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41.
ANDREAS LUEK GEORGE E. MORGAN BJÖRN WISSEL JOHN M. GUNN CHARLES W. RAMCHARAN 《Freshwater Biology》2010,55(8):1616-1627
1. Yellow perch (Perca flavescens) are often the only surviving fish species in acidified lakes. We studied four lakes along a gradient of recovery from acidification and that had different food web complexities. All had abundant yellow perch, two had low piscivore abundance, one had a well‐established piscivore population and one was manipulated by introducing piscivorous smallmouth bass (Micropterus dolomieu). We hypothesised that there would be strong effects on perch abundance, behaviour and diet induced by the presence of piscivores. 2. In the manipulated lake, the bass reduced yellow perch abundance by 75% over a 2‐year period. Concomitantly, perch use of the pelagic habitat fell from 48 to 40%. 3. In contrast to findings from less disturbed systems, yellow perch in the littoral zone of the manipulated lake did not strongly shift from zooplankton to benthic food sources after the arrival of piscivores. Diet analysis using stable carbon isotopes revealed a strong continued reliance on zooplankton in all lakes, independent of the degree of piscivory. The failure to switch to benthos in the refuge area of the littoral zone is most likely related to the depauperate benthos communities in these formerly acidified lakes. 4. Yellow perch in lakes recovering from acidification face a considerable ecological challenge as the necessary switch to benthic diet is hindered by a low abundance of benthos. The arrival of piscivores in these recovering lakes imposes further restrictions on perch access to food items. We infer that future recovery of perch populations (and higher trophic levels) will have to be preceded by the re‐establishment of diverse benthic macroinvertebrate communities in these lakes. 相似文献
42.
JON E. SWENSON BJØRN DAHLE HELENA BUSK OLE OPSETH THOMAS JOHANSEN ARNE SÖDERBERG KJELL WALLIN GORAN CEDERLUND 《The Journal of wildlife management》2007,71(6):1993-1997
Abstract: In North America, brown bears (Ursus arctos) can be a significant predator on moose (Alces alces) calves. Our study in Sweden is the first in which brown bears are the only predator on moose calves. Bears and moose occurred at densities of about 30/1,000 km2 and 920/1,000 km2, respectively, and bears killed about 26% of the calves. Ninety-two percent of the predation took place when calves were <1 month old. Bear predation was probably additive to other natural mortality, which was about 10% in areas both with and without bears. Females that lost their calves in spring produced more calves the following year (1.54 calves/F) than females that kept their calves (1.11 calves/F), which reduced the net loss of calves due to predation to about 22%. 相似文献
43.
Rawlings ND 《The Biochemical journal》2007,403(2):e5-e7
Profound changes in the phosphorylation state of many proteins occur during mitosis. It is well established that many of these mitotic phosphorylations are carried out by archetypal mitotic kinases that are activated only during mitosis, shifting the equilibrium of kinases and phosphatases towards phosphorylation. However, many studies have also detailed the phosphorylation of proteins at mitosis by kinases that are constitutively active throughout the cell cycle. In most cases, it is uncertain how kinases and phosphatases that appear to be constitutively active can induce phosphorylations specifically at mitosis. In this issue of the Biochemical Journal, Escargueil and Larsen provide evidence of an interesting alternative mechanism to attain specific mitotic phosphorylation. A mitosis-specific phosphorylation site in DNA topoisomerase IIalpha, which is recognized by the MPM-2 antibody, is phosphorylated by protein kinase CK2. The authors found that phosphorylation of this site is suppressed during interphase due to competing dephosphorylation by protein phosphatase 2A. Interestingly, protein phosphatase 2A is excluded from the nucleus during early mitosis, allowing CK2 to phosphorylate topoisomerase IIalpha. It is possible that similar mechanisms are used to regulate the phosphorylation of other proteins. 相似文献
44.
Association of Vibrio cholerae O1 El Tor and O139 Bengal with the Copepods Acartia tonsa and Eurytemora affinis
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The association of Vibrio cholerae with zooplankton has been suggested as an important factor in transmission of human epidemic cholera, and the ability to colonize zooplankton surfaces may play a role in the temporal variation and predominance of the two different serogroups (V. cholerae O1 El Tor and O139) in the aquatic environment. To date, interactions between specific serogroups and species of plankton remain poorly understood. Laboratory microcosm experiments were carried out to compare quantitatively the colonization of two copepod species, Acartia tonsa and Eurytemora affinis, by each of the epidemic serogroups. V. cholerae O1 consistently achieved higher abundances than V. cholerae O139 in colonizing adults of each copepod species as well as the multiple life stages of E. affinis. This difference in colonization may be significant in the general predominance of V. cholerae O1 in cholera epidemics in rural Bangladesh where water supplies are taken directly from the environment. 相似文献
45.
46.
