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181.
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Alistair J. Hobday Jock W. Young Osamu Abe Daniel P. Costa Robert K. Cowen Karen Evans Maria A. Gasalla Rudy Kloser Olivier Maury Kevin C. Weng 《Reviews in Fish Biology and Fisheries》2013,23(4):537-546
Climate impacts are now widely reported from coastal marine systems, but less is known for the open ocean. Here we review progress in understanding impacts on large pelagic species presented at an international workshop for the Climate Impacts on Oceanic Top Predators programme, and discuss the future with regard to the next phase of adaptation-focused research. Recent highlights include a plan to map the distribution of key species in the foodweb using both acoustics and biochemical techniques, and development of a new data sharing and access tool for fisheries and associated data, including socio-economic information. A common research focus in pelagic ecosystems is on understanding climate variability and climate change impacts on marine species, but a greater emphasis on developing future scenarios and adaptation options is needed. Workshop participants also concluded that engagement with and provision of science support to regional fisheries management organisations are critical elements for ensuring successful uptake of research. This uptake will be required for future management of fisheries as global warming continues such that some open ocean top predators can be sustainably harvested, impacts on conservation-dependent species can be avoided, and ecosystem function is not compromised. 相似文献
183.
Josefa Bezerra da Silva Eneas Carvalho Rudy A. Hartskeerl Paulo L. Ho 《Current microbiology》2011,62(2):518-524
Leptospirosis is an important epidemic zoonosis worldwide. Currently, there are more than 250 Leptospira pathogenic serovars known that can potentially infect humans. Conventional classification of leptospires with the serovar as the basic taxon, based on serological recognition of lipopolysaccharide (LPS) composition does not correlate well with species determination, based on general genomic features. Here, we investigate the selective amplification of polymorphic regions from the LPS biosynthesis loci (rfb) as a potential tool for serovar typing of Leptospira interrogans species. Eight pairs of primers were designed to target six ORFs from the rfb operon with varying levels of sequence polymorphism. They were tested both separately and multiplexed. Half of these primer pairs produced serovar-specific amplicons, allowing the identification of some specific serovars and also groups of serovars. It was shown that the serovar classification of Leptospira can be accessed by selective amplification of rfb operons in some cases, which may permit a parallel between the serological and the genomic classifications of Leptospira. As a conclusion, the selective amplification of rfb generated promising and already useful results, but it appears necessary to characterize a larger variety of Leptospira genomes or rfb operons to fully develop this method. 相似文献
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Numerical models commonly account for elastic inhomogeneity in cortical bone using power-law scaling relationships with various measures of tissue density, but limited experimental data exists for anatomic variation in elastic anisotropy. A recent study revealed anatomic variation in the magnitude and anisotropy of elastic constants along the entire femoral diaphysis of a single human femur (Espinoza Orías et al., 2009). The objective of this study was to confirm these trends across multiple donors while also considering possible confounding effects of the anatomic quadrant, apparent tissue density, donor age, and gender. Cortical bone specimens were sampled from the whole femora of 9 human donors at 20%, 50%, and 80% of the total femur length. Elastic constants from the main diagonal of the reduced fourth-order tensor were measured on hydrated specimens using ultrasonic wave propagation. The tissue exhibited orthotropy overall and at each location along the length of the diaphysis (p < 0.0001). Elastic anisotropy increased from the mid-diaphysis toward the epiphyses (p < 0.05). The increased elastic anisotropy was primarily caused by a decreased radial elastic constant (C(11)) from the mid-diaphysis toward the epiphyses (p < 0.05), since differences in the circumferential (C(22)) and longitudinal (C(33)) elastic constants were not statistically significant (p > 0.29). Anatomic variation in intracortical porosity may account for these trends, but requires further investigation. The apparent tissue density was positively correlated with the magnitude of each elastic constant (p < 0.0001, R(2) > 0.46), as expected, but was only weakly correlated with C(33)/C(11) (p < 0.05, R(2) = 0.04) and not significantly correlated with C(33)/C(22) and C(11)/C(22). 相似文献
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Predation is a central organizing process affecting populations and communities. Traditionally, ecologists have focused on
the direct effects of predation—the killing of prey. However, predators also have significant sublethal effects on prey populations.
