.5 the embryo is still very small and the wasps, after probing, often restrain from oviposition for a few hours.
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Seed predation impacts heavily on plant populations and community composition in grasslands. In particular, generalist seed predators may contribute to biotic resistance, i.e. the ability of resident species in a community to reduce the success of non-indigenous plant invaders. However, little is known of predators' preferences for seeds of indigenous or non-indigenous plant species or how seed predation varies across communities. We hypothesize that seed predation does not differ between indigenous and non-indigenous plant species and that seed predation is positively related to plant species diversity in the resident community. The seed removal of 36 indigenous and non-indigenous grassland species in seven extensively or intensively managed hay meadows across Switzerland covering a species-richness gradient of 18-50 plant species per unit area (c. 2 m(2)) was studied. In mid-summer 2011, c. 24,000 seeds were exposed to predators in Petri dishes filled with sterilized soil, and the proportions of seeds removed were determined after three days' exposure. These proportions varied among species (9.2-62.5%) and hay meadows (17.8-48.6%). Seed removal was not related to seed size. Moreover, it did not differ between indigenous and non-indigenous species, suggesting that mainly generalist seed predators were active. However, seed predation was positively related to plant species richness across a gradient in the range of 18-38 species per unit area, representing common hay meadows in Switzerland. Our results suggest that generalist post-dispersal seed predation contributes to biotic resistance and may act as a filter to plant invasion by reducing the propagule pressure of non-local plant species.
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A lack of reliably informative biomarkers to distinguish indolent and lethal prostate cancer is one reason this disease is overtreated. miR-221 has been suggested as a biomarker in high-risk prostate cancer, but there is insufficient evidence of its potential utility. Here we report that miR-221 is an independent predictor for cancer-related death, extending and validating earlier findings. By mechanistic investigations we showed that miR-221 regulates cell growth, invasiveness, and apoptosis in prostate cancer at least partially via STAT1/STAT3-mediated activation of the JAK/STAT signaling pathway. miR-221 directly inhibits the expression of SOCS3 and IRF2, two oncogenes that negatively regulate this signaling pathway. miR-221 expression sensitized prostate cancer cells for IFN-γ-mediated growth inhibition. Our findings suggest that miR-221 offers a novel prognostic biomarker and therapeutic target in high-risk prostate cancer.