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991.
Glacier melting and stoichiometric implications for lake community structure: zooplankton species distributions across a natural light gradient 总被引:1,自引:0,他引:1
Cecilia Laspoumaderes Beatriz Modenutti María Sol Souza Marcela Bastidas Navarro Florencia Cuassolo Esteban Balseiro 《Global Change Biology》2013,19(1):316-326
Glaciers around the globe are melting rapidly, threatening the receiving environments of the world's fresh water reservoirs with significant changes. The meltwater, carried by rivers, contains large amounts of suspended sediment particles, producing longitudinal gradients in the receiving lakes. These gradients may result in changes in the light : nutrient ratio that affect grazer performance by altering elemental food quality. Thus, glacial melting may induce a shift in the phytoplankton carbon : nutrient ratio and hence influence the dominance of herbivorous zooplankton through stoichiometric mechanisms. To test this hypothesis, we combined field and experimental data, taking advantage of a natural light intensity gradient caused by glacial clay input in a deep oligotrophic Patagonian lake. Across this gradient, we evaluated the abundances of two consumer taxa with different phosphorus requirements, the copepod Boeckella gracilipes and the cladoceran Daphnia commutata, using a six‐station transect along the lake. We found significant differences in light : nutrient ratio and stoichiometric food quality of the seston, together with a switch from dominance of P‐rich Daphnia in low carbon : nutrient stations to dominance of low‐P copepods in high carbon : nutrient stations. The laboratory experiments confirmed that the difference in the carbon : nutrient ratio across the gradient is sufficient to impair Daphnia growth. The overall patterns are consistent with our prediction that shifts in the environmental light : nutrient ratio as a result of glacial melting would contribute to shifts in the dominance of stoichiometrically contrasting taxa in consumer guilds. 相似文献
992.
D. Rojas C. A. Mancina J. J. Flores‐Martínez L. Navarro 《Journal of evolutionary biology》2013,26(9):1925-1933
Comparative correlational studies of brain size and ecological traits (e.g. feeding habits and habitat complexity) have increased our knowledge about the selective pressures on brain evolution. Studies conducted in bats as a model system assume that shared evolutionary history has a maximum effect on the traits. However, this effect has not been quantified. In addition, the effect of levels of diet specialization on brain size remains unclear. We examined the role of diet on the evolution of brain size in Mormoopidae and Phyllostomidae using two comparative methods. Body mass explained 89% of the variance in brain volume. The effect of feeding behaviour (either characterized as feeding habits, as levels of specialization on a type of item or as handling behaviour) on brain volume was also significant albeit not consistent after controlling for body mass and the strength of the phylogenetic signal (λ). Although the strength of the phylogenetic signal of brain volume and body mass was high when tested individually, λ values in phylogenetic generalized least squares models were significantly different from 1. This suggests that phylogenetic independent contrasts models are not always the best approach for the study of ecological correlates of brain size in New World bats. 相似文献
993.
994.
