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排序方式: 共有263条查询结果,搜索用时 31 毫秒
41.
42.
Comparative studies on the food of the black cormorant Phalacrocorax carbo and the harbour seal Phoca vitulina were carried out in two contrasting habitat types. Both species feed predominantly on bottom-dwelling fish. Black cormorants are able to utilize fish found both on vegetation-covered and naked sea beds at a water depth of less than 10 m, while harbour seals feed mainly on soft sea bottoms above 30 m where vegetation is scarce or lacking. The food overlap of the two piscivores is large in environments where large shallow sea bottoms are available, and small in areas where sea bottoms of soft material is found at greater depth. In areas where the shallow bottoms are covered by vegetation only, cormorants are able to feed on the fish species inhabiting this kind of environment. There is no evidence that these predators make a choice regarding prey species. 相似文献
43.
Ash Bahl Patrick Barton Keith Bowers Moya V. Caffrey Rebecca Denton Peter Gilmour Shaun Hawley Tero Linannen Christopher A. Luckhurst Tobias Mochel Matthew W.D. Perry Robert J. Riley Emma Roe Brian Springthorpe Linda Stein Peter Webborn 《Bioorganic & medicinal chemistry letters》2012,22(21):6694-6699
The discovery and optimisation of a series of zwitterionic CCR3 antagonists is described. Optimisation of the structure led to AZ12436092, a compound with excellent selectivity over activity at hERG and outstanding pharmacokinetics in preclinical species. 相似文献
44.
Liisa Huttunen Pekka Niemelä Vladimir Ossipov Matti Rousi Tero Klemola 《Trees - Structure and Function》2012,26(3):809-819
Subarctic mountain birch (Betula pubescens ssp. czerepanovii) forests in northern Fennoscandia have shown a slight recovery from recent severe defoliation by the winter moth (Operophtera brumata). This development in trees is hypothesized to be a result of ameliorated growing conditions through increased summer temperatures.
We examined if accumulated thermal sum affects the ability of mountain birches to tolerate foliage losses. We quantified the
number of leaf-bearing short shoots, the emergence of inflorescences and the seasonal height growth of long shoots in both
intact and defoliated trees. We also determined the concentrations of carbon and nitrogen in leaves and carbohydrates in roots.
Our results show that defoliation constrained the growth of long shoots, as well as the emergence of inflorescences regardless
of thermal sum accumulation. However, the number of leaf-bearing short shoots did not differ between intact and defoliated
trees. In the both tree groups, the amounts of emerging leaves increased as a response to thermal sum accumulation. Also the
leaf carbon concentration increased in defoliated trees at higher thermal sums, whereas it decreased in intact controls. Generally,
the mean carbohydrate concentrations were greater in roots of defoliated than intact trees. However, with increased thermal
sums, root carbohydrates increased in intact trees but remained the same in defoliated trees. We conclude that thermal sum
accumulation does not greatly promote the recovery of mountain birches. Although the damaged trees produced more leaves at
warmer growing sites, this did not increase their height growth or carbohydrate gain in roots. 相似文献
45.
Kit M. Kovacs Alex Aguilar David Aurioles Vladimir Burkanov Claudio Campagna Nick Gales Tom Gelatt Simon D. Goldsworthy Simon J. Goodman Greg J. G. Hofmeyr Tero Härkönen Lloyd Lowry Christian Lydersen Jan Schipper Tero Sipilä Colin Southwell Simon Stuart Dave Thompson Fritz Trillmich 《Marine Mammal Science》2012,28(2):414-436
46.
