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61.
Strecker AL Casselman JM Fortin MJ Jackson DA Ridgway MS Abrams PA Shuter BJ 《Oecologia》2011,166(3):819-831
Species present in communities are affected by the prevailing environmental conditions, and the traits that these species
display may be sensitive indicators of community responses to environmental change. However, interpretation of community responses
may be confounded by environmental variation at different spatial scales. Using a hierarchical approach, we assessed the spatial
and temporal variation of traits in coastal fish communities in Lake Huron over a 5-year time period (2001–2005) in response
to biotic and abiotic environmental factors. The association of environmental and spatial variables with trophic, life-history,
and thermal traits at two spatial scales (regional basin-scale, local site-scale) was quantified using multivariate statistics
and variation partitioning. We defined these two scales (regional, local) on which to measure variation and then applied this
measurement framework identically in all 5 study years. With this framework, we found that there was no change in the spatial
scales of fish community traits over the course of the study, although there were small inter-annual shifts in the importance
of regional basin- and local site-scale variables in determining community trait composition (e.g., life-history, trophic,
and thermal). The overriding effects of regional-scale variables may be related to inter-annual variation in average summer
temperature. Additionally, drivers of fish community traits were highly variable among study years, with some years dominated
by environmental variation and others dominated by spatially structured variation. The influence of spatial factors on trait
composition was dynamic, which suggests that spatial patterns in fish communities over large landscapes are transient. Air
temperature and vegetation were significant variables in most years, underscoring the importance of future climate change
and shoreline development as drivers of fish community structure. Overall, a trait-based hierarchical framework may be a useful
conservation tool, as it highlights the multi-scaled interactive effect of variables over a large landscape. 相似文献
62.
Genetic studies in mice and humans have revealed a pivotal function for transforming growth factor-beta (TGF-β) in vascular development and maintenance of vascular homeostasis. Mice deficient for various TGF-β signaling components develop an embryonic lethality due to vascular defects. In patients, mutations in TGF-β receptors have been linked to vascular dysplasia like Hereditary Hemorrhagic Telangiectasia (HHT) and pulmonary arterial hypertension (PAH). Besides indirect effects by regulating the expression of angiogenic regulators, TGF-β also has potent direct effects on endothelial cell growth and migration, and we have proposed that TGF-β regulates the activation state of the endothelium via two opposing type I receptor/Smad pathways, activin receptor-like kinase (ALK)1 and ALK5. TGF-β is also critical for the differentiation of mural precursors into pericytes and smooth muscle cells. Furthermore, defective paracrine TGF-β signaling between endothelial and neighboring mural cells may be responsible for a leaky vessel phenotype that is characteristic of HHT. In this review, we discuss our current understanding of the TGF-β signaling pathway and its regulation of endothelial and vascular smooth muscle cell function. 相似文献
63.
Jacopin C Egron MJ Scherman D Herscovici J 《Bioorganic & medicinal chemistry letters》2002,12(11):1447-1450
Starting from long chain alkylamino-alkan-1-ol a series of amino glycolipids were synthesized. This procedure allows a short and convenient preparation of glycosylated cationic lipids for gene delivery. 相似文献
64.
Background
Ecological monitoring and sampling optima are context and location specific. Novel applications (e.g. biodiversity monitoring for environmental service payments) call for renewed efforts to establish reliable and robust monitoring in biodiversity rich areas. As there is little information on the distribution of biodiversity across the Amazon basin, we used altitude as a proxy for biological variables to test whether meso-scale variation can be adequately represented by different sample sizes in a standardized, regular-coverage sampling arrangement.Methodology/Principal Findings
We used Shuttle-Radar-Topography-Mission digital elevation values to evaluate if the regular sampling arrangement in standard RAPELD (rapid assessments (“RAP”) over the long-term (LTER [“PELD” in Portuguese])) grids captured patters in meso-scale spatial variation. The adequacy of different sample sizes (n = 4 to 120) were examined within 32,325 km2/3,232,500 ha (1293×25 km2 sample areas) distributed across the legal Brazilian Amazon. Kolmogorov-Smirnov-tests, correlation and root-mean-square-error were used to measure sample representativeness, similarity and accuracy respectively. Trends and thresholds of these responses in relation to sample size and standard-deviation were modeled using Generalized-Additive-Models and conditional-inference-trees respectively. We found that a regular arrangement of 30 samples captured the distribution of altitude values within these areas. Sample size was more important than sample standard deviation for representativeness and similarity. In contrast, accuracy was more strongly influenced by sample standard deviation. Additionally, analysis of spatially interpolated data showed that spatial patterns in altitude were also recovered within areas using a regular arrangement of 30 samples.Conclusions/Significance
Our findings show that the logistically feasible sample used in the RAPELD system successfully recovers meso-scale altitudinal patterns. This suggests that the sample size and regular arrangement may also be generally appropriate for quantifying spatial patterns in biodiversity at similar scales across at least 90% (≈5 million km2) of the Brazilian Amazon. 相似文献65.
