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61.
Bojsen-Møller J Losnegard T Kemppainen J Viljanen T Kalliokoski KK Hallén J 《Journal of applied physiology (Bethesda, Md. : 1985)》2010,109(6):1895-1903
Due to the complexity of movement in cross-country skiing (XCS), the muscle activation patterns are not well elucidated. Previous studies have applied surface electromyography (SEMG); however, recent gains in three-dimensional (3D) imaging techniques such as positron emission tomography (PET) have rendered an alternative approach to investigate muscle activation. The purpose of the present study was to examine muscle use during double poling (DP) at two work intensities by use of PET. Eight male subjects performed two 20-min DP bouts on separate days. Work intensity was ~ 53 and 74% of peak oxygen uptake (Vo(2peak)), respectively. During exercise 188 ± 8 MBq of [(18)F]fluorodeoxyglucose ([(18)F]FDG) was injected, and subsequent to exercise a full-body PET scan was conducted. Regions of interest (ROI) were defined within 15 relevant muscles, and a glucose uptake index (GUI) was determined for all ROIs. The muscles that span the shoulder and elbow joints, the abdominal muscles, and hip flexors displayed the greatest GUI during DP. Glucose uptake did not increase significantly from low to high intensity in most upper body muscles; however, an increased GUI (P < 0.05) was seen for the knee flexor (27%) and extensor muscles (16%), and for abdominal muscles (21%). The present data confirm previous findings that muscles of the upper limb are the primary working muscles in DP. The present data further suggest that when exercise intensity increases, the muscles that span the lumbar spine, hip, and knee joints contribute increasingly. Finally, PET provides a promising alternative or supplement to existing methods to assess muscle activation in complex human movements. 相似文献
62.
Erna Suutari Jukka Salmela Lauri Paasivirta Markus J. Rantala Katja Tynkkynen Mari Luojumäki Jukka Suhonen 《Journal of Insect Conservation》2009,13(4):413-419
Species with narrow ranges and specialised traits are most at risk, and the extinction wave is further enhanced by coextinctions.
We studied the conservation value and indicator potential of Stratiotes aloides, an aquatic macrophyte that has declined considerably in Europe. Our purpose was to determine whether S. aloides could be used as an indicator of a valuable habitat in terms of macroarthropod diversity and species richness. The potential
occurrence of an internationally endangered Stratiotes-habitat specialist, the dragonfly Aeshna viridis, can increase the conservation value of plant colonies. S. aloides beds harboured diverse macroarthropod fauna often containing species of conservation concern, including A. viridis. Stratiotes is a potential indicator of a valuable habitat, and its indicator value is enhanced by the easy identification of the species.
However, its use as an indicator of a defined macroarthropod community is limited because no particular community type is
connected to it. We suggest that protecting Stratiotes simultaneously conserves valuable arthropod fauna, including A. viridis. 相似文献
63.
Jukka Sakari Pumpanen Jussi Heinonsalo Terhi Rasilo Kaj-Roger Hurme Hannu Ilvesniemi 《Trees - Structure and Function》2009,23(3):611-621
Carbon dioxide is released from the soil to the atmosphere in heterotrophic respiration when the dead organic matter is used
for substrates for soil micro-organisms and soil animals. Respiration of roots and mycorrhiza is another major source of carbon
dioxide in soil CO2 efflux. The partitioning of these two fluxes is essential for understanding the carbon balance of forest ecosystems and for
modelling the carbon cycle within these ecosystems. In this study, we determined the carbon balance of three common tree species
in boreal forest zone, Scots pine, Norway spruce, and Silver birch with gas exchange measurements conducted in laboratory
in controlled temperature and light conditions. We also studied the allocation pattern of assimilated carbon with 14C pulse labelling experiment. The photosynthetic light responses of the tree species were substantially different. The maximum
photosynthetic capacity (P
max) was 2.21 μg CO2 s−1 g−1 in Scots pine, 1.22 μg CO2 s−1 g−1 in Norway spruce and 3.01 μg CO2 s−1 g−1 in Silver birch seedlings. According to the pulse labelling experiments, 43–75% of the assimilated carbon remained in the
aboveground parts of the seedlings. The amount of carbon allocated to root and rhizosphere respiration was about 9–26%, and
the amount of carbon allocated to root and ectomycorrhizal biomass about 13–21% of the total assimilated CO2. The 14CO2 pulse reached the root system within few hours after the labelling and most of the pulse had passed the root system after
48 h. The transport rate of carbon from shoot to roots was fastest in Silver birch seedlings. 相似文献
64.
