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81.
We studied the restoration success of a cut‐away peatland 10 years after restoration by comparing the vegetation and CO2 dynamics with those of a pristine peatland of similar nutrition level and climate. Vegetation and CO2 dynamics were monitored during one growing season. We used DCA (detrended correspondence analysis) and diversity indices to study the vegetation composition within and between the sites, and non‐linear regression models to estimate the seasonal CO2 fluxes and balances of the sites. Based on both DCA and diversity indices, the study plots in the restored site differed more in the vegetation composition than the study plots in the pristine site. The variation in the CO2 fluxes and balance was greater in the restored than in the pristine site, resulting from the heterogeneous vegetation in the restored site. The seasonal net CO2 balance was positive (sink) at both sites, the restored site binding on average 500 ± 410 g CO2/m2 and the pristine site 390 ± 265 g CO2/m2 (statistically not different, p = 0.575). The results indicate that the restoration of the vegetation composition is still incomplete but the vegetation coverage is sufficient for the restored site to function as a sink of atmospheric CO2. 相似文献
82.
Background
Formation of apical compartments underlies the morphogenesis of most epithelial organs during development. The extracellular matrix (ECM), particularly the basement membrane (BM), plays an important role in orienting the apico-basal polarity and thereby the positioning of apical lumens. Integrins have been recognized as essential mediators of matrix-derived polarity signals. The importance of β1-integrins in epithelial polarization is well established but the significance of the accompanying α-subunits have not been analyzed in detail.Principal Findings
Here we demonstrate that two distinct integrin-dependent pathways regulate formation of apical lumens to ensure robust apical membrane biogenesis under different microenvironmental conditions; 1) α2β1- and α6β4-integrins were required to establish a basal cue that depends on Rac1-activity and guides apico-basal cell polarization. 2) α3β1-integrins were implicated in positioning of mitotic spindles in cysts, a process that is essential for Cdc42-driven epithelial hollowing.Significance
Identification of the separate processes driven by particular integrin receptors clarifies the functional hierarchies between the different integrins co-expressed in epithelial cells and provides valuable insight into the complexity of cell-ECM interactions thereby guiding future studies addressing the molecular basis of epithelial morphogenesis during development and disease. 相似文献83.
Factors affecting soil fauna feeding activity in a fragmented lowland temperate deciduous woodland 总被引:1,自引:0,他引:1
British temperate broadleaf woodlands have been widely fragmented since the advent of modern agriculture and development. As a result, a higher proportion of woodland area is now subject to edge effects which can alter the efficiency of ecosystem functions. These areas are particularly sensitive to drought. Decomposition of detritus and nutrient cycling are driven by soil microbe and fauna coactivity. The bait lamina assay was used to assess soil fauna trophic activity in the upper soil horizons at five sites in Wytham Woods, Oxfordshire: two edge, two intermediate and one core site. Faunal trophic activity was highest in the core of the woodland, and lowest at the edge, which was correlated with a decreasing soil moisture gradient. The efficiency of the assay was tested using four different bait flavours: standardised, ash (Fraxinus excelsior L.), oak (Quercus robur L.), and sycamore (Acer pseudoplatanus L.). The standardised bait proved the most efficient flavour in terms of feeding activity. This study suggests that decomposition and nutrient cycling may be compromised in many of the UK's small, fragmented woodlands in the event of drought or climate change. 相似文献
84.
