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991.
Christian K. Tipsmark Kenneth J. Sørensen Katrine Hulgard Steffen S. Madsen 《Comparative biochemistry and physiology. Part A, Molecular & integrative physiology》2010,155(3):361-370
In seawater fishes, osmotic homeostasis requires uptake of ions and water in the intestine and these processes are governed by the combined trans- and paracellular pathways. The current study examined mRNA expression of two tight junction proteins (claudin-15 and -25b) predominantly expressed in the intestine of Atlantic salmon. We examined the response in pyloric caecae, middle and posterior intestine to seawater challenge, during smoltification and after injection with osmoregulatory hormones. Seawater (SW) transfer elevated levels of claudin-15 and -25b while no change was induced throughout the smolt stage. In freshwater, cortisol and growth hormone inhibited claudin-15 expression in the two anterior segments. Claudin-25b was elevated in all intestinal segments by growth hormone, while cortisol had an inhibitory effect. In seawater, prolactin and cortisol inhibited claudin expression. The data suggest that claudin expression is involved in the reorganisation of intestinal epithelium and possibly change paracellular permeability during SW acclimation. The lack of preparatory change during smoltification suggests that this process is not completed during smolt development. The effects of the tested hormones cannot explain the sum of changes induced by salinity, which, like the smoltification data, suggests the importance of additional factors and possibly contact with the imbibed SW per se. 相似文献
992.
Marius Warg Næss Bård-Jørgen Bårdsen Per Fauchald Torkild Tveraa 《Evolution and human behavior》2010,31(4):246-258
While there is a general assumption that labour has a positive effect on pastoral production, studies that have quantified this relationship have been characterized by ambiguous results. This is most likely related to the fact that possible cooperative pastoral production has been little explored in the literature, although it is well documented that nomadic pastoralist households share and exchange labour in so-called cooperative herding groups. Consequently, this study aims at investigating possible cooperative labour-related effects on production among Saami reindeer herders in Norway by using kinship relations as a proxy for cooperation. This study found that cooperative labour investment is important for Saami reindeer herders, but that the effect of kinship and labour needs to be understood in relation to each other. When assessing the effect of labour and kinship simultaneously, both labour and genealogical relationship had positive effects on herd size. We also found a positive interaction between kinship and labour suggesting that high levels of relatedness coupled with a large potential labour pool had an increasingly positive effect on herd size. 相似文献
993.
Lagerström MC Rogoz K Abrahamsen B Persson E Reinius B Nordenankar K Olund C Smith C Mendez JA Chen ZF Wood JN Wallén-Mackenzie A Kullander K 《Neuron》2010,68(3):529-542
The natural response to itch sensation is to scratch, which relieves the itch through an unknown mechanism. Interaction between pain and itch has been frequently demonstrated, and the selectivity hypothesis of itch, based on data from electrophysiological and behavioral experiments, postulates the existence of primary pain afferents capable of repressing itch. Here, we demonstrate that deletion of vesicular glutamate transporter (VGLUT) 2 in a subpopulation of neurons partly overlapping with the vanilloid receptor (TRPV1) primary afferents resulted in a dramatic increase in itch behavior accompanied by a reduced responsiveness to thermal pain. The increased itch behavior was reduced by administration of antihistaminergic drugs and by genetic deletion of the gastrin-releasing peptide receptor, demonstrating a dependence on VGLUT2 to maintain normal levels of both histaminergic and nonhistaminergic itch. This study establishes that VGLUT2 is a major player in TRPV1 thermal nociception and also serves to regulate a normal itch response. 相似文献
994.
Rodrigo Vega Camilla Fløjgaard Andrés Lira‐Noriega Yoshinori Nakazawa Jens‐Christian Svenning Jeremy B. Searle 《Ecography》2010,33(2):260-271
The southern European peninsulas (Iberian, Italian and Balkan) are traditionally recognized as glacial refugia from where many species colonized central and northern Europe after the Last Glacial Maximum (LGM). However, evidence that some species had more northerly refugia is accumulating from phylogeographic, palaeontological and palynological studies, and more recently from species distribution modelling (SDM), but further studies are needed to test the idea of northern refugia in Europe. Here, we take a rarely implemented multidisciplinary approach to assess if the pygmy shrew Sorex minutus, a widespread Eurasian mammal species, had northern refugia during the LGM, and if these influenced its postglacial geographic distribution. First, we evaluated the phylogeographic and population expansion patterns using mtDNA sequence data from 123 pygmy shrews. Then, we used SDM to predict present and past (LGM) potential distributions using two different training data sets, two different algorithms (Maxent and GARP) and climate reconstructions for the LGM with two different general circulation models. An LGM distribution in the southern peninsulas was predicted by the SDM approaches, in line with the occurrence of lineages of S. minutus in these areas. The phylogeographic analyses also indicated a widespread and strictly northern‐central European lineage, not derived from southern peninsulas, and with a postglacial population expansion signature. This was consistent with the SDM predictions of suitable LGM conditions for S. minutus occurring across central and eastern Europe, from unglaciated parts of the British Isles to much of the eastern European Plain. Hence, S. minutus likely persisted in parts of central and eastern Europe during the LGM, from where it colonized other northern areas during the late‐glacial and postglacial periods. Our results provide new insights into the glacial and postglacial colonization history of the European mammal fauna, notably supporting glacial refugia further north than traditionally recognized. 相似文献
995.
