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21.
Cremona Fabien Laas Alo Hanson Paul C. Sepp Margot Nõges Peeter Nõges Tiina 《Ecosystems》2019,22(4):805-817
Ecosystems - We assessed the allochthonous organic carbon (OC) budgets for thirteen hemiboreal lakes using a simple equilibrium model coupled with a Bayesian framework for estimating parameter... 相似文献
22.
Seppo Rytknen Eero J. Vesterinen Coen Westerduin Tiina Levikangas Emma Vatka Marko Mutanen Panu Vlimki Markku Hukkanen Marko Suokas Markku Orell 《Ecology and evolution》2019,9(1):631-639
Diets play a key role in understanding trophic interactions. Knowing the actual structure of food webs contributes greatly to our understanding of biodiversity and ecosystem functioning. The research of prey preferences of different predators requires knowledge not only of the prey consumed, but also of what is available. In this study, we applied DNA metabarcoding to analyze the diet of 4 bird species (willow tits Poecile montanus, Siberian tits Poecile cinctus, great tits Parus major and blue tits Cyanistes caeruleus) by using the feces of nestlings. The availability of their assumed prey (Lepidoptera) was determined from feces of larvae (frass) collected from the main foraging habitat, birch (Betula spp.) canopy. We identified 53 prey species from the nestling feces, of which 11 (21%) were also detected from the frass samples (eight lepidopterans). Approximately 80% of identified prey species in the nestling feces represented lepidopterans, which is in line with the earlier studies on the parids' diet. A subsequent laboratory experiment showed a threshold for fecal sample size and the barcoding success, suggesting that the smallest frass samples do not contain enough larval DNA to be detected by high‐throughput sequencing. To summarize, we apply metabarcoding for the first time in a combined approach to identify available prey (through frass) and consumed prey (via nestling feces), expanding the scope and precision for future dietary studies on insectivorous birds. 相似文献
23.
Holster T Pakkanen O Soininen R Sormunen R Nokelainen M Kivirikko KI Myllyharju J 《The Journal of biological chemistry》2007,282(4):2512-2519
Collagen prolyl 4-hydroxylases (C-P4Hs) catalyze the formation of the 4-hydroxyproline residues that are essential for the generation of triple helical collagen molecules. The vertebrate C-P4Hs I, II, and III are [alpha(I)]2beta2, [alpha(II)]2beta2, and [alpha(III)]2beta2 tetramers with identical beta subunits. We generated mice with targeted inactivation of the P4ha1 gene encoding the catalytic alpha subunit of C-P4H I to analyze its specific functions. The null mice died after E10.5, showing an overall developmental delay and a dilated endoplasmic reticulum in their cells. The capillary walls were frequently ruptured, but the capillary density remained unchanged. The C-P4H activity level in the null embryos and fibroblasts cultured from them was 20% of that in the wild type, being evidently due to the other two isoenzymes. Collagen IV immunofluorescence was almost absent in the basement membranes of the null embryos, and electron microscopy revealed disrupted basement membranes, while immunoelectron microscopy showed a lack of collagen IV in them. The amount of soluble collagen IV was increased in the null embryos and cultured null fibroblasts, indicating a lack of assembly of collagen IV molecules into insoluble structures, probably due to their underhydroxylation and hence abnormal conformation. In contrast, the null embryos had collagen I and III fibrils with a typical cross-striation pattern but slightly increased diameters, and the null fibroblasts secreted fibril-forming collagens, although less efficiently than wild-type cells. The primary cause of death of the null embryos was thus most likely an abnormal assembly of collagen IV. 相似文献
24.
Muhonen P Tennilä T Azhayeva E Parthasarathy RN Janckila AJ Väänänen HK Azhayev A Laitala-Leinonen T 《化学与生物多样性》2007,4(5):858-873
Short interfering RNA (siRNA) molecules with good gene-silencing properties are needed for drug development based on RNA interference (RNAi). An initial step in RNAi is the activation of the RNA-induced silencing complex RISC, which requires degradation of the sense strand of the siRNA duplex. Although various chemical modifications have been introduced to the antisense strand, modifications to the Argonaute2 (Ago2) cleavage site in the sense strand have, so far, not been described in detail. In this work, novel 2'-F-purine modifications were introduced to siRNAs, and their biological efficacies were tested in cells stably expressing human tartrate-resistant acid phosphatase (TRACP). A validated siRNA that contains both purine and pyrimidine nucleotides at the putative Ago2 cleavage site was chemically modified to contain all possible combinations of 2'-fluorinated 2'-deoxypurines and/or 2'-deoxypyrimidines in the antisense and/or sense strands. The capacity of 2'-F-modified siRNAs to knock down their target mRNA and protein was studied, together with monitoring siRNA toxicity. All 2'-F-modified siRNAs resulted in target knockdown at nanomolar concentrations, despite their high thermal stability. These experiments provide the first evidence that RISC activation not only allows 2'-F modifications at the sense-strand cleavage site, but also increase the biological efficacy of modified siRNAs in vitro. 相似文献
25.