Glycomics of bone marrow-derived mesenchymal stem cells can be used to evaluate their cellular differentiation stage 总被引:1,自引:0,他引:1
Annamari Heiskanen Tia Hirvonen Hanna Salo Ulla Impola Anne Olonen Anita Laitinen Sari Tiitinen Suvi Natunen Olli Aitio Halina Miller-Podraza Manfred Wuhrer André M. Deelder Jari Natunen Jarmo Laine Petri Lehenkari Juhani Saarinen Tero Satomaa Leena Valmu 《Glycoconjugate journal》2009,26(3):367-384
Human mesenchymal stem cells (MSCs) are adult multipotent progenitor cells. They hold an enormous therapeutic potential, but
at the moment there is little information on the properties of MSCs, including their surface structures. In the present study,
we analyzed the mesenchymal stem cell glycome by using mass spectrometric profiling as well as a panel of glycan binding proteins.
Structural verifications were obtained by nuclear magnetic resonance spectroscopy, mass spectrometric fragmentation, and glycosidase
digestions. The MSC glycome was compared to the glycome of corresponding osteogenically differentiated cells. More than one
hundred glycan signals were detected in mesenchymal stem cells and osteoblasts differentiated from them. The glycan profiles
of MSCs and osteoblasts were consistently different in biological replicates, indicating that stem cells and osteoblasts have
characteristic glycosylation features. Glycosylation features associated with MSCs rather than differentiated cells included
high-mannose type N-glycans, linear poly-N-acetyllactosamine chains and α2-3-sialylation. Mesenchymal stem cells expressed SSEA-4 and sialyl Lewis x epitopes. Characteristic
glycosylation features that appeared in differentiated osteoblasts included abundant sulfate ester modifications. The results
show that glycosylation analysis can be used to evaluate MSC differentiation state. 相似文献
47.
Jääskeläinen A Soukka T Lamminmäki U Korpimäki T Virta M 《Biotechnology and bioengineering》2009,102(4):1012-1024
Recently, we presented a simple method for generating biological functional protein-based nanoparticles that are ready for use as label agents in bioaffinity assays (J??skel?inen et al., 2007 Small 3:1362-1367). In this process, the particle shell (ferritin protein) and binding molecules are conjugated via genetic fusion, and particles with binding capacity are produced in a single bacterial cultivation. Production is combined with simple, non-chromatographic purification during which Europium ions are introduced into particles to serve as marker agents. Denaturation-refolding has previously performed by means of pH changes. Here, we test urea as an alternative agent for denaturation, and examine techniques to improve refolding of the functional particles. Three different types of binding molecules were employed in our experiments: biotin carboxyl carrier protein (a small protein with 87 amino acids), single chain antibody fragment (a complex binding protein) and calmodulin-binding peptide (27 amino acids). Urea was successfully utilized to generate functional particles with inherent binding activity and label function. Additionally, particle yield was effectively optimized by analyzing various refolding and bacterial production conditions. Our results clearly demonstrate that this simple biological method of producing functional ferritin-based particles is flexible, and different types of binding moieties can be applied by adjusting the production conditions. 相似文献
48.
Ville-Pekka Eronen Rolf O. Lindén Anna Lindroos Mirella Kanerva Tero Aittokallio 《PloS one》2010,5(7)
Recent technological developments in genetic screening approaches have offered the means to start exploring quantitative genotype-phenotype relationships on a large-scale. What remains unclear is the extent to which the quantitative genetic interaction datasets can distinguish the broad spectrum of interaction classes, as compared to existing information on mutation pairs associated with both positive and negative interactions, and whether the scoring of varying degrees of such epistatic effects could be improved by computational means. To address these questions, we introduce here a computational approach for improving the quantitative discrimination power encoded in the genetic interaction screening data. Our matrix approximation model decomposes the original double-mutant fitness matrix into separate components, representing variability across the array and query mutants, which can be utilized for estimating and correcting the single-mutant fitness effects, respectively. When applied to three large-scale quantitative interaction datasets in yeast, we could improve the accuracy of scoring various interaction classes beyond that obtained with the original fitness data, especially in synthetic genetic array (SGA) and in genetic interaction mapping (GIM) datasets. In addition to the known pairs of interactions used in the evaluation of the computational approach, a number of novel interaction pairs were also predicted, along with underlying biological mechanisms, which remained undetected by the original datasets. It was shown that the optimal choice of the scoring function depends heavily on the screening approach and on the interaction class under analysis. Moreover, a simple preprocessing of the fitness matrix could further enhance the discrimination power of the epistatic miniarray profiling (E-MAP) dataset. These systematic evaluation results provide in-depth information on the optimal analysis of the future, large-scale screening experiments. In general, the modeling framework, enabling accurate identification and classification of genetic interactions, provides a solid basis for completing and mining the genetic interaction networks in yeast and other organisms. 相似文献
49.