The opossum, Monodelphis domestica, is born very immature but crawls, unaided, with its forelimbs (FL) from the mother''s birth canal to a nipple where it attaches to pursue its development. What sensory cues guide the newborn to the nipple and trigger its attachment to it? Previous experiments showed that low intensity electrical stimulation of the trigeminal ganglion induces FL movement in in vitro preparations and that trigeminal innervation of the facial skin is well developed in the newborn. The skin does not contain Vater-Pacini or Meissner touch corpuscles at this age, but it contains cells which appear to be Merkel cells (MC). We sought to determine if touch perceived by MC could exert an influence on FL movements. Application of the fluorescent dye AM1-43, which labels sensory cells such as MC, revealed the presence of a large number of labeled cells in the facial epidermis, especially in the snout skin, in newborn opossums. Moreover, calibrated pressure applied to the snout induced bilateral and simultaneous electromyographic responses of the triceps muscle in in vitro preparations of the neuraxis and FL from newborn. These responses increase with stimulation intensity and tend to decrease over time. Removing the facial skin nearly abolished these responses. Metabotropic glutamate 1 receptors being involved in MC neurotransmission, an antagonist of these receptors was applied to the bath, which decreased the EMG responses in a reversible manner. Likewise, bath application of the purinergic type 2 receptors, used by AM1-43 to penetrate sensory cells, also decreased the triceps EMG responses. The combined results support a strong influence of facial mechanosensation on FL movement in newborn opossums, and suggest that this influence could be exerted via MC. 相似文献
66.
Jianzhong Yang Shaozhao Wang Marie-Josée Lorrain Denis Rho Kofi Abokitse Peter C. K. Lau 《Applied microbiology and biotechnology》2009,84(5):867-876
Recombinant Escherichia coli whole-cell biocatalysts harboring either a Baeyer–Villiger monooxygenase or ferulic acid decarboxylase were employed in organic-aqueous
two-phase bioreactor systems. The feasibility of the bioproduction of water-insoluble products, viz., lauryl lactone from
cyclododecanone and 4-vinyl guaiacol from ferulic acid were examined. Using hexadecane as the organic phase, 10∼16 g of lauryl
lactone were produced in a 3-l bioreactor that operated in a semicontinuous mode compared to 2.4 g of product in a batch mode.
For the decarboxylation of ferulic acid, a new recombinant biocatalyst, ferulic acid decarboxylase derived from Bacillus pumilus, was constructed. Selected solvents as well as other parameters for in situ recovery of vinyl guaiacol were investigated.
Up to 13.8 g vinyl guaiacol (purity of 98.4%) were obtained from 25 g of ferulic acid in a 2-l working volume bioreactor by
using octane as organic phase. These selected examples highlight the superiority of the two-phase biotransformations systems
over the conventional batch mode. 相似文献
67.
A commentary on current approaches in the aquatic sciences 总被引:1,自引:0,他引:1
68.
Régis Sodoyer Brigitte Kahn-Perles Torn Strachan Joséphine Sire Marie-José Santoni Corine Layet Pierre Ferrier Bertrand R. Jordan Francois A. Lemonnier 《Immunogenetics》1986,23(4):246-251
The individual contributions of the first two external domains of the HLA-B7 heavy chain to the expression of allele-specific (B7) and locus-specific (B and C) antigenic determinants were investigated using hybrid class I genes. Hybrid genes were constructed in vitro by exon shuffling between the parent genes HLA-B7, HLA-Cw3, HLA-A3, and H-2K
d, and their expression was monitored following transfection into mouse L cells. The results show that most allele-specific antigenic determinants are associated with the first external domain of the 137 heavy chain, whereas all the locus-specific antigenic determinants tested map to the second external domain.Abbreviations used in this paper BSA
bovine serum albumin
- FCS
fetal calf serum
- mAb
monoclonal antibody
- PBL
peripheral blood lymphocytes
- PBS
phosphate-buffered saline 相似文献
69.
Marie-José Delrieu 《BBA》1984,767(2):304-313
Treatments such as trypsinization (50 μg/ml per mg Chl for 1 h), osmotic shock of the chloroplasts or mild heating altered the oxygen evolution in such a way that the properties of the Photosystem II were simplified. After these treatments, the damping of the oscillation pattern of O2 yields induced by a flash series remained the same, irrespective of the level of inhibition induced by the treatment. This damping did not decrease with increasing flash energy, as observed in untreated chloroplasts. The light saturation curve of the S2 → S3 transition of the O2 evolving system no more exhibited the slow-increasing phase at high flash energy observed under normal conditions. The kinetic properties of the O2-evolving system were also simplified. After the treatments cited above, deactivation of S2 and S3 were identical and accelerated with respect to untreated chloroplasts. Turnover kinetics of the transitions S1 → S2 and S2 → S3 were also similar and simpler without a lag for S2 → S3. These results indicate that the treatments mentioned above disconnect one donor from the O2-evolving complex. This donor, under normal conditions, contributes to the increase of the quantum yield of the transition S2 → S3 at high flash energy. This donor is here denoted by D. Our results are in agreement with the following working hypothesis: the large miss, observed on the S2 → S3 transition without any contribution of the donor D, may be due to the fact that the system needs a conformation change of the O2-evolving complex in the S2 state, so that the main donor Y can oxidize the second H2O molecule in the water-splitting complex. In the inactive state corresponding to the absence of a conformation change, the donor D, being different in configuration, is likely to oxidize the S2 state into an S3 state at high light intensity. 相似文献
70.
Marie-Antoinette Baute Robert Baute Gérard Deffieux Marie-José Filleau 《Phytochemistry》1977,16(12):1895-1897
Glucose was the sole compound to be converted to cortalcerone by ‘activated’ blue mycelia of Corticium caeruleum; the first step of this transformation was shown to be the oxidation of glucose to glucosone. The conversion of glucosone to cortalcerone implies a novel enzymatic dehydrating activity which could be specific for C. caeruleum. 相似文献