We investigated how fluctuating predation risk affected the stress physiology of a cyclic population of snowshoe hares (Lepus americanus) in the Yukon, finding that they are extremely sensitive to the fluctuating risk of predation. In years of high predator
numbers, hares had greater plasma cortisol levels at capture, greater fecal cortisol metabolite levels, a greater plasma cortisol
response to a hormone challenge, a greater ability to mobilize energy and poorer body condition. These indices of stress had
the same pattern within years, during the winter and over the breeding season when the hare:lynx ratio was lowest and the
food availability the worst. Previously we have shown that predator-induced maternal stress lowers reproduction and compromises
offspring’s stress axis. We propose that predator-induced changes in hare stress physiology affect their demography through
negative impacts on reproduction and that the low phase of cyclic populations may be the result of predator-induced maternal
stress reducing the fitness of progeny. The hare population cycle has far reaching ramifications on predators, alternate prey,
and vegetation. Thus, predation is the predominant organizing process for much of the North American boreal forest community,
with its indirect signature—stress in hares—producing a pattern of hormonal changes that provides a sensitive reflection of
fluctuating predator pressure that may have long-term demographic consequences. 相似文献
188.
Clinchy M Zanette L Charlier TD Newman AE Schmidt KL Boonstra R Soma KK 《Oecologia》2011,166(3):607-614
Predator-induced changes in the glucocorticoid responses of prey have been proposed to mediate indirect predator effects on
prey demography. Ambiguities exist, however, as to whether differences in predation threat in the environment at large affect
the mean glucocorticoid response in wild birds and mammals, and whether this is likely to affect reproduction. Most studies
to date that have examined glucocorticoid responses to environmental variation in predation threat have evaluated just one
of the several potential measures of the glucocorticoid response, and this may be the source of many ambiguities. We evaluated
multiple measures of the glucocorticoid response [plasma total CORTicosterone, corticosteroid binding globulin (CBG) and free
CORT] in male and female song sparrows (Melospiza melodia) sampled at locations differing in predation threat in the environment at large, where we have previously reported reproductive
differences suggestive of indirect predator effects. Total CORT varied markedly with predation threat in males but not females
whereas the opposite was true for CBG, and both sexes demonstrated the same moderately significant free CORT response. Considering
all three indices, a glucocorticoid response to environmental variation in predation threat was evident in both sexes, whereas
there were ambiguities considering each index singly. We conclude that collecting multiple physiological measures and conducting
multivariate analyses may provide a preferable means of assessing glucocorticoid responses to environmental variation in predation
threat, and so help clarify whether such glucocorticoid changes affect reproduction in wild birds and mammals. 相似文献
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190.
Macroscopic ion channel current is the summation of the stochastic records of individual channel currents and therefore relates to their statistical properties. As a consequence of this relationship, it may be possible to derive certain statistical properties of single channel records or even generate some estimates of the records themselves from the macroscopic current when the direct measurement of single channel currents is not applicable. We present a procedure for generating the single channel records of an ion channel from its macroscopic current when the stochastic process of channel gating has the following two properties: (I) the open duration is independent of the time of opening event and has a single exponential probability density function (pdf), (II) all the channels have the same probability to open at time t. The application of this procedure is considered for cases where direct measurement of single channel records is difficult or impossible. First, the probability density function (pdf) of opening events, a statistical property of single channel records, is derived from the normalized macroscopic current and mean channel open duration. Second, it is shown that under the conditions (I) and (II), a non-stationary Markov model can represent the stochastic process of channel gating. Third, the non-stationary Markov model is calibrated using the results of the first step. The non-stationary formulation increases the model ability to generate a variety of different single channel records compared to common stationary Markov models. The model is then used to generate single channel records and to obtain other statistical properties of the records. Experimental single channel records of inactivating BK potassium channels are used to evaluate how accurately this procedure reconstructs measured single channel sweeps. 相似文献