Fxna, a novel gene differentially expressed in the rat ovary at the time of folliculogenesis, is required for normal ovarian histogenesis 总被引:1,自引:0,他引:1
Garcia-Rudaz C Luna F Tapia V Kerr B Colgin L Galimi F Dissen GA Rawlings ND Ojeda SR 《Development (Cambridge, England)》2007,134(5):945-957
In rodents, the formation of ovarian follicles occurs after birth. In recent years, several factors required for follicular assembly and the growth of the newly formed follicles have been identified. We now describe a novel gene, Fxna, identified by differential display in the neonatal rat ovary. Fxna encodes an mRNA of 5.4 kb, and a protein of 898 amino acids. Fxna is a transmembrane metallopeptidase from family M28, localized to the endoplasmic reticulum. In the ovary, Fxna mRNA is expressed in granulosa cells; its abundance is maximal 48 hours after birth, i.e. during the initiation of follicular assembly. Reducing Fxna mRNA levels via lentiviral-mediated delivery of short hairpin RNAs to neonatal ovaries resulted in substantial loss of primordial, primary and secondary follicles, and structural disorganization of the ovary, with many abnormal follicles containing more than one oocyte and clusters of somatic cells not associated with any oocytes. These abnormalities were not attributable to either increased apoptosis or decreased proliferation of granulosa cells. The results indicate that Fxna is required for the organization of somatic cells and oocytes into discrete follicular structures. As an endoplasmic reticulum-bound peptidase, Fxna may facilitate follicular organization by processing precursor proteins required for intraovarian cell-to-cell communication. 相似文献
47.
The identity,distribution, and impacts of non-native apple snails in the continental United States 总被引:1,自引:0,他引:1
Timothy A Rawlings Kenneth A Hayes Robert H Cowie Timothy M Collins 《BMC evolutionary biology》2007,7(1):97
Background
Since the mid 1990s populations of non-native apple snails (Ampullariidae) have been discovered with increasing frequency in the continental United States. Given the dramatic effects that introduced apple snails have had on both natural habitats and agricultural areas in Southeast Asia, their introduction to the mainland U.S. is cause for concern. We combine phylogenetic analyses of mtDNA sequences with examination of introduced populations and museum collections to clarify the identities, introduced distributions, geographical origins, and introduction histories of apple snails. 相似文献48.
Gemma L. Holliday Amos Bairoch Pantelis G. Bagos Arnaud Chatonnet David J. Craik Robert D. Finn Bernard Henrissat Gerard Manning Nozomi Nagano Claire O'Donovan Neil D. Rawlings Milton Saier Ramanathan Sowdhamini Michael Spedding Narayanaswamy Srinivasan Gert Vriend Patricia C. Babbitt Alex Bateman 《Proteins》2015,83(6):1005-1013
As the volume of data relating to proteins increases, researchers rely more and more on the analysis of published data, thus increasing the importance of good access to these data that vary from the supplemental material of individual articles, all the way to major reference databases with professional staff and long‐term funding. Specialist protein resources fill an important middle ground, providing interactive web interfaces to their databases for a focused topic or family of proteins, using specialized approaches that are not feasible in the major reference databases. Many are labors of love, run by a single lab with little or no dedicated funding and there are many challenges to building and maintaining them. This perspective arose from a meeting of several specialist protein resources and major reference databases held at the Wellcome Trust Genome Campus (Cambridge, UK) on August 11 and 12, 2014. During this meeting some common key challenges involved in creating and maintaining such resources were discussed, along with various approaches to address them. In laying out these challenges, we aim to inform users about how these issues impact our resources and illustrate ways in which our working together could enhance their accuracy, currency, and overall value. Proteins 2015; 83:1005–1013. © 2015 The Authors. Proteins: Structure, Function, and Bioinformatics Published by Wiley Periodicals, Inc. 相似文献
49.
The geo‐classifications of colonial statelessness: The anthropology of Kastom,land and citizenship in the decolonisation of Vanuatu
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Gregory Rawlings 《The Australian journal of anthropology》2015,26(2):145-173
Anthropological accounts of Vanuatu's independence have emphasised both the materiality of land alienation and the importance of kastom (custom) as a symbol of cultural practice, political resistance and national unity in accounts of decolonisation and postcolonial nation‐making. For 74 years indigenous ni‐Vanuatu were stateless and lacked all forms of citizenship and nationality in the Anglo‐French Condominium of the New Hebrides (1906–1980). This article situates anthropological accounts of land, kastom and the state in Vanuatu's transition to independence in relation to statelessness, citizenship and hierarchies of ethnographic authenticity within the geo‐classificatory frameworks of colonial rule established by the condominium. The embodiment of citizenship and demands to end the cumulative humiliations of statelessness that ni‐Vanuatu experienced in the condominium illuminate both tensions and continuities in idealist and materialist accounts of Melanesian nationalisms evident in kastom and land as they were mediated by the emancipatory claims and promises of postcolonial citizenship. 相似文献
50.