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991.
Hjermann DØ Bogstad B Eikeset AM Ottersen G Gjøsaeter H Stenseth NC 《Proceedings. Biological sciences / The Royal Society》2007,274(1610):661-669
Proper management of ecosystems requires an understanding of both the species interactions as well as the effect of climate variation. However, a common problem is that the available time-series are of different lengths. Here, we present a general approach for studying the dynamic structure of such interactions. Specifically, we analyse the recruitment of the world's largest cod stock, the Northeast Arctic cod. Studies based on data starting in the 1970-1980s indicate that this stock is affected by temperature through a variety of pathways. However, the value of such studies is somewhat limited by the fact that they are based on a quite specific ecological and climatic situation. Recently, this stock has consisted of fairly young fish and the spawning stock has consisted of relatively few age groups. In this study, we develop a model for the effect of capelin (the cod's main prey) and herring on cod recruitment since 1973. Based on this model, we analyse data on cod, herring and temperature going back to 1921 and find that food-web effects explain a significant part of the cod recruitment variation back to around 1950. 相似文献
992.
Geisler J Haynes B Ekse D Dowsett M Lønning PE 《The Journal of steroid biochemistry and molecular biology》2007,104(1-2):27-34
The adipocytokine leptin has recently been shown to enhance the expression of aromatase via promoter II and I.3 using an AP-1 motif. Thus, we evaluated the correlation between plasma leptin concentrations and total body aromatization (TBA) as well as plasma levels of estrone (E(1)), estradiol (E(2)) and estrone sulfate (E(1)S) in postmenopausal breast cancer patients. Twenty-two postmenopausal women with metastatic breast cancer, participating in tracer studies for the measurement of total body aromatization (TBA) in vivo, were available. In addition, blood samples for plasma estrogens and leptin measurements were available from another 22 breast cancer patients and 114 healthy postmenopausal women participating in the mammography-screening program. Values for TBA varied from 1.46 to 4.72% while plasma leptin levels ranged from 1.83 to 95.51 ng/ml in the same group of patients. All plasma estrogen levels were in the normal range expected for postmenopausal women. We found a significant correlation between pretreatment leptin levels and TBA (r(s) 0.452, P=0.01). In contrast, basal levels of TBA did not correlate to body mass index (BMI) in the same group of patients. Plasma leptin levels correlated to plasma levels of estradiol (r(s) 0.659, P=0.007), and estrone sulfate (r(s) 0.562, P=0.01) in the group of breast cancer patients (n=44) as well as in the group of healthy postmenopausal women (estradiol, r(s) 0.363, P< or =0.001, estrone sulfate r(s) 0.353, P< or =0.001). In conclusion, we found plasma leptin levels to correlate to TBA in breast cancer patients and to plasma levels of estradiol and estrone sulfate in breast cancer patients as well as in healthy postmenopausal females. These findings suggest that leptin may influence on aromatase activity in vivo, providing a possible link between body weight and plasma estrogen levels as well as breast cancer risk. 相似文献
993.
Factors influencing conservation attitudes of local people in Western Serengeti,Tanzania 总被引:2,自引:0,他引:2
Jafari R. Kideghesho Eivin Røskaft Bjørn P. Kaltenborn 《Biodiversity and Conservation》2007,16(7):2213-2230
Attitudinal studies are increasingly being adopted as tools for evaluating public understanding, acceptance and the impact
of conservation interventions. The findings of these studies have been useful in guiding the policy interventions. Many factors
affect conservation attitudes positively or negatively. The factors inspiring positive attitudes are likely to enhance the
conservation objectives while those inducing negative attitudes may detrimentally undermine these objectives. The magnitude
of the resultant effects of each particular factor is determined by the historical, political, ecological, socio-cultural
and economic conditions and this may call for different management interventions. In this study we examined how conservation
attitudes in western Serengeti are shaped by the following factors: level of conflicts with protected areas; wildlife imposed
constraints (inadequate pasture, water, diseases, loss of livestock during migration, theft and depredation); participation
in the community based project; and socio-demographic factors (age, education level, wealth, immigration, gender and household
size). The results indicated that the level of conflicts, participation in the community based project, inadequate pasture,
lack of water, diseases, wealth and education were important in shaping peoples’ attitudes. However, in a stepwise linear
regression analysis, 59% of the variation in peoples’ attitudes was explained by three variables i.e., conflict level with
protected areas, lack of water and participation in the community based project. In addition to these variables, level of
education also contributed in explaining 51% of the variation in people’s attitude regarding the status of the game reserves.
Five variables (lack of water, level of education, inadequate pasture, participation in the community based project and diseases)
explained 12% of the variation in people’s attitude towards Serengeti National Park. The paper discusses the implications
for conservation of these results and recommends some measures to realise effective conservation of wildlife resources. 相似文献
994.
Roggen H Kehler J Stensbøl TB Hansen T 《Bioorganic & medicinal chemistry letters》2007,17(10):2834-2837
A series of Milnacipran analogs with variation in the aromatic moiety were prepared in high enantiomeric excess. Structure-activity relationships for two parallel enantiomeric series are described. The (-)-(1R,2S)-naphthyl analog (8h) showed the highest potency in the two series and is a triple reuptake inhibitor of the SERT, NET, and DAT. 相似文献
995.