Jouni Aspi Eeva Roininen Jukka Kiiskilä Minna Ruokonen Ilpo Kojola Leo Bljudnik Pjotr Danilov Samuli Heikkinen Erkki Pulliainen 《Conservation Genetics》2009,10(4):815-826
We examined the genetic diversity and structure of wolf populations in northwestern Russia. Populations in Republic of Karelia
and Arkhangelsk Oblast were sampled during 1995–2000, and 43 individuals were genotyped with 10 microsatellite markers. Moreover,
118 previously genotyped wolves from the neighbouring Finnish population were used as a reference population. A relatively
large amount of genetic variation was found in the Russian populations, and the Karelian wolf population tended to be slightly
more polymorphic than the Arkhangelsk population. We found significant inbreeding (F = 0.094) in the Karelian, but not in the Arkhangelsk population. The effective size estimates of the Karelian wolf population
based on the approximate Bayesian computation and linkage disequilibrium methods were 39.9 and 46.7 individuals, respectively.
AMOVA-analysis and exact test of population differentiation suggested clear differentiation between the Karelian, Arkhangelsk
and Finnish wolf populations. Indirect estimates of gene flow based on the level of population differentiation (ϕ
ST
= 0.152) and frequency of private alleles (0.029) both suggested a low level of gene flow between the populations (Nm = 1.4 and Nm = 3.7, respectively). Assignment analysis of Karelian and Finnish populations suggested an even lower number of recent migrants
(less than 0.03) between populations, with a larger amount of migration from Finland to Karelia than vice versa. Our findings
emphasise the role of physical obstacles and territorial behaviour in creating barriers to gene flow between populations in
relatively limited geographical areas, even in large-bodied mammalian species with long-distance dispersal capabilities and
an apparently continuous population structure. 相似文献
65.
We introduce a Bayesian theoretical formulation of the statistical learning problem concerning the genetic structure of populations.
The two key concepts in our derivation are exchangeability in its various forms and random allocation models. Implications
of our results to empirical investigation of the population structure are discussed. 相似文献
66.
The Bayesian model-based approach to inferring hidden genetic population structures using multilocus molecular markers has become a popular tool within certain branches of biology. In particular, it has been shown that heterogeneous data arising from genetically dissimilar latent groups of individuals can be effectively modelled using an unsupervised classification formulation. However, most currently employed models ignore potential linkage within the employed molecular information, and can therefore lead to biased inferences under certain circumstances. Utilizing the general theory of graphical models, we develop a framework that accounts for dependences both within linked molecular marker loci and DNA sequence data. Due to a high level of sequence conservation among eukaryotic species, the latter aspect is particularly relevant for analyzing rapidly evolving microbial species. The advantages of incorporating the dependence due to linkage in the classification models are illustrated by analyses of both simulated data and real samples of Bacillus cereus. 相似文献
67.
Julkunen P Kiviranta P Wilson W Jurvelin JS Korhonen RK 《Journal of biomechanics》2007,40(8):1862-1870
Load-bearing characteristics of articular cartilage are impaired during tissue degeneration. Quantitative microscopy enables in vitro investigation of cartilage structure but determination of tissue functional properties necessitates experimental mechanical testing. The fibril-reinforced poroviscoelastic (FRPVE) model has been used successfully for estimation of cartilage mechanical properties. The model includes realistic collagen network architecture, as shown by microscopic imaging techniques. The aim of the present study was to investigate the relationships between the cartilage proteoglycan (PG) and collagen content as assessed by quantitative microscopic findings, and model-based mechanical parameters of the tissue. Site-specific variation of the collagen network moduli, PG matrix modulus and permeability was analyzed. Cylindrical cartilage samples (n=22) were harvested from various sites of the bovine knee and shoulder joints. Collagen orientation, as quantitated by polarized light microscopy, was incorporated into the finite-element model. Stepwise stress-relaxation experiments in unconfined compression were conducted for the samples, and sample-specific models were fitted to the experimental data in order to determine values of the model parameters. For comparison, Fourier transform infrared imaging and digital densitometry were used for the determination of collagen and PG content in the same samples, respectively. The initial and strain-dependent fibril network moduli as well as the initial permeability correlated significantly with the tissue collagen content. The equilibrium Young's modulus of the nonfibrillar matrix and the strain dependency of permeability were significantly associated with the tissue PG content. The present study demonstrates that modern quantitative microscopic methods in combination with the FRPVE model are feasible methods to characterize the structure-function relationships of articular cartilage. 相似文献
68.
