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991.
Ziad Fajloun Nicolas Andreotti Mohamed Fathallah Jean‐Marc Sabatier Michel De Waard 《Journal of peptide science》2011,17(3):200-210
Maurotoxin (MTX) is a 34‐residue toxin that was isolated initially from the venom of the scorpion Scorpio maurus palmatus. Unlike the other toxins of the α‐KTx6 family (Pi1, Pi4, Pi7, and HsTx1), MTX exhibits a unique disulfide bridge organization of the type C1? C5, C2? C6, C3? C4, and C7? C8 (instead of the conventional C1? C5, C2? C6, C3? C7, and C4? C8, herein referred to as Pi1‐like) that does not prevent its folding along the classic α/β scaffold of scorpion toxins. MTXPi1 is an MTX variant with a conventional pattern of disulfide bridging without any primary structure alteration of the toxin. Here, using MTX and/or MTXPi1 as models, we investigated how the type of folding influences toxin recognition of the Shaker B potassium channel. Amino acid residues of MTX that were studied for Shaker B recognition were selected on the basis of their homologous position in charybdotoxin, a three disulfide‐bridged scorpion toxin also active on this channel type. These residues favored either an MTX‐ or MTXPi1‐like folding. Our data indicate clearly that Lys23 and Tyr32 (two out of ten amino acid residues studied) are the most important residues for Shaker B channel blockage by MTX. For activity on SKCa channels, the same amino acid residues also affect, directly or indirectly, the recognition of SK channels. The molecular modeling technique and computed docking indicate the existence of a correlation between the half cystine pairings of the mutated analogs and their activity on the Shaker B K+ channel. Overall, mutations in MTX could, or could not, change the reorganization of disulfide bridges of this molecule without affecting its α/β scaffold. However, changing of the peptide backbone (cross linking disulfide bridges from MTX‐like type vs MTXPi1‐like type) appears to have less impact on the molecule activity than mutation of certain key amino acids such as Lys23 and Tyr32 in this toxin. Copyright © 2011 European Peptide Society and John Wiley & Sons, Ltd. 相似文献
992.
Abstract. Although the reproductive biology and early life‐history stages of deep‐sea corals are poorly understood, such data are crucial for their conservation and management. Here, we describe the timing of larval release, planula behavior, metamorphosis, settlement, and early juvenile growth of two species of deep‐sea soft corals from the northwest Atlantic. Live colonies of Gersemia fruticosa maintained under flow‐through laboratory conditions released 79 planulae (1.5–2.5 mm long) between April and early June 2007. Peak planulation in G. fruticosa coincided with peaks in the chlorophyll concentration and deposition rates of planktic matter. Metamorphosis and settlement occurred 3–70 d post‐release. The eight primary mesenteries typically appeared within 24 h, and primary polyps grew to a height of ~6–10 mm and a stalk diameter of ~1 mm within 2–3 months. Planulae of Duva florida (1.5–2.5 mm long) were extracted surgically from several colonies and were successfully reared in culture. Primary polyps reached a height of ~3–4 mm within 2–3 months. No budding of primary polyps was observed in either species over 11–13 months of monitoring, suggesting a very slow growth rate. 相似文献
993.