Rilla K Pasonen-Seppänen S Kärnä R Karjalainen HM Törrönen K Koistinen V Tammi MI Tammi RH Teräväinen T Manninen A 《Histochemistry and cell biology》2012,137(2):153-164
The amount of hyaluronan (HA) is low in simple epithelia under normal conditions, but during tumorigenesis, trauma or inflammation
HA is increased on the epithelial cells and surrounding stroma. Excessive HA in epithelia is suggested to interfere with cell–cell
adhesions, resulting in disruption of the epithelial barrier function. In addition, stimulated HA synthesis has been correlated
with epithelial-to-mesenchymal transition and invasion of cancer cells. However, the effects of HA overload on normal epithelial
morphogenesis have not been characterized in detail. Madin-Darby canine kidney (MDCK) cells form polarized epithelial cysts,
when grown in a 3-dimensional (3D) matrix. These cells were used to investigate whether stimulated HA synthesis, induced by
stable overexpression of GFP-HAS3, influences cell polarization and epithelial morphogenesis. GFP-HAS3 expression in polarized
MDCK cells resulted in active HA secretion at apical and basolateral membrane domains. HA-deposits interfered with the formation
of cell–cell junctions, resulting in impaired barrier function. In 3D cyst cultures, HA accumulated into apical lumina and
was also secreted from the basal side. The HAS3-expressing cysts failed to form a single lumen and instead displayed multiple
small lumina. This phenotype was correlated with aberrant mitotic spindle orientation in dividing cells. The results of this
study indicate that excess pericellular HA disturbs the normal cell–cell and cell–ECM interactions in simple epithelia, leading
to aberrant epithelial morphogenesis. The morphological abnormalities observed in 3D epithelial cultures upon stimulated HAS3
expression may be related to premalignant changes, including intraluminal invasion and deregulated epithelialization, probably
mediated by the mitotic spindle orientation defects. 相似文献
85.
Terhi Maula Ibai Artetxe Pia-Maria Grandell J.?Peter Slotte 《Biophysical journal》2012,103(9):1870-1879
The sphingoid bases of sphingolipids, including ceramides, can vary in length from 12 to >20 carbons. To study how such length variation affects the bilayer properties of ceramides, we synthesized ceramides consisting of a C12-, C14-, C16-, C18-, or C20-sphing-4-enin derivative coupled to palmitic acid. The ceramides were studied in mixtures with palmitoyloleoylphosphocholine (POPC) and/or palmitoylsphingomyelin (PSM), and in more complex bilayers also containing cholesterol. The trans-parinaric acid lifetimes showed that 12:1- and 14:1-PCer failed to increase the order of POPC bilayers, whereas 16:1-, 18:1-, and 20:1-PCer induced ordered- or gel-phase formation. Nevertheless, all of the analogs were able to thermally stabilize PSM, and a chain-length-dependent increase in the main phase transition temperature of equimolar PSM/Cer bilayers was revealed by differential scanning calorimetry. Similar thermal stabilization of PSM-rich domains by the ceramides was observed in POPC bilayers with a trans-parinaric acid-quenching assay. A cholestatrienol-quenching assay and sterol partitioning experiments showed that 18:1- and 20:1-PCer formed sterol-excluding gel phases with PSM, reducing the overall bilayer affinity of sterol. The effect of 16:1-PCer on sterol distribution was less dramatic, and no displacement of sterol from the PSM environment was observed with 12:1- and 14:1-PCer. The results are discussed in relation to other structural features that affect the bilayer properties of ceramides. 相似文献
86.
Nearly four centuries after the discovery of lymphatic vessels, the molecular mechanisms underlying their development are beginning to be elucidated. Vascular endothelial growth factor C (VEGF-C) and VEGF-D, via signaling through VEGFR-3, appear to be essential for lymphatic vessel growth. Observations from clinicopathological studies have suggested that lymphatic vessels serve as the primary route for the metastatic spread of tumor cells to regional lymph nodes. Recent studies in animal models have provided convincing evidence that tumor lymphangiogenesis facilitates lymphatic metastasis. However, it is not clear how tumor-associated lymphangiogenesis is regulated, and little is known about how tumor cells escape from the primary tumor and gain entry into the lymphatics. This review examines some of these issues and provides a brief summary of the recent developments in this field of research. 相似文献
87.
88.
