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61.
PEKKA VANHALA KRISTIINA KARHU MIKKO TUOMI KATARINA BJÖRKLÖF HANNU FRITZE HASSE HYVÄRINEN JARI LISKI 《Global Change Biology》2011,17(1):538-550
Changes in soil carbon, the largest terrestrial carbon pool, are critical for the global carbon cycle, atmospheric CO2 levels and climate. Climate warming is predicted to be most pronounced in the northern regions and therefore the large soil carbon pool residing in boreal forests will be subject to larger global warming impact than soil carbon pools in the temperate or the tropical forest. A major uncertainty in current estimates of the terrestrial carbon balance is related to decomposition of soil organic matter (SOM). We hypothesized that when soils are exposed to warmer climate the structure of the ground vegetation will change much more rapidly than the dominant tree species. This change will alter the quality and amount of litter input to the soil and induce changes in microbial communities, thus possibly altering the temperature sensitivity of SOM decomposition. We transferred organic surface soil sections from the northern borders of the boreal forest zone to corresponding forest sites in the southern borders of the boreal forest zone and studied the effects of warmer climate after an adaptation period of 2 years. The results showed that initially ground vegetation and soil microbial community structure and community functions were different in northern and southern forest sites and that 2 years of exposure to warmer climate was long enough to cause changes in these ecological indicators. The rate of SOM decomposition was approximately equally sensitive to temperature irrespective of changes in vegetation or microbial communities in the studied forest sites. However, as temperature sensitivity of the decomposition increases with decreasing temperature regime, the proportional increase in the decomposition rate in northern latitudes could lead to significant carbon losses from the soils. 相似文献
62.
Singaravelu K Padanilam BJ 《American journal of physiology. Renal physiology》2011,300(5):F1130-F1141
The role of p53 in inducing apoptosis following acute kidney injury is well-established; however, the molecular mechanisms remain largely unknown. We report here that the p53 proapoptotic target Siva and its receptor CD27, a member of the tumor necrosis factor receptor family, are upregulated following renal ischemia-reperfusion injury (IRI). Inhibition of Siva using antisense oligonucleotides conferred functional and morphological protection, and it prevented apoptosis postrenal IRI in mice. Renal IRI in CD27-deficient mice displayed functional protection and partial inhibition of apoptosis, suggesting an incomplete role for CD27 in Siva-mediated apoptosis. To further elucidate mechanisms by which Siva elicits apoptosis, in vitro studies were performed. In Siva-transfected LLC-PK(1)cells, Siva is persistently expressed in the nucleus at 3 h onwards and its translocation to mitochondria and the plasma membrane occurred at 6 h. Moreover, Siva overexpression induced mitochondrial permeability, cytochrome c release, caspase-8 and -9 activation, translocation of apoptosis-inducing factor (AIF) to the nucleus, and apoptosis. Inhibition of Siva in ischemic kidneys prevented mitochondrial release of cytochrome c and AIF. These data indicate that Siva function is pivotal in regulating apoptosis in the pathology of renal IRI. Targeting Siva may offer a potential therapeutic strategy for renal IRI. 相似文献
63.
Lissette M. Ruberté Raghu N. Natarajan Gunnar BJ. Andersson 《Journal of biomechanics》2009,42(3):341-348
The current study investigated mechanical predictors for the development of adjacent disc degeneration. A 3-D finite element model of a lumbar spine was modified to simulate two grades of degeneration at the L4–L5 disc. Degeneration was modeled by changes in geometry and material properties. All models were subjected to follower preloads of 800 N and moment loads in the three principal directions of motion using a hybrid protocol. Degeneration caused changes in the loading and motion patterns of the segments above and below the degenerated disc. At the level (L3–L4) above the degenerated disc, the motion increased due to moderate degeneration by 21% under lateral bending, 26% under axial rotation and 28% under flexion/extension. At the level (L5-S1) below the degenerated disc, motion increased only during lateral bending by 20% due to moderate degeneration. Both the L3–L4 and L5-S1 segment showed a monotonic increase in both the maximum von Mises stress and shear stress in the annulus as degeneration progressed for all loading directions, expect extension at L3–L4. The most significant increase in stress was observed at the L5-S1 level during axial rotation with nearly a ten-fold increase in the maximum shear stress and 103% increase in the maximum von Mises stress. The L5-S1 segment also showed a progressive increase in facet contact force for all loading directions with degeneration. Nucleus pressure did not increase significantly for any loading direction at either the caudal or cephalic adjacent segment. Results suggest that single-level degeneration can increase the risk for injury at the adjacent levels. 相似文献
64.
The oligomerization of a family of four genetically clustered human gastrointestinal mucins 总被引:1,自引:0,他引:1
Mucins are synthesized and secreted by many epithelia. They are complex
glycoproteins that offer cytoprotection. In their functional configuration,
mucins form oligomers by a biosynthetic process that is poorly understood.