Raymond H. G. Klaassen Roine Strandberg Mikael Hake Patrik Olofsson Anders P. Tøttrup Thomas Alerstam 《Journal of avian biology》2010,41(2):200-207
Loop migration among birds is characterized by the spring route lying consistently west or east of the autumn route. The existence of loops has been explained by general wind conditions or seasonal differences in habitat distribution. Loop migration has predominantly been studied at the population level, for example by analysing ring recoveries. Here we study loop migration of individual marsh harriers Circus aeruginosus tracked by satellite telemetry. We show that despite a generally narrow migration corridor the harriers travelled in a distinct clockwise loop through Africa and southern Europe, following more westerly routes in spring than in autumn. We used the Normalized Difference Vegetation Index (NDVI) to identify potential feeding habitat in Africa. Suitable habitat seemed always more abundant along the western route, both in spring and autumn, and no important stopover site was found along the eastern route. Observed routes did thus not coincide with seasonal variation in habitat availability. However, favourable habitat might be more important during spring migration, when the crossing of the Sahara seems more challenging, and thus habitat availability might play an indirect role in the harriers’ route choice. Grid‐based wind data were used to reconstruct general wind patterns, and in qualitative agreement with the observed loop marsh harriers predominantly encountered westerly winds in Europe and easterly winds in Africa, both in autumn and in spring. By correlating tail‐ and crosswinds with forward and perpendicular movement rates, respectively, we show that marsh harriers are partially drifted by wind. Thus, we tentatively conclude that wind rather than habitat seems to have an overriding effect on the shape of the migration routes of marsh harriers. General wind conditions seem to play an important role also in the evolution of narrow migratory loops as demonstrated for individual marsh harriers. 相似文献
996.
Mikkel A. J. Kvasnes Torstein Storaas Hans Chr. Pedersen Svein Bjørk Erlend B. Nilsen 《Ecological Research》2010,25(2):367-374
Different species in a given site or population of a given species in different sites may fluctuate in synchrony if they are
affected similarly by factors such as spatially autocorrelated climate, predation, or by dispersal between populations of
one species. We used county wise time series of hunting bag records of four Norwegian tetraonid species covering 24 years
to examine patterns of interspecific and intraspecific synchrony. We estimated synchrony at three spatial scales; national,
regional (consisting of counties with similar climate), and county level. Ecologically related species with overlapping distributions
exhibited strong synchrony across Norway, but there was much variation between the different regions and counties. Regions
with a long coastline to both the North Sea and the Norwegian Ocean exhibited an overall stronger synchrony than those consisting
of more continental areas. Intraspecific synchrony was generally low across all counties, but stronger synchrony between counties
within regions defined by climatic conditions. Synchrony was negatively related to distance between populations in three of
four species. Only the synchrony in willow ptarmigan showed a clear negative relationship with distance, while the other species
had both strong positive and negative correlations at short distances. Strong interspecific synchrony between some species
pairs within regions and weak intraspecific synchrony across counties within regions suggest a stronger synchronizing effect
from environmental factors such as weather or predation and less effect from dispersal. Our results suggest that the complete
tetraonid community is structured by environmental factors affecting the different species similarly and causes widespread
interspecific synchrony. Local factors affecting the population dynamics nevertheless frequently forces neighbouring populations
out of phase. 相似文献
997.