Lasse Lönnqvist Leena Karttunen Terhi Rantamäki Cay Kielty Michael Raghunath Leena Peltonen 《Genomics》1996,36(3):468
Fibrillin-1 is a large cysteine-rich glycoprotein of the 10-nm microfibrils in the extracellular matrix. A spectrum of mutations in the fibrillin-1 gene (FBN1) have been identified in patients with Marfan syndrome (MFS), and the majority of mutations resulting in the neonatal and often lethal form of MFS have been identified in the restricted region of exons 24–32 of theFBN1gene. Here we report a novel point mutation in exon 25 of theFBN1gene in a patient with lethal MFS. The mutation resulted in a molecular defect rarely encountered in human diseases, the creation of an extra consensus sequence forN-glycosylation. Metabolic labeling of the patient fibroblast culture andin vitroexpression of the mutagenized cDNA construct suggest that this novelN-glycosylation site is actually utilized. Immunohistochemical and ultrastructural analyses of the fibroblast cultures of the patient show that this excessiveN-glycosylation severely affects microfibril formationin vitro;this finding emphasizes the importance of correct posttranslational modifications of fibrillin molecules for correct aggregation into microfibrillar structures. 相似文献
89.
Jussi?LampinenEmail author Risto?K.?Heikkinen Paula?Manninen Terhi?Rytt?ri Mikko?Kuussaari 《Biodiversity and Conservation》2018,27(1):217-233
Agricultural intensification has caused drastic declines in the area and species richness of semi-natural grasslands across Europe. Novel habitats, such as power line clearings, provide alternative habitats and niches for grassland species, and might therefore mitigate these declines. However, it is not fully understood which environmental factors determine the occurrence of grassland species in the clearings. Identifying the most important drivers for grassland species occurrence would help understand the value of the clearings for grassland conservation and target enhanced management into clearings with most potential as grassland habitat. We studied the effects of local environmental conditions, and past and present connectivity to semi-natural grasslands, on the species richness of grassland plants and butterflies in 43 power line clearings in Finland. The results of generalized linear models and hierarchical partitioning showed that increasing time since clear-cut and amount of clearing residue decreased the species richness of both species groups, while the cover of mesic habitats increased it. However, the two species groups showed also divergent responses. Present-day local environmental conditions appeared to be the sole driver of grassland butterfly species richness, whereas the richness of grassland plants was related both to current conditions and historical connectivity to grasslands in 1870–1880s. This suggests the presence of an extinction debt in the studied grassland plant communities, emphasizing the need for enhanced management to increase suitable grassland habitat in the clearings. This would diminish the potential future losses of grassland plant species in the clearings and create valuable habitat for grassland butterflies as well. 相似文献
90.
Philip M. Chapman Oliver R. Wearn Terhi Riutta Chris Carbone J. Marcus Rowcliffe Henry Bernard Robert. M. Ewers 《Biodiversity and Conservation》2018,27(12):3155-3169
Understanding temporal change and long-term persistence of species and communities is vital if we are to accurately assess the relative values of human-modified habitats for biodiversity. Despite a large literature and emerging consensus demonstrating a high conservation value of selectively logged tropical rainforests, few studies have taken a long-term perspective. We resampled small mammals (≤?1 kg) in a heavily logged landscape in Sabah, Borneo between 2011 and 2016 to investigate temporal patterns of species-level changes in population density. We found that small mammal population density in heavily logged forest was highly variable among years, consistent with patterns previously observed in unlogged forest, and uncovered evidence suggesting that one species is potentially declining towards local extinction. Across nine species, population densities varied almost sevenfold during our 6-year study period, highlighting the extremely dynamic nature of small mammal communities in this ecosystem. Strictly terrestrial murid species tended to exhibit strong temporal dynamics, whereas semi-arboreal foraging species such as treeshrews had more stable dynamics. We found no relationships between population density and fruit/seed mass, and therefore no evidence that our patterns represent responses to inter-annual mast fruiting of the dominant canopy dipterocarp trees. This may be due to the removal of most of the canopy during logging, and hence the dipterocarp seed resource, although it possibly also reflects spatiotemporal limitations of our data. Our results underline the importance of understanding long-term variability in animal communities before developing conservation and management recommendations for human-altered ecosystems. 相似文献