William H. Clements Jeffrey L. Arnold Todd M. Koel Rob Daley Cathie Jean 《Aquatic Ecology》2011,45(1):137-149
We examined responses of benthic macroinvertebrate communities to natural geothermal discharges in 32 streams in Yellowstone
National Park (YNP), USA. Geothermal discharges played a major role in structuring benthic communities in YNP, as downstream
communities were characterized by low species richness, reduced abundance of EPT taxa and increased abundance of tolerant
caddisflies (Trichoptera), chironomids and non-insects. While some taxa were a subset of tolerant organisms that were also
common at references sites, others (the damselfly Argia sp., the caddisfly Oxyethira sp. and the exotic New Zealand mudsnail Potamopyrgus antipodarum Gray 1843) were found almost exclusively in geothermal streams. Because geothermal waters are a common feature of YNP, monitoring
programs designed to assess long-term status and trends of Yellowstone’s aquatic ecosystems must account for the influence
of these discharges. To separate geothermal effects from other potential anthropogenic disturbances in YNP (e.g., atmospheric
deposition, road construction, wastewater, global change), we developed a multimetric index based on responses of benthic
communities to geothermal discharges. Streams were placed into one of four geothermal categories based on conductivity (reference = < 150 μS/cm; low, moderate and high = 151–300, 301–600 and >600 μS/cm, respectively). The index clearly distinguished among
these categories and showed a well-defined threshold response to geothermal effects at very low levels of conductivity. Although
the index was specific to geothermal effects, the approach used to develop the index has broad applicability for other systems
where impacts of stressors must be assessed within the context of natural environmental gradients. Our findings may provide
important insights into how benthic macroinvertebrate communities respond to global change. Reduced discharge and warmer temperatures
predicted for Rocky Mountain streams may favor the establishment and expansion of exotic species such as New Zealand mudsnails
(P. antipodarum), which are highly tolerant of geothermal influences. 相似文献
994.
Laurent Jean Lamarque Sylvain Delzon Christopher James Lortie 《Biological invasions》2011,13(9):1969-1989
Trees act as ecosystem engineers and invasions by exotic tree species profoundly impact recipient communities. Recently, research
on invasive trees has dramatically increased, enabling the assessment of general trends in tree invasion. Analysing 90 studies
dealing with 45 invasive tree species, we conducted a quantitative review and a meta-analysis to estimate the relevance of
eight leading hypotheses for explaining tree invasions. We also tested whether species functional traits (growth rate, density/cover,
germination, biomass and survival) equally promote tree invasiveness. Overall, our results suggest that several hypotheses,
linked to invasibility or invasiveness, are pertinent to explain tree invasions. Furthermore, more than one hypothesis has
been supported for a given species, which indicates that multiple factors lead to the success of invasive tree species. In
addition, growth rate appears to be the most efficient predictor of invasiveness for invasive trees and could thus be used
as a means to identify potential alien tree invasions. We conclude that further investigations are needed to test the consistency
of some hypotheses across a broader pool of invasive tree species, whilst experimental studies with the same tree species
across a larger range of sites would help to reveal the full suite of factors that affect tree invasions. 相似文献
995.
Mestre O Luo T Dos Vultos T Kremer K Murray A Namouchi A Jackson C Rauzier J Bifani P Warren R Rasolofo V Mei J Gao Q Gicquel B 《PloS one》2011,6(1):e16020
Background
The Beijing family is a successful group of M. tuberculosis strains, often associated with drug resistance and widely distributed throughout the world. Polymorphic genetic markers have been used to type particular M. tuberculosis strains. We recently identified a group of polymorphic DNA repair replication and recombination (3R) genes. It was shown that evolution of M. tuberculosis complex strains can be studied using 3R SNPs and a high-resolution tool for strain discrimination was developed. Here we investigated the genetic diversity and propose a phylogeny for Beijing strains by analyzing polymorphisms in 3R genes.Methodology/Principal Findings
A group of 3R genes was sequenced in a collection of Beijing strains from different geographic origins. Sequence analysis and comparison with the ones of non-Beijing strains identified several SNPs. These SNPs were used to type a larger collection of Beijing strains and allowed identification of 26 different sequence types for which a phylogeny was constructed. Phylogenetic relationships established by sequence types were in agreement with evolutionary pathways suggested by other genetic markers, such as Large Sequence Polymorphisms (LSPs). A recent Beijing genotype (Bmyc10), which included 60% of strains from distinct parts of the world, appeared to be predominant.Conclusions/Significance
We found SNPs in 3R genes associated with the Beijing family, which enabled discrimination of different groups and the proposal of a phylogeny. The Beijing family can be divided into different groups characterized by particular genetic polymorphisms that may reflect pathogenic features. These SNPs are new, potential genetic markers that may contribute to better understand the success of the Beijing family. 相似文献996.