A family of four human gastrointestinal mucin genes (MUC2, MUC5AC, MUC5B,
and MUC6) is clustered to chromosome 11p15.5. To study oligomerization of
these related mucins, we performed metabolic labeling experiments with
[35S]amino acids in LS174T cells, and isolated mucin precursors by specific
immunoprecipitations that were analyzed on SDS-PAGE. Each of the precursors
of MUC2, MUC5AC, MUC5B, and MUC6 formed a single species of
disulfide-linked homo-oligomer within 1 h after pulse labeling. Based on
apparent molecular masses, these oligomeric precursors were most likely
dimers. Inhibition of vesicular RER-to-Golgi transport, with brefeldin A
and CCCP, did not affect the dimerization of MUC2 precursors, localizing
dimerization to the RER. O-Glycosylation of MUC2 followed dimerization.
Inhibition of N- glycosylation by tunicamycin retarded, but did not
inhibit, dimerization, indicating that N-glycans play a role in efficient
dimerization of MUC2 precursors. Based on sequence homology, the ability of
MUC2, MUC5AC, MUC5B and MUC6 to dimerize most likely resides in their
C-terminal domains. Thus, the RER-localized dimerization of secretory
mucins likely proceeds by similar mechanisms, which is an essential step in
the formation of the human gastrointestinal mucus- gels.
相似文献
65.
1. Considerable evidence suggests that the diversity within plant communities may strongly affect the strength of species interactions, but the majority of studies only considered interspecific diversity. 2. This paper examines the effect of intraspecific genetic diversity within Brassica fields on two Brassica specialists, cabbage root fly, and diamondback moth, and on a parasitoid attacking diamondback moths. Genetic diversity was manipulated both in a replacement and an additive design. 3. Both herbivore densities and parasitism rates were higher in smaller plots, with limited responses to increased within‐plot diversity. All species showed variable densities across genotypes, and preference hierarchies were species specific. 4. Responses to plot size in root flies scaled with the diameter‐to‐area ratio, suggesting that patch detectability affected local density, whereas responses by diamondback moths and parasitoids deviated from this ratio. These species differences could be traced to differences in the residence time within patches, where diamondback moths typically spend longer and more variable time periods in patches than root flies. 5. The lack of response to genetic diversity by both herbivores suggests that egg‐laying rates are affected by decisions on the plant and not by attraction from a distance, neither to the plant itself nor the patch. Patterns of differential attack may then be due to different acceptability for studied genotypes. 6. Future theories on insect responses to spatial heterogeneity should focus on species traits and how traits interact with information landscapes in the field. 相似文献
66.
NELSON VALDIVIA JARROD D. STEHBENS BJÖRN HERMELINK SEAN D. CONNELL MARKUS MOLIS MARTIN WAHL 《Austral ecology》2008,33(8):951-962
Local dynamics such as resource enhancement (e.g. nutrient supply) and stochastic events of destruction (disturbances that provide new space) are hypothesized to counteractively affect species diversity and composition. We tested the independent and interactive effects of nutrients and disturbance on the development of assemblages of epibiota attached to vertical surfaces in an oligotrophic system. Nutrient concentrations were manipulated at three levels (ambient, medium and high) while disturbance was manipulated by removing biomass at seven frequencies (0×, 2×, 3×, 4×, 5×, 7×, 12×). Nutrient and disturbance regimes had opposing effects on diversity such that species richness increased with resource enhancement (nutrients) and declined with disturbance. These results support the model that increased heterogeneity of distribution of limiting resources allows the coexistence of species with low and high resource requirements. 相似文献
67.
Abstract The palatability to common carp, Cyprinus carpio L. of three newly developed differently flavoured floating pellets made from a high proportion (40%) of brewer's spent grain (BSG) was tested using a multiple-offer feeding experiment. The addition of ‘bold’ flavours, such as vanilla or strawberry essence, may help mask the unpleasant taste of some piscicides; however, their inclusion must not compromise uptake by carp. There were no significant differences between the consumption rates of the three varieties, and all flavours were readily consumed. Therefore, it is suggested that highly flavoured pellets made with BSG have a strong potential to mask the flavour of an unpalatable toxin, and further research is now needed to test this hypothesis. 相似文献
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69.
Previous studies of the effect of carbonation on taste perception have
suggested that it may be negligible, manifesting primarily in increases in
the perceived intensity of weak salt and sour stimuli. Assuming CO2
solutions in the mouth stimulate only trigeminal nerve endings, this result
is not altogether surprising; however, there are neurophysiological data
indicating that CO2 stimulates gustatory as well as trigeminal fibers. In
that case, carbonation might alter the quality profile of a stimulus
without producing substantial changes in overall taste intensity--much as
occurs when qualitatively different taste stimuli are mixed. To address
this possibility, subjects were asked to rate the total taste intensity of
moderate concentrations of stimuli representing each of the basic tastes
and their binary combinations, with an without added carbonation. They then
subdivided total taste intensity into the proportions of sweetness,
saltiness, sourness, bitterness and 'other taste qualities' they perceived.
The addition of carbonation produced only small increases in ratings of
total taste intensity. However, rather dramatic alterations in the quality
profiles of stimuli were observed, particularly for sweet and salty tastes.
The nature of the interaction is consistent with a direct effect of
carbonation/CO2 on the gustatory system, although the possibility that at
least some of the observed effects reflect trigeminal-gustatory
interactions cannot be ruled out.
相似文献
70.