排序方式: 共有4条查询结果,搜索用时 46 毫秒
1
1.
Votier SC Furness RW Bearhop S Crane JE Caldow RW Catry P Ensor K Hamer KC Hudson AV Kalmbach E Klomp NI Pfeiffer S Phillips RA Prieto I Thompson DR 《Nature》2004,427(6976):727-730
It is clear that discards from commercial fisheries are a key food resource for many seabird species around the world. But predicting the response of seabird communities to changes in discard rates is problematic and requires historical data to elucidate the confounding effects of other, more 'natural' ecological processes. In the North Sea, declining stocks, changes in technical measures, changes in population structure and the establishment of a recovery programme for cod (Gadus morhua) will alter the amount of fish discarded. This region also supports internationally important populations of seabirds, some of which feed extensively, but facultatively, on discards, in particular on undersized haddock (Melanogrammus aeglefinus) and whiting (Merlangius merlangus). Here we use long-term data sets from the northern North Sea to show that there is a direct link between discard availability and discard use by a generalist predator and scavenger--the great skua (Stercorarius skua). Reduced rates of discarding, particularly when coupled with reduced availability of small shoaling pelagic fish such as sandeel (Ammodytes marinus), result in an increase in predation by great skuas on other birds. This switching of prey by a facultative scavenger presents a potentially serious threat to some seabird communities. 相似文献
2.
Shimizu Y Matsuyama H Shiina T Takewaki T Furness JB 《Cellular and molecular life sciences : CMLS》2008,65(2):295-311
In the gastrointestinal tract, tachykinins are peptide neurotransmitters in nerve circuits that regulate intestinal motility,
secretion, and vascular functions. Tachykinins also contribute to transmission from spinal afferents that innervate the gastrointestinal
tract and have roles in the responses of the intestine to inflammation. Tachykinins coexist with acetylcholine, the primary
transmitter of excitatory neurons innervating the muscle, and act as a co-neurotransmitter of excitatory neurons. Excitatory
transmission is mediated through NK1 receptors (primarily on interstitial cells of Cajal) and NK2 receptors on the muscle.
Tachykinins participate in slow excitatory transmission at neuro-neuronal synapses, through NK1 and NK3 receptors, in both
ascending and descending pathways affecting motility. Activation of receptors (NK1 and NK2) on the epithelium causes fluid
secretion. Tachykinin receptors on immune cells are activated during inflammation of the gut. Finally, tachykinins are released
from the central terminals of gastrointestinal afferent neurons in the spinal cord, particularly in nociceptive pathways.
Received 24 March 2007; received after revision 30 August 2007; accepted 14 September 2007 相似文献
3.
Summary The ratio at which adrenaline and noradrenaline are released from the adrenal medulla in response to stimulation of the splanchnic nerve has been established in the conscious calf. The proportion of adrenaline: noradrenaline was closely similar to that in which the 2 amines are stored in the gland and released in response to other stimuli in conscious, but not anaesthetized, calves.Acknowledgments. This work has been supported by a grant from the Agricultural Research Council, and we are also indebted to Dr D.M. Burley (Ciba) for his continued support. It is a pleasure to acknowledge the skilled technical assistance provided by Mr P.M.M. Bircham. 相似文献
4.
1