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991.
Riparian zones are an important strategy to mitigate N and P export to streams. However, their efficiency with respect to nitrate (NO3 ?), ammonium (NH4 +), or soluble reactive phosphorus (SRP) in groundwater remains uncertain in the US Midwest. This study investigates water table fluctuations and NO3 ?, NH4 +, and SRP concentration dynamics in two riparian zone types (outwash vs. glacial till) common in the upper US Midwest. During low water table periods, NO3 ? removal was 93 % at WR (outwash site), and 75 % at LWD (glacial till site); but during high water table periods, NO3 ? removal efficiencies dropped to 50 % at WR, and 14 % at LWD. Median seasonal mass fluxes of NO3 ? removed at WR (9.4–21.7 mg N day?1 m?1 of stream length) and LWD (0.4–1.9 mg N day?1 m?1) were small compared to other riparian zones in glaciated landscapes. The WR site was a small SRP sink (0.114 and 0.118 mg day?1 m?1 during the dry period and wet period, respectively), while LWD acted as a small SRP source to the stream (0.004 mg day?1 m?1 during the dry period; 0.075 mg day?1 m?1 during the wet period). Both LWD and WR acted as sources of NH4 + to the stream with mass fluxes ranging from 0.17 to 7.75 mg N day?1 m?1. Although riparian zones in the US Midwest provide many ecosystem services, results suggest they are unlikely to efficiently mitigate N and P pollution in subsurface flow. 相似文献
992.
Marilyn M. McGowan Priya D. Patel Jolie D. Stroh Daniel T. Blumstein 《Ethology : formerly Zeitschrift fur Tierpsychologie》2014,120(11):1081-1089
Antipredator behavior and risk assessment of many species are affected by the presence of humans and their activities. Previous studies have largely been conducted on birds and mammals and relatively less is known about human impacts on reptiles. We used flight initiation distance (FID) as a measure of risk assessment in inland blue‐tailed skinks (Emoia impar) and tested the direct and indirect effects of humans on risk assessment. We first examined the effects of varying levels and types of human disturbance and activity on skink FID. We found that skinks flushed at significantly longer distances in areas with the least human activity. We then tested the degree to which skinks are able to discriminate different numbers of humans by comparing FID across three different types of approaches. Skinks did not significantly differentiate between a single approacher and a single approacher coming from a group of two other people, but did flush at greater distances when approached by three people simultaneously. Although skinks are not directly harvested or harassed by humans, they have refined human discrimination abilities. Overall, skinks habituate to a variety of human activities and perceive a larger threat when the number of human approachers is greater. 相似文献
993.
Robert L. Kortum Mario R. Fernandez Diane L. Costanzo-Garvey Heidi J. Johnson Kurt W. Fisher Deanna J. Volle Robert E. Lewis 《Molecular and cellular biology》2014,34(18):3461-3472
The molecular scaffold kinase suppressor of Ras 1 (KSR1) regulates the activation of the Raf/MEK/extracellular signal-regulated kinase (ERK) signal transduction pathway. KSR1 disruption in mouse embryo fibroblasts (MEFs) abrogates growth factor-induced ERK activation, H-RasV12-induced replicative senescence, and H-RasV12-induced transformation. Caveolin-1 has been primarily described as a major component of the coating structure of caveolae, which can serve as a lipid binding adaptor protein and coordinates the assembly of Ras, Raf, MEK, and ERK. In this study, we show that KSR1 interacts with caveolin-1 and is responsible for MEK and ERK redistribution to caveolin-1-rich fractions. The interaction between KSR1 and caveolin-1 is essential for optimal activation of ERK as a KSR1 mutant unable to interact with caveolin-1 does not efficiently mediate growth factor-induced ERK activation at the early stages of pathway activation. Furthermore, abolishing the KSR1–caveolin-1 interaction increases growth factor demands to promote H-RasV12-induced proliferation and has adverse effects on H-RasV12-induced cellular senescence and transformation. These data show that caveolin-1 is necessary for optimal KSR1-dependent ERK activation by growth factors and oncogenic Ras. 相似文献
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S.J. Annesley S. ChenL.M. Francione O. SanislavA.J. Chavan C. FarahS.W. De Piazza C.L. StoreyJ. Ilievska S.G. FernandoP.K. Smith S.T. LayP.R. Fisher 《Biochimica et Biophysica Acta (BBA)/General Subjects》2014
Background