Varelius J 《Bioethics》2007,21(3):140-149
In a recent issue of this journal, David Silver and Gerald Dworkin discuss the physicians' role in execution by lethal injection. Dworkin concludes that discussion by stating that, at that point, he is unable to think of an acceptable set of moral principles to support the view that it is illegitimate for physicians to participate in execution by lethal injection that would not rule out certain other plausible moral judgements, namely that euthanasia is under certain conditions legitimate and that organ-donation surgery is sometimes permissible. This article draws attention to some problems in the views of Silver and Dworkin and suggests moral principles which support the three moral views just mentioned. 相似文献
69.
The acyl-CoA binding protein (ACBP) is essential for the fatty acid metabolism, membrane structure, membrane fusion, and ceramide synthesis. Here high resolution crystal structures of human cytosolic liver ACBP, unliganded and liganded with a physiological ligand, myristoyl-CoA are described. The binding of the acyl-CoA molecule induces only few structural differences near the binding pocket. The crystal form of the liganded ACBP, which has two ACBP molecules in the asymmetric unit, shows that in human ACBP the same acyl-CoA binding pocket is present as previously described for the bovine and Plasmodium falciparum ACBP and the mode of binding of the 3'-phosphate-AMP moiety is conserved. Unexpectedly, in one of the acyl-CoA binding pockets the acyl moiety is bound in a reversed mode as compared with the bovine and P. falciparum structures. In this binding mode, the myristoyl-CoA molecule is fully ordered and bound across the two ACBP molecules of the crystallographic asymmetric unit: the 3'-phosphate-AMP moiety is bound in the binding pocket of one ACBP molecule and the acyl chain is bound in the pocket of the other ACBP molecule. The remaining binding pocket cavities of these two ACBP molecules are filled by other ligand fragments. This novel binding mode shows that the acyl moiety can flip out of its classical binding pocket and bind elsewhere, suggesting a mechanism for the acyl-CoA transfer between ACBP and the active site of a target enzyme. This mechanism is of possible relevance for the in vivo function of ACBP. 相似文献
70.
Sensitivity of CO<Subscript>2</Subscript> Exchange of Fen Ecosystem Components to Water Level Variation 总被引:1,自引:0,他引:1
Abstract
Climate change is predicted to bring about a water level (WL) draw-down in boreal peatlands. This study aimed to assess the
effect of WL on the carbon dioxide (CO2) dynamics of a boreal oligotrophic fen ecosystem and its components; Sphagnum mosses, sedges, dwarf shrubs and the underlying peat. We measured CO2 exchange with closed chambers during four growing seasons in a study site that comprised different vegetation treatments.
WL gradient in the site was broadened by surrounding half of the site with a shallow ditch that lowered the WL by 10–25 cm.
We modeled gross photosynthesis (P
G) and ecosystem respiration (R
ECO) and simulated the CO2 exchange in three WL conditions: prevailing and WL draw-down scenarios of 14 and 22 cm. WL draw-down both reduced the P
G and increased the R
ECO, thus leading to a smaller net CO2 uptake in the ecosystem. Of the different components, Sphagnum mosses were most sensitive to WL draw-down and their physiological activities almost ceased. Vascular plant CO2 exchange, en bloc, hardly changed but whereas sedges contributed twice as much to the CO2 exchange as shrubs in the prevailing conditions, the situation was reversed in the WL draw-down scenarios. Peat respiration
was the biggest component in R
ECO in all WL conditions and the increase in R
ECO following the WL draw-down was due to the increase in peat respiration. The results imply that functional diversity buffers
the ecosystem against environmental variability and that in the long term, WL draw-down changes the vegetation composition
of boreal fens. 相似文献