Populations of the autumnal moth, Epirrita autumnata, exhibit cycles with high amplitudes in northernmost Europe, culminating in devastating outbreak densities at favourable
sites. Parasitism by hymenopteran parasitoids has been hypothesised to operate with a delayed density dependence capable of
producing the observed dynamics. It has also been hypothesised that insects in crowded conditions invest greatly in their
immunity as a counter-measure to increased risk of parasitism and pathogen infections. Furthermore, inducible plant defences
consequent to grazing by herbivorous insects may be linked to the performance of parasitoids and pathogens through increased
immunocompetence of the herbivore feeding on the foliage, in which the defence induction has taken place. At ten sampling
sites, we quantified larval abundance, outbreak status and percentage larval parasitism during an extended peak phase of a
population cycle. These population level covariates, together with an individual pupal mass, were used to explain differences
in the immune defence, measured as an encapsulation reaction to artificial antigen. We also conducted a field study for an
investigation of the susceptibility of autumnal moth pupae to naturally occurring pupal parasitoids. We did not find obvious
differences between the encapsulation rate of autumnal moths originating from the sites with different past and current larval
densities and risks for parasitism. The best ranked statistical models included pupal mass and outbreak status as explanatory
variables, although both showed only slight effects on the encapsulation rate. The host resistance test revealed positive
relationships between the encapsulation rate, body size and percentage parasitism of the exposed pupae, indicating that pupal
parasitoids chose, and/or survived better, in large host individuals irrespective of their encapsulation ability. Thus, our
results do not provide support for the hypothesis that variation in the immune function drives or modulates population cycles
of autumnal moths.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorised users. 相似文献
50.
Klemola T Hanhimäki S Ruohomäki K Senn J Tanhuanpää M Kaitaniemi P Ranta H Haukioja E 《Oecologia》2003,135(3):354-361
The mast depression hypothesis has been put forward to explain the 9- to 10-year population cycle of the autumnal moth (Epirrita autumnata; Lepidoptera: Geometridae) in northern Fennoscandia. We analysed long-term data from Finnish Lapland in order to evaluate the critical assumption of the mast depression hypothesis: that better individual performance of herbivores, followed by high annual growth rate of populations, occurs in the year following mast seeding of the host, the mountain birch ( Betula pubescens ssp. czerepanovii). Since mast seeding has been suggested to occur at the expense of chemical defence against herbivores, we bioassayed the quality of birch leaves from the same trees by means of yearly growth trials with autumnal moth larvae. We also measured the size of wild adults as a determinant of potential fecundity of the species in different years. The relative growth rate of larvae was poorer in post-mast years compared to other years, rather than better as assumed by the hypothesis. Conversely, a slight indication of the increase in potential fecundity was observed due to the somewhat larger adult size in post-mast years. Population growth rate estimates, however, showed that the increase in fecundity would have to be much higher to facilitate population increase towards a cyclic peak with outbreak density. Accordingly, our two data sets do not support the assumption of a higher annual growth rate in autumnal moth populations subsequent to mast seeding of the host, thereby contradicting the predictions of the mast depression hypothesis. Temperatures, when indexed by the North Atlantic Oscillation and accumulated thermal sums, were observed to correlate with the abundance or rate of population change of the autumnal moth. The factors underlying the regular population cycles of the autumnal moth, however, remain unidentified. Overall, we suggest that the causal agents in cyclic insect population dynamics should be clarified by field experimentation, since trophic interactions are complex and are further modified by abiotic factors such as climate. 相似文献