Cesare Indiveri Michele Galluccio Mariafrancesca Scalise Lorena Pochini 《Molecular biotechnology》2013,54(2):724-736
The OCTN subfamily includes OCTN1, 2, and 3 which are structurally and functionally related. These transporters are involved in maintenance of the carnitine homeostasis, which is essential in mammals for fatty acid β-oxidation, VLDL assembly, post-translational modifications, and other essential functions. Indeed, defects of these transporters lead to severe pathologies. OCTN1 and OCTN2 are expressed in many human tissues, while OCTN3 gene has been identified only in mouse and rat. The transporters mediate transport of carnitine and other substrates with different efficiencies and mechanisms. In order to over express the three proteins, a screening of many combinations of E. coli strains with plasmid constructs has been conducted. Only Rosetta(DE3) or Rosettagami2(DE3) gave significant expression. Higher protein amounts were firstly obtained with pET-41a(+) or pGEX-4T1 carrying fusion protein tags which required additional purification passages. Vectors carrying only a 6His tag, suitable for single passage purification, were preferred even though they lead to lower initial expression levels. Expressions were then increased optimizing several critical parameters. hOCTN1 was obtained with pH6EX3 in RosettaGami2(DE3)pLysS. hOCTN2 and mOCTN3 were obtained using pET-21a(+) in Rosetta(DE3). In particular, hOCTN2 was expressed only after codon bias, substituting the second triplet CGG with AAA (R2K mutant). The best growth conditions for hOCTN1 and mOCTN3 were 28 °C and 6 h of induction, while 4 h of induction for hOCTN2R2K. The proteins collected in the insoluble fraction of cell lysates, solubilized with sarkosyl, were purified by Ni-chelating chromatography. Final yield was 2.0, 3.0, or 3.5 mg/l of cell culture for mOCTN3, hOCTN1, or hOCTN2R2K. The data indicated that, in spite of the close evolutionary relations, several factors play different critical roles in bacterial expression of the three proteins, thus general criteria cannot be underlined. However, the strategy of dealing with related proteins revealed to be finally successful for over expressing all the three subfamily members. 相似文献
995.
Pint lincRNA connects the p53 pathway with epigenetic silencing by the Polycomb repressive complex 2
996.
Charmina Aguirre-Alvarado Fabiola Zaragoza-Martínez Lorena Rodríguez-Páez Benjamín Nogueda Isabel Baeza Carlos Wong 《Journal of enzyme inhibition and medicinal chemistry》2013,28(2):227-233
The trypanocidal activity of N-allyl (NAOx) and N-propyl (NPOx) oxamates and that of the ethyl esters of N-allyl (Et-NAOx) and N-propyl (Et-NPOx) oxamates were tested on cultured epimastigotes (in vitro) and murine trypanosomiasis (in vivo) using five different T. cruzi strains. NAOx and NPOx did not penetrate intact epimastigotes and therefore we were not able to detect any trypanocidal effect with these oxamates. Whereas the ethyl esters (Et-NAOx and Et-NPOx), acting as prodrugs, exhibited in vitro and in vivo trypanocidal activity on the five tested T. cruzi strains. On the contrary, when Nifurtimox and Benznidazole used as reference drugs were tested, we found that only three of the five tested T. cruzi strains were affected, whereas the other two strains, Miguz and Compostela, were resistant to the in vitro and in vivo trypanocidal activity of these compounds. 相似文献
997.
Silvia Elizondo Miguel A. Chena Lorena Rodríguez-Páez Benjamín Nogueda Isabel Baeza Carlos Wong 《Journal of enzyme inhibition and medicinal chemistry》2013,28(3):265-271
The effect of N-isopropyl oxamate on the activity of α-hydroxyacid dehydrogenase-isozyme II (HADH-isozyme II) from Trypanosoma cruzi was investigated. The kinetic studies showed that this substance was a competitive inhibitor of this isozyme. The attachment of the nonpolar isopropylic branched chain to the nitrogen of oxamate increased 12-fold the affinity of N-isopropyl oxamate for the active site of T. cruzi HADH-isozyme II. N-isopropyl oxamate was a selective inhibitor of HADH-isozyme II, since other T. cruzi dehydrogenases were not inhibited by this substance. Since HADH-isozyme II participates in the energy metabolism of T. cruzi, a trypanocidal effect can be expected with inhibitors of this isozyme. However, although it was not possible to detect any trypanocidal activity with N-isopropyl oxamate when the ethyl ester was tested as a possible trypanocidal prodrug, the expected trypanocidal effect was obtained, comparable to that obtained with nifurtimox and benznidazole. 相似文献
998.
999.
Alonso Rodríguez‐Navarro 《EMBO reports》2013,14(6):493-493
1000.
Lorena?Blanco-Rojas Adrià?ArboixEmail author David?Canovas Marta?Grau-Olivares Joan?Carles?Oliva Morera Olga?Parra 《BMC neurology》2013,13(1):203