Norbertas Noreika Aveliina Helm Maarja
pik Teele Jairus Martti Vasar Ülle Reier Ene Kook Kersti Riibak Liis Kasari Hardi Tullus Tea Tullus Reimo Lutter Ede Oja Andres Saag Tiina Randlane Meelis Prtel 《Oikos》2019,128(11):1653-1665
Ecosystem biomass, soil conditions and the diversity of different taxa are often interrelated. These relationships could originate from biogeographic affinity (varying species pools) or from direct ecological effects within local communities. Disentangling regional and local causes is challenging as the former might mask the latter in natural ecosystems with varying habitat conditions. However, when the species pool contribution is considered in statistics, local ecological effects might be detected. In this study we disentangle the indirect effects of the species pool and direct ecological effects on the complex relationships among wood volume, soil conditions and diversities of different plant and fungal groups in 100 old‐growth forest sites (10 × 10 m) at the border of boreal and nemoral zones in northern Europe. We recorded all species for different vegetation groups: woody and herbaceous vascular plants, terricolous and epiphytic bryophytes and lichens. Fungal communities were detected by DNA‐based analyses from soil samples. Above‐ground wood volume was used as a proxy of biomass. We measured soil pH and nutrient content and obtained modelled climate parameters for each site. Species pool effect was considered by dividing sites into boreal and nemoral groups based on community composition. In order to disentangle direct and indirect effects, we applied variation partitioning, and raw and partial correlations. We found many significant positive relationships among studied variables. Many of these relationships were associated to boreal and nemoral species pools, thus indicating that biogeographic affinity of interacting plants and fungi largely defines forest diversity and functioning. At the same time, several relationships were significant also after considering biogeography: woody plant and ectomycorrhizal fungi diversities with wood volume, many plant and fungal groups with each other, or with soil conditions. These direct ecological interactions could be considered in forestry practices to achieve both economic gain and maintenance of biodiversity. 相似文献
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27.
Acharya G Erkinaro T Mäkikallio K Lappalainen T Rasanen J 《American journal of physiology. Heart and circulatory physiology》2004,286(4):H1266-H1272
We hypothesized that umbilical artery (UA) absolute blood flow velocities measured by Doppler ultrasonography reflect placental volume blood flow (Q(UA)) and placental vascular resistance (R(UA)) in a late gestation fetal sheep model. In addition, we examined the relationships between umbilical artery absolute blood flow velocities and parameters of fetal cardiac function. Twenty-six sheep fetuses were instrumented at 112-132 days of gestation. After a 5-day recovery period, experiments were performed under general anesthesia in 16 normal fetuses, in 5 fetuses after maternal administration of phenylephrine, and in 5 fetuses after placental embolization. The Q(UA) and arterial blood pressures were measured using a transit-time ultrasonic flow probe and a catheter placed into the descending aorta, respectively. UA peak systolic velocity (PSV), end-diastolic velocity (EDV), time-averaged maximum velocity (TAMXV), pulsatility index (PI), mean velocity (V(mean)), fetal cardiac output, ventricular ejection forces, and the proportion of isovolumetric relaxation time (IRT%) in the cardiac cycle were measured with the use of Doppler ultrasonography. Significant positive linear correlations were found between UA EDV, TAMXV, and V(mean) versus Q(UA), whereas UA PI had a significant negative correlation with Q(UA). Significant negative correlations were shown between UA EDV, TAMXV, and V(mean) versus R(UA). A significant positive correlation was present between UA PI and R(UA). Doppler-derived UA parameters did not correlate with fetal arterial blood pressures, cardiac output, ventricular ejection forces or IRT%. In fetal sheep, Doppler-derived UA PI and absolute velocities, except PSV, are closely related to directly measured Q(UA) and R(UA), validating the use of noninvasive Doppler velocimetry in the assessment of placental circulation. 相似文献
28.
29.
Dastmalchi S Church WB Morris MB Iismaa TP Mackay JP 《Journal of structural biology》2004,146(3):261-271
Galanin and its newly discovered relative galanin-like peptide (GALP) are neuropeptides that are implicated in the neuroendocrine regulation of body weight and reproduction. GALP encompasses within its sequence the first 13 residues of galanin, known to be crucial to binding and activation of galanin receptor (GalR) subtypes. Using 2D-NMR and circular dichroism spectroscopy we demonstrated that GALP does not adopt a preferred conformation in pure water alone. However, it shows characteristics of transient turn-like structures in two distinct regions of its sequence, 11-23 and 41-49. These transient ordered structures, nascent helices, probably form stable helical structures upon addition of the helix-inducing solvent, trifluoroethanol, as determined by circular dichroism studies. Secondary structure prediction methods also predict the presence of two helical regions in the sequence of GALP overlapping reasonably with those regions identified as nascent helical structures by experimental methods. 相似文献
30.
Metso S Nikkilä M Laippala P Jaakkola O Solakivi T Lehtimäki T 《Journal of biomedical science》2003,10(3):345-351
OBJECTIVE: Oxidized low-density lipoprotein (LDL) autoantibodies (oxLDLab), apolipoprotein E (apoE) phenotype, postprandial triglyceride changes and LDL size are suggested to be risk factors for coronary artery disease (CAD). Our aim was to study the interaction between these new risk factors among patients with CAD and healthy controls. METHODS: oxLDLab from 31 men with angiographically verified CAD and 31 healthy men were analyzed by enzyme-linked immunosorbent assay. Isoelectric focusing and immunoblotting were used for apoE phenotyping. Triglyceride level was measured after 12 h of fasting and 3, 5 and 7 h after a high-fat meal. Nondenaturing gradient gel electrophoresis was used to separate LDL particles according to size. RESULTS: oxLD- Lab levels increased according to apoE phenotype in the following order: E2 < E3 < E4 (p = 0.004, ANOVA). The postprandial response of triglycerides, the size of LDL particles and the concentration of LDL and high-density lipoprotein (HDL) cholesterol did not differ between apoE phenotypes, and the use of these variables as covariates did not change the statistically significant difference in oxLDLab levels between apoE phenotypes (p = 0.01, ANCOVA). oxLDLab levels did not differ between the patient and control groups. CONCLUSION: We found an association between apoE allele epsilon2 and decreased levels of oxLDLab, which was independent of the postprandial response of triglycerides, the size of LDL particles and plasma LDL and HDL cholesterol levels. The mechanism by which apoE affects oxidation of LDL remains unknown. 相似文献