Jørn Stave Gufu Oba Inger Nordal Nils Chr Stenseth 《Biodiversity and Conservation》2007,16(5):1471-1489
The present study explores traditional ecological knowledge (TEK) of Turkana pastoralists and cultivators in the context of
a riverine forest in northern Kenya. The Turkwel River and its floodplain sustain a thick forest, which is used for grazing
and extraction of non-timber forest products. However, sedentarisation and agricultural expansion have resulted in localised
clear-felling of trees, while river damming has altered the natural flow regime. A series of structured, semi-structured,
and group interviews were combined with a botanical inventory in order to assess the relevance of TEK to ecological research
and forest conservation. Turkana informants gave 102 vernacular names for the 113 woody species. Of these, 85% had a domestic
or pastoral use among the 105 specific uses that were described. Ethnobotanical knowledge was relatively homogenous and not
related to age, gender, or source of livelihood. The informants had in-depth knowledge of some key ecological processes. The
conceived threats to forest survival were primarily cultivation and permanent settlements, while the effects of river damming
and livestock grazing were disputed. A claimed decline in rainfall was confirmed by official data. There is strong evidence
that TEK could be used to generate hypotheses for research and to design sustainable conservation strategies. A revised version
of the indigenous system of tree management should be incorporated into the official forestry policy in order to resolve future
conflicts between pastoralists and cultivators. 相似文献
996.
The substrate for selective substitution in the C10-methyl group in erythromycin A derivatives was 10,11-anhydro-6O-methyl-descladinosylerythromycin. The latter, as an N-oxide, was reacted with NBS in acetic acid to form an allylic acetate. Nucleophilic substitutions and carbylation by Pd-catalysed cross-coupling reactions provided products substituted in the C10-methyl group. Methods for the preparation of 10-methylene derivatives of 11N,12O-cyclocarbamate 3-ketolides are described. The methylene group is part of an alpha,beta-unsaturated carbonyl system involving the 9-keto group. The products from conjugated addition are substituted in the C10-methyl group. 相似文献
997.
Fürstenberger G Epp N Eckl KM Hennies HC Jørgensen C Hallenborg P Kristiansen K Krieg P 《Prostaglandins & other lipid mediators》2007,82(1-4):128-134
12R-lipoxygenase (12R-LOX) and epidermis-type LOX-3 (eLOX-3) are novel members of the multigene family of mammalian LOX. A considerable gap exists between the identification of these enzymes and their biologic function. Here, we present evidence that 12R-LOX and eLOX-3, acting in sequence, and eLOX-3 in combination with another, not yet identified LOX are critically involved in terminal differentiation of keratinocytes and adipocytes, respectively. Mutational inactivation of 12R-LOX and/or eLOX-3 has been found to be associated with development of an inherited ichthyosiform skin disorder in humans and genetic ablation of 12R-LOX causes a severe impairment of the epidermal lipid barrier in mice leading to post-natal death of the animals. In preadipocytes, a LOX-dependent PPARgamma activating ligand is released into the cell supernatant early upon induction of differentiation and available evidence indicates that this ligand is an eLOX-3-derived product. In accordance with this data is the observation that forced expression of eLOX-3 enhances adipocyte differentiation. 相似文献
998.
MicroRNA-133 controls cardiac hypertrophy 总被引:23,自引:0,他引:23
999.
Sørensen KM Jespersgaard C Vuust J Hougaard D Nørgaard-Pedersen B Andersen PS 《Genetic testing》2007,11(1):65-71
As the number of single-nucleotide polymorphism (SNP) screening and other mutation scanning studies have increased explosively, following the development of high-throughput instrumentation, it becomes even more important to have sufficient template DNA. The source of DNA is often limited, especially in epidemiological studies, which require many samples as well as enough DNA to perform numerous SNP screenings or mutation scannings. Therefore, the aim is to solve the problem of stock DNA limitation. This need has been an important reason for the development of whole genome amplification (WGA) methods. Several systems are based on Phi29 polymerase multiple displacement amplification (MDA) or on DNA fragmentation (OmniPlex). Using TaqMan SNP genotyping assays, we have tested four WGA systems -- AmpliQ Genomic Amplifier Kit, GenomiPhi, Repli-g, and GenomePlex -- on DNA extracted from Guthrie cards to evaluate the amplification bias, concordance- and call rates, cost efficiency, and flexibility. All systems successfully amplified picograms of DNA from Guthrie cards to micrograms of product without loss of heterozygosity and with minimal allelic bias. A modified AmpliQ set up was chosen for further evaluation. In all, 2,000 SNP genotyping results from amplified and nonamplified samples were compared and the concordance rates between the samples were 99.7%. The call rate using the TaqMan system was 99.8%. DNA extracted from Guthrie cards and amplified with one of the four evaluated WGA systems is applicable in epidemiological genetic screenings. System choice should be based on requirements for system flexibility, product yield, and use in subsequent analysis. 相似文献
1000.
Nielsen MS Weber RE 《Comparative biochemistry and physiology. Part A, Molecular & integrative physiology》2007,146(3):429-434
Oxygen binding to hemoglobin (Hb) depends on allosteric effectors (CO(2), lactate and protons) that may increase drastically in concentration during exercise. The effectors share common binding sites on the Hb molecules, predicting mutual interaction in their effects on Hb (de)oxygenation. We analysed the effects of lactate and CO(2), separately and in combination, on O(2) binding of purified human Hb at 37 degrees C and physiological pH and chloride values. We demonstrate pH-dependent, inhibitory interactions between lactate binding and CO(2) binding (carbamate formation); at pH 7.4, physiological CO(2) tension ( approximately 43 mm Hg) reduced lactate binding more markedly ( approximately 75%), than lactate (50 mM) inhibited carbamate formation ( approximately 25%). In contrast to previous studies on blood and Hb solutions, we moreover find that added lactate neither 'reverses' oxylabile carbamate formation (resulting in lower carbamate levels in deoxyHb than in oxyHb) nor exerts greater allosteric effects on Hb-O(2) affinity than equal increases in chloride ion concentrations. 相似文献