Niels Jessen Ho-Jin Koh Clifford D. Folmes Cory Wagg Nobuharu Fujii Bo Løfgren Cordula M. Wolf Charles I. Berul Michael F. Hirshman Gary D. Lopaschuk Laurie J. Goodyear 《生物化学与生物物理学报:疾病的分子基础》2010,1802(7-8):593-600
Energy deprivation in the myocardium is associated with impaired heart function and increased morbidity. LKB1 is a kinase that is required for activation of AMP-activated protein kinase (AMPK) as well as 13 AMPK-related protein kinases. AMPK stimulates ATP production during ischemia and prevents post-ischemic dysfunction. We used the Cre–Lox system to generate mice where LKB1 was selectively knocked out in cardiomyocytes and muscle cells (LKB1-KO) to assess the role of LKB1 on cardiac function in these mice.Heart rates of LKB1-KO mice were reduced and ventricle diameter was increased. Ex vivo, cardiac function was impaired during aerobic perfusion of isolated working hearts, and recovery of function after ischemia was reduced. Although oxidative metabolism and mitochondrial function were normal, the AMP/ATP ratio was increased in LKB1-KO hearts. This was associated with a complete ablation of AMPKα2 activity, and a stimulation of signaling through the mammalian target of rapamycin. Our results establish a critical role for LKB1 for normal cardiac function under both aerobic conditions and during recovery after ischemia. Ablation of LKB1 leads to a decreased cardiac efficiency despite normal mitochondrial oxidative metabolism. 相似文献
998.
Marit Espe Raja Mansingh Rathore Zhen-Yu Du Bjørn Liaset Adel El-Mowafi 《Amino acids》2010,39(2):449-460
The current experiment aimed to study whether interactions with lipid metabolism possibly might explain the relative increased
liver weight obtained in fish fed sub-optimal methionine levels. A basal diet based on a blend of plant proteins which is
low in methionine (1.6 g Met/16 g N) was compared to a methionine adequate diet (2.2 g Met/16 g N) prepared by adding dl-methionine (2.4 g/kg) to the basal diet in the expense of wheat grain. Fish oil was used as the lipid source. The diets were
balanced in all nutrients except methionine. The diets were fed to Atlantic salmon (500 g BW) for a period of 3 months. Feed
intake did not differ, rendering the intake of all nutrients except methionine equal. Fish fed the low methionine diet had
an increased liver size relative to body weight, indicating fat deposition in the liver. Fish given the sub-optimal methionine
diet showed about six times higher fatty acid synthase (FAS) activity as compared to the fish fed the adequate methionine
diet, indicating a higher de novo lipogenesis. A significant rise in the liver 18:1 to 18:0 fatty acid ratios also supported
storage of lipids over fatty acid oxidation. Indeed, methionine limitation resulted in significantly higher TAG concentrations
in the liver. Sub-optimal dietary methionine also resulted in lower hepatic taurine concentrations and the total bile acids
concentrations were reduced in faeces and tended to be reduced in plasma. Taken together, our data show that salmon fed sub-optimal
methionine levels had increased relative liver weight and developed signs commonly described in the early stage of non-alcoholic
fatty liver disease in rodent models (increased FAS activity, changed fatty acid ratios and TAG accumulation). 相似文献
999.
Jesper Hedal Kløverpris Kenneth Baltzer Per H. Nielsen 《The International Journal of Life Cycle Assessment》2010,15(1):90-103
Background, aims and scope
Most life cycle inventory data for crops do not include the ultimate (marginal) land use induced by crop consumption. The aims of this study were to present, document and discuss a method which can solve this problem and, furthermore, to present concrete examples for wheat consumption in Brazil, China, Denmark and the USA. A global scope is applied and the simulated adaptation to increased wheat demand corresponds to a long-term temporal scope under present market conditions with present technology. 相似文献1000.
Martin Lappann Heike Claus Tessa Van Alen Morten Harmsen Johannes Elias Søren Molin Ulrich Vogel 《Molecular microbiology》2010,75(6):1355-1371
Major pathogenic clonal complexes (cc) of Neisseria meningitidis differ substantially in their point prevalence among healthy carriers. We show that frequently carried pathogenic cc (e.g. sequence type ST‐41/44 cc and ST‐32 cc) depend on extracellular DNA (eDNA) to initiate in vitro biofilm formation, whereas biofilm formation of cc with low point prevalence (ST‐8 cc and ST‐11 cc) was eDNA‐independent. For initial biofilm formation, a ST‐32 cc type strain, but not a ST‐11 type strain, utilized eDNA. The release of eDNA was mediated by lytic transglycosylase and cytoplasmic N‐acetylmuramyl‐l ‐alanine amidase genes. In late biofilms, outer membrane phospholipase A‐dependent autolysis, which was observed in most cc, but not in ST‐8 and ST‐11 strains, was required for shear force resistance of microcolonies. Taken together, N. meningitidis evolved two different biofilm formation strategies, an eDNA‐dependent one yielding shear force resistant microcolonies, and an eDNA‐independent one. Based on the experimental findings and previous epidemiological observations, we hypothesize that most meningococcal cc display a settler phenotype, which is eDNA‐dependent and results in a stable interaction with the host. On the contrary, spreaders (ST‐11 and ST‐8 cc) are unable to use eDNA for biofilm formation and might compensate for poor colonization properties by high transmission rates. 相似文献