Most neurodegenerative diseases are associated with mitochondrial dysfunction. In humans, mutations in mitochondrial genes result in a range of phenotypic outcomes which do not correlate well with the underlying genetic cause. Other neurodegenerative diseases are caused by mutations that affect the function and trafficking of lysosomes, endosomes and autophagosomes. Many of the complexities of these human diseases can be avoided by studying them in the simple eukaryotic model Dictyostelium discoideum.Scope of review
This review describes research using Dictyostelium to study cytopathological pathways underlying a variety of neurodegenerative diseases including mitochondrial, lysosomal and vesicle trafficking disorders.Major conclusions
Generalised mitochondrial respiratory deficiencies in Dictyostelium produce a consistent pattern of defective phenotypes that are caused by chronic activation of a cellular energy sensor AMPK (AMP-activated protein kinase) and not ATP deficiency per se. Surprisingly, when individual subunits of Complex I are knocked out, both AMPK-dependent and AMPK-independent, subunit-specific phenotypes are observed. Many nonmitochondrial proteins associated with neurological disorders have homologues in Dictyostelium and are associated with the function and trafficking of lysosomes and endosomes. Conversely, some genes associated with neurodegenerative disorders do not have homologues in Dictyostelium and this provides a unique avenue for studying these mutated proteins in the absence of endogeneous protein.General significance
Using the Dictyostelium model we have gained insights into the sublethal cytopathological pathways whose dysregulation contributes to phenotypic outcomes in neurodegenerative disease. This work is beginning to distinguish correlation, cause and effect in the complex network of cross talk between the various organelles involved. This article is part of a Special Issue entitled Frontiers of Mitochondrial Research 相似文献996.
Savitha Kalidas Igor Cestari Severine Monnerat Qiong Li Sandesh Regmi Nicholas Hasle Mehdi Labaied Marilyn Parsons Kenneth Stuart Margaret A. Phillips 《Eukaryotic cell》2014,13(4):504-516
Human African trypanosomiasis (HAT) is an important public health threat in sub-Saharan Africa. Current drugs are unsatisfactory, and new drugs are being sought. Few validated enzyme targets are available to support drug discovery efforts, so our goal was to obtain essentiality data on genes with proven utility as drug targets. Aminoacyl-tRNA synthetases (aaRSs) are known drug targets for bacterial and fungal pathogens and are required for protein synthesis. Here we survey the essentiality of eight Trypanosoma brucei aaRSs by RNA interference (RNAi) gene expression knockdown, covering an enzyme from each major aaRS class: valyl-tRNA synthetase (ValRS) (class Ia), tryptophanyl-tRNA synthetase (TrpRS-1) (class Ib), arginyl-tRNA synthetase (ArgRS) (class Ic), glutamyl-tRNA synthetase (GluRS) (class 1c), threonyl-tRNA synthetase (ThrRS) (class IIa), asparaginyl-tRNA synthetase (AsnRS) (class IIb), and phenylalanyl-tRNA synthetase (α and β) (PheRS) (class IIc). Knockdown of mRNA encoding these enzymes in T. brucei mammalian stage parasites showed that all were essential for parasite growth and survival in vitro. The reduced expression resulted in growth, morphological, cell cycle, and DNA content abnormalities. ThrRS was characterized in greater detail, showing that the purified recombinant enzyme displayed ThrRS activity and that the protein localized to both the cytosol and mitochondrion. Borrelidin, a known inhibitor of ThrRS, was an inhibitor of T. brucei ThrRS and showed antitrypanosomal activity. The data show that aaRSs are essential for T. brucei survival and are likely to be excellent targets for drug discovery efforts. 相似文献
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The sex ratio of the local population influences mating-related behaviours in many species. Recent experiments show that male-biased sex ratios increase the amount of financial resources men will invest in potential mates, suggesting that sex ratios influence allocation of mating effort in humans. To investigate this issue further, we tested for effects of cues to the sex ratio of the local population on the motivational salience of attractiveness in own-sex and opposite-sex faces. We did this using an effort-based key-press task, in which the motivational salience of facial attractiveness was assessed in samples of faces in which the ratio of male to female images was manipulated. The motivational salience of attractive opposite-sex, but not own-sex, faces was greater in the own-sex-biased (high competition for mates) than in the opposite-sex-biased (low competition for mates) condition. Moreover, this effect was not modulated by participant sex. These results present new evidence that sex ratio influences human mating-related behaviours. They also present the first evidence that the perceived sex ratio of the local population may modulate allocation of mating effort in women, as well as men. 相似文献