Wuchty S Arjona D Li A Kotliarov Y Walling J Ahn S Zhang A Maric D Anolik R Zenklusen JC Fine HA 《PloS one》2011,6(2):e14681
Despite progress in the determination of miR interactions, their regulatory role in cancer is only beginning to be unraveled. Utilizing gene expression data from 27 glioblastoma samples we found that the mere knowledge of physical interactions between specific mRNAs and miRs can be used to determine associated regulatory interactions, allowing us to identify 626 associated interactions, involving 128 miRs that putatively modulate the expression of 246 mRNAs. Experimentally determining the expression of miRs, we found an over-representation of over(under)-expressed miRs with various predicted mRNA target sequences. Such significantly associated miRs that putatively bind over-expressed genes strongly tend to have binding sites nearby the 3'UTR of the corresponding mRNAs, suggesting that the presence of the miRs near the translation stop site may be a factor in their regulatory ability. Our analysis predicted a significant association between miR-128 and the protein kinase WEE1, which we subsequently validated experimentally by showing that the over-expression of the naturally under-expressed miR-128 in glioma cells resulted in the inhibition of WEE1 in glioblastoma cells. 相似文献
997.
The concerted development of GABAergic interneurons and glutamatergic neurons is a key feature in the construction of the cerebral cortex. In contrast with glutamatergic neurons, GABAergic interneurons are heterogeneous differing by their axonal and dendritic morphologies, biochemical markers, connectivity, and physiology. Furthermore, interneurons have recently been shown to be generated in a variety of telencephalic structures (the ganglionic eminences, the entopeduncular and preoptic areas and the cortex). This review describes the origin, specification and differentiation of interneurons. These recent developmental studies may help to clarify the classification of mature interneurons. In particular recent studies, including our own, provide compelling evidences that most interneurons are specify after their last division in their region of origin before migration. The roles of target tissues in determining the final physiological properties of interneurons are also discussed. 相似文献
998.
The neuronal cytoskeleton consists of microtubules, actin filaments, neurofilaments, and an array of accessory proteins that regulate and modify these three main filament systems. This essay celebrates the career of Paul Letourneau, a pioneer of the neuronal cytoskeleton, to whom the community owes a debt of gratitude. 相似文献
999.
Delrieu I Yaro S Tamekloé TA Njanpop-Lafourcade BM Tall H Jaillard P Ouedraogo MS Badziklou K Sanou O Drabo A Gessner BD Kambou JL Mueller JE 《PloS one》2011,6(5):e19513
Serogroup X meningococci (NmX) historically have caused sporadic and clustered meningitis cases in sub-Saharan Africa. To study recent NmX epidemiology, we analyzed data from population-based, sentinel and passive surveillance, and outbreak investigations of bacterial meningitis in Togo and Burkina Faso during 2006-2010. Cerebrospinal fluid specimens were analyzed by PCR. In Togo during 2006-2009, NmX accounted for 16% of the 702 confirmed bacterial meningitis cases. Kozah district experienced an NmX outbreak in March 2007 with an NmX seasonal cumulative incidence of 33/100,000. In Burkina Faso during 2007-2010, NmX accounted for 7% of the 778 confirmed bacterial meningitis cases, with an increase from 2009 to 2010 (4% to 35% of all confirmed cases, respectively). In 2010, NmX epidemics occurred in northern and central regions of Burkina Faso; the highest district cumulative incidence of NmX was estimated as 130/100,000 during March-April. Although limited to a few districts, we have documented NmX meningitis epidemics occurring with a seasonal incidence previously only reported in the meningitis belt for NmW135 and NmA, which argues for development of an NmX vaccine. 相似文献
1000.